Apparatus and methods for semiconductor wafer testing

Claim 2

In an automatic system for testing semiconductor wafers, wafer handling stage means including a platform for carrying a semiconductor wafer, mounting means for mounting said platform for rotation about a central axis and for translation of said platform orthogonal to a major surface thereof, platform drive means coupled to said mounting means to drive said platform between a wafer test position and a wafer load position, and stage drive means coupled to said mounting means for rotating said platform to accurately located angular test positions; and probe handling means including carriage means for carrying a test probe parallel to the major surface of a wafer on said platform and carriage drive means for translating said carriage means between a parked position in which a test probe thereon is positioned adjacent and clear of said platform and accurately located test positions along a radius of said platform.

Claim 3

The system of claim 1, wherein said carriage means is adapted to carry a test probe which includes at least one test probe element for contacting or approaching the surface of a semiconductor wafer; and said carriage means includes a probe arm for carrying a test probe; arm mounting means for mounting said probe arm in a cantilevered manner at one end for translation orthogonal to said platform between probe up and probe down positions; and probe drive means coupled to said probe arm to drive said probe arm between said probe down and probe up positions.

Claim 4

The system of claim 1, further comprising probe location sensor means associated with said carriage means for sensing when said test probe means is in said parked position; platform position sensor means associated with said wafer handling stage means for sensing when said platform is in said wafer test position; control means coupled to said platform and stage drive means for controlling the operation thereof; and inhibit means coupled between said control means and said platform -and stage drive means and being coupled to said probe position and. platform position sensor means for sensing the state thereof and for inhibiting operation of said platform drive means by said control means except when said probe position sensor means senses that said carriage means is in said parked position and for inhibiting operation of said stage drive means by said control means except when said platform position sensor means senses that said platform is in said wafer test position.

Claim 5

The system of claim 2, further comprising probe position sensor means associated with said carriage means for sensing when said test probe means is in said parked position; platform position sensor means associated with said stage means for sensing when said platform is in said wafer test position; and probe status sensor means for sensing when said probe arm is in said probe up position; control means coupled to all said drive means for controlling the operation thereof; and inhibit means coupled between said control means and all of said drive means and being coupled to all said sensor means for sensing the state thereof and for inhibiting operation of said platform drive means by said control means except when said probe position sensor means senses that said carriage means is in said parked position, for inhibiting operation of said stage drive means by said control means except when said platform position sensor means senses that said platform is in said wafer test position, and for inhibiting operation of both said stage and carriage drive means except when said probe status sensor senses that said probe arm is in said probe up position.

Claim 6

The system of claim 3 or claim 4, wherein said stage drive means and said carriage drive means each include a drive control circuit providing an output signal on a drive busy lead that indicates when said associated drive means is busy, said inhibit means is coupled to said drive busy leads and further performs the function of inhibiting operation of said probe drive means to lower said test probe means when either of said drive busy leads indicates that said associated drive means is busy.

Claim 8

The system of claim 6, further comprising probe position sensor means associated with said carriage means for sensing when said test probe means is in said parked position; platform position sensor means associated with said stage means for sensing when said platform is in said wafer test position; door sensor means for sensing when said access door is in said open position; control means coupled to said platform and stage drive means and said door drive means for controlling the operation thereof; and inhibit means coupled between said control means and said platform and stage drive means and said door drive means and being coupled to said probe position and platform position sensor means and said door sensor means for sensing the state thereof and for inhibiting operation of said platform drive means by said control means except when said probe position sensor means senses that said carriage means is in said parked position and said door sensor means senses that said door is in said open position and for inhibiting operation of said carriage drive means and said door drive means by said control means except when said platform position sensor means senses that said platform is in said wafer test position.

Claim 10

The system of claim 8, wherein said piston is a hollow piston with the interior thereof communicating with a source of vacuum; said platform includes an arrangement of interconnected grooves formed in a top face thereof and an central aperture extending through said platform to communicate with the interior of said piston to couple vacuum to said grooves.

Claim 11

The system of claim 8, further comprising a base plate; said hollow housing being mounted on said base plate and having a fluid sealing means therebetween to prevent escape of fluid from the interior of said housing at the mounting interface; fluid sealing means extending between an outer wall of said rotor and an inner wall of said housing to prevent escape of fluid from the interior of said housing between said respective walls; said piston being mounted for translation within said rotor with a fluid tight sealing arrangement between the outer wall of said piston and the inner wall of said rotor; and means communicating fluid under pressure through said base plate to the interior of said housing to drive said piston.

Claim 12

The system of claim 10, wherein said piston is a hollow piston; a hollow tube is mounted to said base plate at one end at a position concentric with said piston and extending into the hollow interior thereof; a fluid sealing means is interposed between and interior wall of said piston and the exterior of said hollow tube to provide fluid pressure isolation between the interior of said piston and the interior of said housing; a channel being provided in said base and communicating with said hollow tubing to supply vacuum to said interior of said piston; said platform includes an arrangement of interconnected grooves formed in a top face thereof and an central aperture extending through said platform to communicate with the interior of said piston to couple said vacuum therein to said grooves.

Claim 14

The system of claim 12, further comprising a position marker carried on an exterior surface of said piston for indicating when said piston is in a test position such that said platform is in said wafer test position; said rotor having a window through the wall thereof which is positioned opposite said position marker on said piston when said rotor is in said home position; and optical sensor means mounted in said housing opposite said window in said wall of said rotor for sensing when said piston is in said test position.

Claim 15

The system of claims 6 or any of claims 7 to 13 when appendant to claim 6 further comprising a ' 'protective shroud mounted within said light tight surface defining an opening having generally the same geometric shape as said platform and being dimensioned to have a marginal edge portion contacted by a marginal edge portion of said platform as it travels from the wafer test position toward the wafer load position so that said shroud will thereafter travel with said platform, said shroud having sidewalls extending from said top surface toward said access door to block access to regions under said platform over a major portion of the peripheral area of said platform.

Claim 17

A stage for carrying a workpiece and having the capability of translating said workpiece verti- catty between a stage down and a stage up position and of rotating said workpiece about a central axis of said stage, said stage comprising a hollow cylindrical housing, a hollow cylindrical rotor mounted within said housing and being carried on a pair of upper and lower bearing assemblies to provide :ree rotary motion of said rotor within said housing, a cylindrical piston mounted within said rotor and having one end thereof extending above said rotor and carrying a platform for said workpiece thereon, said piston being keyed to said rotor with a cooperating key and keyway arrangement for rotation of said piston with said rotor; a platform drive means communicating with said piston to drive said piston out of and into said rotor to translate said platform between said stage up and said stage down positions; a stage drive means communicating with said rotor to produce rotation thereof within said housing.

Claim 18

A stage for carrying a workpiece and having the capability of translating said workpiece verti- catty between a stage down and a stage up position and of rotating said workpiece about a central axis of said stage, said stage comprising a hollow cylindrical housing, a hollow cylindrical rotor mounted within said housing and being carried on a pair of upper and lower bearing assemblies to provide :ree rotary motion of said rotor within said housing, a cylindrical piston mounted within said rotor and having one end thereof extending above said rotor and carrying a platform for said workpiece thereon, said piston being keyed to said rotor with a cooperating key and keyway arrangement for rotation of said piston with said rotor; a platform drive means communicating with said piston to drive said piston out of and into said rotor to translate said platform between said stage up and said stage down positions; a stage drive means communicating with said rotor to produce rotation thereof within said housing.

Claim 19

The system of claim 16, wherein said piston is a hollow piston with the interior thereof communicating with a source of vacuum; said platform includes an arrangement of interconnected grooves formed in a top face thereof and an central aperture extending through said platform to communicate with the interior of said piston to couple vacuum to said grooves to hold said workpiece on said platform.

Claim 20

The system of claim 16, further comprising a base plate; said hollow housing being mounted on said base plate and having a fluid sealing means therebetween to prevent escape of fluid from the interior of said housing at the mounting interface; fluid sealing means extending between an outer wall of said rotor and an inner wall of said housing to prevent escape of fluid from the interior of said housing between said respective walls; said piston being mounted for translation within said rotor with a fluid tight sealing arrangement between the outer wall of said piston and the inner wall of said rotor; and means communicating fluid under pressure through said base plate to the interior of said housing to drive said piston.

Claim 21

The system of claim 18, wherein said piston is a hollow piston; a hollow tube is mounted to said base plate at one end at a position concentric with said piston and extending into the hollow interior thereof: a fluid sealing means is interposed between and interior wall of said piston and the exterior of said hollow tube to provide fluid pressure isolation between the interior of said piston and the interior of said housing; a channel being provided in said base and communicating with said hollow tubing to supply vacuum to said interior of said piston; said platform includes an arrangement of interconnected grooves formed in a top face thereof and a central aperture extending through said platform to communicate with the interior of said piston to couple said vacuum therein to said grooves to hold said workpiece on said platform.

Claim 23

The system of claim 20, further comprising a position marker carried on an exterior surface of said piston for indicating when said piston is in a test position such that said platform is in said wafer test position; said rotor having a window through the wall thereof which is positioned opposite said position marker on said piston when said rotor is in said home position; and optical sensor means mounted in said housing opposite said window in said wall of said rotor for sensing when said piston is in said test position.

Claim 24

In a method for detecting the position coordinates of the center of a substantially circular semiconductor wafer resting on a platform capable of rotating about a central axis defining the origin of an r,e coordinate system and for determining the diameter of said wafer, the steps of: disposing a sensor above said platform; moving said sensor along a first path which intersects said wafer at a first circular edge portion thereof; registering the r1,e1 position coordinates of said sensor when it detects a first edge point of said wafer; moving said sensor along a second path which intersects said wafer at a second circular edge portion thereof; registering the r2,82 position coordinates of said sensor when it detects a second edge point of said wafer; moving said sensor along a third path which intersects said wafer at a third circular edge portion thereof; registering the r3,e3 position coordinates of said sensor when it detects a third edge point of said wafer; calculating the rc,ec coordinates of the center of said wafer by finding the coordinates of intersection of two lines which bisect the two chords of a circle defined by the three edge points of said wafer; and calculating the displacement between said rc,ec coordinates and the r,e coordinates of one of said three edge points as the radius of said wafer.

Claim 25

In a method for detecting the position coordinates of the center of a substantially circular semiconductor wafer resting on a platform capable of rotating about a central axis defining the origin of an r,e coordinate system and for determining the diameter of said wafer, the steps of: disposing a sensor above said platform; moving said sensor along a first path which intersects said wafer at a first circular edge portion thereof; registering the r1,e1 position coordinates of said sensor when it detects a first edge point of said wafer; moving said sensor along a second path which intersects said wafer at a second circular edge portion thereof; registering the r2,82 position coordinates of said sensor when it detects a second edge point of said wafer; moving said sensor along a third path which intersects said wafer at a third circular edge portion thereof; registering the r3,e3 position coordinates of said sensor when it detects a third edge point of said wafer; calculating the rc,ec coordinates of the center of said wafer by finding the coordinates of intersection of two lines which bisect the two chords of a circle defined by the three edge points of said wafer; and calculating the displacement between said rc,ec coordinates and the r,e coordinates of one of said three edge points as the radius of said wafer.

Claim 26

In an automatic system for performing sheet resistivity testing on surface layers of semiconductor wafers, wafer handling stage means including a platform for carrying a semiconductor wafer, mounting means for mounting said platform for rotation about a central axis and for translation of said platform orthogonal to a major surface thereof, platform- drive means coupled to said mounting means to drive said platform between a wafer test position and a wafer -load position, and stage drive means coupled to said mounting means for rotating said platform to accurately located angular test positions; probe handling means including carriage means for carrying a test probe parallel to the major surface of a wafer on said platform and carriage drive means for translating said carriage means between a parked position in which a test probe thereon is positioned adjacent and clear of said platform and accurately located test positions along a radius of said platform, said carriage means being adapted to carry a resistivity test probe which includes test probe element for contacting the surface of a semiconductor wafer and including a probe arm for carrying said test probe, arm mounting means for mounting said probe arm in a cantilevered manner at one end for translation orthogonal to said platform between probe up and probe down positions, and probe drive means coupled to said probe arm to drive said probe arm between said probe down and probe up positions; a light tight housing surrounding said platform including an access door therein facing said platform and positioned intermediate said wafer load position and said wafer test position of said platform, means mounting said access door for translation between a closed position and an open position which permits said platform to translate between said wafer load and wafer test positions, and door drive means for driving said door between said open and closed positions; and a sensor arrangement including probe location sensor means associated with said carriage means for sensing when said test probe is in said parked position, probe status sensor means associated with said probe arm for sensing when said test probe is in said probe up position, platform position sensor means associated with said wafer handling stage means for sensing when said platform is in said wafer test position, door position sensor means for sensing when said door is in an open position.

Claim 27

In an automatic system for performing sheet resistivity testing on surface layers of semiconductor wafers, wafer handling stage means including a platform for carrying a semiconductor wafer, mounting means for mounting said platform for rotation about a central axis and for translation of said platform orthogonal to a major surface thereof, platform- drive means coupled to said mounting means to drive said platform between a wafer test position and a wafer -load position, and stage drive means coupled to said mounting means for rotating said platform to accurately located angular test positions; probe handling means including carriage means for carrying a test probe parallel to the major surface of a wafer on said platform and carriage drive means for translating said carriage means between a parked position in which a test probe thereon is positioned adjacent and clear of said platform and accurately located test positions along a radius of said platform, said carriage means being adapted to carry a resistivity test probe which includes test probe element for contacting the surface of a semiconductor wafer and including a probe arm for carrying said test probe, arm mounting means for mounting said probe arm in a cantilevered manner at one end for translation orthogonal to said platform between probe up and probe down positions, and probe drive means coupled to said probe arm to drive said probe arm between said probe down and probe up positions; a light tight housing surrounding said platform including an access door therein facing said platform and positioned intermediate said wafer load position and said wafer test position of said platform, means mounting said access door for translation between a closed position and an open position which permits said platform to translate between said wafer load and wafer test positions, and door drive means for driving said door between said open and closed positions; and a sensor arrangement including probe location sensor means associated with said carriage means for sensing when said test probe is in said parked position, probe status sensor means associated with said probe arm for sensing when said test probe is in said probe up position, platform position sensor means associated with said wafer handling stage means for sensing when said platform is in said wafer test position, door position sensor means for sensing when said door is in an open position.

Claim 28

The system of claim 23, further comprising control circuit means coupled to said platform drive means, said stage drive means, said carriage drive means, said probe drive means and said door drive means for controlling the operation of all of said drive means in response to input control signals; and inhibit circuit means coupled to said sensor arrangement and to said control circuit means for inhibiting operation of said- platform drive means except when said probe position sensor means senses that said carriage means is in said parked position and said door position sensor senses that said door is in an open position, for inhibiting operation of said carriage drive means by said control means except when said platform position sensor means senses that said platform is in said wafter test position and said probe status sensor means senses that said probe arm is in a probe arm up status, for inhibiting operation of said stage drive means except when said probe arm up status sensor senses that said probe arm is in a probe arm up status, and for inhibiting operation of said door drive means except when said platform position sensor senses that said platform is in said wafer test position.

Claim 29

The system of claim 24, wherein said control circuit means includes a separate drive control circuit for each of said stage drive means and said carriage drive means and each of said control circuits provides an output signal on a drive busy lead that indicates when said associated drive means is busy, said inhibit circuit is coupled to said drive busy leads and further performs the function of inhibiting operation of said probe drive means to lower said test probe means when either of said drive busy leads indicates that said associated drive means is busy.

Claim 31

The system of claim 26, wherein said piston is a hollow piston with the interior thereof communicating with a source of vacuum; said platform includes an arrangement of interconnected grooves formed in a top face thereof and an central aperture extending through said platform to communicate with the interior of said piston to couple vacuum to said grooves.

Claim 32

The system of claim 26, further comprising a base plate; said hollow housing being mounted on said base plate and having a fluid sealing means therebetween to prevent escape of fluid from the interior of said housing at the mounting interface; fluid sealing means extending between an outer wall of said rotor and an inner wall of said housing to prevent escape of fluid from the interior of said housing between said respective walls; said piston being mounted for translation within said rotor with a fluid tight sealing arrangement between the outer wall of said piston and the inner wall of said rotor; and means communicating fluid under pressure through said base plate to the interior of said housing to drive said piston.

Claim 33

The system of claim 28, wherein said piston is a hollow piston; a hollow tube is mounted to said base plate at one end at a position concentric with said piston and extending into the hollow interior thereof; a fluid sealing means is interposed between and interior wall of said piston and the exterior of said hollow tube to provide fluid pressure isolation between the interior of said piston and the interior of said housing; a channel being provided in said base and communicating with said hollow tubing to supply vacuum to said interior of said piston; said platform includes an arrangement of interconnected grooves formed in a top face thereof and an central aperture extending through said platform to communicate with the interior of said piston to couple said vacuum therein to said grooves.

Claim 35

The system of claim 30, further comprising a position marker carried on an exterior surface of said piston for indicating when said piston is in a test position such that said platform is in said wafer test position; said rotor having a window through the wall thereof which is positioned opposite said position marker on said piston when said rotor is in said home position; and optical sensor means mounted in said housing opposite said window in said wall of said rotor for sensing when said piston is in said test position.

Claim 37

In a computer controlled machine having a number of mechanical components which move relative to each other under computer control of associated drive means, a plurality of said components having possible positions which conflict with safe movement of other components, sensor means for reporting the positions of said plurality of components, computer means for communicating control command signals to said drive means, and logic means coupled to said sensor means and said computer means for disabling one of said control command signals to one of said drive means when said sensor means reports a component position which conflicts with safe movement of said component associated with said drive means.

Claim 38

In a computer controlled machine having a number of mechanical components which move relative to each other under computer control of associated drive means, a plurality of said components having possible positions which conflict with safe movement of other components, sensor means for reporting the positions of said plurality of components, computer means for communicating control command signals to said drive means, and logic means coupled to said sensor means and said computer means for disabling one of said control command signals to one of said drive means when said sensor means reports a component position which conflicts with safe movement of said component associated with said drive means.

Claim 39

In a method for performing sheet resistivity tests on surface layers of semiconductor wafers, the steps of: disposing a wafer platform in a light tight enclosure having an overhead sliding door; sliding said door to an open position; translating said wafer platform upwards through said open door to a wafer load position to receive a semiconductor wafer thereon; translating said wafer platform downwards through said open door to a wafer test position within said enclosure; sliding said door to a closed position; disposing a resistivity probe over said wafer; rotating said wafer platform to a prearranged angular position coordinate; translating said probe to a prearranged radial position coordinate on said wafer; lowering said probe onto said wafer to make a measurement; raising said probe after completing said measurement; and repeating said rotating, translating, lowering, and raising steps to make measurements on said wafer at a multiplicity of distinct r, 6 coordinates of said wafer.

Claim 40

In a method for performing sheet resistivity tests on surface layers of semiconductor wafers, the steps of: disposing a wafer platform in a light tight enclosure having an overhead sliding door; sliding said door to an open position; translating said wafer platform upwards through said open door to a wafer load position to receive a semiconductor wafer thereon; translating said wafer platform downwards through said open door to a wafer test position within said enclosure; sliding said door to a closed position; disposing a resistivity probe over said wafer; rotating said wafer platform to a prearranged angular position coordinate; translating said probe to a prearranged radial position coordinate on said wafer; lowering said probe onto said wafer to make a measurement; raising said probe after completing said measurement; and repeating said rotating, translating, lowering, and raising steps to make measurements on said wafer at a multiplicity of distinct r, 6 coordinates of said wafer.