JPH03253017A - Wafer and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable a wafer in defective flatness to closely adhere to the stage of a flat aligner without rolling up air in the stage for flattening the surface of the wafer thereby enabling the fine patterns to be formed. CONSTITUTION:After forming silicon films on the surface and rear surface of a silicon wafer 1 by thermal oxidation process, a resist film 3 is formed on the rear surface and then exposed in specific patterns and developed so as to form continuous trench type resist patterns. Next, after etching away the films 2 using the patterns 3a as masks, the wafer 1 is etched away to form the continuous trenches 4 reaching both ends. Then, the multiple trenches reaching both ends of the wafer 1 are formed on the rear surface of the wafer 1. Through these procedures, the wafer 1 in defective flatness can closely adhere to the stage of a flat aligner for flattening the surface of the wafer without rolling up air in the stage, thereby enabling the fine patterns 3a to be formed.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a wafer and a method for manufacturing the same.

In particular, it is used in the manufacture of semiconductor integrated circuits.

(b) Conventional technology In recent years, with the demand for higher integration of semiconductor integrated circuits, the elements and wiring patterns formed on the substrate have become finer, and this has led to the problem of a decrease in the depth of focus of exposure in the photolithography process. te 0ru.

A conventional wafer is a wafer with an unfinished backside.

In the photolithography process, a wafer is exposed to light by placing the wafer, which has elements or intermediates and a photoresist film laminated on the front surface in order and whose back side is unprocessed, on the stage of a flat exposure device that has a suction port. This is done by adhering the back surface to the stage by suction, performing an exposure and focusing operation on the front surface, and then irradiating it with light.

(c) Problems to be Solved by the Invention In the conventional technology, especially when exposing a wafer with impaired flatness, even if the wafer is vacuum suctioned to the stage of a reduction projection exposure device, the flatness cannot be improved. On the other hand, vacuum suction of a wafer with poor flatness may actually impair the flatness. In such a case, there is a problem that the exposure focus is not on the wafer surface and a fine pattern cannot be formed.

This invention was made in order to solve the above-mentioned problems, and it flattens the surface of a wafer whose flatness has been damaged by bringing it into close contact with the stage of a flat exposure device without entraining air. Therefore, it is an object of the present invention to provide a wafer that can form a fine pattern by focusing exposure and a method for manufacturing the same.

(d) Means for Solving the Problems According to the present invention, there is provided a wafer in which continuous fine grooves are provided on the back surface of the wafer at predetermined intervals and reach both end surfaces of the wafer.

The grooves are designed to prevent part of the air between the stage and the wafer placed on the stage of the exposure equipment, which is substantially flat and has a suction port, from being trapped between them by suction (preventing air pockets). ) When a wafer is placed on the stage and air is sucked through the suction port, the wafer is warped and separated by the suction.
When the back side of a new wafer approaches the flat stage surface and is further sucked, air is exhausted from the edge of the wafer through the groove, reducing the warpage of the wafer and eliminating the warpage by bringing the wafer into close contact with the flat stage surface. Shiuruchika is suitable.

The grooves are preferably formed on the back surface of the wafer so that they are wide enough to create air pockets between the wafer and the stage due to the suction, and can be appropriately distributed on the back surface depending on the size of the warp of the wafer. Alternatively, they can be placed uniformly on the back surface of the wafer at predetermined intervals. The interval between these grooves is usually 2 to IO, tv, preferably 5
x7fu degree. It is suitable for the air outlet of this groove to be formed on the end surface of the wafer, and by forming continuous fine grooves on the back surface of the wafer that reach both end surfaces of the wafer, It can be placed.

In addition, this groove has a size that allows at least air to pass through instantaneously, and is also large enough to not impede the suction force of the stage to the wafer (a size that can eliminate warping of the wafer) generated by the suction bow from the suction port. It is necessary to make it fine. A groove that satisfies these requirements usually has a cross section with a width of 50 to 300 .mu.m and a depth of 1 to 10 .mu.m. The specific formation of this groove can be performed by photolithography, etc. According to Photolithography Sho, first, a wafer is turned over and an oxide film, for example, is formed as a protective film on the surface of the wafer to be processed. Next, a resist film is formed by a known method. Patterning of the resist film: The reticle with the grooves and the turns may be attached to a reduction projection exposure device and exposed, or a method may be used in which the wafer is not scanned and a spot light is applied. The subsequent etching of the oxide film and wafer may be isotropic or anisotropic. In isotropic etching, for example, the oxide film can be etched with hydrofluoric acid, and then the wafer (silicon substrate) can be etched with a mixed solution of hydrofluoric acid and nitric acid. In anisotropic etching, a parallel plate type RIE etching apparatus and CHF, gas (in addition, C
H,,C,F,? , ; etc.) can be used to etch the oxide film. After this, parallel plate type RIE etching equipment and SF, gas (or CIt, SiC14°CF,...
CC1, etc.) can be used to etch silicon. After that, remove the resist with sulfuric acid, etc., and then remove the resist with hydrofluoric acid.
Then, the oxide film on both sides of the substrate can be removed to form a groove.

The wafer with the predetermined grooves formed on the back surface as described above is usually formed with an element or an element intermediate and a resist film on the front surface, and then as shown in FIGS. 4(a) and ff( b) It is placed on the stage of a flat wide exposure apparatus having a suction port as shown in FIG. Next, by suctioning from the suction port, the air between the wafer and the stage is discharged through the grooves of the wafer and from the openings of the grooves on both end faces of the wafer, and the wafer is brought into close contact with the stage without entraining air. can be exposed by focusing the exposure on the flat surface, so that the surface is flattened.

(e) Operation Air is passed between the stage of the exposure device and the wafer through the f-groove formed on the back surface of the wafer, and is discharged from both end surfaces of the wafer without creating any air pockets.The wafer is brought into close contact with a flat stage on the surface of the semiconductor substrate. Eliminate warpage.

(f) Example Embodiments of the invention will be described with reference to the drawings.

Example 1 Preparation of grooves on the back side of the wafer As shown in FIGS. 2(a) and (b), grooves with a diameter of 4 inches and
A silicon oxide film 2 is formed on the front and back surfaces of a 525 μm thick silicone wafer 1 by a oxidation method.

Next, as shown in FIGS. 2(C) and (d), a resist film 3 is formed on this back surface, and a predetermined spot is applied to the resist film 3 in a linear manner while scanning the sea urchin/\. By exposing the pattern to light and developing it, a continuous groove-like resist pattern 3a is formed.

Next, as shown in FIG. 2(e), the resist pattern 3a is
Using as a mask, the silicon oxide @2 is etched by aqueous hydrofluoric acid solution, and then the silicone wafer l is etched with a mixed aqueous solution of hydrofluoric acid and nitric acid to form continuous grooves 4 reaching both end faces of the silicone wafer.

Next, the resist pattern 3a and the silicon oxide film 2 are removed as shown in FIG. 2 ([') and L" (g). As a result, the silicon wafer is A silicon wafer is obtained in which a large number of grooves 4 are formed at 4.51 intervals on the back surface 5 of the silicon wafer, each having a cross section of 100 μm in width and 5 μm in depth, reaching both end surfaces of the silicon wafer.

The amount of warpage of this silicon wafer was 5 μm, which was obtained by placing the wafer on a flat table and measuring the maximum height of the substrate surface.

Preparation of element thin film and resist film on the wafer surface Grooves are formed on the back surface of the wafer.Noricon oxide film 7 is formed on the surface of the silicon wafer 1 by thermal oxidation method, and on this is formed by chemical vapor deposition (CVD) method. A tungsten silicide layer 8 having a thickness of 02 μm is laminated.

Next, a resist solution is applied thereon and dried by heating on a hot plate to form a resist film 9 having a thickness of 1 μm. As shown in FIG. 3(a), this wafer was subjected to a warpage of 10 to 20 μm obtained in the same manner as the above measurement.

Exposure of semiconductor substrate As shown in FIG. 4(b), a support member 13a with a flat surface is provided.
The wafer 1 having the warp of 20 μm (see FIG. 3(a)
) is placed and air is sucked through the suction port 12b. As a result, the air that is caught in the lower center of the wafer passes through the groove 4 and is released from the groove openings on both end faces of the wafer (as shown in Figure 3 (b)), causing the wafer to warp. The surface is fixed on the stage llb in a flat state by being released by the suction force. Note that the same process can be performed using a stage as shown in FIG. 4(a) instead of the stage of the exposure apparatus as shown in FIG. 4(b). In FIG. 4(a), lla is the stage of the exposure device, 12a is the suction port,
13a is a flat support member.

Next, the light source of the exposure device is focused on the surface (resist@) of the silicone rubber l, and the silicone web l is exposed to light in a predetermined pattern and developed to form a resist pattern.

The resulting resist pattern was examined under a microscope.
The two most important points are that the fine patterns are formed with high precision.

Comparative Example 1 In Example 1, instead of forming grooves on the back surface of the silicon wafer, a silicon wafer 2I was formed in the same manner as in Example 1 without forming the grooves.
A tungsten solicide film 23 is formed on top via a silicon oxide film 22, and a resist film 25 is formed on this.
child. This wafer had the same amount of warpage as in Example 1 (20 μm
) was there.

Next, this wafer was vacuum-adsorbed onto stage llb of an exposure apparatus in the same manner as in Example 1, and as shown in FIG. wafer surface warpage of 2 to 3 μm
In this state, the light source of the exposure apparatus could not be focused on the surface (resist film) of the silicon wafer 1.

(G) Effects of the Invention According to this invention, even if the flatness of a wafer is impaired, it is possible to flatten the surface of the wafer by bringing it into close contact with the stage of the flat G exposure device without entraining air, and to expose the wafer. It is possible to provide a wafer on which a fine G pattern can be formed by focusing, and a method for manufacturing the same.

[Brief explanation of drawings]

FIG. 1(a) is an explanatory diagram of the f-shaped groove formed on the back surface of the Noricon wafer produced in the embodiment of the present invention, and '41E1(b)
is an enlarged explanatory diagram of the groove, FIGS. 2(a) to (g) are also explanatory diagrams of the process of forming the groove, FIG. 3(a) is an explanatory diagram of warping of the silicon wafer, and FIG. Similarly, FIG. 4 is an explanatory diagram of a silicon wafer vacuum-adsorbed on the stage of an exposure apparatus. FIG. 5 is an explanatory diagram of a silicon wafer vacuum-adsorbed on the stage of a conventional exposure apparatus. be. Groove, 5. Back side of silicon substrate, surface of Norikono substrate, ... Noricon oxide film, - Tungsten soricite layer, resist film, 10 - Amount of warpage, 11b... Stage of exposure device, +2b - Suction port, 13b ...Flat support member. 7. 1a 2a 3a l...Silicon substrate, 2...Silicon oxide film, 3...Resist film, 3a...Resist pattern, III 1! 1 (a) (a) 禦 21 (b) * 1 w (b) (a) Cylindrical stomach

Claims (1)

[Claims] 1. A wafer in which continuous fine grooves are provided on the back surface of the wafer at predetermined intervals and reach both end surfaces of the wafer. 2. Form a protective film on both sides of the wafer, form a resist film on the back side of the wafer, then form a linear pattern that reaches a predetermined wafer edge, then etch the protective film and the wafer, and then remove the protective film and resist film. A method for manufacturing a wafer having microgrooves, which comprises removing.