JPH03246938A - Silicon wafer and its manufacture - Google Patents

Abstract

PURPOSE:To eliminate minute defects by forming a plurality of pits having specified sizes in the surface of a wafer. CONSTITUTION:High purity single crystal silicon formed by Czochralski method (CZ method) is subjected to wafer processing and polished, thereby forming a P(100) silicon wafer 1, which is cleaned for about 20 minutes at 90 deg.C by using ammonia based cleaning fluid having etching action. Thereby fine pits 2 whose size is 0.5-0.05mum are formed, and minute defects on the surface can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a silicon wafer in which a large number of micro pits are formed on the wafer surface by a pulling method, and a method for manufacturing the silicon wafer.

<Prior Art> Conventionally, silicon wafers have been created by slicing single crystal silicon formed by a pulling method using a slicer. The cut wafer is lapped or ground to improve its flatness, and further chemically etched to remove several micrometers of processing distortion during this process.

Then, as a final finishing step, the wafer surface was mirror polished. In this mirror polishing, 0°01~0.1μ
An abrasive made of silicon oxide fine particles of about 1.0 m was used. As a result, the fine irregularities on the wafer surface in this case were approximately several nm square.

<Problem to be solved by the invention> However, in silicon wafers produced by the pulling method, stacking faults (O5F) have conventionally been produced.
It was not known that a large number of micro-defects different from those in the wafer exist inside the wafer.

The applicant of the present application has discovered and confirmed that a large number of minute defects exist inside silicon wafers produced by the pulling method.

They also discovered a new problem in that the electrical properties of silicon wafers are impaired by these minute defects. For example, many minute defects existing at the interface between silicon and a silicon oxide film act as impurities and reduce the withstand voltage of the oxide film. Based on this discovery, the present invention aims to improve the By removing defects,
The purpose is to provide a silicon wafer suitable for LSI and a method for manufacturing the same.

<Means for Solving the Problems> The first invention of the present application provides a silicon wafer formed by a pulling method, with a diameter of 0.5 mm on the surface of the wafer.
A silicon wafer having a plurality of micro pits with a size of ~0.05 μm is provided.

Further, a second invention of the present application provides a method for manufacturing a silicon wafer, in which the surface of a silicon wafer formed by a pulling method is cleaned under predetermined conditions using an ammonia cleaning solution. For example, the temperature of the ammonia cleaning solution and the cleaning time are set so that the etching amount in the depth direction is 0.025 μm.

Functions and Effects> In the silicon wafer according to the first invention of the present application,
The surface of the silicon wafer has a diameter of 0°5~0.05μ.
A plurality of micro pits with a size of m are formed. Therefore, there are no minute defects near the surface of this wafer.

That is, according to the pulling method, a large number of micro defects exist in a silicon wafer. In this silicon wafer, a plurality of micro pits are formed on the silicon wafer surface by removing the micro defects described above on the wafer surface and in the vicinity thereof.

According to the second invention of the present application, single-crystal silicon is pulled up by a pulling method, and a silicon wafer is further created from the single-crystal silicon. After this, as a method to remove minute defects near the surface of this wafer, an N HaOH/H2O2 cleaning solution (NH40
H:H2O2:H20=1:1:5) for 20 to 60 minutes at a temperature of 90° C. or higher, which is higher than in conventional cleaning. This etching removes minute defects near the surface of the silicon wafer. In addition, the surface of the silicon wafer has a diameter of 0.05 μm to 0.05 μm. A plurality of micro pits of 5 μm are formed. An example of this removal is shown in FIG. FIG. 1 is a cross-sectional view showing the vicinity of the surface of a silicon wafer, in which micro pits 20 were formed on the surface of the silicon wafer 10. As shown in FIG. The diameter of this micropitch 20 is 0.25 μm.

As a result, when a silicon oxide film is formed on the surface of a silicon wafer in the production of ULSI, the breakdown voltage of the silicon oxide film is improved because the micro defects at the interface between the silicon oxide film and silicon are reduced. Table 1 shows an example of the relationship between the size of the pits formed here and the results of pressure resistance measurements. As seen from this table 1, 0.05
When pits of ~065 μm are formed, the withstand voltage of the silicon oxide film is improved.

Table 1 Table 2 shows the ammonia cleaning solution (N Ha OH/H202
Cleaning liquid; NH4OH: H2O2: H20=1:
1:5) to clean a silicon wafer and form a plurality of micro pits (diameter 0.25 μm) on the surface thereof, the relationship between the temperature of the cleaning solution and the cleaning time is shown.

Table 2 Furthermore, this silicon wafer is also effective as a standard sample for particle counters used in cleaning processes. That is, by measuring the number of micro pits in the silicon wafer created in this manner in advance, foreign matter such as particles can be completely removed by cleaning the wafer surface with a scrubber or the like. Therefore, this silicon wafer can be used again as a standard sample.

<Example> The present invention will be explained in detail below.

In this embodiment, a pulling method (CZ method) is used to grow the silicon single crystal.

The high-purity single-crystal silicon thus pulled and formed is then wafer processed and polished using a process under normal conditions.

The thus prepared P(100) silicon wafer is etched using an ammonia-based cleaning solution that has an etching effect, such as NH4OH/H2O2/H20 solution (1:1:5), to make the etching effect stronger than usual. Wash at a high temperature of 90°C for about 20 minutes.

As a result, micro pits with a diameter of, for example, about 0.25 μm are formed in areas where micro defects exist on the surface of the silicon wafer.

4,

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a silicon wafer showing the occurrence of micro pits according to the present invention.

Claims (2)

[Claims] (1) In silicon wafers formed by the pulling method, the wafer surface has a diameter of 0.5 to 0.05 μm.
A silicon wafer characterized in that a plurality of micro pits of a size of . (2) A method for manufacturing a silicon wafer, which comprises cleaning the surface of a silicon wafer formed by a pulling method using an ammonia cleaning solution under predetermined conditions.