JPS594115A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to write without developing silicon powder or protrusion that becomes an obstacle to wafer process by forming an covering oxide film on the whole surface of a wafer and making anisotropic etching advance by using etching liquid to the extent that visible steps are formed. CONSTITUTION:A covering oxide film 9 is grown on a wafer 1 by chemical vapor phase growth method or thermal oxidation. Next, a resist film is formed on the whole surface by painting and patterning that corresponds to desired numbering is applied to the film to open a window 10 in the covering oxide film 9. Then, etching is made on the wafer 1 by the ordinary ammonia boring to form a groove 11 with depth of 8-10mum. In the ordinary etching in the wafer process it is about 1mum and it can not be seen, but the steps given by the deep groove are visible and they make it easy to recognize wafers in the following processes, and contribute to high yield in the manufacture of semiconductors.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for numbering wafers (forming numbers, etc.) by anisotropic etching.

(2) Background of the Technology In the manufacture of semiconductor devices, wafers are subjected to various processes (wafer processes), and the first step is to form numbers, etc. on the wafers for identification (1).

To explain such numbering with reference to the plan view of FIG. A number is assigned. This number usually consists of a loft number, a serial number within the loft, etc. Since there are generally 50 wafers in a loft, a minimum of 3 digits and as many as 7 digits are assigned. This numbering makes it possible to recognize each wafer one by one, and numbering is an essential step in the manufacture of semiconductor devices.

(3) Prior Art and Problems Conventionally, numbering in wafer processing has been performed by two methods: a method using a diamond pencil and a numbering method using a laser.

The method using a diamond pencil involves a person using it to write recognizable numbers on the wafer (scribe), and as shown in Figure 1 (cross-sectional view (2) of BL), the silicon on the wafer surface is scraped. The scribe portion 4 is dug in one step. When this happens, silicon chips or fine particles 5 scatter and adhere to the entire surface of the wafer -l, which causes a hindrance to the subsequent wafer process.

In the method using a laser, a dot is dug by irradiating the wafer surface with l/-zasuboso(.), and a number is constructed by a series of these numbers. It was confirmed that silicon powder was scattered.

Therefore, it was proposed to use a laser to engrave numbers on the back side of the wafer (the side opposite to the front side where the devices will be formed). However, when dots are dug on the wafer by laser irradiation, as shown in Figure 1 (C1
As shown in the cross-sectional view, there is a bulge 7 around the excavated point (where the laser spot hit) 6 with a diameter of ~20μM.
formed at a height of

When a wafer 1 that has been subjected to lean-haring using a laser is placed, for example, on a stage 8 for the next process, the wafer is tilted due to the bulges 7 as shown in FIG. 2, and is not arranged tightly and flatly. (3) In FIG. 2, the protuberance 7 is exaggerated by four strokes on the wafer 1, and in the following figures, the same parts as those already illustrated are denoted by the same reference numerals.

Recently, patterns are becoming increasingly finer in order to increase the degree of integration of semiconductor devices. Therefore, the adhesion of silicon powder and the tilted mounting number J pattern of the wafer are disturbed or blurred, which becomes an obstacle to pattern miniaturization, and there is a risk of lowering manufacturing yield and product reliability.

(4) Purpose of the Invention In view of the above-mentioned conventional problems, it is an object of the present invention to provide a method that can perform reliable numbering by a simple means without causing any obstacles to the wafer process.

(5) Structure of the invention and this purpose is according to the invention, crystal orientation (100)
, (211), etc. using anisotropic etching, in which crystals with main faces such as (211) are etched with an alkaline etching solution.
This is achieved by providing a method of forming a visually visible number (4) etc. by a step formed by deeply digging the front or back surface of the wafer.

(6) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

When a crystal having a principal plane with crystal orientation (100) or (211) is etched using an alkaline etching solution, anisotropic etching progresses. In the method of the present invention,
Such anisotropic t'l: Enching is progressed deeply, and by using the step formed by the etching, a number etc. that can be visually seen without appearing on a microscope etc. is written. Therefore, there is no occurrence of silicon bumps, which were unavoidable in the prior art.

Carrying out the method of the present invention] Step 2 with reference to Figure 3 78Q
I will clarify. A cover oxide film 9 is formed on the wafer I by chemical vapor deposition (Cv1) method or thermal oxidation to 2000 to 300%
It grows to a thickness of 0.00 people (Figure (a)). Next, a resist sheet (not shown) is applied and formed on the entire surface, and it is patterned in accordance with desired numbers, etc., and the window 1 is formed on the cover oxide film 9.
Open the window at 0 ((h) in the same figure).

(5) Next, the wafer 1 is etched by ordinary ammonia boiling to form the recesses 11 to a depth of, for example, 8 to 10 μm (FIG. 3(C)). Normal etching in a wafer process is done to a depth of about 1 μm, which is usually not visible to the naked eye, but in the method of the present invention, it is visible due to the step obtained by deep digging as described above, and this will be explained in the following. It facilitates wafer recognition in the process and greatly contributes to improving semiconductor manufacturing yields. Further, the depth of the groove 11 can be freely controlled by adjusting the etching time.

Since an alkaline liquid is used for the wafer in the pre-treatment stage (which is done for the purpose of cleaning the wafer), the method of the present invention can be carried out simultaneously with the wafer pre-treatment, and in particular can be carried out in a separate step. does not require.

Additionally, numbering can be done anywhere on the wafer, either on the front or back side. Traditional numbering was done on the back side of the wafer and near the facet line or periphery, but there are also no restrictions on such location.

Although lv etching using an alkaline solution was used as an example in the above section, the anisotropic etching of the present invention can also be carried out by dry etching. The point is to allow the anisotropic etching to proceed sufficiently to form deep grooves in the wafer and to form numbers etc. that are visible by the stepped steps.

(7) Effects of the Invention As explained in detail above, when the method of the present invention is used, anisotropic etching is used to place a visible identification number etc. on a wafer at a designated location for subsequent use. Since it is possible to write without generating silicon powder or protuberances that would be a hindrance to the Unihub 1 process, it is highly effective in improving the yield of semiconductor device manufacturing and the reliability of products.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the process of performing conventional numbering positions, and its (al is a top view of a wafer) (b)
(C1 is a cross-sectional view of the main part of the wafer, FIG. 2 is a cross-sectional view of the wafer placed on stage-1- (7), and FIG. 3 is a cross-sectional view of the main part of the wafer in the process of carrying out the method of the present invention. 1-wafer, 2-facet line, 3-numbering position, 4-scribe portion, 5-silicon powder, 6-laser spot, 7-bump, 8-stage, 9-cover oxide film, 10-window, 1]-Drilling (8) Figure 1 (CI) Q) (b) (C) ( 67 Figure 2 Section 3

Claims (1)

[Claims] A method of writing an identification number etc. on a wafer, which includes the steps of forming a cover oxide film on the entire surface of the wafer, opening a window in the oxide film corresponding to the pattern of the number, etc., and visual inspection using an alkaline etching solution. Anisotropic etching is progressed to such an extent that a possible step difference is formed.