JPH025546A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device whose silicon layer is uniform in thickness by a method wherein a silicon dioxide film is formed on the surface of a first substrate including the inside of a groove provided to the surface to be a flat insulating film, the above face is pasted onto a second silicon substrate, the first silicon substrate is abraded until the silicon dioxide is exposed, and a semiconductor element is formed on the abraded face. CONSTITUTION:An oxide film 2 formed of silicon dioxide is formed inside a groove after the groove has been provided to a primary surface of a silicon substrate 1, then the groove is filled with a polysilicon 3, and a flat oxide film 2 is formed on the whole surface. Next, the first silicon substrate 1 is pasted onto a second silicon substrate 4 through the intermediary of an oxide film 2, and the substrate 1 is selectively abraded from the rear until the oxide film 2 inside the groove is exposed. An amine is used as an abrasive solution, the abrasion stops automatically when the oxide film 2 is exposed. Therefore, the thickness of a silicon layer becomes nearly equal to the depth of the groove after the abrasion is completed, so that the silicon layer uniform in thickness can be accurately formed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and in particular, relates to a method of manufacturing a semiconductor device having a dielectric isolation structure. [Prior Art] Conventionally, a dielectric isolation structure has been used. As a method for manufacturing a semiconductor device having a sapphire substrate, there is a method of forming a semiconductor element using island-like silicon provided on a sapphire substrate.
n 5apphire, abbreviated as SO5), a method in which oxygen ions are implanted into a silicon substrate, a silicon layer is epitaxially grown, and this silicon layer is formed into an island shape to form a semiconductor element there (Ssparation by Imp).
However, in SO8, the crystallinity of the silicon layer is worse than that of normal pulg-like silicon, and
It has the disadvantage of low mobility of rJf- and holes,
SIMOX requires a large amount of oxygen to be ion-implanted, and has the disadvantage that the shape of the substrate is difficult. recently,
Two silicon substrates are used, and after forming an oxide film on the surface of at least one of the substrates, the two boards are bonded together with the oxide film interposed therebetween. It has been reported that a semiconductor device having a dielectric isolation structure can be formed by using the above two methods. Since this technology can use single crystal silicon to form semiconductor elements, there is no decrease in mobility in SO8, and the bonding process does not require heat treatment or voltage application. It has the advantage of not requiring multiple ion implantations in SIMOX.

[Problem to be solved by the invention]

However, in this bonding technology 7), it is important to form a thin silicon layer for forming a semiconductor element, but the previously reported methods do not allow easy formation of thin silicon layers with good control. It was very difficult. For example, the method of reducing the thickness of the silicon layer by polishing is inexpensive, but it is difficult to obtain a uniform silicon layer with high precision. 2. Another known method is to use an epitaxial wafer and thin the silicon by selective etching to form a semiconductor element formation layer, but this method has the disadvantage that the cost of the epitaxial wafer is high.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate these drawbacks and provide a method for manufacturing a semiconductor device that can form a silicon layer of uniform thickness with high precision without significantly increasing the number of steps.

[Failure to solve the problem]

In order to achieve the above object, a method for manufacturing a semiconductor device according to the present invention includes forming a silicon dioxide film on the surface including the groove formed on one main surface of a first silicon substrate; a step of forming a flat insulating film on one main surface; a step of bonding the first silicon substrate and the second silicon substrate by closely contacting them and performing heat treatment; selectively polishing the silicon substrate from the other main surface to form the bottom of the groove] and polishing until silicon dioxide is exposed; and forming a semiconductor element on the polished surface of the first silicon substrate. This includes:

[Effect]

In the semiconductor device manufacturing method of the present invention, if an amine-based polishing liquid is used for polishing the wafer, the polishing rate for silicon oxide film is 1/100th that of silicon. Polishing stops at the point where the oxide film is exposed. Therefore, when selectively polishing the silicon by forming a silicon oxide region in advance in the silicon, the polishing stops as soon as this silicon oxide is exposed, and the silicon surrounded by the silicon oxide is formed to a constant thickness. be done.

Therefore, silicon can be polished to a constant thickness with high precision just by polishing.

〔Example〕

An embodiment of the method for manufacturing a semiconductor device according to the present invention will be described below with reference to FIGS. 1 to 4. These figures show a cross-section of a portion of the wafer that undergoes each manufacturing step.

First, as shown in FIG. 11, a groove whose surface is covered with an oxide film 2 made of silicon dioxide is formed on the main surface of a first silicon substrate 1. Specifically, after a groove is formed on the main surface of a first silicon substrate 1 by anisotropic dry etching, an oxide film 2 is formed inside the groove by thermal oxidation, and then the groove is filled with polysilicon 3. The silicon substrate 1 and the second silicon substrate 4 are further thermally oxidized to form a flat oxide film 2 on the entire surface, as shown in FIG.
and are chemically bonded together via the oxide film 2 on the surface. In this step, for example, the two silicon substrates described above are subjected to hydrophilic treatment, and then brought into close contact with each other at a high temperature (for example,
This is done by heat treatment at 000°C). This method is called silanol bonding, and is reported, for example, in Oyoi Jitsu, Vol. 56, No. 3, pp. 373-376 (1987). It is also possible to bond between 1 and 1 through an oxide film, and this method can be used, for example, with ink...
National Electron Device Meeting (
IEEE, International Elect
ron DevieMeetinH) Technical
Technical Diquest
), pp. 684-687 (1985).

A similar technique is also reported in Japanese Patent Publication No. 39-17869.8 Next, the first silicon substrate 1 is selectively polished from the back surface to expose the oxide film 2 provided at the bottom of the groove. Polish until By using amine as polishing liquid.

Since the polishing is automatically stopped when the oxide film 2 is exposed, the thickness of the first silicon base @1 after polishing is approximately equal to the depth of the groove described above, and a silicon layer with a uniform thickness can be formed with precision. Can be formed well. Thereafter, as shown in FIG.
1, as shown in FIG.
"Silicon 7, n" silicon 8, n silicon 9, p silicon 10 are formed, and a goo 1-oxide film 5. Ge+=electrode 6
By configuring a semiconductor element by attaching the following, a dielectrically isolated semiconductor device can be obtained. Figure 4 shows a complementary IGFET (Insulated Gate FET).
A semiconductor device is shown in which an n-channel IGFET and a p-channel IGFET are dielectrically separated from each other by connecting an electrode 6 to a goo 1 made of polysilicon.

In the above embodiment, an example is shown in which polysilicon 3 is buried in the groove, but since polysilicon 3 is merely used as a filling material, burying of polysilicon is not necessarily necessary. An oxide film may be formed entirely within the trench, and a flat insulating film made of an oxide film may be further formed on the main surface of the first silicon substrate.

Furthermore, the surface of the insulating film can be formed with a flat surface by adding 1, for example, liquid SiO, without using a planarization process.

〔Effect of the invention〕

As explained above, according to the present invention, semiconductor substrates separated by a dielectric material can be easily manufactured by bonding them together on the oxide film forming surface using silicon wafer bonding technology.6 The thickness can be uniform and accurately controlled. This has the effect of forming a dielectric isolation silicon layer.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views of a portion of a semiconductor wafer illustrating an embodiment of the present invention in the order of steps. 1... First silicon substrate 2... Oxide film 3...
Polysilicon 4... Second silicon substrate 5...
・Gate oxide film 6...Glue electrode 7...
P4' silicon 8...n+silicon 9...
・N silicon 10...P silicon 11...
・Silicon layer

Claims (1)

[Claims] (1) A step of forming a silicon dioxide film on the surface of the first silicon substrate including the inside of the groove formed on the first silicon substrate, and forming a flat insulating film on the first main surface of the silicon substrate; A step of bonding one principal surface of the first silicon substrate and a second silicon substrate by applying heat treatment to the two substrates, and selectively polishing the first silicon substrate from the other principal surface to form the groove bottom. A method for manufacturing a semiconductor device, comprising: polishing the first silicon substrate until silicon dioxide formed on the substrate is exposed; and forming a semiconductor element on the polished surface of the first silicon substrate.