Design for Manufacturing (DFM) practices for productivity improvement have been applied with great success in many industries, including automobile manufacturing, engine design, and consumer electronics. Until now, Moore's Law for IC productivity has been dominated by innovation and invention, not a drive for efficiency. With IC fab costs dramatically increasing, DFM procedures are becoming far more attractive. In this paper, we briefly review the general DFM practices that have been successful in other industries, and report on the results from an example in the semiconductor industry, produced by the SEMATECH Litho/Design Workshops. The results of these workshops have assisted the adoption of advanced lithographic DFM technologies, such as OPC (Optimized Process Correction) and accelerated progress along the Moore's Law productivity curve.

OPC (Optimized Process Correction) Technology is an approach for improving lithographic performance that has received much attention recently. The core of OPC technology is the modification of IC pattern layouts to compensate or 'correct' for IC manufacturing process distortions.This presentation summarizes the results of the SEMATECH project in OPC Validation, designated as project J111. The goal of the project was to examine the present status of OPC technology, to determine some measure of the efficacy of OPC technology, and determine which components (if any) require additional development to be suitable for manufacturing.To this end, an elaborate set of test patterns was created and provided to several commercially viable OPC suppliers. These suppliers converted these using their OPC software for 6 degrees of OPC "aggressiveness" and returned the converted files to SEMATECH. A jobdeck containing all the converted patterns were created, and reticles were fabricated from this jobdeck using 6 different maskmaking processes. Each reticle was then exposed onto standard wafers using plan-of record processes at SEMATECH member companies. The efficacy of the various OPC approaches was then determined by measuring and comparing the patterns produced on these wafers after processing and etching. This protocol was followed for both an I-line process and a DUV process.Significant improvements in lithographic performance were observed in many cases, for both I-line and DUV processes. In the best cases, the data suggest that OPC can improve lithographic performance by 1/2 a generation. The degree of success, however, depended heavily on the choice of maskmaking technique and OPC software supplier, with some combinations significantly better at addressing I-D bias problems, while others made dramatic improvements for 1.5-D or 2-D problems.

The study presented here quantifies the benefit of optical proximity correction (OPC) for an I-line and a DUV wafer process in a systematic way. Masks and wafers made with 6 mask writing techniques and 5 OPC software packages each with 6 degrees of aggressiveness were studied. The benefits for 1-D corrections (isolated/dense bias), 1.5-D effects (line end pullback), and 2-D effects (corner rounding) were evaluted. From the accumulated data in the study, we can conclude that OPC features deliver significantly improved line width uniformity and pattern fidelity to etched wafers. The technology is effective and manufacturable with contemporary mask writers and OPC techniques. Data expansion and mask inspection difficulty factors were also investigated.

In this paper, we introduce standard metrics for the evaluation of three common problems in lithography: 1-D linewidth variation, line-end pullback, and 2-D corner rounding. Metrics that indicate both the magnitude of the problem and the quality of the formed features are presented. These can be used with digitized scanning electron microscope images of features formed from masks with and without overall process correction (OPC) to numerically determine the efficacy of the OPC techniques. All metrics tend to 0 in the case of perfect pattern fidelity.

Use of the phase-shifting mask in lithography allows substantial improvement of the resolution of commercial steppers for periodic circuit patterns, and, in certain cases, features smaller than 200 nm can be fabricated using i-line steppers ((lambda) equals 365 nm). There has therefore been much interest in developing this technology in recent years. In this paper, we examine and compare several approaches to evaluating mask designs for terminated periodic features, narrow gate lines, and contact holes, and compare the simulations with the actual results obtained when one attempts to use these designs in practice. Although we have found atomic force microscopy (AFM) to be a key tool for metrology, we conclude that there is a vital need for mask simulation, fabrication, inspection, and repair techniques to be developed further before these `imaginary' masks can be useful in the real world.

The linear and nonlinear optical properties of polysilanes, and in particular poly(di-n-hexylsilane), have been investigated by vacuum UV spectroscopy and by two-photon induced processes. The electronic structure of the polymer inferred from these measurements is consistent with models which view the polymer as a one-dimensional semiconductor quantum wire. The exciton related optical nonlinearities are also large enough to allow polysilanes to be considered for various nonlinear switching applications.

Polysilane high polymers, which contain only silicon in the polymer backbone show interesting electronic properties which may be ascribed to extensive sigma electron delocalization. Catenated silicon linkages constitute therefore a highly polarizable yet thermally and oxidatively stable alternative to pi electron conjugation. We have measured chi(3) values for third harmonic generation in a variety of polysilane derivatives and one polygermane and find values in the 10(-11)-10(-12) esu range. Although the measured values depend on polymer orientation and to some extent on film thickness, the nonresonant numbers are relatively insensitive to backbone conformation even though significant changes in the linear absorption spectra are observed. The substituted silane polymers are also characterized by strong two-photon absorption which often leads by anisotropic photodestruction to a strong induced birefringence. The spectral response of the two-photon induced birefringence in PDN6S is identical to that determined by two-photon fluorescence excitation. The I(m) chi(3) (- omega; omega, - omega, omega) associated with this resonant transition is large (approximately 6 x 10(-10) esu) and is associated with a significant value for the nonlinear refractive index in the region around 570 nm.

We present here a complete experimental determination of the optical properties and electronic structure of the polymers poly(di-n-pentylsilane) and poly(di-n-hexylsilane) from 2 to 44 eV. The electronic structure revealed by these measurements is consistent with the assignment of the higher-energy transitions to the carbon-based sidechains and the lower-energy transitions to the silicon backbone. The transitions attributed to the silicon backbone correlate well with predictions by an independent band-structure calculation using the local-density approximation.

Polysilane polymers consist of a long catenated silicon backbone with two sidegroups attached to each Si atom in the backbone chain. Delocalization of electrons along the a-bonded backbone results in very large oscillator strengths for UV transitions. Excitation by UV photons decays either by UV fluorescence or scission of the polymer backbone, making these materials useful as deep UV photoresists for microlithography. The large oscillator strengths also give rise to large optical nonlinear susceptibilities, and the ease of forming patterned waveguides by conventional spin coating and UV lithographic techniques make these materials interesting candidates for applications in nonlinear integrated optics.

Birefringence is shown to be induced in polysilane thin films by the process of chain scission induced by nonlinear absorption at visible wavelengths. This writable birefringence is easy to control and can be used for the fabrication of birefringent gratings and other optical devices.

Chain scission induced by two-photon exposure produces a permanent birefringence in polysilane polymer films, which can be used for the formation of birefringent optical elements. Spectroscopy of the effect for poly(di-n-hexylsilane) reveals an unexpected sharp resonance at 579 nm. Models to explain these observations are introduced and discussed

Chain scission induced by two-photon exposure produces a permanent birefringence in polysilane polymer films, which can be used for the formation of birefringent optical elements. Spectroscopy of the effect for poly(di- n -hexylsilane) reveals an unexpected sharp resonance at 580 nm. A comparison of several polysilanes indicates the effect only occurs in polymers with symmetric or near symmetric sidegroups. Models to explain these observations are introduced and discussed.

Linear polysilanes are polymers consisting of a long catenated silicon backbone, with two side groups, usually carbon based, attached to each Si atom in the backbone chain. Electronic and structural properties can vary significantly with the side group, but common to all polysilanes is a degree of electron delocalization along the σ -bonded backbone. This delocalization results in large oscillator strengths for excitations polarized parallel to the backbone. Absorption of UV photons decays either by UV fluorescence or scission of the polymer backbone, making these materials useful as deep UV photoresists for microlithography. These large oscillator strengths also give rise to large optical nonlinear susceptibilities.

The ideal holographic material would have the sensitivity and spatial resolution of silver halide emulsion, the efficiency of dichromated gelatine, the self developing feature of photorefractive crystals, and useful at all laser wavelengths. Unfortunately, no such material exists; those that do exist are characterized in the table below. Photoresist materials have proved especially disappointing. In spite of years of effort, the sensitivity, resolution, efficiency and ease of processing leave almost everything to be desired!

Potassium titanyl phosphate (KTiOPO4,KTP) has been used to generate blue 459-nm radiation by intracavity sum frequency mixing of the circulating 1064-nm laser radiation of a miniature neodymium:yttrium aluminum garnet laser and the 809-nm radiation used as the pump source. A blue output power of approximately 1 mW cw was obtained using 275 mW of pump power from an infrared dye laser. Gain-switched operation leading to high 459-nm peak powers was demonstrated. Direct rapid modulation of the blue radiation was achieved by modulating the pump. In preliminary experiments a high-power laser diode was used as the pump source for the generation of blue radiation.

The new class of polysilane polymers has recently attracted interest as a medium for nonlinear optical interactions. These materials consist of a long (>1000 atoms) σ-bonded silicon backbone with two organic substituent groups attached to each Si atom. As nonlinear materials, these have several advantages over their π-bonded carbon analogs, the polydiacetylenes. First, polysilanes have been extensively investigated as possible photoresists,1 so thin (≤4 μm) films of excellent optical quality can be easily prepared using conventional photoresist technology. Second, the σ-σ* absorption edge is typically in the ultraviolet, so the material is transparent at all visible wavelengths. Finally, this absorption band edge can be shifted by changing the molecular weight, conformation of the Si backbone, or the substituent groups, making resonant enhancement of nonlinear effects at particular wavelengths possible.

Nonlinear optical processes permit the design of miniaturized blue - green laser devices that are pumped by near-infrared sources such as GaAIAs diode lasers. Frequency upconversion of infrared pump light can be achieved by processes that use the nonlinear susceptibility of noncentrosymmetric materials for second harmonic generation or sum-frequency mixing. In addition, two-photon excitation mechanisms including sequential two-step absorption and energy-transfer upconversion can be used to pump visible solid-state lasers with infrared light. The operation of several nonlinear laser devices in the blue - green spectral region has been demonstrated. Intracavity frequency mixing of a 1064-nm Nd:YAG laser and its 809-nm pump source resulted in efficient generation of 459-nm radiation using KTi0PO4 as the nonlinear material. Intracavity frequency doubling of a diode-laser pumped 946-nm Nd:YAG laser was used to generate 473-nm radiation. Two-photon-pumped upconversion lasing at 550nm has been demonstrated in YA103:Er3+ and YLiF4:Er3+ at temperatures <90K using infrared cw dye lasers near 800nm as pump sources.