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In this paper, we investigate the conductance of single walled carbon nanotube (SWCNT) networks at different humidity levels and various device temperatures. The carrier transport processes are analyzed by performing a temperature-dependent conductance study. It is found that the conductance of the SWCNT networks is dominated by the thermal activation carrier hopping over the barriers between CNTs. The average separation between the SWCNTs is found to vary linearly with the humidity levels. The humidity-dependent conductance of the SWCNT network is modeled and compared with the experimental data. The model agrees well with the experimental data.

Planarization has become a necessity for fabricating devices, large and small. Without planarization, only a limited number of layers of interconnects or device structures can be successfully fabricated. CON-TACT planarization is a method that applies and extends the fundamentals of press planarization by utilizing external force to bring an optically flat surface in physical contact with flowable materials. The surface planarity is replicated from that of the optically flat surface to the planarized flowable material surface, which is then hardened and separated afterward from the pressing surface to achieve planarity. In this study, CON-TACT planarization technology has been utilized to planarize various polymer dielectric materials coated on both Si and GaAs topography and device wafers, resulting in both local and global planarity. The polymer materials used in this study include cyclotene, polybenzoxazole, and polyimide. The results show that a topography or step height reduction of up to 98% was achieved. Additionally, the overburden variation from die to die was also significantly reduced with this method. This performance promises great potential for CON-TACT planarization technology to provide more consistent, more reliable, and improved device performance for more sophisticated and complex device designs with higher yield.

Multi-layer lithography processes have been introduced to fabricate very fine structures over a topographic surface for advanced semiconductor device production. The first layer formed on the topographic surface is the planarization layer to provide surface planarity for additional thin layer(s) of material. Such materials could be a photoresist, a hardmask, or both with uniform film thickness for the lithography step to image the structures. However, the large size and distribution variation of the topography structures across the substrate surface have a major impact on the performance of the lithography processes. A new planarization process, contact planarization (CP), has been introduced to improve thickness uniformity and to provide global surface planarity for multi-layer lithography applications. This study focuses on planarizing an experimental organic 1 93-nm BARC layer on via wafers to minimize iso-dense film thickness bias and provide improved global surface planarity for the bilayer photolithography process. In addition, minimum thickness bias improves control of downstream processes such as plasma etching. This paper will discuss this unique planarization process and its performance with various thicknesses of the experimental I 93-nm BARC on via wafers. The photolithography performance of the material and process will be discussed.

In this paper, we report a frequency-modulated (FM) passive wireless sensor tag for ammonia (NH 3 ) sensing. The passive wireless sensor tag consists of a single-walled carbon nanotube (SWCNT) network based an NH 3 sensor, a radio frequency (RF) antenna, a ring oscillator, and other supporting circuits. The SWCNT network-based NH 3 sensor is fabricated on a flexible plastic substrate through printable processes. The printable SWCNT-based NH 3 sensor shows an enhanced sensitivity of 0.76% per part per million (ppm) primarily due to the large surface area of the SWCNT network. The sensor also exhibits a high linearity between the resistance of the sensor and the logarithm of the NH 3 concentration (referred to as log [NH 3 ] henceforth). A simple FM circuit is designed to convert the resistance change of the sensor to the oscillating frequency shift of the circuit. By properly designing the circuit, we have obtained a linear response between the frequency shift and the log [NH 3 ]. The linear response allows one to precisely predict the NH 3 concentration by measuring the frequency shift of the FM wireless sensor tag. Such an FM-modulated passive wireless sensor tag with linear response and enhanced sensitivity is promising for power-less stand-alone low-level NH 3 sensing and monitoring with high accuracy.Index Terms-Carbon nanotube (CNT), ammonia (NH 3 ), gas sensor, wireless sensor.