The ongoing scaling of semiconductor devices necessitates increasing development of new and disruptive technologies. Curvilinear layout design and optical proximity correction (OPC) are among the innovations facilitating these advancements in technologies. However, they face challenges in mask enablement technology, including issues with mask writing, data volume management, design complexity, mask data representation, mask qualification, and metrology. In this paper, curvilinear mask test patterns and measurement methodologies are newly proposed for mask qualification and masks specification. Using contour-based mask metrology, edge placement error (EPE), mean-to-target (MTT) and uniformity (CDU) based on target maximum curvature (TMC) are measured and used as the main qualification metrics instead of traditional metrics such as critical dimensions (CD). These novel methods will partly complement standard qualification methods used for non-curvilinear (Manhattan) masks. A set of unique mask test structures are also proposed to extract the minimum set of curvilinear mask rules which enables experimental definition and verification of the manufacturing process.
To keep up with the pace set by Moore's law, an innovative standard cell architecture called CFET has been proposed recently. Its technical challenge is to stack transistors on top of each other to achieve higher density. Nevertheless, the targeted nodes still require very small dimensions in terms of pitches, critical dimensions (CD) and tip-to-tip, but also in terms of geometries. In this paper we explore the patterning of a 2D local interconnect, Middle of the Line (MOL) layer with aggressive pitches and spaces that has been foreseen as a possible option for this CFET architecture. Multiple patterning solutions are proposed including 1- EUV print with multiple colors, 2- Spacer assisted solutions with multiple cut patterns. Finally, we evaluate the benefit of using 3- High NA EUV lithography as a potential candidate for this type of layer.
Pattern sampling for good OPC models becomes more complex when we consider the nature of a full curvilinear photomasks. Due to the continuously changing angle of post-OPC edges, all angle diffraction spectrum are created in the scanner pupil entrance. For modeling test patterns to cover the possible OPC shapes, various dimensions and curvatures are taken into consideration in the test pattern design. Compared to Manhattan patterns, curvilinear patterns in OPC model calibration requires a multitude of variables to obtain the same coverage. To make the data sampling more effective and efficient, a machine learning-based fuzzy classification of feature vectors is applied. SONR is used to cluster similar patterns based on factors directly related to printability. Then, a representative cluster is chosen to guarantee full coverage of different patterns on the full chip level. These patterns are then used to calibrate OPC models.
According to the Power-Performance-Area requirements in advanced technology node, we already scaled down poly pitch (CPP) and metal pitch (MP) which considered as main factors to form standard cell (SDC) area. However, in recent technology nodes, the scaling of CPP and MP started to slow down, due to the physical limitation. To continue to meet the requirements, combined with Design-Technology co-optimization (DTCO), the height of standard cell would become the main factor here, which we could reduce it by reducing the number of tracks. In this paper, we would introduce 3DIC as one of the design options for 2nm node to keep scaling by reducing the cell height with its specific 3D structure and inserted booster. Also, we would introduce the coming challenges as importing 3D-IC to 2nm technology node.
On a Silicon Photonics integrated circuit, information is carried by the light that propagates within silicon waveguides. The waveguide’s geometry determines the functionality. The curvilinearity of Silicon Photonics designs would raise challenges for the manufacturability. However, so far Silicon Photonics design dimensions are considered relaxed by the industry. Also, the type of shapes that are drawn would generally use rather simple geometry objects. This allows the usage of conventional techniques in the different phases of the manufacturability. Recently has emerged a type of Silicon Photonics design, referred to as “inverse design”. This new technique produces designs that are very exotic and quite unpredictable. It shows complex geometries which critical dimensions require innovative Resolution Enhancement Techniques at the different stages of the Optical Proximity Correction flow. The success of these “inverse designs” relies on a very accurate pattern fidelity. This presentation will demonstrate a flow going from modelling, to OPC and metrology and verification of the manufactured wafer data. This flow permits to tackle the challenges brought newly to the Silicon Photonics environment.
EUV single patterning opportunity for pitch 28nm metal design is explored. Bright field mask combined with a negative tone develop process is used to improve pattern fidelity and overall process window. imec N3 (Foundry N2 equivalent) logic PNR (place and route) designs are used to deliver optimized pupil through source mask optimization and evaluate OPC technology. DFM (Design For Manufacturing) related topics such as dummy metal insertion and design CD retarget are addressed together with critical design rules (e.g. Tip-to-Tip), to provide balanced design and patterning performance. Relevant wafer data are shown as a proof of above optimization process.
With the advent of Multi-beam mask writers, curvilinear shapes are being realized with comparable metrics to Manhattan shapes when it comes to write times which has been the main issue with conventional VSB mask writers. Techniques like PLDC also enhance Multibeam writing of complex curvilinear patterns.
In the past Standard Cell (SDC) design was done with a gear ratio (polypitch/m1pitch) of 1:1. This inadvertently results in congestion on lower layers namely M1 as we try to push the design density. This can be improved by going to a gear ratio of 2/3 by which we derive additional M1 tracks (3 M1 tracks for every 2 poly) but the benefit derived out of a 2/3 gear ratio cell somewhat gets negated with the need for M2 in standard cells where MINT layer doesn’t fully cover M1. To resolve the problem with higher M2 usage in standard cells we can introduce 1.5D or curvilinear routing to make the final/minor routing connections. Here we try to present a study of different challenges and opportunities that arises as a result of introducing curvilinear routing in Standard cells (SDC).
In IN5 technology node when we go for a gear ratio (CPP/M1Pitch) of 2/3 we observe that for every standard cell we will need two variants of the cell. These two variants have M1 which are interleaved and shifted. We can live with only one variant of the cell but this inadvertently leaves gaps in between standard cells as the M1 grids will not align when they are abutted. Further study of the impact of the need of two variants reveals that in some standard cells (~9% in IN5) we end up with using M2 for completing the connections. This has many drawbacks (extra routing resources, congestion on M2, increase in area and reduced performance) which negates the benefit derived with 2/3 gear ratio.
To fix this problem we have two options. One is to use 1.5D routing and the other to use curvilinear routing. With this approach all the benefits of 2/3 gear ratio can be preserved (improved routing density, area and performance) without the need for M2.
A design implementation of the same in IN5 AO22D2 standard cell with CPP of 45nm and M1 pitch of 30nm has been done and the M2 routing (with default approach) has been eliminated. Although this approach has numerous benefits and extended applications (in signal routing) it does present significant challenges when it comes to EDA tools, verification, mask and OPC. We are in the process of evaluating different test cases for design, mask and OPC challenges with curvilinear routing in IN5 SDC. On the design front the challenges include library characterization, PPA and runtime analysis, RC extraction and design verification. On the mask and OPC front some of the challenges include regular versus ILT OPC and their process window comparison, understand the SRAF’s required, mask data volume and MRC.
A comprehensive understanding of the challenges and resolution of the same will entail a new scaling paradigm for standard cell designs and also enhance signal routing which in turn has numerous benefits when it comes to PPA.
Advanced technology nodes are demanding aggressive printability using EUV. EUV printing process inherently brings in stochastic defects. To measure and experience various types of Stochastics in EUV printing, high volume measurements are deemed necessary. Furthermore the classification of the defects in terms of stochastic and systematic is also required. The permutation and combinations of shapes, sizes, and proximity driven stochastics errors are high in numbers, leading to significant increase in the number of test structures needed. Without electrically measurable solutions, the defect test measurement exercise becomes impractical to perform visually. This paper will describe few examples of developing and handling the test structures capable to capture the defects and defect location and further to classify the defects in terms of stochastic or systematic defects.
In this work we are introducing a manufacturing flow for the SALELE Process in details. Starting with layout decomposition, where the drawn layer is decomposed into 4 Masks: 2 Metal-like Masks, and 2 Block-like Masks. Then each of these masks is subjected to Optical Proximity Correction (OPC) process, and here we explain more about the OPC recipe development for each mask. Then we introduce a verification flow that performs two levels of verifications: (a) Litho verification, where the litho fidelity of each mask is quantified based on image quality measurements. (b) Final Manufactured shapes verification vs. expected output. This work has been carried out on an N3 candidate layout designed by IMEC.
This paper summarizes findings for an N5 equivalent M2 (pitch 32) layer patterned by means of SE EUV. Different mask tonalities and resist tonalities have been explored and a full patterning (litho plus etch) process into a BEOL stack has been developed. Resolution enhancement techniques like SRAFs insertion and retargeting have been evaluated and compared to a baseline clip just after OPC. Steps forward have been done to develop a full patterning process using SE EUV, being stochastics and variability the main items to address.
imec’s investigation on EUV single patterning insertion into industry 5nm-relevant logic metal layer is discussed. Achievement and challenge across imaging, OPC, mask data preparation and resulting wafer pattern fidelity are reported with a broad scope.
Best focus shift by mask 3D of isolated feature gets worse by the insertion of SRAF, which puts a negative impact on obtaining large overlap process window across features. imec’s effort across OPC including SMO and mask sizing is discussed with mask rule that affects mask writing. Resist stochastic induced defect is identified as a biggest challenge during the overall optimization, and options to overcome the challenge is investigated. For mask data preparation, dramatic increase in the data volume in EUV mask manufacturing is observed from iArF multiple patterning to EUV single patterning conversion, particularly by the insertion of SRAF. In addition, logic design consideration to make EUV single patterning more affordable compared to alternative patterning option is be discussed.
imec’s DTCO and EUV achievement toward imec 7nm (iN7) technology node which is industry 5nm node
equivalent is reported with a focus on cost and scaling. Patterning-aware design methodology supports both
iArF multiple patterning and EUV under one compliant design rule. FinFET device with contacted poly pitch of
42nm and metal pitch of 32nm with 7.5-track, 6.5-track, and 6-track standard cell library are explored. Scaling
boosters are used to provide additional scaling and die cost benefit while lessening pitch shrink burden, and it
makes EUV insertion more affordable. EUV pattern fidelity is optimized through OPC, SMO, M3D, mask
sizing and SRAF. Processed wafers were characterized and edge-placement-error (EPE) variability is validated
for EUV insertion. Scale-ability and cost of ownership of EUV patterning in aligned with iN7 standard cell
design, integration and patterning specification are discussed.
The imec N7 (iN7) platform has been developed to evaluate EUV patterning of advanced logic BEOL layers. Its design is based on a 42 nm first-level metal (M1) pitch, and a 32 nm pitch for the subsequent metal layers1. With these pitches, the iN7 node is an ‘aggressive’ full-scaled N7, corresponding to IDM N7, or foundry N5.
Regarding the metal 2 layer, imec is evaluating two integration approaches: EUV single print and SAQP+EUV Block. Extensive work is reported on both approaches2,3. The work detailed in this paper will deal about the computational work done prior to tape-out for the EUV direct print option.
We will discuss the EUV source mask optimization for an ASML NXE:3300 EUV scanner. Afterwards we will shortly touch upon OPC compact modeling and more extensively on OPC itself. Based on the current design rules and MRC, printability checks indicate that only limited process windows are obtained. We propose ways to improve the printability through MRC and design. Applying those changes can potentially lead to a sufficient process window.
Silicon photonics has become in the past years an important technology adopted by a growing number of
industrial players to develop their next generation optical transceivers. However most of the technology
platforms established in CMOS fabrication lines are kept captive or open to only a restricted number of
customers. In order to make silicon photonics accessible to a large number of players several initiatives exist
around the world to develop open platforms. In this paper we will present imec’s silicon photonics active
platform accessible through multi-project wafer runs.
ePIXfab-The European Silicon Photonics Support Center continues to provide state-of-the-art silicon photonics solutions to academia and industry for prototyping and research. ePIXfab is a consortium of EU research centers providing diverse expertise in the silicon photonics food chain, from training users in designing silicon photonics chips to fiber pigtailed chips. While ePIXfab provides world-wide users access to advanced silicon photonics it also focuses its attention to expanding the silicon photonics infrastructure through a network of design houses, access partners and industrial collaborations.
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