Precision electrical trimming of very low TCR poly-SiGe resistors

Precision electrical trimming of stacked Si/SiGe polycrystalline resistors available from the extrinsic base structure of a SiGe BiCMOS technology has been demonstrated for the first time. It is shown that pulse current trimming techniques can be used to trim the poly-SiGe resistors by up to 50% from their original values with accuracy better than ±0.5%. The temperature coefficient of resistance (TCR) is shown to be linearly proportional to the percent change in electrically trimmed poly-SiGe resistance. Finally, we demonstrate resistance cycling using an electrical trim/recovery sequence, indicating that the technique is reversible and is governed by dopant segregation/diffusion mechanisms. The results are consistent with those obtained on conventional polysilicon resistors suggesting that the introduction of a strained SiGe layer does not adversely affect the electrical trim properties of these resistors.