US 4,535,531 A · Method and resulting structure for selective multiple base width transistor structures

Abstract

A process is described which permits the fabrication of very narrow base width bipolar transistors in selected areas of an integrated circuit chip and bipolar transistors of wider base width on other selected areas of the same integrated circuit chip. The ability to selectively vary the transistor characteristics from one region of an integrated circuit chip to another provides a degree of freedom for design of integrated circuits which is valuable. The bipolar transistors on an integrated circuit chip are processed up to the point of emitter formation using conventional techniques. But, prior to the emitter formation, the base area which is to be the emitters of the selected region having the very narrow base transistors is dry etched using reactive ion etching. The existing silicon nitride/silicon dioxide layers with the emitter opening therein are used as the etching mask for this reactive ion etching procedure. Once the etching is completed to the desired depth, the normal processing is resumed to form the emitter and rest of the metallization.

Claims15

Dependent claims

A method for making an integrated circuit having two bipolar transistor types each having different operating speeds and amplification characteristics due to said transistor types being formed of different base widths, said method comprising:

providing a monocrystalline silicon substrate having a pattern of regions of said silicon isolated from one another by a dielectric pattern on one major surface of said substrate;
providing a subcollector region within said silicon and spaced from said major surface;
forming a base region in at least certain of said regions of silicon down to said subcollector region wherein said base region has a surface concentration of more than about 1.times.10.sup.18 atoms/cm.sup.3 ;
forming a block-out mask over said major surface in regions where said transistor type of lower said characteristics are desired;
subjecting in areas uncovered by said block-out mask the said base regions wherein an emitter region is planned to be formed to reactive ion etching to form a depression having a depth between about 70 to 100 nanometers;
removing said block-out mask;
forming an emitter region in said etched portion of said base regions and in unetched base regions which were in areas covered by said block-out mask and heating said emitter region wherein the intrinsic base regions are formed of different base widths;
and
making electrical contact to each of the elements of said bipolar transistor types.

6 more elements

Dependencies are inferred from the claim text.

Method and resulting structure for selective multiple base width transistor structures

Life of this patent

Method and resulting structure for selective multiple base width transistor structures

Life of this patent

Abstract

Claims15