Patent Application
20130109198
Carbon and generally amorphous Carbon (a-C) films are used in a variety of semiconductor application. Amorphous Carbon films are for instance used as hardmask material. With introduction of new low-k materials (often porous), film strength drastically decreased and damages (such as deformation) appeared during the various processes steps (chemical mechanical polishing—CMP for instance). Using a-C as hardmask helps preventing those damages on the low-k materials. Other use of hardmask is also as etch mask where it protects the underneath material during the etching steps.
Amorphous carbon material (also called amorphous hydrogenated carbon, a-C, a-C:H) is a widely used material as hardmask for metals, amorphous silicon and dielectric materials (SiO2, SiN . . . ). It is considered that a-C has no long-range crystalline order; a-C is chemically inert, transparent and has very good mechanical properties. Typically, a-C films are deposited using plasma enhanced chemical vapor deposition with a tuned hydrogen ratio (from 10 to 45%).
With the constant miniaturization of the feature sizes of IC circuits, the etching step is becoming more and more challenging. The depth of focus of the lithography also decreases that result in use of thinner masks. When the mask thickness is becoming too small, it starts to be softer and it does not play his role anymore: we have a loss of critical dimension (CD). To solve this issue, new etch resistant hard mask are required. Amorphous carbon layers are commonly used as hard mask material in Reactive Ion Etching (RIE) processes. One important criteria for the etch resistivity will be the Carbon to Hydrogen ratio.
The hardmask can also act as a protecting layer for the sidewall. When the hardmask is etched using S-containing molecule for instance, a passivation layer is formed on the sidewall by reaction of the Carbon etched and the Sulfur generated. (US2009047789A- Hynix)
Very recently, Lee et al (US20100093187) described the use of molecules having a carbon to hydrogen ratio of 2:3 or 1:2 or greater (for instance: acetylene, vinylacetylene, benzene, styrene, toluene, xylene, pyridine, acetophenone, phenol, furan, C3H2, C5H4, monofluorobenzenes, difluorobenzenes, tetrafluorobenzenes, and hexafluorobenzene(s) at low pressure (2-20 Torr) and a temperature range of 300-480° C.
The present invention is related to a method of manufacturing semiconductor devices in which the amorphous carbon is deposited using very high carbon content molecules that are volatiles and reactive. Having a volatile molecule is critical for the facilitization of the proposed solution.
The invention may be summarized in part by the following sentences:
The method of any one of paragraphs [0008]-[00020] or any combinations of two or more of paragraphs [0008]-[00020], further comprising a step of heating or cooling the carbon containing molecule in a container to thereby control a partial vapor pressure of the carbon containing molecule in the container.
The compounds listed in table one have suitable properties for amorphous carbon deposition. Having low hydrogen content makes possible an effective tuning of the carbon to hydrogen ratio in the film. For example, pure hydrogen gas can be used in the process to increase the amount of H in the film, as needed. In one preferred embodiment, a carbon to hydrogen ratio greater than 0.7 enables low Hydrogen content amorphous carbon film deposition. In another preferred embodiment, the carbon to hydrogen ratio is greater than 1.
In another embodiment, C6F6 may be used for co-deposition of both Carbon and Fluorine.
The compounds of table one have suitable physical properties for easy installation and use in semiconductor manufacturing. While not always gases at room temperature, the compounds have a sufficient vapor pressure to make feasible delivery into a chamber with or without a carrier gas.
In another embodiment, the vapors of the chemicals in table one are reacted in a plasma to form new plasma reaction products such as larger molecules or molecular clusters. The plasma reaction products may enhance the amorphous carbon deposition process. Cyclic molecules are preferred when the deposition rate should be higher than is typical for the genus of molecules.
It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and/or the attached drawings.
