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    Applied Surface Analysis Tuesday Sessions
       Session AS-TuP

Paper AS-TuP7
Applications of AFM/SCM in Process Control and Failure Analysis of Semiconductor Devices

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Aspects of Applied Surface Analysis II Poster Session
Presenter: K.-J. Chao, Charles Evans & Associates
Authors: K.-J. Chao, Charles Evans & Associates
J.R. Kingsley, Charles Evans & Associates
H. Ho, Charles Evans & Associates
H. Shen, Charles Evans & Associates
I.D. Ward, Charles Evans & Associates
Correspondent: Click to Email
As the minimum feature size of a semiconductor device continues to shrink, analyses of the engineered structures and materials of semiconductor devices have been very critical in device manufacturing and the development of new generation devices. Furthermore, the performance of a modern device is strongly influenced by its dopant distributions in depth and laterally. Scanning capacitance microscopy (SCM) is one of the techniques that have been developed to reveal the dopant distribution two-dimensionally. In this work, AFM/SCM was applied to both process control and failure analysis of semiconductor devices. Two types of semiconductor devices, Si based and GaAs based, were studied. In the applications of process control, two examples are presented. The first example is to investigate the uniformity of the As layer of a silicon substrate. This sample has a layer of uniformly distributed As region. X-sectioned SCM/AFM study found local non-uniformity in the As layer. The second example is to determine the lateral diffusion length of dopants after the thermal annealing process. A GaAs substrate is masked and patterned by a layer of Si3N4. Zn dopants were thermally dif-fused through a line-opening in the Si3N4 layer into the GaAs substrate. By overlaying the AFM image on top of the SCM image, the lateral diffusion length of the Zn dopants was found to be about 2.2µm away from the edges of the exposed GaAs region. Another important application of AFM/SCM is in the device failure analysis. A failed p-channel transistor was first studied by AFM/SCM. Two levels of dopant concentration were found in the corresponding source and drain regions by SCM. Another way to identify the cause of the failure is to directly compare the failed device with a properly functioning one. We applied AFM/SCM to study the same N-well struc-tures in two devices, one good and the other failed, and found that the depth of the N-well for the failed device is about 0.4µm shorter.