JPH02250055A - Manufacture of photomask and semiconductor device - Google Patents

Abstract

PURPOSE:To reduce pattern defects due to transfer of foreign matter in a photoprocess and to enhance a yield of a semiconductor device by forming an opening specified in a cross-sectional form through at least one part of the pellicle frame for fixing a pellicle to a photomask. CONSTITUTION:The pellicle 12 is fixed to a pellicle frame 13 so as to cover and protect a pattern part on a reticle 11 at a certain equal space apart from it and holes are bored from the outside and inside of a side face of the frame 13 at an angle of about 45 deg. askew so as to meet each other at right angles to form the opening 14, thus permitting any foreign matter coming into the opening 14 to collide with the hole corner of the opening 14, losing its speed, accordingly, intrusion of foreign matter to be prevented, and yet air permeability to be kept, flatness of the pellicle face to be maintained, detection precisions to be enhanced at the time of checking foreign matter, pattern defects due to transfer of foreign matter in the photoprocess, and the yield of the semiconductor device to be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J]
This invention relates to a photomask equipped with a pellicle.

[Prior art 1] In the photo process of semiconductor device manufacturing, it is common to use a reduction projection exposure apparatus (hereinafter referred to as a stepper) as a method of forming a desired resist pattern on a semiconductor substrate. As the miniaturization of elements progresses and the degree of integration increases, transfer of foreign matter onto a photomask (hereinafter referred to as a reticle) has become a problem. The stepper cuts the pattern on the reticle by one-fifth. Alternatively, the image is projected after being reduced to 1/10, but due to improvements in the resolution performance of projection lenses and resists, if there is a micron-order foreign substance on the reticle, there is a possibility that it will be sufficiently transferred. The transferred foreign matter then becomes a pattern defect, deteriorating the function of the semiconductor element and lowering the yield.

Therefore, recently, pellicles have been used as a method to prevent transfer of foreign matter. FIG. 2 is a diagram showing a reticle equipped with a conventional pellicle.
The pattern section on the reticle 21 is covered and fixed at a certain distance from the reticle 21 so as to protect it. Foreign matter in the air adheres to the pellicle 22 in the same way as when there is no pellicle, but the focus position during projection exposure is the same as the reticle 21.
Since it is on a plane, foreign matter on the pellicle 22 is out of focus, and foreign matter at the level of several tens of microns is not transferred. However, foreign matter of 50 microns or more may be transferred, and although foreign matter inspection on the pellicle 22 is still necessary, foreign matter of this size rarely exists in a clean room, and foreign matter management is much easier than before. It became.

By the way, the above-mentioned foreign object inspection on the pellicle 22 surface is performed using an inspection device based on a method of scanning a laser beam on the pellicle 22 surface and detecting the scattered light if a foreign object is present to determine the position and size of the foreign object. is commonly used, and in order to obtain high detection accuracy, it is necessary to ensure sufficient flatness of the pellicle 22 surface.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, the cause of deteriorating the flatness of the pellicle is the difference between the internal pressure and external pressure of the closed chamber surrounded by the pellicle, the pellicle frame, and the reticle. Since the pellicle is a thin film, if the external pressure is higher than the internal pressure, the pellicle will dent inward, and conversely, if the external pressure is lower than the internal pressure, the pellicle will expand outward. When I installed it and moved the reticle to a factory in a high altitude, the bulge in the pellicle was noticeable.
Deformation also occurs when low pressure systems such as typhoons pass through. As described above, the flatness of the pellicle surface was impaired by the deformation of the pellicle surface, making it impossible to inspect foreign particles on the pellicle surface with sufficient detection accuracy, increasing pattern defects due to foreign particle transfer, and lowering yield.

Therefore, in order to eliminate such bulges or dents in the pellicle, it has been proposed to provide an opening 34 serving as a ventilation hole in a part of the pellicle frame 33, as shown in FIG. However, when the opening 34 is provided, the pellicle frame 33
Even if an attempt was made to make the hole of the opening 34 smaller, it would be less than 1 mm with the current processing technology, which may cause foreign matter to enter. Therefore, the opening 34 cannot be kept open all the time, and must usually be covered with adhesive tape or the like. However, in order to keep the pellicle 32 flat at all times, it is desirable to always have an opening 34 for adjusting the air pressure.This method of providing the opening 34 in the pellicle frame 33 prevents foreign matter from entering. The problem is that it must not be done.

Therefore, the present invention is intended to solve such problems, and its purpose is to keep the opening open at all times.
By eliminating the intrusion of foreign matter and maintaining air permeability, the flatness of the pellicle surface is maintained, the detection accuracy during foreign matter inspection is improved, pattern defects caused by foreign matter transfer during the photo process of semiconductor device manufacturing are reduced, and semiconductor The objective is to improve the yield of the device.

[Means for Solving the Problems 1] (1) The photomask of the present invention is a photomask equipped with a pellicle, in which an opening is provided in at least a part of the pellicle frame for mounting the pellicle on the photomask, and The cross-sectional shape of the opening is not rectangular.

(2) The photomask of the present invention is characterized in that the cross-sectional shape of the opening in the photomask described in item 1 is dogleg-shaped.

(3) The photomask of the present invention is the photomask described in item 1 or 2, characterized in that the opening is provided with an adhesive layer or an adhesive layer.

(4) The method for manufacturing a semiconductor device of the present invention is characterized in that the photomask described in item 1, item 2, or item 3 is used in the photo process for manufacturing the semiconductor device. Example 1 FIG. 1 is a diagram showing a reticle equipped with the pellicle of the present invention. As in the past, the pellicle 12 is made of a transparent thin film typified by nitrocellulose, and the pellicle frame 13 is made of aluminum alloy or the like. It is fixed at a certain distance from the reticle 11 via the reticle 11 so as to protect the pattern section on the reticle 11. However, in the side surface of the pellicle frame 13, a hole is made in advance at an angle of about 45 degrees from the inside and the outside by cutting, and one opening 14 is provided so as to intersect in the middle. The diameter of the opening 14 is 1
It is a little less than mm. Furthermore, the opening 14 has a diameter of 10 to 20 μm.
An adhesive layer 15 is formed by applying an adhesive to a thickness of approximately m. This time, we used an acrylic emulsion adhesive. The thus processed aluminum alloy or the like is used as the pellicle frame 13.

〔Effect of the invention〕

As described above, according to the present invention, (1) the cross-sectional shape of the opening 14 is rectangular, that is, it is not linear, so foreign matter hardly enters; (2) the adhesive layer 15 is further provided in the opening 14; By making it difficult for foreign matter to pass through, even if there is no cover such as adhesive tape on the opening 14, foreign matter will not adhere directly to the reticle pattern, and sufficient air permeability in the opening 14 will be maintained. This has the effect that the internal pressure and external pressure of the closed chamber surrounded by the pellicle frame 13 and reticle 11 are equalized, and deformation of the pellicle surface can be prevented. The reason why (1) can be achieved is that even if a foreign object were to enter through the opening 14, the foreign object would collide with the side surface of the opening 14 at least once and lose the speed needed to enter. It will be done. The reason why (2) can be achieved is that even if foreign matter were to enter through the opening 14, the foreign matter would adhere to the adhesive layer 15 and would be unable to do so. These effects were experimentally demonstrated by creating similar openings and adhesive layers in an aluminum alloy plate, forcing an airflow containing foreign matter through it, and measuring the foreign matter in the airflow with a dust counter. It will be done.

As described above, even if the opening 14 of the present invention is left open, no foreign matter can enter, and by maintaining air permeability, the flatness of the pellicle surface is maintained, and the detection accuracy during foreign matter inspection is improved. It is possible to reduce pattern defects caused by transfer of foreign matter during the photo process of semiconductor device manufacturing, and improve the yield of semiconductor devices.

Further, the cross-sectional shape of the opening 14 is not limited to the dogleg shape described in the embodiment, but may be spiral shaped (see FIG. 4(a)), for example.
It is fully expected that a similar effect will be obtained with a shape like the figure 7 shape (Fig. 4(b)).

Further, the opening 14 is not limited to the side surface of the pellicle frame 13, but may be provided in other positions or in multiple locations, and the adhesive or adhesive may be of various types, not limited to the one used in the embodiment. Needless to say.

Note that the same effects can be expected even if the present invention is applied not only to a reticle used in a reduction projection exposure apparatus (stepper) but also to a mask for an 1:1 projection exposure apparatus.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a photomask equipped with a pellicle according to an embodiment of the present invention, Fig. 2 is a projected view of a photomask equipped with a conventional pellicle, and Fig. 3 is a sectional view of a photomask equipped with a conventional pellicle. FIGS. 4(a) and 4(b) are cross-sectional views of a photomask equipped with a pellicle. Eyes, 21.3 12, 22, 3 13, 23, 3 14, 34, 4 15 ・ ・ ・ ・ ・ ・ ・ ・ ・ Photomask 2 ・ ・ Pellicle 3 ・・Pellicle frame 2.43...Aperture...Adhesive layer or above Applicant: Seiko Epson Corporation, company agent, patent attorney: Kizobe Suzuki (and 1 other person) Figure (a) Figure 3 (b) )

Claims (4)

[Claims] (1) A photomask equipped with a pellicle, characterized in that an opening is provided in at least a portion of a pellicle frame for attaching the pellicle to the photomask, and the cross-sectional shape of the opening is not rectangular. . (2) The photomask according to claim 1, wherein the cross-sectional shape of the opening is dogleg-shaped. (3) The photomask according to claim 1 or 2, wherein the opening is provided with an adhesive layer or an adhesive layer. (4) Claim 1 in the photo process of semiconductor device manufacturing.
Alternatively, a method for manufacturing a semiconductor device, comprising using the photomask according to claim 2 or 3.