The present invention relates to a microwave plasma processing method, a microwave processing apparatus and its plasma-head, used for the microwave plasma processing of a large type glass substrate for flat panel display (FPD) or a substrate such as a semiconductor wafer.
For instance, in a microwave plasma CVD processing apparatus for processing a large type glass substrate for FPD or a substrate such as a semiconductor wafer, it has been practiced in the past in such manner that a batch processing of the sheet-by-sheet type has been carried out and the substrates to be processed by plasma CVD processing has been passed through a load-lock chamber kept under vacuum condition and the substrates have been brought into or out of a processing chamber maintained similarly under a predetermined vacuum condition. As a result, each time the substrates were brought into or out of the processing chamber, the processing chamber had to be evacuated and released to atmosphere.
In particular, when two or more different processing procedures had to be applied on the substrates, each of such processing procedures had to be performed in batch processing procedure with the substrates being transferred through a plurality of isolated spaces (i.e. the processing chamber). For this reason, it was not possible to continuously carry out the CVD processing of the substrates, and expensive vacuum processing means had to be used.
Under such circumstances, a new technique has been developed, in which no such vacuum processing means is required and plasma CVD processing is continuously carried out on in-line basis under the atmospheric pressure (normal pressure). In the new plasma CVD technique under normal pressure, a plasma technique is used, which makes it possible to operate under the atmospheric pressure without using vacuum system, and the substrate to be processed such as a semiconductor wafer is continuously subjected to CVD, etching and ashing processing (Non-Patent Reference 1). Further, in this normal pressure plasma CVD technique, semiconductor wafers are placed on a circulating type wafer transfer unit such as a belt conveyer and different types of processing are carried out on flow production (flow shop) system by using a plurality of normal pressure plasma systems (Non-Patent Reference 2).
Also, a new plasma processing apparatus (e.g. CVD apparatus) has been proposed (Patented Reference 1), in which a linear plasma is prepared by using electromagnetic wave, and surface treatment of the object to be processed is performed while relative position between the object to be processed (such as semiconductor wafer) and the plasma is being moved with the surface of the object to be processed maintained at horizontal position with respect to the linear plasma.
Although different types of processing can be continuously carried out by the conventional type microwave plasma CVD method and apparatus as described above, there have been problems in: non-uniformity of microwave at the microwave feeding unit of the plasma head, incompleteness of processing of gas flow and gas shielding, non-uniformity of plasma density due to the standing wave, abnormal discharge at slots of the plasma head, etc.
To solve the problems of the conventional type microwave plasma CVD processing method and processing apparatus as described above, it is an object of the present invention to provide microwave plasma processing method, a microwave plasma processing apparatus, and a plasma head for such apparatus, by which it is possible to generate linear high-density plasma by using high-density microwave source, and different types of film-deposition processing can be continuously performed.
According to the microwave plasma processing method, the microwave plasma processing apparatus and the plasma head of the present invention, linear plasma is generated by microwave, and an object to be processed is processed under the atmospheric pressure or under a pressure near the atmospheric pressure while the object to be processed is being moved by maintaining the surface of the object to be processed at horizontal position with respect to the linear plasma. An H-plane slot antenna is provided on the plasma head. Slots of the H-plane slot antenna are arranged alternately on both sides of the centerline of the waveguide at a pitch of λ g/2, and a uniforming line is arranged with a distance from said slot to the emission end of the plasma head being set to n·λg/2 where the symbol λg represents guide wavelength of microwave.
Also, according to the microwave plasma processing method, the microwave plasma processing apparatus and the plasma head of the present invention, linear plasma is generated by microwave, and an object to be processed is processed under the atmospheric pressure or under a pressure near the atmospheric pressure while the object to be processed is being moved by maintaining the surface of the object to be processed at horizontal position with respect to the linear plasma. An E-plane slot antenna is provided on the plasma head. Slots of the E-plane slot antenna are arranged along the centerline of the waveguide at a pitch of λg, and a uniforming line is arranged with a distance from said slot to the emission end of the plasma head being set to n·λg/2 where the symbol λg represents guide wavelength of microwave.
Further, according to the microwave plasma processing method, the microwave plasma processing apparatus and the plasma head of the present invention, a uniforming line is provided on the plasma head under similar processing conditions, and the uniforming line is made of a material with high dielectric constant. Also, the uniforming line is made of quartz, and its end portion is extended by ¼ λ. Also, an electromagnetic wave absorbing material with high dielectric loss is attached on end portion of the uniforming line to reduce the standing wave on the plasma head where the symbol λ represents free space wavelength of quartz.
Also, according to the microwave plasma processing method, the microwave plasma processing apparatus and the plasma head of the present invention, it is designed in such manner that a film-deposition gas is passed by down-flowing through a film-deposition gas feeding nozzle provided on the plasma head under similar processing conditions, and also, that a film-deposition gas is passed by side-flowing through the film-deposition gas feeding nozzle.
Further, according to the microwave plasma processing method, the microwave plasma processing apparatus and the plasma head of the present invention, a feeding pipe for feeding a shield gas into the plasma head is connected, and by a buffer plate the shield gas is uniformly supplied into the plasma processing chamber downstream of the shield gas feeding pipe. Also, a buffer plate for carrying out uniform exhaust of the gas is provided on exhaust side. A pressure P1 in the plasma processing chamber is set to a value lower than a pressure P3 on the outermost periphery of the plasma head, and the pressure P3 is set to a value lower than a pressure P2 near the buffer plate for performing uniform exhaust, thus preventing the leakage of the gas from the plasma head.
According to the microwave plasma processing method, the microwave plasma processing apparatus and the plasma head of the present invention, linear high-density plasma is generated from the plasma head by using a high-density microwave source. As a result, it is possible to perform continuous CVD processing with high accuracy. Different types of plasma sources are aligned in transporting direction of the substrate to be processed by film-deposition processing. As a result, different types of continuous film deposition can be carried out.
Further, according to the microwave plasma processing method, the microwave plasma processing apparatus and the plasma head, and a uniforming line of the plasma head of the present invention, by setting optimal condition of the basic dimensions and by eliminating the standing wave, more uniform microwave can be emitted through the slit of the plasma head. Also, homogeneity of the film deposition gas can be maintained because of down-flowing and side-flowing of the gas, and this contributes to the improvement of the film deposition rate.
Also, remarkable effects can be provided for gas shielding of the film deposition gas with very high accuracy.
Detailed description will be given below on embodiments of a microwave plasma processing method, a microwave plasma processing apparatus and a plasma head according to the present invention referring to the attached drawings.
[Microwave Plasma CVD Apparatus]
First, as shown in
Here, the substrate G is transported by the robot arm 3a from the transfer module 3. It is then guided in the process module 4 by a guide rolls 9b and is placed on a substrate stage 9a arranged in a circulating endless substrate transport mechanism 9. Then, it is fixed by means such as an electrostatic chuck (not shown) and is moved in the process module 4, and CVD processing is performed by the plasma heads 5. After CVD processing, the substrate G is separated from the substrate stage 9a and is moved from the end of the process module 4 to the next processing stage. The emptied substrate stage 9a is brought back to the starting end of the process module 4 by the endless substrate transport mechanism 9. Under the endless substrate transport mechanism 9, a gas unit 7 and a cooling water unit 8 are provided.
[Plasma Heads]
Plasma heads to be used in the microwave plasma CVD apparatus in the embodiment of the present invention comprise a plurality of unit plasma heads. For instance, three units 5a, 5b, and 5c are arranged in parallel via partition walls (not shown) as shown in
To the plasma heads 5, the microwave feeding unit 50 as shown in
The microwave feeding unit 50 as shown in
As shown in
On the uniforming line 52, spatially more unified wave front of microwave is formed by using microwave with equal phase as emitted from the slot plate 51. This uniforming line 52 is a parallel flat line. More concretely, it is a flat rectangular waveguide with the centerline as the longer axis. By this uniforming line 52, microwaves discretely emitted from each of the slots 53 are unified. A wave front with more uniform intensity is prepared to the direction of the centerline, and the unified microwaves are emitted into plasma through the slit 55.
In particular, as shown in
As shown in
In case of the E-plane antenna, the slots 53 are formed on a waveguide resonator 51b with a spacing of λg along the centerline as shown in
Description will be given on another example of calculation to calculate basic dimensions of the uniforming line 52. As shown in
where
The length 1 of the uniforming line 52 is basically set to the range of λ/4 to ¾λ. The value is determined by simulation. In this calculating procedure, calculation is made by using free space wavelength λ, and not using the guide wavelength λg. Similarly, calculation is made by setting the width of the uniforming line 52 as λ/2.
Further, as shown in
where
By applying calculation ratio of each component as shown in
Further, in order to eliminate the difference in intensity distribution of the microwaves at the plasma head due to the standing wave, a procedure for reducing the standing wave is applied on the uniforming line 52.
In this procedure to reduce the standing wave, the space of the uniforming line 52 is filled with a material such as alumina (Al2O3) with high dielectric constant to shorten the wavelength. In this case, the length 1 of the uniforming line 52 is turned to: λ (free space wavelength) multiplied by an integral number, i.e. 1=n·λ.
Also, as shown in
Further, as shown in
Also, for the purpose of preventing abnormal discharge (sparking) due to the increase of microwave output on the slot and of avoiding the crack of the dielectric substance in the uniforming line 52 due to local temperature increase, the slot plate 51c is made of a rigid metal plate of 3 to 5 mm in thickness as shown in
[How to Pass CVD Gas]
To pass CVD gas for film deposition in the microwave plasma CVD apparatus of the present invention, the following two methods are used: (1) gas down-flowing method, and (2) gas side-flowing method.
(Gas Down-flowing Method)
According to the gas down-flowing method, as shown in
As the result of the gas down-flowing, the film-forming gas flows to a portion with high plasma density, and this extensively improves film forming rate. This is also helpful to maintain homogeneousness of the film-forming gas, and the attachment of the remaining substances to the gas feeding nozzle can be prevented.
(Gas Side-flowing Method)
According to the gas side-flowing procedure, as shown in
By this side-flowing of the gas, homogeneity of the film-forming gas is improved, and exhaust operation can be promoted. Also, this makes it possible to predict the conditions on the film-forming surface and to facilitate the cleaning of the plasma head. Also, the width of the film formed on the substrate can be controlled by adjusting the shape of nozzle tip of the gas feeding port.
(Gas Shielding)
On the plasma head 60 of the microwave plasma CVD apparatus of the present invention, gas shielding is provided as shown in
Specifically, as shown in
Then, as shown in
Number | Date | Country | Kind |
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2003-431939 | Dec 2003 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP04/19772 | 12/24/2004 | WO | 10/4/2006 |