A selected-area CVD method for deposition of sensing films on monolithically integrated gas detectors

• Published in: IEEE electron device letters 1995-06, Vol.16 (6), p.217-219
• Main Authors: Sanjeev Majoo, Schwank, J.W., Gland, J.L., Wise, K.D.
• Format: Article
• Language: English
• Subjects: Applied sciences; Dielectric devices; Dielectric thin films; Electronics; Exact sciences and technology; Gas detectors; Microelectronic fabrication (materials and surfaces technology); Microelectronics; Optical films; Optical microscopy; Probes; Scanning electron microscopy; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Temperature; Thermal decomposition
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/55.790713

A novel method for deposition of thin transducing films on geometrically well-defined areas is reported. The films represent the front-end of monolithically integrated microelectronic gas detectors. These devices contain a 1 μm thick dielectric window equipped with four-point probe electrodes and a boron-diffused silicon heater underneath the window. The central region of the window can be instantaneously switched from room temperature to several hundred /spl deg/C while maintaining excellent thermal uniformity within a 350×350 μm area. Thermally activated CVD of Pt is realized on the heated region by raising the temperature of the central region into the regime of thermal decomposition of Pt precursors such as Pt(PF 3 ) 4 . The growth of thin Pt films is monitored in situ by measuring film resistance, and film growth is terminated once desired film resistance values are reached by cutting off the heater current. This allows to optimize film properties for gas sensing applications. The deposited films are characterized ex situ by optical microscopy and scanning electron microscopy to correlate film morphology with resistance. This method can be easily extended to deposition of other films of interest such as TiO 2 .