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Double layer photoresist process for well self-align and ion implantation masking

  • US 4,767,721 A
  • Filed: 02/10/1986
  • Issued: 08/30/1988
  • Est. Priority Date: 02/10/1986
  • Status: Expired due to Fees
First Claim
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1. A process for forming closely aligned wells or tubs in a semiconductor substrate comprising:

  • (a) providing a semiconductor substrate and depositing a resist mask thereon comprising a lower layer of a first photoresist material and an upper layer of a second photoresist layer, with an opening defining the lateral extent of a first well, said resist mask defining an overhang structure around the periphery of said opening, the thickness of said resist mask being sufficient to withstand ion bombardment;

    (b) implanting ions through said opening to form a first well;

    (c) depositing discontinuous metal over said resist mask and opening to thereby cover said first well, the thickness of said metal covering said first well being sufficient to withstand ion bombardment;

    (d) removing said resist mask and metal thereon, leaving in place the metal covering said first well; and

    (e) implanting ions into said substrate adjacent the metal covering said first well to thereby form a second well directly adjacent said first well, whereby adjacent twin wells are formed in a relatively high yield process requiring a relatively low number of individual process steps.

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