The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 01, 2002
Filed:
Oct. 06, 2000
Ted Johansson, Djursholm, SE;
Hans Norström, Solna, SE;
Telefonaktiebolaget LM Ericsson, Stockholm, SE;
Abstract
A method to improve the characteristics of bipolar silicon high-frequency transistor by adding indium into the base of the transistor is described. Instead of replacing boron in the base with indium to improve the beta-Early voltage product, at the price of high beta and high base resistance, separate boron and indium doping profiles are combined in the base. Thus, a transistor, which preserves most of the properties of pure boron-base transistor, is obtained, but with some parameters improved due to the added indium profile. This “double-profile” or “indium-enhanced” transistor exhibits improved beta-Early voltage product, reduced collector-base capacitance swing and lower temperature dependence of beta, but preserves the advantageous properties of a pure boron-base transistor. For this to work satisfactory, the indium profile must be contained within the boron profile in such a way that the beta and the effective base width are not significantly affected, otherwise the high frequency properties will be degraded. A typical process for fabricating a bipolar silicon high frequency NPN transistor together with some recorded parameters highlighting the benefits of an additional indium implant is presented.