Fully printed organic CMOS technology on plastic substrates for digital and analog applications

Abstract

Drastic efforts have been realized these last years in order to develop complementary organic technology. This is the essential key to produce elementary lowcost circuits for digital and analog applications. Different techniques [1][2][3] are available nowadays to obtain both N-and/or P-type organic devices. Screen printing is one of the most highly awaited low-cost techniques that can be used to produce organic devices and circuits. It has been widely used in P-type organic technologies [4,5]. Now that N-type semiconductors have become much more easily processed, developers are seeking a complete CMOS and lifetime robust technology. Many previous works have reported on a complete solution based on CMOS technology [6][7][8]. Large-area-compatible organic processes have also been demonstrated [9]. Nevertheless some of the technological steps in these latter reports are not fully printed and/or still present some lithography/vacuum deposition steps. We present here a complete fully printed CMOS technology on flexible substrates showing acceptable device performances and digital/analog circuit functionalities, which can lead to more complex designs.Based on our design toolkit we have processed a testchip including single devices, inverters, ring oscillators and simple analog circuits such as current mirrors, differential pairs and cascodes (see Fig. 18.4.7) in order to show the feasibility of our organic CMOS technology.Our organic CMOS top-gate design fabrication is carried out on a 10×10 cm 2 gold-plated 125μm-thick Polyethylene-naphtalate (PEN) substrate. The first step consists of a patterning by laser ablation of source/drain electrodes, which also serves as first level of interconnections, where we attain a 5μm line/space resolution. P-type and N-type semiconductors are then screen printed on the foil and then annealed at a temperature of 100°C in normal atmospheric conditions. The gate dielectric polymer is screen printed above both semiconductors leaving open vias for level interconnections and then annealed. Finally the gate and the second interconnection level are printed with same technique using a conductive silver ink. A final annealing step at 100°C is performed.We have carried out all our measurements in ambient temperature and pressure. In Fig 18.4.1 we show the transfer and output characteristics of both types of devices for the geometry W/L = 2000/20μm. We observe that both types of devices show equivalent levels of ON and OFF state currents. Table 1 (see Fig. 18.4.2) summarizes the important electrical parameters for 2 different transistor geometries. Threshold voltage and saturation mobility for both types of devices have been monitored on the whole set of available transistors to evaluate their respective dispersions. Figure 18.4.3 shows the distributions of N-and P-type threshold voltage and mobility.For digital applications, elementary inverters and ring oscillators have been tested. In Fig. 18.4.4, we present a fully functional inverter (W n =W p =1000μm and L=20μm) and its corresponding 7-st...

Self-heating effects on the electrical instability of fully printed p-type organic thin film transistors

“…P-channel OTFTs, with staggered top-gate configuration, were fabricated on polyethylene-naphtalate (PEN) substrate in a CMOS process. 17 The source and drain gold contacts were defined by laser ablation. The organic semiconductor (solution processed 6,13-bis(triisopropyl-silylethynyl) pentacene derivative, 80 nm thick) as well as the polymeric dielectric gate dielectric (Cytop, 0.75 lm thick) and silver gate electrode are deposited by printing techniques.…”

An Integrated 13.56-MHz RFID Tag in a Printed Organic Complementary TFT Technology on Flexible Substrate

“…The adopted printed complementary organic technology is manufactured on an 11 × 11 cm 2 flexible foil by CEA-Liten [10], [11]. The TFTs are implemented in a top-gate bottom-contact multi-finger structure with a 20-µm channel length on 125-µm thick polyethylene-naphtalate (PEN) substrate.…”

“…In recent years, a printed complementary organic TFT (C-OTFT) technology has been developed [10], [11] and successfully employed to design digital and analog circuits [12], [13], a 4-bit analog-to-digital converter [14] and a light sensor [4]. This technology has been recently used to explore the feasibility of a RFID tag with active envelope detection, making possible to demodulate ASK PWM-coded signals with modulation depth (h) as low as 25% [15].…”

Large-area flexible electronics with organic transistors

“…In terms of low-voltage operation, self assembled monolayer (SAM) [3] realized 1.5 to 3V operation enabling direct silicon organic circuit interface [4] was presented. In terms of printed electronics, some printed CMOS circuits were presented [5]. This section introduces resent progress of organic transistors and their circuit blocks briefly.…”