JP2000082698A - Plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve processing speed and processing uniformity by implementing the smooth circulation of a processing gas through a simple modification of the apparatus when a process using plasma is performed. SOLUTION: An etching gas serving as a processing gas is supplied into a processing chamber 2 via diffusion holes 23 of an upper electrode 21 that extends in the upper region of the chamber 2. A gas diffusion guide 24 opening in a flared manner onto a susceptor 5 constituting a lower electrode is arranged around the electrode 21. The conductance of the etching gas purged from the holes 23 is reduced and a uniform concentration distribution is also achieved, thereby improving etching rate and processing uniformity.

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.

[0002]

2. Description of the Related Art For example, in the case of a plasma processing apparatus, for example, in a semiconductor manufacturing process, it has been widely used for performing a surface treatment of a semiconductor wafer (hereinafter, referred to as a "wafer"). A so-called parallel plate type plasma processing apparatus has advantages such as excellent uniformity, being capable of processing a large-diameter wafer, and the apparatus configuration is relatively simple, so that it is widely used.

In the above-mentioned conventional general parallel plate type plasma processing apparatus, electrodes are provided vertically above and below in a processing chamber so as to face each other, and a wafer to be processed is mounted on, for example, a lower electrode. In the case of an etching process, for example, an etching gas is introduced into the processing chamber, and high-frequency power is applied to the electrodes to generate plasma between the electrodes, and the etchant ions generated by dissociation of the etching gas cause The wafer is configured to be etched. In such a case, the etching gas is directly discharged toward the wafer from a large number of holes of the gas diffusion plate constituting the discharge portion provided on the surface of the upper electrode facing the wafer.

[0004]

However, in a conventional gas diffusion plate, for example, when a quartz shield ring or other members are present around the gas diffusion plate, it may hinder the improvement of the etching rate, or the processing gas may not be improved. May have a subtle effect on the concentration distribution of GaN, thereby hindering the uniformity of the etching process.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to discharge a processing gas more smoothly toward an object to be processed, thereby speeding up processing and making the processing uniform.

[0006]

According to a first aspect of the present invention, there is provided a processing chamber capable of reducing pressure, and an upper electrode and a lower electrode opposed to each other above and below the processing chamber. A plasma configured to discharge a processing gas into a processing chamber from a discharge unit provided on an electrode side, generate plasma between the upper electrode and the lower electrode, and perform processing on an object to be processed on the lower electrode. In the processing apparatus, a gas diffusion guide tapered toward the object to be processed is provided on the periphery of the discharge unit, and a focus ring that is inclined downward from the inside toward the outside is provided on the periphery of the upper end of the lower electrode. Is provided, the plasma processing apparatus is provided.

According to a second aspect of the present invention, a processing chamber which can be depressurized, and upper and lower electrodes opposed to each other above and below the processing chamber, and the processing chamber is processed from a discharge unit provided on the upper electrode side. In a plasma processing apparatus configured to discharge gas, generate plasma between the upper electrode and the lower electrode, and perform processing on a processing target on the lower electrode, a taper is formed toward the processing target. A gas diffusion guide having an opening in a shape is provided on the periphery of the discharge portion, and a gas diffusion exhaust guide having a tapered portion that is inclined downward to the outside is provided on the periphery of the upper edge of the lower electrode. A plasma processing apparatus is provided.

In this case, the gas diffusion and exhaust guide may be formed of a conductive material and grounded.

According to a fourth aspect of the present invention, the gas diffusion and exhaust guide may be integrated with a focus ring provided on a peripheral edge of an upper edge of the lower electrode.

The tapered portion of the gas diffusion guide may be parallel to the tapered portion of the gas diffusion exhaust guide.

The angle formed by the tapered portion of the gas diffusion guide in the horizontal direction is preferably in the range of 25 ° to 30 °.

(Operation) According to the plasma processing apparatus of the present invention, the gas diffusion guide which is tapered toward the object to be processed is provided on the periphery of the discharge section for discharging the processing gas into the processing chamber. On the lower electrode side, a focus ring and a gas diffusion exhaust guide are provided so as to be inclined downward from the inside to the outside, so that the gas flow conductance is reduced, and the processing gas is better directed toward the object to be processed. The gas is discharged and the flow of the gas is smoothed, and the processing can be performed on the object under a preferable atmosphere of the processing gas, and a preferable processing result can be obtained.

Further, if the gas diffusion guide is arranged so as to surround the upper electrode, and the gas diffusion guide, the focus ring and the gas diffusion exhaust guide are configured to be grounded with conductivity. The plasma generated between the electrodes is confined between these ground electrodes, so that the plasma density is improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The present embodiment is an example applied to an etching apparatus, and FIG. 1 schematically shows a cross section of an etching apparatus 1. A processing chamber 2 in the etching apparatus 1 has a processing container 3 formed into a cylindrical shape made of aluminum or the like which has been subjected to anodized aluminum oxide which can be hermetically closed.
And the processing vessel 3 itself is grounded.
An object to be processed, for example, a semiconductor wafer (hereinafter, referred to as a semiconductor wafer) is provided on the bottom of the processing chamber 2 via an insulating support plate 4 such as ceramic.
A substantially columnar susceptor 5 for mounting a “wafer” W is accommodated therein, and this susceptor 5 constitutes a lower electrode.

An annular refrigerant chamber 6 is provided inside the susceptor 5, and a refrigerant for temperature adjustment is introduced into the refrigerant chamber 6 through a refrigerant introduction pipe 7. Circulated and discharged from the refrigerant discharge pipe 8. The cold generated during this time is transferred from the coolant chamber 6 to the wafer W via the susceptor 5, and the processing surface of the wafer W can be cooled to a desired temperature.

Further, the susceptor 5 is provided with a heating means 9 such as a ceramic heater, for example, and heats the susceptor 5 to a desired temperature by power supply from a power supply 10 provided outside the processing vessel 3. It is configured as follows. Therefore, the wafer W can be set and maintained at a predetermined temperature by the cold heat of the refrigerant chamber 6 and the heating means 9.

The susceptor 5 has an electrostatic chuck 1
1 is provided, the wafer W is applied by application of a DC high voltage from a DC
Are held by suction on the upper surface of the electrostatic chuck 11. An annular focus ring 13 made of SiO ₂ is arranged on the upper peripheral edge of the susceptor 5 so as to surround the wafer W held on the electrostatic chuck 11. The focus ring 13 is tapered so as to be inclined downward from the inside to the outside as shown in the figure.

Above the susceptor 5, an upper electrode 21 having a gap length of about 25 mm is supported above the processing vessel 3 via an insulating material 22 so as to face the susceptor 5 in parallel. The upper electrode 21 has a hollow structure, and has a large number of diffusion holes 23 on the surface facing the susceptor 5 and also serves as a discharge portion. An annular gas diffusion guide 24 is provided around the surface of the upper electrode 21 facing the susceptor 5.
Is provided. This gas diffusion guide 24 is made of SiO ₂
And is supported so as to surround the periphery of the upper electrode 21, and is opened in a tapered shape toward the susceptor 5 side. In the present embodiment, the taper angle, that is, the angle (the angle between the upper electrode 21 and the horizontal direction) θ formed by the tapered portion 24a as the surface facing the susceptor 5 of the upper electrode 21 is 30 as shown in FIG. Set to ゜.

A gas inlet 2 is provided at the center of the upper electrode 21.
5 is provided and connected to a processing gas supply source via a valve 26. In the present embodiment, the valve 27,
CF ₄ gas is supplied from the processing gas supply source 29 via the mass flow controller 28, and CH ₄ gas is supplied from the processing gas supply source 32 via the valve 30 and the mass flow controller 31.
The F ₃ gas is passed through the diffusion holes 23 to the processing chamber 2.
It can be supplied inside.

Around the lower part of the susceptor 5 in the processing chamber 2, exhaust pipes 42, 43, etc., which are connected to evacuation means 41 such as a vacuum pump, are connected.
It is possible to evacuate to an arbitrary degree of reduced pressure within a range of 5 mmTorr to 100 mmTorr.

Next, the high-frequency power application system of the etching apparatus 1 will be described. First, a relative low-frequency power supply 51 for outputting a relatively low frequency of 800 kHz is supplied to the susceptor 5 serving as a lower electrode. Is applied via the matching unit 52. On the other hand, upper electrode 2
For example, the frequency is set to 2
A high frequency is applied from a relative high frequency power supply 54 that outputs a 7 MHz relative high frequency power.

A load lock chamber 62 is adjacent to the side of the processing container 3 via a gate valve 61.
In the load lock chamber 62, a transfer means 63 such as a transfer arm for transferring the wafer W to be processed to and from the processing chamber 2 in the processing container 3 is provided.

The main part of the etching apparatus 1 according to the present embodiment is constructed as described above. For example, the operation when etching an oxide film on a silicon wafer W will be described. Valve 61
Is opened, the wafer W is carried into the processing chamber 2 from the load lock chamber 62 by the transfer means 63, and is placed on the electrostatic chuck 11 of the susceptor 5, and then the transfer means 63
Is retracted, and the gate valve 61 is closed. Next, the inside of the processing chamber 2 is depressurized by the evacuation 41, and after reaching a predetermined degree of depressurization, CF ₄ gas is supplied from the processing gas supply source 29 and CHF ₃ gas is supplied from the processing gas supply source 32. And the pressure in the processing chamber 2 is, for example, 10 mmTorr.
Set and maintained.

A relative high frequency having a frequency of 27 MHz is applied to the upper electrode 21 from a relative high frequency power supply 54, and a relative low frequency having a frequency of 800 kHz is applied to the susceptor 5 from the relative low frequency power supply 51. Then, plasma is generated between the upper electrode 21 and the susceptor 5, and the processing gas in the processing chamber 2 is dissociated by the generated plasma. Fluorine radicals generated at that time generate a silicon oxide film (SiO 2) on the surface of the wafer W. ₂ ) is being etched.

Next, an oxide film (S) on the surface of a 6-inch silicon wafer W is actually
The result when iO ₂ ) is etched will be described.
First, the pressure in the processing chamber 2 was set to 10 mmTorr as described above. The flow rate ratio between CF ₄ gas and CHF ₃ gas was 25/75 sccm. Regarding the temperature, the inner bottom of the processing chamber 2 was 20 ° C., the upper part was 30 ° C., and the side was 40 ° C.
Set to ゜ C. And 200 for the upper electrode 21
0 W and 800 W of electric power were applied to the susceptor 5, respectively.

As a result of etching the wafer W under these conditions, the result shown in the graph of FIG. 3 was obtained. The graph of FIG. 3 shows the etching rate at a position shifted outward in the diameter direction (X direction, Y direction) from the center of the wafer W. As can be seen from the graph,
Even at a position 50 mm away from the center, the etching rate is
4000 angstrom / X and Y directions respectively
min, and the average of the measurement points was 4072 Å / min. Regarding the uniformity (U) of the etching rate, U (%) = (ERmax−
ERmin) / 2 · ERave × 100, U =
6.3 (%). Here, ERmax is the maximum etching rate on the wafer W, ERmin is the minimum etching rate on the wafer W, and ERave is the average etching rate.

In order to compare the results with those of the prior art, an etching apparatus having a configuration in which only the gas diffusion guide 24 was removed from the etching apparatus 1 according to the present embodiment while leaving the other components intact was used. Etching was performed on the wafer W under exactly the same conditions as the various conditions, and the results are shown in the graph of FIG. Comparing the graph of FIG. 3 with the graph of FIG. 4, first, the etching rate of the present embodiment is higher than that of the conventional one, and the etching rate is approximately 1000 Å / mi over the entire wafer W.
It can be confirmed that n also has an increased etching rate. Incidentally, the etching rate at the average of the measurement points in FIG. 3 is 3142 angstroms / min, and in actuality, the etching rate of the present embodiment is higher by about 1000 angstroms / min on average.

Next, as can be seen at a glance, the uniformity of the graph in FIG. 3 is gentler in the graph of FIG. 3 than in the graph of FIG. Can be confirmed. In fact, the uniformity (U) obtained by the definition of the uniformity (U) in the etching by the conventional etching apparatus was 12.3%. As described above, that of the present embodiment is 6.3%.
Therefore, it can be confirmed from this point that the present embodiment has improved the uniformity. Also, the difference in the etching rate at the position shifted in the X direction and the Y direction is smaller in the present embodiment than in the related art, and it can be seen that the uniformity of the entire wafer W is improved. Further, the improvement of the etching rate and the uniform processing described above can be seen only by providing the gas diffusion guide 24, so that the present invention can be implemented with a simple modification of an existing apparatus. I have.

The etching apparatus 1 according to the embodiment includes an upper electrode 21 and a susceptor 5 serving as a lower electrode.
However, the present invention is of course applicable to other types of etching processing apparatus. For example, as shown in FIG. 5, the processing vessel 71 and the susceptor 72 are grounded, and a high frequency, for example, 13.56 MHz is applied to the upper electrode 73, that is, a so-called plasma etching (PE) type etching processing apparatus 74. 6, the upper electrode 81 and the processing chamber 82 are grounded, and the rf power is applied to the susceptor 83.
Etching (RIE) type etching processing apparatus 84,
Further, as shown in FIG. 7, only the processing container 91 is grounded, and the same frequency power from a single high-frequency power supply 94 is applied to the upper electrode 92 and the lower electrode 93 via the transformer 95. Are alternately shifted 180 ° from each other, so-called power split type etching processing apparatus 96 is also supplied from processing gas supply source G to processing containers 71, 82,
By providing a tapered annular gas diffusion guide H around each of the upper electrodes 73, 81, and 92 having a discharge portion for discharging a processing gas in the inside 91, the etching rate and uniformity can be improved. is there.

Further, in the etching apparatus 1 according to the above-described embodiment, the focus ring 13 is provided on the peripheral portion of the susceptor 5 serving as the lower electrode. Instead, for example, as shown in FIG. May be provided with a gas diffusion exhaust guide 101. The gas diffusion / exhaust guide 101 has an annular shape as a whole, and has a tapered portion 1 that is inclined downward to an outer portion on its upper surface, that is, on the upper electrode 21 side.
01a. When the gas diffusion and exhaust guide 101 having such a configuration is used, the gas conductance on the exhaust side is reduced, and in combination with the gas diffusion guide 24, the flow of gas in the processing chamber 2 is further smoothed. Further, the etching rate and the uniformity can be improved.

The gas diffusion and exhaust guide 10 shown in FIG.
The taper angle of the first tapered portion 101a is set so as to be parallel to the tapered portion 24a of the gas diffusion guide 24, but it is not always necessary to set the taper angle so as to be parallel. The gas diffusion and exhaust guide 101 may be used together with the focus ring 13 described above. In that case, the gas diffusion and exhaust guide may be grounded to the outer periphery of the focus ring. Further, the shape may be integrated with the focus ring.

The gas diffusion and exhaust guide 101 as described above
Is, of course, not limited to the etching apparatus 1 according to the above-described embodiment, but may be applied to the plasma etching (P) shown in FIG.
The E) type etching apparatus 74, the reactive ion etching (RIE) type etching apparatus 84 shown in FIG. 6, and the power split type etching apparatus 96 shown in FIG. Of course, it is applicable.

By the way, with today's high integration of devices, a finer etching process such as a process of forming a contact hole having a hole diameter of 0.3 μm is required as an etching process. To achieve this, it is necessary to increase the plasma density,
According to the present invention, this can be easily realized while improving the etching rate and uniformity as described above.

That is, the gas diffusion guide 24 in the etching apparatus 1 in the above embodiment is made of a conductive material, and is insulated from the upper electrode 21 and grounded. Then, the gas diffusion exhaust guide 101 shown in FIG.
Is also made of a conductive material, insulated from the susceptor 5, and grounded. According to this configuration, the plasma generated between the upper electrode 21 and the susceptor 5 is confined between the gas diffusion guide 24 and the gas diffusion exhaust guide 101, and the diffusion thereof is prevented. Therefore, the plasma density is improved accordingly, and finer etching processing can be performed. Note that such a plasma confinement configuration is also applied to the above-described plasma etching (PE) type etching processing device 74, reactive ion etching (RIE) type etching processing device 84, and power split type etching processing device 96. Again, of course, it is applicable.

Although the above-described etching apparatus 1 has been described for the case where the object to be processed is a semiconductor wafer, the present invention is not limited to this, and it is of course possible to configure the present invention as an etching apparatus for processing an LCD substrate, for example. It is.

[0036]

According to the plasma processing apparatus of the present invention, the gas flow conductance is reduced, the processing gas is more smoothly discharged toward the object to be processed, and the concentration distribution is made uniform. It is possible to achieve uniformity. Further, for example, in the case of an etching process, it is possible to improve the etching rate and make the etching uniform. In addition, the present invention can be applied to existing devices only by simple device modification.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of an etching apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a main part of a gas diffusion guide in the etching apparatus of FIG. 1;

3 is a graph showing a relationship between a position shifted in a radial direction of a wafer and an etching rate when an oxide film of a silicon wafer is etched using the etching processing apparatus of FIG. 2;

FIG. 4 is a graph showing a relationship between a position shifted in a radial direction of a wafer and an etching rate when an oxide film on a silicon wafer is etched using a conventional etching apparatus having no gas diffusion guide. .

FIG. 5 is an explanatory cross-sectional view of an embodiment in which a gas diffusion guide is provided around an upper electrode of a plasma etching (PE) type etching processing apparatus.

FIG. 6: Reactive ion etching (RIE)
FIG. 3 is a cross-sectional explanatory view of an embodiment in which a gas diffusion guide is provided around an upper electrode of a system of an etching process.

FIG. 7 is an explanatory sectional view of an embodiment in which a gas diffusion guide is provided around an upper electrode of a power split type etching apparatus.

8 is an explanatory sectional view showing a state in which a gas diffusion exhaust guide is grounded in place of the focus ring on the susceptor in the etching processing apparatus of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Etching processing apparatus 2 Processing chamber 3 Processing container 5 Susceptor 13 Focus ring 21 Upper electrode 23 Diffusion hole 24 Gas diffusion guide 24a Taper part 25 Gas inlet 29, 32 Processing gas supply source 51 Relative low frequency power supply 54 Relative high frequency power supply W wafer

 ──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 6-252963 (32) Priority date September 20, 1994 (September 20, 1994) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 7-29940 (32) Priority date January 25, 1995 (Jan. 25, 1995) (33) Priority claim country Japan (JP)

Claims (6)

[Claims] A processing chamber capable of freely reducing pressure, and an upper electrode and a lower electrode opposed to each other above and below the processing chamber, and a processing gas is discharged into the processing chamber from a discharge unit provided on the upper electrode side. Generating a plasma between the upper electrode and the lower electrode,
In a plasma processing apparatus configured to perform processing on an object to be processed on the lower electrode, a gas diffusion guide that is opened in a tapered shape toward the object to be processed is provided on a periphery of the discharge unit; A focus ring that is inclined downward from the inside toward the outside at the periphery of the upper edge of the plasma processing apparatus. 2. A process chamber which can be decompressed, and an upper electrode and a lower electrode opposed to each other above and below the process chamber, and a processing gas is discharged into the processing chamber from a discharge unit provided on the upper electrode side. Generating a plasma between the upper electrode and the lower electrode,
In a plasma processing apparatus configured to perform processing on an object to be processed on the lower electrode, a gas diffusion guide that is opened in a tapered shape toward the object to be processed is provided on a periphery of the discharge unit; A plasma processing apparatus characterized in that a gas diffusion exhaust guide having a tapered portion inclined downward to the outside is provided at a peripheral edge of an upper end edge of the plasma processing apparatus. 3. The gas diffusion exhaust guide is made of a conductive material and is grounded.
3. The plasma processing apparatus according to 1. 4. The plasma processing apparatus according to claim 3, wherein the gas diffusion and exhaust guide is integrated with a focus ring provided on a peripheral edge of an upper edge of the lower electrode. 5. The tapered portion of the gas diffusion guide and the tapered portion of the gas diffusion exhaust guide are parallel to each other.
The plasma processing apparatus according to claim 2. 6. The plasma processing apparatus according to claim 2, wherein the angle formed by the tapered portion of the gas diffusion guide in the horizontal direction is 25 ° to 30 °.