Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2001-08-09
2003-12-02
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S394000
Reexamination Certificate
active
06656645
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a photomask, a method of manufacturing photomask blanks, and a technique for reclaiming a photomask and, more particularly, to a technique which is effectively applied to a photolithography technique used in manufacturing a semiconductor device, a super conductive device, a micro machine, an electronic device, and the like.
BACKGROUND OF THE INVENTION
For example, in manufacturing a semiconductor device, as a method of transferring a micropattern onto a semiconductor wafer, a photolithography technique is used. In the photolithography technique, a projection aligner is popularly used. A pattern of a photomask (to be referred to as a mask hereinafter) set in the projection aligner is transferred onto a semiconductor wafer (to be referred to as a wafer hereinafter) to form a device pattern.
A normal mask used in the photolithography technique is produced by processing a shade material such as chromium (Cr) formed on a transparent quartz substrate. More specifically, the normal mask is constituted such that a shade film made of chromium or the like is formed on a quartz substrate to have a desired shape.
SUMMARY OF THE INVENTION
In recent years, competition in development for semiconductor devices advances, and a large number of masks are required to accelerate a device debug operation. The necessity of producing masks at a low cost becomes high. Although a very high cost is required for pattern delineation, defect inspection for patterns, and the like in manufacturing masks, a cost which is not negligible is required for mask blanks (to be referred to as blanks hereinafter). For example, in an i-line having a wavelength of 365 nm, the cost of delineation or defect inspection is low because an object pattern size is large. In this case, the cost of blanks accounts for about 20% of the total cost of producing the mask. In a mask for a KrF excimer laser having a wavelength of 248 nm, since the degree of flatness of a quartz glass (transparent quartz substrate) influences pattern delineation accuracy, the degrees of flatness are classified into grades. In high-quality blanks, the degree of flatness at a submicron level is required. Since the degree of flatness is obtained by polishing, the yield of blanks having a high degree of flatness is small because a selection method is used. For this reason, the cost of blanks having a high degree of flatness is high. In a mask for an ArF excimer laser having a wavelength of 193 nm or a mask for an F
2
excimer laser having a wavelength of 157 nm, the costs of the blanks increase because manufacturing methods are different from each other from viewpoints of prevention of a color center or a reduction in defect density. For this reason, in manufacturing masks, the cost of blanks cannot be neglected, and the cost must be reduced.
Therefore, masks may be reclaimed to reduce the cost of blanks. More specifically, a wasted mask or a mask which does not pass inspection after a shade pattern made of chromium or the like is formed are subjected to a reclaiming process. A mask reclaiming process examined by the present inventors is as follows, for example. That is, a shade pattern on a major surface of mask blanks made of quartz glass or the like is removed by wet etching or the like. In this case, a slight step is formed on the major surface (surface on which the shade pattern is formed) of the mask blanks. Glass polishing is performed to remove this step. This polishing grinds the step on the major surface to form a surface having a high degree of flatness. Thereafter, particles generated in this step are removed by cleaning, and particle check is performed to reclaim blanks.
However, in the above mask technique, the present inventors found the following problems.
More specifically, when a normal mask is to be reclaimed, the following problems are posed. That is, (1) the polishing step at a high cost is required, (2) the number of times of reclamation is limited because the mask blanks are thinned by polishing as reclamation is repeated (i.e., blanks are thinned), and (3) the degree of flatness is measured again, and the mask is classified by levels because the degree of flatness of the mask blanks is changed by the polishing step. The reclamation of masks is not remarkably advantageous with respect to quality and cost.
The present inventors performed a technical examination from a viewpoint of a mask on the basis of the result of the invention. As a result, as another engagement to reduce the cost of a mask, for example, a so-called resist mask method for forming a shade film by a resist film is disclosed in Japanese Patent Laid-Open Publication No. 5-2189307.
It is an object of the present invention to provide a technique which can reclaim a mask.
It is another object of the present invention to provide a technique which can reclaim a mask while keeping the quality of the mask.
The above objects, other objects, and novel characteristic features of the present invention will be apparent from the description and accompanying drawings of this specification.
The outline of a typical one of the inventions disclosed in this application will be simply described below.
More specifically, according to one aspect of the present invention, a shade pattern constituted by a resist film formed on a mask is stripped, and a new shade pattern constituted by a resist film is formed on the mask to reclaim a mask.
According to another aspect of the present invention, a shade pattern constituted by a resist film formed in an integrated circuit pattern region of a mask on which a shade pattern made of a metal is formed in a peripheral region is strip, and a new shade pattern constituted by a resist film is formed again in the integrated circuit pattern region of the mask on which the shade pattern made of a metal is formed in the peripheral region to reclaim a mask.
According to still another aspect of the present invention, a shade pattern constituted by a resist film and formed in a peripheral circuit pattern region of a mask having a shade pattern formed in an integrated circuit pattern and made of a metal and a shade pattern formed in a peripheral region and made of a metal is stripped, and a new shade pattern constituted by a resist film is formed again in the integrated circuit pattern region of the mask having the shade pattern formed in the integrated circuit pattern region and made of the metal and the shade pattern formed in the peripheral region and made of the metal to reclaim a mask.
According to still another aspect of the present invention, the step of forming a shade pattern constituted by a resist film on a mask and the step of stripping the shade pattern constituted by the resist film are repeated.
Still other aspects of the present invention are as follows:
(1). A method of manufacturing photomask blanks comprising the steps of:
(a) patterning and forming a first shade portion constituted by a resist film on a mask substrate to manufacture a photomask;
(b) performing an exposure process by using the photomask to transfer a desired pattern onto a substrate to be processed; and
(c) stripping the first shade portion constituted by the resist film on the photomask to reclaim photomask blanks constituted by the mask substrate.
(2). A method of manufacturing photomask blanks according to the above (1), further comprising the step of:
forming a mask information pattern on the mask substrate.
(3). A method of manufacturing photomask blanks according to the above (2), wherein
the mask information pattern is formed by one or both of a trench formed in the mask substrate and a shade pattern made of a metal formed on the mask substrate.
(4). A method of manufacturing a photomask comprising the steps of:
(a) preparing a mask substrate having a shade portion made of a metal in a peripheral region around an integrating circuit pattern region;
(b) patterning and forming a first shade portion constituted by a resist film in the integrating circuit pattern region to manufacture a photom
Hasegawa Norio
Tanaka Toshihiko
Terasawa Tsuneo
Renesas Technology Corporation
Rosasco S.
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