METHOD OF REDUCING THE EFFECTS OF PARTICLE IMPINGEMENT ON SHADOW MASKS

• US 3,790,412 A
• Filed: 04/07/1972
• Issued: 02/05/1974
• Est. Priority Date: 04/07/1972
• Status: Expired due to Term

• Current Assignee: Robert Alan Moline
• Original Assignee: Robert Alan Moline
• Inventors: Moline, Robert Alan
• Primary Examiner(s): Rutledge, L. Dewayne
• Assistant Examiner(s): David, J. M.
• Application Number:
  US05/242,124
• Time in Patent Office: 669 Days
• Field of Search: 148/1.5CP 29/579 250/217R,492 353/53
• US Class Current: 438/10
• CPC Class Codes: F01D 5/30 Fixing blades to rotors; Blade roots ; Blade spacers
• CPC Class Codes: H01L 21/00 Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
• CPC Class Codes: H01L 21/265 producing ion implantation
• CPC Class Codes: H01L 21/266 using masks H01L21/26586 takes precedence
• CPC Class Codes: Y10S 148/106 Masks, special
• CPC Class Codes: Y10S 438/944 Shadow

Abstract

Thermal expansion of shadow masks used in ion implantation processes has been found to cause inaccuracies in the ion implanted pattern. Such inaccuracies are reduced or eliminated by first directing a heating current into the mask, monitoring the resistance of the mask, and controlling the heating current in accordance with monitored resistance. As the mask is bombarded with ions, any temperature rise increases the monitored resistance to automatically reduce the heating current, thus compensating for the thermal effect of ion bombardment.

Claims

2. The improvement of claim 1 wherein:

the second energy imparted to the mask is caused by electrical current; and

the step of reducing the second energy imparted to the mask comprises the step of reducing said electrical current.

3. The improvement of claim 2 further comprising the step of:

monitoring the electrical resistance of the mask; and

controlling the electrical current as a function of said monitored electrical resistance.

4. The improvement of claim 3 wherein:

said substrate is a semiconductor substrate; and

the steps of projecting particles through the mask comprises the step of irradiating the mask with ions, some of which are transmitted through openings in the mask to the substrate.

5. The improvement of claim 4 wherein:

the step of transmitting electrical current through the mask comprises the step of transmitting current to a plurality of locations on one side of the mask by a plurality of conductors; and

further comprising the step of equalizing the electrical current distribution in the mask by adjusting the relative resistance of said plurality of conductors.

6. In a method for forming a pattern on a substrate comprising the steps of projecting particles through a mask onto the substrate, the improvement comprising the steps of:

directing a heating current through the mask;

monitoring the electrical resistance of the mask; and

controlling the heating current as a function of said electrical resistance, thereby to compensate for the heating effects of particles impinging on said mask.

7. The improvement of claim 6 wherein:

the step of projecting particles through the mask comprises the step of raster scanning the mask with a beam of ions, thereby to implant in the substrate ions that are projected through the apertures in the mask.