JPS62219524A - Method and apparatus for tuning microwave transmitting window - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for tuning a microwave transparent window, and more particularly to a method and apparatus for maximizing the power transmitted through the window. Although the invention has application in the transfer of microwave power to plasmas, it is particularly suited to plasma-based systems such as those incorporating amorphous semiconductor alloys.

The present invention also includes methods and apparatus for making such devices by exciting plasma with microwave energy to perform plasma deposition from reactant gases.

One of the most important applications of the present invention is the industrial manufacture of electrophotographic devices in which an amorphous semiconductor alloy is coated or deposited on the outer surface of a cylindrical or drum-shaped structure. The present invention aids in the industrial production of flattened electrophotographic drums incorporating amorphous semiconductor alloys.

Silicon is the basis of the vast crystalline semiconductor industry and is the material that gave rise to expensive, high-efficiency (18%) crystalline solar cells for spaceflight. Once crystalline semiconductor technology reached the industrial stage, it became the basis of today's huge semiconductor device manufacturing industry. This is because scientists have grown virtually defect-free crystals of germanium and especially silicon and then turned them into exogenous materials.
This is due to the success in forming conductivity type regions of type and p type. This technology allows the production of 100% in such crystalline materials.
some donor (n) or acceptor (p) in ten thousand
Diffusing dopant materials to introduce these dopants as substitutional impurities into a substantially pure crystalline material, thereby increasing its conductivity and controlling its p-type or n-type conductivity type. It is a technology that The manufacturing process for pn junction crystals is extremely complicated and time consuming, and the manufacturing costs are also high. The production of crystalline materials used in solar cells and current control devices involves growing individual single crystals or germanium crystals under precisely controlled conditions, and when p-n junctions are required, growing these single crystals into extremely small critical masses. It does this by doping it with a dopant.

In short, crystalline silicon devices have fixed parameters that cannot be changed as needed, require large amounts of material, and can only be fabricated in relatively small areas.
It has drawbacks such as high manufacturing cost and time consuming. Devices based on amorphous silicon can eliminate these drawbacks of crystalline silicon. The optical absorption edge of amorphous silicon has properties similar to those of a direct gap semiconductor, meaning that it absorbs the same amount of sunlight as a 50 micron thick crystalline silicon, but is thinner. It requires only 1 micron or less of material. Furthermore, compared to crystalline silicon, amorphous silicon can be manufactured faster and more easily, and over a larger area.

Therefore, if necessary, deposition can be carried out over a relatively large area, although this is limited only by the size of the deposition equipment.Moreover, if it is desired to construct a device equivalent to a p-n junction device of a crystalline semiconductor, p-type doping can be used. type and n
Significant efforts have been made to develop methods for forming amorphous semiconductor alloys or films that can easily form mold materials.

However, such research bore little fruit. Amorphous silicon or germanium (group IV) films usually have defects such as 4-arranged bonding, micro voids, and dangling bonds, resulting in high-density localized states in the energy gap. There was found. The presence of a high density of localized states in the energy gap of U1-quality silicon semiconductor films results in low photoconductivity and short carrier lifetimes, making such films unsuitable for photoresponsive applications. That means no. Furthermore, such films cannot be sufficiently doped or otherwise modified to move the Fermi level closer to the conduction or valence bands, making them less pn-like for use in solar cells and current control devices. It is also unsuitable for making joints.

In an attempt to minimize the above-mentioned problems with amorphous silicon and germanium, W.
E. Spare and P. G. Le Comber are conducting research on "repurchase doping method for amorphous silicon," and their paper is published in 5solidState Communicati.
ons, VOl, 17. pp, 1193-1196
Published in 1975. Their work aims to reduce the localized state of the energy gap in amorphous silicon or germanium to make it more similar to intrinsic crystalline silicon or germanium, and/or to reduce the localized state of the energy gap in amorphous silicon or germanium, making it more similar to intrinsic crystalline silicon or germanium, and/or As in the case of doping, the purpose was to transform the crystalline material into an extrinsic material of p or n conductivity type by substitution doping with a suitable dopant.

The decrease in localized states causes the amorphous silicon film to glow discharge jf
This was achieved by multiplying t. Silane (S/H4)
The gas is passed through a reaction tube and a radio frequency (RF)
The gas is decomposed by glow discharge and the substrate temperature is about 500~6
It was deposited on a substrate at 00'K (227-327°). The material deposited on the substrate in this way is
It was an intrinsically amorphous material consisting of silicon and hydrogen. To make doped amorphous materials, Bosfin (PH3) gas is used for n-type conductivity, and diborane (B2) is used for n-type conductivity.
He ) gas was mixed into the silane gas beforehand, and the mixed gas was passed through the GD-discharge reaction tube under the same operating conditions. The dopant gas concentration is approximately 5 x 10'~10
-2 parts by volume. The material thus deposited probably contained substitutive phosphorus or boron dopants and was found to be an extrinsic material of n or p conductivity type.

Unknown to the researchers cited above, but now well known from the work of others, hydrogen in silane forms dangling bonds of silicon at optimal temperatures during glow discharge deposition. The electronic properties of the amorphous material can be more closely approximated to those of the corresponding crystalline material, since the energy gap localization is substantially reduced.

The method of incorporating hydrogen in the RF deposition method described above is not only limited by the fixed ratio of hydrogen to silicon in silane, but also has a more serious problem with various types of S,
The :H bond form introduces a new anti-bonding state, which may have deleterious consequences for the material.

Therefore, a fundamental problem lies in reducing the density of particularly harmful localized states in terms of effective p- and n-doping of these materials. The resulting localized density of states in RF silane deposited materials narrows the depletion width, thereby limiting the efficiency of solar cells and other devices whose operating efficiency is determined by free carrier drift. RF methods using only silicon and hydrogen to fabricate these materials also result in a high density of surface states, which affects all of the above parameters.

After the development of a method for glow discharge deposition of silicon from silane gas, research began on methods for sputter depositing amorphous silicon films in an atmosphere of a mixture of argon (required in sputter deposition methods) and molecular hydrogen. The effects of such molecular hydrogen on the properties of deposited amorphous silicon films were measured. The study found that hydrogen acts like a modifier, modifying the way the atoms bond to reduce the localization of the energy gap.

However, the degree of reduction in energy gap localization in sputter deposition was much lower than that achieved by the silane deposition method described above. The p and n dopant gases described above were also introduced into the sputtering process to produce p and n doped materials.

The doping efficiency of the material thus obtained was lower than that of the material produced by the glow lightning method. Therefore, neither method has been able to produce effective p-doped materials with acceptor concentrations high enough to produce p-n or p-1-n junction devices industrially.

The n-doping efficiency was also lower than T-collectively acceptable levels, while p-doping was particularly undesirable because it narrowed the bandwidth and increased the number of localized states within the bandgap.

A significantly improved amorphous silicon alloy with a significantly reduced density of localized states in the energy gap and high quality electronic properties was proposed in Stanford R. Opsinski, published October 7, 1980. The glow discharge method described in Alan Meydan, U.S. Pat.
U.S. Patent No. 4□217.3 to Stanford R6□ Opsinski and Masarag Is, issued August 12, 2007.
No. 74, each was successfully manufactured by the vapor deposition method described in the problem. As disclosed in these two patents, which are incorporated herein by reference, fluorine can be introduced into an amorphous silicon semiconductor to reduce the localized density of states. In particular, activated fluorine easily diffuses into and bonds with the amorphous silicon of the amorphous body, and can substantially reduce the localized defect state density therein. This is because fluorine atoms are small and can be easily introduced into an amorphous material. Fluorine binds to the dangling bonds of silicon to form what appears to be a partially ionically stable bond that can change the bond angle at will, resulting in formation by hydrogen and other compensators or modifiers. More stable and efficient compensation or modification is obtained. When fluorine is used alone or in conjunction with hydrogen, hydrogen It is believed that it would be a more effective compensator or modifier. Fluorine is therefore qualitatively different from other halogens and is therefore considered a superhalogen.

For example, fluorine alone or in a very small amount (e.g. 1 atomic %)
Compensation can also be achieved by using a hydrogen element added with □. However, the most desirable amounts of fluorine and hydrogen to be used to form a silicon-hydrogen-fluorine alloy are not such small proportions, but are much larger. The amount of fluorine and hydrogen for alloy formation is, for example, 1 to 5% or more. The new alloy thus formed is believed to have a lower density of defect states in the energy gap than would be achieved by simply neutralizing dangling bonds and similar defect states.

It is believed that this substantial participation of fluorine in the new structural form of the amorphous silicon-containing material, in particular, assists the addition of other alloying materials such as germanium. In addition to the properties listed above, fluorine has an induction effect m17
It is thought that it may also form a local structure of silicon-containing alloys with a hidden effect. While fluorine acts as an element for reducing the density of states, it also affects the bonding of urea by favorably reducing the flame density contributed by hydrogen. The role played by fluorine as an ion in such alloys is considered to be an important factor in the relationship of nearest neighbors.

About 45 years ago, C. Carlson developed the first electrophotographic method based on sulfur materials. Later, organic materials such as polyvinylcarbazole (βVK) and chalcogenides such as selenium and chelenium alloys were proposed for use in child photography.However, these materials...
Both have common drawbacks.

That is, it is difficult to handle because it is toxic, it is easily abraded because it is soft, and its sensitivity to infrared η is poor.

In view of the above-mentioned disadvantages of these materials, investigations were conducted into the possibility of using silicon-based amorphous semiconductor alloys in electrophotography. Amorphous silicon alloys are thought to be effective because they do not have the disadvantage of being hard and have excellent photoresponse to infrared rays. Also, as mentioned earlier, these materials can be made with the density of states reduced to a point where it is believed that the material can be charged to the potential required for electrophotographic reproduction. Accordingly, amorphous semiconductor alloys prepared by the method described above exhibit photoresponsive and structural properties suitable for electrophotographic applications. However, these prior art methods suffer from relatively low deposition rates and low conversion efficiencies of the reactant gas feedstock, which are disadvantageous in terms of industrial utilization of amorphous semiconductor materials. This is an important issue.

A new and improved method for manufacturing 1c electrophotographic devices using amorphous semiconductor alloys is disclosed in U.S. Patent Application No. 580, filed February 14, 1984, in the name of Annette G. Johncock and Stephen J. Hudziens. No. 081, “
``Improved manufacturing method for photoconductive parts and improved photoconductive members manufactured by the method'' (Japanese Unexamined Patent Application Publication No. 1989-1991).
-189274), the contents of which are also incorporated herein by reference. The method described in said patent application is a microwave glow discharge deposition method, which significantly increases the deposition rate and utilization of the gas supply pan yp+. Among the many applications of amorphous semiconductor alloys, the most important requirement that determines whether electrophotographic devices using such materials will be commercially viable is the deposition rate, conversion efficiency of the reactant gas feedstock. and high usage rate. The need for high deposition rates and feedstock conversion efficiencies and utilization is that such devices require non-woven fabrics of about 15 microns or more in thickness to be able to apply surface potentials of about 350 volts. This is because a crystalline semiconductor alloy layer is required. Consequently, amorphous semiconductor alloys can be deposited at sufficient rates and have the desired photoresponsive properties to make such materials commercially viable for electrophotographic devices. .

Electrophotographic devices used industrially usually take the form of cylindrical or drum-like members. A method and apparatus for assisting in depositing an amorphous semiconductor alloy evenly over the outer surface of such a drum to form an electrophotographic device thereon is described by the inventor of the present invention on February 14, 1984. U.S. Patent Application No. 580.086, filed in the names of Nijin W. Fourny, Eric B. Boujonard, Annette G. Johncock, and Shokin Durer;
``Method and Apparatus for Manufacturing Electrophotographic Devices,'' the contents of which are incorporated herein by reference (Japanese Patent Laid-Open No. 186849/1983). In this way, all the advantages of the microwave glow discharge process, including high utilization of the gas feedstock, can be realized at the same time.

The present invention provides a method and apparatus for maximizing and stabilizing the power transmitted into a deposition chamber through a microwave window to further improve the microwave glow discharge process used in the manufacture of the electrophotographic devices described above. do.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for tuning a microwave transparent window to maximize and stabilize the power transmitted to a microwave plasma through the window. , the window is tuned to transmit the power necessary to achieve the desired plasma conditions.

Power transmission through the window is tuned by attaching a pair of tuning structures to the window. The tuning structure may be formed by polymerizing a plurality of small disks or other shaped pieces of dielectric material, such as alumina, adjacent the outer edge of the window. The width or diameter and height of the tuning structure can be adjusted to increase the transmission coefficient, as well as to provide uniformity to plasma excitation and stabilize the plasma, for example in glow discharge deposition. Particular examples of the use of the present invention include:
It can be used in the ffJ construction of electrophotographic devices employing the amorphous semiconductor alloy described in the above-cited pending application.

US Application No. 580.086 provides a method and apparatus for depositing a layer of material on the outer surface of at least one pair of cylindrical members. In this method, an inner chamber is formed by arranging the cylindrical members with their longitudinal axes parallel to each other and with a small interval between their outer surfaces, and the inner chamber is communicated between the cylindrical upper members. forming a narrow passageway therethrough. The method further includes at least one
introducing a type of reactive gas into an inner chamber, the at least one type of reactive gas containing at least one type of element to be deposited, and forming a plasma from the at least one type of reactive gas in the inner chamber; depositing a layer of material containing the at least one element on the outer surface of the cylindrical member;

The interior chamber is formed by arranging a plurality of cylinders 1 with their longitudinal axes substantially parallel to form a substantially closed loop. There is then a slight spacing between the outer surfaces of the adjacent members to form a substantially closed interior chamber and a narrow passageway between the adjacent members communicating with the interior chamber. At least one gas is then introduced through the at least one passageway.

The reaction gases include silane (S・l-14), silicon tetrafluoride (S・F4), germane (GHa), germanium tetrafluoride (GF4), and diborane (B2H6).
), boron trifluoride (BF3), phosphine (PH3)
, phosphorus pentafluoride ('PF5), ammonia (NH3), nitrogen (N2), oxygen (02), methane (CH4) or combinations thereof. A plasma can be formed within the interior chamber by coupling microwave or radio frequency energy into the interior chamber through a microwave transparent window.

U.S. Patent Application No. 580.086 also provides an apparatus for depositing a layer of material on the outer surface of at least one pair of cylindrical members. The apparatus includes a substantially closed deposition chamber and an outer surface of a cylindrical member arranged substantially parallel to the longitudinal axis of the member with a small spacing between the outer surface and the outer surface of the cylindrical member.
and means for forming a narrow interior chamber and for stringing between the members a narrow passage communicating with the interior chamber. The apparatus further includes means for introducing at least one reactive gas into the interior chamber via the narrow passageway, the at least one reactive gas being deposited on the outer surface of the member. Contains at least one type of element. The apparatus further includes means for forming a plasma from the at least one reactant gas within the chamber to deposit a layer of tr material containing the at least one element on the outer surface of the circular member.

This device forms a substantially msg inner chamber by arranging a plurality of cylindrical members with their longitudinal axes substantially parallel and with a small spacing between the outer surfaces of adjacent members. and may include means for providing a narrow passage between each pair of members communicating with the interior chamber. Reaction gas introduction means are arranged to introduce the reaction gas into the interior chamber via at least one narrow passage.

The plasma forming means includes means for coupling microwave energy into the interior chamber through the microwave transparent window. The apparatus further includes means for rotating the cylindrical member about its longitudinal axis and means for rotating the polarity of the microwave energy to facilitate uniform deposition on the outer surface of the cylindrical member. be able to. The reaction gas introducing means includes means for introducing a reaction gas into the inner chamber through at least one narrow passage, and means for introducing a reaction gas into the inner chamber through at least one narrow passage, and a means for introducing a reaction gas into the inner chamber through at least one passage different from that used when introducing the reaction gas. It is desirable to include means for venting unused reaction gases.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1-4 depict the method and apparatus of US patent application Ser. No. 580.086, with the radio frequency embodiment of FIG. 5 removed. U.S. Patent No. 580.0
Regarding the application of the subject matter of No. 86 to the present invention, see No.
This will be explained with reference to FIG. 4, and other new disclosures and structures of the present invention will be explained in detail in the drawings after FIG. 5 and the corresponding portion of the specification.

Referring first to FIG. 1, FIG. 1 is a partial cross-sectional view illustrating an electrophotographic device 10 formed by depositing various materials on the outer surface of a cylindrical member 12 using the present invention. Cylindrical member 12 forms the substrate of electrophotographic device 10. Device 10 includes a first barrier layer 14 deposited on substrate 12, a photoconductive layer 16 deposited on first barrier layer 14, and a second barrier layer 18 deposited on photoconductive layer 16. Contains. Photoconductive layer 16 is preferably formed from an amorphous semiconductor alloy, more particularly an amorphous silicon alloy containing silicon and hydrogen and/or fluorine. Depending on the type of blocking layer 14,18 selected and the type of charge used to charge the device 10, the photoconductive region 16 may also include a small amount of a dopant, such as boron, to provide the region 16 with substantially unique properties. be.

Similarly, the region t@16 can be made into a slightly n-type region without containing a dopant.

The bottom blocking layer 14 prevents charge injection from the substrate 12 into the photoconductive region 16. To this end, the bottom barrier layer 14 may be formed from an amorphous alloy containing silicon and carbon, silicon and oxygen, or silicon and nitrogen to be insulating. When forming such a bottom barrier layer, methane (C)-1 is added to silane (S i H4) and/or silicon tetrafluoride (S i Fa ).
4) A mixed reaction gas containing either ammonia (NHa), nitrogen (N2) or oxygen can be used. This blocking layer is effective when electrophotographic device 10 is charged either positively or negatively.

If you want to positively charge the electrophotographic device 10,
The bottom electron blocking layer 14 is made of, for example, silicon and/-9Q.
- Alternatively, a p-type amorphous silicon alloy formed from a reaction gas containing a mixture of silicon tetrafluoride and an n-type dopant-containing compound such as diborane (B2He) or boron trifluoride (BF3) can be used. Wear. In this case, photoconductive region 16 is also preferably formed from an amorphous silicon alloy containing a small amount of n-type dopant to achieve substantially solid i→ properties.

If a negative charge is desired, the bottom hole blocking layer can be, for example, an n-type amorphous silicon alloy. To form such a barrier layer, silane and/or silicon tetrafluoride must be combined with phosphine (PHa) or phosphorous pentafluoride (PF5).
) can be used as a reaction gas mixed with a compound containing an n-type dopant such as. In this case, it is desirable that the photoconductive layer 16 is also formed from a slightly n-type amorphous silicon alloy.

Top barrier layer 18 may be formed from any of the materials listed for bottom barrier layer 14. That is, the upper barrier layer can be formed from an insulating material or an n-type or n-type amorphous semiconductor alloy as described above. f3Q'? For a detailed description of specific examples, see the aforementioned US patent application Ser. No. 580,081.

As disclosed in the above-mentioned application, it is desirable to have a thick photoconductive region 16, on the order of 10-25 microns, to provide adequate surface potential characteristics of the device. As also disclosed in said continuing application, photoconductive region 16 is required for commercial production of such devices.
It is necessary to deposit the materials forming the structure using a method with a high deposition rate. Conventional radio frequency glow discharge deposition techniques have a thickness of 1
This is not sufficient to form the entire photoconductive region 16 from 0 to 25 microns. However, as described in the above-referenced application, the microwave-excited glow discharge plasma serves to aid in the deposition of photoconductive region 16 such that the Iff deposition rate is such that the manufacture of the associated devices is commercially viable.

The apparatus and method of the present invention improves the use of microwave energy to form plasmas to commercially improve the use of materials in xerographic devices while utilizing gaseous feedstocks at previously unachievable utilization rates. The purpose is to enable deposition at a reasonable rate.

Photoconductive region 16 can be formed from both microwave glow discharge plasmas and radio frequency glow discharge plasmas, and radio frequency energy can also be used to ignite the plasma. When depositing a portion of photoconductive region 16 using radio frequencies, after forming the majority of the region 16 from a microwave energy glow discharge plasma,
The remainder or top of photoconductive region 16 is formed from a radio frequency glow discharge plasma. The apparatus and method of the present invention are capable of operating in both modes so that the drum of an electrophotographic copier can have the desired photoresponsive and charge retention properties that make the device particularly useful for electrophotographic reproduction. We are making it compatible.

Referring now to FIGS. 2 and 3, apparatus 20 is shown. Apparatus 20 is an apparatus capable of practicing the present invention that is configured to deposit one or more layers of preferably amorphous semiconductor alloy material onto a plurality of drums or cylindrical members 12. Apparatus 20 includes a deposition chamber 22 . Deposition chamber 22 includes an outlet 24, which is optionally connected to a pump and configured to evacuate reaction products from the deposition chamber and assist the deposition process by maintaining pressure within the chamber. There is.

The deposition chamber 22 further includes a plurality of reaction gas inlets 2G, 28.
30 from which the reactant gas is introduced into the deposition atmosphere in a manner described below.

A plurality of cylindrical members or drums 12 are arranged inside the deposition chamber 22.
is supported. The drums 12 are arranged with their longitudinal axes substantially parallel and with a small spacing between the outer surfaces of adjacent drums to define an interior chamber 32 by forming a substantially closed loop. ing. To arrange the drum 12 in this manner, the deposition chamber 22 includes a pair of upright walls 34,36 across which a plurality of stationary shafts 38 are supported. Each drum 12 has a pair of disc-shaped spacers IJ40,
42 rotatably mounted on one of the shafts 38? - to be done. The outer diameter of the spacers 40,42 corresponds to the inner diameter of the drums 12, thereby frictionally engaging the inner surface of the drums 12, thereby allowing accurate positioning of each drum with respect to each other. The base 40 includes a sprocket 44 configured to engage a drive chain 46. Drive chain 46 forms a continuous loop around sprocket 44 and drive sprocket 48 of motor 50 . Although drum 12 is shown with support and drive mechanisms within deposition chamber 22, this structure could be provided externally to chamber 22 with a suitable vacuum penetration seal if desired. The above configuration allows the motor 50 to rotate each drum about its own longitudinal axis when energized during the deposition process, as described below, thereby depositing material evenly over the entire outer surface of the drum 12. It becomes easier to do.

As previously mentioned, the drums 12 are arranged with small spacing between their outer surfaces to form an interior chamber 32. As can be seen in FIG. 3, the reactant gases forming the bulk plasma are introduced into the interior chamber 32 through at least one of a plurality of narrow passageways 52 formed between a pair of adjacent drums 12. Ru.

Preferably, the plasma is confined within the interior chamber 32, as can be seen with reference to FIG. 3, where reactant gases are introduced into the interior chamber 32 through every other passageway 52. The surface of the drum 12 rotates and the chamber 32
The intensity of the plasma changes as it enters and exits again. As a result, defects may form in areas of weak plasma within or adjacent to the narrow passageway 52. To prevent the formation of multiple defective areas or layers as material is deposited on the surface of the rotating drum 12, the drum 12 is rotated one or more times to obtain the desired high quality material. It is best to deposit the material to a thickness of .

For example, by rotating drum 12 only once, the desired thickness of material can be deposited to form bottom barrier layer 14.

As can be seen from FIG. 3, a gas shroud 54 is provided for each pair of adjacent drums 12. Each shroud 5
4 in the reaction gas inlet 26, 38.3 by the conduit 56
0. Each shroud 54 defines a reactive gas reservoir 58 adjacent the passageway through which the reactive gas is introduced. The shroud 54 also includes a roughly lateral extension 60 that extends around the circumference of the drum 12 from either side of the reservoir 58 and narrows between the shroud extension 60 and the outer surface of the drum 12. A channel 62 is formed.

The shape of the cicoroud 54 as described above allows the gas reservoir 58 to have a relatively high reaction gas guiding effect, whereas the narrow channel 62 provides a high resistance to the reactive gas, resulting in a low guiding effect. At this time, it is desirable that the vertical conductivity of the reaction gas storage section 58 be much larger than the conductivity of the narrow passage 52 between the drums.

Furthermore, the conductive force of the narrow passageway 52 is much greater than the conductive force of the narrow channel 62. This allows a large portion of the reactant gas to flow into the interior chamber 32, creating an even gas flow along the entire lateral direction of the drum 12.

Shroud 54 further includes sides 64 that overlap the ends of drum 12 and spacers 42,44.

The sides 64 are attached to the end spacers 42, 44 of the drum 12.
They are spaced apart from each other at small intervals and follow narrow channels 62 that run from one end of the drum to the other.

Sides 64 thereby prevent reactant gas from flowing around the ends of the drum. Applicants have discovered that device 20 can be used without shroud 54.

As can be seen in FIG. 3, according to this embodiment, passageways 66 that are not used to introduce reaction gases into interior chamber 32 are used to conduct reaction products from interior chamber 32 and deposition chamber 22. When the pump connected to the exhaust port 24 is energized, the inside of the chamber 22 and the inner chamber 32 are evacuated. At this time, the interior chamber is evacuated via the narrow passage 66. The reaction products are thus removed from chamber 22 and the interior of interior chamber 32 can be maintained at a pressure suitable for deposition.

Apparatus 20 according to this preferred embodiment to facilitate the formation of a deposition plasma, shown at 68 in FIG.
further includes a first microwave energy source 70 and a second microwave energy source 72. The microwave energy sources 70.72 each include an antenna stub 74.76. The microwave energy source 70.72 can be, for example, a microwave frequency magnetron with an output frequency of 2.45 GHz. Magnetron 70.72
are each mounted on a cylindrical waveguide structure 78,80. Stubs 74.76 are connected to the back wall 79. of the waveguide 78.80.
81 at a distance of approximately one quarter of the wavelength of the waveguide. This spacing maximizes the coupling of microwave energy from the stub to the waveguide. Waveguide structures 78,80 are each rotatably mounted to a separate waveguide 82,84. waveguide 8
2.84 protrudes into the deposition chamber 22, and the drum 12
ends near the edge of Lips 86,88 are included at the ends of waveguides 82,84. Each lip part 86□88
Sealing O-rings 90.92 are disposed against each other, each O-ring supporting a respective microwave transparent window 94.96 with a lip 86.88. The microwave transparent windows 94 , 96 together with the drum 12 form a substantially closed interior chamber 32 . Using the present invention, the window 94°9
6 can be maximized and stabilized.

Waveguides 78 , 82 form coupling means for coupling the microwave energy produced by magnetron 70 into interior chamber 32 . Similarly, waveguides 80 , 84 form coupling means for coupling microwave energy generated by magnetron 72 into interior chamber 32 . Microwave energy generated by magnetron 70.72 is radiated by antenna stub 74.76. Antenna stubs 74, 76 determine the polarity of the radiated microwave energy. To prevent interference effects between stubs 74 and 76, it is desirable to angularly displace the antenna stubs from each other. According to this preferred embodiment:
The angle between the stubs is approximately 60°. However, in systems with more drums than six as shown here, the angle of displacement between the antenna stubs 74, 76 will also change. This is because it is desirable to displace the antenna stubs with respect to the drum 12 such that each stub creates the same and uniform microwave energy field within the interior chamber 32.

In addition to enclosing the interior chamber 32, the microwave transparent windows 94,96 also serve to protect the magnetrons 70,72 from the reactant gases. It also serves to prevent plasma formation in the magnetron probes 74, 76 and reduces coupling loss of microwave energy into the interior chamber 32. To this end, the windows 94,96 are formed from a material such as alumina and have a thickness that reduces the reflected power into the waveguides 82,84.

To achieve this, it is best to energize each magnetron in sequence.

For example, if an alternating current is used to energize the magnetron, it can be energized to alternating current during a half-IJ-cycle of alternating current. In this way, interference effects between magnetrons can be further reduced.

As previously mentioned, waveguides 78, 80 are rotatably mounted over respective waveguides 82,84. As a result, each of the magnetron sources 70, 72 has a waveguide 82° 84
Rotation around the vertical axis of 1. to rotate the polarity of the microwave energy and equalize the microwave energy field.

This rotation makes it possible to equalize the time-averaged density of deposited species in the radial direction. Even if the polarization is made circular, the energy field can be equalized.

When using the apparatus 20 of FIGS. 2 and 3 to deposit material on the outer surface of drum 12, and more particularly when depositing a layer of material to form an electrophotographic reproduction machine drum, drum 12 is first
Attach as shown and as described above. Thereafter, the reaction gas is introduced through the inlets 26, 28, and 30 while the chamber 22 is evacuated by a pump connected to the outlet 24. When the reactant gas is introduced into the inner chamber 32, the magnetron 7
0.72 is energized to couple microwave frequency energy into the interior chamber 32 to form a glow discharge plasma therein. Since the inner chamber itself forms a waveguide structure at microwave frequencies, microwave energy can easily flow into the inner chamber 3.
Can be combined with 2.

Motor 50 is then energized to rotate drum 12 about its longitudinal axis. After that, as mentioned above, the magnetron 7
0.72 may also be rotated around the waveguide 82.84. As a result of the above operations, material is deposited evenly over the entire outer surface of drum 12.

It is desirable to heat the drum 12 during the deposition process.

To this end, apparatus 20 further includes a plurality of heating elements 100 mounted to stationary A-shift 38 by spacers 102. As shown in FIG. Since the shaft 38 is stationary, the heating element 1
00 is also static 11- in the drum 12. Heater 100 can take the form of a resistive heating element or an incandescent light bulb.

In order to load the amorphous semiconductor alloy with J(), the drum 12 is heated in advance to 20 to 400°C, preferably to about 300°C.The reaction gas is also heated before being introduced into the inner chamber 32. This incorporates a slag heater within the shroud 54, but the electric light is placed adjacent to the shroud 54 outside the deposition area to keep the shroud 54 at about 300°C.
This can be achieved by heating.

To make an electrophotographic drum such as that shown in FIG. can be formed. When the barrier layer 14 is formed from an insulating material such as silicon nitride, silicon carbide, silicon dioxide, etc., the reactive gas introduced into the interior chamber during the deposition process is silane (S).
t)-14) and/or silicon tetrafluoride (S i
F4) to which methane, nitrogen, ammonia, or oxygen is added may be used. Such a barrier layer can be used for both positively and negatively charging electrophotographic drums.

When the blocking layer 14 is made of an n-type amorphous silicon alloy, the inner chamber 32
The reaction gas introduced may be silane and/or silicon tetrafluoride plus diborane or boron trifluoride. Such a blocking layer is effective when positively charging an electrophotographic drum.

When the blocking layer 14 is formed from an n-type amorphous silicon alloy,
The reaction gas introduced into the inner chamber can be a gas consisting of silane and/or silicon tetrafluoride and phosphine or phosphorous pentafluoride. Such a blocking layer is effective in negatively charging electrophotographic devices.

To fabricate photoconductive region 16, photoconductive region 16 can be an amorphous silicon alloy incorporating silicon, hydrogen and/or fluorine.

Such materials can be deposited from reactive gases consisting of silane and/or silicon tetrafluoride and hydrogen.

Boron trifluoride gas or diborane gas may also be used if the photoconductive region is desired to be substantially intrinsic. If you want to make it slightly n-type, do not use a dopant.

As described in detail in the aforementioned U.S. patent application Ser. There is also. To deposit such materials, germane (GeH,a) or germanium tetrafluoride (GeF4) gas is introduced into the interior chamber 32.
It would be better to introduce it to

Germane or germanium tetrafluoride is silane and/or germanium tetrafluoride.
Alternatively, it can be used with silicon tetrafluoride to form an amorphous silicon-germanium alloy with a narrow bandgap suitable for infrared photoresistance applications.

A top barrier enhancement layer can also be deposited before top barrier layer 18 by RF deposition, also as described in detail in US Patent Application No. 580.081.

Finally, to form the top barrier layer 18, any of the materials and gas mixtures listed above for forming the bottom barrier layer 14 may be used. When depositing either layer 14 or 113.18, it is desirable to introduce a plasma resistant gas such as argon. Also, the pressure inside the inner chamber is approximately 0.05
It should be less than or equal to 10,000 yen.

Referring now to FIG. 4, another apparatus 110 is shown that may carry out the method of the present invention. Apparatus 110 is essentially the same as apparatus 20 of FIG. 2 in terms of power.

Therefore, description of device 110 will be limited to the differences between device 110 and device 20 of FIG. 2.

As can be seen in FIG. 4, the device 110 includes only one microwave energy source magnetron 70. The other magnetron is removed and replaced by plate 11
2 is provided. The plate 112 is in contact with a cylindrical tube 114 which supports a window 96 at its end opposite the plate 112 and a wall 116 at its intermediate portion. As a result, one magnetron 70 can be used to couple microwave energy into the interior chamber 31. Again, magnetron 70 can be rotated about waveguide 82 during deposition to rotate the polarization of the microwave field.

As can also be seen in FIG. 4, the enclosure 110 includes a cylindrical waveguide structure 120 formed of wire mesh or screen. Waveguide structure 120 is disposed within interior chamber 32, preferably at a small spacing with respect to drum 12. This waveguide structure 120 can be used to make the waveguide structure more uniform and continuous, thereby making the propagation of microwave energy within the interior chamber 32 more efficient. However, since the deposition is performed on the waveguide structure 120, the waveguide structure 120 will somewhat reduce the gas utilization of the system.

Next, the present invention will be explained. Applicants have discovered that the tuning of power transmitted through a transparent window is not as simple as originally predicted. It turns out that there are many important conditions to consider, as listed below.
・°“111, Do not fix the frequency of the microwave power generator or magnetron.The frequency is determined by the output power of the magnetron, so it is synchronized with the power supply output pulsation within the band (approximately 50H).
H2) vibrates. Shuichi 4 q - The wave number also fluctuates due to wear of the magnetron, and fluctuates with changes in the temperature and pressure of the magnetron cooling water.

2. As the glow discharge process is performed, the window expands due to temperature changes in the transmission window, so it is inevitable that the size of the deposition chamber will change.

In principle, a separate conventional tuner can compensate for the dielectric discontinuity that the transmission window introduces into the waveguide. However, as confirmed by the applicants,
Such a separate tuner (such as a 42' tab unit) absorbs more power as the mismatch increases. In some cases, separate conventional □ tuners have resulted in power absorption rates of 90% or more.

4. Migro, wave power or radiation transmitted from the window to the process gas must ignite the glow discharge plasma and also carry out plasma "retention."

It is not possible to tune the deposition system for both the and on conditions. This is because the complex permittivity of the ignited plasma is not the same as the complex permittivity of the gas in the plasma-off deposition system.

Some kind of compromise is required.

5. When using various processing gases, the synchronization of the plasma-on state is not necessarily stable. This is because the complex dielectric constant of the plasma and the microwave power absorbed by the plasma couple together through changes in microwave transmission.

The reflected power is related to the plasma conditions to which the microwave energy is subjected, since the plasma conditions, such as the species present from the various reactant gases, depend in part on the amount of power transferred to the plasma.

Applicants have discovered that item 3 above requires that the window structure be provided with a low loss tuning element in close proximity to the window to reduce the constant left wave current of the tuner.

Since acceptable solutions have been found for items 4 and 5 above, no further changes to the tuner structure are necessary.

Applicants originally predicted that the window would need to be matched with respect to one parameter, and that parameter would be adequate transmission over an acceptably wide band. As a result of further research, a second parameter emerged to be addressed. The power reflected by the window shown in FIG.
Referring to the power transmitted by the window in Figure 6, 2
It can be seen that there are two main reflection peaks 150 and 152 (note that the directions of the X and Y axes are reversed in Figures 5 and 6 due to the difference in measuring instruments). required). Peak 150.152 has the following characteristics.

(1) The width of these peaks is extremely narrow, about 2HH2. Measuring instruments must be precisely calibrated to even detect it. Initially, it could not be discovered due to its narrow width.

(2) The frequency at which the peak occurs is determined by the diameter of the transmission window. Therefore, the peak may enter the magnetron frequency band as the window changes or as various fluctuations as described above occur.

(3) The peak introduces a large discontinuity in aligning the window to the plasma.

Applicants interpreted peak 150.152 to be a mode shift in the transmission window. Because the window material, such as alumina, has a high dielectric constant, the optical size of the window (4 inches in diameter in this example) is large enough to support the four propagation modes. The operating frequency of the magnetron is 2.45 GHz in the illustrated example. Other frequencies can also be used according to the invention. The cut-on frequency of the 553 first propagation mode was determined to be substantially the operating frequency. Although this deposition and other plasma systems can operate satisfactorily with any number of propagation modes through the window, they do not seem to operate well when the microwave propagation energy is randomly switched around. At this time, the plasma condition may become unstable and change the tg product parameter, causing the plasma to turn off.

Other operating conditions that should be taken into consideration are shown in the graph of FIG. Operating section 1!111511 represents the relationship between plasma intensity (I) and reflected power (R).

The point of minimum R 156 appears to be the optimal operating condition because it is the point with the lowest loss R, but as the plasma conditions move toward decreasing intensity, R increases rapidly or erratically;
Plasma disappears. Therefore, a compromise operating region 158 in which the system operates is set slightly higher than that, in the R loss region but also in the stable plasma operating region.

To compensate for each of the above conditions, applicants have invented the following tuning method and device. Referring to FIGS. 8 and 9, a microwave transmission window 160 is mounted at the - end of a microwave transmission system 162. Referring to FIGS. A plasma (not shown) will be present on the free side of window 160. A pair of tuning structures 164,166 implement the invention. As shown, each structure 164, 166 includes a plurality of individual portions 16.
It is formed from 8 parts, and these individual parts have windows 160.
to provide the required low loss tuning structure. These portions may be disk-shaped 168 or may have other shapes such as rectangular 168°.

The size of portion 168 and the height of tuning structures 164, 166 are adjusted to provide high window transmission while stabilizing the prism mode excitation. Next, structure 164.1
66 is secured with tape or other adhesive, etc., and the window 160 is tuned to the desired system operation.

Portion 168 and tape or adhesive are selected to minimize microwave absorption and may be formed from the same material as window 160 or other suitable dielectric material. Tuning the system to a compromise between plasma off and on states. This synchronized plasma is brought to a level that can be ignited. At this time, it is also possible to use RF or other signals separately to ignite the plasma. Synchronized Tochizo body 164,1
66 is located on the surface of the window 160 itself so that power loss is substantially minimized as much as possible. A tuning structure, such as a conventional stub, placed adjacent to, but separate from, window 160:1. Power is reflected between the stub and the window, heating the system and thus resulting in power loss. 5 and 6, section 168 moves the magnetron operating frequency to the midpoint between peaks 150 and 152 to provide a stable operating region between the peaks.
width is selected. The heights of the tuning structures 164, 166 are also selected to move the operating R point toward a minimum amount.

(See Figure 5).

Further, although the present invention has been described in detail in connection with the formation of electrophotographic drums, those skilled in the art will appreciate that the method and apparatus of the present invention can be applied to any type of microwave transparent window. and plasma, regardless of type. When silicon is deposited, alumina is preferred as the window material. For silicon-free plasmas, such as the Mi plasma etch system, dielectric materials such as quartz can also be used. Quartz was an undesirable material because the window 160 would have to be cooled to prevent crystallization of the silicon deposited on the window surface when using 11 silicon □ according to applicants' findings. This is because if silicon is deposited on the window surface and crystallized, heat will rise, and therefore system operation may need to be stopped F. Dielectric materials such as alumina with high thermal conductivity are desirable for use with silicon deposition plasmas.

[Brief explanation of drawings]

Figure 1 is US Patent Application No. 580,086. It is a partial cross-sectional view showing a cylindrical member deposited with various materials according to No.
The deposited material number λ constitutes a cylindrical member used as an electrophotographic device in which the present invention can be practiced. FIG. 2 is a side view, partially in section, of an apparatus in which the present invention may be practiced according to US patent application Ser. No. 580,086. FIG. 3 is a cross-sectional view taken along line 3--3 in FIG. FIG. 4 is a partial cross-sectional side view of another apparatus capable of implementing water defense according to US patent application Ser. No. 580.086. FIG. 5 is an explanatory diagram of microwave power reflected from one transmission window. FIG. 6 is an explanatory diagram of the microwave power transmitted by the window of FIG. 5. FIG. 7 is a graph showing the relationship between reflected power and plasma intensity. FIG. 8 is a schematic side view showing an embodiment of the present invention. 9 is a schematic plan view of the embodiment of FIG. 8; FIG. 10... Electrophotographic device, 12...
Cylindrical member, 22...Deposition chamber, 32...
・Inner chamber, 70.72...Microwave energy source, 74.76...Antenna stub, 78, 80.8
2.84... Waveguide, 94,96,160...
- Microwave transmission window, 164.166... Tuning structure, 168... Dielectric part.

Claims (20)

[Claims] (1) A method for tuning a microwave transmission window, which includes the steps of providing a microwave generation means, providing a plasma chamber, and connecting the plasma chamber to the microwave generation means via a dielectric microwave transmission window. by the microwave generating means by providing a step and at least two tuning structures disposed adjacent the outer edge of the window;
tuning the window to maximize the power generated and transmitted through the window into the plasma chamber. 2. The method of claim 1, wherein said tuning step includes forming each of said tuning structures by polymerizing a plurality of dielectric portions. 3. The tuning step includes sizing the width of the dielectric portion and adjusting the height of the tuning structure to maximize the transmitted power. Method. (4) further comprising tuning the dielectric portion to stabilize modes propagating into the plasma chamber;
A method according to claim 3. (5) introducing at least one reactant gas into the plasma chamber before tuning the window and forming a plasma from the reactant gas.
The method described in section. (6) The method according to claim 5, wherein the at least one reactive gas is a semiconductor-containing compound. (7) The method according to claim 6, wherein the at least one reaction gas contains silicon. 8. The method of claim 1, further comprising the step of: (8) maintaining a pressure within the interior chamber at about 0.05 torr or less. (9) The power density of the microwave energy is approximately 0.
2. The method of claim 1, further comprising the step of adjusting from 1 to 1 watt/cm^3. (10) The frequency of the microwave energy is 2.45
2. The method of claim 1, which is gigahertz. (11) An apparatus for tuning a microwave transmission window, comprising: a generation means; a plasma deposition chamber connected to the generation means via a dielectric microwave transmission window; means for tuning the window to maximize power transmitted through the window into the deposition chamber, the tuning means including at least two tuning structures adjacent an outer edge of the window. equipment that includes. 12. The apparatus of claim 11, wherein each of the tuning structures is formed from a plurality of polymerized dielectric portions. 13. The apparatus of claim 12, wherein the dielectric portion is sized in width and the height of the tuning structure is adjusted to maximize the transmitted power. 14. The apparatus of claim 12, wherein the dielectric portion is configured to stabilize modes transmitted into the deposition chamber. 15. The apparatus of claim 12, wherein the window and the dielectric portion are formed from alumina. (16) A tuned microwave transmission window for a plasma deposition system, wherein the system includes microwave generation means coupled to a plasma deposition chamber via the transmission window, and wherein the tuning window a dielectric window member for coupling generation means and isolating the means from the deposition chamber; and a dielectric window member for maximizing the power generated by the generation means and transmitted through the dielectric window member into the deposition chamber. and means for tuning at least two
a tuned microwave transparent window including two tuning structures adjacent an outer edge of the dielectric window member. 17. The apparatus of claim 16, wherein each of the tuning structures is formed from a plurality of polymerized dielectric portions. 18. The apparatus of claim 17, wherein the dielectric portion is sized in width and the height of the tuning structure is adjusted to maximize the transmitted power. 19. The apparatus of claim 18, wherein the dielectric portion is configured to stabilize modes transmitted into the deposition chamber. 20. The apparatus of claim 17, wherein the dielectric window member and the dielectric portion are formed from alumina.