JPH01290229A - Semiconductor wafer - Google Patents

Abstract

PURPOSE:To obtain a semiconductor wafer adapted to a starting material of a device high in the degree of integration by a method wherein a silicon single crystal wafer formed through an FZ method and a single crystal wafer formed through a CZ method or an MCZ method are bonded to each other into one piece. CONSTITUTION:One side of an FZ crystal wafer 1 formed through an FZ (floating zone) method whose oxygen concentration is 5X10<17>atom/cm<2> or less is optically abraded to be formed into a mirror surface 1a and concurrently, for instance, one side of a CZ crystal wafer 2 formed through an MCZ method whose oxygen concentration is 5X10<17> or more is also optically abraded to be formed into a mirror surface 2a. And, wafers 1 and 2 are directly joined together into one piece making the mirror surfaces 1a and 2a adhere to each other. Therefore, a device section is formed of an FZ crystal which scarcely contains oxygen, so that a defect caused by the separation of oxygen is prevented from occurring. By these processes, a semiconductor wafer adapted to a starting material of a device high in the degree of integration can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to semiconductor wafers, and particularly to semiconductor wafers suitable as starting materials for semiconductor elements such as MOS devices.

B9 Summary of the Invention The present invention is a silicon single crystal wafer used as a starting material for device manufacturing, by bonding a silicon single crystal wafer made by the FZ method and a single crystal wafer made by the C2 method or the MCZ method. By integrating,
A semiconductor wafer suitable as a starting material for highly integrated devices is obtained.

C0 Conventional technology Integrated circuit (IC) and large-scale integrated circuit (LSI) MOS
In devices, silicon single crystal wafers are mainly used as the starting material for device manufacturing. Silicon single-crystal wafers are roughly divided into two manufacturing methods: C2 method (Czochr method)
alshi method), MCZ method and FZ method (Floati method)
It is classified into three types: ng Zone method). IC and L
In SI MOS devices, C2 crystal wafers are mainly used, and some MCZ crystal wafers are also used.

A CZ crystal wafer is characterized by a high oxygen concentration within the crystal, which has the advantage of high mechanical strength, but at the same time
Crystal defects such as dStaching Faults are likely to occur due to oxygen precipitates, and furthermore, contaminating impurities are likely to be absorbed into the generated crystal defects, which is a major drawback.

In order to solve this drawback, I G (Instrin
sicGeLtering) wafers and shrimp (Epita)
xial growth) wafers have been devised and used. IG wafers undergo a complex heat treatment to expel oxygen from layers near the wafer surface, resulting in so-called denuded wafers.
This is a denuded zone in which oxygen precipitates are generated in a layer inside the wafer. Therefore, if a MOS device or the like is formed on the surface layer using an IG wafer, defects due to oxygen precipitation will not occur in the device area, and contaminant impurities will be absorbed into the internal layer that does not form the device area (getter). It has the advantage of ring action).

The shrimp wafer aims to achieve the same effect as the ■G wafer by forming an epitaxial growth layer that does not contain oxygen on the wafer surface.

D1 Problems to be Solved by the Invention Since the 1G wafer and shrimp wafer have a surface layer with a low oxygen concentration (forming a device) that is as thin as several μm, they have the following drawbacks.

(1a) Depending on the device manufacturing process, crystal defects may come out from the internal oxygen precipitated layer, impairing the crystallinity of the surface layer.

(lb) When oxygen inside the wafer passes through the surface layer by outward diffusion, minute defects are generated.

As the degree of integration of MOS devices increases (that is, as miniaturization progresses), the above-mentioned drawbacks have been attracting attention as critical problems that reduce the yield of wafers.

The problem of oxygen precipitates is also the same for MCZ wafers.

The FZ wafer has an oxygen concentration three orders of magnitude lower than the CZ wafer, and contains oxygen in an almost negligible amount from the viewpoint of oxygen precipitates. Therefore, FZ crystal wafers are considered suitable for increasing the integration of MOS devices.

However, FZ wafers have the following drawbacks:
It has rarely been used as a starting material for conventional MOS devices.

(2a) Mechanical strength is weak due to extremely low oxygen content.

(2b) Since the content of oxygen is extremely low, dislocations are likely to occur and grow more easily.

(2C) Effect of absorbing contaminant impurities into areas where devices are not formed, such as IG wafers (gettering effect)
There is no.

The present invention solves the above-mentioned problems, and its purpose is to:
By bonding a CZ crystal wafer with a high concentration of oxygen in the crystal to an FZ crystal wafer that contains almost no oxygen,
It is an object of the present invention to provide a semiconductor wafer that can compensate for the drawbacks of an FZ crystal wafer with a CZ crystal wafer.

E1 Means for Solving the Problems In order to achieve the above-mentioned objects, the present invention uses a silicon single crystal wafer with an oxygen concentration of 5x10'' atoms/cx3 or less manufactured by the FZ method and a silicon single crystal wafer manufactured by the CZ method or MCZ method. It is integrated with silicon single crystal Ueno\ with an oxygen concentration of 5 x 10'' or more by adhesion.

Since the F5 action device portion is formed of FZ crystal containing almost no oxygen, defects due to oxygen precipitation do not occur. It also acts to absorb contaminant impurities into a layer (CZ crystal layer) that does not form a device (ge-stuttering effect).

G. Examples Examples of the present invention will be described below with reference to FIGS. 1 and 2.

FIGS. 1(A) to (C) show the steps of manufacturing a semiconductor wafer according to the first embodiment of the present invention. According to this embodiment, the semiconductor wafer is an FZ crystal wafer as shown in FIG. 1(A). 1
One side of the CZ crystal wafer 2 is optically polished to form a mirror surface 1a with a surface roughness of 500 Å or less, and one side of the CZ crystal wafer 2 is similarly optically polished to form a mirror surface 2a with a surface roughness of 500 Å or less. These wafers are directly bonded with their mirror surfaces brought into close contact with each other. Specifically, FZ crystal wafer 1
After cleaning the C2 crystal wafer 2 with pure water, it was dried using a spinner, and the mirror surfaces of both wafers were brought into close contact with each other as shown in FIG.
heat-treated at a temperature of

Next, as shown in FIG. 1C, the bonded FZ crystal side is optically polished to form a mirror surface 1b. The FZ wafer 1 has an oxygen concentration of 5X1017 atoms/ax' or less, and the CZ wafer 2 has an oxygen concentration of 5X10" atoms/CJI3 or more.

Further, other embodiments of the present invention include the following.

(1) An NTD-FZ crystal wafer whose resistivity is more uniformly controlled by neutron irradiation is used instead of the FZ crystal Utsuno.

(2) Instead of the CZ wafer, an MCZC2 crystal wafer 2 with an oxygen concentration of 5×10” atoms/ax3 or more was used.

(3) In order to prevent the occurrence of warping due to the difference in oxygen concentration, FZ crystal Utsuno 3 is further bonded to the CZ wafer 2 as shown in FIG.

If a MOS device is formed on the FZ crystal side using a composite wafer of FZ crystal and CZ crystal produced according to the present invention, the following effects will be produced.

(3a) The device part is made of FZ containing almost no oxygen
Since it is formed into a crystal, defects due to oxygen precipitation do not occur.

(3b) Unlike IG wafers and epitaxial wafers, the layer containing almost no oxygen, that is, the FZ crystal layer, is as thick as several 100 μm, so the device manufacturing process causes crystal defects to occur in the device part rather than in the internal oxygen precipitated layer (C2 crystal layer). It doesn't come out until then. Further, for the same reason, oxygen inside the wafer (CZ crystal part) does not diffuse outward to the device part, so that micro defects do not occur in the device part unlike IG wafers and shrimp wafers.

(3c) It has high mechanical strength because it has a C2 crystal layer with a high oxygen content.

(3d) Since it has a CZ crystal layer with a high oxygen content, it is difficult for dislocations to occur and grow.

(3e) There is an effect (gettering effect) of absorbing contaminant impurities into a layer (CZ crystal layer) that does not form a device.

As a result of the above effects, the silicon single crystal wafer according to the present invention has a higher degree of integration than conventionally used CZ crystal wafers such as IG sea urchin/% and shrimp wafers (specifically, 0.5 μm rule or more). It is suitable as a starting material for MOS devices (with high integration density).

■■1 Effects of the Invention The present invention is as described above, and since a CZ crystal wafer with a high oxygen concentration in the crystal is bonded to an FZ crystal wafer containing almost no oxygen and integrated, a device with a high degree of integration can be obtained. A semiconductor wafer suitable for the starting material can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the manufacturing process of a semiconductor wafer according to an embodiment of the present invention, and FIG. 2 is a diagram showing the configuration of a semiconductor wafer according to another embodiment of the present invention. ■...FZ crystal wafer, 2...CZ crystal wafer, 3
...FZ crystal wafer. ■ 1.3・FZ crystal wafer Ia, Ib・-mirror surface, etc.)

Claims (1)

[Claims] (1) Manufactured by FZ method with oxygen concentration of 5×10^1^
Silicon single crystal wafer with 7 atoms/cm^3 or less and an oxygen concentration of 5 x 10^1^ made by CZ method or MCZ method
A semiconductor wafer characterized by being integrated with a silicon single crystal wafer of 7 or more by adhesion.