WO2004051369A1 - Photomask blank, and photomask - Google Patents

Abstract

In handling a blank for which a large and minute pattern is required, the generation of particles is prevented. A photomask blank having a light blocking film (2) formed only on areas excluding the peripheral edge (IS) on the main surface of a light-permeable substrate (1), the peripheral edge (IS) being the mask-unformed region of the light blocking film (2), the photomask blank being characterized in that the light-permeable substrate (1) is 300 millimeters or more in each side and the width of the film-unformed region (S) is not less than 3 millimeters and in that the light blocking film (2) is patterned by using laser painting.

Description

 Photomask blanks and photomask technical fields

 The present invention relates to a photomask used for transferring a pattern in a lithography technique, and a photomask blank as an original material of the photomask.

 Light

Background art

 The photomask is prepared by first precision-polishing quartz glass or the like to obtain a light-transmitting substrate (polishing step). The main surface of the obtained light-transmitting substrate is subjected to sputtering or the like, for example, containing chromium as a main component. A light-shielding film to be formed (film formation step), apply a resist film on the formed light-shielding film (coating step), selectively expose the applied resist film (exposure step), and develop the exposed resist film. In addition, the light shielding film is patterned by etching (etching step). Here, an intermediate product of the photomask obtained through the above-described film forming process, that is, a material original plate is called a photomask blank.

 By the way, when the photomask or the photomask blank is transported between processes, the outer peripheral portion and the side portion of the light-transmitting substrate are gripped. There is a problem that the light-shielding film is easily peeled off. When the light-shielding film is peeled off, if the peeled-off material adheres to the light-shielding film pattern as particles, defects such as a light-shielding film residue are generated in the pattern. Inevitably increase the number of washings of the blanks or blanks.

Therefore, by preventing the light-shielding film from being formed on the outer periphery of the photomask, the peeling-off of the light-shielding film (particles) generated during handling is reduced. (See Patent Documents 1 and 2). These techniques can be applied to a photomask used in a lithography technique for processing a silicon wafer or the like.

 On the other hand, the above technique is not applied to a blank in which a fine mask pattern is formed using electron beam lithography in the exposure step. This is because, when a fine pattern is drawn, electron beam drawing is performed in the above-mentioned exposure step. However, when drawing a fine pattern using an electron beam, charge-up of the substrate by the electron beam is required. This is because, in order to prevent this, it is necessary to provide conductivity (set up a conductive pin) with a light-shielding film having conductivity even in the outer peripheral portion of the blank.

 For example, in a photomask used for manufacturing a display device such as a liquid crystal display, a finer pattern is required in accordance with a higher definition of the display device and the like. At present, electronic lithography is performed in the process.

 Patent Document 1: Japanese Patent Application Laid-Open No. Sho 60-19444 (page 2, FIG. 1) Patent Document 2: Japanese Patent Publication No. Hei 3-334500 (pages 2, 3; Figure 2) Disclosure of the Invention

 However, photomasks used in the manufacture of display devices such as liquid crystal displays have been increasing in precision in recent years, but have tended to increase in size as the display screens have increased in area. The thicker and heavier the material, the more serious the problem of exfoliation. In other words, when handling a large mask, it may be held firmly using a jig that sandwiches the outer periphery, but the heavier the mask, the more the load applied to the contact with the jig, that is, the outer periphery Therefore, the light-shielding film at that portion is easily peeled off.

In addition, not only the main surface of the substrate but also the side surface of the substrate is mirror-polished. It is thought that the adhesion of the light-shielding film formed around the side surface during film formation increases, and the peeling of the light-shielding film is reduced, and in a photomask for semiconductor manufacturing, the side surface of the substrate is considered. Mirror polishing has been put to practical use. However, in the case of a large mask for a display device or the like, there is an example in which a photomask is detected on a side surface portion in an exposure apparatus (mask aligner), and there is a problem that reflected light cannot be detected if the side surface portion of the substrate is a mirror surface. The board is heavy (about lkg to 15 kg) when the board is held by hand when handling the board. The side surfaces need to be rough due to the increased risk. Therefore, in a large photomask, the light-shielding film on the side surface is more easily peeled off.

 As described above, the problem of the generation of exfoliated matter is particularly serious in a large blank in which a high-precision pattern required in recent years is formed.

 Accordingly, an object of the present invention is to provide a technology capable of preventing generation of particles such as exfoliated matters when handling a blank in which a large and fine mask pattern is formed or a photomask manufactured using the blank. And

 According to the present invention, in the photomask blank, a light-shielding film is formed only on a portion of the main surface of the light-transmitting substrate other than the peripheral edge, and the peripheral portion is an undeposited region of the light-shielding film. A photomask blank is provided, wherein the size of the substrate is not less than 300 [mm] on one side, and the width of the undeposited region is not less than 3 [mm].

 'In the photomask blank of the present invention, it is preferable that the light-shielding film is patterned using laser writing.

Further, in the photomask blank of the present invention, the surface roughness (R a) of the side surface of the translucent substrate is a rough surface of 0.05 to 0.3 m. It is effective for

 According to the present invention, there is also provided a photomask manufactured using the above photomask blank. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a view schematically showing a photomask blank according to an embodiment, (a) is a plan view, and (b) is a cross-sectional view.

 FIG. 2 is an enlarged view schematically showing a peripheral portion of the photomask blank according to the embodiment.

 1 Transparent substrate

 1 S Transparent substrate edge

 1 T translucent substrate end face

 1 C light-transmitting substrate chamfer

 2 Shielding film Best mode for carrying out the invention

 FIG. 1 shows a photomask blank according to an embodiment. In this photomask blank, a light-shielding film 2 is formed only on a portion of the main surface of the light-transmitting substrate 1 other than a peripheral edge 1S, and the peripheral portion 1S is a region where the light-shielding film 2 is not formed. is there.

The translucent substrate 1 is a substrate that is substantially transparent to exposure light. The translucent substrate 1 has a rectangular shape or a square shape in a plan view, and has a size of at least 300 [mm] on one side, that is, at least one of the four sides of the rectangular or square shape. The two sides are more than 300 [mm]. In addition, each side is more than 300 M], that is, a rectangular or square shape is more effective for a photomask, even if the four sides are all larger than 300 [mm]. is there. Such a large photomask is suitable for use, for example, in the manufacture of a liquid crystal display device or the like. Specifically, the size of the light-transmitting substrate 1 is 330 × 450 [mm], 390 × 610 [mm], 500 × 750 [mm], and 520 X 800 [mm] or more.

 The thickness of the translucent substrate 1 is not particularly limited, but a high-precision mask substrate or a large-sized substrate requiring high flatness, such as the photomask of the present invention, tends to be thick. . In one embodiment, the thickness of the translucent substrate 1 is set to 5 to 15 [mm].

 The width A (see FIG. 2) of the undeposited region 1S on the main surface of the translucent substrate 1 is 3 [mm] or more, and preferably 5 [mm]. Good. However, it is preferable that the width A of the undeposited region 1S is set to a value such that the undeposited region 1S does not overlap with a so-called drawing assurance region of a photomask manufactured using this blank. Specifically, when the drawing assurance area is an area excluding 10 [mm] from the peripheral end face of the translucent substrate 1, the width A of the undeposited area 1S is set to 10 [mm] or less. Is preferred.

 In one embodiment, the width A of the unformed region 1S is 5 ± 1 [mm].

 The light-shielding film 2 substantially shields the exposure light, and can be configured using, for example, a metal such as chrome. The light-shielding film may have a multi-layer structure or a continuous layer structure including an anti-reflection layer, a semi-translucent layer, and the like. This light-shielding film 2 is patterned using pattern drawing by a laser drawing device. That is, this photomask blank is for laser writing.

 Hereinafter, a method for manufacturing the photomask blank and a method for manufacturing the photomask using the blank will be described.

 [Polishing process]

First, after precision polishing of quartz glass and the like, chamfering is performed to obtain a vertical length of 300 [ram] As described above, the translucent substrate 1 having a horizontal diameter of 300 mm or more in a plan view is obtained. Here, the side surface (the end surface Π and the chamfered portion 1C) of the translucent substrate 1 does not need to be precisely polished, and may be rough (see FIG. 2). Even if the end face 1T and the chamfered portion 1C are rough, since the light-shielding film 2 is not formed on these portions, there is no problem that the light-shielding film 2 peels off and adheres to the mask pattern surface. In consideration of slippage during handling, the side surface of the substrate, particularly the end surface, is preferably a rough surface having a surface roughness (R a) of 0.05 m or more, more preferably 0.15 m or more. l jLi m or more, most preferably Q.15 im or more. Further, if the side surface of the substrate is too rough, there is a problem that particles potentially embedded in the grooves are generated during cleaning or the like. Considering this point, the side surface of the substrate, particularly the end face, preferably has a surface roughness (R a) of 0.3 m or less, more preferably 0.25 m or less, and most preferably 0.2 m or less. It is as follows. In order to obtain a side portion having a surface roughness (R a) of 0.05 to 0.3 m, it can be performed by controlling a polishing method. For example, a diamond tool (a diamond particle having a predetermined roughness can be obtained). It can be obtained by polishing using a diamond tool with a grain size of # 700 to # 240 in an embedded wheel-shaped grinding wheel).

 The width B of the chamfer 1C (see Fig. 2) is, for example, 0.3 [i! ] To 1.3 [mm].

 (Deposition process)

 Next, the light-shielding film 2 is formed only on the main surface of the obtained light-transmitting substrate 1 except for the peripheral portion 1S. Here, the peripheral portion is a region including the above-described end surface 1T and chamfered portion 1C.

The light shielding film 2 can be formed by sputtering. Sputtering may be performed in a state where the non-film-forming region 1S is masked by a frame-shaped holder (not shown) and the light-transmitting substrate 1 is held. This allows Since the sputter target particles do not adhere to the area masked by the frame-shaped holder on the main surface of the translucent substrate 1, that area can be used as the unfilmed area 1S. At this time, by holding the translucent substrate 1 so that the film formation surface (main surface) faces downward, the problem of particles adhering to the film formation surface can be reduced.

 In addition, by using a conductive member as the frame-shaped holder, the frame-shaped holder can be grounded at the time of sputtering film formation, thereby preventing abnormal discharge. Here, since the width A of the undeposited region 1S is set to 3 mm or more, the width of the frame-shaped holder can be set to 3 mm or more correspondingly. Therefore, sufficient grounding can be ensured during the spattering, so that abnormal discharge can be reliably avoided, and as a result, the yield can be improved.

 Through the above steps, the photomask blank according to the embodiment is completed.

 (Coating process)

 Next, a resist is applied on the formed light shielding film 2 by spin coating or the like. The register used here is a register for laser writing, and specifically, NPR3510PG manufactured by Nagase & Co., Ltd. is exemplified.

 (Exposure step)

 Next, after the applied resist film is backed, it is selectively exposed by laser drawing. At this time, the laser drawing does not need to be performed in a vacuum unlike the electron beam drawing, and can be performed in the atmosphere, so that there is an advantage that a large-scale apparatus is not required. In addition, as the laser drawing apparatus used here, specifically, LRS manufactured by MICRONIC or the like can be mentioned.

 [Etching process]

Next, the exposed resist film is developed to form a resist pattern, and the light-shielding film 2 is etched using the resist pattern as a mask. Then, a light-shielding film pattern is formed. Then, the resist pattern is removed, and thereafter, predetermined cleaning is performed to complete the photomask according to the embodiment.

 According to the present embodiment, the following effects can be obtained.

 (1) Since the photomask blank according to the embodiment is used for laser writing, it is possible to avoid the problem of charge-up in conventional electron beam writing, so that the size is 300 mm or more on one side. Even though it is large, there is no problem even if the width A of the undeposited area 1 S is 3 [mm] or more.

 (2) Large photomask blanks or photomasks (hereinafter referred to as photomasks, etc.) are also heavy, so they must be firmly held during transportation, etc. By setting the width A of the area 1S to 3 [mm] or more, even if the photomask or the like is conveyed in a state where the end face 1T and the chamfered portion 11C are gripped by hand or the like. It is possible to reliably prevent humans or the like from contacting the light shielding film 2. Therefore, the problem of peeling of the light shielding film 2 can be reliably prevented.

 (3) In addition, when the photomask or the like is transported using a holder that holds not only the end surface 1T and the chamfered portions 1C and 1C of the translucent substrate 1 but also the peripheral portion 1S. Even so, since the holding margin can be sufficiently ensured to be 3 mm or more, a large and heavy photomask or the like can be stably and firmly held while reliably preventing the problem of peeling of the light shielding film 2.

(4) As described above, by preventing the outer peripheral portion of the light-shielding film 2 from peeling and removing the source of minute foreign matter (particles), foreign matter adheres to the mask pattern surface such as a photomask. Therefore, a photomask having no defect can be manufactured with high yield. Therefore, the photomasks and the like of the present invention are those in which the mask pattern is particularly fine and strict defect inspections are performed. For example, it is suitable for use as a mask for manufacturing a TFT (thin film transistor).

 (5) In addition, since the number of times of cleaning of a photomask or the like for removing foreign matter, which has been essential in the past, can be reduced, it is possible to improve the direct rate of manufacturing the photomask or the like.

 In the embodiment, a rectangular substrate is illustrated as the translucent substrate 1, but the translucent substrate may be a square. Industrial applicability

 According to the present invention, generation of particles can be prevented when handling a blank requiring a large and fine pattern.

Claims

The scope of the claims 1. In a photomask blank in which a light-shielding film is formed only on the main surface of the light-transmitting substrate except for the peripheral edge, and the peripheral edge is an undeposited region of the light-shielding film,  When the size of the translucent substrate is 300 mm or more on one side,  A photomask blank, wherein the width of the undeposited region is 3 mm or more. 2. The photomask blank according to claim 1, wherein the light-shielding film is patterned using laser writing. 3. The surface roughness (R a) of the side surface of the translucent substrate is 0.05 to 0. 3. The photomask blank according to claim 1, wherein the photomask blank is a rough surface. 4. A photomask manufactured using the photomask blank according to one of claims 1 to 3.