Browse Prior Art Database

Polysilicon Resistor Process

IP.com Disclosure Number: IPCOM000052349D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Leas, JM: AUTHOR [+2]

Abstract

This article describes a process for manufacturing polysilicon resistor using only one mask per resistor value. To avoid grain size growth and boron redistribution caused by high temperatures, the process is implemented after the base and emitter are formed.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 3

Polysilicon Resistor Process

This article describes a process for manufacturing polysilicon resistor using only one mask per resistor value. To avoid grain size growth and boron redistribution caused by high temperatures, the process is implemented after the base and emitter are formed.

Very large-scale integration requires a process for making high-valued resistors with low temperature coefficient of resistance.

It is also desirable to have a low voltage and low land voltage coefficient. High-valued resistors made from monocrystalline silicon have the disadvantage of an increasing temperature coefficient of resistance as the value of the resistor increases. Also, as the resistor value increases, the required implant dose decreases, making the resistor doping profile approach the background epitaxial silicon doping. This makes the resistor sensitive to changes in the insulator on the resistor body and causes the resistor to drift under bias/stress conditions.

Polysilicon resistors can be used to overcome the disadvantages inherent in the use of resistors formed in monocrystalline silicon. Polysilicon resistors can be made in several ways compatible with bipolar transistor technology. The objective of the resistor process should be to reduce the thermal coefficient of resistance and barrier height by reducing the polysilicon grain size. It would also be desirable to use only one mask for every resistor value required. Polysilicon resistivity is inversely proportional to doping dosage, grain size and acceptor concentration, and it is desirable to have a small grain size, low doping dosage, high acceptor concentration and low trapping state density. Low grain size requires low temperature processing. To provide high acceptor concentration and low doping dosage, the boron must be kept from redistribution. This also requires low temperature processing. The above conditions can be attained if high temperature processing is avoided, parti...