JPS6350842A - Cleaning method for photomask - Google Patents

Abstract

PURPOSE:To clean a photomask or reticle without any pattern separation by coating the photomask or reticle right after exposure with an organic protection film by spinning and washing away the protection film with a proper solvent right before the exposure. CONSTITUTION:On a mask substrate 1, Cr2 is patterned and this mask is scrubbed and washed by using pure water 3 to remove dirt. Then, an isopropyl alcohol solution of naphthalene is dripped right after the mask is used in an exposure process to form a protection film 4 by spin coating to 0.1-1.0mum thickness, and the mask is kept at room temperature as it is. The naphthalene film 4 and dirt 5 on its are removed with ethanol 6 right before the exposure. Then, the cycles after the exposure are repeated. Consequently, no dirt sticks directly of the photomask or reticle is improved without the separation of the pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for cleaning a photomask or reticle used in the manufacturing process of semiconductor devices.

[Conventional technology]

A lithography process is an important process in the manufacture of semiconductor devices. In this process, a stepper or aligner device is used to transfer the reticle or mask pattern onto the wafer to form a pattern, but if there is dust on the reticle or mask, it will be transferred as a defect on the wafer during exposure. Ru. Therefore, a cleaning method that completely eliminates dust on the reticle or mask is important. Note that from now on, the term "mask" will be used to refer to both the reticle and the mask.

Conventionally, washing with water has been mainly used as a method for washing masks.

FIG. 2 is a diagram showing this water washing method, and in the figure, 1
2 is a mask substrate, 2 is a pattern made of Cr, 3 is pure water, and 5 is dust.

As shown in FIG. 2(a), a lot of dust 5 adheres to the mask during storage. Therefore, it is necessary to clean this mask, but normally, while rotating the mask, as shown in Figure 2 (b)
As shown in Figure 3, it is washed by spraying pure water 3, and then dried at high speed while being irradiated with an infrared lamp. After drying, it is attached to an exposure device, exposed, and stored again. If the dirt is severe, scrub it with a cloth or brush containing detergent (Mama Lemon (trade name, Lion Co., Ltd.) water).

In addition to the water washing method, there is also a method of attaching a protective film pellicle 7 to the mask to prevent dust 5 from directly adhering to the mask substrate 1, as shown in FIG.

[Problem that the invention seeks to solve]

As semiconductor devices become more highly integrated, patterns on masks become finer and are transferred using exposure equipment with high resolution. As resolution improves, even finer dust particles begin to affect transfer. However, with fine dust, the van der Waals force increases, making it difficult to remove the adsorbed dust. Therefore, if an attempt is made to forcibly remove the mask by scrubbing, there are problems such as peeling of Cr or MoS used as a mask material and generation of other defects.

Further, the method using a pellicle has problems such as the pellicle is expensive and it is difficult to attach the pellicle to a mask from which dust has been completely removed.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a photomask cleaning method that does not cause pattern peeling on a photomask or reticle.

[Means for solving problems]

The photomask cleaning method according to the present invention spin-codes an organic protective film on a photomask or reticle immediately after exposure, and maintains the organic protective film M'! ! The membrane is washed away with an appropriate solvent.

[Effect]

In this invention, the organic protective film on the photomask or reticle prevents dust from directly adhering to the substrate.
Further, by rinsing the protective film with a suitable solvent, dust adhering to the protective film is simultaneously removed.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a mask substrate, 2 is a chromium film patterned on this mask substrate 1, 3 is pure water, 4 is an organic protective film, 5 is dust, and 6 is a solvent for washing away the protective film 4.

The mask cleaning process will be described below. Patterning of Cr2 was performed on the mask substrate 1 (Fig. 1(a)).
. This mask was scrubbed with pure water 3 as in the conventional manner to remove dust (FIG. 1(b)). Then, immediately after using the mask in the exposure process, a solution of naphthalene in isopropyl alcohol is dropped to form a 0.1-1.0 μm mask.
The protective film 4 was spin-coded to a thickness of (Fig. 1 (C1)
, this mask was stored as it was at room temperature (Figure 1 (
d)). Immediately before exposure, the naphthalene film 4 and the dust 5 on it were removed using ethanol 6 (FIG. 1(e)). Then, the cycle of exposure +(C)→+co=+e) in FIG. 1 was repeated.

Incidentally, camphor was used as a protective film in the same way as above.
It may be spin coded to a thickness of 1.0 μm.

Similar effects were also obtained using organic compounds other than naphthalene and camphor, and organic low-molecular polymers.

Furthermore, in the above embodiment, a Cr mask was shown, but
A similar effect was obtained using a Mo Sr2 mask.

〔Effect of the invention〕

As described above, since the photomask cleaning method according to the present invention forms an organic protective film that is easy to remove, the protective film is very inexpensive, dust does not attach directly to the substrate, and it is easy to remove. This has the effect of improving the durability of the photomask or reticle without causing pattern peeling.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a cleaning process showing an embodiment of the present invention, FIG. 2 is a sectional view of a conventional cleaning process, and FIG. 3 is a sectional view of a conventionally used mask with a pellicle. 1 is a mask substrate, 2 is a Cr pattern, 3 is pure water, 4 is a protective film, 5 is dust, 6 is a cleaning solvent, and 7 is a pellicle. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A method for cleaning a photomask or reticle used in the manufacture of semiconductor devices, which includes a step of applying an organic film to the photomask or reticle immediately after being used for exposure with a stepper or aligner, and exposing the photomask or reticle again. A photomask cleaning method comprising the step of removing the organic film with a suitable solvent immediately before use. (2) The photomask cleaning method according to claim 1, wherein the organic film is made of naphthalene or camphor.