In this paper we have analyzed the influence of the mask channel length (LM) on the performance of the 55-nm-hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs), incorporating nitrogen-rich hydrogenated amorphous silicon nitride gate dielectric and phosphorus-doped microcrystalline silicon (n+μc-Si:H) source/drain (S/D) contacts. In our TFTs the n+μc-Si:H S/D contacts have a specific contact resistance around or below 0.5 Ω cm2. We have shown that in our TFTs a field-effect mobility and threshold voltage are dependent on LM, and this dependence is most likely due to the influence of the S/D contact series resistance on TFTs characteristics. Finally, we have demonstrated that if the mask channel length is extended by a ΔL (which is a distance from the S/D via edge at which the electron injection/collection is taking place) the field-effect mobility and threshold voltage are independent of the channel length. In such a case μFE, VT, and ON/OFF current ratio around 0.76 cm2/V s, 2.5 V, and 107, respectively, has been obtained.

Crystallization kinetics of Hercules polypropylenes were studied between 133 and 155°C. using dilatometers. The crystallization rates of these samples became too rapid below 133°C. for accurate dilatometric measurements. One sample (A) was a commercial sample containing stabilizer and 9% extractable polymer (with boiling n‐heptane). B was an experimental extracted sample containing no stabilizer. A portion of B was thermally degraded under vacuum at 350°C. for 7 hr. (C). The DPn′s of A, B, and C were 2300, 7300, and 1200, respectively. Their melting points were determined dilatometrically, under conditions approaching equilibrium, and were 175, 176, and 173°C., respectively. 95% of the crystallization can be described by an Avramitype equation with an n value of 3, indicating a three‐dimensional growth with residual nucleation or a two‐dimensional growth with spontaneous nucleation. The heterogeneities may result from catalyst residues. The crystallization rate of A was lower than that of B or C at a given temperature, possibly due to the presence of atactic polymer. At a given temperature C crystallized faster than B, which may be an effect of the difference in molecular weight. Plotting the rate as a function of the degree of undercooling (ΔT) increases the difference between B and C.

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Device quality phosphorous (P) doped hydrogenated microcrystalline silicon (n+μc - Si:H) has been prepared by using the plasma enhanced chemical vapor deposition technique. The dependence of physical, chemical, structural and electrical properties on substrate temperature have been investigated. Conductivities for thick films up to 12 Ω−lcm−1 and 40 Ω−1cm−1 have been achieved for layers deposited at 300°C and 500°C, respectively. For films 50 nm thick deposited at 300°C a conductivity of about 5 Ω−1cm−1 has been obtained. A maximum average grain size around 30 nm was obtained. The etch rates of P-doped microcrystalline silicon have been found to be between 8 and 10 times higher than that of undoped hydrogenated amorphous silicon (a-Si:H) films deposited at the same temperature. Thin film transistors incorporating heavily P-doped amorphous and microcrystalline layer between source/drain metal and the a-Si:H channel have been fabricated. We show that an n+μc - Si:H source/drain contacts in thin film transistors provides very good characteristics, yielding an average effective field effect mobility, threshold voltage, and on/off current ratio of about 0.9cm2V−1 sec−1, below 4 V, and above 107, respectively.