Yair Eran

Defect dispositioning using mask printability on attenuated phase shift production photomasks

This paper examines the effects of mask printability of various OPC defect types on a MoSi APSM mask using an MSM-100 AIMS tool operating at 248nm as a printability prediction tool. Printability analysis will be used to address differences in intensity, image capture wavelength, defocus, defect size, type, and placement on two substrate materials. Defect correlation to photomask CD error, aerial image intensity error, and MEEF on high-end KrF photomasks will also be studied.

Halftone PSM inspection sensitivity of OPC line/space pattern for 150-nm generation

The process of manufacturing and inspecting 150nm generation reticles, incorporating RETs - Resolution Enhancement Technologies - is discussed. Some of the RETs applied at the lithography stage while exposing the wafer, such as OAI - Off Axis Illumination, others RET are being incorporated into the reticle, such as OPC - Optical Proximity Correction - and PSM - Phase Shift is discussed. Many relevant aspects are discussed in this paper such as the ability to produce those critical layers while keeping good CD linearity, and the ability to detect OPC related defects with current reticle inspection technology.

Definition of new quality criteria and assessment means for masks at 150-nm design rules and beyond

Low-k1 lithography requires enhancement techniques like phase shift and OPC. These techniques impose new and challenging specifications on photomasks. A development to establish means and methods to verify corner rounding, line end shortening, defect printability and the size of jogs, serifs and assist lines in a production worthy manner is based on the assessment of mask production data through a new cluster software tool which combines the output data of a mask defect inspection system, a CD metrology system, an AIMS based mask review station and printing simulation results. Possible definitions of new type photomask quality criteria are discussed and measurement procedures are proposed. As a key application the review of critical features on reticles (OPC, classical defects, contact printability, etc.) at changing stepper conditions ((lambda) , N.A., (sigma) ) is discussed. The concept and the development status of a Photomask Qualification Cluster is presented and early performance results are examined against the target values which are a defect detection sensitivity of 125 nm, optical resolution of 200 nm lines for assist line assessment, CD measurement on lines, contacts and OPC structures with 5 nm repeatability and mask pattern fidelity assessment at printing conditions down to 500 nm lines at reticle level.

Real-time line-width measurements: a new feature for reticle inspection systems

The significance of line width control in mask production has become greater with the lessening of defect size. There are two conventional methods used for controlling line widths dimensions which employed in the manufacturing of masks for sub micron devices. These two methods are the critical dimensions (CD) measurement and the detection of edge defects. Achieving reliable and accurate control of line width errors is one of the most challenging tasks in mask production. Neither of the two methods cited above (namely CD measurement and the detection of edge defects) guarantees the detection of line width errors with good sensitivity over the whole mask area. This stems from the fact that CD measurement provides only statistical data on the mask features whereas applying edge defect detection method checks defects on each edge by itself, and does not supply information on the combined result of error detection on two adjacent edges. For example, a combination of a small edge defect together with a CD non- uniformity which are both within the allowed tolerance, may yield a significant line width error, which will not be detected using the conventional methods (see figure 1). A new approach for the detection of line width errors which overcomes this difficulty is presented. Based on this approach, a new sensitive line width error detector was developed and added to Orbots RT-8000 die-to-database reticle inspection system. This innovative detector operates continuously during the mask inspection process and scans (inspects) the entire area of the reticle for line width errors. The detection is based on a comparison of measured line width that are taken on both the design database and the scanned image of the reticle. In section 2, the motivation for developing this new detector is presented. The section covers an analysis of various defect types, which are difficult to detect using conventional edge detection methods or, alternatively, CD measurements. In section 3, the basic concept of the new approach is introduced together with a description of the new detector and its characteristics. In section 4, the calibration process that took place in order to achieve reliable and repeatable line width measurements is presented. The description of an experiments conducted in order to evaluate the sensitivity of the new detector is given in section 5, followed by a report of the results of this evaluation. The conclusions are presented in section 6.

Improved image acquistion for advanced reticle inspection

The ability to inspect sub-micron features is an essential need for the manufacturing of advanced reticles. The shrinking of the minimal line width and the need for detecting smaller defects present a challenge for die-to-database reticle inspection. To meet this challenge, Orbot-Applied has developed an improved image acquisition (IIA) method and integrated it into its new RT-8000ES Die-to-Database reticle inspection system. The introduction of the IIA module made possible the detection of smaller defects and the ability to inspect smaller features, while maintaining all the other advantages of the field proven RT-8000 system. The evaluation of the RT-8000ES performance included scanning special test reticles with sub-micron features, containing different types of programmed defects of varying sizes. The evaluationss results show the RT-8000ES has the ability to inspect advanced reticles with lines down to 0.6 micron in width, while detecting defects as small as 0.15 microns, with no false defects. With this new improved image acquisition capability, the RT-8000ES has the ability to inspect current and future advanced reticles with high defect detection sensitivity and high reliability.

Mask inspection and real-time linewidth measurements

Controlling line width error is one of the most challenging tasks in mask production. Current methods for monitoring line width are based on either CD measurements or edge defect detection. Neither method guarantees the detection of line width errors with good sensitivity over the whole mask area. For example, a combination of small edge defect together with CD non-uniformity within the allowed tolerance, can yield a significant line width error, which will not be detected using conventional methods. In this paper we are presenting a new approach for line width error detection. The method, a new feature of Orbots RT-8000 die-to-database Reticle Inspection System, is a sensitive detector that operates during the inspection of all the reticles area. The detection is based on a comparison of measured line widths on both the database and the scanned image ofthe reticle. In section 2, the motivation for this new detector is driven. An analysis of various defect types, which are difficult to detected using edge detection approach or CD measurements, is presented. In section 3, the basic concept of the new approach is introduced together with a description of the new detector and its characteristics. In section 4, the calibration process that took place in order to evaluate the sensitivity of the detector is described. The experimental results of this evaluation are reported in section 5.

Die-to-database defect detection for reticles of 64- and 256-Mbit DRAMs

The development and production of 64 and 256 Mbit DRAMs presents new challenges to mask defect detection. As happened during the development of previous generations of DRAMs, the decrease in line/space design rule dictates a similar decrease in the specification of mask defect size. This trend introduces new technologies and new requirements. This paper is concerned with two evolving technologies: layout modification for optical proximity correction (OPC) and phase-shift masks (PSM). The new technologies pose many issues for the mask maker. In this paper the defect detection is addressed. In section 2 few cases of OPC reticle inspection are presented while in section 3 the defect detection of PSM is discussed.

Study of high sensitivity DUV inspection for sub-20nm devices with complex OPCs

EUV lithography has been delayed due to well-known issues such as source power, debris, pellicle, etc. for high volume manufacturing. For this reason, conventional optical lithography has been developed to cover more generations with various kinds of Resolution Enhancement Techniques (RETs) and new process technology like Multiple Patterning Technology (MPT). Presently, industry lithographers have been adopting two similar techniques of the computational OPC scheme such as Inverse Lithography Technology (ILT) and Source Mask Optimization (SMO) [1]. Sub-20 nm node masks including these technologies are very difficult to fabricate due to many small features which are near the limits of mask patterning process. Therefore, these masks require the unseen level of difficulty for inspection. In other words, from the viewpoint of mask inspection, it is very challenging to maintain maximum sensitivities on main features and minimum detection rates on the Sub-Resolution Assist Features (SRAFs). This paper describes the proper technique as the alternative solution to overcome these critical issues with Aerial Imaging (AI) inspection and High Resolution (HR) imaging inspection.

Mask Process Design Optimization Based on Quality Mapping Using Standard Mask Inspection Equipment

With the advent of system-on-chip (SOC) devices, resolving typical problems of composite designs is getting more urgent. The continuous effort for achieving tighter critical dimension (CD) tolerances together with the known phenomena of pattern density loading makes the mask fidelity issue for SOC technology a unique and prominent issue. The typical characteristic of an SOC with respect to CD control is the diversity of linewidths and pattern density over the chip. This paper presents the metrology software called Linewidth Bias Monitor (LBM) as a method to characterize pattern-loading effects on an SOC.

New approach to improve CD uniformity based on mask quality

CD uniformity is one of the key discussion topics in the ramp-up process of new technologies. The impact of mask quality is getting more and more attention in this process. The paper presents improving wafer CD uniformity control by application of new reticle CD qualification procedure. The new procedure is based on combining conventional CD metrology and Linewidth Bias Monitor (LBM) as a standard part of mask inspection.