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US 4,902,633 AGranted
Process for making a bipolar integrated circuit
AssigneeMotorola, Inc.
InventorBertrand F. Cambou
Life of this patent
Estimating the term…
Abstract
A bipolar integrated circuit requiring less silicon area is provided by the use of a three layer epitaxy on top of a substrate. The first epitaxial layer is of the same conductivity type as the substrate and adds additional height to the substrate surrounding the buried layer. The buried layer serves as a collector and it is surrounded by an isolation area. The top two epitaxial layers are of a conductivity type opposite to that of the substrate with the upper most epitaxial layer having a higher dopant density than does the middle epitaxial layer. A master mask is used to provide self-alignment between the isolation area, a collector plug which makes contact to the buried layer, and a base region.
Claims8
A process for making a bipolar integrated circuit, comprising:
- providing a substrate of a first conductivity type and having a first surface;
- selectively forming a buried layer of a second conductivity type in the substrate and extending from the first surface;
- providing a first epitaxial layer of the first conductivity type over the first surface;
- providing a second epitaxial layer of the second conductivity type over the first epitaxial layer;
- providing a third epitaxial layer of the second conductivity type over the second epitaxial layer and having a higher dopant concentration than the second epitaxial layer;
- selectively providing a dopant of the first conductivity type in the third epitaxial layer in a manner to surround the buried layer;
- selectively providing a dopant of the second conductivity type in the third epitaxial layer and positioned over a portion of the buried layer;
- and performing a diffusion to drive in the dopants selectively provided in the third epitaxial layer and simultaneously causing the buried layer to diffuse upwards.
5 more elements
A method for making an integrated circuit, comprising:
- providing a substrate of a first conductivity type and having a first surface;
- providing a dopant of a second conductivity type into the substrate and extending from the first surface;
- providing a first epitaxial layer of the first conductivity type over the first surface;
- providing a second epitaxial layer of the second conductivity type over the first epitaxial layer;
- providing a third epitaxial layer of the second conductivity type over the second epitaxial layer, the third epitaxial layer being of a dopant concentration higher than the second epitaxial layer;
- providing a layer of oxide over the third epitaxial layer;
- providing a dielectric layer over the layer of oxide;
- using a master mask to selectively provide openings in the dielectric layer for an isolation region, a collector plug, and a base region;
- etching thru the oxide in the opening provided for the isolation region and providing a dopant of the first conductivity;
- masking over all the openings except the opening for the collector plug;
- etching through the oxide in the collector plug opening and providing a dopant of the second conductivity type in the collector plug opening;
- diffusing the dopants in the isolation region, in the collector plug, and in the buried layer;
- masking over all the openings except for the base region opening;
- forming a base region of the first conductivity type through the base region opening;
- and forming an emitter area of the second conductivity type in the base region.
12 more elements
A method of providing a bipolar integrated circuit, comprising:
- providing a substrate having a first surface and being of a first conductivity type;
- selectively providing a buried layer of a second conductivity type and having a dopant concentration of approximately 5.times.10.sup.18 atoms per cubic centimeter, the buried layer being provided in the substrate;
- providing a first epitaxial layer of a first conductivity type over the first surface;
- providing a second epitaxial layer of a second conductivity type over the first epitaxial layer;
- providing a third epitaxial layer of the second conductivity type over the second epitaxial layer, the third epitaxial layer having a dopant concentration nearly twice the dopant concentration of the second epitaxial layer;
- selectively providing dopants in the third epitaxial layer of the first conductivity type for an isolation area;
- selectively providing dopants of the second conductivity type in the third epitaxial layer for a collector plug;
- diffusing the selectively provided dopants to form an isolation area having a dopant concentration of approximately 2.times.10.sup.19 atoms per cubic centimeter and to form a collector plug having a dopant concentration of approximately 5.times.10.sup.19 atoms per cubic centimeter and extending thru the third and second epitaxial layers to contact the buried layer;
- selectively forming a base area having dopant concentration of the first conductivity type of approximately 5.times.10.sup.18 atoms per cubic centimeter;
- and forming an emitter area in the base area.
7 more elements
Dependencies are inferred from the claim text.