JP2008053028A - Back electron impact heating method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent breakage of an apparatus by avoiding generation of spark discharge. <P>SOLUTION: This back electron impact heating device includes: a filament 9 arranged behind a heating plate 2 used as a top plate of a heating vessel 1; a heating power source 12 heating the filament 9; an acceleration power source 7 applying an acceleration voltage to the filament 9; and a temperature measurement means measuring the temperature of the heating plate 2. The device is provided with a switching circuit which is structured such that, when the heating plate 2 is heated by carrying a current to the filament 9 from the heating power source 12, the acceleration power source 7 is separated from the filament 9 until the temperature of the heating plate 2 measured by the temperature measurement means reaches a certain set value, and the heating plate 2 is heated only by carrying the current to the filament 9 from the heating power source 12; and, when the temperature of the heating plate 2 measured by the temperature measurement means exceeds the set value, the device is switched over to apply the acceleration voltage to the filament 9 by the acceleration power source 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for placing a heated object such as a semiconductor wafer on a heating plate and heating it to a high temperature, and in particular, heating the heating plate with a filament provided behind the heating plate is accelerated from the filament. The present invention relates to a backside electron impact heating method and apparatus provided with two heating means for causing electrons to collide with a heating plate for heating.

  In a processing process of a semiconductor wafer or the like, a heater of a type in which a substrate is heated on a heating plate is used as a heating means for heating a plate-like member (hereinafter referred to as “substrate”) such as the semiconductor wafer. Yes. For example, FIG. 4 shows a backside electron impact heating apparatus of a type in which accelerated electrons collide from behind the heating plate 32 to heat the heating plate 32 and heat a heated object 40 such as a substrate placed on the heating plate 32. It is.

  Although not shown in FIG. 4, a vacuum chamber is placed and fixed on a table 36 made of a metal such as stainless steel, and a heating container 31 is installed in the vacuum chamber. The heating container 31 is a container-shaped container made of graphite or the like with an open bottom surface, and the top plate is a flat heating plate 32 on which a thin plate-shaped heating object 40 such as a silicon wafer is placed. It is.

  An annular groove is provided in a portion of the table 36 on which the lower end flange portion of the heating container 31 is placed, and a vacuum sealing material 38 is fitted into this groove. On the vacuum seal material 38 fitted in the groove, the lower end flange portion of the peripheral wall 34 of the heating container 31 is placed and fixed.

Further, a filament 39 is attached to the back side of the heating plate 32 by a support column standing inside the heating container 31. A filament heating power source 43 is connected to the filament 39. Further, an acceleration voltage is applied between the filament 39 and the heating plate 32 by an acceleration power source 37. The heating container 31 having the heating plate 32 is grounded and held at a positive potential with respect to the filament 39.
A reflector 33 is attached so as to be positioned below the filament 39. The reflector 33 is electrically connected to the filament 39 and has a negative potential that is the same as that of the filament 39.

  In such a backside electron impact heating device, the filament 39 in the heating container 31 is energized and heated to generate thermoelectrons and a high voltage is applied between the filament 39 and the heating plate 32 by the acceleration power source 37. Is applied to accelerate the thermal electrons and collide with the heating plate 32 maintained at a positive potential. The heating plate 32 is heated by the impact caused by the collision of the thermal electrons, and the heated object 40 can be heated.

  In this backside electron impact heating device, it is necessary to appropriately control the heating temperature of the heated object 40 while measuring the temperature of the heating plate 32. As a temperature measuring means for such a heating plate 32, a thermocouple 35 electrically insulated by an insulator 45 is generally used as shown in FIG. The sheath type thermocouple 24 is drawn into the heating container 31 from the feedthrough provided on the table 36, and the temperature measuring contact at the tip is embedded in the back surface of the heating plate 22. The compensation contact terminal 41 side is connected outside the heating container 31 with a measuring instrument 42 through a compensation lead, and the temperature of the heating plate 32 is measured.

  When the heating object 40 is heated while applying a high voltage between the filament 39 and the heating plate 32 by the acceleration power source 37 using such a backside electron impact heating device, a discharge phenomenon occurs in the process of gradually raising the temperature. Happens. This discharge phenomenon occurs even when the inside of the heating vessel 31 is sufficiently depressurized and the degree of vacuum is increased. This discharge phenomenon is a spark discharge accompanied by a strong sound and light, and occurs in a portion where the distance between the filament 39 and the heating container 31 is narrow. This spark discharge is troublesome to cause damage to the filament 39.

  The minimum voltage Vs required to cause a spark discharge is called a spark voltage. If the electric field is uniform and the temperature is constant, it is determined as a function of the product pd of the interelectrode distance d and the gas pressure p. This is called Paschen's law. As shown in FIG. 2, the curve of Vs with respect to pd is V-shaped, and the minimum value Vsm is called the minimum spark voltage. In air, about 300V, p is Pa, and d is mm. Is 650-950th.

Since the heating container 31 is in a vacuum chamber and is maintained at a vacuum of 1.33 Pa or less (0.01 torr or less), normally no spark discharge should occur even if the temperature is increased. However, in the process of raising the temperature of the heating container 31, gases such as N ₂ , H ₂ O, and O ₂ , mainly N ₂ gas that have been occluded in the heating container 31 are released, and the filament 39 and the heating container 31 are released. It becomes the state where the pressure between became high locally. For this reason, when a voltage of 1.5 KV to 1.7 KV is applied, spark discharge occurs.
JP 2005-56964 A JP 2005-56963 A JP 2005-56628 A JP 2005-56582 A JP 2004-355877 A

  In the present invention, in view of the problem of the conventional backside electron impact heating device, it is possible to provide a backside electron impact heating method and apparatus capable of avoiding the occurrence of spark discharge and thereby preventing damage to equipment. Objective.

  In the present invention, in order to achieve the above object, in the process of raising the temperature by heating the heating plate 2 of the heating container 1, the filament is heated at a temperature at which spark discharge is likely to occur, in other words, at a temperature range at which gas discharge is likely to occur. 9 was heated without applying an accelerating voltage, and an accelerating voltage was applied in a higher temperature range to enable high-temperature heating.

  That is, the backside electron impact heating method according to the present invention accelerates the thermoelectrons emitted from the filament 9 provided behind the heating plate 2 serving as the top plate of the heating container 1 with an acceleration voltage to the heating plate 2. The heating plate 2 is heated by colliding. Then, when heating the heating plate 2 by energizing the filament 9, no acceleration voltage is applied to the filament 9 until the temperature of the heating plate 2 measured by the temperature measuring means reaches a certain set temperature, The heating plate 2 is heated only by the radiant heat of the filament 9, and an acceleration voltage is applied to the filament 9 when the temperature of the heating plate 2 measured by the temperature measuring means exceeds the set temperature.

  Furthermore, the back surface electron impact heating apparatus according to the present invention includes a filament 9 provided behind the heating plate 2 serving as the top plate of the heating container 1, a heating power source 12 for heating the filament 9, and the filament 9. Accelerating power source 7 for applying an accelerating voltage and temperature measuring means for measuring the temperature of the heating plate 2 are provided. Further, when heating the heating plate 2 by energizing the filament 9 from the heating power source 12, the acceleration power source 7 is supplied from the filament 9 until the temperature of the heating plate 2 measured by the temperature measuring means reaches a set temperature. The heating plate 2 is heated only by energization from the heating power source 12 of the filament 9, and when the temperature of the heating plate 2 measured by the temperature measuring means exceeds the set temperature, the acceleration power source 7 applies the filament 9 to the filament 9. A switching circuit that switches to apply the acceleration voltage is provided.

  In such a backside electron impact heating method and apparatus according to the present invention, an acceleration voltage is not applied to the filament 9 until the temperature of the heating plate 2 measured by the temperature measuring means reaches a certain set temperature. By heating the heating plate 2 only with radiant heat, the temperature can be raised through a temperature range where spark discharge is likely to occur. After that, by applying an accelerating voltage to the filament 9 and accelerating the thermal electrons and bombarding the heating plate 2, the high temperature of the heating plate 2 of 1,000 ° C. or more can be easily obtained. .

  As described above, in the backside electron impact heating method and apparatus according to the present invention, damage to equipment due to spark discharge can be avoided by not applying an acceleration voltage to the filament 9 in a temperature range where spark discharge is likely to occur. And in the high temperature range which cannot be achieved only by the radiant heat of the filament 9, it is possible to easily obtain a high temperature by applying an acceleration voltage to the filament 9.

In the present invention, in the process of raising the temperature by heating the heating plate 2 of the heating vessel 1, heating the filament 9 without applying an acceleration voltage in a temperature range where spark discharge is likely to occur, The generation was avoided.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  FIG. 1 is a diagram illustrating an example of a backside electron impact heating apparatus. Although not shown, a vacuum chamber is placed and fixed on a table 6 made of metal such as stainless steel, and the heating container 1 is installed in the vacuum chamber. The heating container 1 is a container having an open bottom surface, and the flat top plate is a thin plate-like heating object 7 such as a silicon wafer, for example, a heating plate 2 on which a substrate is placed. 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 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 of the heating container 1 has a flange shape.

An annular groove is provided at a position where the lower end flange portion of the heating container 1 of the table 6 is placed, and a vacuum sealing material 14 is fitted into this groove. On the vacuum seal material 14 fitted in the groove, the lower end flange portion of the peripheral wall 13 of the heating container 1 is placed and fixed in an airtight manner.
Further, a support column 10 is erected from the table 6 inside the heating container 1, and a plate-shaped holder 15 is supported on the upper end side of the support column 10. Further, the reflector 3 is supported on the holder 15.

  Columnar electrodes 16, 16 that also serve as a filament support are inserted and erected through a feedthrough provided in the table 6 of the vacuum chamber, and a filament 9 is attached to the electrodes 16, 16. The filament 9 is provided behind the heating plate 2 in the heating container 1. A filament heating power source 12 is connected to the filament 9 via electrodes 16 and 16. Further, an acceleration voltage is applied between the filament 9 and the heating plate 2 by a high voltage acceleration power source 7. Here, the acceleration power source 7 is connected to the filament 9 through the switch 4 as needed. More specifically, this switch 4 can be switched between two poles: the acceleration power source 7 is connected to the filament 9 and the filament 9 is grounded.

  The heating container 1 having the heating plate 2 is grounded, and when the switch 4 is on the ground side, the filament 9 is at the same potential as the heating container 1, but when the switch 4 is switched to the acceleration power source 7 side, the heating container 1 Is held at a positive potential with respect to the filament 9. The reflector 3 is electrically connected to the filament 9 and has a negative potential that is the same as that of the filament 9.

  A sheathed thermocouple 5 is inserted into the heating container 1 through a feedthrough provided in the table 6 of the vacuum chamber, and the heating plate 2 is in a state where the upper end portion having the temperature measuring contact is electrically insulated by the insulator 20. It is embedded in it from the underside. The compensation contact 8 of the sheath type thermocouple 5 outside the vacuum chamber is connected to a measuring instrument 11 through a compensation lead, and the temperature of the heating plate 2 is measured. The switch 4 is switched according to the temperature measured by the measuring instrument 11.

Next, a method for heating the heated object 40 placed on the heating plate 2 of the heating container 1 using the back surface electron impact heating device will be described. FIG. 3 is a conceptual diagram showing a power supply control system of the backside electron impact heating apparatus, and is referred to in conjunction with FIG.
First, the filament 9 is energized by the filament heating power source 12 to heat the filament 9 in a state where the vacuum chamber is decompressed and the atmosphere of the heating container 1 is set to a sufficient degree of vacuum. At this time, the switch 4 is set to the ground side in advance, and the filament 9 is set to the same potential as the heating container 1. That is, in this state, no acceleration voltage is applied to the filament 9 by the acceleration power source 7. In this state, the heating of the filament 9 generates radiant heat, thereby heating the heating plate 2.

  The temperature at which spark discharge is likely to occur due to gas discharge from the heating vessel 1 is not uniform depending on the degree of vacuum of the heating vessel 1, the distance between the heating plate 2 and the filament 9, and the voltage applied by the acceleration power source 7, but is normally used In the backside electron impact heating apparatus to be used, the temperature is approximately up to about 800 ° C. The heating plate 2 is heated by the radiant heat of the filament 9 to a temperature exceeding this. The temperature of the heating plate 2 is measured with a measuring device 8 by a thermocouple 5. While measuring this temperature, the current of the filament heating power source 12 is appropriately adjusted.

  When the temperature measured by the measuring device 8 by the thermocouple 5 exceeds the temperature at which spark discharge is likely to occur, the switch 4 is switched to the acceleration power source 7 and an acceleration voltage of about 1.5 KV to 1.7 KV is applied to the filament 9. Then, electrons are collided with the heating plate 2 to start electron impact heating. The application of the acceleration voltage in the first stage avoids the possibility that spark discharge still occurs due to gas molecule emission from the heating container 1. Thereby, the temperature of the heating plate 2 further rises and can easily reach a temperature of 1200 ° C. or higher. Furthermore, after exceeding that temperature, it is possible to reach a temperature of 1500 ° C. or higher by applying an acceleration voltage of about 2.2 KV to 2.8 KV to the filament 9.

It is a general | schematic longitudinal section side view which shows one Example of the back surface electron impact heating apparatus by this invention. It is a graph for showing the concept of Paschen's law. It is a conceptual diagram which shows the control system of the back surface electron impact heating apparatus which is an Example of this invention. It is a schematic vertical side 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 4 Switch 5 Thermocouple 7 Acceleration power supply 9 Filament 12 Heating power supply

Claims (2)

The thermoelectrons emitted from the filament (9) provided behind the heating plate (2), which is the top plate of the heating container (1), are accelerated by an acceleration voltage and collided with the heating plate (2) for heating. In the backside electron impact heating method for heating the plate (2), when the heating plate (2) is heated by energizing the filament (9), the temperature of the heating plate (2) measured by the temperature measuring means is The heating plate (2) is heated only by the radiant heat of the filament (9) without applying an acceleration voltage to the filament (9) until the set temperature is reached, and the heating plate (2) measured by the temperature measuring means ), An acceleration voltage is applied to the filament (9) when the temperature exceeds the set temperature. A filament (9) provided behind the heating plate (2) serving as the top plate of the heating container (1), a heating power source (12) for heating the filament (9), and the filament (9) In a backside electron impact heating apparatus having an acceleration power source (7) for applying an acceleration voltage and a temperature measuring means for measuring the temperature of the heating plate (2), the filament (9) is energized from the heating power source (12). When heating the heating plate (2), the accelerating power supply (7) is disconnected from the filament (9) until the temperature of the heating plate (2) measured by the temperature measuring means reaches a predetermined temperature. The heating plate (2) is heated only by energization from the heating power source (12) of (9), and the temperature of the heating plate (2) measured by the temperature measuring means is Back electron impact heating apparatus, characterized in that it comprises a switching circuit for switching to apply the accelerating voltage to the filament (9) by the acceleration power supply (7) when exceeding the set temperature.

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