Detection of a position of a wafer within a transfer robot vacuum chamber

A method for detecting a location of a wafer within a transfer robot vacuum chamber (TRVC), the method comprising:

• directing, by an illumination unit that is located outside the TRVC, and at an angle of incidence, a transmitted radiation pattern through a transparent window of the TRVC and towards one or more TRVC reflecting elements located below an upper side of a wafer holding element of a transfer robot located within the TRVC;
• generating, by a sensing unit, one or more detection signals indicative of a received radiation pattern that is reflected from the one or more TRVC reflecting elements;
• the received radiation pattern is received at an angle of reflection that equals the angle of incidence;
• wherein the received radiation pattern is a two dimensional array of spaced apart spots when there is no wafer within the TRVC, (b) is a portion of the two dimensional array of spaced apart spots when the wafer partially blocks the transmitted radiation pattern, and (c) is null when the wafer completely blocks the transmitted radiation pattern;
• and
• detecting, by a location processing circuit, the location of the wafer based on the one or more detection signals.

A non-transitory computer readable medium that stores instructions for:

• directing, by an illumination unit and at an angle of incidence, a transmitted radiation pattern through a transparent window of a transfer robot vacuum chamber (TRVC) and towards one or more TRVC reflecting elements located below an upper side of a wafer holding element of the transfer robot;
• wherein the illumination unit that is located outside the TRVC;
• generating, by a sensing unit, one or more detection signals indicative of a received radiation pattern that is reflected from the one or more TRVC reflecting elements;
• the received radiation pattern is received at an angle of reflection that equals the angle of incidence;
• wherein the received radiation pattern is a two dimensional array of spaced apart spots when there is no wafer within the TRVC, (b) is a portion of the two dimensional array of spaced apart spots when the wafer partially blocks the transmitted radiation pattern, and (c) is null when the wafer completely blocks the transmitted radiation pattern;
• and
• detecting, by a location processing circuit, a location of the wafer based on the one or more detection signals.