JPS59102235A - Photomask - Google Patents

Abstract

PURPOSE:To prevent a semiconductor wafer from being broken or cracked, by forming a recessed part on a part opposed to a wafer end part of a face of the side contacting with the wafer of a photomask, when forming a photoresist pattern on the wafer. CONSTITUTION:A photoresist 5 is dropped down onto the surface of a semiconductor wafer 4, rotated at a high speed by a spinner, and the photoresist is applied onto the wafer 4. On the other hand, a recessed part 7 whose depth is >=5mum is formed in the vicinity of the circumference of a face of the side contacting with the wafer 4 of a photomask 1. Subsequently, this photomask 1 is made to adhere closely onto the wafer 4 on which the photoresist is applied, and a photoresist pattern is formed by irradiation of light. In this way, when applying the photoresist 5 to the wafer 4, even if a heaped up part 6 is generated in the circumferential part, the heaped up part 6 is contained in the recessed part 7 of the photomask 1, therefore, the wafer 4 and the photomask 1 are made to adhere closely and satisfactorily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to improvements in photomasks used in the manufacturing process of semiconductor devices.

[Background technology]

Photolithography is an essential step in the manufacturing process of semiconductor devices. In this step, a semiconductor wafer coated with photoresist is pressed against a photomask on which a pattern has been written, and light is irradiated from the photomask side while the semiconductor wafer is in close contact with the photomask.

Coating of photoresist is usually carried out by dropping the photoresist onto the surface of a semiconductor wafer and then rotating the semiconductor wafer at high speed with a spinner. The thickness of the applied photoresist is controlled by adjusting the viscosity of the photoresist and the rotation speed of the spinner, but if the thickness of the photoresist is made to be 2 to 3 μm or more, the photoresist will bulge around the semiconductor wafer. , its thickness is as much as 10 to 30 μm. This development is particularly noticeable when the surface shape of the semiconductor wafer has corners, such as a rectangle.

Using Figures 1 and 2, the conventional photomask
explain.

As shown in FIG. 1, a conventional photomask 1 has a pattern 3 made of a light-shielding agent (for example, emulsion, chromium, ferric oxide) formed on a smooth surface 2.

A photoresist 5 is applied to the periphery of the photomask 1 as described above.
When a wafer 4 with a raised area 6 is pressed against it as shown in FIG. 2, stress is applied to the wafer edge, often resulting in cracking or chipping of the wafer, and the resulting wafer fragments may damage the photomask 1. Patterns are often damaged, rendering the photomask unusable.

Even if the wafer does not crack or chip, the adhesion between the wafer and the photomask is poor near the bulges of the photoresist, and it may not be possible to form a thin photoresist pattern.

[Disclosure of the invention]

The present invention has been made in view of the drawbacks of conventional photomasks as described above. The photomask according to the present invention has a concave portion having a depth of 5 μm or more formed in at least a portion of the surface facing the wafer edge on the surface on which the light shielding agent pattern is formed, that is, the surface in contact with the wafer. It is characterized by being

An embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3(a) is a view of a photomask for a rectangular structure according to the present invention, viewed from the side on which a light shielding agent pattern is formed. FIG. 3(b) is a sectional view of a portion including the four parts 7. The light shielding agent pattern is omitted in the figure.

The recesses 7 having a depth of 5 μm or more are formed in portions corresponding to the four corners of the square wafer 4.

Figure 4 shows a state in which a wafer coated with photoresist is pressed against this photomask and brought into close contact. In the case of square wafers, the rise of photoresist is particularly noticeable at the four corners;
This raised portion is pressed to enter into the four parts 7, and no extra stress is applied to the wafer when the wafer is brought into close contact with the wafer, so that cracking or chipping of the wafer does not occur. This also eliminates the possibility of damaging the light shielding agent pattern. Further, even near the edge of the wafer, the degree of adhesion with the photomask is improved, making it possible to form a thin photoresist pattern.

Another embodiment of the present invention will be described with reference to FIG.

In FIG. 5, a recess 7 is formed over the entire portion corresponding to the wafer periphery. By using this photomask, the same effect as shown in the first embodiment of the present invention can be obtained for a wafer having a large bulge of resist all around the wafer. This second
In the embodiment described above, the shape of the concave portion 7 was rectangular, but for a circular wafer, the shape of the fourth portion 7 may also be circular.

[Industrial applicability]

As explained above, the present invention provides a photomask in which a semiconductor wafer, on which a photoresist pattern is to be formed, on which the photoresist group on the semiconductor wafer is raised at least in a portion of the periphery, is brought into close contact with the photomask. It is.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a photomask for explaining a conventional photomask, FIGS. 3(a) and 4(b),
FIG. 5 is a plan view and a sectional view of a photomask for explaining the present invention in detail. 1... Photomask 2... Surface 3 on which light shielding agent pattern is formed Pattern 4... Semiconductor wafer 5... Photoresist 6... Photoresist rise at wafer edge 7... Four parts

Claims (1)

[Claims] (1) When forming a photoresist pattern on a semiconductor wafer by photolithography, a depth of 5 μm or more is applied to at least a portion of the surface facing the wafer and facing the wafer edge. 1. A photomask comprising four parts.