Ceramic heater and method of making same

Abstract

The electrostatic chuck heater includes a resistance heating element 16. The resistance heating element 16 is configured such that one end to the other end of the resistance heating element 16 is divided into a plurality of sections S. A groove R is provided on the surface of each section S along the length direction of the resistance heating element 16. The connecting portions of the grooves R provided on the adjacent sections S are provided with a protrusion Rm extending along the connecting portion.

Description

TECHNICAL FIELD

[0001] The present application relates to a ceramic heater and a method for manufacturing the same. BACKGROUND

[0002] Conventionally, a ceramic heater for a semiconductor manufacturing apparatus is known. For example, Patent Literature 1 discloses a ceramic heater in which a resistance heating element is provided on a surface of a ceramic substrate and a method for manufacturing the same. Patent Literature 1 also discloses that after the resistance heating element is formed, the resistance heating element is divided into a plurality of sections, the resistance value is measured for each section, and based on the measured resistance value, laser light is irradiated to a section having a low resistance value to form a groove, thereby adjusting the resistance value of the resistance heating element.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2002-190373 SUMMARY

[0006] However, if it is intended to join the grooves provided in adjacent sections to each other without a gap, the joining portions of the grooves to each other sometimes become locally too deep due to repeated irradiation of laser light. At a portion where the depth is locally deep like this, the resistance value is sometimes too high, and the heat generation of the portion is greater than that of other portions, which deteriorates the uniformity of the surface of the ceramic heater.

[0007] The present application has been made to solve the above problem, and has as its main object to provide a ceramic heater having a resistance heating element with grooves, in which the uniformity of the surface of the ceramic heater is improved.

[0008] The ceramic heater of the present application is a ceramic heater having a resistance heating element, in which

[0009] the resistance heating element is divided into a plurality of sections from one end to the other end of the resistance heating element,

[0010] a groove is provided on a surface of the resistance heating element in each section in the length direction of the resistance heating element,

[0011] a protrusion extending along the joining portion is provided at a joining portion of the grooves provided in adjacent sections to each other.

[0012] In the ceramic heater, current flows along the length direction of the resistance heat generating body. Even if the connecting portions of the grooves to each other have protrusions extending along the connecting portions thereof, the current flowing through the resistance heat generating body rarely enters the protrusions to flow therethrough. Therefore, the resistance of the current flowing through the adjacent sections is not greatly affected by the presence of the protrusions. In addition, if the grooves of the adjacent sections are to be formed continuously without gaps by laser, the depth of the connecting portions of the grooves to each other is sometimes too deep. In this case, the resistance of the connecting portions of the grooves to each other in the resistance heat generating body is higher than that of other portions, and thus the heat generation of the connecting portions is sometimes too large as compared with that of other portions, but the present application is not the case. Therefore, the uniformity of the surface of the ceramic heater can be made good.

[0013] The ceramic heater of the present application can be such that, when a cross section obtained by cutting the protrusions along a surface in the length direction of the resistance heat generating body is observed, the protrusions appear in a mountain shape having a base width of 95 μm or less. According to this, the base width of the protrusions is sufficiently small, and thus the current flowing through the resistance heat generating body hardly enters the protrusions to flow therethrough.

[0014] The ceramic heater of the present application can be such that the depth of the grooves is set to the same value (allowable tolerance, error) regardless of the sections, and the width of the grooves is set for each of the sections. According to this, by adjusting the width of the grooves, the resistance of each section of the resistance heat generating body can be adjusted.

[0015] The ceramic heater of the present application can be such that the center line of the grooves coincides with the center line of the resistance heat generating body (allowable tolerance, error). According to this, the temperature distribution in the width direction of the resistance heat generating body is substantially symmetrical about the center line, and thus the uniformity of the surface of the ceramic heater can be easily and favorably maintained.

[0016] The ceramic heater of the present application can be such that the grooves are not provided at portions of the resistance heat generating body where the heat dissipation is low. If the grooves are provided at portions of the resistance heat generating body where the heat dissipation is low, the resistance of the portions increases, the amount of heat generation increases, and on the other hand, the heat is not easily dissipated, and thus a hot spot is easily generated. Here, since the grooves are not provided at portions of the resistance heat generating body where the heat dissipation is low, a hot spot like this is not easily generated. It should be noted that, for example, in the case where a cooling plate is bonded or joined to the lower surface of the ceramic heater, a terminal portion provided at one end or the other end of the resistance heat generating body, or the like can be cited as the portions where the heat dissipation is low. A power feeding terminal that penetrates the cooling plate is connected to the terminal portion, and the power feeding terminal is poor in heat dissipation as compared with the cooling plate, and thus the terminal portion becomes a portion where the heat dissipation is low.

[0017] The ceramic heater of the present application can be such that the length direction of the shape obtained by viewing the section is straight or curved, and the length direction of the shape obtained by viewing the groove is straight. Accordingly, when the groove is formed using a laser, the groove can be formed with good precision.

[0018] The ceramic heater of the present application can be such that the length direction of the shape obtained by viewing the section is straight or curved, and the width of the bottom of the protrusion is constant (allowable tolerance, error) except for both end portions in the width direction of the groove in the connecting portion. Accordingly, in the connecting portion of the grooves to each other, a distribution of resistance along the width direction of the resistance heat generator is hardly generated.

[0019] The method of manufacturing the ceramic heater of the present application includes the following steps:

[0020] (a) forming a resistance heat generator or a precursor thereof in a prescribed pattern on the surface of a first ceramic fired layer or unfired layer;

[0021] (b) irradiating a laser to each of the sections obtained by dividing the resistance heat generator or the precursor thereof along the length direction thereof to form a groove along the length direction of the resistance heat generator or the precursor thereof;

[0022] (c) disposing a second ceramic unfired layer on the surface of the first ceramic fired layer or unfired layer in a manner of covering the resistance heat generator or the precursor thereof to obtain a laminate;

[0023] (d) performing hot-pressing firing on the laminate to thereby obtain a ceramic heater having the resistance heat generator inside a ceramic substrate,

[0024] In the step (b), the connecting portion of the grooves provided in the adjacent sections to each other is left with a protrusion extending along the connecting portion.

[0025] In the step (b) of the method of manufacturing the ceramic heater, the connecting portion of the grooves provided in the adjacent sections to each other is left with a protrusion extending along the connecting portion. For example, the groove provided in one of the adjacent sections is not subjected to the laser for forming the groove in the other section. Accordingly, the grooves of the adjacent sections do not overlap each other, and thus, it is possible to prevent a portion having a deep depth (a portion having a high resistance and being easily heated) from being generated in the connecting portion of the grooves of the adjacent sections.

[0026] The method of manufacturing the ceramic heater is suitable for manufacturing the above-described ceramic heater. For example, in the step (b), when a cross section obtained by cutting the protrusion along the surface in the length direction of the resistance heat generator is observed, the protrusion can appear as a mountain shape having a width of the bottom of 95 μm or less.

[0027] Note that the "ceramic fired layer" is a layer of ceramic that has been fired, and can be a layer of a ceramic sintered body, or a layer of a ceramic pre-sintered body. The "ceramic unfired layer" is a layer of ceramic that has not been fired, and can be a layer of a ceramic powder, or a layer of a ceramic molded body (including a ceramic molded body obtained by drying a molded body, a ceramic molded body obtained by drying and degreasing a molded body, a ceramic green sheet, etc.). The "resistance heat generating body precursor" refers to a product that becomes a resistance heat generating body by firing, and for example refers to a product on which a resistance heat generating body paste has been printed. The "laminate" can be a laminate in which a second ceramic unfired layer is disposed so as to cover a resistance heat generating body or a precursor thereof on the surface of a first ceramic fired layer or unfired layer, or can be a laminate in which a further layer (for example, a third ceramic fired layer or unfired layer in which an electrode or a precursor thereof is provided on the side of the second ceramic unfired layer) is further laminated on the second ceramic unfired layer. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a perspective view of the electrostatic chuck heater 10.

[0029] Figure 2 is a perspective view of the electrostatic chuck heater 10. Figure 1 is a cross-sectional view of A-A of the electrostatic chuck heater 10.

[0030] Figure 3 is an explanatory view of the resistance heat generating body 16 when viewed from above.

[0031] Figure 4 is a perspective view of the portion shown inside the rectangle of the electrostatic chuck heater 10. Figure 3

[0032] Figure 5 is a cross-sectional view of B-B of the electrostatic chuck heater 10. Figure 3

[0033] Figure 6 is an explanatory view of the method of finding the inclination angle a.

[0034] Figure 7 is a histogram in which the horizontal axis is the height of the resistance heat generating body 16 and the vertical axis is the degree.

[0035] Figure 8 is an explanatory view of the method of finding the width of the bottom of the convex portion Rm.

[0036] Figure 9 is a plan view of the curved portion of the resistance heat generating body 16.

[0037] Figure 10 is a manufacturing process diagram of the electrostatic chuck heater 10.

[0038] Figure 11 is an explanatory view of the process in which the resistance heat generating body precursor 66 is formed with the groove U.

[0039] ​​Figure 12 This is a cross-sectional view of trench 68.

[0040] Figure 13 This is a cross-sectional view of the groove U.

[0041] Figure 14 This is a cross-sectional view when the connecting parts of the grooves U are cut off.

[0042] Figure 15 This is a cross-sectional view of the connection between adjacent grooves R in the reference example. Detailed Implementation

[0043] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a perspective view of the electrostatic chuck heater 10 according to this embodiment. Figure 2 yes Figure 1 A-A cross-sectional view, Figure 3 This is an explanatory diagram showing the resistive heating element 16 viewed from above (the area within the rectangle is a magnified view). Figure 4 yes Figure 3 A three-dimensional view of the portion shown within the rectangle. Figure 5 yes Figure 3 B-B cross-section diagram, Figure 6 This is an explanatory diagram illustrating how to calculate the tilt angle α. Figure 7 It's a histogram. Figure 8 This is an explanatory diagram illustrating how to calculate the width of the bottom of the convex part Rm. Figure 9 This is a top view of the curved portion of the resistive heating element 16.

[0044] The electrostatic chuck heater 10 is configured such that an electrostatic electrode 14 and a resistive heating element 16 are embedded inside a ceramic substrate 12. A cooling plate 22 is bonded to the back of the electrostatic chuck heater 10 by means of an adhesive layer 26.

[0045] The ceramic substrate 12 is a circular plate made of ceramic (e.g., alumina or aluminum nitride). A wafer mounting surface 12a capable of mounting a wafer W is provided on the surface of the ceramic substrate 12.

[0046] The electrostatic electrode 14 is a circular conductive thin film substantially parallel to the wafer mounting surface 12a. A rod-shaped terminal (not shown) is electrically connected to the electrostatic electrode 14. The rod-shaped terminal extends downwards from the lower surface of the electrostatic electrode 14, passing through the ceramic substrate 12 and then through the cooling plate 22. The rod-shaped terminal is electrically insulated from the cooling plate 22. The portion of the ceramic substrate 12 above the electrostatic electrode 14 functions as a dielectric layer. Examples of materials for the electrostatic electrode 14 include tungsten carbide, metallic tungsten, molybdenum carbide, and metallic molybdenum; preferably, a material with a coefficient of thermal expansion similar to that of the ceramic to be used.

[0047] The resistance heat generating body 16 is a band-shaped conductive wire provided in a plane substantially parallel to the wafer mounting surface 12a. The band-shaped conductive wire is not particularly limited, and for example, can be set to a width of 0.1 to 10 mm, a thickness of 0.001 to 0.1 mm, and a line-to-line distance of 0.1 to 5 mm. The resistance heat generating body 16 is wired in a non-intersecting band-shaped conductive wire manner from one terminal portion 18 to the other terminal portion 20 in one stroke on the entire ceramic substrate 12. Power supply terminals not shown are electrically connected to the terminal portions 18 and 20 of the resistance heat generating body 16, respectively. These power supply terminals extend downward from the lower surface of the resistance heat generating body 16 through the ceramic substrate 12 and the cooling plate 22. In addition, these power supply terminals are electrically insulated from the cooling plate 22. As the material of the resistance heat generating body 16, for example, tungsten carbide, tungsten metal, molybdenum carbide, molybdenum metal, or the like can be given, and a material having a thermal expansion coefficient close to that of the ceramic to be used is preferable.

[0048] One terminal portion 18 to the other terminal portion 20 of the resistance heat generating body 16 is virtually divided into a plurality of sections S (see Figure 3 , a partial enlarged view). The determination method of the section S in the present embodiment is as follows. That is, a division point dividing the center line 16c of the resistance heat generating body 16 by a certain length is set, a section line orthogonal to the center line 16c is drawn at each division point, and adjacent section lines in the resistance heat generating body 16 are set as a section S therebetween. In this case, the length of each section S is constant. A groove R is provided on the surface of the resistance heat generating body 16 in the length direction of the resistance heat generating body 16 in each section S. The center line Rc when the groove R is observed from above coincides with the center line 16c when the resistance heat generating body 16 is observed from above. Note that the center line Rc and the center line 16c are considered to coincide even if there is a misalignment due to a tolerance or an error. The width of the groove R is set for each section S. For example, Figure 3 , a partial enlarged view of a rectangle, and Figure 4 , the width of the groove R (grooves R1 and R2) provided in adjacent two sections S (sections S1 and S2) is wider in the groove R2 than in the groove R1. The width of the groove R provided in adjacent two sections S is set discretely. However, the width of the groove R provided in adjacent two sections S is sometimes the same. The width of the groove R has a correlation with the resistance and heat generation of the section S in which the groove R is provided. Therefore, the width of the groove R is set based on the resistance and heat generation of the section S of the resistance heat generating body 16. Note that one terminal portion 18 to the other terminal portion 20 of the resistance heat generating body 16 can be divided into two sections S, or can be divided into three or more sections S.

[0049] A cross section obtained by vertically cutting the resistance heat generating body 16 along a plane in the length direction of the resistance heat generating body 16 is observed (see Figure 3When viewing a magnified view of the B-B section, such as... Figure 5 As shown, the grooves R (R1, R2) provided in adjacent intervals S (S1, S2) have a mountain-shaped protrusion Rm at the connection point where the bottom width (lower length b) is 95 μm or less. The current flowing through the resistive heating element 16 hardly flows into the protrusion Rm. Therefore, the resistance of the current flowing through the resistive heating element 16 is almost unaffected by the presence of the protrusion Rm. The mountain-shaped protrusion Rm is preferably, for example, having a height the same as the depth of the groove R, an upper length a of 20 μm to 50 μm, and a lower length b of 95 μm or less, which is longer than the upper length a. The lower length b is preferably 20 μm or more. The inclination angle α of the sidewall (inclined surface) of the protrusion Rm is not particularly limited, but is preferably 10° to 30°. The depth of the groove R is independent of the interval S and is set to the same value. Therefore, by adjusting the width of the groove R, the resistance and heat generation of the interval S in which the groove R is provided can be adjusted. The bottom surface of the groove R has minor irregularities rather than being a completely flat surface. Therefore, the depth of the groove R is an average depth. The depth of the groove R is preferably less than half the thickness of the resistive heating element 16, for example, it can be more than 10 μm and less than 30 μm.

[0050] Here, the method for determining the width (length b) of the bottom of the protrusion Rm and the inclination angle α is explained. First, an SEM image of a cross-section obtained by perpendicularly cutting the connecting portion of adjacent grooves R (R1, R2) of the resistive heating element 16 along the length direction of the resistive heating element 16 is obtained. Specifically, an image of the approximately center of the connecting portion in the width direction of the groove R (refer to...) is obtained. Figure 4 The SEM image of the cross-section obtained by cutting with a single-dotted line. In the SEM image, such as... Figure 6 As shown, an object range of 0.5 mm is set in the width direction of the bottom, including a single side surface (sloping surface) of the protrusion Rm. At this time, the bottom surface of the resistive heating element 16 is calibrated to be approximately horizontal, and one end of the object range ( Figure 6 The left end of the portion and the center of the protrusion Rm are approximately aligned. The bottom surface of the resistive heating element 16 is made horizontal. The height of the resistive heating element 16 is obtained from the image analysis of SEM images over the entire area of ​​the object, at 2.5 μm intervals along the width direction. Then, a histogram is created with the height of the resistive heating element 16 on the horizontal axis and degrees on the vertical axis. The height data interval is 1 μm. An example of a histogram is shown below. Figure 7The first group with a low height and the second group with a high height appear in the histogram. The first group is a group of the heights of the bottom surfaces of the grooves R, and the second group is a group of the heights of the top surfaces of the resistance heat generating bodies 16. In the histogram, the value with the highest degree (the most frequent value) in the first group is regarded as the height HL of the bottom surface of the groove R, and the value with the highest degree (the most frequent value) in the second group is regarded as the height HU of the top surface of the resistance heat generating body 16. In addition, the value obtained by subtracting HL from HU is set as the depth D of the groove R. Then, the value obtained by adding 0.1D to HL is set as the reference height, and the width of the convex portion Rm at the reference height is set as the width (the length b of the lower side) of the bottom of the convex portion Rm. In addition, as shown in FIG. 10, Figure 8 the value obtained by subtracting 0.1D from HU is set as the upper limit value, the heights taken at intervals of 2.5 μm between the reference height of the side surface on one side of the convex portion Rm and the upper limit value are adopted, a regression straight line is found, and the angle formed by the regression straight line and the horizontal line is set as the inclination angle α.

[0051] Regardless of whether the length direction of the shape obtained by viewing the section S of the resistance heat generating body 16 is straight or curved, the length direction of the shape obtained by viewing the groove R is straight. For example, Figure 3 the partial enlarged view shown in FIG. 9, Figure 4 in which the length direction of the shape (the rectangle) obtained by viewing the adjacent sections S (SI, S2) is straight, the length direction of the shape (the rectangle) obtained by viewing the adjacent grooves R (Rl, R2) is also straight. In addition, Figure 9 in which the length direction of the shape (the sector) obtained by viewing the adjacent sections S (SI l, SI 2, SI 3) is curved (a circular arc), the length direction of the shape (the trapezoid) obtained by viewing the adjacent grooves R (Rl l, Rl 2, Rl 3) is straight. Therefore, as described later, the groove R can be formed with good accuracy using a laser.

[0052] In addition, regardless of whether the length direction of the shape obtained by viewing the section S of the resistance heat generating body 16 is straight or curved, the width (the length b of the lower side) of the bottom of the mountain shape of the convex portion Rm is preferably substantially constant except for the vicinity of both ends in the width direction of the groove R in the joint portion. According to this, in the joint portion of the grooves R, a distribution of resistance hardly occurs along the width direction of the resistance heat generating body 16. Figure 5

[0053] The grooves R are not provided in the terminal portions 18, 20 of the resistance heat generating body 16. A power supply terminal that is inserted into the through hole of the cooling plate 22 is connected to the terminal portions 18, 20, but the power supply terminal is poor in heat dissipation compared to the cooling plate 22. Therefore, the terminal portions 18, 20 become portions in which the heat dissipation function is low.

[0054] ​The cooling plate 22 is made of metal (e.g., aluminum) and has a coolant passage 24 through which a coolant (e.g., water) passes. The coolant passage 24 is formed so that the coolant passes through the entire surface of the ceramic substrate 12. Note that a coolant supply port and a coolant discharge port (neither of which is shown) are provided in the coolant passage 24.

[0055] Next, an example of use of the electrostatic chuck heater 10 will be described. When a wafer W is placed on the wafer placement surface 12a of the electrostatic chuck heater 10, a voltage is applied between the electrostatic electrode 14 and the wafer W, whereby the wafer W is attracted to the wafer placement surface 12a by electrostatic force. In this state, plasma CVD film formation or plasma etching is performed on the wafer W. Alternatively, the wafer W is heated by applying a voltage to the resistance heater 16, or the wafer W is cooled by circulating a coolant in the coolant passage 24 of the cooling plate 22, whereby the temperature of the wafer W is controlled to be constant. When a voltage is applied to the resistance heater 16, a voltage is applied between the one terminal portion 18 and the other terminal portion 20 of the resistance heater 16. Then, current flows through the resistance heater 16, so that the resistance heater 16 generates heat, and the wafer W is heated.

[0056] In the present embodiment, the one terminal portion 18 to the other terminal portion 20 of the resistance heater 16 is divided into a plurality of sections S, and a groove R is provided on the surface of the resistance heater 16 in each section S. In the sections S in which the groove R has a wide width, the cross-sectional area of the resistance heater 16 is small, so the resistance is high, and the amount of heat generated is large. In the sections S in which the groove R has a narrow width, the cross-sectional area of the resistance heater 16 is large, so the resistance is low, and the amount of heat generated is small. Therefore, by adjusting the width of the groove R in each section S, the amount of heat generated in each section S of the resistance heater 16 is made to coincide with the target amount of heat generated.

[0057] Next, an example of manufacture of the electrostatic chuck heater 10 will be described. Figure 10 is a manufacturing process diagram of the electrostatic chuck heater 10, Figure 11 is an explanatory diagram of a process in which the groove U is formed in the resistance heater precursor 66, Figure 12 and Figure 13 is a cross-sectional view of the line groove 68 and the groove U when the resistance heater precursor 66 is vertically cut along a surface including the width direction of the resistance heater precursor 66, Figure 14 is a cross-sectional view of a connecting portion between adjacent grooves U when the resistance heater precursor 66 is vertically cut along a surface including the length direction of the resistance heater precursor 66. Hereinafter, a case in which an aluminum oxide substrate is used as the ceramic substrate 12 will be described.

[0058] [1] Production of a molded body (see Figure 10 (A))

[0059] The lower and upper disc-shaped shaped bodies 51, 53 are produced. Each of the shaped bodies 51, 53 is produced, for example, by first placing slurry containing alumina powder (for example, average particle diameter 0.1 to 10 μm), a solvent, a dispersing agent, and a gelling agent into a molding die, allowing the gelling agent to chemically react within the molding die to gel the slurry, and then releasing the shaped body from the molding die, thereby producing each of the shaped bodies 51, 53. The shaped bodies 51, 53 thus obtained are referred to as mold-cast shaped bodies.

[0060] As the solvent, any solvent that dissolves and disperses the dispersing agent and the gelling agent can be used without particular limitation. Examples include hydrocarbon-based solvents (toluene, xylene, solvent naphtha, etc.), ether-based solvents (ethylene glycol monoethyl ether, butyl carbitol, butyl carbitol acetate, etc.), alcohol-based solvents (isopropyl alcohol, 1-butanol, ethanol, 2-ethylhexanol, terpineol, ethylene glycol, glycerol, etc.), ketone-based solvents (acetone, methyl ethyl ketone, etc.), ester-based solvents (butyl acetate, dimethyl glutarate, glyceryl triacetate, etc.), and polybasic acid-based solvents (glutaric acid, etc.). Particularly preferably, a solvent having two or more ester bonds, such as a polybasic acid ester (for example, dimethyl glutarate, etc.), an acid ester of a polyhydric alcohol (for example, glyceryl triacetate, etc.), or the like is used.

[0061] As the dispersing agent, any agent that uniformly disperses the alumina powder in the solvent can be used without particular limitation. Examples include polycarboxylic acid-based copolymers, polycarboxylic acid salts, sorbitan fatty acid esters, polyglycerol fatty acid esters, phosphate ester salt-based copolymers, sulfonic acid salt-based copolymers, polyurethane polyester-based copolymers having tertiary amines, and the like. Particularly preferably, a polycarboxylic acid-based copolymer, a polycarboxylic acid salt, or the like is used. By adding this dispersing agent, the slurry before molding can be made into a low-viscosity slurry having high fluidity.

[0062] As the gelling agent, for example, an isocyanate, a polyhydric alcohol, and a catalyst can be included. Among these, as the isocyanate, any substance having an isocyanate group as a functional group can be used without particular limitation. Examples include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), or a modified body thereof, and the like. Note that, within the molecule, a reactive functional group other than the isocyanate group can be included, and a large number of reactive functional groups can be included as in a polyisocyanate. As the polyhydric alcohol, any substance having two or more hydroxyl groups capable of reacting with the isocyanate group can be used without particular limitation. Examples include ethylene glycol (EG), polyethylene glycol (PEG), propylene glycol (PG), polypropylene glycol (PPG), polytetramethylene glycol (PTMG), polyhexamethylene glycol (PHMG), polyvinyl alcohol (PVA), and the like. As the catalyst, any substance that promotes the urethane reaction of the isocyanate and the polyhydric alcohol can be used without particular limitation. Examples include triethylenediamine, hexamethylenediamine, 6-dimethylamino-1-hexanol, and the like.

[0063] In this process, it is preferable that first, a solvent and a dispersant are added to the alumina powder in a prescribed ratio, and they are mixed for a prescribed time to prepare a slurry precursor, and then, a gelling agent is added to the slurry precursor, and mixing and vacuum defoaming are performed to produce a slurry. The mixing method in the preparation of the slurry precursor and the slurry is not particularly limited, and, for example, a ball mill, a self-rotation type stirrer, a vibration type stirrer, a propeller type stirrer, or the like can be used. Note that the slurry obtained by adding the gelling agent to the slurry precursor starts the chemical reaction (urethane reaction) of the gelling agent over time, and thus, it is preferable to be quickly cast into a molding die. The slurry cast into the molding die is gelled by the chemical reaction of the gelling agent contained in the slurry. The chemical reaction of the gelling agent refers to a reaction in which an isocyanate and a polyol undergo a urethane reaction to become a urethane resin (polyurethane). By the reaction of the gelling agent, the slurry is gelled, and the urethane resin functions as an organic binder.

[0064] [2] Preparation of the calcined body (see Figure 10 (B))

[0065] After drying the lower and upper molded bodies 51, 53, debinding is performed, and further, calcination is performed, whereby the lower and upper calcined bodies 61, 63 are obtained. The purpose of the drying of the molded bodies 51, 53 is to evaporate the solvent contained in the molded bodies 51, 53. The drying temperature and the drying time can be appropriately set according to the solvent used. However, the setting of the drying temperature needs to be made so that the molded bodies 51, 53 do not crack during drying. In addition, the atmosphere can be any one of an atmospheric atmosphere, an inert atmosphere, and a vacuum atmosphere. The purpose of the debinding of the dried molded bodies 51, 53 is to decompose and remove organic matters such as a dispersant, a catalyst, and a binder. The debinding temperature can be appropriately set according to the kind of the organic matter contained, and, for example, can be set to 400 to 600°C. In addition, the atmosphere can be any one of an atmospheric atmosphere, an inert atmosphere, and a vacuum atmosphere. The purpose of the calcination of the debound molded bodies 51, 53 is to increase the strength and to make the handling easy. The calcination temperature is not particularly limited, and, for example, can be set to 750 to 900°C. In addition, the atmosphere can be any one of an atmospheric atmosphere, an inert atmosphere, and a vacuum atmosphere.

[0066] [3] Formation of the resistance heating element precursor (see Figure 10 (C))

[0067] On one side of the lower pre-fired body 61, a paste for the resistance heating element is printed in the same pattern as that for the resistance heating element 16, and then dried to form a resistance heating element precursor 66. On one side of the upper pre-fired body 63, a paste for the electrostatic electrode is printed in the same shape as that for the electrostatic electrode 14, and then dried to form an electrostatic electrode precursor 64. Both pastes contain alumina powder, conductive powder, binder, and solvent. The alumina powder can be, for example, the same powder used in the production of the molded bodies 51 and 53. For example, tungsten carbide powder can be used as the conductive powder. For example, cellulose-based binders (ethyl cellulose, etc.), acrylic-based binders (polymethyl methacrylate, etc.), and vinyl-based binders (polyvinyl butyral, etc.) can be used as binders. For example, terpineol can be used as a solvent. Printing methods can include, for example, screen printing. Printing is performed multiple times. Therefore, each precursor 66 and 64 forms a multilayer structure.

[0068] [4] Formation of grooves (refer to) Figure 10 (D) and Figures 11-14 )

[0069] A groove U is formed in the resistive heating element precursor 66 disposed on one side of the lower pre-burnt body 61. The resistive heating element precursor 66, from one end to the other, is virtually divided into multiple intervals T, similar to the interval S of the resistive heating element 16. Grooves U are formed on the surface of the resistive heating element precursor 66 in each interval T. Using... Figure 11 The picosecond laser processing machine 30 shown forms a groove U. While driving the motors of the current mirror and the stage, the picosecond laser processing machine 30 irradiates a laser 32 along the length of the resistive heating element precursor 66, thereby forming a groove 68. The width of the groove 68 is not particularly limited, but is preferably 10–100 μm, more preferably 20–60 μm. The picosecond laser processing machine 30 arranges multiple grooves 68 in an overlapping manner along the width of the resistive heating element precursor 66, thereby forming the groove U. Regarding the laser 32, the energy is highest at the center of the irradiation position, and decreases towards the outermost position. Therefore, the cross-section of the groove 68 becomes as follows... Figure 12 The shape shown is close to a Gaussian distribution. If the spacing of the grooves 68 is set to half the width of the grooves 68, then the cross-section of the laser 32 when forming the next groove 68 from the current groove 68 is as follows. Figure 12 As shown by the dashed line, the cross-section of laser 32 when forming the next groove 68 is as follows. Figure 12 As shown by the single-dotted line, the cross-section of laser 32 when forming the next groove 68 is as follows. Figure 12 The double-dotted line is shown. Therefore, if the formation of all the above grooves 68 is completed, the result is as follows: Figure 13The bottom surface of the groove U is approximately flat. The groove U is an assembly of grooves 68. The sidewalls of the groove U are inclined relative to the horizontal plane (the surface of the lower pre-fired body 61). Its inclination angle β (refer to...) Figure 13 The angle is preferably 45° or less. Furthermore, considering the machinability of the laser 32, the tilt angle β is preferably 18° or more. The tilt angle β varies depending on the output power of the laser 32 and the number of times the laser 32 processes the same area (the number of times the laser 32 irradiates the same area). The tilt angle β can be solved in the same way as the tilt angle α described above. In this case, instead of SEM images, data is obtained by measuring the height of the resistive heating element precursor 66 at 2.5 μm intervals along the width direction using a stylus probe.

[0070] The moving region of the irradiated part of the laser 32 along the length of the interval T includes: an acceleration region from a stationary state to reaching the target speed, a constant speed region moving at the target speed (constant speed), and a deceleration region from the target speed to a stop. To form the groove U with good accuracy, the laser 32 preferably irradiates in the constant speed region but not in the acceleration or deceleration regions. Furthermore, when forming the groove U by laser processing each interval T of the pre-burnt body 61, the shape of the interval T can be straight or curved, and the shape of the groove 68 is preferably straight. If the interval T is curved, when the groove U is formed with multiple straight grooves 68, the shape of the completed groove U viewed from above is trapezoidal or parallelogram. Therefore, the length of each groove 68 is sometimes different. In this case, if the lengths of the acceleration and deceleration regions are constant regardless of the length of the groove 68, and the length of the constant speed region is controlled to vary according to the length of the groove 68, laser processing becomes easier. In contrast, when the interval T is curved, if the groove U is formed by multiple curved grooves 68, the length of the acceleration zone and the length of the deceleration zone must be changed according to the radius of curvature of the curve, thus making the control more complicated.

[0071] The grooves U(U1, U2) in adjacent intervals T(T1, T2) do not overlap. As a result, as... Figure 14As shown, when a cross section of the resistance heat generating body precursor 66 is observed perpendicularly to the face including the width direction of the resistance heat generating body precursor 66, the connecting portions of the grooves U (Ul, U2) provided in the adjacent sections T (Tl, T2) to each other are formed with the mountain-shaped convex portions Um having a length of the bottom of 95 μm or less. The vertex of the side wall face (inclined face, inclined angle β) of the groove Ul formed in the section Tl near the boundary of the section Tl and the section T2 is still the height of the resistance heat generating body precursor 66 before the groove Ul is formed. The vertex of the side wall face (inclined face) of the groove U2 formed in the section T2 near the boundary of the section Tl and the section T2 is still the height of the resistance heat generating body precursor 66 before the groove U2 is formed. That is, the height of the convex portions Um coincides with the depth of the grooves Ul, U2. For this reason, the grooves Ul, U2 are formed without applying the Gaussian distribution-shaped laser 32 to the boundary of the section Tl and the section T2.

[0072] When the grooves U are formed, first, the thickness distribution of the resistance heat generating body precursor 66 before the grooves U are formed is measured using a laser displacement meter. The measurement is performed at a plurality of measurement points predetermined along the center line of the resistance heat generating body precursor 66. In the present embodiment, the measurement points are set to the intersection points between the center line of the resistance heat generating body precursor 66 and the section lines that divide the sections T. The difference (difference in thickness) between the target value of the thickness predetermined at each measurement point and the measured value of the thickness is found. The target value of the thickness is set based on the target value of the resistance when the resistance heat generating body precursor 66 is fired to produce the resistance heat generating body 16. Then, the number of the line grooves 68 formed in the section from the measurement point to the adjacent measurement point is determined based on the difference in thickness of the measurement point. The depth of the line grooves 68 is a predetermined value. Therefore, the number of the line grooves 68 is changed to change the width of the grooves U, and the cross-sectional area of the grooves U and even the cross-sectional area of the resistance heat generating body precursor 66 are changed. That is, the grooves U are formed so that the cross-sectional areas of the resistance heat generating body precursor 66 at the plurality of measurement points are the target cross-sectional areas predetermined respectively.

[0073] [5] Production of the laminate (see Figure 10 (E))

[0074] The alumina powder is laminated on the face of the lower pre-sintered body 61 on which the resistance heat generating body precursor 66 is provided in a manner of covering the resistance heat generating body precursor 66, and the upper pre-sintered body 63 is laminated on the alumina powder in a manner of contacting the face on which the electrostatic electrode precursor 64 is provided with the alumina powder, and molding is performed to obtain the laminate 50. The laminate 50 is a structure in which the alumina powder layer 62 having the same diameter as the pre-sintered bodies 61, 63 is interposed between the upper and lower pre-sintered bodies 61, 63. As the alumina powder, the same powder as that used when the molded bodies 51, 53 are produced can be used.

[0075] [6] Hot-pressing (see Figure 10 (F))

[0076] The obtained laminate 50 is subjected to hot-pressing while applying pressure in the thickness direction. At this time, the laminate 50 is blocked by the mold and does not expand in the radial direction, and thus is compressed in the thickness direction. The compression rate differs depending on the pressing pressure, and is, for example, 30 to 70%. Accordingly, the resistance heating element precursor 66 is fired to become the resistance heating element 16, the electrostatic electrode precursor 64 is fired to become the electrostatic electrode 14, and the pre-fired bodies 61 and 63 and the alumina powder layer 62 are sintered to be integrated into the ceramic substrate 12. In addition, the sections T, the grooves U, and the protrusions Um become the sections S, the grooves R, and the protrusions Rm. As a result, the electrostatic chuck heater 10 is obtained. In the hot-pressing, the pressing pressure is preferably 30 to 300 kgf / cm2at least at the maximum temperature (firing temperature). More preferably, the pressing pressure is 50 to 250 kgf / cm2. 2 2 In addition, the maximum temperature is appropriately set depending on the kind, particle diameter, and the like of the ceramic powder, and is preferably set to a range of 1000 to 2000°C. The atmosphere is appropriately selected from an atmospheric atmosphere, an inert atmosphere, and a vacuum atmosphere.

[0077] Here, the correspondence between the constituent elements of the present embodiment and the constituent elements of the present application is made clear. The electrostatic chuck heater 10 of the present embodiment corresponds to the ceramic heater of the present application. In addition, the formation of the resistance heating element precursor of the present embodiment (see Figure 10 (C)) corresponds to the process (a) of the present application, the formation of the grooves (see Figure 10 (D) and Figures 11-14 ) corresponds to the process (b), the production of the laminate (see Figure 10 (E)) corresponds to the process (c), the hot-pressing (see Figure 10 (F)) corresponds to the process (d), and the pre-fired body 61 corresponds to the first ceramic fired layer, and the alumina powder layer 62 corresponds to the second ceramic unfired layer.

[0078] In the electrostatic chuck heater 10 of the present embodiment described in detail above, the current flows in the length direction of the resistance heating element 16. Although there is a mountain-shaped protrusion Rm extending along the connecting portion of the grooves R (R1, R2) to each other at the connecting portion thereof, the current flowing in the resistance heating element 16 rarely enters the protrusion Rm to flow. Therefore, the resistance of the current flowing in the adjacent sections S (S1, S2) is not much affected by the presence of the protrusion Rm. In addition, if the grooves R (R1, R2) of the adjacent sections S (S1, S2) are to be formed continuously without gaps, the grooves R (R1, R2) are preferably formed so as to be connected to each other at the protrusions Rm. Figure 15 ​As shown, the depth of the connecting portions Rn of the grooves R (R1, R2) to each other is sometimes too deep. In this case, the resistance of the connecting portions Rn in the resistance heat generating body 16 is higher than that of other portions, so the heat generation of the connecting portions Rn is sometimes too large compared with that of other portions, but this is not the case in the present embodiment. Therefore, the uniformity of the surface of the electrostatic chuck heater 10 can be made good.

[0079] In particular, when a cross section obtained by vertically cutting the resistance heat generating body 16 along a surface in the length direction of the resistance heat generating body 16 is observed, the convex portion Rm appears in a mountain shape with the width of the bottom portion being 95 μm or less. As such, the width of the bottom portion of the convex portion Rm is sufficiently small, so the current flowing through the resistance heat generating body 16 hardly flows through the convex portion Rm. The relationship between the width of the bottom portion of the convex portion Rm and the surface temperature difference before and after the connecting portion was investigated, and as a result, if the width of the bottom portion of the convex portion Rm is 95 μm or less, the surface temperature difference before and after the connecting portion is less than 0.1°C, but if the width of the bottom portion of the convex portion Rm is 100 μm or more, the surface temperature difference before and after the connecting portion exceeds 0.1°C. From this, it is known that if the width of the bottom portion of the convex portion Rm is 95 μm or less, the heat generation amount of the connecting portion and the heat generation amounts before and after the connecting portion are substantially the same, the resistance of the connecting portion and the resistances before and after the connecting portion are substantially the same, and the current flowing through the resistance heat generating body 16 hardly flows through the convex portion Rm.

[0080] In addition, the convex portion Rm in a mountain shape is preferably the same height as the depth of the groove R, the upper side is 20 μm or more and 50 μm or less, and the lower side is longer than the upper side. According to this, when the groove R is formed using a laser, the convex portion Rm can be reliably left at the connecting portions of the grooves R to each other.

[0081] In addition, the depth of the groove R is independent of the interval S and is set to the same value, and the width of the groove R is set for each interval S. Therefore, by adjusting the width of the groove R, the resistance of each interval S of the resistance heat generating body 16 can be adjusted.

[0082] Further, the center line Rc of the groove R coincides with the center line 16c of the resistance heat generating body 16. Therefore, the temperature distribution in the width direction of the resistance heat generating body 16 is substantially symmetrical about the center line 16c, so the uniformity of the surface of the electrostatic chuck heater 10 can be easily and favorably maintained.

[0083] Furthermore, the groove R is not provided in the terminal portions 18, 20 in the resistance heat generating body 16 in which the heat dissipation is low. If the groove R is provided in the terminal portions 18, 20, the resistance of the terminal portions 18, 20 rises, the heat generation amount increases, on the other hand, the heat is not easily dissipated, so a hot spot is easily generated. In the present embodiment, since the groove R is not provided in the terminal portions 18, 20, a hot spot like this is not easily generated.

[0084] Also, the length direction of the shape obtained by viewing the recess R from above is straight regardless of whether the length direction of the shape obtained by viewing the section S from above is straight or curved, and thus the recess R can be formed with high precision when the recess R is formed using a laser. Also, the width of the bottom of the mountain shape of the convex portion Rm is substantially constant regardless of whether the length direction of the shape obtained by viewing the section S from above is straight or curved, and thus a distribution of resistance is hardly generated in the width direction of the resistance heat generating body 16 at the connection portions of the recesses R to each other.

[0085] Also, in the manufacturing method of the electrostatic chuck heater 10, when a cross section obtained by vertically cutting the resistance heat generating body precursor 66 along a surface in the length direction of the resistance heat generating body precursor 66 is observed, a convex portion Um in a mountain shape is left at the connection portion of the recesses U (Ul, U2) provided in the adjacent sections T (Tl, T2) to each other. Accordingly, the recesses U of the adjacent sections T do not overlap each other, and thus a portion having a deep depth (a portion having a high resistance and easily generating heat) can be prevented from being generated at the connection portion of the recesses U of the adjacent sections T to each other.

[0086] Note that the present application is not limited to the above-described embodiments, and can be implemented in various forms as long as they belong to the technical scope of the present application.

[0087] For example, in the above-described embodiments, the electrostatic chuck heater 10 is exemplified as the ceramic heater, but the ceramic heater can be one not having the electrostatic electrode 14. In this case, the laminated body 50 can be manufactured using the pre-sintered body 63 not having the upper portion of the electrostatic electrode precursor 64, and the laminated body 50 can be subjected to hot-press sintering, or the pre-sintered body 63 of the upper portion can be omitted, and the laminated body 50 can be manufactured, and the laminated body 50 can be subjected to hot-press sintering.

[0088] In the above-described embodiments, the alumina powder layer 62 is exemplified as the second ceramic unsintered layer, but an alumina molded body layer or an alumina green sheet can be used instead of the alumina powder layer 62. The alumina molded body layer can be a molded body layer subjected to drying, or a molded body layer subjected to drying and then subjected to debinding.

[0089] In the above-described embodiments, the pre-sintered body 61 is exemplified as the first ceramic sintered layer, but an alumina sintered body can be used instead of the pre-sintered body 61. Alternatively, a ceramic molded body layer or a ceramic green sheet can be used instead of the first ceramic sintered layer. The ceramic molded body layer can be a molded body layer subjected to drying, or a molded body layer subjected to drying and then subjected to debinding.

[0090] In the above embodiment, as the resistance heating element precursor 66 for forming the groove U, a precursor obtained by printing a paste for a resistance heating element and drying it is used, but a precursor obtained by printing, drying, and then performing debinding, or a precursor obtained by printing, drying, debinding, and then performing pre-burning (or firing) can also be used.

[0091] In the above embodiment, the resistance heating element 16 is obtained by wiring in a non-intersecting strip-like conductive line pattern in one stroke over the entire ceramic substrate 12, but is not particularly limited thereto. For example, the ceramic substrate 12 can be divided into a plurality of sections, and a resistance heating element obtained by wiring in a non-intersecting strip-like conductive line pattern in one stroke is provided for each section. In this case, each resistance heating element can have the same structure as the above-described resistance heating element 16.

[0092] In the above embodiment, the electrostatic chuck heater 10 is exemplified as a structure in which the electrostatic electrode 14 and the resistance heating element 16 are embedded in the ceramic substrate 12, but a structure in which the electrostatic electrode 14 is embedded in the ceramic substrate 12 and the resistance heating element 16 is provided on the surface of the ceramic substrate 12 can also be used.

[0093] In the above embodiment, the plurality of sections S are set to a certain length, but are not particularly limited thereto. For example, each of the sections S can be set to a respective length. The same applies to the sections T.

[0094] In the above embodiment, the height of the protrusion Rm is made the same as the depth of the groove R, but the height of the protrusion Rm can also be made a value smaller than the depth of the groove R.

[0095] In the above embodiment, the width of the bottom of the protrusion Rm is set to 95 μm or less, but instead of this, the width of the bottom of the protrusion Rm can be made 1 or more and 20 or less with respect to the depth of the groove R, or in addition to this, the width of the bottom of the protrusion Rm can be made 1 or more and 20 or less with respect to the depth of the groove R. Even in this case, the width of the bottom of the protrusion Rm is sufficiently small, and thus the current flowing through the resistance heating element 16 hardly enters the protrusion Rm to flow therethrough.

[0096] In the above embodiment, the height of the convex portion Rm is the same as the depth of the groove R, the length a of the upper side is 20 μm or more and 50 μm or less, and the length b (width of the bottom) of the lower side is longer than the length of the upper side, but instead of this, the length a of the upper side of the convex portion Rm can be 0 or more and 9 or less with respect to the depth of the groove R, or in addition to this, the length a of the upper side of the convex portion Rm can be 0 or more and 9 or less with respect to the depth of the groove R. Alternatively, the height of the convex portion Rm can be 0.3 or more and 1 or less with respect to the depth of the groove R. Even so, when the groove R is formed by laser, the convex portion Rm can be reliably left at the connection portion of the grooves R to each other.

[0097] In the above embodiment, a part of the plurality of sections S of the resistance heat generating body 16 can not have the groove R.

[0098] This application is based on Japanese Patent Application No. 2020-030725 filed on February 26, 2020, which is hereby incorporated by reference in its entirety into this application.

[0099] Industrial Applicability

[0100] The ceramic heater of the present application is used for, for example, a semiconductor manufacturing device.

[0101] Explanation of Symbols

[0102] 10 electrostatic chuck heater, 12 ceramic substrate, 12a wafer mounting surface, 14 electrostatic electrode, 16 resistance heat generating body, 16c center line, 18, 20 terminal portion, 22 cooling plate, 24 coolant passage, 26 adhesive layer, 30 picosecond laser processing machine, 32 laser, 50 laminate, 51, 53 molded body, 61, 63 pre-fired body, 62 alumina powder layer, 64 electrostatic electrode precursor, 66 resistance heat generating body precursor, 68 line groove, R, R1, R2 groove, Rm convex portion, U, U1, U2 groove, S, S1, S2 section, T, T1, T2 section.

Claims

1. A ceramic heater comprising a resistance heating element, The ceramic heater is characterized in that The resistance heating element is configured such that one end to the other end of the resistance heating element is divided into a plurality of sections, A groove is provided on the surface of the resistance heating element in each of the sections along the length direction of the resistance heating element, A connecting portion of the grooves provided in adjacent sections to each other is provided with a protrusion extending along the connecting portion, When a cross section obtained by cutting the protrusion with a plane along the length direction of the resistance heating element is observed, if a value obtained by adding the groove bottom surface height to 0.1 x the groove depth is set as a reference height, and the width of the protrusion at the reference height is set as the width of the bottom of the protrusion, the protrusion appears as a mountain shape with the width of the bottom being 95 μm or less.

2. The ceramic heater according to claim 1, characterized in that The groove depth is the same value regardless of the sections, The groove width is set for each of the sections.

3. The ceramic heater according to claim 1 or 2, characterized in that The groove center line coincides with the resistance heating element center line.

4. The ceramic heater according to claim 1 or 2, characterized in that The groove is not provided at a portion of the resistance heating element where heat dissipation is low.

5. The ceramic heater according to claim 1 or 2, characterized in that Regardless of whether the length direction of the shape obtained by viewing the section is straight or curved, the length direction of the shape obtained by viewing the groove is straight.

6. The ceramic heater according to claim 1 or 2, characterized in that Regardless of whether the length direction of the shape obtained by viewing the section is straight or curved, the width of the bottom of the protrusion is constant except for both end portions in the groove width direction in the connecting portion.

7. A method of making a ceramic heater, comprising: comprising the following steps: (a) forming a resistance heating element or a precursor thereof in a prescribed pattern on the surface of a first ceramic fired or unfired layer; (b) irradiating laser light to each of sections obtained by dividing the resistance heating element or the precursor thereof along the length direction thereof, thereby forming a groove along the length direction of the resistance heating element or the precursor thereof; (c) disposing a second ceramic unfired layer on the surface of the first ceramic fired or unfired layer in a manner so as to cover the resistance heating element or the precursor thereof, thereby obtaining a laminate; (d) performing hot-pressing firing on the laminate, thereby obtaining a ceramic heater having the resistance heating element inside a ceramic substrate, In the step (b), a connecting portion of the grooves provided in adjacent sections to each other is left with a protrusion extending along the connecting portion, and when a cross section obtained by cutting the protrusion with a plane along the length direction of the resistance heating element is observed, if a value obtained by adding the groove bottom surface height to 0.1 x the groove depth is set as a reference height, and the width of the protrusion at the reference height is set as the width of the bottom of the protrusion, the protrusion appears as a mountain shape with the width of the bottom being 95 μm or less.

Images