What is the main role of 1 megohm resistors in semiconductor assembly?
Based on your question, I make two assumptions, Assumption 1: We are talking about static control in semiconductor workshops. Assumption 2: Operators are involved in handling semiconductors or equipment with semiconductors.
The purpose of the 1 megohm resistor in series with the anti-static wrist strap, heel strap, ground chain, and ground wire is simply to provide safety to the human body by limiting the amount of current that can be conducted through the person's body.
Grounding kits or anti-static wrist straps with 1 or 2 Megohm resistors in series are currently available in the market. The main purpose of the 1 Megohm resistor is to limit the current to 250 microamps at 250VAC, which is just below what most people perceive. The physical perception of electricity flowing in/on the body varies with body size, weight, water content and differences.