In this paper scatterometry sensitivity up to 28nm HP resin pattern and beyond by using RCWA (Rigorous Coupled
Wave-analysis) simulation is described. A criterion, defined as the sum of the absolute difference of the reflectivity
values between the nominal and slightly different conditions from nominal through the spectrum, is introduced. The
criterion of this analysis is a kind of quantification of the sensitivity comparing with 65 nm HP resist pattern of ArF
immersion lithography process.
In this paper the first order analysis of the scatterometry sensitivity up to 45nm HP resin pattern and beyond by using
RCWA (Rigorous Coupled Wave-analysis) simulation is described. A criterion, defined as the sum of the absolute difference of the reflectivity values between the nominal and varied conditions thorough the spectrum, is introduced.
The criterion of this analysis is a kind of quantification of the sensitivity comparing with 65 nm HP resist pattern of ArF
immersion process. Furthermore, the simulated result in this analysis can be used to discuss the extendibility of
scatterometry.
We have proposed a new inspection method of in-line focus and dose control for high-volume manufacturing of
semiconductor. And we have referred to this method as "Focus and Dose Line Navigator (FDLN)". This method can
raise a performance of semiconductor exposure tool and therefore they can go up a yield ratio of semiconductor
device. The method leads the exposure condition (focus and dose) to the center of process window. FDLN calculates
correct exposure condition using the technology of solving the inverse problem. The sequence involves following
process. 1) Creating a focus exposure matrix (FEM) on a test wafer for building some models as supervised data.
The models mean the relational equation between the multi measurement results of resist patterns (e.g. Critical
dimension (CD), height and sidewall angle) and exposure conditions of FEM. 2) Measuring the resist patterns on
production wafers and feeding the measurement data into the library to predict focus and dose. In this time, we have
evaluated the accuracy of FDLN. We made some sample wafers by Canon's exposure tool "FPA-7000AS7". And
we used Veeco's advanced CD-AFM "InSight" as a topography measurement tool.
We have proposed a new inspection method of in-line focus and dose controls for semiconductor high volume
manufacturing. We referred to this method as the focus and dose line navigator (FDLN). Using FDLN, the deviations
from the optimum focus and exposure dose can be obtained by measuring the topography of the resist pattern on a
process wafer that was made under a single-exposure condition. Generally speaking, FDLN belongs to the technology of
solving the inverse problem as scatterometry. The FDLN sequence involves following the two steps. Step 1:creating a
focus exposure matrix (FEM) using a test wafer for building the model as supervised data. The model means the
relational equation between the multi measurement results of resist patterns ( e.g. Critical dimension (CD), height,
sidewall angle) and FEM's exposure conditions. Step 2: measuring the resist patterns on a manufacturing wafers and
feeding the measurement data into the library to extrapolate focus and dose.
In this paper, we explain again about the theorem of the FDLN and show experimental results using the many kind CDmeasurement
tool(the advanced CD-AFM, optical CD measurement tool, the advanced CD-SEM and the Overlay
measurement tool).
With the advancement of lithography, the overlay budget is becoming extremely tight. As the accuracy of overlay is
important for achieving a good yield, the demand for the accuracy of overlay is ever increasing. According to the
International Technology Roadmap for Semiconductors (ITRS), the overlay control budget for the 32nm technology
node will be 5.7nm. The overlay metrology budget is typically 1/10 of the overlay control budget resulting in overlay
metrology total measurement uncertainty (TMU) requirements of 0.57nm for the most challenging use cases of the 32nm
node. The current state of the art imaging overlay metrology technology does not meet this strict requirement, and further
technology development is required to bring it to this level. Especially for exposure tool inspection (e.g. alignment,
overlay, wafer stage and distortion), more high accuracy should be required using 'resist to resist' pattern.
In this work we simulated the measurement sensitivity for two types of scatterometry based overlay metrology, one is
differential signal scatterometry overlay (SCOL), the other is double exposure type (DET).
We have proposed a new inspection method of in-line focus and dose controls for semiconductor volume production. We
referred to this method as the focus and dose line navigator (FDLN). Using FDLN, the deviations from the optimum
focus and exposure dose can be obtained by measuring the topography of the resist pattern on a process wafer that was
made under a single-exposure condition. Generally speaking, FDLN belongs to the technology of solving the inverse
problem as scatterometry. The FDLN sequence involves following the two steps. Step 1:creating a focus exposure matrix
(FEM) using a test wafer for building the model as supervised data. The model means the relational equation between the
multi measurement results of resist patterns ( e.g. Critical dimension (CD), height, sidewall angle) and FEM's exposure
conditions. Step 2: measuring the resist patterns on a production wafers and feeding the measurement data into the
library to extrapolate focus and dose.
In this time, we have evaluated the estimated accuracy of Focus and dose for actual process wafer using the advanced
CD-SEM and we also have developed new algorithm for considering against thermal dose error.
We have proposed a new inspection method of in-line focus and dose controls for semiconductor volume production.
We referred to this method as the focus and dose line navigator (FDLN). Using FDLN, the deviations from the optimum
focus and exposure dose can be obtained by measuring the topography of the resist pattern on a process wafer that was
made under a single-exposure condition. Generally speaking, FDLN belongs to the technology of solving the inverse
problem as scatterometry. The FDLN sequence involves following the two steps. Step 1:creating a focus exposure matrix
(FEM) using a test wafer for building the model as supervised data. The model means the relational equation between the
multi measurement results of resist patterns ( e.g. Critical dimension (CD), height, sidewall angle) and FEM's exposure
conditions. Step 2: measuring the resist patterns on a production wafers and feeding the measurement data into the
library to extrapolate focus and dose. To estimate the accuracy of FDLN, we performed some experiments. We
developed a FEM with an ArF lithography tool and measured the resist patterns of the FEM wafer with the advanced
CD-SEM (Critical Dimension-Scanning Electron Microscope). Using the MPPC (Multiple Parameters Profile
Characterization) data from the advanced CD-SEM, we obtained the following results. Focus: 21.5 nm (4.1 nm) and
Dose: 1.5% (2.0 nm). The numerical value in a parenthesis shows the value of the estimated accuracy with changing CD.
We also show other experimental results in this paper and the application of the focus and dose controls for
semiconductor exposure tool.
Nano-imprint lithography (NIL) has the capability to transfer very fine patterns. As NIL was described in ITRS Roadmap in 2003, there are plans to apply NIL to semiconductor volume production at 32nm half pitch devices. This study is describes the critical issues of nano-imprint tool for semiconductor volume production. For an exposure tool supplier such as CANON, overlay control is not a critical issue for nano-imprint lithography because CANON has experience from proximity X-ray lithography (PXL). CANON can build an overlay system for nano-imprint tool using the CANON PXL's alignment and chip magnification correction technologies easily. Using our background, we focus on the Cost of Ownership (CoO) considering mold durability and compare NIL to Extreme Ultra Violet (EUV) and double patterning (DP) by immersion ArF lithography, to clarify the required specification of NIL from the viewpoint of productivity.
Focus and exposure dose control in lithography is a key challenge for CD (critical dimension) control at 90 nm technology node and beyond. Specially, more high accurate focus control will be necessary for low power MOS devices. Focus and dose line navigator (FDLN) is one of the candidates as in-line controller. The FDLN methodology involves two steps: first, create a focus-dose matrix (FEM) for building the library as supervised data using test wafer. The library means relational equation between the topography of photoresist patterns (line width: CD, height: HT, a side wall angle: SWA) and FEM exposure conditions, second, measure standard production wafer and feed the raw data into the library (which extrapolate focus and dose), which is then provided to the user. Using FDLN, current volume production’s focus and dose deviation from the best condition can be obtained. In this time, we have evaluated FDLN using an optical CD measurement tool and process wafer. STI, Cu-CMP ,metal wafers are used in this time as actual process. We acquired several FEM set of image feature from wafers, which were exposed by ArF scanner. According to our experiment, the estimation precision for focus and dose are below 24nm and below 1.7% respectively. And CD difference in a chip can reduce to one third as compared with the conventional QC method. These results suggest that FDLN can be the solution as in-line focus controller for volume production, enabling the progression toward Advanced Process Control (APC)
KEYWORDS: Inspection, Lithography, Control systems, Statistical analysis, Mining, Data analysis, Manufacturing, Process control, Data mining, Semiconductors
To attain quick turn-around time (TAT) and high yield, it is very important to remove all the problems affecting the semiconductor volume production line. For this purpose, we have used a lithography management system (LMS) as an advanced process control system. The LMS stores the critical dimension and overlay inspection results as well as the log data of the exposure tool in a relational database. This enables a quick and efficient grasp of the productivity under the present conditions and helps to identify the causes of errors. Furthermore, we developed a mining tool, called a log data extraction and correlation miner (LMS-LEC), for factor analysis on the LMS. Despite low correlation between all data, a high correlation may exist between parameters in a certain data domain. The LMS-LEC can mine such correlations easily. With this tool, we can discover previously unknown error sources that have been buried in the vast quantity of data handled by the LMS and thereby increase of the effectiveness of the exposure and inspection tool. The LMS-LEC is an extremely useful software mining tool for “equipment health” monitoring, advanced fault detection, and sophisticated data analysis.
We propose a new inspection method of in-line focus and dose control at semiconductor volume production. We have been referred to this method as Focus & Dose Line Navigator (FDLN). Using FDLN, the deviations from the optimum focus and exposure dose can be obtained by measuring the topography of resist pattern on a process wafer that was made with single exposure condition. Generally speaking, FDLN belongs to the technology of solving the inverse problem as scatterometry. The FDLN sequence involves following two steps. Step 1: creating a focus exposure matrix (FEM) using test wafer for building the library as supervised data. The library means relational equation between the topography of resist patterns (critical dimension (CD), height, side wall angle) and FEM's exposure conditions. Step 2: measuring the topography of resist patterns on production wafers and feeding the topography data into the library to extrapolates focus and dose. To estimate the accuracy of FDLN, we had some experiment. We made a FEM with ArF lithography tool and measured the topography of the FEM with optical CD measurement tool. By using the topography data, we obtained following result as accuracy of FDLN. Focus: 27.0nm (5.2nm) and Dose: 1.8% (1.4nm). The numerical value in a parenthesis shows the value of estimated accuracy into change of CD value. We also show other experimental results and some simulation result in this paper.
In lithography, the alignment error can be categorized into three factors. The first factor is called as Tool Induced Shift (TIS). The second is Wafer Induced Shift (WIS) and the third is the interaction between TIS and WIS. About TIS, we have defined a new evaluation criterion. About WIS, we have shown an error analyzer to quantify and compensate the alignment error using Atomic Force Microscope (AFM) and optical simulation. We have called this analyzer as 'Alignment Offset Analyzer'. This analyzer has the following
features. The topography of an alignment mark and resist surface on the alignment mark are measured individually by the AFM. The two topography data are wrapping over in a signal simulator. Using the wrapped topography, an alignment signal and an alignment measurement offset are calculated. Since the alignment offset can also be calculated before exposure sequence, the alignment offset can be inputted to exposure tool without send-ahead wafers. This time we report the accuracy of the Alignment Offset Analyzer. The alignment offset measured by an exposure tool and the calculated one above mentioned showed a good agreement, and the difference was several nm.
Alignment error that originates in the actual wafer process is one of the factors to deteriorate total overlay accuracy. This error has been called wafer induced shift (WIS). WIS occurs through a change of alignment marks topography under the actual wafer processing. To quantify mark asymmetry WIS, we study the mark asymmetry on tungsten chemical mechanical polishing (CMP) wafers by using an atomic force microscope and define new criterion in this paper. The mark topography of CMP process wafers are measured by AFM and quantified using the new criterion. The asymmetry of the mark topography can be quantified by measuring the profiles of an alignment mark across the wafers. It has been proven, that the rotation error is caused by the asymmetry of the mark topography and the asymmetry is not related to the line width of the mark.
KEYWORDS: Optical alignment, Semiconducting wafers, Chemical analysis, Chemical mechanical planarization, Tungsten, Signal processing, Error analysis, Overlay metrology, Semiconductors, Near field optics
Alignment error that originates in the actual wafer process is one of the factors that deteriorates total overlay accuracy. This error is known as wafer induced shift (WIS). WIS occurs through a change of alignment mark topography during the actual wafer processing. To reduce this error, we propose a tool that will simulate an alignment offset generated by WIS. We have called this tool the Alignment Offset Analyzer. The Alignment Offset Analyzer consists of a profiler for measuring the alignment mark topography and a simulator that simulates the alignment offset. By using the Alignment Offset Analyzer, we simulate the alignment signals from a Tungsten chemical mechanical polishing (CMP) wafer. The simulated alignment signals have an asymmetric shape due to the wafer processing. With these signals, the alignment offset caused by WIS can be estimated prior to the exposure sequence.
Modern overlay metrology tools achieve the required metrology accuracy by controlling critical asymmetries in the imaging optics, and by compensating for the remaining asymmetries through TIS-calibration. We extend our study on the TIS-WIS interaction in stepper alignment optics to the overlay metrology tool, and propose a new method for characterizing residual TIS. This method is based on the examination of the through-focus behavior of the metrology tool on a wafer with a simple, TIS-sensitive structure.
We describe some results of exposure experiments using the present prototype SR stepper which Canon has developed and the novel technology development which is necessary to establish the next generation SR stepper for volume production. Concerning the technology development, we have established (1) two mirror condensing system for full field exposure, (2) ADGL alignment method, (3) magnification correction method, (4) high speed stage stepping method. By adopting these technologies, we have been developing a beta- site machine for volume production and its features and preliminary specifications are described.
As the most critical semiconductor device geometries shrink down to the quarter micron order, requirements for overlay accuracy also become increasingly critical in the actual semiconductor manufacturing process. Factors in overlay error (especially, alignment error) originate in the interaction of process and tool. It is therefore necessary to improve alignment accuracy from both the process and the tool sides. In an effort to solve this as a tool supplier, we at Canon must minimize tool factors to reduce alignment errors caused by the interaction of process and tool factors. We though that we needed some evaluation criteria with such interaction take into account, and redefined the concepts of tool induced shift and wafer induced shift as a criterion. This paper introduces these new concepts and discusses validity of the criteria showing experimental results of alignment accuracy implementing the idea in the real process.
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