Wafer Handling Systems for Semiconductor Automation
Nowadays, semiconductor and electronics companies are offering a full line of industry-leading semiconductor and electronics handling robots. All these robots are built considering their use in cleanroom applications. Speed, accuracy, and reach make semiconductor wafer handling robot ideal for handling delicate semiconductor wafers, LCD panels, organic EL, and solar panels.
Wafer Handling Robots addressed the needs for semiconductor quartz and wafer substrate handling for many years. Semiconductor robot wafer handling robots key feature is beam wafer sensing; and robot self-teach functionality. Wafer robots are used in the semiconductor equipment spectrum for thermal processing systems, metrology systems, deposition systems, and many more systems.
High-Performance Wafer Handling Systems
Nowadays, the total productivity of semiconductor fabrication depends on the performance of the robotic systems. They are also responsible for material handling within the front-end and back-end mini-environments. Without considering the time it may take for the processes, the time for exchanging an unprocessed wafer with an already processed wafer, to increase the performance of the processing machines.
The semiconductor front end wafer handling robots have increased performance demands, and require high accuracy and reliability for driving mechanical constraints. Every processing machine's cost and the size of the manipulating object has increased significantly.
Now, the manufacturers have shifted the directions of wafer handling equipment in the design of mechanical systems with improved manipulating capabilities, optimal application of the wafer handling equipment, implementation of advanced control schemes, and direct-drive actuation by proper analysis of the manipulating task with mathematical modeling, elaborate case studies, simulation, and on-site experiments. They aim to increase the performance capabilities of the robotic wafer handling system from both the control and the mechanical point of view.
The Manipulating Task
In the robotic handling systems (RHS), the common characteristic of the manipulating task is to make constrained straight-line motion at the center of the wafer.
The straight-line segment is coincident with the longitudinal axis of the equipment (an open cassette, FOUP, a process chamber, etc.). The linear motion requires a synchronized vertical move to account for equipment placement inaccuracies or deflections of the robotic-arm.
The linear motion requires a synchronized vertical move to account for equipment placement inaccuracies or deflections of the robotic-arm, whereas ideally, the straight-line segment lies in a horizontal plane. The straight-line motion is characterized as “constrained” when it is not manipulated during the time object is in contact, continuous or intermittent, with the equipment.
The center of the wafer constraints the stay within close vicinity of the center-line of the equipment, which is usually less than 0.5 mm along the path, and at the terminal point. The motion is called “fine” motion and depends on the straight-line segment situated at the center of the robot; there are different approaches performed for manipulating task and various mechanical
structures.
In addition to the constrained straight-line motion, there is another motion, called “gross” motion. It intends to transport wafers between different approach positions, which are just in front of the equipment, and are restricted by the walls of the mini-environments. They have relatively high tolerance between the minimum swinging envelope of the robot and the wall-
constraints whose motion requires less accuracy.
For increasing the performance, the gross motion is expected to be fast and limited by the requirement to hold the wafer on the end-effector. In many cases, the effective blending of both the “fine” and the “gross” motions are required to decrease the wafer exchange or swapping time and to increase the velocity and acceleration of the separate motions.
