JP2002367965A - Equipment and method for plasma processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent dust raising when separating a wafer from a stage after the wafer for a semiconductor device is processed by a plasma processing equipment, and to reduce the damage by reducing stress applied to the wafer. SOLUTION: While a charge neutralizing plasma sequence is conducted after a plasma processing sequence, an evacuation means for a cooling gas which is supplied to the rear surface of the wafer is actuated, and a pressure gauge provided in the exhausting means is monitored. When the pressure reaches a predetermined level, a wafer lift mechanism is actuated to separate the wafer from the stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus and a plasma processing method, and more particularly to a process for separating a semiconductor wafer to be subjected to plasma processing from a stage after the plasma processing.

[0002]

2. Description of the Related Art As is well known, in a semiconductor manufacturing process using a plasma etching apparatus or the like, for example, a semiconductor wafer is transported, placed, and held at a predetermined position on a stage in the apparatus by plasma processing. And then separated and transported from the stage. At this time, the semiconductor wafer in the apparatus is attracted to the stage by the electrostatic chuck,
Is held. On the other hand, in a plasma etching apparatus or the like, a semiconductor wafer is maintained at a predetermined temperature in order to improve etching characteristics. For example, a large number of openings are formed in an electrostatic chuck, and the wafer back surface is statically connected with the openings through the openings. By filling a gas such as helium for cooling with the electric chuck, the wafer during the plasma processing is maintained uniformly and at a predetermined temperature. After the plasma processing of the wafer is performed in such a state, the wafer is lifted and separated from the electrostatic chuck by the pins of the wafer lift mechanism while monitoring the decrease in the cooling gas pressure on the back surface of the wafer.

Here, a series of process sequences including plasma processing of a wafer will be described with reference to FIG. In FIG. 6, time is shown on the horizontal axis, and pressure in the chamber is shown on the vertical axis. The wafer was transferred into the chamber, after placing the wafer on the electrostatic chuck of the stage, supplying a process gas for generating plasma illustrated in t ₁ within the chamber. After chamber pressure t ₂ is stable, start discharging and start a plasma process sequence. After the wafer has been adsorbed by the electrostatic chuck in the stage which a DC voltage is applied at t _3, the gas pressure in the wafer backside when the wafer back to supply cooling inert gas rises,
the pressure at t ₄ is stabilized. At this point, the wafer etching process is started. Then t ₅ in the etching plasma process sequence of completed wafer is completed. In the example of FIG. 6, and supplies into the chamber at t ₆ the different other gases and gas for the preceding plasma process sequence. That wafer neutralization plasma sequence clogging wafer desorption sequence is started from t _6. the voltage applied to the electrostatic chuck is released at t ₇ desorption wafer is started, the wafer by a pin of wafer lift mechanism at t ₈ is separated from the stage, the wafer is unloaded from the chamber at t ₉ Then, the plasma processing on the wafer is completed.
Thus as can be seen from FIG. 6, leaving t ₇ of the wafer gas pressure wafer backside at a higher point than the pressure in the chamber is started.

[0004]

In the plasma processing using the conventional apparatus as described above, when the wafer is lifted and separated from the electrostatic chuck of the stage, the pressure on the back surface of the wafer is higher than the pressure in the chamber. The cooling gas remaining between the back surface and the stage is ejected due to the pressure difference between the chamber and the pressure inside the chamber, causing the wafer to jump on the stage, causing a wafer misalignment or deposits at the wafer edge to fly into the chamber and adhere to the wafer. There has been a problem that the yield of the semiconductor device is reduced, and the throughput is reduced due to the cleanness of the chamber.
Further, when the wafer is lifted by the wrist pin, there is a problem that an excessive stress is generated on the wafer due to a residual suction force of the electrostatic chuck, and the wafer is damaged.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and there is provided a plasma processing method which does not cause wafer displacement or contaminant scattering due to ejection of a residual gas and does not damage the wafer when it is separated from the stage. It is an object of the present invention to provide an apparatus and a plasma processing method for a semiconductor wafer.

[0006]

In the plasma processing apparatus according to the present invention, the cooling gas exhaust means is operated during the execution of the discharge plasma sequence after the end of the plasma processing sequence, and the pressure gauge provided in the exhaust means is operated at a predetermined pressure. After reaching the pressure, the wafer lift mechanism is operated to separate the wafer from the stage.

Further, the same plasma generation gas as that used in the plasma processing sequence is used in the discharge plasma sequence.

Furthermore, a gas different from the plasma processing sequence is used in the static elimination plasma sequence.

Further, the wafer lift mechanism is operated after the gas analyzer detects a gas component different from the cooling gas.

In a plasma processing method for a semiconductor wafer, a gas for cooling is supplied to the back surface of the wafer to reduce the gas pressure during a series of static elimination plasma sequences after a series of plasma processing sequences. Then, a procedure of separating the wafer from the stage by the wafer lift mechanism is performed.

Also, in the plasma processing method, a step of separating the wafer from the stage by a wafer lift mechanism after the gas pressure on the back surface of the wafer becomes lower than the pressure in the chamber.

Also, in the plasma processing method, a fluctuation in gas pressure on the back surface of the wafer is monitored by a pressure gauge, and a signal indicating that the gas pressure has become lower than the pressure in the chamber is actuated to operate a wafer lift mechanism to move the wafer. This is a procedure for separating from the stage.

[0013] Further, in the same plasma processing method, a cooling gas is exhausted during the execution of the static elimination plasma sequence, and a current variation between the wafer and the stage is monitored by an ammeter provided on the stage. After a predetermined threshold is reached, the wafer is separated from the stage.

Also, in the plasma processing method, a step of monitoring a shift value of a voltage applied to the stage by a voltmeter and separating the wafer from the stage after reaching a predetermined threshold value is performed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a plasma processing apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of the present invention using a parallel plate type plasma processing apparatus. The present invention is not limited to a parallel plate type plasma processing apparatus, but may be applied to a plasma processing apparatus such as an ECR type or an inductive coupling type. Good. In the figure, reference numeral 1 denotes a wafer, 2 denotes a chamber, and 3 denotes a stage on which the wafer 1 is mounted. The stage includes an electrostatic chuck (not shown). Reference numeral 4 denotes a wafer lift mechanism, which has a function of placing and separating the wafer 1 on the stage 3 with lift pins. Reference numeral 5 denotes gas supply means for sending a cooling gas to the back surface of the wafer 1, and reference numeral 6 denotes an exhaust means for exhausting the cooling gas. 7 is a control means of this device,
8 is a gas pressure gauge, 9 is a lower electrode, 10 is an upper electrode, 11
Denotes a process gas introduction pipe for plasma processing and a discharge plasma sequence. 12 is a high frequency power supply, 13 is a DC power supply for electrostatic chuck, and 14 is a vacuum pump. Next, a plasma processing sequence and a subsequent static elimination plasma sequence will be described with reference to FIGS.

In FIG. 2, the time is the same as that shown in the conventional example.
The horizontal axis represents the interval, and the vertical axis represents the pressure in the chamber. Chan
The wafer 1 is transferred into the bus 2 and lifted by the wafer lift mechanism 4.
After being placed on the toppin, the lift pin descends and the
It is mounted on an electrostatic chuck provided on the die 3. next
Process for plasma treatment from process gas inlet pipe 11
Gas is introduced. This is referred to as t in FIG.₁Shown in Figure 1 and
2. In FIG. 2, the gas pressure in the chamber 2 rises and becomes stable.
Time t₂Thus, the control means 8 turns on the high frequency power supply 12
Then, a discharge starts between the lower electrodes 9 and 10 and a plasma process is performed.
Processing sequence is started and t₃DC power supply 1
3, a voltage is applied to the electrostatic chuck to hold the wafer 1 by suction.
Be held. The inert gas is supplied from the wafer cooling gas supply means 5.
For example, He gas is supplied to the back surface of the wafer and this He gas
Pressure of the back surface of the wafer 1 due to₄Semiconductor wafer
Etching on c is started. Then, the wafer 1
The zuma processing sequence is t ₅And the processing shown in FIG.
In the first embodiment, the process for the plasma processing sequence is performed.
A gas different from the gas is supplied from the introduction pipe 11 and
The pressure in the chamber slightly increases, t₆More static eliminating plasma sequence
Is started. In addition,
Elimination of the same gas as the process gas for the zuma treatment sequence
When used in a plasma sequence, t₅Plasma of
When the processing sequence is completed,
Start time t₆Is the same time. So in Figure 2
T ₅And t₆Are on the same time axis. And
Plasma processing sequence without increasing chamber pressure
The pressure is kept the same as the pressure. Said t₆Neutralization started at
During the execution of the plasma sequence, t shown in FIG.₇At the time
The exhaust of the cooling He gas on the back surface of the wafer 1 is supplied to the exhaust unit 6.
So started, t ₈Gas exhaust on the back of the wafer is completed
I do. Thus, t₈Back pressure at wafer
Is lower than the pressure in the chamber. This is exhaust means
A signal is output from the pressure gauge 8 provided at
By force₉Ends the plasma sequence for static elimination,
The discharge between the electrodes 9 and 10 stops. The signal is continued
On the stage 3 by the operation of the wafer lift mechanism 4
Of the wafer 1 is performed. Then t₁₀In chamber
Evacuation of the residual gas in 1 is completed. Thus, a series of
After the end of the plasma processing sequence, the wafer 1 is subjected to a charge removing process.
A series of static elimination plasma sequences to be processed
Operated and controlled by the static elimination plasma sequence
Cooling the wafer supplied to the back side of the wafer 1 during the operation
He gas is exhausted to lower the gas pressure on the back surface of the wafer 1
When the pressure becomes lower than the pressure value of the chamber 2
Signal at the point and operate the wafer lift mechanism to
Since stage 1 is separated from stage 3, c
Wafer edge caused by cooling gas pressure remaining on the backside of the wafer
Deposits soar into chamber 2 and wafers
And the yield of semiconductor devices is improved. What
The comparison between the pressure on the backside of the wafer and the pressure in the chamber is vacuum
The detection signal may be output by a meter, etc.
Pressure fluctuation on the back surface of the wafer 1
The wafer 1 is detached from the stage 3
Can be reliably detected. Therefore, as in the past,
The wafer is lifted with the suction force remaining on the page 3
Excessive stress due to the lift pins of the eha lift mechanism 4
No longer acts on c1, preventing breakage of wafer 1.
The yield is improved. Note that the plasma processing sequence
The gas for the static elimination plasma sequence different from the gas used is
Plasma can be generated with an inert gas such as argon or chlorine gas.
Any gas that can be used is acceptable.

Embodiment 2 FIG. FIG. 3 shows a plasma processing apparatus according to the second embodiment. The device of the second embodiment is the same as the device shown in FIG. 1 except that the gas analyzer 15 is provided in the cooling gas exhaust means shown in FIG. 1 of the first embodiment. The processing sequence is the same. During the execution of the static elimination plasma sequence of FIG. 2 described in the first embodiment, the wafer cooling gas is exhausted under the control of the control means 8,
Gas components entering the back surface of the wafer 1 are monitored by this gas analyzer, for example, a quadrupole mass spectrometer 15, and when other gas components enter the back surface of the wafer 1, the chamber 2 is detected.
After confirming that the gas pressure on the back surface of the wafer is lower than the internal pressure, the wafer 1 is separated from the stage 3 by the wafer lift mechanism 4. Thus, by detecting and monitoring the variation of the gas species in the chamber 2 that enters the back surface of the wafer 1, that is, by entering the different gas,
Can be detected as physically detached from the stage 3, so that unreasonable stress application to the wafer 1 by the lift pins can be prevented. Inward movement and wafer misalignment are prevented, and the yield of semiconductor devices is improved.

Embodiment 3 FIG. 4 shows a third embodiment. The processing sequence is the same as in FIG. FIG. 4 is a schematic diagram showing the arrangement of the ammeter 16 provided on the stage 3a. The stage 3a has an electrically divided structure, and the stage 3a is
By monitoring the current value leaking from the wafer, the attenuation of the electrostatic holding force of the wafer 1 is detected by performing the discharge plasma sequence, and thereafter, the wafer 1 is separated from the stage 3a. That is, the wafer 1 is moved from the stage 3a to the wafer 1 after the leakage current value reaches a predetermined threshold value or less.
To operate the wafer lift mechanism to separate the wafers. The current threshold value is determined by the intrinsic characteristics of the plasma processing apparatus, the dimensions of the wafer 1, the device structure, the plasma processing sequence, the static elimination plasma sequence, and other conditions. If the static elimination plasma sequence is performed for a predetermined time or more, a reverse voltage is generated in the electrostatic chuck and the holding force may increase again. Therefore, the monitoring of the current fluctuation and the setting of the threshold value are carefully performed. Will be
By adopting such a method, when the wafer 1 is separated from the stage 3a, no excessive stress is applied, and the damage of the wafer 1 can be prevented.

Embodiment 4 FIG. 5 shows a fourth embodiment. FIG. 5 shows a voltmeter 17 provided in place of the ammeter 16 of the third embodiment. After the voltage applied to the stage 3a having an electrostatic chuck reaches a predetermined threshold value or less, the wafer 1 is separated from the stage 3a. The threshold value of this voltage is determined by various conditions as described above. As described above, there is an effect that the damage of the wafer can be prevented.

[0020]

Since the present invention employs the above-described configuration and processing method, the following effects can be obtained.

During the neutralization plasma sequence after the plasma processing sequence is completed, the cooling gas exhaust means on the back surface of the wafer is operated, and after the pressure gauge provided on the exhaust means reaches a predetermined pressure, the wafer lift mechanism is operated. Since the wafer is separated from the stage, the deposition on the wafer edge due to the gas pressure remaining on the back surface of the wafer does not fly up into the chamber and the wafer is not displaced, thereby preventing contamination of the semiconductor device and improving the yield. This provides an excellent effect that a plasma processing apparatus with improved throughput can be provided.

Further, since the same gas is used for the plasma processing sequence and the static elimination plasma sequence, there is no pressure fluctuation in the chamber, and the throughput of the wafer processing is improved.

Further, the cooling gas exhaust means is operated during the execution of the discharge plasma sequence, and the gas analyzer provided in the exhaust means detects a gas component different from the cooling gas,
Since the wafer lift mechanism is operated after the wafer is detached from the stage, the wafer can be prevented from being broken without applying excessive stress to the wafer, and a plasma processing apparatus can be provided in which the deposited material does not fly up.

Further, there is provided a plasma processing method,
A series of plasma processing sequences and a series of static elimination plasma sequences for subjecting the wafer to static elimination processing after the completion of the sequence are provided. During the static elimination plasma sequence, the cooling gas supplied to the back surface of the wafer is exhausted to reduce the gas pressure. Since the procedure of operating the wafer lift mechanism after the lowering to separate the wafer from the stage is performed, it is possible to provide a plasma processing method with a high yield of the semiconductor device in which the deposit is not soared and with an improved throughput.

Further, since the wafer is separated from the stage after the gas pressure on the back surface of the wafer becomes lower than the pressure in the chamber, the same effect is obtained.

Further, the fluctuation of the gas pressure on the back surface of the wafer is monitored by a pressure gauge, and a signal indicating that the pressure on the back surface of the wafer is lower than the pressure in the chamber or a gas component entering the back surface of the wafer is subjected to gas analysis. After monitoring by the apparatus and confirming that the gas pressure on the back surface of the wafer has become lower than the pressure in the chamber, a procedure of separating the wafer from the stage is performed, so that the same effect is obtained.

Also, the current or voltage flowing between the stages is monitored by an ammeter or a voltmeter provided on the stage,
Since the procedure of separating the wafer from the stage after reaching the predetermined threshold value is performed, an excessive stress is not applied to the wafer, and the effect of preventing damage is exerted.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a sequence of a plasma processing step according to the first to fourth embodiments of the present invention.

FIG. 3 is a configuration diagram of a plasma processing apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an arrangement of an ammeter provided on a stage according to a third embodiment of the present invention.

FIG. 5 is a diagram showing an arrangement of a voltmeter provided on a stage according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a sequence of a conventional plasma processing step.

[Explanation of symbols]

1 wafer, 2 chambers, 3, 3a stage, 4
Wafer lift mechanism, cooling gas supply means, 6 gas exhaust means, 7 control means, 8 pressure gauge, 9 lower electrode,
10 upper electrode, 11 process gas introduction pipe, 12 high frequency power supply, 13 DC power supply, 14 pump, 15 gas analyzer, 16 ammeter, 17 voltmeter.

Continued on front page F term (reference) 4K030 CA04 CA12 EA03 FA02 FA03 FA04 GA02 GA12 KA26 KA39 KA41 5F004 AA14 BA04 BA14 BB20 BB22 BB25 BC04 BC06 CA01 CA02 DA22

Claims (14)

[Claims] 1. A chamber having a plasma generating gas introducing means for performing plasma processing on a semiconductor wafer, a stage provided in the chamber and having an electrostatic chuck for holding the wafer, and the wafer mounted on the stage. In a plasma processing apparatus comprising: a wafer lift mechanism having a function of mounting and separating; a gas supply unit for supplying a cooling gas to the back surface of the wafer; a gas exhaust unit for exhausting the gas; and a control unit. The means operates the cooling gas exhaust means during the static elimination plasma sequence after the end of the plasma processing sequence, monitors the pressure of a pressure gauge provided in the cooling gas exhaust means, and after reaching a predetermined pressure, A plasma processing apparatus for operating a wafer lift mechanism to separate the wafer from the stage. Place. 2. The plasma processing apparatus according to claim 1, wherein the discharge plasma sequence is set and controlled so that the same plasma generation gas as in the plasma processing sequence is used. 3. The plasma processing apparatus according to claim 1, wherein the discharge plasma sequence is set and controlled so that a gas different from the plasma generation gas used in the plasma processing sequence is used. 4. The control means activates the cooling gas exhaust means during the discharge plasma sequence after the end of the plasma processing sequence, and the gas analyzer provided in the cooling gas exhaust means controls the cooling gas exhaust means. 2. The plasma processing apparatus according to claim 1, wherein the wafer lift mechanism is operated after detecting a different gas component. 5. A plasma processing method for performing plasma processing on a semiconductor wafer mounted on a stage provided in a chamber and provided with an electrostatic chuck, comprising: a series of plasma processing sequences; A series of static elimination plasma sequences for performing static elimination processing on the wafer after the sequence is completed, and evacuating a wafer cooling gas supplied to the back surface of the wafer during the static elimination plasma sequence, thereby forming a gas on the rear surface of the wafer. And a step of separating the wafer from the stage by a wafer lift mechanism after the pressure is reduced. 6. The plasma processing method according to claim 5, wherein the same processing gas used in the plasma processing sequence is used as the processing gas used in the discharge plasma sequence. 7. The plasma processing method according to claim 5, wherein the processing gas used in the charge eliminating plasma sequence is different from the processing gas used in the plasma processing sequence. 8. The plasma processing method according to claim 7, wherein the processing gas used in the static elimination plasma sequence is an inert gas. 9. The plasma processing method according to claim 5, wherein a step of separating the wafer from the stage by a wafer lift mechanism after the gas pressure on the back surface of the wafer becomes lower than the pressure in the chamber. 10. A fluctuation in gas pressure on the back surface of the wafer is monitored by a pressure gauge, and an output signal indicating that the gas pressure on the back surface of the wafer is lower than the pressure in the chamber is actuated by a wafer lift mechanism to separate the wafer from the stage. 6. The plasma processing method according to claim 5, wherein steps are taken. 11. A gas for cooling a wafer supplied to a back surface of a wafer is exhausted, and a gas component entering the back surface of the wafer is monitored by a gas analyzer. 6. The plasma processing method according to claim 5, wherein a step of confirming that the temperature has dropped and separating the wafer from the stage by a wafer lift mechanism is performed. 12. The plasma processing method according to claim 11, wherein the gas analyzer is a quadrupole mass spectrometer. 13. A wafer cooling gas supplied to a back surface of a wafer is evacuated during execution of a discharge plasma sequence, and a current variation between the wafer and the stage is monitored by an ammeter provided on a stage. 6. The plasma processing method according to claim 5, wherein after the current value reaches a predetermined threshold, a step of separating the wafer from the stage by a wafer lift mechanism is performed. 14. A gas for cooling a wafer supplied to the back surface of a wafer is evacuated during the execution of the charge eliminating plasma sequence, and a shift value of a voltage applied to the stage is monitored by a voltmeter provided on the stage. 6. The plasma processing method according to claim 5, wherein a step of separating the wafer from a stage by a wafer lift mechanism after the voltage shift value reaches a predetermined threshold value.