薄栅氧化膜的单晶片热壁快速热处理

We have developed single-wafer furnace rapid thermal process (RTP) modules for thermal oxidation of silicon substrates. Dryoxides 20 A and wet oxides 25 A thick were grown on both 200 and 300 mm diam Si wafers with excellent thickness uniformityand repeatability. Thermal oxynitridation in nitric oxide (NO) and reoxidation can provide sub-25 A oxides. The thermal stresswithin the silicon wafer was maintained at low levels. It is demonstrated that high quality thin gate oxide films. comparable tothose grown in a conventional furace. can be generated without the drawbacks associated with lamp-based RTP systems.

Improving gate dielectric properties is a key requirement for en-abling future high performance integrated circuits. For the next sev-eral device generations, silicon dioxide will still be an integral partof advanced gate dielectrics. To simplify and improve many aspectsof rapid thermal processing (RTP) technology, we developed asingle-wafer hot wall RTP system designed for thin oxidation appli-cations as well as low-pressure chemical vapor deposition(LPCVD).1,2 RTp offers a shorter process cycle time and betterwithin-wafer film uniformity than the batch process. It is an attrac-tive technology as future wafer production moves to 300 mm diamsize for cost reduction.

Most single-wafer oxidation tools have been conventionallylamp-heated systems. Some of these systems have difficulty grow-ing high quality oxides in steam or chlorine-containing gases as aresult of using stainless steel as a material of construction. Lampbased tools also suffer from inconsistent temperature measurementand control due to variations in the wafer emissivity.This paper focuses on thermal oxidation of both 200 and 300 mmdiam silicon substrates using a single-wafer RTP tool that utilizes ahot-wall isothermal chamber. It maintains the advantages of batchfurnaces, but does not suffer from reduced throughput for smallbatch sizes nor sensitivity to wafer emissivity variations. Results onthe wafer show excellent process repeatability and uniformity, andslip-free wafers in processes up to 1050°C. The newly developedhot-wall RTP system is capable of producing both wet and dry oxides. Uniform oxide films of sub-25 A can be grown consistentlywith or without NO nitridation.

Experimental

The reactor configuration is shown schematically in Fig. l. Theprocess chamber consists of a quartz chamber surrounded by a heat-ing assembly. The multizone heaters, along with a silicon carbide orSiC-coated graphite thermal diffusion plate, allow the system toachieve excellent thermal uniformity in the upper portion of theprocess tube. The wafer is heated by elevating it from a lower cool-ing chamber to an upper hot chamber. A shutter system thermallyisolates the cooling and hot chambers. The wafer rotation aids ther-mal uniformity as well as uniform gas distribution across the wafer.All films were grown on 200 or 300 mm diam p-type Si(100)wafers. Thermal oxidation and oxynitridation in nitric oxide (NOwere performed using the process sequence as reported previously.Film thickness and uniformity were measured by ellipsometry (49points, 1.5 mm edge exclusion for 200 mm oxides, and 3 mm edgeexclusion for 300 mm oxides). Depth profiles of the nitrided oxideswere analyzed by secondary-ion mass spectrometry (SIMS). Waferswere inspected for crystal slip (dislocation) by an optical magic 

mirror method’ and by a selective dislocation etching technique.The number of added particles on the wafer surface were measuredby a surface particle counter (Tencor SP1). Trace metals in the filmswere analyzed by HF vapor phase decomposition (HFVPD) andinductively coupled plasma-mass spectrometry (ICP-MS) For electrical characterization of the oxide films. metal oxide semiconductor(MOS) capacitors with polysilicon gate electrode implanted withphosphorus were fabricated using HF precleaned wafers prior tothermal oxidation. Electrical oxide thickness (Tox) was extractedfrom the capacitance vs. voltage measurement with a contact area of5 x 10-5 cm2