The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10× tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

Improving resolution in photolithography with a phase-shifting mask

Various methods and systems for utilizing design data in combination with inspection data are provided. One computer-implemented method for binning defects detected on a wafer includes comparing portions of design data proximate positions of the defects in design data space. The method also includes determining if the design data in the portions is at least similar based on results of the comparing step. In addition, the method includes binning the defects in groups such that the portions of the design data proximate the positions of the defects in each of the groups are at least similar. The method further includes storing results of the binning step in a storage medium.

Methods and systems for utilizing design data in combination with inspection data

Lithography is a field in which advances proceed at a swift pace. This book was written to address several needs, and the revisions for the second edition were made with those original objectives in mind. Many new topics have been included in this text commensurate with the progress that has taken place during the past few years, and several subjects are discussed in more detail. This book is intended to serve as an introduction to the science of microlithography for people who are unfamiliar with the subject. Topics directly related to the tools used to manufacture integrated circuits are addressed in depth, including such topics as overlay, the stages of exposure, tools, and light sources. This text also contains numerous references for students who want to investigate particular topics in more detail, and they provide the experienced lithographer with lists of references by topic as well. It is expected that the reader of this book will have a foundation in basic physics and chemistry. No topics will require knowledge of mathematics beyond elementary calculus.

Principles of Lithography

A method for performing design rule checking on OPC corrected or otherwise corrected designs is described. This method comprises accessing a corrected design and generating a simulated image. The simulated image corresponds to a simulation of an image which would be printed on a wafer if the wafer were exposed to an illumination source directed through the corrected design. The characteristics of the illumination source are determined by a set of lithography parameters. In creating the image, additional characteristics can be used to simulate portions of the fabrication process. However, what is important is that a resulting simulated image is created. The simulated image can then be used by the design rule checker. Importantly, the simulated image can be processed to reduce the number of vertices in the simulated image, relative to the number of vertices in the OPC corrected design layout. Also, the simulated image can be compared with an idea layout image, the results of which can then be used to reduce the amount of information that is needed to perform the design rule checking.

Design rule checking system and method

A method and apparatus for the correction of integrated circuit layouts for optical proximity effects which maintains the original true hierarchy of the original layout is provided. Also provided is a method and apparatus for the design rule checking of layouts which have been corrected for optical proximity effects. The OPC correction method comprises providing a hierarchically described integrated circuit layout as a first input (205), and a particular set of OPC correction criteria as a second input (260). The integrated circuit layout is then analyzed to identify features of the layout which meet the provided OPC correction criteria (210, 240). After the areas on the mask which need correction have been identified (310), optical proximity correction data (320) is generated in response to the particular set of correction criteria. Finally, a first program data is generated which stores the generated optical proximity correction data in a hierarchical structure (320) that corresponds to the hierarchical structure of the integrated circuit layout (310). As the output correction data is maintained in true hierarchical format, layouts which are OPC corrected according to this method are able to be processed through conventional design rule checkers with no altering of the data.

Data hierarchy layout correction and verification method and apparatus

Energy levels (dose) are manipulated to modify the resultant photomask representation in a controlled manner such that the final image in the semiconductor device fabrication is close to an ideal image. Feature sizes and shapes are modified by assigning relative mask writer doses rather than physically manipulating feature sizes in layout designs. This approach, based on coding of relative dose information onto the design data, allows continuous scale line width variation for all features without impact to data volume. Two embodiments are described. In the first embodiment, distortion knowledge in the form of a lookup table or convolution function is applied to CAD data which is fractured into numerous designs having specific dose assignments. In the alternative embodiment, distortion knowledge in the form of a lookup table or convolution function is applied to CAD data which generates an attribute file containing hierarchical dose information that is mapped onto the mask data. Both embodiments compensate specific mask feature sizes through dose offsets during the mask exposure process.

Continuous scale optical proximity correction by mask maker dose modulation

Development and application of a new tool for lithographic mask evaluation, the stepper equivalent Aerial Image Measurement System, AIMS

L.Liebmann, A.Molless, D.Dovet, J.WeedIBM Microelectronics, Semiconductor Research and Development Center, Hopewell Junction, N Y 12533tIBM Research, T.J. Watson Research Center, Eastview, NY /0598ABSTRACTThe newly developed Aerial Image Measurement System (AIMSTM*) was used to quantify the lithographicbenefits of several resolution enhancement techniques as compared to standard binary mask imaging. This

Application of the aerial image measurement system (AIMS)TM to the analysis of binary mask imaging and resolution enhancement techniques

This paper presents a comparative analysis of binary `chrome-on-glass,' attenuated, biased rim, and phase edge shifted DUV lithography solutions for advanced circuitry in the sub-250 nm image size regime. Lithography techniques are compared based on design complexity, ground rule impact, process latitude, and cost. Data are presented from aerial image simulations (SPLAT), aerial image measurements (AIMSR), and SEM measurements. Phase edge shifted designs clearly exhibit the largest process window for 200 nm linewidths exposed on a 0.5 NA 248 nm DUV stepper. The complexity of the mask engineering (design as well as manufacture) and exposure process for this `hard' phase shifting technique warrants the study of less powerful but also less restrictive phase shifting options. This paper investigates the tradeoffs associated with various applicable phase shift mask (PSM) techniques and presents recommendations based on specific program requirements.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Comprehensive evaluation of major phase-shift mask technologies for isolated gate structures in logic designs

Application of an Aerial Image Measurement System (AIMSTM) to binary and phase- shift mask fabrication and evaluation is described. The AIMS tool, an optical system which measures the aerial image directly from a mask, provides rapid feedback on lithographic performance for a variety of stepper configurations through modifications of the wavelength, numerical aperture, and illuminator design. The AIMS tool has been applied during the implementation of an alternating phase-shift mask (PSM) fabrication process in order to understand the impact of the etched-quartz sidewall on lithographic performance. AIMS measurements were used to extract the effective phase and transmission as a function of phase- etch depth as well as post-etch treatment condition. A set of basic test structures are proposed which can be used in conjunction with the AIMS tool to automate the extraction of transmission, phase, and second-level overlay for phase-shifting processes such as alternating and attenuating PSM.

J. Tracy Weed

Papers

Continuous scale optical proximity correction by mask maker dose modulation

Development and application of a new tool for lithographic mask evaluation, the stepper equivalent Aerial Image Measurement System, AIMS

Application of the aerial image measurement system (AIMS)TM to the analysis of binary mask imaging and resolution enhancement techniques

Comprehensive evaluation of major phase-shift mask technologies for isolated gate structures in logic designs

Application of an aerial image measurement system to mask fabrication and analysis