Michael T. Mocella

Etch process characterization using neural network methodology: a case study

Polysilicon etching in a single-wafer, parallel-plate, magnetically- enhanced RIE tool has been examined using two different approaches to the non-physical modeling of the system characteristics. The behavior of both process responses (polysilicon and oxide etch rates) and plasma parameters (voltage and current metrics) have been examined as a function of five variables (rf power, pressure, magnetic field, gas flow rate, and He backside cooling). The variable-response mapping was examined using both neural network and response surface approaches. The greater fitting power of the former method is demonstrated in a side-by-side, internally consistent comparison of the same data set using these two approaches.

Abatement of perfluorocompounds (PFCs) in a microwave tubular reactor using O/sub 2/ as an additive gas

This paper discusses the abatement of four perfluorocompounds (PFCs) in a microwave tubular reactor-C/sub 2/F/sub 6/, CF/sub 4/, SF/sub 6/, and CHF/sub 3/. The abatement was carried out using O/sub 2/ as an additive gas, and was studied as a function of O/sub 2/:PPC ratio, flow rate, power and pressure. Near 100% abatement was achieved for all the PFCs investigated. A detailed characterization of C/sub 2/F/sub 6/ abatement using GC, GC/MS, and inline Mass Spectrometer showed the major abatement products to be CO/sub 2/, COF/sub 2/, and F/sub 2/. The parameteric dependence of CF/sub 4/, SF/sub 6/, and CHF/sub 3/ abatement was also characterized experimentally, the major products from CF/sub 4/ abatement were similar to those from C/sub 2/F/sub 6/ abatement. Mass Spectroscopy indicated the main products for SF/sub 6/ abatement were SO/sub 2/F/sub 2/, SO/sub 2/, and F/sub 2/ while those for CHF/sub 3/ were CO/sub 2/, COF/sub 2/, F/sub 2/, and HF. Additional experiments indicate that the microwave abatement unit can be successfully used to abate these PFCs in the Integrated Circuit fabrication facilities.

High-index immersion lithography with second-generation immersion fluids to enable numerical aperatures of 1.55 for cost effective 32-nm half pitches

To identify the most practical and cost-effective technology after water immersion lithography (Gen1) for sub-45 nm half pitches, the semiconductor industry continues to debate the relative merits of water double patterning (feasible, but high cost of ownership), EUV (difficulties with timing and infrastructure issues) and high index immersion lithography (single-exposure optical lithography, needing a suitable high index last lens element [HILLE]). With good progress on the HILLE, high index immersion with numerical apertures of 1.55 or above now seems possible. We continue our work on delivering a commercially-viable high index immersion fluid (Gen2). We have optimized several fluids to meet the required refractive index and absorbance specifications at 193 nm. We are also continuing to examine other property/process requirements relevant to commercial use, such as fluid radiation durability, last lens element contamination and cleaning, resist interactions and profile effects, and particle contamination and prevention. These studies show that both fluid handling issues, as well as active fluid recycling, must be well understood and carefully managed to maintain optimum fluid properties. Low-absorbing third generation immersion fluids, with refractive indices above 1.7 (Gen3), would further expand the resolution of singleexposure 193 nm lithography to below 32 nm half pitch.

Fluorinated compounds for advanced IC interconnect applications: a survey of chemistries and processes

Abstract The semiconductor industry is now in the early stages of an unprecedented change in materials set for the integrated circuit (IC) interconnect structure. The traditional layers of aluminum conductors and silicon dioxide dielectrics are being replaced by copper thin films and a variety of low k candidates, respectively. In many cases, fluorine confers desirable properties on either the precursors or the final films. At the same time, fluorine presents some potentially adverse effects, which have led to a so-called “fear-of-fluorine” in interconnect applications. This paper will review the proposed uses of fluorinated compounds in the interconnect structures, covering both precursors and the resulting thin films. Both the status of technical studies, and the prospects for commercial implementation, will be addressed.

PFC Emission Control Options for Plasma Processing Tools: A Current Assessment

Perfluorocompounds (PFCs) are critical processing gases for a number of plasma-based IC processing steps, especially dry etching and in situ CVD chamber cleaning. The long atmospheric lifetimes and large infrared absorption cross sections for such gases (which include CF 4 , C 2 F 6 , C 3 F 8 , NF 3 , SF 6 , and CHF 3 ) have raised concerns about the contributions of PFC emissions to possible global warming. Global regulatory policies on greenhouse gases are expected to include the PFCs, and the specific attention given to these gases in negotiations between the U.S. government and the semiconductor industry may expand internationally as well. Several options exist for PFC emission control, including process optimization, chemical substitution, capture/recovery/recycle, and destructive abatement (including combustion, reactive adsorption, and plasma decomposition). An assessment of each option will be made in terms of both technical effectiveness (i.e., PFC reduction achievable) as well as implementation issues (e.g., commercialization timing, cost of ownership). PFC users can expect to have several commercial options to choose from to meet future PFC emission control requirements.

Control of Long-Lived Gas Emissions From Semiconductor Processing Equipment

Certain perfluorocompounds (PFCs) - including CF 4 , C 2 F 6 , SF 6 , and NF 3 - are widely used in gas phase thin film processing applications such as dry etching and CVD chamber cleaning. Through a combination of long atmospheric lifetimes and high infrared absorption cross sections, many PFCs have high global warming potentials (GWPs). Abatement of PFC emissions from semiconductor applications is consistent with existing and developing international, national, and industrial policies for the control of greenhouse gas emissions. For PFC applications in the semiconductor industry, there exist a number of promising options for emissions control. These options include destruction (comprising combustion, plasma, and chemical-thermal routes), recovery, and process replacement.