Die-to-Model (D2M) inspection is an innovative approach to running inspection based on a mask design layout data. The
D2M concept takes inspection from the traditional domain of mask pattern to the preferred domain of the wafer aerial
image. To achieve this, D2M transforms the mask layout database into a resist plane aerial image, which in turn is
compared to the aerial image of the mask, captured by the inspection optics.
D2M detection algorithms work similarly to an Aerial D2D (die-to-die) inspection, but instead of comparing a die to
another die it is compared to the aerial image model. D2M is used whenever D2D inspection is not practical (e.g., single
die) or when a validation of mask conformity to design is needed, i.e., for printed pattern fidelity. D2M is of particular
importance for inspection of logic single die masks, where no simplifying assumption of pattern periodicity may be
done. The application can tailor the sensitivity to meet the needs at different locations, such as device area, scribe lines
and periphery.
In this paper we present first test results of the D2M mask inspection application at a mask shop. We describe the
methodology of using D2M, and review the practical aspects of the D2M mask inspection.
With each new process technology node, chip designs increase in complexity and size, leading to a steady
increase in data volumes. As a result, mask data prep flows require more computing resources to maintain
the desired turn-around time (TAT) at a low cost. The effect is aggravated by the fact that a mask house
operates a variety of equipment for mask writing, inspection and metrology - all of which, until now,
require specific data formatting. An industry initiative sponsored by SEMI® has established new public
formats - OASIS® (P39) for general layouts and OASIS.MASK (P44) for mask manufacturing equipment -
that allow for the smallest possible representation of data for various applications. This paper will review a
mask data preparation process for mask inspection based on the OASIS formats that also reads
OASIS.MASK files directly in real time into the inspection tool. An implementation based on standard
parallelized computer hardware will be described and characterized as demonstrating throughputs required
for the 45nm and 32nm technology nodes. An inspection test case will also be reviewed.
Many mask patterns contain small un-inspectable features (Inspection Rule Violations or IRVs) that create significant through-put time (TPT) impact at mask inspection due to excessive false defects. These small features include a) drawn test designs purposely intended to be small for evaluating process capabilities, and b) un-intended small features that result from errors such as overlap of designs, gaps between cells or synthesis errors. Typically, an IRV is a feature smaller than the minimum feature size capability of the mask inspection tool. This paper describes an integrated method to find such IRVs in the data and either fix them or declare that area as not inspectable. The method includes documented drawn size limits for inspectability, data checks at drawn level, data checks at post-fracture, and functions to define 'Do Not Inspect Regions (DNIRs)' for any remaining IRVs in the data. Data checking at post-fracture must comprehend Optical Proximity Correction (OPC), which generates small features that are not IRVs. The defined DNIRs are listed in the jobdeck for automated inspection data preparation with no engineering intervention. The result is improved mask inspection TPT as well as early detection and correction of certain design or synthesis errors.
KEYWORDS: Photomasks, Quartz, Semiconducting wafers, Carbon, Scanning electron microscopy, Atomic force microscopy, Printing, Ion beams, Laser ablation, Deep ultraviolet
In this paper, the effect of laser ablation induced carbon residue and quartz damage near the mask repair region in a sub-half-micron DUV wafer printing process is discussed. In the study, we found that the laser ablation induced carbon residue and quartz damage during a clean-up process of a clear intrusion mask defect repair could cause both phase and transmission errors near the repaired region. As a result, the printing characteristics of the resist in the repaired region are different than that of the defect-free region, especially at defocus conditions. At zero defocus, the resist critical dimension (CD) difference between the repaired and defect-free regions is mainly determined by the repair edge error and the amount of transmission loss which is due to the quartz damage and carbon residue in the clear mask region. At positive defocus, the repaired region tends to print narrower than that of defect-free region and vice versa for the negative defocus conditions. This phenomenon is the result of quartz damage induced phase error in the clear mask area near the repair. This quartz damage induced effect is more pronounced at 0.25 micrometer regime than that of 0.4 micrometer regime. In the study, we also compared wafer level results of laser repaired features to that of focused ion beam repaired features to identify the carbon residue and quartz damage induced effects in the laser repair. Our simulations also predicted the above observed experimental results.
In this paper, the effect of opaque film deposition for 6% embedded phase shift mask (EPSM) clear defect repair in the wafer level via experiment and simulation are discussed. In the experiment, a 248 nm printing tool with 0.5 NA and 0.6 partial coherence were used. All the repairs were done with a laser repair tool. The original clear mask defects are placed on 0.26 micrometer and 0.44 micrometer mask dark lines (1x). The repaired areas as large as 0.26 micrometer multiplied by 0.7 micrometer were studied experimentally. We found in our study that the resist critical dimension (CD) of an opaque repaired region (line) tends to print narrower than that of a defect-free region in a DUV wafer process due to the transmission and phase mismatch. This result is consistent with our simulation prediction. This line narrowing effect could become an issue at 0.25 micrometer design rule since the process window at that design rule is usually very small as compared to that of larger design rules. In the experiment, we also observed resist CD asymmetrical response to the defocus due to laser damage to the quartz. This quartz damage is induced during a follow-up laser ablation process to trim off the excessive repair material near the line edge.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.