Brushing – scrubbing – and general cleaning – Machines – With air blast or suction
Reexamination Certificate
2000-04-28
2001-09-11
Moore, Chris K. (Department: 1744)
Brushing, scrubbing, and general cleaning
Machines
With air blast or suction
C015S316100
Reexamination Certificate
active
06286178
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application Ser. No. 89203856, filed Mar. 10, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing station. More particularly, the present invention relates to a developing station whose suction pad has a groove capable of blowing out a jet of gas to remove residual developer solution from the back surface of a wafer.
2. Description of the Related Art
The fabrication of integrated circuit (IC) involves a large number of steps and complicated operations. In general, a wafer has to go through hundreds of different processing steps and requires one to two months of processing time before each integrated circuit chip is ready for shipment. Principally, the IC industry is a high-tech industry that entails IC design, wafer fabrication, wafer testing and wafer packaging.
Among various IC fabrication steps, photolithography is a dominant process in semiconductor manufacturing. A large number of steps that relate to the fabrication of MOS transistors or structures such as film patterning and doping require performance of photolithographic operations. Typically, a photolithographic operation can be further subdivided into coating, exposure and development.
Using photolithographic development as an example, the process involves removing the exposed photoresist from a wafer by chemical means so that a photoresist pattern is formed. There are a number of methods of photoresist development. However, to be in line with conventional photolithographic operation, most commercial developing station employs what is known as the ‘spray/puddle’ method. The spray/puddle method can be roughly divided into three stages. In the first stage, developer solution is sprayed onto a wafer mounted on a spinner. In the second stage, the wafer remains is a static state for what is known as the puddle development. After development, the wafer is cleaned with water and then dried by spinning.
The aforementioned three-stage process can be entirely completed in the same developing station.
FIG. 1
is a schematic cross-sectional view showing a jet-cleaning device within a conventional developing station. As shown in
FIG. 1
, the developing station includes a spin suction pad
10
, a knife ring
12
and an external ring guard
14
.
The spin suction pad
10
is used for supporting the back surface
18
of a wafer
16
so that developer solution can act on the positive wafer surface
20
. The spin suction pad
10
has an external diameter smaller than the wafer
16
so that the peripheral portion of wafer back surface
18
is exposed. Since capillary action may result in the flow of developer liquid onto the wafer back surface
18
when the positive surface
20
of the wafer
16
is being developed, the wafer back surface
18
may be contaminated.
To prevent the inversion of liquid and contamination of wafer back surface
18
, a plurality of hoses for emitting water jets
22
are normally installed under the spin suction pad
10
. The water jets
22
aim at the back surface
18
so that any developer liquid flowing onto the back surface
18
may be removed. In order to stop the back flow of the water jets from mixing with the developer liquid, the suction pad
10
is surrounded by the knife ring
12
. An external guard ring is also installed to prevent the sputtering of liquid outside the developing station.
However, since the water jets that target the wafer back surface do not form a continuous film of water, cleaning efficiency is rather low. Furthermore, to obtain the optimal cleaning, distance between the knife ring
12
and the wafer back surface
18
must be carefully set. Ideally, the water jets must flow to the edge of the wafer but permit no back flow of the developer liquid. Such an adjustment can be very time-consuming.
SUMMARY OF THE INVENTION
The invention provides a jet-cleaning device for a developing station. The jet-cleaning device comprises of a spin suction pad and knife ring. The spin suction pad is used for supporting a silicon wafer. The spin suction pad has an external diameter smaller than the external diameter of the wafer so that a portion of the wafer back surface is suspended in mid-air when the wafer is mounted on the pad. Inside the suction pad is a groove capable of delivering an air jet onto the exposed wafer back surface so that developer liquid can be blown away. The knife ring is erected under the wafer around the suction pad so that the sputtering of chemical solution back into the suction pad area is prevented.
Inert gases or nitrogen can be used to blow away the chemical solution such as developer liquid. In addition, an external ring guard can be installed around the wafer and the knife ring so that chemical solution will not sputter outside the developing station.
By directing the air jet from the spin suction pad towards the wafer back surface, the back flow of chemical liquid onto wafer back surface is prevented. Hence, there is not need to carry out time-consuming adjustment of knife ring position.
Accordingly, the present invention is to provide a jet-cleaning device for a developing station capable of clearing chemical liquid off the back surface of a wafer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 4541141 (1985-09-01), Le Goff
patent: 5361449 (1994-11-01), Akimoto
patent: 5375291 (1994-12-01), Tateyama et al.
patent: 5421065 (1995-06-01), Tateyama et al.
patent: 5608943 (1997-03-01), Konishi et al.
patent: 5706843 (1998-01-01), Matsuo
Chen Tien-Ya
Ke Chui-Kun
Huang Jiawei
J.C. Patents
Moore Chris K.
United Microelectronics Corp.
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