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USINQ FIELD OXIDATION HEAT CYCLE TO DRIVE IN PUNCH THRU IMPLANT

IP.com Disclosure Number: IPCOM000005532D
Original Publication Date: 1984-Apr-01
Included in the Prior Art Database: 2001-Oct-12
Document File: 2 page(s) / 71K

Publishing Venue

Motorola

Related People

Paul Lin: AUTHOR

Abstract

In conventional MOS device processing, threshold adjustment doping is selectively implanted into the active.device region using thick field oxide as a masking layer. In order to improve punch thru voltage on short channel devices, deep implants were performed either by high voltage or doubly ionized species techniques. If a higher voltage implant is used, more expensive equipment is required. If doubly ionized species is used, the current supplied by the implanier is reduced, slowing processing time. The vertical structure for this kind of conventional processing can be illustrated in Figure 1.

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MOTOROLA Technical Developments Volume4 April 1984

USINQ FIELD OXIDATION HEAT CYCLE TO DRIVE IN PUNCH THRU IMPLANT by Paul Lin

   In conventional MOS device processing, threshold adjustment doping is selectively implanted into the active.device region using thick field oxide as a masking layer. In order to improve punch thru voltage on short channel devices, deep implants were performed either by high voltage or doubly ionized species techniques. If a higher voltage implant is used, more expensive equipment is required. If doubly ionized species is used, the current supplied by the implanier is reduced, slowing processing time. The vertical structure for this kind of conventional processing can be illustrated in Figure 1.

   This disclosure teaches a modified processing sequence in which the punch thru implant will blanket implant all silicon regions before field oxidation. The total field oxidation cycles are adjusted to drive in the punch thru imf5lant and grow the desired field thermal oxides at the same time. This simplifies the total processing sequences and eliminates the requirement of selecting doubly ionized species. Comparative structures are illustrated in Figures 2 and 3.

   Note that the punch thru implant dopant exists in the thin gate region as well as thick field regions for the suggested process, while no punch thru implant dopant existed under the field oxide area for the conventional process. This will also result in agreaterthreshold voltagedifferenc...