JP2014150187A - Plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing apparatus which inhibits local discharge from occurring on an outer surface of a sample table even when having a sample table protective member divided into multiple pieces.SOLUTION: A plasma processing apparatus comprises: a sample table 112; and a sample table protective member for protecting a surface of the sample table 112 which is not covered by a wafer 125 from plasma. The sample table protective member comprises: a susceptor 200 which covers an upper part of the sample table 112; a side wall cover 301 which covers a sample table side wall; and an insulation ring 303 which is disposed so as to cover a gap between the susceptor 200 and the side wall cover 301.

Description

  The present invention relates to a plasma processing apparatus for plasma processing a wafer in a vacuum vessel.

  A plasma etching processing apparatus, which is one of semiconductor wafer processing apparatuses, forms a plasma by supplying a processing gas into a processing container (hereinafter referred to as a vacuum container) whose pressure has been reduced to a vacuum state. Hereinafter, a wafer to be processed is placed on a sample stage), and plasma processing is performed on the wafer. The sample stage mainly has a function of fixing the wafer by electrostatic force, a function of controlling the temperature of the wafer, and a function of applying a high-frequency bias voltage for assisting etching by drawing ions in the plasma.

  The high-frequency bias voltage is directly applied to the metal plate constituting the sample stage, and the potential difference generated in the sheath portion on the wafer acts as a force for attracting ions in the plasma. At this time, if a portion other than the wafer mounting surface of the sample stage is exposed to plasma, ions are also attracted to that part, and unintended local discharge occurs on the sample stage. In order to prevent such abnormal discharge in the vacuum vessel, Patent Document 1 discloses a method of disposing an insulating member for preventing discharge around or on a member that causes abnormal discharge.

  Since the insulating member is exposed to the plasma for a long time and is consumed by the influence of the plasma and the influence of the high frequency bias voltage applied to the sample stage, the insulating member needs to be periodically replaced.

  As a prior art of the protective member of the sample stage as described above, in Patent Document 2, the protective member is divided into two or three parts, so that only the part where the susceptor is consumed or the reaction product is attached is replaced. The method is shown.

Japanese Patent Laid-Open No. 9-92642 JP 2001-230234 A

  In the case where the sample stage protection member has a divided structure as in Patent Document 2, by taking a certain threshold value of the high-frequency bias voltage applied to the wafer between 1.5 kV and 3.0 kV, the energy of the ions increases and the ions are generated. It enters into the gap between the protective members. As a result, the plasma enters the gap and reaches the outer surface of the sample table, thereby causing local discharge on the sample table and impairing the etching performance of the wafer edge.

  An object of the present invention is to provide a plasma processing apparatus capable of suppressing local discharge (abnormal discharge) that occurs on the outer surface of a sample table even when the sample table protection member is divided into a plurality of parts. To do.

In order to solve the above problems, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above-described problems. For example, in a processing chamber in a vacuum vessel, a plasma processing apparatus for processing a wafer disposed inside using plasma.
A sample stage on which the wafer is mounted;
A sample stage protecting member that protects the surface of the sample stage not covered by the wafer from plasma, and
The plasma is characterized in that the sample stage protection member is composed of a susceptor that covers the upper part of the sample stage, a side wall cover that covers the side wall of the sample stage, and an insulating ring that is disposed so as to cover a gap between the susceptor and the side wall cover. A processing device is used.

Further, in a plasma processing apparatus having a vacuum container, a processing chamber disposed in the vacuum container, a sample stage disposed on the processing chamber and placing an object to be processed, and means for generating plasma in the processing chamber,
The sample stage includes a sample stage protection member for protecting a portion not covered with the object to be processed from the plasma,
The sample stage protection member includes a susceptor that covers the upper part of the sample stage,
A side wall cover disposed adjacent to the susceptor and covering the sample stage side wall;
An insulating ring disposed proximate to both the susceptor and the side wall cover;
The threshold of the abnormal discharge high-frequency bias voltage when the susceptor, the side wall cover, and the insulating ring are included is higher than the threshold of the abnormal discharge high-frequency bias voltage when the susceptor and the side wall cover are included. The plasma processing apparatus is characterized by being shifted.

Further, in a plasma processing apparatus having a vacuum container, a processing chamber disposed in the vacuum container, a sample stage disposed on the processing chamber and placing an object to be processed, and means for generating plasma in the processing chamber,
The sample stage includes a sample stage protection member for protecting a portion not covered with the object to be processed from the plasma,
The sample stage protection member includes a susceptor that covers the upper part of the sample stage,
A side wall cover disposed adjacent to the susceptor and covering the sample stage side wall;
An insulating ring disposed proximate to both the susceptor and the side wall cover;
A creeping distance formed by a gap between the susceptor, the side wall cover, and the insulating ring is longer than a creepage distance formed by a gap between the susceptor and the side wall cover.

  According to the present invention, the insulating ring covering the gap between the protective members increases the creepage distance of the gap between the protective members through which the plasma penetrates, thereby making it difficult for the plasma to reach the outer surface of the sample table and causing abnormal discharge. Since the threshold value of the high frequency bias voltage to be generated is shifted to the high voltage side, it is possible to provide a plasma processing apparatus capable of suppressing local discharge generated on the outer surface of the sample table. Furthermore, the insulating ring has a structure that does not overlap with the protective member when viewed from the upper surface of the sample stage, so that both can be replaced simultaneously or separately, and the maintainability of the apparatus is not impaired.

The longitudinal cross-sectional view which shows the outline of a structure of the plasma processing apparatus which concerns on the Example of this invention. The longitudinal cross-sectional view which shows an example of the conventional structure of a sample stand protection member. The longitudinal cross-sectional view which shows the structure of the sample stand protection member in the plasma processing apparatus which concerns on the Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a longitudinal sectional view schematically showing the configuration of a plasma processing apparatus according to an embodiment of the present invention. This apparatus includes a vacuum vessel 100, an electromagnetic field supply means for supplying an electric field and a magnetic field inside the vacuum vessel 100 disposed on the outer periphery above the vacuum vessel, and an interior of the vacuum vessel 100 disposed below the vacuum vessel 100. Exhaust means for exhausting is provided.

  The vacuum vessel 100 includes a processing chamber 101 inside the vacuum vessel 100, and a high-frequency power source 110 that supplies a high frequency into the processing chamber 101 and a solenoid coil that supplies electromagnetic waves into the processing chamber 101 above the vacuum vessel 100. 109, and a vacuum vessel 100 is provided with an exhaust device including a sample stage 112 on which a substrate-like sample to be processed such as a wafer is placed on the upper surface thereof, a turbo molecular pump 120, and the like. .

  The electromagnetic field supply means includes a solenoid coil 109 disposed above the vacuum vessel 100 and a high-frequency power source 110 that supplies electromagnetic waves disposed above the vacuum vessel 100. The electromagnetic wave supplied from the high-frequency power source 110 propagates through the waveguide 107 through an isolator and matching unit 108 (not shown), passes through the resonance space 106, and then passes through the quartz plate 105 and the shower plate 102 to the processing chamber 101. To be introduced.

  The processing chamber 101 has a substantially cylindrical shape, and is a space where plasma is formed when plasma processing is performed on a sample to be processed.

  A cylindrical ceiling member that seals the processing chamber 101 is provided above the processing chamber 101. The ceiling member includes a quartz plate 105 and a shower plate 102 that are made of a dielectric material such as quartz. A minute gap 103 is formed between the plate 105 and the shower plate 102. The minute gap 103 is a cylindrical space, and the shower plate 102 is disposed below the space. The shower plate 102 is provided with a large number of small holes arranged in a plurality of concentric circles. A gas ring 104 is disposed on the outer peripheral side of the quartz plate 105 and the shower plate 102. The gas ring 104 is provided with a gas passage for supplying a processing gas to the minute gap 103, and the processing gas is supplied from the processing gas supply source 123 through the processing gas supply pipe 124 and the gas passage of the gas ring 104. Then, it is supplied to the micro gap 103 and then supplied to the processing chamber 101 evenly distributed through a large number of small holes provided in the shower plate 102.

  A cylindrical side wall member 111 serving as a side wall of the processing chamber is provided on a side surface of the processing chamber 101. The side wall member 111 is disposed in contact with the lower surfaces of the gas ring 104 and the shower plate 102 and partitions the plasma generated in the processing chamber 101.

  The sample stage 112 below the processing chamber 101 has a cylindrical shape, and the upper surface of the sample stage 112 is covered with a dielectric film. A flow path (not shown) is arranged concentrically or spirally inside the sample stage 112, and a refrigerant whose temperature or flow rate (flow velocity) is adjusted by the temperature adjustment unit 115 is introduced into the flow path, and the sample stage 112. The temperature is adjusted. While the wafer 125 is placed on the upper surface of the sample stage 112, it receives heat input from the plasma. By adjusting the temperature of the sample stage 112, the temperature of the wafer 125 placed on the sample stage 112 is adjusted. . Further, in order to improve the heat conduction between the sample stage 112 and the wafer 125, a heat transfer gas channel 113 is provided between the dielectric film on the upper surface of the sample stage 112 and the back surface of the wafer 125, and heat transfer. A gas having heat transfer properties such as He is supplied from the reactive gas supply source 116 through the heat transfer gas supply pipe 127. The pressure of the heat transfer gas supplied is detected by a pressure gauge 128.

  Further, the sample stage 112 includes a DC power source 114 for adsorbing the wafer 125 to the sample stage 112 by static electricity and a high-frequency bias power source 117 for accelerating ions on the surface of the wafer 125 placed on the sample stage 112 during processing. It has.

  On the outer peripheral side of the surface of the sample table 112 on which the wafer is placed, a sample table protection member 126 is disposed to protect the sample table 112 from sputtering and etching by plasma.

  Below the sample stage 112, an exhaust device for evacuating the inside of the vacuum vessel 100 or exhausting gas, plasma, and reaction products is provided. The exhaust device includes an exhaust gate plate 118 that opens and closes an exhaust opening, a conductance variable valve 119 on a passage communicating with the exhaust opening, and a turbo molecular pump 120. Further, an exhaust pump 122 is connected to the turbo molecular pump 120, and reaction products and the like exhausted from the processing chamber 101 by the turbo molecular pump 120 are sent to the exhaust pump 122 through the exhaust pipe 121.

  A wafer 125 to be subjected to a predetermined process with respect to such a plasma etching apparatus is placed on a placement surface on the upper surface of the sample stage 112 and is adsorbed by static electricity by a direct current voltage from a direct current power source 114. Hold.

  In this state, He gas is supplied from the heat transfer gas supply source 116 between the dielectric film on the upper surface of the sample stage 112 and the back surface of the wafer 125 to cool the wafer 125.

  Next, the processing gas is introduced into the minute gap 103 from the processing gas supply source 123 through the processing gas supply pipe 124 and supplied into the processing chamber 101 through a large number of small holes formed in the shower plate 102. Due to the interaction between the electromagnetic wave that has passed through the resonance space 106 and introduced into the processing chamber 101 via the quartz plate 105 and the shower plate 102, and the magnetic field generated by the solenoid coil 109, the processing gas is turned into plasma and plasma is formed above the wafer 125. Is done. Further, high-frequency power is applied to the sample stage 112 by the high-frequency bias power source 117, and ions in the plasma are drawn onto the wafer 125 by the potential difference between the bias potential by the high-frequency bias formed above the upper surface of the wafer 125 and the plasma potential, and etching is performed. The process is started while assisting the reaction. Note that the exhaust gate plate 118 is always open during processing, and the exhaust speed is changed by changing the opening of the conductance variable valve 119 to adjust the pressure in the processing chamber 101.

  After the etching process is finished, the plasma and the high frequency bias are stopped, the supply of the DC voltage from the DC power supply 114 is stopped, and the electrostatic force is reduced and removed.

  Next, as described above, the reaction product in the process chamber 101 and the remaining process gas are exhausted by the functions of the conductance variable valve 119, the turbo molecular pump 120, and the exhaust pump 122.

  The operations of the high frequency power supply 110, DC power supply 114, high frequency bias power supply 117, exhaust gate plate 118, conductance variable valve 119, turbo molecular pump 120, and exhaust pump 122 in the figure are controlled by controllers not shown.

  The detailed structure of the sample stage 112 and the sample stage protection member 126 will be described with reference to FIGS.

  FIG. 2 shows an example of a conventional configuration of the sample stage protection member. The sample stage protection member is placed on the surface formed on the sample stage 112, and is placed on the surface formed on the surface of the sample stage 112 and the susceptor 200 that mainly covers the surface of the sample stage 112 in the same direction as the wafer 125 placement surface. The side wall cover 201 is placed so as to cover the side wall of the sample stage 112. The susceptor 200 and the side wall cover 201 are made of an insulating material such as quartz.

  The susceptor 200 and the side wall cover 201 are not in contact with each other, and a minute gap of about 300 to 500 μm is provided. This is because the susceptor 200 and the side wall cover 201 are consumables that are frequently replaced, and if they are placed in contact with each other, an arrangement error due to the addition of the dimensional tolerances of both parts occurs depending on the part lot.

  The processing chamber side surfaces of the susceptor 200 and the side wall cover 201 are consumed by sputtering mainly by ions in the plasma during the etching process. The amount of consumption per unit time on the surface of the sample table protection member is larger in the vicinity of the upper surface of the sample table 112 on which the wafer 125 is placed than in the vicinity of the side wall of the sample table 112, as the plasma generation point is closer. Therefore, the sample stage protection member is divided into the susceptor 200 and the side wall cover 201, so that only the susceptor 200 or the susceptor 200 and the side wall cover 201 are replaced according to the degree of wear.

  In the minute gap formed by the susceptor 200 and the side wall cover 201, the energy of ions in the surrounding plasma is increased by increasing the high-frequency bias voltage applied to the sample stage 112, and a threshold value with a high-frequency bias voltage exists. When taking the above, ions enter and plasma also enters. The threshold value of the high-frequency bias voltage is uniquely determined by the atmosphere in the processing chamber, the cross-sectional area of the minute gap, and the creepage distance taking the shortest path among the paths passing through the minute gap, and has a value of about 1.5 kV to 3.0 kV. take. The creepage distance in the case of FIG. 2 is a route that passes through points A and B. When the plasma comes into contact with the outer surface of the sample stage 112, a local discharge is caused on the sample stage 112 and the etching performance at the edge of the wafer 125 is impaired.

  FIG. 3 shows the configuration of the sample stage protection member according to the embodiment of the present invention. The sample stage protection member is placed on a surface formed on the sample stage 112, and is a cylindrical shape provided on the outer periphery of the sample stage 112 and the susceptor 200 that mainly covers the surface of the sample stage 112 in the same direction as the wafer 125 placement surface. The mounting table 300, the upper side wall cover 301 that covers the side wall of the sample table 112 and is mounted on the mounting table 300, the lower side wall cover 302 that is mounted on the surface formed on the sample table 112 (not shown), and the mounting table It consists of a cylindrical insulating ring 303 placed on 300 and arranged so as to cover a minute gap formed by the susceptor 200 and the upper side wall cover 301. The susceptor 200, the upper side wall cover 301, the lower side wall cover 302, and the insulating ring 303 are made of an insulating material such as quartz. The mounting table 300 is made of a metal material such as aluminum or stainless steel, is electrically insulated from the sample table 112, and is not applied with a high frequency bias voltage.

  The susceptor 200, the upper side wall cover 301, and the insulating ring 303 are not in contact with each other, and a minute gap of about 300 to 500 μm is provided. This is because the susceptor 200, the upper side wall cover 301, and the insulating ring 303 are consumables that are frequently replaced. If they are placed in contact with each other, placement errors may occur due to the addition of the dimensional tolerances of both parts. .

  The susceptor 200 and the insulating ring 303 are arranged in such a manner that they do not overlap when viewed from above the sample stage 112. In the apparatus maintenance, the sample is prepared by any combination of the susceptor 200 alone, the insulation ring 303 alone, the susceptor 200 and the insulation ring 303, the susceptor 200 and the insulation ring 303 and the upper side wall cover 301, or the sample stage protection member 126. The base protection member 126 is replaced according to the degree of wear.

  In FIG. 3, a minute gap serving as a path for plasma to enter the sample stage 112 is formed by the susceptor 200, the upper side wall cover 301, and the insulating ring 303, and passes through the member surface within the path passing through the minute gap. The shortest route is the creepage distance. The creepage distance in the case of FIG. 3 is a route passing through points A, B, and C. The length of the creepage distance formed by the points A and B is equal to the creepage distance in FIG. That is, the creepage distance in FIG. 3 is longer than the creepage distance in FIG. 2 by the creepage distance formed by points B and C due to the arrangement of the insulating ring 303. This makes it difficult for the plasma to reach the outer surface of the sample table, and the threshold of the high frequency bias voltage that causes abnormal discharge is shifted to the high voltage side. The configuration of the sample stage protection member in FIG. 3 is characterized in that the threshold value of the high-frequency bias voltage when plasma enters the outer surface of the sample stage 112 can be set higher than the configuration of the sample stage protection member in FIG. To do.

When the wafer is etched using the plasma etching apparatus shown in FIG. 1 provided with the sample table protection member shown in FIG. 3, the occurrence of abnormal discharge on the outer surface of the sample table can be suppressed, and a good processed shape can be obtained. I was able to. In addition, by disposing a plurality of sample table protection members apart from each other, it was possible to easily replace a protection member that was consumed after being used many times.
As described above, according to the present embodiment, it is possible to provide a plasma processing apparatus capable of suppressing local discharge generated on the outer surface of the sample table even when the sample table protection member is divided into a plurality of parts. .

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. In addition, the present invention can be applied to various plasma processing apparatuses.

DESCRIPTION OF SYMBOLS 100 ... Vacuum container, 101 ... Processing chamber, 102 ... Shower plate, 103 ... Micro gap, 104 ... Gas ring, 105 ... Quartz plate, 106 ... Resonance space, 107 ... Waveguide, 108 ... Matching device, 109 ... Solenoid coil DESCRIPTION OF SYMBOLS 110 ... High frequency power source, 111 ... Side wall member, 112 ... Sample stand, 113 ... Heat transfer gas flow path, 114 ... DC power supply, 115 ... Temperature control unit, 116 ... Heat transfer gas supply source, 117 ... High frequency bias power supply 118 ... Exhaust gate plate, 119 ... Variable conductance valve, 120 ... Turbo molecular pump, 121 ... Exhaust pipe, 122 ... Exhaust pump, 123 ... Process gas supply source, 124 ... Process gas supply pipe, 125 ... Wafer, 126 ... Sample Table protection member, 127 ... heat transfer gas supply pipe, 128 ... processing chamber pressure gauge, 200 ... susceptor, 201 Sample stage side wall cover, 300 ... table, 301 ... sample stage upper sidewall cover, 302 ... sample stage lower sidewall cover, 303 ... insulating ring.

Claims (6)

A plasma processing apparatus for processing a wafer disposed inside using a plasma in a processing chamber in a vacuum vessel,
A sample stage on which the wafer is mounted;
A sample stage protecting member that protects the surface of the sample stage not covered by the wafer from plasma, and
The plasma is characterized in that the sample stage protection member is composed of a susceptor that covers the upper part of the sample stage, a side wall cover that covers the side wall of the sample stage, and an insulating ring that is disposed so as to cover a gap between the susceptor and the side wall cover. Processing equipment.   The plasma processing apparatus according to claim 1, wherein the susceptor and the insulating ring are arranged so as not to overlap each other when viewed from above the sample stage.   The plasma processing apparatus according to claim 2, wherein the susceptor, the side wall cover, and the insulating ring are arranged so as not to have a contact surface and to have a gap of about 300 to 500 μm. In a plasma processing apparatus having a vacuum vessel, a processing chamber arranged in the vacuum vessel, a sample stage placed in the processing chamber and on which a workpiece is placed, and means for generating plasma in the processing chamber,
The sample stage includes a sample stage protection member for protecting a portion not covered with the object to be processed from the plasma,
The sample stage protection member includes a susceptor that covers the upper part of the sample stage,
A side wall cover disposed adjacent to the susceptor and covering the sample stage side wall;
An insulating ring disposed proximate to both the susceptor and the side wall cover;
The threshold of the abnormal discharge high-frequency bias voltage when the susceptor, the side wall cover, and the insulating ring are included is higher than the threshold of the abnormal discharge high-frequency bias voltage when the susceptor and the side wall cover are included. A plasma processing apparatus characterized by being shifted. In a plasma processing apparatus having a vacuum vessel, a processing chamber arranged in the vacuum vessel, a sample stage placed in the processing chamber and on which a workpiece is placed, and means for generating plasma in the processing chamber,
The sample stage includes a sample stage protection member for protecting a portion not covered with the object to be processed from the plasma,
The sample stage protection member includes a susceptor that covers the upper part of the sample stage,
A side wall cover disposed adjacent to the susceptor and covering the sample stage side wall;
An insulating ring disposed proximate to both the susceptor and the side wall cover;
A plasma processing apparatus, wherein a creepage distance formed by a gap between the susceptor, the side wall cover, and the insulating ring is longer than a creepage distance formed by a gap between the susceptor and the side wall cover.   The plasma processing apparatus according to claim 5, wherein the susceptor, the side wall cover, and the insulating ring are each formed of an insulating material.

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