In the integrated circuit (IC) industry, wafer yield, manufacturing costs, and equipment up time is very important. In many cases, semiconductor fabrication equipment is designed and manufactured whereby one or more of wafer yield, manufacturing costs, or equipment maintenance is adversely affected.
As an example, plasma metal etch processing tools typically use corrosive gasses such as chlorine (Cl.sub.2) and boron trichloride (BCl.sub.3) to define metal features on patterned semiconductor substrates. The process gases are typically delivered from a source gas bottle to a process chamber through a stainless steel gas line. The gases are subjected to an electrical field in the chamber where they form a plasma. The plasma then reacts with the semiconductor substrate in some manner and is then evacuated from the chamber by means of a turbo, blower, and vacuum pump. Therefore, the corrosive gasses are exposed to long transportation paths that have many interfaces between different mechanical structures. The passing of corrosive gases through these interconnect points may be problematic.
Such a problematic system is illustrated in FIGS. 1-2. FIG. 1 is a side view while FIG. 2 is a cross-sectional view of the side view in FIG. 1. FIGS. 1 and 2 illustrate a metal etcher gas distribution system 10. The system 10 has two primary components, a gas fitting 12, and a gas ring 14. The gas fitting 12 has a vacuum coupling radiation laboratory (VCR) inlet thread portion 12a, a nut portion 12c for tightening the gas fitting connection to the gas ring, and a threaded outlet portion 12b. The corrosive metal etch gas is provided from a gas bottle to the portion 12a, through the portion 12c and out the outlet portion 12b. Once the corrosive gas has exited the fitting 12, the corrosive gas enters the ring 14. The gas flows around the gas channel 14b of the ring 14 and is injected into the process chamber 24 of the system 10 via chamber gas inlet holes 14c. Various o-ring regions 20 ensure that leaks are minimized in FIGS. 1-2. A ceramic top window 22 contains the gas in the process chamber and gap barrel 18 of the process chamber abuts an opposite side of the ring 14.
In FIG. 1 the ring 14 is made of aluminum which substantially corrodes when exposed to high concentrations of the metal etch corrosive gas. The exit point of the gas, which is a region directly below the outlet 12b of fitting 12 in FIGS. 1-2, is subject to high concentrations and flows of the corrosive gas. Therefore, even if the fitting is formed using a corrosion resistant material, those portions of the gas ring 14 exposed to the high concentrations of corrosive gas will still corrode at a substantially higher rate over time.
This corrosion can produce particles as well as dangerous leaks in the metal etch system 10. The particles generated by such corrosion produce several problems including "blocked etch". Blocked etch occurs when contamination/particles fall on the wafer. These particles then block the etch process from removing the underlying layer being etched. Once this etch obstruction occurs, the semiconductor wafers will experience depressed yields and potentially require scrapping. In addition, the propensity toward corrosion results in a frequent replacement of the gas rings resulting in significant downtime. Both the downtime and wafer yield loss results in increased manufacturing cost.
To prevent the disadvantageous corrosion of aluminum around the aluminum threads of region 14a, the aluminum material in the gas ring 14 is typically anodized. However, use of anodization on the threaded fittings in the region 14a of the ring 14 to prevent corrosion and excessive particle formation is not a viable alternative because the anodization process does not work well on sharp edges (e.g., threads). Additionally, because of the pitch of the threads in region 14a, anodization, when applied, is not uniformly distributed on the threads. This nonuniform distribution of the anodization results in an insufficient layer of anodization forming over portions of the threads. Therefore, even if the threads in region 14a are exposed to an anodization process, corrosive gases attack exposed areas of inadequately anodized aluminum and corrode the threads of the gas rings.
Therefore, a need exists in the IC industry for a process and apparatus that removes disadvantageous threads from the gas inlet region, enables protective anodization of a sidewall of the inlet region, reduces system corrosion, and better distributes corrosive gases within the metal etch system to improve wafer yield, reduce particle generation, reduce wafer manufacturing costs, reduce equipment downtime, reduce maintenance costs, and/or provides like benefits.