Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2000-08-04
2002-08-13
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C118S7230ER, C118S7230IR, C118S715000, C219S405000, C219S411000, C392S416000, C392S418000
Reexamination Certificate
active
06433314
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to substrate processing chambers. More particularly, the present invention relates to controlling the temperature of a component of a substrate processing chamber.
2. Background of the Related Art
In the fabrication of integrated circuits, vacuum process chambers are generally employed to deposit films on semiconductor substrates. The processes carried out in the vacuum chambers typically provide the deposition or etching of multiple metal, dielectric and semiconductor film layers on the surface of a substrate. Examples of such processes include chemical vapor deposition (CVD), physical vapor deposition (PVD), and etching processes. For CVD, a variety of gases are introduced into the process chamber and act as reactants which deposit material on the substrate surface. A uniform distribution of gas concentration within the processing chamber is highly desirable to ensure a uniform progression of the process because variations in the gas concentration within the process chamber produce non-uniform deposition across the substrate surface resulting in a non-planar topography which can lead to reduced yield and device failure.
Gas distribution plates are commonly utilized in CVD chambers to uniformly introduce processing gas into the processing chamber. A typical gas distribution plate comprises a showerhead disposed at the top portion of the chamber or as part of the chamber lid. Generally, a process gas inlet is connected to the gas distribution plate to supply the processing gas thereto. The processing gas passes through the gas distribution plate into the processing chamber. The deposition reaction of the processing gas is typically temperature dependent. Thus, the temperature of the gas distribution plate must be maintained at a temperature at which reaction will not take place therewith.
If deposition occurs on the showerhead, it may clog the showerhead holes and disturb the process gas distribution into the chamber, causing uneven processing on the substrate surface, or particulates of the deposition material can flake off from the showerhead and drop onto the substrate surface, rendering the substrate useless. Furthermore, improper temperature of the gas delivery system may cause condensation of the process gas within the gas delivery system, and reduce the amount of process gas reaching the process chamber and resulting in inadequate deposition.
In addition to affecting the delivery of process gas to the chamber, the gas distribution plate temperature also affects the substrate temperature, and thus, the deposited film properties, because of the close spacing between the substrate and the chamber lid/gas distribution plate. Typically, because of the low pressures present in CVD processing, the emmisivity of the gas distribution plate is the primary contributor affecting the substrate temperature. Although the substrate temperature is “controlled” by controlling the temperature of the substrate support, film properties such as resistance (R
s
) uniformity and deposition thickness uniformity can be influenced by variations in the substrate temperature caused by showerhead temperature variations.
Currently, “BCS” or Burn-in/Conditioning/Seasoning is the process employed to control the lid/showerhead temperature. Generally, BCS comprises running the plasma process on one or more wafers until the lid and the gas distribution plate reach a steady state processing temperature (when the chamber is burned-in/conditioned/seasoned) while depositing the material throughout the chamber. Typically, the lid and the gas distribution plate are heated gradually by the plasma generated within the chamber during processing until a desired processing temperature is reached and maintained by a balance of heat provided by the plasma less the heat transferred from these components. Alternatively, an active heating element, such as a resistive heater, can be attached to the lid to speed up the heating process to steady state temperatures. Processing at a steady state temperature is desirable because predictable reactions and deposition occur during steady state conditions.
One particular drawback of the BCS method is the “first wafer effect” in which the first few wafers are rendered useless because of temperature inconsistencies which lead to non-uniform processing results between wafers. During the BCS process, the lid and gas distribution plate temperatures are ramped up to the steady state temperature from a cold start or room temperature by the plasma generated in the chamber. Because substrate processing is generally temperature dependent, the temperature variations during the BCS process cause variations in the deposition rate and other reactions on the first few wafers. The inconsistent properties of the film deposited on the first few wafers, as compared to those processed during steady state conditions, renders the first few wafers useless. Temperature variations during processing of different wafers may also cause inconsistent deposition or processing between different wafers of a process run, resulting in undesirable, inconsistent film properties. Also, the BCS process typically is very time consuming and reduces the output because of the preliminary wafers sacrificed in the BCS process.
Undesirable process gas reactions may also occur at the gas distribution plate when the gas distribution plate is heated to too high a temperature by the plasma generated in the chamber. Typically, CVD process gases breakdown at high temperatures, resulting in reduced deposition rate. One attempt to prevent unwanted reaction due to high temperature at the gas distribution plate provides a liquid coolant passage surrounding the showerhead to cool the showerhead by thermal conduction/convection.
FIG. 1
is an exploded perspective view of a gas distribution plate having a liquid coolant passage. The gas distribution plate
120
comprises a base
180
and a liquid passage cover
182
. The gas distribution plate
120
is a dish-shaped device made of thermal conductive material having a circular, centrally disposed cavity
150
defined by the side wall
152
and a bottom plate
154
. A plurality of gas distribution holes
156
disposed on the bottom plate
154
provide the process gas passage into the processing chamber. A beveled lower wall portion
158
joins the side wall
152
with the bottom plate
154
. A flange portion
160
projects outwardly in a horizontal plane to form the upper portion of the gas distribution plate
120
and serves to provide engagement of the gas distribution plate
120
with the base plate of the chamber lid. Fasteners such as bolts or screws secure the plate
120
with the base plate of the chamber lid through a plurality of engagement holes
162
. A gas injection plate depression
130
is formed in the upper surface of the flange portion
160
to facilitate the mounting of a gas injection cover plate onto the gas distribution plate
120
.
The base
180
includes a liquid coolant passage
173
machined or cut out of the base
180
and surrounds the side wall
152
. The liquid passage cover
182
is secured and sealed to the base
180
by fasteners or by welding to form the upper wall of the liquid coolant passage
173
. The liquid passage cover
182
includes an inlet
170
and an outlet
174
, projecting upwardly from the liquid passage cover
182
and having bores
172
and
176
formed therethrough. The liquid coolant passage
173
is not formed as a complete annular passage. A blockage portion
204
is positioned between the inlet portion
206
and the outlet portion
208
of the liquid coolant passage
173
to prevent the liquid coolant from travelling the short arc distance between the inlet portion
206
and the outlet portion
208
. Instead, the liquid coolant enters the liquid coolant passage
173
through the inlet portion
206
, travels completely around the side wall
152
, and exits the channel
186
through the outlet portion
208
.
In operation, the liquid coolant is
Khurana Nitin
Mandrekar Tushar
Tolia Anish
Applied Materials Inc.
Fuqua Shawntina T.
Moser Patterson & Sheridan LLP
Walberg Teresa
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