A 0.2-pm contact filling by 450°C-hydrazine-reduced TiN film with low resistivity

A commercial single-wafer LPCVD reactor was used in these experiments. The methylhydrazine [(CH3)HNNH2: MH, m.p.= -80°C, b.p.= 87"C, vapor pressure= 49.6 TOIT/ 25"C] was used as a reduction gas. Wafer was heated from back-side using infrared heater at temperature from 400 to 500OC. Contact resistance was measured using the Kelvin method and the junction leakage current of Si (n+)/Si @-) diode was measured. Sputter Ti film of 300A was used as a contact metal to Si. The deposition rate of h4H-reduced TiN showed a mass transport-limited reaction, increasing with the MH flow rate, and was several order of magnitude higher than that of "3-reduction (Fig. 1). The high reactivity of MH chemistry agreed with our previous study [2]. The film deposited at 400°C showed a typical 6 phase of TiN structure (Fig. 2). The resistivity decreased as the deposition temperature increased, approaching to 90 pWm at 500°C (Fig. 3). This value was lower than that of MOCVD [3] and was obtained by "3-reduction above 70O0C, as shown in Figure 3. The C1 concentration in TiN film decreased as deposition temperature increased, with a tendency similar to the film resistivity (Fig. 4). The MH-reduced TiN film deposited at 450°C did not generate the A1 corrosion even after exposing to moisture for 168 hours due to the low C1 concentration while the NH3-reduced TiN film generated it (Fig. 5). The A1 corrosion was caused by residual C1 above 3 x 1021 atoms/cm3 in TiN film, as shown by hatched region in Figure 4. The thickness ratio at the bottom to the top was above 70% for the deposition for 0.4 pm contact hole (Fig. 6-a). Even 0.2 pm contact hole was completely filled with TiN film (Fig. 6-b). This suggests that the TiN film can be used for giga-bit interconnects alternated to blanket-W contact filling. The contact resistance for Si (n+) and Si (p+) using blanket-W/MH-reduced TiN electrode was similar to that of the reference (blanket-WPVD-TiN) (Fig. 7). The specific contact resistance for Si (n+) and Si (p+) was 1.9 x 10-7 Q.cm2 and 6.9 x 10-7 Q.cm2, respectively. The junction leakage current for both the experiment and reference was in the order of lo-" A at 5 V (Fig. 8). Thus, MHreduced TiN film did not damage Si contact and acted as a barrier layer for chemical etching during blanket-W deposition. We have succeeded in filling the 0.2 pm-contact by TiN using MH-reduction of Tick. The Tick-MH reaction proves the capability of low-temperature, low-resistivity, and no-damage contact metallization. The 0.2 pm contact filling opens the way the multilevel-interconnection for giga-bit devices.