JPH0354819A - Manufacture of soi substrate - Google Patents

Abstract

PURPOSE:To attain crystallization in a state wherein the whole surface is arranged in uniform directions by a method wherein a polycrystal Si layer or an amorphous Si layer having a region wherein thermal concentration is easy to occur is formed on an underneath substrate and then the heat treatment process is started from the partial region. CONSTITUTION:A polycrystal Si layer 13 is formed on an insulator 12 and then a protrusion 14 is formed on a part of the layer 13. Later, the sidewall around the layer 13 including the protrusion 14 is covered with a sidewall material 15 resistant to thigh temperature. Furthermore, the surface of the layer 13 is covered with a lapping film 16. The heat treatment process is started from the protrusion 14 from a substrate 11 thus prepared. At this time, the polycrystal Si of the protrusion 14 is recrystallized so that the surface 100 may come into contact with the insulator 102 and the sidewall 15 when the polycrystal Si of the protrusion 14 is melted down to be recrystallized. Through these procedures, the crystal in the controlled surface direction can be used as a seed to be deposited at any time.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is based on SoI (Silicon on Ins).
The present invention relates to a method for manufacturing an S (ulator) substrate, and in particular to a method for manufacturing an S (8 substrate) suitable for removing restrictions on the base substrate.

[Prior Art] In recent years, in order to improve the performance of semiconductor devices, research and development of devices having an SOI structure have been actively conducted as a means for improving the performance of semiconductor devices. The SOI structure is a structure in which a thin semiconductor (usually silicon) is layered on an insulator, and devices using such an SOI substrate can have high voltage resistance, high integration, and large area. It is also expected to have excellent radiation resistance.

ZMR (Zone
Melting Recrystallization
The n> method is known. For example, as shown in Figure 5,
An oxide film S i that becomes an insulator layer 2 on a silicon wafer 1
After forming the silicon wafer 02 by thermal oxidation, the window 3 is formed by etching so that a part of the surface of the silicon wafer 1 is exposed. Next, thermal CVD is applied all over the insulator layer 2 and window 3.
The thickness of the polycrystalline silicon layer 4 is 0.5 μm to 1.0 μm by
A film is formed in μm. Furthermore, on the polycrystalline silicon layer 4,
Si02 called capping film 5 is formed by thermal CVD method.
The film is no longer formed and the substrate 10 is completed.

Next, the substrate 10 shaped as shown in FIG.
As shown in the figure, it is set on a carbon susceptor 6. An elongated carbon heater 7 is provided above the substrate 10 and is movable in the direction of the arrow. In this state, first heat the heater inside the carbon susceptor 6 to maintain the entire substrate 10 at, for example, 1350°C, and only the part directly below the carbon heater 7 has a melting point of 141°C.
The temperature is adjusted using the carbon heater 7 so that the temperature exceeds 2°C (for example, 1450°C). First, the carbon heater 7 is placed above the window 3 of the substrate 10, and the polycrystalline silicon in the area of the window 3 is heated. Melt the layer 4. When the carbon heater 7 moves in the direction of the arrow, the temperature becomes below the melting point,
recrystallize. At this time, the underlying silicon wafer 1 is used as a seed crystal, and recrystallization occurs so that the crystals have the same surface orientation. By moving the carbon heater 7, melting and recrystallization occur, and an SO2 substrate having a uniform surface orientation over the entire polycrystalline silicon layer 4 can be formed. Polycrystalline silicon layer 4
The capping film 5 covering the polycrystalline silicon layer 4
It functions to prevent Si from evaporating or curling due to surface tension when it is melted.

The method of manufacturing an SOI substrate using the ZMR method described above has the feature that a uniform SOI substrate can be formed over a wide area (for example, the entire 5-inch wafer).

On the other hand, since the method of manufacturing an SOI substrate using the ZMR method involves high-temperature processing, it is difficult to fabricate a high-performance device using a so-called multilayer structure, in which devices are formed on the underlying silicon wafer 1, and then an SOI structure is formed, and then devices are formed. Not suitable for integration.

A method is also known in which a substrate similar to the substrate 10 shown in FIG. 5 is used, and only the polycrystalline silicon to be melted is melted and recrystallized using a laser, without heating the entire substrate to a high temperature. However, equipment implementing this method is expensive and not suitable for large area SOI substrate formats.

Another known prior art method for manufacturing SOI substrates is called the lateral solid phase orientation method.

In this method, a substrate is prepared in which the polycrystalline silicon layer 4 in the substrate 10 shown in FIG. 5 is replaced with an amorphous silicon layer formed by thermal CVD. Also, in this case, Capping II! 5 is not particularly required.

'IP-The prepared substrate is kept at a relatively low temperature of about 600° C. for 8 to 10 hours. Then, using the silicon wafer 1 as a seed crystal from the window 3, the amorphous silicon layer becomes a single crystal and extends upward to a certain extent, and then to a certain extent in the lateral direction, albeit slowly. In this method, the lateral growth is at most 10 to 40 μm, so the number of windows 3 must be increased in order to obtain a large area SOI substrate.

[Problems to be Solved by the Invention] The conventional techniques described above each have their advantages and disadvantages, but each method requires a seed crystal, which poses a problem in that the selection of a base substrate is restricted. .

An object of the present invention is to provide a method for producing an SOI substrate that is inexpensive and has high throughput, while eliminating the above-mentioned restrictions on the base substrate.

[Means for Solving the Problems] The method for manufacturing an SOI substrate of the present invention uses an insulator as a base substrate, and a polycrystalline silicon layer or an amorphous silicon layer having a partial region where heat tends to concentrate on the base substrate. Preventing the silicon layer,
The method is characterized in that heat treatment is then started from the partial region to convert the polycrystalline silicon or amorphous silicon into a single crystal.

In this invention, the side surface of the polycrystalline silicon or amorphous silicon is made of a material that can withstand the heat treatment (for example, a material that has the same or similar properties as the underlying substrate).
It is preferable to have a structure covered by.

[Function] According to this invention, the area where heat is likely to concentrate has a thickness of 1 μm.
It is possible to form a seed crystal about the size of a square, and using this as a nucleus, the entire surface of a polycrystalline silicon layer or an amorphous silicon layer can be crystallized with uniform plane orientation.

Therefore, it is no longer necessary to use the base substrate as a source of seed crystals, so that restrictions on the base substrate can be eliminated.

[Example] The present invention will be roughly described in detail below with reference to an example shown in the attached drawings. FIG. 2 is a plan view of the substrate 11 used in the present invention, and FIG. 3 is a sectional view of the plan view shown in FIG. As shown in the figure, a substrate 11 is formed by depositing a polycrystalline silicon layer 13 on an insulator 12 such as quartz by thermal CVD.
After that, a portion of the polycrystalline silicon layer 13 is patterned into a rectangular or wedge-shaped tapered shape to form the protrusion 14. Thereafter, at least the protrusion 14
The side wall around the polycrystalline silicon 13 containing the polycrystalline silicon 13 is covered with a side wall material 15 such as SiO2 that can withstand high temperatures. Further, the upper surface of the polycrystalline silicon layer 13 is covered with a wrapping film 16.

Using the substrate 11 prepared in this way, heat treatment is started from the protrusion 14 of the substrate 11 by the ZMR method. 1st
The figure is an explanatory view showing this state, and the polycrystalline silicon layer 13 of the protrusion 14 begins to melt and recrystallize. At this time,
When the polycrystalline silicon of the protrusion 14 melts and recrystallizes,
By the principle of so-called graphoebitaxy, (ioo
) is recrystallized so that the surface is in contact with the insulator 12 and the side wall material 15. Crystals with controlled plane orientations can be used as seeds to grow crystals at any time.

FIG. 4 is an explanatory diagram showing another embodiment of the present invention, and as shown in the figure, a substrate 20 having the following structure is prepared. That is, an amorphous silicon layer 23 (corresponding to the polycrystalline silicon layer 13 in FIG. 2) having protrusions 24 is formed on an oxide film 22 formed on a silicon wafer 21, similar to the substrate 11 shown in FIG. take shape in this case,
A wrapping film is not particularly required. Such a substrate 20
A flash lamp 30 or the like is used to instantaneously apply heat in a pulsed manner from the back side of the plate. Heat is transmitted to the amorphous silicon layer 23 via the silicon wafer 21 and the oxide film 22.

At this time, since heat is concentrated on the protrusion 2, the temperature becomes higher than other areas of the amorphous silicon layer 23. Therefore, since the protrusion 2 portion becomes polycrystalline first, lateral solid phase orientation can be performed using this as a seed crystal. This method allows batch processing and is suitable for bulk production.

The embodiment shown in FIG. 1 and the embodiment shown in FIG. 4 described above are as follows:
Both methods selectively form a seed crystal and begin crystal growth from there.

[Effects of the Invention] According to the present invention, a part of polycrystalline silicon or amorphous silicon on an insulator serving as an SO substrate is patterned into a tapered shape such as a rectangle or a wedge shape, and thereby the part Seed crystals of about 1 μm square can be selectively formed.

Then, using this seed crystal as a core, the entire polycrystalline silicon or amorphous silicon layer can be crystallized with uniform plane orientation.

Furthermore, since it is no longer necessary to use the underlying substrate as a source of seed crystals, the range of applications of SOI devices can be greatly expanded.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of this invention, and FIG.
A plan view showing an example of a substrate used in the embodiment shown in the figure, No. 3
The figure is a sectional view taken along the line AA shown in FIG. 2, FIG. 4 is an explanatory diagram showing another embodiment of the present invention, FIG. 5 is a sectional view of a substrate used in the prior art, and FIG. FIG. 2 is an explanatory diagram showing the principle. 11. 20... Substrate, 12... Insulator, 13...
・Polycrystalline silicon layer, 14, 24...Protrusion, 15・
... Side wall material, 16... Wrapping film, 21... Silicon wafer, 22... Oxide film, Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6

Claims (1)

[Claims] An insulator is used as a base substrate, a polycrystalline silicon layer or an amorphous silicon layer having a part of the region where heat is likely to concentrate is formed on the base substrate, and then heat treatment is started from the part of the region, A method for manufacturing an SOI substrate, comprising monocrystallizing the polycrystalline silicon or amorphous silicon.