Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2001-12-19
2004-09-14
Duda, Kathleen (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S322000
Reexamination Certificate
active
06790564
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing an electronic device such as a semiconductor integrated circuit, a super conductive device, a micro-machine, TFT, or a printed wiring board. In particular, the invention relates to a technique effectively applicable to lithography in the manufacturing process of the semiconductor integrated circuit device.
2. Description of Related Art
In the production of semiconductor integrated circuit devices, lithography is used for transferring a fine pattern on a semiconductor wafer. In the lithography, a projection and exposure system is used and a device pattern is formed by transferring a pattern of a photomask mounted on the projection and exposure system to the semiconductor wafer.
A usual photomask is prepared by fabricating a shade material, such as chromium (Cr) formed on a transparent quartz glass substrate. That is, a shade film made of chromium or the like is formed in a desired shape on a quartz substrate. The shade film is fabricated, for example, as described below. That is, after coating an electron beam sensitive resist on a shade film, a desired pattern is delineated on the electron beam sensitive resist by an electron beam exposure system. Successively, after delineating a resist pattern of a desired shape by development, the shade film is fabricated by dry etching or wet etching using the resist pattern as a mask. Subsequently, after removing the resist, cleaning is conducted to form an opaque pattern of a desired shape on the quartz glass substrate.
In recent years, with an aim of improving the resolution of lithography, various mask structures have been proposed in addition to usual photomasks in which the shade film comprises a chromium or the like in a desired shape as described above. For example, in JP-A-136854/1992, the shade film of the photomask is made semi-transparent and the phase of slight light transmitting the semi-transparent area is inverted to transmit the transparent pattern. That is, the light at a level lower than the sensitivity of a photoresist for transferring the pattern is transmitted through the semi-transparent film and the phase of the light transmitting through the transparent pattern is inverted. Since the phase of the light transmitting via the semi-transparent film is inverted relative to the light transmitting the transparent pattern as a main pattern, the phase is inverted at the boundary and the intensity of light at the boundary approaches zero. Thus, the ratio between the intensity of light passing the transparent pattern and the intensity of light at the boundary of the pattern is relatively increased to obtain a distribution of light intensity with higher contrast compared with the technique not using the semi-transparent film. This is referred to as a half tone type phase shift mask. In the manufacture of the half tone phase shift mask, the shade film of the usual photomask is changed to a half tone phase shift film, which is manufactured substantially in the same step as the manufacturing step for the usual photomask.
Further, there is an exposure method referred to as resolution enhancement which provides patterning resolution much smaller than the exposure wavelength. Among the resolution enhancement processes, a Levenson-type phase shifting exposure process is most effective for forming a fine pattern. In the Levenson-type phase shifting exposure process, a structure called as a phase shifter for inverting the phase of the irradiation light is formed alternately in the irradiation light transmitting area, i.e., in the window where the glass surface is exposed of a usual photomask while the shade are putted therebetween is exposed by using the photomask. Since phase of lights transmitting both of the transmitting areas is inverted, a region where the amplitude of light is reduced to zero is formed in the sandwiched shade area. When the amplitude is zero, the intensity of light is also reduced to zero, and the resolution is improved significantly by about ½ of the exposure wavelength for the alternately arranged shade area (thinner than the window) and the phase shifter area. The photomask having such a shade area and a phase shifter area is referred to as a Levenson-type phase shift mask.
Due to increasing accuracy and versatile arrangements of semiconductor integrated circuit devices, the fabrication accuracy for the photomask used in the lithography also in the usual photomask becomes more stringent. Therefore, a phase shift mask having the special structure as described above becomes necessary. Accordingly, the production cost for such photomasks of about 20 to 40 plates are much more expensive, and the time required for the manufacture of the photomask becomes longer.
On the other hand, JP-A-289307/1993 discloses a method for forming a shade film in the photomask with a resist film instead of existent metal films such as of Cr. This method utilizes benzene (rings) as the main constituent element in a usual electron beam resist or photosensitive resist compositions because that they have an extremely large light absorption band at a wavelength of an ArF excimer laser beam source (about 193 nm). The etching step for the shade film or the resist removing step is not necessary according to this method, which reduces the cost, improves the dimensional accuracy, and reduces the defects of the photomask. In many existent high performance resists used in the KrF excimer laser lithography or electron beam lithography, phenolic polymer resins or derivatives thereof are used for the base polymer matrix providing the coatability. An aromatic ring (benzene ring) structure in such resins has an extremely large absorption maximum near the wavelength of the ArF excimer laser beam, and the transmittance at the wavelength of 193 nm is 1% or less with a film thickness only of 0.1 &mgr;m in such a resin coating layer. Accordingly, in the resist material using the resin described above as the matrix, the transmittance to the ArF excimer laser beam is 0.01% or less even at the film thickness of about 0.3 &mgr;m which is used frequently, which provides a substantially ideal shade film. However, the transmittance of such resin increases near the wavelength of the existent KrF excimer laser beam (about 248 nm) and the transmittance is 30% or more even at the film thickness for forming a fine pattern (usually about 0.3 to 1.0 &mgr;m). Accordingly, such a resist can not be used for the shade film of the photomask in KrF excimer laser lithography.
The technique described above for forming the shade film in the photomask with a resist film of large light absorption at the exposure wavelength (instead of an existent metal film such as made of Cr) creates problems, and countermeasures therefor in the prior art to the photomask for the existent KrF excimer lithography are not disclosed. The subject of this invention is to provide a photomask for KrF excimer laser lithography using an opaque pattern that utilizes the light absorption characteristic of the organic resin composition, and to provide a method applying such a mask to produce semiconductor devices. The KrF excimer laser lithography is an exposure method used in a volume zone of semiconductor devices, and producing semiconductor devices by the KrF excimer laser lithography with such a mask reduces cost, and provides a high accuracy and less defect density.
In various existent kinds of high performance resists, the transmittance is 30% or more near the wavelength of the KrF excimer laser beam (about 248 nm) at a film thickness for forming a fine pattern (usually about 0.3 to 1.0 &mgr;m). Accordingly, the resists described above can not be used as they are for the shade film of the photomask for KrF excimer laser lithography. An obvious countermeasure is to incorporate a compound or a chemical structure having an absorption band in a wavelength region of a KrF excimer laser beam into an existent resist composition of high resolution. However, a light absorption compound that c
Arai Tadashi
Araki Tsutomu
Migitaka Sonoko
Momose Satoshi
Yamaguchi Osamu
A. Marquez, Esq. Juan Carlos
Duda Kathleen
Fisher Esq. Stanley P.
Reed Smith LLP
Renesas Technology Corporation
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