Reaction chamber component having improved temperature uniformity

A component useful for a plasma reaction chamber includes a heat sink such as a temperature-controlled support member and a heated member such as an electrically powered showerhead electrode. The showerhead electrode is peripherally secured to the support member to enclose a gas distribution chamber between a top surface of the electrode and a bottom surface of the support member. A heat transfer member extends between the electrode and the support member and transfers heat from an area of temperature buildup on the top surface of the showerhead electrode to the bottom surface of the support member in order to control the temperature distribution across the showerhead electrode.

FIELD OF THE INVENTION 
The present invention relates to reactors for processing semiconductor 
integrated circuit substrates and specifically to a component which 
controls the temperature distribution across a heated member of the 
reactor. 
BACKGROUND OF THE INVENTION 
Semiconductor processing includes deposition processes such as chemical 
vapor deposition (CVD) of conductive, dielectric and semiconducting 
materials, etching of such layers, ashing of photoresist masking layers, 
etc. In the case of etching, plasma etching is conventionally used to etch 
metal, dielectric and semiconducting materials. 
Showerhead electrodes for plasma processing of semiconductor substrates are 
disclosed in commonly assigned U.S. Pat. Nos. 5,074,456; 5,472,565; 
5,534,751; and 5,569,356. Other showerhead electrode gas distribution 
systems are disclosed in U.S. Pat. Nos. 4,209,357; 4,263,088; 4,270,999; 
4,297,162; 4,534,816; 4,579,618; 4,590,042; 4,593,540; 4,612,077; 
4,780,169; 4,854,263; 5,006,220; 5,134,965; 5,494,713; 5,529,657; 
5,593,540; 5,595,627; 5,614,055; 5,716,485; 5,746,875 and 5,888,907. 
A common requirement in integrated circuit fabrication is the etching of 
openings such as contacts and vias in dielectric materials. The dielectric 
materials include doped silicon oxide such as fluorinated silicon oxide 
(FSG), undoped silicon oxide such as silicon dioxide, silicate glasses 
such as boron phosphate silicate glass (BPSG) and phosphate silicate glass 
(PSG), doped or undoped thermally grown silicon oxide, doped or undoped 
TEOS deposited silicon oxide, etc. The dielectric dopants include boron, 
phosphorus and/or arsenic. The dielectric can overlie a conductive or 
semiconductive layer such as polycrystalline silicon, metals such as 
aluminum, copper, titanium, tungsten, molybdenum or alloys thereof, 
nitrides such as titanium nitride, metal suicides such as titanium 
silicide, cobalt silicide, tungsten silicide, molybdenum silicide, etc. A 
plasma etching technique, wherein a parallel plate plasma reactor is used 
for etching openings in silicon oxide, is disclosed in U.S. Pat. No. 
5,013,398. 
U.S. Pat. No. 5,736,457 describes single and dual "damascene" metallization 
processes. In the "single damascene" approach, vias and conductors are 
formed in separate steps wherein a metallization pattern for either 
conductors or vias is etched into a dielectric layer, a metal layer is 
filled into the etched grooves or via holes in the dielectric layer, and 
the excess metal is removed by chemical mechanical planarization (CMP) or 
by an etch back process. In the "dual damascene" approach, the 
metallization patterns for the vias and conductors are etched in a 
dielectric layer and the etched grooves and via openings are filled with 
metal in a single metal filling and excess metal removal process. 
During the etching process, the showerhead electrode becomes hot. In 
addition, the temperature can vary considerably across the surface of the 
electrode. The temperature difference between the center and the edge of 
the showerhead electrode can be about 100.degree. C. or higher, e.g. about 
200.degree. C. The nonuniform temperature distribution can cause uneven 
plasma density and/or process gas distribution which leads to nonuniform 
etching of the wafer. In showerhead arrangements which are edge cooled, 
this problem becomes greater as the size of the substrate increases since 
the temperature differential between the center and the edge of the 
showerhead electrode will become more pronounced as the diameter of the 
showerhead increases. 
When etching large, twelve-inch (300 mm) wafers with a showerhead 
electrode, controlling the process gas to create a uniform plasma 
distribution is made more difficult. For instance, the number of openings 
in the baffles and showerhead electrode must be increased significantly to 
obtain distribution of the etching gas over a larger area. In addition, as 
the number of openings in the baffles increases and the number of baffles 
increase, the complexity and cost to manufacture such a gas distribution 
apparatus increase greatly. Further, because the flow rate of the process 
gas must be increased in proportion to the increased surface area of the 
wafer, achievement of uniformity with respect to processing ratio, 
selectivity, feature shape and size become more difficult. Moreover, the 
increased size of the showerhead leads to greater temperature gradients 
across the showerhead which can cause uneven processing of the substrate. 
SUMMARY OF THE INVENTION 
According to the present invention the temperature differential across a 
heated member such as a showerhead electrode can be substantially reduced. 
In the case of a showerhead electrode, a controlled temperature 
distribution across the electrode allows more uniform processing of a 
semiconductor substrate. In addition, because the maximum temperature 
reached by the showerhead electrode can be reduced, it is possible to 
increase the useful life of the electrode. 
According to one embodiment of the invention, a component in a reaction 
chamber for processing semiconductor substrates includes a heat sink 
(e.g., a support member), a heated member (e.g., an electrically powered 
showerhead electrode), and a heat transfer member between the heat sink 
and the heated member. The heat transfer member provides a heat flow path 
from an elevated temperature region of the heated member to the heat sink. 
For example, in a parallel plate plasma etch process, heat generated at the 
center of the showerhead electrode is transferred through the heat 
transfer member to the support member, resulting in a low temperature 
differential between the center of the electrode and the periphery of the 
electrode. Consequently, plasma is distributed in a controlled and/or 
substantially uniform manner during substrate processing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For a better understanding of the invention, the following detailed 
description refers to the accompanying drawings, wherein preferred 
exemplary embodiments of the present invention are illustrated and 
described. In addition, the reference numbers used to identify like 
elements in the drawings are the same throughout. 
The present invention provides improvements in obtaining temperature 
control of components of a reaction chamber for processing semiconductor 
substrates such as silicon wafers and flat panel displays. Such components 
include sputtering targets, electrically powered showerhead electrodes, 
showerheads, substrate supports, etc. Such components may or may not be 
cooled by passing coolant therethrough. The invention will now be 
discussed with reference to an electrically powered showerhead electrode. 
During processing of a substrate in a parallel plate plasma etching 
chamber, a surface of a showerhead electrode increases in temperature due 
to, for example, resistive heating resulting from electric power being 
applied to the electrode. The heat generated flows to the heat sink at its 
periphery (where the electrode and the heat sink are secured to one 
another). However, because a center region of the electrode is not in 
direct contact with the heat sink, the temperature of the center region of 
the electrode can be much higher than the periphery of electrode making it 
difficult to satisfactorily control substrate processing. Likewise, due to 
heating of a showerhead, a target or substrate, the showerhead or surface 
below the substrate or target may become hotter in some portions than in 
others. The present invention provides a mechanism to improve temperature 
uniformity of such surfaces. 
The following description discusses the present invention in the context of 
controlling the temperature distribution across a showerhead electrode or 
a substrate support in a plasma reaction chamber. However, the principles 
of the invention can be used to control the temperature distribution 
across other heated members of a reaction chamber for semiconductor 
processing. 
An exemplary reaction chamber component for a plasma etching process is 
shown in FIG. 1 wherein a showerhead electrode 20 is secured to a cooled 
support member 22 to define a gas distribution chamber 23. The temperature 
of the support member 22 can be controlled by circulating coolant through 
cooling channels 24 in the support member 22. 
The showerhead electrode 20 is preferably of silicon but can be of any 
other suitable electrically conductive material such as aluminum, 
graphite, silicon carbide, etc. and gas passes through a plurality of 
openings 26. In the arrangement shown in FIG. 1, the showerhead electrode 
20 has an edge portion 28 which is integral with the electrode. However, 
the edge portion 28 can comprise a separate support ring bonded to the 
outer edge of a circular showerhead plate, as shown in FIG. 3. In either 
case, the outer edge 28 is in thermal and electrical contact with the 
support member 22. The gas distribution chamber 23 is defmed by a top 
surface 30 of the showerhead electrode 20, the edge portion 28 and a 
bottom surface 32 of the support member 22. Process gas is supplied to the 
chamber 23 by a central gas supply 29. However, the process gas can be 
supplied at the periphery of the electrode and/or by more than one gas 
supply. Gas flows downward through the gas distribution chamber and passes 
through the openings 26 in the showerhead electrode 20. 
Electric power (typically RF power, although DC power may be used) is 
supplied to the showerhead electrode 20 in order to energize process gas 
into plasma. When electrical power is applied to the showerhead electrode 
20 resistive heating occurs and the showerhead electrode 20 increases in 
temperature. If heat is removed from only the periphery of the electrode 
20, the temperature at a center region 34 of the showerhead electrode 20 
can increase more quickly than heat can be laterally transferred through 
the showerhead electrode 20 to the edge portion 28. As a result, a large 
temperature differential (e.g., about 100 to 300.degree. C.) can develop 
between the center region 34 of the showerhead electrode 20 and the edge 
portion 28 of the showerhead electrode 20. This large temperature 
differential interferes with the uniform distribution of the process gas 
through the showerhead electrode 20 and/or the uniform distribution of 
power to the plasma. 
A first embodiment of the invention is shown in FIG. 2 wherein a component 
35 according to the present invention includes one or more heat transfer 
members 36 between the center region 34 of the top surface 30 of the 
showerhead electrode 20 and a bottom surface 32 of the 
temperature-controlled support member 22. During plasma processing, heat 
is transferred through the heat transfer members 36 to the 
temperature-controlled support member 22. In this way, the temperature 
difference between the center region 34 and the edge portion 28 of the 
showerhead electrode 20 can be dramatically reduced (e.g., a temperature 
differential less than 50.degree. C., preferably less than 15 to 
20.degree. C. between the edge and the center of an electrode can be 
obtained). As a result, in semiconductor processing such as single wafer 
plasma etching wherein a wafer is below the showerhead electrode, more 
uniform processing can be achieved. 
Heat transfer members 36 are preferably formed of a material which is 
thermally and electrically conductive. However, materials which are not 
electrically conductive, but are still thermally conductive may also be 
used. Suitable materials include ceramic materials such as SiC, Si.sub.3 
N.sub.4, AIN, etc., metals such as Al, Cu, stainless steel, Mo, etc. and 
metal composites such as reinforced metals (e.g., carbon fiber-aluminum or 
copper, boron fiber-aluminum, SiC particle-aluminum, etc.). For example, 
the heat transfer members 36 can be cast aluminum bodies which machined 
into a desired shape. 
The FIG. 2 embodiment includes a baffle assembly which acts to more 
uniformly distribute etching gas to the top surface 30 of the showerhead 
electrode 20. The baffle assembly may include one or more baffle plates 40 
located between the showerhead electrode 20 and the support member 22. The 
baffle plates 40 can be made of aluminum and include one or more cutouts 
42 to accommodate a similarly shaped heat transfer member 36 which fits 
into the cut-out defined space between the bottom surface 32 of the 
support member 22 and the top surface of the showerhead electrode. 
As shown in FIG. 2, the heat transfer member 36 includes a notch 44 which 
allows process gas to flow from the gas supply inlet 29 into plenums 
defmed by the baffle plates. As a result, the gas supplied by the inlet 29 
can be distributed across the surfaces of the baffle plates 40. 
FIG. 3 shows a second embodiment of a component 35 in accordance with the 
invention wherein the baffle plates 40 need not be cut to accommodate a 
heat transfer member 36. Instead, heat transfer members 36 are sandwiched 
between the support member 22, baffle plates 40 and showerhead electrode 
20. The heat transfer members 36 can include gas passages therethrough to 
allow gas from the inlet 29 to be distributed in plenums defined by the 
baffle plates 40. Alternatively, the heat transfer members 36 could be 
solid and the baffle plates could include grooves or channels to allow the 
process gas to circulate freely in the plenums defined by the baffle 
plates. 
A third embodiment of a component 35 according to the present invention is 
shown in FIG. 4 wherein the reaction chamber does not include baffle 
plates between the support member 22 and the showerhead electrode 20. In 
the third embodiment, the heat transfer members 36 are located within a 
gas distribution chamber defmed between the showerhead electrode 20 and 
the support member 22. As shown in FIG. 4, the heat transfer members 36 
include notches 44 which allow process gas to flow between the heat 
transfer members 36 and across the surfaces of the support member 22 and 
the showerhead electrode 20. 
In order to enhance removal of heat from the showerhead electrode 20, the 
heat transfer members 36 preferably have excellent thermal contact with 
both the bottom surface 32 of the support member 22 and the top surface 30 
of the showerhead electrode 20. Ideally, there are no gaps between the 
heat transfer members 36, the heated member (e.g., the showerhead 
electrode 20), and the heat sink (e.g., the support member 22). Good 
thermal contact between these parts can be assured in various ways such as 
by manufacturing the showerhead electrode 20, the heat transfer members 36 
and the support member 22 to provide mating surfaces, providing a 
thermally conductive material such as a gasket of metallic material such 
as indium, silver or the like on opposite sides of the heat transfer 
members, and/or bonding the top surface 30 of the showerhead electrode 20 
with metallic material or conductive adhesive such as an elastomer 
containing electrically and/or thermally conductive particles. 
As seen in more detail in FIG. 4A, the heat transfer members 36 sandwiched 
between the showerhead electrode 20 and the support member 22 are 
concentrically arranged annular rings. The rings include notches 44 
therein to allow process gas to flow across the gas distribution chamber. 
Although three rings are shown in FIGS. 4 and 4A, the number of rings may 
be increased or decreased to achieve a desired heat transfer effect. 
Further, the heat transfer member or members can be in shapes other than 
rings (e.g., the heat transfer member could be in the shape of a central 
hub and radially extending arms or any other suitable shape). Ideally, the 
heat transfer members 36 are arranged to cover a minimum amount of the top 
surface 30 of the showerhead electrode 20 while still achieving the 
desired heat transfer effect. 
Preferably, in order to obtain a more even distribution of gas within a gas 
distribution chamber not including baffle plates, the component 35 can 
include multiple gas supplies 39. In such an arrangement, because the gas 
pressure is highest at the outlet of each gas supply 39, the provision of 
multiple gas supplies 39 allows a more even distribution of gas pressure 
distribution to be obtained compared to that of a single gas supply. 
FIG. 5 shows a fourth embodiment of a component 35 according to the present 
invention wherein the heat transfer member 36 is located between a 
substrate support surface 37 and a support member 41. The surface 37 can 
be part of a bottom electrode which may or may not have an electrostatic 
clamp (ESC) associated therewith. The heat transfer member 36 can be used 
to draw heat away from a portion of the surface 37 to the support member 
41, thereby controlling the temperature differential across the surface 
37. In such a case, the substrate support can omit a He backcooling 
arrangement typically used for cooling substrates such as Si wafers. 
In the foregoing embodiments, the heat transfer members 36 can be separate 
pieces or integral with either the heated member (e.g., the showerhead 
electrode 20) or the heat sink (e.g., support member 22). FIG. 6 shows an 
example of heat transfer members 36 which are integral with the showerhead 
electrode and FIG. 7 shows an example of heat transfer members 36 which 
are integral with the support member 22. If bonding material is used, the 
bonding material should have good thermal and optionally electrical 
conductivity and be compatible in a vacuum environment (e.g., have a low 
vapor pressure so that the material will not significantly contaminate a 
semiconductor processing environment). Suitable bonding materials include 
conductive adhesives such as elastomers or epoxies and solder or brazing 
materials. 
Thus, according to the present invention, in the case of a showerhead 
electrode arrangement, direct or indirect surface to surface contact 
between the center region 34 of the showerhead electrode 20 and the 
temperature-controlled support member 22 can be achieved. In this way, the 
present invention can control the temperature differential between the 
center region 34 and the edge portion 28 of a showerhead electrode 20. 
Such better temperature control across the showerhead electrode 20 can 
provide a more controlled plasma density and/or gas flow/pressure across 
the substrate being processed. 
The present invention has been described with reference to preferred 
embodiments. However, it will be readily apparent to those skilled in the 
art that it is possible to embody the invention in specific forms other 
than as described above without departing from the spirit of the 
invention. The preferred embodiments are illustrative and should not be 
considered restrictive in any way. The scope of the invention is given by 
the appended claims, rather than the preceding description, and all 
variations and equivalents which fall within the range of the claims are 
intended to be embraced therein.