Efficient Si3H8 Based Deposition Process Suitable for High Throughput Cl2 Based SiCP/SiP Cyclic Deposition and Etch Processes

In this paper we demonstrate an efficient Si3H8, (SiH3CH3, and PH3) based deposition process that can be combined with a Cl2 based selective chemical vapor etch process. Various options for Cl2 based SiCP/SiP processes have been discussed and demonstrated [1-4]. The most efficient processes are isothermal and isobaric, since temperature or pressure changes add processing time, introduce complexity and potential instabilities. Therefore, in order to maximize process efficiency and stability, the aim is to compose isothermal and isobaric process recipes. Despite the low processing temperature, high growth rates are obtained [5]. Low processing temperature and high growth rate allow high [C] and [P] concentrations [6]. It has been shown that periodic etching as applied in a CDE process does substantially enhance epitaxial layer quality [1-4][7]. The 12 thickness maps (Fig.1) display deposition thickness patterns for non-rotating wafers (gas flows from top-to-bottom). The temperature uniformity is optimized at 550oC with the gas flow profile evenly distributed across the metering valves. In order to achieve high precursor conversion efficiency, precursor depletion across the wafer is desired. Figures 1 and 2 show the average thickness on the wafer using a 289 point polar map with 3 mm edge exclusion (EE), as well as the maximum and minimum thickness found on the wafer. The largest contributor to non-uniformity is gas phase depletion (consumption of the precursor). Within the narrow temperature and pressure ranges explored, the following can be observed: At the lowest pressure (P2) the Arrhenius plot in Fig. 3 clearly indicates a kinetically limited growth regime up to 550oC. At medium pressure (P3) growth rate saturation is observed @ 550oC with an associated spread in growth rate (from front to rear). At higher pressure (P4) growth rate saturation already starts at 525oC, while at 550oC the thickness decreases by 11 times from the leading to trailing edge. Fig. 4 displays a growth rate increase almost proportional to the reactor pressure for 475 and 500oC. At 525oC growth rate increase shows first signs of saturation and an increasing thickness spread between P3 and P4. At 550oC, the same growth rate saturation occurs between P2 and P3, with a severe depletion at P4. Temperature uniformity and thickness uniformities are substantially enhanced by rotating the wafer on the susceptor (Fig. 5), enabling thickness non-uniformities below ~1% std.-dev. 1-sigma. Important process tuning aspects are discussed. [C] concentration and thickness profiles are, to a good approximation, independently optimized. Since the [C] concentration is strongly temperature dependent, the [C] profile can be adjusted using the radial temperature profile. In the mass flow dominated regime thickness profiles are tuned by adjusting the gas flow distribution profile. The gas flow profile is defined by the outlets with variable flow restriction, such as a multi-port injector (MPI) or any other similar flow control device. Deposition profile and etch profile are decoupled by design. Precursor conversion rate can be kept high at low temperature by using inert carrier gas and by increasing the partial pressure of the reactants.