JPS58177180A - Liquid applicator - Google Patents

Abstract

PURPOSE:To obtain coating film having uniform thickness, while blowing off liquid drops flying out of a workpiece to be coated, in a rotary liquid applicator, by sending air to each periphery of the edges of the rotating workpiece to be coated from the down side toward the upper side. CONSTITUTION:In the liquid applicator for forming the coating film of a solution by dripping the solution onto a workpiece to be coated fixed onto a mounting stand 1 and concurrently rotating the workpiece to be coated, the ascending stream of air sent through an air-ejecting opening provided at a lower part is formed around the periphery of the mounting stand 1. Hence liquid drops flying out of the workpiece to be coated are blown off upwards, so that a coating film having uniform thickness can be formed on the workpiece to be coated without the mixing of the liquid drops in the coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a solution coating device that coats a solution onto a substrate surface with a uniform thickness using a spin coating method.

The spin coating method is to drop a solution to be coated onto approximately the center surface of an object to be coated, such as a semiconductor wafer, and by rotating the object, the droplets are spread uniformly over the surface of the object by centrifugal force. This is a method in which the solution is applied while being spread to a certain thickness, and has been conventionally used as an apparatus for applying a surface treatment solution to round wafers and the like.

A solution coating device using this method is extremely useful as a means of forming a solution film of uniform thickness on a round object to be coated. It is used when applying a diffusion solution containing a diffusion source or when applying a chemical solution to a glass substrate surface.

However, for rectangular objects to be coated, such as semicircular wafers or rectangular glass substrates, with conventional rotary solution coating devices, the solution layer applied to the corners is thick and cannot be coated with a uniform thickness. coating film cannot be obtained. The reason for this is that while the object is being rotated, droplets that have jumped out from the sides of the object are reattached to the corners of the object that has been rotating.
The purpose is to thicken the IJ film by supplying too much solution to this area. That is, in the operation explanatory diagram shown in FIG. 1 (4) (B), the object to be coated B is rotated at high speed around its center, and the solution dropped onto the surface is rotated by the centrifugal force. It is extended toward the periphery of body B. The solution that has reached the peripheral area is further flung as droplets to the outside of the object to be coated B by centrifugal force. For example, the solution located at point L in the figure flies as a droplet with a predetermined momentum in the direction in which centrifugal force, inertial force, surface tension, etc. Part A rotates and comes into contact with this droplet, and the flying droplet is mixed with the solution of object B at corner part A again.

Therefore, the coating solution is supplied to the corner A in excess compared to other parts, and the components of the solution that has become droplets tend to change due to the dispersion of water and the specific gravity tends to increase. The viscosity of the solution in part A increases, and as a result, the coating film in corner part A becomes thicker.

If the thickness of the coating film becomes non-uniform, the dopant diffusion plate and diffusion 4 from the diffusion solution (coated IJ film) to the Si wafer used in, for example, solar cell devices will be different at each location, and the device Problems arise such as deterioration of characteristics and reduction in production yield. Therefore, the conventional rotary solution coating apparatus has generally been used as a means for obtaining a uniform coating film on a round object to be coated.

In view of the above-mentioned problems, an object of the present invention is to provide a new and useful solution coating device that can obtain a uniform solution coating film even on a rectangular object by making full use of technical means. That is.

Hereinafter, the present invention will be explained in detail according to embodiments with reference to the drawings. Fig. 2 is an explanatory diagram illustrating the operating principle of a solution coating device that is an embodiment of the present invention.

To explain the case where a semiconductor wafer is used as the object to be coated, a wafer mounting table 1 is connected to a drive shaft 2 that is connected to a drive source and rotates, and a groove is provided on the upper surface of the wafer mounting table 1 for vacuum chucking the wafer. 3 is formed. An ascending air current 4 is formed around the wafer mounting table 1, which is blown from an air outlet below.

A rectangular wafer having a larger shape than this is placed on the wafer mounting table 1, and when the groove 3 portion is sucked with a vacuum pump or the like, the rectangular wafer is vacuum chucked to the top surface of the mounting table 1. Also, all edges of the square wafer are placed under a state where they are blown by the rising air current 4. When the wafer mounting table I and the rectangular wafer are rotated via the drive shaft 2 and a diffusion solution containing a diffusion source for the rectangular wafer is dropped onto the upper surface of the rectangular wafer approximately at the center of rotation, this diffusion solution is subjected to centrifugal force. The wafer is forced to spread over the top surface of the rectangular wafer toward each edge, and a coating film of the diffusion solution is formed on substantially the entire surface. In addition, since the droplets that jump out from the edge of the square wafer are blown upward by the action of the rising air current 4, they do not come into contact with the corners of the rotating square wafer, and the coating film on the top surface of the square wafer changes with the rotation speed. The thickness is controlled to be uniform over almost the entire surface.

FIG. 3 is a configuration diagram of a solution coating apparatus showing one embodiment of the present invention.

The wafer mounting table 1 is connected to a drive source via a drive shaft 2 and is rotationally driven. A vacuum chuck groove 3 formed on the upper surface of the wafer mounting table 1 is connected to a vacuum pump (not shown) via a vacuum passage 5 inside the drive shaft 2. Below the wafer mounting table 1, one or more rows of gas blowing nozzles 6 are provided around the periphery of the rotation, and air, inert gas, or the like is blown upward. A part 8 of the outer frame 7 is opened, and a semiconductor wafer 9 on which, for example, a solar cell element is to be fabricated is placed on the upper surface of the wafer mounting table 1, and the wafer 9 is moved by the suction force of the groove 3 by driving a vacuum pump. The wafer is vacuum chucked onto the upper surface of the wafer mounting table 1. The wafer 9 may be a rectangular wafer such as a semicircle or a square, and is fixedly arranged so that each side of the wafer projects outward from the wafer mounting table. wafer.

A solution supply pipe 1o for dropping a diffusion solution containing a diffusion source to the wafer 9 is vertically provided above the wafer 9. -9.

While rotating the drive shaft 2 to rotate the wafer 9 together with the wafer mounting table 1, the cock 11 is opened and the supply pipe 10 is opened.
The diffusion solution 12 is dropped onto the upper surface of the wafer 9, and air is sent out from the nozzle 6 to form an upward air current around the wafer 9. The diffusion solution 12 on the upper surface of the wafer-9 is
It is spread over the top surface to form a uniform diffusion coating. Further, the droplets of the diffusion solution 12 that fly laterally from the edge of the wafer 9 are energized by the upward airflow blown out from the nozzle 6 and are scattered diagonally upward. If the gas blown out from the nozzle 6 is an inert gas or a reactive gas, and the outer frame 7 is of a sealed structure, a gas phase atmosphere necessary for forming the coating film can be created at the same time.

Although the above embodiment describes the case where a diffusion solution is applied using a semiconductor wafer as an object to be coated, the present invention is not limited to this, and the present invention is not limited to this, and the present invention is not limited to this, and the present invention is not limited to this. It can be used as a means for applying a solution to glass substrates, printed circuit boards, metal plates, resin members, etc. In addition to providing the rising air flow below the wafer mounting table, a mounting table with a larger area than the object to be coated is used, and the object to be coated is fixed to the upper surface of the mounting table, and the upper surface of the mounting table is placed along the edge of the object to be coated. The same purpose can also be achieved by forming a gas blowing slot.

As explained in detail above, according to the present invention, the droplets that jump out from the object to be coated are blown away by the rising air current around the object and escape upward, so that even if the object to be coated is square, the droplets will not jump out from the edges. This prevents droplets from coming into contact with the corners and being mixed into the coating film, making it possible to obtain a coating film with a uniform thickness on the upper surface of the object to be coated.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the operation of a conventional solution coating apparatus. FIG. 2 is an explanatory diagram illustrating the operating principle of a solution coating apparatus that is an embodiment of the present invention. FIG. 3 is a configuration diagram of a solution coating apparatus showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Wafer mounting table, 2... Drive shaft, 3... Groove, 4... Updraft, 5... Vacuum passage, 6... Nozzle, 7... Outer frame, 9... ... Wafer, 10... Supply tube, 12... Diffusion solution. Agent Patent attorney Aihiko Fukushi (and 2 others) (--
Atsushi 21 Figure 3

Claims (1)

[Claims] 1. In a solution coating device that drops a solution onto an object to be coated fixed on a mounting table and forms a coating film of the solution on the upper surface of the object through rotation of the object to be coated. 2. A solution coating device, characterized in that it is coupled with an airflow blowing means for forming an upward airflow that is blown from below to above around each line of the object to be coated during rotational operation.