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Method for detecting control instability in a wafer handling robotic system

IP.com Disclosure Number: IPCOM000034137D
Publication Date: 2005-Jan-17
Document File: 4 page(s) / 79K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for detecting control instability in a wafer handling robotic system. Benefits include improved functionality and improved performance.

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Method for detecting control instability in a wafer handling robotic system

Disclosed is a method for detecting control instability in a wafer handling robotic system. Benefits include improved functionality and improved performance.

Background

      Unstable or inadequately programmed robotic wafer handling systems can cause wafer misalignment, misplacement, and damage. This problem is conventionally highlighted and corrected only after the negative results have occurred.

      Theoretically, every robot arm and wafer handling end-effector system has a specific natural frequency fingerprint (see Figure 1). As a result, each individual system/set up has particular radial ranges in which a harmonic can be excited if system control stability is not programmed adequately to compensate for motor cogging and bearing-induced movements. Lack of on-tool testing that characterizes these extension ranges can cause wafers to be mishandled or broken within the processing equipment.

General description

      The disclosed method is a test method to detect, measure, and determine robot system control instabilities. The method evaluates robotic system performance prior to placing any product or test wafers at risk of loss. Evaluation is also performed on a periodic maintenance schedule. Qualitative and quantitative steps measure defects and assess risk.

              The disclosed method includes a harmonic vibration susceptibility check to determine the adequacy of the stability margin of the design under test.

Advantages

              The disclosed method provides advantages, including:

•             Improved functionality due to providing a test to detect, measure, and determine robot system control instabilities

Detailed description

              The disclosed method is a test methodology for detecting the control stability in a wafer handling robotic system. This method includes the system harmonic vibration test susceptibility check. The test is performed using the following steps:

1.   Take manual control of the system via a remote control device, such as a teach pendant or a laptop with a serial port control, then start an extension of the arm and end effector in the radial direction at slow speed. Slower speeds help to visual detect changes in theta (tangential direction) movements.

2.   Move through entire extension distance, recording visual observations while attempts are made to induce harmonic resonance at the critical extension positions/points (see Figure 2). Force is applied perpendicular to the test area moving in the X/Y plane by tapping with finger or other instrument (see Figure 3). After force is applied, as short waiting period (~30 seconds) is required to determine whether harmonic movement self-sustains or dampens out over time.

3.   All radial positions/ranges that result in excitation of harmonic resonance are recorded and motor error encoder data are collected for analysis/diagnosis and comparison against visual observ...