DC electrical trimming characteristics of polysilicon nanofilms with different doping concentrations

Polysilicon nanofilms (less than 100 nm in thickness) have been proved in our previous experiments to offer large gauge factor (>30) and stable temperature characteristics. This promotes their applications in piezoresistive sensing devices. In order to improve the resistance matching of sensors after fabrication, it is necessary to perform resistor trimming. The electrical trimming is an effective method of correcting resistance error and mismatch. Therefore, in this paper, the electrical trimming characteristics of polysilicon nanofilm (PSNF) resistors with heavy doping concentrations were investigated. For the sample preparation, PSNFs were deposited on thermally oxidized Si substrates by LPCVD at 620degC and doped heavily at different doses by boron ion-implantation and post-annealing. The resistance changes of trimmed resistors were measured after a series of incremental DC current higher than the threshold current density is applied. Based on the as-established interstitial-vacancy (IV) model, it is considered that the phenomenon of electrical trimming is due to the recombination of IV pairs at grain boundaries under the energy excitation of Joule heat generated by high current conduction. Moreover, the occupation of implanted boron dopants to vacancies can restrain the recombination of IV pairs and influence the threshold current density. The experimental results indicate that elevating doping concentration can improve the trimming accuracy and decrease the trimming rate. It can be concluded that electrical trimming is suitable for the correction of resistance mismatch after device packaging.