Ion implant system having grid assembly

• US 8,997,688 B2
• Filed: 01/31/2012
• Issued: 04/07/2015
• Est. Priority Date: 06/23/2009
• Status: Active Grant

• Current Assignee: Intevac
• Original Assignee: Intevac
• Inventors: Adibi, Babak, Chun, Moon
• Primary Examiner(s): Smoot, Stephen W
• Assistant Examiner(s): Chin, Edward
• Application Number:
  US13/363,341
• Publication Number:
  US 20120125259A1
• Time in Patent Office: 1,162 Days
• Field of Search: 438/513, 438/514, 438/57, 438/527, 438/473, 257/E21.334, 118/723
• US Class Current: 118/723.R
• CPC Class Codes: C23C 14/042 using masks
• CPC Class Codes: C23C 14/48 Ion implantation
• CPC Class Codes: H01J 2237/0437 Semiconductor substrate
• CPC Class Codes: H01J 2237/184 Vacuum locks
• CPC Class Codes: H01J 2237/201 for mounting multiple objects
• CPC Class Codes: H01J 2237/327 Arrangements for generating the plasma
• CPC Class Codes: H01J 2237/3365 Plasma source implantation
• CPC Class Codes: H01J 37/185 Means for transferring objects between different enclosures of different pressure or atmosphere
• CPC Class Codes: H01J 37/3171 for ion 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: H01L 21/2236 from or into a plasma phase
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction 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 31/1864 Annealing
• CPC Class Codes: H01L 31/1876 Particular processes or apparatus for batch treatment of the devices
• 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

An ion implantation system having a grid assembly. The system includes a plasma source configured to provide plasma in a plasma region; a first grid plate having a plurality of apertures configured to allow ions from the plasma region to pass therethrough, wherein the first grid plate is configured to be biased by a power supply; a second grid plate having a plurality of apertures configured to allow the ions to pass therethrough subsequent to the ions passing through the first grid plate, wherein the second grid plate is configured to be biased by a power supply; and a substrate holder configured to support a substrate in a position where the substrate is implanted with the ions subsequent to the ions passing through the second grid plate.

Claims

1. A plasma grid implantation system comprising:

a multi-stage differentially pumped system comprising;

a plurality of stages, each with increasing level of vacuum leading to an implant stage having highest level of vacuum;

a plurality of stages each with a decreasing level of vacuum leading away from the implant stage;

a conveyor for transporting substrates to be implanted through the multi-stage differentially pumped system;

a plasma implant system positioned at the implant stage, the plasma implant system comprising;

a plasma source configured to provide plasma in a plasma region;

a first grid plate comprising a plurality of apertures configured to allow ions from the plasma region to pass therethrough, wherein the first grid plate is configured to be positively biased by a power supply;

a second grid plate comprising a plurality of apertures configured to allow the ions to pass therethrough subsequent to the ions passing through the first grid plate, wherein the second grid plate is configured to be negatively biased by a power supply;

a substrate holder configured to support a substrate in a position where the substrate is implanted with the ions subsequent to the ions passing through the second grid plate; and

,

a third grid plate disposed between the second grid plate and the substrate holder, the third grid plate comprising a plurality of apertures configured to allow the ions to pass therethrough subsequent to the ions passing through the second grid plate, the third grid plate being grounded; and

,

wherein the first grid plate and the second grid plates are configured to accelerate ions from the plasma, the second grid plate is configured to suppress electrons that come off the substrate, and the third grid plate is configured to function as beam defining grid.

2. The system of claim 1, wherein:

the position of at least one of the first grid plate, the second grid plate, and the substrate holder is configured to be adjusted between a homogeneous implantation position and a selective implantation position;

the homogeneous implantation position is configured to form a single laterally-homogeneous ion implantation across the substrate on the substrate holder, wherein the single laterally-homogeneous ion implantation is formed from a combination of ions that have passed through different apertures of the second grid plate; and

the selective implantation position is configured to form a plurality of laterally spaced- apart ion implantations of the substrate on the substrate holder, wherein the plurality of laterally spaced-apart ion implantations is formed from ions that have passed through the different apertures of the second grid plate.

3. The system of claim 1, wherein the apertures of at least one of the first grid plate and the second grid plate are substantially circular holes.

4. The system of claim 1, wherein the apertures of at least one of the first grid plate and the second grid plate are elongated slots.

5. The system of claim 1, wherein each one of the apertures of at least one of the first grid plate and the second grid plate comprises a top end and a bottom end, wherein the bottom end is closer to the substrate holder than the top end, and wherein the diameter of each aperture gradually increases from the top end to the bottom end.

6. The system of claim 1, wherein the first grid plate and the second grid plate comprise a material chosen from the group consisting of:

silicon, graphite, silicon carbide, and tungsten.

7. The system of claim 1, further comprising a chamber defined by chamber walls, wherein the plasma region, the first grid plate, and the second grid plate are housed within the chamber, and wherein the chamber walls are configured to repel ions in the plasma region using an electric field.

8. The system of claim 7, wherein one or more magnets are coupled to the chamber walls.

9. The system of claim 1, wherein the first grid plate is configured to be positively-biased, either continuously in DC mode or in pulsed mode.

10. The system of claim 1, wherein the second grid plate is configured to be negatively-biased, either continuously in DC mode or in pulsed mode.

11. The system of claim 1, wherein the first grid plate, the second grid plate, and the substrate holder are all configured to have their positions adjustable.

12. The system of claim 1, wherein the third grid plate is removable.

13. The system of claim 1, wherein first and second grid plates are configured to pass beam-lets of ions, and wherein the substrate is positioned at a distance from the second grid plate such that the beam-lets merge prior to implantation in the substrate.

14. A plasma grid implantation system comprising:

a multi-stage differentially pumped system comprising;

a plurality of stages, each with increasing level of vacuum leading to an implant stage having highest level of vacuum;

a plurality of stages each with a decreasing level of vacuum leading away from the implant stage;

a conveyor for transporting substrates to be implanted through the multi-stage differentially pumped system;

a plasma implant system positioned at the implant stage, the plasma implant system comprising;

a plasma source configured to provide plasma;

a grid assembly comprising a plurality of grid plates, wherein each grid plate comprises a plurality of apertures configured to allow ions from the plasma to pass therethrough; and

,

a substrate holder configured to support a substrate in a position where the substrate is implanted with the ions subsequent to the ions passing through the plurality of apertures of the grid plates, wherein at least one of the substrate holder and the grid plates is configured to be adjusted between a homogeneous implantation position and a selective implantation position, wherein the homogeneous implantation position is configured to enable a single laterally- homogeneous ion implantation across the substrate on the substrate holder, the single laterally-homogeneous ion implantation being formed from a combination of ions that have passed through different apertures of one of the grid plates, and wherein the selective implantation position is configured to enable a plurality of laterally spaced-apart ion implantations of the substrate on the substrate holder, the plurality of laterally spaced-apart ion implantations being formed from ions that have passed through the different apertures of one of the grid plate;

wherein the plurality of grid plates comprises;

a positively biased first grid plate comprising a plurality of apertures configured

to allow ions from the plasma in a plasma region to pass therethrough;

a negatively biased second grid plate comprising a plurality of apertures configured to allow the ions to pass therethrough subsequent to the ions passing through the first grid plate;

a grounded third grid plate comprising a plurality of apertures configured to allow the ions to pass therethrough subsequent to the ions passing through the second grid plate; and

,

wherein the first grid plate and the second grid plates are configured to accelerate ions from the plasma, the second grid plate is configured to suppress electrons that come off the substrate, and the third grid plate is configured to function as beam defining grid.

15. The system of claim 14, wherein the first grid plate is configured to be positively-biased, either continuously in DC mode or in pulsed mode.

16. The system of claim 15, wherein the second grid plate is configured to be negatively-biased, either continuously in DC mode or in pulsed mode.

17. The system of claim 14, wherein the first grid plate, the second grid plate, and the substrate holder are all configured to have their positions adjustable.