JP2840434B2 - Crystal formation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a crystal, and more particularly to a method for forming a crystal in which a single crystal is selectively grown on a substrate having a surface having a low nucleation density. About.

The crystal forming method of the present invention is suitably used for electronic devices such as semiconductor integrated circuits, optical integrated circuits, and magnetic circuits, optical devices, magnetic devices, voltage devices, surface acoustic devices, and the like.

[Prior Art] Conventionally, a single crystal film used for a semiconductor device, an optical device, or the like has been formed by epitaxially growing a single crystal on a single crystal substrate.

For example, on a Si single crystal substrate (silicon wafer)
It is known that Si, Ge, GaAs, etc. are epitaxially grown from a liquid phase, a gas phase, or a solid phase, and that a single crystal such as GaAs, GaAlAs is epitaxially grown on a GaAs single crystal substrate. .

Using the semiconductor film formed in this manner, a semiconductor element and an integrated circuit, a light emitting element such as a semiconductor laser and an LED, and the like are manufactured.

In recent years, research and development of ultra-high-speed transistors using two-dimensional electron gas and super-lattice devices using quantum wells have been actively pursued.
MBE (molecular beam epitaxy) and MOCVD using ultra-high vacuum
(High-precision epitaxial technology such as metal organic chemical vapor deposition).

In such epitaxial growth on a single crystal substrate,
It is necessary to match the lattice constant and the coefficient of thermal expansion between the single crystal material of the base and the epitaxial growth layer.

For example, Si on sapphire, an insulator single crystal substrate,
Although it is possible to grow a single crystal film epitaxially, crystal lattice defects at the interface due to a shift in the lattice constant and diffusion of aluminum, which is a component of sapphire, into the epitaxial layer, etc., pose problems in application to electronic devices and circuits. Has become.

Thus, it can be seen that the conventional method for forming a single crystal film by epitaxial growth largely depends on the base material. Mathews and others are exploring combinations of substrate materials and epitaxial growth layers (EPITAXIAL GROWTH.Acade
mic Press, New York, 1975edited by JWMathews).

Also, the size of the substrate is currently about 6 inches for a Si wafer, and the enlargement of GaAs and sapphire substrates is further delayed.

Further, since the single crystal substrate has a high manufacturing cost, the cost per chip increases.

As described above, in order to form a single crystal layer on which a high-quality device can be manufactured by the conventional method, there is a problem that the type of the base material is limited to an extremely narrow range.

On the other hand, in recent years, research and development of a three-dimensional integrated circuit that achieves high integration and multifunctionality by laminating semiconductor elements in a normal direction of a base has been actively performed.

In addition, research and development of large-area semiconductor devices such as solar cells and liquid crystal pixel switching transistors in which elements are arranged in an array on inexpensive glass are becoming active every year.

What is common to both of them is that a technique of forming a semiconductor film on an amorphous insulator and forming an electronic element such as a transistor thereon is required. In particular, a technique for forming a high-quality single crystal semiconductor over an amorphous insulator is desired.

Generally, when a thin film is deposited on an amorphous insulator substrate such as SiO ₂ , the lack of long-range order of the substrate material results in
The crystalline structure of the deposited film is amorphous or polycrystalline. (Here, an amorphous film is one in which the short-range order of the nearest atom is preserved, but there is no longer long-range order.) A polycrystalline film is a collection of single crystal grains having no specific crystal orientation separated and separated by grain boundaries.) For example, when Si is formed on SiO ₂ by a CVD method, the deposition temperature Is about 600 ° C. or lower, amorphous silicon is obtained, and at temperatures higher than that, polycrystalline silicon having a grain size of several hundreds to several thousand degrees is obtained. However, the grain size of polycrystalline silicon greatly changes depending on the forming conditions.

Furthermore, a polycrystalline film having a large grain size of about a micron or millimeter has been obtained by melting and solidifying an amorphous or polycrystalline film with an energy beam such as a laser or a bar heater (Single-Crystal silicon on non-crystal).
−single-crystal insul-ators.Journal of crystal
Growth vol.63, No.3October, 1983edited by GWCulle
n).

When a transistor is formed on the thin film of each crystal structure formed in this way and the electron mobility is measured from the characteristics, amorphous silicon has a particle size of ~ 0.1 cm ² / V The polycrystalline silicon has a mobility of 1 to 10 cm ² / V · sec, and the polycrystalline silicon having a large grain size by fusion and solidification has the same mobility as that of the single crystal silicon.

From this result, it can be seen that there is a large difference in the electrical characteristics between the element formed in the single crystal region in the crystal grain and the element formed over the grain boundary.

That is, the deposited film on the amorphous has an amorphous or polycrystalline structure, and the device manufactured there has much lower performance than the device manufactured on the single crystal layer.
Therefore, as a use, a simple switching element,
Solar cells and photoelectric conversion elements are limited.

[Problems to be Solved by the Invention] As described above, since the long-range order does not exist on the amorphous substrate surface unlike the single-crystal substrate surface and only the short-range order is retained, the amorphous substrate surface is deposited. The structure of the thin film as it is, at best, can be only polycrystalline with disordered grain boundaries.
Since the amorphous substrate surface has no long-range order and no anisotropy that defines the crystal orientation (normal direction of the substrate and in-plane orientation), it is impossible to control the crystal orientation of the upper layer. there were.

That is, a problem in depositing a single crystal on an amorphous substrate is to establish a technique for controlling a grain boundary position and controlling a crystal orientation.

In the following, a description will be given of a conventional technique relating to control of the position of a grain boundary and control of a crystal orientation and its problems.

As for the control of the grain boundary position, it has been shown that the grain boundary position can be determined by artificially defining the nucleation position in advance (Japanese Patent Laid-Open No. 63-107016).
elective Nucleation based Epitaxy) (T.Yonehara, Y.Nishigaki, H.Mizutani, S.Kondoh, K.Yam
agata, T.Noma and T.Ishikawa, Applied Physics Letter
s vol. 12, pp. 1231, 1988). This technology uses Si ₂ N ₄ on SiO ₂
Is localized, and the nucleation site is formed. A single crystal of Si grows and collides with a crystal grown from an adjacent site to form a grain boundary and determine the position of the grain boundary.

However, the crystal orientation, particularly the in-plane crystal orientation, is not determined solely because Si ₃ N _{4 as} the nucleation surface is amorphous and has no anisotropy.

On the other hand, in 1987, HISmith showed for the first time that it was possible to control the crystal orientation of KCl deposited on an amorphous substrate surface by artificially imparting anisotropy by lithography to the surface of the amorphous substrate, and named it Graphepitaxy ( H.
I. Smith and DCFlanders, Applied Physics Letters v
ol. 32, pp. 349, 1978) (HISmith US Patent No. 4, 33)
3,792,1982).

After that, the grain growth of Ge thin film (T.Yonehara, HISmith,
CVThompson and JEPalmer, Applied Physics Letter
s vol 45, pp, 631,1984), initial growth of Sn (LSDarken a
nd DHLowndere, Applied Physics Letters vol.40, pp.
954, 1987) also confirmed that the artificial relief pattern on the surface of the substrate affected the crystal orientation.

However, KCl and Sn in Graphepitaxy were found to have an effect on the orientation of each separated crystal in the initial stage of its deposition. For continuous layers, crystals were grown by laser annealing after depositing Si (MW Geis, DAFla
nders and HISmith, Applied Physics Letters vol.3
5, pp. 71, 1979) and Ge solid-phase growth (T. Yonehara, HISmit)
h, CVThompson and JEPalmer, Applied Physics Lett
ers vol.45, pp.631, 1984).

However, even in the case of Si and Ge, although the orientation is controlled to some extent, crystal groups are arranged in a mosaic shape, and furthermore, the crystals have grain boundaries with crystals having slightly different crystal orientations. The position was disordered, and a single crystal was not obtained uniformly over a large area.

This is because the three-dimensional crystal orientations of the individual crystals do not completely match, and the nucleation position is not controlled in the surface relief pattern.

An object of the present invention is to provide a method for forming a crystal in which the position of a grain boundary is controlled and a single crystal having a plane orientation and an in-plane orientation is grown.

[Means for Solving the Problems] The method of forming a crystal according to the present invention comprises the steps of:
A cuboid or cubic original seed in which all surfaces are in contact with and surrounded by an insulator is arranged, and the original seed is melted and then solidified again to control the plane orientation and the in-plane orientation. A single crystal, a surface of the single crystal is exposed by removing at least a part of an insulator covering the single crystal, and the exposed single crystal is used as a seed crystal. It is characterized in that crystals are selectively grown.

 Hereinafter, the principle of the present invention will be described.

The plane orientation of the melt-solidified crystal is determined so that the free surface energy of the crystal, the interfacial energy with the substrate, and the like are minimized. For example, polycrystalline Si is melted and solidified on SiO _2, Si
The surface energy itself is stable in (111) orientation, but the interface energy of Si-SiO ₂ is stable in (100) orientation, and the stabilization factor of this interface energy acts strongly, resulting in (100) orientation. Is shown. However, although this Si film has a (100) orientation with respect to the plane of the substrate, the orientation in the plane of the substrate is not controlled at all. In addition, the film that has just melted and solidified forms a large number of grains (granules) because there are many random points in the plane where solidification begins.
As a result, random grain boundaries are generated.

Therefore, in the present invention, the inventors have considered a configuration in which the in-plane orientation of each grain is controlled, and the position of the grain boundary caused by a slight misalignment is also controlled.

First, in controlling the orientation, it was confirmed that the orientation perpendicular to the plane of the base can be controlled to a constant orientation by melting and solidifying the film material as described above. Since no information was given on the in-plane orientation, information on lateral orientation control was given by forming a side wall (plane) perpendicular to the substrate plane. The side wall was formed not only on one side but also on four sides perpendicular to each other, that is, a portion surrounded by the side was formed as a rectangular parallelepiped or a cube, and information on azimuth control was given from four directions only on the side. The cuboid or cube thus formed must be a single crystal that does not contain grain boundaries when melted and solidified, and the influence of the side walls must cover the entire cuboid or cubic original seed So
It must be designed to have a reasonable volume. Specific values will be described later.

The method of controlling the position of the grain boundary can be achieved by patterning a rectangular or cubic original seed at an arbitrary position. That is, if the original seed is patterned at any two points, the crystals grown from each collide at exactly the middle position of the two points to form a grain boundary. If this is patterned into, for example, lattice points with an interval of l, the grain boundaries will also be formed at the respective intermediate positions, and as a result, crystals of a square with one side of l will be regularly arranged vertically and horizontally. Although it seems that grain boundaries do not appear when the results where the plane orientation and the in-plane orientation are completely coincident with each other do not seem to occur, the seeds do not actually shift by 1 arc second in the vertical direction or the in-plane direction of the substrate. To form crystals,
It is difficult to grow and grain boundaries are formed. The point is that the position of the grain boundary is controlled, so long as it is within a range that does not cause a variation in device characteristics due to a variation in orientation during device fabrication. More specifically, the "edge" of the pattern edge generated in a normal photolithography and etching process or a deviation from a design value due to overetching, that is, an angle within several degrees is an allowable range.

A method of forming a crystal film in which both the plane orientation and the in-plane orientation are controlled on an insulating substrate by making full use of a seed crystal formed based on the above idea will be described in an embodiment.

(Example of embodiment) First, the shape and volume of an original seed will be described. As shown in FIG. 1 (A), the original seed is a rectangular solid (or a cube (a = b
= C)). This is because, when a certain direction is preferentially oriented with respect to one plane, if the plane is a rectangular parallelepiped or a cubic, all other planes are preferentially oriented with respect to the equivalent direction.

As for the volume, as described above, when the original seed is melted and solidified, it is small enough not to generate a grain boundary therein, and large enough that the area of the side surface can stably determine the in-plane orientation. Must be something. Specifically, the first
In FIG. (A), the value of a of the original seed is 0.
It is preferably 1 μm or more and 5 μm or less. More preferably 0.5μ
m to 2 μm, the optimum value varies depending on the material and the material of the base. The minimum value is determined by the limit value of the accuracy of the photolithography method used or the minimum area where the stabilization energy with the underlying interface can control the orientation, and the maximum value is determined when solidifying as described above. Is a value experimentally determined as a size at which no grain boundary occurs. However, this value also depends on the value of the height c of the side surface.

The value of the height c of the side face of the rectangular parallelepiped or cube is preferably 01
μm or more, 2 μm or less, more preferably 0.3 μm or more,
It is 1 μm or less. The optimum value differs depending on the sizes of a and b and the material of the original seed. The minimum value is determined as a minimum value at which the side surface influences the determination of the in-plane orientation, and the maximum value is determined as a size that does not cause a grain boundary when solidifying.

All surfaces of the original seed must be covered with an insulator, as shown in FIGS. 1 (B), (C) and (D). FIGS. 1B and 1C show a so-called “embedded type”. This is a type in which a part of the surface of the insulator substrate 1 is patterned in advance into a square or a rectangle and etched to form a rectangular parallelepiped or cubic space, and the original seeds 2 are embedded therein. The insulating film 3 is formed. In this case, the original seed to be embedded has a top surface flush with the surface of the insulator as shown in FIG.
As shown in FIG. 1 (C), the upper surface of the original seed may be lower than the surface of the insulator, that is, the height c of the original seed may be smaller than the etching depth.

On the other hand, FIG. 1 (D) shows a “sidewall forming type”. In this method, an original seed 2 is first patterned into a rectangular parallelepiped on an insulator substrate 1 or a substrate whose surface layer is made of an insulator. If the original seed is a material capable of forming an oxide stably, the exposed surface may be oxidized, or an insulator may be deposited by CVD or the like.

In any case, the material of the wall surface does not necessarily have to match the material of the base 1. For example, in the above “embedded type”, after forming a rectangular parallelepiped or cubic space in the base, an insulating film is formed in this space, the original seed 2 is buried therein, and the insulating film 3 is formed thereon. It is possible.

1 (B), 1 (C) and 1 (D), the upper surface of the original seed is covered with an insulating film 3 which is an insulating material. This means that when the original seed is melted, aggregation or volatilization occurs. It is not applied. The insulating film 3 on the upper surface may be formed by oxidizing the original seed or by depositing an insulator by CVD or the like.

The material of the original seed to be melted can be a semiconductor element such as Si, Ge, Sn, or the like, or a metal, alloy, compound, mixture, or the like such as Au, Ag, Cu, Pt, or Pd.

The insulator (substrate) serving as the non-nucleation surface is made of SiO ₂ , Si _x N _y , SiO
N or the like is used. The same applies to the insulator covering the upper surface.

Next, a process flow will be described with reference to FIG. First, as described with reference to FIG. 1, a rectangular parallelepiped seed 22 is formed on the surface of a substrate 21 having an insulating surface, and all surfaces including the upper surface (the upper surface is covered with an insulating film 23) are formed of insulating material. (FIG. 2 (A)). Next, the substrate 2 is heated at a temperature equal to or higher than the melting point of the original seed 22. As a heating method, an energy beam such as a laser beam or an electron beam is used, or a method such as lamp heating is used.

When all the original seeds on the substrate have melted, the heating is stopped and the molten original seeds are solidified. Then, the insulating film 23, which is an insulator, covering the upper surface of the original seed is removed to expose the single crystal seed crystals 25a and 25b whose in-plane orientation is controlled (FIG. 2 (B)).

The exposed seed crystals 25a and 25b are selectively grown by a selective CVD method. For example, if you want to grow Si, as a source gas, chlorosilane based SiCl ₄ , SiHCl ₃ , SiH ₂ Cl ₂ etc., SiH ₄ , S
A silane type such as i ₂ H _{6 and} a fluorosilane type such as SiF ₄ and SiH ₂ F ₂ can be used. At this time, the growth is performed by using an HCl gas or an HF gas having an etching action together with an H ₂ carrier gas. The growth temperature and pressure vary depending on the type of gas and the composition of the insulating substrate.
It is performed in the range of orr to 250 Torr. The grown crystal 26a grows while being surrounded by facets unique to single crystals,
When it collides with a crystal 26b grown from the adjacent seed crystal 25b,
A grain boundary 28 is formed near the center of the two seed crystals 25a and 25b (FIG. 2 (C)).

If it is desired to form an electronic device or the like on the grown crystal, the crystal is polished if necessary, and the single crystal thin films 27a, 27a
What is necessary is just to form b. Since the position 28 of the grain boundary in this case is known, it is possible to avoid this, and if a device is formed on one island, the same or higher performance as a device on a single crystal can be obtained.

Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

First Embodiment A first embodiment of the present invention will be described with reference to FIGS. 3 (A) to 3 (C) and FIGS. 2 (A) to 2 (D).

First, as shown in FIG. 3 (A), a 4-inch Si wafer was prepared as a substrate 31, and the surface of the substrate was oxidized by 1 μm to form an SiO ₂ layer 32, which was used as a substrate. Next, a part of the surface of the SiO ₂ layer 32 was patterned into a square by a normal photo process, and the square part was etched by RIE (reactive ion etching) to a part of the SiO ₂ layer. At this time, the length of one side of the square (a = b) is 0.8 μm, and the depth c of the etched portion is
Was set to 0.4 μm. A plurality of the same concave portions 33 were formed in a matrix with an interval 1 = 60 μm in both the vertical and horizontal directions.

Next, as shown in FIG. 3 (B), LPCVD
The polycrystalline Si34 was deposited to a thickness of 0.4 μm by using the method. Further polycrystalline S
A resist 35 was coated on the i34 so that the surface became flat.

Next, as shown in FIG. 3 (C), both layers are etched back by RIE until the surface of the SiO ₂ layer 32 is exposed under the condition that the etching rates of the resist 35 and the polycrystalline Si 34 are the same (described below). Then, the polycrystalline Si 34a was left only in the recess 33. Note that the etch-back condition at this time was such that the resist OFPR5000 was used, and the gas used was C ₂ F ₆ / O ₂ as the RIE condition.
= 80/35 (sccm), pressure 50pa, output 2kw.

Next, as shown in FIG. 2A, a 0.6 μm SiO ₂ layer 23 was deposited on the flattened surface by normal pressure CVD. Using a lamp heating device, infrared light is irradiated only from the substrate surface side (the side with polycrystalline Si), and the set surface temperature is 1420 ° C.
After heating for 30 seconds, the heating was stopped. By employing such a heating method, a state can be created in which only the polycrystalline Si22 on the surface is melted and Si on the substrate is not melted.

Next, as shown in FIG. 2 (B), the 0.6 μm SiO ₂ layer 23 used as the cap layer was removed with buffered hydrofluoric acid to expose the surfaces of the single-crystallized Si 25a and 25b.

Next, as shown in FIG. 2 (C), the single crystallized Si25a,
Using 25b as a seed crystal, a Si single crystal was selectively grown. The growth conditions were SiH ₂ Cl ₂ as a source gas, HCl as an additive gas for etching, and H ₂ as a carrier gas at 0.53 and ₂ .
The substrate was placed in a gas mixed at a rate of 0,100 (/ min), the temperature was 1030 ° C., the pressure was 80 Torr, and the growth was performed for 100 minutes. The grown crystals 26a, 26b are seed crystals 25a, 25b, respectively.
And formed a grain boundary 28. The facet shape and facet direction of the appearance were almost the same for all crystals. The obtained crystal was oriented (100) in the direction perpendicular to the substrate, and no other orientation could be observed when measured by X-ray diffraction. Regarding in-plane orientation, ECP (Electron Ch.
When analyzed by an anneling pattern), the patterning direction of the seed crystal was ± 5 from the equivalent direction of (100).
The rotation range was within ゜.

Next, as shown in FIG. 2 (D), the crystal was planarized in order to form an element such as a transistor on the crystal thus obtained. This is the same process as polishing a normal Si wafer, that is, using a weak alkaline solution in which abrasive grains are suspended, rough polishing and finish polishing are performed in the order of crystals 27a,
This was performed until 27b became 1 μm thick. Then, when one n-MOS transistor on one island of the flattened crystal is formed using a normal semiconductor process,
There was almost no variation in the electrical characteristics of each transistor, and the electrical characteristics and the variations were almost the same as those of the n-MOS transistor on the Si wafer formed at the same time.

Second Embodiment A second embodiment will be described with reference to FIGS. 4 (A) to (D) and FIGS. 2 (A) to (D).

First, as shown in FIG. 4 (A), 0.1 μm of polycrystalline Si 42 is deposited on a substrate 41 of a 4-inch diameter fused quartz substrate by LPCVD, and a Si ₃ N ₄ film 43 is further deposited thereon by LPCVD. Was deposited 0.05 μm.

Next, as shown in FIG. 4 (B), the polycrystalline region 42a and the Si ₃ N ₄ film 43a of the 1 × 1 μm ² vertical and horizontal island regions are patterned at 50 μm intervals, and the other portions of the Si ₃ N ₄ film are formed. 43 and polycrystalline Si film 42
Were all etched by RIE.

Next, while as shown in FIG. 4 (C), a polycrystalline Si42a isolated like islands, with the cap of the Si ₃ N ₄ film 43a 0.1
μm was oxidized. Square polycrystalline Si42a seen from above the substrate
Only the peripheral portion of the oxidation, the wall 44 of polycrystalline Si42a is SiO ₂
Thus, the shape was surrounded by the cap of the Si ₃ N ₄ film 43a and the underlying fused quartz substrate 41.

Next, in this state, infrared light is irradiated from both the upper and lower sides of the substrate using a lap heating device, and the set temperature is set at 1500 ° C for 60 hours.
Heated for seconds. Since the substrate 41 of the fused quartz substrate hardly absorbs infrared light, the temperature of the substrate itself rises only up to about 400 ° C., but the Si film 42a, which absorbs a large amount of infrared light, has melted beyond its melting point.

Next, as shown in FIG.
When the molten Si was turned off and solidified into a single crystal, the cap Si ₃ N ₄ layer 43a was heated with hot phosphoric acid (H ₃ PO ₄ , 300
C.). Then, the SiO ₂ 44 on the side wall of the single crystal Si 45 was etched using buffered hydrofluoric acid.

Thereafter, as shown in FIGS. 2 (C) to (D), the first
In the same manner as in the steps of the example, a single crystal of Si was selectively grown using single crystallized Si45 as a seed crystal. The growth conditions were as follows.

SiH ₂ Cl ₂ : HCl: H ₂ = 0.53: 1.6: 100 (/ min), 1030 ° C, 8
The orientation of the crystal obtained at 75 Torr for 75 minutes is controlled similarly to that obtained by the method of the first embodiment, and the n-MO
The S transistor also had the same characteristics as the transistor made in the first embodiment.

(Third Embodiment) Polycrystalline Si is patterned in the same process as the first embodiment,
The state shown in FIG.

Next, using a 5145 ° wavelength of an Ar ion laser, this was irradiated to polycrystalline Si24 and melted. Laser output is 5W
The beam diameter was 0.5 mm, and scanning was performed at a speed of 20 mm / sec. The solidified Si became a single crystal, and the single crystal was grown under the same conditions as in the first embodiment using this as a seed crystal. The orientation of the obtained crystal is controlled similarly to that obtained by the method of the first embodiment, and the n-MOS transistor formed on this crystal has the same characteristics as the transistor formed in the first embodiment. Was.

(Fourth Example) In the same process as in the first example, the material serving as the original seed was patterned to obtain the state shown in FIG. 2 (A). However, the material of the original seed was not polycrystalline Si but polycrystalline Ge. Polycrystalline Ge was formed by an evaporation method. Since the melting point of Ge is 937 ° C., which is sufficiently lower than that of Si, it was annealed and melted at a set temperature of 1000 ° C. for 20 minutes in an annealing furnace used in a normal silicon process.

A single crystal of Si was selectively grown using the extracted single-crystallized Ge as a seed crystal. This crystal is also (100) oriented in the vertical direction of the substrate, similar to the case where Si is used as a seed crystal.
The in-plane orientation also formed a plane equivalent to (100) along each plane direction of the rectangular parallelepiped in the seed crystal formation region.

(Fifth Embodiment) First, as shown in FIG. 5 (A), in the first embodiment, similarly, polycrystalline Si embedded in a concave portion on the surface of a substrate 51 is melted by lamp heating, and a single crystal having a controlled orientation is similarly formed. Crystal seed 55 was formed. However, the substrate 51 was not a Si wafer but a fused quartz substrate.

Next, as shown in FIG. 5 (B), 0.1 μm of polycrystalline Si56 was deposited on the surface of the substrate by LPCVD, and then Si ions were ion-implanted to convert the deposited polycrystal into amorphous Si. . The implantation conditions at this time were as follows: acceleration voltage 60 kv, dose amount 1 × 10 ¹⁵
It was cm ^2. This condition is such that the projection range is slightly closer to the Si film side than the interface between the polycrystalline Si and the fused quartz substrate.

Next, as shown in FIG. 5C, the substrate was annealed at 600 ° C. for 50 hours in an annealing furnace in an N ₂ atmosphere. The amorphous Si film 56 has a single crystal seed crystal 55 as a starting point.
Crystal 57 grew in the solid phase. As a result, a crystal film in which the orientation was aligned to (100) was obtained.

[Effects of the Invention] As described above, according to the present invention, an original seed that is a rectangular parallelepiped or a cubic in which all surfaces are in contact with an insulator and becomes a single crystal when melted and solidified is melted and solidified. As a result, the original seed changes from a non-single crystal to a single crystal having substantially the same plane orientation and in-plane orientation. By selectively growing a semiconductor material or the like using this single crystal as a seed crystal, the position of the grain boundary is controlled, and the plane orientation and the in-plane orientation are uniform.
I can form.

ADVANTAGE OF THE INVENTION According to this invention, the position (number) and orientation of the grain boundary which causes the dispersion | variation of the characteristic in SOI device can be controlled completely, and there exists an effect which can form an element with high uniformity.

[Brief description of the drawings]

FIG. 1 (A) is an explanatory view of the shape of an original seed in an embodiment of an embodiment of the method for forming a crystal of the present invention, and FIGS. 1 (B) to 1 (B).
(D) is a sectional view for explaining the shape of the original seed and the insulator substrate. 2 (A) to 2 (D) are process diagrams showing the manufacturing process of one embodiment of the method for forming a crystal of the present invention. 3 (A) to 3 (C), 4 (A) to 4 (D), and 5 (A) to 5 (C) are process diagrams showing manufacturing steps of an embodiment of the crystal forming method of the present invention. is there. 1,21,41,51 …… Base, 2,22,34a, 42a …… Original seed, 3,23…
... insulating film, 25a, 25b, 45, 55 ... seed crystal, 26a, 26b ... grown single crystal, 27a, 27b ... flattened single crystal, 28 ...
Grain boundary, 31 ...... substrate, 32 ...... SiO ₂ layer, 33 ...... recess, 34,4
2, 42a, 56 ... polycrystalline Si, 35 ... resist, 43, 43a ...
The Si ₃ N ₄ film, 44 ...... Si ₂ walls, 57 ...... crystals.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/205 H01L 21/84 H01L 27/12 C30B 25/18 C23C 16/52

Claims (1)

(57) [Claims] 1. A cubic or cubic original seed, all surfaces of which are in contact with an insulator and are surrounded on a surface of a substrate having a surface with a low nucleation density or in a recess formed in the substrate. Then, the original seed is melted and then solidified again to form a single crystal with a controlled plane orientation and in-plane orientation, and the single crystal surface is exposed by removing at least a part of an insulator covering the single crystal. A method for forming a crystal in which the exposed single crystal is used as a seed crystal and a crystal growth process is performed to selectively grow the single crystal starting from the seed crystal.