X-ray mask structure

Abstract: An X-ray mask structure includes a mask substrate having a pattern; a supporting frame for carrying and supporting the mask substrate; and an adhesive material for fixing the mask substrate to the supporting frame; wherein an stress releasing groove is formed in at least one of the mask substrate and the supporting frame.

Description: This invention relates to an X-ray mask structure usable in an X-ray exposure apparatus for manufacture of semiconductor devices. Figure 1 shows an X-ray mask structure of known type. Denoted at 1 is a supporting frame, denoted at 2 is a mask substrate, denoted at 3 is an adhesive agent and denoted at 4 is a mask pattern. The mask substrate 2 is placed on the supporting frame 1, and the adhesive agent 3 is applied to the whole periphery of the mask substrate, whereby it is held fixed. The supporting frame 1 has a ring-like shape having an opening 15 formed at its center. The mask pattern 4 is formed of an X-ray absorptive material such as Au, for example, and it is formed on a thin film of a few micron thickness, made of an inorganic material such as SiN or SiC, for example. Also, the mask substrate is formed of an inorganic material such as SiN or SiC, for example. The thin film can be formed by back-etching the mask substrate. The supporting frame 1 is provided by a Ti plate of a thickness of about 0.5 - 3 mm. Figure 2 shows another X-ray mask structure of known type. In this example, a recess 5 is formed in a supporting frame 1 and, in this recess 5, a mask substrate 2 is held fixed by using an adhesive agent layer 6. In the X-ray mask structures as described above, there is a difference in coefficient of thermal expansion between the mask substrate and the supporting frame due to a difference in material. Thus, a temperature change causes a thermal stress in the X-ray mask structure, resulting in strain or distortion of the mask pattern. Further, possible contraction of the adhesive agent when the same is set causes a stress in the X-ray mask structure, also resulting in strain or distortion of the mask pattern. Particularly in a case where an adhesive agent is applied to the whole periphery of a mask substrate, such as in the example of Figure 1, non-uniformity in the thickness of the adhesive agent causes variation in quantity of contraction of the adhesive agent when it is set. Thus, by the contraction, an additional stress is applied which results in enlarged pattern distortion. In a case where an adhesive agent layer is provided as in the example of Figure 2, there is a disadvantage that, when the adhesive agent contracts, the flatness of the mask pattern bearing surface is degraded considerably. The English language abstract from Patents Abstracts of Japan Volume 11 No. 244 (E-530) for Japanese Patent Application Publication No. 62-054919 describes an arrangement wherein an X-ray mask is secured to a support by adhesive which is received in adhesive retaining grooves of the support. The adhesive retaining grooves communicate with through holes of the support to allow release of excess adhesive. DE-A-3524196 is concerned with the problem of the reduction of the flatness of an X-ray mask when adhesive is allowed to flow over the mask and the support and describes arrangements in which an X-ray mask is secured by adhesive to a support formed with grooves provided at the adhesive bonding position to control the flow of adhesive so that the adhesive flows into the grooves rather than over the part of the surface carrying the mask pattern. It is accordingly a primary object of the present invention to provide an improved X-ray mask structure by which the effect of a thermal stress or a stress due to contraction of an adhesive agent, can be reduced. According to the present invention, there is provided an X-ray mask structure, comprising a mask substrate having a pattern; a supporting frame for carrying and supporting said mask substrate; an adhesive material for fixing said mask substrate to said supporting frame; and stress releasing groove means provided in at least one of said mask substrate and said supporting frame; characterized in that said groove means delimit a plurality of adhesive material applying portions to which said adhesive material is applied and which are deformable to release stress due to differential thermal expansion between said mask substrate and said supporting frame and stress caused by contraction of said adhesive material whilst setting. Embodiments of the present invention will now be described with reference to the accompanying drawings in which:- Figure 1 is a sectional view of an X-ray mask structure of known type. Figure 2 is a sectional view of another X-ray mask structure of known type. Figure 3 is a sectional view of an X-ray mask structure according to a first embodiment of the present invention. Figure 4 is a sectional view of an X-ray mask structure according to a second embodiment of the present invention. Figure 5 is a top plan view of a supporting frame of the Figure 3 embodiment. Figure 6 is a top plan view of a supporting frame, in a modified form of the Figure 3 embodiment. Figure 7 is a sectional view of an X-ray mask structure according to a third embodiment of the present invention. Figure 8 is a sectional view of an X-ray mask structure according to a fourth embodiment of the present invention. Figure 3 shows a first embodiment of the present invention. Like numerals as those of Figure 1 are assigned to similar or corresponding elements, and explanation therefor is omitted here. Mask substrate 2 and supporting frame 1 are fixed to each other by means of an adhesive agent 3. In a portion of the supporting frame 1 adjacent the adhesive agent material 3, a slit-like stress releasing groove 7 is formed. Such a stress releasing groove may be formed by using electric discharging technique, for example. Figure 5 is a top plan view of the supporting frame 1. Figure 3 corresponds to the section taken on a line A-A in Figure 5. As illustrated, the stress releasing groove 7 has a ring-like shape and, at eight points along the ring, adhesive agent applying portions 14 are defined. As seen in Figure 5, the surface of each adhesive agent applying portion 14 is divided from the surface of the surrounding portion of the supporting frame 1 by the provision of the stress releasing groove 7. Therefore, each adhesive agent applying portion 14 can be deformed relatively easily. Figure 6 is a top plan view showing another example of stress releasing groove 7. In this example, two ring-like grooves 7 are formed in continuous form, wherein at four sites the two ring-like grooves 7 are connected with each other by means of connection grooves 7a. In this example, an adhesive agent is applied to the peripheral portion of the mask substrate at adhesive agent applying portions 14 as illustrated. Figure 4 shows a second embodiment of the present invention. In this embodiment, a stress releasing groove 7 is formed in a mask substrate 2. The remaining portion of this embodiment is essentially the same as the Figure 3 embodiment, in respect to structure and operation. Figure 7 shows a third embodiment of the present invention. In this embodiment, a recess 5 is formed in a supporting frame 1 and, in this recess 5, a mask substrate 2 is fixed by using an adhesive agent layer 6. Stress releasing grooves 7 are formed in the supporting frame 1, at the opposite sides of the adhesive agent layer 6, as illustrated. The mask substrate 2 has alignment marks 8 formed thereon which are to be aligned with alignment marks 9, provided on the supporting frame 1, for the mutual positioning of the mask substrate 2 and the supporting frame 1. Also, to the bottom face of the supporting frame 1, a viewangle controlling plate 11 is fixed by means of an adhesive agent layer 12. The viewangle controlling plate 11 also has alignment marks 10 formed thereon which are to be aligned with the marks 9 of the supporting frame 1, for the mutual positioning of the supporting frame 1 and the viewangle controlling plate 11. In place of providing the alignment marks 10 of the viewangle controlling plate 11, throughbores 13 may be formed in the plate as shown in Figure 8. In accordance with the present invention, as described hereinbefore, a slit-like groove or grooves are formed adjacent to an adhesive agent material for adhering a mask substrate and a supporting frame to each other. Therefore, undesirable distortion or strain of the mask substrate and/or the supporting frame due to a thermal stress or a stress resulting from contraction of the adhesive agent when it is set, can be absorbed or released. It is therefore possible to attain high-precision and high-reliability pattern exposure transfer. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as come within the scope of the following claims.

Claims: An X-ray mask structure, comprising a mask substrate (2) having a pattern (4); a supporting frame (1) for carrying and supporting said mask substrate (2); an adhesive material (3) for fixing said mask substrate to said supporting frame; and stress releasing groove means (7) provided in at least one of said mask substrate (2) and said supporting frame (1); characterized in that said groove means (7) delimit a plurality of adhesive material applying portions (14) to which said adhesive material (3) is applied and which are deformable to release stress due to differential thermal expansion between said mask substrate (2) and said supporting frame (1) and stress caused by contraction of said adhesive material (3) whilst setting. An X-ray mask structure according to claim 1, wherein said supporting frame (1) has a ring-like shape and wherein said stress releasing groove means (7) is formed in a ring-like shape, concentric with the ring-like shape of said supporting frame (1). An X-ray mask structure according to claim 1, wherein said supporting frame (1) has a ring-like shape and the stress relieving groove means (7) comprises a ring-like groove concentric with the supporting frame (1), a number of subsidiary ring-like grooves communicating with the ring-like groove being disposed about the ring-like groove so as each to bound an adhesive material receiving portion (14) of the at least one of said mask substrate (2) and said supporting frame (1). An X-ray mask structure according to claim 1, wherein said stress relieving groove means (7) comprises two ring-like grooves connected to each other by means of connection grooves (7a). An X-ray mask structure according to any one of the preceding claims, wherein the supporting frame (1) is formed with a recess (5) for receiving the mask substrate (2).

Inventors: CHIBA YUJI, FUJIOKA HIDEHIKO, FUKUDA YASUAKI, KARIYA TAKAO, MIYACHI TAKESHI, MIZUSAWA NOBUTOSHI, UZAWA SHUNICHI, CHIBA, YUJI, FUJIOKA, HIDEHIKO, FUKUDA, YASUAKI, KARIYA, TAKAO, MIYACHI, TAKESHI, MIZUSAWA, NOBUTOSHI, UZAWA, SHUNICHI, CHIBA, YUJI, C/O CANON KABUSHIKI KAISHA, FUJIOKA, HIDEHIKO, C/O CANON KABUSHIKI KAISHA, FUKUDA, YASUAKI, C/O CANON KABUSHIKI KAISHA, KARIYA, TAKAO, C/O CANON KABUSHIKI KAISHA, MIYACHI, TAKESHI, C/O CANON KABUSHIKI KAISHA, MIZUSAWA, NOBUTOSHI, C/O CANON KABUSHIKI KAISHA, UZAWA, SHUNICHI, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1991
Main classification: G03F1
IPC codes: G03F1, H01L21, G03F7