JP4839123B2 - Rear electron impact heating device - Google Patents

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 material having excellent electrical continuity between a plate and ground.

  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. As shown in the figure, the peripheral portion of the vacuum chamber 24 is placed on the peripheral portion of the table 26 made of a metal such as stainless steel, and is airtightly fixed. A cooling liquid passage 27 is formed in the table 26, and the table 26 is cooled by passing a cooling liquid such as water through the cooling liquid passage 27.

  On the table 26, a heating container 21 is installed in the vacuum chamber 24. The heating container 21 is a container having an open bottom surface, and a top plate on which a thin plate-like heating object such as a silicon wafer is placed becomes a flat heating plate 22. More specifically, the heating container 21 has a heating plate 22 as a top plate, the upper surface side thereof is closed, and a cylindrical peripheral wall 33 having an opening on the lower surface side is provided below the periphery of the heating plate 22. . The lower end portion of the peripheral wall 33 of the heating container 21 has a flange shape, and this flange portion is applied to the upper surface of the table 26 with the vacuum seal material 28 interposed therebetween, and an annular conductive washer applied on the flange portion. It is fixed by a presser fitting 35 through 36. As a result, the heating container 21 and the table 26 are hermetically sealed by the vacuum sealing material 28 in an electrically conductive state. The table 26 is grounded, and thus the heating vessel 21 is also grounded.

  As a material of such a heating container 21, a conductor such as graphite is used. On the other hand, when the heating container 21 is made of an insulating material such as alumina or silicon nitride, the inner surface of the heating plate 22 or the entire inner surface of the peripheral wall 33 and the lower flange thereof is metalized to form a conductor film. The conductor film is grounded via the conductive washer 36, the presser fitting 35 and the table 26.

  Further, a support column 34 is erected from the table 26 inside the heating container 21, and a plate-shaped holder 32 is supported on the upper end side of the support column 34. Further, a filament support column 37 is erected from the holder 32, and a filament 29 is attached to the filament support column 37. The filament 29 is provided behind the heating plate 22 in the heating container 21. A filament heating power source 30 is connected to the filament 29. Further, an acceleration voltage is applied between the filament 29 and the heating plate 22 by the electron acceleration power source 31 via the heating container 21, the conductive washer 36, the presser fitting 35 and the table 26. As described above, since the heating vessel 21 having the heating plate 22 is grounded, it is held at a positive potential with respect to the filament 29.

  A reflector 23 is attached to an intermediate portion of the filament support column 37 so as to be positioned below the filament 29. The reflector 23 is electrically connected to the filament 29 through the filament support column 37 and has a negative potential that is the same as that of the filament 29.

  In such a backside electron impact heating device, a constant high voltage acceleration voltage is applied between the filament 29 and the heating plate 22 by the electron acceleration power source 31, and when the filament 29 is energized by the filament heating power source 30, the filament 29 Thermoelectrons are emitted from all directions. Here, the downwardly moving thermoelectrons are also reflected by the reflector 23 having a negative potential, and as a result, most of the thermoelectrons emitted from the filament 29 in the vertical direction are accelerated by the accelerating voltage, and the lower surface of the heating plate 22 Collide with. The heating plate 22 is heated by this electron impact. The heat generated in the heating plate 22 is reflected by the reflector 23 provided below the filament 29, so that the heat is prevented from diffusing to an unnecessary part as much as possible. Electrons that collide with the heating plate 22 flow from the peripheral wall 33 of the heating container 21 to the ground via the conductive washer 36, the presser fitting 35, and the table 26.

  Since the inside of the heating container 21 generates thermoelectrons from the filament 29 and collides with the lower surface of the heating plate 22 at a high speed, it must be kept at a high vacuum. The graphite most commonly used as the heating container 21 is porous and has a porosity of about 30%. For this reason, when the heating container 21 is formed of only graphite, the gas outside the heating container 21 flows inside the heating container 21 through the inside of the heating container 21, so that a high vacuum atmosphere in the heating container 21 is generated. I can't keep it.

  In view of this, the entire surface of the heating vessel 21 is coated with a pyrolytic carbon film by chemical vapor deposition (CVD). The pyrolysis-generated carbon film is called pyrotic carbon, and is a very dense film. Therefore, the gas film does not permeate and is effective for maintaining a porous graphite heating vessel in a high vacuum atmosphere.

  However, the pyrolytic carbon film has different physical properties depending on its direction, as shown in Table 1. As is apparent from Table 1, the pyrolytically produced carbon film has a high electrical resistance in the thickness direction, and exhibits conductivity several times that of stainless steel in the surface direction. The ratio of the resistivity in the thickness direction to the surface direction reaches 3 digits or more. This means that when electricity flows in the thickness direction of the film, the electrical resistance becomes extremely higher than when electricity flows in the surface direction.

  As described above, the heating container 21 heats the heating plate 22 that is the top plate with accelerated thermoelectrons, while the lower end flange portion of the peripheral wall 33 is not cooled. The material 28 cannot keep the inside of the heating container 21 in a vacuum. For this reason, the flange portion is pressed by a press fitting 35 having a water cooling mechanism 37 through a conductive washer 36, and the table 26 is also provided with a cooling mechanism 27. Therefore, although the thermal expansion coefficient of the heating container 21 made of graphite, which is a conductive ceramic, is small, distortion occurs due to thermal expansion when in use.

  When the lower flange portion of the heating container 21 is strongly pressed by the presser fitting 35 via the conductive washer 36 in a state where thermal distortion has occurred, the heating container 21 is made of graphite which is weaker than graphite and is less elastic. May be destroyed. Therefore, a slight gap is provided between the flange portion at the lower end of the heating container 21 and the table 26, and a vacuum seal material 28 such as a rubber O-ring is sandwiched between them, and this elastic force is used for vacuum sealing. Yes.

  However, since the flange portion of the heating vessel 21 is pressed against the table 26 by the presser fitting via the conductive washer 36 by the elasticity of the vacuum seal material 28 such as an O-ring, the heating vessel 21, the conductive washer 36, the presser fitting The electrical resistance of the current flow path leading to 35 and the table 26 tends to become unstable. If the elasticity of the vacuum sealing material 28 is increased to increase the pressure for pressing the member, the electrical contact resistance can be stabilized. However, the elasticity of the vacuum sealing material 28 is naturally limited. In particular, the vacuum sealing material 28 that can be sealed so as not to damage the heating container 21 distorted by thermal stress is limited to silicone-based or fluorine-based resins. The sealing material made of these materials has less repulsive force due to elasticity compared to a metal sealing material, and in order to reduce the respective electrical contact resistances of the heating container 21, the conductive washer 36, the presser fitting 35 and the table 26. Is not suitable.

In particular, when the pyrolytic carbon film coated on the surface of the heating container 21 of this backside electron impact heating device becomes thin for reasons such as lifetime, or when any defect occurs in the film, the baking of the heating container 21 is not effective. It is sufficient, and gas and moisture remain on the inner surface of the heating container 21. In such a case, the gas or moisture adsorbed on the thinned portion or defective portion of the coating or on the inner surface of the heating vessel 21 is released into the heating vessel 21. Due to this released gas, the degree of vacuum inside the heating container 21 is momentarily and intermittently lowered, and the high voltage applied between the filament 29 and the heating container 21 cannot be withstood. A withstand voltage failure occurs and an overcurrent flows due to a short circuit. When this short circuit phenomenon occurs, if the contact resistance of the conductive washer 36 is unstable, a leakage current flows directly from the heating vessel 21 to the presser fitting 35 beyond the conductive washer 36 or on the surface of the conductive washer 36. Due to the generated spark, the surface of the conductive washer 36 becomes rough. These cause further increase in electrical contact resistance, or cause defects such as holes and scratches in the pyrolysis-generated carbon film, thereby further reducing the airtightness of the heating container 21. In particular, when a short circuit occurs due to a vacuum baking failure of the heating container 21 at the initial stage of operation, the pyrolytic carbon film is damaged, leading to an increase in cost.
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 electrical contact resistance between the heating vessel and the table is reduced and stabilized, and defects in the pyrolytic carbon film of the heating vessel are reduced. It is an object of the present invention to provide a backside electron impact heating device which can prevent and thereby ensure the airtightness of a heating container stably over a long period of time.

  In the present invention, in order to achieve the above object, a conductive spring contact 5 is inserted together with a vacuum seal material 8 sandwiched between the lower end of the peripheral wall 13 of the heating vessel 1 and the table 6, It is configured to be sandwiched between the lower end flange portion of the peripheral wall 13 of the heating container 1 and the table 6.

In other words, the backside electron impact heating device according to the present invention has a spring contact 5 comprising an elastic vacuum seal 8 and a conductive spring on the table 6 on which the lower end of the peripheral wall 13 of the conductive heating container 1 is placed. Are arranged concentrically, and the lower end portion of the peripheral wall 13 of the heating container 1 is placed on the table 6 with the vacuum seal 8 and the spring contact 5 interposed therebetween, so that the heating container 1 and the table 6 are hermetically sealed. In addition, it is electrically connected . The spring contact 5 is formed by forming a coiled metal wire into a ring shape as a whole.

  In such a backside electron impact heating device, the combined use of the vacuum seal 8 and the spring contact 5 can increase the force of pressing the lower end of the heating container 1 against the table 6 by the repulsive force of their elasticity. The electrical contact resistance between the container 1 and the table 6 can be reduced. Further, since the spring contact 5 is made of metal and has electrical conductivity, the electrical contact between the heating container 1 and the table 6 can be achieved through the spring contact 5. For these reasons, the conduction between the heating container 1 and the table 6 becomes good, and the early breakage of the pyrolytic carbon film associated with the short circuit phenomenon can be prevented.

Further, since the spring contact 5 is not hermetic sealing property, by inserting the vacuum sealing member 8 concentrically with the spring contact 5 between the lower end portion and the table 6 of the heating container 1 of the peripheral wall 13, a vacuum seal 8 Together with the spring contact 5, it is possible to simultaneously realize reduction of electrical contact resistance, stable support of the heating container 1, and the like.

  As described above, in the backside electron impact heating device according to the present invention, the vacuum seal 8 and the spring contact 5 are used in combination at the contact portion between the heating container 1 and the table 6 to reduce the vacuum seal and the electrical contact resistance. A plurality of requirements as a backside electron impact heating device such as stable support of the heating container 1 can be reliably realized. Thereby, the back surface electron impact heating apparatus which can be used stably with a long lifetime can be obtained.

In the present invention, in the backside electron impact heating apparatus according to the present invention, the above-mentioned object is achieved by using the vacuum seal 8 and the spring contact 5 together in the contact portion between the heating container 1 and the table 6.
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 device according to the present invention, and FIG. 2 is an enlarged view of a main part thereof.
A vacuum chamber 4 is mounted and fixed on a table 6 made of a metal such as stainless steel. A coolant passage 7 is formed in the table 6, and the table 6 is cooled by passing a coolant such as water through the coolant passage 7.

  On the table 6, the heating container 1 is installed in the vacuum chamber 4. The heating container 1 is a container having an open bottom surface, and a top plate on which a thin plate-like heating object such as a silicon wafer is placed becomes a flat heating plate 2. More specifically, the heating container 1 has a heating plate 2 as a top plate, the upper surface thereof is closed, and a cylindrical peripheral wall 13 having an opening on the lower surface 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.

  A portion of the table 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 table 6, and the vacuum seal material 8 and the spring contact 5 are fitted into the groove. In the example of FIG. 1, the vacuum seal material 8 is fitted in the groove on the outer peripheral side of the table 6 and the spring contact 5 is fitted in the groove on the inner peripheral side, but the spring contact 5 is placed outside the vacuum seal material 8. May be. A flange portion at the lower end of the peripheral wall 13 of the heating container 1 is placed on the vacuum seal material 8 and the spring contact 5 fitted in these grooves, and the annular conductive portion on which the flange portion is further applied. It is fixed by a presser fitting 15 having a coolant passage 17 through a washer 16. In this state, the heating container 1 and the table 6 are electrically connected and hermetically sealed by the vacuum seal material 8. The table 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 ceramic 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 membrane is grounded through the conductive washer 16, the presser fitting 15 having the coolant passage 17 and the table 6.

  Further, a support column 14 is erected from the table 6 inside the heating container 1, and a flat plate-like holder 12 is supported on the upper end side of the support column 14. Further, 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. A filament heating power supply 10 is connected to the filament 9. Further, an acceleration voltage is applied between the filament 9 and the heating plate 2 by the electron acceleration power source 11 through the heating container 1, the conductive washer 16, the presser fitting 15 and the table 6. The heating container 1 having the heating plate 2 is grounded and held at a positive potential with respect to the filament 9.

  The reflector 3 is attached to an intermediate portion of the filament support column 17 so as to be positioned below the filament 9. The reflector 3 is electrically connected to the filament 9 through the filament support column 17 and has a negative potential that is the same as that of the filament 9.

  In such a backside electron impact heating apparatus, a constant high voltage acceleration voltage is applied between the filament 9 and the heating plate 2 by the electron acceleration power source 11, and when the filament 9 is energized by the filament heating power source 10, the filament 9 Thermoelectrons are emitted from all directions. Of these thermoelectrons, downward thermoelectrons are reflected by the reflector 3 having a negative potential, are accelerated by the acceleration voltage together with the upward thermoelectrons, and collide with the lower surface of the heating plate 2. For this reason, the heating plate 2 is heated by electron impact. The heat generated in the heating plate 2 is reflected by the reflector 3 provided below the filament 9 to prevent the heat 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 conductive washer 16, the presser fitting 15, and the table 6.

  When the heating plate 2 reaches a predetermined temperature, the power supplied to the filament 9 from the filament heating power source 10 is lowered, 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 cooling liquid passing through the presser fitting 16 having the cooling liquid passage 17 and the cooling liquid passage 7 of the table 6, and the temperature of the heating plate 2 is lowered. Is done.

  FIG. 3 shows an example of the spring contact 5 that is inserted and clamped between the flange portion at the lower end of the peripheral wall 13 of the heating container 1 and the table 6. As shown in this figure, the spring contact 5 is formed by bending a coiled metal wire into an annular shape and joining both ends together. The ends of the coiled metal wires are preferably joined by welding or the like and deburred so that the pyrolytic carbon film coated on the surface of the heating vessel 21 is not damaged.

4, Ru FIG der showing an example of the shape of the A-A section cross-section of the spring contact 5. FIG. 3A shows the shape of the AA partial cross section of the spring contact 5 shown in FIG. 3, and the coil is circular. The spring contact 5 is inserted between the flange portion of the lower end portion of the peripheral wall 13 of the heating container 1 and the table 6, and the coil is slightly crushed, so that the shape is close to a circular to flat elliptical shape. . FIG. (B) shows an example in which the shape of the coil is a flat shape close to an ellipse in advance. In this case, when the spring contact 5 is inserted and sandwiched between the flange portion at the lower end of the peripheral wall 13 of the heating container 1 and the table 6, the spring contact 5, the upper and lower flange portions thereof, and the upper surface of the table 6 There is an advantage that the contact length between can be increased.

  FIG.4 (c) is a perspective view which shows a part even if these coils are inclined diagonally. When the coil is tilted obliquely, the elasticity of the coil can be further reduced, and the spring contact 5 is less likely to damage the pyrolytic carbon film.

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 expanded sectional view which shows a part of one Example of the back surface electron impact heating apparatus by this invention. It is a perspective view which shows the example of the spring contact used in one Example of the back surface electron impact heating apparatus by this invention. FIG. 4 is a cross-sectional view taken along the line AA of FIG. 3 showing an example of a cross-sectional shape of a spring contact and a perspective view showing a part of a coil even when tilted. 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 13 Surrounding wall 6 of heating container Table 8 Vacuum seal 5 Spring contact

Claims (2)

A backside electron impact heating device that accelerates the thermoelectrons generated in the filament (9) and collides with the heating plate (2), which is the top plate of the heating container (1), from the backside to generate heat from the heating plate (2). A spring contact (8) comprising an elastic vacuum seal (8) and a conductive spring on a table (6) on which the lower end of the peripheral wall (13) of the conductive heating container (1) is placed. 5) are arranged concentrically, and the lower end of the peripheral wall (13) of the heating vessel (1) is placed on the table (6) with the vacuum seal (8) and the spring contact (5) interposed therebetween. A backside electron impact heating device, wherein the heating container (1) and the table (6) are hermetically sealed and electrically connected . The back surface electron impact heating device according to claim 1, wherein the spring contact (5) is formed by forming a coiled metal wire into a ring shape as a whole.

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