JPH0453124A - Manufacture and apparatus for single-crystal silicon thin film - Google Patents

Abstract

PURPOSE:To obtain a single-crystal thin film having a few rotations in the crystal orientation by sticking an insulator which does not absorb energy beam tightly to the top surface of a sample as a heat sink at the time of making a non-single-crystal semiconductor layer formed on an insulating material a single-crystal one by energy beam. CONSTITUTION:An SiO2 film 2 is deposited on a single-crystal silicon substrate 1. To make a hole la on the SiO2 film 2, the SiO2 film 2 is etched so that a part of the single-crystal silicon substrate 1 is exposed. Then, a non-single-crystal silicon thin film 3 is deposited on the SiO2 film 2 to let it serve for an active layer. And on top of the non-single-crystal silicon thin film 3, another SiO2 film 4 is deposited which would serve for a reflection preventing film. Thus, a sample 8 is obtained. A heat-sink dielectric 6 is attached tightly to the top of the sample 8. To make the polycrystal silicon layer 3 to be a single crystal one, energy beam 7 is cast on the surface of the sample 8. The whole surface of the sample 8 is scanned by the energy beam 7 to obtain a single-crystal silicon thin film 5. After that, the heat sink 6 is removed from the sample 8.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a single crystal thin film used in the field of manufacturing semiconductors, and more specifically to a method for manufacturing a single crystal thin film formed on an amorphous substrate. It also relates to improvements in a method for converting polycrystalline or other non-single-crystal silicon thin films into single crystals by heating them with an energy beam such as a CW laser beam or an electron beam, or with a heater or lamp, and an apparatus for producing the same. .

<Prior art> Conventionally, a non-monocrystalline silicon thin film such as an amorphous or polycrystalline silicon film is formed on an insulating film having a partially perforated portion formed on monocrystalline silicon, and a laser, etc. is applied to this non-monocrystalline silicon thin film. A method has been proposed in which a single-crystal silicon thin film is produced by melting and recrystallizing it by irradiating it with an energy beam. (Japanese Unexamined Patent Publication No. 56-73697) However, although it is possible to obtain a single-crystal silicon thin film whose crystal orientation matches that of the single-crystal silicon substrate in the vicinity of the perforation, the laser beam is emitted from the perforation as it moves away from the perforation. There was a problem that the crystal orientation was largely rotated in the scanning direction of the irradiation.
In the figure, it can be seen that the closer the angle θ of the solid-liquid interface 40 of the energy beam irradiation part to the substrate surface is perpendicular to the substrate surface, as shown in FIG. 4(a), the smaller the temperature gradient in the perpendicular direction is. It is being

However, in the case of the above method, since the thermal conductivity of the insulator layer 2 on the single crystal silicon substrate 1 is similar to that of the non-single crystal silicon layer 4 thereon, the non-single crystal silicon layer 2 as shown in FIG. The solid-liquid interface at the bottom surface of the crystalline silicon layer 4 was shifted inward from the solid-liquid interface at the top surface of the non-single crystal silicon layer 4, causing rotation of the crystal orientation.

In addition, in FIG. 4, 1 is a single crystal silicon substrate, 2 and 4 are
3 is an insulating film, 3 is a non-single crystal silicon, 6 is a heat sink insulator, and 7 is an energy beam.

When using a single-crystal silicon thin film with rotated crystal orientation as described above, the oxidation rate of the single-crystal silicon layer is not constant, resulting in uneven gate oxide film thickness, making it difficult to always obtain transistors with the same characteristics. there were.

Japanese Patent Application Laid-Open No. 64-1224 describes a method for solving the above problem by inserting a silicon thin film into an insulating film. That is, in this publication, a single crystal silicon thin film is obtained by the method shown below.

First, in FIG. 2(a), a single crystal silicon substrate 10
A 10 μm thick Sin film 11 is formed thereon, and a non-single crystal silicon thin film 1 is selectively formed on this 5iOp film 11.
2 to 0. The film is formed to have a thickness of 6 μm. Next, the non-single crystal silicon thin film 12 and S10. Sin again on film 11, film 1
3 is formed to have a thickness of 1.0 μm, and in the area where the non-single crystal thin film is not formed, the 5iOJ 11 and SiC film 13 are etched to expose the single crystal silicon substrate 10, and a part of the hole 10a is formed. Form. Thereafter, a non-single-crystal silicon thin film 14, which will become an active layer, is again formed to a thickness of 0.8 μm, and an SiC film 15 is further formed thereon to a thickness of 0.085 μm as an antireflection film. Next, the sample having the above structure is irradiated with an energy beam or heated 17 using a heater or a lamp to convert the non-single crystal silicon thin film 14 into a single crystal, thereby obtaining a single crystal silicon thin film 16. (FIG. 2(b)) According to this method, when the laser is irradiated, the temperature of the non-single crystal silicon thin film 12 with high thermal conductivity, which is inserted between the Sin film 11 and the Sin film 13, is As the temperature rises, the temperature of the SiC film 13 also rises, so the temperature difference between the SiC film 13 and the non-single crystal silicon layer 12 on the Sin film 13 becomes smaller, and the solid-liquid interface becomes perpendicular to the substrate surface. , and the rotation of the crystal orientation is suppressed.

<Problems to be Solved by the Invention> However, when the above method is used, the process becomes complicated because a non-single crystal silicon thin film is inserted into the insulating film, and the total film thickness becomes thicker. was warped, and cracks were likely to form in the single crystal silicon thin film 16 after it had solidified.

The present invention was devised in view of the above points, and provides a method for melting and recrystallization using energy beam irradiation.
An object of the present invention is to provide a method for easily obtaining a single-crystal silicon thin film with little rotation of crystal orientation.

Means for Solving the Problems> In order to achieve the above object, the present invention irradiates a non-single crystal silicon thin film formed on a single crystal silicon substrate coated with a non-single crystal with a laser beam or an electron beam or In a method of forming a single crystal silicon thin film by melting and recrystallizing by heating with a heater, lamp, etc., the surface of the non-single crystal silicon thin film is coated with
A special feature is that the energy beam is irradiated in close contact with an insulator that does not absorb the energy beam, and a monocrystalline silicon thin film is manufactured. may be formed.

Furthermore, the present invention melts and recrystallizes a non-single-crystal silicon thin film formed on a single-crystal silicon substrate covered with a non-single-crystal insulating film by irradiating a laser beam or an electron beam, or by heating with a heater, lamp, etc. An energy beam annealing apparatus for forming single crystal silicon by forming a single crystal silicon thin film, comprising: a heat sink made of an insulator that is in close contact with the upper surface of the non-single crystal silicon thin film and does not absorb energy beams; A manufacturing device is obtained.

That is, the present invention reduces the temperature gradient in the vertical direction of the non-single crystal silicon layer by closely adhering an insulating film that does not absorb energy beams as a heat sink to the non-single crystal silicon layer to be made into a single crystal. A single-crystal silicon thin film with little crystal orientation rotation is obtained.

When single crystallization is performed using an energy beam, it is said that the rotation of the crystal orientation is caused by the temperature difference between the top and bottom surfaces of the Si film irradiated with the energy beam. By adhering an insulator that does not absorb energy as a heat sink, the temperature difference between the top and bottom surfaces of the silicon thin film is small (and the rotation of the crystal orientation is suppressed. In other words, the heat generated on the top surface of the silicon thin film by the energy beam is transferred by thermal conduction). In order to heat the heat sink insulator, as shown in FIG. 4(a), when the heat sink insulator 6 is brought into close contact with the non-single crystal silicon layer 4 via the antireflection insulating film 5 and the energy beam 7 is irradiated,
The angle θ of the solid-liquid interface 4o with respect to the substrate surface approaches perpendicular,
The temperature gradient in the vertical direction becomes smaller. In contrast, in FIG. 4(b) without the heat sink insulator 6, the angle θ of the solid-liquid interface 40 of the non-single crystal silicon layer 4 with respect to the substrate surface is smaller than that in FIG. The temperature gradient becomes larger.

For example, when using Sin as a heat sink insulator, the thermal conductivity of 5iOz at room temperature is more than two orders of magnitude lower than that of Si, as shown in Figure 5, but at high temperatures it is less than one order of magnitude, making it a suitable material as a heat sink insulator. It can be seen that it is.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) to 1(e) are process diagrams for manufacturing samples used in the present invention.

First, a first layer is placed on a single crystal silicon substrate 1 shown in FIG. 1(a).
As shown in Figure (b), a thin SiC film 2 of 1.0 .mu.m was formed, and the SiC film 2 was etched to expose the single crystal silicon substrate 1 to form a hole 1a.

Next, as shown in FIG. 1(c), a non-single-crystal silicon thin film 3, which will become an active layer, is formed to a thickness of 0.8 μm, and on top of this, a Sin film 4 is formed as an anti-reflection film to a thickness of 0.085 μm. Sample 8 was formed to have a film thickness.

FIG. 3 shows a schematic diagram of an embodiment of an apparatus for carrying out the method of the present invention. 31 is an energy beam generator such as an Ar laser, 33 is an energy beam mirror, 34 is a beam expander that expands the incident beam and emits it;
5 is a beam aperture for uniformizing the intensity of the energy beam 7 emitted from the beam expander; 3;
6 is a converging lens for converging the energy beam 7; 6 is a heat sink dielectric for reducing the temperature difference between the upper and lower surfaces of the silicon thin film; 38 is a movable sample mounting table for irradiating the entire surface of the sample with the energy beam 7. .

Next, we will describe a method using this apparatus to single-crystallize polycrystalline silicon formed on an insulating substrate by irradiating it with an energy beam.

In FIG. 3, the sample 8 is placed on the movable sample mounting table 38.
was installed, and the heat sink dielectric 6 was brought into close contact with the sample 8. Thereafter, in order to monocrystallize the polycrystalline silicon layer 3 of the sample 8, the energy beam 7 is irradiated and at the same time the movable sample mounting table 38 is reciprocated in the direction of the arrow 30a in the figure while moving in the direction of the arrow 30b in the figure. By moving and scanning the energy beam 7 over the entire surface of the sample, a single crystal silicon thin film 5 was obtained as shown in FIG. 1(e). Thereafter, the heat sink 6 was removed from the sample.

When polycrystalline silicon was single-crystallized using the above method, it was possible to obtain single-crystal silicon with less rotation of the crystal orientation even in the part away from the seed compared to the conventional example shown in FIG. 4(b). did it.

(Fig. 6) <Effects of the Invention> According to the present invention, when a non-single crystal semiconductor layer formed on an insulator is made into a single crystal by an energy beam, S is added to the surface.
By closely adhering an insulator that does not absorb the energy beam, such as Si, N, etc., as a heat 7, the solid-liquid interface of the energy beam irradiation area becomes perpendicular to the substrate, resulting in a unit with less rotation of crystal orientation. A crystal thin film can be obtained.

[Brief explanation of drawings]

1(a) to 1(e) are process diagrams showing cross-sectional views of samples for explaining one embodiment of the present invention, and FIG. 2(a)
) and (b) are schematic diagrams showing sample cross sections for explaining the conventional single crystal thin film forming method, FIG. 3 is a schematic diagram of an example apparatus for carrying out the method of the present invention, and FIG. )as well as(
b) is a diagram showing the temperature distribution when the sample is irradiated with an energy beam with and without a heat sink in close contact; Figure 5 is a diagram showing changes in thermal conductivity of Si and SiC due to temperature; Figure 6 The figure is a diagram illustrating the correlation between the rotation of crystal planes when a heat sink is brought into close contact with the heat sink and when it is not brought into close contact with the heat sink. 1... Single crystal silicon substrate, 1a... Exposed portion, 24
・Insulating film, 3... Non-monocrystalline silicon thin film, 5... Single-crystal silicon thin film, 6... Heat sink insulator agent Patent attorney Ume 1) Katsu (and 2 others) Figure 1 Figure 3! Breeding (°K) Fig. 5 1.0 /, 5 2.0 N-r voice I7 collection of distances 1

Claims (1)

[Claims] 1. A non-single-crystal silicon thin film formed on a single-crystal silicon substrate covered with a non-single-crystal insulating film is melted and remelted by laser beam or electron beam irradiation or by heating with a heater, lamp, etc. In the method of manufacturing a single crystal silicon thin film by crystallization, an insulator that does not absorb energy beams is brought into close contact with the surface of the non-single crystal silicon, and a laser beam or an electron beam is irradiated, or heating is performed using a heater, a lamp, etc. A method for producing a single crystal silicon thin film, characterized by: 2. A non-single-crystal silicon thin film formed on a single-crystal silicon substrate covered with a non-single-crystal insulating film is melted and recrystallized by laser beam or electron beam irradiation, or by heating with a heater, lamp, etc. An energy beam annealing apparatus for forming crystalline silicon, characterized by comprising a heat sink made of an insulator that is in close contact with the upper surface of the non-single crystal silicon thin film and does not absorb energy beams.