JPH059089A - Method for growing crystal - Google Patents

Abstract

PURPOSE:To stably obtain the crystal with high productivity by providing an island-shaped nonsingle crystal semiconductor thin film on an insulator base body and once melting the thin film, then recrystallizing the melt and growing the crystal by the single crystal thereof. CONSTITUTION:The island-shaped semiconductor thin film is provided on the amorphous insulator base body or the base body deposited with the amorphous insulator layer on the surface. This semiconductor thin film is then once melted by the heat treatment using lamp heating and is then recrystallized, by which the film is changed to the single crystal of the single body. The semiconductor single crystal is grown with the formed single crystal as a seed crystal. The high productivity is attained since beam annealing by a laser, etc., is not used according to the above-mentioned method. Since the operation is in the simple system of the two, i.e., melting and solidifying, the dependency on the fluctuation in the area of the island-shaped semiconductor film to be patterned first is extremely little and the crystal is stably obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a semiconductor single crystal thin film, and more particularly to a method for growing a crystal suitable for growing a silicon thin film for forming a high performance electronic device having an SOI structure.

[0002]

2. Description of the Related Art A so-called SOI structure in which an electronic element is formed on a semiconductor thin film on an insulating substrate is expected to be applied to a high-performance element because of advantages such as reduction in parasitic capacitance between elements and between the element and the substrate. ing. However, when the insulating substrate is amorphous, the film deposited on it is usually amorphous or at best a polycrystalline film, which is a major obstacle to improving the performance of the device. Therefore, an attempt has been made to form a device on the non-single crystal film deposited on the insulator substrate by annealing the entire surface with a laser beam or an electron beam to form a single crystal (Electronics, Nov.22.pp039- 40,1979).
In addition, the portion to be annealed by a laser beam or an electron beam is not in the entire surface but in a pre-patterned island-shaped region, and thereby one element is formed in a specific single-crystallized region (JP-A-59-59). No. 210638), and similarly, a method of making an island region into a single crystal by laser or electron beam annealing and growing the crystal as a seed crystal (Japanese Patent Publication No. 60-46074). The purpose of single-crystallizing the island region as one element region or epitaxially growing it as a seed crystal is to avoid grain boundaries formed along the beam sweep direction and to enlarge the single crystal region.

In the field of SOI technology for growing a plurality of single crystals on an insulating substrate without using an energy beam, for example, a method based on selective nucleation based on a difference in nucleation density between surface materials is proposed. Has been (T. Yonehara
et al. (1987) Extended Abstracts of the 19th SSDM p
191). This crystal forming method will be described with reference to FIG. First, as shown in FIG. 3-A, regions 302 and 302 'of appropriate diameter having a surface having a higher nucleation density than the surface 303 are arranged on a substrate 301 having a surface 303 having a low nucleation density at appropriate intervals. Set up. When this substrate 301 is subjected to a predetermined crystal formation treatment, deposit nuclei 304, 304 'are generated only on the surfaces of the regions 302, 302', and no nucleation is generated on the surface 303 (Fig. 3-B). ). So area 302,
The surface of 302 'is called a nucleation surface and the surface 303 is called a non-nucleation surface. When the nuclei 304 generated on the nucleation surface 302 are further grown, they become crystal grains 305 (FIG. 3-C), and the nucleation surface 3
The grain boundary 307 is formed by growing beyond the region 02 to reach the non-nucleation surface 303 and eventually coming into contact with the crystal grain 305 'grown from the adjacent nucleation surface 302'. Conventionally, in this crystal forming method, the nucleation surfaces 302 and 302 ′ are
Amorphous Si ₃ N ₄ is used for the non-nucleation surface 303, SiO ₂ is used for the non-nucleation surface 303, and a plurality of Si single crystals are formed by the CVD method (see the above article), and SiO _{2 is used} for the non-nucleation surface 303
An example in which Si ions are implanted into the non-nucleation surface 303 by a focused ion beam to form regions to become the nucleation surfaces 302 and 302 ', and a plurality of Si single crystals are formed by the CVD method (1988 th. 35th application Joint Lecture on Physics, 2
8p-M-9) has been reported. This crystal growth method is hereinafter referred to as "selective nucleus growth method".

Further, it is similar to the above crystal growth method,
A technique for forming a seed crystal of a semiconductor crystal by utilizing an aggregation phenomenon instead of selective nucleation and selectively growing the seed crystal has been reported (1989, 50th Academic Meeting of Applied Physics, 27a-C). -11). In this crystal formation method, a non-single-crystal semiconductor thin film is arranged on an insulator base at an appropriate diameter and at an interval, and this base is subjected to heat treatment in a hydrogen atmosphere, whereby the non-single-crystal semiconductor film is aggregated. And the crystallinity changes to a single crystal while changing the shape into a hemisphere. The obtained single crystal is used as a seed crystal to selectively grow the crystal. Note that this crystal growth method is hereinafter referred to as "aggregated seed crystal growth method".

[0005]

[Problems to be Solved by the Invention]
Among the methods of forming the I structure, the first method using a laser beam or an electron beam is significantly inferior to the crystal growth method by CVD in terms of productivity regardless of whether the annealing region is the entire surface. This is because the crystal growth by CVD can usually process a large number of substrates (wafers) at one time, whereas the one using an energy beam can process only one substrate at a time, and a beam converged on one substrate Is required to be scanned at a fixed speed.

On the other hand, in the above-described CVD crystal growth method, the size of the nucleation region is "selected nucleus growth method", and the size of the non-single crystal semiconductor thin film before aggregation is "aggregation seed crystal growth method". If each is not uniform, there is less possibility that the crystal will not grow at a certain point, or that multiple “nuclei” or “seed crystals” will be formed at a certain point, resulting in the growth of a polycrystal. There is a problem that it does not exist. In particular, the larger the area of the substrate, the greater the problem described above, because the area of the island-shaped region formed during island-shaped patterning depends on the uniformity of the illuminance of the exposure apparatus.

[0007]

The crystal growth method of the present invention comprises a step of forming an island-shaped semiconductor thin film on an amorphous insulator substrate or a substrate having an amorphous insulator layer deposited on the surface thereof, and The method further comprises the steps of once melting the semiconductor thin film by heat treatment by lamp heating and then recrystallizing the semiconductor thin film into a single crystal, and growing the semiconductor single crystal using the generated single crystal as a seed crystal. Is characterized by.

That is, according to the present invention, an island-shaped non-single-crystal semiconductor thin film having a size within a predetermined range is patterned on an insulating substrate, the semiconductor thin film is once melted by a batch treatment by lamp heating, and then re-formed. It is characterized in that a single crystal obtained when crystallized is used as a seed crystal to grow the crystal. According to this method, since beam annealing such as laser is not used, high productivity can be achieved. Further, since the operation is performed by two simple systems of melting and solidifying, the dependence on the "variation" of the area of the island-shaped semiconductor film to be patterned first is extremely small, and a crystal can be stably obtained.

Next, a preferred embodiment of the present invention will be described with reference to FIG.

A. A silicon film 102 is deposited on a substrate 101 having a non-nucleated surface 103 having a low nucleation density on its surface. At this time, first, as the substrate 101 having a non-nucleation surface, a quartz substrate, any other substrate such as ceramics,
Alternatively, atmospheric pressure CVD, low pressure CVD,
It is possible to use a film in which a film containing SiO _x or SiN _y as a main component is deposited by a method such as plasma CVD or sputtering. The base 101 is preferably a material having a melting point higher than that of silicon. However, when the base 101 is a transparent base, the base itself does not absorb visible or infrared light, and only the silicon film absorbs light. In some cases, a material having a melting point lower than that of silicon may be used because it is heated (the melting of silicon is performed in several seconds to several tens of seconds). The silicon film 102 deposited on the substrate 101 may be deposited by low pressure CVD, plasma CVD, sputtering or the like. The film quality may be polycrystalline or amorphous. The film thickness is preferably 0.05 μm or more and 2 μm or less,
More preferably, it is 0.1 μm or more and 1 μm or less. The reason for this is that if the silicon film 102 is thinner than 0.05 μm, the silicon is divided by the surface tension of the molten silicon, and if it is thicker than 2 μm, crystallization occurs from a plurality of points when solidifying from the molten state. First, there is a possibility that a grain boundary will be generated inside the obtained seed crystal, that is, the possibility of becoming a polycrystal becomes large. The optimum film thickness is around 0.5 μm.

B. Using the usual photolithography and etching techniques, the deposited silicon film 102 is
Island-shaped region 1 by patterning into islands at appropriate intervals
02a and 102b are formed. The island region is a rectangle with one side of 5 μm or less, or a polygon or a circle having an area corresponding to the rectangle. This is because if the area is larger than this, crystallization will start at a plurality of locations as in the case where the film thickness is thick, and the seed crystal will become polycrystal. The lower limit of the area of the island-shaped region is not particularly limited, but the size of the island-shaped pattern that can be stably obtained by a normal exposure apparatus is preferably about 0.5 μm or more per side. Considering "illuminance unevenness" of the exposure apparatus and other uncertain factors, the size of one side is more preferably 2 μm or more and 4 μm or less.

Incidentally, when annealing with a laser beam or an electron beam, since the annealing is performed while scanning the beam, the size of the island region may be 5 μm or more. Also, in the case of batch processing by lamp heating, the size of the island region is an important parameter.

C. Before annealing the island-shaped patterned silicon film by lamp heating, a protective layer 106 is usually deposited on the silicon film. Without the protective layer 106, the melted silicon may partially evaporate, flow, or scatter. Protective layer 10
The material of No. 6 is most preferably SiO ₂ , and other materials such as a two-layer structure having a Si ₃ N ₄ layer on the SiO ₂ layer can also be used favorably. The protective layer 106 may have a thickness of about 0.2 to 1 μm. Further, even if the protective layer is not applied in advance, if the heat treatment is performed in an oxygen atmosphere, the SiO ₂ layer is annealed while being formed on the surface of the semiconductor film 102, so that this fully fulfills the role of the protective layer.

D. The substrate is heat-treated by a lamp heating device to melt the island-shaped regions 102a and 102b made of the silicon film 102 on the substrate and crystallize again to obtain single single crystal silicon 104a and 104b. Usually, when heat-treating a thin film, it is often done by heat conduction from the substrate, but when the substrate is a transparent substrate, the temperature does not rise because the substrate does not absorb light, so the annealing effect of the thin film May not be obtained. In such a case, by increasing the film thickness of the silicon film, the amount of light absorption of the film itself can be increased to improve the annealing effect. Alternatively, the substrate may be placed in contact with a susceptor having a large light absorption amount such as SiC, and the silicon film may be annealed by heat conduction from the susceptor.

Single crystallized silicon 104a, 104b
When melted, its outer shape may be slightly changed by its surface tension, but there is no problem in using it as a seed crystal for crystal growth.

E. If there is a protective layer 106, it is etched to form silicon 104a, 1 as a seed crystal.
After exposing 04b, selective growth of the silicon single crystals 105a and 105b is performed by a normal epitaxial device or the like. If the protective layer 106 is SiO _2, it can be etched with a hydrofluoric acid-based etching solution. Single crystal growth of silicon is performed by the CVD method, but SiC is used as a source gas.
chlorosilanes such as l ₄ , SiHCl ₃ , SiH ₂ and Cl ₂ , fluorosilanes such as SiF ₄ and SiH ₂ F ₂ , Si
Silane-based materials such as H ₄ and Si ₂ H ₆ can be used. Since selective growth is performed, an etching gas such as HCl is added, and growth is performed using H ₂ gas as a carrier. Growth temperature is 900-1
It is preferable to carry out the growth at 200 ° C. and the growth pressure within the range of several Torr to 250 Torr.

Since crystals grow three-dimensionally with facets peculiar to single crystals, it is necessary to flatten the crystals in order to form an element.

[First Embodiment] The first embodiment will be described with reference to FIG.

1. As the base body 101 shown in FIG.
An inch diameter fused silica substrate was used. A polycrystalline Si film 10 is formed on this substrate (non-nucleation surface) 101 by a low pressure CVD method.
2 was deposited to 0.5 μm. The deposition conditions are SiH ₄ gas, temperature 620 ° C., flow rate 50 [sccm], pressure 0.3.
Deposition was performed for 50 minutes at Torr.

2. As shown in FIG. 1-B, the deposited polycrystalline silicon film 102 was patterned into an island shape, and the others were etched. The size of the island regions 102a and 102b was a circle having a diameter of 3 μm, and the island regions 102a and 102b were arranged on the square matrix points at intervals of 50 μm.

3. Island-shaped region 1 made of polycrystalline silicon film
A SiO ₂ protective layer 106 of 0.5 μm was deposited on the substrate 101 including 02a and 102b by atmospheric pressure CVD (FIG. 1-C).

4. Then, the substrate was set in a rapid thermal annealer (rapid heat treatment apparatus) and heat-treated to melt the island regions 102a and 102b. At this time, the substrate was placed on a susceptor made of SiC and treated at a susceptor temperature of 1480 ° C. for 3 minutes. The substrate was cooled to room temperature in about 30 seconds after the heat treatment, and single monocrystalline silicon 104a and 104b as shown in FIG. 1-D were obtained.

5. Protective layer 1 using buffered hydrofluoric acid
After removing 06, the substrate was set in the epitaxial reaction furnace, and a single crystal of silicon was grown centering on the seed crystal silicons 104a and 104b. The growth conditions were as follows.

Source gas / etching gas / carrier gas: SiH ₂ Cl ₂ / HCl / H ₂ gas flow rate: 0.53 / 1.80 / 100 (l / mi
n. ) Deposition temperature: 1030 ° C. Deposition pressure: 80 Torr Deposition time: 45 min As a result, as shown in FIG.
5a grew centering on the seed crystal silicon 104a and collided with the silicon single crystal 105b grown from the adjacent seed crystal silicon 104b to generate a grain boundary 107. Then, in order to form an element on the silicon single crystals 105a and 105b, the upper part of the crystal was flattened by applying a normal mirror polishing technique of a silicon wafer, and a square single crystal region with a side of 50 μm was obtained in a matrix. Was given.

[Second Embodiment] A second embodiment will be described with reference to FIG.

1. As the base body 101 shown in FIG.
An inch diameter fused silica substrate was used. The polycrystalline silicon film 10 is formed on the non-nucleation surface of the base 101 by the low pressure CVD method.
2 was deposited to 1 μm. SiH ₄ gas was used as the deposition condition,
Temperature 620 ° C, flow rate 50 [sccm], pressure 0.3To
Deposition was carried out for 100 minutes at rr.

2. As shown in FIG. 1B, the deposited polycrystalline silicon film 102 was patterned into an island shape, and the others were etched to form island areas 102a and 102b. The size of the island area is a square with 4 μm on each side and 50 μm
They were arranged on square matrix points at intervals of.

3. The above substrate was set in a rapid thermal annealer (rapid heat treatment apparatus) and heat treatment was performed to melt the island regions 102a and 102b. At this time, the heat treatment was performed in an oxygen atmosphere. The susceptor used was not a special one but a normal quartz jig. The heat treatment was carried out for 5 minutes with the same power as when the substrate temperature reached 1550 ° C. when the SiC substrate was placed. At this time, a SiO ₂ film was formed on the surface of the island-shaped region, and this played the role of the protective layer 106. Substrate is about 30 after heat treatment
After cooling to room temperature in seconds, the single crystal silicons 104a and 104b as shown in FIG. 1-D were obtained.

4. After that, crystal growth was performed in exactly the same manner as in the first embodiment, and the same result as in the first embodiment was obtained.

[Third Embodiment] The third embodiment will be described with reference to FIG.

1. As the base body 201 shown in FIG.
An inch diameter silicon substrate was used, and the surface of the substrate 203 was oxidized by 0.5 μm as the non-nucleation surface. A polycrystalline silicon film 202 of 0.2 μm was deposited on the non-nucleation surface of this substrate 203 by a low pressure CVD method. The deposition conditions were SiH ₄ gas, temperature 620 ° C., flow rate 50.
Deposition was performed at [sccm] and a pressure of 0.3 Torr for 20 minutes.

2. On the deposited polycrystalline silicon film 202,
Germanium ions 208 were doped using an ion implanter (FIG. 2-B). Ion dose is 2 × 1
It was set to 0 ¹⁶ cm ^-2 .

3. The germanium-doped silicon film 202 is patterned into an island shape as shown in FIG. 2C and the others are etched to form island areas 202a and 202b.
Was formed. At this time, the size of the island region is 4 μm on each side.
The squares were arranged in a matrix with a spacing of 50 μm.

4. As shown in FIG. 2-D, the island-shaped region 202
a, 202b on the patterned substrate, SiO ₂
The protective layer 206 made of a film was formed by using an atmospheric pressure CVD apparatus.
5 μm was deposited. Further, the same substrate was set in the heat treatment apparatus used in the first embodiment and annealed at a substrate temperature of 1350 ° C. for 7 minutes. As a result, the silicon substrate 201 does not change at all, and the germanium-doped silicon film 202 is formed.
Only melted. After the heat treatment, the substrate was cooled to room temperature in 30 seconds to obtain single crystal silicon 204a, 204b.

5. After that, crystal growth is performed in exactly the same manner as in the first embodiment, the silicon single crystal 205a grows around the island-shaped region 204a which is a seed crystal, and the adjacent seed crystal 20 is grown.
Collisions with the silicon single crystal 205b grown from 4b produced grain boundaries 207 (FIG. 2-E). This crystal showed the same result as the first embodiment.

[0036]

As described above, the island-shaped non-single-crystal silicon thin film patterned on the insulating substrate is heat-treated in a batch for a short time by lamp heating to once melt, and the island-shaped silicon is recrystallized. It is possible to form a seed crystal by using a conventional laser or electron beam, or to directly create an element in the annealed region by growing the single crystal silicon using this as a seed crystal. In comparison, the productivity can be significantly improved without lowering the device performance. In addition, the "selective nucleus growth method" is used to generate crystal nuclei from an arbitrary position on the amorphous insulating substrate, or the fine island-shaped non-single-crystal silicon on the amorphous insulating substrate is made into single crystals by utilizing the agglomeration phenomenon. According to the method of the present invention, a seed crystal having a large deposition can be formed, so that more stable crystal growth can be performed, as compared with the "aggregated seed crystal growth method" in which this is used as a seed crystal.

[Brief description of drawings]

FIG. 1 is a process drawing of crystal growth in the first and second embodiments of the present invention.

FIG. 2 is a process drawing of crystal growth in a third embodiment of the present invention.

FIG. 3 is an explanatory diagram of a crystal growth method by a conventional selective nucleus growth method.

[Explanation of symbols]

101, 201 base 102,202 Polycrystalline silicon film 102a, 202a island region 102b, 202b island region 103,203 Non-nucleation surface 104a, 204a Single crystal silicon 104b, 204b Single crystal silicon 105,205 Silicon single crystal 106,206 protective layer 107,207 grain boundaries

Claims (3)

[Claims] 1. A step of providing an island-shaped semiconductor thin film on an amorphous insulating substrate or a substrate having an amorphous insulating layer deposited on the surface, and the semiconductor thin film is once melted by heat treatment by lamp heating, and then, A method of growing a crystal, comprising: a step of converting the single crystal into a single crystal by recrystallization; and a step of growing a semiconductor single crystal using the generated single crystal as a seed crystal. 2. The method for growing a crystal according to claim 1, wherein the island-shaped semiconductor thin film is a non-single-crystal film containing silicon as a main component. 3. The method for growing a crystal according to claim 1, wherein the island-shaped semiconductor thin film has a rectangular shape with a side of 5 μm or less, or a polygonal shape or a circular shape having an area corresponding thereto.