JPH0352250A - Manufacture of dielectric isolating substrate - Google Patents

Abstract

PURPOSE:To make it possible to reduce the cost of a dielectric isolating substrate by filling recess parts in the surface of a first silicon substrate by the diffusion and solidification of alloy of silicon base material having a melting point lower than that of silicon, and bonding both silicon substrates. CONSTITUTION:As a material for bonding both silicon substrates 11 and 17, alloy 16 of silicon base material having a melting point lower than that of silicon is used. The insides of recess parts 13 in the surface of the substrate 11 are filled with the fusion and solidification of the alloy 16, and both substrates 11 and 17 are bonded. The fused liquid of the alloy 16 has a low viscosity coefficient. Therefore, the complete filling of the alloy 16 into the recess parts 13 in the surface of the substrate 11 by the fusing heat treatment of the alloy 16 can be performed even if the alloy shape before fusion is in the state of particles whose diameters are several mum or more or in the state of a thin plate. In this way, depositing steps of bonding junction layers are simplified to a large extent, and the cost of the dielectric isolating substrate can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a dielectric isolation substrate used in a semiconductor integrated device.

(Prior Art) In recent years, a method for manufacturing a dielectrically isolated substrate using substrate bonding technology has been proposed as a method to solve the high cost of manufacturing a substrate, which is a serious disadvantage of the conventional method for manufacturing a dielectrically isolated substrate. ing. Hereinafter, one such manufacturing method, which is disclosed in Japanese Patent Application Laid-Open No. 61-242033, will be explained with reference to FIGS. 4(a) to (2). First, as shown in FIG. 4(a), after forming a recess 2 on the surface of a single crystal silicon substrate 1 by anisotropic etching, the single crystal silicon substrate 1 is oxidized, and the substrate surface including the four parts 2 is formed. An oxide film 3 is formed for insulation isolation. Next, as shown in FIG. 4, a glassy deposited layer 4 of Si-B=O ultrafine particles made of silicon, boron, and oxygen is formed on the oxide film 3, and another silicon substrate is placed on top of it. Place 5. Next, as shown in FIG. 4(c), this is subjected to heat treatment at a temperature of about 1300° C. to sinter the deposited layer 4 and bond the single crystal silicon substrate 1 and the silicon substrate 5 together.

Next, as shown in FIG. 4(2), the back side of the single crystal silicon substrate 1 is removed by grinding and polishing until the tips of the recesses 2 are exposed, thereby obtaining a dielectric isolation substrate.

(Problem to be Solved by the Invention) However, in the method described above, the material that joins both silicon substrates 1 and 5 has a viscosity of 10"l) oj during sintering.
Since glass of se or higher is used, in order to completely fill the concave portion 2 on the surface of the substrate 1 with the deposited layer 4 without any voids by sintering, it is necessary to use ultrafine glass particles with a particle size of 0.05 to 0.2 nm. must be deposited uniformly on the substrate I without any gaps, so there were problems in that it was difficult to control the deposition process and the deposition took a long time. For this reason, the objective of lowering the manufacturing cost of the dielectric isolation substrate could not be fully achieved.

The purpose of the present invention is to eliminate the above-mentioned problem that the production cost of dielectric isolation substrates increases due to the deposition of ultrafine particles, and to provide an economical method for producing dielectric isolation substrates. do.

(Means for Solving the Problems) The present invention provides a method for manufacturing a dielectric separation substrate using substrate bonding technology, in which a substance for bonding both silicon substrates is used.
An alloy of silicon base material having a lower melting point than silicon is used, and by melting and solidifying this alloy, it fills the recess on the surface of the first silicon substrate and joins both silicon substrates. (Function) The melt of the alloy has a low viscosity of about 10t to 10-'poise. Therefore, the complete filling of the alloy into the recesses on the surface of the first silicon substrate by the melting heat treatment of the alloy is difficult because the shape of the alloy before melting is particle-like or thin-plate-like with a grain size of several tens or more. It also becomes possible. And if we can use such large particles or thin plates,
The process of depositing the alloy layer (bonding layer) is greatly simplified.

(Example) Examples of the present invention will be described below with reference to FIGS. 1(a) to (e). First, as shown in FIG. 1(a), a single crystal silicon substrate 1
By performing anisotropic etching using the oxide film 2 as a mask, a recess 13 with a depth of about 50 mm is formed on the surface of 1. Next, as shown in FIG. 1, after removing the oxide film 12, the single-crystal silicon substrate 1l is oxidized, and an oxide film 14 for insulation isolation with a thickness of about 21 is formed on the substrate surface including the recesses 13. After that, a polycrystalline silicon film 15 having a thickness of about 0.6 mm is formed on the oxide film 14.

Next, as shown in FIG. 1(c), a single crystal silicon substrate I
A substrate l6 having a thickness of about 100 mm and made of a silicon-germanium alloy having a melting point lower than that of silicon is placed on the substrate l.
Alternatively, as shown in FIG. 2, particles 16' made of the alloy and having a grain size of about 101 are deposited to a thickness of about 1001. Thereafter, a silicon substrate 17 with a thickness of about 500 mm is placed on top of it, and a silicon substrate 17 with a thickness of about 1350 to 1400 mm
Add heat treatment at ℃.

As a result, as shown in FIG. 1(2), the silicon-germanium alloy substrate 16 or the alloy particles 16' are melted.
The recess 13 is completely filled and then cooled to solidify, and the single crystal silicon substrate 11 and the silicon substrate 17 are bonded via the silicon-germanium alloy layer 18. Here, the silicon-germanium alloy [18] must not melt as a bonding layer even at a heat treatment temperature of about 1200° C. for later device shaping. Figure 3 shows the dependence of the melting point of this silicon-germanium alloy (Si-Ge alloy) on the composition ratio. From this figure, in order to prevent the above-mentioned melting, it is appropriate that the germanium composition ratio in the silicon-germanium alloy is 20 to 40 at%.

The polycrystalline silicon lil5 has a function of helping the molten silicon-germanium alloy to penetrate into the recess 13 and completely fill it, but it can be omitted if the melting heat treatment is performed under reduced pressure.

Next, by removing the back side of the single crystal silicon substrate 1l by grinding and polishing until the tips of the recesses 13 are exposed, the single crystal silicon substrate 1l between the recesses 13 is removed, as shown in FIG. 1(e). A dielectric H substrate is obtained in which each monocrystalline silicon island 19 is insulated and isolated by oxidized MI4 and held by a silicon substrate I7 via a silicon-germanium alloy layer l8. In the above embodiments, a silicon-germanium alloy was used, but in the present invention, silicon-cobalt alloys, silicon-iron alloys, etc., which similarly have silicon as a base material and which have a melting point lower than that of silicon by alloying, are used. You can also use

(Effects of the Invention) As explained in detail above, according to the present invention, an alloy of a silicon base material having a lower melting point than silicon, such as a silicon-germanium alloy, is used as a material for bonding both silicon substrates. , by melting and solidifying the alloy, it fills the recesses on the substrate surface and joins both substrates together. According to this alloy, since the melt has a low viscosity of about 101 to 10-'poise, it is difficult to completely fill the recesses of the substrate surface with the alloy by melt heat treatment of the alloy. This is possible even if the shape is particle-like or thin plate-like with a particle size of several tens or more. Since such large particles or thin plates can be used, the present invention greatly simplifies the process of depositing the bonding layer (alloy layer) and reduces the manufacturing cost of the dielectric isolation substrate.

[Brief explanation of drawings]

Fig. 1 is a process cross-sectional view showing an embodiment of the method for manufacturing a dielectric isolation substrate of the present invention, Fig. 2 is a cross-sectional view showing a partial modification of the above embodiment, and Fig. 3 is a melting point of a silicon-germanium alloy. FIG. 4 is a process sectional view showing a conventional method for manufacturing a dielectric substrate. 11... Single crystal silicon substrate, 13... Concave portion, l4
...Oxide film, l6...Silicon-germanium alloy substrate, 1 6'...Silicon-germanium alloy particles, 17...Silicon base 1, 18...Silicon-germanium alloy layer, 1 9...・Single crystal silicon island. Embodiments of the present invention Example 1 of the present invention Partially modified examples of alloy particles 2 Figure 3 Dependence of melting point of S+ at % Ge Si-Ge alloy on composition ratio

Claims (1)

[Claims] (a) A step of forming a recess on the first main surface side of a first silicon substrate and forming an insulating film on the first main surface side including the recess; A thin plate or layer of particles made of an alloy having silicon as a base material and having a melting point lower than that of silicon is provided on the first main surface side of the first silicon substrate, and a second silicon substrate is placed thereon. (c) Thereafter, only the thin plate or particle layer of the alloy is melted and solidified by heat treatment, and the concave portion of the first silicon substrate is filled with the alloy, and at the same time, the alloy is used to melt and solidify only the thin plate or particle layer of the alloy. A method for manufacturing a dielectrically isolated substrate, comprising: a step of bonding a silicon substrate; and (2) a step of thereafter removing the first silicon substrate from the second main surface side until the tip of the recess is exposed. .