Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Reexamination Certificate
2003-02-27
2004-11-30
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
C219S121540, C118S725000
Reexamination Certificate
active
06825617
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor processing apparatus. In particular, it relates to a semiconductor processing apparatus that processes a semiconductor wafer while adjusting the temperature thereof.
2. Description of the Related Art
With the recent trend toward higher and higher packaging density of semiconductor devices, circuit patterns are becoming increasingly smaller, and dimension precision requirements are being increasingly severe. With this demand, temperature control of the wafer being processed has become very important. For example, in an etching process in which a high aspect ratio is required, in order to implement anisotropic etching, etching is performed while depositing an organic polymer on the side wall of the part being etched. However, deposition of the organic polymer covering the side wall is varied under the influence of temperature. That is, the temperature of the wafer being processed affects the etch rate or the resulting shape, and if the temperature distribution is non-uniform, the amount of deposited sidewall protective film varies in the surface of the wafer. As a result, there arises a problem in that the resulting shape varies with location in the wafer surface, and the circuit patterns of semiconductor elements cut from the wafer and thus, the performances thereof vary among the elements.
In addition, in recent semiconductor manufacturing processes, wafers with larger diameters are handled, and the plasma, the applied power and the heat input from the apparatus to the wafer are increased. For example, in semiconductor manufacture involving a wafer having a diameter of 300 mm, a bias power in the order of 3 kW is applied to the wafer during the process of etching an interlayer insulating film formed on the wafer. In view of such a circumstance, in a semiconductor manufacturing apparatus, it is technically essential that the temperature of the semiconductor wafer is appropriately controlled in the surface of the wafer during the processing thereof.
In a conventional semiconductor manufacturing apparatus using a plasma, a wafer being plasma-processed is electrostatically stuck to and held on a stage (sample holder) by the action of electrostatic chuck provided on the stage. In addition, in order to assure adequate heat transfer between the wafer and the stage to adjust the temperature of the wafer, a heat conductive gas (typically, helium) is introduced to adjust the temperature of the wafer.
The range of the temperature of the wafer to be adjusted varies with the process. For example, the temperature of the stage that holds the wafer is required to be stably controlled over a wide range from a low temperature of −40° C. to a temperature on the order of 100° C. during the processing of the wafer. That is, it has become necessary that even if the wafer stage in the plasma processing apparatus is subjected to a significant heat input ranging widely from low temperature to high temperature, an uniform temperature distribution is provided in the surface of the wafer.
In addition, in recent years, demands for non-volatile memories including MRAM and FeRAM have been increased. To etch the materials of these memories, an extremely high temperature of 400° C. to 500° C. is required. In this case also, since redeposition of a reaction product affects the etching, it is required to properly control the wafer temperature.
As a technique for controlling the temperature of the wafer being processed, there is disclosed a technique in which first and second heat conductive gases are introduced between the wafer and a support for carrying the wafer, and the pressures of the first and second gases are controlled to adjust the heat conduction. In addition, this prior art discloses a technique in which, in order to process the wafer while keeping the temperature thereof constant in the above-described arrangement, an object to be processed for monitoring is used and the temperature distribution in the surface thereof is previously determined, and then, the amounts of the first and second heat conductive gases supplied and discharged via a first and second gas channels are set (for example, see Patent Reference 1).
[Patent Reference 1]
Japanese Patent Laid-Open No. 2002-305188
SUMMARY OF THE INVENTION
However, in the prior art described above, in order to provide a desired temperature distribution on the wafer, it is necessary that the amounts of the first and second heat conductive gases supplied and discharged are registered with a control unit of the apparatus. If they are not registered, it is required to separately measure the surface temperature to find a condition that provide the desired temperature distribution, and thus, it disadvantageously takes a long time to determine the processing condition.
For example, it is difficult for the operator who uses the apparatus to predict the temperature of the wafer before starting the processing and accurately set the operation conditions of the apparatus based on the prediction to implement a desired processing.
Thus, if the operator changes an operation condition of the apparatus or a parameter of the etching processing so as to bring the etching characteristics closer to a desired one, the wafer temperature is also changed in accordance with the set condition values or combination thereof, and thus, the desired etching characteristics cannot be attained. Thus, there is a problem in that the precision of the processing of the semiconductor device is degraded.
For example, a case will be described where a target etch rate is not attained and the bias power is increased to 800 W. Here, it is assumed that the temperature of the wafer finally attained after being processed for 60 seconds at 600 W is known from experiment or measurement by the fluorescent thermometer. Since the temperature of the wafer attained when it is processed at a bias power of 800 W is not known, if the wafer is processed under the same condition, the average temperature thereof varies largely. If the temperature varies largely in this way, the temperature affects the resulting etching characteristics, and thus, it is difficult to assess the effect of the changed condition based on comparison with the previously obtained result and to operate the apparatus under the condition that enables precise processing.
Thus, data concerning the He back side gas pressure, the refrigerant temperature, the initial stage temperature and the like that are not changed if the bias power is increased to 800 W are required. However, according to the prior art, the operator who uses the apparatus must find an adequate condition on a trial-and-error basis, so that it may take a long time to find the adequate condition, and thus, the process of setting an adequate condition and starting operation of the apparatus so as to manufacture products with a predetermined performance is degraded in efficiency. In this example, when the He back side gas pressure is set at 1.5 kPa, the average temperature of 82° C. is attained finally. However, in general, it is difficult for the operator to predict and set the He back side gas pressure down to the second decimal place, and it takes a long time to predict and set the value.
For example, to obtain precise data, the apparatus is operated plural times under different conditions, such as under different He back side gas pressures of 1.4 kPa, 1.5 kPa and 1.6 kPa. During this operation, it is difficult for the apparatus to perform processing so as to implement desired etching, and the throughput of the semiconductor processing is reduced. Besides, even if the data resulting from a plurality of times of operations is used, extremely large number of operations is required to bring the average value of the temperature of the wafer
1
in a direction parallel to the surface thereof within a narrow range (for example, within ±0.5° C.). Therefore, the experiment preceding the processing for manufacturing the semiconductor devices to be shipped takes
Kanai Saburou
Kanno Seiichiro
Kihara Hideki
Nishio Ryoji
Yamamoto Hideyuki
Hitachi High-Technologies Corporation
Philogene Haissa
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