JP2006012484A - Microwave emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make uniform introduction of microwave into a processing chamber and reduction of microwave voltage standing wave ratio compatible with each other with a purpose of providing a device uniformly processing a substance to be processed without imposing overload on a microwave power source circuit. <P>SOLUTION: The microwave emitting device emits microwave from a plurality of slots arranged on an endless annular wave guide, and only the microwave emission rate at the slot nearest to the microwave introducing part of the endless annular wave guide is made smaller than that of the other slots. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for uniformly emitting microwaves. The present invention also relates to an apparatus for processing the surface of a substrate to be processed with plasma generated using the microwave emission apparatus. Furthermore, surface modification to make light-transmitting materials and lenses used in semiconductor dry processes, liquid crystal display devices, etc., anti-reflective treatment of lenses, artificial bone parts such as artificial bones, and to make them more compatible with living bodies and to increase their strength. It relates to processing equipment such as quality processing.

  A microwave introducing device having a conventional endless annular waveguide disclosed in Japanese Patent No. 3118225, Japanese Patent No. 3093718, Japanese Patent No. 2925535, etc. is provided with a plurality of slots in an endless annular waveguide, and plasma Microwaves are supplied into the generation chamber. The microwave propagated from the microwave power source is distributed in two directions at the endless annular waveguide entrance, propagates on both sides of the endless annular waveguide, and propagates into the plasma chamber from a plurality of slots. In order to uniformly introduce microwaves into the plasma chamber, slots having the same shape are arranged in the endless annular waveguide at equal intervals.

  A conventional example will be described in detail with reference to FIG. 8 showing an example of a microwave surface wave interference plasma processing apparatus. DESCRIPTION OF SYMBOLS 1 is a processing chamber, 2 is a to-be-processed substrate, 3 is a to-be-processed substrate mounting base which hold | maintains the to-be-processed substrate 2, 4 is a heater, 5 is a processing gas introduction means, 6 is an exhaust port, 8 is a processing chamber 1 is a slotless endless annular waveguide for introduction into the slot 1, 11 is a slot provided in the endless annular waveguide 8 for every ½ of the wavelength in the microwave tube, and 7 is a microwave in the processing chamber 1. The dielectric window 10 to be introduced is a cooling water channel for cooling the endless annular waveguide. A 4-stub tuner, a directional coupler, an isolator, and a 2.45 GHz microwave power source (not shown) were connected to the microwave introduction unit 99 in order.

  In order to uniformly introduce microwaves into the plasma chamber, six rectangular slots 11 were arranged at equal intervals.

  Microwaves are introduced from the microwave introduction part 99 and propagated to both sides of the endless annular waveguide 8, so that a so-called “antinode” having a strong electric field is generated at intervals of ½ of the in-tube wavelength. A slot 11 is provided at a position between “antinode” and “antinode” where the current flowing through the inner surface of the endless annular waveguide 8 becomes maximum, and microwaves are introduced into the plasma generation chamber 1. Plasma is excited by the microwave introduced into the plasma generation chamber 1.

The uniformly distributed plasma is obtained by the microwave introducing device having the conventional endless annular waveguide described above. However, since the length of the slot 11 is 37 mm and the microwave emission from each slot 11 is reduced, the microwave reflected power when the impedance automatic matching device is not used is about 60% of the microwave incident power. This microwave voltage standing wave ratio is 4, which is large. When the microwave power supply circuit component is used at such a large microwave voltage standing wave ratio, the microwave power supply circuit component is overloaded, and microwave power loss other than the generation of plasma may easily occur.
Japanese Patent No. 3118225 Japanese Patent No. 3093718 Japanese Patent No. 2925535

  As described above, the conventional technique has a problem that the microwave voltage standing wave ratio is increased because the microwaves introduced from the slots are reduced in order to uniformly introduce the microwaves into the processing chamber.

  The microwave emission device of the present invention has been made in view of the above-described problems, and is intended to provide an apparatus for uniformly processing a substrate to be processed without overloading the microwave power supply circuit. The challenge is to achieve both the uniform introduction of microwaves into the room and the reduction of the microwave voltage standing wave ratio.

  The present invention is an apparatus for emitting microwaves from a plurality of slots provided in an endless annular waveguide, wherein only the microwave emission rate of the slot closest to the microwave introduction portion to the endless annular waveguide is measured. The other feature is that the slot has a higher microwave emission rate than the microwave emission rate of the slot, so that the above problem can be solved.

  The slot provided in the endless annular waveguide of the microwave emission device of the present invention has a larger opening area than the slot of the prior art, so that more microwaves are emitted from the slot and the microwave voltage standing wave ratio is smaller. is doing. In addition, by making the microwave emission rate of the slot closest to the microwave introduction portion of the endless annular waveguide of the microwave emission device of the present invention smaller than that of the other slots, the microwave power intensity is highest in the endless annular waveguide. The microwave power emitted from the large microwave introduction portion is made substantially equal to the microwave power emitted from the other slots, and the microwaves are uniformly emitted from the slots provided in the endless annular waveguide. As described above, by appropriately selecting the microwave emission rate of the slot closest to the microwave introduction part and the microwave emission rate of the other slots, both microwave uniform emission and reduction of the microwave voltage standing wave ratio can be achieved. The above problem has been solved.

  The microwave emission rate from the slot provided in the endless annular waveguide of the microwave emission device of the present invention is adjusted by the slot opening area. Increasing the slot length in the vicinity of half the wavelength in the microwave tube in the endless annular waveguide can decrease the slot impedance and increase the microwave emission rate, and shortening the slot length increases the slot impedance. The microwave emission rate can be reduced. Further, if the slot width is reduced, the slot impedance can be increased and the microwave emission rate can be reduced, and if the slot width is increased, the slot impedance can be reduced and the microwave emission rate can be increased. Therefore, the microwave emission rate from the slot provided in the endless annular waveguide can be adjusted by the slot opening area, and the microwave emission rate from the slot can be increased as the slot opening area is increased.

  The opening area of the slot closest to the microwave introduction part to the endless annular waveguide of the microwave emission device of the present invention is preferably 50% or more and less than 100%, more preferably 80 or more and 100% of the other slot opening area. The above problem of achieving both uniform microwave emission and reduced microwave voltage standing wave ratio has been solved by making the slot length less than, more preferably, ½ of the wavelength in the microwave tube.

  The microwave emission rate from the slot provided in the endless annular waveguide of the microwave emission device of the present invention is adjusted by the slot depth. When the slot depth is increased, the impedance can be increased and the microwave emission rate can be decreased.

  By making the depth of the slot closest to the microwave introduction portion into the endless annular waveguide of the microwave emission device of the present invention preferably longer than the same slot depth as twice, but shorter than twice, The above-mentioned problem of achieving both emission and reducing the microwave voltage standing wave ratio has been solved.

  Prior art microwave emission devices give priority to microwave emission uniformity over microwave voltage standing wave ratio, but the microwave emission device of the present invention achieves both microwave emission uniformity and microwave voltage standing wave ratio reduction. To do. Therefore, the microwave emission device of the present invention has sufficient inventive step as compared with the prior art.

  In addition, the conventional microwave emission device does not limit the slot shape, but uses a fixed-shape slot in the end, and the microwave of the slot closest to the microwave introduction portion to the endless annular waveguide of the present invention is used. The effect of reducing only the wave emission rate is not disclosed. Therefore, the microwave emission device of the present invention is sufficiently novel as compared with the prior art.

  The microwave emission device of the present invention can safely use a microwave power supply circuit by emitting microwaves from a slot provided in an endless annular waveguide as uniformly as in the prior art and a microwave voltage standing wave ratio. It has the effect of reducing both to 2 or less. In addition, this makes it possible to provide an apparatus for uniformly processing a substrate to be processed without overloading the microwave power supply circuit.

(Embodiment 1)
An example of the microwave emission apparatus of the present invention will be described in detail with reference to FIG. DESCRIPTION OF SYMBOLS 1 is a processing chamber, 2 is a to-be-processed substrate, 3 is a to-be-processed substrate mounting base holding the to-be-processed substrate 2, 4 is a heater, 5 is a process gas introduction means, 6 is an exhaust port, 8 is a microwave processing chamber 1, a slotted endless annular waveguide 99 for introducing the microwave into the endless annular waveguide 8; a slot 11 provided in the endless annular waveguide 8; 98; Is a slot under the microwave introduction portion, 7 is a dielectric window for introducing the microwave into the processing chamber 1, and 10 is a cooling water channel built in the endless annular waveguide 8. A 4-stub tuner, a directional coupler, an isolator, and a 2.45 GHz microwave power source (not shown) were connected to the microwave introduction unit 99 in order.

  The cross-sectional dimension of the inner wall of the endless annular waveguide 8 is 27 mm × 96 mm, which is the same as the WRT-2 standard waveguide. The center diameter of the endless annular waveguide 8 is 152 mm. The material of the endless annular waveguide 8 is aluminum having good thermal conductivity and electrical conductivity.

  FIG. 2 shows an example of slot arrangement. The slots 11 and 98 are provided in an electric field portion having a strong microwave standing wave that appears every ½ of the wavelength in the microwave tube. The slots 11 and 98 are rectangular, 3 mm wide and 2 mm deep, and are arranged at an angle of 60 degrees and a slot central diameter of 152 mm. The length of the lower slot 98 of the microwave introduction part 99 is 45 mm, and the length of the other slot 11 is shorter than 48 mm. The opening area of the slot 98 below the microwave introduction part 99 is 94% of that of the other slot 11.

  The substrate to be processed is nitrided by the microwave emission apparatus of the present invention. Cooling water flows through the cooling water passage 10 to cool the endless annular waveguide 8 to room temperature. The to-be-processed base | substrate mounting base 3 is heated with the heater 4, and is 200 degreeC. The substrate 2 to be processed having a silicon oxide film with a thickness of 2 nm on the surface is transported to and mounted on the substrate to be processed holding table 3. Next, the processing chamber 1 is evacuated through an exhaust system (not shown). Subsequently, nitrogen gas is introduced into the processing chamber 1 through the processing gas introduction means 5. Next, a conductance valve provided in the exhaust system is adjusted to hold the processing chamber 1 at 130 Pa. A microwave of 1.5 kW is supplied from the microwave power source to the processing chamber 1 through the endless annular waveguide 8 and the dielectric 7, and plasma is generated in the processing chamber 1. The microwave introduced into the endless annular waveguide 8 is divided into left and right, propagates with an in-tube wavelength longer than the free space, and is introduced into the processing chamber 1 from the slots 98 and 11 through the dielectric 7, The surface of the dielectric 7 propagates as a surface wave. This surface wave interferes between adjacent slots and forms a surface wave standing wave. Plasma is generated by the surface standing waves. Nitrogen ions in the plasma are transported to the vicinity of the substrate 2 to be processed by diffusion or the like, accelerated by an ion sheath generated on the surface of the substrate 2 to be processed, and collide with the substrate 2 to be processed. After 1 minute, the microwave power source is stopped, the nitrogen gas is stopped, the inside of the processing chamber 1 is evacuated to 0.1 Pa or less, and then the substrate 2 to be processed is transferred to the outside of the processing chamber 1.

  After the nitriding treatment, the silicon oxide equivalent thickness of the silicon oxynitride film on the surface of the substrate to be treated 2 was measured with an ellipsometer manufactured by KLA Tencor and found to be 2.7 ± 0.2 nm. This is the same uniformity as in the case of using fixed-length slots in which all the slot lengths are 37 mm.

  Further, the microwave reflected power during the plasma treatment was reduced to about 30% of the microwave incident power. This is approximately 1.7 when expressed in terms of the microwave voltage standing wave ratio, and the microwave power supply circuit is improved until it can be used safely. In the present invention, the slot length is 48 mm and 45 mm longer than those of the prior art, and the slot opening area is increased, so that the microwave emissivity can be improved and the microwave voltage standing wave ratio can be reduced.

  Thus, the microwave emission device of the present invention has the effect of achieving both the microwave emission uniformity and the low microwave voltage standing wave ratio.

  Further, the slots 11 and 98 are provided in a portion where the surface current of the microwave standing wave that appears at every half of the wavelength in the microwave tube is strong. Providing a slot in a portion of the microwave standing wave where the surface current is strong makes it easy to emit the microwave from the slot to the processing chamber 1 and has the effect of reducing the microwave voltage standing wave ratio. This is apparent from the fact that microwaves could hardly be introduced into the processing chamber 1 in an experiment in which a slot was provided in an electric field portion where microwave standing waves were weak. Further, by arranging the slots at equal intervals, there is an effect that the microwaves are evenly emitted to the processing chamber 1.

  In this embodiment, the slot lengths are 48 mm and 45 mm, but the present invention is not limited to this. The slot length may range from approximately 40 to 60 mm. Further, the length of the slot 98 closest to the microwave introduction portion 99 may be approximately 50 to less than 100% of the length of the other slot 11.

(Embodiment 2)
An example in which the microwave emission rate of the slot of the microwave emission device of the present invention is adjusted by changing the slot opening area according to the slot width as shown in the slot arrangement example of FIG.

  The slots 11 and 98 are provided in an electric field portion having a strong microwave standing wave that appears every ½ of the wavelength in the microwave tube. The slots 11 and 98 are rectangular, and are arranged at an angle of 60 degrees and a slot center diameter of 152 mm. The width of the lower slot 98 of the microwave introduction part 99 is narrower than the width of the other slot 11. Further, the opening area of the slot 98 under the microwave introduction part 99 is smaller than the other slots 11.

  Only the width of the slot 98 closest to the microwave introduction part 99 is made narrower than the width of the other slot 11, and the effect of achieving both the microwave emission uniformity and the low microwave voltage standing wave ratio is obtained.

  The width of the other slot 11 may be in the range of approximately 1 to 5 mm. Further, the width of the slot 98 closest to the microwave introduction part 99 may be approximately 50 to less than 100% of the width of the other slot 11.

  Compared with changing the slot length by changing the slot length, it is easier to obtain microwave emission uniformity when changing the slot width. This is because the slot opening area can be changed more greatly with a small variation in width, so that the slot arrangement symmetry is easily obtained.

(Embodiment 3)
An example in which the microwave emission rate of the slot of the microwave emission device of the present invention is adjusted by the slot depth as shown in the slot cross-sectional example of FIG. When the slot is deepened, the microwave emission rate decreases. For example, in a rectangle of 42 mm × 3 mm, the microwave emission rate becomes substantially zero at a depth of 5 mm or more.

  In order to make the depth of the slot 98 below the microwave introduction part 99 deeper than the other slots 11, in FIGS. 4A and 4B, the slot plate in the vicinity of the slot 98 is made thick. 4C and 4D, the slot depth near the slot 11 is reduced. The opening areas of the slot 11 and the slot 98 are equal. These slots can be machined by methods such as cutting, welding, attaching a good electrical conductor, and fitting differently machined slots.

  Only the depth of the slot 98 closest to the microwave introduction part 99 is made deeper than the other slots 11, and the effect of achieving both the microwave emission uniformity and the low microwave voltage standing wave ratio is obtained.

  The optimum slot depth is determined by the number of slots and the slot shape. If the slot 11 depth is 2 mm in a 42 mm × 3 mm rectangular slot, the slot 98 depth may be in the range of approximately 2 to 4 mm.

  The processed shape around the slot 98 is not limited to the example of FIG. 4, as long as it is a gentle shape so as not to discharge and to reduce the reflection of the microwave so that it is neither too thick nor too thin. For example, it may be a circular hill or a multistage slope.

(Embodiment 4)
An example of the microwave emission apparatus of the present invention will be described with reference to FIG. 5 is further provided with a heat transfer body 96 for releasing the heat of the dielectric window 7 to the endless annular waveguide 8 in the embodiment of FIG.

  The vicinity of the slot 11 is made thinner than the vicinity of the slot 98. The opening areas of the slot 11 and the slot 98 are equal.

  The heat transfer body 96 releases heat from the dielectric window 7 to the cooling water channel 7. The dielectric window 7 is heated to 200 to 250 ° C. by the plasma. When the dielectric window 7 becomes high temperature, the vacuum seal O-ring under the dielectric window 7 is worn out or the dielectric window 7 is easily damaged by thermal stress. Therefore, the dielectric window 7 is cooled.

  When the endless annular waveguide lower portion 95 excluding the vicinity of the slot 11 is thickened, the heat transferred from the dielectric window 7 to the endless annular waveguide lower portion 95 via the heat transfer body 96 can be easily transferred to the cooling water channel 10, Keep body window 7 cooler. By keeping the dielectric window 7 at a low temperature, wear of the vacuum seal O-ring is suppressed, and damage to the dielectric window 7 due to thermal stress is prevented. That is, by increasing the thickness of the endless annular waveguide lower portion 95 excluding the vicinity of the slot 11, the effect of preventing the dielectric window 7 from being damaged and the O-ring from being worn is obtained.

  By making only the slot depth of the lower slot 98 of the microwave introduction part 99 deeper than that of the other slots 11, the effect of achieving both the microwave emission uniformity and the low microwave voltage standing wave ratio can be obtained.

  The heat transfer body 96 is preferably a dielectric having good thermal conductivity. For example, a heat transfer rubber sheet manufactured by Shin-Etsu Chemical may be used.

(Embodiment 5)
An example of the microwave emission apparatus of the present invention will be described with reference to FIG. The example of the microwave emission apparatus of FIG. 6 further includes one microwave introducing unit 99 in the embodiment of FIG. Microwaves are divided into left and right at the E branch 97 and introduced into the endless annular waveguide 8. The microwave introduced into the endless annular waveguide 8 is further divided into left and right parts, propagates with an in-tube wavelength longer than the free space, and is introduced into the processing chamber 1 from the slots 98 and 11 via the dielectric 7. The surface of the dielectric 7 propagates as a surface wave. This surface wave interferes between adjacent slots and forms an electric field.

  The microwave emission rate of the slots 98 below the two microwave introduction portions 99 is smaller than the other slots 11. Further, the microwave emission rates of the slots 98 are equal to each other. The microwave emission rate from the slot may be adjusted by the slot opening area or by the slot depth.

  By making the microwave emission efficiency of the lower slot 98 of the microwave introduction part 99 smaller than that of the other slots 11, the effect of achieving both the microwave emission uniformity and the low microwave voltage standing wave ratio can be obtained.

  By using a plurality of microwave introduction parts, the microwave emission uniformity is improved. In the endless annular waveguide 8, if the left and right symmetry as viewed from the microwave introduction portion deteriorates for some reason, the microwave power equal to the left and right cannot be distributed, and the microwave emission uniformity deteriorates. Further, as the distance from the microwave introduction part 99 of the endless annular waveguide 8 increases, the microwave intensity in the endless annular waveguide 8 decreases, and the microwave emission uniformity deteriorates. If a plurality of microwave introduction parts 99 are provided as in this embodiment, the left-right distribution bias of the microwaves can be alleviated, and the distance to the slot farthest from the microwave introduction part 99 can be shortened, so that the microwave emission uniformity can be reduced. Get an improvement effect.

  In these embodiments, the slot is rectangular, but the present invention is not limited to this. As shown in the example of the slot shape in FIG. 7, it may be a waveform, or (may be the original text) a parallelogram or an ellipse. However, a sharp shape is not preferable because it easily discharges.

  Further, the microwave emission rate of the slot 98 is made smaller than that of the slot 11 by changing the width and length of the same shape, but this is not restrictive. For example, the slot 11 may be rectangular and the slot 98 may be an ellipse or a waveform, or vice versa. Further, the microwave emission rate may be adjusted by combining the slot depth, shape, width, and length.

Example of microwave emission device of the present invention Slot layout example Slot layout example Slot cross-section example Example of microwave emission device of the present invention Example of microwave emission device of the present invention Example of slot shape Example of conventional microwave emission device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing chamber 2 Substrate 3 Substrate mounting table 4 Heater 5 Processing gas introduction means 6 Exhaust port 7 Dielectric window 8 Endless annular waveguide with slot 10 Cooling channel 11 Slot 95 Lower end of endless annular waveguide 96 Heat transfer body 97 E branch 98 Microwave introduction lower slot 99 Microwave introduction

Claims (6)

  An apparatus for emitting microwaves from a plurality of slots provided in an endless annular waveguide, wherein only the microwave emission rate of the slot closest to the microwave introduction portion to the endless annular waveguide is determined for other slots. A microwave emission apparatus characterized by being made smaller than the microwave emission rate.   The microwave emission device according to claim 1, wherein the microwave emission rate is adjusted by a slot opening area.   3. The microwave emission device according to claim 2, wherein the opening area of the slot closest to the microwave introduction portion into the endless annular waveguide is set to be 50% or more and less than 100% of the other slot opening area. .   The microwave emission device according to claim 1, wherein the microwave emission rate is adjusted by a slot depth.   5. The microwave emission device according to claim 4, wherein the depth of the slot closest to the microwave introduction portion to the endless annular waveguide is longer than the other slot depths and shorter than twice.   A processing chamber, a window that transmits microwaves from the microwave emission device to the processing chamber, a means for introducing gas into the processing chamber, a means for exhausting the processing chamber, and a non-processing substrate holding means. 2. The microwave emission device according to claim 1, wherein the microwave is emitted to the chamber.

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