JPH05152216A - Plasma treatment equipment - Google Patents

Abstract

PURPOSE:To provide a plasma treatment equipment having a microwave introducing window, which is assembled and mounted simply and sufficiently resists pressure load applied to the microwave introducing window and in which microwave power induced into a plasma treatment chamber is maximized, as a microwave introducing window installed the coupling section of the plasma treatment chamber and a microwave waveguide. CONSTITUTION:Fitting structure by an upper flange section 6 and a lower flange section 7 is used for the coupling of a conical type microwave waveguide 3 and a plasma treatment chamber 1, and a microwave introducing window (a dielectric discoidal member) 5 having specified material quality and specified thickness is held by these flange sections. The quality of material and the thickness of the microwave introducing window 5 are selected so that the reflectivity of microwaves is minimized and they resist vacuum force applied to the sectional area of the introducing window at that time. When the frequency of microwaves is 2.45GHz, the thickness of quartz is brought to 33mm when the quartz is used as the quality of material of the microwave introducing window 5, the thickness of alumina ceramics is brought to 21mm when alumina ceramics are employed, and tolerance is brought to approximately + or -1mm respectively.

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 using microwaves, and more particularly, it utilizes charged particles in plasma generated in a processing chamber to perform sputtering or etching on the surface of a substrate or to use a material gas. The present invention relates to a plasma processing apparatus suitable for, for example, a semiconductor manufacturing apparatus or the like, which is suitable for forming a film by promoting the reaction.

[0002]

2. Description of the Related Art In some plasma processing apparatuses, for example, a microwave waveguide coupled to a plasma processing chamber is used to generate plasma in the processing chamber by the microwave energy introduced by the microwave waveguide. The microwave waveguide and the plasma processing chamber are generally partitioned by a partition (a microwave introduction opening sealing plate) that holds the vacuum in the processing chamber while allowing microwaves to pass therethrough.

Since this partition wall transmits microwaves,
Generally, the material is a dielectric, but under certain conditions, the microwave is reflected by the partition wall or there is a dielectric loss due to the material of the partition wall. There is a risk that the microwave will not be efficiently transmitted into the processing chamber, or that the temperature will rise locally due to the power loss.

Therefore, in JP-A-60-203001, in order to suppress the microwave power loss in the partition wall as much as possible, a plurality of dielectric plates, which are sufficiently thin compared to the microwave wavelength, are arranged side by side in the microwave waveguide. The thing is made into a partition, a microwave is made to inject perpendicularly to this, the dielectric board space is adjusted so that the reflection of the microwave in each partition may be offset, and the reflectance of the microwave should be minimized as a whole. , A technique for improving the efficiency of introducing microwaves into a processing chamber is disclosed.

[0005]

The prior art is characterized by using a plurality of thin dielectric plates, but an apparatus for supplying microwave power from a large area opening into a processing chamber in a low pressure atmosphere. In the above, since the vacuum force applied to the partition wall increases with the area of the waveguide, the structure in which the dielectric plate keeps the airtightness inside and outside the processing chamber is not reliable in the strength of the dielectric and the dielectric plate is damaged. As a result, the airtightness of the processing chamber may be broken. Further, in the prior art, in order to minimize the reflectance of microwaves, the distance between the dielectric plates must be adjusted, and highly accurate assembly and mounting work is required.

Therefore, in the prior art, the efficiency of maintenance work in a plasma processing apparatus having a large processing capacity with a large microwave introduction opening area from the waveguide to the processing chamber is not taken into consideration, and the handling is troublesome. However, there is a problem that the increased processing capacity cannot be fully utilized.

The object of the present invention is to easily install and assemble a partition wall for introducing microwaves, which is installed at a joint portion between a waveguide having a large area opening and a processing chamber, and to prevent pressure from the atmosphere. It is an object of the present invention to provide a plasma processing apparatus that can withstand a load sufficiently and can keep microwave power introduction efficiency into a processing chamber sufficiently high.

[0008]

SUMMARY OF THE INVENTION The above object is to provide a flange-like fitting member at a connecting portion between an opening portion of a microwave waveguide having a cone-shaped opening portion such as a pyramid shape and a plasma processing chamber. And a dielectric plate-shaped member (microwave introduction window) for sealing the opening, which is sandwiched and held in the fitting portion of the flange-shaped fitting member. In addition,
At this time, the shape of the opening of the microwave waveguide and the dielectric plate-like member may be rectangular (including square) or circular.

[0009]

The flange-shaped fitting member allows the microwave waveguide and the dielectric plate-shaped member to be attached to and detached from the plasma processing chamber. Therefore, the microwave waveguide and the dielectric plate member can be arbitrarily removed from the plasma processing chamber, and the maintenance can be easily performed.

At this time, the material and the thickness of the microwave introduction window (dielectric plate member) are generated at the boundaries before and after the microwave introduction window with respect to the wavelength of the microwave incident on the microwave introduction window and passing therethrough. The reflected wave is canceled out of the microwave introduction window, the reflectance is minimized, and the one that can withstand the vacuum force applied to the cross-sectional area of the position where the introduction window is installed in the waveguide is selected.

The microwave frequency is 2.45G.
In the case of Hz, the thickness is 33 mm when quartz is used as the material of the microwave introduction window, and 21 mm when alumina ceramics is used. There is a permissible range of about ± 1 mm in a range where reflectance does not matter in practical use.

Further, by selecting the thickness of the microwave introduction window which has sufficient strength against vacuum load and minimum reflectance, airtightness can be maintained with one introduction window, and the inside of the introduction window can be maintained. As a result of minimizing the standing wave, the microwave power loss in the introduction window is minimized, and the maximum microwave power can be efficiently supplied into the processing chamber.

Further, as compared with the method in which the microwave introducing window is constituted by a plurality of dielectric plates, the microwave introducing window may be constituted by one sheet of dielectric material, so that the airtight holding portion is small and the assembly is possible. Installation work is also easy.

[0014]

The plasma processing apparatus according to the present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 shows an embodiment of the present invention. In the figure, reference numeral 1 denotes a plasma processing chamber, in which a low pressure atmosphere (several m
The substrate 8 mounted on the substrate holder 9 is housed therein for plasma processing. A rectangular microwave waveguide 2 serves to transmit microwave power of 2.45 GHz from a microwave generation source (not shown).

A conical microwave waveguide 3 serves to supply the microwave power of 2.45 GHz supplied by the rectangular microwave waveguide 2 into the plasma processing chamber 1 through the opening 4 having a large area. For this reason, it is made of a microwave waveguide that is spread in a conical shape toward the plasma processing chamber 1 side.

Reference numeral 5 is a microwave introduction window (dielectric disk-shaped member)
Then, the inside of the plasma processing chamber 1 made of a quartz plate having a thickness of 33 ± 1 mm and closing the opening 4 of the conical microwave waveguide 3 and having a low atmospheric pressure of several mm torr is in a state of almost atmospheric pressure. It serves to hermetically seal from the inside of the conical microwave waveguide 3 at.

An upper flange 6 is formed as a part of the conical microwave waveguide 3, and its inner surface forms an upper part near the opening 4 of the conical microwave waveguide 3. .. Reference numeral 7 denotes a lower flange portion, which is made as a part of the plasma processing chamber 1 and has an inner surface having a conical microwave waveguide 3
The opening 4 is formed.

The upper flange portion 6 and the lower flange portion 7 each have a cylindrical fitting portion paired with each other as shown in the drawing, and an O-ring seal is provided at the abutting portion of the fitting portion. The microwave introduction window 5 is sandwiched and held via
As a result, airtightness is maintained and a low atmospheric pressure atmosphere in the plasma processing chamber 1 is maintained. It is designed to be airtight.

Reference numeral 8 denotes a vacuum pump, which has a function of exhausting the inside of the plasma processing chamber 1 when necessary and maintaining a low atmospheric pressure atmosphere in the plasma processing chamber 1. Reference numeral 9 denotes an electromagnetic coil for generating a magnetic field, which is installed on the outer circumference of the microwave waveguide 3 and the plasma processing chamber 1 and serves to generate a magnetic field in the plasma processing chamber 1. Reference numeral 10 is a second microwave introduction window, which is made of an alumina ceramics plate having a thickness of 21 ± 1 mm brazed in the microwave waveguide 2, and even when the microwave introduction window 5 in the opening 4 is damaged, The airtightness is maintained. Reference numeral 11 denotes a substrate holder, which has a function of placing and holding a semiconductor substrate 12 to be processed at a predetermined position in the plasma processing chamber 1.

In the plasma processing apparatus according to this embodiment,
A microwave supplied from a microwave generation source such as a microwave oscillator (not shown) to the processing chamber 1 through the microwave waveguides 2 and 3, and a magnetic field generated in the plasma processing chamber 1 by the magnetic field generation coil 9. The gas gas in the plasma processing chamber 1 forms discharge plasma due to the interaction of 1), and the plasma is used to perform processing such as sputtering, etching, or film formation on the semiconductor substrate 12.

At this time, in this embodiment, the microwave to be introduced into the plasma processing chamber 1 is supplied into the plasma processing chamber 1 from the large-sized opening 4 by the action of the conical microwave waveguide 3. Therefore, a plasma processing apparatus having a large processing capacity can be easily obtained.

Further, according to this embodiment, the connecting portion between the conical microwave waveguide 3 and the plasma processing chamber 1 is constituted by the fitting of the upper flange portion 6 and the lower flange portion 7, and the microwave introduction window. Since the hermetic sealing of No. 5 is provided by the O-ring seal, the plasma processing chamber 1
The microwave waveguides 2 and 3 can be easily removed from the plasma processing chamber 1 for internal maintenance.

FIG. 2 shows how the reflectance of the microwave changes with the thickness of the dielectric disk-shaped member forming the microwave introduction window 5. The microwave in the waveguide having the dielectric medium is shown in FIG. If the wavelength is λg, the thickness t of the microwave introduction window 5 that minimizes the microwave reflectance is t = λg /
Given in 2.

As a practical permissible range, when the reflectance is suppressed within 5%, the microwave frequency is 2.4.
At 5 GHz, t = 33 ± 1 mm when the material of the microwave introduction window 5 is quartz, and t = 21 ± 1 mm when alumina ceramics is selected.

The microwave introduction window having the above-mentioned thickness must satisfy the strength against the vacuum load necessary for plasma processing. FIG. 3 shows a relationship between the microwave waveguide diameter D (equal to the diameter of the microwave introduction window 5) D and the window thickness t at which the reflectance is minimum, and the distributed load model applied to the disk for the vacuum load. 3 shows the relationship between the diameter D of the microwave introduction window and the thickness t satisfying the safety range when the safety factor for stress is 10 for alumina ceramics.

As is clear from FIG. 3, the upper region of the straight line showing the relationship between the diameter D and the thickness t is the safe range, and when the disc material is quartz, D = 200 mm or more, and in the case of alumina ceramics. It can be seen that the thickness t at which the reflectance is minimum takes a constant value when D = 100 mm or more. Regarding the strength, with respect to quartz having a thickness t = 33 mm, a circular microwave introduction window diameter D = 580 mm or less and a thickness t
It can be seen that if the circular microwave introduction window diameter D = 760 mm or less with respect to alumina ceramics of = 21 mm, the safety range against vacuum load is satisfied.

Next, FIG. 4 shows the plasma processing chamber 1 for the microwave power of two types of cases in which the thickness t of the microwave introduction window 5 made of quartz is 5 mm and 33 mm.
It shows the measured value of the density of the plasma generated in the case, and in the case where the thickness was 33 mm, the thickness was 5 m.
It can be seen that for a case of m, a predetermined plasma density can be obtained with about one-half the microwave power.

Therefore, according to the above-mentioned embodiment, since the plasma is efficiently generated in this way, the reflection of the microwaves in the microwave introduction window 5 is suppressed to the minimum, and as a result, the microwave is reflected. It can be seen that the waves are transmitted in the plasma processing chamber 1 sufficiently efficiently.

FIG. 5 shows another embodiment of the present invention. In this embodiment, the gas blowing plate 13 is provided below the microwave introduction window 5 made of quartz in the embodiment of FIG. 1 (the plasma processing chamber side). This gas blowing plate 13 is made of a quartz plate like the microwave introduction window 5 and has a large number of small holes 13a.
Is provided, and is disposed with a gap g having a predetermined dimension between the microwave introduction window 5 and the microwave introduction window 5.

For this reason, therefore, a cylindrical flange insertion portion 14 is provided in the plasma processing chamber 1, and the same upper flange portion 6 and lower flange portion 7 as those in the embodiment of FIG. 1 are inserted and fitted into this flange insertion portion 14. By being combined, the conical microwave waveguide 3 is attached to the plasma processing chamber 1, and
The microwave introduction window 5 has an upper flange portion 6 and a lower flange portion 7.
It is designed to be sandwiched between and held.

At this time, for positioning the microwave introduction window 5 and the gas blowing plate 13, a ring-shaped protruding portion 14a is formed inside the flange insertion portion 14 so that the positioning can be obtained. As well as
A gas introduction passage 16 also formed in the flange insertion portion 14 communicates with a gap g between the microwave introduction window 5 and the gas blowing plate 13. Here, the gas introduced from the gas introduction passage 16 passes through the ring-shaped passage 17 formed by the notch portion formed in the lower flange portion 7 and the ring-shaped protruding portion 14a to form the gap g.
It has become possible to lead to.

Therefore, according to this embodiment, the gas required for plasma processing is supplied from the large number of small holes 13a formed in the gas blowing plate 13 to the semiconductor substrate 12 which is the workpiece.
It can be uniformly blown from above, and an appropriate plasma treatment can be easily obtained. In the embodiment of FIG. 5, the combined thickness of the microwave introduction window 5 and the gas blowing plate 13, that is, the total thickness of them is the same as the embodiment of FIG. It is also made to have a size of 33 mm so as to satisfy the condition of.

Therefore, also in this embodiment, the microwave introduction window 5 and the gas blowing plate 13 can withstand a vacuum load sufficiently, and the plasma generation efficiency in the plasma processing chamber 1 is also sufficiently improved. Is.

In the above embodiments, the conical microwave waveguide 3 is used as the microwave waveguide for supplying the microwave from the microwave generation source to the plasma processing chamber. However, the present invention is not limited to this. Any microwave waveguide having a cone-shaped and widened opening may be used, and for example, a pyramidal microwave waveguide may be used. Not to mention good things. Then, in this case, the microwave introduction window (dielectric disk-shaped member) 5 in the above-mentioned embodiment is also rectangular.
It goes without saying that it is necessary to use a (square) dielectric plate member.

[0035]

According to the present invention, even a large-area microwave introduction window installed at the joint between the processing chamber and the microwave waveguide can be easily assembled and attached, and can be added to the microwave introduction window. It is possible to easily obtain a plasma processing apparatus that has a microwave introduction window that can sufficiently withstand a pressure load and that maximizes the microwave power introduced into the processing chamber.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing a relationship between a thickness t according to a material of a microwave introduction window and a reflectance with respect to microwaves.

FIG. 3 is a characteristic diagram showing a safety limit value of a thickness t with respect to a diameter D of a microwave introduction window.

FIG. 4 is a characteristic diagram showing the relationship between the density of plasma generated in the processing chamber and the microwave power according to the thickness of the quartz microwave introduction window in the embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing another embodiment of the plasma processing apparatus according to the present invention.

[Explanation of symbols]

 1 Plasma Processing Room 2 Microwave Waveguide 3 Conical Microwave Waveguide 4 Opening 5 Microwave Introducing Window (Dielectric Disc Member) 6 Upper Flange 7 Lower Flange 8 Vacuum Pump 9 Electromagnetic Coil 10 Second Micro Wave introduction window 11 Substrate holder 12 Semiconductor substrate 13 Gas blowing plate 13a Small hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Tezuka 1168 Moriyama-cho, Hitachi City, Ibaraki Prefecture Hiritsu Manufacturing Co., Ltd.Energy Research Institute (72) Ken Ken Yoshioka 1168 Moriyama-cho, Hitachi City, Ibaraki Hitachi (72) Inventor Kenzo Shima, 1-1 1-1 Sachimachi, Hitachi, Ibaraki Prefecture Hitachi Co., Ltd. Hitachi factory, Hitachi (72) Inventor, Junji Sato 3-1-1, Saiwaicho, Hitachi, Ibaraki Stock company Hitachi Ltd.Hitachi factory

Claims (5)

[Claims] 1. A microwave from a microwave generation source,
In a plasma processing apparatus of a system for supplying to a plasma processing chamber by using a microwave waveguide having a cone-shaped and widened opening, a pair formed with a fitting portion at a connecting portion between the opening and the plasma processing chamber. Flange member,
A dielectric plate-shaped member for sealing the opening, which is sandwiched and held in a fitting portion of the flange member, is provided, and the microwave waveguide and the plate-shaped member can be freely attached to and detached from the plasma processing chamber. A plasma processing apparatus having the above configuration. 2. The invention according to claim 1, wherein the microwave supplied from the microwave source has a frequency of 2.45.
GHz, the material of the dielectric plate-shaped member is quartz, and the thickness thereof is selected to be 33 ± 1 mm. 3. The invention according to claim 1, wherein the microwave supplied from the microwave source has a frequency of 2.45.
The plasma processing apparatus is characterized in that the frequency is GHz, the material of the dielectric plate member is alumina ceramics, and the thickness thereof is selected to be 21 ± 1 mm. 4. The plasma processing according to claim 1, wherein a dielectric partition member is provided in a portion of the microwave waveguide from the microwave generation source to the opening. apparatus. 5. The dielectric plate-shaped member according to claim 1, wherein a dielectric plate-shaped member having a plurality of pores arranged in parallel with a gap having a predetermined dimension is provided on the side of the plasma processing chamber of the dielectric plate-shaped member. The plasma processing apparatus is configured so that gas required for plasma processing is supplied from the gap between the two dielectric plate-shaped members into the plasma processing chamber through the plurality of pores. ..