U.S. patent application number 11/171449 was filed with the patent office on 2006-01-26 for piezoelectric device and acousto-electric transducer and method for manufacturing the same.
Invention is credited to Yoshiaki Nagaura.
Application Number | 20060016065 11/171449 |
Document ID | / |
Family ID | 27344405 |
Filed Date | 2006-01-26 |
United States Patent
Application |
20060016065 |
Kind Code |
A1 |
Nagaura; Yoshiaki |
January 26, 2006 |
Piezoelectric device and acousto-electric transducer and method for
manufacturing the same
Abstract
A lens shape piezoelectric device which is thinner than the
manufacture limit thickness, which is conventionally difficult to
manufacture, and a method for manufacturing the same. The
piezoelectric device has a oscillation part having at least two
steps where one side thereof is planar and the opposite side is
thickest at a peripheral holding portion and thinner toward the
central portion. A piezoelectric element of another embodiment has
an oscillation part of at least two steps where the peripheral
holding portion is thickest on both sides and the thickness
decreases toward the central portion. In these piezoelectric
devices, at least one side of the thinnest central portion of the
oscillation part has a convex lens shape. A pair of electrodes are
vacuum deposited in the center of these oscillation parts on both
sides, and a gold wire is led as a lead wire from each
electrode.
Inventors: |
Nagaura; Yoshiaki;
(Chikushino-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
27344405 |
Appl. No.: |
11/171449 |
Filed: |
July 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10333130 |
Jan 16, 2003 |
6952074 |
|
|
PCT/JP01/06128 |
Jul 16, 2001 |
|
|
|
11171449 |
Jul 1, 2005 |
|
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|
Current U.S.
Class: |
29/594 ;
29/609.1; 310/367 |
Current CPC
Class: |
Y10T 29/4908 20150115;
Y10T 29/49005 20150115; H03H 9/132 20130101; H03H 9/19 20130101;
H03H 3/02 20130101; H03H 9/02157 20130101; H01L 41/337
20130101 |
Class at
Publication: |
029/594 ;
310/367; 029/609.1 |
International
Class: |
H01L 41/04 20060101
H01L041/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 2000 |
JP |
2000-251675 |
Feb 19, 2001 |
JP |
2001-091394 |
Jun 5, 2001 |
JP |
2001-209997 |
Claims
1. A manufacturing method of said acousto-electric transducer,
which makes the oscillation part of a final thickness and target
profile, after the final profile is formed on the surface of
piezoelectric material which is thicker than the final thickness,
and the surface of said piezoelectric material is reactively etched
and homogeneously decreasing the thickness from both ends toward
the central region of said piezoelectric material.
2. A manufacturing method of said piezoelectric device, which makes
the oscillation part of a final thickness and target profile inside
the central region of a rod in hollow cylindrical shape, after the
final profile is formed on the surface of a rod made from the
piezoelectric material, and the surface of said rod except the wall
of said rod is processed by the dry etching and homogeneously
decreasing the thickness from both ends toward the central region
of said rod.
3. A manufacturing method of said acousto-electric transducer,
which makes the oscillation part of a final thickness and target
profile, after the final profile is formed on the surface of
piezoelectric material which is thicker than the final thickness,
and the surface of said piezoelectric material is processed by the
dry etching and homogeneously decreasing the thickness from both
ends toward the central region of said piezoelectric material.
4. A manufacturing method of said piezoelectric device, which makes
the oscillation part of a final thickness and target profile inside
the central region of a rod in hollow cylindrical shape, after the
final profile is formed on the surface of a rod made from the
piezoelectric material, and the surface of said rod except the wall
of said rod is processed by the dry etching and homogeneously
decreasing the thickness from both ends toward the central region
of said rod.
5. A manufacturing method of said piezoelectric device, which makes
the piezoelectric material in a lens shape identical to an
auxiliary blank, after said auxiliary blank in the final lens shape
is closely attached to both ends of the rod made from the
piezoelectric material, and the surface of said auxiliary blank
attached to the rod is processed by the dry etching, and then the
surface of said auxiliary blank is shaved at first and next the
surface of the piezoelectric material.
6. A manufacturing method of said piezoelectric device, which makes
the piezoelectric material in a lens shape with a holder identical
to an auxiliary blank, after said auxiliary blank in the final lens
shape is closely attached to both ends of the rod made from the
piezoelectric material, and the surface of said auxiliary blank
attached to the rod is processed by the dry etching, and then the
surface of said auxiliary blank is shaved at first, and next the
surface of the piezoelectric material is also shaved.
Description
[0001] This is a divisional application of Ser. No. 10/333,130,
filed Jan. 16, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] This invention is related to a piezoelectric device and an
acousto-electric transducer, and the method for manufacturing the
same, which enables the characteristic frequency to be extremely
higher.
[0004] 2. Description of Related Art
[0005] Quartz oscillators (resonators), as one of piezoelectric
devices, are used for a wide variety of application fields such as
fundamental frequency generators of communication apparatus and
sensing instrumentation and clock sources of general computers,
office automation information equipment, home appliances, and so
forth. It has been required for those characteristic frequencies to
be higher by decreasing the thickness of their oscillators
(resonators) in order to achieve the high performance of the
information processing and transfer capabilities. Also the
lens-line type finishing was proposed to produce higher quality
oscillators (resonators), and these performances were accomplished
for those relatively lower frequency domains.
[0006] Quartz oscillators are the essential electronic devices for
digital machines such as communication equipment, computers, and so
forth. It is demanded for those oscillators to increase the primary
oscillation frequency by decreasing the thickness in order to
achieve the high performance of the information processing and
transfer abilities. Especially for mobile communication, the
fundamental frequency is required to be higher for the small sizing
and power saving management.
[0007] Quartz oscillators have been generally manufactured by the
mechanical polishing and chemical wet etching processes. The former
polishing shows the fine surface finish, however it cannot machine
in lower than 30 .mu.m. The latter etching has the advantage of
decreasing deteriorated surface in principle, but it has the
limitation of thickness due to the etching channel generation and
so forth. On the other hand, the reactive ion etching (RIE),
inductive coupled plasma etching (ICP) or plasma-etching process
(abbreviated as chemical dry etching) makes the damaged surface
layer, however the dry etching allows the device to be thin without
the inconvenient surface roughness.
[0008] The novel mass-productive manufacturing method of high
frequency quartz oscillator is developed, by combining efficiently
the advantages of these processes. However the problem of reducing
the thickness of those oscillators (resonators) by the dual-face
polishing method (dual-face polishing machine) is presently
incapable reducing the thickness to less than 30.0 .mu.m (=55.6
MHz).
[0009] Furthermore, when oscillators were finishing in lens shape,
it was extremely difficult to make the curved surface on the thin
plate, and there existed no machining method of mass production
with low cost.
SUMMARY OF THE INVENTION
[0010] Thereafter the present invention was developed to solve
these problems, and shall make possible the manufacture the lens
shape piezoelectric device, which is thinner than the thickness
limitation in the conventional method.
[0011] In order to solve previously mentioned problems, the
piezoelectric device of present invention has one flat surface, and
the other side has the thickest peripheral holding portion and a
central oscillation part connected by at least two steps, which one
side is decreasing the thickness toward the central region. Also
another type of piezoelectric device has the thickest peripheral
holding portion and the central oscillation part at least with two
steps, and both sides are decreasing in thickness toward the
central region.
[0012] The oscillating part at the thinnest center of piezoelectric
device is in convex lens shape at least for the one surface.
[0013] Furthermore the present invention enables the piezoelectric
device to be manufactured to make the first oscillating part to be
seen toward the crystal orientation of the piezoelectric material
at the central part of a nearly rectangular quartz blank, and
afterward to make the second oscillating part so as not to be seen
toward the crystal orientation of the piezoelectric material.
[0014] Furthermore, an acousto-electric transducer of the present
invention is manufactured so as to make the final shape profile at
both end surfaces of piezoelectric rod, and to make the end surface
of above stick as homogeneously and relatively decreasing the
thickness toward the central direction of the rod in the similar
geometric shape by a dry etching process such as RIE, without
machining the outer wall thickness of the rod. Then the oscillating
part at the inner central region of the cylindrical rod is made the
oscillation device with the final thickness and profile.
[0015] A pair of electrodes is vacuum deposited in the center of
these vibrating parts on both sides, and a gold wire is led as a
lead wire from each electrode.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 illustrates the flow chart of manufacturing process
for the present invention.
[0017] FIG. 2 illustrates the design diagram of forming the convex
lens shape of piezoelectric device for the present invention.
[0018] FIG. 3 illustrates a characteristic diagram of
reactance-frequency for the thick quartz resonator which blank is
AT-cut.
[0019] FIG. 4 illustrates a characteristic oscillation diagram of
reactance-frequency for the thick quartz resonator which blank is
AT-cut, and the plane and longitude diagrams of single-sided
inverted mesa type quartz resonator with one step.
[0020] FIG. 5 illustrates a characteristic diagram of
reactance-frequency for the thin quartz resonator which blank is
AT-cut.
[0021] FIG. 6 illustrates a measurement diagram of quartz resonator
shape by an interference microscope.
[0022] FIG. 7 illustrates a characteristic diagram of
reactance-frequency for the thin quartz resonator which blank is
AT-cut.
[0023] FIG. 8 illustrates a graph to show the level difference
(P-V) between the peak and valley versus the changing quartz
resonator thickness.
[0024] FIG. 9 shows an inverse graph of curvature radius in a
convex lens shape to form single-sided inverse mesa type with one
step.
[0025] FIG. 10 shows a roughness graph of the central concave
surface part for the single-sided inverse mesa type with one
step.
[0026] FIG. 11 shows a cross section for a real example of present
acousto-electric transducer.
[0027] FIG. 12 is an upper surface diagram of the real example
proposed above.
[0028] FIG. 13 is a cross section to show the machining method
proposed above.
[0029] FIG. 14 is a side diagram to show the machining tools for a
real example proposed above.
[0030] FIG. 15 is the side and A-A cross section diagrams to show
the whetstone for a real example proposed above.
[0031] FIG. 16 is a cross section diagram to show a real example
proposed above.
[0032] FIG. 17 illustrates a side and plane diagrams to show
another whetstone for a real example proposed above.
[0033] FIGS. 18-20 respectively illustrate cross sections of other
machining tools for the real examples proposed above.
[0034] FIG. 21 illustrates the side and upper diagrams to show the
manufacturing charts of the machining tools for a real example
proposed above.
[0035] FIG. 22 illustrates the enlarged side and upper diagrams to
show the manufacturing charts of the machining tools proposed
above.
[0036] FIGS. 23-30 respectively illustrate cross sections of
oscillators (resonators) to show those manufacturing processes for
acousto-electric transducers and other applications of the present
invention
[0037] FIG. 31 is a front diagram of state, which has gold lead
from electrode in this invention.
[0038] FIGS. 32-54 respectively show upper and cross section
diagrams of oscillators (resonators) for real examples in this
invention.
[0039] FIG. 55 shows a shape measurement diagram of manufactured
quartz oscillator sample 1 with two steps single-sided concave
type, which is measured by an interference microscope (laser
interferometer).
[0040] FIG. 56 illustrates a shape measurement diagram of
manufactured quartz oscillator sample 1 with two steps single-sided
grooved type, which is enlarged by an interference microscope.
[0041] FIG. 57 illustrates a photograph (Normanski micrograph or
differential interference micrometer) of manufactured quartz
resonator sample 1 with two steps single-sided grooved type in
FIGS. 55 and 56.
[0042] FIGS. 58 and 59 respectively illustrate upper diagrams and
cross section diagrams of real quartz oscillator (resonator)
samples in the present invention.
[0043] FIG. 60 illustrates a shape measurement diagram of
manufactured quartz resonator sample 2 with two steps single sided
concave type, which is studied by an interference microscope.
[0044] FIG. 61 illustrates a shape measurement diagram of
manufactured quartz resonator sample 2 in FIG. 60 with two steps
single-sided concave type, which is enlarged by an interference
microscope.
[0045] FIG. 62 illustrates a photograph (Normanski micrograph) of
manufactured quartz resonator sample 2 with two steps single-sided
concave type in FIGS. 60 and 61.
[0046] FIGS. 63 and 64 respectively illustrate upper diagrams and
cross section diagrams of real quartz oscillator (resonator)
samples in the present invention.
[0047] FIG. 65 illustrates a surface-shape measurement diagram of
manufactured quartz oscillator sample 3 with two steps double-sided
grooved type, which is studied by an interference microscope.
[0048] FIG. 66 illustrates a surface-shape measurement diagram of
manufactured quartz oscillator sample 3 in FIG. 65 with two steps
double-sided grooved type, which is enlarged by an interference
microscope.
[0049] FIG. 67 illustrates a rear surface measurement diagram of
manufactured quartz oscillator sample 3 in FIG. 65 with two steps
double-sided grooved type, which is studied by an interference
microscope.
[0050] FIG. 68 illustrates a rear surface measurement diagram of
manufactured quartz oscillator sample 3 in FIG. 63 with two steps
double-sided grooved type, which is enlarged by an interference
microscope.
[0051] FIG. 69 illustrates a photograph (Normanski micrograph) of
manufactured quartz oscillator sample 3 with two steps double-sided
grooved type in FIGS. 65 and 66.
[0052] FIG. 70 illustrates upper diagrams and cross section
diagrams of real quartz oscillator sample in the present
invention.
[0053] FIG. 71 illustrates a surface-shape measurement diagram of
manufactured quartz oscillator sample 4 with two steps double-sided
concave type, which is studied by an interference microscope.
[0054] FIG. 72 illustrates a rear shape measurement diagram of
manufactured quartz oscillator sample 4 in FIG. 71 with two steps
double-sided grooved type, which is studied by an interference
microscope.
[0055] FIG. 73 illustrates a surface photograph (Normanski
micrograph) of manufactured quartz oscillator sample 4 with two
steps double-sided grooved type in FIG. 71.
[0056] FIG. 74 illustrates a rear surface photograph (Normanski
micrograph) of manufactured quartz oscillator sample 4 with two
steps double-sided grooved type in FIG. 72.
[0057] FIG. 75 illustrates upper diagrams and cross section
diagrams of real quartz sample in the present invention.
[0058] FIG. 76 illustrates a surface-shape measurement diagram of
manufactured quartz oscillator sample 5 with two steps single-sided
grooved type, which is studied by an interference microscope.
[0059] FIG. 77 illustrates a surface photograph (Normanski
micrograph) of manufactured quartz oscillator sample 5 with two
steps single-sided grooved type in FIG. 76.
[0060] FIG. 78 illustrates a surface-shape measurement diagram of
manufactured quartz oscillator sample 6 with conventional one step
double-sided inverse mesa type, which is studied by interference
microscope made by Hoffman in USA.
[0061] FIG. 79 illustrates a surface shape measurement diagram of
manufactured quartz oscillator sample 6 in FIG. 78, which is
enlarged by an interference microscope.
[0062] FIG. 80 illustrates a rear-surface shape measurement diagram
of manufactured quartz oscillator sample 6 in FIG. 78, which is
studied by an interference microscope.
[0063] FIG. 81 illustrates a rear-surface shape measurement diagram
of manufactured quartz oscillator sample 6 in FIG. 78, which is
enlarged by an interference microscope.
[0064] FIG. 82 illustrates a surface photograph (Normanski
micrograph) of manufactured quartz oscillator sample 6 in FIG.
78.
[0065] FIGS. 83 and 84 respectively illustrate characteristic
oscillation diagrams of reactance-frequency for the thinnest quartz
oscillator which blank is AT-cut, and the plane and longitude
diagrams of single-sided grooved type quartz oscillator with two
steps.
[0066] FIGS. 85 and 86 illustrates a characteristic oscillation
diagram of reactance-frequency for the thin quartz resonator which
blank is AT-cut, and the plane and longitude diagrams of
double-sided grooved type quartz oscillator with two steps.
[0067] FIG. 87 illustrates a characteristic oscillation diagram of
reactance-frequency of manufactured quartz oscillator with AT-cut,
and conventional one step double-sided inverse mesa type, which is
studied by interference microscope made by Hoffman in USA.
[0068] FIGS. 88 and 89 illustrate dimension diagrams of
manufactured sample as three steps single-sided grooved type quartz
oscillator.
[0069] FIGS. 90 and 91 illustrate dimension diagrams of
manufactured sample as three steps double-sided grooved type quartz
oscillator.
[0070] FIG. 92 illustrates a machining sample pressurized from both
sides by dual face polishing machine for three steps double-sided
grooved type quartz oscillator in FIG. 88(f).
[0071] FIG. 93 shows a cross section diagram of another sample with
plural steps in this invention.
[0072] FIGS. 94 and 95 illustrate surface profile measurement
diagrams of manufactured sample 2, which is pressurized from both
sides by dual face polishing machine (polishing table) for two
steps single-sided grooved type quartz oscillator.
[0073] FIG. 96 is a chart to show a parallelism error of parallel
plate.
DETAILED DESCRIPTION OF THE INVENTION
[0074] FIG. 1 shows a manufacturing method for the present
invention. At first the quartz blank 100 (FIG. 1(a)) is cut to 50
.mu.m from artificial quartz, then a part of one side (upper
surface) is solved by etching with hydrogen fluoride, and a concave
groove 101 is made (FIG. 1(b)). The oscillation part is generated
by the thin layer between this pit 101 and the lower surface of
quartz blank 100, the remaining part becomes the frame 102, which
is attached by electrodes. These are same as the conventional
manufacturing methods.
[0075] As the next step, the whole lower surface is processed by a
dry etching as ion etching (hereafter ion etching process) with
hydrogen fluoride, and the quartz blank 100 becomes thinner FIG.
1(c). This ion etching process is to sputter silicone atoms in
silicone dioxide at the surface of quartz blank 100, when the
electric voltage is impressed to fluorine atoms and accelerate ions
after the molecular bondages are cut in the plasma state.
[0076] As mentioned previously, it is not possible for the sole
chemical wet etching to decrease the thickness thinner than 20
.mu.m. Afterwards the ion etching process will decrease the
thickness down to approximately 10.3 .mu.m.
[0077] The target thickness is 10 .mu.m. However, the ion etching
process alone will not achieve the target thickness. The ion
etching can decrease the thickness, however this has the
disadvantage of forming an ion-damaged layer, which is unknown
defect with non-crystalline component at the mono-crystalline
surface, since the ion etching process uses atomic collisions. The
thickness of the layer is approximately 0.2-0.3 .mu.m.
[0078] Therefore we employed the mechanical polishing. The dual
face polishing machine does the job to polish the final processing
(FIG. 1(d)), and it machines the blank down to 10.3 .mu.m with the
surface layer 0.3 .mu.m. The dual face polishing machine structure
is similar to a planet gear. At first the quartz plate 100 is set
to the steel carrier 106, which corresponds to the planet gear and
rotates with axis-rotation at the same time, and the blank 100 is
sandwiched between the lower fixed table 104 and the upper table
103. Both fixed tables are patched by foamed poly-urethane
polishing pad 105.
[0079] Thereafter, cerium oxide whetstone powder is streaming with
water, the quartz blank 100 held by carrier 106 rotates around its
own axis between the lower and upper tables 103, 104, also the
upper table 103 rotates, and then the quartz 100 can be
polished.
[0080] As shown in FIG. 1(e), the lower surface of quartz blank 100
becomes curved in convex lens shape. This lens shape is known to be
efficient in generating more steady oscillation, since spurious
oscillation (secondary vibration) as the erroneous reaction for
electronics does not appear.
[0081] FIG. 2 will show how the convex lens shape of the blank is
formed.
[0082] The polished quantity is proportional to the polishing
pressure. The frame 102 of concave quartz blank 100 after the ion
etching is strongly pressurized to be polished between the upper
table 103 and lower table 104, and the grooved part for oscillation
is slightly impressed only by the lower table 104. Furthermore the
polishing force at the central region of the concaved structure
part 101 is weaker (FIG. 2(a)). Therefore the polished mass is at
minimum at the center of the concave part 101, it becomes maximum
at the frame part 102, and the polished quantity among these parts
changes with a curvature like a part of a sphere. As a consequence,
the quartz oscillator was finished in the convex lens shape (FIG.
2(b)). The thickest central part of the lens is as thin as 10
.mu.m.
[0083] As understood from the above, the dual polishing machine
cuts only 0.3 .mu.m. This small amount of polishing enables the
damaged layer to be removed and shaped in a convex lens shape. In
other words, the chemical etching and dry etching process
corresponds to the coarse machining, and the dual face polishing
processing corresponds to the fine machining.
[0084] The combination of these polishing processes in this
invention makes the piezoelectric device thinner than the
conventional one, and also the oscillation part in a convex lens
shape makes it steady in electric vibration without the spurious
one.
[0085] This invention presents the manufacturing method of a high
frequency quartz oscillator with an efficient combination of
chemical wet etching (abbreviated as chemical etching), reactive
ion etching (RIE), inductive coupled plasma etching (dry etching)
and mechanical polishing. As a result, we could manufacture the
high frequency quartz oscillator in a piano-convex type with a
general dual face polishing machine, when the quartz blank was in
one step single-sided inverted mesa type.
[0086] FIG. 3(a) illustrates a reactance-frequency characteristic
example of quartz oscillator, which is made by RIE and ion milling
(or plasma etching). There exists the spurious peak near the
primary peak at the resonance frequency. This is thought to be due
to the ion damage of the dry etching process. After the dry etched
surface was manually polished, the spurious peaks were removed as
shown in FIG. 3(b), the electric property was improved. Therefore
the ion-damaged layer of the dry etching process was found to be
extremely thin as 0.3 .mu.m, and this could be removed by the
mechanical polishing process.
[0087] In order to mass-produce quartz blanks in one step single
sided inverse mesa type by chemical etching, quartz wafers were
masked and chemically etched. The shape is shown in FIG. 4(a). The
oscillating part of a 73.4 .mu.m thick quartz wafer was chemically
etched down to 32.68 .mu.m, and the depth of the etched pit was
sufficiently deep with acceptable surface roughness.
[0088] A reactance-frequency property of this quartz blank is seen
in FIG. 4(b). This is similar to that of the dry etching process as
shown in FIG. 3(a).
[0089] In order to achieve higher frequency, the dry etching
process of the mechanical polishing process with the dual face
polishing machine was employed to decrease the thickness. Here
before the ion-damaged layer must be removed, the surface side of
dry etching was selected to be the planar surface of quartz blank
in single-sided inverse mesa type. This RIE processing condition
was the standard one. It is possible for the ion damage to be
decreased by small RF power and high pressure. However this means a
slower ion etching rate, and the first dry etching was performed in
the high efficient mode, and the third one was performed in the low
damage condition. By the way, the removed mass was controlled by
the processing time of the first dry etching process. FIG. 5 shows
the reactance-frequency of the machined blank after the series of
above processing. After performing these processes, four machined
blanks were produced by one chemical etching and three dry
etchings.
[0090] FIG. 6 shows the polishing condition and the mechanical
polishing result. The quartz blank in a single-sided inverse mesa
type with one step after the previous process was polished by the
dual-face polishing machine. In this case, it was polished by the
conventional processing condition. However two upper polishing
plates were made from iron and aluminum to study the damage to the
thin oscillation part and the effect of the shape. When the upper
polishing plate is made from iron, the pressure to quartz is 1.8
times stronger than aluminum.
[0091] When the mechanical polishing was executed with the dual
face polishing machine, the blank could be machined without any
fear of the first problem of breaking the thin oscillation part.
The second target of forming the shape was successfully
accomplished as shown in FIG. 6. This FIG. 6 illustrates the
measured result of the shape when the inference microscope was used
to observe the flat surface of the quartz oscillation part in the
single-sided inverse mesa type with one step. Then the oscillation
part was found to be protruding in a convex lens shape. This shape
is apparently spherical, and the opposite side is basically planar.
Therefore, although the dual face polishing machine is designed to
form a planar surface, this machine can make the single-sided
convex quartz oscillator, when the polished material is a quartz
blank of the single-sided inverse mesa type.
[0092] The principle of this shaping mechanism is seen as follows.
When the quartz blank in one step single-sided inverse mesa type
with thin oscillation part is impressed with the polishing
pressure, the thin part is distorted toward the cavity direction
and this part cannot be substantially polished. After the polishing
process is finished and the polishing pressure is relieved, the
thin part (which is distorted toward the pit) rebounds to the
opposite side, and this shape becomes the protruded lens shape.
[0093] FIG. 7 illustrates a characteristic diagram of acoustic
reactance-frequency for four blanks and two machining pressures.
The electric property (a) after the polishing process is remarkably
improved compared to that (b) before the polishing process, and
this can oscillate in a high frequency. The spurious resonance
before the polishing process (b) is eliminated by the polishing
process, and the sharp resonance curve is observed. However, if
this thickness becomes too thin or the polishing pressure becomes
too strong, the spurious resonance appears, although the primary
peak remains. There exists an optimum pressure and an
aperture/thickness ratio.
[0094] FIG. 8 illustrates the form and surface roughness as a
function of the resonator thickness, i.e. the changing graph to
show the level difference (P-V) between the peak and valley at the
central oscillation part (1.44.times.1.31 mm) versus the quartz
resonator thickness. FIG. 9 shows the inverse of finished curvature
radius in convex lens shape as a function of the thickness. Since
FIG. 8 is identical to FIG. 9 in cases of the aluminum fixed table,
but are different from the iron table, the shape is thought to be
pure spherical for Al and distorted one for Fe. On the other hand,
the concave curvature of the quartz oscillator increased when the
thickness increased in one step single-sided inverse mesa type.
This means the machining distortion rate when the convex lens shape
was formed at the planar surface. The electric property will be
improved when the optimum condition is chosen for the polishing and
heat processing rates.
[0095] FIG. 10 shows the roughness at the concave central part
versus the thickness. The free whetstone powder changes the
roughness even where the polishing pad does not make contact. For
the chemical etching process, the roughness was Ra 2.6 nm, it
deteriorated to Ra 7 nm where the typical concave and convex
stripes appeared due to the chemical polishing. This roughness will
be relieved, when the ion damaged layer is cut by the mechanical
polishing in 0.3-0.4 .mu.m thickness, after the concave part (one
step single-sided inverse mesa type or one step double-sided
inverse mesa type) is formed by dry etching process.
[0096] Also FIG. 10 shows that the property of a one step
double-sided inverse mesa type was demonstrated to be improved by
the dual-face polishing machine, same as the one step single-sided
inverse mesa type, after the blank was processed by the dry
etching.
[0097] Based on these results, the electrically high performance
quartz oscillator was proved to be made above 334 MHz high
frequency, when the aperture thickness ratio (d/t) was from 50 to
150 (optimum 80).
[0098] The following theme concerns the acousto-electric transducer
as an application of the piezoelectric device of this
invention.
[0099] While a conventional detection and prediction of earthquake
was executed by ocean observation, underground structure probe,
earth magnetic observation, ground movement measurements between
two points with GPS and Laser, and so forth, acoustic wave
observation due to the earthquake and Tsunami will be one of these
detection and prediction. A focused microphone can transform the
acoustic wave to an electric signal, which is convenient to record
and analyze, but it is difficult to detect the acoustic wave at the
specific frequency due to the picking up of noises.
[0100] FIGS. 11 from (a) to (e) illustrate variously executed
examples of acousto-electric transducer of piezoelectric device in
this invention. In FIG. 11, cylinders 21 and 54 are made from
piezoelectric material of mono-crystalline such as quartz and
lithium niobium oxide or other ceramics as such barium titan oxide.
In FIG. 11 a pressure receiver 22 is located at the center of
cylinders 21 and 54, two electrodes 23 and 24 are vaporized by
metal on the pressure receiver, gold lead wires 26 are pasted to
electrodes 23 and 24 by electrically conductive adhesive, and the
amplifier is connected between electrodes 23 and 24 to measure the
inductive voltage. (Electrodes 23, 24 and amplifier 25 are
illustrated only in FIG. 11(a).) FIG. 11(a) is bi-convex type, (b)
is bi-concave type, (c) is planar, (d) is convex-concave type, and
(e) is plano-convex type. As seen FIG. 11(a), rooms A and B are
formed by two plugs 55, which seal the inside of cylinder 21, and
seal the inside of cylinder 54, respectively. Both rooms A and B
are de-pressurized (if possible vacuum or inert gas filling), and
both cylinders 21 and 54 catch acoustic waves along parallel and
vertical axes. This structure allows the pressure receiver 22 to
catch signal intensively compared to the case without cylinders 21
and 54. Then we made the precise pressuresensor, since the pressure
receiver 22 can easily hear the external vibration with slender
cylinders 21 and 54. When the cylinders are not evacuated, the
cylinders must be filled with inert gas.
[0101] FIG. 12 shows the upper surface diagram of the
acousto-electric transducer in FIGS. 11(a) and (b), the hole or
space part 47 is formed at the pressure plate 22. Then the
vibration at the left cylinder 21 and right cylinder 54 moves
freely from part A to B and vice versa, and the vibration at A
resonates with B at the central part. Consequently the pressure
receiver 22 at the central part vibrates more strongly, when there
is a hole or space 47. By the way there exists a specific good case
without the hole or space 47.
[0102] In this paragraph, the method, which was proposed in the
previous invention by the present applicant, is described to
explain the mechanical formation of the pressure receiver 22. In
the fundamental method, the circular rod 30, which is made from a
piezoelectric material such as quartz, barium titan oxide, lithium
niobium or other ceramics and so on as shown in FIG. 13, is held by
a chuck 31 of a polishing machine such as a lathe. The tool holder
34, which has a freely rotating whetstone with diamond powder on
the surface, is fixed by the tool holder 34. The whetstone 32 is
spherical to be cut at the opposite side as seen in FIG. 14, and
this is freely rotatably held by the axis holder 36 at the tip of
the holding arm 35. At the outer part of the whetstone 32, there
are V shape grooves 32a as shown in FIG. 15(a) and the enlarged
diagram of FIG. 15(b) taken along section line A-A, one inner wall
of groove 32a is directional to the surface at the central part.
The whetstone 32 is rotated at high speed by an air jet stream,
which is generated by an air nozzle 40, that is disposed in a
tangential direction (preferably 8.about.50 rpm), and the polished
blank is slowly cut (for example 1 .mu.m/min). During the polishing
time, a jet nozzle 41 ejects water, cools the whetstone 32, and
wipes out the polished waste. When the whetstone 32 is rotated, the
circular rod 30 is rotated around the axis as shown in FIG. 13, and
it becomes circular or a circular hole is formed by the whetstone
32.
[0103] Also when the polishing surface of pressured surface 22 is
convex as shown in FIG. 16, a dram type whetstone 32' is used as
seen in FIG. 17((a) is the front view and (b) is the plan view).
When the polishing surface of pressured surface 22 is flat, a flat
type whetstone 32'' is used as seen in FIG. 17(c). Otherwise, the
whetstone 32, which is much smaller than the hole diameter as shown
in FIG. 18, rotates along the curved surface of pressured surface
22 with the same machining tool 33 in FIG. 14 of NC machine.
[0104] At the same time, a chuck 31 rotates and polishes the
pressured surface with a circular rod 30. Also the tool to make the
hole or space part 47 is a whetstone 32'' in FIG. 17(d), which does
not cut the holding part 47 and machines the hole or space part 47.
Of course the tool to make the hole or space part 47 can be a
conventional drill, which is electrically gilt by diamonds.
[0105] Also the circular hole of the machining tool can be the
usual rotating one around the axis, for example, a spherical
whetstone as shown in FIG. 19 or a disk type one as shown in FIG.
20. After the whetstone 32 has completed the coarse machining, the
polishing whetstone 32'' (instead of the whetstone 32), which is
made from felt or buff and so forth, can do the fine lapping
process. This whetstone 32'''' of felt or buff with grooves 32a can
be rotated an by air jet stream, which is generated by air nozzle
40 as with the whetstone 32, and it can easily perform the
polishing step.
[0106] FIGS. 21 and 22 illustrate manufacturing charts of the
cutting and polishing machines which structure is shown in FIG. 14.
The diameter of whetstone 32 is 20 mm, and the depth of grooves
32(a) are 1 mm. The following measured figures are the rotation
number of whetstone 32 and air pressure, when the air nozzle 40 of
a cutting and polishing machine with 16 grooves ejects air directed
tangentially at the periphery of whetstone 40. [0107] {circumflex
over (1)} Air pressure is 0.5 atmosphere, and rotation of whetstone
32 is about 12,200 rpm. [0108] {circumflex over (2)} Air pressure
is 1.0 atmosphere, and rotation of whetstone 32 is about 22,000
rpm. [0109] {circumflex over (3)} Air pressure is 2.0 atmosphere,
and rotation of whetstone 32 is about 37,500 rpm. [0110]
{circumflex over (4)} Air pressure is 3.0 atmosphere, and rotation
of whetstone 32 is about 47,800 rpm. [0111] {circumflex over (5)}
Air pressure is 4.0 atmosphere, and rotation of whetstone 32 is
about 50,000 rpm, which is the bearing limitation.
[0112] Also, instead of the cutting whetstone 32 the cutting and
polishing machine in FIGS. 21 and 22, we can use the polishing
whetstone shown in FIG. 17(e), which is made from iron, aluminum,
metal as cupper, buff, felt, glass, plastics, ceramics or others.
The machining method shown in FIG. 13, which uses polishing
whetstone 32'''' and a polishing agent such as diamond paste,
cerium oxide, alumina, GC or others, can cut and polish
piezoelectric material such as quartz in various shapes as shown in
FIG. 11 at the same time. It is the reason for the polishing
machine to cut and polish at the same time, since the whetstone
32'''' in FIG. 17(e) can easily rotate up to 50,000 rpm at the
bearing limit. As this can be efficiently done only with the
polishing process, this method, which uses this polishing whetstone
32'''' of felt, buff, iron, or others, can cut and polish
piezoelectric material such as extremely thin quartz at the same
time.
[0113] The above paragraph explains the manufacturing method, which
was previously invented by us, and the following introduces newly
invented acousto-electric transducer.
[0114] Initially, we will explain the method of forming the convex
lens type pressure receiver 22 (oscillation surface) in FIG. 23 at
the center of piezoelectric material in a hollow cylindrical shape
in as shown FIG. 11(a). [0115] (a) The first product, the target of
which is to form the convex lens shape 20a, is made from both ends
of cylindrical piezoelectric material 20 by means of mechanical
polishing, etching process, or the like. [0116] (b) Only a
cylindrical part of the first product in the convex lens shape is
processed by the dry etching process (RIE or CIP process), other
parts are not etched. This process can be executed by setting the
ring mask, which is made from glass, quartz, tungsten, nickel, pure
iron, plastic or other materials, on the end of the cylindrical
piezoelectric material 20. [0117] (c) This process continues to the
central part of the piezoelectric material 20 as shown in FIG.
23(c). [0118] (d) After the dry etching process reaches the
predetermined length at the central part, the same dry etching
process is undertook from the opposite surface. In practice, this
is done by inverting the piezoelectric material 20, not by moving
the dry etching machine. [0119] (e) As shown in FIG. 23(e), after
the convex lens shape is formed at the central part of
piezoelectric material 20, the ion-damaged layer, which is
generated by the dry etching process in 0.2 .mu.m-0.3 .mu.m depth,
is removed by the mechanical polishing method. Then we have the
oscillator (resonator) with electrically excellent performance,
since the lens shape of ring support type is formed at the
cylindrical central part as shown in FIG. 23(f).
[0120] FIG. 24 illustrates the machining stage to process the
pressure receiver (oscillating surface), of which one side is in a
convex lens shape and the other side is flat.
[0121] FIG. 25 illustrates the machining stage to process the
pressure receiver (oscillating surface), of which one side is in a
convex lens shape and the other side is concave.
[0122] FIG. 26 illustrates the machining stage to process the
pressure receiver (oscillating surface), of which both sides are
flat FIG. 27 illustrates another machining process for forming a
hollow cylindrical oscillator. The successive engineering stages is
described as follows. [0123] (a) The first product, the target of
which is to form the convex lens shape 20a, is made from both ends
of cylindrical piezoelectric material 20 by means of mechanical
polishing, etching process, or the like. [0124] (b) Only a
cylindrical part of the first product in the convex lens shape is
processed by the dry etching (RIE or CIP process), other parts are
not etched. This process can be executed by setting a hollow
cylinder 52, which is smaller than the material 20 and made from
glass, quartz, tungsten, nickel, pure iron, plastic, or other
material, on the end of the cylindrical piezoelectric material 20.
Then the dry etching process is simultaneously performed at the
inner and outer surfaces of piezoelectric hollow cylinder 52. At
the same time, the end surface of the cylinder 52 is shaven. [0125]
(c) This process continues to the central part of the piezoelectric
material 20 as shown in FIG. 27(c). [0126] (d) After the dry
etching process reaches the predetermined length of the central
part, the same dry etching process is undertook from the opposite
surface. In practice, this is done by inverting the piezoelectric
material 20, not by moving the dry etching machine. [0127] (e) As
shown in FIG. 27(e), after the convex lens shape is formed at the
central part of piezoelectric material 20, the ion-damaged layer,
which is generated by the dry etching process in 0.2
.mu.m.about.0.3 .mu.m depth, is removed by the mechanical polishing
method. Then we have the oscillator (resonator) with electrically
excellent performance, since the lens shape of ring support type is
formed at the cylindrical central part, and a lens shape shown in
FIG. 27(f) is formed at the central part of hollow cylinder, we get
the oscillator (resonator), which contains the holding part in a
ring-support shape and is electrically excellent.
[0128] Although FIG. 27 shows the example of producing the
bi-convex lens shape, other shapes of the oscillator in those
arbitrary shapes can be made also by processing to maintain the
initial shape.
[0129] The following paragraph introduces a processing method to
make the convex lens shape oscillator (resonator), which is
connected to an extremely thin connector.
[0130] FIGS. 28 and 29 show the processing method, and this is
explained as follows. [0131] (1) The first product, the target of
which is to form the convex lens shape 20a, is made from both ends
of a thick piezoelectric plate 20 by means of mechanical polishing,
etching process, or the like. [0132] (2) Only a cylindrical part of
the first product in the convex lens shape is processed by the dry
etching process, as other parts are not etched. This process can be
executed by setting a hollow cylindrical auxiliary tool 50 (on the
top of the first product), which is smaller than the hollow
cylinder 20 and made from glass, quartz, tungsten, nickel, pure
iron, plastic or other material, and the surface of the tool 50 and
the both ends are shaven by the dry etching process at the same
time or successively (step one end in this sample). Then, after the
convex lens shape is formed at the central part of piezoelectric
material 20, the ion-damaged layer, which is generated by the dry
etching process in 0.2 .mu.m.about.0.3 .mu.m depth, is removed by
the mechanical polishing method. Then we have the oscillator with
electrically excellent performance, since the lens shape of ring
support type is formed at the cylindrical central part, and a lens
shape in FIG. 27(f) is formed at the central part of hollow
cylinder, we get the oscillator (resonator), which outer surface is
in a ring-support shape with the holding part.
[0133] Although FIGS. 28 and 29 show the example of producing the
convex lens shape, other shapes of the oscillator (resonator) in
piano-convex, bi-convex, concavo-convex, or other arbitrary shapes,
can be made also by processing to maintain the initial shape, when
both surfaces of the piezoelectric material 20 are machined in
flat, concave or other shapes.
[0134] FIG. 29 illustrates another process to make the convex lens
shape oscillation part (resonation part) with a very thin connector
in the ring shape holder. This is described step by step as
follows. [0135] (1) At both ends of the piezoelectric disk, a
convex lens type auxiliary blank 51 is pressingly set by using the
mechanical polishing process, press formation (to make lens),
etching process, or other means. Otherwise, the auxiliary blank 51
is pasted on the piezoelectric material 20 by using resist (for
instance OSPR resist made in Tokyo Ohka Kogyo Ltd.) or other
adhesives. Here the material of the auxiliary blank 51 is glass,
optical glass, lens, quartz, tungsten, nickel, pure iron, plastics,
or other material. [0136] (2) Only the convex lens shape part of
auxiliary blank 51 is dry etched, a hollow cylindrical auxiliary
tool 50, which is made from glass, optical glass, lens, quartz,
tungsten, nickel, pure iron, plastics or other material, is set on
the top of the auxiliary blank 51, in order not to etch other part
of the convex lens shape. And the surface of auxiliary tool 50 is
homogeneously shaven by dry etching process at the same time. Then
the surface of blank 51 is etched at first, next the surface of
piezoelectric material 20 is shaven, and an ultra thin convex lens
shape is formed at the central part in hollow cylindrical shape.
After the mechanical lapping process removes the 0.2
.mu.m.about.0.3 .mu.m ion-damaged layer, which is followed by the
dry etching, and finally formed is the electrically excellent
oscillator, which has the lens shape in the hollow cylindrical
central part and the ring-support type holder at the outer
part.
[0137] FIG. 30 shows the auxiliary blank 51, which is made by a
pressing process or others in the lens shape at the hollow
cylindrical central part and the ring-support type holder, and this
is different from FIGS. 28 and 29. Quartz oscillators, which have
the lens shape in the hollow cylindrical central part and also have
the ring-support type holder at the outer part as shown in FIG.
30(f), can be conveniently made without using the auxiliary tool
50, which is made from glass, optical glass, lens, quartz,
tungsten, nickel, pure iron, plastics, or other materials.
[0138] The material of the auxiliary blank 51 can be made from
glass, optical glass, lens, quartz, tungsten, nickel, pure iron,
plastics or others, however the best material is quartz glass
similar to quartz crystal to press the auxiliary blank 51, but
other material is to be useful. In FIG. 30 the convex lens
auxiliary blank 51 is set by pressing on both sides of
piezoelectric material 20 or pasted by resist adhesives and dry
etched, however other arbitrary shapes such as plano-convex,
bi-flat, concavo-convex, bi-convex are to be made by processing the
auxiliary blank 51 in convex lens, concave lens or other shapes and
by decreasing the thickness of the initial shape by the dry etching
process.
[0139] Electrodes 23 and 24 in FIG. 31 are made by vapor depositing
Al, Ag, Au and so forth on both sides of the oscillator
(resonator), which is made by the above process. Also, the ultra
slender gold wire 26 (for example 18 .mu.m) is pasted to the
electrode with a bonding machine or electrically conductive
adhesive. Usually the electrode and lead wire are made by
vaporization only, however the electrode only is vaporized and
afterwards the gold wire is pasted to the electrode, since the
electrode and lead wire cannot be made solely by the vaporization
when the diameter of the hollow cylinder is very small and
slender.
[0140] Other examples are illustrated in FIGS. 32, 33, 34 and 35.
In order to mass produce quartz blanks in two steps double-sided
grooved type by the chemical wet etching and dry etching process,
the quartz wafer is masked and etched by the wet or dry process in
these cases. These shapes are shown in FIGS. 32(a), 33, 34(a) and
35(a).
[0141] In these examples, an 80 .mu.m thick quartz wafer is masked
as the first step, then the oscillation part is processed in every
25 .mu.m from both sides of the quartz wafer by chemical etching or
dry etching as shown in FIGS. 32(b), 33(b), 34(b) and 35(b), and
the thickness of oscillation part becomes 30 .mu.m after these
etching processes. Then, the quartz wafer an masked as the second
step, the 30 .mu.m oscillation part is processed in every 13 .mu.m
from both sides by chemical etching or dry etching as shown in
FIGS. 32(c), 33(c), 34(c) and 35(c), and the thickness of the
oscillation part becomes 4 .mu.m after these etching processes.
[0142] Like the circle shapes shown in FIGS. 32(a) and 33(a),
hexagonal shape shown in FIG. 34(a), square shape shown in FIG.
35(a), or other quartz wafer shapes can be masked as the first step
so as to be 30 .mu.m thick of the oscillation part by the chemical
etching or dry etching. As the second masking process shown in
FIGS. 32(c), 33(c), 34(c), and 35(c), the thickness of the
oscillation part is processed in order to be 4 .mu.m.
[0143] This method has the following merits. [0144] {circumflex
over (1)} Although the outer shape is square or rectangular, the
shape of the oscillation part becomes pure circular or circle,
which is electrically excellent. [0145] {circumflex over (2)} As
shown in FIGS. 32 and 33, when the outer shape of quartz blank is
square or rectangular, and the shape of the oscillation part is
purely circular or in circle, it becomes difficult for the crystal
orientation to be seen, since the crystal orientation has no mark.
Then the crystal orientation is marked by etching in a specific
shape as shown in FIG. 32(a) and FIG. 33(a), when the shape of the
oscillation part is processed to be circular. [0146] {circumflex
over (3)} As shown in FIGS. 32, 33, 34 and 35, when the outer shape
of quartz blank is square, mass production becomes easy compared to
the circular case, because the cutting is conveniently done. [0147]
{circumflex over (4)} The outer shape of the quartz blank can be
square, however the electric property of quartz oscillator becomes
more excellent, when the shape of oscillation part is purely
circular or in circle. [0148] {circumflex over (5)} As shown in
FIGS. 32(c), 33(c), 34(c), and 35 (c), the ratio of diameter over
the thickness (d/t) is to be approximately 80 and the optimum
diameter of the oscillation part is 4 .mu.m.times.80=0.32 mm in
order to get the best electric performance, when the oscillation
part is 4 .mu.m thick. When the initial quartz blank is 80 .mu.m
thick and the oscillation diameter is 0.32 mm, it is impossible for
the circular oscillation part to be processed down to 4 .mu.m thick
by only one masking after the chemical etching of 76 .mu.m. When
the diameter of oscillation part becomes as small as 0.32 mm, the
chemical etching cannot be homogeneously processed due to the
surface tension of solution as hydrogen fluoride and the
crystalline anisotropy. When the chemical etching is successively
processed more than two times, it become possible for the blank of
the small diameter less than 0.32 mm to be shaved. [0149]
{circumflex over (6)} In the case of the dry etching process, there
exists no problem for the diameter of the oscillation part to be as
small as 0.32 mm. [0150] {circumflex over (7)} When this is in two
steps wise shape and the thickness is decreased step by step, the
mechanical polishing process can easily remove the damaged layer,
which is generated during the chemical or dry etching.
[0151] FIGS. 36, 37, 38, and 39 illustrate quartz blank samples of
a two stepped single-sided concave shape, which are different from
those in FIGS. 32, 33, 34 and 35. In these examples, the quartz
wafer is masked and processed by chemical and dry etching to
produce massively. These shapes are illustrated in FIGS. 36(a),
37(a), 38(a), and 39 (a). Initially, an 80 .mu.m thick quartz wafer
is masked in the first stage, and one side of the wafer is shaved
by 60 .mu.m by chemical etching and dry etching as shown in FIGS.
36(b), 37(b), 38(b), and 39(b), and the thickness becomes 20 .mu.m.
Then the 20 .mu.m wafer is masked in the second stage, and it is
shaved in 16 .mu.m by chemical etching and dry etching as shown in
FIGS. 36(c), 37(c), 38(c), and 39(c), and the thickness finally
becomes 4 .mu.m.
[0152] These processes serve to reduce the oscillation part to 4
.mu.m, and have the following merits in addition to those shown in
FIGS. 32, 33, 34 and 35. [0153] {circumflex over (1)} After this is
masked twice or more than two times to make the aperture ratio
larger, processed by chemical etching and dry chemical etching, and
then mechanically polished as shown in FIG. 2(a), the aperture
ratio(d/t) becomes approximately 80 and the electrical property is
at an optimum. FIG. 38(c) illustrates the cross section, and this
structure is concave in order to widen the pressure distribution.
This concave structure is not plano-convex with a larger curvature,
it really becomes like a convex lens similar to concavo-convex or
bi-convex shape, which electric property is ideal, and we complete
the ultra thin quartz oscillator less than 0.5 .mu.m. For example
of BT-cut, the primary frequency of fundamental wave becomes
approximately 5.0 GHz. Also, it is possible to use other materials
such as AT-cut, SC-cut, FC-cut, IT-cut, and other cuts. [0154]
{circumflex over (2)} When the outer region of oscillation part is
structured so as to be another concave shape or stepwise, this
electrode can be easily made, even if the target diameter of the
oscillation part is extremely small. [0155] {circumflex over (3)}
After the chemical etching and dry etching processes are completed,
the polishing process to remove the ion damaged layer (changed
layer due to the process) is conveniently executed, since the
thickness of quartz blank is, step by step, decreasing toward the
center.
[0156] FIGS. 40, 41, 42, and 43 illustrate the manufacturing method
of a quartz oscillator in a two-stepped single sided concave shape.
As shown in FIGS. 40(b), 41(b), 42(b), and 43(b), one surface of 80
.mu.m thick quartz wafer is masked as the first stage, and one side
of the wafer, which diameter is 0.32 mm and pure circular
(otherwise circular, square, hexagonal or other shape), is shaved
16 .mu.m by chemical etching and dry etching. Then the quartz wafer
is masked in the second stage, one side of wafer is shaved 60 .mu.m
by chemical etching and dry etching as shown in FIGS. 40(c), 41(c),
42(c), and 43(c), where the diameter is 1.6 mm and the shape is
circular, square, hexagonal or others, and the thickness becomes 4
.mu.m and the diameter of the oscillation part is 0.32 mm.
[0157] Also, the mechanically polished shape as shown in FIGS.
40(c), 41(c), 42(c), and 43(c) can remarkably improve the
electrical performance, after the chemical etching and dry etching
processes are done and the polishing process to remove the ion
damaged layer due to the etching is properly executed.
[0158] FIGS. 44, 45, 46, and 47 illustrate manufacturing processes
of quartz oscillators in two steps double-sided grooved types.
[0159] As shown in FIGS. 44 (b), 45 (b), 46 (b) and 47 (b), one
surface of 80 .mu.m thick quartz wafer is masked in the first
stage, and one side of the wafer, which diameter is 0.32 mm and
pure circular (otherwise nearly circular), is shaved 12 .mu.m by
chemical etching and dry etching. Then the quartz wafer is masked
in the second stage, and both sides of the wafer are shaved 26
.mu.m by chemical etching and dry etching as shown in FIGS. 44(c),
45(c), 46(c), and 47(c), where the diameter is 1.6 mm and the shape
is circular, square, hexagonal, or others. The thickness becomes 4
u m and the diameter of the oscillation part is 0.32 mm.
[0160] FIG. 48 illustrates an optimum dimension diagram, in which
the oscillation part becomes 0.8 .mu.m. In the case of AT-cut, the
0.8 .mu.m thickness of the oscillation part means to complete a
quartz oscillator of 2.1 GHz approximately. Then the next hand
phone will becomes extremely small.
[0161] The oscillation part becomes the shape as shown in FIGS.
44(c), 45(c), 46(c), 47(c), and 48(c), after the chemical etching,
dry etching and mechanical polishing process by a dual-face
polishing machine (polishing table) and other polishing means to
remove the damaged layer due to the etching. In this case, since
the oscillation part of the quartz blank becomes stepwise and the
oscillating diameter is large as illustrated in FIGS. 44(c), 45(c),
46(c), 47 and 48(c), the polishing agent such as cerium oxide can
smoothly penetrate from both sides during the polishing process by
the polishing table, barrel polishing machine, or ultrasonic
polishing method. Therefore, the mechanical polishing process
becomes efficient, and the electric performance of the quartz
oscillator becomes ideal.
[0162] Here the following three problems occur during mass
production. [0163] {circumflex over (1)} From the result of the
examination, when a single-sided grooved type oscillator with two
steps is processed to be piano-convex shape, the optimum aperture
ratio (d/t) is approximately 80. [0164] {circumflex over (2)} The
dimension of the blank is bigger than 1 inch.times.1 inch, and the
thickness becomes larger than 80 .mu.m. [0165] {circumflex over
(3)} The quartz crystal is anisotropy, and the anisotropy appears
when the chemical etching shaves more deeply than 1/20 of the
oscillation diameter.
[0166] In order to clear these three problems, two chemical etching
processes in FIGS. 49, 50, 51, 52, and 53 are employed by the
relative etching process. At first, the central oscillation part
with a small diameter is etched, and secondly, the second
oscillation part (the second groove) with larger diameter is
etched.
[0167] FIGS. 49, 50, 51, 52, and 53 illustrate shapes and
dimensions that satisfy the above conditions. When the quartz
oscillator in a two-stepped single-sided concave shape is made by a
pressurized polishing process from both sides with the dual-face
polishing machine or a one-face polishing process, the planar
surface which is at the opposite side of the chemical etching
becomes a convex lens shape nearly as piano-convex, concavo-convex,
or bi-convex, which is ideal for the electric performance.
[0168] FIGS. 55 and 56 illustrate the first shape example of two
steps single-sided concave quartz oscillator, which were measured
by an interference microscope, after the oscillator was made on the
basis of the manufacturing diagram in FIG. 54. When the peak to
valley of the surface profile is shown in FIGS. 55 and 56, the
surface is manufactured to be as accurate as approximately 0.002
.mu.m roughness. Also, the shape accuracy is made to be almost
purely circular. Furthermore, measured data in FIG. 56 shows that
the parallel accuracy is around 0.02 .mu.m thick at the center of
the first oscillation part, however this does not affect the
electrical performance of the quartz oscillator.
[0169] FIG. 57 shows the first photo sample (Normanski microgram)
of two steps single-sided grooved type quartz oscillator in FIGS.
55 and 56. Based on the photograph in FIG. 57, the quartz
anisotropy is said not to be observed.
[0170] FIG. 58 shows the changing state to the convex lens shape of
the first oscillation part in FIG. 58(c), wherein the quartz
oscillator in FIG. 54(c) is made by pressurizing from both
sides.
[0171] FIGS. 60 and 61 illustrate the second upper surface shape
example of two steps single-sided grooved type quartz oscillator,
which were measured by an interference microscope, after the
oscillator was made on the basis of the manufacturing diagram in
FIG. 59. When the peak to valley of the surface profile is shown in
FIGS. 60 and 61, the surface is manufactured to be as accurate as
approximately 0.003 .mu.m roughness similar to FIGS. 55 and 56.
Also the shape accuracy is made to be almost purely circular.
Furthermore, the measured data in FIG. 61 shows that the parallel
accuracy is around 0.02 .mu.m thick at the oscillation part, which
is the same as in FIG. 56, however this inversely affects the
better electrical performance of a quartz oscillator due to the
bi-convex shape.
[0172] FIG. 62 shows the second photo sample (Normanski microgram)
of the two-stepped single-sided grooved type quartz oscillator in
FIGS. 60 and 61. Based on this photograph in FIG. 62, the quartz
anisotropy is not observed, which is the same as the first photo
sample in FIG. 57.
[0173] FIG. 63 shows the changing state to the convex lens shape of
the first oscillation part in FIG. 63(c), when the quartz
oscillator in FIG. 59(c) is made by pressurizing from both
sides.
[0174] FIGS. 65 and 66 illustrate the second upper surface shape
example of two steps double-sided grooved type quartz oscillator,
which were measured by an interference microscope, after the
oscillator was made on the basis of the manufacturing diagram in
FIG. 64. When the peak to valley of the surface profile is shown in
FIGS. 65 and 66, the surface is manufactured in order to be as
accurate as approximately 0.003 .mu.m roughness similar to FIGS. 55
and 56. Also the shape accuracy is made to be almost purely
circular. Furthermore, the measured data in FIG. 66 shows that the
parallel accuracy is around 0.02 .mu.m thick at the oscillation
part, which is the same as in FIG. 56, however this inversely
affects the better electrical performance of quartz oscillator due
to the bi-convex shape.
[0175] FIGS. 67 and 68 illustrate the third shape example of two
steps double-sided grooved type quartz oscillator, whose rear
surfaces were measured by an interference microscope. When the peak
to valley of surface profile is seen in FIGS. 67 and 68, the rear
surface is manufactured to be as accurate as approximately 0.004
.mu.m roughness similar to FIGS. 55 and 56. Also the shape accuracy
is made to be almost purely circular. Furthermore, the measured
data in FIG. 68 shows that the parallel accuracy is around 0.02
.mu.m thick at the oscillation part, which is the same as in FIG.
66.
[0176] FIG. 69 shows the third photo sample (Normanski microgram)
of two steps double-sided grooved type quartz oscillator in FIGS.
65 and 66. Based on the photograph in FIG. 69, the quartz
anisotropy is not observed as in FIG. 57.
[0177] FIG. 71 illustrates the fourth example of two steps
double-sided grooved type quartz oscillator surface, which was made
by the manufacturing diagram in FIG. 70 and the front surface was
measured by an interference microscope. When the peak to valley of
the surface profile is seen in FIG. 71, the front surface is
manufactured so as not to be as accurate as approximately 1.0 .mu.m
roughness, which is quite different from FIGS. 55 and 56. Also the
shape accuracy is made to be distorted and not to be circular FIG.
72 illustrates the fourth example of two steps double-sided grooved
type quartz oscillator surface, which was made by the manufacturing
diagram in FIG. 70 and the rear surface was measured by an
interference microscope. When the peak to valley of surface profile
is seen in FIG. 72, the front surface is manufactured to be worse
than approximately 2.0 .mu.m roughness, which is quite different
from FIGS. 55 and 56. Also the shape accuracy is made to be
distorted and nearly elliptic similar to FIG. 71.
[0178] FIGS. 73 and 74 show the fourth photo samples (Normanski
microgram of front and rear surfaces) of two steps single-sided
grooved type quartz oscillator in FIGS. 71 and 72. Based on the
photographs in FIGS. 73 and 74, the front and rear surfaces are
made to be distorted and nearly elliptic due to the anisotropy, and
these are quite different from that in FIG. 57.
[0179] FIG. 76 illustrates the fifth surface example of two steps
double-sided grooved type quartz oscillator, which was made by the
manufacturing diagram in FIG. 75 and the rear surface was measured
by an interference microscope. When the peak to valley of surface
profile is seen in FIG. 76, the surface is manufactured to be worse
as unobservable, which is quite different from FIGS. 55 and 56.
Also the shape accuracy is made to be much more distorted and worse
elliptic than the fourth case in FIGS. 71 and 72.
[0180] FIG. 77 shows the fifth photo sample (Normanski microgram)
of two steps single-sided grooved type quartz oscillator in FIG.
76. Based on the photograph in FIG. 77, the surface is made to be
distorted and nearly elliptic due to the anisotropy, and this is
quite different from that in FIG. 57.
[0181] FIGS. 78 and 79 show the sixth shape diagram of the
conventional quartz oscillator front surface in one step
double-sided inverse mesa type, which is approximately 5 .mu.m
thick and made by Hoffman Inc. in the USA. The peak to valley of
the shape diagram in FIGS. 78 and 79 is approximately 0.008 .mu.m,
however the surface accuracy is worse than that of the two-stepped
grooved type in FIGS. 56, 61, 66, and 68. Also the large wave is
observed on the surface of the oscillation part.
[0182] FIGS. 80 and 81 show the sixth rear surface shape diagram of
one step double-sided inverse mesa type conventional quartz
oscillator, which is approximately 5 .mu.m thick as seen in FIGS.
78 and 79. The peak to valley of the rear shape diagram is
approximately 0.025 .mu.m and worse than the front surface in FIGS.
78 and 79. Furthermore the surface accuracy is ten times worse than
that of two steps concave type in FIGS. 56, 61, 66, and 68. Also
the large wave is observed on the surface of the oscillation part.
Therefore, the surface accuracy and parallel accuracy of the two
steps grooved type are found to be better than those of one step
inverse mesa type.
[0183] FIG. 82 shows a surface photo (Normanski microgram) of the
sixth manufactured sample in double-sided inverse mesa type seen in
FIGS. 78 and 79.
CONCLUSIONS
[0184] {circumflex over (1)} As demonstrated in the above examples,
there exists no anisotropy of quartz oscillators in every case of
the first manufactured sample of two steps single-sided grooved
type in FIGS. 55 and 56, the second sample of two steps
single-sided grooved type in FIGS. 60 and 61, and the third sample
of two steps double-sided grooved type in FIGS. 65 and 66. [0185]
{circumflex over (2)} The surface accuracy and shape accuracy of
the fourth quartz oscillator sample in steps double-sided grooved
type in FIG. 71 and of the fifth quartz oscillator sample in steps
single-sided grooved type in FIG. 76 are measured to be worse than
those of the first, second, and third samples. This is found to be
due to the quartz anisotropy. [0186] {circumflex over (3)} It is
found to be the reason for the quartz anisotropy of first, second,
and third samples not to observed (not for the fourth and fifth
samples), why the larger diameter oscillation part (the second
oscillation part) of the first, second, and third samples in FIGS.
54, 59, and 64 are chemically etched at first, and the smaller
first oscillation part is done secondly, and why the smaller
diameter oscillation part (the first oscillation part) of the
fourth and fifth samples in FIGS. 70 and 75 are chemically etched
at first, and the larger second oscillation part is done secondly
(these are etched relatively at the same time). [0187] {circumflex
over (4)} The first, second, and third samples are proved to be
machined in ultra fine accuracy, the fourth and fifth samples are
not, however the latter devices can be used as the lower grade
quartz oscillator. On the contrary, the first, second, and third
oscillators show more than one hundred times better accuracy
compared to the fourth and fifth cases. Therefore the former three
manufacturing methods should be utilized for the ultra accurate
quartz oscillator as shown in FIGS. 54, 59, and 64.
[0188] The following paragraph shows the frequency, wave shape and
resonance characteristics of quartz oscillator in two steps shape.
[0189] {circumflex over (1)} FIGS. 83, 84, 85 and 86 show measured
resonance characteristics of the second quartz oscillator in two
steps single-sided grooved type in FIGS. 59, 64, and 70, and of the
third and fourth ones in two steps double-sided grooved type.
[0190] {circumflex over (2)} Resonance characteristics in FIGS. 83,
84, 85, and 86 are measured at the first oscillation part in FIGS.
54(c), 64(c) and 70(c), not at the larger second grooved region
(second oscillation part) in FIGS. 54(b), 64(b) and 70(b). [0191]
{circumflex over (3)} FIGS. 83 and 84 are measured resonance
characteristics of the second quartz oscillator example, which are
made based on the diagrams in FIG. 59 for two steps single-sided
grooved type. When a material blank is AT-cut, it is thought to be
the most excellent electrical performance in the world at present
for the resonant point at 184.872 MHz in FIG. 83 and 181.232 MHz in
FIG. 84 to see the resonance characteristics in FIGS. 83 and 84.
[0192] {circumflex over (4)} FIG. 85 shows measured resonance
characteristics of the fourth quartz oscillator example, which is
made based on the diagram in FIG. 70 for two steps double-sided
grooved type. When the material blank is AT-cut, it is thought to
be the most excellent electrical performance in the world at
present for the resonant point at 257.369 MHz to see the resonance
characteristics in FIG. 85. [0193] {circumflex over (5)} FIG. 86
shows measured resonance characteristics of the third quartz
oscillator example, which is made based on the diagram in FIG. 64
for two steps double-sided grooved type. It is thought to be the
most excellent electrical performance in the world at present for
the resonant point at 283.178 MHz to see the resonance
characteristics in FIG. 86. [0194] {circumflex over (6)} FIG. 87 is
measured resonance characteristics of the sixth quartz oscillator
example, which is made by Hoffman Inc. in USA for one step
double-sided inverse mesa type and oscillation part is
approximately 5 u m. [0195] {circumflex over (7)} When the
resonance property of one step double-sided inverse mesa type in
FIG. 87 is compared both to those of two steps single-sided grooved
type in FIGS. 83 and 84 and to two steps double-sided grooved type
in FIGS. 85 and 86, the electrical resonance characteristics in
FIGS. 83, 84, 85, and 86 is much better than that in FIG. 87,
although these frequencies are slightly different. [0196]
{circumflex over (8)} It is thought to be due to the present two
steps grooved shape for electrical resonance characteristics of two
steps single-sided grooved type in FIGS. 83 and 84 and of two steps
double-sided grooved type in FIGS. 85 and 86, to be much better
than that of Hoffman's resonator in one step inverse mesa type in
FIG. 87. [0197] {circumflex over (9)} The large area of the second
grooved part (second oscillation part) in two steps grooved stereo
type in FIGS. 59(b), 64(b), and 70(c) is not vibrated, the first
oscillation part in very small diameter is only vibrated, and the
first oscillation part is demonstrated to contribute solely for the
electrical resonance. [0198] {circumflex over (10)} The above
discovery implies that the ultra high frequency resonance over 160
GHz primary wave (approximately 0.015 .mu.m thick), with BT-cut,
for example, can be oscillated in near future, and that it can be
possible for electrically ideal quartz oscillator to be made in
concavo-convex lens shape rather than in two steps single-grooved
plano-convex type.
[0199] FIGS. 88 and 89 show dimensional manufacturing drawings of
quartz oscillators in three steps single-sided grooved type. When
these quartz oscillators in three steps single-sided grooved type
are compared to those in two steps single-sided grooved type,
electric characteristics of the former are found to be better than
those of the latter. The reason is due to the three step stereo
structure and the efficient energy utilization.
[0200] The quartz oscillator in FIG. 88 is nearly an eight-sided
polygonal shape at the first oscillation part and circular at the
second and third oscillation part, on the other hand, the quartz
oscillator in FIG. 89 is nearly an eight-sided polygonal shape at
the second oscillation part similar to the first part.
[0201] FIGS. 90 and 91 show dimensional manufacturing drawings of
quartz oscillators in three steps double-sided grooved type. When
these quartz oscillators in three steps double-sided grooved type
are compared to those in two steps double-sided grooved type,
electric characteristics of the former are found to be much better
than those of the latter. The reason is due to the three step
stereo structure and the efficient energy utilization.
[0202] The quartz oscillator in FIG. 90 is nearly an eight-sided
polygonal shape at the first oscillation part and circular at the
second and third oscillation part. On the other hand, the quartz
oscillator in FIG. 91 is nearly an eight-sided polygonal shape at
the second oscillation part similar to the first part.
[0203] FIG. 92 illustrates the mechanical polishing example, where
quartz oscillator in the three-stepped single-sided grooved type in
FIG. 88(f) is machined by pressurizing from the upper and lower
tables of a dual-face polishing machine (polishing table). This
polishing process can make three steps single-sided quartz
oscillator, whose shape is approximately equal to concavo-convex in
FIG. 92 (f) rather than single-sided convex.
[0204] The reason to become nearly concavo-convex lens shape in
FIG. 92(f) is that the quartz oscillator in the parallel plate type
has poor electrical resonance with spurious oscillations, since the
high frequency quartz resonator becomes extremely thin and the
parallel accuracy allowance is very severe. On the other hand, the
quartz resonator in convex lens shape shows excellent electrical
performance, since the parallel accuracy allowance is not so sever
as that of the parallel plate.
[0205] FIGS. 94 and 95 show measured surface shapes of the second
quartz oscillator example in two steps single-sided grooved type,
which is made by the manufacture diagram in FIG. 59 after
pressurizing between upper and lower tables of a dual-face
polishing machine (polishing table) as seen in FIGS. 60, 61, and
62.
[0206] The single-sided grooved type is seen as the second
manufactured examples in FIGS. 59 and 60, the seventh one in FIG.
94 and the eighth in FIG. 95. However the interference stripes
(Newton rings) were observed both in the seventh example in FIG. 94
and the eighth one in FIG. 95, which are machined by the polishing
table. The difference between the seventh case and eighth case is
that the seventh example in FIG. 94 is polished during 30 minutes,
and the eighth one in FIG. 95 is polished during 60 minutes. The
seventh example becomes concavo-convex in FIG. 63(c), and the shape
of the originally planar surface is slightly 1.25 .mu.m convex
toward the lower direction. The eighth example also becomes
concavo-convex in FIG. 63(c), and the shape of the originally
planar surface is measured to be 3.5 .mu.m convex toward the lower
direction by the interference microscope.
[0207] Therefore, the protruding grade is found to be proportional
to the polishing time.
[0208] The electrical property of the eighth quartz oscillator
example in FIG. 95 is much better than the seventh example in FIG.
94.
[0209] Based on these results for the seventh and eighth
manufacturing cases, the quartz oscillators in the two-stepped
single-sided grooved type are found to become convex lens shape,
which is introduced in FIGS. 1, 2, and 6 as the one step inverse
mesa type.
[0210] The dotted line a-b in FIGS. 94 and 95 is the boundary
layer, which divides the first oscillation part and second grooved
part (second oscillation part). When the dotted line a-b is the
boundary, which divides the first oscillation part and second
grooved part (second oscillation part), the second part becomes
slightly convex lens shape, the quartz oscillator is measured to
become more clearly concavo-convex shape (one side is concave and
another side is convex) with larger curvature than that of one step
single-sided inverse mesa type in FIGS. 1, 2, and 6. Also two steps
single-sided grooved type in FIGS. 94 and 95 becomes larger
curvature type (the lower line is widened), and concavo-convex
(rather than plano-convex) in more protruding convex lens shape
than those of one step inverse mesa type in FIG. 6.
[0211] Therefore, three steps or more than three steps single-sided
grooved type becomes larger curvature shape (the lower line is
widen), and concavo-convex shape in more protruding convex lens
type than those of two steps single-sided grooved type.
[0212] FIG. 93 illustrated another shape of the above example.
FIGS. 93(a) and (b) show one case of a double-sided grooved device
in which one side has one step and another side has two steps,
FIGS. 93(c) and (d) show the case which one side has one step and
another side is three steps, and FIGS. 93(e) and (f) show another
case which one side is two steps and another side is three steps.
When the shape in FIGS. 93(a), (c), and (e) are polished by
pressurizing between upper and lower tables of a dual-face
polishing table (polishing table), the central oscillation part
becomes a convex lens shape as shown in FIGS. 93(b), (d), and
(f).
[0213] FIG. 96 is a stating diagram of the parallel accuracy for a
parallel plate. FIGS. 96(a), (b), and (c) illustrate objects of 100
mm, 50 mm, and 25 mm with the same incline angle. The cross section
height of a 100 mm object is 2 mm and 4 mm high. The cross section
height of a 50 mm object is 2 mm and approximately 3 mm high. The
cross section height of a 25 mm object is 2 mm and approximately
2.3 mm high. Thus, it is found even for the same inclination
objects that the error between these heights is smaller as the
length is shorter. This phenomena can explain the following.
[0214] It must be parallel or in convex lens shape for the quartz
oscillator to perform ideal electrical characteristics. The best
parallel error is ideally 0, however it is practically impossible
to make the plate with zero error of parallelism. Besides, the size
of wafer becomes larger in these years, and the thickness becomes
thicker as the size becomes bigger. The typical wafer size is 60 mm
high, 30 mm wide, and 80 .mu.m thick at the present. As the size of
wafer becomes larger, the parallel error is inversely bigger.
[0215] When a quartz blank is chemically etched, the quartz
anisotropy generates. As the method for avoiding this anisotropy,
this must not be chemically etched more than 1/20 of the aperture
(diameter). For example, if the thickness of the oscillation part
is 5 .mu.m of an 80 .mu.m thick wafer, and the remaining 75 .mu.m
is chemically etched, the aperture (diameter) should be 1500
.mu.m=1.5 mm, which is 20 times of 75 .mu.m.
[0216] When the oscillation part of a quartz oscillator is 5 .mu.m
thick, the diameter of the oscillation part is enough to be 80
times of the thickness both for parallel plate and convex lens
shape since the aperture (diameter) is sufficient to be 0.4 mm for
the 5 .mu.m thick oscillation part.
[0217] When the same parallel plate is used, the parallel error of
1.5 mm diameter is quite different from that of 0.4 mm diameter. In
conclusion, the smaller the aperture is, the smaller the parallel
error of the oscillation part is relatively, when parallel error of
the wafer is same. In order to make a small aperture quartz
oscillator, it is necessary to avoid the original quartz
anisotropy, and it is found to be the most optimum for two or three
steps single-sided grooved or double-sided grooved shape, since the
minimum thickness of wafer is 80 .mu.m.
[0218] The resonance characteristics is best in FIGS. 83, 84, 85,
and 86, since the oscillation part aperture is designed to be
small, and the parallel error of the parallel plate relatively
becomes small first of all. The second reason is thought to be that
the impressed energy is efficiently utilized in two steps grooved
type. The third reason is that the surface accuracy is between
0.002 .mu.m and 0.004 .mu.m due to the chemical etching process,
when the oscillation aperture is small and the shape is two steps
grooved type as shown in FIGS. 56, 61, 66, and 68.
[0219] When quartz oscillator in FIG. 56 is measured by a
photograph in FIG. 57, the oscillation aperture (diameter) is 0.12
mm, and the surface accuracy is 0.002 .mu.m. In the case of the
quartz oscillator in FIG. 61, the oscillation aperture is measured
to be 0.59 mm by the photograph in FIG. 62, and the surface
accuracy is 0.003 .mu.m. In cases of quartz oscillator in FIGS. 68
and 66, the oscillation aperture is measured to be 0.95 mm by the
photograph in FIG. 69, and the surface accuracy is 0.004 .mu.m. The
above events demonstrate that the smaller the oscillation aperture
is, the higher the surface machining accuracy is.
Effect of Invention
[0220] (1) When both ends of a cylindrical blank are made at first
to be the final target as lens, single-sided convex, single-sided
groove, or planar shape, the oscillation part with a predetermined
thickness can be shaped in the hollow cylindrical piezoelectric
element, by shaving homogeneously to be circular from the cylinder
end with a dry etching process. [0221] (2) The following effect
will arise, when the planar piezoelectric blank is attached by an
auxiliary mold in convex lens or convex lens shape, or when the
auxiliary mold shape is pressed to the end of piezoelectric
material by dry etching process after the auxiliary mold is pasted
to the piezoelectric material with dry etching process. When the
press forming makes the optical lens of flat and convex (or
concave) shape with the outer ring-support (in frame shape) holder,
and the auxiliary mold as the optical lens is attached to the
planar piezoelectric material and shaved by the dry etching
process, the planar piezoelectric surface is processed to be in the
same lens shape with the high surface accuracy as the conventional
lens, which is machined by press forming or other mechanical
polishing processes. Then we can conveniently manufacture the ultra
accurate quartz oscillator (quartz resonator), which is in lens
shape at the central part and accompanied by the outer holder in
the ring-support shape (frame shape or hollow bamboo cylinder
shape). [0222] (3) Furthermore, since the crystal axis of quartz
can be easily identical to the machining axis of optical lens, the
quartz oscillator becomes electrically excellent. [0223] (4) The
final surface accuracy becomes equal to the original surface
accuracy at both ends of the cylinder shape. However, the intrinsic
electrical characteristics of the piezoelectric element will not
restore, if the ion-damaged layer due to the dry etching process is
removed. [0224] (5) If the cylinder is machined to be in the hollow
cylinder shape by the mechanical process, it is difficult for the
deep groove to be machined. [0225] (6) When the piezoelectric
material is formed to be in hollow cylinder shape by the dry
etching process, the lens shaped oscillator is made at the central
part of hollow cylinder, which hole diameter is approximately 10
mm, hole length is from 1.0 cm to 15 cm, and thickness is around 1
mm. [0226] (7) It is actually extremely difficult for the hollow
cylinder thickness to be machined only by the mechanical process,
however the present invention to use the dry etching can
manufacture oscillators in ultra high performance, since this
invention enables the processing to be in lens shape at the central
part with the holder of extremely thin bamboo hollow cylinder and
ring-support shape (bamboo type hollow cylinder shape) at the outer
part. [0227] (8) The thickness of the bamboo type hollow cylinder
can be polished to be extremely thin, since the dry etching process
is performed at the same time both for outer and inner surfaces of
the bamboo type ring-support shape. [0228] (9) If the ion-damaged
layer is not considered during the dry etching process (RIE or
CIP), the ultra thin lens shape can be manufactured after both ends
are shaved in the same accuracy as the original one at the end of
the cylinder. [0229] (10) Since we can manufacture oscillators,
whose walls are quite thin, hole diameter is small, hole length of
bamboo hollow cylinder is long, central pressure sensor part is in
the convex or concave lens shape, and it makes high performance to
catch an acoustic wave. [0230] (11) When the outer diameter of
small oscillator in bamboo type hollow cylinder shape is less than
1/2 inch, for example, the pressure or the temperature of oil,
methane gas, and so on is always measured at the same time, after
this is inserted into the pipe under say 5000 m of ground to pump
oil, methane etc. [0231] (12) The diameter of a conventional
pressure sensor (called quartz sensor) is as large as about 3/4
inch, and this cannot always be inserted into the drilling pipe to
get oil and methane. [0232] (13) This high performance of the
pressure sensor can detect oil and methane gas in extremely deep
underground.
[0233] If it is two steps single-sided grooved type or double-sided
grooved type (abbreviation for grooved type or grooved resonators),
after the second oscillation part (second grooved part) in
circular, triangular, rectangular, hexagonal, or other shapes to
mark the crystal orientation of piezoelectric material is machined
inside or at the central part in square or rectangular shape, the
inside or the central region of the second oscillation part is
again formed so as to be pure circular, quasi-circular, triangular,
square, hexagonal, or other shapes. The following effects are
observed. [0234] {circumflex over (1)} Since the shape of the
rectangular quartz blank is machined to be pure circular,
quasi-circular or other shapes, the piezoelectric device achieves
more excellent electric performance. [0235] {circumflex over (2)}
Since the outer shape of the quartz blank can be in the form of a
rectangular shape even if the oscillation part is purely circular
or quasi-circular, the quartz wafer can be automatically cut, and
then mass production becomes easy. [0236] {circumflex over (3)}
Even when the oscillation part is in accurately circular or
quasi-circular shape, the crystal axis direction can be
conveniently recognized. [0237] {circumflex over (4)} When the
extremely small oscillation part is manufactured by the chemical
etching process, the shape is formed to avoid to be affected by the
surface tension and crystal anisotropy due to the chemical etching
step by step. [0238] {circumflex over (5)} Since the most ideal
frequency of oscillation energy at the first circular vibrating
part is dissipated from the outer second oscillation part (second
grooved part) toward the outer periphery step by step, the quartz
oscillator becomes to show the excellent ideal electrical
performance. [0239] {circumflex over (6)} As the oscillation part
is made to be very small and the aperture ratio (d/t) is set to
around 80 by forming the oscillation part to be stepwise thin, the
electrically excellent quartz oscillator can be manufactured, when
the primary frequency is more than 400 MHz (less than 4 .mu.m thick
for AT-cut) for the AT-cut case. [0240] {circumflex over (7)} After
the quartz oscillator is cut to be rectangular, the pure circular
or quasi-circular first oscillation part is made, and another
circular second oscillation part (second grooved part) is also made
inside or at the central region of the first oscillation part to
mark the crystal orientation. By this manufacturing method, after
the direction marking slit is cut to find the crystal orientation
as shown in FIGS. 32(a), 36(a), 40(a), and 44(a). By forming a
crescent shape type in FIGS. 33(a), 37(a), 41(a), and 45(b), both
the first oscillation part and the second one (second grooved part)
can be formed to be pure-circular or quasi-circular, and the quartz
blank is conveniently cut and massively produced from the quartz
wafer to be in the rectangular outer shape. [0241] {circumflex over
(8)} If the oscillation part is not made to be in thin at least two
steps shape by chemically etching the first oscillation part and
the second one (second grooved part), the wafer is thick as 80
.mu.m. When the frequency of oscillation part is high as 2.1 GHz at
AT-cut, the oscillation part is approximately 0.8 .mu.m, the
aperture ratio is found to be around 80 to resonate the best wave.
Then the diameter of the oscillation part is extremely small as 0.8
.mu.m.times.80=64 .mu.m, the homogeneous chemical etching becomes
impossible due to the surface tension of liquid solution as
hydrogen fluoride etc for the chemical etching or crystal
anisotropy, if the oscillation parts are not chemically etched to
be thin step by step. [0242] {circumflex over (9)} Furthermore,
when the aperture diameter is 64 .mu.m, the chemically etched depth
by hydrogen fluoride is at most 3.2 .mu.m (for instance
approximately 1/20 of the diameter). If the chemical etching is
deeper than this, the quartz crystal anisotropy appears, and the
flat surface accuracy becomes poor. Therefore, the ultra high
frequency quartz oscillator must be manufactured by forming at
least two steps shape with the chemical etching, since the aperture
ratio is found to be about 80 to make electrically high-level
quartz oscillator. [0243] {circumflex over (10)} When the diameter
of the first oscillation part becomes extremely small as 64 .mu.m
or 0.32 mm, the shape of the second oscillation part becomes
triangular, rectangular, or hexagonal except pure-circular or
quasi-circular. Since the shape is too small, this can be better to
be pure circular or quasi circular, however this can be triangular,
rectangular, hexagonal, or other shapes. [0244] {circumflex over
(11)} Since the electrode to oscillate only the second oscillation
part is attached by photo resist chemical etching process to the
front and rear surfaces of the first oscillation part, whose
diameter is very small as approximately 0.32 mm and shape is
pure-circular or quasi-circular, the second part does not
oscillate, and the electrically ideal oscillator (resonator) is
made to resonate at more high frequency without the spurious
signal. [0245] {circumflex over (12)} When the quartz is relatively
and chemically etched by using two or three steps or the plural
steps shape, the chemical etching can shave the deep groove, which
must be deeper than 1/20 of the oscillation part diameter to avoid
the quartz crystal anisotropy. [0246] {circumflex over (13)} After
the first chemical etching makes at first the pure circular or
quasi circular shape, whose first oscillation part diameter is 0.32
mm and depth is 16 .mu.m for example, the first and second
oscillation parts are chemically and relatively etched step by step
in order to make form the rectangular, hexagonal, or other shapes
with 1.6 mm diameter at the outer part of circular shape, and the
anisotropy problem can be solved. [0247] {circumflex over (14)} As
discussed above, since the quartz anisotropy problem is relatively
solved by chemical etching process with two steps more deeply than
1/20 of the aperture diameter, it becomes possible for mass
production of high frequency quartz oscillator by using over 80
.mu.m thick and more than 1 inch.times.1 inch wafer plate.
[0248] After the blank is selected to be the quartz crystal unit in
the chemically etched single-sided grooved type of more than two
steps shape, this is etched by the reactive ion etching (RIE) and
polished by dual-face polishing machine, the AT-cut quartz
oscillator is successfully developed over 467 MHz fundamental
frequency. This quartz oscillator processed by this method is
nearly in the concavo-convex or bi-convex shape rather than
plano-convex shape as the ideal convex lens type, and this shows
the excellent reactance-frequency characteristics.
[0249] This machining method demonstrates that the optimum aperture
ratio d/t (diameter/thickness) is 80. As the consequence, when the
quartz oscillator with very high frequency is required to be
manufactured, the aperture diameter d becomes small, since the
diameter d is proportional to the thickness t, which is extremely
thin. When the diameter becomes small, the quartz oscillator shows
the anisotropy problem, the parallel accuracy cannot be maintained
due to the chemical etching process, since the quartz wafer is
shaved to be deeper than 1/20 of the diameter d. This problem was
solved in the following methods. At first, the first chemical
etching is done, after the depth of the first oscillation part is
selected to be less than 1/20 of the aperture diameter d which is
80 times of the thickness t corresponding to the frequency, and
next we chemically etched the second oscillation part (second
grooved part), whose diameter is much larger than the first
oscillation part (outer region of the first oscillation part) and
is not affected by d/t (80:1 or 100:1) problem. Since the first and
second oscillation part (grooved part) is chemically and
respectively etched with two steps, the quartz anisotropy property
is solved.
[0250] Also, even if the quartz wafer blank is thick, the aperture
d of oscillation part can be very small. Therefore we can
mass-produce the ultra high frequency quartz oscillator whose
electric characteristic is ideal and extremely thin in the
plano-convex shape. This problem was solved in the following way.
At first, the first chemical etching is done, after the depth of
the first oscillation part is selected to be less than 1/20 of the
aperture diameter d which is 80 or 100 times of the thickness t
corresponding to the frequency, and secondly we chemically etched
the second oscillation part (second grooved part), whose diameter
is much larger than the first oscillation part (outer region of the
first oscillation part) and is not affected by d/t problem. Since
the first and second oscillation part (grooved part) is chemically
and respectively etched step by step, the quartz anisotropy
property is finally solved. When another method from FIG. 32 to
FIG. 38 is used instead of the above process, the second grooved
part (second oscillation part) is chemically etched or processed by
the dry etching at first, and the central first oscillation part is
formed to be purely circular or quasi circular, and then this
method is found to be the best way, since the quartz anisotropy
problem is not observed as previously explained.
[0251] By the way, even if the quartz wafer blank is thick, the
aperture d of oscillation part can be very small. Therefore we can
mass-produce the electrically ideal ultra high frequency quartz
oscillator, which is extremely thin in the plano-convex shape.
[0252] As shown on U.S. Pat. No. 3,694,677 On Sep. 26, 1972, Dr.
Gunter K. Guttwein, Dr. Arthur D. Ballato, Dr. Theodre J. Lukaszek
invented quartz oscillators of one step inverted mesa type
(single-sided inverted mesa type and double-sided inverted mesa
type) at US Army. This time we manufactured novel quartz
oscillators of single-sided grooved type in two steps shape by
using the chemical etching process or dry etching, which were found
to have the following advantages over the former quartz oscillators
in one step shape. [0253] {circumflex over (1)} When the aperture
ratio (d/t) is chosen to be optimum, the oscillation area is made
to be small as possible. Then the waved shape is prevented and
becomes small on the oscillation surface, when the oscillation part
is made to be thin as 5 .mu.m. Also the surface accuracy becomes at
least ten times better. [0254] {circumflex over (2)} Since the
quartz anisotropy is avoided by selecting the aperture ratio to be
80:1 (d/t), the surface accuracy is improved for any quartz blank
thickness. [0255] {circumflex over (3)} The latter new two steps
oscillator has the structure of the optimum aperture ratio as 80:1
(d/t) regardless of quartz plate thickness t. [0256] {circumflex
over (4)} Tough resonators against the mechanical shock and
acceleration can be made, since the thick plate improves the
structural and dynamic strength. Furthermore the step type quartz
oscillators of two or more than two steps shape enables us to
resist more strong shock. [0257] {circumflex over (5)} Since the
former one step quartz oscillator in single-sided inverse mesa type
and double-sided inverted mesa type are apt to make pin holes, the
one step resonator etched down to 5 .mu.m cannot be mass-produced.
The latter two steps one can be mass-produced down to 5 .mu.m.
[0258] {circumflex over (6)} While one step inverted mesa type
device needs only one chemical etching process, the two steps
double-sided grooved type requires two etching processes. However
the electrical property becomes improved, and the quartz oscillator
device over 70 MHz will become two steps double-sided grooved type
in the near future. [0259] {circumflex over (7)} When the
single-sided inverted mesa type or doubled sided inverted mesa type
in one step shape becomes thinner than 5 .mu.m, the aperture ratio
(d/t) must be larger due to the quartz anisotropy, and then there
appears the wave shape (like up and down hills) on the oscillation
part. Also the surface accuracy on the oscillation part becomes
worse than 0.02 .mu.m. [0260] {circumflex over (8)} In case of
grooved type in two steps shape, there are few waves, and the
surface accuracy is approximately 0.003 .mu.m. And these are ten
times better than those of inverted mesa type in one step shape.
[0261] {circumflex over (9)} In case of grooved type in two or more
steps, since there are the second grooved part (second oscillation
part) and third grooved part (third oscillation part), the
oscillation energy impressed on the small first central oscillation
part (oscillating surface with electric voltage) is efficiently and
smoothly used at the second and third outer oscillation part step
by step, and the resonator shows the excellent electrical
performance. [0262] {circumflex over (10)} In case of the
single-sided grooved type in two steps shape, the device can be
mass-produced to be thinner than 5 .mu.m. After the oscillation
surface of the blank is made to be thinner than 5 .mu.m, the blank
is polished by the polishing machine to impress mechanical pressure
on the quartz plate both from upper and lower sides in order to
confine the energy. As a consequence, ideal quartz oscillators in
the concavo-convex or bi-convex lens shape, rather than the
conventional piano-convex, are thought to be made to show better
electric property approximately as 5.0 GHz fundamental frequency
for BT-cut below 0.5 .mu.m. Furthermore, in the near future, it
will be possible for the quartz oscillator to be developed as thin
as approximately 0.015 .mu.m (primary frequency as 160 GHz for
BT-cut).
[0263] The accurate name of the single-sided inverted mesa type or
double-sided inverted mesa type with two steps in this invention
should be called as the single-sided grooved type or double-sided
grooved type (abbreviated as grooved type or grooved resonators
type). The reasons of these names are as follows. [0264]
{circumflex over (1)} Even when the outer shape is pure circular,
the central oscillation part can be in purely circular shape, which
contributes to better electrical performance. [0265] {circumflex
over (2)} The oscillation energy impressed on the small first
central oscillation part is efficiently and smoothly used at the
second grooved part (second oscillation part) and third outer
grooved part (third oscillation part) step by step. [0266]
{circumflex over (3)} The electrode can be made smoothly in step
shape. [0267] {circumflex over (4)} The quartz blank can be made to
be thick, while the oscillation part is processed to be very thin.
[0268] {circumflex over (5)} Based on the above items, the one step
inverted mesa type invented by the US Army is quite different from
the grooved type in this invention. Therefore, this is named as the
grooved type or grooved resonators type.
[0269] The following papers were introduced to show that the
aperture ratio (d/t) should be approximately 80 in order to achieve
the best electrical performance. [0270] {circumflex over (1)} 1999
IEEE International Frequency Control Symposium, pp. 425-428. [0271]
{circumflex over (4)} 21st (1999) Piezoelectric Devices Conference
and Exhibition, pp. 4/1-4/6. [0272] {circumflex over (3)} 2000
IEEE/EIA International Frequency Control Symposium &
Exhibition, pp 255-259.
[0273] This invention is related to the manufacturing process of a
grooved type device in two or more than two steps stereo shape by
using the chemical etching, and then this can apply to a wide
variety of semi-conducting electronic materials such as silicone,
gallium arsenate, and so forth in addition to the piezoelectric
material as quartz, lithium niobium, etc.
INDUSTRIAL APPLICABILITY
[0274] This invention can be used for a wide variety of fields such
as communication equipment, instrumentation, general computer,
office automation information technology, home appliance
microcomputer, and so forth.
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