JPH08293542A - Method for manufacturing dielectric isolation substrate - Google Patents

Abstract

(57) [Abstract] [Purpose] A simple process for producing a substrate with good insulation and separation without the occurrence of voids on the joint surface that would cause peeling or chipping (chipping) of the substrate in the device manufacturing process, which would reduce yield. It is intended to be provided by. A step of implanting oxygen ions from one surface of a silicon substrate, a step of joining the silicon substrate and a supporting substrate with a glass layer, and a step of polishing the other surface of the silicon substrate with a silicon oxide layer And a step of forming a plurality of island-shaped semiconductor layers separated from each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate and a method of manufacturing the same, and more particularly to a substrate and a dielectric isolation technique relating to a dielectric isolation method suitable for manufacturing a highly functional or high performance semiconductor device.

[0002]

2. Description of the Related Art Dielectric isolation technology, which is known as a method for isolating semiconductor single crystal regions from each other, has a very good insulation isolation between devices as compared with standard junction isolation technology, and limits the application circuit. It is suitable for high-voltage and high-current power ICs because it has a small amount. EPIC (Epitaxial Passivated Integrated Circuit) is a typical dielectric isolation method.
Although the cuit) method is known, various other methods have been studied due to problems with large-diameter wafers and manufacturing costs. One of them is SOI (Silicon On Insulator) technology for manufacturing a substrate by bonding a plurality of semiconductor substrates together. As a method for bonding substrates, for example, Japanese Patent Laid-Open No.
There are methods disclosed in JP-A-1-242033 and JP-A-62-177938.

[0003]

As shown in FIG. 1, a conventional substrate manufactured by this kind of bonding method is usually an island-shaped semiconductor layer 11 covered with an insulating film 12 such as SiO _2. Are adhered to the support substrate 15 by the glass layer 13. According to this manufacturing method, a large-diameter wafer with less warpage can be obtained at a relatively low cost, but there are still problems. In particular, depending on the manufacturing conditions and the thickness of each layer, voids (holes) may be generated in the groove, which may cause peeling or chipping (chips) of the substrate in the device manufacturing process and reduce the yield. Become.

In another conventional technique, a semiconductor substrate and a supporting substrate are bonded together using a glass layer, and then polishing is performed from the opposite surface of the semiconductor substrate to form a semiconductor layer (element forming layer) and a glass layer. After manufacturing an SOI substrate in which a supporting substrate is layered, a separation groove is formed in a semiconductor layer by a chemical method or a physical method, the groove is filled with polysilicon, and the surface is polished again to obtain a dielectric layer. A body separation substrate is manufactured. However, this method has a problem that a very complicated polishing process is required twice.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks of the conventional dielectric isolation substrate and to provide a substrate which is free from voids and has good insulation isolation by a simple process.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a step of implanting oxygen ions from one surface of a silicon substrate to form a silicon oxide layer for separation, and the silicon substrate and a supporting substrate are bonded by a glass layer. And a step of polishing the other surface of the silicon substrate to form a plurality of island-shaped semiconductor layers separated by the silicon oxide layer. .

[0007]

The oxygen ion implantation of the present invention is a step performed to form a separating silicon oxide layer in a wall shape in the vertical direction with respect to the silicon substrate. When the accelerated oxygen ions are implanted into the substrate, the oxygen ions penetrate deep inside the substrate when the energy for colliding with the substrate surface is large, and when the energy is small, the oxygen ions stay in a shallow range from the substrate. Therefore, when the energy of oxygen ions to be implanted into the substrate is changed, the implantation depth can have a distribution. After that, when heat treatment is performed to diffuse oxygen ions, the oxygen ions react with silicon and become insulating silicon oxide, which is formed as a wall-shaped layer in the vertical direction of the substrate.

Since the surface of the silicon substrate is flat in the step of joining the silicon substrate and the supporting substrate thus processed to each other by the glass layer, the occurrence of voids due to insufficient filling of the glass substance or the like does not occur.

In the next step, the other surface of the silicon substrate is polished until the wall-shaped silicon oxide layer is exposed on the surface, whereby a substrate having a structure in which the silicon layer is divided by the silicon oxide layer is obtained. . Since the silicon oxide layer has a high insulating property, the silicon layers are separated from each other in an island shape.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

First, as shown in FIG. 2 (a), a mask 21 having a window portion 40 in which a position for implanting oxygen ions is specified is formed on the surface of a silicon substrate. Specifically, for example, the N type has a resistivity of 10 to 30 Ω · cm, and a plane orientation <100>.
The surface of the silicon substrate 10 having a diameter of 4 inches and a thickness of 525 μm is thermally oxidized to form a thermal oxide film having a thickness of 0.5 μm, and this is photoetched to form a patterned thermal oxide film mask. 21 is produced. It should be noted that this mask may be one that does not allow oxygen ions to pass therethrough, and the material and thickness thereof can be appropriately selected. For example, it may be formed of a nitride film. Next, as shown in FIG. 2B, the surface is thermally oxidized again to form a 0.1 μm thermal oxide film 22. The film thickness at this time may be appropriately changed within a range in which oxygen ions can pass.

Next, accelerated oxygen ions are implanted into the surface of the substrate through the window 40, and oxygen ions are implanted so that the oxygen ions are distributed within the substrate, for example, 0 to 2.0 μm. In this implantation, for example, oxygen introduced into a high electric field is bombarded with plasma or accelerated electrons to form oxygen ions, which are accelerated to 20 keV to 250 keV, and 400 to 60
It is made to collide with a silicon substrate heated to 0 ° C. so that the oxygen ion concentration in the substrate becomes 5 × 10 ¹⁷ to 1 × 10 ¹⁹ atoms / cm ² .

Next, after the thermal oxide film on the substrate surface is once removed using an etching solution such as hydrogen fluoride as shown in FIG. 2D, an insulating film 23 (FIG. 2E) is formed on the surface. Form.
This insulating film will be the bottom of the island-shaped silicon layer through the subsequent steps. The insulating film may be an insulating substance such as a silicon oxide film or a silicon nitride film and has high adhesiveness to the silicon substrate. Also, it can be a multilayer. The thickness of the insulating film is about 0.5 to 3.0 μm. From the viewpoint of high reliability, an oxide film (thermal oxide film) manufactured by a thermal oxidation process is suitable, and a thickness of about 2.0 μm is suitable. In the thermal oxidation step, the entire substrate receives heat, so that the oxygen ions implanted earlier diffuse inside the substrate and simultaneously react with silicon, so that the insulating silicon oxide layer 3 is formed.
1 is formed. When the insulating film is formed in a process that does not involve heat treatment, it is necessary to perform heat treatment at about 1000 to 1300 ° C. Further, when heat treatment is performed in the subsequent steps, it can be substituted.

The silicon substrate processed in this way is shown in FIG.
As described above, the support substrate 15 and the glass layer 13 are used for bonding.
It This support substrate is composed of the silicon substrate 10 and the glass.
And a supporting substrate made of a material having a thermal expansion coefficient close to that of the insulating layer 13.
Is particularly preferably a silicon substrate. Also,
Layer is SiO₂Is the main component, and B₂O₃, P₂O_Fiveetc
It contains impurities. Especially for the production of glass layers
Without limitation, it can be manufactured by soot deposition method or CVD method.
You can The soot method is preferable because it is easy to manufacture. Su
In the manufacturing by the oxidization method, for example, on the surface of the oxide film 23,
Gaseous SiCl _FourAnd gaseous BCl₃The hydrogen and the acid
It is obtained by supplying it to a burning flame (oxyhydrogen flame) consisting of elementary substances and decomposing it.
The soot-like substance to be deposited is deposited to a thickness of about 50 μm,
Soot the silicon substrate 15 of 500 μm, which is a supporting substrate,
On top of a stack of particulate matter, and
If the temperature is raised to about 1280 ° C in an elementary atmosphere and heated,
Simultaneously when the soot-like substance sinters and the volume shrinks to a thickness of 5 μm
The glass layer 13 is formed into a uniform glass and
The silicon substrates are bonded together uniformly.

Finally, as shown in FIG. 3B, the silicon substrate 10 is polished from the other surface until the wall-shaped silicon oxide layer is exposed to form island-shaped element forming regions. A plurality of separated island-shaped silicon layers 11 are obtained. The dielectric isolation substrate thus obtained has the structure of FIG.

When the dielectric isolation substrate thus manufactured is subjected to an ultrasonic image exploration apparatus (UH Pulse 200 manufactured by Olympus Co., Ltd.) before polishing, the surface is examined with an optical microscope after polishing, and generation of voids is observed. Not done. The withstand voltage between islands of the island-shaped silicon layer in this dielectric isolation substrate was 700 V when the distance between islands was 10 μm.

[0017]

According to the present invention, since no voids are generated on the bonding surface of the substrate, the substrate is not peeled off or chipped (chip) in the manufacturing process of the element, and the yield is not reduced. Further, according to the present invention, since the dielectric isolation substrate can be manufactured by performing the laborious polishing process only once, it is possible to provide the substrate with good insulation separation by a simple process.

[Brief description of drawings]

FIG. 1 is a diagram showing a dielectric isolation substrate manufactured by a conventional dielectric isolation technique.

FIG. 2 is a diagram showing a manufacturing process of the present invention.

FIG. 3 is a diagram showing a manufacturing process of the present invention.

FIG. 4 is a diagram showing a dielectric isolation substrate manufactured according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 silicon substrate 11 island-shaped semiconductor layer 12 insulating film (thermal oxide film of silicon) 13 glass layer 15 support substrate 21 mask 22 thermal oxide film 23 insulating film 30 injected oxygen ions 31 silicon oxide layer formed in wall shape 40 Mask window

Claims (1)

[Claims] 1. A step of implanting oxygen ions from one surface of a silicon substrate to form a silicon oxide layer for separation, a step of joining the silicon substrate and a supporting substrate with a glass layer, and And a step of polishing the other surface to form a plurality of island-shaped semiconductor layers separated by the silicon oxide layer.