Scanning Transmission Electron Microscopy for Critical Dimension Monitoring in Wafer Manufacturing

Abstract

Automated scanning transmission electron microscopy (STEM) metrology provides critical dimension (CD) measurements an order of magnitude more precise than comparable scanning electron microscopy (SEM) measurements. New developments in automation now also provide throughput and response time sufficient to support high volume microelectronic manufacturing processes. The newly developed methodology includes automated, focused ion beam (FIB) based sample preparation; innovative, ex-situ sample extraction; and automated metrology. Although originally developed to control the production of thin film magnetic heads for data storage, the technique is fully applicable to any wafer-based manufacturing process.

Downstream Plasma Technology for Cleaning TEM Samples on Carbon Films

“…This can be an issue for TEM carbon film users because the carbon film is extensively used as a support on TEM grids for both materials science and biological applications. For example, our laboratory routinely loads from 10 to 50 ex-situ lifted-out TEM samples on a carbon film Cu-grid in order to support the high volume wafer-based manufacturing process [6]. If the carbon support film is damaged before the hydrocarbon contamination layer on the TEM samples is removed, valuable information in TEM samples will be lost.…”

Automated S/TEM metrology on advanced semiconductor gate structures

“…The major features for metrology are defined in Figure 3. The use of CD-SEM to make such measurements as those in Figure 3 was found to have two major limitations: the contrast and resolution available in a given SEM image 3 . In this case, resolution is limited by the sample interaction volume, rather than the diameter of the electron beam.…”

“…TEM mode is appropriate for other applications, but the observed phase and diffraction contrast tends to interfere with accurate structural metrology (see Figure 4). Automated STEM-based metrology has been widely adopted within the HDD industry 3,4 , and has created a paradigm shift in the way S/TEM is viewed and used (see Table 2). It has become the process of record for metrology of their most challenging processes.…”

Repeatability of Automated FIB Prepared TEM Samples with Low keV Cleaning

“…The solutions discussed here were developed for full wafer production line process monitoring in the data storage and semiconductor industries, where a manufacturing facility may be required to produce and measure tens of thousands of STEM images in the course of a year to maintain product yield [2] [3]. These solutions have also been applied to use cases where there are different sites of interest on each wafer, such as failure analysis, by replacing a pattern recognition step with an interface that allows an operator to identify and queue sites of interest via mouse clicks [4].…”