JP2006066742A - Heater and wafer heating device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent heater in which a temperature difference in a wafer face is set so as to be 0.4°C or lower, the change quantity of the resistance value of a resistance heating body is made small, and the temperature variation of a wafer is made small even when heating and cooling are repeated, and a wafer heating device using the heater. <P>SOLUTION: This heater is provided with a band-shaped resistance heating body on the surface of a plate-shaped body, and a groove which is almost parallel with the longitudinal direction of the band of the resistance heating body. The resistance heating body is constituted of the composite material of an insulating composition and a conductive composition, and the density of the conductive composition on the surface of the groove is set so as to be smaller than the density of the internal conductive composition of the resistance heating body. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wafer heating apparatus mainly used for heating a wafer. For example, a thin film is formed on a wafer such as a semiconductor wafer, a liquid crystal device or a circuit board, or a resist solution applied on the wafer. The present invention relates to a heater suitable for forming a resist film by dry baking.

  2. Description of the Related Art A heater for heating a semiconductor wafer (hereinafter abbreviated as a wafer) is used in a semiconductor thin film forming process, an etching process, a resist film baking process, and the like in a manufacturing process of a semiconductor manufacturing apparatus.

  The conventional semiconductor manufacturing apparatus has a batch type that heats a plurality of wafers at once and a sheet type that heats one wafer at a time, and the single wafer type has excellent temperature controllability. As miniaturization and improvement in accuracy of wafer heat treatment temperature are required, ceramic heaters are widely used.

  As such a ceramic heater, for example, Patent Document 1 and Patent Document 2 propose a ceramic heater 71 as shown in FIG.

  This ceramic heater 71 has a plate-like body 72 and a metal case 79 as main components, and nitride ceramics or carbide is formed in an opening of a bottomed metal case 79 made of metal such as aluminum. A plate-like body 72 made of ceramics is fixed with a bolt 80 via a heat insulating connecting member 74 made of a resin, and the upper surface thereof is used as a mounting surface 73 on which the wafer W is placed. A concentric resistance heating element 75 as shown in FIG. 17 was provided.

  Furthermore, a power supply terminal 77 is brazed to the terminal portion of the resistance heating element 75, and the power supply terminal 77 is inserted into a lead wire drawing hole 76 formed in the bottom 79 a of the metal case 79. 78 to be electrically connected.

  By the way, in such a heater 71, it is important to make the temperature distribution of the wafer uniform in order to form a homogeneous film on the entire surface of the wafer W and to make the heating reaction state of the resist film uniform. . Therefore, until now, in order to reduce the temperature difference in the surface of the wafer, the resistance distribution of the resistance heating element 75 is adjusted, or the temperature of the resistance heating element 75 is divided and controlled. However, the resistance heating element produced by the printing method has a problem that the film thickness varies and a resistance value as designed cannot be obtained. Therefore, as a method for adjusting the resistance distribution, Patent Document 3, Patent Document 4 and Patent Document 5, a method of adjusting the resistance by forming a groove with a laser beam is disclosed.

  Further, as in Patent Document 6, the resistance heating element is corrugated and the corrugated portion is trimmed with a laser, or a plurality of grooves m are formed with a laser at the end of the band of the resistance heating element, and the resistance is adjusted. A method for improving the temperature distribution of the wafer W is disclosed in Patent Document 7.

However, although the temperature difference in the wafer surface is small, it is still insufficient to form a homogeneous film on the entire surface of the wafer W, and a heater capable of heating the temperature distribution more uniformly has been demanded.
JP 2001-203156 A JP 2001-313249 A JP 2001-244059 A JP 2002-141159 A JP 2002-151235 A JP 2002-43031 A JP 2002-203666 A

  However, in the methods such as Patent Document 6 and Patent Document 7, it is possible to improve the temperature distribution to some extent. However, the resistance value of the heater formed by the above method changes as heating and cooling are repeated. There is a problem that the soaking balance on the wafer surface is lost and the temperature difference on the wafer surface exceeds 0.4 ° C.

  Thus, as a result of intensive studies on the above problems, the present inventors have provided a belt-like resistance heating element on the surface of the plate-like body, and a heater provided with a groove substantially parallel to the longitudinal direction of the band of the resistance heating element. The resistance heating element is made of a composite material of an insulating composition and a conductive composition, and the density of the conductive composition on the surface of the groove is smaller than the density of the conductive composition inside the resistance heating element. Features.

  Further, in the heater provided with a strip-like resistance heating element on the surface of the plate-like body, and provided with a groove substantially parallel to the longitudinal direction of the strip of the resistance heating element, the resistance heating element includes an insulating composition and a conductive composition. And the conductive composition on the surface of the groove is circular.

  Further, in the heater provided with a strip-like resistance heating element on the surface of the plate-like body, and provided with a groove substantially parallel to the longitudinal direction of the strip of the resistance heating element, the resistance heating element includes an insulating composition and a conductive composition. The lightness of the surface of the groove is smaller than the lightness of the surface of the resistance heating element.

  Moreover, the average diameter of the conductive composition on the surface of the groove is 1 to 20 μm.

  Further, the resistance heating element has a lump of the insulating composition surrounded by a large number of the conductive particles in its cross section.

  The plate-like ceramic body has a strip-like resistance heating element, and has a group of a plurality of grooves that are substantially parallel to the longitudinal direction of the strip of the resistance heating element and have the same length. It is characterized by being in the center of the width of the belt of the heating element.

  Further, the width of the group is within 90% of the width of the band of the resistance heating element.

  The depth of the groove is 20% to 75% of the width of the groove.

  Further, the groove is formed by a laser beam.

  According to the present invention, the heater is provided with a mounting surface on which a wafer is placed on the side opposite to the surface on which the resistance heating element of the plate-like ceramic body is formed, and power is supplied independently to the resistance heating element. And a metal case that surrounds the power supply unit to form a wafer heating apparatus.

  The temperature difference within the wafer surface is as small as 0.4 ° C. or less, and it is possible to provide a heater in which the variation in resistance value of the resistance heating element is small and the temperature variation of the wafer is small even when heating and cooling are repeated.

  Embodiments of the present invention will be described below.

  FIG. 1 is a cross-sectional view showing an example of a case where a heater 1 according to the present invention is used as a wafer heating device. One main surface of a plate-like body 2 made of ceramics mainly composed of silicon carbide or aluminum nitride is shown in FIG. A mounting surface 3 on which the wafer W is placed is provided, a resistance heating element 5 is formed on the other main surface, and a heat equalizing plate 100 having a power feeding portion 6 electrically connected to the resistance heating element 5 is provided. The power supply terminal 11 is connected to the part 6. A metal case 19 surrounding these power feeding portions 6 is fixed to the peripheral portion of the other main surface of the plate-like body 2.

  Further, the wafer lift pins 14 can move the wafer W up and down through a hole penetrating the plate-like ceramic body 2 so that the wafer W can be placed on or removed from the placement surface 3. Then, the power supply terminal 11 is connected to the power supply unit 6 and power is supplied from the outside, and the wafer W can be heated while the temperature measuring element 10 measures the temperature of the plate-like body 2.

  The wafer W is held in a state of being lifted from the mounting surface 3 by the wafer support pins 8, and temperature variations due to, for example, contact of the wafer W can be prevented. Further, when the resistance heating element 5 is divided into a plurality of blocks, it is preferable to uniformly heat the wafer W on the mounting surface 3 by independently controlling the temperature of each block.

  As the conductive composition contained in the resistance heating element 5, it is preferable to use a Pt group metal, Au, or an alloy thereof having good heat resistance and oxidation resistance as a main component. Further, the resistance heating element 5 may include an insulating composition composed of 30 to 75% by weight of a glass component in order to improve the adhesion to the plate-like body 2 and the sinterability of the resistance heating element 5 itself. preferable.

  FIG. 2 shows an example of a spiral resistance heating element 5. FIG. 3 shows an example of another resistance heating element 5. The resistance heating element 5 includes a concentric arc-shaped resistance heating element 5 positioned on the outer peripheral portion of the plate-like body 2 and a plurality of concentric resistance heating elements 5 in the center. Further, in order to improve the thermal uniformity, the resistance heating element 5 is divided into a total of six patterns including four patterns in the peripheral portion and two patterns in the central portion. Any of them may be a resistance heating element 5 that can uniformly heat the mounting surface 3.

  FIG. 4 shows another example of the resistance heating element 5. The resistance heating element 5 is divided into a total of five resistance heating elements 5, four at the periphery and one at the center.

  In any case, the resistance heating element 5 has a width of 1 to 20 mm and a thickness of 5 to 50 μm, and can be formed by a screen printing method. Then, the pattern shape is designed so that the temperature difference in the wafer W surface becomes small with reference to the center line of the belt-like resistance heating element 5.

  The heater 1 according to the present invention includes a strip-like resistance heating element 5 on the surface of a plate-like body 2, and the heater 1 having a groove m substantially parallel to the longitudinal direction of the strip of the resistance heating element 5. 5 is composed of a composite material of the insulating composition 52 and the conductive composition 51, and the density of the conductive composition 51 on the surface of the groove is smaller than the density of the conductive composition 51 inside the resistance heating element 5. It is characterized by.

  As shown in FIG. 5, the density of the conductive composition 51a on the surface of the groove m formed in the resistance heating element 5 is made smaller than the density of the conductive composition 51 inside the resistance heating element 5, thereby forming the groove m. The value of the specific resistance on the surface is larger than the value of the internal specific resistance from the surface of the groove. This is because the current flowing on the surface of the groove m is reduced, and the growth of micro cracks on the surface can be suppressed.

  When the groove m is formed by the laser beam, a micro crack is generated on the surface of the groove m, and when the resistance heating element 5 is repeatedly energized, the micro crack grows and changes in resistance value. This is because the difference may become large and it may be difficult to maintain the thermal uniformity, but the growth of microcracks can be prevented by reducing the density of the conductive composition 51a on the surface of the groove m.

  In order to reduce the density of the conductive composition 51a on the surface of the groove m, the particle size of the insulating composition 52 of the resistance heating element 5 is made larger than the particle size of the conductive composition 51 as shown in FIG. Thus, the dispersion of the conductive composition 51 can be biased, or can be achieved by using a paste in which the conductive composition 51 having an average particle size of 0.5 to 1.5 μm is aggregated. When the resistance heating element 5 is formed by using the paste thus agglomerated and grooves are formed by laser light, it is considered that the agglomerated conductive composition 51 is appropriately aggregated to produce a conductive composition having a large particle size. .

  When the groove m is formed by laser light using the conductive composition 51 and the insulating composition 52 described above, the insulating composition 52 and the conductive composition 51 are melted and re-solidified, so that the conductivity of the surface of the groove m is increased. The composition 51a is preferably formed into a large circle as shown in FIG. 5 due to surface tension. This is because the thermal stress generated at the interface between the conductive composition 51a and the insulating composition 52 can be relaxed by making the shape circular.

  The circular shape means that the conductive composition 51 on the surface of the groove is observed with a scanning microscope, and the shape of the conductive composition 51 converted to the direction perpendicular to the surface of the resistance heating element is the same as that of the conductive composition 51. A circle having a difference ((D1−D2) / D2) × 100 of the diameters D1 and D2 between the circumscribed circle and the inscribed circle within 30% of the outer shape was defined as a circle.

  Further, the heater 1 of the present invention is characterized in that the lightness of the surface of the groove m is smaller than the lightness of the surface of the resistance heating element 5.

  A metal micrograph of the resistance heating element 5 in which the groove m is formed is photographed, and the brightness of the groove m is smaller than the brightness of the resistance heating element 5 in the portion without the groove m of the resistance heating element 5.

  Since the density of the conductive composition 51 is small on the surface of the groove m of the resistance heating element 5, it is considered that the amount of light reflected by the conductive composition 51 is reduced and the brightness is lower than that of the portion without the groove m. It is done. If the lightness of the groove m is small, the surface current of the groove m is smaller than the surface of the resistance heating element 5 without the groove m, and cracks are generated from the surface of the groove m even if the temperature heating cycle of rapidly heating or cooling the resistance heating element 5 is repeated. And the resistance of the resistance heating element 5 is not changed or disconnected, and excellent characteristics can be obtained.

  Moreover, it is preferable that the average particle diameter of the electroconductive composition 51 of the surface of the groove | channel m is 1-20 micrometers. Thus, it is preferable to increase the particle size of the conductive composition 51 on the surface of the groove m, thereby reducing the number of the conductive compositions 51 and reducing the surface density. When the average particle size of the conductive composition 51 is less than 1 μm, the effect of stress relaxation is small, and there is a possibility that a crack extends from the surface of the groove m to the inside of the resistance heating element 5.

  Further, if the average particle size of the conductive composition 51 exceeds 20 μm, the particle size of the conductive composition 51 is too large, and cracks may occur at the interface between the conductive composition 51 and the insulating composition 52. there were. More preferably, it is 5-10 micrometers.

  The density of the conductive composition 51 can be calculated by determining the area ratio occupied by the conductive composition 51 from the groove m and the internal reflection electron micrograph by image analysis or the like. The average particle size of the conductive composition 51 can be obtained by image analysis.

  Further, in order to reduce the density of the conductive composition 51 in the groove m, as described above, a lump of the insulating composition 52 surrounded by conductive particles made of a large number of conductive compositions 51 is formed. Preferably there is. This is because, when there is a lump of the insulating composition in this way, when the groove m is formed by laser light, the diameter of the conductive composition 51a on the surface of the groove m is increased, and the density can be reduced.

  Further, the groove m of the heater 1 of the present invention has a group g of a plurality of grooves m substantially parallel to the longitudinal direction of the band of the resistance heating element 5, and the group g has a width of the band of the resistance heating element 5. It is preferable that it exists in a center part.

  In the sectional view perpendicular to the longitudinal direction of the resistance heating element 5 as shown in FIG. 9, the sectional areas of the resistance heating elements 5a and 5b on both sides of the resistance heating element 5 divided by the group g are substantially equal. That is, the resistance values of the resistance heating elements 5a and 5b are substantially equal. Therefore, the heat generation amount becomes substantially equal in the left and right directions in the width direction of the resistance heating elements 5a and 5b, and the width of the band of the resistance heating element 5 is adjusted even if the variation of the partial resistance value of the resistance heating element 5 is adjusted by forming the group g. The center line of the direction does not change greatly from the design position, and the soaking plate 100 can be heated uniformly by forming the groove m in the designed resistance heating element 5 and adjusting the resistance. The temperature difference can be reduced.

  On the other hand, when the center in the width direction of the group g is shifted from the center in the width direction of the resistance heating element 5 as shown in FIG. 13 and FIG. That part is likely to generate heat. For this reason, the right and left heat generation balance is lost in the width direction of the band of the resistance heating element 5 and a temperature difference is generated in the width direction, so that the in-plane temperature difference of the wafer W may be increased.

  The width Wg of the group g is preferably within 90% of the width Wh of the band of the resistance heating element 5. This is because the resistance heating element 5 which is usually fine and complicated is formed by the screen printing method, and the cross-sectional area of the resistance heating element 5 formed by the screen printing method is the width of the band of the resistance heating element 5 as shown in FIG. This is because the thickness of the left and right regions of 5% is reduced. The groove m is formed by a laser beam or the like. The size of the groove m is determined by the output of the laser beam and the irradiation time, and the output and irradiation time are not changed during processing of the normal groove m. This is almost the same. Therefore, when the groove m is formed in a location within 90% of the width of the band of the resistance heating element 5 excluding the region having a small thickness at the peripheral portion, there is no possibility that the groove m penetrates the resistance heating element 5, and the groove m The possibility of generating cracks at the bottom is small and preferable. More preferably, it is within 60%. However, when the groove m is formed so as to exceed 90% of the width of the band of the resistance heating element 5, the groove m is formed in a portion where the film thickness at both ends of the resistance heating element 5 is thin. This is because there is a possibility that microcracks may be generated by penetrating 5 or irradiating the plate-like body 2 with laser light. Furthermore, if the micro cracks are generated, if the heater 1 is repeatedly heated and cooled, the temperature difference on the surface of the wafer W becomes large and the thermal uniformity may be deteriorated. In the worst case, the plate-like body may be destroyed.

  Further, the depth of each of the grooves m1, m2,... Forming the group g of the grooves m is preferably in the range of 20% to 75% of the width Wm of the grooves m (groove depth / groove width = 20). ~ 75%). This is because if it is less than 20%, the change in resistance value due to the formation of one groove m is small and the adjustment range of the resistance value is also small, so it becomes difficult to sufficiently reduce the in-plane temperature difference of the wafer W. It is.

  Further, when the depth of the groove m exceeds 75% of the width Wm, the energy of the first pulse of the laser is large and a micro crack is generated at the bottom of the resistance heating element 5, and when heating and cooling are repeated, the micro crack grows. This is because a change in the resistance value of the resistance heating element 5 occurs, and if the resistance value changes, the in-plane temperature difference of the wafer W becomes large and it may not be possible to maintain the thermal uniformity. More preferably, it is 30 to 50%.

  Further, a group g composed of a plurality of grooves m1, m2,... Approximately parallel to the longitudinal direction of the band of the resistance heating element 5 is formed, and the group includes a plurality of the groups g, and the group g1 It is preferable that the gap Gg with the group g2 is smaller than the width Wh of the band.

  Since the resistance heating element 5 is formed by screen printing, when the resistance heating element 5 is formed, a slight positional deviation from the design position occurs. For this reason, a deviation between the set position of the plate-like body 2 and the position of the resistance heating element 5 occurs. Therefore, when the group g composed of the long grooves m1, m2,... Is formed in the resistance heating element 5 without providing the gap Gg between the group g1 and the group g2, the subtle positional deviation increases as shown in FIG. Even if it is aligned with the center at the start point P1, the group g is formed at the position deviated from the center of the band width at the end point P2. Therefore, the cross-sectional areas serving as current paths are greatly different on the right and left of the cross section of the resistance heating element 5 adjacent to the end point P2 of the group g. There is a risk that the internal temperature difference will increase.

  In order to prevent the occurrence of the problem, the group g is divided into a plurality of groups as shown in FIG. 8, and the gap Gg between the plurality of groups g1 and g2 is larger than the width Wh of the band of the resistance heating element 5. Small is preferable. By doing so, the change in the amount of heat generation on the left and right of the band of the resistance heating element 5 is small, and the portion of the gap Gg becomes a bypass of the left and right bands divided by the groove m, so that the current flow is not biased and heat is generated. This is because it becomes uniform.

  On the other hand, when the gap Gg is larger than the width Wh of the band, the amount of heat generated at the point Gg becomes small, and when heated, the point becomes a cool spot, and the temperature of the wafer W is lowered only at that point, resulting in poor overall heat uniformity. Become. Therefore, the gap Gg between the groups g is preferably smaller than the band width Wh.

  Further, the interval between the groups g of the grooves is preferably 1 mm or less. This is because if it is 1 mm or less, the bias of the current can be prevented and the possibility of generating a cool spot is small.

  In addition, since laser trimming is normally performed in the atmosphere, the main component is Pt, Au, or an alloy thereof, which is a noble metal having good heat resistance and oxidation resistance, as a conduction component contained in the resistance heating element 5. Is preferably used. As the resistance heating element 5, it is preferable to mix 30 to 70% by weight of a glass component in order to improve adhesion to the insulating layer and sinterability of the resistance heating element itself.

  Further, as shown in FIG. 1, the ceramic heater of the present invention is obtained by joining a ceramic heater comprising a resistance heating element 5 to a soaking plate 100 to a metal case 19 and connecting a power supply terminal 11 to the power supply section 6. is there. At this time, since the connecting means between the power supply unit 6 and the power supply terminal 11 is pressed by the elastic body 18, the difference in expansion due to the temperature difference between the heat equalizing plate 100 and the metal case 19 can be mitigated by sliding of the contact portion. It can be set as a favorable wafer heating apparatus with respect to the heat cycle in use. As the elastic body 18 as the pressing means, a coiled spring as shown in FIG. 1 or a plate spring or the like may be used for pressing.

  As a pressing force of these elastic bodies 18, a load of 0.3 N or more may be applied to the power feeding terminal 11. The reason why the pressing force of the elastic body 18 is 0.3 N or more is that the power supply terminal 11 must move in response to the dimensional change due to the expansion and contraction of the heat equalizing plate 100 and the metal case 19. Since the upper power supply terminal 11 is pressed against the power supply unit 6 from the lower surface of the heat equalizing plate 100, the power supply terminal 11 is prevented from being separated from the power supply unit 6 due to friction with the sliding portion of the power supply terminal 11. is there.

  Moreover, it is preferable that the shape of the contact surface side with the electric power feeding part 6 of the electric power feeding terminal 11 shall be 0.5-4 mm. Furthermore, as the insulating material for holding the power supply terminal 11, a PEEK (polyethoxyethoxyketone resin) material in which glass fibers are dispersed can be used at a temperature of 200 ° C. or lower depending on the use temperature. In addition, when used at a temperature higher than that, it is possible to use a ceramic insulating material made of alumina, mullite or the like.

  At this time, it is preferable that at least the contact portion of the power supply terminal 11 with the power supply portion 6 is formed of a metal composed of at least one of Ni, Cr, Ag, Au, stainless steel, and a platinum group metal. Specifically, contact failure due to oxidation of the surface of the power supply terminal is prevented by forming the power supply terminal 11 itself with the metal or by inserting a metal foil made of the metal between the power supply terminal 11 and the power supply unit 6. In addition, the durability of the soaking plate 100 can be improved. Specifically, when a metal foil made of at least one of Ni, Cr, Ag, Au, stainless steel, and platinum metal is inserted between the power supply unit 6 and the power supply terminal 11, the reliability of electrical contact is achieved. At the same time, the dimensional difference caused by the temperature difference between the soaking plate 100 and the metal case 19 can be alleviated by the slip of the surface of the metal foil.

  Further, if the surface of the power supply terminal 11 is subjected to brazing or sandblasting to prevent the contact from becoming a point contact by roughening the surface, the contact reliability can be further improved.

  The soaking plate 100 is installed on the metal case 19 so as to cover the opening. The metal case 19 has a side wall portion and a single-layer or multilayer plate-like structure portion. The plate-like structure is provided with a power supply terminal 11 for electrical connection with a power supply unit 6 for supplying power to the resistance heating element 5 of the heat equalizing plate 100 via an insulating material. It is pressed by the power feeding part 6 on the surface of 100. The temperature measuring element 10 is installed in the vicinity of the wafer placement surface 3 in the center of the heat equalizing plate 100 and adjusts the temperature of the heat equalizing plate 100 based on the temperature of the temperature measuring element 10. When the resistance heating element 5 is divided into a plurality of blocks and individually controlled in temperature, the temperature measuring element 10 is installed in each block of the resistance heating element 5.

  Further, the soaking plate 100 may be formed with a gas injection port 12 for cooling the soaking plate 100 and an opening for exhausting gas. By providing a cooling mechanism for the soaking plate 100 in this way, the tact time can be shortened by forming a semiconductor thin film or a resist film on the surface of the wafer W or etching the surface.

  Moreover, it is preferable that a plate-shaped structure part is made into two or more layers. If this is a single layer, it takes time to reduce the in-plane temperature difference of the wafer W, which is not preferable. The uppermost layer of the plate-like structure part is desirably installed at a distance of 5 to 15 mm from the heat equalizing plate 100. This facilitates soaking by the mutual radiant heat of the soaking plate 100 and the plate-like structure, and since there is a heat insulating effect with other layers, the time until the in-plane temperature difference of the wafer W becomes small. Becomes shorter. Further, at the time of cooling, the gas that has received the heat of the surface of the soaking plate 100 from the gas injection port 12 is sequentially discharged out of the layer, and new cooling gas can cool the surface of the soaking plate 100, so that the cooling time Can be shortened.

  Further, the lift pins 14 installed in the metal case 19 so as to be movable up and down perform operations such as placing the wafer W on the placement surface 3 and lifting it from the placement surface 3. The wafer W is held in a state of being lifted from the mounting surface 3 by the wafer support pins 8 so as to prevent temperature variation due to contact with each other.

  In order to heat the wafer W by the heater 1, the wafer W carried to the upper side of the mounting surface 3 by the unillustrated transfer arm is supported by the lift pins 14, and then the lift pins 14 are lowered to move the wafer W. Is placed on the mounting surface 3.

  If the soaking plate 100 is formed of, for example, a silicon carbide sintered body, a boron carbide sintered body, a boron nitride sintered body, an aluminum nitride sintered body, or a silicon nitride sintered body, it deforms even when heat is applied. Since the plate pressure can be reduced, the heating time until heating to a predetermined processing temperature and the cooling time until cooling from the predetermined processing temperature to near room temperature can be shortened, thereby improving productivity. it can.

In the silicon carbide sintered body forming the plate-like body 2, boron (B) and carbon (C) are added as sintering aids to the main component silicon carbide, or alumina (Al ₂ O ₃ ) is added. It can be obtained by adding a metal oxide such as yttria (Y ₂ O ₃ ), mixing well, processing into a flat plate, and firing at 1900-2100 ° C. Silicon carbide may be either mainly α-type or β-type.

  As the boron nitride sintered body, boron nitride as a main component is mixed with 30 to 45% by weight of aluminum nitride and 5 to 10% by weight of rare earth element oxide as a sintering aid. A sintered body can be obtained by hot-press firing at ° C. Another method for obtaining a sintered body of boron nitride is to mix and sinter borosilicate glass, but this is not preferable because the thermal conductivity is significantly reduced.

In addition, the aluminum nitride sintered body forming the plate-like body 2 has a rare earth element oxide such as Y ₂ O ₃ or Yb ₂ O ₃ as a sintering aid for the main component aluminum nitride, if necessary. Then, an alkaline earth metal oxide such as CaO is added and mixed sufficiently, and after processing into a flat plate, it is obtained by firing at 1900 to 2100 ° C. in nitrogen gas.

  The boron carbide sintered body is obtained by mixing 3 to 10% by weight of carbon as a sintering aid with boron carbide as a main component, and performing hot press firing at 2100 to 2200 ° C. be able to.

The silicon nitride-based sintered body forming the plate-like body 2 has 3 to 12% by weight of rare earth element oxide and 0.5 to 3% by weight as a sintering aid with respect to silicon nitride as a main component. al ₂ O _3, further mixing SiO ₂ so that 1.5 to 5 wt% as SiO ₂ content in the sintered body, to obtain a sintered body by hot press firing at 1,650 to 1,750 ° C. Can do. The amount of SiO ₂ shown here is intentionally added including SiO ₂ generated from impurity oxygen contained in the silicon nitride raw material, the amount of SiO ₂ as an impurity contained in other additives, and the influence from the atmosphere. it is the SiO ₂ of the sum.

  In addition, the temperature of the soaking plate 100 is measured by the temperature measuring element 10 whose tip is embedded in the soaking plate 100. As the temperature measuring element 10, it is preferable to use a sheath type thermocouple having an outer diameter of 1.0 mm or less from the viewpoint of responsiveness and workability of holding. Further, the middle of the temperature measuring element 10 is held by the plate-like structure portion of the metal case 19 so that no force is applied to the tip portion embedded in the soaking plate 100. The tip of the temperature measuring element 10 is formed with a hole in the heat equalizing plate 100, and is fixed to the inner wall surface of a cylindrical metal body installed therein by a spring material to improve temperature measurement reliability. This is preferable.

  Further, when these heaters 1 are used for forming a resist film, if a material mainly composed of nitride as the plate-like body 2 is used, it reacts with moisture in the atmosphere to generate ammonia gas and generate resist. In order to deteriorate the film, in this case, it is preferable to use a plate-like body 2 made of a carbide of silicon carbide or boron carbide.

  At this time, it is necessary that the sintering aid does not contain nitrides that may react with water to form ammonia or amines. Thereby, it is possible to form fine wirings on the wafer W with high density.

  Furthermore, it is preferable that the main surface opposite to the mounting surface 3 of the heat equalizing plate 100 is polished to a flatness of 20 μm or less and a surface roughness of 0.1 to 0.5 μm with a center line average roughness (Ra). .

  On the other hand, when a silicon carbide sintered body is used as the plate-like body 2, glass or resin is used as an insulating layer for maintaining insulation between the semi-conductive plate-like body 2 and the resistance heating element 5. Is possible. Here, when glass is used, if the thickness is less than 100 μm, the withstand voltage is less than 1.5 KV and the insulation cannot be maintained. Conversely, if the thickness exceeds 600 μm, the silicon carbide-based firing forming the soaking plate 100 is performed. Since the difference in thermal expansion coefficient from the bonded body becomes too large, cracks are generated and the insulating layer does not function. Therefore, when glass is used as the insulating layer, the thickness of the insulating layer is preferably formed in the range of 100 to 600 μm, and more preferably in the range of 200 to 350 μm.

  When the plate-like body 2 is formed of a ceramic sintered body mainly composed of aluminum nitride, sufficient glass is added to the resistance heating element 5 with respect to the plate-like body 2, thereby providing sufficient adhesion strength. If obtained, the insulating layer can be omitted.

The glass forming this insulating layer may be either crystalline or amorphous, and the heat expansion temperature is 200 ° C. or higher and the thermal expansion coefficient in the temperature range of 0 to 200 ° C. constitutes the soaking plate 100. It is preferable to appropriately select and use a ceramic having a thermal expansion coefficient in the range of −5 to + 5 × 10 ⁻⁷ / ° C. That is, if a glass having a thermal expansion coefficient outside the above range is used, the difference in thermal expansion from the ceramic forming the soaking plate 100 becomes too large, so that there are defects such as cracks and peeling during cooling after baking the glass. It is because it is easy to occur.

  Next, when a resin is used for the insulating layer, if the thickness is less than 30 μm, the withstand voltage is less than 1.5 kV and the insulation cannot be maintained, and the resistance heating element 5 is trimmed by laser processing or the like. At that time, the insulating layer is damaged, and it does not function as the insulating layer. On the other hand, if the thickness exceeds 150 μm, the amount of evaporation of the solvent and moisture generated during the baking of the resin increases, and a peeling portion on the foam called a bulge is formed between the soaking plate 100 and heat transfer is caused by the presence of this peeling portion. Is deteriorated, so that the soaking of the mounting surface 3 is hindered. Therefore, when using resin as an insulating layer, it is preferable to form the thickness of an insulating layer in the range of 30-150 micrometers, and it is preferable to form in the range of 60-150 micrometers desirably.

  Further, when the insulating layer is formed of a resin, it is preferable to use a polyimide resin, a polyimide amide resin, a polyamide resin, or the like in consideration of heat resistance of 200 ° C. or more and adhesiveness with the resistance heating element 5.

  In addition, as a means for depositing an insulating layer made of glass or resin on the plate-like body 2, an appropriate amount of the glass paste or resin paste is dropped on the center of the soaking plate, and spread and applied uniformly by spin coating. Or after being uniformly applied by a screen printing method, dipping method, spray coating method or the like, the glass paste may be baked at a temperature of 600 ° C., and the resin may be baked at a temperature of 300 ° C. or more. When glass is used as the insulating layer, the plate-like body 2 made of a silicon carbide sintered body or an aluminum nitride sintered body is heated to a temperature of about 1200 ° C. in advance, and the surface on which the insulating layer is deposited is oxidized. By doing so, the adhesiveness with the insulating layer made of glass can be enhanced.

  In addition, although the above embodiment demonstrated the apparatus which heats a semiconductor wafer, the heater of this invention can be used for the heating of not only a semiconductor wafer but various plate-shaped bodies and other objects.

  A silicon carbide sintered body having a thermal conductivity of 80 W / (m · K) is ground to produce a plurality of soaking plates having a plate thickness of 4 mm and an outer diameter of 230 mm. In order to deposit an insulating layer on one main surface, a glass paste prepared by kneading ethyl cellulose as a binder and terpineol as an organic solvent into glass powder was laid by screen printing and heated to 150 ° C. After drying the organic solvent, degreasing treatment was performed at 550 ° C. for 30 minutes, and baking was performed at a temperature of 700 to 900 ° C. to form an insulating layer made of glass having a thickness of 200 μm. Next, in order to deposit a resistance heating element on the insulating layer, 20 wt% Au powder, 10 wt% Pt powder and 70 wt% glass were printed as a conductive material in a predetermined pattern shape. Thereafter, the organic solvent was dried by heating to 150 ° C., degreased at 450 ° C. for 30 minutes, and then baked at a temperature of 500 to 700 ° C. to form a resistance heating element having a thickness of 50 μm.

  The average particle size of Au and Pt, which are conductive compositions used for the resistance heating element, was 0.5 μm. Moreover, glass powder was added as an insulating composition, and the average particle diameter was 1.5 μm and 20 μm. In addition, each sample No. 1-3 were produced.

  When the dispersion state of the internal conductive composition after forming the resistance heating element was confirmed, Sample No. 1, No. 1 No. 2 had a large glass lump and was in a dispersed state as shown in FIG.

  Sample No. 3 was in a dispersed state as shown in FIG.

  The resistance heating element has a five-pattern configuration in which the central portion and the outer peripheral portion are divided into four in the circumferential direction.

  Each pattern of the resistance heating element thus produced was divided into about 50 locations, and the difference between the resistance value designed at each location and the measured resistance value was irradiated with a laser beam to form a groove to adjust the resistance. As a method for forming the groove, a YAG laser manufactured by NEC was used. The laser beam was irradiated with a wavelength of 1.06 μm, a pulse frequency of 1 kHz, a laser output of 0.4 W, and a processing speed of 5 mm / sec.

  In addition, the width | variety of the groove | channel produced on the said conditions was about 50-60 micrometers, and the depth was about 20-25 micrometers. And the pitch which is the space | interval of the groove | channel formed in each group was about 65 micrometers, and the number of the largest groove | channels was 13.

  Sample No. The conductive composition on the surface of the grooves 1 and 2 was a circle of 2 to 5 μm, and the density of the conductive composition on the surface of the groove was smaller than the internal density.

  On the other hand, Sample No. The density of the conductive composition on the surface of the groove 3 was almost the same as the inside as shown in FIG.

  Moreover, it confirmed also about each brightness. As a simple method for confirming the difference in brightness, first, each surface was photographed with a metallurgical microscope, and a black and white copy of the photograph was taken to confirm the intensity of white. The brightness increases as the white color increases, and conversely decreases as the black color increases. As a result, Sample Nos. 1 and 2 were stronger in black on the surface of the groove and lighter than the surface other than the groove. On the other hand, Sample No. 3 had no difference in brightness.

  Then, the soaking plate is attached to a metal case, and a temperature measuring element, a power feeding terminal and the like are attached to the sample No. 1-3 heaters were completed.

  When the surface of the groove group g of the completed sample was confirmed by SEM of 200 times, as shown in Table 1, 5 μm long microcracks were confirmed.

In addition, the length of the crack was measured by the linear distance from the starting point to the ending point of the crack, and the average value was obtained.

  Thereafter, sample No. A silicon wafer with a temperature measuring element is placed on the placement surface of the heaters 1 to 3 and the heater is heated so that the average temperature of the entire wafer becomes 200 ° C. The temperature difference in the wafer surface was measured.

  Thereafter, sample No. Apply a voltage to the heaters 1 to 3 so that the average temperature of the wafer surface temperature is from room temperature to 350 ° C. in 1 minute, hold it for 3 minutes, and then cool it to 40 ° C. or less in 2 minutes. The thermal cycle was repeated 5000 times. Then, the subsequent groove portion was observed, the resistance change rate of each resistance heating element of each sample, and the temperature difference in the wafer surface were measured.

  The resistance change rate of the resistance heating element of each sample was obtained by dividing the resistance change amount by the initial resistance value. When there are a plurality of resistance change rates, the maximum value is shown in the table as the resistance change rate. Further, the rate of change in resistance of the resistance heating element is preferably within 3% where the temperature difference on the wafer surface falls within 0.1 ° C., and preferably within 1% where the temperature difference on the wafer surface falls within 0.03 ° C. A resistance change rate is more preferable.

Each result is as shown in Table 1.

  As shown in Table 1, sample Nos. 1 and 2 in which the density of the conductive composition on the surface of the groove is smaller than the density of the conductive composition inside the resistance heating element are the particle sizes of the glass that is the insulating composition. The growth of microcracks was not observed. Further, even when the cooling cycle was repeated 5000 times, the changes in resistance value were 0.7% and 0.6%, respectively, and the changes were small. Further, the temperature differences in the wafer surface were 0.37 ° C. and 0.38 ° C., and the temperature differences in the wafer surface were small and good after the cooling cycle.

  On the other hand, Sample No. 3 in which the density of the conductive composition on the surface of the groove was larger than the density of the conductive composition inside the resistance heating element had microcracks growing to about 50 μm after the cooling and heating cycle. Therefore, the resistance value of the heating resistor also changed by about 5%, the temperature difference in the wafer surface became as large as 0.86 ° C., and could not be used continuously.

  In addition, the sample No. 1 in which the lightness of the surface of the groove is smaller than the lightness of the surface of the resistance heating element other than the groove. 1 and 2 show that the temperature difference in the wafer surface after the cooling / heating cycle is as small as 0.37 ° C. and 0.38 ° C., and the resistance change rate is also as small as 1% or less, indicating excellent characteristics.

  In the same manner as in Example 1, Sample No. 4-8 were produced. Sample No. The insulating compositions 4 to 8 were made of glass, and the average particle size was 1.5 μm, 5 μm, 20 μm, 40 μm, and 60 μm. And the average diameter of the electroconductive composition of the surface after forming a groove | channel by a laser beam became 0.5 micrometer, 1 micrometer 3.2 micrometer, 8.5 micrometer, and 20 micrometers. In addition, the average diameter of the electroconductive composition was shown by the diameter of the circle equivalent to the average area of 20 electroconductive compositions from the surface SEM photograph.

  Thereafter, the surface was observed and the thermal cycle of 5000 cycles was performed in the same manner as in Example 1, and the variation rate of the resistance value and the variation in the wafer temperature were confirmed.

The results are shown in Table 2.

  As shown in Table 2, the sample No. 1 in which the particle size of the conductive composition on the surface of the groove group is about 0.5 μm. In No. 4, microcracks grew to 10 μm after the thermal cycle, resulting in a resistance change of 2.8%.

  On the other hand, Sample No. in which the conductive composition is circular and the particle size of the conductive composition on the surface of the groove of the group is 1 to 20 μm. Nos. 5 to 8 showed no growth of microcracks, and the change in resistance value was 1% or less, which was found to be more preferable.

  A glass of a resistance heating element was mixed with an average particle diameter of 1.5 μm and 20 μm, which showed good results in Example 1, a sample was prepared by the same method as in Example 1, and a group of grooves was formed by a laser beam. .

  The center of the group which is an aggregate of grooves is formed at the center of the band of the resistance heating element. It was set to 9. In addition, a sample in which the center of the group is formed at a position of 25% from the end of the belt is designated as Sample No. It was set to 10. Further, a sample in which a groove was formed from the end of the band was designated as Sample No. It was set to 11. The central part of the band of the resistance heating element is a range of ± 5% of the width from the center of the range of the band width. And it evaluated similarly to Example 1. FIG.

The results are shown in Table 3.

  As shown in Table 3, the sample No. 9 of the present invention in which a group of grooves is formed in the central portion of the band of the resistance heating element has an in-plane temperature difference of 0.29 ° C. on the surface of the wafer W and a temperature distribution. Small and good results were shown.

  On the other hand, Sample Nos. 10 and 11 in which grooves were formed by shifting the center of the group were 0.35 ° C. and 0.39 ° C., respectively, and the temperature difference in the wafer surface was Sample No. It was big compared with 9.

  A sample was prepared in the same manner as in Example 3, and a groove group was formed by a laser beam. The center of the groove group is the central portion that showed good results in Example 3, and the width of the groove group was adjusted by changing the pitch, which is the interval between the grooves. 50%, 70%, 90%, 95%, and 100% of the width of the heating element band. Thereafter, a voltage is applied so that the average surface temperature of the wafer is from room temperature to 350 ° C. in 1 minute, and held for 3 minutes, and then cooled to 40 ° C. or less in 2 minutes. The cycle was repeated 5000 times. And the observation of the groove part before and after that and the resistance change rate of each resistance heating element of each sample were measured.

The results are shown in Table 4.

  As can be seen from the results in Table 4, the samples formed with the groove width of sample Nos. 12 to 14 within 90% of the width of the belt are excellent in thermal resistance of 5000 cycles and the resistance change is 1% or less respectively. Met.

  On the other hand, sample Nos. 15 and 16 are sample nos. The resistance change was large compared to 12-14.

  A sample was prepared in the same manner as in Example 3, and a group of grooves was formed by laser. The center of the groove group is the central portion that showed good results in Example 3, and the width of the groove group was within 90% of the width of the band of the resistance heating element that showed good results in Example 4. did. Further, the laser beam power was changed from 0.1 to 0.6 W, and the groove depth was adjusted to 10%, 20%, 50%, 75%, and 85% of the groove width.

  And the heat cycle test was done like Example 1, and the change rate of resistance value was confirmed. The results are shown in Table 5.

In addition, the resistance value with the largest resistance change rate was described among the resistance values before and after the durability of the five resistance heating elements.

  In sample No. 17 in which the resistance of each part of the resistance heating element was adjusted with the groove depth being 10% of the groove width, the resistance value of each part could not be adjusted sufficiently. The temperature in the surface of the wafer W could not be reduced while the temperature remained large.

  In Sample Nos. 18 to 20, the groove depth was 20% to 75%, and the resistance change rate after 5000 thermal cycles was within 1%, which was a good result.

  However, the depth of the groove of sample No. 21 was 85% of the width, and the resistance value of the resistance heating element changed by 2.04%.

It is sectional drawing of the heater of this invention. It is a figure which shows the resistance heating element in the heater of this invention. It is a figure which shows the resistance heating element in the heater of this invention. It is a figure which shows the resistance heating element in the heater of this invention. It is an enlarged view of the resistance heating element in the heater of the present invention. It is an enlarged view of the resistance heating element in the heater of the present invention. It is an enlarged view of the resistance heating element in the heater of the present invention. It is an enlarged view of the resistance heating element in the heater of the present invention. It is sectional drawing of the resistance heating element in the heater of this invention. It is sectional drawing of the resistance heating element in the heater of this invention. It is an enlarged view of a resistance heating element in a conventional ceramic heater. It is an enlarged view of a resistance heating element in a conventional ceramic heater. It is sectional drawing of the resistance heating element in the conventional ceramic heater. It is sectional drawing of the resistance heating element in the conventional ceramic heater. It is a figure which shows the resistance heating element in the conventional ceramic heater. It is sectional drawing of the conventional wafer heating apparatus. It is a figure which shows the resistance heating element in the conventional wafer heating apparatus.

Explanation of symbols

W: Wafer m: Groove g: Groove group
DESCRIPTION OF SYMBOLS 1, 71: Ceramic heater 2, 72: Plate-shaped ceramic body 3, 73: Mounting surface 5, 75: Resistance heating element 6: Feeding part 8: Support pin 10: Temperature measuring element 11, 77: Feeding terminal 12: Gas Injection ports 14 and 45: Lift pin 15: Lift pin guide 16, 80: Bolt 18: Elastic body 19, 79: Metal case 20: Nut 21: Reinforcement member 51: Conductive composition 52: Insulative composition 76: Lead wire drawing Hole 78: Lead wire 100: Heat equalizing plate

Claims (10)

A heater having a strip-like resistance heating element on a surface of a plate-like body and a groove substantially parallel to the longitudinal direction of the strip of the resistance heating element, wherein the resistance heating element is a composite of an insulating composition and a conductive composition. A heater comprising a material, wherein the density of the conductive composition on the surface of the groove is smaller than the density of the conductive composition inside the resistance heating element. A heater having a strip-like resistance heating element on a surface of a plate-like body and a groove substantially parallel to the longitudinal direction of the strip of the resistance heating element, wherein the resistance heating element is a composite of an insulating composition and a conductive composition. A heater comprising a material, wherein the conductive composition on the surface of the groove is substantially circular. A heater having a strip-like resistance heating element on a surface of a plate-like body and a groove substantially parallel to the longitudinal direction of the strip of the resistance heating element, wherein the resistance heating element is a composite of an insulating composition and a conductive composition. A heater made of a material, wherein the brightness of the surface of the groove is smaller than the brightness of the other surface of the resistance heating element. The heater according to claim 2 or 3, wherein an average diameter of the conductive composition on the surface of the groove is 1 to 20 µm. The heater according to any one of claims 1 to 4, wherein the resistance heating element has a lump of the insulating composition surrounded by a large number of the conductive particles in its cross section. The groove has a group of a plurality of grooves substantially parallel to the longitudinal direction of the band of the resistance heating element, and the group is at a central portion of the width of the band of the resistance heating element. The heater in any one of -5. The heater according to any one of claims 5 to 6, wherein the width of the group is within 90% of the width of the band of the resistance heating element. The heater according to any one of claims 1 to 7, wherein a depth of the groove is 20% to 75% of a width of the groove. The heater according to claim 1, wherein the groove is formed by a laser beam. The heater according to any one of claims 1 to 9, further comprising a mounting surface on which a wafer is placed on a side opposite to a surface on which the resistance heating element of the plate-like body is formed, and power is independently supplied to the resistance heating element. A wafer heating apparatus comprising: a power feeding unit to be supplied; and a metal case surrounding the power feeding unit.

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