JPH0452614B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a drying method for obtaining a particularly dust-free surface after washing with water.

(b) Background of the technology Currently, semiconductor components and circuit components are required to be small and large in capacity, and fine patterns are often created using thin film technology and photolithography.

Thin films of metals, resistors, insulators, etc. are made using various thin film forming methods such as vacuum evaporation, sputter evaporation, and ion beam evaporation, but the thickness of the thin film in these cases ranges from several hundred to several thousand. On the other hand, there are many μ-order fine particles floating in the air or in water, but if these particles adhere to the thin film forming substrate, it is impossible to expect an improvement in the yield of good products. The present invention relates to a drying method for obtaining a clean surface after washing with water.

(c) Prior art and problems Semiconductor devices, magnetic bubble memory devices, surface acoustic wave filters, etc. are made by forming fine patterns on semiconductor crystal substrates, magnetic crystal substrates, dielectric crystal substrates, etc., respectively. The substrate used for this is a polished substrate with a thickness of about 500 μm, on which a fine pattern is created using thin film formation technology and photoetching technology.

After polishing or chemical etching, washing with water is performed to completely remove polishing powder and etching solution, but in order to form a thin film, a completely dust-free and clean surface is required. It is necessary to wash with water so that no particulates adhere to the drying surface, as adhesion of particulates may cause a decrease in yield.

A photomask substrate will be explained below as an example. A photomask is made of transparent quartz or glass and has a thickness of approximately
Chrome metal was formed on a 2.5 mm substrate to a thickness of approximately 1000 mm, and a pattern was formed on this using photolithography, and it was coated on the semiconductor crystal substrate or dielectric crystal substrate mentioned above. This is an original plate used when performing projection exposure or contact exposure on a photoresist film. Therefore, high pattern accuracy is required and there must be no scratches or contamination.

Furthermore, even if the product is in good condition, it is easily damaged during use, so its service life is relatively short and it must be replaced with a new one.

Therefore, for photomasks that become defective during photomask formation or use, the Cr layer on the surface is removed by etching, and then both sides are polished (wrapped) using a polishing machine to remove several μm of the surface layer and reused as a photomask. It is customary.

Such substrates are thoroughly ultrasonically cleaned and then dried to obtain a clean substrate surface, but in this case the presence of fine particles contained in the cleaning water poses a problem.

In other words, the final step of cleaning is performed using pure water that has been purified using an ion exchange resin after passing through a filter, so most inorganic ions such as anions and cations are removed. As a result, there are 20 to 100 microsleeve particles with an average pore diameter of 0.2 μm per c.c. This subdivision consists of microorganisms such as bacteria, minute dust, and fine particles of ion exchange resin. If these fine particles adhere to the substrate surface during drying, the fine particles are larger than the thickness of the deposited Cr film, often causing defects.

In addition, although pure water has a small number of particles in its purified state, the sterilizers have been removed during the ion exchange process, making it easy for fungi and other microorganisms to propagate and grow. Usually contains a considerable number of fine particles with a particle size of 0.1 μm or more.

And if such fine particles exist on the substrate,
It interferes with the adhesion of Cr metal and tends to peel off, causing mask defects.

(d) Object of the Invention An object of the present invention is to provide a drying method that reduces the adhesion of fine particles to a substrate in a dry state after washing with water.

(e) Structure of the Invention After freezing the water on the substrate to be processed after water washing, the substrate is fixed to a sample holding stand provided in a processing chamber equipped with a drying gas supply port and a lamp heater, A dust-free method that dries the substrate by rotating the spinner in a dry gas atmosphere in the processing chamber and simultaneously heating the substrate by energizing the lamp heater and scattering the water generated by melting the ice on the substrate using centrifugal force. This can be achieved by a drying method.

(f) Embodiments of the Invention It is common practice to remove contaminants and foreign substances on the surface of the substrate by dissolving, polishing, or other methods, then repeat washing with water, finally washing with pure water, and drying. This is the drying method.

However, as mentioned above, pure water contains a considerable number of fine particles, and this number tends to increase over time.

Therefore, if the substrate is dried as is, precipitation of fine particles on the substrate surface is unavoidable.

Therefore, the present invention separates fine particles from the substrate surface by utilizing the principle that foreign substances are removed when water freezes and crystals develop.

Here, the crystal structure of ice has a tetrahedral structure with oxygen ions O ^-- at the center and hydrogen ions H ⁺ at the apex.
Hydrogen bonds are formed due to the electronegativity of O ^-- , and all H ⁺ are shared and connected in three dimensions, and H ⁺ has a crystal structure located on the line connecting O ^-- . .

When water is cooled and becomes ice, apart from cases in which it is rapidly cooled to form fine polycrystalline aggregates and incorporate fine particles into the boundaries, as the ice grows, fine particles are excluded from the crystal lattice and are not present in the crystal. A state is obtained in which no foreign substances exist.

In the drying method according to the present invention, the substrate is lowered to 0° C. or lower to crystallize the water adhering to the surface, thereby separating the fine particles from the substrate surface, and drying while maintaining this state.

As a method, the cleaned substrate is placed in a holding frame and moved to an atmosphere below 0°C to freeze the water adhering to the surface, and then taken out and shown in Figures 1 and 2. Infrared lamp 1 as shown in
A substrate 3 is set on a spinner 2 equipped with a top. Here, FIG. 1 is a block diagram of a drying apparatus according to the present invention equipped with a spinner 2, and FIG.
Although the water on the surface of the substrate 3 is frozen, the amount of adhering water is small, so that it is easy to take out from the frame and also easy to attach to the spinner 2.

Here, the spinner 2 is equipped with a vacuum chuck mechanism, and the substrate 3 is held by a vacuum suction mechanism that penetrates the axis of the rotating shaft 5 rotated at high speed by the motor 4 and reaches the surface of the sample holder 6. In this case, a structure is adopted in which the claw portion 7 prevents slipping.

Such a spinner 2 has, for example, a door that can be opened and closed on one side, through which a substrate 3 can be mounted, and an infrared lamp 1 for heating the substrate on the top, and a supply of dry air, dry nitrogen N ₂ , etc. on the side. It is provided in a draft 10 provided with a hole 9. Then, the substrate 3 is always kept in a dry atmosphere, the infrared lamp is turned on in synchronization with the start switch of the motor 4, and the ice 8 on the surface of the substrate 3 is melted and scattered by centrifugal force, and is rapidly dried. ing.

In this way, by creating a state in which the substrate 3 is free from fine particles after cleaning and rapidly drying it, a surface condition with a very small amount of fine particles attached can be obtained. When using this type of substrate drying method, conventionally when observing a dried substrate with a microscope, the particle size was observed within the field of view.
Although several fine particles of 1,000 or more were always present within the visual field, when the method of the present invention is carried out, no fine particles can be observed in most cases.

(g) Effects of the invention The present invention has a particle size of 1000〓 as in photomask formation.
This was done to improve the yield in substrate drying, where the presence of small particles affects the yield, and by carrying out the present invention, the adhesion of fine particles is reduced, making it possible to improve the yield.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the structure of a drying device used to carry out the present invention, and FIG. 2 is a plan view of a spinner section. In the figure, 1 is an infrared lamp, 2 is a spinner, 3 is a substrate, 7 is a claw part, 8 is ice, 9 is a dry gas supply port, and 10 is a draft.

Claims (1)

[Claims] 1. After freezing the water on the substrate to be processed which has been washed with water, the substrate is fixed on a sample holding stand of a spinner installed in a processing chamber equipped with a drying gas supply port and a lamp heater, and the substrate is With a dry gas atmosphere in the room, the spinner is rotated and the lamp heater is energized at the same time to heat the substrate, and the water generated by melting the ice on the substrate is scattered by centrifugal force to dry the substrate. A dust-free drying method characterized by: