JPS61193151A - Structure of pellicle frame - Google Patents

Abstract

PURPOSE:To facilitate recovery of expensive pellicle frames when defects of a pattern or pieces of dust are found on a reticle face, and to reduce cost by dividing the pellicle frame into outer and inner two layer parts. CONSTITUTION:The pellicle frames are divided into two parts, and a pellicle film 2 is stretched on the end face of the pellicle frame 1. The pellicle frame 1 is inserted and fit to the inside pellicle frame 5, with a buffering film 6 made of rubber or plastics inserted between them. The height of the frame 1 is made higher than the frame 5, and the end face of the frame 1 is enhanced in precision to form both pellicle films 2 into parallel planes to a reticle plane 3, thus forming the parallel protective structure of of the upper and lower planes of the reticle 3. When the reticle 3 is checked for defects by using a projection exposure method and a detection wafer, and it is judged that it is off-grade, the outside pellicle frame 1 can be easily released from the inside frame 5 by turning and pulling the frame 1, and the released frame can be reused.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] By dividing the structure of the pellicle frame used to protect the reticle in the reduction projection exposure method into two parts, the pellicle frame can be easily removed and reused in the event of a defect.

[Industrial application field]

As a method of exposing a pattern to a resist on a wafer using light, there are a method of directly exposing a resist with a mask, a proximity exposure method, and a projection exposure method.

In the projection exposure method, reduction projection exposure methods such as 5:1, 10:1, etc. have recently been used rather than 1:1 exposure due to the demand for fine processing due to higher integration.

In the case of the reduction projection exposure method, a mask called a reticle is used, in which a chrome pattern of 5 or 10 times the size of the pattern on the actual wafer is deposited on a glass plate.

The present invention relates to an improvement in a pellicle structure used to prevent defects in the wafer exposure process due to dust adhering to the reticle.

[Conventional technology]

FIG. 2 shows an example of a conventional reduction projection exposure apparatus.

Generally, the area that can be projected onto a wafer using the reduction projection exposure method is about 20 x 2On+m, and in order to expose the entire wafer surface with a large area of about 4.5 inches, the wafer must be fixed using the step-and-repeat method. The moving table 14 is mechanically and precisely moved in the x and y directions for repeated exposure.

In this case, a pattern 5 times or 10 times larger is drawn on the reticle 3, and usually a plurality of chip patterns are drawn. FIG. 3 shows the case of six chip patterns.

This reticle will be used many times for mass-produced wafer exposure, but dust adhesion during the process cannot be avoided even in the creel room.

To prevent this, a protective film called a pellicle is used. The principle diagram of the projection exposure method using a pellicle structure is shown in the 4th page.
As shown in the figure.

The pellicles are used as a pair above and below the reticle 3,
They each consist of a pellicle frame 1 and a pellicle membrane 2 stretched over the end face of the pellicle frame. The pellicle film 2 is made of a very thin film made of nitrocellulose material and has good light transmittance.

When there is no pellicle, the dust A on the reticle surface is reduced by the lens and focuses B on the wafer (fourth
Figure (al) shows scratches on the exposure pattern.

The dust A that is protected by the pellicle film 2 and attached to the pellicle film is isolated from the reticle surface 3, so it does not form an image on the wafer and does not remain as a pattern image (
Figure 4(b)).

Dust on the pellicle membrane can be removed by air blowing or cleaning.

[Problem that the invention seeks to solve]

In the conventional method described above, the reticle 3
After the pellicle frame L was attached to the pellicle frame, a precise pattern inspection was carried out, and when a defective pattern was discovered, it was difficult to repair the pellicle.

These defects may be caused by defects in the original pattern itself drawn on the reticle, or may be caused by dust that adhered to the reticle before the pellicle was attached.

In either case, once the pellicle frame is fixed to the reticle, if a defect is found on the reticle surface and the inspection fails, the pellicle frame is strongly fixed to the reticle with adhesive, so the thin pellicle film 2 will not be damaged. It is extremely difficult to peel it off.

Currently, most pellicles have no choice but to be discarded.

Therefore, a very expensive pellicle must be sacrificed.

[Means for solving problems]

The above problem can be solved by dividing the pellicle frame into two inner and outer frame structures 1.5 as shown in FIG.

That is, a pellicle frame 1 to which a pellicle film 2 is pasted and a pellicle frame 5 to be fixed to the other reticle 3 are prepared.

A buffer film 6 made of rubber or plastic is provided on the outer periphery of the pellicle frame 5, and the pellicle frame 1 is inserted into the pellicle frame 5, fitted, and fixed.

[Effect]

By dividing the pellicle frame into two parts and creating a 1°5 frame structure with two layers, the inner and outer layers, when a defect is discovered in the reticle part and requires repair, the pellicle frame has a two-layer structure, the inner and outer parts. , the pellicle frame 1 to which the pellicle membrane is attached can be easily removed.

Furthermore, the removed pellicle frame can be reused.

〔Example〕

An embodiment according to the present invention will be explained in detail with reference to FIG.

The pellicle frame is divided into two parts, and the pellicle frame 1 has a pellicle membrane 2 attached to its end face.

The pellicle membrane is made of 1μ nitrocellulose as before.
A thin film of less than m is attached to the end face with highly accurate film thickness and flatness.

The pellicle frame 1 is inserted into and fitted into the pellicle frame 5 inside the pellicle frame 5 through a buffer film 6 made of rubber or plastic provided around the outer periphery of the pellicle frame 5 .

By selecting the height of the pellicle frame 1 to be greater than 5 and increasing the precision of the end surface, the pellicle film surface 2 is formed as a plane parallel to the reticle 3.

By attaching the pellicle frame to both the upper and lower surfaces of the reticle surface, a structure for protecting the reticle surface is obtained.

If the above-mentioned reticle is inspected for defects using a projection exposure method using an inspection wafer and is determined to be rejected, it can be easily removed from the pellicle frame 5 by pulling the outer pellicle frame 1 while rotating it. It is possible.

The removed pellicle frame can be reused.

〔Effect of the invention〕

As explained above, by dividing the pellicle frame into two component parts, the inner and outer layers, when pattern defects or dust are discovered on the reticle surface, the expensive pellicle frame can be easily recovered, contributing to cost reduction. It is important to do so.

[Brief explanation of the drawing]

FIG. 1 is a structural cross-sectional view of a pellicle frame according to the present invention; FIG. 2 is a perspective view of a reduction projection exposure apparatus; Figure 3 shows the pattern on the reticle and wafer. FIG. 4 shows a principle diagram showing the effect of Beritaru. In the drawing, ■, 5 is a pellicle frame, 2 is Verital membrane, 3 is the reticle, 4 is a wafer, 6 is a buffer film; 11 is a light source; 12 is a lens, 13 is a reduction lens; 14 is a moving table; are shown respectively. 1'/L-you' (Rifle Reisen 4 Koku R Gong Figure 1

Claims (1)

[Claims] Consisting of a two-layered pellicle frame, an inner and outer layer, one end surface of a first pellicle frame (5) of the two-layered pellicle frame is adhered to a reticle (3), and the pellicle frame (5) The outer periphery of the second pellicle frame (1) is provided with a buffer film (6) made of rubber or plastic, and one end surface of the second pellicle frame (1) is provided with a pellicle film (2).
A structure of a pellicle frame characterized by a structure in which the buffer membrane (6) of the first pellicle frame is tightened and integrated by fitting it to the outside of the buffer membrane (6) of the first pellicle frame.