An Investigation of Human Body Electrostatic Discharge

The electronics industry has recognized the significance of Electrostatic Discharge (ESD) as a potential source of damage, especially to semiconductor devices, for some time. During that time, there has been an ongoing effort to develop a meaningful human body ESD pulse and equipment which is capable of repeatedly applying that pulse at various voltage levels to a semiconductor device. The intent was to determine a part's ability to withstand an ESD pulse at a certain voltage level and use that information as an indicator of the part's robustness. Presently, available equipment is capable of applying an ESD pulse frequently described in specifications such as MIL-STD 883C as the human body pulse; but is this the right pulse? Recent technical papers have raised some interesting questions about the ESD waveform and methods for capturing this waveform. Specifications such as IEC 801-2 have also contributed to the apparent confusion on ESD waveforms and, together, these sources of information were the catalyst that stimulated this investigation. TODAY'S ELECTRONICS INDUSTRY applications place an increasing number of requirements upon systems and component devices: semiconductor packaging and feature size is smaller, power requirements and operating temperatures are higher, and reliability demands have increased significantly. Designing for the elimination of early life device failures is a key factor in meeting these reliability requirements. Electrostatic discharge (ESD) events are recognized as a significant contributor of early life failures and failures throughout the operating life of a semiconductor device. Although present integrated circuit designs include ESD protection circuitry, the effectiveness of this protection must be determined in a manner which will ensure its effectiveness in the "real world" if the part is to meet the reliability requirements of the application. ESD has been studied for some time, and there is reasonable agreement on three (3) models for this phenomena: The Human Body Model (HBM), Machine Model (MM), and Charged Device Model (CDM). In this paper, we will be focusing on the HBM and some concerns we have about the model as presently defined. Under various conditions, the human body can be charged with electrical energy and transfer that charge to a semiconductor device through normal handling or assembly operations. To evaluate the effectiveness of the protection circuitry in an integrated circuit, HBM ESD testing is performed. This HBM pulse is intended to simulate the human body type ESD conditions the part would experience during normal usage. The ESD testing is also used to determine the immunity or susceptibility level of a system or part to the HBM ESD event. Several different Human Body Model (HBM) ESD simulation circuits and pulse waveforms exist, including Military Standard MIL-STD 883C [1] (see Figure 1), International Electrotechnical Commission (IEC) 801-2 [2] (see Figure 2), and others. The basic objective of this paper is to explore the following question: Do the present test specifications dealing with the human body ESD event define a