JP2005191561A - Electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic chuck which can increase the plasma resistance and abrasion resistance without jump up of a held substrate, caused by residual charge and can quickly and uniformly control the in-plane temperature of the front face of the held substrate to a specified temperature or a specified temperature distribution. <P>SOLUTION: An electrostatic chuck 16, which holds a wafer W by using electrostatic force, has multiple protrusions 16C that make contact with the wafer W. The protrusions 16C are made of a ceramic dielectric 16A, which includes alumina crystal grains having an average grain diameter of 1 to 2 μm, and comprise faces to make contact with the wafer W, which are formed so as to have a surface roughness of Ra 0.2 to 0.3 μm that depends on the grain diameter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrostatic chuck for attracting and fixing a substrate to be attracted by electrostatic force. More specifically, the present invention relates to increasing wear resistance during processing of a substrate to be attracted and controlling the in-plane temperature of the substrate to be attracted to a desired temperature. It is related with the electrostatic chuck which can do.

  For example, as shown in FIG. 12, the conventional electrostatic chuck 1 is used as a part of a mounting body of a plasma processing apparatus when plasma processing is performed on a substrate to be attracted (for example, a wafer) W. It is used for adsorbing and fixing to the upper surface of the mounting body 2 by electrostatic force. A focus ring 3 is disposed around the mounting surface of the mounting body 2, and the wafer W on the electrostatic chuck 1 is surrounded by the focus ring 3.

  Further, a high frequency power source 4 is connected to the mounting body 2 through a matching unit 4A, and a predetermined high frequency power is applied from the high frequency power source 4 under a predetermined degree of vacuum between the upper electrode (not shown). Process gas plasma is generated and focused on the upper surface of the wafer W by the focus ring 3. A coolant passage 2A is formed inside the mounting body 2, and the mounting body 2 is cooled by circulating the coolant through the coolant passage 2A, and the wafer W is maintained at a predetermined temperature. In addition, a gas passage 2B of a heat conductive gas (for example, He gas) is formed inside the mounting body 2, and the gas passage 2B is opened at a plurality of locations on the top surface of the mounting body 2.

  A through hole 1A corresponding to the gas passage 2B is formed in the electrostatic chuck 1, and the He gas supplied from the gas passage 2B is supplied to the gap between the mounting body 2 and the wafer W from the through hole 1A of the electrostatic chuck 1. Then, thermal conductivity is imparted to the slit between the electrostatic chuck 1 and the wafer W, and the wafer W is efficiently cooled by the mounting body 2. The electrostatic chuck 1 is formed of, for example, an alumina sintered body or a ceramic made of alumina spraying, and an electrode plate 1B connected to a DC power source 5 is interposed therein. The electrostatic chuck 1 electrostatically attracts the wafer W with an electrostatic force generated by a high voltage applied from the DC power supply 5. In addition, a plurality of lifter pins (not shown) are provided on the mounting body 2 so as to be movable up and down, and the wafer W is transferred on the electrostatic chuck 1 by these lifter pins.

  By the way, the electrostatic chuck by ceramic spraying has a brittle adsorption surface of the wafer W, generates particles composed of the components, and the particles are likely to adhere to the back surface of the wafer W, which causes cross contamination in the cleaning process of the wafer W. There is a problem. Further, the surface of the electrostatic chuck 1 is gradually roughened and the surface state is changed while the operation of attracting and separating the wafer W is repeated, and the wafer temperature cannot be controlled as in the initial stage, and the wafer temperature is changed with time. There was also a problem of change.

  On the other hand, the electrostatic chuck 1 formed of an alumina sintered body or the like is disclosed in, for example, Patent Document 1 and Patent Document 2. Patent Document 1 describes an electrostatic chuck with improved corrosion resistance against halogen-based plasma. Further, Patent Document 2 describes an electrostatic chuck having a plurality of dots formed on the surface. In the case of these electrostatic chucks, the above-described problems can be solved.

Japanese Patent No. 3348140 JP 2000-332091 A

  However, in the case of the electrostatic chuck described in Patent Document 1, plasma resistance can be improved. However, as in the case of ceramic spraying, the gap between the electrostatic chuck and the wafer W is narrow, and the electrostatic chuck Therefore, when the wafer W is pulled away from the electrostatic chuck using the lifter pins, there is a possibility that the wafer W may be flipped up by the lifter pins due to the adsorption force due to the residual charge of the electrostatic chuck.

  Further, in the case of the electrostatic chuck described in Patent Document 2, since a large number of dots are formed on the attracting surface, the problem relating to the flip-up of the wafer W can be solved. However, the dot height of the electrostatic chuck is as low as 5 μm or less, and even when a heat conductive gas is supplied to the gap between the electrostatic chuck and the wafer W, it is difficult to spread uniformly over the entire surface of the wafer W. It cannot be controlled, and a radial groove is provided on the surface of the electrostatic chuck so that the heat conductive gas spreads over the entire surface of the wafer W. However, heat generated by the heat conductive gas in the groove portion and the other portions is used. There is a problem that it is difficult to uniformly control the in-plane temperature, which easily causes a difference in transmission. In addition, since the contact area between the dots and the wafer W is as large as 20%, it has not been possible to control the temperature or temperature distribution to a desired temperature with the heat conductive gas. Further, in the case of this electrostatic chuck, the plasma resistance is not clear.

  The present invention has been made in order to solve the above-mentioned problems, and does not cause the substrate to be adsorbed to jump due to residual charges, and can improve plasma resistance and wear resistance, as well as the in-plane temperature of the entire surface of the substrate to be adsorbed. It is an object of the present invention to provide an electrostatic chuck capable of quickly and uniformly controlling a desired temperature or temperature distribution.

  The electrostatic chuck according to claim 1 of the present invention is an electrostatic chuck that attracts a substrate to be attracted using electrostatic force, and the electrostatic chuck has a plurality of protrusions that are in contact with the substrate to be attracted. And the protrusion is formed of a ceramic dielectric containing crystal particles having a predetermined particle size, and the contact surface of the protrusion with the substrate to be adsorbed is a surface roughness depending on the particle size. It is characterized by forming at a time.

  The electrostatic chuck according to a second aspect of the present invention is the electrostatic chuck according to the first aspect, wherein the particle size is 1 to 2 μm, and the surface roughness of the contact surface is Ra 0.2 to 0.3 μm. It is characterized by being.

  According to a third aspect of the present invention, in the electrostatic chuck according to the first or second aspect, the ceramic dielectric is mainly composed of aluminum oxide. .

  According to a fourth aspect of the present invention, in the electrostatic chuck according to the third aspect, the ceramic dielectric contains silicon carbide.

  Further, in the electrostatic chuck according to claim 5 of the present invention, in the invention according to any one of claims 1 to 4, the hardness of the protrusion is set to Hv 2000 or more in terms of Vickers hardness. It is characterized by.

  An electrostatic chuck according to a sixth aspect of the present invention is the electrostatic chuck according to any one of the first to fifth aspects, wherein the plurality of protrusions contact each unit area of the substrate to be attracted. The area ratio is set to 15% or less.

  The electrostatic chuck according to claim 7 of the present invention is the electrostatic chuck according to claim 6, wherein the protrusion is formed as a cylindrical protrusion having a diameter of 0.5 mm or less. It is.

  The electrostatic chuck according to claim 8 of the present invention is characterized in that, in the invention according to claim 6 or 7, the distance between the plurality of protrusions is set to 1 mm or less. It is.

  The electrostatic chuck according to claim 9 of the present invention is characterized in that, in the invention according to any one of claims 6 to 8, the height of the protrusion is set to 30 μm or more. It is what.

  An electrostatic chuck according to a tenth aspect of the present invention is the electrostatic chuck according to any one of the first to ninth aspects, wherein the surface roughness of the contact surface is reached over time by plasma cleaning. It is characterized in that the surface roughness is set to be possible.

  An electrostatic chuck according to an eleventh aspect of the present invention uses an electrostatic force to adsorb a substrate to be adsorbed and supplies a heat conduction gas to the back surface of the substrate to be adsorbed without a groove. An electrostatic chuck having a mechanism for cooling a substrate to be attracted, wherein the electrostatic chuck has a plurality of protrusions in contact with the substrate to be attracted, and a unit area of the substrate to be attracted of the protrusions The hit contact area ratio is set to 15% or less, and the height of the protrusion is set to 30 μm or more.

  According to a twelfth aspect of the present invention, in the electrostatic chuck according to the eleventh aspect, the protrusion is formed as a columnar protrusion having a diameter of 0.5 mm or less. It is.

  According to a thirteenth aspect of the present invention, in the electrostatic chuck according to the eleventh or twelfth aspect, the surface roughness of the contact surface is set to Ra 0.25 μm or less. Is.

  Further, in the electrostatic chuck according to claim 14 of the present invention, in the invention according to any one of claims 11 to 13, the distance between the plurality of protrusions is set to 1 mm or less. It is characterized by.

  The electrostatic chuck according to a fifteenth aspect of the present invention is the electrostatic chuck according to any one of the eleventh to fourteenth aspects, wherein the electrostatic chuck is disposed on the outer peripheral edge and the inner side thereof. First and second annular projections that are in contact with the suction substrate and formed between the first and second annular projections and inside the second annular projection, respectively. It has the 1st and 2nd gas supply port which supplies the gas for thermal conduction in an area | region, respectively, It is characterized by the above-mentioned.

  According to a sixteenth aspect of the present invention, in the electrostatic chuck according to the fifteenth aspect, the width of the second annular protrusion is set to 1.0 mm to 1.5 mm and the second annular protrusion is set. The distance from the protrusion adjacent to the protrusion is set to 2 mm or less.

  An electrostatic chuck according to a seventeenth aspect of the present invention is an electrostatic chuck that attracts a substrate to be attracted using electrostatic force, and the electrostatic chuck is formed on the outer peripheral edge and the inside thereof. 1st, 2nd which has the 1st, 2nd annular projection part which contacts a substrate to be attracted, and is formed between the 1st, 2nd annular projection parts, and the inside of the 2nd annular projection part, respectively The first and second gas supply ports for supplying the heat conduction gas respectively in the region are provided.

  An electrostatic chuck according to an eighteenth aspect of the present invention is the electrostatic chuck according to the seventeenth aspect, wherein the first region and the second region are different from the first and second annular protrusions, respectively. The first protrusion and the second protrusion have a contact area with the substrate to be adsorbed, a number density of the protrusions, and a height of the protrusions. At least one of the above is different.

  An electrostatic chuck according to a nineteenth aspect of the present invention is the electrostatic chuck according to the eighteenth aspect, wherein the ratio of the contact area of the first protrusion with the substrate to be attracted is determined by the second protrusion. It is characterized in that it is set larger than the contact area ratio with the suction substrate.

  An electrostatic chuck according to a twentieth aspect of the present invention is the electrostatic chuck according to the nineteenth aspect, wherein the contact area ratio of the second protrusion to the attracted substrate per unit area is 15% or less. It is characterized by setting.

  The electrostatic chuck according to claim 21 of the present invention is characterized in that, in the invention according to claim 18, the height of the first protrusion is set lower than the height of the second protrusion. To do.

  Further, in the electrostatic chuck according to claim 22 of the present invention, in the invention according to any one of claims 18 to 21, the height of the second protrusion is set to 30 μm or more. It is characterized by.

  An electrostatic chuck according to a twenty-third aspect of the present invention is the electrostatic chuck according to any one of the eighteenth to twenty-second aspects, wherein the number density of the first protrusions is set to be equal to that of the second protrusions. It is characterized by being set larger than the number density.

  An electrostatic chuck according to a twenty-fourth aspect of the present invention is the electrostatic chuck according to any one of the eighteenth to twenty-third aspects, wherein each of the first and second protrusions has a cylindrical shape with the same diameter. And each diameter is 0.5 mm or less.

  According to the invention described in claims 1 to 24 of the present invention, the plasma resistance and the wear resistance can be improved, the in-plane temperature of the entire surface of the substrate to be adsorbed can be controlled uniformly, and the An electrostatic chuck that can stabilize the temperature controllability of the suction substrate can be provided.

  When the electrostatic chuck of the present invention is used, for example, in a plasma processing apparatus, suitable results have been obtained. Hereinafter, an electrostatic chuck used in the plasma processing apparatus will be described as an example.

Hereinafter, the present invention will be described based on the embodiments shown in FIGS.
For example, as shown in FIG. 1, the plasma processing apparatus 10 of the present embodiment has a chamber 11 that can maintain a high vacuum, and a substrate that is placed in the chamber 11 and on which a substrate to be adsorbed (for example, a wafer) W is placed. A mounting body 12 and an insulator 13 that electrically insulates the mounting body 12 from the chamber 11 are provided, and a predetermined degree of vacuum is maintained by a vacuum exhaust system 14 connected to the chamber 11 via an exhaust pipe 14A. A predetermined plasma process is performed on the wafer W in the chamber 11.

  The placement body 12 includes an electrode 15 and an electrostatic chuck 16 attached to the electrode 15 with an adhesive. A high frequency power supply 17 is connected to the electrode 15, and a predetermined high frequency power is applied from the high frequency power supply 17 to the electrode 15 to generate plasma in the chamber 11. In addition, a coolant channel 15A is formed in the electrode 15, a predetermined coolant is supplied into the coolant channel 15A, and the wafer W is controlled to a predetermined temperature via the electrode 15 and the electrostatic chuck 16. As will be described later, a high voltage DC power source 18 is connected to the electrostatic chuck 16, and a high voltage is applied from the high voltage DC power source 18 to the electrostatic chuck 16 to generate an electrostatic force on the electrostatic chuck 16. The wafer W is adsorbed and fixed on 16.

  Further, a heat conductive gas such as He gas is supplied to the mounting body 12 and the heat conductivity between the electrostatic chuck 16 and the wafer W is increased by the heat conductive gas as will be described later. Is controlled uniformly. That is, a supply source 19 for supplying a heat conductive gas is connected to the mounting body 12 via a gas pipe 19A, and the gas pipe 19A is branched into two systems of first and second branch pipes 19B and 19C. Yes. First and second gas pressure controllers 20A and 20B and valves 21A and 21B are attached to the first and second branch pipes 19B and 19C, respectively, and the first and second branches are provided by these valves 21A and 21B. The pipes 19B and 19C are opened and closed, and the pressure of the heat conductive gas is controlled by the gas pressure controllers 20A and 20B. The first and second branch pipes 19B and 19C further branch on the upstream side of the valves 21A and 21B, and are connected to the vacuum exhaust system 14 via the valves 22A and 22B and the orifices 23A and 23B. The heat conductive gas is kept at a predetermined supply pressure.

  Thus, as shown in FIGS. 1, 2, and 4, the electrostatic chuck 16 includes a ceramic dielectric 16A bonded to the electrode 15 with an adhesive A, and an electrode formed in the ceramic dielectric 16A. And the layer 16B. A large number of protrusions 16C are uniformly distributed on the entire surface of the electrostatic chuck 16 on the suction surface, that is, the upper surface of the ceramic dielectric 16A. By providing a large number of protrusions 16C in this way, the influence of residual charges in the electrostatic chuck 16 can be reduced, and jumping up when the wafer W is separated from the electrostatic chuck 16 can be prevented. For example, as shown in FIG. 2, these protrusions 16 </ b> C are arranged at substantially equal intervals, and each upper end is formed flat as a contact surface with the wafer W.

  The contact area of the plurality of protrusions 16C with the wafer W is preferably set to 15% or less per unit area of the wafer W. The smaller the ratio of the contact area to the wafer W, the easier it is to control the wafer temperature with the thermally conductive gas, but if it is too small, the protrusion formed of ceramic having a higher thermal conductivity than the thermally conductive gas. The heat conduction between the wafer W and the refrigerant through the part 16C is reduced, and the equilibrium temperature of the wafer W is increased. If the contact area ratio per unit area of the wafer W exceeds 15%, the temperature controllability by the heat conductive gas is lowered, which is not preferable. In this embodiment, it is set to 15% in order to realize a desired equilibrium temperature and temperature controllability.

  The controllability of the wafer temperature by the heat conductive gas greatly varies depending on the total gas contact area between the bottom surface between the protrusions 16C and the side surface of the protrusion 16C. That is, the heat conduction to the wafer W by the thermally conductive gas is not limited to the heat conduction from the portion in direct contact with the back surface of the wafer W, but the protrusion 16C is formed from the bottom surface between the protrusions 16C and the side surface of the protrusion 16C. There is heat conduction through. Therefore, the larger the total gas area, the better the heat conduction efficiency with the heat conductive gas.

  When the total contact area of the wafer W and the protruding portion 16C is the same, the higher the height of the protruding portion 16C, the larger the area of the side surface of the protruding portion 16C, and the larger the total gas contact area, which is preferable. Further, when a plurality of protrusions having the same shape in the horizontal cross section at an arbitrary height of each protrusion 16C are formed, the smaller the horizontal cross section (contact surface with the wafer W) of each protrusion 16C is, the smaller the protrusion is. This is preferable because the total gas contact area becomes large.

  The protrusion 16C preferably has a contact area ratio [(protrusion surface contact portion / wafer area) × 100%] per unit area of the wafer W and the protrusion 16C set to 15% or less. Considering the controllability of the wafer temperature, the protrusion 16C preferably has a diameter of 0.5 mm or less and a height of 30 μm or more, and more preferably 40 μm or more. Further, if the aspect ratio (height / diameter) of the diameter and height of the protrusion 16C is greater than 1, the protrusion 16C may be damaged due to rubbing with the wafer W or the like. The upper limit is preferably set to a range of 1 or less in terms of aspect ratio. Each protrusion 16C has, for example, a columnar shape, a horizontal section diameter of 0.5 mm, and a height of 30 μm.

  In order to increase the total side surface area of the protruding portion 16C, the horizontal cross-sectional shape may be an elliptical shape or a rectangular shape instead of a circular shape, and the side surface of the protruding portion 16C is not a vertical surface but is inclined or stepped. A structure having a large lower cross section may be used. In addition, it is preferable that the edge portion at the tip of the protrusion 16C has a curved shape in order to suppress generation of particles due to shaving. In this case, the contact surface with the wafer W is only the portion that does not include the curved surface portion and contacts the wafer W.

  Further, as shown in FIG. 4, the distance δ between the plurality of protrusions 16C is 2 mm or less, preferably 1 mm or less, more preferably approximately equal to the thickness t of the wafer W or shorter than the thickness t. It is preferable that it is set. By setting the distance δ and the thickness t substantially equal, the time for transferring heat from the upper surface of the protrusion 16C to the surface of the wafer W is substantially equal to the time for transferring heat from the protrusion 16C to the adjacent protrusion 16C. The temperature difference between the protrusion 16C and the space on the W surface is reduced.

  Further, it is preferable that the protrusion 16C has a high height because the heat conductive gas instantaneously reaches the entire space between the electrostatic chuck 16 and the wafer W. Taking such points into consideration, the height of the protrusion 16C is preferably set to the above-described height of 30 μm or more, more preferably 40 μm or more. If it is less than 30 μm, it takes a long time for the thermally conductive gas to reach the entire space between the electrostatic chuck 16 and the wafer W, and the controllability of the wafer temperature may be reduced. Data demonstrating this is shown in FIG. FIG. 5 is a graph showing the relationship between the arrival distance of the thermally conductive gas and the time on the wafer W when the height of the protrusion 16C is 10 μm and 30 μm. As is apparent from FIG. 5, when the height of the protrusion 16C is 10 μm, the arrival time of the heat conductive gas increases abruptly as the distance from the gas supply unit increases, but the height is 30 μm or more. In this case, it can be seen that the entire wafer W is reached instantaneously.

  Furthermore, when the height of the protrusion 16C is as low as about 10 μm, a gas diffusion mechanism such as a groove is provided on the bottom surface where the protrusion 16C is formed, and the heat conductive gas is quickly supplied via the gas diffusion mechanism. It was necessary to diffuse and reach the entire wafer W in a short time. In the present embodiment, as described above, by setting the height of the protruding portion 16C to 30 μm or higher, there is no need to provide a gas diffusion mechanism, reducing the manufacturing cost and causing problems such as uneven temperature in the groove. It does not occur.

  As shown in FIGS. 1 and 3, the outer peripheral edge of the electrostatic chuck 16 is formed with a first annular protrusion 16D having the same height as many protrusions 16C, and the annular protrusion 16D is used to It functions as a seal ring that seals the heat conductive gas supplied to the gap between the electric chuck 16 and the wafer W within the wafer W surface. A second annular projection 16E is formed on the inner side of the first annular projection 16D, concentrically with the first annular projection 16D, at the same height as the plurality of projections 16C, and this annular projection 16E. Thus, the region in the first annular protrusion 16D is divided into two. That is, as shown in FIG. 3, a ring-shaped first region 16F is formed between the first annular protrusion 16D and the second annular protrusion 16E, and is formed inside the second annular protrusion 16E. A circular second region 16G is formed, and the second annular protrusion 16E functions as a seal ring between the first and second regions 16F and 16G. Note that the protrusion 16C is not shown in FIG.

  Accordingly, when the wafer W is electrostatically attracted by the electrostatic chuck 16, the wafer W comes into contact with the multiple protrusions 16 </ b> C and the first and second annular protrusions 16 </ b> D and 16 </ b> E, respectively, and between the wafer W and the electrostatic chuck 16. In addition, two spaces corresponding to the first and second regions 16F and 16G are formed. Hereinafter, the spaces corresponding to the first and second regions 16F and 16G will be referred to as first and second spaces 16F and 16G as necessary.

  Thus, a plurality of first and second gas supply ports 16H and 16I are formed in the first and second regions 16F and 16G, respectively, as shown in FIG. 3, and these gas supply ports 16H and 16I are formed. As will be described later, the first and second branch pipes 19B and 19C are connected to each. In FIG. 3, 16J is a hole through which the lifter pin 24 moves up and down.

  As shown in FIG. 1, the first and second branch pipes 19B and 19C are connected to the first and second annular recesses 13A and 13B formed on the upper surface of the insulator 13, and these annular recesses 13A and 13B are connected. A heat conductive gas is supplied inside. As shown in the figure, the electrode 15 and the electrostatic chuck 16 are formed with first and second communication passages 25 and 26 communicating with the first and second regions 16F and 16G, respectively. Therefore, the heat conductive gas of the gas supply source 19 is supplied from the first and second branch pipes 19B and 19C, the first and second annular recesses 13A and 13B, the first and second communication passages 25 and 26, and the first and second communication passages 25 and 26. 1. It reaches the first and second spaces 16F, 16G of the electrostatic chuck 16 via the second gas supply ports 16H, 16I.

  The space between the electrostatic chuck 16 and the wafer W is supplied into the spaces 16F and 16G by dividing the space into first and second spaces 16F and 16G by the first and second annular protrusions 16D and 16E. The pressure of the thermally conductive gas can be individually controlled. When the plasma processing of the wafer W is performed, the temperature of the outer peripheral edge portion of the wafer W becomes higher than that of the inner side. Therefore, the pressure of the heat conductive gas in the first space 16F is set high, for example, 40 Torr to increase the heat conductivity, and the pressure of the heat conductive gas in the second space 16G is set low, for example, 10 Torr. By setting the thermal conductivity in the first space 16F higher than the thermal conductivity in the second space 16G, the temperature of the entire surface of the wafer W can be controlled uniformly.

  Further, if the protrusions 16C in the first and second spaces 16F and 16G are defined as first and second protrusions, respectively, the contact area ratio of the first protrusions to the wafer W is set to the second Although the heat conduction between the wafer W and the coolant through the protrusion 16C can be increased by setting the protrusion area larger than the contact area ratio of the wafer W, the temperature of the entire wafer W can be uniformly controlled. The temperature controllability by the heat conduction gas at the periphery of the wafer is lower than that inside. At this time, by setting the number density of the first protrusions to be larger than the number density of the second protrusions with the same contact area ratio, the temperature controllability by the thermally conductive gas at the peripheral edge of the wafer W can be improved. Further, by setting the height of the first protrusion to be lower than the height of the second protrusion, the temperature of the wafer peripheral portion can be similarly lowered.

  In this way, by adopting a configuration in which the space between the electrostatic chuck 16 and the wafer W is divided into two and the pressure of the heat conductive gas is controlled independently, the wafer temperature at the periphery and the center of the wafer W can be adjusted. Since it can be controlled independently, for example, even if the plasma state is non-uniform, it is possible to uniformly control the etching rate, etching shape, etc. in the wafer W surface.

  The distance between the second annular protrusion 16E and the nearest protrusion 16C arranged in a ring shape in the first and second spaces 16F and 16G is 2 mm or less, preferably 1 mm or less, more preferably It is preferably set to be substantially equal to the thickness t of the wafer W or shorter than the thickness t. A groove having a plurality of types of widths is provided between the protrusion regions that are considered to be structures that are more likely to have an influence in order to observe the influence of the gap between the second annular protrusion 16E and the nearest protrusion 16C on heat conduction. The case was verified.

FIGS. 6A and 6B show the results of heat conduction analysis performed under the following setting conditions using the finite element method. That is, the temperature distribution and temperature difference distribution in the wafer shown in FIGS. 6A and 6B are as follows: the contact area ratio of the protrusion region is 15%, the height is 30 μm, the backside gas pressure is 15 Torr, and the wafer thickness. The temperature of the lower electrode is set to 25 ° C. so that the temperature of the wafer W becomes 60 ° C., the heat input to the wafer is 3.4 W / cm ² , and the groove depth (infinite The calculation results are shown in which the length) is set to 100 μm, which is more easily affected, and the groove width is set to five types of 0 mm, 1 mm, 2 mm, 3 mm, and 4 mm.

  Further, the wafer coated with the resist under the above conditions was actually etched by oxygen plasma, and the etching speed was measured. When the groove width was 1.7 mm, the resist was etched and the effect of etching on the groove was not affected. Confirmed that there is no. Comparing the analysis results with the experimental results, in the analysis results shown in FIGS. 6A and 6B, when the groove width is 2 mm, the temperature difference between the center of the wafer groove width and the periphery thereof is about 1 ° C. From this, it can be seen that the groove width is preferably set to 2 mm or less in order to suppress the temperature difference around the groove to 1 ° C. or less. At this time, if the interval between the protrusions is larger than the groove width, the temperature difference becomes large. Therefore, it is preferably set to 1 mm or less, and more preferably set to the thickness of the wafer W or less. In the present embodiment, the distance between the second annular protrusion 16E and the nearest protrusion 16C is set to 0.5 mm. Therefore, even if the electrostatic chuck 16 is formed on the back surface of the wafer W by the protrusion 16C having a small contact area ratio, a desired temperature distribution is realized over the entire surface of the wafer W without being affected by the second annular protrusion 16E. be able to.

  Backside gas (He) under the conditions that the contact area ratio per unit area between the wafer W and the protrusion 16C is 15%, each protrusion 16C is cylindrical, the diameter of the horizontal section is 0.5 mm, and the height is 30 μm. When the wafer W is adsorbed with the electrode temperature set at 25 ° C. so that the pressure is 5 Torr at the center, 40 Torr at the peripheral portion, and the temperature of the wafer W is 60 ° C., the temperature is 95% of the ultimate equilibrium temperature. The time required to reach 14.4 seconds was approximately the same temperature response as the conventional ceramic sprayed electrostatic chuck. Therefore, in order to improve the temperature responsiveness, the contact area ratio per unit area between the wafer W and the protrusion 16C is set to 15% or less, and the horizontal cross section of the cylindrical protrusion 16C (with the same contact area ratio) It was demonstrated that it is preferable to set the diameter of the contact surface with the wafer) to 0.5 mm or less and the height to 30 μm or more. In this case, since the equilibrium temperature rises, it is preferable to set the cooling capacity high by lowering the refrigerant temperature.

7 (a) and 7 (b) show heat conduction performed on the influence of the seal width of the first and second annular protrusions 16D and 16E on the temperature distribution using the finite element method under the following setting conditions. The result of the analysis is shown. That is, the temperature distribution and temperature difference distribution in the wafer shown in FIGS. 7A and 7B are as follows: the contact area ratio of the protrusion is 15%, the height is 30 μm, the backside gas pressure is 15 Torr, and the wafer thickness. Is set to 0.7 mm, the temperature of the lower electrode is set to 25 ° C. so that the temperature of the wafer W is 60 ° C., the heat input to the wafer is 3.4 W / cm ² , and the seal height is 30 μm. It shows the result of setting and setting the seal width to 5 types of 0 mm, 0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm.

  Furthermore, since the temperature difference is preferably within about 1 ° C. from the point of resist etching rate, it has been found that the seal width is preferably set to 1.5 mm or less. At this time, if the seal width is too narrow, the backside gas may leak, so it is preferable to set it to 1 mm or more. Regarding the gas leak, when the surface roughness Ra of the annular protrusion is 0.2 to 0.3 μm, a seal width of 3 mm or more is required to suppress the leak amount to 1 sccm or less. In the case of the second annular protrusion 15E, even if there is a slight leak, there is little influence, so it is preferable to set it in the range of 1.0 to 1.5 mm.

  Thus, the ceramic dielectric 16A forming the electrostatic chuck 16 includes crystal particles having a predetermined average particle diameter, and the contact surface (upper surface) of the protrusion 16C with the wafer W has an average particle diameter of the crystal particles. It is formed (processed) with a surface roughness that depends on. The surface roughness that depends on the average grain size of the crystal grains changes over time as the surface of the ceramic dielectric is sputtered by dry cleaning with plasma, and finally reaches a certain surface roughness and exceeds that surface. This refers to the surface roughness when the roughness is stable without changing. The surface roughness at the time of stabilization becomes smaller as the average particle size of the crystal particles is smaller, and becomes larger as the average particle size of the crystal particles is larger.

  In this embodiment, the average particle diameter of the crystal particles is 1 to 2 μm, and the surface roughness finally reached by dry cleaning with plasma is Ra 0.2 to 0.3 μm. Therefore, the surface roughness of the protrusion 16C is processed in advance to Ra 0.2 to 0.3 μm. As a result, even if dry cleaning is repeated a plurality of times, the surface of the protrusion 16C does not become rougher than the surface roughness, stable heat transfer performance can be maintained from start to finish, and controllability of the wafer temperature is stable from start to finish. When the average grain size of the crystal grains is larger than 2 μm, it is sputtered by plasma treatment and changes with time, and the stable surface roughness becomes larger than 0.3 μm. It is necessary to process to a larger predetermined surface roughness. On the other hand, when the average grain size is smaller than 1 μm, it is sputtered by the plasma treatment and changes with time, and the stable surface roughness becomes smaller than 0.2 μm. It is necessary to process to a predetermined surface roughness smaller than 0.2 μm.

FIG. 8 shows the operation time of the electrostatic chuck of this embodiment having a high Vickers hardness and the electrostatic chuck not included in the present invention (exposing the electrostatic chuck to the O ₂ plasma without placing the wafer W. It is the graph which compared the surface roughness of each projection part 16C with the integration time of wafer dry cleaning). In FIG. 8, the electrostatic chuck of the present embodiment is indicated by ●, and the average particle size of the crystal particles was 1 to 2 μm. In addition, electrostatic chucks not included in the present invention are indicated by ▲, and the average grain size of the crystal grains was 12 μm. As is apparent from this figure, the surface roughness of the electrostatic chuck outside the present invention rapidly increases from about 0.1 μm to 0.6 μm after 40 hours from the start of the operation time, and after 40 hours, the surface roughness increases. It deteriorates in a rough state of 0.5 to 0.6 μm and is almost stable. On the other hand, the electrostatic chuck 16 of the present embodiment slightly increases from a surface roughness of less than 0.1 μm at the start of operation to a little over 0.1 μm after 100 hours of operation, but the roughness due to plasma is slight. I understand.

  Since the surface roughness of the protrusion 16C is stable with the surface roughness depending on the particle size of the crystal particles even if the average particle size of the crystal particles is different, the surface roughness is obtained by processing the surface roughness to be stable in advance. Roughness change with time can be eliminated. That is, in the case of the electrostatic chuck of the present embodiment shown in FIG. 8, it is processed in advance to about Ra 0.25 μm (the control width is Ra 0.2 to 0.3 μm because the processing accuracy varies). In the case of the electrostatic chuck other than the present invention shown in FIG. 4, it can be understood that it should be processed in advance to about Ra 0.5 to 0.6 μm.

  The ceramic dielectric 16A that forms the electrostatic chuck 16 is preferably an alumina sintered body mainly composed of aluminum oxide, and the sintered body preferably contains silicon carbide. Hardness and wear resistance can be increased by adding silicon carbide. The electrostatic chuck 16 is more preferably a sintered body fired under high temperature and pressure. By baking under high temperature and high pressure, the electrostatic chuck 16 can be further increased in hardness, can have a Vickers hardness of Hv2000 or higher, and can further improve plasma resistance and wear resistance. As a result, it is possible to prevent the upper surface of the protrusion 16C from being roughened by the wafer W being attracted or pulled away.

  FIG. 9 is a graph comparing the plasma resistance of the sintered body used in the electrostatic chuck 16 of the present embodiment and other ceramics. In FIG. 9, the sintered body used in this embodiment is shown as Sample No. 3 containing silicon carbide and fired under high temperature and high pressure, and the Vickers hardness Hv was 2200. The other sample No. 1 was a general electrostatic chuck by alumina spraying, and its Vickers hardness Hv was 1000. Sample No. 2 was an electrostatic chuck made of a ceramic dielectric obtained by sintering a green sheet of aluminum oxide under normal pressure, and its Vickers hardness Hv was 1000. Sample No. 4 is an electrostatic chuck made of a ceramic dielectric composed mainly of aluminum oxide and sintered under a condition different from that of No. 2 under normal pressure, and its Vickers hardness Hv is 1400. . As is clear from FIG. 9, it can be seen that any sample other than the present embodiment has a Vickers hardness Hv lower than 2000, a high consumption rate due to plasma, and poor plasma resistance.

  FIG. 10 is a graph showing the relationship between the surface roughness of the protrusion 16C and the waferless dry cleaning time in the electrostatic chuck 16 of this embodiment. As the electrostatic chuck 16, a sintered body having an alumina particle crystal grain size of about 1 μm is used. As shown in FIG. 10, the protrusion 16 C has a surface roughness Ra in the range of 0.09 to 0.29 μm. Then, the relationship between each electrostatic chuck 16 and the dry cleaning time was observed. As is apparent from FIG. 10, it was demonstrated that the electrostatic chuck 16 having any surface roughness converges to a certain surface roughness with the passage of the cleaning time. And it turns out that this convergence value is Ra0.25micrometer. This value was 1.7 μm in terms of other surface roughness Ry. The plasma potential (Vpp) at the time of waferless dry cleaning was 600V.

  FIG. 11 shows the relationship between the surface roughness of the protrusion 16C and the wafer temperature with respect to various pressures of the heat conductive gas (He gas). As is clear from FIG. 11, when the surface roughness Ra of the protrusion 16C is larger than 0.2 μm, the wafer temperature gradually increases, and the cooling efficiency from the mounting body 12 side gradually decreases. I understand. In particular, the cooling efficiency tends to decrease sharply from the surface roughness Ra of around 0.27 μm. However, it can be seen that when the surface roughness Ra is smaller than 0.2 μm, a substantially constant cooling efficiency is exhibited. Accordingly, even if the surface roughness Ra of the protrusion 16C is in the range of 0.2 to 0.25 μm of the present invention, the thermal conductive gas pressure is 8 ° C. at 10 Torr and 3 ° C. at 40 Torr. The fluctuation can be suppressed and stable cooling efficiency can be maintained. That is, the influence of the surface roughness Ra is small when the surface roughness Ra of the protrusion 16C tip is 0.25 μm or less, and a substantially constant cooling efficiency is exhibited when the surface roughness Ra is 0.2 μm or less. Note that 40 Torr and 10 Torr are pressures in the first and second spaces 16F and 16G of the electrostatic chuck 16 of the present embodiment.

  When finishing the tip surface of the protrusion 16C, the surface roughness Ra is preferably set to 0.25 μm or less, more preferably 0.2 μm or less, so that the surface roughness Ra slightly changes due to processing variations or the like. However, the cooling efficiency is hardly affected by the surface roughness Ra. Even if the tip surface of the protrusion 16C is designed to have a predetermined contact area, the actual contact area is actually smaller than the actual design value due to the influence of the surface roughness Ra. When the surface roughness Ra is large, the equilibrium temperature of the wafer W increases as shown in FIG. 11 even with the same backside gas pressure. Therefore, when designing an electrostatic chuck, it is necessary to set the surface roughness Ra small to lower the equilibrium temperature. As described above, the surface roughness Ra is 0.25 μm or less, more preferably 0.2 μm or less.

  As described above, according to this embodiment, the electrostatic chuck 16 has the plurality of protrusions 16C that come into contact with the wafer W, and the protrusions 16C have alumina crystal particles having an average particle diameter of 1 to 2 μm. Since the contact surface of the protrusion 16C with the wafer W is processed to a surface roughness (0.2 to 0.3 μm) depending on the average particle diameter, the plasma resistance is increased. The surface roughness of the protrusions 16C hardly changes even when dry cleaning is repeated, and the controllability of the wafer temperature can be improved and the controllability of the wafer temperature can be stabilized. Further, when the wafer W is pulled away from the electrostatic chuck 16, there is no splashing of the wafer W due to residual charges and no contamination from the electrostatic chuck 16.

  Moreover, according to this embodiment, since the ceramic dielectric of the electrostatic chuck 16 contains silicon carbide, the hardness and wear resistance can be further improved. Further, since the Vickers hardness of the protrusion 16C is set to Hv2000 or more, it is possible to improve the wear resistance by dry cleaning using plasma.

  Further, since the contact area ratio per unit wafer area of the plurality of protrusions is set to 15% or less, the controllability of the wafer temperature can be further improved, and the entire surface of the wafer W can be controlled to a desired temperature. Further, since the contact surface of each protrusion 16C is formed in a columnar shape having a diameter of 0.5 mm or less, the heat conductivity by the protrusion 16C and the heat conductive gas is good, and the heat conductivity that contacts the wafer W is good. In combination with heat transfer from the gas, the wafer can be controlled to a desired temperature. In addition, since the distance δ between the plurality of protrusions 16C and 16C is set to be equal to or less than the distance t corresponding to the thickness t of the wafer W, the wafer portion that does not contact the protrusion 16C and the wafer portion that contacts the protrusion 16C are uniformly heated. As a result, the entire surface of the wafer W can be cooled to a desired temperature.

  Furthermore, since the protrusion 16C is set to a height of 30 μm or more, the heat conductive gas can be spread over the entire wafer W in a short time without forming a groove for the heat conductive gas, and the temperature of the entire surface of the wafer W can be increased. Can increase the responsiveness. The electrostatic chuck 16 has first and second annular protrusions 16D and 16E, and is provided between the first and second annular protrusions 16D and 16E and inside the second annular protrusion 16E. Since the first and second spaces 16F and 16G formed respectively have the first and second gas supply ports 16H and 16I for supplying the heat conduction gas, respectively, the first and second spaces 16F and 16G are provided. The temperature tends to increase by individually controlling the pressure of the heat conduction gas supplied into the first space 16F and setting the pressure of the heat conduction gas in the first space 16F higher than that in the second space 16G. The temperature of the outer peripheral edge of the wafer W can be cooled more efficiently than the inside, and the entire surface of the wafer W can be controlled to a desired temperature.

  In addition, this invention is not restrict | limited to the said embodiment at all. It is included in the present invention unless the gist of the present invention is changed.

  The present invention can be used as an electrostatic chuck for a plasma processing apparatus or the like.

It is a block diagram which shows the plasma processing apparatus to which one Embodiment of the electrostatic chuck of this invention is applied. It is a top view which expands and shows the distribution state of the projection part of the electrostatic chuck shown in FIG. It is a top view which shows the electrostatic chuck shown in FIG. It is a fragmentary sectional view which expands and shows the principal part of the electrostatic chuck shown in FIG. It is a graph which shows the relationship between the height of the protrusion part of the electrostatic chuck shown in FIG. 1, the arrival distance and arrival time of the heat conductive gas in a wafer. The graph which shows the heat conduction analysis result for observing the influence on the wafer temperature of the surface groove | channel of an electrostatic chuck, (a) is a graph which shows the groove width and the temperature distribution of the wafer in the vicinity, (b) is the temperature difference It is a graph which shows distribution. The graph which shows the heat conduction analysis result for observing the influence on the wafer temperature of the annular protrusion part of an electrostatic chuck, (a) is a graph which shows the temperature distribution of the wafer in the seal width and its vicinity, (b) is the temperature. It is a graph which shows difference distribution. It is a graph which shows the time-dependent change of the surface roughness of the electrostatic chuck shown in FIG. 1 and the conventional electrostatic chuck. It is a graph which shows the relationship between the electrostatic chuck | zipper shown in FIG. 1, the conventional electrostatic chuck, and the consumption rate by plasma. It is a graph which shows the relationship between the surface roughness of the electrostatic chuck shown in FIG. 1, and dry cleaning. 2 is a graph showing the relationship between the gas pressure of a thermally conductive gas, the surface roughness of the electrostatic chuck shown in FIG. 1, and the wafer W temperature. It is a block diagram which shows the plasma processing apparatus to which the conventional electrostatic chuck is applied.

Explanation of symbols

16 Electrostatic chuck 16A Ceramic dielectric 16C Protrusion 16D First annular protrusion 16E Second annular protrusion 16H First gas supply port 16I Second gas supply port

Claims (24)

  An electrostatic chuck for adsorbing a substrate to be attracted using electrostatic force, wherein the electrostatic chuck has a plurality of protrusions that come into contact with the substrate to be attracted, and the protrusions are formed into predetermined grains. An electrostatic chuck comprising: a ceramic dielectric containing crystal particles having a diameter; and a contact surface of the protrusion with the attracted substrate is formed to have a surface roughness depending on the particle diameter.   The electrostatic chuck according to claim 1, wherein the particle size is 1 to 2 μm, and the surface roughness of the contact surface is Ra 0.2 to 0.3 μm.   The electrostatic chuck according to claim 1, wherein the ceramic dielectric is mainly composed of aluminum oxide.   The electrostatic chuck according to claim 3, wherein the ceramic dielectric contains silicon carbide.   5. The electrostatic chuck according to claim 1, wherein the hardness of the protrusion is set to Hv 2000 or more in terms of Vickers hardness.   The electrostatic chuck according to claim 1, wherein a contact area ratio of the plurality of protrusions per unit area of the substrate to be attracted is set to 15% or less.   The electrostatic chuck according to claim 6, wherein the protrusion is formed as a columnar protrusion having a diameter of 0.5 mm or less.   The electrostatic chuck according to claim 6 or 7, wherein a distance between the plurality of protrusions is set to 1 mm or less.   The electrostatic chuck according to claim 6, wherein a height of the protrusion is set to 30 μm or more.   The electrostatic chuck according to any one of claims 1 to 9, wherein the surface roughness of the contact surface is set to a surface roughness that can be reached with time by plasma cleaning.   An electrostatic chuck having a mechanism for adsorbing a substrate to be adsorbed using electrostatic force and supplying a heat conduction gas to the back surface of the substrate to be adsorbed without a groove to cool the substrate to be adsorbed. The electrostatic chuck has a plurality of protrusions that are in contact with the substrate to be attracted, and sets a contact area ratio of the protrusions per unit area of the substrate to be attracted to 15% or less and the protrusions. The electrostatic chuck is characterized in that the height of is set to 30 μm or more.   The electrostatic chuck according to claim 11, wherein the protrusion is formed as a columnar protrusion having a diameter of 0.5 mm or less.   The electrostatic chuck according to claim 11 or 12, wherein a surface roughness of the contact surface is set to Ra 0.25 µm or less.   The electrostatic chuck according to claim 11, wherein a distance between the plurality of protrusions is set to 1 mm or less.   The electrostatic chuck has first and second annular protrusions that contact the attracted substrate on the outer peripheral edge and the inner side thereof, and between the first and second annular protrusions and the second 15. A first gas supply port and a second gas supply port for supplying heat conduction gas respectively in first and second regions respectively formed inside the annular protrusions. The electrostatic chuck according to any one of the above.   16. The width of the second annular protrusion is set to 1.0 mm to 1.5 mm, and the distance from the protrusion adjacent to the second annular protrusion is set to 2 mm or less. The electrostatic chuck described in 1.   An electrostatic chuck for attracting a substrate to be attracted using electrostatic force, wherein the electrostatic chuck has an outer peripheral edge portion and first and second annular protrusions that are in contact with the substrate to be attracted inside thereof. And first and second heat supply gases for supplying heat conduction gas into first and second regions formed between the first and second annular projections and inside the second annular projection, respectively. An electrostatic chuck having two gas supply ports.   The first region and the second region each have a plurality of first and second protrusions different from the first and second annular protrusions, and the first protrusion and the second protrusion are The electrostatic chuck according to claim 17, wherein at least one of a contact area per unit area with the substrate to be attracted, a number density of the respective protrusions, and a height of each of the protrusions is different. .   The contact area ratio per unit area of the first protrusion with the substrate to be adsorbed is set larger than the contact area ratio of the second protrusion with the substrate to be adsorbed per unit area. Item 19. The electrostatic chuck according to Item 18.   The electrostatic chuck according to claim 19, wherein a contact area ratio per unit area of the second protrusion with the attracted substrate is set to 15% or less.   The electrostatic chuck according to claim 18, wherein the height of the first protrusion is set lower than the height of the second protrusion.   The electrostatic chuck according to any one of claims 18 to 21, wherein the height of the second protrusion is set to 30 µm or more.   The electrostatic chuck according to any one of claims 18 to 22, wherein the number density of the first protrusions is set larger than the number density of the second protrusions.   24. The static according to any one of claims 18 to 23, wherein each of the first and second protrusions has a columnar shape with the same diameter, and each diameter is 0.5 mm or less. Electric chuck.

Images