EP0040306A1 - Method for producing large grain semiconductor ribbons - Google Patents
Method for producing large grain semiconductor ribbons Download PDFInfo
- Publication number
- EP0040306A1 EP0040306A1 EP81102203A EP81102203A EP0040306A1 EP 0040306 A1 EP0040306 A1 EP 0040306A1 EP 81102203 A EP81102203 A EP 81102203A EP 81102203 A EP81102203 A EP 81102203A EP 0040306 A1 EP0040306 A1 EP 0040306A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- wheel
- semiconductor material
- ribbons
- semiconductor
- psig
- 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.)
- Granted
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
- B22D11/0637—Accessories therefor
- B22D11/0697—Accessories therefor for casting in a protected atmosphere
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/005—Continuous casting of metals, i.e. casting in indefinite lengths of wire
Definitions
- This invention relates to the manufacture of large grain semiconductor ribbons suitable for solar cell applications.
- Another object of the invention is to establish a method for production of semiconductor ribbons with an average grain size of about 20 ⁇ m and greater.
- Still another object of this invention is .to provide a method for producing semiconductor ribbons with a coherent oxide.
- Yet another object of the invention is to provide a method for the production of substantial volumes of silicon ribbon.
- the present invention as claimed provides a method for fabricating large grain semiconductor ribbons, wherein a molten semiconductor material is discharged onto a rotating cylindrical surface which is rotating with a linear velocity of not greater than 36 m/s.
- FIG. 1 A device suitable for the implementation of this invention is illustrated in FIG. 1.
- a tube 10 is employed for containing a molten semiconductor material 12.
- the semiconductor material 12 is maintained molten by a furnace 14 which surrounds the tube 10.
- the tube 10 has a nozzle 16 which is employed to direct a molten stream 18 of the semiconductor material 12. Examples of such semiconductor materials are Si, Ge, and Ga-As.
- a gas supply tube 20 feeds gas into the tube 10 via a regulating valve 22.
- the regulating valve 22 controls pressure in the tube 10 above the molten semiconductor material 12. This pressure serves to discharge the molten semiconductor material 12 through the nozzle 16 and forms the stream 18.
- the stream 18 impinges on a rotating wheel 24.
- the stream 18 impacts the wheel 24 at an angle 6 such that there is a component of the stream direction which is in the direction of a tangent to the rotating wheel 24 at the point of contact 25. This component should be in the direction of the rotation.
- the wheel 24 is driven from a power drive 26 such as a motor.
- the wheel 24 should be a conducting material. Stainless steel, as well as copper, have been found to be satisfactory materials.
- the stream 18 impinges on the rotating cylindrical surface 28 thereby generating a semiconductor ribbon 30.
- a gas is supplied to the gas supply tube 20 and pressure.? in the tube 10 is maintained above the semiconductor material by the regulating valve 22. This pressure p controls the discharge of the stream 18 from the nozzle 16. The stream 18 impinges upon the wheel 24 which is rotating as illustrated with an angular speed ⁇ .
- the cylindrical surface 28 may not obtain velocities greater than 36 m/s without substantially reducing the ultimate average grain size of the resulting semiconductor ribbon 30.
- FIG.. 2 offers a graphical representation of the effect of wheel speed on the average grain size.
- semiconductor material ribbons were generated on a copper wheel, having a diameter of 7,6 cm.
- Curves A, B and C are for silicon where the molten silicon is heated to about 1500 C and the gas injection pressure p was maintained at respectively 4 psig, 8 psig, and 15 psig for a nozzle having a nominal opening 1 mm in diameter. As the pressure is increased the ribbon becomes thinner and above about 15 psig the ribbon becomes discontinuous and forms flakes. It is apparent that as one increases the pressure there is an increase in the ultimate grain size which can be obtained.
- Wheel speed has a marked effect on the ultimate grain size. It can be seen that at rpm (revolutions per minute) values of about 9000, i.e. a surface speed of about 36 m/s, the grain size has dropped to the neighborhood of slightly less than 10 ⁇ m and as the velocity of the wheel is further increased the change in grain size is not substantially affected. This decrease in grain size occurs for all pressures studied. The drop is sharpest for curves B and C.
- the velocity of the wheel is presented both in terms of rotational speed (rpm) and the linear velocity (m/s) of the cylindrical surface 28.
- the pressures are given in terms of the gas ejection pressure for the resulting semiconductor stream 18. It was found that changing the orifice diameter from 0,5 mm to 1,5 mm did not noticeably affect the grain size of the resulting ribbons.
- the linear velocity of the surface of the wheel as well as ejection pressure are the appropriate parameters for the control of relative grain size of the resulting ribbon. These parameters can be maintained independent of the geometry of the equipment employed.
- Curve D of FIG. 2 illustrates the effect of velocity on the grain size of germanium semiconductor ribbons. These ribbons were generated from molten germanium which was heated to about 1000 0 C and ejected at a pressure of 15 psig through a nozzle having a nominal diameter of 1 mm. As can be seen by comparing curves C and D, the germanium data as is the case for the silicon data show little dependence of size or speed at low speeds. The tabular data used to generate curve D has been incorporated into Table I.
- Both germanium and silicon form oxides on the surface of the resulting ribbons when the ribbons are generated in an atmosphere of air. These oxides are sufficient to provide an intermediate layer between the silicon and a metal deposited thereon. The resulting metal silicon junctions form Schottky barriers.
- the oxide may be prevented by generating the ribbon under a protective atmosphere.
- Argon and helium have been found to be effective atmospheres in which to generate the ribbons.
- the wheel 24 and nozzle 16 should be placed in a chamber 32 as illustrated by the broken line in FIG. 1. This chamber will allow the atmosphere to be controlled.
- the present invention will be of use in the semiconductor industry and in particular in solar cell production.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Liquid Deposition Of Substances Of Which Semiconductor Devices Are Composed (AREA)
- Photovoltaic Devices (AREA)
Abstract
Description
- This invention relates to the manufacture of large grain semiconductor ribbons suitable for solar cell applications.
- Dropwise deposition of a semiconductor liquid into a contoured mold has been employed to generate homogeneous bodies. One such patent teaching this technique is U.S. patent 3,367,394 by M. Roder et al. J. Meuleman et al in U.S. patent 4,124,411 employs a dropwise technique to form on a substrate a layer of a semiconductor material. While the latter technique allows the production of layers of semiconductors suitable for solar cells, the generation of these layers is slow and an appropriate substrate must be prepared.
- It has been reported that equipment classically employed to produce amorphous alloy ribbons can be used to generate polycrystalline ribbons of silicon which can be employed for solar cells. The crystalline silicon ribbons so produced are deposited in an evacuated chamber and have a small grain size. N. Tsuya and K.I. Arai, report in Solid State Physics (in Japanese) 13, 237 (1978), an average grain size of several pm. They have reported the results for the same operating conditions in J. Applied Phys., 18, 207 (1979), where the grain size is reported as 2 to 3 µm.
- These small grains are substantially smaller than those which should be employed to maintain a reasonable efficiency in any resulting solar cell. In order to obtain an efficiency of approximately 10% it would be required that the grain size be increased by an order of magnitude to approximately 10 to 30 µm.
- It is an object of the invention to establish a method for producing a semiconductor ribbon of suitable quality for solar cells.
- Another object of the invention is to establish a method for production of semiconductor ribbons with an average grain size of about 20 µm and greater.
- Still another object of this invention is .to provide a method for producing semiconductor ribbons with a coherent oxide.
- Yet another object of the invention is to provide a method for the production of substantial volumes of silicon ribbon.
- The present invention as claimed provides a method for fabricating large grain semiconductor ribbons, wherein a molten semiconductor material is discharged onto a rotating cylindrical surface which is rotating with a linear velocity of not greater than 36 m/s.
- These and other objects, features and advantages of the invention will become apparent from the following description, accompanying drawings, and appended claims in which various novel features of the invention are more particularly set forth.
- FIG. 1 is a schematic representation of a ribbon caster suitable for practicing the invention.
- FIG. 2 is a graphical depiction of the effect of wheel speed and injection pressure on grain size.
- A device suitable for the implementation of this invention is illustrated in FIG. 1. A
tube 10 is employed for containing amolten semiconductor material 12. Thesemiconductor material 12 is maintained molten by afurnace 14 which surrounds thetube 10. Thetube 10 has anozzle 16 which is employed to direct amolten stream 18 of thesemiconductor material 12. Examples of such semiconductor materials are Si, Ge, and Ga-As. Agas supply tube 20 feeds gas into thetube 10 via a regulatingvalve 22. The regulatingvalve 22 controls pressure in thetube 10 above themolten semiconductor material 12. This pressure serves to discharge themolten semiconductor material 12 through thenozzle 16 and forms thestream 18. Thestream 18 impinges on a rotatingwheel 24. Preferably thestream 18 impacts thewheel 24 at an angle 6 such that there is a component of the stream direction which is in the direction of a tangent to the rotatingwheel 24 at the point ofcontact 25. This component should be in the direction of the rotation. Thewheel 24 is driven from apower drive 26 such as a motor. Thewheel 24 should be a conducting material. Stainless steel, as well as copper, have been found to be satisfactory materials. During operation thestream 18 impinges on the rotatingcylindrical surface 28 thereby generating asemiconductor ribbon 30. - In carrying the invention into practice a gas is supplied to the
gas supply tube 20 and pressure.? in thetube 10 is maintained above the semiconductor material by the regulatingvalve 22. This pressure p controls the discharge of thestream 18 from thenozzle 16. Thestream 18 impinges upon thewheel 24 which is rotating as illustrated with an angular speed ω. - It has been found that when the ribbon is generated in air it is preferred to use a
copper wheel 24. When a copper wheel is used it is advisable to gold plate thecylindrical surface 28 of the wheel to avoid oxidation of the copper during operation. - It has also been found that, when the injection pressure p in the insulating tube is maintained at or above 8 psig (psig being defined as pounds per square inch gauge where reference pressure is the gas pressure at the wheel; 1 psi = 6,9 kPa) and the
nozzle 18 has an opening of a nominal diameter of 1 mm, asatisfactory ribbon 30 can be maintained when the linear velocity of thecylindrical surface 28 is in excess of 8 m/s. It is furthermore preferred that the angle of incidence 0 of thestream 18 with respect to thecylindrical surface 28 be from about 9° to 15° when defined with respect to an extended diameter passing through the point ofcontact 25. - In addition to the lower limits on the linear velocity of the
cylindrical surface 28 which is required to maintain asemiconductor ribbon 30, thecylindrical surface 28 may not obtain velocities greater than 36 m/s without substantially reducing the ultimate average grain size of the resultingsemiconductor ribbon 30. - FIG.. 2 offers a graphical representation of the effect of wheel speed on the average grain size. For these curves semiconductor material ribbons were generated on a copper wheel, having a diameter of 7,6 cm. Curves A, B and C are for silicon where the molten silicon is heated to about 1500 C and the gas injection pressure p was maintained at respectively 4 psig, 8 psig, and 15 psig for a nozzle having a
nominal opening 1 mm in diameter. As the pressure is increased the ribbon becomes thinner and above about 15 psig the ribbon becomes discontinuous and forms flakes. It is apparent that as one increases the pressure there is an increase in the ultimate grain size which can be obtained. - Wheel speed has a marked effect on the ultimate grain size. It can be seen that at rpm (revolutions per minute) values of about 9000, i.e. a surface speed of about 36 m/s, the grain size has dropped to the neighborhood of slightly less than 10 µm and as the velocity of the wheel is further increased the change in grain size is not substantially affected. This decrease in grain size occurs for all pressures studied. The drop is sharpest for curves B and C.
- It is felt that one plausible explanation for the relatively large grain sizes produced at the higher rotational speed of the
wheel 24 when compared to the earlier reported work of N. Tsuya and K.I. Arai is that in the present study asmaller wheel 24 was employed. To obtain the same surface velocity with a smaller wheel requires a greater rotational speed. Greater rotational speed will result in a greater centrifugal force acting on the ribbon. The centrifugal force may act to reduce contact with the wheel and thereby lessen the cooling effect of the wheel and thereby reduce the cooling rate of the ribbon. A slower cooling rate may account for the larger grain size. - It is also apparent that, once the velocity has been slowed sufficiently to produce a large grain size, further reduction in the wheel velocity does not substantially change the grain size. The data used to generate these curves of FIG. 2 is contained in Table I.
- The velocity of the wheel is presented both in terms of rotational speed (rpm) and the linear velocity (m/s) of the
cylindrical surface 28. The pressures are given in terms of the gas ejection pressure for the resultingsemiconductor stream 18. It was found that changing the orifice diameter from 0,5 mm to 1,5 mm did not noticeably affect the grain size of the resulting ribbons. Furthermore, it should be appreciated that the linear velocity of the surface of the wheel as well as ejection pressure are the appropriate parameters for the control of relative grain size of the resulting ribbon. These parameters can be maintained independent of the geometry of the equipment employed. - Curve D of FIG. 2 illustrates the effect of velocity on the grain size of germanium semiconductor ribbons. These ribbons were generated from molten germanium which was heated to about 10000C and ejected at a pressure of 15 psig through a nozzle having a nominal diameter of 1 mm. As can be seen by comparing curves C and D, the germanium data as is the case for the silicon data show little dependence of size or speed at low speeds. The tabular data used to generate curve D has been incorporated into Table I.
- Both germanium and silicon form oxides on the surface of the resulting ribbons when the ribbons are generated in an atmosphere of air. These oxides are sufficient to provide an intermediate layer between the silicon and a metal deposited thereon. The resulting metal silicon junctions form Schottky barriers.
- The oxide may be prevented by generating the ribbon under a protective atmosphere. Argon and helium have been found to be effective atmospheres in which to generate the ribbons. In the event that a protective atsmophere is sought, the
wheel 24 andnozzle 16 should be placed in achamber 32 as illustrated by the broken line in FIG. 1. This chamber will allow the atmosphere to be controlled. - The present invention will be of use in the semiconductor industry and in particular in solar cell production.
- While the present invention has been illustrated and described in terms of preferred modes, it is to be understood that these modes are by way of illustration and not limitation and the right is reserved to all changes and modifications coming within the scope of the invention as defined in the appended claims.
Claims (10)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US15025780A | 1980-05-15 | 1980-05-15 | |
US150257 | 1980-05-15 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0040306A1 true EP0040306A1 (en) | 1981-11-25 |
EP0040306B1 EP0040306B1 (en) | 1984-07-25 |
Family
ID=22533727
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP81102203A Expired EP0040306B1 (en) | 1980-05-15 | 1981-03-24 | Method for producing large grain semiconductor ribbons |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0040306B1 (en) |
JP (1) | JPS577119A (en) |
DE (1) | DE3164971D1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1987000460A1 (en) * | 1985-07-21 | 1987-01-29 | Concast Standard Ag | Process and device for casting metal strip directly from the molten mass |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP6654751B2 (en) | 2016-09-14 | 2020-02-26 | トヨタ自動車株式会社 | Transmission for vehicles |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3812901A (en) * | 1973-01-30 | 1974-05-28 | Battelle Development Corp | Method of producing continuous filaments using a rotating heat-extracting member |
US4177856A (en) * | 1978-08-28 | 1979-12-11 | General Electric Company | Critical gas boundary layer Reynolds number for enhanced processing of wide glassy alloy ribbons |
DE2830522A1 (en) * | 1978-07-12 | 1980-01-31 | Licentia Gmbh | Silicon strip foil or sheet for solar cells - made by pouring molten stream of silicon onto rotating plate or wheel so continuous cast prod. is obtd. |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3297436A (en) * | 1965-06-03 | 1967-01-10 | California Inst Res Found | Method for making a novel solid metal alloy and products produced thereby |
US4142571A (en) * | 1976-10-22 | 1979-03-06 | Allied Chemical Corporation | Continuous casting method for metallic strips |
JPS5472954A (en) * | 1977-11-23 | 1979-06-11 | Noboru Tsuya | Semiconductor thin film and method of fabricating same |
JPS5552218A (en) * | 1978-10-12 | 1980-04-16 | Noboru Tsuya | Semiconductor thin belt and manufacturing method thereof |
-
1981
- 1981-03-24 DE DE8181102203T patent/DE3164971D1/en not_active Expired
- 1981-03-24 EP EP81102203A patent/EP0040306B1/en not_active Expired
- 1981-04-06 JP JP5067881A patent/JPS577119A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3812901A (en) * | 1973-01-30 | 1974-05-28 | Battelle Development Corp | Method of producing continuous filaments using a rotating heat-extracting member |
DE2830522A1 (en) * | 1978-07-12 | 1980-01-31 | Licentia Gmbh | Silicon strip foil or sheet for solar cells - made by pouring molten stream of silicon onto rotating plate or wheel so continuous cast prod. is obtd. |
US4177856A (en) * | 1978-08-28 | 1979-12-11 | General Electric Company | Critical gas boundary layer Reynolds number for enhanced processing of wide glassy alloy ribbons |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1987000460A1 (en) * | 1985-07-21 | 1987-01-29 | Concast Standard Ag | Process and device for casting metal strip directly from the molten mass |
Also Published As
Publication number | Publication date |
---|---|
DE3164971D1 (en) | 1984-08-30 |
EP0040306B1 (en) | 1984-07-25 |
JPS577119A (en) | 1982-01-14 |
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