JPH03191072A - Microwave plasma treating device - Google Patents

Abstract

PURPOSE:To prevent the breakage of a microwave transmitting window and to eliminate the need for the downtime by providing a refrigerant passage to a member in contact with the window to enable to cool the window. CONSTITUTION:The microwave plasma treating device is formed with a vacuum vessel 101, the microwave transmitting window 105, a microwave launcher 103, a coaxial tube 106, a holder 109 for a sample to be treated, etc., and cooling passages 122 and 125 are provided to the members 103 and 114 in contact with the window 105 to uniformly cool the window 105. The launcher 103 is provided with a tapered part 113 for setting a microwave propagation path. The microwave 117 from a microwave oscillator is propagated to the launcher 103 by the coaxial tube 106. Furthermore, the holder 109 is opposed to the window 105 in a discharge space 107.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a microwave plasma processing apparatus, particularly used for processing such as sample etching, deposited film formation, sputtering, cleaning, resist ashing, etc. using plasma. The present invention relates to a microwave plasma processing apparatus.

[Conventional technology]

Plasma processing method involves turning a specific substance into plasma to generate highly active radicals and ions, and bringing these radicals and ions into contact with the object to be processed, etching, deposited film formation, sputtering, cleaning, and ashing. (ashing) etc. refers to a processing method, and the plasma processing apparatus refers to an apparatus used to carry out the plasma processing method.

Conventionally, such a plasma processing apparatus includes a plasma processing chamber formed of a vacuum container having a raw material gas inlet and a vacuum exhaust port, and an electromagnetic wave that supplies energy to convert raw material gas supplied to the plasma processing chamber into plasma. It consists of a device that supplies

By the way, the plasma processing method relies on the strong activity of radicals and ions mentioned above, and by appropriately selecting the density of radicals and ions, the temperature of the object to be processed, etc., various treatments such as etching and deposited film formation can be performed. It is a feature of the plasma processing method that it can be performed as desired, and what is important in the plasma processing method is efficient generation of radicals and ions.

Conventionally, as a medium that provides plasma energy, 1
High-frequency electromagnetic waves of about 3.56 MHz were used, but in recent years it has been found that high-density plasma can be efficiently generated by using microwaves of about 2.45 G) Plasma processing methods have attracted attention, and several devices have been proposed for this purpose.

For example, Japanese Patent Laid-Open No. 52-26175 discloses an apparatus in which a microwave-transmitting vacuum vessel is placed inside a waveguide to generate plasma, and a sample is processed using the plasma.

Furthermore, JP-A-60-120525 discloses that electrons are efficiently accelerated by an electric field generated by microwaves and a magnetic field generated by a magnetic field generator placed outside the discharge chamber, collide with neutral molecules, and cause ionization. , an apparatus for performing processing using generated high-density plasma has been disclosed. When using this device, plasma can be generated efficiently, especially if the magnitude of the magnetic field is determined so that the cyclotron frequency of electrons and the frequency of microwaves match. -・Commonly used 2, 45
For GHz, the magnetic field magnitude is 875 Gauss.

The present inventor previously developed a device as shown in FIG. 6, which improves the drawbacks such as poor processing speed in this device, that is, a device that transmits microwaves from the outer periphery of the microwave transmission window to the microwave transmission window. The apparatus is configured so that the microwave is completely radiated into the discharge space of the vacuum vessel, and thereby plasma is generated efficiently and uniformly distributed in the discharge space, and the generated plasma We have invented a plasma processing apparatus that can efficiently perform uniform etching or ashing of a sample and uniform film formation on a substrate 42. (Japanese Patent Application No. 63-10082) In Fig. 6, 10 is a vacuum container for keeping the processing section in vacuum, +02 is a gas inlet for introducing processing scum into the vacuum container, and 103 is a microwave The microwave launcher 1107 that emits plasma is located in a discharge chamber where plasma exists,
104 is a mask for radiating microwaves into the discharge chamber 107, which is a conductor plate with slits or slots; 105;
106a and 106b are microwave transmitting windows made of a dielectric material such as quartz, alumina, boron nitride, forsterite, etc. and vacuum-sealing between the inside of the microwave launcher 103 and the discharge chamber 107; 108 is a sample to be processed, 109 is a sample holder, 1+10 is a vacuum evacuation system to maintain the processing pressure in the discharge chamber, and 111 is a coaxial tube outer conductor and an inner conductor for supplying microwaves to the discharge chamber. 112 is a microwave propagation path, 113 is a taper for suppressing microwave reflection, 114 is an intermediate conductor plate for forming a two-layer structure, and 115 is for direct contact between the conductor plate 104 and the plasma. 116 is a surface for vacuum-sealing the microwave window.

In the device with the above configuration, the microwave (usually 2.45G)12) generated by the microwave oscillator is supplied by a waveguide to an isolator that absorbs the microwave returning to the microwave oscillator, and then to a microwave launcher. -1
The signal is sent to a coaxial converter equipped with a tuner for matching with the waveguide 03, where its propagation path is converted from a waveguide to a coaxial tube and supplied to the microwave launcher 103. On the other hand, processing gases such as c12 for etching a Si substrate, SiH4 for amorphous Si film deposition, and 02 for resist ashing are supplied from the gas introduction L]]02. The microwave enters the microwave launcher from the upper layer to the lower layer along the propagation path 112. This lower layer also serves as a vacuum sealing window and is vacuum sealed at the surface 116, and is made of a material that absorbs little microwaves, such as quartz or alumina. The microwave propagates toward the center within the microwave transmission window 105 and is gradually radiated from a slit or slot provided in the window. The emitted microwaves prevent metal contamination, pass through the insulator 115 with low microwave absorption, reach the discharge chamber 107, and create a microwave electric field inside.
Plasma is efficiently generated by the magnetron effect of this electric field and the magnetic field generated by the air-core coil 111.

In addition, the magnitude of the magnetic field is set to the same value as the electron cyclotron frequency and the microwave frequency (87 at 2,45 Gl-1z).
5 Gauss), electrons are accelerated resonantly and plasma is generated more efficiently.

The sample is treated with the ions and radicals present in the plasma thus generated. Plasma density, temperature, and ion valence, which have a strong influence on sample processing, depend on the intensity of the emitted microwaves, and their spatial distribution strongly depends on the microwave radiation distribution.

The microwave radiation distribution can be arbitrarily changed by changing the distribution of the slits or slots in the conductor plate 104 and the width of the slits or slots. For example, when the shape of the slit is spiral, if the microwave intensity at the center is strong, the slit interval can be made larger at the center and smaller at the periphery to make the microwave radiation distribution uniform. It is possible to perform uniform processing.

[Invention or problem to be solved]

However, in the conventional example mentioned above, the microwave transmission window 105 and the microwave launcher 103 are heated by the plasma generated in the discharge chamber through the insulating plate 115 and the conductive plate 104, and since there is no cooling structure, the temperature rises up to 150" after approximately one hour of operation. C
The temperature rises to a certain degree. Alumina, which is commonly used as a window material, may be damaged if the thickness is 10 mm or more and the diameter is 200 mm or more and there is a temperature difference of about 80"C or more inside the alumina. If the alumina is damaged, the microwave transmission window will be exposed to atmospheric pressure. There is a possibility of serious accident due to
For this reason, it is necessary to keep the temperature difference to 50° C. or less for safety reasons.

Also, although not shown, the microwave launcher has an O
Are materials such as rings, epoxy adhesives, silicone adhesives, etc. used?The optimum temperature for these is 80°C or lower, and if this temperature is exceeded, problems such as vacuum leaks and peeling of the adhesive parts may occur. There is a point. Furthermore, if the operating time is shortened and sufficient downtime is allowed for cooling, productivity will be significantly reduced.

The present invention solves the above-mentioned problems of the conventional apparatus shown in FIG. 6, and provides a microwave plasma processing apparatus equipped with an effective cooling system.

(Means for Solving the Problems) The present invention provides a vacuum container having a discharge space and a means for supplying raw material gas to the discharge space, and a vacuum container that emits microwaves into the discharge space in a direction perpendicular to the direction of microwave propagation. A microwave launcher comprising at least a flat microwave transmission window and a tapered part for setting a microwave propagation path, and a microwave launcher that transmits microwaves from a microwave oscillator.
A microwave plasma processing apparatus comprising at least a coaxial tube that propagates to the microwave launcher, and a sample holder to be processed disposed in a discharge space facing the microwave transmission window. A microwave plasma processing apparatus is characterized in that a member in contact with the transmission window is provided with a coolant flow path for cooling the transmission window. Without arranging any part that would disturb the electromagnetic field, the member in contact with the microwave transmission window is directly cooled by the refrigerant flowing within the member, and the resulting bundled heat transfer effect cools the transmission window. This makes it possible to prevent thermal damage.

The device of the present invention basically includes a vacuum container having a discharge space and a source gas supply means, a microwave launcher having at least a flat microwave transmission window and a tapered portion, and propagating microwaves to the microwave launcher. A microwave plasma apparatus comprising at least a coaxial tube and a sample holder to be processed, and having the above configuration,
In addition to these, various means and members may be included. For example, one is equipped with a means for applying a magnetic field using an air-core coil to increase the efficiency of plasma generation generated by microwaves, the other is equipped with a means for applying high-frequency power to a sample holder to be processed to accelerate the generated ions, and Similarly, a microwave launcher is equipped with a means for applying high-frequency power, and a microwave launcher is equipped with an ion extraction electrode below the discharge space to increase ion energy. The present invention can be applied to any device capable of performing membrane treatment or the like.

The microwave transmission window (hereinafter referred to as "transmission window") used in the device of the present invention has a flat plate shape, and microwaves are introduced from the outer periphery or the center and propagate in the radial direction within the transmission window, The microwave is gradually radiated into the discharge space in a direction perpendicular to the propagation direction.

Further, the microwave emitting surface of the transmission window includes a conductor plate provided with slots or slits for uniformly emitting microwaves, and a protection plate that transmits microwaves to prevent metal sputtering from the conductor plate. etc. may be provided, and the plasma density distribution generated by microwave radiation can be made more uniform.

A microwave launcher is a device that emits microwaves into a discharge space, and basically has a transmission window and a tapered part as its main parts. However, when introducing microwaves from the outer periphery of the transmission window, a conductor A plate (referred to as an intermediate conductor plate) may be placed on the transmission window to guide the microwave propagating from the coaxial tube to the outer periphery of the transmission window.

In the present invention, the refrigerant flow path for cooling the transmission window is
1. This is a refrigerant flow path provided in a member in contact with the transmission window of the microwave launcher to directly cool the member, and as the refrigerant flows through the flow path, the transmission window is indirectly cooled. In other words, it can be cooled by the heat transfer effect. Note: The cooling channel should have a channel arrangement that is effective in suppressing temperature rise due to plasma generation in the transmission window, and should have as large an internal surface area as possible. For example, if the intermediate conductor plate has a hollow structure and is used as a coolant flow path, it becomes possible to cool almost the front surface of the transmission window opposite to the radiation surface (the surface facing the discharge space) and the surface (back surface). Since it is located at the center of the transmission window and changes the propagation path of the microwave, it is made into a hollow structure and used as a coolant flow path. Seahs Danzushi Nnaru. Cooling can be achieved in the same way by encircling the flow channels without making the entire structure hollow. It is more effective to perform cooling from the center and cooling from the back side at the same time. In addition to these, microwave launchers
By providing a refrigerant flow path at a location that is not in contact with the transmission window, it is possible to suppress the temperature rise of the microwave launcher itself, and by combining this with cooling of the parts that are in contact with the transmission window, it is possible to more effectively cool the transmission window. Cooling can be performed.

The means for introducing and extracting the refrigerant into the microwave launcher is preferably one that does not affect the microwave propagation path, and in this sense it is preferable to provide a refrigerant introduction and extraction path inside the center conductor of the coaxial tube. However, it is also possible to introduce the refrigerant directly into the outer structure of the microwave launcher through a pipe or the like.

Refrigerants that can be used in the present invention include water, alcohol, chlorofluorocarbon gas, etc. The cooling energy of the refrigerant generates heat in plasma. Good morning. The transmission window may be controlled within a predetermined temperature range by specifically setting the temperature, etc. in T and Camellia 1 [Examples] The present invention will be further explained with reference to Examples below.

Embodiment 1 FIG. 1 is a schematic diagram showing an embodiment of an apparatus that best represents the features of the present invention, and in the same figure, Il:la.

113b is a tapered part for changing the microwave propagation path, 1I6a, ll6b are vacuum seal surfaces, 119 is a microwave absorber, 120.123 is a cooling water inlet, 121
．． 124 is the same discharge port, +22 is the cooling water channel provided inside the intermediate conductor plate +14, +25 is the microwave launcher-1
03, and the same reference numerals as in FIG. 6 indicate the same ones as in FIG. 6. Here, the cooling water inlet 120 and the same outlet 1
2] is the inner conductor 106b inside the center conductor (made of copper) of the coaxial pipe.
) is provided as a hollow double structure, and the cooling water channel 122 is provided as a hollow double structure with an intermediate conductor plate 14 (made of copper). Note that if the cooling water inlet and outlet are reversed and the flow direction is reversed, the temperature gradient of the transmission window will change slightly, but there is no problem. The transmission window 105 is made of alumina and has a diameter of 200 mm and a thickness of 10 mm.

Next, etching of a Si wafer using the apparatus with the above configuration will be described.

The Si wafer is placed on the sample holder 109, and the vacuum container 101 is preliminarily evacuated using the vacuum evacuation system 110.
Evacuate to below r. Next, as a processing gas, C12, S
F6 or a mixture thereof is supplied from the gas introduction port 102, and the pressure inside the vacuum container 101 is increased to 2 x 10-'torr.
~5 some value of X1O-3torr (usually 3
Maintain the temperature at O-3 torr.

Next, cooling water from the cooling water inlet 120.123 (temperature is 3
0° C. or lower, and the flow rate is 5j2/min or more), the cooling water is introduced into the water channel 122 inside the intermediate conductor plate 114 and the water channel 125 inside the microwave launcher 103, and is brought into contact with the intermediate conductor plate 114. Microwave transparent window +
04 and the microwave launcher 103 itself.

Next, a microwave oscillator oscillates a microwave (usually 2
．． 45Gt+z, 200W~1.2KW) is a waveguide (
It is rectangular and absorbs microwaves sent to the isolator and reflected from the load side by the H81 mode (normal propagation mode), protects the microwave oscillator, and matches the load with the tuner. Following the propagation path 112, the propagation path is converted from a waveguide to a coaxial tube composed of a coaxial outer conductor 106a and an inner coaxial conductor 106b. here plunger 1
18 performs conversion matching from a waveguide to a coaxial tube. The microwave further follows the propagation path 112 and enters the upper part of the microwave launcher 103 while suppressing the reflection of the microwave by tapers 113a and 1I3b, and advances in the radial direction from the center to the outer periphery to fill the gap in the outer periphery. It enters the outer periphery of the transparent window +05. Microwave is transparent window +0
5 from the outer periphery toward the center, gradually radiating from a spiral slit 201 installed in the conductor plate 104 as shown in FIG. 2 or a rectangular slot 301 as shown in FIG. The microwaves that did not exit from the slit or slots are finally sent to the non-reflection microwave absorber 1.
Absorbed by 19. Therefore, since there is no reflected wave, the transmission window 10
There are no standing waves in 5. The microwave radiated from the slit or slot generates plasma I! of the conductor plate. J! The plasma enters the discharge chamber 107 through a plasma-transmissive insulating plate 115 provided to prevent dew, and plasma is generated by interaction with the magnetic field generated by the air-core coil 111. At this time, the magnitude of the magnetic field is set to the value at which electron cyclotron resonance occurs (
2.45GH7, 875 Gauss) generates plasma very efficiently. The generated plasma has good uniformity because there is no standing wave in the microwave transmission window 105 and there is no non-uniformity caused by it. Ions CI”, CI□“, SFe in the plasma generated as above
", SFS", SF4", SF3", SF2"
, SF”.

Bi and radical CI', CI□, SF6', SF5
“, SF4”.

The Si wafer is etched using SF3'', SF2'', SFI', and Bi, and since highly uniform plasma is used, uniform etching can be achieved.

The temperature of the transmission window is 200 to 4 when no cooling water is used.
However, in this example, the temperature of the transmission window only rises to about 40 to 50°C, and the temperature of the middle open ring body plate 1
14 almost covers the top surface of the transmission window 104, so the transmission window is cooled almost uniformly from the top surface, so even if the temperature difference in the thickness direction of the transmission window is 2 cm or less, it is 10 degrees Celsius.
As a result, thermal damage can be prevented. Using the heat transfer equation to find the temperature difference in the thickness direction of the transmission window caused by this example, it is estimated that the amount of heat received from the plasma through the insulating plate 115 during etching is that all of the microwave power is converted into thermal energy. If we estimate that half of the heat will be transferred to the microwave launcher side and the other half to the sample holder side, even if the heat is transferred only through the transmission window 105 to the intermediate conductor plate 114, the transmission window +
The temperature difference between the surface on the discharge chamber side and the surface on the intermediate conductor plate 114 side of 05 is 3 degrees Celsius at a thickness of about 1 cm (thick enough for a microwave transmission window with a diameter of about 200+n+n to withstand atmospheric pressure).
It can be calculated as the degree.

The above estimate is the maximum value, so the actual value is smaller than this. Moreover, it can be further suppressed by increasing the amount of cooling water or lowering the temperature.

Example 2 Next, FIG. 4 shows a transmission window 1 which is another embodiment of the device of the present invention.
05 shows the configuration of a microwave plasma processing apparatus having a structure for introducing or extracting microwaves at the center. In the same figure, +
06a, +06c, +06b are the coaxial outer conductor, pronator/external conductor, inner pronator conductor, and ll3a, respectively.

+13b and 113c are tapers for changing the microwave propagation path without reflection, and the same reference numerals as in FIGS. 1 and 6 indicate the same ones as in FIGS. 1 and 6. In this embodiment, the inside of the tapered portion is hollow and a cooling water channel is provided.

Next, with the above configuration, a sample is placed in advance in the vacuum container 101 in the same way as in the previous example, and the vacuum container 101 is evacuated and processing gas is flowed into the discharge space 107 to bring the inside of the container to a predetermined pressure. Cooling water is introduced from the cooling water inlets 120 and 123, passes through the cooling water channel 122 to cool the taper 113b, and cools down from the center of the transmission window 105 through the vacuum sealing surface 116b. On the other hand, the outer periphery of the tongue is cooled by the microwave launcher 103 through the vacuum sealing surface 106a.

The flow rate of the cooling water is 5jZ/min, and the temperature is about 30°C or less.

Similar to the first embodiment, the microwaves leaving the tuner propagate through the coaxial tube composed of the coaxial tube outer conductor 106a and the pronating and outer conductor 106c according to the propagation path 112, and enter the upper layer of the microwave launcher 103. The microwave propagates from the center in the radial direction toward the outer periphery, wraps around the outer periphery of the microwave transmission window 105 through the gap in the outer periphery, and enters the outer periphery of the transmission window. The microwaves are gradually emitted from the slits or slots made in the conductor plate 104 shown in the figure, and the surplus microwaves that proceed toward the center and reach the center are transmitted through the microwave transmission window 105 by tapers 113b and 113c to be coaxially transmitted. Outer conductor 10
6c and the same inner conductor [06b], then enters the waveguide 117 and is finally absorbed by the microwave absorber.

Similar to the embodiment shown in FIG. 1, plasma is generated by the microwaves radiated from the slit or slot, and desired processing is performed. The heat from the plasma causes the transparent window 10 to
5. The temperature of the microwave launcher 103 reaches 6. Figure 5 shows the temperature distribution for week J [105]. The size of the meaning of the word is 10 cm in radius, 1 cm in thickness, and the material is alumina and IK.
This is a case where half of the input microwave power of W uniformly enters the surface of the transmission window on the discharge chamber side as thermal energy. As shown in the figure, the vacuum seal surface 106 on the outer periphery is
When cooled by conduction only from b, the temperature difference between the center and the outer periphery was about 84°C, but when the center was cooled, the temperature difference decreased to about 44°C. By performing cooling from the center in this manner, it is possible to reduce the temperature difference between the center and the outer periphery and prevent thermal damage to the microwave transmission window.

Note that the present invention is not limited to the above-mentioned two examples, but can be applied to other microwave plasma apparatuses in which microwaves are supplied to the discharge chamber by a microwave launcher having the same structure. For example, one that applies high frequency power (500 KHz to 20 MHz) to the sample holder or microwave launcher,
By installing an ion extraction electrode in the discharge chamber, it can be applied to a device that extracts ions from the discharge chamber, accelerates them, and irradiates the sample.

〔Effect of the invention〕

As explained above, the cooling structure is provided without disturbing the microwave propagation space, and the microwave transmission window is cooled from the opposite side to the discharge chamber or from the center to prevent damage to the cord, and to avoid downtime for cooling. Because it is necessary, it has the effect of improving productivity.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of a microwave plasma processing apparatus in Embodiment 1 of the present invention, and FIGS. 2 and 3 are plan views of a conductor plate having slits and slots that can be used in the apparatus of the present invention, respectively. , FIG. 4 is a schematic diagram showing the configuration of the microwave plasma processing apparatus in Example 2, and FIG.
This figure is a diagram showing the temperature difference of the microwave transmission window caused by the apparatus shown in FIG. 4, and FIG. 6 is a schematic diagram showing the configuration of a conventional microwave plasma processing apparatus. 101 Vacuum container + 02 Gas inlet 103 Microwave launcher 104 Mask (conductor flat plate with slits or slots) 05 Microwave transmission window 06 Coaxial tube a outer conductor, b inner conductor, C inner and outer conductor discharge chamber sample sample to be processed Holder vacuum pumping system air core coil microwave plasma 14 15 intermediate conductor plate insulating plate 17 18 19 120.123 121.124 122.125 waveguide matching plunger non-reflective microwave absorber cooling water inlet cooling water outlet Cooling channel 01 Spiral slot 01 Rectangular slot

Claims (5)

[Claims] (1) A vacuum container having a discharge space and a means for supplying raw material gas to the discharge space, a flat microwave transmission window that radiates microwaves into the discharge space in a direction perpendicular to the microwave propagation direction, and a microwave A microwave launcher including at least a tapered portion for setting a wave propagation path, a coaxial tube for propagating microwaves from a microwave oscillator to the microwave launcher, and a cover disposed in the discharge space facing the microwave transmission window. A microwave plasma processing apparatus comprising at least a processing sample holder, characterized in that a member in contact with the microwave transmission window of the microwave launcher is provided with a coolant flow path for cooling the transmission window. Microwave plasma processing equipment. (2) Claim characterized in that the microwave launcher has a conductor plate for allowing microwaves to enter from the outer periphery of the microwave transmission window, and the refrigerant flow path is provided in the conductor plate. The device described in (1). (3) The device according to claim (1) or (2), wherein the refrigerant flow path is provided in the tapered portion. (4) The device according to claim (1), wherein a refrigerant introduction/exhaust path connected to the refrigerant flow path is provided inside the center conductor of the coaxial tube. (5) The device according to claim (1), wherein a member of the microwave launcher that is not in contact with the microwave transmission window is also provided with a coolant flow path.