JP2011029444A - Plasma processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing apparatus capable of inhibiting occurrence of charging damage in plasma extinction without adversely influencing process performance and generating foreign matter. <P>SOLUTION: The plasma processing apparatus includes a wafer mounting electrode 103 having a wafer mounted and connected with a high-frequency bias power source and having high-frequency power applied, an upper electrode 102 oppositely provided to the wafer mounting electrode 103, and a conductive ring 105 provided around the wafer mounting electrode 103 and having high-frequency voltage applied. In extinguishing plasma serving as transient plasma, a ratio of the high-frequency voltage applied to the conductive ring 105 for the high-frequency voltage applied to the wafer mounting electrode 103 is controlled so that a difference between self bias at the center of the wafer and self bias around a wafer circumference can be reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a plasma processing apparatus used in a manufacturing process of a semiconductor integrated circuit device.

  As processing using plasma in the manufacturing process of a semiconductor integrated circuit device, plasma deposition and plasma etching are known. The plasma processing apparatus is disclosed in Patent Documents 1 to 4, for example.

JP 2005-203489 A JP 2008-251866 A JP 2009-71292 A JP 2004-273797 A

  The plasma processing is processing for etching the surface of a sample placed on a sample stage provided with a conductive ring and depositing on the sample surface using plasma of a reactive gas introduced into a vacuum processing chamber. After finishing this process, the plasma is extinguished. When the plasma is extinguished, the source output applied to the upper electrode for generating plasma and the bias output stop timing applied to the sample stage on which the sample is mounted are randomly shifted from the timing of the stop switches. I understood. This timing shift may cause charging damage to the sample.

  In Patent Document 1, in a plasma etching apparatus, a voltage applied to a component (conductive ring) around a mounting electrode provided on a sample stage on which a semiconductor substrate (wafer) for forming a semiconductor device is mounted is increased. Thus, a technique has been disclosed that eliminates defects in the processing shape in high-speed etching with high power even with a worn conductive ring. Conventionally, when controlling the voltage of the conductive ring, the voltage is controlled by the ratio to the electrode voltage so that the processing shape of the wafer edge in the plasma processing is vertical, and the ratio is the height of the conductive ring, etc. The optimal value was determined. In addition, in order to alleviate the adverse effect on the component life and the etching performance on the wafer edge due to the consumption of the conductive ring, there is a design that can set the voltage applied to the conductive ring smaller than the electrode. However, this Patent Document 1 does not have a concept of changing the voltage ratio at the time of ignition and extinguishing of plasma in any case. In addition, the source high-frequency power supply and the lower electrode high-frequency power supply cannot be turned on and off at the same time due to the characteristics of each power supply (ON and OFF timings are shifted). The problem that the potential difference occurs and charging damage is likely to occur has not been solved.

  Patent Document 2 discloses a technique for reducing in-plane uniformity of a processing shape and charging damage by controlling temperature adjustment of a ring-shaped member based on a gas temperature distribution in a processing chamber. Further, in Patent Document 3, a first period having a first amplitude for generating plasma and a second period having a second amplitude that does not substantially generate plasma are alternately repeated at a predetermined cycle. A method of adjusting a high frequency power source for plasma generation is disclosed. However, there is no disclosure or suggestion regarding charging damage caused by the timing of stopping the source output or the bias output at the time of extinguishing the plasma and the timing of each stop switch, and countermeasures against them.

  Patent Document 4 discloses a technique for preventing charging damage during plasma extinguishing by setting the distance between the upper electrode and the lower electrode wider than that during plasma processing. However, there is no disclosure or suggestion regarding charging damage caused by the timing of stopping the source output or the bias output at the time of plasma extinguishing not matching the timing of each stop switch. Moreover, in Patent Document 4, when shifting from the plasma processing step to the plasma extinguishing step, the interval between the upper electrode and the lower electrode is increased, so that the lower electrode is lowered and the plasma becomes unstable. For this reason, process performance may be adversely affected and foreign substances may increase.

  An object of the present invention is to provide a plasma processing apparatus capable of suppressing the occurrence of charging damage during plasma extinguishing without adversely affecting the process performance and without generating foreign matter.

  As one mode for achieving the above object, a vacuum plasma processing chamber, means for supplying a gas to the vacuum plasma processing chamber, a wafer is mounted, and a wafer is mounted to which a high frequency bias power source is applied and a high frequency power is applied. A placement electrode, an upper electrode opposed to the wafer placement electrode, a source power source for applying a high frequency power as plasma generating means to the upper electrode, and a high frequency voltage disposed at a peripheral portion of the wafer placement electrode. Applied to the wafer mounting electrode so that the difference between the self bias at the center of the wafer and the self bias at the outer periphery of the wafer can be reduced in extinguishing the plasma that is a transient plasma. And a control unit for controlling a ratio of the high frequency voltage applied to the conductive ring to the high frequency voltage to be applied. And Zuma processing apparatus.

  Further, a vacuum plasma processing chamber, means for supplying gas to the vacuum plasma processing chamber, a wafer mounting electrode on which a wafer is mounted and connected to a high frequency bias power source and high frequency power is applied, and the wafer mounting electrode An upper electrode facing the substrate, a magnetic field generating means for controlling the plasma distribution, a source power source for applying a high frequency power to the upper electrode as a plasma generating means, and a high frequency voltage applied to the periphery of the wafer mounting electrode. Applied to the wafer mounting electrode so that the difference between the self bias at the center of the wafer and the self bias at the outer periphery of the wafer can be reduced in extinguishing the plasma, which is a transient plasma, in a plasma processing apparatus having a conductive ring. The ratio of the high frequency voltage applied to the conductive ring with respect to the high frequency voltage to be applied is controlled and is different from the magnetic field strength during plasma processing. The plasma processing apparatus characterized by further comprising a control unit for controlling the that field strength.

  It is possible to provide a plasma processing apparatus capable of suppressing the occurrence of charging damage during plasma extinguishing without adversely affecting process performance and without generating foreign matter.

1 is a schematic view of a plasma etching apparatus according to Example 1. FIG. It is a graph which shows the plasma digestion sequence which concerns on Example 1, and a self-bias change, (a) is conventional, (b) is the case where the distribution ratio of the voltage of a conductive ring is changed at the time of plasma extinction, (c) is electroconductivity. This shows the case where the distribution ratio of the voltage of the magnetic ring is changed during the extinction of the plasma and the magnetic field setting is changed. It is a graph which shows the plasma digestion sequence which concerns on Example 2, and a self-bias change, (a) is conventional, (b) is the case where the distribution ratio of the voltage of an electroconductive ring is changed at the time of plasma extinction, (c) is electroconductivity. This shows the case where the distribution ratio of the voltage of the magnetic ring is changed during the extinction of the plasma and the magnetic field setting is changed. FIG. 5 shows a schematic view of a plasma etching apparatus according to a third embodiment. 4 is a plan view of a lower electrode and a conductive ring used in the plasma etching apparatus according to Examples 1 and 3. FIG.

  In a plasma processing apparatus, when extinguishing plasma, which is transient plasma, a conductive ring against a high-frequency voltage applied to the wafer mounting electrode so that the difference between the self-bias at the center of the wafer and the self-bias at the outer periphery of the wafer can be reduced. The ratio of the high-frequency voltage applied to is controlled. Thereby, charging damage can be reduced.

  Examples will be described in detail below.

  The first embodiment will be described below with reference to the drawings. FIG. 1 is a schematic view of a plasma etching apparatus according to this embodiment. The etching apparatus includes an upper antenna (electrode) 102 and a lower electrode 103 disposed opposite to each other in a plasma processing chamber 101 that can be evacuated to a vacuum, and a semiconductor product substrate (wafer) 104 is mounted on the lower electrode 103. Can be placed. A conductive ring 105 is provided around the lower electrode. The conductive ring 105 is disposed so as to surround the lower electrode 103 as shown in FIG. Further, a 100 to 300 MHz source high frequency power source 106 for generating plasma and a 2 to 5 MHz lower electrode high frequency power source 107 are installed. The power of the lower electrode high-frequency power source 107 is distributed to the conductive ring component 105 by the distribution circuit 108, and the distribution ratio can be controlled. Reference numeral 112 denotes a control unit that controls the distribution circuit 108 in accordance with the output state of the source high-frequency power source 106 and the output state of the lower electrode high-frequency power source 107.

  Further, a gas supply system 109 for supplying gas to the plasma processing chamber, an exhaust system 110 having a function of adjusting the exhaust speed, and a magnetic field generating coil 111 for controlling the plasma distribution are provided.

  Using this plasma etching apparatus, a process for etching holes in a high aspect ratio insulating film was performed. During the plasma treatment of this process, argon, oxygen, or fluorocarbon gas is introduced from the gas supply system 109, the pressure is adjusted to 0.5 Pa to 10 Pa, and a current of 2 to 10 A is applied to the magnetic field generating coil 111. The source output was 400 to 2000 W, the bias output was 3000 W to 8000 W, and the voltage ratio to the conductive ring component 105 was 0.6 to 0.9.

  The difference in self-bias in the wafer surface that causes charging damage during steady processing during the plasma processing was brought close to zero due to the structure of the lower electrode 103 (not shown), the structure of the plasma processing chamber components, the plasma processing conditions, and the like.

  The sequence at the time of plasma extinguishing of the etching apparatus according to the present embodiment will be described with reference to FIG. Plasma extinguishing (plasma OFF), which is a transient plasma, is when the plasma processing in a certain etching step is completed and the plasma is turned off and the process proceeds to the next etching step. In addition, both the source high-frequency power source and the lower electrode high-frequency power source are turned off when the plasma is extinguished, but they cannot be turned off at the same time due to the characteristics of the power sources. ). For this reason, charging damage occurs due to a self-bias difference in the wafer surface.

  2 shows the center of the wafer from the source output of the source high-frequency power source, the bias output of the lower electrode high-frequency power source, the voltage distribution ratio distributed to the conductive ring components, the current of the magnetic field generating coil, and the absolute value of the self-bias on the wafer periphery. The time change of the difference between the absolute value of the self-bias at the center of the wafer and the absolute value of the self-bias at the outer periphery of the wafer 104 shown by subtracting the absolute value of the self-bias in FIG. The vertical axis is normalized and displayed by the value at the time of etching plasma. The horizontal axis of the graph represents 0 when the etching plasma is finished and digestion is started. 2 (a), 2 (b), and 2 (c) respectively show (a) the conventional case, (b) when the voltage distribution ratio of the conductive ring is changed during plasma digestion, and (c) the conductive ring. In this case, the distribution ratio of the voltage is changed and the magnetic field setting is changed.

  First, at the steady time T1 of the plasma processing before starting the plasma digestion, the difference between the self bias at the center of the wafer 104 and the self bias at the outer periphery of the wafer was almost zero.

  In the sequence of this embodiment, the ratio of the high frequency bias output to the source output at the time T2 during plasma digestion is higher at the transient plasma time T2 than at the plasma processing time T1, and in the conventional method, as shown in FIG. The difference between the self-bias at the center of the wafer and the self-bias at the outer periphery of the wafer is increased to a level L1 that causes damage.

  On the other hand, when the ratio of the high frequency voltage applied to the conductive ring at T2 in the transient plasma is increased, the absolute value of the self-bias at the wafer center and the self at the wafer outer periphery as shown in FIG. Since the waveform of the difference from the absolute value of the bias shifted to the negative side and the absolute value of the difference changed in a smaller range, charging damage was reduced. When the source output is turned off before the high frequency bias output (the actual output is turned off, not the power switch is turned off) at the time of plasma extinguishing as in this embodiment, the control unit 112 supplies the conductive ring to the conductive ring. The distribution circuit 108 is controlled so that the voltage ratio becomes larger than that during plasma processing.

  The charging mechanism can be reduced by the following mechanism. Since the high frequency bias power grounds the side wall of the plasma processing chamber to some extent, the impedance between the wafer central portion and the wafer outer peripheral portion cannot be ignored relative to the impedance between the wafer outer peripheral portion and the plasma processing chamber side wall. In the normal case, the self-bias distribution in the wafer plane caused by the high-frequency bias power has a larger absolute value of the self-bias at the wafer outer periphery than at the wafer center.

  When the high-frequency bias power supply output ratio increases during transient plasma, the absolute value of the self-bias at the outer periphery of the wafer tends to be larger than that at the center of the wafer than during plasma processing. At this time, by increasing the high-frequency voltage ratio of the conductive ring and increasing the thickness of the sheath, the impedance between the conductive ring and the side wall of the plasma processing chamber can be increased. By reducing the electron current flowing into the wafer outer peripheral portion at the same rate, the difference between the self bias at the wafer central portion and the self bias at the wafer outer peripheral portion is reduced, so that charging damage can be reduced.

  Further, by increasing the voltage ratio of the conductive ring, decreasing the coil current, and changing the magnetic field to be smaller, as shown in FIG. The difference with the self-bias of the part was reduced, and the charging damage was reduced. Control of the coil current was also performed using the control unit 112.

  The charging mechanism can be reduced by the following mechanism. By controlling the magnetic field to become weaker during transient plasma, the plasma density at the center increases, and the absolute value of the self-bias at the wafer center increases, so that the wafer center and the wafer outer periphery are relatively The self-bias difference is reduced, and charging damage can be reduced.

  According to this embodiment, when the plasma output is extinguished, if the source output is turned off before the bias output, the voltage ratio of the conductive ring is increased as compared with the plasma processing, thereby adversely affecting the process performance. Thus, it is possible to provide a plasma processing apparatus capable of suppressing the occurrence of charging damage during plasma extinguishing without causing foreign matter and without generating foreign matter. Moreover, generation | occurrence | production of charging damage can be suppressed more by interrupting | blocking a magnetic field generation | occurrence | production coil current.

  A second embodiment will be described with reference to FIG. The configuration of the figure is the same as that of FIG. The plasma processing apparatus used is the same as that in the first embodiment. In the sequence of the present embodiment, since the high frequency bias output first decreases, the ratio of the high frequency bias output to the source output becomes lower than T1 during the plasma processing in T2 during the transient plasma during plasma digestion. As shown in FIG. 3A, the absolute value of the self-bias at the center of the wafer is larger than the self-bias at the periphery of the wafer, so that the difference between the self-bias at the center of the wafer and the self-bias at the periphery of the wafer is large. It became level L2 causing damage.

  On the other hand, when the ratio of the high-frequency voltage applied to the conductive ring component during T2 in the transient plasma is decreased, the absolute value of the self-bias at the wafer center and the wafer outer periphery as shown in FIG. The waveform of the difference from the absolute value of the self-bias shifts to the positive side so that the absolute value of the difference between the absolute value of the self-bias at the wafer center and the absolute value of the self-bias at the wafer outer periphery changes within a smaller range. As a result, charging damage has been reduced.

  If the high-frequency bias output is turned off before the source output during plasma extinction as in this embodiment (the actual output is turned off, not the power switch is turned off), the control unit 112 supplies the conductive ring to the conductive ring. The distribution circuit 108 is controlled so that the voltage ratio becomes smaller than that during plasma processing.

  The charging mechanism can be reduced by the following mechanism. When the source power source output ratio is increased, the plasma density distribution becomes deeper at the center than during plasma processing, and the absolute value of the self-bias at the center of the wafer tends to be larger than the absolute value of the self-bias at the outer periphery of the wafer. At this time, by reducing the high-frequency voltage ratio of the conductive ring and thinning the sheath, the impedance between the conductive ring and the side wall of the plasma processing chamber is lowered, and the electron current flowing into the wafer center and the wafer outer periphery By increasing the electron current flowing into the portion at the same rate, the difference between the self bias at the center of the wafer and the self bias at the outer periphery of the wafer can be reduced, and charging damage can be reduced.

  Further, by reducing the high-frequency voltage ratio of the conductive ring, increasing the coil current, and strengthening the magnetic field, as shown in FIG. The difference in charging was reduced and charging damage was reduced. Control of the coil current was also performed using the control unit 112.

  The charging damage could be reduced by expanding the plasma distribution from the center to the outer periphery by controlling the magnetic field to be stronger during transient plasma, so that the absolute value of the self-bias at the outer periphery of the wafer is at the center of the wafer. Charging damage can be reduced because the difference between the self-bias at the center of the wafer and the self-bias at the outer periphery of the wafer is reduced relative to the absolute value of the self-bias.

  According to the present embodiment, when the plasma output is extinguished, if the bias output is turned off before the source output, the voltage ratio of the conductive ring is made smaller than that in the plasma processing, thereby adversely affecting the process performance. Thus, it is possible to provide a plasma processing apparatus capable of suppressing the occurrence of charging damage during plasma extinguishing without causing foreign matter and without generating foreign matter. Further, by making the magnetic field generating coil current larger than that at the time of process processing, the generation of charging damage can be further suppressed.

  A third embodiment will be described with reference to FIG. The matters described in the first and second embodiments and not described in the present embodiment are the same as those described above.

  FIG. 4 is a schematic view of a plasma etching apparatus according to the third embodiment. This etching apparatus is provided with a high-frequency bias power source 401 that is applied to the conductive ring 105 separately from the high-frequency bias power source 107 for the wafer mounting electrode, and both the high-frequency bias power sources 107 and 401 are controlled in phase by the phase controller 402. did.

  Further, each high-frequency bias voltage was monitored, and the power of the power source was controlled by the control unit 403 so that the voltage of the conductive ring 105 was a constant ratio with respect to the voltage of the wafer mounting electrode (lower electrode) 103. The controller 403 can also control the current flowing through the magnetic field generating coil 111. In this etching apparatus, the high-frequency voltage ratio of the conductive ring 105 can be controlled in a wide range.

  Also in this embodiment, as shown in FIGS. 2B and 2C and FIGS. 3B and 3C, charging damage can be suppressed.

  According to the present embodiment, it is possible to provide a plasma processing apparatus capable of suppressing the occurrence of charging damage during plasma extinguishing without adversely affecting process performance and without generating foreign matter.

101: Plasma processing chamber, 102: Upper antenna, 103: Lower electrode, 104: Semiconductor substrate, 105: Conductive ring, 106: Source high frequency power source, 107: High frequency bias power source, 108: Distribution circuit, 109: Gas supply system, 110: exhaust system, 111: magnetic field generating coil, 112: control unit, 401: high frequency bias power source for conductive ring, 402: phase controller, 403: control unit.

Claims (8)

A vacuum plasma processing chamber; means for supplying gas to the vacuum plasma processing chamber; a wafer mounting electrode on which a wafer is mounted and connected to a high frequency bias power supply; and a high frequency power is applied to the wafer mounting electrode. In a plasma processing apparatus, comprising: an upper electrode, a source power source that applies high-frequency power to the upper electrode as plasma generating means, and a conductive ring that is disposed at a peripheral portion of the wafer mounting electrode and to which a high-frequency voltage is applied ,
When extinguishing the plasma, which is a transient plasma, applied to the conductive ring against the high frequency voltage applied to the wafer mounting electrode so that the difference between the self bias at the wafer center and the self bias at the wafer outer periphery can be reduced. A plasma processing apparatus further comprising a control unit for controlling a ratio of the high-frequency voltage. The plasma processing apparatus according to claim 1,
The control unit controls the ratio to be higher than the voltage ratio during plasma processing when the output of the source power source is lower than the output of the high frequency bias power source during plasma digestion. A plasma processing apparatus. The plasma processing apparatus according to claim 1,
The control unit controls to reduce the ratio from the voltage ratio at the time of plasma processing when the high-frequency bias power output becomes lower than the source power output during the plasma digestion. A plasma processing apparatus. A vacuum plasma processing chamber; means for supplying gas to the vacuum plasma processing chamber; a wafer mounting electrode on which a wafer is mounted and connected to a high frequency bias power supply; and a high frequency power is applied to the wafer mounting electrode. The upper electrode, the magnetic field generating means for controlling the plasma distribution, the source power source for applying high frequency power as the plasma generating means to the upper electrode, and the high frequency voltage are applied to the periphery of the wafer mounting electrode. In a plasma processing apparatus having a conductive ring,
When extinguishing plasma, which is a transient plasma, applied to the conductive ring against a high frequency voltage applied to the wafer mounting electrode so as to reduce the difference between the self bias at the wafer center and the self bias at the wafer outer periphery. A plasma processing apparatus further comprising a control unit that controls the ratio of the high-frequency voltage and controls the magnetic field intensity to be different from the magnetic field intensity during the plasma processing. The plasma processing apparatus according to claim 4, wherein
The magnetic field generating means is a magnetic field generating coil,
The control unit controls to reduce the current flowing through the magnetic field generating coil when plasma extinguishing, when the output of the source power source becomes lower than the output of the high frequency bias power source than during plasma processing. A plasma processing apparatus characterized by being a thing. The plasma processing apparatus according to claim 4, wherein
The magnetic field generating means is a magnetic field generating coil,
The control unit controls to increase the current flowing through the magnetic field generating coil when plasma extinguishing, when the output of the high-frequency bias power source becomes lower than the output of the source power source than during plasma processing. A plasma processing apparatus characterized by being a thing. The plasma processing apparatus according to claim 1,
The plasma processing apparatus is characterized in that the change of the ratio is performed using a high frequency bias power source connected to the wafer mounting electrode and a distribution circuit for distributing the voltage of the high frequency bias power source. The plasma processing apparatus according to claim 1.
A high-frequency bias power source connected to the wafer mounting electrode and a phase controller for controlling the phase of the high-frequency bias power source connected to the conductive ring; A plasma processing apparatus for controlling the temperature.

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