Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of...
Reexamination Certificate
2000-05-15
2001-02-13
Bowers, Charles (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
C438S778000, C438S905000, C427S585000, C427S588000
Reexamination Certificate
active
06187691
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a film-forming method of forming a thin film on a substrate-to-be-processed. It particularly relates to a film-forming method of homogenizing a thin film formed on each substrate-to-be-processed when forming a thin film continuously on multiple substrates-to-be-processed.
2. Description of the Related Art
A plasma CVD (Chemical Vapor Deposition) apparatus forms a thin film on the surface of a substrate-to-be-processed by applying radio-frequency power between an upper electrode, which also functions as a showerhead which supplies a reaction gas to a processing chamber, and a lower electrode which also functions as a loading platform for loading substrates-to-be-processed such as semiconductor wafers. Sediment is left on inner walls, etc. of the processing chamber during this film-forming process. If this comes off, it causes particle contamination in the next film-forming process. For this reason, the processing chamber is cleaned periodically.
For such apparatuses, when a lot (one lot can be, for example, one cassette (25 wafers)) is processed continuously, the film-forming process and the cleaning process are repeated alternately. After maintenance of the apparatus is performed, until the result of a film quality inspection of wafer processing is obtained, a stand-by situation where no film forming is performed occurs between the lot processes.
The number of stand-by times shows a tendency to increase particularly as the number of semiconductor manufacturing plants which manufacture semiconductor devices with more different types in smaller lots increases, as a diameter of wafer becomes larger in recent years, and as semiconductor devices are more diversified.
SUMMARY OF THE INVENTION
If this stand-by situation continues for a certain time, a surface temperature of electrode parts on which a semiconductor wafer is loaded drops and a temperature of the wafer loaded on it also drops. Consequently, even if other processing conditions are set identically, in the continuous lot process, it causes a negative influence such as a decline in density and change in film composition on a thin film formed on the first and the second semiconductor wafers after the stand-by period. For this reason, film characteristics such as workability and hygroscopicity resistance, which are designed when a semiconductor device is manufactured, are spoiled. This eventually results in malfunction of the semiconductor device, i.e., a cause of defective products and a decline in yield.
The negative influence on film-forming occurring immediately after stand-by has become serious due to increased heat capacity of a wafer itself as a diameter of the wafer which is a substrate-to-be-processed recently increases.
The present invention was achieved to solve this task, and it aims to provide a film-forming method which prevents a negative influence on the characteristics of film forming caused by a drop in a temperature of an electrode which is a loading platform for loading a substrate-to-be-processed.
Another object of the present invention is to provide the above-mentioned film-forming method which forms a homogeneous film during continuous lot processing.
The film-forming method according to the present invention which achieves the above-mentioned objects has upper and lower electrodes in a processing chamber, between which radio-frequency power is applied, and which forms a thin film on a substrate-to-be-processed in a film-forming apparatus which heats an electrode on which the substrate-to-be-processed is loaded, and which is characterized in that at the end of a stand-by period and before the film-forming process is initiated by loading a substrate-to-be-processed on the electrode, a process of raising a temperature of the lower electrode is included. This film-forming process can be a continuous film-forming process where after stand-by, a substrate-to-be-processed is conveyed and is loaded on the electrode and the film-forming process is performed continuously on multiple substrates-to-be-processed. In an embodiment, the temperature of the lower electrode reaches a temperature for continuous film formation ± approximately 5° C. In the above, when it is not technically practical to measure the temperature of the electrode to confirm that the temperature reaches a desired temperature, by monitoring the thickness of films formed on substrates, it is possible to determine whether the temperature control is appropriate based on uniformity of thickness of the formed films. Incidentally, the temperature of the electrode is considered to be 5-10° C. higher than the temperature of a substrate placed thereon.
A heater heats an electrode on which a substrate-to-be-processed is loaded and raises a temperature to a desired level. If the electrode and the heater are not incorporated (when they are divided by being fastened with screws, etc.), a temperature of the electrode cannot be raised quickly to a desired level (a temperature for film formation ± approximately 5° C.). At this time, by supplying gas to a processing chamber, the heat of the heater can be effectively transmitted to the electrode on which a substrate-to-be-processed is loaded and the electrode can be heated quickly. For example, the pressure of the chamber is maintained conventionally at several mTorr during a stand-by period until a first substrate is loaded in the chamber, and thus even if the temperature of the heater is set at 420° C., the temperature of the lower electrode (susceptor) has decreased to 320-350° C. at the end of the stand-by period. By raising the pressure of the chamber, heat transfer from the heater to the lower electrode can be improved significantly. In the above, the temperature of the lower electrode can be approximately 50° C. higher than the conventional embodiment.
In the above, for the pressure of the processing chamber with gas supplied, pressure no less than 1 Torr is preferable (in an embodiment, 4±1 Torr). Gas to be supplied to the processing chamber can be a cleaning gas which is activated by a remote plasma discharge apparatus.
Additionally, a process of raising the temperature of the electrode can be a process of supplying gas including a reaction gas into the processing chamber and generating plasma. Further, the process of raising the electrode temperature can include a process of dummy-cleaning a dummy film on the electrode, which is formed by this plasma. In this case, for example, when a silicon nitride film is formed, gas which contains more than one type of gas containing fluorine such as NF
3
is excited by a remote plasma apparatus and is brought in the processing chamber and a dummy film is removed by dummy cleaning. Because of heat generated at the reaction of the film and the cleaning gas, a surface temperature of the electrode rises effectively. Moreover, after the dummy-cleaning process, a process of supplying gas to the processing chamber can be included.
Furthermore, if a process of raising temperature of the electrode is performed before a substrate-to-be-processed is conveyed to the processing chamber, processing time can be shortened.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow.
REFERENCES:
patent: 5567661 (1996-10-01), Nishio et al.
patent: 5865896 (1999-02-01)
Arai Hiroki
Fukuda Hideaki
Yoshizaki Yu
ASM Japan K.K.
Bowers Charles
Ghyka Alexander G.
Knobee Martens Olson & Bear LLP
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