GRID FOR PLASMA ION IMPLANT

• US 20140170795A1
• Filed: 12/19/2013
• Published: 06/19/2014
• Est. Priority Date: 12/19/2012
• Status: Active Grant

• Current Assignee: Intevac
• Original Assignee: Intevac
• Inventors: Prabhakar, Vinay, Adibi, Babak
• Granted Patent: US 9,318,332 B2
• Time in Patent Office: Days
• US Class Current: 438/57
• CPC Class Codes: H01J 2237/20 Positioning, supporting, modifying or maintaining the physical state of objects being observed or treated
• CPC Class Codes: H01J 2237/3365 Plasma source implantation
• CPC Class Codes: H01J 37/32412 Plasma immersion ion implantation
• CPC Class Codes: H01J 37/32422 Arrangement for selecting ions or species in the plasma
• CPC Class Codes: H01J 37/32623 Mechanical discharge control means
• CPC Class Codes: H01L 21/266 using masks H01L21/26586 takes precedence
• CPC Class Codes: H01L 21/426 using masks
• CPC Class Codes: H01L 31/0516 specially adapted for interconnection of back-contact solar cells
• CPC Class Codes: H01L 31/0682 back-junction, i.e. rearside emitter, solar cells, e.g. interdigitated base-emitter regions back-junction cells
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/188 Apparatus specially adapted for automatic interconnection of solar cells in a module
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A grid for minimizing effects of ion divergence in plasma ion implant. The plasma grid is made of a flat plate having a plurality of holes, wherein the holes are arranged in a plurality of rows and a plurality of columns thereby forming beamlets of ions that diverge in one direction. A mask is used to form the implanted shapes on the wafer, wherein the holes in the mask are oriented orthogonally to the direction of beamlet divergence.

Claims

1. A grid for a plasma ion implant, comprising:

a flat plate having a plurality of elongated holes dispersed over its surface, each of the elongated holes having a cross-sectional shape of an elongated oval having a major axis and minor axis, and having a defined depth extending through the flat plate, wherein a major axis of each of the elongated holes is configured to be aligned in a direction perpendicular to a long axis of features to be implanted on a substrate when the grid is installed inside a plasma ion implant system.

2. The grid of claim 1, wherein the plurality of elongated holes are arranged in a plurality of rows and a plurality of columns, such that each of the holes in each column are aligned with the holes in the preceding and following column, such that a line passing through the major axis of holes in the same row would intersect at a right angle a line passing through the minor axis of holes aligned in the same column.

3. The grid of claim 1, wherein the plurality of elongated holes are arranged in a plurality of rows and a plurality of columns, such that each of the holes in each column is shifted from alignment with the holes in the preceding and following column, such that a line passing through the center of all of the holes in a selected column forms an acute angle with a line passing through the major axis of holes in the same row.

4. The grid of claim 1, wherein the plurality of elongated holes are arranged in a plurality of rows and a plurality of columns enclosed within a rectangular area, such that each of the holes in each column is shifted from alignment with the holes in the preceding and following column, such that a line passing through the center of all of the holes in a selected row forms an acute angle with sides of the rectangular area.

5. The grid of claim 1, wherein the plurality of elongated holes are arranged in a plurality of rows and a plurality of columns thereby forming dead zones in between the holes, such that each of the holes in each column is shifted from alignment with the holes in the preceding and following column, such that a line passing through the center of all of the dead zones in a selected row forms an acute angle with a direction of travel of a substrate to be implanted.

6. A grid for a plasma ion implant, comprising:

a flat plate having a plurality of round holes, wherein the holes are arranged in a plurality of rows and a plurality of columns within a rectangular area and wherein each of the holes in each column is shifted from alignment with the holes in the preceding and following column, such that a line passing through the center of all of the holes in a selected row forms an acute angle with sides of the rectangular area.

7. A grid for a plasma ion implant, comprising:

a flat plate having a plurality of round holes, wherein the holes are arranged in a plurality of rows and a plurality of columns and wherein each of the holes in each column is shifted from alignment with the holes in the preceding and following column, such that a line passing through the center of all of the holes in a selected row forms an acute angle with the direction of travel of a substrate to be implanted.

8. A grid for a plasma ion implant, comprising:

a flat plate having a plurality of round holes, wherein the holes are arranged in a plurality of rows and a plurality of columns thereby forming dead zones in between the holes, such that each of the holes in each column is shifted from alignment with the holes in the preceding and following column, such that a line passing through the center of all of the dead zones in a selected row forms an acute angle with a direction of travel of a substrate to be implanted.

9. A combination of exit grid and implant mask for a plasma-based ion implant system, wherein:

the exit grid comprises a flat plate having a plurality of elongated holes dispersed over its surface, each of the elongated holes having a cross-sectional shape of an elongated oval having a major axis and minor axis, and having a defined depth extending through the flat plate to enable ions to pass through the elongated holes;

the implant mask comprises a flat plate having a plurality of linear holes dispersed over its surface, each of the linear holes having a cross-sectional shape of an elongated oval having a long axis and short axis, and having a defined depth extending through the flat plate to enable ions to pass through the linear holes, wherein the linear holes are arranged in a plurality of parallel rows and linear holes in each row are separated from each other by ion blocking bridges; and

,

wherein a major axis of each of the elongated holes is aligned in a direction perpendicular to a long axis of the linear holes.

10. The combination of claim 9, wherein the plurality of elongated holes of the exit grid are arranged in a plurality of rows and a plurality of columns, such that each of the holes in each column are aligned with the holes in the preceding and following column, such that a line passing through the major axis of holes in the same row would intersect at a right angle a line passing through the minor axis of holes aligned in the same column.

11. The combination of claim 9, wherein the plurality of elongated holes of the exit grid are arranged in a plurality of rows and a plurality of columns, such that each of the holes in each column is shifted from alignment with the holes in the preceding and following column, such that a line passing through the center of all of the holes in a selected column forms an acute angle with a line passing through the major axis of holes in the same row.

12. A plasma ion implant system, comprising:

a processing chamber;

a grid assembly placed in the plasma chamber and dividing the processing chamber into a plasma section and ion implant section;

a transport mechanism for transporting substrates in a travel direction and positioning the substrate under the grid assembly;

wherein the grid assembly comprises a flat plate having a plurality of holes, wherein the holes are arranged in a plurality of rows and a plurality of columns and wherein each of the holes in each column is shifted from alignment with the holes in the preceding and following column, such that a line passing through the center of all of the holes in a selected row forms an acute angle with the travel direction.

13. The system of claim 12, wherein each of the holes has a cross-sectional shape of an elongated oval having a major axis and minor axis, and having a defined depth extending through the flat plate to enable ions to pass through the elongated holes.

14. The system of claim 13, further comprising a mask comprising a flat plate having a plurality of linear holes dispersed over its surface, each of the linear holes having a cross-sectional shape of an elongated oval having a long axis and short axis, and having a defined depth extending through the flat plate to enable ions to pass through the linear holes, wherein the linear holes are arranged in a plurality of parallel rows and linear holes in each row are separated from each other by ion blocking bridges.

15. The system of claim 14, wherein a major axis of each of the holes of the flat plate is aligned in a direction perpendicular to a long axis of the linear holes of the mask.

16. The system of claim 15, wherein the flat plate is coupled to ground potential.

17. The system of claim 16, wherein the substrates are coupled to ground potential.

18. The system of claim 15, wherein the transport mechanism comprises a conveyor.

19. An ion implant system, comprising:

a processing chamber;

a plasma grid placed in the plasma chamber and dividing the processing chamber into a plasma section and ion implant section, the plasma grid comprising a plurality of holes configured to enable ions to pass from the plasma chamber into the processing chamber by forming ion beamlets, wherein ions in the ion beamlets diverge in a first direction;

a mask positioned below the plasma grid and comprising a flat plate having a plurality of holes arranged as parallel lines, wherein each hole is shaped as a line segment and wherein ion blocking bridges are provided between each two line segments in a row, and wherein the line segments are oriented in a second direction perpendicular to the first direction.

20. A method for implanting ions into a substrate to thereby form parallel implanted lines in the substrate, comprising:

introducing a substrate to be implanted into a plasma processing chamber;

positioning a mask at a predetermined gap above the substrate, the mask comprising a plurality of line segments arranged in parallel rows, wherein line segments in each row are separated by bridges that block ions impinging thereupon and the line segments in each row correspond to one implanted line;

igniting plasma in the plasma processing chamber and extracting ions from the plasma so as to form beamlets of ions having divergence in a direction parallel to the direction of the rows; and

,

directing the beamlets to pass through the mask and implant into the substrate to thereby form the parallel implanted lines.

21. The method of claim 20, wherein the predetermined gap is calculated to enable diverging beamlets to implant ions at locations on the substrate that are positioned directly below the bridges, to thereby implant the plurality implanted lines, wherein each line has length corresponding to the sum of all the line segments and bridges on one row of the mask.

22. The method of claim 21, wherein extracting the ions further comprises forming beamlets that have no divergence in a direction perpendicular to the direction of the rows.