Telefonaktiebolaget Lm Ericsson (publ)

Matts Rydberg

Ulf Smith

A resistor has a resistor body of polycrystalline silicon and electric contact regions arranged on and/or in the resistor body, so that a resistor part is formed between the contact regions, which gives the resistor its resistance. The material in the resistor body is doped with for example boron to define its resistance. To give the resistor a good long term stability the resistor part is protected by one or more oxide based blocking layers produced from transition metals. These blocking layers can prevent movable kinds of atoms such as hydrogen from reaching the unsaturated bonds in the polysilicon. Such movable kinds of atoms can for example exist in passivation layers located outermost in an integrated electronic circuit in which the resistor is included. The blocking layers can be produced from layers having 30% titanium and 70% tungsten, which are oxidized using hydrogen peroxide.

Polysilicon resistor and a method of producing it

A resistor has a resistor body of polycrystalline silicon and electric terminals arranged on and/or in the resistor body. A resistor portion is thus formed between the terminals, which gives the resistor its resistance. The material in the resistor body is doped with for example boron. In order to block unsaturated silicon bonds in grain boundaries to a sufficient extent and thereby give the resistor a good long-time stability, fluorine atoms are added to the material. They are added in such a high concentration that all of the otherwise unsaturated bonds are coupled to fluorine atoms. Further, it is provided in the manufacture of the resistor that the concentration is maintained at the originally high value. When ion implanting dopants and fluorine atoms it can be accomplished by performing an annealing after implanting dopants at a high temperature and then a further annealing operation at a low temperature after the subsequent implantation of fluorine.

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Matts Rydberg