Abstract:
An electrostatic chuck (ESC) for a wafer which directs a cooling gas to predetermined cooling areas of the wafer mounted on the chuck. Ring type sealing members divide the mounted wafer into the predetermined cooling areas and the predetermined cooling areas are independently supplied with a helium cooling gas. Each of the predetermined cooling areas is supplied through a separate conduit system wherein each conduit system has a single inlet into the chuck and a plurality of outlets which emit the helium gas into a respective one of the predetermined cooling areas. The plurality of outlets for each predetermined cooling area may communicate with the inlet via a respective plurality of branch conduits or via one or more branch conduits and a peripheral conduit which connects the plurality of outlets. By independently controlling the predetermined cooling areas, temperature variations on the wafer are effectively controlled.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2003-50448, filed Jul. 23, 2003 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an electrostatic chuck (ESC) for a wafer, and more particularly to an ESC for a wafer which reduces heat generated in the wafer by supplying a helium gas through a helium supply passage simply and conveniently.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, a manufacturing process for a wafer as a kind of semiconductor element proceeds inside a chamber which is a sealed reaction container, and an ESC which retains the wafer using an electrostatic interaction is installed inside of the chamber.  
         [0006]     The ESC is widely used in an etching device, or a chemical vapor deposition device, and especially for controlling a temperature of the wafer installed in the ESC in a semiconductor manufacturing process. The temperature of the wafer seriously affects completed semiconductor element aspects such as uniformity, profile, repeatability and the like. Therefore, the ESC continuously cools the wafer using the helium gas to prevent the wafer from being destroyed because of a high temperature generated during wafer processing.  
         [0007]     As shown in  FIG. 1 ,  FIG. 2A  and  FIG. 2B , a conventional ESC for a wafer comprises a base  2  in which a wafer  7  is mounted; a center hole  3  provided in a center of the base  2 , and emitting a helium gas to a center part  7   a  of the wafer  7 ; a plurality of edge holes  4  formed at an outer side of the base  2  and emitting the helium gas to an edge part  7   b  of the wafer  7 ; an inner circular hole  5  connecting the plurality of edge holes  4  with each other; and a radial shaped connection hole  6  connecting the center hole  3  and the edge holes  4 .  
         [0008]     The ESC  1  increases a most outside height difference d of the base  2  to increase a volume in which the helium gas is filled, thereby maintaining a temperature distribution in the edge part  7   b  and the center part  7   a  of the wafer  7  uniformly, and decreases the width of the center hole  3  to be small compared with a width of each edge hole  4 , thereby increasing the amount of the helium gas emitted through the edge holes  4  to uniformly cool down the center part  7   a  and the edge part  7   b  of the wafer  7 .  
         [0009]     However, the conventional ESC  1  for a wafer has a problem of distributing the helium gas unevenly because a mounted condition and a process tolerance of the wafer  7  cause a leakage of the helium gas and the helium gas is supplied to the center part  7   a  and the edge part  7   b  of the wafer  7  asynchronously. Also, the amount of the helium gas flowing into the wafer  7  through the center hole  3  is not enough to prevent a temperature of the edge part  7   b  from being increased.  
         [0010]     It is difficult to make an overall temperature in the wafer  7  uniform using the most outside height difference d of the ESC  1 , and increasing the size of the edge hole  4  to supply a massive amount of the helium gas to the edge part  7   b  of the wafer  7  may cause arching by plasma generated during the process, thereby shortening a lifecycle of the ESC  1 .  
         [0011]     Recently, an ESC (Electrostatic Chuck) designed to cool down a center part and an edge part of a wafer using an independent helium gas supply hole considering the above problem is disclosed Japanese Patent First Publication No. 2002-305238, and Japanese Patent First Publication No. 1989-251735, but the ESC of the publications has a complicated structure for supplying the helium gas, thereby reducing ESC productivity and an efficiency of cooling.  
       SUMMARY OF THE INVENTION  
       [0012]     Accordingly, an aspect of the present invention is to provide an electrostatic chuck (ESC) which decreases a temperature difference between an edge part and a center part of a wafer to improve an efficiency of cooling.  
         [0013]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
         [0014]     The foregoing and/or other aspects of the present invention are achieved by providing an ESC for a wafer comprising a base on which the wafer is mounted; a ring-type first sealing member provided in an upper end part of the base; a ring-type second sealing member separately provided inside the first sealing member and in an upper side of the base, and dividing the wafer into an edge part and a center part when the wafer is mounted; a first helium supply passage formed branched inside the base, and emitting a helium gas to the edge part of the wafer; and a second helium supply passage provided inside the base having a difference with the first helium supply passage in height, and emitting the helium gas to the center part of the wafer.  
         [0015]     According to an aspect of the present invention, the first helium gas supply passage comprises a first helium inlet provided in a bottom center of the base; a plurality of first helium gas outlets provided in an outer upper part of the base corresponding to the edge part of the wafer; and a first inner conduit formed branched from the first helium gas inlet, and connected to the first helium gas outlet.  
         [0016]     According to an aspect of the present invention, the first inner conduit comprises a plurality of first branch conduit connected to the first helium gas inlet; and a first circular conduit connected to the first branch conduit and the first helium gas outlet.  
         [0017]     According to an aspect of the present invention, the second helium gas supply passage comprises a second helium inlet provided in a bottom center of the base; a plurality of second helium gas outlets provided in an upper part of the base corresponding to the center part of the wafer; and a second inner conduit formed branched from the second helium gas inlet, and connected to the second helium gas outlet.  
         [0018]     According to an aspect of the present invention, the second inner conduit comprises a plurality of second branch conduits connected to the second helium gas inlet; and a second circular conduit connected to the second branch conduit and the second helium outlet.  
         [0019]     According to another aspect of the present invention, the forgoing and other aspects may be also achieved by providing the ESC, further comprising a ring typed third sealing member separated into from the second inner conduit and provided in the upper side of the base, and dividing the center part of the wafer when the wafer is mounted; and a third helium gas supply passage provided inside of the base having a difference with the second helium gas supply conduit in height, and emitting the helium gas to the divided center part of the wafer respectively.  
         [0020]     According to an aspect of the present invention, the third helium gas supply passage comprises a third helium gas inlet provided in a bottom center of the base; a plurality of third helium gas outlets provided in an upper part of the base corresponding to the divided center part respectively; and a third inner conduit formed branched from the third helium gas inlet having a difference with the second inner conduit in height, and connected to the third helium gas outlet.  
         [0021]     According to an aspect of the present invention, the third inner conduit comprises a plurality of third branch conduits connected to the third helium gas inlet; and a third circular conduit connected to the third branch conduit and the third helium gas outlet. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The above and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0023]      FIG. 1  is a bottom view of a conventional electrostatic chuck (ESC) for a wafer;  
         [0024]      FIG. 2A  is a sectional view of a conventional ESC for a wafer in use;  
         [0025]      FIG. 2B  is an enlarged view of a portion of  FIG. 2A ;  
         [0026]      FIG. 3  is a top view of an ESC for a wafer according to a first embodiment of the present invention;  
         [0027]      FIG. 4  is a bottom view illustrating a helium gas supply hole of the ESC for a wafer according to the first embodiment in the present invention;  
         [0028]      FIG. 5  is a sectional view for illustrating the ESC for a wafer in use according to the first embodiment of the present invention;  
         [0029]      FIG. 6  is a top view of an ESC for a wafer according to a second embodiment of the present invention;  
         [0030]      FIG. 7  is a bottom view illustrating a helium gas supply hole of the ESC for a wafer according to the second embodiment of the present invention; and  
         [0031]      FIG. 8  is a sectional view for illustrating the ESC for a wafer in use according to the second embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.  
         [0033]      FIG. 3  is a top view of an electrostatic chuck (ESC) for a wafer according to a first embodiment of the present invention,  FIG. 4  is a bottom view illustrating helium gas supply passages of the ESC for a wafer according to the first embodiment in the present invention, and  FIG. 5  is a sectional of view for illustrating the ESC for a wafer in use according to the first embodiment of the present invention. As shown in  FIGS. 3, 4  and  5 , the ESC for a wafer according to the present invention comprises a base  20  on which a wafer  10  is mountable; a first ring shaped sealing member  30  provided on an outer portion of an upper end of the base  20 ; a second ring shaped sealing member  40  provided on the upper end of the base  20  to separate an inner portion of the upper end from the first sealing member  30 , and dividing the wafer  10  into an edge part  12  and a center part  14  when the wafer  10  is mounted on the ESC; a first helium supply passage  50  formed branched in the base  20 , and to emit a helium gas to the edge part  12  of the water  10 ; and a second helium supply passage  60  formed branched in the base  20  to emit the helium gas to the center part  14  of the water  10 .  
         [0034]     The wafer  10  is fixed by an electrostatic interaction between an electrostatic field generated by applying direct current voltage to the base  20  and the wafer  10 , and a size and a shape of the base  20  can be variously changed if required.  
         [0035]     The first sealing member  30  and the second sealing member  40  are circular, and restrict a flow of the helium gas respectively supplied to the edge part  12  and the center part  14  of the wafer  10 .  
         [0036]     The first helium supply passage  50  comprises a first helium gas inlet  52  provided in a bottom center of the base  20 ; a plurality of helium gas outlets  54  provided in an outer upper part of the base  20  corresponding to the edge part  12  of the wafer  10 , and to emit the helium gas to the edge part  12  of the wafer  10 ; and a first inner conduit  56  formed branched from the first helium gas inlet  52  and connected to the first helium gas outlets  54 .  
         [0037]     The first helium gas inlet  52  may be selectively provided at a convenient location in a bottom part of the base  20 , but preferably provided in a bottom center of the base  20  to enhance a cooling efficiency of the wafer  10  having the helium gas supplied to the edge part  12  and the center part  14  of the wafer  10  synchronously.  
         [0038]     The plurality of first helium gas outlets  54  are provided along an outer circumference of the base  20  at regular intervals to emit the helium gas corresponding to the edge part  12  of the wafer  10 .  
         [0039]     The first inner conduit  56  may comprise a plurality of first branch conduits  55   a  (one of which is shown) connected to the first helium gas inlet  52 , and a first circular conduit  55   b  connected to the first branch conduits  55   a  and the first helium gas outlets  54 . Alternatively, the first inner conduit  56  may be formed by omitting the first circular conduit  55   b , making a number of the first branch conduits  55   a  and a number of first helium gas outlets  54  the same; and arranging each first branch conduit  55   a  to be in fluid communication with a respective one of the first helium gas outlets  54 .  
         [0040]     Respective sizes of the first helium gas inlet  52 , the second helium gas outlet  54 , and the first inner conduit  56  are selected to be within a range of not generating an arcing.  
         [0041]     The second helium gas supply passage  60  comprises a second helium gas inlet  62  provided in a bottom center of the base  20 ; a plurality of helium gas outlets  64  provided in an upper part of the base  20  corresponding to a center part of the wafer  10 ; and a second inner conduit  66  provided branched from the second helium gas inlet  62 . The second inner conduit  66  is offset from the first inner conduit  56 , and connected to the second helium gas outlets  64 .  
         [0042]     The second inner conduit  66  is formed offset from the first inner conduit  56  to minimize a limit on positioning the second helium gas passage  60 , and to thereby emit the helium gas to the center part  14  of the wafer  10  uniformly.  
         [0043]     A position of the second helium gas inlet  62  is changeable if required, but it is preferable to be provided in a bottom center of the base  10  within a range of not interrupting the first helium gas inlet  52  to enhance a cooling efficiency of the wafer  10  by having the helium gas supplied to the edge part  12  and the center part  14  of the wafer  10  synchronously.  
         [0044]     The plurality of second helium gas outlets  64  are provided along a circumference of the base  20  at regular intervals to emit the helium gas corresponding to the center part  14  of the wafer  10 . The intervals may be varied as necessary.  
         [0045]     The second inner conduit  66  may comprise a plurality of second branch conduits  65   a  connected to the second helium gas inlet  62 , and a second circular conduit  65   b  connected to the second branch conduit  65   a  and the second helium gas outlets  64 . Alternatively, in the second helium gas supply passage  60 , the second inner conduit  66  may be formed omitting the second circular conduit  65   b , making a number of the second branch conduits  65   a  and a number of second helium gas outlets  64  the same, and arranging each second branch conduit  65   a  to fluidly communicate with a respective one of the second helium gas outlets  64 .  
         [0046]     The first helium supply passage  50  and the second helium supply passage  60  are separately provided, thereby enabling the amount of the helium gas and a time the helium gas is supplied to the edge part  12  to be selectively controlled independently of an amount of the helium gas and the time the helium gas is supplied to the center part  14  of the wafer  10 .  
         [0047]     An operation condition of the ESC for a wafer described above with reference to  FIGS. 3, 4  and  5  is as follows.  
         [0048]     Helium gas is flowed in through the first helium gas inlet  52  of the first helium supply passage  50  which is provided in the base  20  and flows outwardly through the base  20  along the branched first inner conduit  56 , and then emitted through the plurality of first helium gas outlets  54 , thereby cooling the edge part  12  of the wafer  10  evenly. The helium gas emitted through the first helium gas outlet  54  flows between the first sealing member  30 , the second sealing member  40 , the base  20 , and the wafer  10 , when the wafer  10  is chucked on the base  20 , therefore the helium gas can be intensively supplied to the edge part  12  of the wafer  10 .  
         [0049]     Likewise, helium gas is flowed through the second helium gas inlet  62  of the second helium supply passage  60  which is penetratingly provided in the base  20  and flows outwardly through the base  20  along the branched second inner conduit  66 , and then emitted through the plurality of second helium gas outlets  64 , thereby cooling the center part  14  of the wafer  10  uniformly. The helium gas emitted through the second helium gas outlets  64  stays inwardly of the second sealing member  40  when the wafer  10  is chucked on the base  20 , thereby the helium gas may be intensively supplied to the center part  14  of the wafer  10 .  
         [0050]      FIG. 6  is a top view illustrating an ESC for a wafer according to a second embodiment of the present invention,  FIG. 7  is a bottom view illustrating a helium gas supply passage of the ESC for a wafer according to the second embodiment of the present invention, and  FIG. 8  is a sectional view illustrating the ESC for a wafer in use according to the second embodiment of the present invention.  
         [0051]     The second embodiment of the invention comprises the features illustrated in  FIGS. 4, 5  and  6  and further comprises the additional features illustrated with respect to  FIGS. 6, 7  and  8 . In the description of the second embodiment, only the additional features will be discussed in order to avoid redundancy in the description.  
         [0052]     As shown in  FIGS. 6, 7  and  8 , the center part  14  of the wafer  10  is further divided into a central part  14   a  and a surrounding part  14   b  to further enhance cooling efficiency. In the second embodiment, the ESC for a wafer further comprises a ring-type third sealing member  70  which divides the center part  14  of the wafer  10  into the central part  14   a  and the surrounding part  14   b  when the wafer is mounted; and a third helium supply passage  80  provided to be branched inside of the base  20  and offset from the first helium gas supply passage  50  and the second helium gas supply passage  60 . The third helium supply passage  80  emits the helium gas to the central part  14   a  of the wafer  10 .  
         [0053]     The third helium gas supply passage  80  comprises a third helium gas inlet  82  provided at the bottom the base  20 ; a plurality of third helium gas outlets  84  provided in an upper part of the base  20  corresponding to the central part  14   a  of the wafer  10 ; a third inner conduit  86  provided branched from the third helium gas inlet  82  and offset from the second inner conduit  66 , and connected to the third helium gas outlets  84 .  
         [0054]     The third inner conduit  86  may comprise a plurality of third branch conduits  85   a , and a third circular conduit  85   b  connected to the third branch conduit  85   a  and the third helium gas outlets  84 .  
         [0055]     Descriptions and functions of the first sealing member  30 , the second sealing member  40 , the first helium gas supply passage  50  and the second helium gas supply passage  60  illustrated in  FIGS. 6, 7  and  8  are the same in the descriptions and functions described with respect to  FIGS. 3, 4  and  5  and further such descriptions and functions will be not be repeated in the description of the second embodiment.  
         [0056]     In the second embodiment, the third sealing member  70  is added to an upper side of the base  20 , a plurality of third sealing members  70  and corresponding helium supply passages may be provided, thereby cooling the center part  14  of the wafer  10  in segments.  
         [0057]     With the above configuration, the present invention provides an ESC which decreases a temperature difference between an edge part and a center part of a wafer to improve the efficiency of cooling. Helium gas supply passages are provided in multiple layers to balance a time gap in supplying the helium gas, and to minimize a limit on positioning the helium gas supply passages.  
         [0058]     Although a few embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.