JP2007115736A - Wafer heating hot plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer heating hot plate in which occurrence of particles can be reduced as much as possible, and which can suitably be used especially for a coater developer used especially in a photolithography process of a wafer. <P>SOLUTION: The wafer heating hot plate is formed of a complex 1 of a ceramic, a semiconductor and/or a metal. A heating element 2 where a metal foil is patterned is arranged with the complex 1 through an insulating layer 3. A movable cooling module 5 is disposed in the plate. Si-SiC or Al-SiC or Al-AlN is desirable as a material of the complex 1. It is desirable that thermal conductivity of the complex 1 is 150 W/mK or above, and a thermal expansion coefficient is 12×10<SP>-6</SP>/K or below. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wafer heating hot plate for placing or separating and heat-treating a wafer, and more specifically, for wafer heating that can be used particularly suitably for a coater developer or the like used for wafer photolithography. Regarding hot plate.

  Conventionally, in a semiconductor manufacturing process, various processes such as a film forming process and an etching process are performed on a wafer. In a semiconductor manufacturing apparatus that performs processing on such a wafer, a hot plate for holding and heating the wafer is used.

  For example, in the photolithography process, a resist film pattern is formed on the wafer. In this step, the wafer is washed, heated and dried, cooled, and then a resist film is applied to the wafer surface. The wafer is mounted on a hot plate in a photolithography processing apparatus, heated and dried, and then subjected to processing such as exposure and development.

  In this photolithography process, it is necessary to reduce particles generated from hot plates and other parts, so-called particles. This is because if the particles adhere to the wafer, the pattern at that portion cannot be formed, causing a defect in the semiconductor chip. Particularly in recent years, since the fine wiring of a semiconductor chip is progressing, it is very important to suppress the generation of particles.

  Further, these wafer processes are required to be completed in as short a time as possible in order to improve the throughput. Therefore, the inventors have studied a semiconductor manufacturing apparatus having a cooling means in order to cool the heated heater in a short time. For example, Japanese Unexamined Patent Application Publication No. 2004-014655 (Patent Document 1) has proposed a semiconductor manufacturing apparatus including a cooling block that can be contacted or separated on the surface of the heater opposite to the wafer mounting surface. Further, in Japanese Patent Laid-Open No. 2005-150506 (Patent Document 2), a cooling liquid flow path is formed in the cooling block to further improve the cooling rate and to make the heater temperature uniform from the start of cooling to the end of cooling. We have proposed a semiconductor manufacturing system that keeps up.

JP 2004-014655 A JP 2005-150506 A

  As described above, with the progress of miniaturization in semiconductors in recent years, reduction of generation of particles that cause defects due to adhesion to a wafer is required for a hot plate that performs heat treatment of the wafer. The generation source of particles is affected by the atmosphere and environment of the equipment where the hot plate is installed, but in semiconductor manufacturing equipment installed in a highly controlled clean room, the particles generated in the clean room are compared. Therefore, it is required to suppress the generation of particles from the hot plate itself.

  The hot plate is usually installed in a container and heats the loaded wafer and then unloads. During that time, the hot plate itself undergoes a predetermined thermal cycle, and particles may be generated due to the influence. Further, in a hot plate provided with a movable cooling module, particles can be generated by contact between the hot plate and the cooling module. Furthermore, in the case of a hot plate that places wafers apart, static electricity is generated due to friction with the proximity for separation, and particles stay near the proximity, increasing the amount of adhesion to the wafer. There was a problem.

  In view of such conventional circumstances, the present invention can reduce the generation of particles as much as possible, and can be particularly preferably used for a coater developer or the like used in a wafer photolithography process. The object is to provide a hot plate.

  In order to achieve the above object, a wafer heating hot plate provided by the present invention is a wafer heating hot plate for heating a wafer mounted or spaced apart, and the material of the hot plate is ceramic, semiconductor and / or Or it is a composite_body | complex with a metal, It is characterized by the above-mentioned. This wafer heating hot plate preferably has a heating element through an insulating layer between the hot plate and the composite, and the heating element is obtained by patterning a metal foil.

In the hot plate for heating a wafer according to the present invention, the material of the composite is any one of silicon-silicon carbide (Si-SiC), aluminum-silicon carbide (Al-SiC), and aluminum-aluminum nitride (Al-AlN). It is preferable that In particular, the thermal conductivity of the composite is preferably 150 W / mK or more, and the thermal expansion coefficient of the composite is preferably 12 × 10 ⁻⁶ / K or less.

  Furthermore, the wafer heating hot plate according to the present invention may include a movable cooling module.

  The present invention also provides a semiconductor manufacturing apparatus comprising the above-described wafer heating hot plate according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, while being excellent in soaking | uniform-heating property, the hot plate for a wafer heating which reduced generation | occurrence | production of particle | grains as much as possible can be provided. Therefore, the hot plate for heating a wafer of the present invention can be suitably used particularly for a coater developer used in a wafer photolithography process.

  In general, ceramics used as a hot plate are produced by sintering and hardening raw material powder. Therefore, when viewed microscopically, ceramics are formed by combining fine particles, and usually there are grain boundary components between the particles. Since the grain boundary component and the particle component are slightly different from each other, the coefficient of thermal expansion is naturally slightly different. In particular, in ceramics that have been sintered with the addition of a sintering aid, there are parts that differ in composition from the particles that are the main component of ceramics, mainly in parts where the composition is segregated by the sintering aid. To do. In such a portion, when ceramics are used as a hot plate, particles are easily lost due to the thermal cycle, and the particles are likely to become particles. In addition, since there are not a few pores in the ceramic, the particles fall off from these portions and become particles.

  In order to suppress the generation of such particles, in the present invention, a composite of metal and / or semiconductor and ceramics is used as the material of the hot plate. In a composite of metal and / or semiconductor and ceramic, metal or semiconductor exists between the ceramic particles and surrounds the individual ceramic particles. Therefore, a hot plate composed of a composite of metal and / or semiconductor and ceramics has a structure in which particles do not easily fall off, so that generation of particles can be reduced even when a thermal cycle is applied. .

  For example, in the case of a composite of aluminum (Al) and silicon carbide (SiC), the silicon carbide particles exist independently, or some of the particles are bonded together. Aluminum exists in the gaps between the silicon carbide particles. Since the thermal expansion coefficient of aluminum is larger than that of silicon carbide, when heat is applied to this composite, the aluminum present between the particles expands more than silicon carbide, so that the silicon carbide particles are less likely to fall off the surface. In addition, the generation of particles can be suppressed.

As a composite of metal and / or semiconductor and ceramics used as the hot plate of the present invention, in addition to the above-mentioned aluminum-silicon carbide (Al-SiC) composite, a silicon-silicon carbide (Si-SiC) composite, An aluminum-aluminum oxide (Al-Ai ₂ O ₃ ) composite, an aluminum-aluminum nitride (Al-AlN) composite, and the like can be given. Any of these composites can be suitably used as a hot plate for a semiconductor manufacturing apparatus because generation of particles is suppressed by the above mechanism.

  The composite of metal and / or semiconductor and ceramics preferably has a thermal conductivity of 150 W / mK or more. This is because the thermal uniformity of the hot plate is improved by having a thermal conductivity of 150 W / mK or more. Examples of the composite having such a high thermal conductivity include an aluminum-silicon carbide (Al-SiC) composite, a silicon-silicon carbide (Si-SiC) composite, and an aluminum-aluminum nitride (Al-AlN) composite. is there. Further, when silicon carbide (SiC) is used as the ceramic component of the composite, ammonia is not generated when aluminum nitride (AlN) is used when used as a hot plate, which is particularly preferable.

Further, the composite of metal and / or semiconductor and ceramics preferably has a thermal expansion coefficient of 12 × 10 ⁻⁶ / K or less. For example, when a wafer is placed on a hot plate in a heated state, the wafer receives heat from the hot plate and thermally expands, and conversely, the hot plate takes heat away from the wafer and contracts. At this time, when the hot plate is set to a predetermined temperature, the thermal expansion of the wafer becomes a predetermined amount. However, since the thermal contraction amount of the hot plate depends on the thermal thermal expansion coefficient, it is preferable that the thermal expansion coefficient of the hot plate is small. In particular, when the thermal expansion coefficient is 12 × 10 ⁻⁶ / K or less, the amount of generated particles is reduced. Further, when proximity is formed on the wafer mounting surface of the hot plate, rubbing is likely to occur between the proximity and the wafer, so that the thermal expansion coefficient of the composite is 12 × 10 ⁻⁶ / K or less. Is preferred.

  Further, the composite of metal and / or semiconductor and ceramics preferably has a porosity of less than 1%. When the porosity of the composite is 1% or more, when used as a hot plate, particles tend to stay in the pores, and the amount of particles adhering to the wafer increases, which is not preferable.

  The above-described composite of metal and / or semiconductor and ceramics can be produced by a known method. For example, there is a method in which a metal powder and / or semiconductor powder and a ceramic powder are mixed and then heat-cast or sintered to form a composite. The composite can also be obtained by a method in which ceramic powder is molded or sintered in advance to form a porous molded body, and then a molten metal and / or semiconductor is infiltrated into the porous molded body of the ceramic. .

  The hot plate requires a heating element for heating, but the above-described composite of metal and / or semiconductor and ceramics is generally conductive, so it is difficult to directly form the heating element on the composite. . Therefore, when a heating element is formed on a composite that becomes a hot plate, an insulating layer is formed between the composite and the composite, for example, an insulating layer is formed on the surface of the composite, and the heating element is formed on the insulating layer. Form.

  As a method for forming the insulating layer, there is a method in which a composite of metal and / or semiconductor and ceramic is heat-treated in an air atmosphere or an oxidizing atmosphere to form an oxide film on the surface. Alternatively, the insulating layer can also be formed by applying and baking an insulating paste such as silica, alumina, or various types of glass on the surface of the composite. Then, a circuit pattern of the heating element can be formed on the insulating layer by, for example, screen printing or vapor deposition. However, in such a method, the thermal expansion coefficient of the oxide film or the heating element and the thermal expansion coefficient of the composite are often different. May be.

  In order to prevent the generation of particles due to such a cause, it is preferable to install the patterned heating element in the composite by etching the metal foil into a predetermined pattern. Even in this case, in order to ensure insulation between the composite and the heating element, an insulating film may be formed as described above, or an insulating paste may be applied and baked. As a more preferred method, the insulating layer can be formed using a sheet of heat resistant resin represented by, for example, silicon resin or polyimide resin. Furthermore, it is also possible to install the heat-resistant resin sheet on the heating element and sandwich the heating element with an insulating layer. In addition, the heat-resistant resin component (liquid) is applied to a metal foil in a predetermined thickness, dried and cured, and then the metal foil is etched to form a heating element, or the heating element obtained by patterning the metal foil It is also possible to apply a resin component (liquid) and dry cure.

  The heating element formed as described above can be fixed by being screwed or sandwiched with a fixing plate on the opposite side of the wafer mounting surface of the composite of metal and / or semiconductor and ceramics. As the fixing plate, ceramics, heat resistant resin, metal or the like can be used. When the fixing plate to be used is conductive, the insulating property can be ensured between the heating element and the fixing plate by installing the heat-resistant resin between the heating element as described above. As will be described later, when a movable cooling module is installed, a resin or metal is suitable as the fixing plate.

  In the present invention, a cooling module can be installed on the opposite side of the wafer mounting surface with respect to a hot plate made of a composite of metal and / or semiconductor and ceramics. The cooling module can rapidly cool the hot plate by removing the heat when the hot plate needs to be cooled. Further, when heating the hot plate, it is preferable to separate the cooling module from the hot plate so that the temperature can be increased efficiently. Therefore, the cooling module is preferably movable, and as a method for making the cooling module movable, lifting means such as an air cylinder can be used. Using a movable cooling module in this manner is preferable because the cooling rate of the hot plate can be significantly improved and the throughput can be increased.

  The material of the cooling module is not particularly limited, but aluminum, copper, or an alloy thereof is preferable because it has a relatively high thermal conductivity and can quickly take away the heat of the hot plate. Also, stainless steel, magnesium alloy, nickel, and other metal materials can be used. Furthermore, in order to impart oxidation resistance to the cooling module, a metal film having oxidation resistance such as nickel, gold, or silver can be formed using a technique such as plating or thermal spraying.

  When the above-described movable cooling module is used, the conventional ceramic heater and hot plate are rubbed with the cooling module, and not a few particles are generated. However, in the hot plate made of a composite of metal and / or semiconductor and ceramics according to the present invention, the ceramic particles are covered with the metal or semiconductor, so that even if rubbing occurs, the ceramic particles are difficult to fall off, Generation can be greatly reduced. Moreover, even when a heating element is installed on the opposite side of the wafer mounting surface of the hot plate, the generation of particles is prevented by installing a resin or metal fixing plate on the contact surface with the movable cooling module. be able to.

  When priority is given to the cooling rate of the hot plate, the cooling module may be fixed to the hot plate. As a fixing form, a heating element having a structure sandwiched between insulating layers on the opposite side of the wafer mounting surface of the hot plate can be installed, and the cooling module can be fixed to the lower surface thereof. As another fixing mode, there is a method in which a cooling module is directly installed on the opposite side of the wafer mounting surface of the hot plate, and a heating element having a structure in which both sides are sandwiched by insulating layers on the lower surface thereof is fixed. Although there is no restriction | limiting in particular in the fixing method, For example, it can fix by mechanical methods, such as screwing and clamping. In the case of fixing by screwing, it is preferable to set the number of screws to 3 or more, and further 6 or more, because the adhesion between the two is enhanced and the cooling capacity of the hot plate is further improved.

  When the cooling module is fixed to the hot plate as described above, a soft material having deformability and heat resistance and high thermal conductivity is inserted between the opposite side of the wafer mounting surface of the hot plate and the cooling module. be able to. As such a flexible material, thermally conductive grease or resin can be used. By inserting such a soft material between the hot plate and the cooling module, the flatness and warpage of each other can be relaxed and the contact area can be increased, so that the original cooling capacity of the cooling module can be further increased. This can be achieved and the cooling rate can be increased.

  A refrigerant can flow through the cooling module. By flowing the refrigerant, the heat of the cooling module can be quickly removed, and further the cooling rate of the heating element can be improved. The refrigerant to be used may be selected from commonly used refrigerants such as water and fluorinate, but water is most preferable in view of the specific heat and the price. Moreover, when fixing a cooling module with respect to a hotplate, it is also possible to heat up, without flowing a refrigerant | coolant to a cooling module. In this case, since the refrigerant does not flow into the cooling module, the heat generated by the heating element is not lost to the refrigerant and escapes out of the system, and more efficient temperature rise is possible. However, even in this case, it is preferable to cool the hot plate efficiently by flowing a coolant through the cooling module during cooling.

  As a method of forming the flow path for flowing the coolant to the cooling module, for example, two aluminum plates or copper (oxygen-free copper) plate is prepared, and a groove serving as a flow path is formed on one plate by machining or the like After that, nickel plating is performed on the entire surface in order to improve corrosion resistance and oxidation resistance. The other nickel-plated plate is stacked on this grooved plate, and a sealing material such as an O-ring is inserted around the groove to be a flow path so that no water leaks. Laminate the boards. Alternatively, two plates can be brazed and joined, and in that case, a stainless steel pipe can be brazed and joined simultaneously to the refrigerant inlet / outlet of the flow path.

  As another flow path forming method, a cooling module can be obtained by attaching a pipe serving as a flow path for flowing a refrigerant to a cooling plate made of an aluminum plate or a copper plate. In this case, the cooling efficiency can be further improved by forming a counterbored groove having a shape close to the cross-sectional shape of the pipe in the cooling plate and bringing the pipe into close contact with the groove. Moreover, in order to improve the adhesiveness of a cooling pipe and a cooling plate, you may insert thermally conductive resin, ceramics, etc. as an intervening layer.

  The above-described hot plate comprising a composite of the metal and / or semiconductor of the present invention and ceramics can be preferably used in a semiconductor manufacturing apparatus because the amount of particles generated can be reduced as compared with a conventional ceramic hot plate. can do. In particular, the hot plate of the present invention can be particularly suitably used for a coater developer or the like used in a wafer photolithography process.

  As a method for placing the wafer on the hot plate, there is a method of placing the wafer separately on the hot plate using so-called proximity. In this method, for example, three or more countersunk holes are formed on the hot plate, and a ceramic ball having a diameter larger than the depth of the countersink hole and smaller than the diameter of the countersink hole is inserted therein, The ceramic ball supports the wafer. However, since the diameter of the ceramic ball is smaller than the diameter of the countersink hole, it is inevitable that the ceramic ball moves in the countersink hole.

  At this time, since the conventional hot plate is ceramic, static electricity is generated between the ceramic ball moving in the countersink hole, and particles near the ceramic ball stay near the proximity, and when the wafer is placed, Particles adhere to the wafer.

  In contrast, in the case of a hot plate formed of a composite of a metal and / or semiconductor of the present invention and ceramics, static electricity is generated even if the ceramic ball moves in the countersink hole because the hot plate is a conductor. Therefore, particles do not stay. Therefore, even with a hot plate using proximity, the amount of particles adhering to the wafer can be reduced as compared with the conventional case.

[Example 1]
As a substrate for hot plate, an AlN substrate made of conventional ceramics is prepared, and five kinds of substrates shown in Table 1 below made of a composite of a metal and / or semiconductor of the present invention and ceramics, that is, Si- SiC substrate, Al—SiC substrate (added with (immersion)) prepared by a permeation method, Al—SiC substrate (added with (cast)) prepared by a casting method, an Al—AlN substrate, and an Al—Al ₂ O ₃ substrate Prepared. All the substrates had a porosity of less than 1%. The dimensions of these substrates are 320 mm in diameter and 10 mm in thickness, and 10 countersunk holes with a diameter of 1.1 mm and a depth of 0.9 mm are formed on the wafer mounting surface, and alumina balls with a diameter of 1 mm are placed there. Proximity.

  Next, for the ceramic substrate, a heating paste circuit is formed with W paste by screen printing on the opposite side of the wafer mounting surface, and after baking, a glass paste is used to ensure insulation on the heating plate surface. Was applied to a thickness of 100 μm and baked to obtain an AlN hot plate. Moreover, about the board | substrate of the said 5 types of composite_body | complex, the stainless steel foil was installed on the polyimide foil, and the heat generating body was formed by etching. Further, a liquid polyimide resin was applied on the heating element, dried and cured. This heating element was placed on the opposite side of the wafer mounting surface, pressed by a fixing plate having a thickness of 1 mm, and fixed to the composite substrate by screwing. As shown in FIG. 1, the obtained composite hot plate includes a composite 1, a heating element 2 made of patterned stainless steel foil, and a polyimide insulating layer 3 disposed on both surfaces of the heating element 2. , And a fixing plate 4 for fixing them to the opposite side of the wafer mounting surface of the composite 1.

  Each of the above hot plates (not provided with a cooling module) is installed in the container 6, energized by the heating element 2, heated to 180 ° C., and then 12 inches of normal temperature silicon on the wafer mounting surface The wafer was placed and heat-treated. Thereafter, the number of particles having a diameter of 0.2 μm or more adhering to the contact surface side of the wafer with the hot plate was measured using a light scattering type particle counter. Further, the thermal uniformity of the hot plate at 180 ° C. was also measured with a wafer thermometer equipped with a resistance temperature detector. Furthermore, the amount of ammonia generated was measured with a gas detector tube. The obtained results are shown in Table 1 below.

  From the results in Table 1, it can be seen that by using a hot plate made of a composite of a metal and / or a semiconductor and ceramics, the amount of particles generated can be significantly reduced as compared with a conventional ceramic hot plate. In addition, it can be seen that a hot plate made of Al—SiC, Al—SiC, or Al—AlN having a thermal conductivity of 150 W / mK or more is excellent in heat uniformity. Note that generation of ammonia was not observed on the hot plate not using AlN.

[Example 2]
The number of particles adhering to the contact surface side of the wafer with the hot plate, heat uniformity, and generation of ammonia in the same manner as in Example 1 except that the wafer was placed directly on the hot plate without using proximity. The amount was measured, and the results obtained are shown in Table 2 below.

  Moreover, it replaced with the Si-SiC composite whose porosity is less than 1% used in the said Example 1, and produced the same hot plate as the said Example 1 using the Si-SiC composite whose porosity is 2%. Without using proximity, the wafer was placed directly on the hot plate, and the number of particles, thermal uniformity and ammonia generation amount were measured in the same manner as described above. As a result, the thermal uniformity and the amount of ammonia generated were similar to the results shown in Table 2 above, but the number of particles increased to 42.

[Example 3]
As shown in FIG. 1, a movable cooling module 5 was installed on the opposite side of the wafer placement surface for each hot plate produced in Example 1 above. As shown in FIG. 2, the cooling module 5 has a countersink groove having a radius of 4.5 mm formed on an Al plate 7 having a diameter of 320 mm and a thickness of 8 mm, and a Cu pipe 8 having a diameter of 4 mm is installed in the groove. A thermally conductive silicon resin 9 was disposed between the Cu pipe 8 and the Al plate 7. The Cu pipe 8 was screwed to the Al plate 7 using a stainless steel fixing band 10 to form a cooling module 5.

  After each hot plate was heated to 180 ° C., energization to the hot plate was stopped, and the hot plate was cooled to 70 ° C. by pressing the cooling module against the hot plate. At that time, 25 ° C. water was passed through the Cu pipe at a rate of 1 liter / min. As a result, it took 20 minutes or more to cool the hot plate to which the cooling module was not installed to 70 ° C., but all those that pressed the cooling module cooled to 70 ° C. within 5 minutes. I was able to. Further, the amount of particles generated at this time was measured in the same manner as in Example 1, and the obtained results are shown in Table 3 below.

  From the above results, when the movable cooling module was installed on the hot plate, the number of particles was greatly increased in the conventional ceramic hot plate as compared with the case of Example 1 in which the movable cooling module was not installed. On the other hand, in a hot plate made of a composite of metal and / or semiconductor and ceramics, it can be seen that the generation amount of particles can be suppressed even when a movable cooling module is installed.

It is a schematic sectional drawing which shows one specific example of the hot plate by this invention. It is a schematic sectional drawing which shows one specific example of the cooling module used for the hot plate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Composite body 2 Heat generating body 3 Insulating layer 4 Fixing board 5 Cooling module 6 Container 7 Al board 8 Cu pipe 9 Thermally conductive silicon resin 10 Fixing band

Claims (7)

  A wafer heating hot plate for mounting or separating and heating a wafer, wherein the material of the hot plate is a composite of a semiconductor and / or a metal and ceramics.   2. The wafer heating hot plate according to claim 1, wherein a heating element is provided between the composite and an insulating layer, and the heating element is obtained by patterning a metal foil.   3. The wafer heating hot plate according to claim 1, wherein a material of the composite is any one of silicon-silicon carbide, aluminum-silicon carbide, and aluminum-aluminum nitride.   4. The wafer heating hot plate according to claim 1, wherein the composite has a thermal conductivity of 150 W / mK or more. 5. 5. The wafer heating hot plate according to claim 1, wherein the composite has a thermal expansion coefficient of 12 × 10 ⁻⁶ / K or less.   The hot plate for heating a wafer according to claim 1, further comprising a movable cooling module. A semiconductor manufacturing apparatus comprising the wafer heating hot plate according to claim 1.

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