Cleaning and liquid contact with solids – Processes – For metallic – siliceous – or calcareous basework – including...
Reexamination Certificate
1999-10-25
2001-11-13
Kunemund, Robert (Department: 1765)
Cleaning and liquid contact with solids
Processes
For metallic, siliceous, or calcareous basework, including...
C134S003000, C134S022100, C134S041000, C438S745000
Reexamination Certificate
active
06315834
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for removing extraneous matter by using fluorine-containing neutral solution, and especially to a method for removing extraneous matter from a stainless device applied in a semiconductor-manufacturing process by using fluorine-containing solution.
BACKGROUND OF THE INVENTION
Borophosphosilicate glass (BPSG) has been extensively used as the doped silicon oxide layer material for semiconductor wafers, and the BPSG layer is usually formed by atmospheric pressure chemical vapor deposition (APCVD). The BPSG layers are formed for filling gaps between adjacent metal lines in integrated circuits and for interlayer dielectric isolation.
While the APCVD process is performed, not only the semiconductor wafers but the equipment, such as the pipes and tanks, will also be covered by particles and powders. These particles will cluster together and adhere on the surface of the pipe or tank as an extraneous layer. If the pipe is choked up with the extraneous layer and some particles fall down on the semiconductor wafers, the deposition uniformity and thickness of the BPSG layer will be seriously affected. Therefore, the pipes, tanks, covers, and vessels of the APCVD system need to be cleaned (this cleaning procedure is called “preventive maintenance”) after a predetermined number of wafers are deposited.
However, cleaning the APCVD system is not an easy task. The pipes and tanks of the APCVD system are usually made of stainless steel. General cleaning solutions can not totally remove all extraneous matters from the stainless devices, and the strong acid solutions, such as hydrofluoric acid (HF), will gradually corrode the stainless devices. Therefore, most manufacturers of the APCVD system advise users to scrub the stainless devices with brushes. Since the shapes of the pipe and tank are usually very complicated, it is hard to scrub out the extraneous matters completely with brushes. Some extraneous matters may still stay on the APCVD system. In order to ensure that all extraneous matters are totally removed, users must waste a lot of time for cleaning the APCVD system and testing whether the APCVD system is completely cleaned or not so that the working hours of the APCVD system is shortened and the cost is increased.
In addition, while the APCVD system is cleaning, particles and toxic gas will be spread into the air. When a maintenance man is brushing the APCVD system, he possibly inhales the harmful air.
It is therefore attempted by the applicant to deal with the above situation encountered with the prior art.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a novel method for removing extraneous matters from a stainless device applied in a semiconductor-manufacturing process.
It is another object of the present invention to provide a novel method for removing extraneous matters from a stainless device without requiring expensive equipment or complicated test procedures such that the cleaning process can be carried out using significantly less time to further reduce the production cost.
The method of the present invention includes the steps of (a) providing a container for holding a fluorine-containing neutral solution therein, and (b) immersing the stainless device in the fluorine-containing neutral solution to remove the extraneous matters from the stainless device.
According to the present invention, the stainless device can be a stainless pipe, a stainless tank, a stainless cover, or a stainless vessel of a APCVD system used in the semiconductor-manufacturing process, preferably a borophosphosilicate glass (BPSG) depositing process.
The extraneous matters are formed during the semiconductor-manufacturing process and remained on a surface of the stainless device as a silicon oxide layer.
The container for holding the fluorine-containing neutral solution is made of a material sufficient for resisting the corrosion of the fluorine-containing neutral solution. The fluorine-containing neutral solution is made from neutralizing hydrofluoric acid (HF) with ammonium hydroxide (NH
4
OH), neutralizing hydrofluoric acid (HF) with ammonium fluoride (NH
4
F), or dissolving ammonium acid fluoride (NH
4
F) in a deionized water (DIW). The pH value of the fluorine-containing neutral solution is preferably ranged from about 6 to about 8.
According to the present invention, after the step (b), the method further includes a step of (c) heating the fluorine-containing solution to facilitate an effect of removing the extraneous matters from the stainless device.
In accordance with the present invention, the fluorine-containing neutral solution can be heated by a heater or by the reaction heat released from a neutralizing reaction for forming the fluorine-containing neutral solution.
Preferably, the fluorine-containing neutral solution is heated up to about 40° C.
According to the present invention, the method further includes a step of swirling the fluorine-containing neutral solution by using a pump or generating bubbles from a bottom of the container so that the fluorine-containing neutral solution can be enhanced to flow around the stainless steel to facilitate the effect of removing the extraneous matters from the stainless device.
Preferably, the bubbles are nitrogen (N
2
) bubbles or clean-dry-air (CDA) bubbles, and the stainless device is immersed in the fluorine-containing neutral solution by a basket, wherein the basket is made of a material sufficient for resisting the corrosion of the fluorine-containing neutral solution.
REFERENCES:
patent: 5587103 (1996-12-01), Dennis
patent: 5681448 (1997-10-01), Uchiyama et al.
patent: 5972123 (1999-10-01), Verhaverbeke
patent: 5998260 (1999-12-01), Lin
Chen Chienfeng
Chen Chin-Hsien
Chen Weng-Yi
Chung Hunter
Chung Ping-Chung
Kunemund Robert
Tran Binh X.
UTEK Semiconductor Corp.
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