James N. Wiley

Results from a new die-to-database reticle inspection platform

A new DUV die-to-database high-resolution reticle defect inspection platform has been developed. This platform is designed to meet the 90nm through 65nm node 248/193nm lithography reticle qualification requirements of the IC industry. These design nodes typically include: COG layers, EPSM layers, and AltPSM layers, plus aggressive OPC which includes jogs, serifs, and SRAF (sub-resolution assist features). The architecture and technology of the new inspection platform is described. Die-to-database inspection results are shown on standard programmed defect test reticles, as well as, advanced 90nm through 65nm node reticles from industry sources. Results show high sensitivity and low false detections being achieved.

Results from a new reticle defect inspection platform

A new DUV high-resolution reticle defect inspection platform has been developed to meet the sub-90nm node 248/193nm lithography reticle qualification requirements of the IC industry. This advanced lithography process typically includes COG layers, EPSM layers, and AltPSM layers; aggressive OPC is typically used which includes jogs, serifs, and SRAF (sub-resolution assist features). The architecture and performance of the new reticle defect inspection platform is described. Die-to-die inspection results on standard programmed defect test reticles are presented showing typically 50nm edge placement defect sensitivity, 80nm point defect sensitivity, 5.5% flux defect sensitivity, and 100nm quartz phase defect sensitivity. Low false detection results are also shown on 90nm node and below product reticles. Direct comparisons with UV wavelength inspections show measurable sensitivity improvement and a reduction in false detections. New lithography oriented defect detectors are discussed and data shown.

High-resolution ultraviolet defect inspection of DAP (darkfield alternate phase) reticles

The manufacturing implementation of alternating aperture PSMs (AltPSM) has been gated by the impacts these techniques have on reticle manufacturing, specifically reticle defect inspection and repair. Die-to-die inspection techniques have been achieved for some clearfield multiphase alternate phase reticles, but the required die-to-database solutions are not currently available with defect inspection systems. In response to these mask manufacturing issues and IC design layout issues, resolution enhancing techniques based on Darkfield Alternate Phase (DAP) reticle designs are now of growing importance. A DAP Programmed Evaluation Reticle, DAPPER, was fabricated and inspected on a new high numerical aperture ultraviolet reticle inspection system. The results show reasonable defect sensitivity performance in the presence of both reticle geometry and quartz etch topography characteristic of 130-nm node advanced logic circuit DAP reticles.

Multibeam high-resolution UV wavelength reticle inspection

A new reticle inspection system with three parallel scanning laser beams for UV imaging for both contamination and pattern inspection has been developed to detect defects on advanced reticles for DUV steppers and low k1 lithography for .13um and extensions to .10um design rules. The development of the new three beam architecture at UV wavelength has significantly increased system throughput while improving the resolution of the imaging optics for inspecting advanced reticles including Halftone, Tri-Tone, and Alternating PSM

Reticle inspection system using DUV wavelength and new alogorithm platform for advanced reticle inspection for 0.13-μm technology node

KLA-Tencor has developed a fourth-generation reticle inspection system, the KLA-Tencor 570, using DUV imaging to detect 100-nm defects on advanced OPC and PSM reticles for the 0.13 micron technology node production and 0.10 micron technology development. This system contains innovations in optics, electronics, mechanics, algorithms, and software. The DUV wavelength of the optical system improves the resolution and thus the minimum linewidth capability. A low- noise optical system generates high-quality images to improve productivity, facilitate defect classification, and reduce operator errors. The United Inspection Computer (UIC), a high-speed scalable computational engine, renders database data to create an image of the mask for die-to- database inspections. The UIC uses the new Ultra-Performance Algorithm, which provides high detection sensitivity at high speed for D:D and D:DB inspections. UPA can handle complex structures such as advanced OPC and phase shift mask. TI places no fundamental requirement on the size of OPC features. UPA classified defects automatically. The operator can select sensitivity settings independently for each defect type. Since UPA measures the CD of every feature on the reticle, it can also make total plate quality measurements for statistical process control of mask manufacturing. A new reticle handling system reduces overhead time and allows easy loading and unloading of the reticle. This system manipulates 6-inch and 230-mm reticles with and without pellicles. A flexible adapter design allows the system to mix different reticle sizes. A new data preparation system executes on a multi-processor computer with a 64-bit operating system to minimize data preparation time. This DPS architecture allows the operator to change various inspection parameters such as pixel size, alignment points, DNIRs and rotation without the need for re-prep, thereby improving productivity and flexibility. The KLA- Tencor 570 also allows optional remote Data Prep. Test results indicate that the KLA-Tencor 570 already meets its sensitivity specifications on a Verimask VT 690 in both die- to-die and die-to-database modes.

Effects of transparent and transmission reduction reticle defects

Transparent and transmission defects were studied by performing wafer printability studies. An Orion test reticle was fabricated with programmed thin resist artifacts on a conventional binary reticle to simulate transparent defects. The transparent defects on the Orion reticle printed larger than equivalent design size programmed chrome defects. Programmed transmission defects were created on contact geometry by selectively depositing thin layers of chromium over contacts on the reticle. The effect on wafer focus/exposure curves of contact transmission defects was studied.

High-resolution UV wavelength reticle contamination inspection

A new reticle inspection system with laser UV imaging for contamination inspection has been developed to detect contamination defects on advanced reticles for DUV steppers and low k1 lithography. The extension to UV wavelength improves the resolution of the imaging optics while maintaining compatibility with current STARlight inspection algorithms, thus improving both sensitivity and minimum linewidth capability. This enables inspection of reticles for 4X lithography design rules at 0.18 micrometers , 0.15 micrometers and 0.13 micrometers . The system also is capable of inspecting Tri-Tone PSM and reticles with OPC assist bars.

Inspecting the new generation of reticles using UV imaging

The manufacturing of advanced reticles for deep UV steppers has stressed the mask industrys writing, processing, inspection and repair capabilities. Meeting technology demands has been especially arduous for reticle defect inspection with the rapid evolution of both novel PSM materials and OPC geometries. Also, the switch to a 4x- reduction ratio and every-lower k1 wafer lithography has resulted in increased overall defect printability. To respond to these challenges, a new reticle inspection system with laser UV imaging has been evaluated and shown to achieve mask defect sensitivity of 150 nm and below on DUV EA-PSM and OPC masks.

High-resolution UV wavelength reticle inspection

A new reticle inspection system with laser UV imaging has been developed to detect defects on advanced reticles for DUV steppers. The extension to UV wavelength improves the resolution of the imaging optics while maintaining compatibility with current inspection algorithms, thus improving sensitivity and minimum linewidth capability. A system level description of the changes made to the optics, mechanics, and software are presented. Using both programmed defect test masks and real production reticles, initial observations of the nature and frequency of defects detected with this 150 nm sensitivity instrument will be presented. Preliminary characteristics of this system include the number and types of defects captured at multiple pixel sizes. Comparisons with non-UV systems illustrate the advantage of utilizing shorter wavelengths for reticle inspection. The quality of defect review images has a direct impact on the effectiveness and ease-of-use of reticle inspection systems. The high quality, UV images available from the new system can be viewed in both normal and sharpened defect review displays. The defect review images show the result of high NA, UV laser imaging and image sharpening applied at defect review.

Printability of backside reticle defects

A 6 inch by 6 inch by 0.250 inch test reticle was manufactured with contact arrays on the image side and arrays of opaque chrome defects on the backside. A focus exposure matrix was printed using a 5X i-line and a 4X DUV ASM stepper to determine the smallest backside defect that would print. A defect was considered printable if it left any visible mark on the resist. At i-line the isolated minimum printable backside defect (MPBD) was 60 micrometers and the clustered MPBD was a 10 micrometers defect in a 10 by 10 array with 40 micrometers centers. At DUV the isolated minimum printable backside defect was 30 micrometers and the clustered MPBD was a 5 micrometers defect in a 10 by 10 array with 20 micrometers centers. Printability was found to be inversely proportional to NA and sigma. For both clusters and isolated defects, printability appear to be a function of the total chrome area in the region. The smallest defects printed at the highest exposure.