Photo-mask and method of production thereof

Abstract: A method of manufacturing a photo-mask, which includes the steps of applying a resist film (3) onto a substrate (1) of quartz, glass and the like, subjecting the resist film (3) to light exposure and development to form a fine resist pattern (4), etching the mask substrate (1) covered by the fine resist pattern (4) so as to cause a non-light transmitting thin film (2) of Cr, Ta, etc. to adhere thereon by vapor deposition, sputtering and the like, and removing the thin film (2) on the resist pattern (4) together with the resist film (3), thereby to form the photo-mask. The disclosure is also directed to a photo-mask manufactured by the above method.

Description: The present invention generally relates to a photo-mask and more particularly, to a method of manufacturing a photo-mask to be employed for a pattern exposure process (lithography) in a production line of an optical disc, and a photo-mask produced by said manufacturing method. Commonly, a photo-mask has been employed for the formation of a pattern on an optical disc by a light exposure system. The conventional manufacturing process for such a photo-mask generally includes manufacturing steps as shown, for example, in Figs. 4(a) to 4(e). More specifically, at a step in Fig. 4(a), a non-light transmitting film 2 of Cr or the like is formed on a mask substrate 1 by vapor deposition, sputtering, etc., and then, at a step in Fig. 4(b), a resist film 3 is applied onto said thin film 2. Thereafter, by subjecting said resist film 3 to exposure and development, a resist pattern 4 is formed (Fig. 4(c)). Subsequently, the thin film 2 is subjected to etching (Fig. 4(d)), and finally, the resist film 3 is removed, thereby to form the photo-mask having a mask pattern 5 (Fig. 4(e)). The photo-mask manufactured by the conventional method as described above, however, has such a disadvantage that various faults tend to be formed therein, since separation of the mask pattern takes place in a cleaning process and the like. Furthermore, owing to the recent tendency toward recording at a higher density, the mask-pattern has been required to be finer, and thus, it has become necessary to solve the defect in the conventional method as referred to above. JP-A 59 172 648 discloses a mask substrate having thereon a light transmitting thin film which in turn has grooves therein filled with a light shielding second thin film forming a mask pattern. The substrate is formed into the opening at the central portion thereof and therefore, the substrate is not present at the portion confronting the golden thin film (9) of the substrate. WO 84/03571 discloses an optical structure filter with polished surfaces used for example as a working mask for the photolithographic fabrication of prefabricated microelectronic elements. The filtering layer is comprised of a locally homogenous transmission substance wherein, according to the pattern, are implanted ions preferably metal ions with an energy higher than lkeV for producing the pattern, respectively the differential transmission patterns. Accordingly, an essential object of the present invention is to provide a method of manufacturing a highly reliable photo-mask with a long life and not readily subjected to such a defect as separation of a mask-pattern, etc., with substantial elimination of disadvantages inherent in the conventional manufacturing methods of this kind. Another important object of the present invention is to provide a superior photo-mask produced by the manufacturing method as referred to above. In accomplishing these and other objects, according to one aspect of the present invention, there is provided a novel method of manufacturing a photo-mask as defined in claim 1 with a process according to claim 3. In preferred aspect, the present invention provides a method of manufacturing a photo-mask, which includes the steps of causing a light-transmitting thin film of Si 3 N 4 , etc. to adhere onto a light-transmitting mask substrate of quartz, glass, etc. by vapor deposition, sputtering, etc., applying a resist film thereonto, subjecting the resist film to light exposure and development to form a fine resist pattern, further subjecting said thin film to isotropic etching in a state as covered by said resist pattern so as to form a groove means in a portion not covered by said resist pattern, further applying thereon a light-shielding thin film of Cr, Ta and the like by vapor deposition, sputtering, etc. and removing said light-shielding thin film adhering to the portion of the resist pattern together with said resist film. The resist pattern for the mask pattern is formed on the first thin film having the nature in which the isotropic etching proceeds in the dry etching process. Accordingly, the first thin film is formed with side etching in the dry etching process, and therefore, the resist film, etc. may be readily removed to provide a high accuracy for the mask pattern. Since the manufacturing method of the photo-mask according to the present invention may be effected through utilization of the conventional photo-mask manufacturing technique, there is such an advantage that it can be readily put into actual application, with less requirements for new installation and facilities. In another aspect of the present invention, there is provided the novel photo-mask which includes a substrate of quartz, glass, etc., and an opaque metal layer such as Ta, Cr and the like filled in a groove means formed by removing part of said substrate, with the surface of said metal layer being formed to be generally flush with the surface of said substrate. These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which: Figs. 1(a) to 1(f) are schematic sectional diagrams showing manufacturing steps of a photo-mask according to the present invention; Figs. 2(a) and 2(b) are fragmentary side sectional views showing the configuration of a groove in the course of manufacturing the photo-mask; Fig. 3 is a fragmentary side sectional view of the photo-mask produced by the method of Figs. 1(a) to 1(f) ; Figs. 4(a) to 4(e) are schematic sectional diagrams showing manufacturing steps of a conventional photo-mask (already referred to); and Fig. 5 is a fragmentary side sectional view of the conventional photo-mask. Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. Referring to Figs. 1(a) to 1(f), there is sequentially shown in the order of manufacturing steps, a method of manufacturing a photo-mask according to the present invention as follows. Step (i) Onto a light-transmitting mask substrate 1 made of quartz, glass or the like, a thin film 6 (e.g., Si 3 N 4 is suitable) transmitting light such as ultraviolet rays and the like, and having a nature in which isotropic etching proceeds in a dry etching process, is caused to adhere by vapor deposition, sputtering, etc. (Fig. 3(a)). Step (ii) After application of the above thin film 6, a resist film 3 is further applied thereon (Fig. 1(b)). Step (iii) The resist film 3 is subjected to light exposure through employment of an electron beam or laser light so as to form a resist pattern 4 through a developing process (Fig. 1(c)) . Step (iv) In the state as covered by the resist pattern 4, the thin film 6 is subjected to dry etching to form grooves in said thin film 6. Here, since isotropic etching proceeds in the thin film 6, a side etching is formed (Fig. 1(d)). Step (v) After completion of the above etching, and in the state as covered by the resist pattern 4, a thin film 2 of Cr, Ta or the like not transmitting light such as ultraviolet rays, etc. therethrough is caused to adhere thereonto by vapor deposition, sputtering or the like (Fig. 1(e)) . Step (vi) Finally, the thin film 2 adhering onto the resist pattern 4 is separated together with the resist pattern 4, thereby to form the photo-mask having a mask pattern 5 (Fig. 1(f)). Subsequently, Fig. 2(a) shows a fragmentary cross section of a photo-mask in which grooves are formed without providing the thin film 6 on the mask substrate 1, while Fig. 2(b) shows a similar view in which grooves are formed by providing the thin film 6 on the substrate 1. In the photo-mask of Fig 2(a) , owing to the absence of the thin film 6, anisotropic etching proceeds in the mask substrate 1 of quartz, glass or the like. Therefore, the thin film 2 undesirably covers pattern side wall portions W, and it becomes difficult to separate the thin film 2 adhering to the upper portion of the resist film 3. On the other hand, in the photo-mask of Fig. 2(b), since the thin film 6 is present, isotropic etching proceeds in said thin film 6, thereby to form side etching portions S. Due to the fact that discontinuous portions are formed in the side etching portions S when the thin film 2 is affixed, said thin film 2 adhering to the portions of the resist pattern 4 may be readily separated together with the resist film 3. Fig. 3 shows a fragmentary cross section of the photo-mask prepared by the method of the present invention. In this case, the contact face F with respect to the external object (not shown) is located on the surface of the mask substrate 1, and the external force due to washing, etc., is absorbed into the surface of said substrate, and thus, the mask pattern 5 becomes very difficult to be separated. By this embodiment of the present invention as described so far, separation of the mask pattern does not readily take place, and accordingly, a highly reliable photo-mask with a long life may be advantageously provided. Furthermore, according to the manufacturing method of the present invention, the edge shape of the mask pattern may be accurately formed, without inviting any problems such as faulty electrical conduction.

Claims: A photo mask comprising a light-transmitting substrate (1) and a light transmitting first thin film (6) formed on said mask substrate (1) and a mask pattern (5) of a light shielding thin film (2) formed in grooves on said light transmitting first thin film (6). The photo mask as defined in claim 1, wherein said substrate (1) comprises quartz or glass and said light shielding thin film (2) comprises Cr or Ta. A method of manufacturing the photo mask according to claims 1 or 2 by forming a light transmitting first thin film (6) on a light-transmitting mask substrate (1), applying a resist film (3) on said first thin film (6), subjecting said resist film (3) to light exposure and development, subjecting said first thin film (6) to etching to form grooves, applying on said fine resist pattern (4) and said grooves a light shielding second thin film (2) and removing said light shielding second thin film (2) formed on said resist pattern (4) together with said resist film (3), characterized by isotropic etching so as to form and widen grooves in a portion of said first film (6) not covered by said resist pattern (4). A method of claim 3 wherein said resist film (3) is subjected to the light exposure of an electron beam or laser light. A method of claim 3 wherein said light shielding thin film (2) is adhered by vapor deposition or sputtering.

Inventors: HIROKANE JUNJI, INUI TETSUYA, KATAYAMA HIROYUKI, MIEDA MICHINOBU, MIYAKE TOMOYUKI, OHTA KENJI, TAKAHASHI AKIRA, VAN KAZUO, WASHO JUNICHI, HIROKANE, JUNJI, INUI, TETSUYA, KATAYAMA, HIROYUKI, MIEDA, MICHINOBU, MIYAKE, TOMOYUKI, OHTA, KENJI, TAKAHASHI, AKIRA, VAN, KAZUO, WASHO, JUNICHI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1987
Main classification: G03F1
IPC codes: G03F1, G11B7