Resistance Characteristics of Thin Films and Contacts in CMOS under Cryogenic Temperature and High Magnetic Field Environment

This paper investigates the resistance characteristics of thin film and contact structures in a 90-nm CMOS process under cryogenic temperature and high magnetic field environment for the first time. The temperature dependences of the test structures were measured at the ambient temperatures of 300 K, 150 K, 77 K and 4.2 K, respectively. To understand the magnetic field dependence of the test structures at the temperatures, measurements were also performed under the magnetic fields of 0 T, 2 T, 4 T and 6 T, respectively. The sheet resistances and the contact resistances are analyzed along with the magnetoresistances under the various conditions. All test structures showed a decreasing sheet resistance or contact resistance as the temperature decreases. The sheet resistance of a thin films with a lower value drops faster as the temperature decreases. The metal thin film and the metal-to-n+ contact showed the maximum resistance change of 89.5% and 35%, respectively, over the temperature range. Meanwhile, negligible magnetoresistances are observed except the metal thin film, which shows a higher magnetoresistance under a lower temperature and higher magnetic field. The maximum magnetoresistance of the metal thin film is measured to be 10.4% for the horizontal magnetic field of 6 T at 4.2 K.