David Alles

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.

Measuring line-edge roughness of masks with DUV light

Line edges on masks are not perfectly smooth and straight due to writer shot placement errors and randomness in photo-resist processes. This mask roughness may affect local CD defects and CD non-uniformity on the printed wafer. We are able to measure some aspects of line edge roughness using line-space patterns and DUV light in an inspection tool. Analyzing inspection images can make visible both edge placement errors with periodic character (writer generated) and more-random, higher-spatial frequency variations (photo-resist process generated). Our technique observes relative edge placement errors of <1 nm. For example, on one mask the periodic peak-to-peak writer errors are 4 nm, the random edge noise has a standard deviation of about 1.3 nm, and there are ~7 nm steps in the edge position, about one per 200 micron mask field. These values are affected by the inspection tool lateral resolution and thus are actually higher than these values. However, this method is useful in monitoring mask relative edge quality.

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.

Results from a new 193nm die-to-database reticle inspection platform

A new die-to-database high-resolution reticle defect inspection system has been developed for the 45nm logic node and extendable to the 32nm node (also the comparable memory nodes). These nodes will use predominantly 193nm immersion lithography although EUV may also be used. According to recent surveys, the predominant reticle types for the 45nm node are 6% simple tri-tone and COG. Other advanced reticle types may also be used for these nodes including: dark field alternating, Mask Enhancer, complex tri-tone, high transmission, CPL, EUV, etc. Finally, aggressive model based OPC will typically be used which will include many small structures such as jogs, serifs, and SRAF (sub-resolution assist features) with accompanying very small gaps between adjacent structures. The current generation of inspection systems is inadequate to meet these requirements. The architecture and performance of a new die-to-database inspection system is described. This new system is designed to inspect the aforementioned reticle types in die-to-database and die-to-die modes. Recent results from internal testing of the prototype systems are shown. The results include standard programmed defect test reticles and advanced 45nm and 32nm node reticles from industry sources. The results show high sensitivity and low false detections being achieved.