JPH0653207A - Plasma treatment apparatus - Google Patents

Abstract

PURPOSE:To provide a plasma treatment apparatus wherein a cooling structure which is excellent in an electric insulating property and a heat-insulating property is provided even when a lower-part electrode is used as the side of a cathode. CONSTITUTION:In a plasma treatment apparatus, a coolant housing part 16 through which a coolant such as liquid nitrogen or the like is made to flow is formed on a mounting stand 8 on which an object W to be treated is mounted. A coolant supply port 80 for the coolant housing part 16 and a coolant supply passage 18 as well as a coolant discharge port 82 and a coolant discharge passage 20 are connected respectively by using vacuum double-tube joints 84, 86 composed of a material provided with a specific characteristic, e.g. a ceramic. Thereby, the heat-insulating property of the plasma treatment apparatus is ensured while its insulating property with reference to a high frequency is being maintained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a plasma processing apparatus.

[0002]

2. Description of the Related Art Generally, in a semiconductor manufacturing process, an object to be processed, for example, a semiconductor wafer is repeatedly subjected to a plasma process such as a sputtering process or an etching process in various processing apparatuses. For example, in the plasma etching process, a plasma is generated by applying a high frequency between the electrodes in a state where a process gas is introduced into the processing container, and the reactive ions generated at this time cause the surface of the semiconductor wafer placed on the lower electrode to be removed. It is performed by etching. Then, when plasma processing is performed on a wafer due to miniaturization and high integration of semiconductor integrated circuits,
For example, liquid nitrogen as a coolant is circulated through the mounting table to maintain the wafer temperature at a relatively low temperature. For the purpose of improving the efficiency of plasma processing, a high frequency power source may be applied to the lower electrode, that is, the wafer mounting table side to be the cathode side, and the upper electrode side may be the ground side to make the distance between the upper and lower electrodes very close. Has been done.

[0003]

By the way, as described above, in order to apply a high frequency to the lower electrode side to make it the cathode side, and to supply a coolant such as liquid nitrogen to this portion, the lower electrode of the mounting table is to be used. The joint portion between the cooling means and the supply passage for supplying the liquid refrigerant to the cooling means must have a structure capable of withstanding a low temperature while maintaining insulation between the mounting table and the processing container or the pipe. Therefore, in the related art, a pipe made of an insulator such as Teflon is used in the joint portion, and a Teflon tape is wound around the pipe for insulation. However, when this type of Teflon is used, the insulating property can be maintained, but since Teflon itself is a polymer, the difference in heat shrinkage between this Teflon and the metal such as stainless steel used for the joint part. Accordingly, there is an improvement in that the cooling medium leaks. In particular, this difference in heat shrinkage does not cause a problem in a normal operating temperature range, but it cannot be ignored because the joint portion is exposed to extremely low temperature such as liquid nitrogen.

It is also conceivable to use a vacuum double tube formed of a metal material such as stainless steel as another joint structure. In this case, the heat insulating property is relatively excellent, but as described above, When applying a high frequency to the electrode and using this as the cathode side, it was not realistic because a separate insulating measure had to be taken. The present invention has been made to pay attention to the above problems and to solve them effectively. An object of the present invention is to provide a plasma processing apparatus having a cooling structure having excellent electrical insulation and heat insulation even when the lower electrode is on the cathode side.

[0005]

According to the present invention, in order to solve the above problems, an object to be processed is placed on a mounting table provided in a processing container, and the object to be processed is subjected to plasma treatment. In the plasma processing apparatus, while forming a refrigerant containing portion for circulating the refrigerant while storing the refrigerant on the mounting table, between the refrigerant supply port of the refrigerant containing part and an external refrigerant supply passage, and the refrigerant outlet of the refrigerant containing part. A vacuum double pipe joint made of an electrical insulating material, which has low thermal conductivity and a small difference in thermal expansion and contraction compared with a metal material, is connected between the external refrigerant discharge passage and the external refrigerant discharge passage.

[0006]

Since the present invention is configured as described above, low thermal conductivity is provided between the refrigerant supply port and the refrigerant supply passage of the refrigerant accommodating portion of the mounting table and between the refrigerant discharge port and the refrigerant discharge passage. In addition, since a vacuum double tube joint made of an electrically insulating material, such as ceramics, which has a smaller difference in thermal expansion and contraction compared with a metal material is used, even if a high frequency is applied to the mounting table side having the lower electrode. This can be insulated from the processing container and the refrigerant passage, and the leakage of cold heat to the outside can be significantly reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the processing apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. 1 is a sectional view showing a main part of a plasma processing apparatus according to the present invention, FIG. 2 is a sectional view showing an embodiment of the plasma processing apparatus according to the present invention, and FIG. 3 is FIG.
FIG. 3 is a schematic exploded view showing a mounting table of the plasma processing apparatus shown in FIG. In this embodiment, a plasma etching apparatus will be described as an example of the plasma processing apparatus. As shown in the figure, the etching apparatus 2 has a processing container 4 formed of a conductive material such as aluminum in a cylindrical or rectangular shape. The processing container 4 is provided at the bottom of the processing container 4.
A substantially columnar mounting table 8 for mounting an object to be processed, for example, a semiconductor wafer W, is housed while being insulated from the bottom portion 6. The mounting table 8 includes a susceptor supporting table 10 formed of aluminum or the like in a cylindrical shape, and a bolt 12 on the susceptor supporting table 10.
And a susceptor 14 made of aluminum or the like which is detachably attached.

The susceptor support 10 has a coolant accommodating portion, for example, a cooling jacket 1 that stores and circulates the coolant.
6, a coolant such as liquid nitrogen is introduced into the jacket 16 through the coolant supply passage 18, circulates in the jacket, and is discharged out of the container through the coolant discharge passage 20. The above-mentioned susceptor 14 is formed in a disk shape with its center portion protruding, and an electrostatic chuck 22 is formed in the wafer mounting portion at the center thereof with an area substantially the same as the wafer area. The electrostatic chuck 22 is formed, for example, by sandwiching a conductive film 24 such as a copper foil in an insulating state between two polymer polyimide films. The conductive film 24 is a filter that cuts a high frequency on the way by a voltage supply lead 26. It is connected to the DC high voltage source 28 via 27. Therefore, by applying a high voltage to the conductive film 24,
The wafer W is configured to be sucked and held by the Coulomb force on the upper surface of the chuck 22. A gas passage 30 for supplying a heat transfer gas such as He to the back surface of the wafer W is formed in the susceptor support 10 and the susceptor 14. The electrostatic chuck 22 also has a large number of vent holes (not shown) through which the heat transfer gas passes.

An annular focus ring 32 is arranged on the upper edge of the susceptor 14 so as to surround the wafer W. The focus ring 32 is made of an insulating material that does not attract the reactive ions, and allows the reactive ions to effectively enter only the semiconductor wafer W inside. The susceptor 14 is provided with a pipe lead 34 made of a hollow conductor that penetrates the susceptor support 10. The pipe lead 34 has a wiring 36.
Is connected to a high frequency power source 38 for generating plasma of 380 KHz, for example. Therefore, the susceptor 14
Will be configured as the lower electrode. A filter 40 for noise cutting and a capacitor 42 for matching are sequentially provided on the wiring 36.

Above the susceptor 14, the upper electrode 4 is grounded at a distance of about 15 to 20 mm.
4 are provided, a process gas, for example, an etching gas such as CF ₄ is supplied to the upper electrode 44 through a gas supply pipe 46, and a large number of small holes 48 formed on the electrode surface of the upper electrode 44. The etching gas is blown out into the processing space below. An exhaust pipe 50 is connected to the lower side wall of the processing container 4 so that the atmosphere inside the processing container 4 can be exhausted by an exhaust pump (not shown).

A temperature adjusting heater 52 is provided between the electrostatic chuck 22 and the refrigerant accommodating portion 16. Specifically, the heater 52 is a plate-shaped ceramic heater having a thickness of about several mm.
As shown in FIG. 2, the upper surface of the susceptor support 10 is completely accommodated in the heater accommodating groove 56 formed in the upper portion of the heater fixing base 54. The heater fixing base 54 is made of a material having a good heat transfer property, such as aluminum. The size of the heater 52 is preferably set to be substantially the same as the wafer area, and the cooling heat from the cooling jacket 16 located below this is controlled to transfer to the wafer W. The temperature of W can be adjusted.

A through hole (not shown) through which a pusher pin or the like penetrates through the temperature adjusting heater 52 and the heater fixing base 54.
Etc. are formed. An appropriate number of bolt holes 58 are formed in the peripheral portion of the heater fixing base 54, and the fixing base 54 is detachably attached to the susceptor support base 10 side with bolts 60. Further, on the lower surface of the susceptor 14, an accommodation recess 62 for accommodating the entire heater fixing base 54 is provided.
The heater fixing base 54 is connected to the gas passage 30 in order to supply a heat transfer medium such as He to the boundary between the upper surface of the heater 52 and the lower surface of the accommodation recess 62 of the susceptor 14. The divided branch path 64 (see FIG. 2) is formed. The power supply lead 6 is connected to the heater 52.
6 is connected, and the filter 6 is connected to the lead 66.
A power source 68 is connected via 7 to supply a predetermined power to the heater 52.

Further, the electrostatic chuck 22 has a thermometer utilizing the fact that the round-trip time of light changes depending on the temperature in order to detect the wafer temperature, for example, a temperature detector composed of a Luxtron or a thermocouple. 70 is provided. The temperature detector 70 is connected with a temperature detection lead 72 that transmits a detected value. This temperature detection lead 72
Is composed of an optical fiber when a Luxtron is used as the temperature detector 70, but an ordinary conductor is used when a thermocouple is used. In this case, a filter 74 for removing high frequency noise is used. A control unit 7 including, for example, a computer or the like, which is provided on the way and controls the entire apparatus.
6 is input. The control unit 76 controls the entire apparatus by a predetermined program as described above, and for example, the high frequency power source 38, the power source 68 to the heater 52,
The distribution of the DC high voltage source 28 to the electrostatic chuck 22 is controlled.

In particular, in the present embodiment, various wirings which are susceptible to the high frequency for plasma generation, for example, the power supply lead 66 connected to the heater, the voltage supply lead 26 connected to the electrostatic chuck 22, All the temperature detection leads 72 connected to the temperature detector 70 are housed in the pipe lead 34 that supplies a high frequency for plasma, so that the high frequency noise does not affect the outside. Then, as described above, each of the leads 66, 26, 7
2 is a filter 67 for cutting high frequency noise,
27 and 74 are connected. Further, an insulator 78 is provided in a penetrating portion of the bottom of the processing container of the pipe lead 34 to electrically insulate it from the container side. And FIG.
As also shown in FIG.
0 and the refrigerant supply passage 18 and between the refrigerant discharge port 82 and the refrigerant discharge passage 20 are connected by vacuum double pipe joints 84 and 86, respectively, which are features of the present invention. The electrical insulation between 10 and the processing container bottom 6 and the refrigerant passages 18 and 20 is achieved, and the leakage of cold heat to the processing container bottom 6 side is prevented.

Since the vacuum double pipe joints 84 and 86 provided at the refrigerant supply port 80 and the refrigerant discharge port 82 are formed and provided in the same manner, the vacuum double pipe joint 84 is representatively shown in FIG. The attached state is shown.
The vacuum double pipe joint 84 has a central inner pipe 88 made of an electrically insulating material, for example, ceramics, which has a low thermal conductivity and has a small difference in thermal expansion and contraction compared with a metal material, for example, stainless steel, and an outside of the pipe 88. An outer pipe 90 made of ceramics and concentrically arranged with a predetermined distance therebetween is provided to form a double pipe structure. The inner pipe 88 and the outer pipe 90, which are concentric, are provided with an intermediate joining member 94, for example, made of stainless steel, in which a flow passage 92 is formed in the central portion, and the joining member 94 has an upper portion. Similarly, an upper joining member 98 made of, for example, aluminum or the like, in which a flow path 96 is formed in the central portion, is joined. Then, the lower end of the flow path 92 of the intermediate joining member 94 is joined to the inner pipe 88, and the upper end of the upper joining member 98 is joined to the refrigerant supply port 8.
By mounting it on 0, the refrigerant can be introduced into the cooling jacket 16.

The intermediate joining member 94 has an inner center joining member 94A whose lower end is joined to the upper end of the inner pipe 88, and a periphery of the inner central joining member 94A which is concentric with the lower end of the outer pipe 90. Outer central joint member 9 joined to
4B and these inner and outer central joint members 94
Between A and 94B, the inner pipe 88 and the outer pipe 9 are
An annular chamber formed between 0 and 0, that is, a vacuum chamber 100.
A communication passage 102 is formed for communicating between the vacuum chamber 100 and the outside of the processing chamber 4.
Therefore, by vacuuming the inside of the processing container 4 at the time of processing, the inside of the vacuum chamber 100 is brought into a vacuum state so that cold heat can be prevented from being transmitted to the outside. The inner intermediate joining member 94A is provided with a heat insulating material 104 made of, for example, Teflon for preventing the transmission of the cooling in the vertical direction. Then, the lower end portion of the outer intermediate joint member 94B is fixed to the step portion of the through hole of the container bottom portion 6 via the seal member 106 such as an O-ring.

On the other hand, the inner and outer pipes 88 and 90 described above.
A lower joining member 108 made of, for example, stainless steel and having a channel 106 formed in the central portion is provided at the lower end portion of the. The coolant supply passage 18 has a double pipe structure made of, for example, a stainless pipe, and the upper end of the inner stainless pipe 18A through which liquid nitrogen as a coolant passes is joined to the lower end of the flow passage 106 of the lower joining member 108. ,
Refrigerant can be supplied into the vacuum double tube joint 84. An inner auxiliary stainless pipe 18C is provided at the upper end of the inner stainless pipe 18A so as to surround the outer pipe 90 via the auxiliary member 110. The upper ends of the inner auxiliary stainless pipe 18C and the outer stainless pipe 18B are provided. Is connected to the lower surface of the container bottom 112 via a flange 112 made of, for example, stainless steel.

Next, the operation of this embodiment configured as described above will be described. First, the wafer W is placed on the upper portion of the susceptor 14 of the processing container 4 which is depressurized to a predetermined pressure from a load lock chamber (not shown), for example, about 1 × 10 ⁻⁴ to several Torr, and the wafer W is placed by the electrostatic chuck 22. Adsorbed and held on the susceptor 14 side by Coulomb force. Then, a high frequency is applied between the upper electrode 44 and the lower electrode (susceptor) 14 through the pipe lead 34 to generate plasma, and at the same time, a process gas is caused to flow from the upper electrode 44 side into the processing space to perform etching I do. Further, since the wafer is excessively heated above a predetermined set temperature by the heat generated by the plasma, the susceptor support 1 may be cooled to cool the wafer.
A coolant such as liquid nitrogen is circulated in the cooling jacket 16 of 0 to maintain this portion at −196 ° C., and the cold heat from this portion is supplied to the wafer W via the susceptor 14 on the upper portion.
It is designed to be cooled.

A temperature adjusting heater 52 is provided between the cooling jacket 16 and the wafer W to adjust the amount of heat generated at this portion to adjust the cold heat transferred to the wafer W, thereby keeping the wafer W at a predetermined temperature. The temperature is maintained at, for example, about -150 ° C. In the conventional device, the temperature of the wafer is controlled by controlling the temperature of the cooling medium itself. Further, the distance between the cooling jacket and the wafer is long, and there are many interfaces for joining members, so that the thermal response is high. It was very bad. On the other hand, in this embodiment, as described above, the cooling jacket 16 is fixed at a constant low temperature, for example, −196 ° C., whereas the heater 52 is mounted on the wafer W by, for example, 15 to 15.
Since it is installed close to a distance of up to 20 mm,
This change in the amount of heat generated by the heater 52 promptly appears as a change in the temperature of the wafer W. Therefore, the thermal responsiveness is good and the wafer temperature can be quickly controlled. Therefore, the heater 5
Wafer cooling temperature only with liquid nitrogen when 2 is turned off, for example, -160 ° C. (a temperature difference of 36 ° C. with liquid nitrogen (−196 ° C. is a loss due to a susceptor) is set as the minimum temperature value, and the temperature is further increased to room temperature. It is possible to control the wafer temperature quickly and linearly within the temperature range of. The temperature control may be performed only by the heater 52 with the supply of liquid nitrogen cut off.

Further, since the heat transfer gas such as He cooled through the gas passage 30 is introduced into the interface between the heater 52 and the susceptor 14 and the lower surface of the wafer W, the heat transfer efficiency between the upper and lower sides is improved. The thermal response described above can be further improved without deterioration. Also, the pipe lead 3
The high frequency wave passing through 4 is transmitted to the peripheral portion of the pipe due to the skin effect, and various leads 26, 66, 7 which are influenced by the high frequency and generate induced noise in the pipe lead 34.
No. 2 is accommodated and the filters 27, 67, 74 for cutting high frequency noise are provided on the outlet side, so that the control system is not adversely affected.

When the susceptor, which is a consumable item damaged by plasma, is replaced, the susceptor 14 can be easily removed by loosening the bolt 12 connecting the susceptor 14 and the susceptor support 10. Further, when the heater 52 is damaged due to overcurrent and the heater is deteriorated due to its life, maintenance work such as heater replacement is performed. In this case, the bolts are further removed with the susceptor 14 removed as described above. By removing 60, the heater 52 can be removed from the susceptor support 10 together with the heater fixing base 54, and the replacement work of the heater 52 can be easily performed.

In the above embodiments, the case where liquid nitrogen is used as the cooling medium and the ceramic heater is used as the temperature adjusting heater 52 has been described, but the present invention is not limited to this.
For example, liquid helium or the like may be used as the cooling medium, and another type of heater may be used as the heater. Further, during the plasma treatment, as described above, liquid nitrogen (−196 ° C.) is introduced into the cooling jacket 16 which is the refrigerant containing portion via the inside pipe 88 of the refrigerant supply passage 18, and the refrigerant is It passes through the jacket 16 while staying and is discharged through the coolant discharge passage 20, and the wafer W is cooled by this cold heat.

In this case, the vacuum double pipe joint 84 is
Inner pipe 88 made of an insulating material such as ceramics
Since the double pipe structure of the outer pipe 90 and the outer pipe 90 is provided, a high frequency power source is applied and the cooling jacket 16 on the cathode side, that is, the lower electrode side and the coolant supply passage 18 are completely insulated. . Also, the inner pipe 88
The space formed between the outer pipe 90 and the outer pipe 90 is communicated with the inside of the processing container 4 through the communication passage 102. Therefore, this space is maintained in a vacuum state like the inside of the processing container 4, and the vacuum chamber is maintained. Therefore, the cold heat transferred by convection from the inner pipe 88 that is in direct contact with the liquid nitrogen to the outer pipe 90 can be greatly reduced.

A lower joining member 108 made of stainless steel for supporting the lower ends of the inner pipe 88 and the outer pipe 90.
Is in direct contact with the refrigerant, so that cold heat is transferred to the outer pipe 90.
Is transmitted from the lower end to the upper end of the vacuum chamber 100. However, since the outer pipe 90 is made of ceramics having a low heat transfer property, a large temperature gradient is generated in the upward direction and the vacuum chamber 100 has a large temperature gradient. Inner pipe 88 by action
The convection cold heat supplied from the outer pipe 90 is extremely small, and as a result, the cold heat reaching the upper end portion of the outer pipe 90 is very small, and the cold heat escaping to the processing container bottom 6 side, that is, the outside is greatly reduced. be able to. Further, since the heat insulating material 104 made of Teflon is interposed in the intermediate joining member 94 forming the upper portion of the vacuum double pipe joint 84, the cold heat transmitted to the processing container bottom 6 side is greatly reduced from this point. It is possible to improve the heat insulation property as a whole. With this configuration,
It has become possible to maintain the temperature difference between the refrigerant and the bottom portion 6 of the processing container at about 100 ° C. or higher.

Further, in the present embodiment, the inner pipe 8
As a constituent member of 8, a metal material supporting the upper and lower ends,
That is, since a material having a relatively small difference in thermal expansion and contraction rate from stainless steel, for example, ceramics is used, the difference in thermal expansion and contraction is small and problems such as refrigerant leakage do not occur. The vacuum double tube joint described above is particularly useful for a plasma processing apparatus that processes a wafer in a low temperature region of -50 ° C or lower, particularly in a low temperature region of about -150 ° C. Further, in the above embodiment, the operation of the vacuum double pipe joint 84 on the refrigerant supply side has been described, but it goes without saying that the vacuum double tube joint 86 on the refrigerant discharge side also operates in exactly the same manner. In the above embodiments, the plasma etching apparatus has been described as an example, but the present invention is not limited to this, and the present invention is also applicable to other plasma processing apparatuses such as a plasma CVD apparatus, a plasma ashing apparatus, and a plasma sputtering apparatus. Of course, you can.

[0026]

As described above, according to the present invention, the following excellent operational effects can be exhibited. Since the vacuum double pipe joint having a predetermined property is used for the coolant supply / discharge unit of the coolant storage unit, it is possible to maintain high insulation properties for the coolant storage unit while maintaining insulation properties for the plasma electrode.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a plasma processing apparatus according to the present invention.

FIG. 2 is a sectional view showing an embodiment of a plasma processing apparatus according to the present invention.

FIG. 3 is a schematic exploded view showing a mounting table of the plasma processing apparatus shown in FIG.

[Explanation of symbols]

 2 Etching device 4 Processing container 6 Bottom part 8 Mounting table 14 Susceptor (lower electrode) 16 Cooling jacket (refrigerant accommodating part) 18 Refrigerant supply passage 20 Refrigerant discharge passage 38 High frequency power supply 44 Upper electrode 80 Refrigerant supply port 82 Refrigerant discharge port 84, 86 Vacuum double pipe joint 88 Inner pipe 90 Outer pipe 100 Vacuum chamber 102 Communication passage W Semiconductor wafer (processing target)

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H01L 21/302 C 9277-4M H05H 1/28 9014-2G

Claims (4)

[Claims] 1. In a plasma processing apparatus, wherein an object to be processed is placed on a mounting table provided in a processing container, and plasma processing is performed on the object to be processed. While forming the accommodating part, the thermal conductivity between the refrigerant supply port of the refrigerant accommodating part and the external refrigerant supply passage and between the refrigerant exhaust port of the refrigerant accommodating part and the external refrigerant discharge passage is low and A plasma processing apparatus characterized by being connected by a vacuum double tube joint made of an electrical insulating material having a smaller difference in thermal expansion and contraction compared to a metal material. 2. The plasma processing apparatus according to claim 1, wherein a vacuum chamber of the vacuum double tube joint is connected to the inside of the processing container. 3. The plasma processing apparatus according to claim 1, wherein the electrically insulating material is made of ceramics. 4. The liquid refrigerant is liquid nitrogen or CFC R14.
4. The plasma processing apparatus according to claim 1, further comprising: