JPH0616537B2 - Method for manufacturing semiconductor substrate - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a semiconductor substrate, particularly SOI (Silicon on Insulato).
r) relates to a method of manufacturing a substrate.

[Technical background of the invention]

As is well known, when manufacturing a semiconductor device, for example, SOS is used.
(Silicon on Sapphine) substrate is used. Such an SOS substrate is usually manufactured by sufficiently smoothing the surface of a sapphire substrate (wafer) and then forming a thin single crystal silicon layer on the substrate surface by vapor phase growth.

[Problems of background technology]

However, according to the conventional technique, a problem occurs in the crystallinity of the single crystal silicon layer, which causes the generation of crystal defects and the deterioration of electrical characteristics. This is because the crystal structure of the wafer is affected in the initial stage of the vapor phase growth process, and it is difficult to take the original crystal structure. In other words, a film thickness of several hundred Å is required until the complete crystal structure is obtained. Therefore, a complete crystal layer is formed in the upper layer of the single crystal silicon layer, but crystal defects are likely to occur in the complete crystal layer due to the influence of the incomplete crystal layer in the lower layer, and the leak current increases in the incomplete crystal layer. When the elements are formed on the semiconductor substrate due to deterioration in electrical characteristics such as the above, it is an obstacle to speeding up and increasing the density of the element.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a semiconductor substrate capable of preventing the occurrence of crystal defects and the deterioration of electrical characteristics, and increasing the speed and density of elements. To do.

[Outline of Invention]

The present invention has the above-mentioned object by stacking a semiconductor layer having a sufficiently smooth surface and an insulating substrate having a smooth surface so that the smooth surfaces are in contact with each other and then thermocompression bonding. It aims to achieve it. That is, a semiconductor layer whose surface is sufficiently smoothed by polishing and an insulating substrate whose surface is sufficiently smoothed by polishing are prepared in separate steps and then thermocompression-bonded to integrate them. As in the prior art, generation of an incomplete crystal layer that depends on the crystal structure of the semiconductor substrate is avoided at the initial stage of growth, and a semiconductor substrate having a semiconductor layer in a completely crystalline state is formed.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. 1 (a) to 1 (c).

First, the surface of a silicon single crystal substrate 1 having a specific resistance of 0.002 cm, which is highly doped with arsenic as a semiconductor substrate, is mirror-polished. Subsequently, a 0.5 μm thick silicon single crystal layer 2 as a semiconductor layer was grown on this substrate 1 by a general vapor phase growth technique (first (a) shown). Then
In the same manner as above, a SiO ₂ substrate 3 as an insulating substrate whose surface is mirror-polished is prepared, and the substrate 1 is provided on the surface of the substrate 1 with the single crystal layer 2 of the substrate 1 being the surface of the SiO ₂ substrate 3. Layered to touch. Then, thermocompression bonding was performed for 1 hour at 950 ° C. and 500 g / cm ^{3 in} a vacuum of 1 × 10 ⁻⁴ torr (shown in FIG. 1 (b)). Further, after the temperature was lowered, the silicon single crystal substrate 1 was removed using a fluorine-nitric acid-based etching solution having an etching rate selectivity depending on the impurity concentration to manufacture a semiconductor substrate. Note that the etching _{solution, HF: HNO 3: CH 3} COOH-1:
3: 8 was used, and the etching speed at this time was 2.3 μm / min in the silicon single crystal substrate 1 and almost zero in the silicon single crystal layer 2 (shown in FIG. 1 (c)).

Therefore, according to the present invention, after the silicon single crystal substrate 1 having the silicon single crystal layer 2 and the SiO ₂ substrate 3 are produced in separate steps, they are thermocompression bonded to selectively produce the silicon single crystal substrate 1. Since etching is performed, the silicon single crystal layer 2 having more complete crystallinity than that of the conventional one can be obtained.

Therefore, it is possible to prevent the crystal defects and the deterioration of electric characteristics, which have been problems in the past, and to increase the speed and density of the device. In the above embodiment, the silicon single crystal layer 2 and SiO
_When the lapped sections before and after thermocompression bonding with the _two substrates 3 were photographed with a microscope, the schematic diagrams shown in FIGS. 2 (a) and 2 (b) were obtained. Here, (a) of the figure shows the state before thermocompression bonding, and (b) of the figure shows the state after thermocompression bonding. From FIGS. 2A and 2B, the boundary surface 4 was present between the silicon single crystal layer 2 and the SiO ₂ substrate 3 before the thermocompression bonding, but this boundary surface 4 disappeared completely after the thermocompression bonding. Can be confirmed. This is because SiO ₂ has a property as a viscoelastic body and viscous flow remarkably occurs at a high temperature. Further, an SOS substrate having a silicon single crystal layer having a thickness of 0.3 μm provided on a sapphire substrate was manufactured by the conventional vapor phase growth method and the method of the present invention, and leakage current between diffusion electrodes provided at a constant distance was measured. When measured, the current value according to the present invention showed a two-digit decrease. From this, it can be confirmed that the method of the present invention is superior to the conventional method.

In the above example, the silicon single crystal substrate having the silicon single crystal layer formed thereon and the SiO ₂ substrate were thermocompression bonded,
When the silicon single crystal layer is thick, only the silicon single crystal may be thermocompression bonded to the SiO ₂ substrate. Further, although the silicon single crystal plate is used in the above-mentioned embodiment, the present invention is not limited to this.

〔The invention's effect〕

As described above in detail, according to the present invention, the crystalline semiconductor layer is prepared separately from the insulating substrate, and then the both are integrally formed. It is possible to provide a method of manufacturing a semiconductor substrate capable of preventing deterioration of the device, increasing the device speed, and increasing the density.

[Brief description of drawings]

1 (a) to 1 (c) are sectional views showing a method of manufacturing a semiconductor substrate according to an embodiment of the present invention in the order of steps, and FIG. 2 (a) is thermocompression bonding of a silicon single crystal layer and a SiO ₂ substrate. The schematic diagram showing the state of the previous lapped cross section taken by a microscope, and FIG. 6B is the schematic diagram showing the state of the lapped cross section after thermocompression bonding of the silicon single crystal layer and the SiO ₂ substrate taken with the microscope. is there. 1 ... Silicon single crystal substrate (semiconductor substrate), 2 ... Silicon single crystal layer (semiconductor layer), 3 ... SiO ₂ substrate (insulating substrate), 4 ... Boundary surface.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-51-18475 (JP, A) JP-B 37-114 (JP, B1) JP-B 49-26455 (JP, B1) 44th Applied Physics Academic Proceedings 1983. September 25 P. 614 (lecture number 26a-D-9)

Claims (1)

[Claims] 1. A Si semiconductor layer having a sufficiently smooth surface and a SiO ₂ layer having a sufficiently smooth surface are joined on the smooth surface, and the Si is formed by thermocompression bonding at a temperature of 950 ° C. or higher.
A method for manufacturing a semiconductor substrate, comprising a step of eliminating a boundary surface where the surface of the semiconductor layer and the surface of the SiO ₂ layer are joined.