Patent Application
20070274020
The present invention relates to semiconductor device manufacturing equipment, and, more particularly, to an electrostatic chuck (ESC) and a chuck base having a cooling path or channel for cooling a wafer.
In a reaction chamber of semiconductor device manufacturing equipment, for example, a dry etcher, is mounted a chuck for supporting a semiconductor wafer during a process. The chuck may be an electrostatic chuck. The chuck is mounted on a chuck base, which is disposed at the rear surface of the chuck. The chuck base serves to support the chuck. The chuck base is provided with a cooling channel for maintaining a constant temperature of the chuck, and therefore, uniformly cooling the semiconductor wafer located on the chuck.
The electrostatic chuck fixes the wafer using an electrostatic force. To this end, the electrostatic chuck has a structure for generating an electrostatic force or electrostatic adsorptive force, for example, a structure comprising an electrode and a dielectric film surrounding the electrode. In order to increase yield rate of wafers, on the other hand, it is essentially required to maintain a constant temperature of the wafer reacting to plasma during a process, for example, during an etching process. When the temperature of the entire wafer is not uniformly maintained, defectiveness, such as poor distribution of critical dimensions on the wafer is generated during the etching process.
The electrostatic chuck is provided at the surface thereof with a refrigerant channel, for example, a helium (He) channel, for cooling the wafer to maintain a constant temperature of the wafer. The shape of such a helium channel directly affects the temperature distribution of the entire wafer. For this reason, various attempts have been made to change the shape of the helium channel to accomplish uniform temperature control on the wafer.
At present, a dielectric film, in which an electrode for supplying electric power necessary to generate an electrostatic force is disposed, is formed by coating a dielectric material. The dielectric film formed by coating the dielectric material has a relatively large thickness, and therefore, it is necessary that high direct current voltage be applied to the electrode in order to generate a sufficient electrostatic force. However, application of such high direct current voltage leads to damage to semiconductor devices formed on the wafer, which decreases yield rate of wafers.
Also, anodized film may be easily peeled off due to arcing at the edge part of the electrostatic chuck when high direct current voltage is applied. As a result, the service life of the electrostatic chuck may be reduced, and impurities may be generated in the reaction chamber.
It is first required to maintain a constant temperature of the chuck in order to accomplish uniform temperature control on the wafer. To this end, various attempts have been made. For example, a cooling channel may be provided at the chuck base to maintain a constant temperature of the chuck, by which the wafer can be uniformly cooled.
The plan shape and the arrangement of the cooling channel formed at the chuck base are considered parameters for uniformly cooling the chuck. Especially, improvement of the plan shape of the cooling channel to effectively reduce temperature deviation at the chuck or the wafer has been devised.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an electrostatic chuck having a cooling channel that is capable of minimizing temperature deviation of a wafer mounted on the electrostatic chuck, thereby improving uniformity of critical dimensions in the wafer, and therefore, increasing yield rate of wafers.
It is another object of the present invention to provide a chuck base having a newly shaped cooling channel that is capable of maintaining a constant chuck temperature, thereby effectively reducing temperature deviation generated at the chuck or a wafer and effectively cooling the wafer.
In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of an electrostatic chuck comprising: a chuck base for supporting a wafer; a dielectric film mounted on the chuck base, the dielectric film having an electrode for supplying direct current voltage to provide an electrostatic force necessary to fix the wafer, the electrode being disposed in the dielectric film; and a cooling channel for supplying refrigerant to the dielectric film to control the temperature of the wafer, the cooling channel comprising: at least two first cooling channel parts formed at the surface of the dielectric film corresponding to the edge part of the wafer such that the first cooling channel parts form concentric circles; second cooling channel parts formed at the surface of the dielectric film such that the first cooling channel parts are connected to each other through the second cooling channel parts; first through channels formed through the dielectric film for supplying the refrigerant to the first and second cooling channel parts; and a second through channel formed through the center of the dielectric film for supplying the refrigerant to the center of the wafer.
Preferably, the dielectric film is a dielectric sheet comprising stacked dielectric sheet parts, between which the electrode is disposed, the dielectric sheet being attached to the chuck base while being compressed.
Preferably, the inside part of the first cooling channel parts, which is near to the center of the dielectric film, is disposed within the distance corresponding to not more than ¼ of the diameter of the wafer from the circumference of the dielectric film at the most.
Preferably, the number of the second cooling channel parts is eight, and the first through channels, whose number is equal to that of the second cooling channel parts, are connected to the second cooling channel parts adjacent to the connections between the second cooling channel parts and the outside part of the first cooling channel parts, respectively.
In accordance with another aspect of the present invention, there is provided a chuck base for supporting and cooling a chuck on which a wafer is located. The chuck base comprises: a base body for supporting a chuck, on which a wafer is located; and a cooling channel for cooling the chuck, the cooling channel comprising: a curved part, which extends outward from the center of the chuck base under the surface of the chuck base, which is opposite to the chuck, in the shape of a cross; and a circular part connected to the curved part, the circular part being formed in the shape of a circle around the cross-shaped part.
Preferably, the chuck base further comprises: a connection part disposed between one end of the cross-shaped part and one end of the circular part for connecting the cross-shaped part and the circular part, whereby the cooling channel begins at the other end of the cross-shaped part, and ends at the other end of the circular part.
Preferably, the base body is provided with four first through holes, through which lift pins for locating the wafer on the chuck are inserted, and the cooling channel is curved such that the four first through holes are disposed between the cross-shaped part and the circular part, and the cross-shaped part extends around the first through holes.
Preferably, the base body is provided with second through holes for supplying electric power necessary to generate an electrostatic force to the chuck, and the cooling channel is curved such that the cross-shaped part extends around the inside parts of the second through holes.
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
An electrostatic chuck according to a preferred embodiment of the present invention is schematically shown in FIGS. 1 to 14.
Referring to
On the chuck base 200 is formed a dielectric film 400. Generally, the dielectric film 400 may be formed by anodizing. In the preferred embodiment of the present invention, however, an additional dielectric sheet, which is manufactured in the shape of a sheet, is attached to the surface of the chuck base 200 while being compressed. In the illustrated embodiment, the dielectric sheet comprises a first dielectric sheet part 401 and a second dielectric sheet part 402 stacked on the first dielectric sheet part 401, although the dielectric sheet may comprise a plurality of stacked dielectric sheet parts.
Between the first dielectric sheet part 401 and the second dielectric sheet part 402 is disposed a thin electrode 300. As a result, the electrode 300 is provided in the dielectric film 400. The electrode 300 may be made of a conductive metal material, such as copper (Cu), aluminum (Al) or molybdenum (Mo). Alternatively, such a conductive metal material may be coated on the first dielectric sheet part 401.
In the case that the dielectric film 400 is formed by attaching and compressing the dielectric sheet, it is possible to form the dielectric sheet with a dielectric material having excellent dielectric characteristics, and therefore, more excellent dielectric characteristics are realized. Also in the case that the dielectric film 400 is formed by attaching and compressing the dielectric sheet, it is possible to uniformly decrease the thickness of the entire dielectric film 400, especially, the thickness of the second dielectric sheet part 402 between the electrode 300 and the wafer 100. Consequently, an electrostatic adsorptive force can be sufficiently generated although low direct current voltage (V) is applied to the electrode 300.
If the thickness of the dielectric film 400 is approximately 1.3 mm, the thickness of the first dielectric sheet part 401 is approximately 0.7 mm, which is relatively large, and the thickness of the second dielectric sheet part 402 is approximately 0.3 mm, which is relatively small. As a result, the thickness of the electrode 300 is approximately 0.3 mm.
Application of low direct current voltage (V) reduces the probability of occurrence of arcing and prevents the dielectric film 400 from being damaged due to such arcing or the anodized film from being peeled off, and therefore, the service life of the electrostatic chuck from being decreased. In addition, impurities are effectively prevented from being generated in a reaction chamber.
Also, application of low direct current voltage (V) reduces the electric charge in the second dielectric sheet part 402, and therefore, it is possible to more smoothly separate the wafer 100 from the chuck base 200. Specifically, the net charge when the wafer 100 is separated rapidly amounts to zero, and therefore, the wafer 100 can be separated without sliding or being damaged.
Application of low direct current voltage (V) is very advantageous in preventing spark discharge, which may be generated under lower pressure, for example, several mTorr, in the reaction chamber when the wafer 100 is separated.
At the surface of the dielectric film 400 of the electrostatic chuck is formed a cooling channel 500 for cooling the wafer 100. The cooling channel 500 supplies helium (He) as refrigerant to the rear surface 100 for cooling the wafer 100 to control the temperature of the wafer 100, which will be described below in detail. The conventional type of cooling channel causes the difference in temperature between the center part and the edge part of the wafer, and therefore, it is difficult to control critical dimensions of the device. The present invention proposes a new type of cooling channel 500 that is capable of accomplishing uniform temperature distribution throughout the wafer 100, and therefore, minimizing temperature deviation.
Although not shown in
FIGS. 2 to 6 show the chuck base constituting the electrostatic chuck according to the preferred embodiment of the present invention, and FIGS. 8 to 11 show the sheet-shaped dielectric film constituting the electrostatic chuck according to the preferred embodiment of the present invention, the sheet-shaped dielectric film being attached to the chuck base while being compressed.
Specifically,
Referring first to FIGS. 2 to 7, the chuck base 200 is made of aluminum, and is constructed such that a step is formed between the front surface 210 of the chuck base 200, which faces the wafer 100, and an edge part 230 of the chuck base 200, as shown in
The edge part 230 is provided with a plurality of through holes 231, through which fixing members of the chuck base 200, for example, bolts, are inserted. The entire edge part 230 is anodized such that an insulation film covers the edge part. However, the front surface 210 of the chuck base 200 is maintained bare. To the front surface 210 is attached the dielectric film 400 while being compressed as shown in FIGS. 8 to 11.
As shown in
Referring to
Referring back to
Referring to
The second supply through hole 217 is connected to the intersecting part of the distribution channels 251, as shown in
Consequently, helium is simultaneously distributed to the first supply through holes 215 and the second supply through hole 217 through the distribution channels 251.
Referring to FIGS. 8 to 11, the dielectric film 400 is formed in the shape of stacked sheets such that the electrode 300 is disposed in the dielectric film 400. As shown in
The cooling channel 500 is formed at the upper surface of the dielectric film 400 for controlling the temperature of the wafer 100, i.e., cooling the wafer 100. The cooling channel 500 comprises at least two groove-shaped first cooling channel parts 501 and 503, which are disposed on the dielectric film 400 corresponding to the edge part of the wafer 100 such that the first cooling channel parts 501 and 503 form concentric circles. Between the first cooling channel parts 501 and 503 are disposed a plurality of second cooling channel parts 505, which are arranged in the radial direction such that the first cooling channel parts 501 and 503 are connected to each other through the second cooling channel parts 505. The thickness of the entire dielectric film 400 is merely approximately 1.3 mm, and therefore, each of the first cooling channel parts 501 and 503 and/or the second cooling channel parts 505 is formed in the shape of a groove having a depth of approximately 0.1 mm and a width of approximately 1 mm.
The dielectric film 400 is provided with first through channels 515, which are formed though the dielectric film 400 for supplying helium as refrigerant to the first cooling channel parts 501 and 503 and the second cooling channel parts 505. The first through channels 515 are aligned with the first supply through holes 215 formed at the chuck base 200, respectively. At a position of the dielectric film 400 corresponding to the center of the wafer 100 is formed a second through channel 517 for injecting helium as refrigerant to the rear surface of the wafer 100. Each of the first and second through channels 515 and 517 has a diameter of approximately 0.5 mm.
In the cooling channel 500 with the above-stated construction, the first and second cooling channel parts 501 and 505 are disposed adjacent to the edge part of the wafer 100. In other words, the cooling channel 500 is constructed such that a relatively large portion of refrigerant is supplied to the edge part of the wafer 100 as compared to the center part of the wafer 100. Especially, the cooling channel 500 is constructed such that only helium as refrigerant injected from the second through channel 517 is supplied to the center part of the wafer 100. Consequently, the concentrically arranged first cooling channel parts 501 and 503 or the second cooling channel parts 505, which are connection channels, do not extend to the center part of the wafer 100.
For example, the cooling channel 500 is constructed such that the inside part of the first cooling channel parts 501 and 503, i.e., the first cooling channel part 501, is disposed within the distance corresponding to not more than ¼ of the diameter of the wafer 100 from the circumference of the wafer 100 at the most. If the diameter of the wafer 100 is 200 mm, the first inner cooling channel part 501 is approximately 38 mm from the circumference of the wafer 100 or the circumference of the dielectric film 400. Practically, the position of the first cooling channel part 501 may be disposed adjacent to the lift holes 413 or the circumference of the dielectric film 400 or the wafer 100.
If the cooling channel 500 is disposed adjacent to the edge part of the wafer 100, the temperate at the edge part of the wafer 100 can be effectively controlled. When a dry etching process is performed, the temperature deviation is greater at the edge part of the wafer 100 than at the center part of the wafer 100. According to the present invention, however, the cooling channels 501, 503 and 505, through which helium flows, are concentrically disposed at the positions of the dielectric film 400 corresponding to the edge part of the wafer 100, whereby such temperature deviation is effectively prevented.
Helium can be simultaneously injected through the second through channel 517 and the first through channels 515, which is accomplished by the provisions of the distribution channels 251 formed at the rear surface 250 of the chuck base 200 as described above with reference to
The shape of the cooling channel 500 according to the preferred embodiment of the present invention may be variously modified. Nevertheless, concentrically arranged cooling channels and connection channels are disposed adjacent to the edge part of the wafer in all modifications.
Referring to
Referring to
Referring to
The temperature of a semiconductor wafer 800, which is located on the chuck 700, may be increased in the course of the process, and therefore, the temperature of the chuck 700 may be increased. Such increase of temperature greatly affects the process, and as a result, undesired defectiveness, such as nonuniform critical dimensions, may be caused. For this reason, a cooling unit for controlling or compensating for the increase of temperature to maintain a constant temperature of the wafer 800 or the chuck 700 is required.
The preferred embodiment of the present invention provides a cooling channel, serving as the cooling unit, formed at the chuck base 600.
Referring to
The cooling channel 610 may be formed by forming a groove at the upper surface 601 of the base body of the chuck base 600 and placing a cover part 619 on the groove such that the groove is covered by the cover part 619. The cover part 619 is placed on the groove, and is then fixed to the upper surface of the base body of the chuck base 600 by welding. As a result, the groove is hermetically sealed, and therefore, refrigerant, for example, demineralized water, is prevented from flowing out of the cooling channel 610 or onto the chuck base 600.
The cooling channel 610 is disposed over a broad area of the chuck base such that the entire area of the chuck 700 and the entire area of the semiconductor wafer 800 can be effectively and uniformly cooled by the cooling channel 610. Specifically, the cooling channel 610 is formed under the upper surface 601 of the chuck base 600 in the shape of a curve such that the cooling channel 610 extends over the broad area of the chuck base.
For example, the cooling channel 610 comprises a curved part, which extends outward from the center of the upper surface 601 of the chuck base 600 in the shape of a cross, i.e., a cross-shaped part 611, as shown in
Inlet and outlet ports 617 for allowing refrigerant to be introduced into the cooling channel 610 therethrough are formed such that the inlet and outlet ports 617 are opposite to each other. Specifically, one of the inlet and outlet ports 617 is disposed at one end of the cross-shaped part 611, and therefore, the cooling channel 610 begins at the inlet and outlet port 617 disposed at the end of the cross-shaped part 611. Also, the other inlet and outlet port 617 is disposed at one end of the circular part 615, and therefore, the cooling channel 610 ends at the inlet and outlet port 617 disposed at the end of the circular part 615. Consequently, the cooling channel 610 extends from the inlet and outlet port 617 disposed at the end of the cross-shaped part 611 to the inlet and outlet port 617 disposed at the end of the circular part 615. The cooling channel may further comprise a connection part 613 disposed between the other end of the cross-shaped part 611 and the other end of the circular part 615 for connecting the cross-shaped part 611 and the circular part 615. At this time, it is preferable that the two inlet and outlet ports 617 are opposite to each other while the connection part 613 is disposed between the two inlet and outlet ports 617.
The circular part 615 of the cooling channel 610 is disposed along the circumference the chuck base in the shape of a circle while the cross-shaped part 611 of the cooling channel 610 is disposed inside the circular part 615. The chuck base 600 is generally provided with a plurality of through holes 621 and 625. For example, lift pins (not shown), which are used to locate the semiconductor wafer 800 on the chuck 700 or remove the semiconductor wafer 800 from the chuck 700, support the semiconductor wafer 800 through the chuck base 600 and the chuck 700. Consequently, the first through holes 621 is formed at the chuck base 600 such that the lift pins can be inserted through the first through holes 621, respectively.
The number of the first through holes 621 corresponds to the number of the lift pins. In the illustrated embodiment of the present invention, the number of the lift pins is four such that the semiconductor wafer 800 can be stably located on the chuck base, and therefore, four first through holes 121 are disposed as shown in
It is required that the cooling channel 110 not extend over the first through holes 121 and the cooling channel 110 extend over a broad area of the chuck base. Consequently, the first through holes 121 are disposed between the cross-shaped part 111 and the circular part 115 of the cooling channel 110, and therefore, the cross-shaped part 111 of the cooling channel 110 is curved such that the cross-shaped part 111 extends around the first through holes 121.
When the chuck 700 is an electrostatic chuck as shown in
In addition to the cooling channel 610, various structures, such as nut-shaped grooves, for connection between the chuck base 600 and the chuck 700, for example, bolt-nut connection, may be provided at the upper surface 601 of the chuck base 600. Also, various structures, such as nut-shaped grooves, for connection between the chuck base 600 and the chamber may be provided at the lower surface 603 of the chuck base 600. Furthermore, the chuck base 600 may be provided at the center part of the upper surface 601 thereof with a helium supply hole for supplying helium (He) to the rear surface of the wafer 800.
As apparent from the above description, the cooling channel, through which helium as refrigerant flows, are disposed at the electrostatic chuck corresponding to the edge part of the wafer according to the present invention. Consequently, the present invention has the effect of more effectively controlling the temperature of the edge part of the wafer. When a dry etching process is performed, the temperature deviation is greater at the edge part of the wafer than at the center part of the wafer. According to the present invention, however, such temperature deviation is compensated for, and therefore, occurrence of the temperature deviation is effectively prevented.
In the preferred embodiment of the present invention, the dielectric film is formed by attaching and compressing the dielectric sheet. As a result, it is possible to form the dielectric sheet with a dielectric material having excellent dielectric characteristics, and therefore, more excellent dielectric characteristics are realized. Also, it is possible to uniformly decrease the thickness of the second dielectric sheet part between the electrode and the wafer. Therefore, an electrostatic adsorptive force can be sufficiently generated although low direct current voltage (V) is applied to the electrode. Consequently, the present invention has the effect of preventing the electrostatic chuck or the wafer from being damaged due to arcing, remarkably increasing the service life of the electrostatic chuck, and considerably increasing yield rate of wafers.
In the chuck base according to the present invention, the cooling channel is disposed under the upper surface of the chuck base while the cooling channel is curved such that the cooling channel extends over the broad area of the chuck base. As a result, the entire area of the chuck disposed on the chuck base is more effectively and uniformly cooled, and therefore, the entire area of the wafer located on the chuck is more effectively and uniformly cooled. Consequently, the present invention has the effect of effectively preventing occurrence of temperature deviation at the wafer or the chuck, and maintaining a constant temperature of the wafer or the chuck. Especially, the cooling channel comprises the cross-shaped part and the circular part disposed around the cross-shaped part, and therefore, more uniform temperature control is accomplished over the entire area of the chuck or the wafer.
The present invention is applied to the industrial field using a reaction chamber having an electrostatic chuck for supporting wafers and a chuck base disposed under the electrostatic chuck.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2003-0094412 | Dec 2003 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR04/03387 | 12/22/2004 | WO | 4/26/2007 |
