JP6060889B2 - Heater unit for wafer heating - Google Patents

Description

  The present invention relates to a wafer heating heater unit that heats a semiconductor wafer mounted on a mounting surface from its lower surface.

  In the manufacturing process of a semiconductor device such as an LSI, various processes such as film formation and etching are performed on a semiconductor wafer. These processes often involve a wafer heating step. In this case, a wafer heating heater unit is used for heating the wafer mounted on the mounting surface from the lower surface thereof at a predetermined temperature. This heater unit is mounted on a semiconductor manufacturing apparatus such as a coater developer used for wafer photolithography, a wafer prober used for semiconductor inspection, and a CVD apparatus used for film formation.

  For example, in a coater developer, a wafer is cleaned and the cleaning solution is dried by heating, and then the wafer is cooled, a resist film is applied to the surface, and the wafer is transported into a photolithography chamber. A heater unit for heating the wafer is installed in the chamber. After the wafer is mounted on the mounting surface of the heater unit and the resist film is dried, processing such as exposure and development is performed. Thereby, patterning of the resist film is performed.

  In the wafer processing in the semiconductor manufacturing apparatus as described above, it is required to improve the throughput by shortening the processing time as much as possible. Therefore, in the heat treatment of the wafer, the wafer is mounted on the placement surface of the heater unit, subjected to a predetermined heat treatment, and the wafer after the heat treatment is taken from the placement surface and transferred to the next process. Strict temperature control and thermal uniformity on the wafer mounting surface are required. In addition, in the case where a step of increasing or decreasing the temperature by changing the set temperature of the heater is included, it is desired that the heater quickly responds to the set temperature. Needless to say, the heater unit is required to have high reliability.

  Under such circumstances, Patent Document 1 discloses a heater unit that heats a wafer placed on a placement surface from its lower surface. In this heater unit, a heating element is in contact with the lower surface of the heater substrate having a wafer mounting surface on the upper surface, and a heat equalizing plate having a higher thermal conductivity than the heater substrate is placed under the heating element via a heat insulating layer. The structure is attached. And when a heat generating body is metal foil, sandwiching this metal foil with the insulating resin layer which has heat resistance, for example is described.

JP 2008-1118080 A

  However, the above-described heater unit structure of Patent Document 1 has a problem that if the thickness of the insulating resin layer is increased, the heat transfer performance in the thickness direction is deteriorated. For example, it takes too much time to change the set temperature. It was. Conversely, when it is necessary to reduce the thickness of the insulating resin layer, there is a trade-off relationship between the heat transfer performance and the insulation performance, so a choice of a material that has the desired heat transfer without sacrificing insulation However, there was a problem that the cost was high.

  In addition, when an organic material is selected in consideration of only satisfying heat transfer properties and insulation properties, the heat resistance may be limited, and the wafer heating heater may not be used at a high temperature. For example, when a silicone resin is used as the organic material for the insulating layer, the upper limit of the heat resistance temperature is about 150 ° C. Therefore, when the heat resistance temperature is exceeded, the insulation performance deteriorates or the heater unit is There may be a problem that the resin is fused to the mounting table or the soaking plate.

  In particular, when the resin is fused, the free thermal expansion of the mounting table or the soaking plate is constrained and deformed into a convex shape, causing problems such as deterioration of the soaking performance on the wafer mounting surface. . Moreover, the actual heating element and the insulating layer covering it may become higher than the temperature assumed in the design stage due to various conditions such as the heat capacity, thickness, and installation environment of the mounting table. As a result, the newly installed heater unit After starting the operation, a certain amount of time passed and a problem was discovered, which could impair trust. The present invention has been made in view of the problems of the above-described conventional heater unit, and can be used at a higher temperature than the conventional heater unit, has excellent heat uniformity on the wafer mounting surface, and has high reliability. It aims at providing the heater unit which has.

  In order to achieve the above object, a heater unit for heating a wafer provided by the present invention includes a mounting table having a mounting surface on which an object to be processed is mounted, a support plate for supporting the mounting table, and the mounting table described above. And the heat generating unit provided between the support plate and the heat generating unit, the heat generating unit abutting the heat generating layer, the insulating layer sandwiching the heat generating layer from above and below, the mounting table and the support plate, respectively. It has a releasable fluororesin layer.

  According to the present invention, it is possible to use in a higher temperature range than the conventional heater unit, and it is excellent in heat uniformity on the wafer mounting surface and can maintain the initial performance over a long period of time. A high heater can be provided.

It is a longitudinal cross-sectional view which shows typically one specific example of the heater unit for wafer heating which concerns on this invention. It is a longitudinal cross-sectional view which shows typically a specific example of the heating unit of FIG. It is a longitudinal cross-sectional view which shows typically the specific example of the structure of the refrigerant flow path which the cooling mechanism of FIG. 1 has. It is a longitudinal cross-sectional view which shows a mode that the cooling mechanism of FIG. 1 reciprocates between a contact position and a separation position. It is a longitudinal cross-sectional view which shows typically the other specific example of the heater unit for wafer heating which concerns on this invention. It is a longitudinal cross-sectional view which shows typically the other specific example of the heater unit for wafer heating which concerns on this invention.

  First, embodiments of the present invention will be listed and described. A heater unit for heating a wafer according to an embodiment of the present invention includes a mounting table having a mounting surface on which an object to be processed is mounted, a support plate that supports the mounting table, and a space between the mounting table and the supporting plate. A heat generating unit, the heat generating unit includes a heat generating layer, an insulating layer that sandwiches the heat generating layer from above and below, a releasable fluororesin layer that contacts the mounting table and the support plate, respectively. It is what has. As a result, the heater can be used in a higher temperature range than the conventional heater unit, has excellent heat uniformity on the wafer mounting surface, and can maintain the initial performance over a long period of time. Can be provided.

  In the above-described heater unit for heating a wafer according to the embodiment of the present invention, the insulating layer is preferably formed of a polyimide resin. Polyimide resin has high heat resistance compared to other organic materials, and can be used in a high temperature range exceeding 200 ° C., for example, and has a sufficient insulation performance for electrical equipment even if it is a thin film of 50 μm. A heater unit having a small resistance can be provided.

  Next, a specific example of the wafer heating heater unit of the present invention will be described with reference to FIG. The wafer heating heater unit shown in FIG. 1 has a substantially disk-shaped mounting table 1 having a wafer mounting surface 1a on the upper surface and an outer diameter substantially equal to that of the mounting table 1. A substantially disc-shaped support plate 2 that supports the lower surface side over substantially the entire surface, and a thin disc shape having an outer diameter substantially equal to that of the mounting table 1 and the support plate 2 provided so as to be sandwiched therebetween. And the heat generating unit 3. The mounting table 1 and the support plate 2 sandwiching the heat generating unit 3 from above and below are supported by leg portions 11 standing from the bottom in a stainless steel container 10 having an open top.

  As the material for the mounting table 1 and the support plate 2, for example, ceramics, a composite including ceramics, or metal can be used. Since ceramics and composites including this are excellent in machining accuracy, the flatness of the wafer mounting surface 1a can be kept good. In addition, because it is excellent in rigidity (Young's modulus), it does not deform even if the plate thickness is reduced, so the heat capacity of the entire heater unit can be reduced by making it thinner compared to conventional thick iron-based materials, so the temperature raising and lowering speed It becomes possible to speed up. Further, by selecting a material having relatively high thermal conductivity among ceramics, high temperature uniformity on the wafer mounting surface 1a can be achieved while maintaining flatness and a small heat capacity on the wafer mounting surface 1a. Can be realized.

  On the other hand, in the case of a metal, in addition to being general-purpose and cost-effective, the thermal conductivity is higher than that of ceramics, so that extremely high temperature uniformity can be realized on the wafer mounting surface 1a. In the conventional heater unit formed of metal, depending on the processing temperature, it is necessary to increase the thickness in order to maintain the flatness on the wafer mounting surface 1a. For example, a ceramic plate having excellent rigidity is selected as the support plate 2. Thus, even if the mounting table 1 is formed of a thin metal, it is possible to maintain good flatness. As described above, the material of the mounting table 1 and the support plate 2 can be appropriately selected according to the wafer processing process and the specifications of the equipment required thereby. However, in general, the material on the wafer mounting surface 1a. From the viewpoint of temperature uniformity, it is preferable to use a material having high thermal conductivity.

  Examples of such a material having high thermal conductivity include copper, aluminum, silicon carbide, aluminum nitride, and materials containing these (for example, Si—SiC, Al—SiC). In addition, as described above, at least one of the mounting table 1 and the support plate 2 is formed of a material having high rigidity, that is, among the materials having high thermal conductivity, aluminum nitride or silicon carbide, or a composite containing the same. It is preferable to do. The reason is that when both the mounting table 1 and the support plate 2 are made of materials having relatively low rigidity such as aluminum, deformation or the like is likely to occur due to heat cycle, and as a result, the heat generating unit 3 This is because there is a possibility that the temperature uniformity on the wafer mounting surface 1a becomes non-uniform due to a change in adhesion to a cooling plate, which will be described later, or a change in the shape of the wafer mounting surface 1a.

  As described above, when the mounting table 1 and the support plate 2 are formed of different materials, or when the cooling mechanism is brought into contact with the lower surface of the support plate 2 as will be described later, the wafer as the object to be heated is further changed to the wafer. When mounted on the mounting surface 1a, a temperature difference or a thermal expansion difference occurs between the mounting table 1 and the support plate 2. Therefore, the mounting table 1 and the support plate 2 are preferably mechanically coupled to each other. . Specific examples of the mechanical coupling method include coupling by screwing and coupling by suspending a spring, but screwing is more preferable in terms of stability.

  In the case of screwing, for example, the mounting table 1 and the support plate 2 are placed below the screw holes that penetrate the support plate 2 in the thickness direction so that the mounting table 1 and the support plate 2 can be freely thermally expanded in the direction of the wafer mounting surface 1a. A male screw is inserted from the side and screwed into a female screw portion provided on the lower surface side of the mounting table 1, and between the seat surface of the male screw and the lower surface of the support plate 2, which is a contact portion, for example, It is preferable to interpose a bearing.

  The mounting table 1 is preferably provided with a temperature sensor 4 for controlling the amount of power supplied to a resistance heating element (described later) of the heat generating unit 3. A resistance temperature detector can be used for the temperature sensor 4. The resistance temperature detector is formed, for example, with a temperature measuring element portion made of an insulating ceramic substrate having a flat portion, and a platinum resistor is formed on the flat portion by a film forming method such as vapor deposition, and adjusted to a predetermined resistance value. Then, the lead wire 5 is connected to the electrode pad portion by a bonding method such as bonding, and the platinum resistor and the electrode pad portion can be covered with an insulating film. By using the temperature measuring element having such a structure, the temperature measuring resistor can be reduced in size and the heat capacity thereof can be reduced, and the mounting table 1 can be made thinner, so that the temperature responsiveness can be improved.

  The resistance temperature detector is preferably bonded to the mounting table 1 using an adhesive. In this case, an adhesive mainly composed of an organic resin such as a silicone resin or an epoxy resin, or a combination of an inorganic material such as ceramic particles and a binder component can be used. In particular, an adhesive mainly composed of a silicone resin is suitable because it has elasticity and can absorb a slight difference in thermal expansion between the temperature measuring element portion and the mounting table 1, and is an adhesive mainly composed of an epoxy resin. The agent is suitable because it has heat resistance that can withstand the temperature range necessary for the heat treatment.

  As shown in FIG. 1, the resistance temperature detector is preferably mounted in a counterbore hole 1b provided by machining or the like on the surface of the mounting table 1 opposite to the wafer mounting surface 1a. The counterbore 1b preferably has a flat portion on the bottom, side, or entire surface. The reason is that the flat portion of the temperature measuring element portion and the flat portion in the counterbore hole 1b can be brought into contact with each other, so that it is possible to increase the heat transfer area between the temperature measuring element portion and the mounting table. This is because a high temperature response can be obtained.

  For example, the shape of the counterbore hole 1b can be a rectangular parallelepiped, and can be installed such that the flat surface portion of the temperature measuring element portion is in contact with the rectangular side wall portion, the rectangular bottom surface, or both. Moreover, the shape of the counterbore hole 1b may be cylindrical, and the flat bottom surface of the circular shape may be finished to be a flat surface so that the flat surface portion of the temperature measuring element portion is brought into contact with the bottom surface. It is preferable that the position where the temperature measuring element unit abuts in the counterbore 1b described above is within a range of 30% of the thickness of the mounting table 1 in the vertical direction from the center in the thickness direction of the mounting table 1. This position can be achieved by adjusting the depth of the counterbored hole 1b formed by machining or matching the shape of the counterbored hole 1b with the shape of the temperature measuring element portion.

  In the temperature control of the heater unit, not only control in a steady state but also detecting that the surface temperature of the wafer placement surface 1a is lowered by placing the wafer to be heated on the wafer placement surface 1a, thereby It is also required to heat the heater unit. For this reason, if the contact position of the temperature measuring element unit is located above 30% of the thickness of the mounting table 1 from the center in the thickness direction of the mounting table 1, the wafer mounting surface 1a is too close. Although the temperature responsiveness when the object to be heated is mounted is improved, the distance from the heat generating unit 3 is increased, so that the resistance heating element of the heat generating unit 3 is overheated and exceeds the ideal heat treatment, and the wafer mounting surface. There is a possibility that problems such as impaired temperature uniformity in 1a may occur. Further, in the mounting table 1, there may be a problem that the thickness between the bottom surface of the counterbore hole 1b and the wafer mounting surface 1a becomes too thin to obtain mechanical strength.

  On the other hand, when the contact position of the temperature measuring element portion is positioned below 30% of the thickness of the mounting table 1 from the center in the thickness direction of the mounting table 1, the object to be heated is placed on the wafer mounting surface 1a. Since the detection of the temperature drop of the mounting table 1 is delayed, the timing for supplying the necessary amount of heat to the object to be heated is delayed, and there is a possibility that problems such as insufficient processing within a predetermined heat treatment time may occur.

  The adhesive used when attaching the temperature measuring element portion to the counterbore 1b generally has a low thermal conductivity. Therefore, the adhesive can become a thermal resistance when heat is transferred from the heat generating unit 3 or the mounting table 1. In order to suppress this problem, a cap (not shown) that can be fitted into the opening of the counterbore 1b is attached to the surface opposite to the surface facing the bottom of the counterbore 1b in the temperature measuring element. Is preferred.

  It is preferable to select a material with high thermal conductivity for this cap in consideration of heat transfer to the temperature measuring element portion. Examples of such materials include copper, aluminum, nickel and the like from the viewpoint of cost and versatility. In addition, by using the same material as the mounting table 1, it is possible to reduce deformation of the mounting table 1 due to a difference in thermal expansion coefficient and thermal stress applied to the temperature measuring element unit. When a general-purpose metal having a difference in thermal expansion coefficient from the mounting table material is selected with an emphasis on cost, the mounting table 1 can be designed by designing the cap smaller in consideration of the difference in thermal expansion amount. Deformation, thermal stress applied to the temperature measuring element portion, and the like can be suppressed.

  As described above, since the lead wire 5 is connected to the resistance temperature detector, a slight heat escape occurs along the lead wire 5, and there is a possibility that a deviation occurs between the detected temperature and the actual temperature. is there. In order to suppress this problem, a part of the lead wire 5 may be brought into contact with or close to the surface of the mounting table 1 opposite to the wafer mounting surface 1 a or the lower surface of the support plate 2. As a result, the temperature of the lead wire 5 at the contact or adjacent portion can be made substantially the same as the temperature of the resistance temperature detector, so that the heat escape from the lead wire 5 can be reduced. As described above, as a method of bringing a part of the lead wire 5 into contact or in proximity, it may be bonded to the lower surface of the mounting table 1 or the lower surface of the support plate 2 using an adhesive. At that time, it is preferable to make the contact or proximity length as long as possible.

  As shown in FIG. 2, the heat generating unit 3 has a resistance heating element 31. The resistance heating element 31 is obtained by patterning a metal foil made of stainless steel, nickel-chromium, or the like into, for example, a spiral shape by etching or laser processing. The heating element circuit formed by patterning in this way may have different heat generation densities in a plane parallel to the wafer placement surface 1a. For example, by considering the installation environment of the mounting table 1 such as the type of the object to be heated and the ease of heat radiation to the outer wall of the chamber, the wafer mounting surface is designed to have a high heat generation density in a specific region such as the outer peripheral side. The temperature uniformity in 1a can be improved.

  In this way, when the heat generation density is locally varied, it can be realized by a method such as changing the pitch of the conductive lines constituting the heat generating circuit in one resistance heat generating body as described above, For example, two types of resistance heating elements on the inner peripheral side and the outer peripheral side may be provided in a plane parallel to the surface 1a, or a plurality of resistance heating elements may be provided divided in the circumferential direction. In this way, when the resistance heating element is divided into a plurality of areas and the resistance heating elements are provided, the temperature of each divided area can be detected and the heating value of the resistance heating element can be individually controlled. .

  Further, the resistance heating element 31 may be provided not only in a single layer but also in a plurality of layers. For example, auxiliary resistive heat generation that supplies power only when the set temperature is changed, at a position different from the resistance heating element in which the amount of power supplied to the heating element circuit is controlled based on the temperature detected by the temperature sensor 4 described above. A body may be provided. In this case, it is necessary to interpose a sheet for electrical insulation between these two resistance heating elements. In order to quickly transmit heat generated during power feeding or heat transfer from the mounting table 1 during cooling, it is important that the mounting table 1 and the support plate 2 be arranged so that no gap is generated. is there. If there is a gap, the gap portion expands when the heat generating unit 3 is heated, which causes peeling of the heating element layer and dielectric breakdown, and there is no heat medium, which also causes abnormal heat generation.

  Insulating sheets 32 and 33 are provided above and below the resistance heating element 31, respectively. Thereby, even if the mounting table 1 and the support plate 2 are formed of a conductive material, the insulation of the resistance heating element 31 is ensured. It is desirable to use insulating sheets 32 and 33 having a high thermal conductivity as much as possible. If the thermal conductivity of the insulating sheets 32 and 33 is high, the temperature variation on the wafer mounting surface 1a that may be caused by the structure of the resistance heating element 31, the environment in which the heater unit is installed, or the like can be reduced. This is because it is possible to provide a heater unit with high heat uniformity on the mounting surface 1a. The insulating sheets 32 and 33 are flexible on the surface facing the mounting table 1 and the support plate 2 and have a higher thermal conductivity in the plane direction than the mounting table 1 and the support plate 2, for example, aluminum sheets 100 to 250 W / m · K. Alternatively, a high thermal conductive sheet such as a copper sheet 400 W / m · K or a graphite sheet 200 to 1700 W / m · K may be disposed.

  When a material with low thermal conductivity is selected for the insulating sheets 32 and 33, it is preferable to make the thickness as thin as possible within a range in which insulation is ensured. This is because if the sheet is thin, the heat resistance layer is thin, so that rapid heat transfer can be expected. The insulating sheets 32 and 33 are preferably flexible as compared with the mounting table 1 and the support plate 2. The reason is that a small gap caused by each flatness can be filled and the effect of the heat conduction and heat capacity of the support plate 2 can be maximized by suppressing the local thermal resistance, so that the wafer mounting surface 1a. This is because a heater unit having high temperature uniformity and stable against disturbances such as the environment can be obtained.

  Examples of the insulating sheets 32 and 33 that satisfy such conditions include polyimide resin. The polyimide resin can be used even in a temperature range exceeding 200 ° C. The polyimide resin and the resistance heating element 31 can be integrated by thermocompression bonding. By integrating in this way, mutual adhesiveness can be increased and the thermal resistance of the interface can be lowered. As a result, the local thermal resistance can be reduced, so that the heat transfer can be enhanced, and the effect of the heat capacity of the heater unit can be maximized. Further, as the resistance heating element 31 repeats expansion and contraction due to a thermal environmental load due to the integration, positional deviation with respect to the planar direction is less likely to occur, and a highly reliable heater unit can be manufactured.

  In addition, since the space | gap between the adjacent conductive lines of the circuit of the resistance heating element 31 patterned causes thermal resistance, it is desirable to fill this space | gap. It is conceivable to fill the gap with the above-described flexible insulating sheet. However, as the patterning becomes finer and the width and pitch of the conductive lines become denser, the filling with the insulating sheet becomes more difficult. Therefore, it is preferable that an adhesive component is interposed between the insulating sheets 32 and 33 and the resistance heating element 31 and that a gap between adjacent conductive wires is filled with the adhesive component. As the adhesive component, a film or varnish containing a thermoplastic or thermosetting polyimide resin is effective. By applying this adhesive component to the gaps between the insulating sheets 32 and 33 and the resistance heating element 31 and between the adjacent conductive wires, and thermocompression bonding under appropriate temperature and pressure conditions, good heat transfer performance Can be obtained.

  Further, when forming the heating element circuit of the resistance heating element 31 by etching the metal foil, the metal foil between the adjacent conductive lines is not completely removed but is not in contact with the heating element circuit. The metal foil may be left in a separated state. As a result, the gap between adjacent conductive wires can be filled with a metal foil layer having the same thickness and the same material as the heating element circuit, so that the thermal conductivity can be increased over the entire surface rather than filling with the above-described insulating sheet or adhesive component. It is possible to make the temperature uniform over the entire area and further improve the thermal uniformity on the wafer mounting surface 1a. Further, when the mounting table 1 and the support plate 2 are mechanically coupled by screwing, a metal foil layer that is not in contact with the heating element circuit is also left around the screwing part. Since the thickness of the layer provided with the resistance heating element 31 can be made substantially constant except for the screw hole portion, local deformation of the mounting table 1 and the support plate 2 due to the axial force when the screw is tightened is prevented. be able to.

  Insulating sheets 32 and 33 covering the upper and lower sides of the resistance heating element 31 are provided with releasable fluororesins 34 and 35 on the surface facing the mounting table 1 and the surface facing the support plate 2, respectively. These releasable fluororesins 34 and 35 can be formed, for example, by coating the surfaces of insulating sheets 32 and 33 covering the top and bottom of the resistance heating element 31. Alternatively, when the insulating sheets 32 and 33 are thermocompression bonded to the resistance heating element 31, the surface of the insulating sheets 32 and 33 is covered with a fluororesin sheet so that an extremely thin fluororesin layer is formed on the surfaces of the insulating sheets 32 and 33. Can be pasted.

  Accordingly, it is possible to prevent the insulating sheets 32 and 33 made of, for example, polyimide resin from being fused with the mounting table 1 and the support plate 2, and each of the mounting table 1 and the support plate 2 can be freely thermally expanded. Thus, deformation of the mounting table can be suppressed. As a result, it can be used in a higher temperature range than the conventional heater unit. The types and thicknesses of these releasable fluororesins 34 and 35 depend on the conditions of the heater unit such as the thickness of the resistance heating element and the number of laminated layers, and the flatness of the auxiliary materials used when thermocompression bonding is performed. Although it is determined as appropriate, it is generally preferable to use a thickness of about 10 nm to 10 μm. When this thickness exceeds 10 μm, it becomes a heat insulating layer and hinders heat transfer. On the other hand, if it is less than 10 nm, a precise coating technique is required, which is not preferable because it becomes expensive.

  Returning to FIG. 1 again, the heater unit according to an embodiment of the present invention includes a cooling mechanism 6 below the support plate 2. This cooling mechanism 6 is formed with a refrigerant flow path (not shown) through which an antifreeze liquid such as a fluorine-based refrigerant capable of selecting a temperature range including below zero, a refrigerant such as air, and general water can be circulated. . These refrigerants can be circulated with a cooling device such as a chiller, whereby the cooling mechanism 6 can be maintained within a desired temperature range. Note that the cooling mechanism 6 may be cooled by continuously blowing air with a compressor or the like.

  The cooling mechanism 6 has, for example, a metal pipe such as Cu as a coolant channel along the surface of a metal plate-like member, and a stainless steel joint is attached to both ends of the metal pipe and the metal pipe is held down. The pressing plate and the plate member can be mechanically coupled with a screw or the like while pressed against the plate member by a plate (this structure is also referred to as a pipe type). The material of the plate-like member is preferably selected from the group consisting of copper, aluminum, nickel, magnesium, titanium having good thermal conductivity, an alloy mainly containing at least one of these, or stainless steel. Among these, since copper has a large heat capacity, the structure of contacting and separating as described later requires a large amount of heat to be taken from the object to be cooled, and is suitable for cooling at high speed. However, since copper has a large specific gravity, aluminum having a small specific gravity and capable of being reduced in weight is preferable in addition to having excellent thermal conductivity when there is a weight limitation or when it is not preferable from the viewpoint of handling.

  In order to obtain higher thermal efficiency, for example, a spiral counterbore groove 62 is provided on the surface of the cooling plate 61 opposite to the surface facing the support plate 2 as shown in FIG. A metal pipe 63 for circulating the refrigerant formed in a spiral shape in 62 may be installed. At that time, in order to maintain good heat transfer between the metal pipe 63 and the cooling plate 61, it is more preferable to bond and fix the surface of the metal pipe 63 and the inner surface of the counterbore groove 62 with caulking material, sealant, adhesive, or the like. preferable.

  Alternatively, as shown in FIGS. 3B and 3C, two plate-like members 64a and 64b of substantially the same shape made of the same material are prepared and flowed by machining on one surface of one of the plate-like members. By forming a groove to be a path 65, stacking the other plate-like member so as to cover this flow path 65, and integrating these two plate-like members 64a and 64b by a coupling means such as brazing, for example. You may produce (this structure is also called brazing system). In this case, as described above, the groove serving as the flow path 65 may be processed only on one side of the two plate-like members 64a and 64b, or both plate-like members 64c, 64d may be processed on both sides facing each other. The brazing method has a higher heat exchange rate than the pipe method because the refrigerant directly contacts the plate-like member, and is suitable for cooling at high speed.

  As shown in FIGS. 4A and 4B, the cooling mechanism 6 is attached to an elevating mechanism 66 composed of an air cylinder or the like. As a result, the lifting mechanism 66 is operated to move away from the lower surface of the support plate 2 as shown in FIG. 4A, or to contact the lower surface of the support plate 2 as shown in FIG. 4B. It becomes possible. In this elevating mechanism 66, it is preferable to increase the contact thrust to the support plate 2 as much as possible under the restrictions such as the installation environment of the heater unit and the allowable weight and dimensions. Thereby, the thermal resistance which arises in the surface where the cooling mechanism 6 and the support plate 2 contact | abut mutually can be made small. As a result, it is possible to improve the in-plane temperature distribution by eliminating the local thermal resistance as well as reducing the cooling time.

  The thrust of the elevating mechanism 66 is desirably equal to or greater than the mass of the cooling mechanism 6. Further, immediately after the cooling mechanism 6 contacts the lower surface of the support plate 2, both contact surfaces may be vacuum-sucked. Thereby, since mutual adhesiveness improves further, it can be made to cool more rapidly. The cooling mechanism 6 is preferably provided with a through hole for inserting the power supply wiring to the heat generating unit 3 and the lead wire 5 of the temperature sensor 4 at the same position as the support plate 2 when viewed from above. The cooling mechanism 6 may be subjected to a surface treatment as necessary. For this surface treatment, Ni plating with high corrosion resistance and oxidation resistance is desirable.

  In the heater unit described above, the cooling mechanism 6 provided with the refrigerant flow path is reciprocated and directly cooled. However, the structure is not limited to this structure, and as shown in FIG. The cooling stage 7 having a not-shown) is fixed, and the cooling block 8 having no refrigerant flow path is reciprocated so as to contact the upper surface of the cooling stage 7 or the lower surface of the support plate 2. (This structure is also referred to as an indirect cooling method). The materials of the cooling stage 7 and the cooling block 8 are preferably the same as those of the cooling mechanism 6 described above. The cooling stage 7 and the cooling block 8 are preferably provided with through holes for inserting the power supply wiring of the heat generating unit 3 and the lead wires 5 of the temperature sensor 4.

  Since the cooling block 8 can be made simple and lightweight by the indirect cooling method described above, the cooling block 8 itself can be reciprocated more frequently than in the case of FIG. 1 to maintain the temperature of the cooling block 8 at a low temperature. Therefore, when the cooling block 8 is brought into contact with the lower surface of the support plate 2, a large temperature difference between the cooling block 8 and the support plate 2 can be ensured, and the cooling rate can be improved. In addition, since no coolant channel is formed in the cooling block 8, heat can be evenly taken from the entire lower surface of the support plate 2. Therefore, the temperature distribution on the wafer placement surface 1a is less likely to be attached during cooling. The direct or indirect cooling method described above and its specific structure are selected in consideration of the space and cost given to the equipment.

  An intervening layer having cushioning properties in the thickness direction can be provided between the upper surface of the cooling mechanism 6 or the cooling block 8 and the lower surface of the support plate 2. This intervening layer may be disposed on the surface that contacts the support plate 2 in the cooling mechanism 6 or the cooling block 8, or may be disposed on the surface that contacts the cooling mechanism 6 or the cooling block 8 in the support plate 2. Alternatively, it may be disposed on both of them, but it is preferable to provide the cooling mechanism 6 or the cooling block 8 on a surface that contacts the lower surface of the support plate 2. This is because a constant thermal load is always applied to the lower surface of the support plate 2, so that the intervening layer is worn out due to the thermal history, or depending on the operating temperature of the heater unit, the intervening layer and its mounting method are limited. Because it will be done. FIG. 3 shows an example in which an intervening layer 9 is provided on the upper surface of the cooling mechanism 6.

  The intervening layer is preferably formed of foam metal or metal mesh. Or you may form with the material which has heat resistance, such as a graphite sheet, a fluororesin, a polyimide, and a silicone resin. The intervening layer preferably has a high thermal conductivity, and more preferably has a thermal conductivity of 1 W / m · K or more. This is because if it is less than 1 W / m · K, the thermal resistance increases and the cooling rate becomes slow. In addition, it becomes possible to make thermal resistance smaller by using resin containing heat conductive fillers, such as carbon.

  It is preferable that the intervening layer has flexibility. Without flexibility, when the upper surface of the cooling mechanism 6 or the cooling block 8 is brought into contact with the lower surface of the support plate 2, local gaps due to the flatness of each contact surface may be filled with an intervening layer. This is because it becomes difficult and it becomes difficult to suppress temperature variations during cooling. The flatness of the upper surface of the cooling mechanism 6 and the cooling block 8 and the lower surface of the support plate 2 and the surface conditions such as partial irregularities, protrusions, scratches, flashes, burr, and foreign matters that occur during machining. Among the above-described materials, silicone resin is particularly preferable as a highly flexible material that can absorb water.

  The thickness of the intervening layer is thicker than the sum of the flatness of the lower surface in contact with the cooling mechanism 6 and the cooling block 8 in the support plate 2 and the flatness of the upper surface in contact with the support plate 2 in the cooling mechanism 6 and the cooling block 8. It is preferable that it is in the range of 0.1 to 3 mm. When the thickness of the intervening layer is less than 0.1 mm, the sum of the flatness of the lower surface of the support plate 2 described above and the flatness of the upper surfaces of the cooling mechanism 6 and the cooling block 8 so as not to cause local voids. Is required to be less than 0.1 mm, so that strict processing accuracy is required. Therefore, mass production becomes difficult and the manufacturing cost becomes high, and the intervening layer itself is too thin and difficult to handle. It is because there is a possibility of causing. On the other hand, if the thickness of the intervening layer exceeds 3 mm, the thermal resistance during cooling increases excessively, the cooling rate becomes slow, and there is a problem in making the heater unit compact.

  It is preferable that the flatness of the surface contacting the cooling mechanism 6 and the cooling block 8 in the support plate 2 and the flatness of the surface contacting the support plate 2 in the cooling mechanism 6 and the cooling block 8 are each 0.5 mm or less. . When this flatness exceeds 0.5 mm, it becomes difficult to maintain good contact with the intervening layer, and in order to maintain good contact, the intervening layer can be made thicker, and the thermal resistance is increased to slow down the cooling rate. It is because there is a possibility of making it. In addition to the flatness being 0.5 mm or less as described above, the flatness of the surface contacting the cooling mechanism 6 or the cooling block 8 in the support plate 2 as described above, the cooling mechanism 6 or the cooling block, and the like. In FIG. 8, it is more preferable that the sum total of the flatness of the surface contacting the support plate 2 is 0.1 mm or less. This is because the thickness of the intervening layer can be theoretically reduced to 0.1 mm, so that the thermal resistance is reduced and cooling can be performed at high speed.

  The intervening layer is preferably provided in a region of 10% or more and 90% or less of the area contacting the cooling mechanism 6 or the cooling block 8 on the lower surface of the support plate 2. If this is less than 10%, the area is too small and the cooling rate becomes slow. On the other hand, it is physically difficult to provide more than 90%. The method for attaching the intervening layer is not particularly limited as long as it can be fixed, but for example, it is preferably attached by adhesion using an adhesive means such as an adhesive, double-sided tape, or adhesive resin. In this case, it is desirable that the bonding means is thin, has high thermal conductivity, and low thermal resistance. In the case of a sheet having a certain dimension, it may be mechanically fixed by screwing or the like.

  As shown in FIG. 5, when the cooling stage 7 and the cooling block 8 are used, the above-described intervening layer may be disposed on the surface of the cooling block 8 that contacts the upper surface of the cooling stage 7. Thereby, the heat transfer between the cooling stage 7 and the cooling block 8 is made more uniform over the entire contact surface, which contributes to reducing the transient temperature distribution during cooling.

  As mentioned above, although the specific example was given and demonstrated about the heater unit for wafer heating of this invention, this invention is not limited to the specific example which concerns, It implements in the various aspects of the range which does not deviate from the main point of this invention. Is possible. For example, instead of providing the refrigerant flow path in the cooling mechanism 6 or the cooling stage 7, the flow path 21 may be directly provided in the support plate like the support plate 20 with a cooling function shown in FIG.

Example 1
A disk-shaped copper plate having a diameter of 320 mm and a thickness of 3 mm is prepared as a mounting table, and a counterbore hole whose bottom surface is located in the center in the thickness direction is formed from the lower surface side opposite to the wafer mounting surface. A temperature sensor was installed in contact. On the other hand, a disc-shaped Si—SiC plate having a diameter of 320 mm × a thickness of 3 mm was prepared as a support plate. Further, a circuit pattern was formed by etching on a stainless steel foil having a thickness of 20 μm as a resistance heating element, and a power feeding cable was attached to the terminal portion.

  The resistance heating element was covered with a polyimide sheet having a thickness of 50 μm and thermocompression bonded. At this time, the surface of the polyimide sheet opposite to the surface in contact with the stainless steel foil was covered with a fluororesin sheet and then thermocompression bonded. In this way, a heat generating unit was produced in which a very thin releasable fluororesin layer was formed on the surface of a polyimide sheet sandwiching a film-like resistance heating element.

  The heat generating unit was sandwiched between the mounting table and the support plate, and mechanically coupled by inserting a screw into a through hole provided in advance in the support plate and screwing the mounting table. A screw provided with a bearing on the seat surface was used as this screw so that the mounting table and the support plate were not deformed due to a difference in thermal expansion. Next, as a cooling mechanism, a phosphorous deoxidized copper pipe having an outer diameter of 6 mm and a wall thickness of 1 mm was attached to one side of a disc-shaped aluminum alloy plate having a diameter of 320 mm and a thickness of 12 mm using a screw. Joints for supplying and discharging the refrigerant were attached to both ends of the copper pipe. Furthermore, a through-hole through which the above-described power supply cable, the lead wire of the temperature sensor, and a leg portion standing from the bottom of the container described later is inserted.

  Next, a stainless steel container composed of a 1.5 mm thick side wall and a 3 mm thick bottom was prepared. This container was provided with a through hole for the lead wire of the power supply cable and the temperature sensor, and an opening through which the rod of the air cylinder for raising and lowering the cooling mechanism described above was inserted. And after attaching a cooling mechanism to the front-end | tip of the rod which protrudes / projects from this opening part, the coupling | bonding body of the mounting base and support plate which clamps the said heat generating unit was attached to the front-end | tip of the leg erected from the bottom part. In this way, a heater unit of Sample 1 was produced. The separation distance between the lower surface of the support plate and the upper surface of the cooling mechanism when the rod of the air cylinder was retracted was 10 mm.

  For comparison, a heater unit of sample 2 was manufactured in the same manner as the heater unit of sample 1 except that a 500 μm silicone resin sheet was used instead of the 50 μm-thick polyimide as the insulating layer of the heater unit. Further, a heater unit of Sample 3 was manufactured in the same manner as the heater unit of Sample 1 except that a fluororesin film was not formed on the surface of the polyimide film having a thickness of 50 μm.

  The heater units of Samples 1 to 3 were each heated from room temperature to 250 ° C. and then held at 250 ° C. for 1 hour. And the temperature of the wafer mounting surface in the steady state of 250 ° C. was measured using a contact thermometer, and the difference between the maximum temperature and the minimum temperature was calculated as a soaking range (° C.). Next, after the 1 hour had passed, the air cylinder was operated while supplying water to the copper pipe to raise the cooling mechanism, and brought into contact with the lower surface of the support plate. In this state, the temperature of the heater unit was lowered to near room temperature, and then the flatness of the wafer mounting surface was measured. The results are listed in Table 1 below.

  As can be seen from Table 1 above, the heater unit of Sample 2 had a poor soaking range, and the flatness was significantly deteriorated only by raising the temperature once. When disassembled and examined, the silicone resin was cured and the flexibility observed in the initial state was lost. For this reason, good heat transfer between the mounting table and the support plate is lost due to curing due to high temperature, the local gap causes abnormal temperature distribution, and the mounting table is deformed due to the generation of local gaps. Estimated.

  Although the heater unit of Sample 3 was lighter than the heater unit of Sample 2, the flatness was deteriorated. Furthermore, when disassembled and examined, it was fused to the surface opposite to the mounting surface of the mounting table with which the polyimide film abuts. When the surface of the mounting table that was in contact with the polyimide film after disassembly was analyzed, C, which is the main component of polyimide, was detected. That is, it is estimated that the polyimide film melted at a high temperature and adhered to the mounting table. Further, since the mounting table and the polyimide resin have different coefficients of thermal expansion, it is presumed that the mounting table is deformed by restraining the thermal expansion and contraction of the mounting table by fusing at a high temperature.

  On the other hand, the heater unit of Sample 1 had a good soaking range and no deterioration in flatness was confirmed. Even when disassembled and examined, there was no fusion to the mounting table as observed in the heater unit of Sample 3. This can be presumed to be due to the fact that the fluororesin film formed on the surface of the polyimide film becomes a lubricant at a high temperature and can be freely thermally expanded and contracted.

(Example 2)
The same heater unit of sample 1 and sample 3 manufactured in Example 1 above was manufactured again, and the temperature change at 250 ° C. and 100 ° C. was set as one heat cycle, and this was repeated 1000 times. Changes in the external appearance of the unit and flatness measurement on the wafer mounting surface were performed. The results are listed in Table 2 below.

  As can be seen from Table 2 above, the heater unit of Sample 3 had a significantly deteriorated flatness of 79 μm after 1000 heat cycles. Furthermore, when disassembled and examined, polyimide was fused to the mounting table in the same manner as in Example 1, and wrinkles were observed around the outer periphery, and peeling of the polyimide film was observed in a part thereof. It was. This is presumably due to the same reason as in the first embodiment. On the other hand, in the heater unit of Sample 1, there was no change in flatness and no change in appearance was observed. Further, the polyimide was not fused to the mounting table or the support plate. The reason why such a good result was obtained is presumed to be the same as in Example 1.

DESCRIPTION OF SYMBOLS 1 Mounting stand 1a Wafer mounting surface 1b Counterbore hole 2 Support plate 3 Heating unit 4 Temperature sensor 5 Lead wire 6 Cooling mechanism 7 Cooling stage 8 Cooling block 9 Intervening layer 10 Container 11 Leg part 20 Supporting plate with cooling function 21 Flow path 31 Resistance heating element 32, 33 Insulating sheet 34, 35 Releasable fluororesin 61 Cooling plate 62 Counterbored groove 63 Metal pipe 64a, 64b, 64c, 64d Plate member 65 Flow path 66 Elevating mechanism

Claims (3)

A wafer having a mounting table having a mounting surface on which a wafer to be processed is mounted, a support plate for supporting the mounting table, and a heat generating unit provided between the mounting table and the supporting plate. A heater unit for heating, wherein the mounting table and the support plate are made of different materials and mechanically coupled to each other, and the heating unit includes a heating element layer and upper and lower heating element layers. consists of a dielectric layer sandwiched from the both insulating layers, the mounting table and the fluorine resin layer of each of the support plate 10nm~10μm thickness abutment surfaces are coated wafer heater unit.   The heater unit for heating a wafer according to claim 1, wherein the insulating layer is formed of a polyimide resin. The heater unit for heating a wafer according to claim 1 or 2, wherein the mechanical coupling is screwing with a screw having a bearing function on a seating surface.

Images