Method of forming self-aligned P contact

Details Method of forming self-aligned P contact Method of forming self-aligned P contact

1986-03-07

1988-01-05

Hearn, Brian E.

Fishing, trapping, and vermin destroying

437 30, 437 31, 437 51, 437188, 437931, H01L 21265, H01L 2140

Patent

active

047176784

ABSTRACT:
Disclosed is a process for forming self-aligned low resistance ohmic contact to a P doped region (e.g., base of an NPN device) in conjunction with forming similar contact to a (highly) N doped region (e.g., emitter of NPN). After forming a P doped region in an N type monocrystalline silicon body and masking it with an insulator (e.g. dual oxide-nitride) layer, the highly doped N region (hereafter, N+ region) is formed in a portion of the P doped region by selectively opening the insulator layer and introducing N dopant therethrough. This opening also serves as contact opening for the N+ region. contact opening for the P region is formed by selectively etching the insulator layer. The structure is subjected to a low temperature steam oxidation to from an oxide layers in the P contact and N+ contact regions, the oxide in the N+ contact being about 3-5 times thicker than that in the P contact region due to the significantly higher oxidation rate of the N+ region relative to the P doped region. The oxide in the P contact is etched off while retaining a substantial portion of the oxide grown in the N+ contact region. P type dopant is then introduced into the P contact opening to achieve solid solubility limit of the P dopant species in silicon. The oxide remaining in the N+ contact region is removed and contact metallurgy is established with all contacts.

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