JP3202877B2 - Plasma ashing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma ashing apparatus.

[0002]

2. Description of the Related Art Generally, in the process of manufacturing a semiconductor device, a process of forming a film on a semiconductor wafer and etching the film into a predetermined pattern by a fine processing technique is repeatedly performed. When performing the etching process, the wafer surface is etched in a pattern shape using the cured resist film as a mask, and then the ashing process is performed to remove an unnecessary resist film. Has become.

Here, a conventional plasma ashing apparatus will be described with reference to FIG. As shown in the figure, the ashing apparatus 2 has a bell jar-shaped processing container 4, and a pair of upper and lower electrodes 6A and 6B are provided outside the upper stage. A high-frequency power supply 10 oscillating at, for example, 13.56 MHz is connected to the upper electrode 6A via a matching circuit 8.

A mounting table 12 for adsorbing and holding the semiconductor wafer W by, for example, a vacuum chuck or the like is arranged inside the processing container 4. The mounting table 12 has a heater 16 controlled by a temperature control unit 14 and a cooling unit 12. A cooling water pipe 20 whose coolant flow rate is controlled by the section 18 is built in. The mounting table 12 can be moved up and down by elevating means 22. A gas supply system 28 having a mass flow controller 24 and a processing gas supply source 26 is connected to an upper portion of the processing container 4.

When ashing is performed on a wafer etched using a resist film as a mask using the above-described apparatus, the etched wafer is placed on a mounting table 12 and heated to about 300 ° C. by a heater 16. By maintaining a reduced pressure atmosphere while supplying oxygen into the processing vessel 4 and applying a high frequency voltage to the upper electrode 6A, plasma is generated between the electrodes 6A and 6B, and a part of the oxygen gas is activated. Then, it becomes ozone, and the ozone-containing gas flows down in the container toward the wafer surface.

The ozone that has flowed down is heated by the atmosphere around the wafer and decomposed, generating a large amount of oxygen atom radicals. Then, the radicals react with the resist film on the wafer surface to vaporize the resist film, and the resist is ashed. In addition to the above-described apparatus example, a so-called parallel-plate-type ashing apparatus in which a flat upper electrode and a lower electrode are arranged in parallel in a processing vessel so as to face each other and plasma is generated therebetween. Is also known.

[0007]

However, in the above-mentioned bell jar type ashing apparatus and parallel plate type ashing apparatus, plasma having a very high density cannot be formed, and therefore, the amount of generated radicals is low. Is not so many. Therefore, it takes a relatively long time to ashing a resist film having a predetermined thickness without an extremely high ashing rate, and there is a problem that the ashing efficiency cannot be sufficiently increased.

The present invention focuses on the above problems,
It was created to solve this effectively. An object of the present invention is to provide a plasma ashing apparatus in which the plasma density is increased by adopting an inductive coupling method for generating plasma.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a plasma processing method for ashing a resist film formed on a surface of an object to be processed mounted on a mounting table of a processing container. In the ashing apparatus, an antenna member connected to a high-frequency power supply is provided at a position facing the mounting table to supply the generated energy of the plasma, and the antenna member has a high power supplied thereto.
A modulation unit for modulating a frequency voltage is connected .

[0010]

According to the present invention, a radio wave is generated by applying a high-frequency voltage to an antenna member provided spirally on the ceiling of a processing vessel, and a plasma discharge is excited by the radio wave. Process gas is activated,
Many atomic radicals are generated. The density of the plasma at this time is higher than that of the conventional plasma generation method described above, so that the amount of active species generated by the plasma discharge excitation is considerably increased, and it is possible to increase the ashing rate. Become.

In addition , since the high-frequency voltage applied to the antenna member is modulated by, for example, on-off control or by increasing or decreasing the interval of a predetermined length to suppress the supply energy, excessive supply of ions is prevented . At the same time, generation can be suppressed and the amount of active species can be increased accordingly.

Further, by disposing a grid between the antenna member and the mounting table, it is possible to trap ions which may damage the surface of the object to be processed by the grid. In particular, by applying a constant bias voltage to the grid or synchronized with the modulation of the high-frequency voltage applied to the antenna member, ions passing through the grid toward the surface of the object to be processed can be pulled back, further damaging the grid. Can be suppressed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the plasma ashing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of the plasma ashing apparatus of the present invention, FIG. 2 is a schematic configuration view showing a cluster apparatus provided with the ashing apparatus shown in FIG. 1, FIG. 3 is a plan view showing an antenna member, and FIG. FIG. 5 is a cross-sectional view of an object to be processed for explaining an operation from a process to an ashing process. FIG. 5 is a diagram showing a mode of modulating a high-frequency voltage applied to an antenna member. FIG.

First, a cluster device provided with the device of the present invention will be described with reference to FIG.
A common transfer chamber 32 having a substantially rectangular shape capable of being evacuated is provided. One side surface of the common transfer chamber 32 has a well-known, for example, parallel plate type for etching a semiconductor wafer as an object to be processed. Is connected via a gate valve G1 which can be opened and closed. Further, the other two side surfaces of the common transfer chamber 32 are provided with first and second plasma ashing apparatuses 36A according to the present invention for performing an ashing process including, for example, light etching, on the semiconductor wafer after the etching process. 3
6B are connected via gate valves G2 and G3, respectively.

Further, on the remaining side surface of the common transfer chamber 32,
The first and second cassette chambers 38A and 38B are connected via gate valves G4 and G5, respectively, and the wafers are loaded and unloaded to and from the cluster device 30 outside the cassette chambers 38A and 38B. Gate valves G6 and G7 that are opened and closed at the time are provided, respectively. Each of the cassette chambers 38A and 38B is capable of being evacuated. For example, the first cassette chamber 38A stores a cassette C containing an unprocessed semiconductor wafer W, and the second cassette chamber 38B stores a processed semiconductor wafer. The cassette C containing W is stored.

At the center of the common transfer chamber 32, a multi-joint arm mechanism 40 which can be extended and contracted and turned is installed, and a wafer W can be held at the tip of this arm 40A. Therefore, an unprocessed wafer can be taken out of the first cassette chamber 38A by the arm mechanism 40 and loaded in the order of the plasma etching apparatus 34 and either one of the ashing apparatuses 36A or 36B to sequentially perform the corresponding processing. ing.

The reason why two ashing devices are provided for one etching device is that the time required for ashing is longer than the time required for etching, so that the ashing device is used in order to increase the overall processing efficiency. Many were provided.

Next, the ashing device will be described with reference to FIG. Two ashing devices 36A, 3
6B is configured in exactly the same way, and here, for example, the first ashing device 36A will be described as an example. As shown in FIG. 1, this plasma ashing apparatus 36A
It has a processing container 42 made of, for example, aluminum and formed into a bottomed shape with an open ceiling. A mounting table 44 made of, for example, aluminum as a lower electrode on which the semiconductor wafer W is mounted is mounted in the processing container 42.
It is provided above. An electrostatic chuck 52 connected to, for example, a high-voltage DC source 48 via an open / close switch 50 is provided on a mounting surface, which is an upper surface of the mounting table 44, so that the wafer is attracted and held by Coulomb force. ing.

A heating means such as a ceramic heater 54 is embedded in the mounting table 44, and a heating power supply 56 is connected to the heater via an open / close switch 58. The mounting table 44 and the processing container 42
Are both grounded to zero potential. The processing container 4
An exhaust system 60 provided with a vacuum pump (not shown) is connected to the bottom of the common transfer chamber 3.
The gate valve G2 which allows communication and closure between the gate valve G2 and the gate valve G2
Is provided.

A gas introduction nozzle 62 for introducing a processing gas is provided through the side wall of the processing container 42, and a gas passage 64 is connected to the nozzle 62. In this embodiment, not only the ashing process of the normal resist film, but also the so-called light etching for simultaneously etching the damaged layer of the wafer surface damaged by the previous process is performed. First, an etching gas such as CF ₄ or CFH ₃ is slightly mixed. For this purpose, the gas passage 64 is connected to the mass flow controller 6.
6A, an oxygen supply source 72 connected to an oxygen source 70 with an on-off valve 68A
B, an ashing gas source 7 with an on-off valve 68B
4 is connected to an ashing gas supply system 76. As the ashing gas, for example, CF ₄ gas or the like is used for light etching.

On the other hand, a ceiling plate 78 made of an insulating material that can transmit electromagnetic waves, for example, quartz, is confidentially provided through a sealing member 80 such as an O-ring at the opening of the ceiling of the processing container 42. I have. The thickness of the ceiling plate 78 is large enough to withstand the vacuum pressure in the processing container 42.
It is set to about 5 mm.

On the top surface of the quartz ceiling plate 78, FIG.
As shown in FIG. 2, a conductor, for example, an antenna member 82 made of copper, which is spirally wound, for example, two to three times over substantially the entire surface, is provided. A high-frequency power supply system 86 provided with a high-frequency power supply 84 of 13.56 MHz, for example, is connected between the center end and the outer peripheral end of the antenna member 82. A matching circuit 88 for improving the application efficiency and a modulation unit 90 for modulating a high-frequency power supplied to the antenna member 82 into a predetermined waveform are interposed.

Therefore, the modulation section 90 is provided on the antenna member 82.
A high-frequency voltage having a predetermined waveform modulated by the above can be applied, and an electromagnetic wave generated by this passes through the quartz ceiling plate 78 to reach the processing space S, where the processing gas is excited to generate plasma. It will give birth. Here, the shape of the antenna member 82 is not limited to a spiral shape having two or three turns, and may be set to a ring shape having one turn or a spiral shape having four or more turns. Not only a circular shape as shown in the example, but also a rectangular shape may be set. Further, in the mode of the high-frequency voltage modulation in the modulation section 90, for example, as described later, for example, the modulation can be performed such that the on / off operation is repeated or the intensity of the voltage is repeated (see FIG. 5).

The entire antenna member 82 is covered by a mesh-shaped shield 92 made of, for example, a wire mesh in order to prevent leakage of electromagnetic waves to the outside, and the shield 92 is grounded. The ceiling plate 78 and the mounting table 44
A grid 94 made of, for example, a mesh-shaped wire mesh having a large number of slits 102 is installed over substantially the entire upper surface of the mounting table 44. The grid 94 has, for example, a variable DC power supply 96 and a modulation A bias means 100 comprising a circuit 98 is connected.

The grid member 94 is grounded or a predetermined bias voltage is applied to the antenna member 82.
Intermittently in synchronization with the supply of a high-frequency voltage to the semiconductor device, ions that cause wafer damage can be captured and trapped. In order to achieve the synchronization, the modulation circuit 98 of the bias unit 100 and the modulation unit 90 of the high-frequency power supply system 86 are controlled by a control unit 103 including, for example, a microcomputer.

Next, the operation of the present embodiment configured as described above will be described. In FIG. 2, first, if the inside of the first cassette chamber 38A for storing the unprocessed wafer is evacuated, the gate valve G4 that separates the inside of the first cassette chamber 38A from the inside of the common transfer chamber 32 that has been evacuated in advance is opened. By expanding and contracting the articulated arm mechanism 40 in the common transfer chamber 32, an unprocessed wafer in the first cassette chamber 38A is held at the end of the arm. Next, a gate valve G for partitioning between the common transfer chamber 32 and the plasma etching apparatus 34.
1 is opened, the unprocessed wafer at the tip of the arm is loaded into the etching device 34, and plasma etching is performed on the wafer. In this etching, for example, CHF ₃ or CF
_A predetermined amount of an etching gas such as ₄ is supplied as an inert gas such as a He gas or an Ar gas as a carrier gas, and a high frequency power of 13.56 MHz, for example, is applied to the upper and lower electrodes to perform normal plasma etching.

The state of the wafer W at this time is as follows. The unprocessed wafer is, for example, as shown in FIG.
An SiO ₂ film 104 is formed on an i-wafer, and a patterned resist film 106 is formed on this film. When the etching process is performed using the resist film 106 as a mask as described above, portions of the SiO ₂ film 104 that are not covered by the resist film 106 are shaved, as shown in FIG. In this case, generally, the silicon surface 108 exposed due to the anisotropic etching tends to be relatively damaged. Therefore, in the next ashing step, not only the ashing of the resist film,
Light etching for slightly shaving the damaged surface 108 is also performed at the same time.

First, when the etching process is completed in the etching apparatus 34 as described above, the wafer subjected to the etching process is unloaded through the gate valve G1 that has been opened, and then the first or second wafer is processed. Out of the plasma ashing devices 36A and 36B, for example, the empty ashing device such as 36A, and simultaneously performs the ashing and the light etching as described above. On the other hand, during this time, the next unprocessed wafer is
Is etched in the same manner as described above, and the wafer after the completion of the etching is loaded into the other ashing device 36B to perform ashing and light etching simultaneously. Since the time required for the etching process is relatively shorter than the time required for the ashing, the wafer processed by the etching device 34 is distributed to the first and second ashing devices 36A and 36B and loaded. Is done. Then, the processed wafer after the ashing and the light etching is completed is stored by the arm mechanism 40 in the second cassette chamber 38B for storing the processed wafer.

Here, a case where ashing and light etching are performed simultaneously will be described. An etched wafer W placed on the surface of the mounting table 44 in an ashing device, for example, 36A, is strongly attracted and held by the electrostatic chuck 52 by Coulomb force.
While supplying a predetermined amount of oxygen from the ashing gas supply system 76 and a predetermined amount of ashing gas, for example, CF ₄ or CFH _{3, the} inside of the processing container 42 is processed at a process pressure, for example, within a range of several tens mTorr to about 2 Torr. Maintain pressure.

By energizing the ceramic heater 54, the temperature of the wafer is maintained at a process temperature equal to or higher than room temperature, for example, about 300 ° C. At the same time, when high-frequency power is applied to the antenna member 80 provided on the upper surface of the quartz ceiling portion 78, the electromagnetic waves transmitted through the ceiling plate 78 are processed in the processing space S.
The gas staying in the chamber is excited by its induction operation to be turned into plasma. By the plasma discharge excitation, the gas elements are activated to become ozone and fluorine active species, and the ozone is mainly consumed by ashing which reacts with the resist film 106 to vaporize it, and the active species of the fluorine atoms cause damage. It will be consumed when soft etching the received silicon surface 108. FIG. 4C shows a cross section of the wafer when ashing and soft etching are completed.

Here, since the inductive coupling method using the antenna member 82 is employed for plasma generation, the density of generated plasma can be increased as compared with the conventional parallel plate type, and therefore, the As a result, the amount of the active species is increased, and the ashing efficiency can be greatly improved. Further, the gas in the processing space S is ionized by the generated dense plasma and ions are also generated. However, most of the ions are trapped and eliminated by the grid 34 provided above the mounting table 44. The possibility of colliding with and damaging the wafer surface can be greatly reduced. At the same time, since the mounting table 44 is grounded and is at zero potential, ions are not drawn into the wafer side, and the occurrence of wafer damage can be greatly suppressed.

At the time of ashing, the antenna member 8
The high-frequency voltage applied to FIG.
As shown in (B), it is preferable that the modulation is performed by the modulation unit 90. In the case of the modulation waveform shown in FIG. 5A, the supply of power is stopped for a predetermined time T2, for example, several tens to several hundreds of seconds after applying high-frequency power for a predetermined time T1, for example, several tens of microseconds. That is, on and off are repeatedly performed. In the case of the waveform shown in FIG. 5B, the supply of the high-frequency power is not completely stopped when the power is turned off in FIG. 5A, but a small amount of power is supplied during this time. It is modulated to be attached. The following effects are produced by turning on / off the power or increasing or decreasing the power.

That is, if a large amount of high-frequency power is continuously supplied without modulation, the electron temperature becomes excessively high and dissociation into ions is accelerated, but ashing may damage the wafer. Since there is no need for mild active species, there is a need for a mild active species. By providing the off-time T2 or a time when power is weak as described above, the plasma is cooled to prevent excessive generation of ions, and at the same time, a large amount of active species is generated. As a result, the ashing efficiency can be further improved. On-time T1 and off-time T of high frequency power
The relationship with 2 is not limited to the above numerical examples as long as the off-time T2 is sufficient to cool the plasma.

The grid 94 may be continuously grounded during the ashing process to make it zero potential.
Alternatively, the bias voltage of the grid 94 may be changed in synchronization with the modulation of the high-frequency voltage applied to the antenna member 82 as shown in FIG. FIG. 6A shows an example of the modulation of the high-frequency voltage applied to the antenna member 82, and FIGS. 6B and 6C show examples of the modulation of the bias voltage, respectively. In the case shown in FIG. 6B, during the ON period T1 during which power is supplied to the antenna member 82, the grid 94 is set to zero potential, and during the OFF period T2 when no power is supplied to the antenna member, This shows a state where the grid 94 is set to a negative potential of, for example, minus several tens of volts. In the case shown in FIG. 6C, the modulation is substantially the same as the modulation shown in FIG. 6B. However, only when the supply of power to the antenna member 82 is stopped, a delay is applied for a short time Δt. The difference is that the potential of the grid 94 is set to a negative potential.

As described above, by setting the grid to a negative potential when the power is not supplied to the antenna member 82 or when the power is supplied only slightly, the grid 9
4, the positive ions approaching the wafer W side can be pulled back to the grid 94 side and trapped. Therefore, it is possible to prevent the ions from colliding with the wafer surface, thereby further increasing the occurrence of wafer damage. It becomes possible to suppress. The modulation of the bias potential of the grid is not limited to the above, and may be modulated so as to set the grid to a positive potential, for example, in synchronization with the modulation of the supply voltage to the antenna member. Can be taken.

In the above-described embodiment, a case has been described in which ashing and light etching are simultaneously performed in order to form, for example, a gate with little damage to the silicon surface. However, the present invention is not limited to this. It is needless to say that the present invention can be applied to the case where the above method is implemented.

In the above embodiment, the case where the antenna member 82 is disposed outside the processing container 42 has been described. However, the present invention is not limited to this. For example, the antenna member 82 may be covered with an insulating material while the inner surface of the ceiling plate 78 is covered. It may be provided on the side. Further, as a plasma generation method, a combination of an inductive coupling type and a helicon resonance method, a combination of an inductive coupling type and a helical resonance method, an inductive coupling type and an ECR (ECR)
Electron Cyclotron Resonan
ce) A combination of the methods can also be used. Further, the object to be processed is not limited to a semiconductor wafer, and any object to be subjected to plasma ashing, such as an LCD substrate, can be applied. Further, the ashing gas is not limited to those described above, but may be SiH ₄ ,
AsH ₃ , PH ₃ , B ₂ H ₆ , CF ₄ , SF ₆ , N ₂ O
Can be used to convert these into plasma, for example, S
The remaining resist formed on the iO ₂ film can be ashed.

[0038]

As described above, according to the plasma ashing apparatus of the present invention, the following excellent effects can be obtained. Since the ashing plasma is generated by the induction action of the electromagnetic wave radiated from the antenna member, it is possible to generate a plasma having a higher density than, for example, the conventional parallel plate type,
Ashing efficiency can be greatly improved. In addition, since the high-frequency voltage supplied to the antenna member is modulated, it is possible to generate a large amount of active species that contribute to ashing while suppressing the generation of ions that damage the object to be processed. Ashing efficiency can be further improved while suppressing occurrence. Furthermore, by providing a grid between the antenna member and the mounting table,
Ions that damage the object can be trapped, and the occurrence of damage can be suppressed while maintaining high ashing efficiency. Furthermore, to the grid, by supplying in synchronism with the applied high frequency voltage to the antenna member by changing the bias voltage, it is possible to further enhance the trapping efficiency of ions, Ru can suppress the occurrence of damage.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a plasma ashing apparatus of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a cluster device including the ashing device illustrated in FIG. 1;

FIG. 3 is a plan view showing an antenna member.

FIG. 4 is a cross-sectional view of an object to be processed for explaining an operation from an etching step to an ashing step.

FIG. 5 is a diagram showing a mode of modulation of a high-frequency voltage applied to an antenna member.

FIG. 6 is a diagram illustrating a relationship between an applied voltage of an antenna member and an applied voltage of a grid.

FIG. 7 is a sectional view showing an example of a conventional plasma ashing apparatus.

DESCRIPTION OF SYMBOLS 30 Cluster device 32 Common transfer chamber 34 Plasma etching device 36A First plasma ashing device 36B Second plasma ashing device 40 Articulated arm mechanism 42 Processing vessel 44 Mounting table 48 High-voltage DC source 54 Ceramic heater 70 Oxygen Source 72 Oxygen supply system 74 Ashing gas source 76 Ashing gas supply system 78 Ceiling plate 82 Antenna member 84 High frequency power supply 90 Modulation section 94 Grid 98 Modulation circuit 100 Biasing means 104 SiO ₂ film 106 Resist film W Semiconductor wafer (workpiece)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-280029 (JP, A) JP-A-7-235393 (JP, A) JP-A-7-302787 (JP, A) JP-A-4- 7827 (JP, A) JP-A-2-235332 (JP, A) JP-A-6-196295 (JP, A) JP-A-4-290428 (JP, A) JP-A-5-15312 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05H 1/46 H01L 21/3065

Claims (6)

(57) [Claims] 1. A plasma ashing apparatus for ashing a resist film formed on a surface of an object to be processed mounted on a mounting table of a processing container by plasma, wherein the mounting table is used to supply energy generated by the plasma. A plasma ashing apparatus comprising: an antenna member connected to a high-frequency power supply at a position facing the antenna; and a modulation unit for modulating a high-frequency voltage supplied to the antenna member is connected to the antenna member. . 2. A plasma ashing apparatus for ashing a resist film formed on a surface of an object to be processed mounted on a mounting table of a processing container by using plasma, wherein the mounting table is used to supply generated energy of the plasma. An antenna member connected to a high-frequency power supply is provided at a position facing the antenna, and a grid for trapping ions generated in the processing container is provided between the mounting table and the antenna member. Plasma ashing apparatus. 3. The plasma ashing apparatus according to claim 1, wherein the modulation unit modulates the output high-frequency voltage so that the output high-frequency voltage changes on / off or changes at a predetermined interval. 4. The plasma ashing apparatus according to claim 2, wherein said grid is grounded. 5. The plasma ashing apparatus according to claim 2, wherein the grid is connected to a bias unit that changes in synchronization with a high-frequency voltage applied to the antenna member. 6. The plasma ashing apparatus according to claim 1, wherein the mounting table is grounded.