Igor Turovets

A holistic metrology approach: hybrid metrology utilizing scatterometry, CD-AFM, and CD-SEM

Shrinking design rules and reduced process tolerances require tight control of CD linewidth, feature shape, and profile of the printed geometry. The Holistic Metrology approach consists of utilizing all available information from different sources like data from other toolsets, multiple optical channels, multiple targets, etc. to optimize metrology recipe and improve measurement performance. Various in-line critical dimension (CD) metrology toolsets like Scatterometry OCD (Optical CD), CD-SEM (CD Scanning Electron Microscope) and CD-AFM (CD Atomic Force Microscope) are typically utilized individually in fabs. Each of these toolsets has its own set of limitations that are intrinsic to specific measurement technique and algorithm. Here we define Hybrid Metrology to be the use of any two or more metrology toolsets in combination to measure the same dataset. We demonstrate the benefits of the Hybrid Metrology on two test structures: 22nm node Gate Develop Inspect (DI) & 32nm node FinFET Gate Final Inspect (FI). We will cover measurement results obtained using typical BKM as well as those obtained by utilizing the Hybrid Metrology approach. Measurement performance will be compared using standard metrology metrics for example accuracy and precision.

Holistic metrology approach: hybrid metrology utilizing scatterometry, critical dimension-atomic force microscope and critical dimension-scanning electron microscope

Shrinking design rules and reduced process tolerances require tight control of critical dimension (CD) linewidth, feature shape, and profile of the printed geometry. The holistic metrology approach consists of utilizing all available information from different sources such as data from other toolsets, multiple optical channels, multiple targets, etc., to optimize metrology recipe and improve measurement performance. Various in-line CD metrology toolsets such as scatterometry optical CD, CD-SEM, and CD-AFM are typically utilized individually in fabs. Each of these toolsets has its own set of limitations that are intrinsic to specific measurement technique and algorithm. Here we define hybrid metrology to be the use of any two or more metrology toolsets in combination to measure the same dataset. We demonstrate the benefits of the hybrid metrology on two test structures: 22-nm-node gate develop inspect and 32-nm-node fin-shaped field effect transistor gate final inspect. We will cover measurement results obtained using typical BKM (nonhybrid, single toolset standard results) as well as those obtained by utilizing the hybrid metrology approach. Measurement performance will be compared using standard metrology metrics; for example, accuracy and precision.

Hybrid metrology solution for 1X node technology

The accelerated pace of the semiconductor industry in recent years is putting a strain on existing dimensional metrology equipments (such as CDSEM, AFM, Scatterometry) to keep up with ever-increasing metrology challenges. However, a revolution appears to be forming with the recent advent of Hybrid Metrology (HM) - a practice of combining measurements from multiple equipment types in order to enable or improve measurement performance. In this paper we extend our previous work on HM to measure advanced 1X node layers - EUV and Negative Tone Develop (NTD) resist as well as 3D etch structures such as FinFETs. We study the issue of data quality and matching between toolsets involved in hybridization, and propose a unique optimization methodology to overcome these effects. We demonstrate measurement improvement for these advanced structures using HM by verifying the data with reference tools (AFM, XSEM, TEM). We also study enhanced OCD models for litho structures by modeling Line-edge roughness (LER) and validate its impact on profile accuracy. Finally, we investigate hybrid calibration of CDSEM to measure in-die resist line height by Pattern Top Roughness (PTR) methodology.

Hybrid approach to optical CD metrology of directed self-assembly lithography

Directed Self Assembly (DSA) for contact layers is a challenging process in need of reliable metrology for tight process control. Key parameters of interest are guide CD, polymer CD, and residual polymer thickness at the bottom of the guide cavity. We show that Optical CD (OCD) provides the needed performance for DSA contact metrology. The measurement, done with a multi-channel spectroscopic reflectometry (SR) system, is enhanced through elements of a Holistic Metrology approach such as Injection and Hybrid Metrology.

Innovative scatterometry approach for self-aligned quadruple patterning (SAQP) process control

In this work, capabilities of scatterometry at various steps of the self-aligned quadruple patterning (SAQP) process flow for 7nm (N7) technology node are demonstrated including the pitch walk measurement on the final fin etch step. The scatterometry solutions for each step are verified using reference metrology and the capability to follow the planned process design-of-experiment (DOE) and the sensitivity to catch the small process variations are demonstrated. Pitch walk, which is pitch variation in the four line/space (L/S) populations, is one of the main process challenges for SAQP. Scatterometry, which is a versatile optical technique for critical dimensions (CD) and shape metrology, can find the direct measurement of pitch walk challenging because it is a very weak parameter. In this work, the pitch walk measurement is managed via scatterometry using an advanced technique of parallel interpretation of scatterometry pads with varying pitches. The three populations of trenches could be clearly distinguished with the scatterometry and the consistency with the reference data and with the process DOE are presented. In addition, the root cause of the within-wafer non-uniformity of fin CD is determined. The measurements were done on-site at IMEC as a part of the process development and control of the IMEC SAQP processes [1]. All in all, in this work it is demonstrated that scatterometry is capable of monitoring each process step of FEOL SAQP and it can measure three different space populations separately and extract pitch walk information at the final fin etch step.

A holistic metrology approach: multi-channel scatterometry for complex applications

Improvement in metrology performance when using a combination of multiple optical channels vs. standard single optical channel is studied. Two standard applications (gate etch 4x and STI etch 2x) are investigated theoretically and experimentally. The results show that while individual channels might have increased performance for few individual parameters each - it is the combination of channels that provides the best overall performance for all parameters.

Optical metrology for advanced process control: full module metrology solutions

Optical metrology is the workhorse metrology in manufacturing and key enabler to patterning process control. Recent advances in device architecture are gradually shifting the need for process control from the lithography module to other patterning processes (etch, trim, clean, LER/LWR treatments, etc..). Complex multi-patterning integration solutions, where the final pattern is the result of multiple process steps require a step-by-step holistic process control and a uniformly accurate holistic metrology solution for pattern transfer for the entire module. For effective process control, more process “knobs” are needed, and a tighter integration of metrology with process architecture.

Alternative approach for direct APC using scatterometry data

Scatterometry is a promising method, capable of providing accurate profile information for a large range of applications. However, applying scatterometry to the production environment and applying it to APC is still difficult. In this paper we propose an alternative approach in which we apply a Neural Network to directly correlate scatterometry raw data and the lithography process control parameters. The proposed method is much easier to use than normal scatterometry, and can therefore be applied to APC much faster.