Flexible semiconductor devices: fingerprint sensor and electrophoretic display on plastic [TFT based]

Abstract

We are on the brink of a new era in flexible semiconductor devices. Outstanding devices, such as a fingerprint sensor (FPS) and an active-matrix electrophoretic display (AM-EPD), are fabricated on a plastic sheet, using thinfilm transistor (TFT) technology. The devices are first fabricated on a gluss substrate with high-performance low-temperature processed polycrystalline silicon (LTPS) TFTs, then later transferred onto a plastic sheet. The FPS and AM-EPD devices on plastic are presented in this paper as examples offlexible semiconductor devices.

Polysilicon thin-film transistors on polymer substrates

“…The device characteristics do not show appreciable degradation after the transfer process and excellent device performance are then obtained on plastic substrates (field effect mobility of 124 cm 2 /Vs for electrons and of 63 cm 2 /Vs for holes [2]). Different applications of the SUFTLA technology were demonstrated, including a backplane for liquid crystal displays (LCDs) with integrated drivers [2] or a fingerprint sensor and an electrophoretic display [3]. Transfer processes similar to SUFTLA and based on the substrate removal were proposed by Asano and Kinoshita [4] and by Wang et al [5,6].…”

“…The first approach has been originally proposed by Shimoda and coworkers at Seiko EPSON, who developed the surface-free technology by laser annealing (SUFTLA) that enables the transfer of thin-film devices from an original substrate to another substrate by using laser irradiation [2,3]. LTPS TFTS are fabricated on glass substrates according to conventional process, then the devices are first attached by using a water soluble adhesive to a temporary substrate and detached from the glass substrate by laser irradiation and finally are transferred to a plastic substrate [2].…”

“…Different thin film transistor (TFT) technologies have been demonstrated on polymeric substrates, including hydrogenated amorphous silicon [1], organic materials [1], oxide semiconductors [1] and low-temperature polycrystalline silicon [2][3][4][5][6][7][8]. Among the different TFT technologies, LTPS offers best device performance as well as the possibility to provide CMOS circuits.…”

Analysis and design of a wide micro beam as a pressure gauge for high sensitivity MEMS fingerprint sensors

“…MEMS devices have been the recent interest in fingerprint acquisition systems such as the works done by Souza and Wise 1997;Charlot et al 2004;Takao et al 2004;Knapp 2004;Fojimori et al 2005;Sato et al 2003Sato et al , 2004Sato et al , 2005. MEMS Capacitive fingerprint sensors offer many advantages over existing technologies for biometrics extraction.…”

“…They are a promising alternative due to low power consumption, non bulky structures and no turn on temperature drifts. Recent prototypes have tried to fabricate the sensor on flexible substrate (Takao et al 2004), improve sensitivity (Sato et al 2004), make the device immune to finger surface condition (Sato et al 2003), make a single chip sensor (Fojimori et al 2005), or other modifications but most are not commercially manufactured which means there are still rooms for improvements on price and performance.…”