1. Field of the Invention
The present invention relates to a heat processing apparatus and heat processing method for heating a substrate, which are used for manufacturing semiconductor devices while performing a coating/developing process on a substrate, such as a semiconductor wafer.
2. Description of the Related Art
In a photolithography step for semiconductor devices, a resist is applied onto a semiconductor wafer (which will be simply referred to as “wafer” hereinafter) to form a resist film. Then, the resist film is subjected to a light exposure process in accordance with a predetermined circuit pattern. Then, the light-exposed pattern thus formed is subjected to a developing process to form a circuit pattern on the resist film.
In a photolithography step of this type, various heat processes are performed, such as a heat process (pre-baking) performed subsequently to coating of a resist or a chemical solution for, e.g., a BARC, a heat process (post exposure baking) performed subsequently to light exposure, and a heat process (post baking) performed subsequently to development.
In general, these heat processes are performed by a heat processing apparatus (hot plate unit) provided with a heating plate (hot plate) heated by a heater. Conventionally, in a heat processing apparatus of this type, the following gas flow control is typically adopted to perform a heat process on a wafer as uniform as possible. Specifically, during the heat process, the heating plate is covered with a cover, in which gas flows are formed from around the heating plate toward the center, and gas is exhausted upward from the center of the cover.
In recent years, circuit patters of semiconductor devices show rapid progress in decreasing the line width, in decreasing the size, and in increasing the degree of integration, which requires the process uniformity of heat processes to be further improved. However, by use of the gas flow control described above, it has become difficult to attain desired process uniformity, particularly uniformity concerning gas flows relative to a wafer, which is necessary to uniformize critical dimensions (CD). Accordingly, it is required to provide a technique for performing a heat process with higher uniformity. As a technique for realizing a heat process with higher uniformity, Jpn. Pat. Appln. KOKAI Publication No. 2003-318091 discloses a technique for performing a heat process while supplying gas flows from above uniformly onto the entire surface of a substrate. According to this technique, since the gas flows uniformly strike the entire surface of the substrate, such as a wafer, it is possible to improve the process uniformity, particularly uniformity in the film thickness of a coating film.
However, devices for the next generation require very minute patterns with a CD value of 50 nm or less, in which even slight dust may cause a defect. Accordingly, it is necessary to swiftly remove sublimed substances and so forth generated by a heat process. In this respect, the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-318091 mentioned above cannot sufficiently remove sublimed substances and so forth, and thus it may deteriorate the yield of products. Particularly, such deterioration in the yield due to sublimed substances is easily caused in a coating film for argon fluoride (ArF) having a short wavelength. This coating film is used for further improving the resolving power of light exposure in accordance with a CD for the next generation.
Further, depending on coating films, heat processes of this kind include processes that should give weight to CD uniformity and processes that should give weight to an improvement in the product yield by removing substances, such as sublimed substances, that generate dust. However, the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-318091 mentioned above cannot address the latter type. Accordingly, there is a great demand for a heat processing technique that can address these two types.