Low-resistance phosphorus-doped Si films through blue laser diode annealing

Abstract

The effect of activated annealing on Si films using a new semiconductor blue laser was studied for application to the thin-film transistor (TFT) system on a panel. As a result of the blue laser diode annealing of the continuous-wave (CW) scanning mode at 500 mm/s for 50-nm-thick heavily phosphorus-doped Si films, drastic crystallization occurred while maintaining the surface's smoothness. By irradiating the laser power between 5 and 8 W for chemical vapour deposition films, the grain size was successively controlled by forming micrograins to large grains as well as to anisotropic long crystal grains. Correspondingly, the resistivity decreased depending on the increase in the electron mobility while the high carrier concentration values were retained for the various grained structures. The dopant activation rate was estimated to be 100% in the Si network in spite of the polycrystalline phase. The heavily doped Si film is expected to be applied to electrodes in high-performance TFTs as an advanced low-temperature polysilicon process on glass or flexible plastic sheets.

Low-temperature poly Si TFTs via BLDA for a Ne-sputtered Si film using sputtered gate SiO2

“…To study the effect of the impurity species incorporated into a Si film on the crystallization behavior using BLDA, a heavily phosphorus-doped Si film was deposited via RF sputtering using Ne or Ar as the sputtered gas against a single-crystalline Si target with low resistivity (0.0013-0.0016 cm, ∼ 6 × 10 19 cm −3 ). As a result [18], the sheet resistance of the Si films irradiated above the 4 W condition was drastically decreased for both the cases of Ne and Ar sputtered deposition, and the obtained values are lower for the Ne case than for the Ar case, as shown in Figure 1. By adopting Ne as the sputtering gas, the maximum endured laser power for the Si film was extended towards a much higher power.…”

“…In general, for the sputtering technique, although a much higher amount of an inactive gas with a lighter mass is incorporated into the thin film [25], the gas atom is effused out more efficiently after thermal annealing [7,26]. To develop a higher-performance TFT system on a flexible polymer sheet, the deposition condition for the sputtering, such as a desirable impurity content and its amorphous phase state for the Si network, should be taken into account to realize an effective crystallization close to the CVD Si film [18,27]. For the PE [19,24] (b) For the PE CVD Si film [23,24].…”

Low-temperature poly-Si TFTs of metal source and drain using blue-laser-diode annealing (BLDA)

“…As the atomic radius of Ne is smaller than that of argon (Ar), the Ne atoms in the Si film are expected to be effectively effused during BLDA in spite of the fact that the amount of atoms incorporated into the film is higher for lower-mass Ne than for Ar [10][11][12]. On the other hand, for comparison, fine-grained poly-Si can be obtained not only for the CVD a-Si film but also for the sputtered a-Si film.…”

“…For the TFT fabrication, a 50-nm-thick channel Si layer was deposited via RF sputtering using neon (Ne) gas at room temperature [9,10].…”

Review—Technology Trends of Poly-Si TFTs from the Viewpoints of Crystallization and Device Performance

“…To investigate the optimum conditions of laser irradiation (e.g. the wave length, energy fluence, and the pulse number), multistep XeCl ELA, 6 solid-phase crystallization (SPC) followed by ELA, 7 single-step XeCl ELA, 8 Pd or Nd:YAG laser crystallization, [9][10][11][12][13] and blue laser crystallization 14 have been studied. In addition, Matsuo, one of the authors of the present work, participated in a joint development project with Sanyo Electric Company and strongly contributed to the manufacturing of the world's first LTPS TFT LCDs 15 and to the development of the novel low-temperature solid-phase ELA crystallization technology for poly-Si TFTs for LCD projector light-valves.…”