Fabrication method of photomask-blank

Abstract

PROBLEM TO BE SOLVED: To provide a fabrication method of a photomask-blank that has a reduced number of particle-caused defects. ŽSOLUTION: A susceptor 11 having the most basic structure has a three-layer structure including a first and a second transparent quartz part 11a and an opaque quartz part 11b sandwiched therebetween. For example, the opaque quartz part 11b is made of "foamed quartz". The opacity to flash light is determined to fall within an appropriate range based on the material or thickness of the opaque quartz part 11b, taking into consideration the composition or thickness of a thin film formed on a substrate 10 and various conditions concerning the energy of the irradiation light during flash light irradiation or the like. The stack structure may by composed of a stack of a plurality of opaque quartz layers having different opacities, or of a stack of n layers comprising light transmitting materials (wherein n is a natural number equal to or more than 2), and at least one of the n layers has an opacity different from that of other layers. Ž

Description

technical field [0001] The invention relates to a method for manufacturing a photomask-blank. In particular, the present invention relates to a technique for manufacturing a photomask substrate, which is a base material for photomasks used in semiconductor integrated circuits, charge-coupled devices (CCDs), Fine processing of color filters and magnetic heads of liquid crystal devices (LCD). Background technique [0002] The packaging density of semiconductor integrated circuits is increasing, and the exposure wavelength of exposure equipment used in photolithography for manufacturing semiconductor integrated circuits and the like is becoming shorter and shorter in order to improve resolution. According to the lithography blueprint in the International Semiconductor Technology Blueprint (ITRS) updated in 2004, the main light source is changed from the ultraviolet light source of g light (wavelength λ=436nm) or i light (wavelength λ=365nm) to a shorter wavelength light source...

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Problems solved by technology

[0012] On the other hand, as can be seen from the above formula (2), although the reduction of the exposure wavelength is effective for the reduction of the resolvable linewidth RP, it has the problem of causing a reduction in the depth of focus DOF, which in turn adversely affects the Production yield

However, the decrease in exposure wavelength also leads to a decrease in the depth of focus DOF, and thus has the problem that if the flatness of the photomask is insufficient, focus errors are caused, resulting in lower production yields

However, these devices have problems in that the substrate itself is damaged due to an increase in the temperature of the substrate by excessively giving energy, or the productivity is lowered due to prolongation of the processing time.

[0027] However, in the case where processing using a flash lamp is performed as described in prior art document 2, flash irradiation causes generation of particles in the chamber by a mechanism described later, and these particles adhere to the substrate and cannot pass through subsequent cleaning to remove

Therefore, there arises a problem that the number of defects caused by particles in the photomask substrate increases

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