JPH0127999B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to improving the crystallinity of solid films grown on the surface of a solid support;
In particular, the present invention relates to enhancing epitaxy (hereinafter referred to as epi-positioning) to provide regularly oriented thin films of relatively large area by a practical method.

Much modern engineering uses thin solid coatings on the surface of solid supports. Thermal evaporation, DC sputtering,
A number of methods have been used to deposit such thin films, including RF sputtering, ion beam deposition, chemical vapor deposition, plating, molecular beam deposition, and deposition from the liquid phase.

The structure of thin films can be amorphous (i.e., the film atoms are not arranged in any crystalline order), polycrystalline (i.e.,
A film is composed of many small regions, and in each region, atoms are arranged in a regular crystalline order.
(their crystal axes do not coincide with each other), preferred orientation (i.e., the film is composed of many small regions, in each region the atoms are arranged in a regular crystalline order, and the majority of the small regions one or more of the crystal axes are parallel) or epi-configured (ie, the film is primarily of a single crystal orientation). The thin film is made of the same material (i.e. the same element or compound) as the support.
or may have a different chemical composition from the support.
If the membrane has an epi configuration, the former is called a "homoepi configuration" and the latter is called a "hetero epi configuration."

In general, techniques for obtaining high quality amorphous and polycrystalline films (particularly metals) are well developed and well understood. However, there are few techniques for obtaining high quality epitaxially aligned films and suitable alignment films, and only a few combinations of films as top layers and base layers have been successful. In most cases, the membranes exhibit a high degree of crystallinity defects [STPicraux, GTThomas, “Correlation of ion channeling and electron
microscopy results in the evaluation of
heteroepitaxial silicon”J.Appl.Phys.vol44,
pp. 594-602 (1973)]. In some cases, high temperatures are required to achieve epitaxial placement or preferred orientation, and differences in thermal expansion of the membrane and support cause increased stress and sometimes tearing when the sample is cooled to room temperature. There are a number of important cases (particularly in electronic, acoustic, and optical devices) in which the use of alignment coatings, epitaxial alignment coatings, etc.
With three notable exceptions, such films are not of sufficient quality or do not have a sufficient number of combinations (coating and support) or orientation to meet the requirements.

Current or conventional methods for growing well-oriented and epitaxially aligned films are based on deposition parameters (e.g. Composition and orientation of the support, attachment method,
based on the selection of combinations (deposition rate, temperature, pressure).
A fundamental drawback of this method is that it is not always possible to control or reproduce all of the factors that influence the nucleation and growth of the coating. Moreover, the number of epitaxial configuration combinations and orientations to which this method can be applied is limited.

An important object of the present invention is to overcome the drawbacks of conventional methods for obtaining epitaxially aligned and well-oriented films, and to directly control the nucleation, growth, and orientation of film growth on solid surfaces in a controllable manner. The goal is to provide technology that has an impact.

A second object of the present invention is to control the crystal orientation of a thin film grown on a solid surface for the above purpose.

A third object of the present invention is to achieve one or more of the above two objects while reducing the number and size of defects in crystalline thin films grown on solid surfaces.

A fourth object of the present invention is to obtain an epitaxially aligned or well-oriented coating at a moderate temperature, thereby avoiding the generation of stresses induced by differences in thermal expansion between the film and the support while achieving one of the above three objects. The goal is to achieve one or more of the following:

The present invention proposes that the phenomena of nucleation, growth, and changes in crystal orientation that occur in the initial stages of film formation on a solid surface can be combined with a surface relief structure and a point defect (point defect).
based on the discovery that it is influenced and controlled by It is well known that natural defects such as steps or point defects on crystal surfaces can function as nucleation sites for deposited substances. Some examples of the effects of point defect arrays on nucleation and growth in epitaxially placed films include the paper by Distler et al. [GIDistler, “Epitaxy as a Matrix
“Replicating Process”, Thin Solid Films,
vol32, pages 157-162 (1976); GIDistler, VP
Vlasor, VM Kaneosky, “Orientational and
Long Range Effects in Epitaxy”，Thin Solid
Films, vol. 33, pp. 287-300 (1976)]. Distler et al. further suggest that point defects on a surface naturally occur approximately in the form of a matrix or lattice, and that general epitaxial placement and orientation effects in crystallization are due to the presence of the point defect lattice.

According to the invention, surface relief steps or arrays of point defects are intentionally created on the solid surface, whereby the process of coating formation and growth is controlled in a controlled manner.

Creating a regular array of surface relief steps or point defects on a solid surface to enhance the crystallinity of a thin solid film grown on a solid surface is diametrically opposed to conventional methods for growing thin films. Conventional methods seek to eliminate as much natural surface relief steps or point defects as possible.

The present invention includes a method for arranging defects, such as surface relief steps or point defects, on a solid surface;
Included are methods in which the deposited material is deposited on a solid surface in such a way that the crystal orientation of the deposited material is controlled by an array of surface relief steps or point defects.

For a given combination of membrane and support as an overlying layer and for a given deposition method, the surface relief structure or geometric pattern of point defects that is valid for the nucleation and growth that is applicable for that combination and deposition method. depends on the exact mechanism. This geometric pattern is generally a simple grid with repeating elements spaced apart by a distance of 1/2 μm or less (in some cases 1 μm is sufficient). The depth of the surface relief structures can vary from less than 1 nm to about 1 μm. Preferably, there are sets of steps and/or point defects, each set surrounded by a plane that is generally perpendicular to the support surface and generally parallel to a plane that surrounds another set. The angle formed by the intersecting planes is 30°, or an integer multiple of π/6 radians). Numerous other features, objects, and advantages of the invention will become apparent from this description when read in conjunction with the accompanying drawings.

FIG. 1 is a partial cross-sectional view of a solid body coated with a thin film according to the method of the invention.

FIG. 2 is a cross-sectional view of a combination block illustrating the use of soft x-rays to form controlled relief patterns on a solid support in accordance with the present invention.

FIG. 3 is a cross-sectional view of the relief pattern formed as shown in FIG. 2.

FIG. 4 is a sectional view showing the relief structure after etching.

FIG. 5 shows a means for depositing thin layers onto a solid support using an ion beam sputter.

FIG. 6 is an enlarged perspective view of a solid support having regularly spaced steps according to the method of the invention, suitable for receiving epitaxial or preferred orientation layers.

The accompanying drawings, in particular Figures 1-4, illustrate a method for creating relief structures on solid surfaces according to the present invention. As seen in the partial cross-section of FIG. 1, a solid body 1 is coated with a radiation-sensitive polymer film 2 (commonly referred to as "resist").
One example of such a membrane material is polymethyl methacrylate. This film was then exposed to X as shown in Figure 2.
Line lithographic printing (HISmith, DL, July 3, 1973)
American patent granted to Spears, E. Stern
No. 3743842 “X-ray Lithographic Apparatus
The mask 3 consists of a membrane 4 (relatively transparent to X-rays) and an absorber 5 (formed in a pattern of periodic or semi-periodic elements such as a grating). ).
Soft x-rays 6 from a source 7 pass through a mask 3 so that the shadow of the absorber pattern 5 is projected onto the surface of the radiation-sensitive polymer 2.

After exposure, a relief pattern is created in the radiation-sensitive polymer by a development process. In the case of polymethyl methacrylate, development can be accomplished, for example, in a solution of 40% dimethyl isobutyl ketone and 60% isopropyl alcohol, which removes the areas of the polymer directly exposed to soft X-ray radiation. The areas protected from X-ray radiation by the shedding of the absorber pattern 5 of the polymer 2 remain undissolved and therefore become floating parts of the relief, as shown in FIG. Many other radiation sensitive polymers and development methods can be used within the principles of the present invention.

Patterns on radiation-sensitive polymer films can be created using photolithography, electron beam lithography, and holographic methods.
It can be exposed by a number of other methods, including graphic methods. X-ray plate techniques are particularly well suited because they can expose patterns with linewidths of 1000 Å or less with sharp vertical sidewalls. Using carbon K X-rays with a wavelength of 44.7 Å, it seems possible to resolve 50 Å using the X-ray plate method. Polymer relief structures can also be created by in situ polymerization.

After the creation of the polymeric relief structure 8, the solid support 1 is etched to remove the polymer, thereby leaving the relief structure 9 on the surface of the solid, as seen in FIG. The method of etching depends on the chemical properties of the solid and the resistance of the polymer to various etching conditions. For example, if PMMA is used as the polymer relief pattern material, a relief structure with sharp vertical sidewalls can be etched into the SiO ₂ structure by reactive ion etching.

Although steep vertical sidewalls are preferred, the principles of the invention are also applicable to discontinuities formed by sloped sidewalls, including those formed by undercuts. Alternatively, ion beam etching, wet chemical etching or gas plasma etching can be used as the etching method. An alternative method to create relief structures on _SiO2 surfaces is
The method is to deposit SiO ₂ or SiO or a mixture of both onto the polymer relief structure and then dissolve the polymer in a suitable organic solvent. This results in
A relief structure of SiO ₂ , SiO, or both is left on the surface. To convert this relief structure into high-quality SiO ₂ , the support can be fired in an oxygen oven at temperatures at or near 1000°C.

An array of point defects can be created on a support surface by exposing the support surface to radiation in a pattern. For example, a line of point defects can be created by scanning a high-energy, highly focused electron beam over a sample surface in a suitable pattern. Alternatively, a pattern of point defects can be created using ion bombardment through a mask. High-energy photons can also be used.

After creating a relief structure or array of point defects on a solid surface, a substance is deposited on the surface to form a thin film. This relief structure or array of point defects has the effect of controlling the nucleation and growth of the film, so that
A film with a predetermined crystal orientation and low point defect density is obtained. A number of methods can be used to deposit thin film materials onto solid surfaces having surface relief structures or arrays of point defects. These methods include evaporation, RF sputtering, DC sputtering, ion beam sputtering, chemical vapor deposition, molecular beam deposition, plating, and deposition from the liquid phase. An ion beam sputter as shown in FIG. 5 was used and the material deposited on the SiO ₂ support was germanium. An ion source 10 emits an ion beam that impinges on a target 12 of adherent material. A substance 13 sputtered from a target 12 is deposited on a support 1 having a surface relief structure 9 .

The present invention lends itself to the production of devices with thin films of 0 to 3 microns thick, but also lends itself to the growth of larger crystals. The raw film can serve as a seed from which larger crystals are grown using conventional crystal growth methods.

FIG. 6 shows a highly enlarged perspective view of a regularly stepped support according to the invention capable of receiving an epitaxially placed surface layer. There are sets of steps, each bounded by a plane parallel to the plane surrounding the other sets of steps. The intersecting enclosing planes intersect at 90° or π/2 radial (30° or an integer multiple of π/6 radial). The planes may intersect at 60° or π/3 radians (which is also an integer multiple of 30° or π/6 radians). It is also preferred that adjacent parallel surrounding planes be less than 1 micron (typically 500 Å or 1/20 micron as shown in Figure 6). The depth of the step or point defect is from 1 atom to 1/2
Preferably it is in the micron range.

Having thus described novel configurations and techniques for providing relatively large area epitaxial films and well-oriented films in an economical, practical and repeatable manner, those skilled in the art will appreciate the concepts of the present invention. Obviously, many changes and modifications may be made without departing from the specific arrangements and techniques disclosed herein.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a solid body coated with a thin film according to the method of the invention. FIG. 2 is a cross-sectional view of a combination block illustrating the use of soft x-rays to form controlled relief patterns on a solid support in accordance with the present invention. FIG. 3 is a cross-sectional view of the relief pattern formed as shown in FIG. 2. FIG. 4 is a sectional view showing the relief structure after etching. FIG. 5 shows a means for depositing thin layers onto a solid support using an ion beam sputter. FIG. 6 is an enlarged perspective view of a solid support with regularly spaced steps according to the present invention suitable for receiving layers of epitaxial placement or preferred orientation. DESCRIPTION OF SYMBOLS 1... Solid support, 2... Polymer film (resist), 3... Mask, 5... Absorber, 6... Soft X-ray, 7... X-ray source, 9... Relief structure, 1
0...Ion source.

Claims (1)

[Claims] 1. At a predetermined position on the surface of a solid base material,
intentionally forming a plurality of artificial defects having predetermined geometric shapes selected from the group consisting of: 1) artificial point defects; and 2) artificial surface relief structures, wherein the adjacent artificial the separation distance between artificial defects is narrowed to less than 1 μm so that both adjacent pairs of artificial defects can sufficiently influence the crystal orientation of the thin film to be deposited; and then the thin film is deposited on said surface. forming a substantially epitaxial or preferably oriented layer in said thin film by causing said thin film to be adjacent to each other while said forming material is in contact with said artificial defect; a layer of crystalline orientation substantially influenced by the geometry of artificial defects); 2. The method of claim 1, further comprising the step of maintaining substantially equal inter-row separation of the artificial defects. 3. The method of enhancing epitaxy and preferred orientation according to claim 1, further comprising the step of making the artificial defects into cross-arrays. 4. The method of claim 3, further comprising the step of maintaining substantially equal separation between parallel rows. 5. The method of enhancing epitaxy and preferred orientation according to claim 1, further comprising the step of forming an artificial point defect within the artificial defect. 6. The method of enhancing epitaxy and preferred orientation according to claim 1, further comprising the step of forming an artificial step within the artificial defect. 7. The method of claim 6, further comprising the step of arranging said artificial steps at substantially equal intervals. 8. The method of claim 6, further comprising the step of forming an artificial step substantially perpendicular to the artificial step. 9 The size of each defect in the direction perpendicular to the substrate surface is
The method of claim 1, further comprising the step of forming said artificial defects in the range of 1 atom to 1/2 micron. 10. The method of enhancing epitaxy and preferred orientation according to claim 3, further comprising the step of arranging the artificial defects in rows that intersect at an angle that is an integral multiple of π/6 radians. . 11. The method of enhancing epitaxy and preferred orientation according to claim 3, further comprising the step of forming an artificial point defect within the artificial defect. 12. The method of claim 3, further comprising the step of forming an artificial step within the artificial defect. 13. The method of claim 6, wherein said artificial step has substantially vertical walls. 14. The method of enhancing epitaxy and preferred orientation according to claim 6, wherein the artificial step has an inclined wall. 15. The method of claim 1, wherein said artificial surface relief structure comprises a structure having a preselected shape surrounded by substantially horizontal surfaces.