JP4654738B2 - Plasma processing equipment - Google Patents

Description

  The present invention relates to a plasma processing apparatus for plasma processing a processing object such as a wafer.

  A plasma processing apparatus is known as an apparatus for performing a surface treatment of a processing object such as a wafer. The plasma processing apparatus generates plasma in a reduced-pressure atmosphere, and performs an etching process on the surface of a processing object by the physical and chemical action of the plasma. Plasma is a high-frequency voltage applied to an upper electrode or a lower electrode in a processing chamber in a state where a sealed processing chamber of the plasma processing apparatus is depressurized to a predetermined pressure and a plasma generating gas (hereinafter simply referred to as “gas”) is supplied. Generated by applying a voltage.

  In such plasma processing, it may be desirable to generate high-density plasma depending on the processing purpose. For example, when performing plasma etching on a silicon substrate such as a wafer, a method is used in which a relatively high pressure gas is uniformly blown and supplied to the surface of the silicon wafer in order to improve processing efficiency.

As a parallel plate type electrode member suitable for such plasma processing, a member made of a breathable porous plate, which is a sintered body of ceramic particles, is known (Patent Documents 1, 2, and 3). If an electrode member made of such a porous plate is used, high-density plasma can be uniformly generated and stable plasma treatment can be performed with high etching efficiency.
JP 2002-231638 A Japanese Patent Laid-Open No. 2003-7682 JP 2003-282462 A

  When a processing object is placed on a stage, which is a lower electrode in a processing chamber, and a plasma treatment is started by applying a high frequency voltage to the upper electrode or the lower electrode, a porous plate on the upper electrode side that is the counter electrode of the lower electrode Suddenly rises in temperature. A typical porous plate has a diameter of about 220 mm or 320 mm and a thickness of about 2 to 10 mm. However, the entire porous plate does not rise in temperature uniformly and faces the stage ( Usually, the temperature near the center of the lower surface first suddenly rises (typically, it suddenly rises from room temperature to about 200 ° C. in about 30 seconds), and the outer edge of the porous plate is slowly lagging behind the center. The temperature rises. As a result, the porous plate is distorted due to uneven temperature rise, and the porous plate has cracks on the outer edge thereof (the porous plate is generally a circular plate, so the outer peripheral edge is radially cracked). There was a problem that it breaks and breaks.

  Accordingly, the present invention performs uniform and stable plasma processing by preventing the porous plate from being damaged due to cracks at the outer edge due to thermal expansion accompanying rapid temperature rise during plasma processing. It is an object of the present invention to provide a plasma processing apparatus that can perform the above processing.

The plasma processing apparatus according to claim 1, a stage that is a lower electrode, a counter electrode that is an upper electrode that is above the stage and faces the stage, and a processing chamber in which the stage and the counter electrode are disposed, A plasma processing apparatus for supplying a plasma generating gas to a plasma processing space between the stage and the counter electrode to generate plasma to perform plasma processing on a processing object placed on the stage. The counter electrode has a gas permeable disc formed of a main body portion in which a gas supply port is formed, and a sintered body of ceramic particles disposed below the main body portion so as to close the gas supply port. A porous plate and a support member for supporting the outer peripheral edge of the porous plate, and a slit penetrating in the thickness direction of the outer peripheral edge of the porous plate in the radial direction of the porous plate. Long Multiple formed at a pitch in the direction, and disposed a buffer member made of a ring-shaped elastic member in plan view between the said body portion of said outer periphery of said porous plate, said support The member is a storage body that houses the porous plate therein, and includes a protruding portion that protrudes inward. The protruding portion supports the outer peripheral edge of the porous plate from below, and the protruding portion Projecting inward from the slit of the porous plate housed in the support member to close the slit .

According to the present invention, when plasma treatment is started, the air-permeable disk-shaped porous plate made of a sintered body of ceramic particles suddenly rises in temperature from the vicinity of the central portion of the opposing surface of the stage, particularly at the outer edge portion. In this case, distortion occurs as the temperature rises. However, since this distortion is absorbed by the slit, the porous plate is not damaged, and stable plasma treatment can be performed. Further, by closing the slit with the support member, gas leakage from the slit can be prevented, and uniform and stable plasma can be generated in the entire processing space.

  1 is a cross-sectional view of a plasma processing apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view of a porous plate according to an embodiment of the present invention, and FIG. 3 is a porous plate according to an embodiment of the present invention. FIG. 4 is a partially enlarged cross-sectional view of the upper electrode portion in one embodiment of the present invention.

  First, the plasma processing apparatus will be described with reference to FIG. In FIG. 1, the inside of a vacuum chamber 1 is a processing chamber 2 for performing plasma processing. In the processing chamber 2, a lower electrode 3 and an upper electrode 4 are arranged facing each other in the vertical direction, and are parallel plate type. The plasma processing apparatus is configured.

  The lower electrode 3 is composed of a stage 31 that is a high-frequency electrode and a protrusion 32 that protrudes downward from the center thereof, and the interior of the vacuum chamber 1 is interposed via an insulating member 33 disposed on the outer edge of the stage 31. It is attached to. A high frequency power supply unit 5 is connected to the protruding portion 32 of the lower electrode 3. An exhaust path 6 is formed at the side of the insulating member 33, and the inside of the processing chamber 2 is vacuumed by an exhaust unit 7 such as a vacuum pump. A processing object W such as a wafer is placed on the stage 31.

  The upper electrode 4, which is a counter electrode, includes a flat plate (disk) -shaped main body 41, an annular support member 45 provided on the outer periphery of the lower surface of the main body 41, and a support member 45 below the main body 41. It is composed of a porous plate 43 housed inside, and is attached to the vacuum chamber 1 via a protruding portion 42 that protrudes upward from the central portion of the main body portion 41. The porous plate 43 is air permeable made of a sintered body of ceramic particles similar to that described in the above cited documents 1 to 3. The support member 45 is provided with a protruding portion 45 ′ protruding inward (center side) from the inner wall lower portion, and the porous plate 43 has an outer edge portion (the porous plate 43 of the present embodiment is Since it is a disc, the outer peripheral edge portion) is placed on the protruding portion 45 ′ and stored in an internal space formed by the main body portion 41 and the support member 45.

2 and 3, the porous plate 43 provided on the upper electrode 4 side has a disk shape, and the slits S are arranged at a pitch at the outer peripheral edge portion so that the radial direction of the porous plate 43 is the longitudinal direction. The porous plate 43 is formed so as to penetrate in the thickness direction (vertical direction). When the diameter of the porous plate 43 is about 220 mm or 320 mm, the length L1 of the slit S is preferably about 3 to 10 mm, the width L2 is about 0.5 mm to 1.0 mm, and preferably the slit S is 120 mm. It is formed with the following pitch L3.

  FIG. 4 shows a desirable coupling structure of the main body 41, the support member 45, and the porous plate 43. The support member 45 is coupled to the main body 41 by a fastener such as a bolt 10 or a nut 11. The upper surface a of the protrusion 45 ′ is an inwardly tapered surface that is downwardly inclined, and the outer peripheral edge lower surface b of the porous plate 43 is an outwardly tapered surface that is inclined upwardly. b is tightly joined so as not to generate a gap. Further, the protrusion 45 ′ extends inward (center side) from the slit S, and therefore, the lower surface side of the slit S is closed by the protrusion 45 ′. The airtightness of the supply port T (described later) is maintained, and the gas supplied to the gas supply port T is prevented from leaking from the slit S to the plasma generation space A.

  The upper surface of the porous plate 43 near the outer peripheral edge has a tapered surface c that is inclined downward toward the outside, and the buffer member 12 is interposed between the main body 41 near the outer peripheral edge of the porous plate 43. It is arranged. The buffer member 12 is made of an elastic material such as resin rubber, has a ring shape in plan view, and is a gas supply port that is a narrow gas flow space between the lower surface side of the main body 41 and the porous plate 43. T-tightness is secured.

  In FIG. 1, a gas supply path 46 is formed in the main body portion 41 and the protruding portion 42 so as to penetrate up and down. The main body portion 41 is grounded to the ground portion 44. The gas in the gas supply unit 13 is supplied from the gas supply path 46 to the gas supply port T, passes through the porous plate 43, and enters a plasma generation space (plasma processing space) A between the lower electrode 3 and the upper electrode 4. Supplied. Although the upper electrode 4 is grounded in the present embodiment, the lower electrode 3 may be grounded and the upper electrode 4 may be connected to a high frequency power source.

  This plasma processing apparatus has the above configuration, and the operation will be described next. In a state where the processing object W is placed on the stage 31, the exhaust unit 7 is operated to decompress the inside of the processing chamber 2. If the inside of the processing chamber 2 is depressurized to a predetermined pressure, a gas is supplied from the gas supply unit 13 to the gas supply port T and passes through the porous plate 43 to generate a plasma generation space A between the electrodes 3 and 4. To send. When a high frequency voltage is applied to the lower electrode 3 in this state, plasma is generated in the plasma generation space A, and the processing target W is subjected to surface treatment such as plasma etching.

  When the plasma processing is started as described above, the temperature of the plasma generation space A rapidly rises, and the temperature of the porous plate 43 suddenly rises from the vicinity of the center portion of the facing surface (lower surface) facing the lower electrode 3. Due to the thermal expansion associated with this temperature rise, the porous plate 43 is distorted particularly at the outer peripheral edge thereof, but this distortion is absorbed by the slit S, so that cracks that cause gas leakage are generated at the outer peripheral edge. Is not generated, and a uniform and stable plasma treatment is performed.

  According to the present invention, during the plasma processing, strain is generated in the outer edge portion of the porous plate due to thermal expansion accompanying a rapid temperature rise, but since this strain is absorbed by the slit, cracks are generated in the outer edge portion, etc. Thus, the porous plate is not damaged, so that stable plasma processing can be performed, and it is particularly useful as a plasma processing apparatus for surface etching of a wafer or the like.

Sectional drawing of the plasma processing apparatus in one embodiment of this invention The perspective view of the porous board in one embodiment of this invention The perspective view of the supporting member in which the porous board in one embodiment of this invention was accommodated The partial expanded sectional view of the upper electrode part in one embodiment of this invention

Explanation of symbols

1 Vacuum chamber 2 Processing chamber 3 Lower electrode 4 Upper electrode (counter electrode)
31 Stage 41 Body 43 Porous plate 45 Support member 45 'Protrusion A Plasma generation space (plasma processing space)
S Slit T Gas supply port W Object to be treated

Claims (1)

A stage that is a lower electrode; a counter electrode that is an upper electrode that is above the stage and faces the stage; and a processing chamber in which the stage and the counter electrode are disposed. A plasma processing apparatus for generating a plasma by supplying a plasma generating gas to a plasma processing space in between to perform plasma processing of a processing object placed on the stage,
The counter electrode has a gas-permeable disk-shaped body portion having a gas supply port and a ceramic particle sintered body disposed below the body portion so as to close the gas supply port. A porous plate and a support member for supporting the outer peripheral edge portion of the porous plate, and a slit penetrating the outer peripheral edge portion of the porous plate in the thickness direction extends in the radial direction of the porous plate. A plurality of cushioning members made of a ring-shaped elastic material in plan view are disposed between the outer peripheral edge of the porous plate and the main body of the porous plate at a pitch in the direction .
The support member is a storage body that stores the porous plate therein, and includes a protruding portion that protrudes inward, and the protruding portion supports the outer peripheral edge of the porous plate from below,
The plasma processing apparatus, wherein the protrusion protrudes inward from the slit of the porous plate housed in the support member to close the slit .

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