JP2001044175A - Plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing apparatus which can stabilize discharging. SOLUTION: In this plasma processing apparatus, a process gas G is introduced into the interior of a discharge tube 6, a microwave M guided via a microwave waveguide 10 is irradiated to the gas G in the discharge tube 6 to generate a plasma in the discharge tube 6, and an object 3 to be processed is processed with the use of the plasma. The waveguide 10 has a slit 12, through which the microwave M is emitted toward the interior of the tube 6. The slit 6 is formed being elongated along the tube direction of the waveguide 10, the dimensions of the waveguide 10 and the length of the slit 12 in its longitudinal direction are set, so that the length of the slit 12 in the longitudinal direction is nearly equal to the length of half-wavelength of the microwave M in the waveguide 10, and plasma generated directly close to the slit is focused on one location.

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 more particularly, to a plasma generated by irradiating a process gas in a discharge tube or a vacuum vessel with microwaves, and using the plasma to process an object to be processed. The present invention relates to a plasma processing apparatus for processing.

[0002]

2. Description of the Related Art As an apparatus for processing an object to be processed such as a silicon wafer for semiconductor manufacturing or a glass substrate for a liquid crystal display, a plasma process for performing dry etching or ashing of the object using microwave plasma. There is a device.

[0003] There are several types of plasma processing apparatuses. For example, a process gas is introduced into a discharge tube formed of a dielectric, and a microwave guided through a microwave waveguide is introduced. 2. Description of the Related Art There is an apparatus that irradiates a process gas inside a discharge tube to generate plasma inside the discharge tube to process an object to be processed.

In this type of plasma processing apparatus, active species are generated from a process gas by generating plasma inside a discharge tube, and the active species is guided to a processing chamber formed inside a vacuum vessel to be covered. It is supplied to the surface of the processed object and subjected to a surface treatment such as dry etching or ashing.

[0005] As another example of the plasma processing apparatus, a microwave guided through a microwave waveguide is used.
The process gas introduced into the vacuum vessel is introduced through a microwave transmitting window member made of a dielectric material provided in the vacuum vessel, and the process gas introduced into the vacuum vessel is irradiated with microwaves to generate plasma inside the vacuum vessel. In some cases, the processing is performed on an object to be processed.

[0006] This type of plasma processing apparatus includes a plasma processing apparatus in which a plasma generated inside a vacuum vessel is brought into contact with the surface of an object to be processed and subjected to a surface treatment such as etching or ashing using active species in the plasma. In some cases, a generation region and a processing chamber are separated from each other, and a downflow from plasma is guided to the surface of the object to be processed to perform a surface treatment such as etching or ashing.

As a dielectric for forming the above-mentioned discharge tube or microwave transmitting window member, quartz, alumina or the like can be used.

As a process gas, for example, when etching a thin film on the surface of an object to be processed, oxygen gas (O ₂ ) or a gas obtained by adding a fluorine-based gas such as CF ₄ or NF ₃ to oxygen gas. Is used.

In the above-described conventional plasma processing apparatus, microwaves are introduced into the discharge tube or the vacuum vessel through the microwave waveguide as described above. Microwaves are radiated from the elongated slit formed along the discharge tube or the inside of the vacuum vessel.

This is called a so-called slot antenna system, and in a plasma processing apparatus employing this slot antenna system, a microwave is passed through a slit in a form corresponding to an electromagnetic field distribution of a microwave formed inside a microwave waveguide. Is released.

A typical example of the microwave waveguide is a rectangular waveguide having a rectangular cross section, for example, WRJ-2, a standard of the Japan Electronic Machinery Manufacturers Association.

FIG. 5 is a sectional view showing a plasma generator of a conventional plasma processing apparatus having a discharge tube. As shown in FIG. 5, a discharge tube 51 in which a discharge chamber 50 is formed is shown.
Below, a microwave waveguide 52 having a square cross section is
The discharge tube 51 extends along the tube axis direction. On the upper surface of the microwave waveguide 52, a slit 53 for emitting the microwave M toward the discharge chamber 50 of the discharge tube 51 is provided.
The microwave waveguide 52 is formed in an elongated shape along the tube axis direction.

Then, the process gas G flowing through the discharge tube 51 is irradiated with the microwave M introduced into the discharge chamber 50 through the slit 53 to generate a plasma in the discharge chamber 50. The slit 53 provided in the microwave waveguide 52 has a length that is an integral multiple of λg / 2 with respect to the wavelength λg of the microwave inside the microwave waveguide 52 (hereinafter referred to as “in-tube wavelength λg”). Is set to

[0014]

By the way, in the case of a rectangular waveguide usually used as a microwave waveguide, the guide wavelength λg is usually more than ten cm, whereas the discharge region (discharge chamber) of the discharge tube ) Or the size of the vacuum chamber (process chamber) is usually several tens of cm.

For this reason, the longitudinal length of the slit formed in the microwave waveguide for generating uniform plasma inside the discharge tube or the vacuum vessel is 2 to 5 times λg / 2 or more. That is all.

When a slit having a length of 2 to 5 times λg / 2 is provided as described above, the irradiation of the standing wave 54 inside the microwave waveguide 52 as shown in FIG. There are a plurality of places where the electromagnetic field of the obtained microwave takes the maximum value. Then, the distribution of the generated plasma also includes a plurality of high-density portions, which means that the plasma is generated at a plurality of portions.

When plasma is generated at a plurality of locations as described above, it is extremely difficult to make all plasmas have the same intensity (density). Usually, only one location is strong and the other locations are weak. Further, as time passes, a place where the plasma is strong moves to a part where the plasma was weak, and the distribution of the plasma changes. In general, when the intensity of the plasma is low, the discharge tends to be unstable, which results in the movement of the unstable place with time.

If the discharge is unstable during the processing of the processing object, for example, during the etching processing, the etching rate and the in-plane uniformity of the etching of the processing object vary for each processing object, and the yield is high. There is a problem that becomes worse.

In the case where the end point of etching is detected by a change in the intensity of light generated during the etching of an object to be processed, if the plasma discharge is unstable, the etching end point detector malfunctions, and the end point of the etching ends. There is a problem that detection becomes impossible.

The present invention has been made in consideration of the above circumstances, and has as its object to provide a plasma processing apparatus capable of stabilizing discharge.

[0021]

In order to achieve the above object, the present invention introduces a process gas into a discharge tube,
Plasma processing for irradiating a process gas inside the discharge tube with a microwave guided through a microwave waveguide to generate plasma inside the discharge tube, and processing an object to be processed using the plasma In the device, the microwave waveguide has a slit for emitting microwaves toward the inside of the discharge tube, and the slit is elongated along the tube axis direction of the microwave waveguide. The size of the microwave waveguide and the length of the slit in the longitudinal direction such that the longitudinal length of the slit and the half-wavelength of the microwave in the microwave waveguide are substantially equal. , And the generation of plasma generated in the immediate vicinity of the slit is provided at one location.

Here, "the length in the longitudinal direction of the slit is substantially equal to the half-wave length of the microwave in the microwave waveguide" includes the case where both lengths are the same. In addition, a difference in length between the slits is allowed as long as the plasma generated in the immediate vicinity of the slit is located at one location.

In order to achieve the above object, the present invention provides a method of introducing a microwave guided through a microwave waveguide into a vacuum vessel through a microwave transmitting window member provided in the vacuum vessel. In a plasma processing apparatus for irradiating a process gas introduced into the vacuum container with microwaves to generate plasma inside the vacuum container and processing an object to be processed using the plasma, The side surface of the waveguide on the vacuum vessel side has a slit for emitting microwaves toward the inside of the vacuum vessel, and the slit is elongated along the tube axis direction of the microwave waveguide. The length and the length of the microwave waveguide are set so that the length in the longitudinal direction of the slit is substantially equal to the half-wavelength of the microwave in the microwave waveguide. Set the longitudinal length of the slit, characterized in that the generation of plasma generated by the slit nearest to the one place.

Here, "the length in the longitudinal direction of the slit and the length of a half wavelength of the microwave in the microwave waveguide are substantially equal" includes a case where both lengths are the same. In addition, a difference in length between the slits is allowed as long as the plasma generated in the immediate vicinity of the slit is located at one location.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Hereinafter, a plasma processing apparatus according to a first embodiment of the present invention will be described with reference to FIGS. The plasma processing apparatus according to the present embodiment is a discharge separation type chemical dry etching apparatus that includes a discharge chamber separated from the processing chamber and generates microwave plasma in the discharge chamber.

FIG. 1 is a schematic diagram showing a schematic configuration of a plasma processing apparatus according to the present embodiment. As shown in FIG. 1, this apparatus includes a vacuum vessel 1 in which a processing chamber 2 is formed. In addition, a mounting table 4 on which the workpiece 3 is mounted is provided inside the vacuum vessel 1.

Further, one end of a gas introduction tube 5 is connected to the vacuum vessel 1, and one end of a discharge tube 6 formed of a dielectric is connected to the other end of the gas introduction tube 5. A discharge chamber 9 is formed inside the discharge tube 6.

The other end of the discharge tube 6 is provided with a gas inlet 7 for introducing a process gas G into the inside of the discharge tube 6. A microwave waveguide 10 for supplying a microwave is connected.

Here, quartz, alumina or the like can be used as a dielectric for forming the discharge tube 6.

FIG. 2 is a perspective view showing a plasma generator of the plasma processing apparatus according to the present embodiment. As shown in FIG. 2, the microwave waveguide 10 extends along the tube axis of the discharge tube 6. Has been established. On the upper surface of the microwave waveguide 10, a slit 12 for radiating the microwave M is formed inside the discharge tube 6, and the slit 12 is formed in an elongated shape. A shield member 20 for shielding microwaves is provided above the microwave waveguide 10 so as to surround the discharge tube 6.

In the plasma processing apparatus according to the present embodiment, the microwave waveguide is set such that the length of the slit 12 in the longitudinal direction is substantially equal to the half wavelength of the microwave M in the microwave waveguide 10. The dimensions of the tube 10 and the length of the slit 12 in the longitudinal direction are set.

Here, the wavelength (wavelength λg) of the microwave M in the microwave waveguide 10 is determined by the frequency of the microwave M and the sectional shape of the microwave waveguide 10. In the case of the conventional plasma processing apparatus, as described above, the guide wavelength λg in the rectangular waveguide is tens of cm, but by shortening the length of the long side of the cross section of the microwave waveguide, it is theoretically infinite. The guide wavelength λg can be extended to a large extent.

FIG. 3 is a cross-sectional view of the plasma generating section shown in FIG. 2. In FIG.
0 indicates the length of the long side of the inside rectangular cross section. And
The wavelength λg of the microwave M in the microwave waveguide 10 is increased, and the length of the slit 12 in the longitudinal direction and the half wavelength λg of the microwave M in the microwave waveguide 10 are increased as described above.
The length L of the long piece of the microwave waveguide 10 is set shorter than that of the conventional microwave waveguide 52 shown in FIG.

The process gas G supplied from the gas inlet 7 is supplied to the discharge tube 6 via the microwave waveguide 10.
Is irradiated with the microwaves M supplied to the inside thereof, and is turned into plasma, whereby active species are generated in the process gas. This active species is supplied to the vacuum vessel 1 through the gas introduction pipe 5.
The workpiece 3 is transported to the inside of the processing chamber 2 and supplied to the surface of the workpiece 3 placed on the mounting table 4, whereby the surface treatment of the workpiece 3 is performed.

In this plasma processing apparatus, the object to be processed is
Etching of thin film on the surface and resist on the surface of the workpiece
Used for ashing etc., for example, etchin
When performing oxygen (O 2) as a process gas₂) Mo
Or oxygen to CF₄, NF ₃Fluorine gas such as
The added gas is used.

Here, in general, when the electromagnetic field distribution in the microwave waveguide is matched by the matching device, standing waves are generated at intervals of the guide wavelength λg.

In the plasma processing apparatus according to the present embodiment, the length of the slit 12 in the longitudinal direction is substantially equal to the length of the half wavelength λg / 2 of the microwave M in the microwave waveguide 10. Since the size of the microwave waveguide 10 and the length in the longitudinal direction of the slit 12 are set, the distance from the node of the standing wave generated in the microwave waveguide 10 to the node corresponds to the length of the slit 12. However, there is only one place in the discharge chamber 9 where the electromagnetic field strength is strong.

Strictly speaking, since the microwave M propagates as a surface wave in the discharge tube 6, discharge occurs at a plurality of places. Since the stability of the discharge is determined by the state of the plasma, if the input power is constant, the plasma generated in the region immediately above the slit is stabilized by stabilizing the plasma immediately above the slit.

As described above, in the plasma processing apparatus according to the present embodiment, the size of the microwave waveguide 10 is changed from the conventional value, and the wavelength of the standing wave is changed according to the size of the discharge chamber 9. Since the plasma in the discharge chamber 9 in the discharge tube 6 can be concentrated at one location to stabilize the discharge, even when a plurality of workpieces 3 are continuously processed, the gap between the workpieces 3 can be reduced. The etching rate during processing and the in-plane uniformity of the etching do not vary,
As a result, the yield can be improved.

Second Embodiment Next, a plasma processing apparatus according to a second embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a schematic diagram showing a schematic configuration of the plasma processing apparatus according to the present embodiment. This apparatus is provided with a vacuum vessel 40 capable of evacuating the inside. A processing chamber 41 is formed. The processing chamber 41 is provided with, for example, a mounting table 42 for mounting the workpiece 3 having a surface coated with a resist.

An outlet end of the microwave waveguide 43 is connected to an upper portion of the vacuum vessel 40, and a gap between the outlet end of the microwave waveguide 43 and the inside of the vacuum vessel 40 is provided.
A microwave transmission window member 44 made of a dielectric is interposed. Further, the entrance end of the microwave waveguide 43 is connected to a microwave transmitter 45 for generating a microwave M.

Then, the microwave M propagated in the microwave waveguide 43 is introduced into the vacuum vessel 40 through the microwave transmitting window member 44. In addition, as a dielectric material forming the microwave transmission window member 44, quartz, Teflon, alumina, or the like can be used.

In the upper part of the processing chamber 41, the plasma generation region 4
6, a metal mesh 47 for partitioning is provided.
A gas inlet 48 is formed between the metal mesh 47 and the microwave transmitting window member 44.

Further, on the lower surface of the microwave waveguide 43, that is, on the surface facing the microwave transmitting window member 44, a slit 49 for radiating the microwave M into the vacuum vessel 41 is provided.
Are formed in an elongated shape along the tube axis direction of the microwave waveguide 43.

In the plasma processing apparatus according to the present embodiment, the length of the slit 49 in the longitudinal direction is substantially equal to the length of the half wavelength λg / 2 of the microwave M in the microwave waveguide 43. The dimensions of the microwave waveguide 43 and the length of the slit 49 in the longitudinal direction are set.

With the plasma processing apparatus shown in FIG.
For example, when performing the ashing process on the workpiece 3, the workpiece 3 is first loaded into the processing chamber 41 evacuated and placed on the mounting table 42. Next, after the inside of the processing chamber 41 reaches a required degree of vacuum, the process gas G is introduced into the vacuum vessel 40 through the gas inlet 48. Here, the process gas is oxygen (O ₂ ), or the oxygen is CF ₄ or NF _3.
For example, a gas to which a fluorine-based gas such as the above is added is used. In order to increase the efficiency of the ashing process,
Are heated by heating means not shown.

Next, when the degree of vacuum in the processing chamber 41 is stabilized, the microwave transmitter 45 is operated to generate a microwave, and the microwave is propagated through the microwave waveguide 43. The microwave propagating through the microwave waveguide 43 is radiated from the slit 49, passes through the microwave transmitting window member 44, and is introduced into the plasma generation region 46 above the vacuum vessel 40. Then, the plasma generation region 46
The process gas inside is excited by microwaves and turned into plasma.

Then, mainly electrically neutral radicals in the plasma permeate the metal mesh 47 and reach the workpiece 3 placed on the mounting table 42 to perform an ashing process. Here, the metal mesh 47 plays a role of protecting the processing target (semiconductor device or the like) 3 from charged particles such as ions generated in the plasma generation region 46.

In the plasma processing apparatus according to the present embodiment, the length of the slit 49 in the longitudinal direction is substantially equal to the length of the half wavelength λg / 2 of the microwave M in the microwave waveguide 43. Since the size of the microwave waveguide 43 and the length in the longitudinal direction of the slit 49 are set, the distance from the node of the standing wave generated in the microwave waveguide 43 to the node corresponds to the length of the slit 49. However, there is only one place where the electromagnetic field strength is strong in the plasma generation region 46.

Strictly speaking, the microwave transmitting window member 44
Since the microwave M propagates as a surface wave in the inside, discharge occurs at a plurality of places. However, in places other than the area immediately below the slit 49, the stability of the discharge is determined by the input power and the state of the plasma in the area immediately below the slit 49. Therefore, if the input power is constant, the plasma generated in the region immediately below the slit is stabilized by stabilizing the plasma immediately below the slit.

As described above, in the plasma processing apparatus according to the present embodiment, the size of the microwave waveguide 43 is changed from the conventional value, and the wavelength of the standing wave is changed according to the size of the plasma generation region 46. , Plasma generation region 46
Can stabilize the discharge by concentrating the plasma in one place, so that even when a plurality of workpieces 3 are continuously processed, ashing (etching) is performed between the workpieces 3 during processing. The in-plane uniformity of speed and ashing (etching) does not vary, and the yield can be improved.

[0053]

As described above, according to the plasma processing apparatus of the present invention, the longitudinal length of the slit of the microwave waveguide is substantially equal to the half-wave length of the microwave in the microwave waveguide. Since the size of the microwave waveguide and the length of the slit in the longitudinal direction are set as described above, it is possible to stabilize the discharge for generating the plasma, and to continuously process a plurality of workpieces. In this case, the processing speed and the in-plane uniformity of the processing do not vary among the objects to be processed, and the yield can be improved.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing a plasma generation unit of the plasma processing apparatus shown in FIG.

FIG. 3 is a cross-sectional view showing a plasma generating unit of the plasma processing apparatus shown in FIG.

FIG. 4 is a schematic diagram showing a schematic configuration of a plasma processing apparatus according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a plasma generation unit of a conventional plasma processing apparatus.

[Explanation of symbols]

 Reference Signs List 1, 40 Vacuum container 2, 41 Processing chamber 3 Object to be processed 4, 42 Mounting table 5 Gas inlet tube 6 Discharge tube 7, 48 Gas inlet 8 Exhaust port 9 Discharge chamber 10, 43 Microwave waveguide 11 Standing wave 12 , 49 Slit 44 Microwave transmission window member 45 Microwave transmitter 46 Plasma generation area G Process gas M Microwave

Claims (2)

[Claims] 1. A process gas is introduced into a discharge tube, a microwave guided through a microwave waveguide is applied to a process gas inside the discharge tube, and a plasma is generated inside the discharge tube. In the plasma processing apparatus for processing an object to be processed using the plasma, the microwave waveguide has a slit for emitting microwaves toward the inside of the discharge tube, and the slit is Are formed in an elongated shape along the tube axis direction of the microwave waveguide, and the length of the slit in the longitudinal direction is substantially equal to the half-wave length of the microwave in the microwave waveguide. A plasma processing apparatus, wherein the size of the microwave waveguide and the length in the longitudinal direction of the slit are set, and the generation of plasma generated in the immediate vicinity of the slit is made in one place. 2. A microwave guided through a microwave waveguide is introduced into the vacuum vessel through a microwave transmitting window member provided in the vacuum vessel, and is introduced into the vacuum vessel. A plasma processing apparatus that irradiates the process gas with microwaves to generate plasma inside the vacuum vessel and processes the workpiece using the plasma, wherein a side surface of the microwave waveguide on the vacuum vessel side. Has a slit for emitting microwaves toward the inside of the vacuum container, the slit is formed in an elongated shape along the tube axis direction of the microwave waveguide, the slit The size of the microwave waveguide and the length of the slit in the longitudinal direction are set so that the length in the longitudinal direction and the half-wavelength of the microwave in the microwave waveguide are substantially equal, A plasma processing apparatus characterized in that plasma generated in the vicinity of a slit is generated in one place.