JP2002237462A - Plasma-treating apparatus and window material for transmitting microwave used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a reliable, long-life plasma-treating apparatus by preventing a microwave-introducing window material from being cracked. SOLUTION: For solving the conventional, technical problem, the thickness of the window material is optimized. More specifically, the thickness of a section around a window that easily becomes a breakdown starting point due to the operation of tensile stress is increased, and a central section where electromagnetic waves pass is thinned, thus minimizing thermal stress due to the absorption of electromagnetic waves. Further, tensile stress at a periphery where a breakdown easily occurs is minimized to prevent the window material from being damaged. More specifically, a transmission window for the electromagnetic waves for excitation in a plasma-generating apparatus is made of a ceramics material and the thickness at the center is larger than a peripheral section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus and a window material for transmitting electromagnetic waves for excitation such as microwaves used in the plasma processing apparatus, and more particularly to a plasma processing apparatus having an improved service life and a window for transmitting electromagnetic waves for excitation used therefor. About materials.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a CVD apparatus for forming a film on a semiconductor wafer or an etching apparatus for performing fine processing on a semiconductor wafer is provided with a semiconductor manufacturing apparatus having a plasma generating mechanism for the purpose of high integration. The device is being used. For example, as schematically shown in FIG. 6, a semiconductor processing apparatus such as a CVD apparatus using an electron cyclotron resonance having a microwave generation chamber 1 and a processing chamber 7 is known. According to this apparatus, plasma can be formed without electrodes and in a high vacuum, and film formation or etching can be performed with high density and low damage.

Here, a microwave generation chamber 1 and a waveguide 2,
The processing chamber 7 is separated from the processing chamber 7 by a microwave introduction window 13 via an O-ring 4.
A magnetic field forming coil 6 for forming a magnetic field is arranged. Further, the processing chamber 7 has a gas supply port 10 for supplying a film-forming gas and an atmosphere gas, a gas exhaust port 11 for evacuating the processing chamber 7, and a monitoring window 12 for monitoring the inside of the processing chamber 7. A support / mounting table 9 for supporting the semiconductor wafer 8 directly or via a susceptor (not shown) is provided in the chamber 7.

[0004] Film formation by this CVD apparatus is performed as follows. That is, after the semiconductor wafer 8 is mounted on the support / mounting table 9 and the inside of the processing chamber 7 is evacuated, a film forming gas and an atmosphere gas are supplied from the gas supply port 10. On the other hand, the microwave generated in the microwave generation chamber 1 is introduced into the processing chamber 7 through the microwave introduction window 13. In addition, by energizing the coil 6 in accordance with the introduction of the microwave to generate a magnetic field, high-density plasma is generated in the processing chamber 7. The plasma energy decomposes the film-forming gas into an atomic state, and deposits and forms a film on the surface of the semiconductor wafer 8.

By the way, in this type of manufacturing apparatus,
The microwave introduction window material 13 is manufactured from a ceramic plate material such as aluminum nitride or aluminum oxide. These materials are widely used because of their high heat resistance and excellent plasma resistance.

[0006]

By the way, in the above-mentioned plasma processing apparatus, a large temperature difference occurs between a peripheral portion and a central portion of a window material that transmits an electromagnetic wave for excitation such as a microwave when used. This is because when a part of the energy of the electromagnetic wave passes through the window, it is absorbed by the window material to generate heat. Further, since the incident side of the electromagnetic wave is at atmospheric pressure and the plasma processing chamber separated from the window is under vacuum, an O-ring is often used for vacuum sealing. However, since the O-ring has only a heat-resistant temperature up to 200 ° C., it is common to use the O-ring receiving portion with water cooling. Since such a water-cooled structure lowers the temperature around the window, the temperature difference from the center of the window becomes larger.

[0007] Such a temperature difference causes thermal stress inside the window. When the output of the electromagnetic wave to be applied is increased, the temperature difference increases, and when the generated thermal stress exceeds the breaking stress of the window material, the window may be broken and become unusable.

In recent years, silicon wafers have become larger in diameter, and the tendency for cracks to occur due to the above-mentioned thermal factors is increasing more and more. In other words, this tendency increases as the size of the window increases, and it is necessary to develop a window that is resistant to cracking in order to cope with an increase in the diameter of the wafer. Also,
In a window having a large diameter, the stress as a vacuum bulkhead is also increased, and the risk of destruction is further increased by being superimposed on the above-mentioned thermal stress.

Further, in recent years, there has been a demand for increasing the number of processed wafers per unit time and an increase in the output of an electromagnetic wave to be input in order to improve production efficiency. From this point of view, a highly reliable electromagnetic wave transmission window that is difficult to crack has been desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents generation and destruction of cracks in a window material for transmitting electromagnetic waves for excitation such as microwaves, thereby providing a highly reliable and long-life plasma processing apparatus. It is intended to realize.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and by optimizing the thickness of a window material, that is, a tensile stress acts to become a fracture starting point. Increase the thickness of the window area that is easy to
By reducing the thickness of the central part that transmits electromagnetic waves, heat generation due to the absorption of electromagnetic waves is minimized, and furthermore, the tensile stress in the vicinity where breakage is likely to occur is minimized, so that windows are less likely to break. .

That is, a first aspect of the present invention is a plasma processing apparatus for processing a semiconductor wafer by irradiating an excitation electromagnetic wave into a processing chamber in which a semiconductor wafer as an object to be processed is mounted to generate plasma. A plasma processing apparatus characterized in that a ceramic plate having a thickness at a central portion smaller than a thickness at a peripheral portion is used as an electromagnetic wave transmitting window material for excitation.

The thickness of the central portion of the exciting electromagnetic wave transmitting window material is larger than a value obtained by multiplying the diameter of the exciting electromagnetic wave transmitting window by 0.020, and the thickness of the peripheral portion is 1% of the thickness of the central portion. It is preferably from 2 times to 15 times.

The shape of the exciting electromagnetic wave transmitting window is as follows:
It is a rotationally symmetric body whose axis of rotation is perpendicular to the plane,
When the thickness of the peripheral portion of the excitation electromagnetic wave transmitting window material is t1 and the thickness of the central portion is t2, the expression (t2 + (t1−t2)) is obtained.
It is preferable that the diameter of the virtual circle connecting the window portions having the thickness expressed by (/ 2) is not less than １ ／ and not more than 95/100 of the diameter of the window.

Furthermore, the cross section of the recess cut perpendicularly to the plane of the excitation electromagnetic wave transmitting window may be any of a truncated conical recess, a curved recess, or a stepped recess with a chamfered corner. Further, the concave portion of the excitation electromagnetic wave transmission window,
It may be formed on at least one surface of the window material, or may be formed on both surfaces.

The electromagnetic wave transmitting window material for excitation is made of at least one ceramic selected from aluminum nitride, aluminum oxide, and YAG. The more preferable electromagnetic wave transmitting window material for excitation is aluminum nitride or aluminum oxide.

In the present invention, the exciting electromagnetic wave is not limited to a microwave having a frequency of 2.45 GHz, but may be an electromagnetic wave having various frequencies.

Next, a second aspect of the present invention relates to a plasma processing apparatus for processing a semiconductor wafer by irradiating an excitation electromagnetic wave into a processing chamber in which a semiconductor wafer as an object to be processed is mounted to generate plasma. The electromagnetic wave transmitting window for a plasma processing apparatus is characterized in that the excitation electromagnetic wave transmitting window used is a ceramic plate material in which the thickness of a central portion is thinner than the thickness of a peripheral portion as an exciting electromagnetic wave transmitting window material. is there.

The thickness of the central part of the exciting electromagnetic wave transmitting window material is larger than the value obtained by multiplying the diameter of the exciting electromagnetic wave transmitting window by 0.020, and the thickness of the peripheral part is 1% of the thickness of the central part. It is preferably from 2 times to 15 times.

Further, the excitation electromagnetic wave transmitting window has a shape as follows:
When the thickness of the periphery of the electromagnetic wave transmitting window material for excitation is t1 and the thickness of the center is t2, the expression (t2 + (t1−t2) / 2) is obtained. It is preferable that the diameter of the virtual circle connecting the window material portions having the wall thickness represented by ()) is not less than ４ of the diameter of the window and not more than 95/100.

It is preferable that the cross-sectional shape of the concave portion cut perpendicular to the plane of the excitation electromagnetic wave transmission window is any one of a truncated cone, a curved line, and a stepped shape with a chamfered corner.

The recess of the exciting electromagnetic wave transmitting window may be formed on one surface of the window material or on both surfaces.

The electromagnetic wave transmitting window material for excitation used in the present invention is made of aluminum nitride, aluminum oxide, and Y.
At least one ceramic selected from AG. Further, it is preferable that the excitation electromagnetic wave transmitting window material is aluminum nitride or aluminum oxide.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plasma processing apparatus according to the present invention will be described with reference to the drawings. (Processing Apparatus) FIG. 1 is a schematic view of a plasma processing apparatus of the present invention. In FIG. 1, reference numeral 1 denotes an excitation electromagnetic wave generation chamber which oscillates a microwave which is, for example, a 2.45 GHz excitation electromagnetic wave. This microwave
After passing through the excitation electromagnetic wave transmission window 3 via the waveguide 2,
The light is radiated to the cavity resonator 5. A coil 6 is arranged around the cavity resonator 5 so as to generate a magnetic field. Further, the processing chamber 7 is connected to a gas supply port 10 for supplying a processing gas and an atmosphere gas, and a gas exhaust port 11 connected to a vacuum exhaust pump (not shown) for evacuating the processing chamber 7. Is evacuated and a processing gas is supplied. By optimizing the frequency of the excitation electromagnetic wave and the magnetic flux density of the magnetic field, resonance can be efficiently performed and high-density plasma can be generated. The semiconductor wafer 8 as the object to be processed is irradiated to perform required processing such as film formation or etching.

According to the present invention, in such a plasma processing apparatus, as the excitation electromagnetic wave transmitting window 3, a window material made of a ceramic plate and having a central portion made thinner than a peripheral portion is used. Thereby, the thermal stress of the window material due to the excitation electromagnetic wave is reduced.

(Window Material) The shape of the exciting electromagnetic wave transmitting window material used in the present invention will be described below. The present invention is characterized in that the central part of the electromagnetic wave transmitting window material for excitation is made thinner than the peripheral part. That is, the thickness of the center portion of the excitation electromagnetic wave transmitting window material must be larger than a value obtained by multiplying the diameter of the window by 0.020. If the thickness of the central portion is smaller than this, if the processing chamber is placed in a high vacuum, sufficient strength as a vacuum partition cannot be maintained.

It is desirable that the thickness of the peripheral portion of the exciting electromagnetic wave transmitting window material be 1.2 to 15 times the thickness of the central portion. When the thickness of the peripheral part of the electromagnetic wave transmitting window material for excitation is 1.2 times or less the thickness of the central part, the effect of the present invention for preventing the damage to the tensile stress in the peripheral part due to the generation of thermal stress is small and the thickness is uniform. It will not be much different from a conventional window. If it is 15 times or more, the resistance to the tensile stress in the peripheral portion caused by the generation of the thermal stress is sufficient, but the strength of the peripheral portion to the breaking stress is excessive, and it becomes meaningless in design.

The shape of the excitation electromagnetic wave transmission window is shown in FIG.
As shown in FIG. 3, only one surface of the window material may be concave, or as shown in FIG. 3, both surfaces may be concave. In these shapes, the concave surface may be a linear plane,
Desirably, it is a curved plane. FIG.
As shown in (2), the shape may be stepwise processed so that the center portion is thinned, but in such a shape, it is preferable to perform an appropriate chamfering process on the step portion.

Further, the relationship between the irradiation diameter of the excitation electromagnetic wave that irradiates the thin portion of the excitation electromagnetic wave transmitting window material and the diameter of the thin portion of the window material affects the life of the window material, and the excitation electromagnetic wave irradiation. Will affect the efficiency of plasma generation. In other words, it is important to design the apparatus so that most of the radiation excitation electromagnetic wave passes through the thin portion of the window material. For this purpose, as shown in FIG. 5, when the exciting electromagnetic wave transmitting window material in the present embodiment is rotationally symmetric about the center of the plane, the thickness of the thickest portion of the window material is defined as t1. When the thickness of the thinnest portion is t2, the portion where the thickness is smaller than the thickest portion by the thickness of (t1 + t2) / 2 is traced to be a virtual circle in FIG. It is desirable to control the thickness of the window material so that the diameter of this virtual circle is not less than 1/4 and not more than 95/100 of the diameter of the window. When the diameter of the virtual circle is 1/4 or less of the diameter of the window, the thick portion is applied to the heat-generating portion due to the transmission of the electromagnetic wave. It will not be much different from the window of the product. On the other hand, when the diameter of the virtual circle is 95/100 or more of the diameter of the window, there is an effect of resistance to the tensile stress at the peripheral portion, which is the object of the present invention, but there is a problem in handling and manufacturing. In the case of using the excitation electromagnetic wave transmission window having the concave portions formed on both surfaces, it is desirable that the diameter of the virtual circle on both surfaces be within the above range.

By designing the electromagnetic wave transmission window for excitation under the above-described conditions, a reliable plasma processing apparatus in which the life of the window material in the plasma processing apparatus, which is an object of the present invention, is greatly improved can be realized. In the excitation electromagnetic wave transmitting window of the present invention, the center portion is thinned, but the peripheral portion for gripping the window material is thick, and the entire window material is firmly supported by the thick outer periphery, so that the strength is improved. Problem does not occur.

(Material) Aluminum nitride, aluminum oxide, YAG, etc. can be used as ceramics constituting the electromagnetic wave transmitting window material for excitation. Aluminum nitride and aluminum oxide are particularly preferable in terms of plasma resistance and strength. preferable. This electromagnetic wave transmitting window material for excitation can be manufactured in the same manner as a high-purity ceramic member in an ordinary semiconductor manufacturing apparatus.

The preferred electromagnetic wave transmitting window material for excitation in the present invention is an aluminum nitride disc-shaped sintered body having a diameter of 100 mm.
This is a single-sided concave window material having a thickness of about 300 mm, a thickness of a peripheral part of 10 to 30 mm, a thickness of a central part of 5 to 15 mm, and a diameter of a virtual circle in FIG. 5 of 40 to 120 mm.

Hereinafter, the present invention will be described with reference to examples.

Examples and Comparative Examples One side of an aluminum nitride disk having a diameter of 220 mm and a thickness of 20 mm was made concave by grinding to produce an excitation electromagnetic wave transmission window of the present invention shown in FIG. The thickness at the center is 8m
m. The diameter of the virtual circle shown in FIG. 5 was 90 mm. On the other hand, the conventional example has a diameter of 220 mm and a thickness of 20 mm.
mm aluminum nitride windows were fabricated. These samples were attached to a microwave device, and the microwave output was changed variously to generate plasma for 10 minutes. In each experiment, a five-sheet test was performed to check the number of broken window materials. Table 1 shows the results. The numerical values in the table are the number of cracks / the number of tests.

[0035]

[Table 1]

As is evident from the results in Table 1, the electromagnetic wave transmitting window material for excitation provided with the concave portion of the present invention could be used without any destruction up to a microwave output of 1400 W. The conventional electromagnetic wave transmitting window material for excitation without forming a concave portion has already been broken at a microwave output of 1200 W, which proved that the window material of the present invention has high reliability.

[0037]

According to the present invention, even in a plasma processing apparatus using a high-output excitation electromagnetic wave, the generation or destruction of the window material can be effectively prevented, and a highly reliable plasma generator and its use. Window material could be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a plasma processing apparatus of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of an example of an excitation electromagnetic wave transmission window of the present invention.

FIG. 3 is a cross-sectional view illustrating a schematic configuration of another example of the excitation electromagnetic wave transmission window of the present invention.

FIG. 4 is a sectional view showing a schematic configuration of another example of the excitation electromagnetic wave transmission window of the present invention.

FIG. 5 is a cross-sectional view showing a schematic configuration of another example of the excitation electromagnetic wave transmission window of the present invention.

FIG. 6 is a sectional view showing a schematic configuration of a conventional plasma processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Microwave generation chamber 2 ... Waveguide 3 ... Electromagnetic wave transmission window for excitation 4 ... O-ring 5 ... Cavity resonance chamber 6 ... Magnetic field forming coil 7 ... Processing chamber 8 ... Semiconductor wafer 9 ... ... Semiconductor wafer support / mounting table 10 ... Process gas supply port 11 ... Gas discharge port

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masami Amano 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. (72) Inventor Noriaki Kashiwa 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics, Inc F term in development laboratory (reference) 4K030 CA04 FA01 KA30 KA46 LA15 5F045 AA09 BB20 EH03 EH17

Claims (14)

[Claims] 1. A plasma processing apparatus for processing a semiconductor wafer by irradiating an excitation electromagnetic wave into a processing chamber in which a semiconductor wafer as an object to be processed is mounted and generating a plasma, as a window material for transmitting an electromagnetic wave for excitation. A plasma processing apparatus using a ceramic plate material in which a thickness at a central portion is smaller than a thickness at a peripheral portion. 2. A thickness of a central portion of the electromagnetic wave transmitting window material for excitation is larger than a value obtained by multiplying a diameter of the electromagnetic wave transmitting window for excitation by 0.020, and a thickness of a peripheral portion is a thickness of the central portion. 2. The plasma processing apparatus according to claim 1, wherein the value is 1.2 times or more and 15 times or less. 3. The exciting electromagnetic wave transmitting window has a rotationally symmetric shape with respect to the center of the plane, and the thickness of the peripheral portion of the exciting electromagnetic wave transmitting window material is t1, and the thickness of the central portion is t1. When t2 is set, the diameter of the virtual circle connecting the window portions having the wall thickness represented by the formula (t2 + (t1-t2) / 2) is equal to or more than 1/4 of the diameter of the window and equal to or less than 95/100. The plasma processing apparatus according to claim 1 or 2, wherein: 4. A cross section of the recess cut perpendicular to the plane of the excitation electromagnetic wave transmission window is a truncated cone, a curve, or a step with a chamfered corner. The plasma processing apparatus according to claim 1. 5. The plasma processing apparatus according to claim 1, wherein the concave portion of the exciting electromagnetic wave transmitting window is formed on at least one surface of the window material. 6. The electromagnetic wave transmitting window material for excitation is at least one kind of ceramics selected from aluminum nitride, aluminum oxide, and YAG. Plasma processing equipment. 7. The plasma processing apparatus according to claim 1, wherein the excitation electromagnetic wave is a microwave. 8. An excitation electromagnetic wave transmission window used in a plasma processing apparatus for processing a semiconductor wafer by irradiating an excitation electromagnetic wave into a processing chamber in which a semiconductor wafer as a processing object is mounted to generate plasma. An electromagnetic wave transmitting window for a plasma processing apparatus, wherein a ceramic plate having a center portion having a smaller thickness than a peripheral portion is used as an exciting electromagnetic wave transmitting window material. 9. A thickness of a central portion of the exciting electromagnetic wave transmitting window material is larger than a value obtained by multiplying a diameter of the exciting electromagnetic wave transmitting window by 0.020, and a thickness of a peripheral portion is a thickness of the central portion. 9. The electromagnetic wave transmission window for a plasma processing apparatus according to claim 8, wherein said window is 1.2 times or more and 15 times or less. 10. The excitation electromagnetic wave transmitting window is rotationally symmetric about the center of the plane, and the thickness of the peripheral portion of the exciting electromagnetic wave transmitting window material is t1, and the thickness of the central portion is t1. t2
Where the diameter of the imaginary circle connecting the window material portions having the wall thickness expressed by the formula (t2 + (t1-t2) / 2) is not less than 1/4 of the diameter of the window and not more than 95/100. The electromagnetic wave transmission window for a plasma processing apparatus according to claim 8 or 9, wherein: 11. The cross section of the recess cut perpendicular to the plane of the excitation electromagnetic wave transmission window is any of a truncated cone, a curve, or a step having a chamfered corner. An electromagnetic wave transmission window for a plasma processing apparatus according to any one of claims 8 to 10. 12. The electromagnetic wave transmission for a plasma processing apparatus according to claim 8, wherein the recess of the excitation electromagnetic wave transmission window is formed on at least one surface of the window material. window. 13. The electromagnetic wave transmitting window material for excitation is at least one kind of ceramics selected from aluminum nitride, aluminum oxide, and YAG. Electromagnetic wave transmission window for plasma processing equipment. 14. An electromagnetic wave transmission window for a plasma processing apparatus according to claim 8, wherein said excitation electromagnetic wave is a microwave.