JP2009043951A - Back surface electron bombardment heating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the temperature gradient of a heating plate under a high temperature, and to heat a heating object at a uniform temperature. <P>SOLUTION: The back surface electron bombardment heating apparatus accelerates electrons generated in filaments 9 and makes them collide with one another from behind the heating plate 2 which is the top plate of a heating container 1 to heat the heating plate 2. Then, on a position surrounded by the filaments 9 behind the hating plate 2, an electron shielding body 4 for shielding the electrons flying to the heating plate 2 is provided. The electron shielding body 4 has the same potential as that of the filaments 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heating device that heats a heated object such as a semiconductor wafer to a high temperature, and in particular, it is a backside electron impact heating device of a type that heats a heating plate by colliding accelerated electrons with the heating plate from behind. The present invention relates to a backside electron impact heating device provided with an electron shielding plate for limiting electrons flying to the center of the plate.

  As a heating means for heating a plate-like member such as a semiconductor wafer in a processing process of a semiconductor wafer or the like, there is a back surface electron impact heating device of a type in which accelerated electrons collide behind the heating plate to generate heat. in use. In this backside electron impact heating device, the thermoelectrons generated by energizing the filament are accelerated at a high voltage, and the thermoelectrons collide behind the heating plate to cause the heating plate to generate heat. Then, the plate placed on the heating plate is heated.

FIG. 5 is a diagram showing a conventional example of a backside electron impact heating device.
The heating container 1 is installed in a vacuum chamber (not shown), and the inside of the vacuum chamber is evacuated so that the entire heating container 1 is placed in a vacuum space.

  The heating container 1 is a container having an open bottom surface, and a top plate on which a thin plate-like heating object 7 such as a silicon wafer is placed becomes a flat heating plate 2. In other words, the heating container 1 has a heating plate 2 as a top plate, the upper surface side thereof is closed, and a cylindrical peripheral wall 13 having an opening on the lower surface side is provided below the periphery of the heating plate 2.

  The lower end portion of the peripheral wall 13 of the heating vessel 1 has a flange shape, and this lower flange portion is applied to the upper surface of the lower frame 6 with the vacuum seal material 8 interposed therebetween, and a holding metal fitting 18 through a conductive washer 16. It is fixed by. Accordingly, the lower frame 6 is grounded, and the heating container 1 and the lower frame 6 are electrically connected, so that the heating container 1 is also grounded.

  As the material of the heating container 1, a conductor such as graphite is used. On the other hand, when the heating container 1 is made of ceramics such as alumina or silicon nitride and is made of an insulator, the inner surface of the heating plate 2 and the entire inner and outer surfaces of the peripheral wall 13 and the lower flange thereof are metallized to form a conductor film. The conductor film is grounded via the conductive washer 16 and the presser fitting 18 and the lower frame 6.

  A support column 14 is erected from the lower frame 6 inside the heating container 1, and a plate-like holder 12 is supported on the upper end side of the support column 14. A filament support column 17 is erected from the holder 12, and the filament 9 is attached to the filament support column 17. The filament 9 is provided behind the heating plate 2 in the heating container 1.

  The lead wire 15 of the filament 9 is pulled out from the lower frame 6 to the outside of the heating container 1 through a ceramic terminal or the like and connected to the filament heating power source 10. An acceleration voltage is applied to the filament 9 by an electron acceleration power source 11. As described above, since the heating container 1 having the heating plate 2 is grounded, it is held at a positive potential with respect to the filament 9.

  A shield plate 3 having heat resistance and conductivity is supported in the middle of the column 14 so as to be positioned below the filament 9. The shielding plate 3 is electrically connected to the filament 9 through the support column 14, and is set to a negative potential that is the same as that of the filament 9.

  In such a backside electron impact heating device, when the filament 9 is energized by the filament heating power source 10, thermoelectrons are emitted from the filament 9. Further, when a constant high voltage acceleration voltage is applied between the filament 9 and the heating plate 2 by the electron acceleration power source 11, the emitted thermoelectrons are accelerated by the acceleration voltage and collide with the lower surface of the heating plate 2. . Since some of the emitted thermoelectrons are also reflected by the shielding plate 3 having a negative potential, as a result, most of the thermoelectrons emitted from the filament 9 come into the heating plate 2 and collide with it. 2 is heated. The heat generated in the heating plate 2 is reflected by the shielding plate 3 provided below the filament 9, and the heat is prevented from diffusing to an unnecessary part as much as possible. Electrons that collide with the heating plate 2 flow from the peripheral wall 13 of the heating container 1 to the ground via the lower frame 6.

  A general heating device is based on an electric resistance heating means that supplies electricity to a resistor such as metal or graphite and heats a heated object using heat generated by the electric resistance. However, the back electron impact heating device described above is excellent in thermal efficiency because the electrons generated in the filament 9 are accelerated by a high voltage and collided with the heating plate 2 held at a positive potential with respect to the filament 9 and heated. If the acceleration voltage is 5 KV or less, X-rays are not generated and electrons collide with the heating plate 2 while spreading due to repulsion between electrons, so that heating does not concentrate only near the filament 9 of the heating plate 2. . Furthermore, in order to heat only the heating plate 2 of the heating container 21, the plate-like shielding plate 3 maintained at a negative potential is installed behind the filament 9 with respect to the heating plate 2. The thermoelectrons thus reflected are reflected by the shielding plate 3 so that only the heating plate 2 can be heated.

The shielding plate 3 in the heating container 1 of the backside electron impact heating device reflects electrons and also reflects the radiant heat from the heating plate 22.
In general, there are three forms of heat transfer: heat radiation, heat conduction, and heat convection. However, the electric heat in the vacuum is only heat radiation, and even in the atmosphere, heating by heat radiation and heat conduction is performed substantially when the heating element and the heated object are close to each other. In addition, when the temperature of the heating element is 500 ° C. or less, the heat transfer form varies depending on the conditions such as the heating temperature, the heating method, the temperature distribution, etc., such as heating by radiant heat is not effective.

  On the other hand, in a backside electron impact heating device, a shield plate that requires reflection of electrons together with reflection of radiant heat is different from a shield plate that only reflects radiant heat, and it cannot reflect electrons simply by low emissivity. . That is, unless the negative voltage with respect to the heating plate 22 is maintained at a negative potential with respect to the heating plate 2 and the negative voltage with respect to the heating plate 22 is not increased to substantially the same potential as the filament 9, the reflection of electrons is bad.

  Thus, in order to maintain the shielding plate 3 at a negative potential with respect to the heating plate 2, the shielding plate 3 must be a good conductor. Even with a plate made of an insulator such as ceramics, thermionic charge can be reflected by charging up thermionic electrons, but because of the leading edge, the potential distribution difference is large and unstable. In addition, since the charge-up potential changes according to the potential of the filament, there is a problem that control is difficult. For this reason, as the shielding plate 3 used for the backside electron impact heating device, a metal that can be easily made to have the same potential as the filament and is easily electrically connected is used, and among them, the radiation rate that reflects the radiation heat is low. The material is preferred.

  In the backside electron impact heating device, the heat generated by the collision of electrons with the heating plate 2 heats the heating plate 2 and heats the heated object 7 placed thereon. At this time, the heat of the heating plate 2 is transmitted to the lower frame 6 through the peripheral wall 13 of the heating container 1 and radiated. For this reason, the heat plate 2 has a larger amount of heat radiation in the surrounding area than in the center. For this reason, the heating plate 2 has a temperature gradient in which the temperature at the center is higher than the temperature at the periphery. That is, a uniform temperature distribution cannot be obtained.

In general, since electrons and electrons are the same charge (minus), they repel and try to spread outside the center of the heating plate 2, but this effect alone does not make the temperature of the heating plate 2 uniform. Therefore, as a countermeasure against the occurrence of such a temperature gradient, the filament 9 is arranged in a ring shape so that a large number of electrons collide with the back of the heating plate 2, particularly in the surrounding area. However, if the filaments 9 are simply arranged in a ring shape, electrons cannot be sufficiently collected in the peripheral portion of the heating plate 2 compared to the central portion of the heating plate 2, and the central portion of the heating plate 2 is inevitably compared with the peripheral portion of the heating plate 2. It is unavoidable that a temperature gradient occurs as the temperature increases.
Japanese Patent Laid-Open No. 2005-056582 JP 2004-355877 A JP 2003-178864 A

  In the present invention, in view of the problems in the conventional backside electron impact heating device, the backside that can reduce the temperature gradient of the heating plate at high temperature and level the heating temperature distribution of the heated object 7 placed thereon. An object is to provide an electron impact heating device.

  In the present invention, in order to achieve the above object, the electron shield 4 that can restrict the destination of electrons flying from the filament 9 toward the heating plate 2 to the peripheral portion of the heating plate 2 is provided, and the temperature tends to increase. It restricts the flying of electrons to the center of the heating plate 2, makes it easier for hot electrons to gather around the periphery of the heating plate 2, and suppresses temperature deviation.

  That is, the back surface electron impact heating apparatus according to the present invention heats the heating plate 2 by accelerating and colliding electrons generated in the filament 9 from behind the heating plate 2 which is the top plate of the heating container 1. is there. An electron shield 4 that shields electrons flying toward the heating plate 2 is provided behind the heating plate 2 and surrounded by the filament 9.

  In such a backside electron impact heating apparatus, an electron shield 4 for shielding electrons flying toward the center of the heating plate 2 is provided behind the heating plate 2 and surrounded by the filament 9. For this reason, electrons are restricted from flying to the central portion of the heating plate 2, and electrons can be collected and fly to the peripheral portion of the heating plate 2 accordingly. This suppresses heating of the central portion of the heating plate 2 that tends to increase in temperature, and promotes heating of the peripheral portion of the heating plate 2 that easily radiates heat. Therefore, the temperature gradient of the heating plate 2 can be reduced.

  The electron shield 4 is provided with fine electron passing holes that transmit electrons flying from the filament 9 toward the heating plate 2. In addition, the potential of the electron shield 4 with respect to the heating plate 2 can be varied from a negative potential to a zero potential or a positive potential. Thus, the amount of electrons flying toward the heating plate 2 can be controlled by transmitting or reflecting the electrons flying toward the heating plate 2 through the electron transmission holes of the electron shield 4. That is, the temperature at the center of the heating plate 2 can be controlled to control the temperature distribution.

  Further, when the electronic shield 4 is provided so that the distance to the heating plate 2 can be variably adjusted, the distance from the electronic shield 4 to the heating plate 2 is adjusted to fly to the center of the heating plate 2. The amount of electrons can be adjusted. Thereby, it can be set as an appropriate distance with respect to the heating plate 2 of the electron shield 4 according to the generated temperature gradient. In addition, by changing the size and shape of the electron shield 4, it is possible to change the area where the flying of electrons to the central part of the heating plate 2 can be restricted, so that the temperature distribution can be made more uniform according to the situation. Yes.

  As described above, in the backside electron impact heating device according to the present invention, heating of the central portion of the heating plate 2 that tends to increase in temperature is suppressed, and heating of the peripheral portion of the heating plate 2 that easily releases heat is promoted. Thus, the temperature gradient of the heating plate 2 can be reduced, so that the heating temperature distribution of the heated object 7 can be leveled. Thereby, heating of an appropriate heating thing is attained.

In the present invention, in the backside electron impact heating apparatus according to the present invention, the above-described object is achieved by providing the electron shield 4 that restricts electrons from flying at the center of the heating plate 2.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

FIG. 1 is a diagram showing an embodiment of a backside electron impact heating apparatus according to the present invention.
A heating container 1 is installed on a lower frame 6 made of a metal such as stainless steel. The heating container 1 is a container having an open bottom surface, and a top plate on which a thin plate-like heating object 7 such as a silicon wafer is placed becomes a flat heating plate 2. In other words, the heating container 1 has a heating plate 2 as a top plate, the upper surface side thereof is closed, and a cylindrical peripheral wall 13 having an opening on the lower surface side is provided below the periphery of the heating plate 2. A lower end portion of the peripheral wall 13 of the heating container 1 has a flange shape. The heating container 1 is installed in a vacuum chamber (not shown), and the whole of the heating container 1 becomes a vacuum space by reducing the pressure in the vacuum chamber.

  A portion of the lower frame 6 on which the flange portion of the heating container 1 is placed is provided with a concentric groove around the central axis of the lower frame 6, and a vacuum seal material 8 is fitted into the groove. A flange portion at the lower end portion of the peripheral wall 13 of the heating container 1 is placed on the vacuum seal material 8 fitted in the groove, and this flange portion is further supported by the lower frame 6 by the holding metal fitting 18 via the conductive washer 16. It is fixed to. In this state, the heating container 1 and the lower frame 6 are electrically connected and are hermetically sealed by the vacuum sealing material 8. The lower frame 6 is grounded, and thus the heating container 1 is also grounded.

  As the material of the heating container 1, a conductor such as graphite is used. On the other hand, when the heating container 1 is made of ceramics such as alumina or silicon nitride and is made of an insulator, the inner surface of the heating plate 2 and the entire inner and outer surfaces of the peripheral wall 13 are metallized to form a conductor film. The film is grounded via the holding washer 18 and the lower frame 6 via the conductive washer 16.

  A support column 14 is erected from the lower frame 6 inside the heating container 1, and a plate-like holder 12 is supported on the upper end side of the support column 14. A filament support column 17 is erected from the holder 12, and the filament 9 is attached to the filament support column 17. This filament 9 is ring-shaped, and this ring is horizontal. In the case of the figure, triple ring-shaped filaments 9 are arranged vertically. The filament 9 is provided behind the heating plate 2 in the heating container 1, but is disposed mainly behind the peripheral portion of the heating plate 2 because of the ring shape.

  The lead wire 15 of the filament 9 is pulled out from the lower frame 6 to the outside of the heating container 1 through a ceramic terminal or the like and connected to the filament heating power source 10. Further, an acceleration voltage is applied to one of the lead wires 4 of the filament 9 by an electron acceleration power source 11. The heating container 1 having the heating plate 2 is grounded and held at a positive potential with respect to the filament 9.

  A shielding plate 3 is supported on the filament support column 17 so as to be positioned below the filament 9. The shielding plate 3 is electrically connected to the filament 9 through the shielding plate support column 18 and has a negative potential that is the same as that of the filament 9. This shielding plate 3 is made of graphite as a base material, and the surface of the base material is coated with pyrolytic graphite having a thermal conductivity about three times higher than that of graphite, or a high melting point metal such as Mo or W.

  From the holder 12, a support column 5 different from the filament support column 17 is erected, and the electron shield 4 is attached to the upper end of the support column 5. This electron shield 4 is made of the same material as that of the shield plate 3, but has a fine electron passage hole that transmits electrons flying from the filament 9 toward the heating plate 2 like a mesh or punching metal. It is distributed. In the illustrated example, the shape is such that the cup is turned down. The position is behind the center portion of the heating plate 2, between the heating plate 2 and the shielding plate 3, and is a position surrounded by the ring-shaped filament 9. The electron shield 4 can change the potential with respect to the heating plate 2 from a negative potential to a zero potential or a positive potential. Further, the distance of the electron shield 4 to the heating plate 2, that is, the vertical position in FIG. 1, can be changed by adjusting the mounting position on the column 5.

  In such a backside electron impact heating device, a high voltage acceleration voltage is applied between the filament 9 and the heating plate 2, and when the filament 9 is energized, thermoelectrons are emitted from the filament 9 and the acceleration voltage is applied. And collide with the lower surface of the heating plate 2. For this reason, the heating plate 2 is heated by electron impact. Some of the thermoelectrons are reflected by the shielding plate 3 and the electron shielding body 4 having a negative potential. Further, the heat generated in the heating plate 2 is reflected by the shielding plate 3 provided below the filament 9, and it is possible to prevent the heat from diffusing to an unnecessary part as much as possible. Electrons that collide with the heating plate 2 flow to the ground from the peripheral wall 13 of the heating container 1 through the conductive washer 16, the presser fitting 18, and the lower flange 6.

  During heating of the heating plate 2, the electron shield 4 is behind the central portion of the heating plate 2 and is surrounded by the ring-shaped filament 9. If the potential of the electron shield 4 is a negative potential with respect to the heating plate 2, electrons flying from the filament 9 toward the central portion of the heating plate 2 as schematically shown in FIGS. 2 and 3A. Are reflected and fly toward the peripheral portion of the heating plate 2. In this way, electrons flying to the central portion of the heating plate 2 are limited by the electron shield 4, and the electrons are directed toward the peripheral portion of the heating plate 2 by that amount. As a result, the heating of the central portion of the heating plate 2 that tends to increase in temperature is suppressed, the heating of the peripheral portion of the heating plate 2 that easily radiates heat is promoted, and the temperature gradient of the heating plate 2 can be reduced.

On the other hand, as schematically shown in FIG. 3B, when the potential of the electron shield 4 is 0 with respect to the heating plate 2, the electrons flying from the filament 9 toward the central portion of the heating plate 2 are transmitted. Then, the electrons collide with the heating plate 2. Thereby, the temperature of the center part of the heating plate 2 is raised.
Thus, the temperature distribution of the heating plate 2 can be arbitrarily controlled by varying the potential of the electron shield 4.

  By adjusting the distance of the electron shield 4 to the heating plate 2, the degree of restriction of the amount of electrons flying to the central portion of the heating plate 2 is changed, and the amount of electrons flying to the central portion is adjusted. I can do it. Thereby, it can be set as an appropriate distance with respect to the heating plate 2 of the electron shield 4 according to the generated temperature gradient.

  When the heating plate 2 reaches a predetermined temperature, the electric power supplied to the filament 9 is reduced, and the temperature of the heating plate 2 is maintained at the predetermined temperature. And when predetermined time passes, the electricity supply to the filament 9 will be stopped and the heating of the heating plate 2 will be stopped. After that, most of the heat in the heating container 1 is cooled by the coolant passing through the coolant passage (not shown) of the presser fitting 18 having the conductive washer 16 and the lower frame 6, but the cooling fluid passing through the coolant passage. Then, the temperature of the heating plate 2 is lowered.

  FIG. 4 is a longitudinal side view showing each example of the electron shield 4. FIG. 4A shows the electron shield 4 in the shape of the cup which has been turned down with reference to FIGS. 1 and 2. FIG. 4B shows a cylindrical electron shield 4 whose top and bottom are open. FIG. 4C shows an umbrella-shaped electronic shield 4. FIG. 4D shows an electronic shield 4 that combines an umbrella shape and a cylindrical shape. FIG. 4E shows a flat electron shield 4. These shields are appropriately used according to the temperature gradient generated in the heating plate 2. In addition to the selection of these shapes, by changing the size of the electron shield 4, it is possible to change the area where the flying of electrons to the central part of the heating plate 2 can be restricted, so that the temperature distribution according to the situation Can be made more uniform.

  The backside electron impact heating apparatus according to the present invention can heat the heating plate 2 to a high temperature and can reduce the temperature gradient of the heating plate 2, so that a heated object such as a semiconductor wafer can be heated to a high temperature at a uniform temperature. It is suitable for heating and can be used for a heating process of a semiconductor wafer in a semiconductor manufacturing process.

It is a schematic longitudinal cross-sectional view which shows one Example of the back surface electron impact heating apparatus by this invention. It is a principal part conceptual diagram which shows the shielding operation of the electron by the electron shield of the back surface electron impact heating apparatus by this invention. It is a conceptual diagram which shows the operation | movement of an electron when the electric potential of the electron shield of the back surface electron impact heating apparatus by this invention is changed. It is a vertical side view which shows each example of the electronic shielding body of one Example of the back surface electron impact heating apparatus by this invention. It is a schematic longitudinal cross-sectional view which shows the prior art example of a back surface electron impact heating apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating container 2 Heating plate 3 Shielding plate 4 Electronic shielding body 9 Filament

Claims (4)

In a backside electron impact heating device that heats the heating plate (2) by accelerating and colliding electrons generated in the filament (9) from behind the heating plate (2) which is the top plate of the heating container (1) An electron shield (4) for shielding electrons flying toward the center of the heating plate (2) is provided behind the heating plate (2) and surrounded by the filament (9). A backside electron impact heating device characterized by the above. 2. The backside electron according to claim 1, wherein the electron shield (4) is provided with dispersed fine electron passage holes that transmit electrons flying from the filament (9) toward the heating plate (2). Impact heating device. The potential of the electron shield (4) with respect to the heating plate (2) is varied from a negative potential to 0 potential or a positive potential, and the amount of electrons flying toward the heating plate (2) is controlled to control the heating plate (2 The backside electron impact heating apparatus according to claim 2, which controls the temperature distribution of The backside electron impact heating device according to any one of claims 1 to 3, wherein the electron shield (4) is provided so that the distance to the heating plate (2) can be variably adjusted.

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