U.S. patent application number 09/821235 was filed with the patent office on 2001-11-22 for method of recording/reproducing an information signal.
This patent application is currently assigned to Sony Corporation. Invention is credited to Aratani, Katsushisa.
Application Number | 20010043545 09/821235 |
Document ID | / |
Family ID | 16656615 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010043545 |
Kind Code |
A1 |
Aratani, Katsushisa |
November 22, 2001 |
Method of recording/reproducing an information signal
Abstract
Disclosed is a method of recording/reproducing information
signals at an access speed in the order of .mu.s, a recording
density of 1 to 10 GBs/cm.sup.2, and a data transfer rate in the
order of Gbit/sec without breakage of the data. The method includes
the steps of: making a head device face to a memory medium having a
flat recording surface, the head device including a plurality of
head elements two-dimensionally arranged each of which has at its
leading end a flat portion having an area of 0.1 .mu.m.sup.2 or
less; moving the head device relative to the memory medium a
distance more than a gap between two adjacent ones of the head
elements; and recording an information signal at a specific
position of the recording surface at a recording density of 1
Gbit/cm.sup.2 or more, or reproducing an information signal
previously recorded on the recording surface at a specific position
by the head device.
Inventors: |
Aratani, Katsushisa; (Chiba,
JP) |
Correspondence
Address: |
David R. Metzger, Esq.
SONNENSCHEIN NATH & ROSENTHAL
P.O. Box #061080
Wacker Drive Station, Sears Tower
Chicago
IL
60606-1080
US
|
Assignee: |
Sony Corporation
|
Family ID: |
16656615 |
Appl. No.: |
09/821235 |
Filed: |
March 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09821235 |
Mar 29, 2001 |
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09130318 |
Aug 7, 1998 |
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6249503 |
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Current U.S.
Class: |
369/95 ; 369/126;
977/725; G9B/11; G9B/21.003; G9B/9 |
Current CPC
Class: |
Y10S 977/724 20130101;
G11B 11/00 20130101; Y10S 977/86 20130101; G11B 9/1409 20130101;
Y10S 977/943 20130101; G11B 9/14 20130101; G11B 21/02 20130101;
G11B 23/0014 20130101; G11B 9/1472 20130101; Y10S 977/935 20130101;
Y10S 977/947 20130101; Y10S 977/861 20130101; B82Y 10/00 20130101;
G11B 9/1418 20130101; G11B 9/00 20130101; G11B 9/04 20130101; Y10S
977/869 20130101 |
Class at
Publication: |
369/95 ;
369/126 |
International
Class: |
G11B 007/20; G11B
009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 1997 |
JP |
P09-214492 |
Claims
What is claimed is:
1. A head element for recording or reproducing an information
signal, comprising: a flat portion formed at a leading end of said
head element, wherein the area of said flat portion is 0.1 gm.sup.2
or-less and is one-tenth or more of a recording cell size of a
memory medium or the area of one bit.
2. A head element for recording or reproducing an information
signal, comprising: a leading end portion formed into a columnar
shape extending longer in the direction perpendicular to the
surface of a substrate of said head element.
3. A head element according to claim 1 or 2, wherein said leading
end of said head element comprises a conductive member for
recording or detecting an information signal and a non-conductive
member adjacent to said conductive member, said non-conductive
member being not allowed to record or detect an information
signal.
4. A head device comprising: a plurality of head elements described
in any one of claims 1 to 3, which are two-dimensionally arranged
on the surface of a substrate of said head device with a specific
pitch.
5. A head device comprising: a plurality of head elements described
in any one of claims 1 to 3, which are arranged on a substrate of
said head device at a density of 25 heads/cm.sup.2 or more.
6. A head element or a head device according to any one of claims 2
to 5, wherein said substrate is a conductive substrate.
7. A head device comprising: a plurality of head elements having
mechanisms, said mechanisms allowing each of said head elements to
be independently moved a specific distance in the direction
perpendicular to a substrate of said head device.
8. A head element and a head device according to any one of claims
1 to 7, wherein each of said head elements is driven a
micro-distance in either or both of the X-axis direction and the
Y-axis direction by an electrostatic force or piezoelectric
effect.
9. A memory medium in which an address signal is formed of an
information signal to be two-dimensionally recorded on a recording
plane.
10. A memory medium in which an address signal is formed on a
recording surface in the form of two-dimensional
irregularities.
11. A memory medium in which a recording surface on which an
information signal is to be recorded is divided into information
signal recording sectors of the same number as that of head
elements of a head device for recording or reproducing an
information signal described in any one of claims 4 to 8.
12. A memory medium in which irregularities corresponding to an
information signal are formed on the surface by injection-molding
or extrusion-molding.
13. A memory medium according to any one of claims 9 to 12, wherein
the substrate is made from a conductive material or is a
non-conductive substrate on the surface of which a conductive thin
layer is formed.
14. A memory medium according to claim 13, wherein the recording
surface is covered with a conductive carbon thin film or a
diamond-like carbon thin film.
15. A memory medium comprising: a substrate flattened without
irregularities or partially formed with irregularities, the surface
of which is covered with a thin film, wherein said thin film is
made from a material allowing an impedance between said memory
medium and a head element to be locally changed before and after
local application of an electric field, current, heat or pressure
by said head element.
16. A method of recording/reproducing an information signal,
comprising the steps of: making a head device face to a memory
medium having a flat recording surface, said head device including
a plurality of head elements two-dimensionally arranged each of
which has at its leading end a flat portion having an area of 0.1
.mu.m.sup.2 or less; moving said head device relative to said
memory medium a distance more than a gap between two adjacent ones
of said head elements; and recording an information signal at a
specific position of said recording surface at a recording density
of 1 Gbit/cm.sup.2 or more, or reproducing an information signal
previously recorded on said recording surface at a specific
position by said head device.
17. A method of recording/reproducing an information signal,
comprising the steps of: sectioning a recording surface of said
memory medium described in claim 11 into sectors; and dividing an
information signal of the same information signal series into parts
and dispersedly recording the parts of the information signal on
different ones of said sectors in the form of irregularities at a
recording density of 1 Gbit/cm.sup.2 or more.
18. A method of recording/reproducing an information signal
according to claim 16 or 17, wherein an information signal is
recorded on the recording surface of said memory medium in the form
of irregularities or an information signal recorded on the
recording surface of said memory medium in the form of
irregularities is reproduced.
19. A method of recording/reproducing an information signal
according to claim 18, wherein the information signal recorded on
the recording surface in the form of irregularities is reproduced
by applying an electric field between said head element and the
recording surface of said memory medium, and detecting an impedance
between said head element and said memory medium, said impedance
being changed due to said irregularities corresponding to the
information signal,
20. A method of recording/reproducing an information signal
according to claim 19, wherein the information signal recorded on
the recording surface in the form of irregularities is reproduced
by detecting an impedance between said head element and the
recording surface of said memory medium while bringing the leading
end of said head element not in contact with the recesses of the
irregularities but in contact with the projections of the
irregularities.
21. A method of recording/reproducing an information signal
according to any one of claims 16 to 18, wherein the information
signal is reproduced by applying an electric field having a
frequency higher than a mechanical primary resonance frequency of a
driving portion of said head device between the leading end of said
head element and the recording surface of said memory medium, and
detecting a current modulated depending on the information
signal.
22. A method of recording/reproducing an information signal
according to any one of claims 16 to 21, wherein an information
signal is recorded or reproduced by moving said head device
relative to said memory medium in a state in which part of said
head elements of said head device face to the recording surface of
said memory medium.
23. An apparatus for recording/reproducing an information signal,
comprising: a memory medium including a flat information signal
recording surface; a head device arranged to be opposed to and in
parallel to said information signal recording surface of said
memory medium, said head device including a plurality of head
elements described in claim 1 two-dimensionally arranged with a
specific pitch; an applying device for applying an electric field,
current, heat or pressure between said information signal recording
surface of said memory medium and each of said head elements; a
driving device for moving said head device relative to said memory
medium an extreme micro-distance; and a recording/reproducing
circuit for supplying an information signal to be recorded to each
of said head elements of said head device or taking out the
information signal recorded on said memory medium by each of said
head elements.
24. An apparatus for recording/reproducing an information signal
according to claim 23, wherein said applying device applies an
electric field having a frequency higher than a mechanical primary
resonance frequency of said driving portion between each of said
head elements of said head device and the recording surface of said
memory medium.
25. A method of manufacturing a micro-head element, comprising: a
first step of forming a sacrifice layer made from a resist on a
flat surface of a conductive substrate in such a manner that a
central portion of said sacrifice layer is formed into a
trapezoidal shape in cross section; a second step of forming a
metal film having a thickness of one to several .mu.m over the
entire surface of said conductive substrate in such a manner as to
cover the surface of said sacrifice layer; a third step of forming
a symmetrical spring pattern on a central portion of said
trapezoidal metal film; a fourth step of forming a micro-resist
film having one side less than the thickness of said metal film on
a central portion of said spring pattern; a fifth step of etching
said metal film directly before said micro-resist film is perfectly
separated from said metal film, to form a micro-head element
including a leading end having a flat portion; and a sixth step of
removing said sacrifice layer and said micro-resist film, to form a
spring, made from said metal film, for elastically supporting said
micro-head element.
26. A method of manufacturing a micro-head element, comprising: a
first step of forming an insulating film having a specific
thickness on the surface of a substrate which has a conductivity at
least on the surface; a second step of forming a mask on said
insulating film at a specific position except for a portion
equivalent to the cross-section of a columnar head element to be
manufactured; a third step of removing a portion of said insulating
film equivalent to the cross section of said columnar head element;
and a fourth step of forming a metal layer in the portion from
which said insulating film is removed by plating, to form said
columnar head element.
27. A method of recording/reproducing an information signal, in
which an information signal is reproduced from a flat memory medium
on which information is two-dimensionally arranged and recorded, by
moving a head element, arranged to be opposed to and in parallel to
the information signal recording surface of said memory medium,
relative to said memory medium, comprising the steps of:
two-dimensionally sampling a reproducing signal at an interval
being a half or less of a pitch between signals two-dimensionally
arranged on said memory medium; temporarily storing a specific
amount of the data in a buffer memory; identifying, from said
reproducing signal, an address signal as two-dimensional positional
information stored on said memory medium; and signal-processing a
time at which the address signal is reproduced, a relative speed
between said head element and said memory medium, a relative moving
direction between said head element and said memory medium, and a
data row stored in said buffer memory, thereby decoding the content
of the data at a specific position on said memory medium.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method of recording
information signals in digital form on a memory medium at a
relatively high density or reproducing (or detecting) information
signals previously recorded in digital form on a memory medium at a
relatively high density, and a head device and a memory medium used
for the recording/reproducing method.
[0002] Various kinds of large-capacity memories are presently
known, for example, a semiconductor memory represented by a DRAM or
Flash memory, a magnetic tape represented by a video recorder, and
a disk memory represented by a compact disk or hard disk. These
memories having problems, for example, in terms of high bit cost
and low access speed may be not suitably used for the future
information inputting/outputting apparatuses such as a
microprocessor or network requiring the more increased data
transfer rate and data capacity. A related art hard disk, optical
disk or magnetic tape is lower two digits or more in cost per unit
data (bit) than a semiconductor memory; however, it is
significantly inferior in access time, data transfer time and
volume of the disk to the semiconductor memory.
[0003] At present, with the enhanced performances of computers and
the increased communication speed of information networks, the
quantity of data to be processed has become larger and the
processing rate of data to be processed has become high. To meet
such technical development, it is desired to realize a read only
memory and a writable memory with the cost per bit kept
substantially comparable to that of a magnetic disk or optical disk
and with the access time, data transfer time and volume of the
memory increased to the levels comparable to those of a
semiconductor memory.
[0004] The size of a semiconductor chip, for example, used in a
DRAM has become larger with the progressing technical generation,
and it is expected that the size of a semiconductor chip be more
than about 3.times.3 cm at the 4 Gbit-generation. In this case, the
area including a package will be about 12 cm.sup.2. To be used like
such a DRAM, a memory to be developed is desired to have a size
smaller than the above value and a low bit cost.
[0005] The memory capacity stored in the above-described area
(about 12 cm.sup.2) is preferably equivalent to a capacity, for
example, which is capable of storing dynamic images for about one
hour, and more specifically, the memory capacity is required to
have about 12 Gbits, that is, a memory density of at least 1
Gbit/cm.sup.2 in consideration of digital image signals with the
compressed frequency band.
[0006] As the memory capable of meeting the above-described
requirement, there have been extensively studied memories of a type
using a so-called SPM (Scanning Probe Microscope) such as a STM
(Scanning Tunneling Microscope) or AFM (Atomic Force
Microscope).
[0007] Such a memory has been described in detail, for example, in
"H. J. Mamin et al.: IBM J. Res. Develop. Vol. 39, 681 (1995)".
This memory detects an information signal using a head device 100
shown in FIG. 10A. The head device 100 has a beam cantilevered with
its one end fixed on a head substrate 102, which is generally
called a cantilever 103, and a head element 101 as a signal
detecting portion (hereinafter, referred to simply as "head
element") formed at the leading end of the cantilever 103. The head
element 101 is sharply pointed into the shape of a triangular or
quadrangular prism by a semiconductor process. The leading end of
the head element 101 sharply pointed up to the level of atomic size
is moved close to the surface of a substance to be measured (data
surface in the case of the memory), and an interatomic force acting
between the head element 101 and the surface of the substance or a
tunneling current flowing therebetween is directly or indirectly
measured, to thus obtain information therefrom.
[0008] B. D. Terris et al. have reported in "Appl. Phys. Lett.
69(27), 4262(1996)" a method of preparing a data patten applicable
to a disk-like medium by an electron beam plotting apparatus,
transferring the patten on an ultraviolet cured resin layer formed
on a glass disk by a so-called glass 2P process to prepare a data
disk, and reproducing data signals stored in the disk by an
AFM.
[0009] H. J. Mamin et al. have reported in "Sensors and Actuators
A48, 215(1995)" a method of bringing a leading end of an AFM in
contact with a high polymer substrate, heating the leading end of
the AFM by laser to melt the surface of the high polymer substrate,
thereby recording data on the surface of the high polymer
substrate, and reproducing the data at a reproducing rate as high
as 1 Mbit/sec by the AFM.
[0010] The apparatus for recording/reproducing information signals
in each of these documents carries out recording/reproducing with
the disk medium rotated using one AFM head.
[0011] H. Kado et al. have reported in "Appl. Phys. Lett. 66(22),
2961(1995)" a method of forming a platinum thin film on a silicon
substrate and also forming an amorphous GeSb.sub.2Te.sub.4 film
thereon, carrying out recording by applying a pulsive electric
field between a sharpened conductive head element and the platinum
thin film, and carrying out reproducing by detecting a difference
in electric conductivity as a change in current.
[0012] The above detection of data using the AFM, however, is not
suitable for reproducing information signals at a high rate because
the interatomic force is converted into a mechanical displacement
of the cantilever 103 and the displacement is detected by a
displacement meter using a piezoelectric effect or laser. Also in
the case where information signals are recorded or reproduced on or
from a rotating disk-like recording medium, the above detection of
data using the AFM is disadvantageous in that it takes a time to
wait rotation and the access speed becomes low.
[0013] To improve an effective data transfer rate, there has been
known a method of carrying out parallel processing using a
plurality of head devices. For example, S. C. Minne et al. have
reported in "Appl. Phys. Lett. 67(26), 3918(1995)" an apparatus in
which two AFM head devices with leading ends of head elements
separated 100 .mu.m from each other are arranged in parallel
whereby images of a grating with a cycle of 5 .mu.m are reproduced.
In this parallel processing apparatus, ZnO having a piezoelectric
effect is used for part of each cantilever to individually displace
the two cantilevers in the depth direction, and the size of the
cantilever becomes larger (length: 420 .mu.m, width: 85 .mu.m) for
sufficiently ensuring the displacement, with a result that the
mechanical resonance frequency becomes low to reduce the data
transfer rate. Accordingly, even in the case of using a plurality
of the AFM head devices, the data transfer rate is not improved so
much.
[0014] The data reproducing apparatus (microscope) using a
plurality of the head elements described in the above document does
not report a method or mechanism of detecting or correcting a
positional relationship between each head element and desired data
in the direction parallel to the surface to be measured, causing a
problem that the address management for data which is important for
the memory apparatus cannot be performed. Even if each distance and
positional relationship between two pieces of respective head
elements has been clearly measured and also the positional
relationship between either one of the head elements and the
address of the data surface has been measured, the relationship
between each head element and the data position cannot be kept
resulting from a difference in thermal expansion coefficient
between the head array and the substrate of the recording medium,
for example, caused by temperature change.
[0015] In the memory apparatus using the SPM, since the leading end
of the head element 101 of the head device 100 is very sharpened as
shown in FIG. 10B and only the leading end of the head element 101
is brought in contact with the data surface, if an impact force is
applied to the memory apparatus during reproducing of data, the
data surface in contact with the leading end of the head element
101 may be applied with a very high local pressure, which causes a
fear of breakage of data stored in the data surface. For example,
S. C. Minne et al. have reported in "Sensors and Actuators A48, 215
(1955)" that a leading end of a head element is formed into a
spherical shape having a curvature of 100 nm or less. A spring
constant of the cantilever is in the order of 1 N/m. Now, it is
assumed that a leading end of a head element applied with an impact
force is displaced 10 nm on the data surface side and is brought in
contact with the data surface; and the leading end of the head
element is formed into a flat circular shape having a radius of 10
nm. In this case, a pressure applied to the flat circle portion is
as very high as 3.times.10.sup.7 N/m.sup.2, which will cause
breakage data stored on the data surface of a medium, insofar as
the medium is made from a usual material. Even if there does not
occur breakage of data, since the leading end of the head element
is worn, there arises another problem that the shape of the leading
end is changed and thereby the resolution in recording or
reproducing is reduced.
[0016] In the above-described recording/reproducing method proposed
by H. Kado, since a current value upon reproducing is 10 pA at a
location where information signals have been not recorded and is 1
nA at a location where information signals have been recorded, a
reproducing signal with a sufficient S/N can be obtained when the
data reproducing rate is low because the frequency band of the
reproducing signal is narrow; however, a reproducing signal with a
sufficient S/N cannot be ensured at the above small signal current
of about 1 nA when the data reproducing rate is high because the
frequency band of the reproducing signal becomes wide.
SUMMARY OF THE INVENTION
[0017] An object of the present invention is to provide a method of
recording/reproducing information signals on/from a ROM and a
writable memory medium at an access speed in the order of .mu.s, a
recording density of 1 to 10 GBS/cm.sup.2, and a data transfer rate
in the order of Gbit/sec without breakage of the data.
[0018] To achieve the above object, according to the present
invention, there is provided a method of recording/reproducing an
information signal, including the steps of: making a head device
face to a memory medium having a flat recording surface, the head
device including a plurality of head elements two-dimensionally
arranged each of which has at its leading end a flat portion having
an area of 0.1 .mu.m.sup.2 or less; moving the head device relative
to the memory medium a distance more than a gap between two
adjacent ones of the head elements; and recording an information
signal at a specific position of the recording surface at a
recording density of 1 Gbit/cm.sup.2 or more, or reproducing an
information signal previously recorded on the recording surface at
a specific position by the head device.
[0019] As described above, according to the method of and apparatus
for recording/reproducing information signals in accordance with
the present invention, there can be obtained a ROM system and a
writable memory system having an access speed in the order of
.mu.s, a recording density of 1 to 10 GBs/cm.sup.2, and a data
transfer rate in the order of Gbit/s.
[0020] The information signal recording/reproducing apparatus of
the present invention is inferior in processing rate and
reliability to a semiconductor memory but is lower two digits or
more in bit cost than the semiconductor memory, and therefore, it
can be applied to a variety of technical fields. That is to say,
the recording/reproducing apparatus of the present invention may be
used in applications including a CD, MD, electronic game machine,
DVD and video camera, in place of an optical disk and a magnetic
disk, particularly, it may be effectively used for a portable CD
player called a walkman, digital camera or may be used in place of
a hard disk for a lap top type computer or the terminal of a
portable computer.
[0021] The method of and apparatus for recording/reproducing
information signals in accordance with the present invention are
also very effectively used for applications which require
processing of a large amount of data, high speed retrieval, and
high speed access, for example, for a recognition data base for
video recognition and image recognition and a data bank for video
demand distribution.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a side view, with an essential portion enlarged,
showing the shape of a leading end of a head element as a first
embodiment of the present invention;
[0023] FIG. 2 is a side view, with an essential portion enlarged,
showing the shape of a leading end of a head element as a second
embodiment of the present invention;
[0024] FIG. 3 is a side view, with an essential portion enlarged,
showing the shape of a leading end of a head element as a third
embodiment of the present invention;
[0025] FIG. 4 is a side view, with an essential portion enlarged,
showing the shape of a leading end of a head element as a fourth
embodiment of the present invention;
[0026] FIG. 5 is a conceptional view illustrating a method of
recording/reproducing information signals according to the present
invention;
[0027] FIG. 6 is a conceptional plan view of a memory medium
suitably used for the method of recording/reproducing information
signals according to the present invention;
[0028] FIG. 7 is a conceptional plan view of a head device suitably
used for the method of recording/reproducing information signals
according to the present invention;
[0029] FIGS. 8A to 8H are process diagrams illustrating a method of
manufacturing the head device as the first embodiment of the
present invention;
[0030] FIGS. 9A to 9D are process diagrams illustrating a method of
manufacturing the head device as the second embodiment of the
present invention; and
[0031] FIGS. 10A and 10B are conceptional views showing a related
art head device, wherein FIG. 10A is a side view of the head device
and FIG. 10B is a side view, with an essential portion enlarged,
showing a head element of the head device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Hereinafter, embodiments of the present invention will be
described with reference to the accompanying drawings.
[0033] Referring first to FIGS. 1 to 4, there will be described
various head elements of the present invention.
[0034] FIG. 1 is a side view, with an essential portion enlarged,
showing the shape of a leading end of a head element as a first
embodiment of the present invention; FIG. 2 is a side view, with an
essential portion enlarged, showing the shape of a leading end of a
head element as a second embodiment of the present invention; FIG.
3 is a side view, with an essential portion enlarged, showing the
shape of a head element as a third embodiment of the present
invention; and FIG. 4 is a side view, with an essential portion
enlarged, showing the shape of a leading end of a head element as a
fourth embodiment of the present invention.
[0035] First, the head element as the first embodiment of the
present invention will be described with reference to FIG. 1.
[0036] As described above, the leading end of the related art head
element, shown in FIG. 10B, is pointed sharply enough to allow
detection of a change at the atomic size level, and is regarded as
a semi-spherical shape having a very small curvature in an enlarged
view, so that when the leading end of the related art head element
is brought in contact with a memory medium, the contact point of
the memory medium is locally applied with a very high pressure,
causing a fear of breakage of data stored on the memory medium. The
head element shown in FIG. 1 is intended to solve such a
disadvantage.
[0037] In FIG. 1, reference numeral 1A indicate the head element of
the present invention. To reduce a pressure applied to a memory
medium at the time of the above collision, a leading end 2 of the
head element 1A as an information signal detecting portion or an
information signal detecting electrode is flattened as indicated by
reference numeral 3. Taking it into account to detect an
information signal recorded at a density of 1 Gbit/cm.sup.2 or
more, the size of the leading end of the head element 1A is
required to be in a range of 0.1 .mu.m.sup.2 or less.
[0038] The larger the area of the flat portion 3 becomes, the more
the force generated at the collision with a memory medium is
dispersed. As a result, the probability of breakage of data is
reduced. For example, in the case where the cell size of data to be
reproduced (detected) is 0.1.times.0.1 .mu.m and it is judged
whether the data is "1" or "0" on the basis of the presence or
absence of a recess of the cell size, the spacial resolution upon
reproducing may be set at a value in the order of the cell size.
Assuming that the resolution is set at a value being a half of the
cell size, that is, 0.05.times.0.05 .mu.m, the size of the flat
portion 3 of the leading end 2 of the head element 1A may be set at
a value in the same order, that is, 0.05.times.0.05 .mu.m. The
contact area of the flat portion 3 is a square having one side of
0.05 .mu.m, although the contact area of the leading end of the
related art head element is a circle having a radius of 10 nm. That
is, the area ratio therebetween becomes 8, and thereby the impact
pressure applied to the flat portion 3 upon collision is reduced to
one-eighth of the impact pressure applied to the leading end of the
related art head element upon collision. It is to be noted that the
wording "flat" means not only a perfect flat state but also a
surface somewhat coarsened or a shape having a curvature similar to
or smoother than that of the data cell size.
[0039] Although only the flattening of the leading end of the head
element exhibits an effect of reducing the impact upon collision,
the structure of a head element 1B as the second embodiment shown
in FIG. 2 is more effective, in which a peripheral portion 4 of a
conductive leading end 2 is made from a non-conductive material,
whereby the contact area with a memory medium upon collision is
extended without substantially extending the area of a flat portion
3 of the leading end 2 as the information signal recording portion
or detecting portion.
[0040] The leading end of the head element may be formed into a
shape different from a prism or needle as in the related art AFM.
Concretely, as shown in FIG. 3, a head element IC as the third
embodiment of the present invention is configured such that a thin
film as a leading end 2 is formed on the surface of a substrate 5
made from a nonconductive material, whereby the flatness of the
leading end 2 can be more easily ensured.
[0041] The shape of the leading end 2 of each of the head element
IC shown in FIG. 3 and the head element 1B shown in FIG. 2 is
advantageous as follows: namely, in the case of reproducing a
memory medium on which information signals are recorded (stored) in
the form of irregularities, the leading end 2 is prevented from
being erroneously bitten in each recess of the irregularities of
the memory medium because the flat portion 3 of the leading end 2
can be wider than the area of the recess. This is effective to
essentially prevent an error of a reproducing signal or mechanical
breakage of the data surface caused by erroneous biting of the
leading end 2 in the recess.
[0042] A head element 1D as the fourth embodiment of the present
invention shown in FIG. 4 is configured such that a leading end 2
having a columnar structure is formed on the surface of a substrate
5. With this structure, even if the edge of the leading end 2 is
worn, the size of the leading end 2 is not changed, whereby the
spacial resolution in recording or reproducing is not reduced.
[0043] In the case where the area of the flat portion of the
leading end of each head element is enlarged to make wider the
contact area with a memory medium as described above, there is a
possibility that the data surface of the memory medium is degraded
by friction and wear. To protect of the data surface of the memory
medium or the leading end 2 of the head element, either or both of
them are preferably formed with a conductive material having a
small friction coefficient and a large hardness. For example,
either or both of them may be covered with a film made from carbon
or carbon hydride (diamond like carbon) by a sputtering or CVD
process. It is effective that such a film is further thinly coated
with a lubricant made from a high polymer material. The high
polymer lubricant preferably has a conductivity; however, even if
the high polymer lubricant is insulating, it allows reproducing
using ac current insofar as it has a thin film thickness.
[0044] A method of increasing a data transfer rate upon reproducing
data will be described below.
[0045] For reproducing a large-capacity of data instantly, it is
required to increase a data transfer rate as well as an access
speed.
[0046] To increase a data transfer rate, it is important to ensure
a sufficient S/N even in a wide frequency band, and to adopt a
reproducing method which is essentially not limited to the data
transfer rate, for example, a reproducing method limited to the
resonance frequency of the apparatus. In the case of the AFM or
STM, the spacial resolution is very high; however, the output is
dependent on a very weak force or current such as an interatomic
force or tunneling current, so that it is difficult to obtain a
large reproducing signal and hence to obtain a sufficient S/N in a
wide frequency band.
[0047] In view of the foregoing, according to the present
invention, there is adopted a method of reproducing information
signals in which the data "1" or "2" is made to correspond to
switching of a current and reproducing is performed by
turn-on/turn-off of the current.
[0048] FIG. 5 is a conceptional view of an information signal
recording/reproducing apparatus as an embodiment for illustrating
the method of recording/reproducing information signals according
to the present invention; FIG. 6 is a conceptional plan view of a
memory medium suitably used for the method of recording/reproducing
information signals according to the present invention; and FIG. 7
is a conceptional plan view of a head device suitably used for the
method of recording/reproducing information signals according to
the present invention.
[0049] In FIG. 5, reference numeral 10 indicates an information
signal recording/reproducing apparatus as the embodiment of the
present invention. The recording/reproducing apparatus 10 includes
a memory medium 20 shown in FIG. 6, a head device 30 shown in FIG.
7, a power supply 11, and an amplifier 12.
[0050] It is to be noted that in the specification the wording
"recording/reproducing apparatus" means not only an apparatus
having both the "recording and reproducing" functions but also an
apparatus having only the "recording" function or the "reproducing"
function.
[0051] The memory medium 20 of the present invention has a
structure shown in FIGS. 5 and 7 in which a conductive layer 22 is
formed on a quadrilateral shaped flat conductive substrate 21. The
recording surface of the conductive layer 22 is, as shown in FIG.
6, sectioned into a plurality of sectors 23 arranged, for example,
in a cross-cut pattern. One sector 23 is a unit data area which
allows reproducing by a specific one head element 1. On each sector
23 are recorded information signals in the form of
irregularities.
[0052] The head device 30 is so configured as shown in FIGS. 5 and
7 in which a number of head elements 1 (of a type selected from the
head elements 1A, 1B and 1C) are arranged, on a substrate 5, in a
specific two-dimensional pattern, for example, in such a matrix
pattern that the head elements 1 correspond to the sectors 23 of
the memory medium 20 on a one-for-one basis in the X-direction and
the Y-direction with the distance (pitch) between at least the
adjacent heads on the X-direction set at a value of Pa and with the
head pitch in the Y-direction set at a value of Pb. That is to say,
one head element 1 operates in one sector 23 as a recording region
or reproducing region.
[0053] The method of reproducing information signals according to
the present invention using the recording/reproducing apparatus 10
of the present invention will be described below.
[0054] FIG. 5 shows a principle of reproducing information signals
previously recorded in the form of irregularities on each sector 23
of the memory medium 20 in a state in which the head device 30 is
brought in contact with the memory medium 20. Referring to FIG. 5,
an electric field is applied between the conductive substrate 21 of
the memory medium 20 and the head element 1 by the power supply 11.
While not shown, a mechanism is provided for suitably bringing the
head element 1 in contact with the memory medium 20, and only when
the head element 1 is brought in contact with the projection of the
irregularities of the memory medium 20, a current is allowed to
flow from the head element 1 to the memory medium 20. Such a
current is current-voltage converted and amplified by the amplifier
12 into a large signal voltage.
[0055] In the case where the contact area of the head element 1 in
contact with the memory medium 20 is 0.05.times.0.05 .mu.m,
assuming that the current density is 5.times.10.sup.8 A/m.sup.2, a
current of 1.4 .mu.A flows only when the head element 1 is brought
in contact with the projection of the memory medium 20, and
assuming that the resistance upon current-voltage conversion is 500
hm, the current of 1.4 .mu.A is current-voltage converted into a
voltage of 70 .mu.V. Accordingly, a sufficient S/N can be obtained
even for a reproducing signal frequency band of 10 MHz.
[0056] In the case of using the resistance of 500 hm upon
current-voltage conversion, a thermal noise of the resistance
becomes predominant as the noise in the ideal case. Assuming that
the signal frequency band is 10 MHz and the temperature is 300 K,
the thermal noise current is calculated into a value of 57 nA. The
signal current of at least 200 nA, preferably, 570 nA is required
for reproducing a digital signal in a state not being obstructed by
the noise current. In the case of reproducing information signals
at the above current density of 5.times.10.sup.8 A/m.sup.2, the
contact area of the head element 1 in contact with the memory
medium 20 becomes at least 0.0004 .mu.m.sup.2, preferably, 0.0011
.mu.m.sup.2, and accordingly, if the contact portion of the head
element 1 has a square shape, the size of the contact portion
becomes at least 0.02.times.0.02 .mu.m, preferably,
0.033.times.0.033 .mu.m.
[0057] In the embodiment shown in FIG. 5, a dc electric field is
applied to the head element 1; however, an ac electric field may be
applied thereto. In the case where an extremely thin insulating
layer is formed on the head element 1 or on the reproduced surface
of the memory medium 20 or in the case where a space such as an
extremely thin air layer is formed between the head element 1 and
the reproduced surface of the memory medium 20, it is preferred to
apply an ac electric field having a high frequency.
[0058] In the case of using a focus mechanism for bringing the head
device 30 in contact with the memory medium 20 using an
electrostatic force, there is a fear of interference between the
electric field required for signal detection and the electric field
required for the focus mechanism. To avoid such an inconvenience,
it is preferred to use, for signal detection, an ac electric field
having a frequency very higher than the resonance frequency of a
movable portion of the head device 30.
[0059] In the above-described document "H. Kado et al.: Appl. Phys.
Lett. 66(22), 2961(1995)", information signals are reproduced from
the writable memory medium made from amorphous GeSb.sub.2Te.sub.4
by making use of a change in electric conductivity between states
before and after recording. In this technique, since the
reproducing signal current is as weak as 1 nA, it is difficult to
carry out reproducing at a high rate. The reason why the
reproducing signal current is weak is that if the reproducing
current is large, the conductivity of the non-recorded portion of
the memory medium 20 will be changed, that is, the recording will
be performed, and consequently the reproducing current cannot be
set at a large value. To make large the reproducing current, it is
required to make large a current value to start recording on the
non-recorded portion. To meet such a requirement, it is effective
to change the composition of the material, film thickness, or the
shape of the head element.
[0060] As described in the above embodiment, for the read only
memory medium 20, the possibility of recording is very small and
thereby the upper limit of the reproducing current can be
increased. For a writable type memory medium, control of the
current to start recording differs depending on the recording
mechanism. In general, the recording mechanism is classified into a
type in which recording is performed by heat generated due to flow
of a current, a type in which recording is performed by an electric
field locally increased, and a type in which recording is performed
by a pressure generated upon collision between a head element
(probe) and a memory medium. In each type of the recording
mechanism, the sharper the leading end of the head element (probe),
the smaller the current to start recording. Accordingly, it is
difficult to obtain a large reproducing current. From this
viewpoint, the leading end of the head element (probe) is desired
to a flat structure which allows a reproducing signal current of 10
nA or more.
[0061] For carrying out rapid access, it is desired to make the
movable portion as small and light as possible and also to make the
moving distance as short as possible. A disk medium utilizing
apparatus such as a hard disk apparatus or optical disk apparatus
generally mounts one head per one recording surface and moves the
disk medium in the radial direction thereof by a swing arm or
linear actuator. It may be considered that a number of magnetic
heads or optical heads are arranged in the radial direction to
reduce the moving distance per one head, thereby improving the
access speed to the desired radial position; however, this method
has disadvantages that the magnetic head or optical head is high in
cost per one head and also the volume is large and thereby the size
of the memory apparatus is increased. Actually, the method of
improving the access speed by arranging a number of magnetic heads
or optical heads has been not adopted.
[0062] On the contrary, since the head device 30 of the present
invention is extremely small and a plurality of the head elements
can be easily manufactured (as will be described later), the head
device 30 can be configured to have a multi-head as shown in FIG.
5. The head device 30 of the present invention can be also
configured such that a plurality of heads are arranged in the
radial direction of a rotating memory medium such as a disk,
whereby the heads can be accessed to all of the information signals
recorded on the memory medium by moving each head at least a
distance more than a pitch between the adjacent heads in the radial
direction of the memory medium.
[0063] In the above configuration, assuming that the head pitch is
1 mm, the heads can be instantly accessed to desired tracks only by
moving them a distance of 1 mm.
[0064] Even in the case of adopting such a configuration, however,
for a rotating type disk medium, it takes a time to wait rotation.
To cope with such an inconvenience, it may be considered to rotate
the disk medium at a high speed; however, this method has a problem
in terms of stability and reliability of a spindle motor.
[0065] According to the present invention, as shown in FIGS. 5 to
7, the access speed is improved by bringing the head device 30
having a plurality of the head elements 1 arranged in a matrix
pattern in contact with the recording surface of the memory medium
20, and moving the head device 30 relative to the memory medium 20
a pitch P of the head element 1.
[0066] The head device 30 can be moved in the X and Y directions by
moving a movable stage on which the head device 30 is mounted, for
example, using a stepping motor, DC motor, or piezoelectric
actuator.
[0067] In the case where the pitch P between the head elements 1 is
2 mm, that is, in the case where the arrangement density of the
head elements 1 of the head device 30 is 25 head elements/cm.sup.2,
a movement distance to a data position is about 1 mm. In this case,
assuming that an average driving speed of the actuator is 1 m/s,
the access speed becomes 1 ms which is faster several times than
the related art one. If the pitch P between the head elements is
made shorter, for example, to 0.2 mm, the access speed can be made
fast to 100 .mu.s.
[0068] As described above, in the case of reproducing information
signals recorded on the memory medium 20 using the head device 30
including a plurality of the head elements 1, data stored on a
plurality of the sectors 23 of the memory medium 20 can be
simultaneously reproduced by the plurality of the head elements 1.
For a long information signal, it is undesirable to continuously
reproduce it by one head element 1. Such a long information signal
may be first divided into parts and recorded on a plurality of
different ones of the sectors 23 on the memory medium 20. In this
case, the long information signal can be reproduced for a short
time by simultaneously scanning a plurality of ones of the head
elements 1 correspondingly to the plurality of ones of the sectors
23 on which the parts of the long information signal are
recorded.
[0069] In addition to the reproducing rate, the head device 30 has
another advantage. When an information signal is divided into parts
and recorded on a plurality of ones of the sectors 23 as described
above, even if a part of the information signal stored on a certain
sector 23 is broken or a certain head element 1 is broken down, it
is possible to eliminate such a fear that all of the parts of the
information signal cannot be reproduced, and to carry out
reproducing with no error using suitable error collection. As a
result, it is effective to divide an information signal into parts
and record the parts on different ones of the sectors 23.
[0070] A plurality of recording/reproducing apparatuses 10 may be
prepared by changing the combination of the head device 30 and the
memory medium 20 for each recording/reproducing apparatus, wherein
an information signal in the same information signal series is
dispersedly recorded on or reproduced from different ones of the
plurality of different recording/reproducing apparatuses 10, to
thereby improve the reliability or improve the effective data
transfer rate.
[0071] The addressing method using the above recording/reproducing
apparatus 10 will be described below.
[0072] To reproduce a desired information signal, it is necessary
to confirm at what position the desired information signal is
recorded on the memory medium 20 and access the head device 30 to
the position, and more specific, it is necessary to confirm
positional information of the desired information signal and move
the head element 1 to the position (in the in-plane direction and
the depth direction). Here, the positional adjustment in the
in-plane direction (X, Y direction) is called "positioning" and the
positional adjustment in the depth direction is called "focusing"
for the sake of convenience.
[0073] To make each head element 1 of the head device 30 face to
the corresponding sector 23 of the memory medium 20 and carry out
positioning of the head element 1 to the sector 23 upon recording
or reproducing, it is desired to move the entire head device 30 or
move the memory medium 20 with the head device 30 fixed. For
carrying out the positioning, each head element 1 must be moved in
the in-plane direction a distance of about the pitch P between the
head elements 1. For example, in the case where the pitch P between
the head elements 1 is 0.1.times.0.1 mm, each head element 1 can be
moved a distance of 0.1 mm or more. In the case of independently
positioning the head elements 1, there must be provided actuators
each capable of moving each head element 1 a distance of 0.1 mm or
more. That is to say, each mechanism movable the pitch P between
the two adjacent head elements 1 must be formed within a gap
between the two adjacent head elements 1. This is difficult to be
realized. On the contrary, there is no problem in the case of
moving the entire head device 30 a distance of about 0.1 mm.
[0074] The movement of the entire head device 30, however, is
disadvantageous in carrying out fine positioning between each head
element 1 and the position of a desired information signal. This is
because the movement of the entire head device 30 makes it
impossible to correct an error of the pitch P between the head
elements 1 caused at steps of manufacturing the head device 30, an
error of the interval between information signals caused at steps
of manufacturing the memory medium 20, or an error of positioning
caused by a difference in thermal expansion coefficient between the
memory medium 20 and the head device 30 depending on a change in
service environment, for example, temperature and moisture.
[0075] To carry out the error correction (hereinafter, referred to
as "fine positioning"), it is effective to provide an actuator
capable of moving each head element 1 a micro-distance. In the case
of the above positioning, the head element 1 is moved a distance of
0.1 mm; however, in the case of fine positioning, the head element
1 is sufficient to be moved a distance of one-tenth or less of the
pitch P between the head elements 1. Accordingly, fine positioning
can be sufficiently achieved using a small-sized actuator using a
piezoelectric element.
[0076] In this way, the head device 30 of the present invention is
controlled in two steps: the positioning (course positioning) step
for moving the entire head device 30 and the fine positioning step
for finely moving each head element 1.
[0077] In addition to the above two-step control, there is a more
simplified recording/reproducing method in which only the course
positioning is performed and the fine positioning is not performed.
In this method, after each head element 1 is substantially moved by
course positioning to a position where reproducing or recording is
to be performed, information signals on the periphery of the
position are collectively reproduced or recorded; and in the case
of reproducing, the information signals thus obtained are stored in
a buffer memory and then data at the desired position is specified
by signal processing. For example, in the case of reproducing
information signals along a line called a track on which the
information signals are recorded, the reproducing is performed
without tracking control. In this case, by reproducing information
signals at a cycle being twice or more of at least a cycle (pitch)
of the track, the desired information signal can be restored by the
subsequent signal processing. In the case where information signals
are two-dimensionally recorded, information signals may be
reproduced at a cycle being twice of a cycle in each of the
X-direction and the Y-direction. Here, the size of the leading end
of the head element 1 may be set at a large value to make high the
spacial resolution and make large a signal current, and more
specifically, the length of the head element 1 is desired to be in
a range of one-tenth to one-half of the pitch of the above
track.
[0078] The information signals are preferably stored in the buffer
memory as digital signals discontinuous with time for ease of the
subsequent signal processing. The sampling cycle for taking signals
in the buffer memory is desired to be a length equivalent of the
cell size or one bit of the information signal or a time being a
half or less that required for movement of the head device by
course positioning.
[0079] If both the memory medium 20 and the head device 30 are very
excellent in terms of smoothness and flatness, focusing may be
omitted; however, actually, it is difficult to keep constant the
flatness of each of the memory medium 20 and the head device 30 by
the effect of deformation due to temperature and moisture or
warping due to the film stress. Assuming that the size of the
memory medium 20 is 2.times.2 mm.sup.2 and the angle of warping is
2.degree., the heights in the depth direction at both the ends of
the memory medium 20 are different 70 .mu.m from each other. Like
the above-described positioning case, it is difficult to provide
actuator's functions capable of moving the head elements the above
distance for each head element. Accordingly, even in this case, a
two-step control is effective like the above positioning case.
[0080] To achieve rough focusing, it is desirably simple to flatten
both the head device 30 and the memory medium 20. For this purpose,
a substrate of each of the head device 30 and the memory medium 20
may be formed of a thick plate made from a material having a large
elastic modulus; or the substrate of the head device 30 may be
formed of a thick plate made from a less deformable material having
a larger elastic modulus while the substrate of the memory medium
20 may be formed of a thin plate made from a deformable material
having a small elastic modulus. Upon recording/reproducing, the
above memory medium 20 is brought in close-contact with the flat
stage or the head device 30 is pushed on the memory medium 20 to
thus obtain a desired flatness.
[0081] As the less deformable material having a large elastic
modulus, there may be used a ceramic material such as glass, or a
metal such as silicon, aluminum, or stainless steel. As the
deformable material, there may be used a high polymer such as
acrylic resin, polycarbonate, or nylon.
[0082] It is effective to bring the memory medium 20 in
close-contact with the stage or the head device 30 using an
electrostatic force.
[0083] To achieve fine focusing, it is desired to mount actuator
mechanisms movable about 10 .mu.m or less in the depth direction
independently on respective head elements 1. The actuator mechanism
is represented by an electrostatic element or piezoelectric
element. Whether or not the head element 1 is in contact with the
memory medium 20 is judged by monitoring an impedance in a
reproducing signal line or recording circuit. Accordingly, the
contact of the head element 1 with the memory medium 2 can be
stably feed-back controlled using the signal thus monitored. The
fine focusing mechanism may be provided per one head element 1 as
described above, or may be provided per one of a plurality of
adjacent head elements 1.
[0084] In addition to an information signal, an address signal for
giving a relative position of the memory medium 20 to the head
element 1 or the head device 30 is recorded on the memory medium
20. To be more specific, the address signal, which is for giving
two-dimensional positional information in the sector 23, may be
previously recorded on the memory medium 20 in the form of
irregularities, or may be recorded on the memory medium 20 by the
head device 30 upon recording.
[0085] A method of manufacturing the memory medium 20 will be
described below.
[0086] The read only memory medium 20 is preferably configured such
that fine irregularities formed on the substrate surface are used
as signals. Like a compact disk, an original plate on which a
pattern of fine irregularities is formed by photolithography or
using an electron beam plotting apparatus is prepared, and a
substrate with the pattern of fine irregularities is formed by
injection-molding or extrusion-molding using the original plate as
a die, to obtain a memory medium.
[0087] Alternatively, a substrate coated with an ultraviolet cured
resin is separately prepared, and a pattern of fine irregularities
is formed on the resin layer using a so-called 2P (Photo
Polymerization) process.
[0088] The substrate may be made from glass or metal as well as a
high polymer such as acrylic resin or polycarbonate.
[0089] The writable memory medium 20 is prepared by preparing a
flat substrate with no irregularities or a substrate on part of
which irregularities as an address signal are formed by the
above-described method, and forming, on the substrate, a material
allowing an impedance between the head element 1 and the memory
medium 20 to be locally changed before and after local application
of an electric field, current, heat, or pressure.
[0090] As such a material, there may be used amorphous
GeSb.sub.2T.sub.4 described in the above-described document, a high
polymer dissolved or deformed by heat or pressure, a capacitor for
storing electric charges, or a ferroelectric material.
[0091] The head element 1 or the head device 30 can be formed on a
flat substrate made from glass or the like by a semiconductor
process. The movable portion for fine focusing is formed of a
membrane supported on the substrate by means of a cantilever beam
or a double-end fixed beam using a micromachinning process. In
addition, ICs such as a focus-servo controller, head amplifier, and
current driver may be integratedly mounted in the substrate of the
head device 30.
[0092] An embodiment of a method of manufacturing the head device
30 will be described with reference to FIGS. 8A to 8H and FIGS. 9A
to 9D.
[0093] FIGS. 8A to 8H are process diagrams illustrating a method of
manufacturing the head device as the first embodiment of the
present invention; and FIGS. 9A to 9D are process diagrams
illustrating a method of manufacturing the head device as the
second embodiment of the present invention.
[0094] First, at the step shown in FIG. 8A, there is prepared a
substrate 31 (equivalent to the substrate 5 of the head device 30)
formed of a silicon wafer containing an impurity at a relatively
high concentration (that is, having a conductivity). The substrate
31 may be already formed with a signal processing circuit or
current driver.
[0095] A so-called sacrifice layer having a trapezoidal cross
section is, at the step shown in FIG. 8B, patterned on-the surface
of the substrate 31 by a micromachinning process. The sacrifice
layer will be removed later by etching. The material for forming
the sacrifice layer is suitably selected from a photoresist,
aluminum and SiO.sub.2 in consideration of the combination with
other materials which will be formed in the subsequent steps. Here,
a photoresist is patterned by exposure and development. Reference
numeral 32 indicates the photoresist pattern.
[0096] Then, at the step shown in FIG. 8C, a film 33 made from an
aluminum alloy is formed to a thickness of one to several .mu.m.
The film 33 will be formed into a vertically movable spring member
functioning as a fine focusing mechanism.
[0097] The aluminum alloy film 33 is patterned into a pattern 34 at
the step shown in FIG. 8D. The pattern 34 has a plurality of
central portions functioning as a plurality of springs, positioned
over an approximately central portion of the trapezoidal
photoresist pattern 32, and a peripheral portion-fixed on the
periphery of the substrate 31. In addition, FIG. 8D-(B) is a
sectional view taken on line A-A of FIG. 8D-(A).
[0098] The process goes on to the step shown in FIG. 8E at which a
fine square patten of a photoresist 35, having one side less than
the thickness of the aluminum alloy film 33, is-formed at a central
portion of the aluminum alloy film 33 positioned over an
approximately center of the trapezoidal photoresist pattern 32.
[0099] The aluminum alloy film 33 is isotropically etched using
phosphoric acid at the step shown in FIG. 8F. At this time, the
etching is completed before the square photoresist 35 is perfectly
separated from the aluminum alloy film 33 so that the leading end
of the aluminum alloy film 33 remains as a flat portion.
[0100] The substrate 31 is annealed in a gas atmosphere containing
oxygen at the step shown in FIG. 8G. With this annealing, the
stress caused in the aluminum alloy film 33 can be relieved, and
the surface of the aluminum alloy film 33 except for the leading
end (which is in contact with the micro-photoresist 35) for forming
a head element is oxidized to be converted into the insulating
surface.
[0101] After annealing, the trapezoidal photoresist 32 and the
micro-photoresist 35 are removed by a resist releasing agent at the
step shown in FIG. 8H. As a result, a cavity 6 is formed between
the aluminum alloy film 33 and the substrate 31 (equivalent to the
substrate 5 shown in FIGS. 3 and 4); a portion of the trapezoidal
aluminum alloy film 33 over the cavity 6 forms a spring 7; and a
head element 1 including a leading end 2 having a flat shape 3 is
formed at-a central portion of the spring 7. It is to be noted that
the head element thus formed is indicated by the same reference
numeral 1 as that of the head element shown in FIGS. 3 and 4.
[0102] Finally, the silicon substrate 31 is provided with an
electrode, followed by application of a DC bias voltage, and
amorphous carbon hydride is selectively formed on the flat portion
made from the aluminum alloy having a conductive surface by CVD
(Chemical Vapor Deposition) process, to obtain the head element
1.
[0103] Although only one head element is shown in FIGS. 8A to 8H
used for description of this embodiment, a number of head elements
can be simultaneously formed on the substrate 31 and also a number
of head devices 30 can be simultaneously manufactured in accordance
with the manufacturing process of this embodiment.
[0104] The method of manufacturing the head device as the second
embodiment of the present invention will be described with
reference to FIGS. 9A to 9D. In this manufacturing method, the
columnar head element ID shown in FIG. 4 is manufactured.
[0105] First, at the step shown in FIG. 9A, a thick insulating film
42 having a thickness of about 1 .mu.m is formed on the surface of
a substrate 41 which has a conductivity at least on its surface.
The insulating film 42 may be made from silicon oxide, silicon
nitride, photoresist, or polyimide.
[0106] At the step shown in FIG. 9B, a mask 43 made from a material
withstanding etching for the insulating film 42 is formed on the
insulating film 42 except for a portion equivalent to the columnar
leading end of the head element 1D. In addition, the mask 43 is
preferably formed by X-ray lithography using synchrotron radiation
or photolithography using ultraviolet rays having a short
wavelength such as a ArF excimer laser.
[0107] Then, at the step shown in FIG. 9C, a portion of the
insulating film 42 equivalent to the leading end of the head
element ID is anisotropically removed by RIE (Reactive Ion
Etching), to form a leading end forming portion 44.
[0108] After removal of the mask 43, at the step shown in FIG. 9D,
a metal such as nickel is formed in the leading end forming portion
44 by plating using the conductive substrate 41 as an electrode, to
form a leading end 2. The surface of the leading end 2 thus formed
is finished by polishing to improve the flatness thereof.
[0109] In this way, the head element 1D including the columnar
leading end 2 shown in FIG. 4 is obtained.
[0110] Although only one head element is shown in FIGS. 9A to 9D
used for description of this embodiment, like the previous
embodiment, a number of head elements can be simultaneously formed
on the substrate 41 and also a number of head devices 30 can be
simultaneously manufactured in accordance with the manufacturing
process of this embodiment.
[0111] While the preferred embodiments of the present invention
have been described using specific terms, such description is for
illustrative purposes only, and it is to be understood that many
changes and variations may be made without departing from the scope
or spirit of the following claims.
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