Chung-sam Jun

Development of automated contact inspection system using in-line CD SEM

We have developed an automated contact inspection system using an in-line CD SEM and applied it to monitor contact etching processes. As the design rule shrinks, monitoring of the contact etching, which cannot be detected by the conventional optical inspection systems, are becoming one of the most critical issues in semiconductor processing. Though there are e-beam based inspection systems or manual inspection sequence with in-line SEM (Scanning Electron Microscope), monitoring small and electrical defects has a few fundamental limitations. E-beam inspection systems have low throughput and a high price as a mass production tool. In the case of the manual inspection system, the inspection result depends on the operator and it is difficult to quantify the defect data. We have developed an automated contact inspection system to overcome these limitations. The system is composed of a data processing system and an in-line SEM. The automated in-line SEM inspects and stores the images of specified points on the wafer. The data processing system receives and manipulates the images to indicate the etching problem. It was shown that the scanning electron image of the contact is related to failures such as insufficient etching or residuals inside the contact.

Exact and reliable overlay metrology in nanoscale semiconductor devices using an image processing method

Abstract. As semiconductor processing becomes more complicated and pattern sizes shrink, the overlay metrology has become one of the most important issues in the semiconductor industry. Therefore, in order to obtain correct, reliable overlay values in semiconductor fabrication facilities (fab), quantization methods for the efficient management and implementation of a measurement algorithm are required, as well as an understanding of the target structures in the semiconductor device. We implemented correct, reliable overlay values in the pattern using the image processing method. The quantization method, through correlation analysis and a new algorithm for target structures, were able to improve the sensitivity to misalignment in the pattern and enable more stable and credible in-line measurement by decreasing the distribution of the residuals in overlay values. Since overlay values of the pattern in the fab were measured and managed more reliably and quickly, it is expected that our study will be able to contribute to the yield enhancement of semiconductor companies.

Si Crystallization Monitoring Using EBSD Technique

The stacked structure of a semiconductor device is aggressively tried to solve the limit of device size, which has been reduced by the condensation of device design. To make the stacked device, we should make single crystal Si layer for upper transistors using the crystallization of amorphous Si layer deposited on the thick ILD layer. The fast process feedback is strongly needed to optimize and to check the process. We proposed electron back scattered diffraction (EBSD) method to monitor the Si crystallization process. The crystallization of a-Si film is monitored using the crystalline orientation map, the (001) crystal direction map and area, and the grain size distribution. For the mass production of devices, we are developing an in-fab metrology tool of EBSD

A new method for wafer quality monitoring using semiconductor process big data

In this paper we proposed a new semiconductor quality monitoring methodology – Process Sensor Log Analysis (PSLA) – using process sensor data for the detection of wafer defectivity and quality monitoring. We developed exclusive key parameter selection algorithm and user friendly system which is able to handle large amount of big data very effectively. Several production wafers were selected and analyzed based on the risk analysis of process driven defects, for example alignment quality of process layers. Thickness of spin-coated material can be measured using PSLA without conventional metrology process. In addition, chip yield impact was verified by matching key parameter changes with electrical die sort (EDS) fail maps at the end of the production step. From this work, we were able to determine that process robustness and product yields could be improved by monitoring the key factors in the process big data.

In‐line Quantitative Dose Metrology of Ultra‐thin Gate Oxide

In‐line quantitative dose monitoring has been successfully performed with the E‐beam Induced X‐ray fluoresecence technique. Nitrogen and other elemental doses have been quantified for ultra‐thin gate oxides with oxynitride and high k dielectrics, and compared with the other analytical tools and electrical elements of non‐contact CV method. Nitrogen concentration extracted from Low energy Electron induced X‐ray Emission Spectrometry (LEXES) showed good correlation with that of XPS, and the effects of each elemental composition on EOT and leakage current were investigated. The results suggest that the non‐destructive dose metrology with LEXES can be used to control and monitor the ultrathin gate‐oxide process during CMOS fabrication even for product samples owing to the small analyzing spot size. Moreover, the results of the high k dielectrics suggest that dose monitoring is applicable to other elemental quantification of ULSI thin films.