Method and apparatus for low voltage plasma doping using dual pulses

• US 6,335,536 B1
• Filed: 10/27/1999
• Issued: 01/01/2002
• Est. Priority Date: 10/27/1999
• Status: Expired due to Fees

• Current Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Original Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Inventors: Fang, Ziwei, Goeckner, Matthew J.
• Primary Examiner(s): Mills, Gregory
• Assistant Examiner(s): HASSANZADEH, PARVIZ
• Application Number:
  US09/427,872
• Time in Patent Office: 797 Days
• Field of Search: 250/492.3, 250/492.21, 250/492.23, 118/723.E, 118/715, 118/723.R, 156/345, 427/585, 427/569, 315/111.21, 315/111.31, 315/111.61, 315/111.71, 315/111.81, 315/111.91, 315/111.01
• US Class Current: 250/492.3
• CPC Class Codes: H01J 37/32009 Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources plasma generation in general H05H1/24
• CPC Class Codes: H01J 37/32412 Plasma immersion ion implantation

Abstract

A pulsed plasma doping system separates the plasma ignition function from the ion implantation function. An ignition voltage pulse is supplied to an ionizable gas and an implantation voltage pulse is applied to the target. The implantation voltage pulse can be generated from the ignition voltage pulse or can be generated separately from the ignition voltage pulse. Ions may be implanted in the target at an energy level that is below the Paschen curve for the system.

Claims

1. A pulsed plasma doping system for implanting ions in a target, the system comprising:

a vacuum chamber to contain an ionizable gas;

an anode coupled to a reference voltage, the anode disposed within the vacuum chamber;

a plasma source cathode disposed within the vacuum chamber;

a first high voltage pulse source to provide an ignition voltage pulse V_plas, having a first amplitude, to the plasma source cathode;

an implantation cathode to support the target; and

an implantation voltage pulse source to supply an implantation voltage pulse V_imp, having a second amplitude, to the implantation cathode;

wherein the implantation voltage pulse V_imp and the ignition voltage pulse V_plas are in a timed relationship to one another and have one or more different parameters, and

a control device setting the first amplitude greater than the second amplitude.

2. The system as recited in claim 1, wherein the implantation voltage pulse source comprises:

a voltage divider network coupled to the ignition voltage pulse source.

3. The system as recited in claim 1, wherein the implantation voltage pulse source comprises:

a second high voltage pulse source; and

a synchronization device, coupled to the first and second high voltage pulse sources, to control a timed relationship between the implantation voltage pulse V_imp and the ignition voltage pulse V_plas.

4. The system as recited in claim 3, wherein:

the synchronization device controls the first and second high voltage pulse sources so that the implantation voltage pulse V_imp and the ignition voltage pulse V_plas are substantially concurrent.

5. The system as recited in claim 3, wherein:

the synchronization device controls the first and second high voltage pulse sources so that the implantation voltage pulse V_imp begins after and ends before the ignition voltage pulse V_plas.

6. The system as recited in claim 1, wherein the implantation voltage pulse V_imp and the ignition voltage pulse V_plas overlay in time, at least partially, with one another.

7. The system as recited in claim 1, wherein the implantation voltage pulse V_imp occurs after the ignition voltage pulse V_plas has ended.