Resist plasma-developed

L First manufacturing use of chemically amplified resists Plasma-developed resist first described X-ray proximity lithography demonstrated Bis-azide rubber resists introduced DNO-novolac resist for microelectronics introduced Photoresist technology first applied to transistor fabrication DNO-novolac resist patented by Kalle... 

Fig. 37. Resist images obtained with a cross-linking monocomponent TSI resist (PHOST polymer), cross-linked by photo-oxidation using light at 193-nm wavelength. After exposure, the film was treated with a vapor of dimethyl silyl dimethyl amine and then plasma developed using O2—RIE (122).

In 1979, Smith and co-workers described the development of a system they called PDF (which presumably stands for Plasma Developable Photoresist) that is based on the use of a material, the structure of which has not yet been divulged 61). In this process the resist is coated in the usual fashion and exposed optically. The exposed film is then subjected to a baking cycle that produces a relief image of negative-tone that is, depressions are generated in unexposed areas (Figure 45). This relief structure is... 

Figure 43. A schematic representation of the PDF, plasma developed resist...

Figure 44. A schematic representation of the plasma developed x-ray resist process. Exposure serves to covalenty bind the monomer (m) into the polymer matrix (p). Heating (fixing) drives out (volatilizes) the monomer except where it is "locked in place" by exposure. Plasma treatment converts the silicon to Si02 which retards the etch rate in the exposed areas through formation of a metallic oxide (MO) layer.

Figure 13. Schematic of plasma-developed resist film composed of polymer host (P) and volatile monomer (m). Processing steps are (a) exposure which locks monomer in place, (b) fixing which removes unlocked monomer, (c) plasma development. (Reproduced with permission from...

One feature which is still lacking in x-ray resists is a highly sensitive positive resist. It seems unlikely that a breakthrough will be achieved using traditional chemical approaches although recent work with plasma-developable systems is encouraging (see later section). 

Figure 3.33. Schematic and mechanistic representation of plasma development of a PMIPK-azide resist.

Figure 3.34. Ion implantation for the design of a plasma-developable negative resist. Reproduced with permission from reference 122. Copyright 1981 American Institute of Physics.)...

Figure 3.35. Negative plasma-development process via selective silylation of a positive-negative resist.

The third class of dry-developable resists involves heating the exposed resist films in a development step. This development method does not require expensive etching tools, is therefore economical, and could alleviate the potential problem of exposure tool contamination associated with the self-developing resist systems. Many of the plasma-developable resist systems involving a relief-bake step, as discussed in Section 3.2.4.1, have the thermal development characteristics to a certain extent. In the thermally developable resist scheme, development is minimal during irradiation but completed to the substrate upon postbaking. 

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