Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2000-10-17
2002-10-08
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S7230ER, C156S345340, C156S345350, C156S345470
Reexamination Certificate
active
06460482
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas shower unit for a semiconductor manufacturing apparatus. In particular, the invention relates to a gas shower unit used in a semiconductor manufacturing apparatus such as CVD apparatus, plasma CVD apparatus, etching apparatus and plasma etching apparatus for the purpose of uniformly supplying reactant gas to a semiconductor wafer.
2. Description of the Background Art
For etching of a semiconductor wafer surface or depositing of a film thereon, a method has been employed according to which gas for etching or for film deposition is supplied by means of batch processing to a large number of wafers held on racks, and then the wafers are heated as required from the outer periphery (hot wall method).
However, as requirements become severer for higher integration and speed of semiconductor devices, a problem arises of non-uniform etching and unequal quality of completed films due to difference in temperature and gas flow depending on the location in a semiconductor manufacturing apparatus. Then, another type of semiconductor manufacturing apparatus has gradually been used instead that employs single wafer processing in which a plurality of etching apparatuses and film deposition apparatuses are arranged side by side and wafers are transported automatically by a loader through the apparatuses where the wafers are processed one by one.
In the semiconductor manufacturing apparatus employing the single wafer processing, a semiconductor wafer is placed on the surface of a holder made of ceramics or metal. The wafer is secured onto the holder surface statically, mechanically, or by applying voltage to an electrode provided in the holder so as to fasten the wafer by an electrostatic force. The surface temperature of the semiconductor wafer held on the holder is precisely controlled in order to adjust the film deposition rate or etching rate in the process of CVD (Chemical Vapor Deposition), plasma CVD, etching, plasma etching or the like. For this temperature control, the wafer holder has a heater therein to heat the outermost surface of the holder and accordingly heat the semiconductor wafer by heat transfer. In order to cut the manufacturing cost of semiconductor devices, an attempt is made to increase the diameter of a semiconductor wafer and thus increase the number of semiconductor chips produced from one wafer. If the diameter of the semiconductor wafer is increased, it is more severely required to uniformly heat the outermost surface of the wafer holder in order to avoid different reaction environments in etching or film deposition within a semiconductor manufacturing apparatus.
Further, if reactant gas is merely supplied through a pipe attached to a chamber of the semiconductor manufacturing apparatus, gas does not uniformly flow through respective regions where the gas is directly and indirectly supplied respectively. As a result, the reactant gas has different concentrations on the surface of a semiconductor wafer. Control accordingly becomes difficult for realizing uniform etching or film deposition on the surface of the semiconductor wafer. Then, for the purpose of uniformly supplying gas onto the semiconductor wafer and thus maintaining a constant concentration of the reactant gas, a method is employed according to which a gas shower unit is positioned directly above the semiconductor wafer, the shower unit being formed of a sheetlike base material with a large number of through holes formed therein. This method enables gas to blow out as if from a showerhead, and consequently the gas concentration can be made as constant as possible on the semiconductor wafer surface.
The temperature at which the gas is caused to react is different depending on the type of reactant gas. Approximately, the temperature is 100 to 400° C. for high-temperature etching, 200 to 500° C., for plasma CVD and 400 to 800° C. for CVD.
Usually the wafer holder has a heater therein to directly heat a wafer and adjust temperature to the one required for reaction. If a reactant gas at room temperature is directly supplied from the gas shower unit, the reactant gas is suddenly heated on the wafer and accordingly the wafer temperature is decreased. Therefore, it is difficult to make the gas temperature constant especially over the surface of a large-area wafer and the reaction rate varies depending on the location on the wafer, so that a film having a uniform thickness is difficult to produce.
Then, a method of preliminary heating a reactant gas may be employed according to which the reactant gas is supplied into a chamber from piping provided outside a semiconductor manufacturing apparatus, and the gas is heated by a heater and then passed through a gas shower unit.
However, if the reactant gas is heated in advance before being passed through the gas shower unit, the reactant gas starts reacting before passing through the through holes of the gas shower unit. A resultant problem is clogging of the through holes of the gas shower unit or wastefully generated reaction products in the pre-heating portion. Another problem is that reaction products peel off to generate particles attaching onto the wafer surface as foreign matters or contaminants.
In order to solve above problems, a heater may be provided in a gas shower unit. If the gas shower unit having a heater therein is produced by providing a heater coil or wire between ceramics compact pieces and hot-press sintering them, the thickness of a base material of the gas shower unit is 10 mm or more because the heater coil embedded within the base material has an outer diameter of approximately 3 to 6 mm. As a result, through holes are likely to clog. Further, since the through holes should be formed not to touch the heater coil, there is a limitation on locations where the through holes are to be made. In this case, in many regions, the interval between through holes is 3 to 6 mm or more. In addition, if the gas shower unit has a greater thickness due to an embedded coil, the through holes are accordingly longer and thus likely to clog as described above.
A further method employed for ensuring uniform heating on a wafer where reaction occurs is that a gas shower unit is warmed by heat radiated from a wafer holder which has a heater therein and is located under a wafer, and after the gas shower unit is warmed to a predetermined temperature, gas is supplied therefrom.
In film deposition, a film is stacked not only on a wafer as a product but also on the gas shower unit, wafer holder and chamber. When the stacked film increases in thickness, thermal stress causes peeling of the film, which generates particles attached onto the product wafer, and accordingly defect occurs. Therefore, the surfaces of components within the chamber should be cleaned frequently. The optimum temperature for film deposition and that for cleaning are different. In general, such a gas as ClF3, NF3 or the like is used for cleaning. Since this type of gas would have too great etching power if used at the film deposition temperature, temperature in cleaning should be made lower than the film deposition temperature so as not to excessively damage the surfaces of the gas shower unit, wafer holder and chamber. Then, the temperature should be changed in the course from film deposition (high temperature), cleaning flow temperature), then to film deposition (high temperature) and so on. The gas shower unit having no heater therein is heated only by heat radiated from the heater located below and accordingly takes a considerable time to reach a predetermined temperature. In this case, the incorporated cleaning process constitutes a main factor in decrease of throughput in wafer processing.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a gas shower unit for a semiconductor manufacturing apparatus and to provide a semiconductor manufacturing apparatus including therein the gas shower unit, to enable reaction to occur uniformly within a chamber of the semiconductor manufacturing appar
Kuibira Akira
Nakata Hirohiko
Fasse W. F.
Fasse W. G.
Hassanzadeh P.
Mills Gregory
Sumitomo Electric Industries Ltd.
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