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1、METROLOGY1INTRODUCTION AND SCOPE21.1Introduction21.2Scope31.3Infrastructure Needs42DIFFICULT CHALLENGES43MICROSCOPY44LITHOGRAPHY METROLOGY64.1Line Roughness84.2Measurement Uncertainty94.3Explanation Of Uncertainty In Tables Met3 And Met4115FRONT END PROCESSES METROLOGY115.1Starting Materials125.2Sur
2、face preparation125.3Thermal/thin films125.4Strained Si processes135.5FERAM135.6Doping technology1363D INTERCONNECT METROLOGY146.1Bonding overlay156.2Bonded interface void detection166.3Bonded interface defect identification166.4Bonded interface defect review166.5Edge bevel defects176.6Bond strength
3、 uniformity176.7Bonded Wafer Pair thickness176.8TSV etch depth186.9TSV etch profile186.10TSV liner, barrier, seed thickness186.11Shape and stress196.123D Metrology for Copper nail and Pillars197INTERCONNECT METROLOGY207.1CU-LOW METALLIZATION ISSUES AND METROLOGY NEEDS207.1.1Cu Metallization Issues20
4、7.1.2Cu Metallization Metrology217.2Low Dielectrics Issues And Metrology Needs227.2.1Low Dielectric Issues227.2.2Low- Metrology228MATERIALS AND CONTAMINATION CHARACTERIZATION238.1Materials and contamination in strain-based devices259METROLOGY FOR EMERGING RESEARCH MATERIALS AND DEVICES269.13D Atomic
5、 Imaging and Spectroscopy28ABERRATION CORRECTED TEM AND STEM W/ELS283D ATOM PROBE289.2Other Microscopy Needs including Scanning Probe Microscopy299.3Optical Properties of Nanomaterials309.4Electrical Characterization for Emerging Materials and Devices3110REFERENCE MATERIALS3111REFERENCE MEASUREMENT
6、SYSTEM331 Introduction and Scope 1.1 IntroductionMetrology is defined as the science of measurement. The ITRS Metrology Roadmap describes new challenges facing metrology and describes a pathway for research and development of metrology with the goal of extending CMOS and accelerating Beyond CMOS. Me
7、trology also provides the measurement capability necessary for cost-effective manufacturing. As such, the metrology chapter of the ITRS focuses on difficult measurement needs, metrology tool development, and standards. The roadmap for feature size reduction drives the timeline for metrology solution
8、s for new materials, process, and structures. Metrology methods must routinely measure near and at atomic scale dimensions which require a thorough understanding of nano-scale materials properties and of the physics involved in making the measurement. Novel materials and geometries, such as 3D gates
9、 and strained silicon channels, add to the complexity of measurements. Metrology development must be done in the context of these issues. Metrology enables tool improvement, ramping in pilot lines and factory start-ups, and improvement of yield in mature factories. Metrology can reduce the cost of m
10、anufacturing and the time-to-market for new products through better characterization of process tools and processes. The increasing diversity of chip types will spread already limited metrology resources over a wider range of challenges. The metrology community including suppliers, chip manufacturer
11、s, consortia, and research institutions must provide cooperative research, development, and prototyping in order to meet the ITRS timeline. The lack of certainty in the structures and materials of future technology generations makes the definition of future metrology needs less clear than in the pas
12、t. However, it is clear that 3D device structures will be introduced by at least some companies as early as the 22 nm node. Such 3D device structures invalidate many of the starting assumptions for the modeling and analyses of conventional metrologies necessitating an increased emphasis on metrology
13、 techniques which can provide true 3D information. The 3D nature of both front end and interconnect devices and structures provides many challenges for all areas of metrology including critical dimensions. Although advancements in materials characterization methods, such as aberration corrected tran
14、smission electron microscopy, have achieved atomic resolution for 2D materials, including single layer graphene, critical dimension measurement with nm level precision is difficult to achieve particularly for 3D structures. Feature shape characterization and metrology done largely in 2D will need to
15、 evolve to 3D. The 2011 ITRS expands on the new urgency for Metrology for 3D Interconnects to include wafer alignment, interface bonding, and through silicon vias (TSV). Moreover, it is entirely possible that different materials will be used by different manufacturers at a given technology generatio
16、n, potentially requiring different metrologies. In the near term, advances in electrical and physical metrology for high- and low- dielectric films must continue. The strong interest in EUV Lithography is driving the need for new mask metrology. The requirement for technology for measurement of devi
17、ces on ultra-thin and possibly strained silicon on insulator comes from the best available information that is discussed in the Front End Processes Roadmap. The increasing emphasis on active area measurements instead of test structures in scribe (kerf) lines places new demands on metrology. Measurem
18、ent of relevant properties, such as stress or strain, in a nano-sized, buried area such as the channel of a small dimension gate is a difficult task. Often, one must measure a film or structure property at the surface and use modeling to determine the resultant property of a buried layer. Long-term
19、needs at the sub-16 nm technology generation are difficult to address due to the lack of clarity of device design and interconnect technology. The selection of a replacement for copper interconnect remains a research challenge. Although materials characterization and some existing inline metrology a
20、pply to new device and interconnect structures, development of manufacturing capable metrology requires a more certain knowledge of materials, devices, and interconnect structures. The 2011 ITRS also includes the addition of a MEMS section(need metrology?). Metrology tool development requires access
21、 to new materials and structures if it is to be successful. It requires state-of-the-art capabilities to be made available for fabrication of necessary standards and development of metrology methodologies in advance of production. The pace of feature size reduction and the introduction of new materi
22、als and structures challenge existing measurement capability. In some instances, existing methods can be extended for several technology generations. In other cases, necessary measurements may be done with inadequate equipment. Long-term research into nano-devices may provide both new measurement me
23、thods and potential test vehicles for metrology. A greater attention to expanding close ties between metrology development and process development is needed. When the metrology is well matched to the processes and process tools, ramping times for pilot lines and factories are reduced. An appropriate
24、 combination of well-engineered tools and appropriate metrology is necessary to maximize productivity while maintaining acceptable cost of ownership. The fundamental challenge for factory metrology will be the measurement and control of atomic dimensions while maintaining profitable high volume manu
25、facturing. In manufacturing, metrology is connected to factory-wide automation that includes database and intelligent information from data capability. Off-line materials characterization is also evolving toward compatibility with factory-wide automation. All areas of measurement technology (especia
26、lly those covered in the Yield Enhancement chapter) are being combined with computer integrated manufacturing (CIM) and data management systems for information-based process control. Although integrated metrology still needs a universal definition, it has become the term associated with the slow mig
27、ration from offline to inline and in situ measurements. The proper combination of offline, inline, and in situ measurements will enable advanced process control and rapid yield learning. The expected trend involves the combined use of modeling with measurement of features at the wafer surface. The M
28、etrology roadmap has repeated the call for a proactive research, development, and supplier base for many years. The relationship between metrology and process technology development needs fundamental restructuring. In the past the challenge has been to develop metrology ahead of target process techn
29、ology. Today we face major uncertainty from unresolved choices of fundamentally new materials and radically different device designs. Understanding the interaction between metrology data and information and optimum feed-back, feed forward, and real-time process control are key to restructuring the r
30、elationship between metrology and process technology. A new section has been added to the Metrology Roadmap that covers metrology needs for emerging technology paradigms. 1.2 Scope The metrology topics covered in the 2011 Metrology roadmap are microscopy; critical dimension (CD) and overlay; film th
31、ickness and profile; materials and contamination analysis; 3D metrology; emerging research materials and devices; and reference materials. These topics are reported in the following sections in this chapter: Microscopy; Lithography Metrology; Front End Processes Metrology; 3D Interconnect Metrology;
32、 Traditional Interconnect Metrology; Materials and Contamination Characterization; Metrology for Emerging Research Materials Devices; Reference Materials; and Reference Measurement Systems. International cooperation in the development of new metrology technology and standards will be required. Both
33、metrology and process research and development organizations must work together with the industry including both the supplier and IC manufacturer. Earlier cooperation between IC manufacturers and metrology suppliers will provide technology roadmaps that maximize the effectiveness of measurement equi
34、pment. Research institutes focusing on metrology, process, and standards; standards organizations; metrology tool suppliers; and the university community should continue to cooperate on standardization and improvement of methods and on production of reference materials. Despite the existence of stan
35、dardized definitions and procedures for metrics, individualized implementation of metrics such as measurement precision to tolerance (P/T) ratio is typical.1 The P/T ratio is used to evaluate automated measurement capability for use in statistical process control and relates the measurement variatio
36、n (precision) of the metrology cluster to the product specification limits. Determination of measurement tool variations is sometimes carried out using reference materials that are not representative of the product or process of interest. Thus, the measurement tool precision information may not refl
37、ect measurement-tool induced variations on product wafers. It is also possible that the sensitivity of the instrument could be insufficient to detect small but unacceptable process variations. There is a need for metrics that accurately describe the resolution capability of metrology tools for use i
38、n statistical process control. The inverse of the measurement precision-to-process variability is sometimes called the signal-to-noise ratio or the discrimination ratio. However, because the type of resolution depends on the process, specific metrics may be required (e.g. thickness and width require
39、 spatial resolution while levels of metallic contaminants on the surface require atomic percent resolution). There is a new need for a standardized approach to determination of precision when the metrology tool provides discrete instead of continuous data. This situation occurs, for example, when si
40、gnificant differences are smaller than the instrument resolution. The principles of integrated metrology can be applied to stand-alone and sensor-based metrology itself. Factors that impact tool calibration and measurement precision such as small changes in ambient temperature and humidity could be
41、monitored and used to improve metrology tool performance and thus improve statistical process control. Wafer manufacturers, process tool suppliers, pilot lines, and factory start-ups all have different timing and measurement requirements. The need for a shorter ramp-up time for pilot lines means tha
42、t characterization of tools and processes prior to pilot line startup must improve. However, as the process matures, the need for metrology should decrease. As device dimensions shrink, the challenge for physical metrology will be to keep pace with inline electrical testing that provides critical el
43、ectrical performance data. 1.3 Infrastructure Needs A healthy industry infrastructure is required if suppliers are to provide cost-effective metrology tools, sensors, controllers, and reference materials. New research and development will be required if opportunities such as MEMS-based metrology and
44、 nanotechnology are to make the transition from R&D to commercialized products. Many metrology suppliers are small companies that find the cost of providing new tools for leading-edge activities prohibitive. Initial sales of metrology tools are to tool and process developers. Sustained, high-volume
45、sales of the same metrology equipment to chip manufacturers do not occur until several years later. The present infrastructure cannot support this delayed return on investment. Funding that meets the investment requirements of the supplier community is needed to take new technology from proof of con
46、cept to prototype systems and finally to volume sales.2 Difficult Challenges3 Microscopy Microscopy is used in most of the core technology processes where two-dimensional distributions, that is digital images of the shape and appearance of integrated circuit (IC) features, reveal important informati
47、on. Usually, imaging is the first, but many times the only step in the “being able to see it, measure it, and control it” chain. Microscopes typically employ light, electron beam, or scanned probe methods. Beyond imaging, online microscopy applications include critical dimension (CD) and overlay mea
48、surements along with detection, review, and automatic classification of defects and particles. Because of the high value and quantity of wafers, the need for rapid, non-destructive, inline imaging and measurement is growing. Due to the changing aspect ratios of IC features, besides the traditional l
49、ateral feature size (for example, linewidth measurement) full three-dimensional shape measurements are gaining importance and should be available inline. Development of new metrology methods that use and take the full advantage of advanced digital image processing and analysis techniques, telepresence, and networked measurement tools will be nee
