Substrate heat treatment apparatus

A substrate heat treatment apparatus includes a heat-treating plate having a flat upper surface, support devices formed of a heat-resistant resin for contacting and supporting a substrate, a seal device disposed annularly for rendering gastight a space formed between the substrate and heat-treating plate, and exhaust bores for exhausting gas from the space. The support devices are formed of resin, and the upper surface of the heat-treating plate is made flat, whereby a reduced difference in the rate of heat transfer occurs between contact parts and non-contact parts on the surface of the substrate. Consequently, the substrate is heat-treated effectively while suppressing variations in heat history over the surface of the substrate.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a substrate heat treatment apparatus for heat-treating substrates such as semiconductor wafers, glass substrates for liquid crystal displays, glass substrates for photomasks and substrates for optical disks (hereinafter simply called “substrates”). More particularly, the invention relates to a technique for heat-treating a substrate as sucked in a position slightly spaced from a heat-treating plate.

(2) Description of the Related Art

With an increasingly fine line width of patterns formed on substrates today, the requirements for line width uniformity have become stringent, which has led to a strong demand for temperature uniformity in baking treatment in photolithography, especially in baking treatment after exposure (PEB: Post Exposure Bake). However, with enlarged substrate sizes, increased curvatures of substrates take place in the semiconductor manufacturing process. It is difficult to satisfy the requirements for temperature uniformity in a proximity heating mode that heats each substrate only by placing the substrate as separated by a minute space from a heat-treating plate.

Thus, a suction bake mode has been proposed in order to perform uniform heat treatment even for curved substrates. This type of apparatus includes a heat-treating plate with a heater, support elements and a sealer arranged on the upper surface of the heat-treating plate, and exhaust bores formed in the upper surface of the heat-treating plate.

The support elements are in the form of bulges and dimples formed by machining the upper surface of the heat-treating plate (as disclosed in Japanese Unexamined Patent Publication H2-290013 (1990), for example), or metallic projections formed on the upper surface of the heat-treating plate and coated with resin (as disclosed in Japanese Unexamined Patent Publication H10-284360 (1998), for example). The sealer is in the form of a ring disposed in a position for contacting edges of a substrate. With these apparatus, the substrate is sucked as the sealer closes lateral areas of a space formed between the heat-treating plate and the substrate supported by the support elements, and gas is exhausted from this space through the exhaust bores. By sucking the substrate in this way, any curvature of the substrate is corrected whereby the substrate is heated uniformly.

The conventional apparatus noted above have the following drawbacks.

In the former construction, the bulges and dimples are formed of the same material as the heat-treating plate, and have a much higher thermal conductivity than air. Therefore, the thermal resistance between the bulges and the substrate in direct contact is much smaller than the thermal resistance between the dimples and the substrate not in direct contact but interposed by space. In time of heat treatment, therefore, heat is transferred faster to the parts (contact parts) of the substrate in contact with the bulges than to the parts (non-contact parts) of the substrate out of contact with the bulges. The rate of temperature increase differs greatly between the contact parts and non-contact parts, causing serious variations in heat history over the substrate surface. As a result, a pattern of uniform line width cannot be formed on the substrate.

In the latter construction, surfaces of the projections are coated with resin in order to prevent metallic contamination. Since the interiors of the projections are metal with high thermal conductivity, heat is positively transferred to the parts (contact parts) of the substrate in contact with the projections. On the other hand, heat transfer to the parts (non-contact parts) of the substrate out of contact with the projections takes place through a gas layer, and is relatively small in amount. This results in the inconvenience of the rate of temperature increase differing greatly between the contact parts and non-contact parts, causing serious variations in heat history over the substrate surface.

SUMMARY OF THE INVENTION

This invention has been made having regard to the state of the art noted above, and its object is to provide a substrate heat treatment apparatus for heat-treating a substrate effectively while suppressing variations in heat history over a substrate surface between contact parts in contact with support devices and non-contact parts out of contact with the support devices.

The above object is fulfilled, according to this invention, by a substrate heat treatment apparatus for heat-treating a substrate, comprising a heat-treating plate having a flat upper surface; support devices arranged on the upper surface of the heat-treating plate and formed of a heat-resistant resin for contacting and supporting the substrate; a seal device disposed annularly on the upper surface of the heat-treating plate for contacting edges of the substrate to render gastight a space formed between the substrate and the heat-treating plate; and exhaust bores for exhausting gas from the space.

According to this invention, the seal device renders gastight the space formed between the substrate and the heat-treating plate. The exhaust bores are provided for exhausting gas from this space, thereby holding the substrate by suction. In this way, the separation of the substrate and heat-treating plate can be maintained uniform. Further, the support devices are formed of resin, and the upper surface of the heat-treating plate is made flat. This reduces the difference in the rate of heat transfer between contact parts on the surface of the substrate in contact with the heat-treating plate, and non-contact parts out of contact with the heat-treating plate. Consequently, the substrate can be heat-treated effectively while suppressing variations in heat history over the surface of the substrate.

In the above apparatus, the support devices may be porous. The porous support devices can further reduce the difference in the rate of heat transfer between the contact parts and non-contact parts.

The support devices may be arranged separately from one another for point contact with the substrate. Since the area of contact between the support devices and substrate is reduced, the variations in heat history over the substrate surface can be further suppressed.

The support devices may be arranged regularly. This arrangement can suppress flexion of the substrate.

Each of the support devices may have a sectional shape becoming smaller from a lower portion to an upper portion that contacts the substrate. This is effective to prevent the support devices from buckling when the substrate is sucked.

The support devices may be arranged in concentric circles for line contact with the substrate. The support devices can maintain the separation of the substrate and heat-treating plate uniform, thereby suppressing variations in heat history over the substrate surface.

Each of the support devices may have groove portions for allowing communication between regions inside and outside thereof. Then, the space formed between the substrate and heat-treating plate is not divided by the support devices. Consequently, the substrate can be sucked effectively by exhausting gas through the exhaust bores.

In the above apparatus, each of the support devices may have a sectional shape becoming smaller from a lower portion to an upper portion that contacts the substrate. This is effective to prevent the support devices from buckling when the substrate is sucked.

The support devices may be a sheet-like object having projections formed thereon for contacting the substrate. Such support devices are simple in construction.

The projections may be arranged to make point contact with the substrate. Since the area of contact between the support devices and substrate is reduced, the variations in heat history over the substrate surface can be further suppressed.

The projections may be arranged regularly. This arrangement can suppress flexion of the substrate.

The projections may be arranged in concentric circles. The support devices can maintain the separation of the substrate and heat-treating plate uniform, thereby suppressing variations in heat history over the substrate surface.

Each of the projections may have groove portions for allowing communication between regions inside and outside thereof. Then, the space formed between the substrate and heat-treating plate is not divided by the support devices (projections). Consequently, the substrate can be sucked effectively by exhausting gas through the exhaust bores.

Each of the projections may have a sectional shape becoming smaller from a lower portion to an upper portion that contacts the substrate. This is effective to prevent the support devices from buckling when the substrate is sucked.

The sheet-like object may include a ring-shaped ridge for contacting the edges of the substrate to render gastight the space formed between the substrate and the heat-treating plate, thereby acting as the seal device. Such support devices and seal device are simple in construction.

The support devices may include granular objects, and a coating layer covering the granular objects. Such support devices are simple in construction.

The apparatus may further comprise a resin layer disposed between the support devices and the heat-treating plate. The resin layer allows the support devices to be arranged appropriately.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will be described in detail hereinafter with reference to the drawings.

Embodiment 1 of this invention will be described hereinafter with reference to the drawings.

FIG. 1is a view in vertical section showing an outline of a substrate heat treatment apparatus in Embodiment 1.

FIG. 2is a plan view of a heat-treating plate.

A heat-treating plate1for supporting a substrate or wafer W under treatment is circular and has a slightly larger diameter than the wafer W in plan view. The upper surface of the plate1is flat. The heat-treating plate1is formed of a metal such as copper or aluminum having high thermal conductivity, for example. The heat-treating plate1has a heating element3such as a mica heater mounted therein. A heat transfer portion5between the heating element3and the upper surface of heat-treating plate1has a plurality of heat pipes, not shown, embedded therein. Cooling grooves, not shown, are formed between the heat pipes for circulating a cooling fluid.

The heat-treating plate1has a plurality of (55inFIG. 2) support elements11arranged on the upper surface thereof for contacting and supporting the lower surface of the wafer W. The support elements11are formed of heat-resistant resin. Preferably, the resin is resistant to chemicals also. Further, it is preferred that the resin is a porous material. Specifically, such material may, for example, be polyimide, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyetheretherketone (PEEK), polyphenylene sulphide (PPS), polyvinylidene fluoride (PVDF), polyethersulfone (PES), polysulfone (PSF), polyetherimide (PEI), or heat-resistant rubber materials. Regarding the thermal conductivity of support elements11, polyimide is 0.12 W/m·K and PTFE is 0.25 W/m·K, far lower than copper (372 W/m·K) and aluminum (183 W/m·K), and close to air (0.026 W/m·K).

Each support element11has a sectional shape tapering from a lower portion to an upper portion that contacts the wafer W. Specifically, each support element11is pillar-shaped with a diameter enlarging from the upper portion that contacts the wafer W to the lower portion. The height of support elements11, preferably, is 40 to 120 μm, and its preferred diameter is 0.1 to 2mm.

The support elements11are arranged separately from one another. In this embodiment, the support elements11are arranged regularly. Specifically, equilateral triangles are assumed to be arranged regularly and continually on the upper surface of heat-treating plate1(inFIG. 2, the equilateral triangles are shown in alternate long and short dash lines). The support elements11are attached to apexes of these equilateral triangles by adhesive or by thermal fusion. One of the support elements11is located at a center point P of the heat-treating plate1. Each support element11supports the wafer W through point contact. The support elements11correspond to the support devices in this invention.

The heat-treating plate1has a ring-shaped sealer15mounted on the upper surface thereof and having an inside diameter slightly smaller than the outside diameter of the wafer W in plan view. The sealer15contacts edge regions of the wafer W to render gastight a minute space (also called proximity gap) “ms” formed between the heat-treating plate1and the wafer W supported by the support elements11. The sealer15, preferably, is formed of polyimide resin which has heat resistance and elasticity, for example. Another usable material is fluororesin. The sealer15need not be formed of the same the material as the support elements11. It is preferred that the sealer15usually has a projecting height exceeding the height of support elements11by a squeeze margin corresponding to an amount of compression occurring when the wafer W is drawn by suction. Thus, the sealer15, when in contact with the peripheral regions of the wafer W, is compressed to the same height as the support elements11, to enhance gastightness of the minute space “ms”. The sealer15corresponds to the seal device in this invention.

Further, the heat-treating plate1has exhaust bores17formed in the upper surface thereof for exhausting gas from the minute space “ms”. The plurality of (e.g. four) exhaust bores17are arranged equidistantly in the circumferential direction. Each exhaust bore17extends down to the lower surface of heat-treating plate1. One end of exhaust piping21is connected commonly to these exhaust bores17, and a vacuum suction source23is connected to the other end of the exhaust piping21. This vacuum suction source23is a vacuum utility provided for a cleanroom, for example. The exhaust piping21has a pressure regulating valve25for regulating pressure (negative pressure) in the minute space “ms”, and a pressure gauge27for measuring the pressure. The exhaust piping21may also have a switch valve with a vacuum breaker. The exhaust piping21and vacuum suction source23function as an exhaust device.

The heat-treating plate1further includes transfer members31for transferring the wafer W to and from a transport device not shown. The transfer members31are rod-shaped, and are formed of ceramics, for example. In this embodiment, the heat-treating plate1has three perforations33formed to extend vertically therethrough, in positions corresponding to the apexes of an equilateral triangle centering on the center point P of heat-treating plate1and clear of the support elements11in plan view. The transfer members31are inserted in the perforations33, respectively. The transfer members31have lower ends thereof commonly connected to a single support base35. The support base35is connected to a working rod of an air cylinder37. The air cylinder35is operable to raise and lower the support base35. These transfer members31, support base35and air cylinder37function as a substrate transfer device.

A controller41performs an overall control of the apparatus, i.e. controls output of the heating element3noted hereinbefore, switching operation of the pressure regulating valve25, driving of the vacuum suction source23, and driving of the air cylinder37. These controls are performed based on a recipe stored beforehand. The switching operation of the pressure regulating valve25is based on results of detection by the pressure gauge27. The controller41is realized by a central processing unit (CPU) which performs various processes, a RAM (Random Access Memory) used as the workspace for operation processes, and a storage medium such as a fixed disk for storing a variety of information.

Operation of the substrate heat treatment apparatus having the above construction will be described with reference toFIG. 3.FIG. 3is a flow chart illustrating a procedure of treatment by the substrate heat treatment apparatus. Temperature control of the heating element3, for example, is assumed to have already been carried out according to the recipe, and will be omitted from the following description.

As the transport device, not shown, loads a wafer W in horizontal posture into the apparatus, the controller41drives the air cylinder37to raise the support base35. The transfer members31project above the upper surface of heat-treating plate1, and receive the wafer W. Subsequently, the air cylinder37is reversed to lower the transfer members31. The wafer W is supported through point contact by the support elements11, and the minute space “ms” is formed between the wafer W and heat-treating plate1. The edge regions of wafer W contact the sealer15to render the minute space “ms” gastight.

The controller41drives the vacuum suction source23, and operates the pressure regulating valve25. As a result, the gas (i.e. air or nitrogen) in the minute space “ms” is exhausted through the exhaust bores17and exhaust piping21. The pressure in the minute space “ms” is adjusted to a negative pressure. As a result, the wafer W is sucked toward the heat-treating plate1. A curvature of wafer W, if any, is corrected to follow the support elements11and sealer15.

This process will particularly be described with reference toFIGS. 4A,4B,5A and5B. The curvature of wafer W includes a case where, as shown inFIG. 4A, the wafer W is curved to have the central part bulging upward (dome-like curvature), and a case where, as shown inFIG. 5A, the wafer W is curved to have the central part bulging downward (bowl-like curvature).

When the wafer W with the central part bulging upward is in place, the sealer15is in contact with the wafer W to render the minute space “ms” gastight. Thus, the wafer W is drawn toward the heat-treating plate1by suction until the central part of wafer W contacts the support elements11. As a result, the curvature of wafer W is corrected to be substantially level as shown inFIG. 4B. On the other hand, when the wafer W with the central part bulging downward is in place, the wafer W is still out of contact with the sealer15so that the minute space “ms” is open sideways. However, the suction applied in this state will cause gas to flow from the ambient through the gap between the wafer W and sealer15into the minute space “ms”, producing Bernoulli effect to draw the edge regions of wafer W downward (FIG. 5Ashows air flows in two-dot chain lines). The sealer15will soon contact the edge regions of the wafer W to render the minute space “ms”. The curvature of wafer W is corrected to be substantially level as shown inFIG. 5B.

A predetermined heat treatment is carried out for the wafer W while maintaining the wafer W in the suction-supported state for a predetermined time. At this time, heat is transferred from the support elements11to contact parts C of the surface of wafer W in contact with the support elements11. To non-contact parts D of the surface of wafer W out of contact with the support elements11, heat is transferred by heat conduction from the gas in the minute space “ms” heated by the heat-treating plate1.

Upon completion of the heat treatment performed for the predetermined time, the controller41stops the vacuum suction source23and closes the pressure regulating valve25, to stop the gas exhaustion from the minute space “ms” and return the pressure in the minute space “ms” to atmospheric pressure. As a result, the wafer W is released from suction. Subsequently, the air cylinder37is driven to raise the transfer members31and wafer W. In this state, the transport device, not shown, unloads the wafer W from the apparatus.

According to this substrate heat treatment apparatus, as described above, the wafer W is sucked and held in place by exhausting gas from the minute space “ms”. Thus, the separation of the wafer W and heat-treating plate1can be made uniform. The support elements11are formed of resin, whereby the thermal conductivity of support elements11per se is brought close to the thermal conductivity of air. Compared with the case of using support elements formed of metal, a reduced difference in the rate of heat transfer occurs between contact parts C and non-contact parts D on the surface of wafer. Further, the upper surface of heat-treating plate1is made flat. Compared with the case of using a heat-treating plate with bulges and dimples, a reduced difference in the rate of heat transfer occurs between contact parts C and non-contact parts D on the surface of wafer W. Consequently, the wafer W can be heat-treated effectively while suppressing variations in heat history over the surface of wafer W. As a result, a pattern of uniform line width can be formed on the wafer W.

The support elements11support the wafer W through point contact, to reduce the area of contact with the wafer W, thereby further suppressing variations in heat history over the surface of wafer W. Generation of particles can also be prevented. The support elements11have a sectional shape enlarging from the upper portion to the lower portion. This is effective to prevent the support elements11from buckling when the wafer W is sucked. Edges at the upper potion of each support element11are hardly subjected to damage such as chipping. With the support elements11formed of a porous resin, the rate of heat transfer to the contact parts C can be brought closer to the rate of heat transfer to the non-contact parts D on the surface of wafer W.

Embodiment 2 of this invention will be described hereinafter with reference to the drawings. Like reference numerals are used to identify like parts which are the same as in Embodiment 1 and will not particularly be described.FIG. 6Ais a plan view of a heat-treating plate.FIG. 6Bis a view in vertical section of the heat-treating plate.

Embodiment 2 is different from Embodiment 1 in support elements12. The heat-treating plate1has a plurality of (e.g. four) support elements12arranged in concentric circles. More particularly, the support elements12are ring-shaped, different in diameter, and arranged concentrically about the center point P on the upper surface of heat-treating plate1. Each support element12has a sectional shape tapering from a lower portion to an upper portion that contacts a wafer W. Grooves18are formed in varied positions of each support element12for allowing communication between regions inside and outside each support element12. The support elements12are formed of the same material as the support elements11described in Embodiment 1, for example. Each support element12supports the wafer W through line contact. At this time, the grooves18serve as vents between the regions inside and outside each support element12. The support elements12correspond to the support devices in this invention. The grooves18correspond to the groove portions in this invention.

Operation of the substrate heat treatment apparatus in Embodiment 2 in time of sucking the wafer W will be described.

The minute space “ms” formed between the wafer W and heat-treating plate1is a single space communicating through the grooves18, without being divided by each support element12. The controller41operates the vacuum suction source23and pressure regulating valve25to adjust the pressure in the minute space “ms” to a negative pressure. The wafer W is drawn toward the heat-treating plate1, and is leveled to follow the support elements12and sealer15.

According to the substrate heat treatment apparatus in Embodiment 2 also, the separation of the wafer W and heat-treating plate1can be maintained uniform. The support elements12are formed of resin, and the upper surface of heat-treating plate1is made flat. As a result, the wafer W can be heat-treated effectively while suppressing variations in heat history over the surface of wafer W.

Embodiment 3 of this invention will be described hereinafter with reference toFIG. 7. Like reference numerals are used to identify like parts which are the same as in Embodiment 1 and will not particularly be described.FIG. 7is a sectional view of a heat-treating plate.

Embodiment 3 is different from Embodiment 1 in having a support and seal member13instead of the support elements11and sealer15. The support and seal member13is a sheet-like object having projections13bformed thereon for contacting a wafer W. More particularly, the support and seal member13includes a sheet-like base13acovering the entire surface of heat-treating plate1and having, formed thereon, a plurality of projections13b, and a ring-shaped ridge13chaving an inside diameter slightly smaller than the outside diameter of the wafer W. The support and seal member13has openings formed in positions opposed to the exhaust bores17and perforations33.

Each projection13bis pillar-shaped, and makes a point contact with the wafer W. Each projection13bhas a sectional shape tapering from a lower portion to an upper portion that contacts the wafer W. The diameter of each projection13b, preferably, is 0.1 to 2 mm. The height of projections13bincluding the thickness of the base13a, preferably, is 70 to 250 μm, and that excluding the thickness of the base13a(i.e. projecting height from the upper surface of base13a), preferably, is 40 to 120 μm . The projections13bare arranged regularly on the base13a. In this embodiment, as are the support elements11in Embodiment 1, the projections13bare arranged in positions corresponding to the apexes of equilateral triangles assumed to be arranged regularly and continually.

The height of ridge13cis equal to the height of projections13b. The width of ridge13c, preferably, is 0.01 to 2 mm. The ridge13ccontacts the edge regions of the wafer W to render the space formed by the wafer W gastight.

The support and seal member13is formed of the same material as the support elements11described in Embodiment 1, for example. This support and seal member13is obtained by etching a resin sheet (resin layer or resin film). However, the method of manufacturing the support and seal member13is not limited to the above. The projections13band ridge13cmay be formed on the base13aby heat welding. The support and seal member13may be formed as an integral object, by punching or laser processing a resin sheet.

The support and seal member13is mechanically fixed by bolts51or the like to edge regions of the heat-treating plate1. Instead, the support and seal member13may be bonded to the upper surface of heat-treating plate1with a heat-resistant adhesive, for example. The support and seal member13corresponds to the support devices in this invention, and also to the seal device in this invention.

Operation of the substrate heat treatment apparatus in Embodiment 3 in time of heat-treating the wafer W will be described.

When heat-treating the wafer W, heat is transferred from the support and seal member13to contact parts E of the surface of wafer W in contact with the support and seal member13. To non-contact parts F out of contact with the support and seal member13, heat is transferred by heat conduction from the gas in the minute space “ms”. To the gas in the minute space “ms”, heat is transferred from the heat-treating plate1through the base13a.

According to the substrate heat treatment apparatus in Embodiment 3 also, the separation of the wafer W and heat-treating plate1can be maintained uniform. The support and seal member13is formed of resin, and the upper surface of heat-treating plate1is made flat. As a result, the wafer W can be heat-treated effectively while suppressing variations in heat history over the surface of wafer W.

Since heat is transferred to the gas in the minute space “ms” through the base13a, slight variations in the temperature distribution over the heat-treating plate1(e.g. ±0.2 degrees) are absorbed to heat the gas in the minute space “ms” uniformly. Consequently, the heat conduction from the gas in the minute space “ms” to the wafer W is made uniform.

The support and seal member13having the projections13band ridge13ccontributes toward a simple construction. The ridge13cformed integral with the base13aand projections13bis positively prevented from separating or falling from the heat-treating plate1, compared with the sealer15and support elements11attached separately as described in Embodiment 1.

Embodiment 4 of this invention will be described hereinafter with reference toFIG. 8. Like reference numerals are used to identify like parts which are the same as in Embodiment 1 and will not particularly be described.FIG. 8is a sectional view of a heat-treating plate. Embodiment 4 is different from Embodiment 1 in having support elements14instead of the support elements11. The support elements14include granular objects14aand a coating layer14bcovering the granular objects14a. Further, the support elements14include, as a lower layer, a resin layer14ccoating the upper surface of heat-treating plate1.

The resin layer14cis applied and formed inwardly of the sealer15on the heat-treating plate1. The granular objects14aare arranged on this resin layer14c, and the coating layer14bis formed to cover the granular objects14a. The positions of support elements14where the granular objects14aare arranged bulge higher than the portions with no granular objects. These bulging positions contact and support the wafer W. The support elements14are formed of the same material as the support elements11in Embodiment 1. However, the granular objects14a, coating layer14band resin layer14cneed not be the same material. The support elements14correspond to the support devices in this invention.

According to the substrate heat treatment apparatus in Embodiment 4 also, the separation of the wafer W and heat-treating plate1can be maintained uniform. The support elements14are formed of resin, and the upper surface of heat-treating plate1is made flat. As a result, the wafer W can be heat-treated effectively while suppressing variations in heat history over the surface of wafer W.

Embodiment 5 of this invention will be described hereinafter with reference to the drawings. Like reference numerals are used to identify like parts which are the same as in Embodiment 1 and will not particularly be described.FIG. 9Ais a plan view of a heat-treating plate.FIG. 9Bis a view in vertical section of the heat-treating plate.

Embodiment 5 includes a support member51and the sealer15. The support member51is a sheet-like object having projections51bformed thereon for contacting a wafer W. More particularly, the support member51includes a sheet-like base51acovering the heat-treating plate1inwardly of the sealer15and having, formed thereon, a plurality of continuous projections51barranged in concentric circles. The projections51bare ring-shaped and different in diameter, and arranged about the center point P on the upper surface of heat-treating plate1. Each projection51bhas a sectional shape tapering from a lower portion to an upper portion that contacts the wafer W. Grooves53are formed in varied positions of each projection51bfor allowing communication between regions inside and outside each projection51b. The support member51is formed of the same material as the support elements11described in Embodiment 1, for example. The support member51has openings formed in positions opposed to the exhaust bores17and perforations33. The support member51corresponds to the support devices in this invention. The grooves53correspond to the groove portions in this invention.

Operation of the substrate heat treatment apparatus in Embodiment 5 in time of sucking the wafer W will be described.

The support member51supports the wafer W through line contact. At this time, the grooves53serve as vents between the regions inside and outside each projection51b. That is, the minute space “ms” formed between the wafer W and heat-treating plate1is a single space communicating through the grooves53, without being divided by the support member51. The pressure in the minute space “ms” is adjusted to a negative pressure by exhausting gas from the minute space “ms” through the exhaust bores17. The wafer W is drawn toward the heat-treating plate1, and is leveled to follow the support member51and sealer15.

Thus, according to the substrate heat treatment apparatus in Embodiment 5 also, the separation of the wafer W and heat-treating plate1can be maintained uniform.

Since heat is transferred to the gas in the minute space “ms” through the base51a, slight variations in the temperature distribution over the heat-treating plate1(e.g. ±0.2 degrees) are absorbed to heat the gas in the minute space “ms” uniformly. Consequently, the heat conduction from the gas in the minute space “ms” to the wafer W is made uniform.

This invention is not limited to the foregoing embodiments, but may be modified as follows:

(1) Embodiment 1 described hereinbefore shows an arrangement of support elements11by way of example. This arrangement may be varied as appropriate.

(2) In Embodiments 1, 2, 3 and 5 described hereinbefore, each of the support elements11and12and projections13band51bhas a sectional shape considerably varying from the upper portion to the lower portion. This shape is not limitative, but their diameter may be the same from the upper portion to the lower portion.

(3) In Embodiment 2 described hereinbefore, grooves18are formed in each support element12. The grooves18may be replaced with other appropriate means for allowing communication between the regions inside and outside each support element. Instead of forming the grooves18in each support element12, grooves or through-holes may be formed in the heat-treating plate1, for example.

(4) In Embodiment 4 described hereinbefore, the support elements14include the granular objects14a, coating layer14band resin layer14c. The resin layer14cmay be omitted, with the granular objects14aarranged directly on the upper surface of heat-treating plate1.

(5) In each embodiment described hereinbefore, the wafer W is circular. This is not limitative, but rectangular or otherwise shaped substrates may be treated. In this case, the shape of sealer15may be changed from circular to an appropriate shape according to the shape of substrates.

(6) In each embodiment described hereinbefore, heat pipes are embedded in the heat transfer portion5. The invention is applicable also to a substrate heat treatment apparatus having no heat pipes.