JPH0368126A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable the identification marks for an acceptable chip to be made simply and easily on a wafer surface by a method wherein an insulating film is formed in the wafer end on the surface of a semiconductor substrate and then sectional marks are formed by the insulating film. CONSTITUTION:Specific preprocessing is performed on a wafer 1; an insulating film 2 comprising Si3N4 is formed on the whole surface of the wafer 1; any other part of the film 2 excluding specific region is etched away. At this time, a protective film against an etchant having a pattern corresponding to the specific region is formed on the insulating film 2 so as to leave 21 the insulating film 2 on the specific region only. At this time, during the exposure processing of the protective film, a photomask having the pattern wherein the whole insulating film 2 excluding the region to be left is shielded is relatively aligned with the wafer 1 while the shielded parts corresponding to wafer identification marks 3 are formed on the specific part in the exposure region so as to form the protective film having opening parts corresponding to the identification marks 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to improvement of a wafer process during the manufacture of a semiconductor device.

[Conventional technology]

Conventionally, in order to simultaneously manufacture multiple semiconductor devices, a semiconductor substrate called a wafer is used, and multiple semiconductor devices are formed on the semiconductor substrate using a desired technology such as film formation technology or photolithography technology. However, after that, each semiconductor device is usually subdivided into small pieces C (hereinafter referred to as chips). The process of forming a desired semiconductor device using this desired semiconductor substrate is usually called a wafer process, and in this wafer process, the edge of the wafer comes into contact with a jig that performs various treatments. There are areas where good quality chips cannot be obtained due to various constraints such as scratches caused by wafer handling or tools such as bin sets for handling wafers. or,
Due to various constraints, wafers are usually circular thin plates (often with some notches or notches (usually called facets or orientation flats) for the purpose of indicating the crystal orientation), and if the semiconductor chip surface is a rectangular or Because the wafer is square, there are areas at the edge of the wafer that are inherently imperfect in shape, and due to the above two reasons, there are areas at the edge of the wafer where good chips cannot be obtained. Since the wafer process was performed without clearly marking this area, it was necessary to measure the electrical characteristics of all chips on the wafer by some method (this process is usually called the wafer test process), and after marking the defective chips. However, since there may be pattern defects at the wafer edge, for example, visual inspection may be performed, or even if there is no defective mark within 5 mm from the wafer edge, even if it is electrically OK, it is unconditionally determined to be defective. They used methods such as

Additionally, semiconductor devices formed on a wafer at the same time may have high-frequency characteristics that are difficult to measure in the wafer testing process, if it is unclear whether or not the semiconductor devices on the wafer have characteristics that truly match the purpose. (if required)
In this case, the characteristics of the semiconductor devices on the wafer are measured in advance, and only if the chips pass the judgment criteria are the remaining chips on the wafer subjected to subsequent processes (assembly, inspection process). This is usually done primarily for reasons of economy. In this case, the wafer is divided into several sections, and chips extracted from the sections by a desired method are used for assembly and inspection, and this step is called a preliminary evaluation step.

[Problem to be solved by the invention]

Although there is an area at the edge of the wafer where only chips that should be considered defective exist as described above, in the past, the wafer process was performed without specifying the area B, so the wafer process ended. After that, all chips on this wafer are electrically measured, and even after some defect marks are given on defective chips, chips at the edges are visually inspected. Because measures such as marking some chips as defective were taken, it was difficult to accurately determine the number of true good chips in one unit.
When a large number of chips (for example, -5 chips) are formed in a sea urchin, it takes a lot of effort to accurately determine the number of good chips.

Furthermore, when carrying out the wafer process, there are the following problems. In other words, conventionally in the wafer process for manufacturing semiconductor devices, multiple wafers are treated as one unit block and each process is performed, and this unit block is generally called a lot. (Lot). and,
The number of wafers constituting these 10 wafers is appropriately set in accordance with each process to be processed, and usually, the actual loft size is about several to several dozen wafers.

In addition, in the wafer process, there are processes in which it is not necessary to identify individual wafers when the same process is performed, but in many cases, even when the same process is performed,
Check wafer-to-wafer variations or
When it is necessary to partially change the processing conditions during the process, symbols such as letters and/or numbers (hereinafter referred to as identification symbols) are used to identify each individual wafer.
I was trying to write it down.

Here, the following methods are available for writing and displaying this identification symbol on the surface of the sea urchin. Namely, 5. (a) A method in which an identification symbol is handwritten on the back or front surface of the wafer using a diamond pen or the like.

(b) A method of imprinting an identification symbol directly on the wafer using a laser beam.

(C) A method in which a photoresist film is formed on the surface of a wafer by photolithography and an identification symbol is displayed using an identification symbol display device, a so-called wafer titler device.

Each of the conventional identification symbol display means for individual wafers as described above has the following characteristics. That is,
First, in the case of method (a) above, the identification symbol is directly marked on each wafer, so it has the advantage of being less expensive, but the writing itself depends on the level of skill of the operator. If the scribing force is too weak, it will be difficult to make even markings, but if the scribing force is too strong, minute powder (pieces) may form as a result of the scribing. Although it is a simple method, it has the drawback that these materials can contaminate the wafer later, and the applied force can cause stress on the wafer, which can easily cause cracks in the subsequent process. It required skill on the part of the person.

In addition, method (b) above requires special equipment for generating and controlling laser light, which incurs a large amount of cost and requires great care; This is not a problem in practical use when the semiconductor wafer material is silicon, but when it is a compound semiconductor wafer (e.g. GaAs wafer),
This method cannot be applied because the crystal decomposes when irradiated with laser light and generates harmful substances, that is, As compounds in this case.

Furthermore, in the case of method (c) above, the identification symbol generator (
Usually, a combination of multiple letters and numbers can be displayed.

) By irradiating the pattern formed by the combination of the light-shielding parts with the desired light, it is possible to display an identification symbol by transferring it to the photoresist film formed on the wafer, but here too, a special device called a wafer titler is used. This method requires a large amount of money, and has the disadvantage of requiring an extra photolithography process just to display the identification symbol.

This invention was made to solve the two main problems mentioned above.The purpose of this invention is to clearly identify the areas (mainly the edges of the wafer) where good chips cannot be obtained on the surface of the wafer. In order to clarify the number of good chips by displaying the number of good chips, we decided to simply and easily display an identification symbol on each wafer without using any special equipment. The present invention provides a method for manufacturing a semiconductor device in which a semiconductor device is obtained, and also provides a method for forming marks (patterns) for dividing a wafer into desired regions (sections).

[Means to solve the problem]

In the method for manufacturing a semiconductor device according to the present invention, at the start of the wafer process, an insulating film is formed on the entire surface of the sea urchin using a desired film formation technique, and then a continuous boundary is formed along almost the entire circumference of the sea urchin. At the same time, marks (patterns) for dividing the wafer into desired areas (sections) are formed by selectively leaving this insulating film on the wafer edge ζ, and also by selectively leaving this remaining insulating film. The idea is to form an identification symbol for sea urchins within the sea urchin.

[Effect]

In the method for manufacturing a semiconductor device of the present invention, an area where an insulating film is formed is formed on the outer periphery of the wafer at the start of the wafer process, so that the remaining part of the insulating film is an area where good chips cannot be formed. This is obvious in the subsequent process, and the wafer identification symbol is formed within the remaining portion of the insulating film, so this symbol is used during the wafer process.
It is possible to clearly distinguish the sections on the wafer, and since marks (patterns) for dividing the wafer are formed at the same time as the remaining portions of the insulating film, the sections on the wafer can be clearly distinguished.

〔Example〕

An embodiment of the method for manufacturing a semiconductor device according to the present invention will be described below with reference to FIGS. 1 to 4.

FIGS. 1 to 3 are a flat diagram and a cross-sectional diagram, respectively, showing an outline of an implementation method for solving the above-mentioned problems at the same time, which is an embodiment of the present invention.

FIG. 1(b) shows a semiconductor wafer having a desired structure, for example, a GaAs wafer with a diameter of approximately 50 mm. Here, having a desired structure refers to the structure formed on this wafer (1). A GaAs wafer or the like is shown, which has a concentration and thickness suitable for a semiconductor device, for example, a GaAs MFSFET, and has an active layer epitaxially grown on a GaAs substrate formed on top.

The wafer (1) in FIG. 1 is subjected to a desired pretreatment to remove the Ga pits on the GaAs by, for example, hydrochloric acid boiling, followed by cleaning with pure water, drying, etc.), and then using, for example, a plasma CVD apparatus. Then, apply S to the entire top surface of the wafer.
An insulating film made of i, N, (silicon nitride) (
2) is shown in FIGS. 2(a) and 2(b).

This insulating film (2) is made of, for example, Sin, (silane) and NH,
(ammonia) using a chemical reaction between both gases, approximately 2
It is grown to a thickness of about 100 OA under heating conditions of 80°C.

Subsequently, all portions of this insulating film except for desired regions are removed by etching. This etching can be easily removed, for example, by etching with an aqueous solution of hydrofluoric acid and ammonium fluoride (a well-known hydrofluoric acid buffer solution). During this etching, if a protective film against the etching solution 2ζ having a pattern corresponding to a desired area is formed on the insulating film, only the area corresponding to this protective film can remain without being etched. It is possible. After the etching process is completed, if this protective film is removed using a well-known technique, the insulating film remains only in the desired areas, and the other parts are completely removed (Figures 3(a) and 3(b)). ).

In this case, as the above-mentioned protective film, for example, O
By using MR-83■ photoresist, exposing only the area corresponding to the protective film, and then performing predetermined processing to form a photoresist pattern with the desired pattern, the above purpose can be easily achieved. It is possible to form a film.

During this exposure process, a photomask with a pattern that blocks light except for the area where the insulating film is to remain is aligned relative to the wafer, and the light-blocking part corresponding to the wafer identification symbol is placed in the area where the protective film is to be formed. If it is formed in a desired portion within the wafer identification symbol (that is, within the exposure area), a protective film having an opening corresponding to the wafer identification symbol can be formed after a predetermined process such as development is performed.

Next, FIG. 4 shows another embodiment of a further improved method of manufacturing a semiconductor device.

That is, in the manufacturing method of the embodiment shown in this figure, the symbol 0♦ indicates a semiconductor wafer (here, for example, GaAs wafer) on which an identification symbol is displayed.

In this case, although not shown, a desired negative type photoresist such as OMR-83 is coated on the surface of one semiconductor wafer c, and prebaking under appropriate conditions has been completed, and (2) is a photomask displaying a desired mask pattern, in this case a photomask constructed using a transparent material such as quartz glass, and corresponding to the semiconductor wafer 0υ, an insulating film made of, for example, oxidized black or 2 A light-shielding portion is formed only in the area other than the area where the film is to remain, and these semiconductor wafer O
D and the photomask (2) have completed relative alignment, so-called mask alignment.

Therefore, in the case of a photolithography process in the production of economical semiconductor devices, exposure processing is performed after the completion of the above-mentioned mask alignment, but in this implementation method, at least A filter made of a transparent material such as quartz glass for identification and having a size that completely covers GP to the semiconductor urchin is attached to the light source side (not shown) and the photomask (
Insert the photomask (2) between the photomask (2) and align it, or if necessary, place it directly on the side of the light source of the photomask (2) so that it overlaps with the photomask (2). Exposure processing is performed by irradiating the material with a light beam under appropriate conditions.

In addition, the filter for displaying the identification symbol (to) corresponds to the transparent part of the photomask (2) and is in contact with the wafer, for example, specifically the wafer O.
An identification pattern consisting of letters, numbers, or a combination thereof is displayed in an area corresponding to the inner part within about 5an near the outermost side of υ. It is formed as a light-shielding part that blocks light in the same way as the pattern in .

Therefore, after the exposure process has been performed on the wafer c3p through the filter for displaying the identification symbol, and after the desired development, fixing, and inspection steps have been completed, the wafer 01 is The part corresponding to the pattern formed in the light-shielding part of mask 0 is displayed as the opening part, and at the same time, the filter for displaying the identification symbol (
The portion corresponding to the identification symbol pattern (to) is displayed as an identification symbol with a similar opening shape.

Furthermore, as a filter for displaying the identification symbol, a plurality of sheets each displaying a different identification symbol pattern are prepared, and these are selectively exchanged and used for each wafer. For example, mutually different identification symbols can be displayed on each wafer 01) to be processed, and further,
If necessary, it is also possible to display different identification symbols on all ten wafers.

Moreover, in order to manufacture the filter □□□ displaying the different identification symbol patterns, it can be obtained relatively easily by using conventionally well-known mask manufacturing technology, and it can be applied to this example. The filters can be used almost semi-permanently.

The light-shielding portion of the photomask (2) is an area that matches the shape of the chip to be formed, that is, assuming that the length and width of one chip are ymm and x, respectively, this area has a length of nymm. , the side is n'x (n.

If the stepped shape is formed such that n' is an integer), a region on the semiconductor wafer where no insulating film is present can be effectively used as a chip forming region. In addition, this light-shielding part has a shape such that all of its edges can be accommodated on the semiconductor wafer, and it is necessary to place the light-shielding part so that the wafer edge does not cross the light-shielding part. mark (4 in Fig. 3(a)) when dividing the wafer into desired sections (regions)
(part). In the case of No. 1 J(a), for example, the mark (4) used to divide the wafer into six sections.
are formed on the wafer, and the wafer can be clearly divided into six sections (for example, sections A'-F).

In the above embodiments, a GaAs wafer is used as the semiconductor wafer, but the invention is not necessarily limited to this. In addition, although Si, N, was used as an example of the insulating film,
It is not limited to this.

(Effects of the Invention) As described above, according to the present invention, an insulating film having a continuous boundary almost along the outer periphery is formed on the semiconductor wafer at the edge of the semiconductor wafer, and at the same time, the wafer is Provides landmarks for dividing into sections.

It is formed on the edge film, and then the desired wafer process is performed without any change from the conventional process, so it is possible to form the semiconductor chip in the same process as the conventional process, and the formation area of the defective chip can be clearly identified in advance. Since the steps in this area can be treated as bad unconditionally,
The number of non-defective chips in the wafer test can be used as the number of non-defective chips on the wafer, making it possible to accurately grasp the number of non-defective chips.

Moreover, since marks for dividing the wafer into desired sections are formed on the insulating film at the same time, the position of the chip to be extracted is determined from the wafer in the process of pre-assembling and inspecting each section (preliminary evaluation step). Since it is constant for each
The evaluation in the preliminary evaluation process no longer varies depending on the sampling location.

In addition, by using a method of selectively leaving this insulating film using photolithography technology, it is possible to display an identification symbol on the surface of the sea urchin without affecting the surface of the wafer in any way. This can be done extremely easily and always in a uniform manner using conventional equipment and methods without any need for equipment or extra processing steps for displaying f.

[Brief explanation of drawings]

1(a)(b) to FIG. 3(a)(b) are plan views and cross-sectional views of each step showing an embodiment of the method for manufacturing a semiconductor device of the present invention, and FIG. It is an explanatory diagram showing another example of a strong company. (1>... semiconductor wafer (GaAs wafer), 12)
...Insulating film, συ...GaAs i, ■...Remaining insulating film, (3)...Wafer identification symbol, 61)--
・Semiconductor wafer, (2)...photomask, -...
Identification symbol display filter, circle... Light rays irradiated for exposure, (4)... Purpose (for displaying sections/4). In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In the wafer process for forming semiconductor devices on a semiconductor substrate, an insulating film having a continuous boundary almost along the outer periphery of the wafer is formed at the edge of the wafer on the surface of the semiconductor substrate, and the corresponding section on the wafer is clearly marked. A method of manufacturing a semiconductor device, comprising forming a mark (pattern) using the insulating film, and then performing a desired wafer process.