JP4274168B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method for performing plasma processing on a thin plate substrate such as a silicon wafer.

In the manufacturing process of silicon wafers used in semiconductor devices, stress relief after thinning to reduce the thickness of the substrate by mechanical polishing and dicing to divide the silicon wafer into individual parts are performed by plasma processing. Done. In this plasma processing, the silicon wafer is mounted on a substrate mounting portion provided on the discharge electrode of the plasma processing apparatus in a posture in which the surface to be processed, that is, the surface opposite to the circuit forming surface faces upward, and vacuum suction or the like. (See, for example, Patent Document 1).
JP 2001-210624 A

  Since the silicon wafer is a thin plate-like substrate and is in a state of being adsorbed on the mounting surface of the substrate mounting portion in the plasma processing process, it remains in close contact with the mounting surface even after the suction holding is released after the plasma processing is completed. Become. For this reason, when carrying out a silicon wafer after plasma processing, there existed a problem that it was difficult to take out a silicon wafer stably from a board | substrate mounting part. This problem increases with an increase in the size of the silicon wafer, and is particularly noticeable when the silicon wafer is held on the mounting surface via a protective tape.

  Therefore, an object of the present invention is to provide a plasma processing apparatus and a plasma processing method capable of stably and easily peeling a plate-like substrate from a substrate mounting portion.

  The plasma processing apparatus of the present invention is a plasma processing apparatus for performing plasma processing on a plate-like substrate, and includes a processing container for forming a processing space for performing the plasma processing in a reduced pressure atmosphere, and a vacuum for exhausting the processing container. An exhaust part, a substrate mounting part provided in the processing container and provided with a mounting surface on which the plate-like substrate is placed, substrate holding means for holding the plate-like substrate on the mounting surface, Blowing means for separating the plate-like substrate from the mounting surface by blowing gas through a vent hole opened in the mounting surface, plasma generating means for generating plasma in the processing space, and the vacuum exhaust A control unit for controlling the substrate, the substrate holding unit, the plasma generating unit, and the blowing unit, and in the atmosphere introduction step of introducing the atmosphere into the processing container after the plasma processing is completed, the pressure of the processing space There is actuated said blowing means at a timing before reaching the atmospheric pressure, to separate the plate-like substrate from the mounting surface.

  The plasma processing method of the present invention is a plasma processing method for performing plasma processing in a state where a plate-like substrate is held on a mounting surface of a substrate mounting portion in a processing space formed in a processing container. A holding step for placing and holding the plate-like substrate on the substrate, a depressurizing step for depressurizing the processing space by evacuating the inside of the processing container, and generating plasma in the processing space to place it on the mounting surface. A plasma processing step of performing plasma processing on the placed plate-like substrate, and an air introduction step of introducing air into the processing container, and in the air introduction step, before the pressure of the processing space reaches atmospheric pressure At the timing, the plate-like substrate is peeled off from the mounting surface by blowing out gas through a vent hole opened in the mounting surface.

  According to the present invention, in the air introduction process for introducing air into the processing container, the gas is blown out through the vent hole opened in the mounting surface at a timing before the pressure of the processing space reaches atmospheric pressure. By peeling the plate-like substrate from the mounting surface, the plate-like substrate can be peeled from the substrate mounting portion stably and easily.

  Next, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are cross-sectional views of the plasma processing apparatus according to the first embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of the control system of the plasma processing apparatus according to the first embodiment of the present invention. 6 is a flow chart of a plasma processing method according to an embodiment of the present invention, and FIGS. 5 and 7 show changes over time in the pressure of a processing space and the pressure of a suction / blow circuit in the plasma processing method of an embodiment of the present invention. It is a graph to show.

  First, the plasma processing apparatus will be described with reference to FIGS. In FIG. 1, the plasma processing apparatus includes a vacuum chamber 1 as a processing container, and a processing space 2 for performing plasma processing in a reduced-pressure atmosphere is formed in the vacuum chamber 1. Inside the vacuum chamber 1, a lower electrode 3 and an upper electrode 4 are disposed so as to face each other in the vertical direction. The lower electrode 3 is mounted in a state of being electrically insulated from the vacuum chamber 1 by a support portion 3 a extending downward, and the outer periphery is held by a dielectric 7 mounted at the bottom of the vacuum chamber 1. The upper electrode 4 is mounted in a state where it is electrically connected to the vacuum chamber 1 by a support portion 4a extending upward.

  The upper surface of the lower electrode 3 is a mounting surface on which a silicon wafer 6 that is a plate substrate to be processed is mounted. Therefore, the lower electrode 3 is a substrate mounting portion provided in the vacuum chamber 1 as a processing container and provided with a mounting surface on which a silicon wafer 6 as a plate-like substrate is mounted. Here, the silicon wafer 6 is in a state after the surface opposite to the circuit formation surface is mechanically polished, and is placed with the circuit formation surface to which the protective mask 5 made of resin is attached facing downward. And the damage layer produced | generated by grinding | polishing process is removed by plasma-processing the mechanical polishing surface on the opposite side of a circuit formation surface. That is, the silicon wafer 6 is mounted on the mounting surface via the protective tape 5 attached to the opposite surface of the plasma processing surface.

  A transport port 1 a for carrying in and out the substrate is provided on the side surface of the vacuum chamber 1, and the transport port 1 a can be opened and closed by a door 8. The door 8 is driven by a door opening / closing mechanism 24. When the silicon wafer 6 is transported, as shown in FIG. 2, the transport head 22 that holds the silicon wafer 6 by suction is opened by the transport arm 23 while the door 8 is opened by the door opening / closing mechanism 24. Through the vacuum chamber 1. Thereby, the silicon wafer 6 is mounted on the mounting surface of the lower electrode 3, and the processed silicon wafer 6 is unloaded from the vacuum chamber 1.

  The vacuum chamber 1 is provided with an air supply / exhaust port 1 b, and the processing space 2 is connected to a first path switching valve 10 via a first pressure sensor 9. A vent valve 11 and a first opening / closing valve 12 are connected to the air supply port 10a side and the exhaust port 10b side of the first path switching valve 10, respectively, and the first opening / closing valve 12 is further connected to a vacuum exhaust pump. 13 is connected. The first open / close valve 12 is opened while the first path switching valve 10 is switched to the exhaust port 10b side, and the vacuum exhaust pump 13 is driven, whereby the vacuum chamber 1 is evacuated and the processing space 2 is exhausted. Is depressurized. Further, by opening the vent valve 11 in a state where the first path switching valve 10 is switched to the air supply port 10a side, the atmosphere is introduced into the vacuum chamber 1 and the processing space 2 is evacuated. . The vacuum exhaust pump 13 is a vacuum exhaust unit that exhausts the inside of the vacuum chamber 1.

A shower plate 4 b made of a porous member such as a sintered material is attached to the lower surface of the upper electrode 4. The shower plate 4b is connected to a vent hole 4c provided through the support 4a, and the process gas supply unit 14 is connected to the vent hole 4c. By driving the process gas supply unit 14, the process gas is blown out to the silicon wafer 6 placed on the lower electrode 3 through the shower plate 4b for plasma processing. In the present embodiment, a fluorine-based gas such as sulfur hexafluoride is used as a process gas for the etching process on the silicon wafer 6.

  A suction hole 3b is opened on the upper surface of the lower electrode 3, and the suction hole 3b is connected to a suction / blow circuit described below through a vent hole 3c provided through the support portion 3a. ing. That is, the vent hole 3c is connected to the second path switching valve 17 via the second pressure sensor 15, and the second path switching valve 17 has a suction port 17a side and an air supply port 17b side, respectively. Two on-off valves 20 and a blow valve 18 are connected. A vacuum suction pump 21 and an air supply source 19 are further connected to the second opening / closing valve 20 and the blow valve 18, respectively.

  With the second path switching valve 17 switched to the suction port 17a side, the second opening / closing valve 20 is opened, and the vacuum suction pump 21 is driven, whereby vacuum suction is performed from the suction hole 3b. A silicon wafer 6 is held on the mounting surface of the electrode 3 by vacuum suction. Therefore, the suction hole 3 b, the vent hole 3 c, and the vacuum suction pump 21 serve as a substrate holding unit that holds the silicon wafer 6, which is a plate-like substrate, on the mounting surface of the lower electrode 3. As the substrate holding means, the silicon wafer 6 may be held on the mounting surface by electrostatic force in combination with holding the silicon wafer 6 by vacuum suction.

  Further, by switching the second path switching valve 17 to the air supply port 17b side and opening the blow valve 18, a blow operation for blowing out the positive pressure air supplied from the air supply source 19 from the adsorption hole 3b is performed. As a result, the silicon wafer 6 placed on the upper surface of the lower electrode 3 is peeled off from the placement surface. That is, the suction hole 3b, the vent hole 3c, and the air supply source 19 are blow means for peeling the silicon wafer 6 from the mounting surface of the lower electrode 3 by blowing out gas through the vent hole opened in the mounting surface. It has become.

  A high frequency power supply unit 16 is electrically connected to the support unit 3a. By driving the high frequency power supply unit 16, a high frequency power supply is connected between the upper electrode 4 and the lower electrode 3 that are grounded via the vacuum chamber 1. A voltage is applied. After the vacuum chamber 1 is evacuated and the processing space 2 is depressurized, a plasma discharge is generated between the lower electrode 3 and the upper electrode 4 by driving the high-frequency power supply unit 16 with the process gas supplied to the processing space 2. As a result, the process gas shifts to a plasma state in the processing space 2. And the plasma process of the process target surface of the silicon wafer 6 is performed by this plasma. Therefore, the vacuum suction pump 21, the process gas supply unit 14, and the high frequency power supply unit 16 serve as plasma generating means for generating plasma in the processing space 2. The plasma generating means is not limited to the parallel plate system including the upper electrode and the lower electrode, and may be a microwave or dielectric coupling type plasma generating means.

  Next, the control system will be described with reference to FIG. In FIG. 3, the control part 30 controls each part shown below. First, by controlling the door opening / closing mechanism 24, operation control during the transfer of the silicon wafer 6 by a transfer device such as the transfer head 22 and the transfer arm 23 is performed. By controlling the first open / close valve 12, the vacuum pump 13, the vent valve 11, and the process gas supply unit 14, the pressure in the processing space 2 is controlled and the process gas is supplied to the processing space 2. At this time, the processing pressure in the processing space 2 can be set to a desired pressure by referring to the measurement value of the first pressure sensor 9.

Then, by controlling the second path switching valve 17, the second opening / closing valve 20, the vacuum suction pump 21, and the blow valve 18, suction / blow is performed through the suction hole 3 b opened in the upper surface of the lower electrode 3. Control the behavior. At this time, the suction pressure and the blow pressure can be set to desired pressures by referring to the measurement value of the second pressure sensor 15. That is, in the above configuration, the control unit 30 controls the vacuum exhaust unit, the substrate holding unit, the plasma generating unit, and the blowing unit.

  Then, the control unit 30 controls the evacuation unit, the substrate holding unit, the plasma generating unit, and the blowing unit, so that the atmosphere is introduced into the vacuum chamber 1 after the plasma processing is completed, as described in the explanation of the plasma processing method below. In the air introduction process, the blowing means is operated at a timing before the pressure in the processing space 2 reaches the atmospheric pressure so that the silicon wafer 6 is peeled off from the mounting surface of the lower electrode 3. At this time, after the blow means is operated, before the pressure in the processing space 2 reaches atmospheric pressure, the control unit 30 performs operation control so as to stop the operation of the blow means.

  This plasma processing apparatus is configured as described above. Hereinafter, a plasma processing method executed by this plasma processing apparatus will be described along the flow of FIG. 4 with reference to FIG. FIG. 5 shows the first pressure (pressure in the processing space 2) that is the measured pressure of the first pressure sensor 9 and the measured pressure of the second pressure sensor 15 at each timing (T1 to T16) shown in FIG. The graph shows a time-dependent change in a certain second pressure (pressure in the suction / blow circuit), where the first pressure Pa shown by a bold line indicates the pressure in the processing space 2 and the second pressure Pb shown by a thin line shows suction / Each of the second pressures of the blow circuit is shown.

  When the plasma processing operation is started, first, the door 8 is opened, and the silicon wafer 6 as a processing target is carried into the processing space 2 and placed on the lower electrode 3. In this state, the second pressure Pb and the first pressure Pa are both equal to the atmospheric pressure P0. Then, vacuum suction for sucking and holding the silicon wafer 6 on the mounting surface of the lower electrode 3 is started at timing T1. As a result, the second pressure Pb decreases to a predetermined adsorption pressure Pb1, and the silicon wafer 6 is adsorbed and held on the mounting surface (holding process). Thereafter, the adsorption pressure Pb1 is maintained.

  Next, at timing T2, the door 8 is closed, and evacuation in the vacuum chamber 1 is started. As a result, the processing space 2 is depressurized and the first pressure Pa starts to decrease (decompression step), and decreases to the lowest pressure Pa1 at the timing T3 when the supply of the process gas is started. When the process gas is supplied at timing 3, the first pressure Pa rises from Pa1 at timing T3 to a predetermined processing pressure Pa2 defined by the plasma processing conditions. Pa2 is maintained.

  Thereafter, plasma discharge is started at timing T4. Thereby, plasma is generated in the processing space 2 and the silicon wafer 6 mounted on the mounting surface is subjected to plasma processing (plasma processing step). Then, the plasma discharge is terminated at a timing T5 when a predetermined plasma processing time has elapsed, and the supply of plasma gas is stopped. At this time, since the vacuum evacuation is continuing, the first pressure Pa decreases again, and by stopping the vacuum evacuation at the timing T6, the pressure becomes a constant pressure Pa3 substantially the same as the pressure Pa1.

  At timing T7, the vent valve 11 and the first path switching valve 10 are operated to start venting in the chamber (first in-chamber vent). As a result, the first pressure Pa starts to rise. That is, at the timing T7, an air introduction process for introducing air into the vacuum chamber 1 is started. After that, at the timing T8 when the first vent in the chamber is temporarily stopped, the pressure becomes a constant pressure Pa4, and the pressure difference from the atmospheric pressure P0 becomes small.

  Then, vacuum suction of the silicon wafer 6 by the lower electrode 3 is stopped at timing T9, and blowing from the suction hole 3b is started at timing T10. Thereby, the first pressure Pa rises somewhat from Pa4, and reaches Pa5 after the timing T11 when the blow is stopped. Then, by this blow operation, the second pressure Pb rises from Pb1 to the blow pressure Pb2 set between the atmospheric pressures P0 and Pa5, and then stops at the blow and is equal to the first pressure Pa (here, The pressure is reduced to Pa5).

  By this blowing operation, the second pressure Pb temporarily becomes higher than the first pressure Pa, and air is ejected from the adsorption holes 3 b in the processing space 2. As a result, air is blown to the lower surface of the silicon wafer 6 that is in close contact with the mounting surface of the lower electrode 3 in the plasma treatment, and the silicon wafer 6 is peeled off from the mounting surface of the lower electrode 3. At this time, since the inside of the processing space 2 is under a reduced pressure atmosphere, the air ejected from the adsorption hole 3b diffuses quickly. Therefore, problems such as displacement of the silicon wafer 6 due to air staying between the mounting surface of the lower electrode 3 and the lower surface of the silicon wafer 6 do not occur. At this time, by appropriately selecting the level of the pressure Pa4, the balance between the peeling effect of the silicon wafer 6 by blowing and the positional stability of the silicon wafer 6 at the time of blowing can be optimally set.

  Then, the chamber vent is restarted at the timing T12 (second chamber vent), and the atmosphere is introduced into the vacuum chamber 1, whereby the first pressure Pa rises to the atmospheric pressure P0. Next, the door 8 is opened at timing T13, and the transport head 22 enters the vacuum chamber 1 at timing T14. Thereafter, blow from the suction hole 3b is started again at the timing T15, and the peeling of the silicon wafer 6 when the silicon wafer 6 is taken out from the lower electrode 3 by the transport head 22 is promoted. Then, the blow is stopped at timing T16, and one cycle of the plasma processing is completed.

  The above-described plasma processing method is a plasma processing method for performing plasma processing in a state where the silicon wafer 6 is held on the mounting surface of the lower electrode 3 in the processing space 2 formed in the vacuum chamber 1. A holding step for placing and holding the silicon wafer 6, a decompression step for depressurizing the processing space 2 by evacuating the inside of the vacuum chamber 1, and generating plasma in the processing space 2 to be placed on the placement surface. This process includes a plasma processing step for plasma processing of the silicon wafer 6 and an air introduction step for introducing air into the vacuum chamber 1.

  In the air introduction process, the silicon wafer 6 is peeled off from the mounting surface by blowing out gas through the suction holes 3b opened in the mounting surface at a timing before the pressure of the processing space 2 reaches atmospheric pressure. Further, the gas blowing is stopped before the pressure in the processing space 2 reaches the atmospheric pressure.

  By adopting such a method, when a thin plate substrate such as a silicon wafer, which is likely to remain in close contact with the mounting surface even after the completion of the plasma processing after the completion of the plasma processing, is applied from the substrate mounting stage to the silicon The wafer can be taken out stably. In particular, when an electrostatic attraction means is adopted as a holding means for holding the silicon wafer 6 on the mounting surface, the effect of the present invention becomes remarkable.

In the above embodiment, when blowing from the suction hole 3b for peeling the silicon wafer 6, the vent in the chamber is divided into two times to increase the pressure in the processing space 2 in two stages. 6 and 7, the in-chamber venting may be performed in one stage. That is, FIG. 6 and FIG. 7 omit the first in-chamber vent performed at the timing T7 to the timing T8 in the embodiment shown in FIG. 4 and FIG. Timings T1 to T6 are the same as those in the embodiment shown in FIGS.

  In this embodiment, the blow for peeling the silicon wafer 6 is performed in a state where the first pressure Pa is Pa3 lower than Pa4 shown in FIG. Then, the second pressure Pb is increased to Pb3 (set to a pressure lower than Pb2) by the blowing operation, and the silicon wafer 6 is moved by the pressure difference between the first pressure Pa and the second pressure Pb in this process. Peel from the lower electrode 3. Thereafter, venting in the chamber is performed at timing 10 to increase the first pressure Pa to the atmospheric pressure P0 at a time. The timing after timing T11 is the same as the timing after timing T13 in FIGS.

  The plasma processing apparatus and the plasma processing method of the present invention have an effect that the peeling of the plate-like substrate from the substrate mounting stage can be performed stably and easily. And useful.

Sectional drawing of the plasma processing apparatus of one embodiment of this invention Sectional drawing of the plasma processing apparatus of one embodiment of this invention The block diagram which shows the structure of the control system of the plasma processing apparatus of one embodiment of this invention The flowchart of the plasma processing method of one embodiment of this invention The graph which shows the time-dependent change of the pressure of the process space and the pressure of a suction / blow circuit in the plasma processing method of one embodiment of this invention The flowchart of the plasma processing method of one embodiment of this invention The graph which shows the time-dependent change of the pressure of the process space and the pressure of a suction / blow circuit in the plasma processing method of one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Processing space 3 Lower electrode 4 Upper electrode 6 Silicon wafer 8 Door 13 Vacuum exhaust pump 14 Process gas supply part 16 High frequency power supply part 21 Vacuum adsorption pump

Claims (6)

A plasma processing apparatus for performing plasma processing of a plate-shaped substrate,
A processing container for forming a processing space for performing the plasma processing in a reduced-pressure atmosphere, a vacuum exhaust unit for exhausting the inside of the processing container, and a mounting surface provided in the processing container on which the plate-like substrate is mounted A substrate mounting portion provided with a substrate holding means for holding the plate-shaped substrate on the mounting surface, and blowing the gas through a vent hole opened on the mounting surface. Blowing means for separating from the mounting surface, plasma generating means for generating plasma in the processing space, and a control unit for controlling the vacuum exhaust part, substrate holding means, plasma generating means and blowing means,
In the air introduction step of introducing air into the processing container after the plasma processing is finished, the blowing unit is operated at a timing before the pressure of the processing space reaches atmospheric pressure, so that the plate-like substrate is placed on the mounting surface. A plasma processing apparatus, wherein the plasma processing apparatus is peeled off.   The plasma processing apparatus according to claim 1, wherein the plate-like substrate is placed on the placement surface via a protective tape attached to a surface opposite to the plasma treatment surface.   2. The plasma processing apparatus according to claim 1, wherein after the blow means is operated, the operation of the blow means is stopped before the pressure in the processing space reaches atmospheric pressure. A plasma processing method for performing plasma processing in a state where a plate-like substrate is held on a mounting surface of a substrate mounting portion in a processing space formed in a processing container,
The holding step of placing and holding the plate-like substrate on the mounting surface, the depressurizing step of depressurizing the processing space by evacuating the inside of the processing container, and generating plasma in the processing space, A plasma processing step of plasma processing the plate-like substrate placed on the mounting surface, and an air introduction step of introducing air into the processing container,
In the air introduction step, the plate-like substrate is placed on the placement surface by blowing out gas through a vent hole opened on the placement surface at a timing before the pressure of the processing space reaches atmospheric pressure. A plasma processing method characterized by peeling from a plasma. The plasma processing method according to claim 4, wherein the plate-like substrate is placed on the placement surface via a protective tape attached to a surface opposite to the plasma treatment surface. 5. The plasma processing method according to claim 4 , wherein, in the air introduction step, the gas blowing is stopped before the pressure in the processing space reaches atmospheric pressure.

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