JPS59148346A - Substrate for semiconductor device - Google Patents

Abstract

PURPOSE:To perform control of the thermal gradient of the surface layer of an insulating body readily, by including lanthanide ions in the insulating body layer when recrystallization is performed by laser annealing. CONSTITUTION:The laser annealing of an amorphous or polycrystalline silicon film 5, which is deposited on an insulating substrate 3, is performed and recrystallization is attained. At this time, the surface of the insulating body is formed by an insulating body 4, in which lanthanide metal ions having large absorption coefficient with respect to laser are doped. Then, the insulating body 4, which separates a device region, is sufficiently heated, and a silicon device froming region having excellent uniformity in orientation can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a substrate for forming a single crystal silicon film with good crystallinity on an insulator.

The technique of forming a single crystal silicon film on an insulator is useful for increasing the speed of devices or making them three-dimensional, and various methods have been tried. As one method, an amorphous or polycrystalline silicon film is deposited on an insulator, and the silicon film is recrystallized by laser annealing to form a polycrystalline silicon film with large grains. There is a method of obtaining a film or island-like single crystal silicon. 〔for example,
T, I Kamins et al IBBE l1ielectro
A polycrystalline silicon film is deposited on quartz glass using the n Device Letters vol method, and recrystallized by laser annealing using a neodymium YAG (Nd:YAG) laser as a laser.
) A preferentially oriented silicon film is obtained. [Kimura et al., Japan Society of Applied Physics, Applied Electronics Materials Subcommittee N11393 (1982).
5.25) P7] When forming a device on such a silicon film, it is preferable that the orientation of each single crystal silicon grain is aligned in order to reduce variations in device characteristics. The silicon film has as many grains as possible in the direction perpendicular to the substrate surface (100)
It is desirable that it be oriented. However, although the laser-annealed recrystallized silicon film obtained by depositing the entire surface on an insulating substrate is good from the point of view of crystallographic conformation, when actually trying to form a device, the following problems occur. There are some obstacles.

This is because the surface has large irregularities, cracks occur, and a single silicon duplex does not necessarily correspond to the device formation region. As a method to avoid these problems, there is a method of separating the device formation region into islands and embedding them on the surface of the insulating substrate. (Special application 1986-136
292) When the present inventors evaluated the buried island-shaped silicon film described above by laser annealing, they found that the surface remained flat for a long time and there were no cracks. If the absorption coefficient of the silicon film used for the laser is small, the effect of heat escaping from the insulator region of the side wall of the silicon island embedded in the groove will be severe, making it difficult to melt the silicon film. Alternatively, although a good 100) orientation is obtained in some cases, the uniformity of the orientation is still insufficient.

For example, in the IXo, 5- or so region containing silicon duplex recrystallized by laser annealing, there may be a region where the angular distribution width of the (100) orientation is within 10, and a region where the IQX5- is wide. Then, the above angular distribution width is 3
It may even be 0 or more. The present invention further improves and develops the method of embedding a silicon film, in which at least the insulator surface layer forming the device is formed with a surface dry layer so as to absorb laser light, and the peripheral part of the groove region is It also has a heated structure and is characterized by controlling the thermal gradient of the insulator surface layer in order to obtain an island-like silicon film with controlled orientation.

EMBODIMENT OF THE INVENTION Hereinafter, one Example will be shown and the present invention will be explained in detail using the drawings. FIG. 1 is a schematic cross-sectional view for explaining a conventional example. A quartz glass substrate is used as an insulating substrate, and grooves are formed as a silicon vice formation area using phosphorography technology.Next, a polycrystalline silicon film is deposited on the substrate using an LPCVD method, and a silicone film is further deposited on the non-device formation area. 0 is a schematic diagram of a cross-section of a substrate removed by boring Since B does not absorb laser energy, it is not heated. The side wall portion B is heated only by the heat conducted when the silicon film 1 is heated. In such a case, if the laser energy is insufficient, the buried silicon film 1
Even if sufficient energy was applied to recrystallize, the uniformity of the (100) orientation was poor. As a result of examining various substrates using the groove depth d% and the tile interval It was found that this is due to the fact that the solid-liquid interface is not parallel to the bottom surface A of the substrate. Therefore, when recrystallizing the buried silicon film by laser annealing as described above, it is necessary to have a structure that can sufficiently heat the side walls of the trench. Under such conditions, the solid-liquid interface during recrystallization A recrystallized silicon film is obtained which is parallel to the bottom surface and preferentially oriented <100> in the direction perpendicular to the substrate.

FIG. 2 is a schematic cross-sectional view of a substrate having a structure in which sidewall portions of grooves are heated, which is an embodiment of the present invention. 3 is an insulating substrate serving as a base; 4 is a light-absorbing insulator doped with lanthanide metal ions that absorb laser; and 5 is a buried island-shaped silicon film.

First, a method for forming the substrate shown in FIG. 2 will be briefly described. The base insulator 3 has a diameter of 50 mm and a plate thickness of 350 μm.
Next, a light-absorbing insulating film 4 is formed on the quartz glass to a thickness of 90 m using a sputtering method using as a target silicon dioxide doped with lanthanide metal ions to a desired content. Make sure to deposit 2 to 5 μm. Next, grooves with a depth of 0.7 .beta.m were formed by phosphorography and plasma etching. The groove that will become the device formation area is 10XI O-μm mushroom, 10X20-
, lIm'', and 20 x 20 mm snow. The spacing between the grooves was 1 to 5 μm.

Next, a polycrystalline silicon film was deposited to a thickness of 0.7 μm on the insulator film by the LPCVD method. Next, the unnecessary silicon film not forming the sib vice was removed by borising, and an island-shaped silicon 5 as shown in FIG. 2 was created. As the light-absorbing insulator film 4, a silicon dioxide (Sing) film doped with lanthanide metal ions was used. For example, a silicon dioxide film doped with 5% neodymium (Nd) is A
It has large optical absorption near 0.5 μm, which corresponds to the wavelength of r laser light. In addition, the silicon dioxide film doped with samarium (Sm) is made of neodymium YAG (Nd:YA).
) Has light absorption near I Am, which corresponds to the wavelength of the laser beam. Lanthanide metal ions exhibit light absorption involving d-electrons, and have a heating effect when doped into an insulator such as silicon dioxide (Sing).

The substrate surface shown in FIG. 2 is annealed with Ar laser light or Nd:YkGV laser light depending on the light absorption wavelength of the insulator film 4, and the buried island-shaped silicon film in the device formation area is recrystallized. When the crystallographic conformation was evaluated using X-ray diffraction, it was found that the vertical direction of the substrate was (100) oriented, and the region where the half-width in the X-ray rocking car was within 1° was 10.
It spread over a wide area about x511j. It was found that the orientation was more than io times better than the amount of orientation obtained when the insulator surface had a structure in which it was not heated, as shown in Figure 1. Furthermore, according to electron microscopy, the embedded island-like silicon film consists of 9 single grains.
Although no defects were seen, a Kikuchi pattern was also seen, indicating the integrity of the crystal.

In the above embodiments, a light-absorbing insulator film such as a silicon dioxide film doped with lanthanide metal ions was used as the insulator surface layer in order to increase light absorption. A quartz glass doped with lanthanide metal ions over the entire substrate may be used as the insulating substrate. Further, the present invention is also effective when a substrate having an oxidized silicon substrate surface or a material containing alumina as a main component, etc., other than quartz glass, is used as the insulating material.

As described above, when an amorphous or polycrystalline silicon film deposited on an insulating substrate is recrystallized by laser annealing, at least the surface layer of the electrically insulating material is absorbed by the laser. The present invention provides a silicon semiconductor substrate formed of an insulator doped with lanthanide metal ions having a large coefficient and having an island-like silicon film embedded in a groove formed in the insulator as a device formation region. By laser annealing this, the insulator separating the device regions is also sufficiently heated, resulting in a silicon device formation region with excellent orientation uniformity.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a conventional substrate used to explain the present invention. FIG. 2 is a schematic diagram showing a cross section of the substrate structure of the present invention. 1.5... Island silicon film, 2... Groove, 3... Insulator substrate, 4... Light absorbing insulator film.

Claims (1)

[Claims] - For semiconductor devices in which an insulating layer is provided on at least the surface, an island Kg is formed on the surface of the insulating layer, and a silicon film recrystallized by laser annealing is embedded in this groove. 1. A substrate for a semiconductor device, wherein the insulating layer contains lanthanide metal ions.