Query: Defect inspection of wafers by laser scattering

Candidate papers:

abstract: The sections in this article are 1 Defect Reduction Cycle in Semiconductor Manufacturing 2 Inspection in the IC Manufacturing Process Life Cycle 3 Optical Imaging Technology 4 Laser Scattering Technology 5 Measurement of Optical Scatter from Contaminants on Wafers 6 Automatic Defect Classification 7 Future Challenges 8 Conclusions 9 Acknowledgments
author_names: Vijay Sankaran

Charles Weber

Fred Lakhani

Kenneth W Tobin
title: Inspection in Semiconductor Manufacturing
year: 1999

abstract: Abstract This paper reviews defect inspection methods and instruments for evaluating semiconductor wafers by using elastic light scattering. The discussion focuses on the following instrument characteristics: minimum detectable size for the adhering particle, inspection throughput, detectability of microroughness and detectability of crystal defects at the subsurface and in the volume. By analyzing the detection mechanisms of laser surface scanners, scatterometers and infrared tomography systems, the unique capabilities of elastic light scattering for defect detection are revealed.
author_names: Katsumi Takami
title: Defect inspection of wafers by laser scattering
year: 1997

abstract: As IC feature sizes become smaller and smaller, requirements for Critical Dimension (CD) variations control have become a critical issue. A new process for the control and correction of intra field CD variations (Critical Dimension Control or CDC) was applied and it's influence on defects detection and photo masks inspection capabilities at different modes of inspection was investigated. CD Control (CDC) of the photomask is a process in which Deep UV transmittance is selectively altered by patterns of small partially scattering shading elements (Shade in ElementTm) inside the quartz. The shading elements are formed by a process of shooting an ultrafast laser beam focused inside the mask substrate, resulting in localized intra volume breakdown inside the quartz which creates local pixels of modified index of refraction (delta n) An array of such pixels with constant density constitutes one shading element. Process patterns are predetermined according to a CD variations map which may be supplied from wafer CD SEM, Optical CD or mask aerial imaging simulation tool (AIMS) Thus by changing local photomask transmission levels, it is possible to correct for the CD variations inside the field. Attenuation level, or optical density of the shading elements depends on the laser pulse energy, distance between pixels, number of layers and the size of the shading element itself. Since photomask transmittance is being changed, qualification of the impact of the transmittance changes on the defect detection and analysis capabilities are required. In this study, the principles of patterning of scattering elements inside transparent media by focusing of ultra short laser pulses were introduced and explained. Analysis of the effects to both mask and wafer due to the CDC process was verified by full printing process applied to wafers, and by aerial imaging simulation tool. More tests for CDC required also tests by automatic reticle inspection tool to be production worthy for the 65nm node and beyond.
author_names: Eitan Zait

Vladimir Dmitriev

Sergey V Oshemkov

Guy Ben-Zvi

Dany Michaelis
title: CD variations correction by local transmission control of photomasks done with a novel laser based process
venue: SPIE Advanced Lithography
year: 2006

abstract: Abstract Crack detection in welded structures of dissimilar material using guided waves is not well developed. This paper scrutinizes the effect of material discontinuity in plate structures and the excessive plastic deformation, within friction stir welded (FSW) joints, on the propagation behavior of guided waves toward their application in weld assessment. Quantifying the scattering, attenuation and group velocities of the guided waves when they propagate across different media, as well as determining the elastic properties of the material within the weld will provide rich information about the behavior of ultrasonic waves. Three pristine defect free friction stir welded plates were used in this study. The first specimen was a weld of dissimilar materials aluminum/magnesium alloy (AA6061 T6/AZ31B) the second was of dissimilar aluminum alloy grades (AA6060/AA7020 T651) and the third was of the same aluminum grade (AA7020 T651/AA7020 T651) The elastic properties across all the welds were extrapolated using nano indentation technique. Ultrasonic guided waves were excited and measured using piezoelectric wafers and laser Doppler vibrometer (LDV) Additionally, a sensor network design was implemented on the three specimens using piezoelectric transducers. Wave reflections, based on the LDV results and the information collected from the sensor network, were observed at the weld zone of the AA6061 T6/AZ31B FSW plate, while no reflections were detected at the weld zones in the AA7020 T651/AA7020 T651 and AA6060/AA7020 T651 plates. The results were correlated with the measurements obtained from the nano indentation experiment, where a sharp change in the elastic properties of the base metals in the AA6061 T6/AZ31B welded joint were detected, unlike the other two plates that showed constant elastic properties across the weld zones. The results showed that the amount of scattering at the joints is a function of the wave propagation direction. It was noticed that the average wave reflection generated when the wave crossed from the AZ31B to the AA6061 T6 base metal was around 35% of the incident signal, but it reduced to 25% when the wave propagation direction was reversed. Characterizing ultrasonic waves in FSWs and the behavior of the incident and reflected waves in the welded zones will further improve on the technology used for inspection and monitoring of solid state welded joints.
author_names: Jaafar Ali Tarraf

Samir Mustapha

Mohammad A Fakih

Mohammad Harb

Hongjian Wang

G Ayoub

Ramsey F Hamade
title: Application of ultrasonic waves towards the inspection of similar and dissimilar friction stir welded joints
year: 2018

abstract: Image data management in the semiconductor manufacturing environment is becoming more problematic as the size of silicon wafers continues to increase, while the dimension of critical features continues to shrink. Fabricators rely on a growing host of image generating inspection tools to monitor complex device manufacturing processes. These inspection tools include optical and laser scattering microscopy, confocal microscopy, scanning electron microscopy, and atomic force microscopy. The number of images that are being generated are on the order of 20,000 to 30,000 each week in some fabrication facilities today. Manufacturers currently maintain on the order of 500,000 images in their data management systems for extended periods of time. Gleaning the historical value from these large image repositories for yield improvement is difficult to accomplish using the standard database methods currently associated with these data sets (e.g. performing queries based on time and date, lot numbers, wafer identification numbers, etc. Researchers at the Oak Ridge National Laboratory have developed and tested a content based image retrieval technology that is specific to manufacturing environments. In this paper, we describe the feature representation of semiconductor defect images along with methods of indexing and retrieval, and results from initial field testing in the semiconductor manufacturing environment.
author_names: Kenneth W Tobin

Thomas P Karnowski

Lloyd F Arrowood

Regina K Ferrell

James S Goddard

Fred Lakhani
title: Content Based Image Retrieval for Semiconductor Process Characterization
venue: EURASIP J. Adv. Signal Process.
year: 2002

abstract: A defect detection algorithm for wafer inspection based on laser scanning is presented. Microscopic anomalies, contaminants, and process induced pattern defects result in a two dimensional (2 D) laser scattering signature, which closely resembles the coherent point spread function of the scanning laser beam. This point spread function is a 2 D Gaussian in the majority of cases and can be characterized by four parameters. The algorithm fits Gaussian surfaces to sampled data points. Events are accepted or rejected on the basis of how similar the Gaussian parameters are to that of the point spread function, known a priori. It is shown that the algorithm achieves a 95% capture for submicron particles and pattern defects on typical logic and array wafer regions. Results demonstrating the algorithm's performance relative to mechanical and electronic noise and to signal resolution are presented.
author_names: Mehrdad Nikoonahad

Christopher Edward Wayman

S A Biellak
title: Defect detection algorithm for wafer inspection based on laser scanning
year: 1997

abstract: Tungsten sheet wafers and tetraethylorthosilicate (TEOS) wafers were planarized on chemical mechanical planarization (CMP) tools and cleaned using a mechanical wafer cleaner. Post CMP buffing processes on the primary or secondary polisher platens were investigated. Using laser scattering wafer inspection systems and atomic force microscopy we demonstrated that the buffing process strongly affects the defect density on both the TEOS and tungsten CMP wafers and the roughness power spectrum density of the tungsten CMP wafers. A "pH shock" to the TEOS wafers during oxide CMP on the primary platen resulted in a high defect density. The changes in zeta potential of the slurry particles and the TEOS surfaces during the pH shock might have caused the variations in the defect density. TEOS wafers polished with a tungsten slurry were also cleaned on a wafer cleaner with diluted HF solutions. The HF solution cleaning further enabled a reduction of the defect density. Defect densities measured on the same TEOS wafers using SFS6220 and SFS6420 were compared. The results indicated that some of the defect counts may be attributed to the intrusion defects and background noise from the surface roughness.
author_names: James Y Shen

Wesley D Costas

Lee Melbourne Cook

Jeffrey J Farber
title: The Effects of Post Chemical Mechanical Planaization Buffing on Defect Density of Tungsten and Oxide Wafers
year: 1998

abstract: As reticle enhancement techniques (OPC, PSM) become more commonly used in multi masking levels for 130nm node and below, the need for a better and more precise reticle specification will be even greater. OPC and sub nominal assist feature like scattering bar represent a challenge for mask metrology tools. Consequentiy, defect inspection for advanced reticles has become a gating step for both Mask shops and Wafer Fabs alike. In this paper, a binary defect test reticle with and without OPC/SB features, manufactured by Dupont Photomask's Reticle Technology Center, was used for the study. The reticle was made using the ALTA 3500 Laser Writer Tool and dry chrome etch process. Reticle inspection results from KLA363UV for 0. 13 um design rule patterns in both Clear and Dark polarities, with bump, divot and pinhole programmed defects between 0.1 and 0.6 um sizes (at 4x) were shown. These results were then compared to the wafer printability using ArF 193nm lithography. The impact of each defect type on 0.13 um Isolated, Semi Dense and Dense lines was evaluated for 10% CD tolerance to provide an assessment on the KLA363UV inspection tool capability. A set of edge defects (bump and divot) and point defect (hole between line ends) from 0.1 to 0.6 um on the reticle (4x) were repaired using the Seiko SIR 3xxx tool at DPI RTC. The printability of repairs on wafer at 193nm exposure wavelength was evaluated. CD of repaired features was compared to that of nominal feature for both reticle and resist wafer to evaluate the repair effectiveness. Finally, a defect specification for 0.13 um design rule binary reticle using ArF lithography is discussed.
author_names: Khoi Anh Phan

Christopher Alan Spence

John A Riddick

Jerry Xiaoming Chen

Matt J Lamantia

Hugo A Villa
title: Correlation of reticle defects detectability and repairs to ArF wafer printability for 0.13 mm design rule with binary OPC/SB mask
venue: SPIE Photomask Technology
year: 2001

abstract: Microscratches and particles are becoming a serious problem associated with the introduction of CMP to IC processing. This paper describes a new surface inspection system for a blank wafer with emphasis on the discrimination technique between microscratches and particles. The system first detects both defects by means of the laser scattering technique as is the case of a conventional particle inspection tool, followed by a newly developed discrimination procedure based on the difference of angular distribution of the scattered light. The discrimination rate which is defined as the ratio of the correctly classified defects to the total defects detected was evaluated to be 85% or more on actual CMP processed wafers.
author_names: Ichiro Moriyama

Yoshikazu Tanabe

Ichirou Ishimaru

Makoto Noguchi

K Mizukami
title: Surface inspection system with automatic discrimination of microscratches and particles on chemical mechanical polished wafers
venue: 1999 IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings (Cat No.99CH36314)
year: 1999

abstract: A technique utilizing a scanning laser beam has been implemented to examine the surfaces of materials that are used in the form of flat plates or thin deposited films in the field of microelectronics. Unwanted holes in opaque films deposited onto transparent substrates can be detected by sensing the light transmitted through the holes or defects on a reflective surface can be detected by virtue of their light scattering properties.A typical application is the inspection of silicon wafers that have been highly polished preparatory to film deposition for the planar technology of semiconductor device building. Defects as small as one micron can be detected. An entire wafer 5 cm in diameter can be scanned in 40 seconds to give: 1) a total defect count, and 2) a map of defect locations displayed on an oscilloscope screen.
author_names: Delmont R Oswald

David Farnham Munro
title: A laser scan technique for electronic materials surface evaluation
year: 1974