Patent Publication Number: US-2020294825-A1

Title: Substrate heat treatment apparatus

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a field of semiconductor devices manufacture, and more particularly relates to a substrate heat treatment apparatus for heat treating a substrate. 
     BACKGROUND 
     A photolithography process is an essential part of semiconductor devices manufacture. In the photolithography process, various heat treatments are performed, such as a soft bake after spin coating photoresist on a substrate, a post-exposure bake, and a hard bake after developing. When heat treating the substrate for manufacturing the semiconductor devices, with the improvement of precision of the semiconductor devices, a high degree of temperature uniformity is required during the heat treating process. In a conventional substrate heat treatment apparatus, the substrate is generally placed on a bake plate to heat directly. Although this way of placing the substrate on the bake plate to heat directly is simple, it is hard to guarantee that the substrate is heated evenly because of the warpage of the substrate. Even the substrate looks very flat, but actually, the substrate may still have a certain degree of warpage. Especially, if the substrate is an ultra thin substrate, the warpage of the substrate may be more obviously. As shown in  FIG. 12 a    to  FIG. 12 c   , a substrate  1215  may be upward convex, downward concave, or both. No matter what form of the warpage the substrate  1215  has, if the substrate  1215  is placed on a bake plate  1202  to heat directly, because the distance (h) between any point of the substrate  1215  and the bake plate  1202  is different, and a temperature gradient exists in the space above the bake plate  1202 , therefore, the substrate  1215  is heated unevenly during the heat treating process. The temperature of the substrate  1215  is non-uniform after heat treatment, which brings an adverse effect on the quality of the semiconductor devices or even makes the substrate  1215  scrap.  FIG. 13  shows the relationship between the heated temperature t(h) of any point of the substrate  1215  and the distance (h) between the any point of the substrate  1215  and the bake plate  1202 . It can be seen that the heated temperature t(h) decreases with the increase of the distance (h). Moreover, before the substrate  1215  is heat treated, the substrate  1215  may undergo such as coating, developing processes. When the substrate  1215  is placed on the bake plate  1202  to heat, organic solvent, such as hot photoresist on the substrate  1215  easily flows back and dirties the bake plate  1202 . 
     SUMMARY 
     The present invention provides a substrate heat treatment apparatus for heat treating a substrate, comprising a bake plate, a plurality of support components, a baffle plate, and a driving device. The bake plate defines at least one gas passage. The plurality of support components support the substrate. The baffle plate is fixed on a top surface of the bake plate. The baffle plate surrounds the substrate and a gap is formed between an inner circumferential wall of the baffle plate and the substrate. A driving device drives the plurality of support components to move up or down. When heat treating the substrate, a hot gas is supplied to the space between the substrate and the top surface of the bake plate through the gas passage of the bake plate, and the hot gas flows out through the gap formed between the inner circumferential wall of the baffle plate and the substrate. 
     As described above, the advantage of the substrate heat treatment apparatus of the present invention at least includes three aspects. Firstly, no matter whether the substrate is warped or not, through supplying the hot gas to the space between the substrate and the top surface of the bake plate to increase the gas convection and form the isothermal layer between the substrate and the top surface of the bake plate, the substrate is heated evenly. Secondly, because of the baffle plate, the substrate center aligns with the bake plate, and for the gap formed between the inner circumferential wall of the baffle plate and the substrate is small enough, the flow of the hot gas around the substrate flowing out from the gap is uniform no matter whether the substrate is warped or not for forming the isothermal layer between the substrate and the top surface of the bake plate. Thirdly, because the gap formed between the inner circumferential wall of the baffle plate and the substrate is small and the hot gas is continuously supplied to the space between the substrate and the top surface of the bake plate during the heat treating process, and mixed gas of the hot gas and organic solvent is exhausted continuously, the organic solvent on the substrate is hard to flow back to the support components and the bake plate, avoiding frequently cleaning the support components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view showing a substrate heat treatment apparatus for heat treating a substrate according to an exemplary embodiment of the present invention. 
         FIG. 2  is a cross sectional view showing the substrate heat treatment apparatus loading or unloading the substrate. 
         FIG. 3  is a cross sectional view showing a substrate heat treatment apparatus for heat treating a substrate according to another exemplary embodiment of the present invention. 
         FIG. 4  is a cross sectional view showing a substrate heat treatment apparatus for heat treating a substrate according to another exemplary embodiment of the present invention. 
         FIG. 5  is a cross sectional view showing the substrate heat treatment apparatus loading or unloading the substrate. 
         FIG. 6  is a cross sectional view showing a substrate heat treatment apparatus for heat treating a substrate according to another exemplary embodiment of the present invention. 
         FIG. 7  is a top view showing a baffle plate combining with a plurality of position-restricted pins for a substrate center alignment and a gap formed between an inner circumferential wall of the baffle plate and the substrate. 
         FIG. 8  is a side view showing the position-restricted pin. 
         FIG. 9 a    is an exploded view of a support component of the substrate heat treatment apparatus of the present invention. 
         FIG. 9 b    is a perspective view of the support component of the substrate heat treatment apparatus of the present invention. 
         FIG. 10 a    to  FIG. 10 c    show using the substrate heat treatment apparatus of the present invention to heat treat a substrate which is upward convex, downward concave or both. 
         FIG. 11  shows the relationship between the heated temperature t(h) of any point of the substrate and the distance (h) between the any point of the substrate and a bake plate when using the substrate heat treatment apparatus of the present invention to heat treat the substrate. 
         FIG. 12 a    to  FIG. 12 c    show using a conventional substrate heat treatment apparatus to heat treat a substrate which is upward convex, downward concave or both. 
         FIG. 13  shows the relationship between the heated temperature t(h) of any point of the substrate and the distance (h) between the any point of the substrate and a bake plate when using the conventional substrate heat treatment apparatus to heat treat the substrate. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a substrate heat treatment apparatus for heat treating a substrate according to an exemplary embodiment of the present invention is illustrated. The substrate heat treatment apparatus has a heat insulation holder  101 , a bake plate  102 , a baffle plate  103 , a lift cover  104 , and a plurality of support components  110 . The bake plate  102  is disposed in the heat insulation holder  101  for heating a substrate  115 . The bake plate  102  can be a circular electric heating panel which is made of aluminum. During the heat treating process, the temperature distribution on a top surface of the bake plate  102  is very uniform. The size of the bake plate  102  is determined by the size of the substrate  115  in order to heat treat the substrate  115  with different size. For example, in view that the size of the substrate  115  which is commonly used now is 8 inch or 12 inch, the diameter of the bake plate  102  can be 350 mm. Therefore, the bake plate  102  can heat treat the substrate  115  which size is 8 inch or 12 inch. 
     The bake plate  102  is received in the heat insulation holder  101  and the center of the bake plate  102  is aligned with the center of the heat insulation holder  101 . An interval  114  is formed between a side wall of the bake plate  102  and the heat insulation holder  101  for avoiding the temperature characteristic of the side wall of the bake plate  102  being affected and the heat insulation holder  101  being squeezed by the bake plate  102  when the bake plate  102  expands by heat. The heat insulation holder  101  is made of high-temperature-resistant material, such as ceramic. The center of the heat insulation holder  101  defines a first gas passage  1011 . The first gas passage  1011  passes through the heat insulation holder  101 . The center of the bake plate  102  defines a second gas passage  1021 . The second gas passage  1021  passes through the bake plate  102  and communicates with the first gas passage  1011 . One end of the first gas passage  1011  communicates with the second gas passage  1021  and the other end of the first gas passage  1011  connects to a gas line  106  which is wrapped by a thermal insulation material. A gas heater  107  is disposed on the gas line  106  for heating the gas in the gas line  106 , so that a hot gas is supplied to the space between the substrate  115  and the top surface of the bake plate  102  through the first gas passage  1011  and the second gas passage  1021 . The substrate  115  is supported above the top surface of the bake plate  102  by the plurality of support components  110  which respectively pass through the heat insulation holder  101  and the bake plate  102 . The plurality of support components  110  are fixed on a support arm  109 . The support arm  109  connects to a driving device  108 . The driving device  108  drives the support arm  109  to move up or down, which brings the plurality of support components  110  to move up or down, which further brings the substrate  115  to move up or down for adjusting the distance between the substrate  115  and the top surface of the bake plate  102  or for loading or unloading the substrate  115 . The driving device  108  can be a motor. 
     As shown in  FIGS. 9 a  and 9 b   , in an embodiment, the support component  110  has an anti-slip pin  1101  and a support shaft  1102 . The anti-slip pin  1101  has a ball-shaped head for supporting the substrate  115 . The anti-slip pin  1101  is mounted on a top end of the support shaft  1102  by a way of, such as thread locking, so that it is easy to disassemble and replace the anti-slip pin  1101 . Because the anti-slip pin  1101  has an anti-slip function, therefore, the anti-slip pin  1101  prevents the substrate  115  from horizontally moving when the substrate  115  is placed on the anti-slip pin  1101  and moves up or down. A bottom end of the support shaft  1102  is fixed on the support arm  109 . 
     The baffle plate  103  is fixed on the top surface of the bake plate  102 , and the baffle plate  103  can be dismountable. The baffle plate  103  surrounds the substrate  115  and a gap  113  is formed between an inner circumferential wall of the baffle plate  103  and the substrate  115 . The gap  113  is in the range of 0.1 mm-1 mm, and preferably 0.1 mm-0.5 mm. The baffle plate  103  has a guide plane  1031  for conveniently loading the substrate  115  on the support components  110 . The guide plane  1031  is tilted and has an angle with the vertical plane. The angle is less than 20 degrees, and preferably is 15 degrees. The material of the baffle plate  103  can be ceramic or stainless steel wrapped by a thermal insulation material. 
     The lift cover  104  is disposed above the baffle plate  103 . The lift cover  104  has a hollow cavity  1041 . The lift cover  104  defines an inlet port  1042  and an exhaust interface  1043 . The inlet port  1042  and the exhaust interface  1043  communicate with the hollow cavity  1041  and the exhaust interface  1043  connects to an exhaust system. Through the inlet port  1042  and the exhaust interface  1043 , mixed gas generated during the heat treating process can be exhausted. The lift cover  104  also defines a drain port  1044  communicating with the hollow cavity  1041 . 
     A temperature sensor  111  is disposed in the bake plate  102  for monitoring the temperature of the bake plate  102 . The temperature sensor  111  can be a thermocouple. The heat insulation holder  101  is disposed on a pedestal  112 . 
     When using the substrate heat treatment apparatus of the present invention to heat treat the substrate  115  which has undergone, for example, spin coating photoresist, as shown in  FIG. 2 , the driving device  108  drives the support arm  109  to move up to make the plurality of support components  110  arrive at a loading position. Then the substrate  115  is placed on the plurality of support components  110  by using, such as a robot arm  116 . The driving device  108  drives the support arm  109  to move down to make the substrate  115  arrive at a process position. There is a distance between the substrate  115  and the top surface of the bake plate  102 . So the substrate  115  doesn&#39;t contact the top surface of the bake plate  102 . The size of the distance is determined by the process requirement. Hot inert gas or hot nitrogen, is supplied to the space between the substrate  115  and the top surface of the bake plate  102  through the first gas passage  1011  and the second gas passage  1021 . Taking the hot inert gas for example, the temperature of the hot inert gas can be the same as the temperature of the bake plate  102 , or close to the temperature of the bake plate  102 . Through supplying the hot inert gas to the space between the substrate  115  and the top surface of the bake plate  102 , the gas convection is increased and an isothermal layer is formed between the substrate  115  and the top surface of the bake plate  102 , which makes the rate of heat conduction be same and destroys the temperature gradient in the space above the top surface of the bake plate  602 , therefore, the substrate  115  is heated evenly during the heat treating process no matter whether the substrate  115  is warped or not. The mixed gas generated during the heat treating process is exhausted into the hollow cavity  1041  through the inlet port  1042  and the mixed gas in the hollow cavity  1041  is exhausted out through the exhaust interface  1043 . Before the substrate  115  is heat treated, the substrate  115  may undergo such as coating, developing processes. When the substrate  115  is heat treated, organic solvent, such as photoresist on the substrate  115  is volatilized and exhausted into the hollow cavity  1041  along with the hot inert gas. The organic solvent is condensed in the hollow cavity  1041  and is drained out from the drain port  1044 . Because the gap  113  formed between the inner circumferential wall of the baffle plate  103  and the substrate  115  is small enough and the hot inert gas is continuously supplied to the space between the substrate  115  and the top surface of the bake plate  102  during the heat treating process, the organic solvent on the substrate  115  is hard to flow back to the support components  110  and the bake plate  102 . Moreover, the substrate heat treatment apparatus of the present invention has the baffle plate  103  fixed on the top surface of the bake plate  102 , when the substrate  115  is heat treated by using the substrate heat treatment apparatus of the present invention, the substrate  115  is easy to center align with the bake plate  102 . When the robot arm  116  loads or unloads the substrate  115 , there is no need to center align any more. Besides, for the gap  113  formed between the inner circumferential wall of the baffle plate  103  and the substrate  115  is small enough, the flow of the hot inert gas around the substrate  115  flowing out from the gap  113  is uniform no matter whether the substrate  115  is warped or not for forming the isothermal layer between the substrate  115  and the top surface of the bake plate  102 . After the substrate  115  is heat treated, the driving device  108  drives the support arm  109  to move up to make the plurality of support components  110  arrive at an unloading position. The robot arm  116  takes away the substrate  115  from the support components  110  and the hot inert gas is stopped to supply. 
     As shown in  FIGS. 10 a  to 10 c    and  FIG. 11 , even if the substrate  115  is upward convex, downward concave or both, because of supplying the hot inert gas to the space between the substrate  115  and the top surface of the bake plate  102  to increase the gas convection and form the isothermal layer between the substrate  115  and the top surface of the bake plate  102 , although the distance (h) between any point of the substrate  115  and the bake plate  102  is different, the substrate  115  is heated evenly and the temperature of the substrate  115  is uniform after heat treatment. 
     As shown in  FIG. 3 , in another embodiment, the heat insulation holder  101  and the bake plate  102  respectively define a plurality of first gas passages  1011  and a plurality of second gas passages  1021  for supplying the hot gas to the space between the substrate  115  and the top surface of the bake plate  102 . The plurality of first gas passages  1011  respectively connect to the gas line  106 . 
     As shown in  FIG. 4  and  FIG. 5 , in another embodiment, for avoiding the substrate  115  misaligning to induce the substrate  115  to contact the baffle plate  103 , a plurality of position-restricted pins  117  are vertically inserted in the baffle plate  103  and the bake plate  102 . The plurality of position-restricted pins  117  are uniformly distributed along the inner circumferential wall of the baffle plate  103 . As shown in  FIG. 8 , every position-restricted pin  117  has a guiding section  1171  and a restricting section  1172 . As shown in  FIG. 7 , when the substrate  115  is placed on the support components  110  and moves down to the process position along the guiding sections  1171 , the substrate  115  is restricted by the restricting sections  1172 , so that the substrate  115  can center align with the bake plate  102  and the gap  113  is formed between the inner circumferential wall of the baffle plate  103  and the substrate  115 . 
     As shown in  FIG. 6 , comparing to the embodiment disclosed in  FIG. 4  and  FIG. 5 , the heat insulation holder  101  and the bake plate  102  in another embodiment disclosed in  FIG. 6  respectively define a plurality of first gas passages  1011  and a plurality of second gas passages  1021  for supplying the hot gas to the space between the substrate  115  and the top surface of the bake plate  102 . The plurality of first gas passages  1011  respectively connect to the gas line  106 . 
     As described above, the advantage of the substrate heat treatment apparatus of the present invention at least includes three aspects. Firstly, no matter whether the substrate  115  is warpping or not, through supplying hot gas to the space between the substrate  115  and the top surface of the bake plate  102  to increase the gas convection and form the isothermal layer between the substrate  115  and the top surface of the bake plate  102 , the substrate  115  is heated evenly. Secondly, because of the baffle plate  103  and the position-restricted pins  117 , the substrate  115  automatically center aligns with the bake plate  102 . Besides, for the gap  113  formed between the inner circumferential wall of the baffle plate  103  and the substrate  115  is small enough, the flow of the hot gas around the substrate  115  flowing out from the gap  113  is uniform no matter whether the substrate  115  is warped or not for forming the isothermal layer between the substrate  115  and the top surface of the bake plate  102 . Thirdly, because the gap  113  formed between the inner circumferential wall of the baffle plate  103  and the substrate  115  is small and the hot gas is continuously supplied to the space between the substrate  115  and the top surface of the bake plate  102  during the heat treating process, and mixed gas of the hot gas and organic solvent is exhausted continuously, the organic solvent on the substrate  115  is hard to flow back to the support components  110  and the bake plate  102 , avoiding frequently cleaning the support components  110 . 
     The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to those skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.