Susceptors for semiconductor device manufacturing

Abstract

This invention provides a susceptor for semiconductor device manufacturing that improves thermal conductivity and enables uniform and precise processing of the entire surface of a processing substrate, such as a wafer. [Solution] The susceptor for semiconductor device manufacturing is preferably a disc-shaped device made of single-crystal silicon or polycrystalline silicon with a first and second parallel surface, having a resistivity of 10 Ω·cm or less, having one or more recesses for accommodating a processing substrate formed on the substrate mounting surface of the first surface, having a warp of 20 μm or less measured on the substrate mounting surface side, and preferably having a warp formed in a direction that makes the substrate mounting surface convex.

Description

Technical Field

[0001] The present invention relates to a susceptor used in a manufacturing process of semiconductor devices.

Background Art

[0002] A susceptor (sometimes also called a carrier for conveyance or a tray) used in a manufacturing process of semiconductor devices is used as a pedestal when placing wafers thereon and performing batch processing in a large chamber, or when processing small-diameter wafers smaller than the existing diameter handled by semiconductor manufacturing equipment or development cut-out wafers (also called chips).

[0003] By the way, in etching, plasma CVD, and ion implantation devices that require temperature control for film formation uniformity and the like, an electrostatic chuck mechanism, a heater mechanism, etc. exist on the installation stage. Since these devices are processed in a vacuum chamber, a heat transfer mechanism is required for heat transfer. Conventionally, there are methods such as embedding an electrode in a susceptor to form an electrostatic chuck for heat transfer, completely removing the back surface of a small-diameter wafer and controlling the temperature with an electrostatic chuck, and attaching a heat transfer grease or a heat transfer sheet to the back surface of the wafer. The material of the susceptor is selected by the device, such as alumina, SiN, SiC, carbon, graphite, etc.

[0004] [[ID=I9]] For example, Patent Document 1 discloses a tray (susceptor) in which the lower surface side in contact with an electrostatic adsorption device is made of a material having a volume resistivity of 1 × 10 13 Ω·cm or less, and the upper surface side exposed to plasma is made of a material having a volume resistivity exceeding 1 × 10 13 Ω·cm, and the lower surface is closely attached to a tray mounting table (stage) for heat conduction. Specific materials include, as the lower layer, silicon carbide, or a material in which a conductive material such as titanium carbide or carbon fiber is dispersed in aluminum nitride, and as the upper layer, alumina, quartz, aluminum nitride, yttria, zirconia, etc.

[0005] Patent Document 2 discloses a transport tray (susceptor) in which a recess corresponding to the outer shape of the substrate to be processed is formed on the substrate mounting surface of the transport tray (susceptor), and an annular sealing means is provided along the outer circumference of the bottom surface of the recess, and a pressing means is provided to press the outer surface of the substrate to be processed, which is placed in the recess, against the sealing means, and a cooling gas can be supplied to the space on the back side of the substrate to be processed placed in the recess via a gas passage leading to the recess. In this case, it is stated that the transport tray is made of a material such as silicon oxide, stainless steel, or aluminum. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-10975 [Patent Document 2] Japanese Patent Publication No. 2008-171996 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, when alumina or similar materials are used as the susceptor material, as in Patent Document 1, the thermal conductivity is poor, and there is a risk of cracking if subjected to thermal shock. To prevent cracking due to thermal shock, preheating in a preheating chamber before the processing chamber is sometimes performed, but this makes the work complicated. Also, in the case of insulating materials such as alumina, electrostatic attraction is not possible with general electrostatic chucks such as Coulomb type, so a metal plating film may be applied to the susceptor, but this raises concerns about metal contamination. In structures that include sealing means and pressing means, as in Patent Document 2, the sealing means impairs heat transfer to the outer periphery of the processing substrate, and the pressing means leaves a portion of the outer periphery unprocessed, resulting in a poor yield of device chips that can be obtained from a single wafer. Furthermore, using metal as the material for the transport tray raises concerns about metal contamination.

[0008] This invention has been made in view of these circumstances, and aims to provide a susceptor for semiconductor device manufacturing that can be adsorbed by an electrostatic chuck, has improved thermal conductivity, and can process the entire surface of a processing substrate such as a wafer with uniform precision. [Means for solving the problem]

[0009] The susceptor for semiconductor device manufacturing according to the present invention is formed in the shape of a plate having a first surface and a second surface, and is made of silicon.

[0010] Silicon has a higher thermal conductivity and superior thermal conductivity compared to alumina and silicon carbide, and also has a low resistivity, allowing it to be adsorbed by an electrostatic chuck. Therefore, a susceptor can be properly installed on the stage of a plasma processing device, and the entire surface of the wafer placed on the susceptor is heated uniformly, making it possible to manufacture high-quality devices. Furthermore, both single-crystal silicon and polycrystalline silicon can be used as the silicon. In this embodiment, the polycrystalline silicon includes columnar silicon.

[0011] In the semiconductor device manufacturing susceptor of the present invention, it is preferable that the resistivity is 10 Ω·cm or less. Because the susceptor of the present invention has a low resistivity, it is easily attracted by electrostatic chucks and can be widely used with various types of electrostatic chucks, including Coulomb type chucks.

[0012] In the semiconductor device manufacturing susceptor of the present invention, the first surface is a substrate mounting surface, the second surface is placed on a surface plate and the height of the first surface is measured, and the average value of the central height measured at multiple locations in a circular area within 1 / 3 of the diameter is taken as the average value of the central height H1, the average value of the annular area height measured at multiple locations in an annular area outside the circular area that surrounds the central area is taken as the average value of the annular area height H2, and the average value of the outer peripheral area height measured at multiple locations in an area outside the annular area that is within 98% of the diameter is taken as the average value of the outer peripheral area height H3, it is desirable that H1 ≥ H2 ≥ H3.

[0013] This height distribution results in either a flat, planar shape overall, or a dome-shaped curve with a convex center, which allows for proper adsorption to an electrostatic chuck and excellent heat conduction.

[0014] In the semiconductor device manufacturing susceptor of the present invention, it is preferable that the susceptor be disc-shaped with a diameter of 200 mm or more and 450 mm or less, and a thickness of 0.5 mm or more and 5 mm or less, and that the standard deviations of the central height, the annular region height, and the outer peripheral region height are each 7 μm or less. Because the variation in height is small, it is possible to form a surface without undulations or localized irregularities, resulting in better adhesion to the electrostatic chuck.

[0015] In the semiconductor device manufacturing susceptor of the present invention, it is preferable that the maximum height position of the space formed between the second surface and the base plate is located on the second surface side in the central region, and that its maximum height is 20 μm or less. The susceptor of the present invention has a small height gap between the second surface and the surface when placed on a surface plate, allowing the substrate to be stably mounted on the substrate mounting surface.

[0016] In the semiconductor device manufacturing susceptor of the present invention, it is preferable that the substrate mounting surface is curved in a dome shape in a direction that makes it convex. When this susceptor is placed on the stage, it is positioned so as to cover the stage surface with a concave surface. The gas supplied from below circulates between the stage and the susceptor while remaining trapped, allowing for efficient heat conduction.

[0017] In the semiconductor device manufacturing susceptor of the present invention, one or more recesses for accommodating a processing substrate are formed on the substrate mounting surface. [Effects of the Invention]

[0018] According to the susceptor for manufacturing a semiconductor device of the present invention, it has high thermal conductivity, excellent thermal conductivity, low specific resistance value, and can be adsorbed by an electrostatic chuck. Therefore, the susceptor can be appropriately installed on the stage of the plasma processing apparatus, the entire surface of the wafer placed on the susceptor is uniformly heated, and it becomes possible to manufacture high-quality devices.

Brief Description of the Drawings

[0019] [Figure 1] It is a plan view showing a susceptor of an embodiment of the present invention. [Figure 2] It is a cross-sectional view taken along the line A-A of FIG. 1 as viewed in the arrow direction. [Figure 3] It is a flowchart showing a manufacturing method of a susceptor of an embodiment. [Figure 4] It is a cross-sectional view showing a state where the susceptor is placed on the stage of the plasma processing apparatus. [Figure 5] It is a diagram for explaining a method of measuring the surface shape of the susceptor, (a) is a state where the second surface is placed on a surface plate for measurement, (b) is a state where the first surface is placed on a surface plate for measurement, and (c) shows planar measurement points. [Figure 6] It is a diagram showing the shapes measured by the method shown in (a) of FIG. 5 for four types of susceptors due to differences in polishing methods in planarization.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0021] In one embodiment, a susceptor 1 for semiconductor device manufacturing (hereinafter simply referred to as "susceptor") is made of single-crystal silicon or polycrystalline silicon, and is formed in a disc shape with a first surface 1a and a second surface 1b parallel to each other. In this embodiment, the silicon susceptor is mainly composed of silicon and may contain unavoidable impurities for adjusting the resistivity or purity during production, and may also contain dopants such as B and P. The silicon susceptor 1 has a thermal conductivity of 140 W / m·K or more and 180 W / m·K or less (for example, 160 W / m·K) at room temperature of 27°C, and a resistivity of 1 × 10⁻¹⁶ -4 Ω cm or more 1×10 3 It is less than or equal to Ω·cm. This resistivity is 1 × 10⁻⁶ 2 It is preferable to have a thermal conductivity of Ω·cm or less, and more preferably 1 × 10 Ω·cm or less. This is because the thermal conductivity λ of silicon can be expressed as the sum of the thermal conductivity λe of electrons due to the amount of dopants, which are electric carriers, and the thermal conductivity λp of silicon lattice vibrations. The thermal conductivity of lattice vibrations is affected by the influence of phonons, phonon boundary scattering, impurity scattering, and grain boundary scattering.

[0022] Therefore, according to physical principles, a silicon suitable for a silicon susceptor is one with a small amount of dopant to increase the thermal conductivity of electrons, and large grain boundaries that prevent boundary scattering under the influence of phonons. In particular, to increase the thermal conductivity, if dopants are added to a resistivity of about 10 Ω·cm, the thermoelectric coefficient at low temperatures will improve, and a value of 1000 W / m·K will be obtained at -173°C. The first surface 1a is designated as the substrate mounting surface, and multiple recesses 2 for accommodating the processing substrate (wafer) W are formed on the first surface 1a (three in the example shown in Figures 1 and 2). The susceptor 1 has a substrate mounting surface and is used for transporting and processing substrates (e.g., wafers).

[0023] Furthermore, in this susceptor 1, as shown in Figure 5(a), the second surface 1b is placed on a surface plate P, and the height of the first surface (substrate mounting surface) 1a is measured from above using a laser displacement meter as indicated by the arrow. As shown in Figure 5(c), the average value of the central height measured at multiple locations (measurement points are indicated by M in the figure) within the circular central region F1 up to 1 / 3 of the diameter D1 of the susceptor 1 is taken as the average value of the central height H1, the average value of the annular region height measured at multiple locations outside the central region F1 and surrounding the central region F1 is taken as the average value of the annular region height H2, and the average value of the outer peripheral region height measured at multiple locations outside the annular region F2 and up to 98% of the diameter D1 of the susceptor 1 is taken as the average value of the outer peripheral region height H3. In this case, H1 ≥ H2 ≥ H3 is set. In other words, the entire structure is either a flat planar shape (H1=H2=H3) or a dome-shaped curve where the height gradually decreases from the center to the outer edge {(H1≧H2>H3) or (H1>H2≧H3)}. Alternatively, susceptor 1 may have a dome-shaped curve where the height gradually decreases from the center to the outer edge (H1>H2>H3). Note that the dome-shaped curve in susceptor 1 may have substantially flat portions within each of the above-mentioned regions (F1, F2, F3).

[0024] Furthermore, if the heights H1 to H3 of each region F1 to F3 are approximately equal, then H1≧H2≧H3, H1≧H2≦H3, or H1≦H2≧H3 are also acceptable. In this case, the height difference |H1-H2| or |H2-H3| must be 0.4 μm or less, or |H1-H3| must be 0.4 μm or less.

[0025] Furthermore, the standard deviation of the height of each of these regions is 7 μm or less. Preferably, the standard deviation of the height of each region is 3 μm or less, and even more preferably, the standard deviation of the height of each region is 2.5 μm or less.

[0026] In this case, the reason for setting the outer peripheral region F3 to within 98% of the diameter D1 of the susceptor 1 is that the outer peripheral edge of the susceptor 1 is machined, such as by rounding the edges, which reduces its thickness, and this machined portion is avoided from the measurement target.

[0027] Furthermore, when measuring the height as described above, it is necessary to exclude the influence of the flatness of the base plate P. For example, before placing the susceptor 1, the height of the base plate P can be measured at multiple points (for example, one point at the center and four points at 90° intervals in the outer regions) in the area where the central region F1 of the susceptor 1 is placed and the annular region F2 and outer region F3 are placed. The surface obtained based on these measurements can be used as the reference surface of the base plate P, and by measuring the height relative to this reference surface, the influence of the flatness of the base plate P can be eliminated.

[0028] Furthermore, the maximum height (referred to as warpage) h from the base plate P on the second surface 1b, opposite to the substrate mounting surface 1a, is 20 μm or less, indicating either a flat state without warpage or a slight warpage towards the substrate mounting surface 1a. This warpage h can be determined by using a laser scanning device to scan the entire surface of the susceptor with a laser, measuring the height from the base plate P on both sides (first surface 1a and second surface 1b), and then combining these measurements and performing image processing and correction calculations.

[0029] Specifically, similar to the height measurement described above, the second surface 1b of the susceptor 1 is placed on the surface plate P as shown in Figure 5(a), and the height of the first surface 1a is measured at multiple locations (multiple locations in each of the central region F1, annular region F2, and outer peripheral region F3) while excluding the influence of the flatness of the surface plate P. Then, the susceptor 1 is turned over and the first surface 1a is placed on the surface plate P as shown in Figure 5(b), and the height of the second surface 1b is measured at multiple locations in the same state, excluding the influence of the flatness of the surface plate P. By subtracting the thickness of the susceptor 1 from the difference in the measured values ​​at the same location on the plane, the distribution of the height of the space S (see Figure 5(a)) between the second surface 1b and the surface plate P when the second surface 1b is placed on the surface plate P can be determined. As mentioned above, if the maximum value of the height of this space S is defined as the warp h, then this warp h is 25 μm or less. Warpage can also be measured by placing a CNC (Computer Numerical Control) image measuring instrument or a CNC contact measuring instrument on a surface plate and measuring its height. It is more preferable that the curvature h be 20 μm or less. Although not particularly limited, the curvature h may be 15 μm or less, or 10 μm or less. Furthermore, the curvature h may be 0.1 μm or more.

[0030] The dimensions of this susceptor 1 are not necessarily limited, but for example, it is formed in a disc shape with a diameter of 200 mm to 450 mm and a thickness of 0.5 mm to 5 mm. This diameter may also be 220 mm to 280 mm or 320 mm to 430 mm. Furthermore, the recess 2 is formed in a circular shape with a diameter of 50 mm to 200 mm and a depth of 0.25 mm to 1 mm. Therefore, the thickness of the bottom wall of the recess 2 is formed to be between 0.25 mm and 4.75 mm. One to 30 recesses 2 are formed in one susceptor 1. The wafer (processing substrate) W housed in the recess 2 is formed in the shape of a disc with a diameter of 50 mm to 200 mm and a thickness of 0.220 to 1 mm.

[0031] The susceptor 1, constructed in this manner, is manufactured from a silicon ingot through the processes shown in Figure 3. Specifically, the ingot is sliced ​​into a disc shape (cutting), heat-treated to remove distortion (heat treatment), processed into the outer shape by grinding, etc. (shaping (outer shape)), and a recess 2 of the substrate mounting surface 1a is formed (shaping (boring)).

[0032] In this boring process, silicon is a hard, brittle material that is prone to chipping and cracking. Furthermore, because the susceptor is thin (less than 3mm thick), extreme care is required during processing. For example, in radial boring, increasing the depth of cut or increasing the processing speed will raise the temperature of both the tool and the workpiece, leading to heat buildup and thermal deformation (in both the tool and the workpiece). Continuing processing in this thermally deformed state will result in significant warping.

[0033] Therefore, when forming this recess 2, machining is performed from the outer circumference side to the inner circumference side of the susceptor 1. At this time, warping is suppressed by machining while rotating the susceptor 1 around its center, and by using an appropriate cutting tool angle, cutting speed, and cutting depth. When a part of the circumferential direction of the susceptor 1 is machined, the machined area receives a force pressing on the surface from the tool, so a force is generated in the direction that the surrounding area of ​​the machined area lifts up. If this pressing force is too large, undulation is likely to occur in the circumferential direction. For this reason, by machining the susceptor 1 little by little in a concentric manner with an appropriate pressing force while rotating it, the occurrence of undulating deformation along the circumferential direction is suppressed. In addition, it is important to make the amount of machining (cutting depth) small (i.e., thin) so that as little heat and distortion as possible remains in the susceptor 1 during machining. Warping is suppressed by machining with a small amount of machining and taking time.

[0034] After shaping (boring), the surface is flattened to a predetermined thickness by polishing both sides (flattening), then washed to finish the product, and finally inspected for appearance, dimensions, etc.

[0035] The susceptor 1 formed in this manner is held by a holding mechanism such as a robot hand, and the processing substrate (wafer) W is placed in the recess 2 of its substrate mounting surface 1a. These processing substrates W are then transferred together to a plasma processing device such as a plasma etching device or a film deposition device such as a CVD device.

[0036] To describe the stage on which the susceptor 1 is mounted in the plasma processing apparatus, as shown in Figure 4, this stage 11 has an electrostatic chuck 12 and a base 13 that supports the electrostatic chuck 12. The electrostatic chuck 12 has an electrode portion 14 and a dielectric layer 15 that covers its surface, and a plurality of grooves 16 are provided on the upper surface of the dielectric layer 15. These grooves 16 are formed on the entire surface of the electrostatic chuck 12 by combining radial, annular, and other shapes. The base 13 integrally holds the electrostatic chuck 12 and has a cooling water channel 17 through which a refrigerant flows.

[0037] Furthermore, a heat transfer gas supply passage 18 is formed to penetrate vertically through the base 13 and the electrostatic chuck 12, and communicates with a groove 16 in the dielectric layer 15. This heat transfer gas supply passage 18 communicates with a part of the groove 16, and the groove 16 is formed to release the heat transfer gas supplied from the heat transfer gas supply passage 18 radially outward while diffusing it onto the surface of the stage 11. In the example shown in Figure 4, one heat transfer gas supply passage 18 is formed in the center of the stage 11, but multiple heat transfer gas supply passages 18 may be formed parallel to each other. Helium (He) gas is generally used as the heat transfer gas.

[0038] The susceptor 1, with the processing substrate W housed in the recess 2, is placed on the stage 11 and held in place by the electrostatic chuck 12. Since the susceptor 1 is made of silicon, it has a low resistivity and is reliably held in place by the electrostatic chuck 12. The bottom wall of the recess 2 is formed thinly, and the processing substrate W inside the recess 2 is also a silicon wafer, so this processing substrate W also adheres closely to the bottom surface of the recess 2 due to the suction force of the electrostatic chuck 12.

[0039] With the susceptor 1 in place, a small space is formed between the susceptor 1 and the electrostatic chuck 12 by the groove 16. When a heat transfer gas, such as helium gas, which has been temperature-controlled by heat exchange with the electrostatic chuck (internal heater and internal heat transfer medium liquid), is supplied to this small space via the heat transfer gas supply passage 18, the heat transfer gas flows through the groove 16 to the entire surface of the small space between the susceptor 1 and the electrostatic chuck 12, performs heat exchange for temperature control of the susceptor, and is then released radially outward from the electrostatic chuck 12. In this way, the susceptor 1 is temperature-controlled (heated or cooled) by the heat transfer gas, and the processing substrate W in the recess 2 is uniformly temperature-controlled via the susceptor 1.

[0040] In this case, the susceptor 1 is held in place by the electrostatic chuck 12 on the stage 11, and the upward force due to the heat transfer gas must not exceed the adsorption force of the electrostatic chuck 12. Then, the necessary plasma treatment is performed on the upper surface of the processing substrate (wafer) W.

[0041] In the plasma processing described above, since the susceptor 1 is made of silicon, it has high thermal conductivity, and due to its excellent thermal conductivity, the entire surface is uniformly heated by the heat transfer gas flowing along its back surface (second surface) 1b. Therefore, the processing substrate (wafer) W in the recess 2 is also heated uniformly within the plane, allowing plasma processing such as etching and film deposition to be performed uniformly within the plane, making it possible to manufacture high-quality semiconductor devices.

[0042] Furthermore, if the susceptor 1 has a slight warp (for example, a convex warp of 0.1 μm to 20 μm), since this warp is formed to be convex towards the substrate mounting surface 1a, when it is placed on the stage 11 of the plasma processing apparatus, the concave surface of the back surface (second surface) 1b overlaps the surface of the stage 11. As a result, a space is formed between the susceptor and the surface of the stage 11. A groove 16 is formed on the surface of the stage 11, and the formation of this space allows the heat transfer gas supplied from the heat transfer gas supply passage 18 to spread into the space through the groove 16, and heat is transferred from that space to the entire surface of the back surface 1b of the susceptor 1, thereby enhancing the heat transfer effect and allowing the susceptor 1 to be heated quickly and uniformly.

[0043] If the warp of the susceptor 1 is reversed (the substrate mounting surface 1a side becomes concave), a gap is formed between it and the surface of the stage 11, which is open at the outer periphery. As a result, heat transfer gas does not easily accumulate, and heat is not easily transferred to the susceptor 1, which is undesirable. However, even if the warp is such that the substrate mounting surface 1a is convex, if the warp becomes too large, the processing substrate W housed in the recess 2 will not be stable within the recess 2, the plasma will be incident at an angle, and so on, which affects the plasma processing quality and is undesirable. Therefore, it is best to keep the warp to 20 μm or less, preferably 10 μm or less.

[0044] Furthermore, the susceptor 1 is formed from single-crystal silicon or polycrystalline silicon. In this case, polycrystalline silicon (for example, columnar silicon) consists of multiple crystals, and therefore grain boundaries exist. For this reason, when the susceptor 1 is formed from polycrystalline silicon, minute irregularities (about a few μm) are created on the surface due to the grain boundaries. Therefore, when using a susceptor 1 made of this polycrystalline silicon, the heat transfer gas flows along the surface of the susceptor 1 along the minute irregularities on the stage 11, allowing for faster heat transfer. In addition, the purity of the silicon, which is the main component of the susceptor 1, is 99.99% (4N) or higher, and may be 99.9999% (6N) or higher, or even 99.999999999% (11N) or higher.

[0045] It should be noted that the present invention is not limited to the configuration of the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, grooves for circulating heat transfer gas may be formed on the back surface (second surface) 1b of the susceptor 1, in which case the grooves 16 on the stage may or may not be present.

[0046] Furthermore, for temperature control of the processing substrate W within the recess 2, through holes leading to the bottom surface of the recess 2 may be formed in the thickness direction of the susceptor 1. A portion of the heat transfer gas supplied from the heat transfer gas supply passage 18 reaches the back surface of the processing substrate W within the recess 2 through the through holes, enabling direct heat exchange with the processing substrate W and improving heat transfer efficiency. In this case as well, it is necessary to ensure that the upward force due to the heat transfer gas from the through holes does not exceed the adsorption force of the electrostatic chuck acting on the processing substrate W. [Examples]

[0047] First, a susceptor was fabricated by forming three 100mm diameter recesses on the first surface of a silicon disc (2mm thick, 230mm in diameter) with a resistivity of 10Ω·cm. By changing the polishing method during the flattening process, the following four types of susceptors were produced.

[0048] A: The workpiece was rotated on a rotary stage, and the machining tool was brought into contact with it in the circumferential direction with appropriate machining pressure and rotational speed to machine it in a concentric circular shape. B: The workpiece was rotated on a rotary stage, and the machining tool was applied in a circumferential direction with a larger machining pressure than in case A. C: The workpiece was fixed on a fixed stage, and the machining tool was rotated parallel to the workpiece from above while machining was performed in one direction in the +X direction. D: The workpiece was fixed on a fixed stage, and the machining tool was rotated vertically from above relative to the workpiece while machining was performed in one direction in the +X direction.

[0049] For these four types of susceptors, the second surface of the susceptor was placed on a surface plate, and the height of multiple points in the central region F1 and the annular region F2 of the first surface (substrate mounting surface) was measured from above the first surface to determine the shape of the first surface. As shown by M in Figure 5(c), the measurement points were 9 locations in the central region F1 including the center of the circle, 8 locations in the annular region F2, and 8 locations in the outer region F3.

[0050] In this measurement, the location where recess 2 is formed may also be the measurement point. In that case, the measurement will be significantly different from other measurements in the same area. However, by considering the size (diameter, depth) and location of the recess, the shape is determined by determining whether the significantly different measurement in the same area is due to the bottom surface of recess 2 or due to undulation.

[0051] The results of these measurements are shown in Figure 6. The leftmost column in Figure 6 is a schematic diagram showing the height distribution of the susceptor's surface shape in terms of brightness, indicating that areas of the same brightness are at the same height. The three columns on the right show, from left to right, cross-sections in the X, Y, and 45° directions (see Figure 5(c) for these cross-sectional directions). In Figure 6, the surface plate is shown as a horizontally arranged rectangle, and the susceptor is shown on top of it as a thick solid line. The surface shape shown in Figure 6 can be briefly explained as follows:

[0052] A: In cross-sections along the X-axis, Y-axis, and any of the diagonal directions between them, the central region is higher, and in the annular region, it gradually decreases from the center towards the outer edge (it curves in a dome shape, convex towards the first surface). B: Stress concentration occurs in areas where the processing pressure was excessive, and the surrounding area deforms in the opposite direction to relieve the stress. As a result, undulation occurs circumferentially, with high and low regions occurring at approximately 90° intervals. In cross-sections along the C:Y axis, the central part is curved and convex, but in cross-sections along the X axis and oblique angles, it deforms by curving upward in one direction in the positive direction. The cross-section along the D:Y axis is almost flat, but the cross-sections along the X axis and at an angle are deformed, curving upward in one direction in the positive direction.

[0053] Then, for these four types of susceptors, each susceptor was installed in a Johnson-Rahbeck type electrostatic chuck having a hyperbolic internal electrode. Heat transfer gas (He) was supplied to the heat transfer gas flow path at a predetermined pressure, and the adsorption voltage was changed to confirm the pressure sealing state by the susceptor.

[0054] Tests where the heat transfer gas could be sealed and there were no subsequent adsorption abnormalities (excessive static electricity buildup preventing detachment) were marked with a circle (○). Tests where adsorption did not occur at all, or where adsorption occurred but detachment was not possible, were marked with a cross (×). Tests where the heat transfer gas at a pressure of 1000 Pa could be sealed and heat exchange was possible were marked with a circle (○), and tests where the heat transfer gas at a pressure of 2000 Pa could be sealed and heat exchange was more efficient were marked with a double circle (◎). The ESC (electrostatic chuck) voltage was varied as shown in the table, and the tests were conducted at a stage temperature of 40°C (temperature of the refrigerant flowing through the stage). The results are shown in Table 1.

[0055] [Table 1]

[0056] The results in Table 1 show that susceptors A, C, and D were able to seal the heat transfer gas at the specified pressure at adsorption voltages of 250V, 500V, 1000V, and 2500V, demonstrating good adsorption and desorption performance. They performed particularly well at adsorption voltages of 500V and above. In contrast, susceptor B was unable to adsorb at an adsorption voltage of 250V, indicating that adsorption is difficult without higher voltages.

[0057] Furthermore, each susceptor was installed in the plasma etching apparatus and plasma irradiation was performed. The plasma conditions were as follows: a radio frequency (RF) power supply output of 300W, argon (Ar) gas flow rate of 100 sccm, and pressure of 10 Pa for 60 seconds. The test was performed at a stage temperature of 40°C, and the susceptor surface temperature was measured using a temperature label. A bipolar Johnson-Rahbeck type electrostatic chuck was used, and the adsorption voltage was set to 2500V. The results are shown in Table 2.

[0058] [Table 2]

[0059] It can be seen that susceptor A is sufficiently cooled. Next, the cooling effect decreased in the order of susceptors C and D, and finally susceptor D. Only A remained below 100°C. When a wafer coated with resin resist, which is normally used for masking, is placed as the processing substrate, a temperature of 100°C or lower is preferable. However, a temperature of around 150°C is considered to be practically acceptable if the wafer uses heat-resistant resins such as polyimide or if the processing substrate is an inorganic material that does not undergo thermal degradation.

[0060] Next, the second surface was placed on a surface plate, and the heights of the first surface 1a and the second surface 1b from the surface plate P were measured, as shown in Figures 5(a) and (b). The height distribution of the space S formed between the surface plate P and the second surface 1b was measured by subtracting the thickness of the susceptor from the difference between these heights. The maximum height h and the heights of each region—the central region F1, the annular region F2, and the outer peripheral region F3—were measured, and the mean values ​​H1 to H3 and the standard deviation were calculated for each region F1 to F3. The results are shown in Table 3.

[0061] [Table 3]

[0062] As shown in Table 3, the average height H1 of the central region F1, the average height H2 of the annular region F2, and the average height H3 of the outer region F3 decrease in that order (H1>H2>H3), indicating that the overall shape is curved and convex towards the first surface. The standard deviation was also less than 2.1, indicating small variability. Specifically, in susceptor A, the average height H1 of the central region F1 was 12.2 μm, the average height H2 of the annular region F2 was 8.6 μm, and the average height H3 of the outer region F3 was 2.9 μm. If the average height of each region is H1=H2=H3, it will be a flat shape without curvature, but it may also be H1>H2≧H3 or H1≧H2>H3. Furthermore, in susceptor A, the difference (|H1-H3|) between the average height H1 of the central region F1 and the average height H3 of the outer region F3 is 9.3 μm, and this difference may be in the range of 6 μm to 20 μm.

[0063] Similarly, in the case of susceptor C, the measured values ​​decrease in the order of the average height H1 of the central region F1, H2 of the annular region F2, and H3 of the outer region F3. However, the standard deviation in the outer region is 9.4, which is much larger than that of susceptor A. This is thought to be due to the presence of raised areas in the outer region, as shown in Figure 6, for C. A standard deviation of 7 μm or less is preferred for the measured height, and a standard deviation of 3 μm or less is considered more preferable. In susceptors B and D, the height of the central region is large, but the average height of the outer region F3 is greater than that of the annular region F2, indicating that a curved shape with a convex first surface has not been obtained.

[0064] Next, three 100mm diameter recesses were formed in several silicon discs (2mm thick, 230mm in diameter) with different resistivity values. As a comparative example, a susceptor made of sintered alumina with the same shape was also fabricated.

[0065] First, for each of these silicon susceptors and sintered alumina susceptors, they were placed on a surface plate, and the height of both sides was measured using a laser scanning device as described above (see Figures 5(a) and 5(b)). The warp h was then measured after removing the effect of the surface plate's undulation. As a result, the warpage h of the silicon susceptor was kept below 25 μm. In particular, the warpage h of susceptor A was below 15 μm. In contrast, the warpage h of the susceptor made by alumina sintering was above 200 μm and could not be measured.

[0066] Next, susceptors were installed in the Coulomb-type electrostatic chuck and the Johnson-Rahbeck-type electrostatic chuck, respectively. Heat transfer gas (He) was supplied to the heat transfer gas flow path at a predetermined pressure, and the adsorption voltage was changed to confirm the pressure sealing state by the susceptor. The Coulomb-type electrostatic chuck was a unipolar type with one internal electrode, while the Johnson-Rahbeck-type electrostatic chuck was a bipolar type with two internal electrodes.

[0067] A ○ indicates that the heat transfer gas could be sealed and there were no subsequent adsorption abnormalities (excessive static electricity buildup preventing detachment). A × indicates that adsorption did not occur at all, or that adsorption occurred but detachment was not possible. A ○ indicates that the heat transfer gas at a pressure of 1000 Pa could be sealed and heat exchange could occur, and a ◎ indicates that the heat transfer gas at a pressure of 2000 Pa could be sealed and heat exchange was more efficient. The ESC (electrostatic chuck) voltage was varied as shown in the table, and the stage temperature was 40℃ (stage temperature). The test was conducted at the temperature of the refrigerant flowing through the system.

[0068] Table 4 shows the case for a Coulomb-type electrostatic chuck, and Table 5 shows the case for a Johnson-Rabec-type electrostatic chuck. The values ​​in the silicon column indicate the resistivity of silicon.

[0069] [Table 4]

[0070] [Table 5]

[0071] As can be seen from Tables 4 and 5, silicon susceptors, in the case of Coulomb-type electrostatic chucks, were able to seal and exchange heat with a heat transfer gas at a predetermined pressure, regardless of whether the adsorption voltage was 500V or 1000V. Furthermore, in the case of Johnson-Rahbeck-type electrostatic chucks, both adsorption and detachment were good over a wide range of adsorption voltages from 250V to 2500V. In contrast, sintered alumina susceptors could not be attracted by Coulomb-type electrostatic chucks, and even with Johnson-Larbek-type electrostatic chucks, they could only be attracted at a high attraction voltage (2500V).

[0072] Next, each susceptor was installed in the plasma etching apparatus, and plasma irradiation was performed. The plasma conditions were as follows: a radio frequency (RF) power supply output of 300W, argon (Ar) gas flow rate of 100 sccm, and pressure of 10 Pa for 60 seconds. The test was performed at a stage temperature of 40°C, and the susceptor surface temperature was measured using a temperature label. For the 500V suction voltage test, a unipolar Coulomb-type electrostatic chuck was used, while for the 2500V test, a bipolar Johnson-Rahbeck-type electrostatic chuck was used. The results are shown in Table 6.

[0073] [Table 6]

[0074] The alumina susceptor experienced an abnormal temperature increase due to plasma irradiation, and subsequently cracked due to rapid cooling after the treatment. This demonstrates that Coulomb-type electrostatic chucks are difficult to apply to insulating materials. In contrast, silicon susceptors were applicable to both Coulomb-type and Johnson-Larbek-type electrostatic chucks and were properly temperature-controlled. [Explanation of symbols]

[0075] 1 Susceptor 1a First side (board mounting side) 1b Second side (back side) 2 recesses 11 stages 12 Electrostatic Chuck 13 Base 14 Electrode section 15 Dielectric layer 16 groove 17 Cooling Channel 18 Heat transfer gas supply path F1 central area F2 annular region F3 outer area P Surface Plate S space

Claims

1. A susceptor for semiconductor device manufacturing, characterized by being formed in a plate shape having a first surface and a second surface, and being made of silicon.

2. The susceptor for semiconductor device manufacturing according to claim 1, characterized in that the resistivity is 10 Ω·cm or less.

3. A susceptor for semiconductor device manufacturing according to claim 1 or 2, wherein the first surface is a substrate mounting surface, the height of the first surface is measured by placing the second surface on a surface plate, and the average value of the central height measured at multiple locations in a circular central region within 1 / 3 of the diameter is defined as the average value of the central height H1, the average value of the annular region height measured at multiple locations in an annular region surrounding the central region outside the central region is defined as the average value of the annular region height H2, and the average value of the outer peripheral region height measured at multiple locations in a region outside the annular region within 98% of the diameter is defined as the average value of the outer peripheral region height H3, wherein H1 ≥ H2 ≥ H3.

4. The susceptor for manufacturing semiconductor devices according to claim 3, characterized in that it is a disc-shaped object with a diameter of 200 mm or more and 450 mm or less, and a thickness of 0.5 mm or more and 5 mm or less, and the standard deviations of the height of the central part, the height of the annular region, and the height of the outer peripheral region are each 7 μm or less.

5. The susceptor for semiconductor device manufacturing according to claim 4, characterized in that the maximum height position of the space formed between the second surface and the base plate is located on the second surface side in the central region, and its maximum height is 20 μm or less.

6. The semiconductor device manufacturing susceptor according to claim 3, characterized in that the substrate mounting surface is warped in a direction that makes it convex.

7. The semiconductor device manufacturing susceptor according to claim 3, characterized in that one or more recesses for accommodating a processing substrate are formed on the substrate mounting surface.

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