JPS62128520A - Semiconductor wafer and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent contamination resulting from an Si lump particulate matter, and to improve yield largely by forming a blocking film for obviating autodoping onto the back except a peripheral section. CONSTITUTION:A peripheral section is bevelled from upper and lower sections in the circumferential surface of a wafer 1, the circumferential surface of the wafer consists of inclined planes 1a, 1b and arcuate sections 1c taking approximately arcuate shapes tying the outer end edges of both inclined planes 1a, 1b, and a blocking film 2, which is made of SiO2 and thickness thereof extends over approximately 0.1-1mum, is formed on the back. According to a manufacturing process, the periphery is bevelled and the inclined planes 1a, 1b and the arcuate sections 1c are shaped previously in the wafer 1, and the blocking film 2 is attached. The blocking film 2 formed up to the circumferential surface containing at least inclined planes 1a, 1b and arcuate sections 1c of the wafer 1 or the peripheral section of the back of the wafer 1 exceeding the circumferential surface, a section by approximately 0-5mm to the central side from end edge sections, is removed. A main surface 1d is finished in a specular manner. Accordingly, since there is no blocking layer even when a reaction gas is brought into contact with the circumferential surface of the wafer in the process of epitaxial growth, no Si lump particle is formed, thus preventing contamination resulting from an adhesion onto the main surface of the wafer of lump particulate silicon.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor wafer used as a substrate for various semiconductor devices and a method for using the same.

[Prior art]

School epitaxial wafers are often doped with impurities at a high concentration to have either p-type or n-type conductivity.

For example, impurities such as boron (B) are added to the silicon wafer when the conductivity type is p-type, and phosphorus (P), antimony (Sb), arsenic (As), etc. are added to the silicon wafer when the conductivity type is n-type. Doped to a high concentration. However, when the wafer is heated to a high temperature (1000-1200° C.) in order to epitaxially grow silicon on such a doped wafer, B.

It is known that a so-called autodoping phenomenon occurs in which P, Sb, As, etc. jump out of the substrate wafer and enter the epitaxially grown layer, changing the electrical characteristics.

B, P, Sb, As, and the like are prevented from flying out from the wafer on the front surface side by the formation of an epitaxial growth layer, and therefore mainly from the peripheral surface and back surface side of the wafer. Conventionally, therefore, a method has been adopted in which a film of 5iOz and/or Si3N+ is formed as a blocking film in this portion to prevent autodoping.

FIG. 7 is an explanatory diagram of the conventional process of forming an epitaxial layer on a wafer. As shown in FIG. The wafer 1 is chamfered to form a peripheral surface consisting of inclined surfaces 1a and 1b and an arc-shaped portion IC between them, and after removing the damaged layer by chemical etching, blocking is performed on the wafer 1 by an atmospheric pressure CvD method and a mature oxidation method. Forms a film. Figure 7 (
B) shows a case in which one or two layers of 5i02 and/or Si3N4 blocking film are laminated by an atmospheric pressure CVD method, and FIG. 7 (a) by a thermal oxidation method. When the atmospheric pressure CVD method is used, the blocking film is thin on the main surface of the wafer l, and when the thermal oxidation method is used, the blocking film has a substantially uniform thickness over the entire surface.

When the formation of the blocking film 2 is completed, the main surface of the wafer 1 is polished to remove the blocking film 2 formed on the main surface and finish the main surface into a mirror surface.

As a result, as shown in FIG. 7(c), a wafer 1 is obtained in which the blocking film 2 is adhered to the entire back side and the peripheral surface except approximately half of the inclined surface 1a on the main surface side. An epitaxial layer 3 is formed on the main surface of the wafer 1 as shown in FIG. 7(d).

[Problem that the invention seeks to solve]

By the way, when epitaxial growth of silicon is performed on the main surface of the wafer 1 having the blocking film 2 obtained as described above, it is true that the epitaxial layer 3 is formed on the main surface of the wafer 1 (in the process). Since the blocking film 2 is formed on the circumferential surface and the back surface of the wafer 1, autodoping from the wafer 711 to the epitaxial N3 is significantly suppressed, and the quality of the epitaxial layer 3 itself can be improved.

Figure 8 shows the degree of autodoping S when a blocking film is formed (solid line) and when it is not formed (broken line).
This is a graph showing the test results of R (spreading resistance), where the horizontal axis shows the depth from the surface of the epitaxial layer, and the vertical axis shows the impurity concentration (logarithmic arbitrary unit), which shows the impurity concentration in the epitaxial layer. It can be seen that this is significantly reduced by forming the blocking film.

However, on the other hand, as is clear from FIG. 7(d), during the epitaxial growth process on the main surface of the wafer 1, silicon in the reaction gas blocks as polysilicon1112, especially on the peripheral surface of the wafer 1 in the form of many lumps and grains. This lumpy and granular silicon 3a is produced in a semiconductor device (
j! ! There was a problem in that during the manufacturing process of the blocking film, it fell off from the surface of the blocking film and adhered to the surface of the epitaxial layer 3, causing contamination and reducing the yield.

Figure 9 (a) is a micrograph taken along the line ■-■ in Figure 7 (d), and Figure 9 (b) is a microscope photograph taken along the line ■'-■' in Figure 7 (d). . As will be seen, many lumps and particles of Si are generated on the surface of the blocking film on the peripheral surface.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and its purpose is to focus on the fact that Si lumps and particles are formed on the blocking film on the peripheral surface of the wafer, and to By removing the blocking film on the back side as widely as possible within the allowable range of autodoping, there is almost no generation of St lumps and particles, and contamination caused by this can be prevented, resulting in a significant increase in yield. It is an object of the present invention to provide a semiconductor wafer and a method for manufacturing the same that can improve the performance of the semiconductor wafer.

The semiconductor wafer according to the present invention is characterized in that it has a blocking film for preventing autodoping on the back surface except for the peripheral portion thereof.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is a cross-sectional structural diagram of a semiconductor wafer according to the present invention (hereinafter referred to as a product of the present invention), and in the figure l indicates a semiconductor wafer made of Si (hereinafter simply referred to as a wafer). The circumferential surface of the wafer 1 consists of inclined surfaces 1a, Ib whose peripheral edges are chamfered from the top and bottom, and an arc-shaped portion IC forming a substantially circular arc connecting the outer edges of the double-ended inclined surfaces 1a, lb. A blocking film 2 is adhered to the entire back side of the lower inclined surface 1b except for the area from the edge to a position closer to the center by about 3 fl. The blocking film is 5i
Made of 02 (or 5i3N4) and has a thickness of 0.1 to 1μ
It's about the same size as a sardine. The formation area of the blocking film 2 is not necessarily limited to the above-mentioned range (the peripheral surface of the wafer where Si lumps and particles are likely to be formed, that is, the back side of the wafer 1 excluding the inclined surface 1a + lb and the arcuate portion IC1). The effect of autodoping may be within an allowable range. However, if the area of the blocking film 2 is made too small, an autodoping phenomenon will occur and the electrical characteristics will change, which is not preferable.

The material of the blocking film 2 is not limited to 5i02 film, but may also be Si3N4 film, 5i02, Si3
It may also be constructed by laminating two films each made of N4.

FIG. 2 is a schematic diagram showing the manufacturing process of the product of the present invention described above. First, as shown in FIG. Now, here is Figure 2 (b).

A blocking film 2 is attached as shown in (portion').

For example, when using the atmospheric pressure CVD method, the main surface 1d of the wafer l
The wafer 1 is placed on a band (not shown) in the reactor with the wafer 1 facing downward, and the wafer 1 is heated to form a lower surface and an inclined surface 1 facing upward.
Apply 5i02 (and/or 5i3N4) to the required thickness of 0.1 to 1.0 μ+ on the peripheral surface including a, lb, and arcuate portion 1c.
w). In the case of atmospheric pressure CVD, a small gap is formed between the pad and the main surface 1d of the wafer 1, so the blocking film 2 is formed on the back surface of the wafer 1 as shown in FIG. 2(b).

It is formed thinly not only on the peripheral surface but also on the main surface 1d.

Note that the blocking film 2 may be formed by a thermal oxidation method instead of the atmospheric pressure CVD method, and in this case, the blocking film 2 is formed approximately uniformly over the entire surface of the wafer 1 as shown in FIG. becomes.

The substrate 1 on which the blocking film 2 has been formed is further coated on the circumferential surface of the wafer l including at least the inclined surfaces 1a, lb and the arcuate portion 1c, or beyond this, as shown in FIGS. 1, the blocking film 2 formed from the peripheral edge, that is, from the edge to the center, is removed. FIG. 3.4 is a schematic diagram showing a method for removing the blocking film 2 in the above-mentioned portion, with FIG. 3 showing a method using a chemical etching method and FIG. 4 showing a method using a mechanical polishing method.

In FIG. 3, the wafer 1 is fixed to the chuck 12 of the rotary drive shaft 11, and while the wafer 1 is being rotated around the drive shaft 11, the etching solution is soaked into the surface of the blocking film 2 to be removed, including the circumferential surface of the wafer 1. The head 14 containing the nonwoven fabric 13 is pressed against the blocking film 2 covering the circumferential surface and partially the front and back surfaces of the wafer 1, and the main and back surfaces excluding the circumferential surface and the peripheral edge are removed as shown in FIG. 2(c). A wafer 1 with the blocking film 2 left on is obtained.

In the mechanical polishing method shown in FIG. 4, the wafer 1 is similarly fixed to the chuck 12 of the rotary drive shaft 11, and while the wafer 1 is being rotated, the polishing grindstone 15 is moved along the circumferential surface of the wafer 1 on the inclined surface 1a + the arcuate portion 1c, and the inclined surface. 1b.

Furthermore, the blocking film 2 is removed by moving it over the peripheral edges of the main surface and the back surface.

Next, blocking I on the back and main surfaces! A mirror finish is applied to the main surface ld side of the wafer 1 with 1i12 attached,
The blocking film 2 formed on the main surface 1d is removed and the main surface 1d is finished to a mirror surface to obtain the product of the present invention as shown in FIG. In the above-mentioned embodiment, the main surface 1d is mirror-finished after the pronking film is removed from the peripheral surface of the wafer, but the main surface 1d may be mirror-finished first.

FIG. 5 shows i:r- as shown in FIG. 1 obtained as described above.
3 is a schematic cross-sectional view of a state in which an epitaxial NOHIFg is formed on the main surface la of the - shell 1, and 3 in the figure indicates an epitaxial layer. Other parts are the same as those in the embodiment shown in FIG. 1, and corresponding parts are given the same numbers and explanations are omitted.

Figure 6 (a) shows the peripheral part of the product of the present invention as shown in Figure 5.
Figure 6 (b) is a micrograph taken from the v'-v' line of the peripheral surface of the product of the present invention with an epitaxial growth layer formed on the main surface. There is.

As is clear from these photographs, in the conventional product, a large number of lump-grain silicon 3a are formed on the wafer circumferential surface as shown in FIG. 9 (b), but in the product of the present invention, as shown in FIG. )
As shown in the figure, it can be seen that all the aggregates are not produced.

[Effect] As described above, in the product and method of the present invention, the blocking film is formed only on the back surface of the wafer, so even if the reaction gas comes into contact with the wafer peripheral surface during the epitaxial growth process, no Si lumps are formed. Therefore, in the manufacturing process of semiconductor devices, silicon granules are not generated from the wafer surface and adhere to the wafer soil surface, which is an excellent cause of contamination.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the product of the present invention, Fig. 2 is an explanatory diagram showing the manufacturing process of the method of the invention, Figs. 5
The figure is a cross-sectional view when an epitaxial layer is formed on the wafer shown in Figure 1, Figure 6 (A) is a micrograph taken from the V-V line direction in Figure 5, and Figure 6 (B) is a cross-sectional view of the epitaxial layer formed on the wafer shown in Figure 1. v' in Figure 5
A microscopic photograph seen from the -v' line, Figure 7 is an explanatory diagram showing the manufacturing process of the conventional product, Figure 8 is a graph showing the state of impurity diffusion from the wafer to the epitaxial layer, and Figure 9 (A).
7(d) is a microscopic photograph taken along the line ■-■, and FIG. 9(b) is a microscopic photograph taken along the line ■'--■' of FIG. 7(d). 1... Wafer la, lb... Inclined surface 1c.
...Arc-shaped portion 2...Blocking film 3...Epitaxial layer patent Applicant Kyushu Denshi Konku Co., Ltd. Agent Patent attorney Noboru Kono 1 Reason! (Il lb $ 2 Diagram calculation 3 Concave $ 4 Zuhoki 5 Agon drawing's clean IF (in η 1-1oo, g-1 (b) No change) (a) Part 9 Diagram procedural amendment (method) % formula % 1. Indication of the case 1985 Patent Application No. 26'1838 2. Name of the invention Semiconductor wafer and its manufacturing method 3. Person making the amendment Relationship to the case Patent applicant location Oaza, Kohoku-cho, Kishima-gun, Saga Prefecture 2201 Kamioda Name: Kyushu Electronic Metals Co., Ltd. Representative: Toshio Ikeshima 4, Agent: 543 Address: 1-14-22 Shitennoji, Tennoji-ku, Osaka City
Nisshin Building No. 207 Kawahan Patent Office (Telephone: 06-779-3088) February 5, 1985 (shipment date 61.2.25) "Brief explanation of drawings" column and drawing 7, i# positive contents 7-1 “Brief explanation of the drawings” column (page 12, lines 13 to 15 of [11 specifications] [6
The statement "Figure (a) is a microscopic photograph" should be corrected as follows. "Figure 6 (a) is a schematic partial plan view seen from the V-V line direction in Figure 5, and Figure 6 (b) is a schematic partial side view seen from the V'-v' line direction in Figure 5. Figure,” (2) Page 12 1
In lines 8 to 20, the statement ``Figure 9 (a) is a microscopic photograph'' should be corrected as follows. ``Figure 9 (a) is a schematic partial plan view of Figure 7 (d) seen from the ■-■ line direction, Figure 9 (b) is Figure 7 (d) ■''
Viewed from the direction of the −■′ line. "Schematic Partial Side View" Figures 6 and 9 of the 7-2 drawing are corrected as shown in the attached sheet. 8. Attached W Cheek Inventory (1) Corrected drawings 1 copy Procedural amendment (voluntary) March 4, 1985

Claims (1)

[Claims] 1. A semiconductor wafer, characterized in that a blocking film for preventing autodoping is provided on the back surface of the wafer except for the peripheral edge thereof. 2. The semiconductor wafer according to claim 1, wherein the blocking film for preventing autodoping is a silicon oxide film, a silicon nitride film, or a film having a composite two-layer structure of an oxide film and a nitride film. 3. A semiconductor wafer comprising a blocking film for preventing autodoping on the back surface except for the peripheral portion thereof, and an epitaxial layer grown on the main surface. 4. The semiconductor wafer according to claim 3, wherein the blocking film for preventing autodoping is a silicon oxide film, a nitride film, or a film having a composite two-layer structure of an oxide film and a nitride film. 5. In a method for manufacturing a disk-shaped semiconductor wafer in which a blocking film for preventing autodoping is formed on a part of the surface, excluding the main surface of the semiconductor wafer, at least the entire back surface of the semiconductor wafer opposite to the main surface and A method for manufacturing a semiconductor wafer, comprising the steps of forming a blocking film over the circumferential surface, and removing the blocking film from the circumferential surface.