Abstract: A method of manufacturing a heterojunction BiCMOS IC. (100) includes forming a gate electrode (121, 131), forming a protective layer (901, 902) over the gate electrode, forming a semiconductor layer (1101) over the protective layer, depositing an electrically insulative layer (1102, 1103) over the semiconductor layer, using a mask layer (1104) to define a doped region (225) in the semiconductor layer and to define a hole (1201) in the electrically insulative layer, forming an electrically conductive layer (1301) over the electrically insulative layer, using another mask layer (1302) to define an emitter region (240) in the electrically conductive layer and to define an intrinsic base region (231) and a portion of an extrinsic base region (232) in the electrically conductive layer, and using yet another mask layer (1502) to define another portion of the extrinsic base region in the electrically conductive layer.

Abstract: Adjacent buried contacts (11, 12, 13) formed at the principal surface of a well or substrate region (14) of a semiconductor device, each having a doped contact region (29, 30 31) of one conductivity type and a punch-through prevention region (36, 37, 38) of the opposite conductivity type surrounding the lower portion of the doped contact region are provided. The punch-through prevention region may advantageously be of the same conductivity type as the substrate. By performing an extra implant or other impurity introduction step while the mask to etch the contacts through the dielectric layer remains in place, the procedure to provide punch-through protected buried contacts may be easily integrated into current processes without the need for an extra mask. Such a structure and procedure enables buried contacts to be spaced closely together without over-doping the well region (14) in which source-drain regions (40, 42, 44, 46) are also formed thus avoiding a degradation in device performance.

Abstract: A compact SRAM cell and method for its fabrication are disclosed. The small size of the SRAM cell is achieved by fabricating a diode load immediately above the gate electrode of each of the cross coupled transistors of the cell. In accordance with one embodiment, the gate electrode and diode structure include, in sequence, an N-type doped polycrystalline silicon layer, an electrically conductive diffusion barrier layer, a P-type doped polycrystalline silicon layer and an N-type doped polycrystalline layer.

Abstract: A process of forming a conductive material layer in at least two steps by forming a conductive material layer from a plurality of thin layers of conductive material. The use of a two-step formation process for the conductive material layer permits process versatility in incorporating implantation steps and patterning steps between formation of the thin layers of conductive material. Direct transfer from dielectric layer formation to conductive material layer formation steps, and performing the intermediate process steps in the same piece of equipment as the thin conductive layer formation assists in adhesion of the thin layers to each other to form the total conductive material layer. The use of in situ doped semiconductor material, such as in situ doped polycrystalline silicon and in situ doped amorphous silicon reduces the exposure of other dopants that may be present to thermal cycles of high temperature, greater than 900.degree. C., that causes these dopants to migrate undesirably.

Abstract: A bulge well structure for trench devices in wells of a conductivity type opposite to that of the substrate where the bottom of the trench has localized, extra doping. The additional doping into the bottom of the trench prior to device formation may be implanted while the photoresist mask for the trench formation is still in place. In one embodiment of the method, the trenches and the bulge or well extension formations at their bottoms are created before isolation regions are formed. The structure and method permit increased doping only where needed and are compatible with thin epitaxial layers and sharp transition interfaces of epitaxy with substrate for optimum latchup protection. No extra masks are required and the tight packing allowed by trench technology is not altered. Protection against soft errors and junction leakage by forming DRAM trench capacitors in a well of opposite conductivity type from the substrate may be provided.

Abstract: A method of using removable sidewall spacers to minimize the need for mask levels in forming lightly doped drains (LDDs) in the formation of CMOS integrated circuits. Aluminum or chemical vapor deposition (CVD) metals such as tungsten are suitable materials to form removable sidewall spacers which exist around CMOS gates during heavily doped source/drain region implants. Other materials such as CVD polysilicon may also be useful for the sidewall spacers. The sidewall spacers are removed before implantation of the lightly doped drain regions around the gates. This implanation sequence is exactly the reverse of what is currently practiced for lightly doped drain formation. The invention also includes the use of a differential oxide layer. A second set of disposable sidewall spacers or the use of permanent sidewall spacers form optional embodiments.

Abstract: A method of using removable sidewall spacers to minimize the need for mask levels in forming lightly doped drains (LDDS) in the formation of CMOS integrated circuits. Aluminum or chemical vapor deposition (CVD) metals such as tungsten are suitable materials to form removable sidewall spacers which exist around CMOS gates during heavily doped source/drain region implants. Conformal materials such as CVD polysilicon may also be employed for this purpose. The sidewall spacers are removed before implantation of the lightly doped drain regions around the gates. This implantation sequence is exactly the reverse of what is currently practiced for lightly doped drain formation.

Abstract: A deep, buried n.sup.- channel blanket implant beneath both n.sup.- channel and p-channel devices in MOS integrated circuits, whether complementary MOS (CMOS) or not. It is known to use deep, lightly-doped n.sup.- channel implant to improve the characteristics of p-channel (PMOS) devices, although one skilled in the art would expect such an n.sup.- implant to be detrimental to n-channel (NMOS) devices. It has been discovered that such implants not only do not degrade the NMOS devices, but in fact improve their performance, with respect to body effect and junction capacitance.