Robotic Transport Arm Stiffness and Precision
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Solution Overview
Problem
Conventional robotic transport apparatuses face challenges in achieving precise repeatability in substrate positioning, particularly in semiconductor substrate processing, where accuracy within 5 to 25 microns is required, due to issues of hysteresis and lack of stiffness in the arm linkage.
Innovation Solution
A robotic transport arm with lightweight, stiff drive links and a transmission linkage system that includes bi-axially rigid links and a lost motion switch, connected to a coaxial drive section, which minimizes residual motion and enhances the stiffness of the arm, allowing for precise extension and retraction of the end effector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional substrate transport apparatus is used, then the system is simpler and easier to manufacture, but the placement repeatability deteriorates (cannot achieve 5-25 micron precision)
Solution Approach 1:
The arm linkage is divided into multiple segments (first arm, second arm, third arm) connected by joints, with each segment having specific functions. This segmentation allows for precise control of each degree of freedom while maintaining overall system stiffness, enabling sub-25 micron placement repeatability despite the increased complexity of the multi-segment structure.
Solution Approach 2:
The patent specifies precise parameter ranges for the arm linkage components, including link lengths, joint angles, and stiffness values. By carefully controlling these parameters, the system achieves the required placement repeatability of 5-25 microns while managing the complexity through standardized component specifications.
2Speed
If the arm linkage is made lighter, then the speed and responsiveness improve, but the stiffness deteriorates (increasing hysteresis and reducing precision)
Solution Approach 1:
The arm linkage components are constructed using composite materials that provide high stiffness-to-weight ratio. This allows the arms to be lightweight for fast response while maintaining the structural stiffness needed to minimize hysteresis and achieve precise placement repeatability within 5-25 microns.
Solution Approach 2:
The patent employs curved or articulated arm designs rather than simple straight links, optimizing the distribution of mass and stiffness. The curved geometries provide structural rigidity while minimizing weight, enabling rapid positioning with high precision and reduced hysteresis effects.
Data Source
AI summary
A transport apparatus including a frame, a drive section connected to the frame, the drive section having at least one drive axis, at least one arm having an end effector configured for holding a substrate, the at least one arm being connected to the drive section by a transmission link and having at least one degree of freedom axis effecting extension and retraction of the end effector with respect to the at least one arm, and a bearing connected to the frame and the end effector, the bearing defining a guideway that defines the at least one degree of freedom axis.