JPS591385B2 - Spin coating method and device - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement in a spin coating method and apparatus.

A spin coating method is usually used to form a photoresist film on the surface of a substrate to be processed in a patterning step in the manufacturing process of semiconductor devices or photomasks. As shown in FIG. 1, in this spin coating method, a substrate 3 to be processed, such as a semiconductor substrate or a mask substrate, is adsorbed onto a rotary head 2 provided in a tank 1 of a spin coating device. The photoresist solution is dripped onto the substrate 3 to be processed by a photoresist solution supply nozzle 4 led out from a photoresist tank (not shown), and the drop is applied by rotating the rotating head 2 at a predetermined rotation speed. The photoresist solution is spread over the surface of the substrate 3 to be processed to form a thin film 5 of the photoresist solution.

The thickness of the thin film 5 is such that the centrifugal force acting on the photoresist liquid due to the rotation of the rotating head and the surface tension depending on the viscosity of the photoresist liquid are in balance.
It was believed that by controlling the viscosity and rotational speed, a desired film thickness could be obtained with high precision.

However, since the atmosphere inside the tank 1 is actually exhausted through an exhaust port 6 connected to an exhaust system (not shown), the solvent in the photoresist solution is rapidly vaporized while the thin film 5 is being formed. removed.

Therefore, the viscosity of the photoresist liquid cannot be kept constant during the formation of the thin film 5. For the reasons mentioned above, the film thickness of the photoresist film formed by the conventional spin coating method and equipment is
±IOC%], and the dimensions of a pattern formed using such a photoresist film have a variation of ±0.1%.
A variation of ~0.2 [μm] occurs.

In the case of a fine pattern with a pattern size of 2 [μm] or 1 [μm], the above-mentioned dimensional error becomes a big problem. Such problems occur not only when forming a photoresist film, but also when, for example, spin coating a resin liquid or liquid glass. SUMMARY OF THE INVENTION An object of the present invention is to provide a spin coating method and apparatus capable of forming a liquid thin film without vaporizing the liquid agent in the liquid and removing the solvent by evaporation after the film thickness reaches an equilibrium state. . The feature of the spin coating method of the present invention is that the atmosphere around the substrate to be processed is maintained during the liquid thin film formation period. After the agent gas is brought into a saturated state and the thickness of the thin film reaches an equilibrium state, the atmosphere is brought into a state where the agent gas is unsaturated and the solvent gas is removed by evaporation.

Further, the spin coating apparatus of the present invention is characterized by a nearly sealable opening/closing lid at the upper opening of the tank, a gas blowing nozzle and a photoresist supply nozzle at the top of the rotating head of the opening/closing lid, and an approximately airtight exhaust port at the bottom of the tank. A sealable shut-off valve and apply it to the desired position of the tank or shut-off lid? The reason is that an inlet is provided for a solvent of the same type as the liqueur contained in the liquid, or a vaporized gas thereof. An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view of a main part showing an embodiment of the spin coating apparatus of the present invention, and the spin coating method of the present invention will be explained with reference to this figure. In this figure, the same parts as in FIG. 1 are indicated using the same reference numerals.

In this example, the following items were newly added to the conventional spin coating device. That is, an opening/closing lid 11 is provided at the opening at the top of the tank 1, a dry nitrogen blowing nozzle and the photoresist liquid supply nozzle 4 are attached to the center of the rotating head of the opening/closing lid, and an opening/closing valve 13 is installed at the exhaust port 6. , even more? Agent introduction port 14
was provided at the bottom of tank 1. Next, a method of forming a photoresist film using the above-mentioned spin coating apparatus will be described.

First, the substrate 3 to be processed, such as a silicon substrate, is adsorbed onto the rotary head 1, the opening/closing lid 11 is covered, and the opening/closing valve 13 is then closed.
is closed, and the inside of the tank 1 is almost sealed.

Then, a solvent of the same type as the solvent contained in the photoresist solution used is injected into the tank 1 from the inlet 14. The thickening agent for the photoresist solution is usually ethyl cellosolve acetate or a mixture of this with xylene and butyl acetate, and since both are organic substances with a low boiling point, they easily vaporize when injected into the tank 1. Since the inside of the tank 1 is substantially sealed, the atmosphere inside the tank is saturated with the vaporized gas of the preservative. Note that the above-mentioned sealed state may be such that the above-mentioned reagent gas can be maintained in a substantially saturated state, and therefore, there is no problem even if there is some leakage.
After this, the photoresist liquid is dropped from the supply nozzle 4 onto the substrate 3 to be processed, and the rotary head 2 is rotated to spread the dropped photoresist liquid over the surface of the substrate 3 to be processed.

In this embodiment, the atmosphere in the tank 1 is saturated with gas of the same kind of solvent as the fermentation agent in the photoresist solution, so that the dropwise droplet in the photoresist solution does not vaporize. Therefore, the viscosity of the photoresist liquid is kept constant, and a thin film 5 of the photoresist liquid is formed having a film thickness determined by the initial viscosity of the photoresist liquid used and the rotational speed.
After the thickness of the thin film 5 reaches an equilibrium state, the on-off valve 13 is opened and the atmosphere inside the tank is exhausted, and the blow-off nozzle 1
2, a gas free of the solvent gas, such as dry nitrogen, is introduced into the tank 1.

By doing this, the vapor pressure of the solvent gas in the atmosphere inside the tank 1 is rapidly reduced, and the evaporation of the liqueur in the thin film 5 is started. Further, the vaporized solvent gas is introduced from the blow-off nozzle 12, drawn into the exhaust system, and carried away by the nitrogen flow flowing along the surface of the substrate 3 to be processed, so that the vapor pressure of the solvent gas near the surface of the thin film 5 is always kept low. drooping Therefore, the sulfur agent in the thin film 5 is rapidly removed, and the thin film 5 is formed into a photoresist film having a desired thickness. In order to determine the time required for the thickness of the thin film 5 to reach an equilibrium state during the above process,
Any commonly used method may be used.

For example, when a thin film is irradiated with a monochromatic light beam, interference fringes appear due to the optical path difference between the two reflected waves reflected from the thin film surface and the substrate surface.Moreover, the interference fringes are not stable while the film thickness changes, and the film thickness It is possible to take advantage of the fact that the interference fringes become stable when becomes constant.

That is, the time t required from the time the rotary head starts rotating until the interference fringes become stable is determined in advance according to the type of photoresist, its viscosity, and the rotational speed of the rotary head, and the atmosphere in the bath 1 is changed after the rotary head 3 starts rotating. It is only necessary to set the time until this is performed longer than the above-mentioned time t. As described above, according to this embodiment, until the thickness of the thin film 5 reaches an equilibrium state, the ? Is it used because the agent does not vaporize and therefore the viscosity does not change? By controlling the viscosity of the liquid and the rotation speed of the rotating head, the thickness of the thin film 5 can be controlled with high precision. Note that the present invention is not limited to the above embodiments,
Furthermore, various modifications can be made.

For example, to saturate the atmosphere in the tank with solvent gas, is it from the inlet 14? Instead of injecting the drug, an addictive gas may be delivered.

Further, the position and number of guide holes 14 may be selected as appropriate.

Further, the present invention can be used not only when forming a photoresist film but also when forming a resin film or an inorganic film such as molten glass.

The thin film formed by the spin coating method and spin coating apparatus of the present invention briefly explained above has very small variation in film thickness. Therefore, for example, if a photoresist film formed according to the present invention is used, fine patterns can be formed with high precision, and the contribution to fine processing such as the manufacture of semiconductor devices is extremely large.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a conventional spin coating apparatus. FIG. 2 is a sectional view of a main part of an embodiment of a spin coating apparatus of the present invention. In the figure, 1 is a tank, 2 is a rotating head, 3 is a substrate to be processed, 4 is a supply nozzle, 5 is a thin film, 6 is an exhaust port, 11 is an opening/closing lid, 12 is a gas blowing nozzle, 13 is an opening/closing valve, and 14 is The air conditioning agent inlet is shown.

Claims (1)

[Scope of Claims] 1. A solution in which a desired material is dissolved in a predetermined solvent is dropped onto a substrate to be processed which is adsorbed onto a rotating head, and by rotating the rotating head, the dropped solution is applied to the substrate to be processed. In a spin coating method in which a thin film of the solution is formed by spreading it on the surface and the solvent in the thin film of the solution is removed by evaporation to form a thin film made of a desired material, while the thin film of the solution is being formed, the surroundings of the substrate to be processed are It is characterized by comprising the steps of making the atmosphere substantially saturated with a solvent gas of the same type as the solvent, and making the atmosphere unsaturated with the solvent gas after the thickness of the thin solution film reaches an equilibrium state. Rotary coating method. 2. A rotating head for adsorbing a substrate to be processed in a tank having an opening at the top, and a supply nozzle for dropping a solution of a desired material dissolved in a predetermined solvent onto the substrate to be processed, on the top of the rotating head. , a rotary coating device in which an exhaust port is provided at the bottom of the tank for discharging a solvent gas vaporized from the dropped solution; A gas blowing nozzle and the supply nozzle are provided on the upper part of the rotating head, a substantially sealable on-off valve is provided on the exhaust port, and an inlet for a solvent of the same kind as the above-mentioned solvent or the solvent gas is provided at a desired position on the tank or on the open-close lid. A rotary coating device characterized by being provided with.