U.S. patent number 3,645,788 [Application Number 05/016,446] was granted by the patent office on 1972-02-29 for method of forming multiple-layer structures including magnetic domains.
This patent grant is currently assigned to North American Rockwell Corporation. Invention is credited to Paul J. Besser, Thomas N. Hamilton, David M. Heinz, Jack E. Mee, George R. Pulliam.
United States Patent |
3,645,788 |
Mee , et al. |
February 29, 1972 |
METHOD OF FORMING MULTIPLE-LAYER STRUCTURES INCLUDING MAGNETIC
DOMAINS
Abstract
A composite consisting of multiple-layer structures, the basic
structure of which is a chemically vapor-deposited film on a
substrate wafer, disclosed herein. The film is of such material
appropriate for creating therein single-wall magnetic domains which
are capable of being moved about in predetermined directions within
the thickness of the film and in the plane of the film. Devices are
adapted to the film for sensing the motion of these domains thereby
enabling application of these structures toward circuits which may
be particularly utilized in memory or logic applications. A
complete family of film on substrate materials are fabricated
through a unique process, one of the steps of the process relates
to establishment of the exact location of the substrate within the
reactor at which deposition of the film upon the substrate is to be
made in order to obtain the desired film characteristics. Included
are provisions for making multiple film layers to result in a
matrix of films and hence a multitude of such circuits. Films used
are comprised of at least three and four elements.
Inventors: |
Mee; Jack E. (Orange County,
CA), Heinz; David M. (Orange County, CA), Hamilton;
Thomas N. (Orange County, CA), Besser; Paul J. (Orange
County, CA), Pulliam; George R. (Orange County, CA) |
Assignee: |
North American Rockwell
Corporation (N/A)
|
Family
ID: |
26688607 |
Appl.
No.: |
05/016,446 |
Filed: |
March 4, 1970 |
Current U.S.
Class: |
117/86; 117/88;
117/89; 117/944; 117/947; 427/131 |
Current CPC
Class: |
H01F
41/20 (20130101); C23C 16/404 (20130101); H01F
10/22 (20130101); H01F 10/265 (20130101) |
Current International
Class: |
C23C
16/40 (20060101); H01F 10/22 (20060101); H01F
10/10 (20060101); H01F 41/20 (20060101); H01F
41/14 (20060101); H01f 010/06 () |
Field of
Search: |
;117/235,239,212,215,217,236,240 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
IBM Tech. Dis. Bull., Vol. 5, No. 4, Sept. 62, page 44-45, Tessor
et al. Multilayered Thin Films..
|
Primary Examiner: Martin; William D.
Assistant Examiner: Pianalto; Bernard D.
Claims
We claim:
1. A method of forming a composite structure suitable for
containing bubble domains therein comprising the steps of
providing a single-crystal substrate, and
forming a magnetic single-crystal iron-containing film having a
thickness less than 25 microns on said substrate with sufficient
mechanical strain in said film to provide said film with sufficient
uniaxial anisotropy for the formation of bubble domains
therein,
whereby said film has a JQ-oxide formulation wherein,
the J constituent of said film formulation has at least two
elements selected from the group consisting of cerium,
praseodymium, neodymium, promethium, samarium, europium,
gadolinium, terbium, dysprosium, holmium, erbium, thulium,
ytterbium, lutetium, lanthanum and yttrium, and
the Q constituent of said film formulation is taken from the group
consisting of iron, iron and aluminum, iron and gallium, iron and
indium, iron and scandium, iron and titanium, iron and vanadium,
iron and chromium, and iron and manganese.
2. A method as described in claim 1 whereby said JQ-oxide film is
defined as J.sub.3 Q.sub.5 O.sub.12 and where "3" is the sum of the
two elements of the J constituent and where "5" is the sum of the
two elements of the Q constituent when Q has two elements.
3. A method as described in claim 1 whereby said JQ-oxide film is
defined as J.sub.1 Q.sub.1 O.sub.3 and where "1" is the sum of the
two elements of the J constituent and where "1" is the sum of the
two elements of the Q constituent when Q has two elements.
4. A method as described in claim 1 whereby said single-crystal
substrate has a JQ-oxide formulation wherein:
the J constituent of said substrate formulation is at least one
element selected from the group consisting of cerium, praseodymium,
neodymium, promethium, samarium, europium, gadolinium, terbium,
dysprosium, holmium, erbium, thulium, ytterbium, lutetium,
lanthanum, yttrium, magnesium, calcium, strontium, barium, lead,
cadmium, lithium, sodium and potassium, and
the Q constituent of said substrate formulation is at least one
element selected from the group consisting of indium, gallium,
scandium, titanium, vanadium, chromium, manganese, rhodium,
zirconium, hafnium, molybdenum, tungsten, niobium, tantalum, and
aluminum.
5. A method as described in claim 4 whereby:
said J constituent of said substrate formulation is at least one
element selected from the group consisting of cerium, praseodymium,
neodymium, promethium, samarium, europium, gadolinium, terbium,
dysprosium, holmium, erbium, thulium, ytterbium, lutetium,
lanthanum and yttrium; and
said Q constituent of said substrate formulation is at least one
element selected from the group consisting of indium, gallium,
scandium, titanium, vanadium, chromium, manganese, rhodium, and
aluminum.
6. A method as described in claim 1 whereby the film is formed by
the steps of
conducting at least one of a plurality of metal halides into the
reaction chamber,
injecting at least one reacting gas and at least one carrier gas
into the reaction chamber reaction therein with the metal halides
thereby producing reaction products of the halides and gases,
inserting a test sample for selecting the location of said
substrate within said reaction chamber,
removing said test sample, and
inserting said substrate at the selected location for deposition of
at least one of the reaction products on said substrate to form
said monocrystalline film thereon.
7. A method of forming a bubble domain comprising the steps of
providing a single-crystal substrate, and
forming a first magnetic single-crystal iron-containing film on
said substrate with sufficient mechanical strain in said film to
provide said film with sufficient uniaxial anisotropy for the
formation of bubble domains therein and having a thickness less
than 25 microns,
whereby said film has a JQ-oxide formulation wherein,
the J constituent of said film formulation has at least two
elements selected from the group consisting of cerium,
praseodymium, neodymium, promethium, samarium, europium,
gadolinium, terbium, dysprosium, holmium, erbium, thulium,
ytterbium, lutetium, lanthanum and yttrium, and
the Q constituent of said film formulation is taken from the group
consisting of iron, iron and aluminum, iron and gallium, iron and
indium, iron and scandium, iron and titanium, iron and vanadium,
iron and chromium, and iron and manganese, and
forming a second magnetic single-crystal iron-containing film
having a JQ-oxide formulation wherein said J and said Q
constituents are taken from the same groups as set forth for said
first single-crystal film, said second film having sufficient
mechanical strain therein to provide sufficient uniaxial anisotropy
for the formation of bubble domains therein and having a thickness
less than 25 microns.
Description
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a chemical vapor deposition process and
product resulting therefrom for epitaxially growing oxygen compound
films of yttrium, lanthanum or any of the lanthanide group of
elements mixed with certain metals or other elements and deposited
on a substrate wafer comprising a variety of compounds for
obtaining a composite of a multiple-layer structure. This composite
structure has utility in magnetic devices as well as in
particularly useful in logic devices or circuits due to the
capability of creation of single-wall magnetic domains in the films
thereof.
2. Prior Art
The current interest in orthoferrite single crystals has been
aroused by the ability to produce mobile single-domain wall or
bubble magnetic domains in thin plates of proper crystallographic
orientation as described in a paper by A. H. Bobeck entitled
"Properties and Device Applications of Magnetic Domains in
Orthoferrites," published in the "Bell System Technical Journal,"
Volume 46, page 1,901 (1967). These domains can be manipulated by
magnetic fields to perform logic and memory functions as
demonstrated in a patent to A. H. Bobeck et al., U.S. Pat. No.
3,460.116, issued Aug. 5, 1969.
Bulk orthoferrite crystals have been grown from solution, either by
a molten flux technique as described in a patent to J. P. Remeika,
U.S. Pat. No. 3,079,240, issued Feb. 26, 1963, or a hydrothermal
technique as described in a paper by E. D. Kolb, D. L. Wood, and R.
A. Laudise entitled "The Hydrothermal Growth of Rare Earth
Orthoferrite," published in the "Journal of Applied Physics,"
Volume 39, page 1,362 (1968). Both growth methods as stated by the
authors of these publications are prone to produce crystals with
solvent inclusions or voids, and solvent chemical substitution in
the crystal is described for example in a paper by J. P. Remeika
and T. Y. Kometoni entitled "Lead Substitution in Flux Grown Single
Crystal Rare Earth Orthoferrites," published in "Material Research
Bulletin," Volume 3, page 895 (1968) and the above-listed paper on
hydrothermal growth by E. D. Kolb, D. L. Wood and R. A. Laudise.
Single crystals resulting from either of these growth processes
must be sliced and polished down to thin wafers of proper
crystallographic orientation. Although very thin orthoferrite
layers are desired, the limit of mechanical polishing is a few
thousandths of an inch beyond which breakage becomes excessive. In
addition, polishing scratches must be eliminated for they impede
magnetic domain motion.
Techniques are known for obtaining magnetic oxide films on
crystalline substrates include spraying a suspension of reactants
on heated substrates, vacuum-depositing metal alloys with
subsequent oxidation, and chemically depositing on a substrate from
mixed nitrate solutions followed by a firing of the material. More
recently, certain films have been prepared by electron beam
evaporation and by r-f sputtering.
Cech and Alessandrini in a paper entitled "Preparation of FeO, NiO,
and CoO Crystals by Halide Decomposition," published in
"Transaction of the American Society of Metals," Volume 50, page
150 (1959), reported the epitaxial growth of certain materials by a
chemical vapor deposition method. Others independently extended the
techniques reported and showed that complex metal oxides could also
be grown epitaxially by the chemical vapor deposition method. In
general, chemical vapor deposition methods have produced films with
desirable properties but the films have been difficult to
reproduce.
As has been reported by A. H. Bobeck, R. F. Fischer, A. J.
Perneski, J. P. Remeika and L. G. Van Uitert in a paper
"Application of Orthoferrites to Domain Wall Devices," published in
the "IEEE Transactions on Magnetics," Volume MAG-5 (1969), there is
a minimum domain diameter for each orthoferrite which is
characteristic of that material at room temperature and for which a
specific sample thickness is required. One way of reducing the
characteristic domain diameter that has been described in the
literature by V. F. Gianola, D. H. Smith, A. A. Thiele and L. G.
Van Uitert in a paper "Material Requirements for Circular Magnetic
Doman Devices," published in the "IEEE Transactions on Magnetics,"
Volume MAG-5 (1969), is for example to form solid solutions with
samarium orthoferrite which has properties that depress the minimum
domain diameter.
Sheets or films of polycrystalline magnetizable metals which may be
subjected to magnetic influences for the purpose of creating
magnetic domains have been shown in a patent to K. D. Broadbent,
U.S. Pat. No. 2,919,432, issued Dec. 29, 1959. That patent
specifically describes a thin-sheet domain-wall shift register in
which a reverse magnetized domain, bounded by leading and trailing
domain walls, is nucleated at an input position in the sheet and
propaged along a first axis in the sheet by a step-along multiphase
propagation field. Such a domain-wall device usually requires or is
characterized by anisotropic magnetic sheet where propagation of a
reverse domain is either along the easy or the hard axis and the
domain walls bounding that reverse domain extend to the edge of the
sheet in the direction orthogonal to the axis of propagation.
Inasmuch as the walls of the domain are bounded by the edge of the
sheet, propagation of those domains is constrained to one of the
axis along a transverse direction of the sheet.
In a patent to A. H. Bobeck et al., U.S. Pat. No. 3,460,116, issued
Aug. 5, 1969, it is shown that a reverse magnetized domain may be
bounded by a single-wall domain. Such a domain differs from the
reverse domain propagated in the Broadbent patent in that the
single-wall domain, encompassing the former, has a cross-sectional
shape independent of the breadth of the sheet, or in other words is
not bounded by the edge of the sheet. These domains are referred to
as single-wall domains.
The major disadvantages of both the Broadbent and Bobeck patents
are that the former resorts to the use of an anisotropic film or
sheet of material which results in striped or fingerlike domains
substantially across the entire width or length of the sheet, while
the latter patent does not utilize a substrate wafer for providing
structural support of the sheet of material, thereby preventing the
formation of very thin sheets of material for example thicknesses
below 25 microns which offer advantages in high-domain density
applications.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a chemical
vapor deposition process for epitaxially producing at least one
film, containing oxide compounds having such a structure as the
pseudo-perovskite or garnet type comprised of at least one element
selected from the group consisting of the lanthanides, lanthanum or
yttrium and having at least another element selected from the group
consisting of aluminum, gallium, indium, scandium, titanium,
vanadium, chromium, manganese, and iron. The pseudo-perovskite for
perovskitelike-type of crystal structure is one having atoms with
the symmetrical relationship of those in a perovskite lattice, but
which has been distorted from cubic symmetry. This film is
deposited by the process stated below on an oxide substrate
compound wafer having at least one element selected from the group
consisting of the lanthanides, lanthanum, yttrium, magnesium,
calcium, strontium, barium, lead, cadmium, lithium, sodium or
potassium, and having at least another element which is selected
from the group consisting of gallium, indium, scandium, titanium,
vanadium, chromium, manganese, iron, rhodium, zirconium, hafnium,
molybdenum, tungsten, niobium, tantalum or aluminum.
It is a further object of the invention to provide the stated film
on the substrate so as to enable extremely thin films to be
chemically deposited and structurally supported thereon.
It is still a further object to provide a film compound attached to
the substrate wafer wherein the film may be suitable for producing
single-wall magnetic domains therein, the single-wall magnetic
domains behaving in a manner attributable to a single-wall domain
within a virtually isotropic medium. The behavior of the
single-wall magnetic domain and an exemplary device showing utility
of said domain is described in detail in the invention to A. H.
Bobeck et al., U.S. Pat. No. 3,460,116, issued Aug. 5, 1969, and
for the purpose of describing the theory of operation of the device
set forth therein, and the principles of creating, propagating and
sensing single-wall magnetic domains in virtually isotropic films,
this patent is incorporated herein by reference.
It is therefore also an object of this invention to provide a
process and a film-on-substrate structure wherein the film and
substrate provided will be single-crystalline in character and
where said at least one film will have virtually isotropic magnetic
characteristics in the plane of the film, and alternately have
embedded or attached thereto means for providing at least one
single-wall domain in the film at predetermined locations in the
film, means for propagating said single-wall domains in any
direction parallel to and within the plane or thickness of the
film, and sensing means which are responsive to propagation of the
single-wall domain so as to determine the shift or presence of the
single-wall domain with said film.
It is yet a further object to utilize the properties of the film
once deposited on the substrate and the single-wall magnetic
domains therein as may be created, for a multitude of purposes, one
of which is addressed to logic circuitry applications.
It is a further objective to provide a plurality of such films as
hereinabove stated inclusive of the several means for creating,
propagating and sensing single-wall domains therein on the same
substrate for providing integrated logic devices.
Briefly in accordance with the invention, a plurality of films and
substrates as hereinabove stated have been determined usable for
the purpose of creating magnetic domains in predetermined
locations, propagation thereof in substantially all directions in
the plane of said at least one film with virtually equal degree of
energy applied to move said domain and with means for sensing the
shift in position of any of said magnetic domains for logic circuit
applications. The structure of a shift register, illustrated and
completely described in the Bobeck patent, are therefore described
hereinbelow with respect to such component portions as are adapted
to or are in magnetic communication with the film itself for
execution of the creation, propagation and sensing functions of the
magnetic domains. The equipment external to the film per se is not
illustrated, as exemplary equipment used in connection with devices
having single-wall magnetic domains and propagation thereof are
completely explained in the Bobeck patent. The instant invention,
however, utilizes specific compounds for both the film and the
substrate wafer which provide the desired results with added
advantages of providing structural support for the film so that
very thin films of less than 25 microns thick, formed by the
inventive process to provide advantages of very small domain areas
and hence higher densities of single-wall magnetic domains.
In films of single-crystalline rare earth orthoferrites, it is
possible to establish cylindrical magnetic domains. The net
magnetization direction of these domains in most orthoferrites is
perpendicular to the (001) plane at room temperature. With
application of an increasing magnetic field to oppose the domain
magnetization, the cylindrical domains shrink to a minimum diameter
and then collapse. For many applications, high densities of
domains, and hence small domain diameters, are desirable.
One way of reducing the domain diameter results from the type of
growth described herein which makes use of the magnetostrictive
effect in epitaxial deposits. On cooling from the deposition
temperature, the difference in thermal expansion between the
deposit and the substrate produces mechanical strain in each. The
deposit can be properly strained so that the magnetostrictive
effect reduces the effective anisotropy constant in epitaxial (001)
orthoferrite films. Since the domain diameter is proportional to
the anisotrophy constant, the minimum domain diameter is reduced.
Even if the magnetostrictive effect is not completely isotropic, it
would not appreciably affect the virtually isotropic motion of
cylindrical domains in the (001) plane.
Chemical vapor deposition of orthoferrite films on oriented
substrates provide quite pure orthoferrites since extraneous
chemicals which might be incorporated into the crystal are not
present. Epitaxial films can routinely be controlled to a fraction
of a thousandth of an inch by controlling the duration of the
growth process. Since substrates are oriented and polished before
being used, no polishing of the orthoferrite is necessary. Thus
chemical vapor deposition of orthoferrite films yields deposits
which are purer, more perfect and thinner than bulk crystal growth
methods.
The inventive process includes such steps as are necessary to
determine the best physical location of the substrate in the
reaction chamber in order to obtain the desired deposit of film on
the substrate. The process also includes the steps of elevating the
temperature of a substrate (or seed) crystal in a reaction chamber
and reacting oxidizing gases and/or oxygen with gases of certain
metal halides at the substrate crystal or wafer surface to deposit
film as well as depositing a multiple number of films insulated
from each other.
The process further provides for depositing films of
single-crystalline structure on single-crystal substrate wafers in
accordance with the materials selected, and in accordance with the
control steps used towards accomplishment of the aforesaid product
or group of products.
The process described herein contains a sequence of steps necessary
to determine the proper deposition conditions and the best physical
location of the substrate in the reaction chamber in order to
reproduce the desired type of deposit.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a cross section view of the reaction chamber used in the
inventive process;
FIG. 2 is a plan view of a shift register illustrative of one type
of device that may be fabricated by the inventive process;
FIG. 3 is a cross section taken at plane 3--3 of FIG. 2 showing
details of the wires embedded in a layer. These wires are used for
connecting to external equipments for generating, propagating and
sensing motion of the single-wall magnetic domains created in the
film of the device; and
FIG. 4 is a cross section taken at plane 3--3 of FIG. 2 showing a
mirror-image film and layer containing wires embedded therein on
both major deposition surfaces of the substrate.
EXEMPLARY EMBODIMENT
In chemical vapor deposition processes, reactant vapors are brought
together near a crystal substrate (or seed) so that they react to
deposit an orthoferrite film on a substrate wafer. Chemical vapor
depositions involve the reaction between a lanthanide, lanthanum or
yttrium halide and an iron halide and oxygen, although not limited
to these elements or compounds. The reaction chamber permits
evaporation of the individual metal halides and intimate mixing of
the vapors before they react with oxygen gas.
FIG. 1 illustrates a T-shaped reactor as shown at 10 for use in
film deposition. FIGS. 2 and 3 are illustrative of a logic device
created by the process. The reactor is designed for relatively high
temperatures to accommodate for example the low volatility of
metallic halide source materials. The T-shaped reactor includes
horizontal chamber 20 and vertical chamber 30. Disposed about the
horizontal chamber is reaction zone heater 21. Individual heaters
31, 32, and 33 are disposed about the vertical chamber to control
source material temperatures. Enclosed within the vertical chamber
are crucibles 34 and 35 for retaining source materials therein.
These crucibles are inserted in premix tube 36, positioned and
adjusted to their proper locations, are held thereat and are
enclosed within premix tube 36. Tubular means 37 has an inlet
therein for introducing HCl gas therein as an aid in transporting
the source material in crucible 34 so as to transport the source
material thereof in gas form to reaction chamber 20. Tubular means
37 is also used for raising or lowering crucible 34 within premix
tube 36. Crucible 35 is adjusted within the premix tube by means of
support rod 38. Tubular inlet 39 is provided in premix tube 36 for
injection therethrough of helium vapors. The entire premix tube 36
containing crucibles 34 and 35 together with ends of members 37,
38, and 39, extending from the premix tube can be moved up or down
vertically as desired within chamber 30. Premix tube 36 is provided
with an exit opening 40 at the upper end thereof for conducting the
vaporized source materials mixed with the several carrier gases
injected into the premix tube 36.
The flow rate of the source material from crucible 35 can be varied
by varying the temperature of heater 33 for the particular
embodiment shown. The flow rate of the source material from
crucible 34 can also be varied by varying the temperature of heater
31 and, in addition, by varying the flow rate of the gas introduced
into the crucible from the inlet of means 37. The horizontal
reaction chamber includes inlet 22 through which helium and oxygen
gases may be injected, and has exhaust output 23 for emitting gases
from the chamber. The gases from opening 40 transport the premixed
metal halide vapors into the reaction zone of the reactor.
The crystal (or seed) substrate 26 is placed on a fused-silica
holder 25 in horizontal chamber 20. The position of holder 25 may
be adjusted during the process if desired.
Generally, during the process, the temperature of the crystal
substrate wafer is elevated by means of the reaction zone heater
21. The source material heaters 31, 32 and 33 are elevated to
temperatures which provide approximately 0.1 atm. of vapor pressure
of each metal halide.
After each heater has reached the desired temperature the premix
tube 36 containing the source material crucibles 34 and 35 is
raised into position in the vertical chamber 30. Gases are
introduced into the vertical chamber through inlet in member 37 and
through tubular means 39 to conduct the metal halide vapors through
opening 40 of the premix tube into the horizontal reaction chamber
20. Oxygen from inlet 22 of chamber 20 is then reacted with the
metal halide vapors at the upper portion of the substrate crystal
surface to produce the desired growth compound thereon.
Specifically, an example of a typical reaction is expressable in
the following approximate formulation:
GdC1.sub.3 (g)+ FeC1.sub.2 (g)+ (3/2)0.sub.2 (g).fwdarw.
GdFe0.sub.3 (s)+ (5/2)C1.sub.2 (g)
The substrate crystal for the gadolinium orthoferrite film may be
yttrium orthoaluminate or one of the other substrate compounds
listed hereinbelow. Anhydrous gadolinium chloride (GdC1.sub.3) and
iron (II) chloride (FeC1.sub.2) are contained in individual
crucibles in their separate temperature zones of chamber 30.
Dry helium is introduced into the premix tube at inlet 39 to
transport the GdC1.sub.3 and FeC1.sub.2 vapors, which are the
reacting vapors of the metal halides, from the crucibles into the
reaction zone of the horizontal chamber 20. Dry hydrogen chloride
(HCl) gas introduced at inlet 37 flows directly into crucible 34
which holds the GdC1.sub.3. The HCl gas sweeps the heavy GdC1.sub.3
vapors out of the crucible into the helium gas stream and prevents
the very reactive GdC1.sub.3 vapors from reacting at an
uncontrollably fast rate with the oxygen gas from inlet 22. Helium
is injected through inlet 22, along with oxygen into the horizontal
chamber 20.
The reaction deposition zone is in the downstream portion of the
horizontal chamber in proximity of the T-junction of chambers 20
and 30. The substrate wafer 26 is placed on holder 25 which is
inserted into the upstream portion of chamber 20. The process
parameters such as heat from heaters 31, 32 and 33 and gas flows
through 22, 37 and 39 members may be adjusted until the desired
reaction conditions are obtained, at which time substrate seed or
wafer 26 on quartz holder 25 may be positioned in the downstream
portion of chamber 20. To obtain information as to the exact
location where the desired vapor is ready for deposition on the
substrate, a test sample material similar to wafer 26 or a fused
quartz test plate may be inserted on holder 25 in the proximity of
the T-junction. A reddish-brown-colored film will deposit on the
material substituting for wafer 26 indicative of the orthoferrite
deposition zone, when conditions for deposition and location of
deposition zone are both proper. Only 2 to 4 minutes of reaction
time is used for this test. Thereafter, the substituting test
sample is removed and substrate 26 on holder 25 is inserted into
chamber 20 through inlet 22 and positioned exactly as determined by
the calibrations on rod 28 which is determinative of test sample
positioning, so that vapors of the reaction are permitted to be
deposited on the upper surface of substrate 26, thereby forming the
desired monocrystalline film on the monocrystalline substrate
wafer.
Details as to the positioning of the substrate in chamber 20 are
important. Holder 25 has apertures 27 at either end thereof which
are used for inserting therein a hooked end of calibrated rod 28.
Rod 28 positions holder 25 in its proper location so as to obtain
the reddish-brown deposition on the test sample. When the
reddish-brown color is obtained, the marking at rod 28 coinciding
with the edge of opening 22 is noted, so that holder 25 with actual
substrate 26 thereon may be reinserted and exactly positioned at
the location where the reddish-brown deposition occurred. Rod 28 is
removed thereafter until the film has been completely deposited, at
which time rod 28 is again used for removing holder 25 together
with deposited film 29 on substrate 26.
It should be noted that normally the film will deposit on the
surface of the substrate 26 which is not contiguous or in contact
with holder 25. Upon deposition of the film on one surface thereof,
the other surface, previously in contact with holder 25 may be
coated with a similar film by simply inverting the substrate so
that the now-coated surface is adjoining the surface of holder
25.
It should also be noted that the above-stated process may be used
in conjunction with a mask for masking such upper portions of the
upper surface of substrate wafer 26 that are not desired to be
coated with film 29 and leave such portions as desired to be coated
uncovered by the mask, a plurality of films such as 29 on any one
surface of substrate wafer 26 may therefore be produced in this
manner.
An orthoferrite film composition having three metals is exemplified
in column D of table 1, below. A typical reaction which results in
one of these films is expressed by the following formula:
YC1.sub.3 +GdC1.sub.3 +2FeC1.sub.2 +30.sub.2 .fwdarw.2Y.sub.o 5
Gd.sub.o 5 FeO.sub.3 +5C1.sub.2
The orthoferrite film produced will as in the above test-sampling
for color also show a reddish-brown color deposit on the test
sample material.
When films such as garnet-type preparations are desired an
additional inlet 50 is provided so that dry hydrogen chloride gas
may be injected therein directly for the purpose of providing
proper film deposits on substrate material 26.
A garnet film composition having three metals is exemplified in
column E of table 1, below. A typical reaction which results in one
of these films is expressed by the following formula: 3YC1.sub.3
+3GdC1.sub.3 +1OFeCl.sub.2 +120.sub. 2 .fwdarw.2Y.sub.1 5 Gd.sub.1
5 Fe.sub.5 O.sub.12 +19Cl.sub.2
The garnet film produced will as in the above test-sampling for
color show a yellow-green color deposit on the test sample
material.
When a third metallic constituent is to be incorporated into
growing film, its anhydrous halide vapor must be added to those in
premix chamber 36. The location of the source material container
for this metal halide depends on the temperature which is required
to produce an adequate vapor pressure. Thus, if it needs a higher
temperature than either of the other metal halides, an additional
crucible may be added above the location of 34 (not shown) and the
temperatures of heaters 31 and 32 may be adjusted accordingly. If
it evaporates at a temperature very close to that of one of the
other constituents, it may be placed in an adjacent crucible (not
shown) or it may be added in the proper compositional ratio to the
contents of either 34 or 35. If the metal halide evaporates at a
temperature between that of the two other constituents, an
additional crucible (not shown) may be installed between the
locations of 34 and 35. If the metal halide evaporates at a
temperature below that of the lower crucible, an additional
crucible (not shown) may be installed in tube 36 but below crucible
35. If the material evaporates at such a low temperature that any
location within the vertical portion of the T reaction chamber is
excessive, the material may be heated to a more modest temperature
external to the reaction chamber 30.
Films are formed on substrates in accordance with the examples in
the Table 1 below, which specifies the control process parameters
that were considered. ##SPC1##
Although only details of several compositions have been illustrated
in Table 1, it is understood that all compositions as composed of
the element formulations given in Table 2 below are applicable to
this invention. For example it was shown in columns D and E that
equal quantities of yttrium and gadolinium were present in the
film. It is to be understood that these quantities need not be
equal and in fact may be varied as desired.
Several combinations of film and substrate materials have been
illustrated as examples in Table 1 above. However, a number of
other combinations may be provided by combining at least two of the
elements of the film material with at least two of the elements of
the substrate material indicated in Table 2 below, wherein, if the
film material is to be used for providing single-wall magnetic
domains, one of the two elements thereof should be the element iron
(Fe).
---------------------------------------------------------------------------
TABLE 2
Film Compound Formula Substrate Compound Formula JQ-oxide JQ-oxide
J Portion Q Portion J Portion Q Portion
__________________________________________________________________________
cerium aluminum cerium gallium praseodymium gallium praseodymium
indium neodymium indium neodymium scandium promethium scandium
promethium titanium samarium titanium samarium vanadium europium
vanadium europium chromium gadolinium chromium gadolinium manganese
terbium manganese terbium iron dysprosium iron dysprosium rhodium
holmium holmium zirconium erbium erbium hafnium thulium thulium
molybdenum ytterbium ytterbium niobium lutetium lutetium tantalum
lanthanum lanthanum tungsten yttrium yttrium aluminum magnesium
calcium strontium barium lead cadmium lithium sodium potassium
__________________________________________________________________________
The elements of the group of lanthanides are herein defined as
cerium, praseodymium, neodymium, promethium, samarium, europium,
gadolinium, terbium, dysprosium, holmium, erbium, thulium,
ytterbium, lutetium.
Following deposition of a single-crystalline orthoferrite or garnet
layers on a substrate, useful devices may be made such as described
by U.S. Pat. No. 3,460,116. Referring to FIGS. 2 and 3, a shift
register is shown at 100. A similar shift register is substantially
depicted in U.S. Pat. No. 3,460,116 and its manner of operation is
discussed in detail therein.
The device 100 shown in FIGS. 2 and 3 which will therefore be made
by this process will be comprised of substrate 26 with film 29
deposited thereon. When the device at 100 having the capability of
producing, propagating and sensing single-wall domains is
completed, the configuration will include at least one insulating
layer 101 such as silicon monoxide (SiO) or Magnesium fluoride
(MgF.sub.2) which will be attached to film 29 and have the several
means for producing, propagating and sensing single-wall domains
embedded therein and held securely thereby.
One approach to preparing layer 101 includes evaporating a metallic
conductor 102 on the surface of film 29 through a suitable mask
superimposed on the surface of film 29, said mask having the
pattern of conductor 102 therein. This evaporation may be performed
in a chamber similar to that shown in FIG. 1, wherein the contents
of vessel 34 are metallic granules such as copper, gold, silver or
aluminum, the other vessel 35 being removed, temperatures adjusted
and oxygen flow eliminated. Following this step, the mask is
removed and vessel 34 may be loaded with the insulating granules
such as MgF.sub.2 which are evaporated and deposited as a film over
conductor 102 and over the remaining unexposed surface of film 29.
Thereafter, another mask having pattern of wire 103 may be
superimposed on the insulating surface and by having suitable
metallic material in vessel 34, the pattern of wire 103 may be
deposited in a similar manner as the pattern of conductor 102 was
deposited. After removing the mask of wire 103, an additional
coating of insulating material may be deposited over the surface of
wire 103 and over the remaining portions of the previously
deposited insulating film. A mask having pattern of wire 104 may
then be laid down over the insulating surface and additional
conductive material deposited by the same evaporation method used
to form wire 104. Similarly, wires 105 and 106 may be formed by
having the patterns thereof in masks as wire 104 and additional
conductive material deposited. Also similarly, the masks being
removed, additional insulating material is deposited over wires
104, 105 and 106 and over the unexposed insulating surface upon
which said wires have been deposited. A mask having pattern of wire
107 is then laid down over the surface and wire 107 is formed in a
similar manner to formation of the other wires on the insulating
surface. The mask is then removed and additional insulating
material is deposited over the wire 107 and the unexposed
insulating surface in the same manner as previously accomplished. A
mask having a pattern of wire 108 is then laid over the insulating
surface and conductor 108 is formed by the same vacuum deposition
method. Finally, the mask is removed and insulating material is
deposited over conductor 108 covering said conductor and possibly
portions of the remaining unexposed insulating surface, thereby
encapsulating all the wires within layer 101 which is now firmly
attached to the surface of film 29.
It is noted that in connection with the deposition of wires 104,
105 and 106 and at their crossover points, and possible crossover
with wires 102, 103, 107 and 108, that a wire need not be deposited
in its entirety at one time, which results in the requirement that
insulating material be deposited between these various wires at
their crossover locations. Suitable masks may be used in providing
portions of wire depositions and insulation depositions so that the
total number of individual depositions may be reduced.
It is noted that by using a suitable mask in conjunction with the
process of providing layer 101 to cover such portions as are not
desired to have a layer such as 101 formed thereon and by leaving
uncovered by the mask such portions as desired to be formed with
layers such as layer 101, a plurality of layers such as layer 101
on any one surface of film 29 or on groups of films such as 29 may
be produced in the same manner as layer 101 was produced.
FIG. 4 illustrates deposition of a film 29' on the other major
unexposed surface of wafer 26 and thereon layer 101'. Film 29' is
identical in substantive matter as film 29, and layer 101', is
identical to layer 101. Both films 29 and 29' are therefore
deposited in the same way, and both layers 101 and 101' are also
both deposited in the same way and may contain the identical wires
embedded therein. FIG. 4 is therefore illustrative of a multilayer
device having magnetic domains. It is also conceivable that
multiple films of magnetic nonmagnetic materials on top of each
other may be deposited sequentially on the same side of the
substrate surface, employing JQ combination for film formation from
Table 2 to produce the magnetic and/or nonmagnetic layers of films
and/or substrates.
A useful orthoferrite or garnet device at 100 will require means
101 for generating, propagating and detecting single-wall magnetic
domains in film 29. A current pulse in loop 103 provides means for
drawing a positive region from border 130 of device 100 up to
location 110, and a pulse on wire 104 at 111, isolates a portion of
the positive region at location 110, thereby generating a
single-wall magnetic domain thereat. By sequentially pulsing wires
104, 105 and 106 respectively at 111, 112, and 113, the single-wall
magnetic domain is propagated along the shift register shown herein
from location 110 to intermediate locations 125 and 126, ultimately
terminating at location 114. At location 114, an interrogation
pulse in wire 107 collapses the single-wall magnetic domain,
inducing a detection pulse in wire 108.
The shift register device has been discussed for the purpose of
enabling the illustration of the types of additional fabrication
processes required in connection with the orthoferrite or garnet
layer on a substrate in the form of a useful device. Other types of
devices may also require current carrying conductors, and in
addition, employ magnetic layers, semiconductor layers or external
optical light source and other detecting components. Wire 102 is
connected to an initializing circuit for providing a pulse therein
so as to rearrange the domains in film 29 to provide the border
thereof as explained in U.S. Pat. No. 3,460,116.
In another approach to preparing layer 101, the current-carrying
conductors may be metal films laid down by vacuum evaporation.
Typically, copper, aluminum, or gold may be used. The conductor
patterns may be defined by masking during evaporation, or the
entire area may be coated and the patterns defined by
photolithographic etching processes, well known in the
semiconductor device arts. Each of the conductors must be
electrically isolated from the others so that layers of insulation,
such as silicon monoxide (SiO) or magnesium fluoride (MgF.sub.2),
may be evaporated between metal evaporations as hereinabove
described. Here again, the region covered by the insulating
material may be limited by masking during evaporation or the entire
area may be coated and patterns defined by photolithographic
etching processes. The number of separate evaporation steps will
depend on the number of conductor crossovers, and the ingenuity in
designing patterns for conductor and insulator depositions.
For other types of devices which employ magnetic or semiconductor
layers on the surface of the orthoferrite or garnet films, suitable
layers may be deposited by vacuum evaporation or chemical vapor
deposition. Typically, magnetic nickel-iron alloy compositions may
be evaporated on certain regions of the orthoferrite layer to
provide small local fields which assist in holding or moving the
single-wall magnetic domains.
It should be noted that the wires shown in layer 101 or 101' could
have also been replaced by magnetic means communicating with the
film or films to create, propagate and/or sense the change in
position of the created and propagated single-wall magnetic
domains.
It should be also noted that the additional film 29' deposited on
the substrate as shown or in such other manner as described is also
of the pseudopervoskite type structure and single-crystalline.
Hence, due to the magnetization requirements, the components of
film formulation would be iron and the remaining metallic component
may be one or more of the elements detailed in Table 2. The
magnetic materials or compounds of films 29 or 29' will have a
first magnetization direction substantially orthogonal to an
imaginary plane parallel to the thickness of said film and
providing for at least one single-wall magnetic domain with a
second magnetization direction opposite to the first magnetization
direction and having a boundary unconstrained along said second
magnetization direction, said single-wall magnetic domain being
free to move in a plurality of directions substantially orthogonal
to the second magnetization direction. At least one of the
constituents of the JQ combination of the substrate wafer
formulation is different from at least one of the constituents of
the JQ combination of the film formulation. Such difference
stresses the film which may thereby contribute to a substantial
reduction in the area of the magnetic domain thus formed. The area
of the domain, by the means established for creating same, is
oriented orthogonally to the second magnetization direction, such
area lying in said imaginary plane.
* * * * *