JPH0320030A - Cleaning method for wafer - Google Patents

Abstract

PURPOSE:To eliminate remainder of trace pattern on a solid state image sensor by always beating a wafer surface with washing shower while the wafer is exposed in the air. CONSTITUTION:While a wafer 6 is moved manually or automatically by a conveyor between buses 1 and 3, the wafer 6 is beaten with washing shower 9. Accordingly, the water droplets on the wafer 6 are not steady at a predetermined position even if the droplets are formed while it is exposed in the air. The remainder of the residue in the water droplet at a predetermined position on the wafer 6 as a trace is eliminated. Thus, a trace pattern of the residue in the droplet does not remain in a solid state image sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for wet cleaning semiconductor wafers.

BACKGROUND OF THE INVENTION The surface of a semiconductor wafer can be made water repellent by etching it with a hydrofluoric acid-based etchant using a wet etching method. FIG. 2 shows a conceptual diagram of the process order of an example of a conventional wet etching or wet cleaning method.

In FIG. 2, first, a cassette 6 in which a wafer 6 is set is immersed in a wet etching bath 1 for a predetermined time to remove an oxide film and perform drainage treatment. After that, the first flush bath 2
Then, the cassette 6 is transferred manually or by a conveyance device to the secondary washing bath 3, and a final washing process is performed. The cassette 6 that has undergone the final water washing process is set in the swinner drainer 4 using a manual case or an automatic conveyance device, and water droplets on the wafer surface are removed.

The type and number of water washing baths are selected to be optimal depending on the purpose of wet processing. What these processes have in common is that the wafer 6 alternately passes through liquid and air. That is, while the wafer 6 is moved between each bus by a manual or automatic transfer device, the wafer surface is exposed to air, and the wafer 6 is transferred to the next pass with droplets remaining on some areas of the surface. It will be done.

Problems to be Solved by the Invention As mentioned above, during the wet processing process, the wafer is exposed to the air inside the casing with water droplets formed on the wafer surface. Such water droplets tend to remain on the wafer surface especially after the wafer surface has been subjected to water repellent treatment. When the water droplet is in a formed state, residue in the water droplet adheres to the wafer surface, and once attached, the residue remains as a water droplet trace on the wafer surface.
Difficult to remove. If these traces remain, for example, in the photodiode region of a solid-state imaging device, there is a problem in that the aforementioned trace pattern of the residue in the water droplets appears on the image screen captured by a camera using this solid-state imaging device.

In order to obtain good images, it is necessary to eliminate traces of water droplets as mentioned above, which are induced during the manufacturing process of solid-state imaging devices.

Means for Solving the Problem It must be ensured that water droplets do not form when the wafer is exposed to air. Even if the water droplet is kept in shape, the water droplet must not be held in a constant state for a period of time necessary for the residue in the water droplet to remain as a trace. As a means to do that, manually change between each pass! While the wafer is being moved by an automatic transfer device or by an automatic transfer device, the surface of the wafer is continuously showered with water.

Operation By using the method described above, water droplets on the wafer surface while exposed to air will not remain stationary at a fixed position even if the water droplets are formed. Therefore, the residue in the water droplets does not remain as traces at a certain position on the wafer surface, and a solid-state imaging device with high quality images can be manufactured.

Embodiment FIG. 1 is a conceptual diagram of an embodiment of the present invention. Wet etching pass 1 contains an etching solution that makes the wafer surface water repellent. The wafer that has become water repellent in this bath is moved to the first water washing bath 2 manually or by an automatic transfer device. During this movement, a shower 9 is caused to be applied to the wafer surface by pure water guided by the shower system line 8 . After being washed for a predetermined time in the first washing pass, the wafer is transferred to the second washing pass 3 by a manual or automatic transfer device. Since the wafer 6 is exposed to the air during this movement, the shower 9 is applied to the wafer 6 during this movement.

Ueha 6 after the final washing in the second washing pass 3
is transferred to the spinner drainer 4. Since the wafer surface is exposed to the atmosphere during this relocation, the shower 9 is arranged to shower the wafer surface. When the spinner drainer 4 starts rotating, the shower 9 is stopped.

As shown in this embodiment, a water washing shower is applied to the wafer surface while the wafer is exposed to the air in a series of wet processing lines.

Effects of the Invention As described above, according to the present invention, the wafer surface is continuously showered with water while the wafer is exposed to the air, so that even after the wafer becomes water repellent, the area on the wafer surface remains clean. Since the water droplets no longer stand still at certain points, no traces of residue in the water droplets will be generated on the wafer surface. Therefore, a solid-state image sensor manufactured on such a wet processing line can provide high-quality images without leaving any trace patterns.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a wet processing line according to an embodiment of the present invention, and FIG. 2 is a conceptual diagram of a conventional wet processing line. 1... Wet etching panu, 2...
・First flush bath, 3...Second flush bath, 4
...Spinner drainer, 5...Cassette, 6...Wafer, 7...Cassette movement between passes, 8... Shower system line, 9...Shower.

Claims (2)

[Claims] (1) A wafer cleaning method characterized in that the wafer is pulled out from a liquid into the air, and the wafer surface is exposed to the air and a shower is applied to the wafer surface while water droplets remain. (2) The wafer cleaning method according to claim 1, wherein the shower is a flush shower.