JP2005136104A - Electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic chuck, wherein a gas for controlling the temperature of a member to be sucked, such as a wafer, is made to spread over the entire part of the member instantaneously, to be sucked in an instant and thereby the whole part of the wafer can be quickly held at the same temperature, without causing variations in the temperature of the wafer. <P>SOLUTION: Over the entire surface of a suction face 3 for sucking the wafer which corresponds to the rear face of the wafer to be sucked, annular gas grooves 13 and linking gas grooves 14 for supplying the gas are formed. Gas discharge ports 21, for sending the gas into the gas grooves 13 and 14, are formed at many places of the gas grooves 13 and 14 so that they are disposed over the whole region of the rear face of the wafer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  INDUSTRIAL APPLICABILITY The present invention is used for fixing semiconductor wafers, correcting flatness, transporting, etc. in a semiconductor manufacturing apparatus such as a dry etching apparatus, an ion implantation apparatus or an electron beam apparatus used for manufacturing a semiconductor wafer. The present invention relates to an electrostatic chuck.

  In a semiconductor manufacturing process, in order to accurately process a semiconductor wafer (for example, a silicon wafer) such as film formation or dry etching, it is necessary to hold (fix) the semiconductor wafer while maintaining its flatness. is there. As such a holding means, an electrostatic chuck that chucks a wafer by electrostatic force is widely used because it can be used even in a vacuum. Such an electrostatic chuck has, for example, a pair of electrodes formed inside an insulator (insulating plate), and a semiconductor wafer or the like is generated by electrostatic force generated by applying a voltage between the electrodes. A member to be sucked (hereinafter also simply referred to as a wafer) is sucked.

  By the way, also in the manufacture of such a wafer, improvement in the manufacturing yield, increase in the number of processed sheets per unit time (improvement in productivity), and the like are strongly demanded. For this reason, in a method of processing a wafer at a relatively low temperature such as dry etching, there is a demand to uniformly cool the wafer to a target temperature as soon as possible during the processing. In order to meet such a demand, a gas groove (concave) for supplying an inert gas (hereinafter also simply referred to as gas) such as He or Ar is provided over the entire adsorption surface of the electrostatic chuck. is there. That is, in this device, the temperature of the entire surface of the wafer is controlled by filling a gas in a space formed by the gas groove and the attracted surface of the adsorbed wafer (Patent Documents 1 and 2). ).

  Here, Patent Document 1 discloses a gas groove formed over the entire adsorption surface. The gas grooves are provided so that a plurality of annular grooves arranged concentrically and a plurality of radial grooves arranged and formed in communication are communicated with each other. In this apparatus, a gas outlet (gas inlet) connected to the gas groove is provided in the center of the adsorption surface, and the gas is introduced from the gas outlet toward the gas groove so that the gas flows over the entire area of the wafer. It is supposed to be spread over.

  Further, in Patent Document 2, a partition groove (gas groove) is provided in a radial direction between the annular grooves on the outer side of at least the second annular groove from the center of the annular grooves in Patent Document 1. Have been disclosed. The electrostatic chuck is surrounded by a wafer mounting surface (mounting surface) surrounded by two adjacent annular grooves and two adjacent radial grooves, and by two adjacent annular grooves, the radial grooves, and the partition grooves. Each installation surface such as an installation surface has a substantially equal area. That is, in Patent Document 2, the temperature distribution on the surface of the wafer can be made uniform by setting each installation surface surrounded by the gas groove to have substantially the same area as that of Patent Document 1, respectively. That's it.

In each of such electrostatic chucks, the flow of gas blown out from the gas outlet toward the gas groove is as follows. That is, the gas blown out from the center of the electrostatic chuck is distributed almost simultaneously to the radial grooves arranged in a branching manner, and flows in a radially outward direction so as to rush straight along the groove. And in each radial groove | channel, it strikes against the wall surface of the groove outer side in the intersection with the outermost annular groove, and changes direction to the right and left of the annular groove and flows. Subsequently, in order from the outer annular groove, the same flows in the inner annular groove, and flows to the entire gas groove. In the electrostatic chuck described in Patent Document 2, gas flows basically in the same manner. However, in this case, the gas flows into each partition groove through the annular groove, but the flow is also considered to flow sequentially from the one connected to the annular groove located outside.
Japanese Patent No. 2626618 JP 2002-170868 A

  When the wafer is adsorbed by the electrostatic chuck described in Patent Documents 1 and 2 and gas is caused to flow in the gas groove, the gas flown from the central gas outlet rushes outward in the radial groove, and then concentrically. A plurality of annular grooves arranged in a shape flow from the outside to the inside in order with a time lag, and finally the gas groove is filled with gas. For this reason, the temperature of the wafer is controlled as the gas flows, and therefore the temperature of the entire wafer cannot be equalized at the initial stage of gas filling. In addition, there is a problem that it takes a long time to make the temperature of the entire wafer uniform.

  As described above, in the device described in the above-mentioned patent document, the entire surface of the adsorbed wafer cannot be cooled at the same cooling rate, and the entire temperature tends to vary. In addition, there is a problem that it takes time until the entire wafer has a uniform temperature distribution, which is a cause of reducing the processing efficiency of the wafer.

  In the electrostatic chuck, the gas for temperature control of the member to be attracted such as a wafer is instantaneously spread over the entire member to be attracted, and the entire temperature is not changed without causing the entire temperature to vary. Is to be kept at the same temperature quickly.

In order to achieve the above object, the present invention according to claim 1 is an electrostatic chuck including an electrode for attracting a member to be attracted by an electrostatic force inside an insulator, and the member to be attracted is attracted. A gas channel for supplying a gas for supplying a temperature control gas for the member to be adsorbed over the entire area corresponding to the back surface of the member to be adsorbed among the adsorption surfaces, and a gas flow path for feeding the gas into the gas groove In the electrostatic chuck itself,
The gas outlets in the gas flow path for feeding gas into the gas grooves are opened at a number of locations in the gas grooves so as to correspond to the entire area of the back surface of the adsorbed member. Features.

  According to a second aspect of the present invention, the gas groove includes a plurality of annular gas grooves arranged concentrically and a plurality of connecting gas grooves that connect the annular gas grooves adjacent to each other inside and outside. The electrostatic chuck according to claim 1, wherein

  According to a third aspect of the present invention, in the electrostatic chuck according to the second aspect, the annular gas groove is an annular shape, and the connecting gas grooves are arranged radially.

  The invention according to claim 4 is the electrostatic chuck according to claim 2 or 3, wherein the gas outlet is provided at a connection point between the annular gas groove and the connection gas groove. is there.

  According to the electrostatic chuck of the present invention, a large number of the gas grooves are provided so that gas outlets in the gas flow path for feeding gas into the gas grooves are present corresponding to the entire back surface of the attracted member. Therefore, the gas can flow quickly from the gas outlet to the entire gas groove, and there is no time lag in the entire gas groove, so that the gas can be distributed instantaneously. That is, according to the electrostatic chuck of the present invention, gas for temperature control is simultaneously applied to the entire space formed between the member to be adsorbed such as a wafer adsorbed on the adsorption surface and the gas groove. Since it spreads instantaneously, the entire temperature can be quickly maintained at the target optimum temperature without causing variations in the temperature of the entire wafer.

  According to the electrostatic chuck of claim 2, in addition to the above-described effect, the gas can circulate or go back and forth between the annular gas grooves adjacent to the inside and outside by the plurality of connecting gas grooves, so that the temperature is made uniform. There is a peculiar effect that it is easy to make. Furthermore, according to the electrostatic chuck according to claim 3, gas is uniformly distributed to the attracted member by concentrically adsorbing a circular attracted member (for example, a semiconductor wafer) at the center of the attracting surface. Easy to touch. Therefore, there is an effect that it is easy to suppress heat unevenness. The effect of the electrostatic chuck according to the fourth aspect will be described in the best mode for carrying out the invention described below.

A first embodiment of the present invention will be described in detail with reference to FIGS. 1 is a plan view of an electrostatic chuck according to the present invention, FIG. 2 is an enlarged view of a portion A thereof, and a further enlarged view of the portion, and FIG. 3 is a cross-sectional view of the electrostatic chuck of FIG. FIG. 4 is a sectional view taken along the line CC of FIG. In the figure, reference numeral 1 denotes an electrostatic chuck. In this example, the ceramic chuck is made of alumina (Al ₂ O ₃ ) as a main component and has a laminated structure (for example, 10 layers) having a constant thickness (5 mm), and has a diameter of 300 mm. It has a circular flat plate shape. However, the predetermined width part 5 connected to the outer peripheral surface 4 on the suction surface 3 side is made one step lower than the suction surface 3. Note that such an electrostatic chuck 1 is usually provided with a flat surface 51 on an upper portion of a base member (for example, made of an aluminum alloy) 50 having a disc shape (or a truncated cone) as shown by a two-dot chain line in FIG. Are bonded and fixed with silicon resin or the like.

  Such an electrostatic chuck 1 has an upper surface that serves as an adsorption surface 3 that adsorbs and holds the semiconductor wafer 101 as an adsorbed member (adsorbed body). The suction surface 3 is finished to a flat surface with a high degree of flatness and surface roughness, and has a minute width (for example, set in a range of 1 to 3 mm) and a minute depth (for example, 1 to 3 mm). The gas groove 11 having a substantially rectangular cross section is set in a range of 5 to 20 μm. In the present embodiment, the gas groove 11 includes a plurality of annular gas grooves 13 arranged concentrically with respect to the electrostatic chuck 1 and a plurality of connecting gas grooves 14 that connect the annular gas grooves 13 adjacent to each other inside and outside. ing. In this example, the annular gas groove 13 is an annular shape, and the interval (pitch) in the radial direction between the annular gas grooves 13 is substantially constant. However, strictly speaking, a part of the outermost annular gas groove 13 is linearly formed.

  Further, the connecting gas grooves 14 are arranged radially from the center of the electrostatic chuck 1. The connecting gas grooves 14 (also referred to as radial gas grooves) are arranged at smaller radial angular intervals in the portion closer to the outer periphery than in the portion closer to the center of the electrostatic chuck 1. The arrangement is basically staggered across the annular gas groove 13. It should be noted that the outermost circumference and the connecting gas groove 14 arranged next to the inner circumference (inner circumference side) have the same radial angular interval. Thus, the gas groove 11 in this embodiment is arranged and formed over the entire area of the adsorption surface 3 of the electrostatic chuck 1 so as to be continuous at the connection point (intersection) between the annular gas groove 13 and the connection gas groove 14. Is formed.

  In such an electrostatic chuck 1, a portion of the attracting surface 3 excluding the gas groove 11 is a flat surface having the same height and is a mounting surface 16 on which the wafer 101 is mounted. The mounting surface 16 includes a large number of mounting surfaces 16 partitioned by the annular gas groove 13 and the connecting gas groove 14 and has a sector shape close to a trapezoid. However, gas grooves (radial gas grooves) 15 are provided radially at intervals of 90 degrees so as to communicate with the annular gas groove 13 inside the annular gas groove 13 closest to the innermost periphery. Each mounting surface 18 here has a ¼ arc sector shape.

  The gas grooves 11 having such a planar arrangement are connected so that substantially all the inner and outer peripheral ends of the radial gas grooves 14 abut against the continuous annular gas grooves 13, and the connection point (intersection point) is T-shaped. It is a crossing (three-way intersection). In this embodiment, the gas outlet 21 is opened at all the connecting points that form the outer peripheral edge of the radial gas groove 14 among the connecting points. The gas outlet 21 is also opened at the connection point (intersection) of the radial gas grooves 15 at the center. In addition, as shown in FIG. 3, these gas outflow ports 21 are formed as follows so as to continue to the gas flow path 22 provided inside the electrostatic chuck 1 itself.

  That is, as shown in FIG. 3, the internal gas flow path 22 communicates from the gas supply source in the order of the rear surface side vertical hole 23, the tunnel-shaped intermediate horizontal hole 24, and the upper surface (adsorption surface 3) side vertical hole 25. It is formed as follows. However, as shown in FIG. 4, the intermediate horizontal hole 24 has a plurality of annular horizontal holes 24 a concentrically provided at the same position as the annular gas groove 13 and one radial direction extending from the center. It consists of a straight lateral hole 24b provided so as to communicate with the annular lateral hole 24a. The upper surface side vertical hole 25 has an upper end opening into the annular gas groove 13 having each radius to form a gas outlet 21, and a lower end portion communicating with the annular horizontal hole 24a having each radius. 23 is communicated with the straight lateral hole 24b at the center of the electrostatic chuck 1 itself in plan view, and is opened on the back surface 7. And the opening in this back surface 7 is made into the gas inflow port which flows gas into such a gas flow path 22.

  For example, the cross section of each gas flow path 22 inside the electrostatic chuck 1 itself is set as follows. The upper surface side vertical hole 25 has a diameter of 0.3 mm, and the back surface side vertical hole 23 has a diameter of 5 mm. The intermediate lateral hole 24 has a rectangular cross section with a height of 2 mm and a width of 2 mm. Since the electrostatic chuck 1 is used while being fixed to the upper surface 51 of the base member 50, the back surface side vertical hole 23 of the electrostatic chuck 1 is formed in the base member 51, the gas supply channel 54. Via a pipe and connected to a gas source (not shown).

  A pair of electrostatic chucking electrodes 28 and 29 are embedded between the suction surface 3 and the intermediate lateral hole 24. The electrodes 28 and 29 are connected to a power source via a relay line (not shown). By applying a DC voltage to the electrodes 28 and 29, an electrostatic attractive force is generated, and the semiconductor wafer (adsorbed member) 101 is formed on the adsorption surface 3. It is comprised so that it may adsorb | suck. Further, in this embodiment, three lift holes 30 are formed through the thickness direction at equal angular intervals on a concentric circumference in plan view, and are sucked by lift pins (extruding pins) not shown. It is formed so as to constitute lift means for separating (detaching) the released wafer 101 from the suction surface 3. Of the connecting gas grooves 14 between the inner and outer annular gas grooves 13 adjacent to each other with the lift hole 30 in between, the lift hole 30 is formed in a circular shape surrounding the lift hole 30.

  In such an electrostatic chuck 1 of this embodiment, the wafer 101 is placed on the suction surface 3 and a predetermined voltage is applied between the electrodes 28 and 29 to suck and hold it. Gas is fed from the gas source into the internal gas flow path 22. By doing so, the gas is fed into the gas groove 11 from the many gas outlets 21 through the back surface side vertical hole 23, the intermediate horizontal hole 24, and the top surface side vertical hole 25. The introduced gas is filled in a space formed by the back surface 102 of the wafer 101 and the gas groove 11. As a result, the entire wafer 101 is controlled to be cooled to a predetermined temperature. At this time, the gas fed into the gas groove 11 passes through the annular gas groove 13 and the connection gas from a number of gas outlets 21 provided at a number of T-shaped intersections (connection points) existing in the entire area of the gas groove 11. Since the gas enters the gas groove 11 including the groove 14, the entire surface of the back surface 102 of the wafer 101 is instantaneously distributed. Therefore, the entire wafer 101 can be quickly maintained at the target temperature without causing variations in the overall temperature. That is, according to the electrostatic chuck 1 of the present embodiment, the gas that has flowed from the large number of gas outlets 21 to the gas groove 11 starts the radial gas grooves 14 from the large number of gas outlets 21 as the starting point. At the same time as it flows toward the center of the gas flow, it flows toward both sides of the annular gas groove 13. Then, such a flow toward three directions is simultaneously performed at a number of T-shaped intersections, and the flow distance is short, so that the gas instantaneously spreads over the entire gas groove 11.

  That is, in the present embodiment, the gas outlet 21 is compared with that in which the inflow of gas into the gas groove is performed from the gas outlet located only in the center, as in the electrostatic chuck described in the above-described conventional patent document. Since a large number of gas grooves 11 are provided in the entire gas groove 11, the time required from the start of gas flow into the gas groove 11 until filling can be remarkably shortened. Therefore, the gas can be instantaneously distributed over the entire area of the wafer 101 without a time lag, and the temperature of the entire wafer 101 can be maintained at a desired temperature in a short time without variations in temperature.

  In particular, in this embodiment, since the gas outlet 21 is provided at the T-shaped intersection of the gas groove 11, the gas can be branched and flowed in three directions at the same time at the multiple gas outlets 21. This has the effect that the gas can be filled more quickly.

The electrostatic chuck 1 described above can be manufactured, for example, by laminating and press-bonding a predetermined ceramic green sheet mainly composed of alumina (Al ₂ O ₃ ), followed by sintering. The outline (one example) of the manufacturing method is as follows. The ceramic layer that forms the back surface (lowermost layer) is made by laminating three 0.5 mm thick green sheets, and then laminating four 0.5 mm thick green sheets on which the intermediate horizontal holes 24 are formed. To do. And under that state, a back side vertical hole 23 is made, and processing for the intermediate horizontal hole 24 is performed.

  Next, two 0.5 mm-thick green sheets are laminated, an electrode metallized paste (conductor paste such as tungsten) is printed on the upper surface, and an adsorption surface forming green sheet is laminated on the printed surface of the metallized paste. Then, pressure bonding is performed and the upper surface side vertical hole 25 is formed. Thereafter, this laminate is laminated on the green sheet processed for the intermediate lateral hole 24 with the green sheet for forming the adsorption surface facing up, and is pressed and fired. Then, after the firing, the front and back surfaces are polished and finished to the desired parallelism and surface roughness, and then gas grooves are formed on the suction surface side by polishing (machining), sandblasting, ultrasonic processing, or the like. . By doing so, the electrostatic chuck 1 described above can be manufactured.

  In the above-described embodiment, the gas outlet 21 is provided only at the connection point between the outer end of the radial gas groove 14 and the annular gas groove 13, but in addition to this, the inner end of the radial gas groove 14 is provided. It may also be provided at a connection point between the annular gas groove 13 and the annular gas groove 13. If it does in this way, the gas outflow port 21 will increase and the gas which flows out out of one gas outflow port 21 will spread over the whole gas groove only by moving a further short distance. For this reason, gas can be spread over the entire gas groove more quickly. That is, it is preferable to provide as many gas outlets as possible in the entire gas groove.

  Moreover, in the said form, although the connection gas groove 14 except the thing near a center part was arrange | positioned so that gas could move linearly only between the adjacent annular gas grooves 13, among the gas grooves 11, in this invention, May be a radial gas groove extending straight from the center to the annular groove 13 near the outer periphery of the electrostatic chuck 1. In this case, a gas outlet may be provided at a connection point (intersection) between the radial gas groove and the annular gas groove. This is because the gas can be branched and flowed in four directions from one gas outlet, so that the gas can be spread all over the gas groove more quickly.

  Further, in the above-described embodiment, the connecting gas groove 14 is the radial gas groove 14 extending in the radial direction. However, this may be inclined instead of the radial direction. In the above-described embodiment, the annular gas groove 13 is annular, but it may be rectangular (square frame). That is, the gas groove only needs to be provided in an arrangement in which gas is supplied over the entire area corresponding to the back surface of the member to be adsorbed, and any arrangement may be employed. For example, even in an electrostatic chuck having a gas groove such as a mesh shape, a spider web shape, or a grid shape, the gas outlet for feeding gas into the gas groove corresponds to the entire back surface of the attracted member. It is only necessary to open the gas groove at a number of locations so as to exist.

  Further, in the above-described embodiment, as the gas flow path 22, a tunnel-shaped intermediate horizontal hole 24 is provided inside the electrostatic chuck 1, and one back side vertical hole 23 communicating with the intermediate horizontal hole 24 is provided on the back surface 7. However, the gas flow path 22 is not limited to this. FIG. 5 shows one example. That is, the gas flow path of the electrostatic chuck according to the present invention penetrates in the thickness direction of the electrostatic chuck 71 together with each gas outlet 21 provided to open to the gas groove 11 as shown in FIG. It is good also as what provided the gas flow path 72 of the vertical hole. In this case, for example, a gas flow path inside the electrostatic chuck in the above-described embodiment is used so that gas can be supplied to the gas flow path 72 of each vertical hole through the base member 50. A gas flow path may be provided in the base member 50. In FIG. 5, the same parts as those in the above-described embodiment are denoted by the same reference numerals.

  The present invention is not limited to the scope of the above description, and can be embodied by appropriately modifying the design without departing from the scope of the invention. As a matter of course, the electrostatic chuck may be formed of a ceramic other than alumina. Moreover, it can also form with insulators other than a ceramic. In the above description, the member to be adsorbed is a semiconductor wafer and the cooling gas is allowed to flow into the gas groove. However, the present invention is not limited to this. The present invention can be widely applied to an electrostatic chuck in which a gas controlled to a desired temperature is allowed to flow into a gas groove. Furthermore, although it has been embodied in a configuration in which a member to be attracted is attracted by applying a predetermined voltage between a pair of internal electrodes embedded in the electrostatic chuck (bipolar type), it is predetermined between the internal electrode and the attracting member. Needless to say, the present invention can also be embodied in a structure (single pole type) that applies the above voltage. Further, the present invention can also be embodied in an electrostatic chuck having a configuration in which a heater electrode (resistance heating element) is embedded between the back surface of the electrostatic chuck of the above embodiment and an intermediate horizontal hole in the gas flow path.

The top view of the electrostatic chuck which concerns on this invention. The A section enlarged view of FIG. 1, and the further enlarged view of the part. FIG. 2 is a cross-sectional view of the electrostatic chuck of FIG. 1 taken along line B-B and a partially enlarged view thereof. CC sectional view taken on the line of FIG. Sectional drawing of another example of the electrostatic chuck which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 71 Electrostatic chuck 3 Adsorption surface 11 Gas groove 13 Annular gas groove 14 Linked gas groove 22 Gas flow path 21 Gas outlet 101 Wafer (adsorbed member)
102 Back side of wafer

Claims (4)

An electrostatic chuck comprising an electrode for attracting a member to be attracted by an electrostatic force inside an insulator, wherein the entire area corresponding to the back surface of the member to be attracted among the attracting surfaces for attracting the member to be attracted In addition, a gas groove for supplying a temperature control gas for the member to be adsorbed is provided, and a gas flow path for feeding gas into the gas groove is provided in the electrostatic chuck itself.
The gas outlets in the gas flow path for feeding gas into the gas grooves are opened at a number of locations in the gas grooves so as to correspond to the entire area of the back surface of the adsorbed member. Features an electrostatic chuck.   2. The gas groove includes a plurality of annular gas grooves arranged concentrically and a plurality of connecting gas grooves that connect the annular gas grooves adjacent to each other inside and outside. The electrostatic chuck described in 1.   The electrostatic chuck according to claim 2, wherein the annular gas groove is annular, and the connecting gas grooves are arranged radially.   The electrostatic chuck according to claim 2, wherein the gas outlet is provided at a connection point between the annular gas groove and the connection gas groove.

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