Brushing – scrubbing – and general cleaning – Machines – With air blast or suction
Reexamination Certificate
2000-05-03
2001-09-18
Moore, Chris K. (Department: 1744)
Brushing, scrubbing, and general cleaning
Machines
With air blast or suction
C015S316100
Reexamination Certificate
active
06289550
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 89203855, 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 having a plurality of air nozzles, in which each nozzle capable of blowing a jet of air onto the back surface of a wafer so that residual developer solution is removed.
2. Description of the Related Art
The fabrication of an integrated circuit (IC) involves a large number of complicated steps. In general, a wafer has to go through hundreds of different steps that require 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 the many IC fabrication steps, photolithography is a one of the most critical. 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. A conventional photolithographic operation can be further divided into stages including 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 patterned photoresist layer is formed. There are a number of methods for developing photoresist. 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 is carried out in three stages. In the first stage, developer is sprayed onto a wafer mounted on a spinner. In the second stage, the wafer remains is a static state for carrying out what is known as 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 to support 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 nozzles 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 back flowing developer liquid may be removed. In order to stop the back flow of water jets mixed 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, the water jets that target the wafer back surface do not form a continuous film of wafer, and 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 a spin suction pad, a plurality of air nozzles and a knife ring. The spin suction pad is used to support 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 exposed when the wafer is mounted on the pad. The plurality of air nozzles are positioned in the substrate under the spin suction pad for targeting jets of air at the exposed back surface of the wafer so that chemical solution dripping from above the wafer can be removed. 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 aiming air jets at the wafer back surface, the back flow of chemical liquid onto wafer back surface is prevented. Hence, there is no need to carry out time-consuming adjustment of knife ring position. Accordingly, the present invention provides a jet-cleaning device for a developing station capable of clearing developer liquid off from the back surface of a wafer but without time-consuming adjustments.
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
Charles C. H. Wu & Associates
Moore Chris K.
United Microelectronics Corp.
Wu Charles C. H.
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