Stc, Inc

Other

Roger L Baker

Peter D Scovell

Peter F Blomley

Gary J Tomkins

David W McNeil

An air conditioning system for supplying air conditioned air to a passenger compartment of a motor vehicle has left and right hand side distribution ducts connected to a blower by a common distribution chamber. The blower causes air to flow through the common distribution chamber into the left and right hand side distribution ducts via an air conditioning unit. Each of the distribution ducts includes a distribution valve to vary the flow through the respective distribution duct and through a dump duct that exhausts air outside of the passenger compartment. Each of the dump ducts has the same resistance to flow as the respective distribution duct to which it is connected. The flow from the distribution ducts is adjusted by varying the proportion of air that flows through the cooperating dump duct without affecting the flow from the other distribution duct or requiring the blower speed to be altered.

Balanced flow air conditioning system

A fully self-aligned polycrystalline silicon emitter bipolar transistor. Self-alignment of the p.sup.+ base contact (12) is achieved by using oxidized sidewalls (8) (sidewall spacers) of the emitter mesa (7) as part of the p.sup.+ base contact implantation mask. Collector contact (13) alignment can be achieved using oxidized sidewalls (17) of polycrystalline silicon alignment mesas (14) defined in the same polysilicon as the emitter mesa (7) but deposited on oxide (2) rather than the implanted base region (5).

Method of manufacturing a bipolar transistor

A process for fabricating a CMOS compatible bipolar transistor is described. The transistor, which is of the polysilicon emitter type, is fabricated by forming a p-type layer in a well, providing a polysilicon emitter in contact with the layer, using the emitter as a mask to implant p.sup.+ -type base contact regions, and applying contacts to the device.

Method of fabricating a bi-CMOS device

A fully self-aligned polycrystalline silicon emitter bipolar transistor. Self-alignment of the p.sup.+ base contact (12) is achieved by using oxidised sidewalls (8) (sidewall spacers) of the emitter mesa (7) as part of the p.sup.+ base contact implantation mask. Collector contact (13) alignment can be achieved using oxidised sidewalls (17) of polycrystalline silicon alignment mesas (14) defined in the same polysilicon as the emitter mesa (7) but deposited on oxide (2) rather than the implanted base region (5).

Semiconductor devices

A bipolar transistor structure (1) which can be used in an integrated circuit where bipolar (1) and CMOS transistors (2,3) are formed simultaneously on one substrate. In integrated circuit form the material, for example polycrystalline silicon, used for the gates (11,21) of the CMOS transistors is also used for the emitters (29) of the bipolar transistors, the collectors of the bipolar devices are comprised by doped wells (5) in the substrate (4) and the base contacts of the bipolar devices are comprised by regions (27,27a) equivalent to source and drain regions (17,18) of the n-well MOS transistors and bridged by base implants (28). The conventional CMOS processing is modified by the addition of two masking steps and one implant (base implant). One masking step defines the area for the base implant (18) and the other masking step defines an area of the oxide (30) over the base implant which must be removed to allow contact between the polycrystalline silicon (29), which is suitably doped to provide the emitter, and the base ( 27,27a,28). The base contacts are produced in a semi-self-aligned manner.

Method of making Bicmos devices

A method of manufacturing a bipolar transistor (1) with semi-self-aligned p.sup.+ base contacts (27,27a). A p-type base region (28) is formed in a surface region of an n-type region 5 comprising a collector. An element (29) of, for example, n.sup.+ doped polycrystalline silicon, and comprising an emitter, is formed on the surface in contact with the base region (28). The base contacts (27,27a) are formed by implantation and using the element (29) as a mask. An n.sup.+ collector contact (25) is made to the n-tpe region (5).

A bipolar transistor structure (1) which can be used in an integrated circuit where bipolar (1) and CMOS transistors (2,3) are formed simultaneously on one substrate. In integrated circuit form the material, for example polycrystalline silicon, used for the gates (11,21) of the CMOS transistors is also used for the emitters (29) of the bipolar transistors, the collectors of the bipolar devices are comprised by doped wells (5) in the substrate (4) and the base contacts of the bipolar devices are comprised by regions (27,27a) equivalent to source and drain regions (17,18) of the n-well MOS transistors and bridged by base implants (28). The conventional CMOS processing is modified by the addition of two masking steps and one implant (base implant). One masking step defines the area for the base implant (28) and the other masking step defines an area of the oxide (30) over the base implant which must be removed to allow contact between the polycrystalline silicon (29), which is suitably doped to provide the emitter, and the base ( 27,27a,28). The base contacts are produced in a semi-self-aligned manner.

In making bipolar transistors, an interfacial oxide layer (5) is formed over ther monocrystalline region (1), and polysilicon (6) is formed both thereon as an extrinsic emitter region. After doping the polysilicon a monocrystalline emitter region (4) is produced in the base region by diffusion from the extrinsic polysilicon emitter region. The oxide layer (5) acts as a diffusion barrier to ensure that excessive dopant does not reach the monocrystalline region. After the above operation, a thermal treatment is effected at a higher temperature, e.g. 1100.degree. C., for a few seconds, which breaks down the interfacial oxide layer referred to above. This temporary use of the interfacial oxide layer leads to better and more consistant transistor characteristics.

Growing community of inventors

Chelmsford, United Kingdom

Roger L Baker