Method of reducing the erosion rate of semiconductor processing apparatus exposed to halogen-containing plasmas

Abstract

A ceramic article useful in semiconductor processing, which is resistant to erosion by halogen-containing plasmas. The ceramic article is formed from a combination of yttrium oxide and zirconium oxide. In a first embodiment, the ceramic article includes ceramic which is formed from yttrium oxide at a molar concentration ranging from about 90 mole % to about 70 mole %, and zirconium oxide at a molar concentration ranging from about 10 mole % to about 30 mole %. In a second embodiment, the ceramic article includes ceramic which is formed from zirconium oxide at a molar concentration ranging from about 96 mole % to about 94 mole %, and yttrium oxide at a molar concentration ranging from about 4 mole % to about 6 mole %.

Description

[0001]The present application is related to a series of applications filed by various inventors of the present application, many of the applications relate to the use of a yttrium-oxide comprising ceramic in the form of a coating, to provide a plasma-resistant surface which is useful in semiconductor processing applications. The applications include U.S. application Ser. No. 10 / 075,967 of Sun et al., filed Feb. 14, 2002, titled: “Yttrium Oxide Based Surface Coating For Semiconductor IC Processing Vacuum Chambers”, which issued as U.S. Pat. No. 6,776,873 on Aug. 17, 2004; U.S. application Ser. No. 10 / 898,113 of Sun et al., filed Jul. 22, 2004, titled: “Clean Dense Yttrium Oxide Coating Protecting Semiconductor Apparatus”, which is currently pending; and U.S. application Ser. No. 10 / 918,232, of Sun et al., filed Aug. 13, 2004, titled: “Gas Distribution Plate Fabricated From A Solid Yttrium Oxide-Comprising Substrate”, which is currently pending. Additional related applications filed, ...

AI Technical Summary

Benefits of technology

[0015]Semiconductor processing conditions expose semiconductor processing apparatus, such as the interior of processing chambers and the surfaces of components within the processing chambers, to a variety of chemical reagents and plasma ions which attack processing apparatus surfaces. The effect of the attack on an apparatus surface is frequently referred to as erosion of the apparatus surface. It is possible to reduce the erosion rate by selecting a particular material composition for the apparatus surfaces. A protective material may be applied as a coating over the apparatus surface; however, this may not be the best solution to avoiding erosion. The coating is constantly getting thinner (eroding) during a plasma etch, and there is an increased risk that the substrate beneath the coating will be attacked by the plasma penetrating the coating layer. The coating layer may flake off during plasma processing due to residual stress. While such problems will be significantly reduced by using a coating of the erosion-resistant materials described in embodiments herein, in many instances it may be advantageous to form an entire apparatus component from the erosion-resistant materials. However, frequently the materials which are more erosion-resistant are more crystalline, and an improvement in erosion resistance comes at a cost, in the form of decreased mechanical properties (such as ductility) of the apparatus. Ceramic materials which are formed from an oxide of a Group IIIA, IIIB, IVB and VB element, or combinations thereof, have been demonstrated to provide erosion resistance to halogen-comprising plasmas. Embodiments of the present invention pertain to reducing the erosion rate of a ceramic material, typically comprising a Group IIIA, IIIB, IVB, or a Group IVB element, or combinations thereof, while maintaining acceptable mechanical properties or improving mechanical properties of the component parts made of the ceramic material.

[0018]The addition of zirconium oxide powder to yttrium oxide powder at a concentration of zirconium oxide, ranging from about 0.1 mole % to about 65 mole %, after consolidation by conventional ceramic processing, provides a single solid solution with a cubic yttria crystal structure phase or a cubic fluorite-type crystal structure phase, or provides a mixed solid solution of cubic yttria crystal structure phase and cubic fluorite-type crystal structure phase. For the cubic yttria crystal structure, the cell parameter of the solid solution is smaller than that of the pure cubic yttrium oxide crystalline structure, due to the formation of yttrium vacancy. For the cubic fluorite-type crystal structure, the cell parameter of the solid solution is smaller than that of the pure cubic fluorite-type structure, due to the formation of oxygen vacancy. The smaller cell parameter improves the plasma resistance properties of the solid solution of zirconium oxide in yttrium oxide. For example, the erosion rate of a pure solid yttrium oxide ceramic in a CF4 / CHF3 plasma is about 0.3 μm / hr. The erosion rate (the rate at which a surface is removed in μm (of thickness) / hr) of a solid ceramic of about 69 mole % yttrium oxide and about 31 mole % zirconium oxide is about 0.1 μm / hr, a 3 times slower erosion rate than pure solid yttrium oxide. This unexpected decrease in erosion rate extends the lifetime of a process chamber liner or an internal apparatus component within the process chamber, so that the replacement frequency for such apparatus is reduced, reducing apparatus down time; and, the particle and metal contamination level generated during a plasma process is reduced, enabling a device fabrication with ever shrinking geometry with reduced overall cost of the processing apparatus per wafer processed, on the average.

[0019]While the 0.1 μm / hr erosion rate for the zirconium oxide-containing yttrium oxide solid solution is surprisingly better than that of yttrium oxide at 0.3 μm / hr, and considerably better than of a solid aluminum oxide ceramic at 1.44 μm / hr in the CF4 / CHF3 plasma, the mechanical properties of the zirconium oxide-containing yttrium oxide solid solution illustrate that an improvement in flexural strength and fracture toughness would be helpful.

[0022]After mixing of at least one of the alternative oxides listed above with the Y2O3 and ZrO2 powders used to form a solid solution, the combination of powders was compacted by unidirectionally mechanical pressing or cold isostatic pressing of the granular powder formed by spray drying with a typical content of binders. The green body was then pressureless sintered using techniques known in the art. Upon cooling of the sintered body, a single phase or two phase solid solution forms, where the solid solution is a “multi-element-doped” solid solution. One solid solution exhibits a cubic yttria crystal structure, and another solid solution exhibits the cubic fluorite-type crystal structure. The solid solution has excellent plasma resistance, typically better erosion resistance than that of the aluminum oxide-comprising solid solutions discussed herein. However, the mechanical properties of the yttria-zirconia-alumina system are somewhat better. All of these multi-doped solid solutions exhibit excellent plasma erosion resistance and improved mechanical properties in comparison with previously known yttrium oxide-zirconium oxide solid solutions.

Problems solved by technology

Plasmas used for plasma-enhanced chemical vapor deposition processes often tend to be corrosive as well.

However, the integrity of the anodization layer may be deteriorated by impurities in the aluminum or aluminum alloy, so that corrosion begins to occur early, shortening the life span of the protective coating.

However, current materials used for protective layers deteriorate over time and eventually leave the aluminum alloy subject to attack by the plasma, even though the life span of the protective layer is extended over that of anodized aluminum.

However, due to the concentration of reactive species which are present at the surface of the gas distribution plate, the lifetime of the gas distribution plate has typically been limited, from about 8 processing days to about 80 processing days, depending on the corrosivity of the plasma created in the processing chamber.

This translates to low costs of manufacturing, reduced wafer defects, increased lifetime, and increased mean time between cleaning.

However, the plasma resistance properties of these ceramic materials is not adequate in many instances, particularly when a fluorine plasma source gas is involved.

The recent introduction of Y2O3 ceramic shows improved plasma resistance properties, but this material generally exhibits weak mechanical properties that limits its applications for general use in semiconductor processing components, processing kits, and chamber liners.

A protective material may be applied as a coating over the apparatus surface; however, this may not be the best solution to avoiding erosion.

The coating is constantly getting thinner (eroding) during a plasma etch, and there is an increased risk that the substrate beneath the coating will be attacked by the plasma penetrating the coating layer.

However, frequently the materials which are more erosion-resistant are more crystalline, and an improvement in erosion resistance comes at a cost, in the form of decreased mechanical properties (such as ductility) of the apparatus.

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