JP2010123843A - Electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that many particles are generated at the time when a workpiece is gradually removed by a lift pin, due to the fact that the contact time and gliding time with the vertex surface of the projection part of an attraction surface on the internal circumference portion of the workpiece removed at the end are longer than those of the external circumference portion removed at the beginning, because of the warpage of the workpiece. <P>SOLUTION: An electrostatic chuck 1 includes an electrostatic attraction electrode 3 on one principal plane or the inside of a plate shape ceramic body 2, and an attraction surface 2a for attracting and holding a wafer on the other principal plane. In the electrostatic chuck 1 having many convex parts 6 on the attraction surface 2a, the projection portion 6 includes a surface R 9 between the vertex surface 8 and a circumference surface 10, and the curvature of the surface R 9 is larger in the area of the internal side than in the area of the external circumference of the attraction surface 2a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a static film used for fixing, correcting, and transporting a workpiece such as a silicon wafer for semiconductor use, for example, in a film forming apparatus and an etching apparatus such as a PVD apparatus, a CVD apparatus, an ion plating apparatus, and a vapor deposition apparatus. The present invention relates to an electric chuck.

  Conventionally, in a film forming apparatus and an etching apparatus such as a PVD apparatus, a CVD apparatus, an ion plating apparatus, and a vapor deposition apparatus, the surface of a plate-like body finished flat and smooth is processed in order to fix the object to be processed with high accuracy. An object is forcibly adsorbed, and an electrostatic chuck using electrostatic attraction force is used as the adsorbing means.

  Conventional electrostatic chucks used in these film forming apparatuses and etching apparatuses include an electrode for electrostatic attraction on one main surface (one widest surface) or inside of a plate-shaped ceramic body, and the above plate-shaped ceramic chuck. The other main surface (the other widest surface) of the ceramic body is an adsorption surface. Then, by applying a voltage to the electrode for electrostatic attraction and expressing electrostatic attraction force such as Coulomb force due to dielectric polarization or Johnson-Rahbek force due to a minute leakage current between the workpiece and the workpiece, Can be forcibly adsorbed and fixed to the adsorption surface.

  In such an electrostatic chuck, a lift pin device for separating a silicon wafer or the like of a workpiece from the attracting surface has one main surface (a workpiece and a workpiece) of a plate-like ceramic body corresponding to the peripheral portion of the workpiece. It is installed on the opposite main surface (back surface) side. For example, a lift pin of a lift pin device moves up and down through a through-hole formed in the peripheral part of a plate-like ceramic body, and the tip of the lift pin pushes up the workpiece when the workpiece is released from the suction surface. The work piece is separated from the suction surface by.

  In recent years, in the above electrostatic chuck, the attracting surface is made an uneven surface by a blast method or the like, and the top surface of the convex portion of the uneven surface or the entire surface of the uneven surface is mirror-polished to be a fixed holding surface of the workpiece, An electrostatic chuck having a structure in which the concave portion of the concave and convex surface is used as a cooling gas supply path such as helium gas is known.

  In such an electrostatic chuck, the total area of the top surface of the convex portion is within a predetermined range with respect to the attracting surface, thereby securing the attraction force of the workpiece, and only the top surface of the convex portion is covered. Since it is the contact surface of the workpiece, it is possible to suitably shorten the workpiece separation time due to residual adsorption.

Furthermore, the structure of the convex portion is not only the top surface of the convex portion, but also a curve between the top surface and the peripheral surface of the convex portion, so that the space between the top surface and the peripheral surface of the convex portion is chamfered, Excess particles (hereinafter also referred to as particles) generated when the workpiece and the convex portion slide and the surface of the workpiece and the surface of the convex portion are finely cut are reduced.
Japanese Patent No. 3784274 Japanese Patent No.4094262

  By the way, in the semiconductor industry using the above-mentioned electrostatic chuck, there is a demand for improvement in added value and cost reduction by integrating more advanced ICs. As an important item that satisfies the requirement, specifically, from the viewpoint of achieving both the miniaturization of wiring and the improvement of yield, particle reduction during semiconductor manufacturing is cited as an even more important issue than before.

  This generation of particles occurs more frequently when the workpiece is detached than when the workpiece is electrostatically attracted to the electrostatic chuck. Improvements have been made (see, for example, Patent Document 2).

  This detachment mechanism is as follows: 1) When lifting the workpiece, the lift pin is raised, and first the outer periphery of the workpiece lifted by the lift pin is detached from the adsorption surface. 2) Subsequently, the workpiece is removed from the adsorption surface. It is a gradual process with a time difference that it gradually separates inward.

  However, regarding the particles generated when the workpiece is detached, the following problems still remain in the conventional electrostatic chuck in which the workpiece is stacked on the top surface of the convex portion.

  That is, when the work piece is stepwise detached by the lift pins, as shown in FIG. 5, the work piece 51 bends, and the region 53 inside the work piece 51 that is finally detached is first detached. The contact and sliding time of the convex portion 56 of the suction surface 52a with the R surface 56c is longer than that of the outer peripheral portion, and there is a problem that particles are generated.

  In FIG. 5, 50 is an electrostatic chuck, 52 is a plate-shaped ceramic body, 56a is the top surface of the convex portion 56, 56b is the peripheral surface of the convex portion 56, 57 is an electrode for electrostatic adsorption, and 58 is a gas introduction hole. It is. FIG. 5B is an enlarged cross-sectional view in which the F portion of FIG.

  This problem stems from the fact that the hardness of the ceramic body constituting the suction surface is different from the hardness of the silicon wafer that is the work piece. Even if the R surface between the surfaces and the concave portions formed between the convex portions are mirror-finished, they are not completely eliminated.

  Further, the electrostatic chuck holds the workpiece only by the top surface of the convex portion, and the predetermined area is set so that the total area of the top surface of the convex portion is not too small with respect to the area of the attracting surface. Even within the range, the electrostatic attraction force is essentially reduced.

  In addition, cooling helium gas is likely to leak from the outer peripheral region of the workpiece and the suction surface, particularly from the gap between the top surface of the outermost convex portion and the workpiece. There is a problem that particles generated by contact and sliding of the workpiece are scattered in the semiconductor manufacturing apparatus.

  Accordingly, the present invention has been completed in view of the above-described conventional problems, and the object thereof is to perform fixed holding, correction, and conveyance of a workpiece while effectively reducing the generation of particles. It is to provide a possible electrostatic chuck.

  The electrostatic chuck of the present invention has an electrostatic chucking electrode on one main surface or inside of a plate-like ceramic body, and the other main surface is a chucking surface for chucking and holding a wafer, and a plurality of convex portions on the chucking surface. The convex portion has an R surface between the top surface and the peripheral surface, and the curvature of the R surface is larger in the inner region than the outer peripheral region of the attraction surface. To do.

  Moreover, the electrostatic chuck of the present invention is characterized in that, in the above configuration, the convex portion is circular in a top view.

  In the electrostatic chuck of the present invention, in the configuration described above, the attracting surface has a circular shape with a radius r, the outer peripheral region is outside the radius r / 2, and the inner region is the radius r. It is characterized by being inside of / 2.

  Moreover, the electrostatic chuck of the present invention is characterized in that, in the above configuration, the vertical cross-sectional shapes of the R surface and the top surface of the convex portion in the inner region are semicircular.

  Moreover, the electrostatic chuck of the present invention is characterized in that, in the above-described configuration, the curvature of the R surface gradually increases from the outer peripheral region to the central portion of the attracting surface. .

  The electrostatic chuck according to the present invention is characterized in that, in the above configuration, the attraction surface has irregularities between the convex portions.

  Moreover, the electrostatic chuck of the present invention is characterized in that, in the above-described configuration, the unevenness is a curved surface having a smooth bottom surface or peripheral edge of the top surface.

  Moreover, the electrostatic chuck of the present invention is characterized in that, in the above configuration, the area of the top surface of the convex portion is larger in the outer peripheral region than in the inner region.

  The electrostatic chuck according to the present invention is characterized in that, in the above-described configuration, the chucking surface has a peripheral wall on an outer periphery thereof, and the electrostatic chucking electrode extends below the peripheral wall. is there.

  According to the electrostatic chuck of the present invention, an electrostatic chucking electrode is provided on one main surface or inside of the plate-like ceramic body, and the other main surface is used as a suction surface for sucking and holding the wafer, and a large number of protrusions are formed on the suction surface. In the electrostatic chuck having a portion, the convex portion is an R surface between the top surface and the peripheral surface, and the curvature of the R surface is larger in the inner region than the outer peripheral region of the attracting surface. When the workpiece is detached from the suction surface, the curvature of the R surface between the top surface of the convex portion and the peripheral surface is determined in the region inside the suction surface where the contact time and sliding time between the convex portion and the workpiece are long. By increasing the size, the contact area between the convex portion and the workpiece is reduced in the region inside the suction surface, and the frictional force is reduced. As a result, the generation of particles can be reduced.

  In the electrostatic chuck of the present invention, in the above configuration, when the convex portion is circular in a top view, the cooling helium gas can easily circulate between the convex portions in the adsorption surface, and the workpiece Particles adhering to the suction surface side can be easily removed.

  In the electrostatic chuck of the present invention, in the above configuration, the attracting surface has a circular shape with a radius r, the outer peripheral region is outside the radius r / 2, and the inner region is more than the radius r / 2. Can also effectively reduce particles generated in the inner region.

  In the electrostatic chuck of the present invention, in the above configuration, when the vertical cross-sectional shape of the R surface and the top surface of the convex portion in the inner region is a semicircle, the electrostatic chuck is bent in the inner region of the attracting surface. The workpiece has a small contact area and a small frictional force with respect to the R surface of the convex portion, and the generation of particles can be reduced more effectively.

  Further, in the electrostatic chuck of the present invention, in the above configuration, when the curvature of the R surface gradually increases from the outer peripheral region of the suction surface toward the center portion, the curvature of the R surface suddenly increases on the suction surface. The part which changes greatly is lost, and the detachment of the workpiece in such a part is eliminated. As a result, the workpiece is sequentially detached from the outer peripheral portion of the suction surface toward the center portion, so that even if particles adhere to the back surface (surface to be sucked) of the workpiece, the workpiece does not scatter around the periphery.

  In the electrostatic chuck of the present invention, in the above configuration, when the attracting surface has irregularities between the convex portions, the particles generated by contact and sliding between the workpiece and the convex portions are irregularities between the convex portions. It is possible to collect in the concave portion. Also, when the workpiece comes into contact between the projections when the workpiece is detached by the lift pins, the contact area and frictional force of the workpiece are reduced by the unevenness between the projections, and the generation of particles is more effectively reduced. be able to.

  In the electrostatic chuck of the present invention, in the above-described configuration, when the unevenness is a smooth curved surface at the bottom surface or the top surface, the workpiece contacts between the convex portions when the workpiece is detached by the lift pin. In this case, the contact area and frictional force of the workpiece can be reduced by the unevenness between the convex portions, and generation of particles due to contact and sliding of the workpiece can be reduced more effectively.

  In the electrostatic chuck of the present invention, in the above configuration, when the area of the top surface of the convex portion is larger in the outer peripheral region than in the inner region, the attracting force on the top surface of the convex portion in the outer peripheral region. The helium gas for cooling is difficult to leak. As a result, even if particles are generated on the surface on the suction surface side of the workpiece, the particles are not scattered around.

  The electrostatic chuck of the present invention has a peripheral wall on the outer periphery of the suction surface in the above configuration, and when the electrostatic chucking electrode extends below the peripheral wall, the workpiece is also attracted to the peripheral wall. In addition, scattering of particles due to helium gas leakage can be effectively suppressed while compensating for a decrease in the adsorption force due to the top surface of the convex portion.

  Hereinafter, an example of an embodiment of an electrostatic chuck of the present invention will be described in detail with reference to the drawings.

  The embodiments shown here are specifically described in order to make the gist of the present invention more clear, and do not limit the present invention unless otherwise specified.

  1A and 1B are views showing an electrostatic chuck according to the present invention, in which FIG. 1A is a top view thereof and FIG. 1B is a longitudinal sectional view thereof.

  The electrostatic chuck 1 includes a pair of electrostatic chucking electrodes 3 embedded in a disk-shaped plate-like ceramic body 2 having a size similar to that of a workpiece such as a silicon wafer. As shown in the dot pattern of FIG. 1A, a large number of convex portions 6 are formed on the other main surface of the ceramic body 2, and the top surface 8 of the convex portions 6 is used as an adsorption fixing surface.

  The workpiece is attracted and fixed by loading the workpiece on the convex portion 6 and energizing the electrostatic adsorption electrode 3 via a power supply terminal (not shown) to connect the electrostatic adsorption electrode 3 and the workpiece. This is achieved by developing an electrostatic adsorption force between the object and the object.

  Further, a gas flow path 5 is formed between the convex portion 6 and the convex portion 6. The central portion of the plate-like ceramic body 2 is formed with a gas introduction hole 7 that communicates from one main surface (the lower surface of the plate-like ceramic body 2 in FIG. 1B) to the bottom surface of the gas flow path 5. When the workpiece is adsorbed on the top surface 8 of the part 6, a cooling gas such as helium gas is supplied to the space formed by the workpiece and the gas flow path 5. Thereby, the heat transfer characteristic between the gas flow path 5 and the workpiece is enhanced, the heat transfer between the top surface 8 of the convex portion 6 which is the adsorption fixing surface and the workpiece is improved, and the workpiece is processed. The temperature distribution is controlled to be uniform.

  In the electrostatic chuck 1 shown in FIG. 1, the peripheral wall 4 is formed on the outer peripheral edge of the other main surface of the plate-like ceramic body 2 (the upper surface of the plate-like ceramic body 2 in FIG. 1B). The space formed by the convex portion 6 of the adsorption surface 2a, the workpiece, and the gas flow path 5 is a closed space, and a large amount of cooling gas supplied from the gas introduction hole 7 is prevented from leaking to the outside. . The peripheral wall 4 may be installed according to the purpose, or may not be installed. The peripheral wall 4 may be formed integrally with the plate-shaped ceramic body 2 or may be formed as a member separate from the plate-shaped ceramic body 2 and combined.

  2A to 2D are diagrams showing various examples of the configuration of the convex portion 6. 3A to 3D are views for explaining that the curvature of the R surface of the convex portion 6 of the electrostatic chuck 1 is different between the outer peripheral region and the inner region. ) Is a longitudinal sectional view of the electrostatic chuck 1 showing the position of the convex portion, FIG. 3B is an enlarged sectional view and a top view of part A of FIG. 3A, and FIG. 3C is part B of FIG. FIG. 3D is an enlarged cross-sectional view of a portion C of FIG. 3A.

  As shown in FIG. 2A, the top surface 8 of the convex portion 6 is basically a flat surface, and the peripheral surface 10 is basically a vertical surface. An R surface 9 is formed between the top surface 8 and the peripheral surface 10, and the R surface 9 is a smooth curve in the sectional view.

  In the region inside the suction surface 2 a, the surface (lower surface) on the suction surface 2 a side of the workpiece bent so as to be convex downward when the workpiece is detached with the lift pin is located on the convex portion 6. The parallelism cannot be maintained, and the bending deformation stress appears as a stress pressing the convex portion 6.

  Therefore, as shown in FIGS. 3A to 3C, the curvature 9 of the R surface of the inner region of the suction surface 2a, for example, the convex portion 6 of the B portion, and the outer peripheral region, for example, the convex portion of the A portion. By making the curvature larger than the curvature of the R surface of 6, it becomes difficult for the workpiece to contact not only the top surface 8 of the convex portion 6 but also the R surface 9 that is particularly prone to generate particles, resulting in contact and sliding of the workpiece. There is a tendency to reduce wear damage due to motion.

  Regarding this tendency, the following (1) to (3) are known.

  (1) This tendency is maintained even when the total area of the top surface 8 of the convex portion 6 is larger in the inner region than the outer peripheral region. In this case, 1) the convex portion 6 of the suction surface 2a has a single width (or diameter), and there are many convex portions 6 in the inner region, and 2) the width of the convex portion 6 in the inner region is When the width of the convex portion 6 is larger than the width of the convex portion 6 in the outer peripheral region, that is, when the top surface 8 of the convex portion 6 in the inner region is larger than the top surface 8 of the convex portion 6 in the outer peripheral region. . The generation of particles in the inner area of the suction surface 2a is caused by the fact that the stress by which the workpiece bent against the convex portion 6 presses the convex portion 6 rather than pressing the workpiece against the top surface 8. This is because the sliding friction between the object and the R surface of the convex portion 6 is increased.

  (2) This tendency is maintained when the total area of the top surface 8 of the convex portion 6 is the same in the inner region and the outer peripheral region of the suction surface 2a. This is the same reason as (1).

  (3) This tendency is maintained when the total area of the top surface 8 of the convex portion 6 is larger in the outer peripheral region than in the inner region of the suction surface 2a. In this case, 1) there are two convex portions 6 in contact with the workpiece, and 2) there are two cases where the width of the convex portion 6 in the inner region is small, and the R surface of the convex portion 6 where the particles are generated is small.

  Furthermore, even if this tendency is a case where the shape of the convex part 6 is a truncated cone shape having a tapered (tapered) peripheral surface 11 as shown in FIG. ), It is maintained even in the case of a polygonal column such as a quadrangular prism or an octagonal column. In particular, as shown in FIG. 2A, the convex portion 6 is preferably a cylindrical shape having a circular shape when viewed from the top, and in this case, the convex portion 6 has a circumferential shape like the polygonal columnar convex portion 6. There is no ridgeline on the surface 10 and the cooling gas flows easily without any obstacles. For this reason, there exists an effect that the particle adhering to the adsorption surface 2a side of the workpiece is easily removed.

  When the suction surface 2a has a circular shape with a radius r, preferably, as shown in FIG. 3A, the outer peripheral region is outside the radius r / 2 and the inner region is the radius r /. It is better to be inside than 2. In this case, it is possible to effectively avoid the convex portion 6 from coming into contact with and sliding on the bent workpiece in the region inside r / 2, and particles can be further reduced.

  Moreover, as shown in FIG.3 (d), it is preferable that the longitudinal cross-sectional shape of R surface 9 and the top surface 12 of the convex part 6 in an inner area | region is semicircular (the whole shape is hemispherical). In this case, the workpiece bent in the inner region of the suction surface 2a is less likely to come into contact with the R surface 9 of the convex portion 6, and the generation of particles can be effectively suppressed.

  As shown in FIGS. 2C and 2D, when the convex portion 6 is a polygonal columnar shape such as a quadrangular prism or an octagonal column, as shown in FIG. The longitudinal cross-sectional shape of the R surface 9 and the top surface 12 may be semicircular (the overall shape is hemispherical). In this case, depending on the longitudinal section, the longitudinal section may have another shape such as a square shape instead of a semicircular shape. Furthermore, the shape of the R surface 9 and the top surface 12 may be a shape such as a partial cylindrical shape.

  Further, as shown in FIGS. 3A to 3D, it is preferable that the curvature of the R surface 9 gradually increases from the outer peripheral region of the suction surface 2a toward the central portion. In this case, since there is no portion where the curvature of the R surface 9 changes suddenly, the workpiece is sequentially detached from the outer peripheral portion of the suction surface 2a toward the central portion, and the back surface (sucked) of the workpiece. Even if particles adhere to the surface, that is, the surface facing the attracting surface 2a, it does not scatter around.

  By the way, the central portion of the suction surface 2a here is a region closer to the center in the inner region. For example, when the suction surface 2a has a circular shape with a radius r, the radius r / 10 or less of the suction surface 2a. Refers to the extent of the area.

  In the gas flow path 5 between the convex portions 6 shown in FIG. 1, as shown in FIG. 4 (b), irregularities 42 are formed between the convex portions 6, and the irregularities are used as pockets for collecting particles. Can do. That is, the surface area for adsorbing particles can be increased because the portions other than the convex portions 6 for fixing and holding the workpiece have many concave and convex portions 42. The unevenness 42 has little influence on its function even if the size is uniform or non-uniform.

  The specific size of the unevenness 42, particularly the depth (height) of the unevenness 42, with respect to the ceramic resistance (impedance) on the electrostatic adsorption electrode 3 that expresses the electrostatic attractive force of the plate-like ceramic body 2, As the size and depth are increased, it is properly determined within the range where there is no adverse effect such as low resistance.

  When the workpiece to be bent comes into contact between the convex portions 6 when the workpiece is detached, the unevenness 42 can reduce the contact area and the sliding area with the workpiece and suppress the generation of particles. . More preferably, the unevenness 42 between the protrusions 6 is preferably formed with a smooth curved surface, and in this case, generation of particles due to contact and sliding of the workpiece can be reduced more effectively.

  In practice, there is no particular problem if the arithmetic average roughness Ra of the unevenness 42 is 5 μm or less, but preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1 μm or less, the curved surface of the unevenness 42 is smooth. Since friction due to contact and sliding with the workpiece can be further reduced, generation of particles can be further reduced.

  As a method of forming the convex portion 6 on the adsorption surface 2a of the plate-like ceramic body 2, first, the other main surface of the plate-like ceramic body 2 is a sandblasting method using a mask, a machining method, an ultrasonic processing method, or the like. Using a known method, the convex portion 6 having a height of several μm to several tens of μm is formed in a predetermined pattern shape.

  Next, lapping is performed so that the top surface 8 of the convex portion 6 surrounded by the gas flow path 5 is flat and located on the same plane. At this time, the lap plate made of cast iron is used, and the top surface 8 of the convex portion 6 is subjected to surface polishing using diamond abrasive grains having a size of 10 μm to 1 μm. Further, finish polishing may be performed using a copper disk or a tin disk.

  Next, the surface of the plate-like ceramic body 2 is formed using a surface polishing machine in which a yarn bundle obtained by bundling a nylon thread having a wire diameter of 0.3 mm is implanted in a base like a toothbrush and a large-sized polishing pad appropriately disposed is attached. The adsorption surface 2a is polished. That is, scanning is performed while rotating from the peripheral part to the central part of the rotating plate-shaped ceramic body 2 while pressing the polishing surface of the large polishing pad. At that time, surface polishing is performed while supplying diamond slurry between the plate-like ceramic body 2 and the large polishing pad. Thereby, the convex part 6 which has the R surface 9 between the top surface 8 and the surrounding surface 10 can be formed.

  In order to make the R surface 9 of the convex portion 6 have different curvatures in the outer peripheral region and the inner region of the suction surface 2a, the scanning speed of the surface polishing machine can be appropriately changed. That is, in order to reduce the curvature of the R surface 9 in the outer peripheral region of the suction surface 2a and increase the curvature of the R surface 9 in the inner region, the scanning speed is increased in the outer peripheral region and the inner region. The scanning speed may be reduced with

  The material of the yarn bundle that composes the polishing pad is polyamide fiber typified by nylon, organic synthetic fiber such as polypropylene, polyester, polybutylene terephthalate, etc., animal and vegetable natural fiber, metal wire such as phosphor bronze, tin, etc. Any known material or material may be used according to the purpose. Moreover, the wire diameter of the yarn may be appropriately selected depending on the material and material selected for the yarn.

  Further, the simplest method for forming the unevenness 42 between the convex portions 6 is a method of forming the unevenness 42 at the same time by the sandblasting method when the gas flow path 5 is first formed. The abrasive grains used at this time are preferably made of silicon carbide, alumina, glass beads, diamond, etc., and have a particle size of about 80 mesh passing product to 300 mesh non-passing product. Further, after forming the gas flow path 5 as described above, the unevenness 42 may be subjected to a machining method, an ultrasonic processing method, or the like in order to obtain a predetermined shape again.

  The unevenness 42 is formed by polishing at the same time as the convex portion 6 by surface polishing, and the bottom surface or the peripheral edge of the top surface of the unevenness 42 can be a smooth curved surface.

  By making the area of the top surface 8 of the convex portion 6 in the outer peripheral region of the suction surface 2a larger than the area of the top surface 8 of the convex portion 6 in the inner region, the apex of the convex portion 6 in the outer peripheral region. The electrostatic attraction force of the surface 8 is increased, and the workpiece can be firmly fixed and held. For this reason, the helium gas for cooling is less likely to leak from the convex portion 6 in the outer peripheral region. That is, the surface formed by the workpiece suction surface 2a side, the convex portion 6 and the gas flow path 5 is a closed space, and even if particles are generated on the workpiece suction surface 2a side, It can be prevented from being scattered around.

  Further, as shown in FIG. 4A, the peripheral wall 4 is provided on the outer periphery of the attracting surface 2a, and the extending portion 41 of the electrostatic chucking electrode 3 is provided below the peripheral wall 4, so that the peripheral wall 4 is also covered. The workpiece can be adsorbed and fixed to compensate for the decrease in the adsorbing force due to the top surface 8 of the convex portion 6, and the scattering of particles due to the leak of helium gas can be effectively suppressed.

  Examples of the electrostatic chuck of the present invention will be described below.

  The electrostatic chuck 1 having the configuration shown in FIG. 3 and the conventional electrostatic chuck 50 shown in FIG. 5 were produced.

  The electrostatic chuck 1 having the configuration of FIG. 3 was produced by the following steps (A) to (D).

  (A) First, in order to form the convex portion 6 on the adsorption surface 2a of the plate-like ceramic body 2, the convex portion 6 is viewed from the other main surface of the plate-like ceramic body 2 by a sandblasting method using a mask. To form a predetermined pattern shape.

  (B) Next, lapping processing was performed so that the top surface 8 of the convex portion 6 was flat and positioned on the same plane. At this time, the lap plate made of cast iron was used, and the top surface 8 of the convex portion 6 was subjected to surface polishing using diamond abrasive grains having a particle size of 3 μm.

  (C) Next, using a surface polishing machine in which a yarn bundle obtained by bundling a nylon thread (polyamide fiber) having a wire diameter of 0.3 mm is planted on a base like a toothbrush, and a large polishing pad appropriately disposed is attached. The adsorption surface 2a of the plate-like ceramic body 2 was polished. That is, scanning was performed while rotating from the peripheral part to the center part of the rotating plate-shaped ceramic body 2 while pressing the polishing surface of the large polishing pad. At that time, surface polishing was performed while supplying diamond slurry between the plate-like ceramic body 2 and the large polishing pad. Thereby, the convex part 6 which has the R surface 9 between the top surface 8 and the surrounding surface 10 was formed.

  (D) Next, with respect to the R surface 9 of the convex portion 6, the surface polishing machine is scanned so that the curvature of the R surface 9 gradually increases from the outer peripheral region of the suction surface 2a toward the central portion. Changed speed appropriately. That is, the scanning speed was gradually decreased from the outer peripheral area of the suction surface 2a toward the center.

  The electrostatic chuck 50 having the conventional configuration shown in FIG. 5 was produced by the steps (A) to (C) described above.

  For each of the electrostatic chuck 1 and the electrostatic chuck 50, after the silicon wafer was attracted and fixed in the vacuum chamber, the number of particles adhering to the silicon wafer and the increase in the number of particles in the vacuum chamber were measured.

  The electrostatic chuck 1 and the electrostatic chuck 50 all have the same product size, material, and the like. Here, the convex parts 6 and 56 were formed on the entire surface of the suction surface 2a at a uniform pitch. That is, the total area ratio of the top surfaces 8 and 56a of the convex portions 6 and 56 in the region outside the radius r / 2 and the region inside the radius r / 2 is 67%: 33%. The height of the convex portions 6 and 56 was 9 μm.

  A plurality of electrostatic chucks 1 were produced in order to evaluate various shapes of the convex portions 6.

  In the evaluation, the electrostatic chuck 1 and 50 is installed in the vacuum chamber, and a silicon wafer having a diameter of 8 inches is placed on the top surfaces 8 and 56a of the convex portions 6 and 56 of the electrostatic chuck 1 and 50. Thus, the electrostatic chucking electrodes 3 and 57 were energized to develop an electrostatic chucking force, and the silicon wafer was fixedly held on the top surfaces 8 and 56a of the protrusions 6 and 56.

  Thereafter, helium gas is supplied from the gas introduction holes 7 and 58, and with the back pressure of 700 Pa applied to the silicon wafer, the energization to the electrostatic adsorption electrodes 3 and 57 is stopped, and the silicon wafer is placed in the vacuum chamber. It was made to detach | leave from adsorption | suction surface 2a, 52a using the lift pin.

  At this time, the increase in the number of particles in the vacuum chamber and the number of particles attached to the silicon wafer were measured with a particle counter. These results are shown in Table 1.

表１に示すように、まず、Ｎｏ．１１の従来の構成の静電チャック５０は、吸着面５２ａの全域で凸部５６のＲ面５６ｃの曲率が単一であり、この場合、シリコンウエハの吸着面２ａ側の面に付着しているパーティクル数が１２００個、真空チャンバー内のパーティクル数の増加数も３００個と極めて多かった。シリコンウエハについて、パーティクルの付着位置を確認すると、吸着面５２ａの内側の領域５３におけるパーティクルが非常に多かった。特に、凸部５６の頂面５６ａよりも、Ｒ面５６ｃと当接する位置にパーティクルの付着が目立っていた。これは、シリコンウエハが吸着面５２ａから離脱する際に撓んだことで、シリコンウエハが押しつけられる頂面５６ａよりも、摺動し摩擦が大きなＲ面５６ｃでパーティクルが発生したと考えられる。

As shown in Table 1, first, No. In the electrostatic chuck 50 having the conventional configuration of No. 11, the curvature of the R surface 56c of the convex portion 56 is single throughout the suction surface 52a, and in this case, it adheres to the surface on the suction surface 2a side of the silicon wafer. The number of particles was 1200, and the increase in the number of particles in the vacuum chamber was 300, which was extremely large. When the adhesion position of the particles on the silicon wafer was confirmed, the number of particles in the region 53 inside the suction surface 52a was very large. In particular, the adhesion of particles was more conspicuous at the position where it abuts on the R surface 56 c than on the top surface 56 a of the convex portion 56. This is presumably because particles are generated on the R surface 56c that slides and has a larger friction than the top surface 56a against which the silicon wafer is pressed because the silicon wafer is bent when it is detached from the suction surface 52a.

  On the other hand, the curvature of the R surface 9 of the convex portion 6 was increased in the inner region (region on the inner peripheral side than r / 2) of the outer peripheral region. In 1-10, the number of particles adhering to the silicon wafer was significantly reduced. Further, the number of particles in the vacuum chamber increased very little to 50 or less.

  From this, it is considered that the wear and damage of the silicon wafer due to the sliding of the silicon wafer and the convex portion 6 mainly occurred on the R surface 9 of the convex portion 6. This is because when the silicon wafer is detached with the lift pins, the surface of the bent silicon wafer on the suction surface 2a side has been slid for a long time with the convex portion 6 in the region inside the suction surface 2a. It can be said that.

  Here, no. 5 and No. 7 or No. 6 and no. 8, the diameter of the cylinder forming the convex portion 6 in the inner area of the suction surface 2 a is the same as or larger than the diameter of the cylinder forming the convex section 6 in the outer peripheral area. If the curvature of the R surface 9 of the convex portion 6 is large in the region inside the region, there is no large difference in the number of particles. That is, even if the area of the top surface 8 of the convex portion 6 in the inner region is larger than the area of the top surface 8 of the convex portion 6 in the outer peripheral region, the curvature of the R surface 9 is dominant in terms of the number of particles. I found out.

  No. From 1 to 5, the number of particles was small when the shape of the convex portion 6 was a columnar shape or a truncated cone shape. This is considered to be because the cooling gas easily flows and the particles adhering to the silicon wafer can be easily removed in the case of the columnar or frustoconical convex portion 6.

  No. 5 and No. 9 or No. 9 and No. 10, it was found that the number of particles can be further reduced by making the vertical cross-sectional shape of the convex portion 6 in the region on the inner peripheral side from r / 2 into a semicircular shape. The larger the number of convex portions 6 having a semicircular cross-sectional shape, the better, and the number of particles is further reduced. This is because the curvature of the R surface 9 of the convex portion 6 is further increased by making the vertical cross-sectional shape of the convex portion 6 in the region inside the adsorption surface 2a semicircular, and the R of the silicon wafer that is bent at the time of detachment. This is considered to be because contact and sliding on the surface 9 are easily avoided.

  In particular, no. 5 and No. 6 or No. 7 and no. 8, when the curvature of the R surface 9 of the convex portion 6 gradually increases from the outer peripheral region toward the central portion of the electrostatic chuck 1, the increase in the number of particles in the vacuum chamber is significantly reduced. I understand that. Therefore, if the curvature of the R surface 9 is not changed suddenly, the silicon wafer is sequentially detached from the outer peripheral portion of the suction surface 2a toward the central portion, and as a result, particles adhering to the silicon wafer are moved to the periphery. It was found that it does not scatter and does not contaminate the atmosphere in the vacuum chamber.

  In the same manner as in Example 1, an electrostatic chuck 1 of the present invention having the configuration of FIG. The total area of the top surface 8 of the convex portion 6 is variously changed in the outer peripheral region and the inner region of the suction surface 2a, and the number of particles adhering to the silicon wafer after the silicon wafer is suction fixed in the vacuum chamber The increase in the number of particles in the vacuum chamber was measured.

  The product size and material of the electrostatic chuck 1 are all standardized. Here, the height of the convex portion 6 was 9 μm, and all the convex portions 6 were circular cylinders having a top view shape of 3 mm in diameter.

  Among the seven types of electrostatic chucks 1, there are ones having projections and depressions 42 between the projections 6, and ones having extension portions 41 of the electrostatic chucking electrodes 3 below the peripheral wall 4. The measurement results are shown in Table 2.

表２より、まず、Ｎｏ．１とＮｏ．２あるいはＮｏ．４とＮｏ．５より、凸部６間のガス流路５に凹凸４２を形成した場合、パーティクルが低減することが分かった。測定終了後に、静電チャック１を真空チャンバーから取り出し、詳細に観察すると、凹凸４２の凹部に細かいパーティクルが捕獲されていることが分かった。これは、凹凸４２がガス流路５の全域にわたって形成されたことで、パーティクルを吸着捕集する表面積が増加したことにより、凹凸４２がパーティクル捕集のポケットを形成したためと考える。

From Table 2, first of all, 1 and No. 2 or No. 4 and no. 5 indicates that particles are reduced when the irregularities 42 are formed in the gas flow path 5 between the convex portions 6. When the electrostatic chuck 1 was taken out of the vacuum chamber after the measurement was completed and observed in detail, it was found that fine particles were captured in the recesses of the irregularities 42. This is considered to be because the irregularities 42 formed pockets for collecting particles because the irregularities 42 were formed over the entire area of the gas flow path 5 and the surface area for adsorbing and collecting particles increased.

  For the top surface 8 of the convex portion 6, the From 1, 4, 7, the area ratio of the top surface 8 of the convex portion 6 is changed between the outer peripheral area and the inner area of the suction surface 2a, and the area ratio is increased or the same in the inner area. It has been found that if the curvature of the R surface 9 of the convex portion 6 is large in the region inside the outer peripheral region, there is no large difference in the total number of particles. That is, it was found that the area ratio is not dominant with respect to the number of particles, but the curvature of the R surface 9 is dominant with respect to the generation of particles.

  By the way, as described above, the total number of particles does not change depending on the area ratio, but the number of particles in the vacuum chamber increases as the area ratio of the top surface 8 of the convex portion 6 in the inner region clearly decreases. It shows a trend. This is because by increasing the area ratio in the outer peripheral region, the adsorption holding force of the silicon wafer in the outer peripheral region is strengthened. For this reason, the top surface 8 of the silicon wafer and the convex portion 6 and the gas flow path 5 are increased. This indicates that the cooling gas is less likely to leak from the space formed by the above, and the space formed by the silicon wafer, the top surface 8 of the convex portion 6, the gas flow path 5, and the peripheral wall 4. For this reason, it is considered that the increase in the number of particles in the vacuum chamber has decreased.

  Furthermore, no. 2 and No. 3 or No. 5 and No. 6, when the extended portion 41 of the electrostatic chucking electrode 3 is provided below the peripheral wall 4, the number of particles in the vacuum chamber is further suppressed. This is presumably because cooling gas leakage was further suppressed.

An example of the electrostatic chuck of this Embodiment is shown, (a) is a top view of the electrostatic chuck, and (b) is a longitudinal sectional view of the electrostatic chuck. (A)-(d) is the longitudinal cross-sectional view and top view which show the various structural examples of the convex part in the electrostatic chuck of this Embodiment. (A)-(d) demonstrates the structure of the convex part of the electrostatic chuck of this Embodiment, (a) is the longitudinal cross-section of the electrostatic chuck which shows the position A, B, C of a convex part FIG. 4B is an enlarged vertical sectional view and a top view of the portion A in FIG. 4A, FIG. 4C is a longitudinal sectional view and an enlarged top view of the portion B in FIG. It is the longitudinal cross-sectional view which expanded the C section. (A), (b) shows the other example of the electrostatic chuck of this Embodiment, (a) is a longitudinal cross-sectional view of an electrostatic chuck, (b) is the longitudinal cross-sectional view which expanded the D section of (a). It is. (A), (b) shows the conventional electrostatic chuck, (a) is the longitudinal cross-sectional view of the conventional electrostatic chuck, (b) is the longitudinal cross-sectional view which expanded the F section of (a).

Explanation of symbols

1: electrostatic chuck 2: plate-like ceramic body 2a: adsorption surface 3: electrode for electrostatic adsorption 4: peripheral wall 5: gas flow path 6: convex portion 7: gas introduction hole 8: top surface 9 of convex portion: convex portion R surface 10: convex surface 42: irregularities between convex parts

Claims (9)

  In the electrostatic chuck having an electrostatic chucking electrode on one main surface or inside of the plate-shaped ceramic body and the other main surface serving as a suction surface for sucking and holding the wafer, and having a plurality of convex portions on the suction surface, The electrostatic chuck characterized in that the convex portion has an R surface between the top surface and the peripheral surface, and the curvature of the R surface is larger in an inner region than the outer peripheral region of the attracting surface.   The electrostatic chuck according to claim 1, wherein the convex portion has a circular shape in a top view.   2. The suction surface is circular with a radius r, the outer peripheral region is outside the radius r / 2, and the inner region is inside the radius r / 2. Alternatively, the electrostatic chuck according to claim 2.   The electrostatic chuck according to any one of claims 1 to 3, wherein a longitudinal cross-sectional shape of the R surface and the top surface of the convex portion in the inner region is a semicircular shape.   4. The electrostatic chuck according to claim 1, wherein a curvature of the R surface gradually increases from a region of the outer peripheral portion of the attracting surface toward a central portion. 5.   The electrostatic chuck according to claim 1, wherein the attraction surface has irregularities between the convex portions.   The electrostatic chuck according to claim 6, wherein each of the irregularities is a curved surface having a smooth bottom surface or a peripheral edge of the top surface.   The electrostatic chuck according to claim 1, wherein an area of a top surface of the convex portion is larger in the region of the outer peripheral portion than in the inner region.   The electrostatic chuck according to claim 1, further comprising a peripheral wall on an outer periphery of the attraction surface, and the electrostatic attraction electrode extending below the peripheral wall.

Images