JPS6362252A - Manufacture of dielectric isolation substrate - Google Patents

Abstract

PURPOSE:To obtain a dielectric isolation substrate using a bonding material for preventing it from being deformed due to warpage by sufficiently smoothly polishing the surfaces of two semiconductor substrates, and directly contacting the polished surfaces in sufficiently clean atmosphere. CONSTITUTION:After a separating V-shaped groove is formed approx. 50 microns deep with an alkaline etchant which mainly contains KOH on an N-type single crystal silicon substrate 1 of surface index (100), a thermal oxide film 2 is formed approx. 1 micron in an oxidative atmosphere, and a polycrystalline polysilicon 3 is deposited approx. 80 microns thereon. Then, a polycrystalline silicon side is so chemically or mechanically polished as to be sufficiently smoothly to form a polished surface 4 of polycrystalline polysilicon to complete the polishing before exposing the film 2. Further, the mirrorpolished sides of the surfaces opposed to another single crystal silicon substrate 5 of the substrate are directed to be contacted, and heat-treated at 200 deg.C or higher to be bonded. Accordingly, semiconductor devices having different thicknesses of islands of the single crystal silicon can be easily manufactured to ignore the warpage of the substrate.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method for manufacturing a dielectric insulation isolation substrate.

(Prior Art) Conventionally, the so-called dielectric isolation method in which each element is isolated using an insulator, such as in ICJPLSI, has the following advantages over p-n junction isolation: (1) Leakage current can be extremely reduced by % (
It has advantages such as 2) the withstand voltage can be increased, and (3) there is no need to pay attention to the direction of voltage application. Ideal dielectric isolation is achieved by completely encasing each element with an insulator except for electrode connections. Such an element can be formed using, for example, an SO8 substrate in which silicon is epitaxially grown on sapphire. However, sapphire is expensive, its crystal consistency with silicon is not perfect, and the types of devices that can be manufactured are limited for reasons such as the inability to obtain a high-quality single crystal and the inability to make the film thick enough. Many dielectric isolation methods that do not use an insulating substrate such as sapphire have been proposed so far. An example thereof will be explained with reference to FIGS. 3(a) to 3(d).

First, FIG. 3(a) shows a silicon single-crystal substrate 31 that is etched using an anisotropic etching technique using an alkaline etching solution that has a (100) crystal orientation as its main surface and has different etching rates depending on the crystal orientation. Separation 7-shaped groove 32
The entire surface is covered with an insulating film 33 such as a Si film or the like, as shown in FIG. 3(b). Thereafter, a polycrystalline silicon support layer 34 is deposited on the insulating film as shown in FIG. 3(C).

Next, the silicon substrate 31 is turned upside down and polished off by etching or the like until each single crystal is completely separated.

As shown in FIG. 3(d), semiconductor layers 3s (a) and (b) are formed within the separated single crystal 31 (a) and (b).
to obtain dielectrically isolated elements.

' The biggest problem with such conventional methods is that it is essential to form a support layer. For example, even in the case of commonly used polycrystalline silicon, the deposition rate is slow, so it takes a very long time to obtain a sufficient thickness to withstand polishing and other steps. Furthermore, if polycrystalline silicon is formed to a sufficient thickness, warping will occur due to the difference in thermal expansion coefficients between polycrystalline silicon and single crystal silicon, and deformation due to warping of several hundred microns may occur in some cases. The photo-etching process after forming the body layer is difficult, resulting in a very poor product yield.

(Problems to be Solved by the Invention) The present invention improves the above-mentioned problems of the prior art and provides a method for manufacturing a dielectric insulation isolation substrate using a bonded body that prevents deformation due to warping. purpose.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides strong substrate bonding by directly bringing the polished surfaces of two semiconductor substrates into close contact with each other in a sufficiently clean atmosphere when the surfaces of two semiconductor substrates have been sufficiently polished. Based on the knowledge that it is possible to obtain dielectric materials, we will apply this technology to dielectric separation.

(Function) The depth of the V-shaped groove for isolation between elements in a dielectrically isolated semiconductor device is generally several tens of microns, and when a polycrystalline silicon layer is formed to the extent that it is sufficiently filled with 1C, warping of the substrate can be ignored. Therefore, by completing the formation of the polycrystalline silicon layer just before warpage occurs, polishing the surface sufficiently smooth, and then forming a strong substrate assembly using the above-mentioned method, a highly reliable dielectric insulating separated substrate with no warpage can be obtained. It becomes possible to manufacture.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment showing a cross-sectional structure of the present invention, in which single crystal islands 1a and 1 of different thicknesses are surrounded by a dielectric film 2.
Impurity diffusion layers 7a and 7b are introduced into the semiconductor device 7a and 7b, respectively, to form a dielectrically isolated semiconductor device. The polycrystalline silicon 3 for embedding is polished sufficiently smooth and a dielectric film 6 is interposed between it and the second single-crystal silicon substrate 5 to be bonded to form a bonded body at the position 4. It constitutes a separate substrate.

Figures 2(a) to 2(e) are diagrams showing an embodiment in which a dielectric insulation isolation substrate is actually manufactured using the present invention. In FIG. 2, 7-shaped grooves for separation are formed at a depth of approximately 50 microns on an N-type single crystal silicon substrate 1 having a surface index of (100) using, for example, an alkaline etching solution containing KOH as a main component. In the figure, the difference in level between the mesas is different because the desired level difference can be easily formed by performing a generally known photo-etching process twice.

In FIG. 2(bl), a thermal oxide film 2 of about 1 micron is formed in an oxidizing atmosphere, and polycrystalline silicon 3 of about 80 micron is deposited thereon as shown in FIG. 2(C).

Next, as shown in FIG. 2(d), the polycrystalline silicon side is chemically or mechanically polished to make it sufficiently smooth, and the polishing is completed before the thermal oxide film 2 is exposed. A polished surface 4 of polysilicon is formed. Further, the polycrystalline polysilicon of the above substrate and the other single crystal silicon substrate 5 covered with the thermal oxide film 6 are brought into close contact with each other with the mirror-polished sides of their opposing surfaces facing each other as shown in FIG. 2(e). and then heat-treated at a temperature of 200° C. or higher to bond them. The single crystal silicon substrate 1 side of the substrate assembly thus formed is ground down by polishing, etching, etc. until each single crystal is completely separated, and the keyaki-zukuri dielectric insulation is separated as shown in Fig. 1. The board can be completed.

In the above embodiment, for the polycrystalline silicon surface to be bonded,
A semiconductor single-crystal silicon substrate was used.

Something using a polycrystalline silicon substrate? The present invention can also be applied to ζ.

〔Effect of the invention〕

According to the present invention, it is possible to easily fabricate semiconductor devices in which dielectrically separated single-crystal silicon islands have different thicknesses, the warpage of the substrate can be ignored, and it is possible to fabricate semiconductor devices in a shorter time than with conventional techniques. It is easy to manufacture, highly reliable, and the thickness of the single crystal silicon substrate of the support layer can be selected arbitrarily, so there is no problem in handling even if the diameter of the silicon wafer becomes large. 1. A dielectric insulation isolation substrate with high yield can be provided.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an embodiment of the present invention, Fig. 2 is a process cross-sectional view for explaining a manufacturing method of an embodiment of the present invention, and Fig. 3 is a conventional method of manufacturing a dielectric insulation isolation substrate. FIG. 1: Semiconductor single crystal silicon substrate with crystal plane (100) as the main surface, 2: Insulating film, 3: Polycrystalline silicon layer. 4: Polished surface (joint surface) of polycrystalline silicon layer, 5: Semiconductor single crystal silicon substrate, 6: Insulating film. Agent Patent Attorney Noriyuki Chika Yudo Kikuo Takehana Figure 1 Figure 2

Claims (2)

[Claims] (1) After etching the surface of a semiconductor single crystal silicon substrate into a desired shape, this surface is covered with a dielectric film, and a support layer is further formed. In a method for manufacturing a dielectric insulating substrate having an island region, a support layer is formed by interposing a dielectric film between a polycrystalline silicon layer and a second semiconductor single crystal silicon substrate to form a bonded body. A method for manufacturing a dielectric insulation isolation substrate. (2) The method for manufacturing a dielectric insulating isolated substrate according to claim 1, characterized in that the support layer to be bonded is formed by the polycrystalline silicon layer and the semiconductor polycrystalline silicon substrate. .