JPH03283532A - Silicon substrate for discrete element - Google Patents

Abstract

PURPOSE:To reduce crystal defects after diffusion and also precipitates by performing a predetermined thickness etching on one side of a silicon wafer after lapping. CONSTITUTION:A portion of a silicon wafer 1, 0.5 to 1.5mum from the surface thereof, is removed by alkali etching. The range of the alkali etching is the removal of a crushed layer 2 formed by lapping. An etching allowance should be 0.5 to 1.5mum, and preferably 1.0+ or -0.5mum. As a consequence, the crushed layer formed on the lapped wafer can be removed completely, permitting contamina tion in the crushed layer to be removed. In addition, the amount of precipitates is small. A decrease in the yield of devices can be prevented and crystal characteristics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in silicon substrates for discrete devices.

(Prior technology) Generally, silicon substrates for discrete devices go through the steps of ingot → cutting → chamfering → lapping, then are cleaned and put into the collector diffusion process, where an impurity diffusion layer is formed on the surface and the product is manufactured. becomes.

(Problem to be solved by the invention) The conventional silicon substrate for discrete elements described above is
The products are cleaned and supplied before being put into the diffusion process, but this cleaning only cleans up to about 0.1μ from the surface (line a in Figure 1), so contaminants in the crushed layer are removed. There are problems in that it is difficult to remove, and the amount of precipitates (particles) generated from the lapped surface becomes extremely large, reducing device yield.

The present invention has been made in view of the problems of the conventional technology as described above, and its purpose is to improve crystal properties with less generation of crystal defects and less generation of precipitates after diffusion. Another object of the present invention is to provide a silicon substrate for a discrete element.

(Means for Solving the Problems) In order to achieve the above object, the silicon substrate for discrete elements in the present invention is characterized in that the silicon wafer after lapping is etched by 0.5 to 1.5 μm on one side. .

Alkali etching, acid etching, etc. are used as the above etching process, and the etching depth is the same as the fracture layer (0,5
~1.0 μm) to completely remove 0.5 to 1.5 μm.

If the etching is less than 0.5 .mu.m, a fractured layer remains on the surface of the silicon substrate, and the amount of precipitates generated after diffusion becomes extremely large, which is undesirable because it reduces device yield.

Furthermore, if the etching thickness is 1.5 .mu.mm or more, crystal defects (line defects) generated after diffusion become dense, which is undesirable since quality deteriorates.

(Function) According to the above means, by etching the silicon wafer after lapping by 0.5 to 1.5 μm from the surface, the fracture layer (0
, 5-1.0 μm) are completely removed, resulting in fewer precipitates forming after diffusion and improved crystal properties.

(Effects of the Invention) E. As detailed above, the silicon substrate for discrete elements of the invention is a silicon wafer that has been lapped and is etched by 0.5 to 1.5 μm on one side. The fractured layer that has been formed can be completely removed and therefore the contaminants in the fractured layer can be removed.

In addition, by setting the etching depth to 0.5 to 1.5 μm, there are few precipitates generated after diffusion, which prevents a decrease in device yield, and improves crystal characteristics, thereby providing a high-quality silicon substrate. I can do it.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. In the figure, 1 indicates a silicon wafer after lapping, and 0.5 to 1.5 μm from the surface of the silicon wafer 1 is etched by alkali etching. Remove.

The range to be removed by alkali etching is to remove the crushed layer (0.5 to 1.0 μm) 2 formed by lapping.

In addition, the number (density) of etch pits on the silicon wafer surface after etching and diffusion by alkali etching.
The precipitate density is as shown in Figure 2, and the etching is 0.5 to 1.5 μm, preferably 1.0±0.
It is understood that a range of 5 μm is most effective.

Further, for the above-mentioned alkaline etching, an aqueous solution of potassium hydroxide (KOH) is used.

Next, the results of an experiment in which the amount of impurities deposited between the product of the present invention and the conventional product will be explained.

[Experiment sample]

Product of the present invention: After lapping, the silicon wafer was etched to a depth of 1.0 μm using a potassium hydroxide (KOH) etching solution to remove the fractured layer.

Conventional product: A silicon wafer that has been wrapped and cleaned with a 1% aqueous solution of sodium hydroxide (NaOH) to a thickness of 0.1μ or less.

[Impurity analysis method]

Put pure water in a sealed bag, put the experimental sample (invention product, conventional product) in it, heat it, dissolve the impurities on the sample wafer surface in the pure water, and analyze the pure water to find out the impurities. (Mad method for determining quantity).

〔result of analysis〕

As shown in the table below.

(As is clear from the experimental results of Ionchrome and above, the conventional product leaves a fractured layer and contains many impurities, but the product of the present invention removes the fractured layer and only crack layer 3 remains. Therefore, the amount of impurities is significantly reduced and a high-quality silicon substrate can be obtained.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a cross-sectional view showing a silicon wafer after lapping. FIG. 2 is a diagram showing the relationship between etch pit density and precipitate density after etching and diffusion. In the figure, 1: Silicon wafer: fracture layer

Claims (1)

[Claims] The silicon wafer after lapping is 0.5~1.
A silicon substrate for discrete devices characterized by being etched by 5 μm.