CA1267865A - Anode for magnetic sputtering of gradient films - Google Patents
Anode for magnetic sputtering of gradient filmsInfo
- Publication number
- CA1267865A CA1267865A CA000493096A CA493096A CA1267865A CA 1267865 A CA1267865 A CA 1267865A CA 000493096 A CA000493096 A CA 000493096A CA 493096 A CA493096 A CA 493096A CA 1267865 A CA1267865 A CA 1267865A
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- CA
- Canada
- Prior art keywords
- anode
- cathode
- sputtering surface
- coating
- sputtering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Abstract of the Disclosure An improved anode-system for producing uniform gradient coatings by magnetic sputtering is disclosed, comprising a pair of anode plates asymmetrically designed and positioned along the length of the cathode. The magnetic flux lines form a tunnel in a closed loop on the sputtering surface. The glow discharge is confined by the magnetic field to the region adjacent the sputtering surface.
Description
~267865 Background of;the Invention This invention relates generallv eo the art of magnetic sputtering, and more parelcularly to the a~t of anode designs fcr magnetlc sputtering.
U.S. Patent No. 4,166,018 to Chapin describes a sputtering apparatus in which a magnetic field i9 formed adjacent a planar sputtering surface, the field comprising arcbing llnes of flux over a closed loop eroslon region on the sputtering surface. Chapln teaches that the conf~guration of the anode is relatlvely unimportant, but it ls preferred that the anode be of relatlvely small size compared to the :
cathode surface. In the illustrated embodimen~, the anode comprises a bar of relatlvely small cross-section which extends around the cathode spaced from its perimeter.
In prior art literature on magnetic sputtering, the design of the anode system is typically either~ignored or dismissed as relatlvely unimportan~t, However, it is disclosed iD U.S. Patent No. ~f~ 7~, 7Z~ to Gillery et al that appropriate anode design is essentlal to attaining very uniform sputeered films, particularly in reactlve sp~lttPring processes, and most especially when depositing insulating layers, s~lch as titanium oxide.
.
i7~365 _ummary of the Invention The present invention involves an anode system designed to provide a thickness gradient in a sputtered fil~ across and along a substrate surface. The new anode system is particularly well designed for use with an elongated rectangular cathode of the type typically used in a scanning magentron sputtering coating apparatus. The anode system may comprise a single anode, but generally comprises two separate anode plates disposed on opposite sides of the cathode or on opposite sides of the substrate. The configuration of the anodes ls very inportant. The length of the anode is determined by the pattern of coating desired. The width of the anode is less important, but is preferably substantially less than the length, since the effectiveness of the anode diminshes with distance from the cathode. The thickness of the anode is preferably =inimal. An elongated strip of metal of the desired configuration provides a particularly suitable anode plate.
In a preferred embodiment of the present invention, anode systems are shaped to provide coatings with uniform gradients of thickness deposlted with either stationary or scanning cathodes.
This feature is of particular importance in the sputtering of electrocnoductive materials, which, as a result, can be deposlted as fllms with gradient conductivity.
Brief Description of the Drawin~
Figure 1 illustrates an elongated rectangular cathode 1 with a single elongated shaped anode 2 pnsitioned above the substrate 3. The pattern of gradient coating obtained is shown on the surface of substrate 3 with broken lines.
U.S. Patent No. 4,166,018 to Chapin describes a sputtering apparatus in which a magnetic field i9 formed adjacent a planar sputtering surface, the field comprising arcbing llnes of flux over a closed loop eroslon region on the sputtering surface. Chapln teaches that the conf~guration of the anode is relatlvely unimportant, but it ls preferred that the anode be of relatlvely small size compared to the :
cathode surface. In the illustrated embodimen~, the anode comprises a bar of relatlvely small cross-section which extends around the cathode spaced from its perimeter.
In prior art literature on magnetic sputtering, the design of the anode system is typically either~ignored or dismissed as relatlvely unimportan~t, However, it is disclosed iD U.S. Patent No. ~f~ 7~, 7Z~ to Gillery et al that appropriate anode design is essentlal to attaining very uniform sputeered films, particularly in reactlve sp~lttPring processes, and most especially when depositing insulating layers, s~lch as titanium oxide.
.
i7~365 _ummary of the Invention The present invention involves an anode system designed to provide a thickness gradient in a sputtered fil~ across and along a substrate surface. The new anode system is particularly well designed for use with an elongated rectangular cathode of the type typically used in a scanning magentron sputtering coating apparatus. The anode system may comprise a single anode, but generally comprises two separate anode plates disposed on opposite sides of the cathode or on opposite sides of the substrate. The configuration of the anodes ls very inportant. The length of the anode is determined by the pattern of coating desired. The width of the anode is less important, but is preferably substantially less than the length, since the effectiveness of the anode diminshes with distance from the cathode. The thickness of the anode is preferably =inimal. An elongated strip of metal of the desired configuration provides a particularly suitable anode plate.
In a preferred embodiment of the present invention, anode systems are shaped to provide coatings with uniform gradients of thickness deposlted with either stationary or scanning cathodes.
This feature is of particular importance in the sputtering of electrocnoductive materials, which, as a result, can be deposlted as fllms with gradient conductivity.
Brief Description of the Drawin~
Figure 1 illustrates an elongated rectangular cathode 1 with a single elongated shaped anode 2 pnsitioned above the substrate 3. The pattern of gradient coating obtained is shown on the surface of substrate 3 with broken lines.
-2-"`',,'~
8~i5 Figure 2 illustrates an elongated rectangular cathode 1 with apair of elongated shaped anodes 2 positioned on opposite sides of the cathode 1 above substrate 3. The pattern of gradient caating i5 shown on the surface of substrate 3 with broken lines.
Detailed Description of the Preferred Embodiments . _ . . _ ~ . . .
In a typical commercially available magnetic sputtering coating apparatus, the anode supplied consists of an elongated loop of copper tubing disposed on one side of an elongated rectangular ca~hode. In operation, this system deposits a coating of extremely poor uniformity.
For example, when sputtering a titanium oxide film from a titanium metal cathode 40 inches (l meter) long and 6 inches (15 centimeters) wide scanning over a distance of 24 inches (61 centimeters) at a distance o 3 inches (7.6 centimeters) from the substrate in an atmosphere of 13 percent oxygen in argon at an average current density of 0.0625 amps per square inch (0.0097 amps per square centimeter), the thickness of the coating varies by 30 percent. Typically, a thick band of coating is formed along one edge of the substrate and bands of varying thickness are formed in the center.
In the development of the present invention~ it was deduced from a series of experiments that as electrons lPave the face of the cathode and travel in the magnetic tunnel created by the magnetic field developed by the sputtering apparatus, they begin to lose Qnergy and are attracted to the anode. As a result, it was discovered, the shape of the anode and its proximity to the maguetic tunnel tend to affect the curren~
flow along the cathode, thereby determine the rate o~ deposition of the coating, and ultlmntely control the film thickness.
The ne~ anode designs provide for the deposition of a desired gradient film, and may comprise either a single anode or a pair of anodes disposed on opposite sides of a cathode, or positioned adjacent the substrate. The effective surfaces of the anodes may be parallel with the sputtering surface of the cathode, or tangentially spaced from the major dimension of the glo~
discharge area.
In one preferred embodiment of the present invention, a pair of shaped anodes 2 is disposed on opposite sides of a substrate as in Figure 2. The effective surfaces of the anodes are the top surfaces which are parallel, in fact essentailly coplanar, with the sputtering surface of the scanning cathode.
The anode plates are typically strips of copper metal, preferably water-cooled. The length of the anodes is substantially equal to the parallel dimension of the substrate surface on which the thickest area of coating is to be deposited. The ~idth is less important, since the effectiveness of the anode surface decreases wlth distance from the catbode. The thickness of the anodes is even less important, and may be minimal. Elongated strips of metal, preferably copper, provide particlarly suit~ble anodes.
When the anode design described above is used in the deposition of titanium oxide from a titanium metal cathode, the effective surface6 of the andes tend to lose efficiency as they become coated with an insulation layer of titanium oxide ~hich is scattered back from the substrate surface olltQ the anode surfaces. For this reason, a more preferred embodiment of the .~
~26~7~
present invention is an anodes design wherein a pair of elongated shaped anodes is disposed on opposite sides of an elongated rectangular cathode. The anodes may be spaced laterally from the cathode, but are preferably also vertically displaced, typically by about l.S inches (about 3.8 centimeters). In this embodiment, the upper surfaces of the anode are the effective sur~aces.
Although sputtered material will eventually be deposited on the top surface of the anodes as well as the bottom surfaces, the effective upper surfaces uill be coated with titanium oxide in a more reduced, and-thus more conductive, state, and will therefore not decrease in efficiency as quickly.
As here discribed, an asymmetrical anode design is required in order to from a coating of gradient thickness.
Asymmetry with respect to both the major and minor axes of the sputtering surface is preferred. Although the present invention has been discussed in detail above with respect to a titanium cathode, copper anodes and a scanning apparatus, various other target materials, such as indium, may be used, as well as other anode metals and configurations. Either scanning or stationary cathodes may be used to produce gradient coatings. The present invention will be ur~her understood from the description of the specific examples which follow.
Example I
A stationary titanium cathodes with a sputtering surface measuring 6 by 40 inches (15 by 102 centime~ s) ls spaced about 3 inches (about 7.6 centimeters) from a glass substrate having approximately th same dimensions.
-5a-i7~3~S
A single copper anode shaped and positioned as illustrated in Figure 1 is used in this example. The cathode is sputtered at an average current density of 0.0625 a~ps per square inch (0.0097 amps per square centimeter) ~or about S minutes in an atmosphere of 13 percent oxygen in argon at a pressure of 6 x Torr. The -Sb-.
7~
resultant titanium oxide coating has a thickness pattern as sho~m by the dotted lines in Figure 1. The thlckest ~rea of coating in the smaller ellipse has a thickness of about Z700 Angstroms. The thickness of the coating gradiently decreases outwardly such that at the area depicted by the larger ellipse, the coating has a thickness of about 2000 Angstroms.
The curved broken llnes represent coating arens having thicknesses of about 1400 and 700 Angstroms respectively.
Example II
A stationary cathode is sputtered to coat a glass substrate with titanium oxide as in Example I except that a pair of copper anodes shaped and posi~ioned as in Figure 2 is employed. A titanium oxide coating with a uniform thickness gradient is produced. The thickest portion of the coating, as illustrated by the central ellipse in Figure 2, has a thickness of about 2700 Angstroms. The coating thickness decreases gradually toward the perimeter of the substrate. In the area shown by the curved lines in Figure 2, the coating has a thickness of about 1400 Angstroms.
The above examples are offered only to illustrate the pxesent invention. Other anode shapes, sizes and positions may be employed to form coatings of other gradient thicknesses. While the examples above employ a stationary cathode, a scanning cathode or moving substrate may be employed to form coatings with bands of gradient thickness. Of course, the cathode, anode and substrate may be comprised of a variety of materials lnown in the art. The scope of the inventlon is defined by the following claims.
8~i5 Figure 2 illustrates an elongated rectangular cathode 1 with apair of elongated shaped anodes 2 positioned on opposite sides of the cathode 1 above substrate 3. The pattern of gradient caating i5 shown on the surface of substrate 3 with broken lines.
Detailed Description of the Preferred Embodiments . _ . . _ ~ . . .
In a typical commercially available magnetic sputtering coating apparatus, the anode supplied consists of an elongated loop of copper tubing disposed on one side of an elongated rectangular ca~hode. In operation, this system deposits a coating of extremely poor uniformity.
For example, when sputtering a titanium oxide film from a titanium metal cathode 40 inches (l meter) long and 6 inches (15 centimeters) wide scanning over a distance of 24 inches (61 centimeters) at a distance o 3 inches (7.6 centimeters) from the substrate in an atmosphere of 13 percent oxygen in argon at an average current density of 0.0625 amps per square inch (0.0097 amps per square centimeter), the thickness of the coating varies by 30 percent. Typically, a thick band of coating is formed along one edge of the substrate and bands of varying thickness are formed in the center.
In the development of the present invention~ it was deduced from a series of experiments that as electrons lPave the face of the cathode and travel in the magnetic tunnel created by the magnetic field developed by the sputtering apparatus, they begin to lose Qnergy and are attracted to the anode. As a result, it was discovered, the shape of the anode and its proximity to the maguetic tunnel tend to affect the curren~
flow along the cathode, thereby determine the rate o~ deposition of the coating, and ultlmntely control the film thickness.
The ne~ anode designs provide for the deposition of a desired gradient film, and may comprise either a single anode or a pair of anodes disposed on opposite sides of a cathode, or positioned adjacent the substrate. The effective surfaces of the anodes may be parallel with the sputtering surface of the cathode, or tangentially spaced from the major dimension of the glo~
discharge area.
In one preferred embodiment of the present invention, a pair of shaped anodes 2 is disposed on opposite sides of a substrate as in Figure 2. The effective surfaces of the anodes are the top surfaces which are parallel, in fact essentailly coplanar, with the sputtering surface of the scanning cathode.
The anode plates are typically strips of copper metal, preferably water-cooled. The length of the anodes is substantially equal to the parallel dimension of the substrate surface on which the thickest area of coating is to be deposited. The ~idth is less important, since the effectiveness of the anode surface decreases wlth distance from the catbode. The thickness of the anodes is even less important, and may be minimal. Elongated strips of metal, preferably copper, provide particlarly suit~ble anodes.
When the anode design described above is used in the deposition of titanium oxide from a titanium metal cathode, the effective surface6 of the andes tend to lose efficiency as they become coated with an insulation layer of titanium oxide ~hich is scattered back from the substrate surface olltQ the anode surfaces. For this reason, a more preferred embodiment of the .~
~26~7~
present invention is an anodes design wherein a pair of elongated shaped anodes is disposed on opposite sides of an elongated rectangular cathode. The anodes may be spaced laterally from the cathode, but are preferably also vertically displaced, typically by about l.S inches (about 3.8 centimeters). In this embodiment, the upper surfaces of the anode are the effective sur~aces.
Although sputtered material will eventually be deposited on the top surface of the anodes as well as the bottom surfaces, the effective upper surfaces uill be coated with titanium oxide in a more reduced, and-thus more conductive, state, and will therefore not decrease in efficiency as quickly.
As here discribed, an asymmetrical anode design is required in order to from a coating of gradient thickness.
Asymmetry with respect to both the major and minor axes of the sputtering surface is preferred. Although the present invention has been discussed in detail above with respect to a titanium cathode, copper anodes and a scanning apparatus, various other target materials, such as indium, may be used, as well as other anode metals and configurations. Either scanning or stationary cathodes may be used to produce gradient coatings. The present invention will be ur~her understood from the description of the specific examples which follow.
Example I
A stationary titanium cathodes with a sputtering surface measuring 6 by 40 inches (15 by 102 centime~ s) ls spaced about 3 inches (about 7.6 centimeters) from a glass substrate having approximately th same dimensions.
-5a-i7~3~S
A single copper anode shaped and positioned as illustrated in Figure 1 is used in this example. The cathode is sputtered at an average current density of 0.0625 a~ps per square inch (0.0097 amps per square centimeter) ~or about S minutes in an atmosphere of 13 percent oxygen in argon at a pressure of 6 x Torr. The -Sb-.
7~
resultant titanium oxide coating has a thickness pattern as sho~m by the dotted lines in Figure 1. The thlckest ~rea of coating in the smaller ellipse has a thickness of about Z700 Angstroms. The thickness of the coating gradiently decreases outwardly such that at the area depicted by the larger ellipse, the coating has a thickness of about 2000 Angstroms.
The curved broken llnes represent coating arens having thicknesses of about 1400 and 700 Angstroms respectively.
Example II
A stationary cathode is sputtered to coat a glass substrate with titanium oxide as in Example I except that a pair of copper anodes shaped and posi~ioned as in Figure 2 is employed. A titanium oxide coating with a uniform thickness gradient is produced. The thickest portion of the coating, as illustrated by the central ellipse in Figure 2, has a thickness of about 2700 Angstroms. The coating thickness decreases gradually toward the perimeter of the substrate. In the area shown by the curved lines in Figure 2, the coating has a thickness of about 1400 Angstroms.
The above examples are offered only to illustrate the pxesent invention. Other anode shapes, sizes and positions may be employed to form coatings of other gradient thicknesses. While the examples above employ a stationary cathode, a scanning cathode or moving substrate may be employed to form coatings with bands of gradient thickness. Of course, the cathode, anode and substrate may be comprised of a variety of materials lnown in the art. The scope of the inventlon is defined by the following claims.
Claims (6)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In an apparatus for coating a substrate comprising a cathode having a substantially planar surface consisting of a material to be sputtered, magnet means for producing a magnetic field having lines of flux which extend in a curve from said sputtering surface and return thereto to form a magnetic tunnel over a closed loop erosion region on said sputtering surface, an anode positioned to produce an accelerating electric field adjacent said sputtering surface for producing a glow discharge confined by said magnetic field to the region adjacent said sputtering surface and within said magnetic tunnel, and means for connecting said cathode and said anode to a source of electrical potential, the improvement which comprises said anode being asymmetrically designed and positioned, and spaced from the major dimension of said magnetic tunnel outside the zone of glow discharge confinement, in order to provide a sputtered coating of gradient thickness.
2. The improved apparatus according to claim 1, wherein the cathode is of elongated rectangular shape, and the anode comprises a pair of anode plates positioned on opposite sides of the cathode.
3. The improved apparatus according to claim 2, wherein each anode plate is of elongated shape substantially the same length as the parallel dimension of the substrate surface to be coated with the thickest portion of the gradient coating.
4. The improved apparatus according to claim 3, wherein the effective surfaces of the anode plates are substantially coplanar with the sputtering surface of the cathode.
5. The improved apparatus according to claim 4, wherein the effective surfaces of the anode plates are positioned tangentially spaced from the glow discharge.
6. In an apparatus for coating a substrate comprising a cathode having a substantially planar surface consisting of a material to be sputtered, magnet means for producing a magnetic field having lines of flux which extend in a curve from said sputtering surface and return thereto to form a magnetic tunnel over a closed loop erosion region on said sputtering surface, an anode positioned to produce an acceleration electric field adjacent said sputtering surface for producing a glow discharge confined by said magnetic field to the region adjacent said sputtering surface and within said magnetic tunnel, and means for connecting said cathode and said anode to a source of electric potential, the improvement which comprises said anode being asymmetrically designed to produce a gradient sputtered coating.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US661,748 | 1984-10-17 | ||
| US06/661,748 US4744880A (en) | 1984-01-17 | 1984-10-17 | Anode for magnetic sputtering of gradient films |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1267865A true CA1267865A (en) | 1990-04-17 |
Family
ID=24654953
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000493096A Expired CA1267865A (en) | 1984-10-17 | 1985-10-16 | Anode for magnetic sputtering of gradient films |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1267865A (en) |
-
1985
- 1985-10-16 CA CA000493096A patent/CA1267865A/en not_active Expired
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