George R. Misium

Manufacturability Issues Of The DESIRE Process

Surface-imaging schemes are an attractive alternative to overcome many of the limitations optical microlithography is presently facing. A good example of this type of approach is the so-called DESIRE process. A preliminary performance characterization of the DESIRE process showed a significant increase in resolution and process latitude. However, new process variables must be understood and technical challenges overcome before this process can be successfully implemented in a manufacturing environment. The purpose of this paper is to explore these new process variables and suggest solutions for the implementation of the DESIRE process in high-volume production of semiconductor devices.

Silicon diffusion characteristics of different surface imaging resists

This paper describes a study of the silylation characteristics of different resists that are suitable for single-layer, surface-imaging patterning applications. In particular, the effect of different process parameters on the silicon diffusion in UCBs Plasmask®resist is discussed. The diffusion profile of silicon in the resist is decorated by a staining technique followed by SEM analysis. This allows for two-dimensional resolution of the diffusion profiles and the observation of other process attributes. Links are established among exposure, silylation and etch by observing silylated profiles. It is shown that the silylation profile characteristics are dominated by the resist image created during exposure. Also, the effects of post-exposure bake and silylating agent temperature are presented. Diffusion profiles for MacDermids PR1024 are also shown.

Surface imaging lithography at 248 nm

This paper discusses the use of surface imaging lithography for deep UV step and repeat applications. In particular, results obtained using the DESIRE process are presented. It is shown that surface imaging is a very attractive option for 248 nm lithography given the small depth of focus of steppers working at this wavelength and the lack of standard, commercially available, photoresists able to fulfill the requirements of deep UV lithography. First, the concept of surface imaging lithography and the DESIRE process are reviewed. Next, results obtained using g‐line resists exposed at 248 nm are presented. Although the results are acceptable, the exposure requirements are prohibitive. A deep UV formulation of the resist allows for higher silylation temperatures and the consequent reduction in exposure requirements to the 100 mJ/cm2 range. The focus latitude for 0.5 μm lines is ∼1.5 μm, while the uniformity across the wafer, for the same lines, is 5%. The etch is done using a highly selective process in a pa...

Applying deep ultraviolet lithography

This paper discusses the application of a deep wafer stepper and associated photoresist systems to advanced semiconductor processing. It is shown that, even with the limited number of photoresists available, deep UV lithography is a viable candidate for advanced processes requiring half micron and smaller features. First, the performance of the exposure tool is discussed; lens performance data including image field curvature, and distortion is shown. Next, results obtained using two different approaches for photoresist processing are discussed. Single layer wet developed photoresist processing is shown to be useable in those cases where topography is not severe. Surface imaging photoresist approaches using the DESIRE process are shown to be applicable in cases where topography is an issue or broader process latitude is required.

Defect generation in dry-develop lithography: assessment through electrical characterization

This paper preseni3 an experimental evaluation of defect generation and device damage in dry develop lithography a compared to 3tandard -wet develop- lithography. A 3tandard g-line process and the DESIRE® process were compared. Defect generation wa evaluated by u3ing electrical te3t structure3 to measure open and 3hort defects on aluminum and polysilicon. The short defect densitie3 were very aimilar for both lithographie, while the open den3ities were larger for dry developed wafers. Thi3 i. attributed to the ue of a negative tone resist. Device damage wa aJ3e33ed by processing and characterizing capacitors and active devices. No device damage inherent to the use of plasmas for lithography was identified.

Submicron Single-Layer Lithography Using Reactive Ion Etching

This paper describes the application of reactive ion etching to submicron single-layer lithography. It is shown that the etch selectivity of silicon containing resists is a strong function of the ion energy; that is, the selectivity increases for low ion energies. That supports the use of magnetically enhanced ion etchers for the development of single-layer silylated photoresists since the ion energy in these reactors is low for most process conditions. This paper shows that by a proper design of the reactor and the process good selectivity can also be achieved in a reactive ion etcher. This allows for the use of a simple reactor for some dry-develop lithography applications. The conditions leading to good selectivity as well as several submicron applications are described in this paper.