JPH0479993B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a cubic single crystal semiconductor layer on an insulating layer formed on a cubic single crystal semiconductor substrate. .

[Prior art] Conventionally, a method of melting and resolidifying a polycrystalline silicon layer on an insulating layer using a laser beam to form a single crystal has attracted attention as a basic technology for semiconductor devices with new structures, such as three-dimensional structures. It has been.

Referring to the cross-sectional view in Figure 8, Texas Instruments HW Lam et al. (ECS Meeting, 1980
The lateral seeding method published by Extended Abstract in 2010 is illustrated. An insulating layer 12 is formed on a single crystal silicon substrate 10, and a polycrystalline silicon layer 13 to be made into a single crystal is formed on the insulating layer 12. This silicon layer 13 is seeded into the substrate crystal 10 through the opening 11 of the insulating layer 12, and is melted and resolidified into a single crystal by a laser beam 14 scanning from left to right. This method is considered to be an ideal crystal growth technique because the crystal orientation of the single-crystal silicon layer 13 is completely determined by the substrate crystal, and is published in Japan in Japanese Patent Publication No. 12087/1987. has been done.

However, this method, which was thought to be superior in principle, has not been successful in practice. That is, the seeded crystal growth of the semiconductor layer 13 progresses only about 100 to 200 μm from the opening 11, and many crystal defects such as stacking faults and twins occur, so that it is difficult to say that it is a good single crystal layer. It was hot.

[Problems to be Solved by the Invention] The reason why the above-mentioned lateral seeding method has not been successful is that the beam scanning was performed without any measures to compensate for the power distribution of the laser beam, which is close to the Gaussian distribution. This is because it was melted and re-solidified. That is, the region of the silicon layer 13 irradiated by the laser beam 14 has a temperature distribution as shown in FIG. 9A in a direction transverse to the scanning direction of the beam. In FIG. 9B, a plan view of such a temperature region moving on the silicon layer 13 is shown in comparison with a cross-sectional view as shown in FIG. 8. Laser beam 14 moves in the direction indicated by the thick arrow. At this time, as shown by a large number of thin arrows, a large number of elongated crystals extend and grow from the low-temperature areas on both sides of the beam movement toward the central axis of the scanning zone. Since these elongated crystals meet in the center of the scanning band, the growth of the region (hatched region S) of the silicon layer 13 seeded in the opening 11 and made into a single crystal is subsequently inhibited. That is, the growth of this single crystal region S is limited to only 100 to 200 μm from the opening.

In an attempt to prevent crystals from entering from both side edges of the scanning band, FIGS. 10A, 10B,
Attempts have also been made to form an antireflection film on the silicon layer 13 as illustrated in FIG. 10C. FIG. 10A is a plan view showing antireflection films 15 and 16 formed on silicon layer 13. Stripes 16 of the antireflection film having a predetermined width are arranged at predetermined intervals along the scanning direction of the laser beam. Further, an anti-reflection band is placed directly above the opening 11 to compensate for the temperature drop caused by the heat escaping to the substrate 10 through the opening.
5 is provided. Figures 10B and 10C are lines 10B-10 in Figure 10A, respectively.
B shows a cross-sectional structure taken along line 10C-10C. In this case, in the direction transverse to the scanning direction of the laser beam, the effect of the stripes 16 forms a periodically fluctuating temperature distribution wave, which causes the crystals from both edges of the scanning band to penetrate into the central part. It is an attempt to prevent this from happening. Similarly, attempts have been made to control the heat distribution in the direction transverse to the scanning direction by varying the thickness of the underlying oxide film. However, in both attempts, opening 11
It was not possible to achieve growth of single crystals larger than 200 μm.

An object of the present invention is to overcome the above-mentioned problems and provide a method for growing a large-area semiconductor single-crystal layer on an insulating layer formed on a single-crystal semiconductor substrate.

[Means for Solving the Problems] A method for growing a cubic semiconductor single crystal according to the present invention includes seeding a polycrystalline semiconductor layer on an insulating layer into a single crystal of a semiconductor substrate through a seeding opening, The energy beam is scanned while partially melting and resolidifying the semiconductor layer, and the resolidifying liquid-solid interface of the semiconductor layer that moves along with the scanning is moved while being aligned with one or more {111} planes. This is what I did.

[Function] In the method for growing a semiconductor single crystal layer according to the present invention, the {111} plane, which is generally the most stable in a cubic semiconductor crystal, is moved to coincide with the liquid-solid interface (crystal growth plane), so that the crystal growth is This is the most stable process, with extremely little strain that would cause grain boundaries or crystal defects, resulting in long single crystal growth.

[Example] FIG. 1 shows a silicon single crystal substrate used in an example of the present invention. Its principal plane is the (001) plane, and the orientation flat plane is the (11) plane.
0) surface.

Referring to FIGS. 2A and 2B, a wafer for growing a semiconductor single crystal layer using the semiconductor substrate of FIG. 1 is schematically illustrated. FIG. 2A is a plan view showing a part of the wafer, and FIG. 2B shows a cross-sectional structure taken along line 2B--2B in FIG. 2A. An insulating layer 12 having a seeding opening 11 with a width of about 10 μm is formed on a silicon single crystal substrate 10, and a silicon polycrystalline layer 13 to be made into a single crystal is formed on the insulating layer 12. . silicon layer 1
3, patterned antireflection films 15 and 16 are formed in the same manner as in FIG. 10A. However, in the case of this embodiment, the stripes 16 arranged along the scanning direction of the laser beam are formed on the substrate single crystal 1.
It is made to coincide with the [100] direction of 0. moreover,
This wafer surface has a thin insulating film 17 for surface protection.
is provided.

FIGS. 3A and 3B schematically illustrate the situation when a wafer such as the one shown in FIG. 3 is scanned from left to right with a laser beam. For laser beam scanning, for example, a continuously oscillating argon laser of about 15 W can be used, and a beam with a spot size of about 100 μm can be scanned at a speed of about 12 cm/sec. Of the silicon layer 13 irradiated with the laser beam 14, the antireflection stripe 16
The area below absorbs the laser energy well and therefore has a higher temperature than other areas. Then, waves with a periodic temperature distribution corresponding to the period of the stripes 16 are formed in a direction transverse to the scanning direction of the laser beam. Therefore, at the liquid-solid interface at the tip of the single crystal growth of the silicon layer 13, resolidification is delayed in the region immediately below the stripe 16, and solidification proceeds in other regions. As a result, the liquid-solid interface of crystal growth becomes serrated, as indicated by reference numeral 20 in Figure 3A. In addition, the silicon layer 13
Since the heat inside escapes toward the opening 11 and downward, the liquid-solid interface 20 proceeds below the silicon layer 13 and is sent upward, as shown in FIG. 3B.

In the perspective view of a part of the wafer shown in FIG. 4, inheriting the crystal orientation from the substrate single crystal 10,
The combination of {111} planes in the single crystal region of the silicon layer 13 that is growing in the [100] direction on the insulating layer 12 forms a sawtooth-like boundary as indicated by reference numeral 30. be able to.
That is, the lines of intersection of the (111) plane and the (111) plane with the base insulating layer 12 intersect at 90 degrees to form a sawtooth-like boundary 30 similar to the liquid-solid interface 20 in FIG. 3A. Further, this boundary 30 extends in the [100] direction below the silicon layer 13,
It lags behind in the upward direction. This is similar to the liquid-solid interface 20 in FIG. 3B.

Therefore, the width of the opening 11, the antireflection film 15
By appropriately setting the thickness of the stripes 16 and the width and spacing of the stripes 16, it is possible to make the liquid-solid interface 20 of crystal growth coincide with the boundary 30 that is a combination of the (111) plane and the (111) plane. can. In this case, the single crystal grows while the {111} plane, which is the most stable crystal plane of silicon, moves, so the strain that causes grain boundaries and crystal defects is extremely small, and a stable single crystal is grown. There will be growth.

The upper part of FIG. 5 shows an optical micrograph of the single-crystal growth zone of the silicon layer 13 obtained in this manner, and the structure is illustrated in the lower part. This single crystal growth zone has a 9μm opening 11 and a thickness of 500nm.
antireflection films 15 and 1 made of silicon nitride films of
6 and a surface protection film made of a silicon nitride film with a thickness of 60 Å. The single-crystal band in the photo has been seco-etched to show crystal defects, but as illustrated in the diagram at the bottom, there are no crystal defects except for sub-grain boundaries (sub-GB) parallel to the single-crystal band. Not observed, 1 from the opening (seed)
Crystals grow over a length of mm or more.

FIG. 6 shows a silicon single crystal substrate that can be used in another embodiment. The main surface of this substrate is the (110) plane, and the orientation flat surface is the (110) plane.

7A and 7B are perspective views similar to FIG. 4 in the case where the silicon layer 13 is single-crystalized using the silicon single-crystal substrate 10 of FIG. 6. FIG. FIG. 7A shows the case where the single crystal is grown in the [110] direction, and FIG. 7B shows the case where the single crystal is grown in the [001] direction. In Figures 7A and 7B, (11
1) Planes The (111) planes intersect at solid angles of 109.47° and 70.52°, respectively, and both planes stand vertically within the silicon layer 13. Therefore, in order to make the interface formed by such a combination of {111} planes coincide with the liquid-solid interface of single crystal growth, the width of the opening 11 in the underlying insulating layer is made as small as about 2 μm. Furthermore, the width and spacing of the stripes 16 are set to 4 μm and 10 μm, respectively, in the case of FIG. 7A, and
In the case shown in the figure, they may be set to 6 μm and 10 μm, respectively.
In this way, the difference in heat dissipation between the upper and lower sides of the silicon layer 13 is small, and the liquid-solid interface can be made to coincide with the combined interface of the {111} planes in both FIGS. 7A and 7B. I can do it. thus,
As in the case of using a single crystal substrate having a (001) plane as its main surface, the silicon layer 13 is successfully single crystallized.
However, the main surface of the single crystal layer 13 in this case is (110)
(001) when using the board shown in Figure 1.
Needless to say, it will be a big deal.

Although the above embodiments have been described by specifying specific surface orientations and axial orientations, it is clear that equivalent combinations of surface orientations and axial orientations that have an equivalent relationship can be equally implemented.

Furthermore, in the above embodiments, the case where a laser beam is used has been described, but similar results can be obtained by using, for example, a linear electron beam.

[Effects of the Invention] As described above, according to the method for growing a cubic semiconductor single crystal layer according to the invention, a layer is formed by combining the liquid-solid interface of crystal growth with the {111} plane, which is a stable crystal plane. Since it is made to coincide with the boundary, a high quality single crystal semiconductor layer is formed without introducing crystal grain boundaries or crystal defects.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a silicon single crystal substrate used in the present invention. FIGS. 2A and 2B are diagrams showing the structure of a wafer for forming a silicon single crystal layer according to the present invention. FIGS. 3A and 3B are diagrams illustrating the state of scanning by a laser beam according to the present invention. FIG. 4 is a perspective view illustrating the relationship between the wafer shown in FIGS. 3A and 3B and the boundary formed by the combination of {111} planes. FIG. 5 is an optical microscope photograph of a single crystal layer obtained in an example according to the present invention. FIG. 6 is a perspective view of a silicon single crystal substrate used in another embodiment of the present invention. 7A and 7B are perspective views showing the relationship between a wafer using the silicon single crystal substrate of FIG. 6 and a boundary formed by a combination of {111} planes. FIG. 8 is a sectional view showing a conventional lateral seeding method. FIG. 9A is a diagram illustrating the temperature distribution of a semiconductor layer to be single-crystalized in the conventional lateral seeding method, and FIG. 9B is a diagram illustrating the melted and resolidified structure when scanned with such temperature distribution. It is. FIG. 10A is a top view of a conventional wafer having an anti-reflection coating pattern for modifying temperature distribution as shown in FIG. 9A, and FIGS. 10B and 10C are cross-sectional views of the wafer of FIG. 10A. be. In the figure, 10 is a silicon substrate, 11 is an opening for seeding, 12 is a base insulating layer, 13 is a polycrystalline silicon layer, 14 is a laser beam, and 15 is an opening 11
16 is a stripe of the antireflection film, 17 is an insulating film for surface protection, 20 is a liquid-solid interface of single crystal growth, and 30 is a boundary formed by a combination of {111} planes. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A cubic single crystal semiconductor substrate, and 1.
an insulating layer formed on a main surface and having a seeding opening that exposes a part of the main surface; and a cubic crystal formed on the insulating layer and seeded into the substrate through the opening. A wafer having a polycrystalline semiconductor layer is prepared, and an energy beam is scanned while partially melting and resolidifying the semiconductor layer, thereby seeding the semiconductor layer through the opening with the substrate. A method for single-crystallizing a semiconductor single crystal, characterized in that the re-solidified liquid-solid interface of the semiconductor layer, which moves as the energy beam scans, is moved while aligning with one or more {111} planes. How to grow layers. 2. Claim 1, wherein thin anti-reflection film bands having a predetermined width are provided at predetermined intervals on the semiconductor layer along the scanning direction of the energy beam. A method for growing a semiconductor crystal layer as described. 3. The method for growing a semiconductor single crystal layer according to claim 2, wherein an antireflection film is also formed on the semiconductor layer in a region immediately above the opening. 4. Claims 1 to 3, characterized in that the main surface is one {100} plane, and the scanning direction of the energy beam is one <100> direction within the main surface. A method for growing a semiconductor single crystal layer as described in any of the above. 5. Claims 1 to 3, wherein the main surface is one {110} plane, and the scanning direction of the energy beam is one <110> direction within the main surface. A method for growing a semiconductor single crystal layer as described in any of the above. 6. Claims 1 to 3, characterized in that the main surface is one {110} plane, and the scanning direction of the energy beam is one <100> direction within the main surface. A method for growing a semiconductor single crystal layer as described in any of the above. 7. The method for growing a semiconductor single crystal layer according to any one of claims 1 to 6, wherein the substrate and the semiconductor layer are made of silicon. 8. The semiconductor single crystal layer according to any one of claims 1 to 7, wherein the wafer has a surface protected by a thin insulating surface protection film. How to grow. 9. The energy beam is a continuous wave argon laser beam and includes at least one of wavelengths of 4880 Å and 5145 Å. A method for growing semiconductor single crystal layers. 10. The method for growing a semiconductor single crystal layer according to any one of claims 1 to 8, wherein the energy beam is a continuous electron beam.