JPS61244029A - Prevention of uneven spin coating and spin coater - Google Patents

Abstract

PURPOSE:To reduce any uneven coating due to bubbles remarkably, forming coated films with excellent evenness, by a method wherein coating agent is dripped on the position distant from the rotary center of coated material. CONSTITUTION:The center B of nozzle 4 is arranged on the position distant by e from the rotary center A of a coated material 1. When coating agent 5 is dripped from a deflectively located nozzle 4, the dripped coating agent 5 is spread almost circularly on the position deflected from the rotary center A of coated material 1. The dripped amount of coating agent 5 shall be specified to get over the rotary center A toward the opposite side. When a spindle 3 is rotated, bubbles 6 are externally blown away rapidly together with the coating agent 5 disappearing from the coated material 1 since the bubbles 6 being distant from the rotary center A, the coating agent 5 around the bubbles 6 is subject to relatively intensive centrifugal force. Through these procedures, any uneven coating due to explosion of bubbles 6 can be reduced remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of spin-coating a coating material such as a resist onto the surface of a material to be coated such as a semiconductor substrate, and a spin coater therefor. It is about prevention.

[Conventional technology]

As shown in FIG. 3, the spin coater is equipped with a chuck 2 at the upper end of a spindle 3 that holds the material 1 to be coated by vacuum suction or other means, and a nozzle 4 for dropping a coating agent 5 above the center of the chuck 2. The coating agent 5 is dropped onto the rotation center of the coating material 1, and the spindle 3 is rotated at a high speed of 1000 r, p, m. A coating film of #111 order is formed. In a conventional spin coater, the nozzle 4 is rotated 30 times on the spindle in order to spread the coating agent 5 dropped onto the material to be coated to a more uniform thickness over the entire surface of the material to be coated 1 by centrifugal force caused by the rotation of the spindle 3. As shown in FIGS. 3 and 4, the coating agent 5 is placed on the center A, and the coating material 5 is dripped onto the center of the workpiece 1 held concentrically with the spindle 3 while it is rotating. It had become.

[Problem that the invention seeks to solve]

Incidentally, when applying a resist onto a semiconductor substrate by a spin coating method, uniformity of the thickness of the applied film is very important, and FIGS. 3 and 4 were the most common.

The inventors of the present application have made the following findings as a result of intensive research on the occurrence of coating unevenness. That is, the coating agent 5 dripped from the nozzle 4 may be contaminated with air bubbles due to leaks in the piping system leading from the container (not shown) storing the coating agent 5 to the nozzle 4 or gas generated from a filter provided along the way. Also, when a drop is dropped from the nozzle 4 onto the material 1 to be coated, a fourth droplet is formed near the center position of the drop.
Small bubbles 6 as shown in the figure are generated. The bubbles 6 burst when the coating agent 5 is spread over the surface of the material 10 and the thickness thereof becomes thinner than the diameter of the bubbles 6, thereby causing uneven coating as shown in FIG. When the air bubbles 6 are located very close to the rotation center of the material I, the air bubbles 6 will keep the material (
It remains on the top and ruptures near the final stage of spin coating, resulting in the uneven coating 7.

[Means for solving problems]

The present invention relates to dropping a coating agent onto a position offset from the rotation center of a material to be coated, and a spin coater for this purpose.

[For production]

If the coating agent is dropped at a position offset from the rotation center of the material to be coated, air bubbles are unlikely to be located very close to the rotation center. Air bubbles located away from the center of rotation will be thrown out from the surface of the material due to centrifugal force at a relatively early stage after the material starts rotating, and the coating film will reach a thickness such that bubble bursting becomes a problem. When the coating material becomes thin, there are almost no air bubbles on the material to be coated, and the occurrence of a coating film due to the air bubbles is greatly reduced.

〔Example〕

1 and 2 showing one embodiment of the present invention will be explained below. Note that the same parts as in FIGS. 3 and 4 described above are denoted by the same reference numerals, and some explanations will be omitted. As shown in FIG. 1, the center B of the nozzle 4 is offset from the rotation center A of the material 1 to be coated by a distance e. This nozzle 4 may be movably supported using flexible piping such as a vinyl hose (not shown) on the base end side, or the nozzle 4 may be rotated around a position away from the rotation center A of the gold coated material 1. The distance e can be adjusted as appropriate by attaching the distance e.

Next, the coating action by this device will be explained. When the coating agent 5 is dripped onto the material 1 to be coated from the nozzle 4 positioned eccentrically as described above, the dropped coating agent 5 will spread onto the material 1 to be coated, as clearly shown in FIG. It spreads in a substantially circular shape at a position eccentric from the rotation center A. The dropping amount of coating agent 5 is
A predetermined amount of the coating agent 5 is left on the opposite side (the left side in FIG. 1.2) beyond the center of rotation A.

When the coating material 5 is dropped onto the material 1 to be coated in this way, the bubbles 6 will be generated at positions shifted from the center of rotation A, as shown in FIG.

Next, when the spindle 3 is rotated, the air bubbles 6 are separated from the center of rotation A, and the coating agent 5 in this area is subjected to a relatively large centrifugal force, so that the air bubbles 6 together with the coating agent 5 move outward quickly. When the coating agent 5 is blown away and is spread thinly on the surface of the material 10 to be coated by centrifugal force, the air bubbles 6 are not visible from above the material 1 to be coated. Therefore, the occurrence of uneven coating due to the bursting of the bubbles 6 is greatly reduced.

The effect can be sufficiently obtained if the distance e between the rotation center A and the center B of the nozzle 4 is about 2 degrees.

Note that if this distance e is made too large, the amount of 50 drops of coating agent must be increased, so it is preferable to keep it at about 10 mm.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to greatly reduce coating unevenness caused by air bubbles in a coating agent dropped onto a material to be coated, and to obtain a coating film with extremely good uniformity.
A very large effect can be obtained when applying resist to semiconductor substrates, etc.

[Brief explanation of drawings]

Fig. 1 is a side view of the main part showing an embodiment of the present invention, Fig. 2 is a plan view with the nozzle of Fig. 1 omitted, Fig. 3 is a side view of the main part showing a conventional example, and Fig. FIG. 3 is a plan view with the nozzle omitted, and FIG. 5 is a plan view showing how uneven coating occurs when spin coating is performed by a conventional example. 1...material to be coated, 2...chuck,
3...Spindle, 4...Nozzle, 5...Coating agent, 6...Bubble,
7...Uneven coating.

Claims (1)

[Scope of Claims] 1. In spin coating, in which a coating agent is applied dropwise onto a material to be coated and the material is rotated to spread the coating agent over the surface of the material to be coated, A method for preventing uneven coating that is characterized by applying drops at a position offset from the center of rotation of the material. 2. The method for preventing uneven coating according to claim 1, wherein the amount of deviation from the center of rotation is 2 to 10 mm. 3. The method for preventing uneven coating according to claim 1 or 2, wherein the material to be coated is a semiconductor substrate and the coating agent is a resist. 4. In a spin coater consisting of a chuck that holds a material to be coated, a spindle to which the chuck is attached and rotated, and a nozzle for dropping a coating agent provided opposite to the chuck, the nozzle is moved from the center of rotation of the spindle. A spin coater characterized by being arranged in a staggered manner. 5. The spin coater according to claim 4, wherein the nozzle is mounted so as to be movable in the radial direction of the spindle.