Method and apparatus for enhancing the accuracy of scanner systems

An optical photoplotter comprising:

• an optical source for generating an exposure beam;
• a platen surface for receiving a substrate;
• a raster scanning means for advancing relative to said substrate an optical beam across a substrate surface in a first direction forming a scan line and for cooperatively advancing relative to said substrate surface said optical beam in a second direction substantially perpendicular to said first direction;
• a signal generator means for generating a plurality of clock signals each of which is phase shifted relative to another such that said clock signals are spaced within a master clock signal period, at least one of said plurality of clock signals being transmitted to said raster scanning means to control the advancement of said optical beam in said first direction;
• a memory means for storing error signals indicative of deviations of said substrate surface from preferred values thereof;
• and
• a controller for transmitting control signals in dependence on said error signals to said signal generator means, said signal generator means being responsive to each of said control signals to transmit one of said plurality of phase-shifted clock signals to said raster scanning means, said transmitted clock signal being selected based on a respective error signal to compensate for corresponding deviations in said substrate surface and substantially avoid deviations in the scan line.

In a photoplotter having a platen defining a surface for receiving a substrate;

• a raster scanning means for advancing relative to said substrate an optical beam across a substrate surface in a first direction forming a scan line;
• a signal generator means for generating a clock signal configured to control the advancement of said optical beam in said first direction;
• a method of compensation for errors in said scan line comprising the steps of:
• generating signals indicative of measured values of platen surface geometry;
• comparing said measured platen surface geometry signal values with signal values corresponding to preferred values of platen surface geometry and generating error value signals, each error value signal being indicative of a respective deviation of said measured platen surface geometry from said preferred signal values of platen surface geometry;
• and
• transmitting control signals to said signal generator means, each control signal corresponding to a respective error value signal to adjust the phase of said clock signal in dependence on the respective error signal magnitude, thereby compensating for deviations in a respective area of said platen surface and substantially avoiding errors in a segment of said scan line.

A method of providing compensation for inaccuracies in a scanning optical system that has a platen for receiving a substrate and a scanning means responsive to a clock signal for advancing relative to said substrate an optical beam across said substrate surface forming a scan line, said method comprising the steps of:

• generating command signal values for registration marks positioned about a substrate surface;
• exposing a calibration substrate to an optical beam so as to image said registration marks therein;
• generating signals indicative of the measured positions of said registration marks in said substrate surface;
• comparing said measured registration mark position signal values with said command position signal values to generate error signals corresponding to deviations of said measured registration mark positions from said command signal value positions;
• and
• generating control signals corresponding to respective error signals, each control signal being selected to adjust the phase of said clock signal in dependence on the magnitude of said respective error signal to compensate for the deviations corresponding to the respective error signal, thereby removing said deviations from a segment of said scan line.

A method of providing compensation for inaccuracies in a scanning optical system that has a platen for receiving a substrate and a scanning means responsive to a clock signal for advancing relative to said substrate an optical beam across said substrate surface forming a scan line, said method comprising the steps of:

• generating command signal values for registration marks positioned about a substrate surface;
• exposing a calibration substrate to an optical beam so as to image said registration marks therein;
• generating signals indicative of the measured position of said registration marks in said substrate surface;
• comparing said measured registration mark position signal values with said command position signal values to generate error signals corresponding to deviations of said measured registration mark positions from said command signal value positions;
• generating control signals to adjust the phase of said clock signal in dependence on said error signal magnitude, and remove said deviations from a segment of said scan line;
• storing said control signals;
• generating signals indicative of a remeasured position of said registration marks in said substrate surface;
• comparing said remeasured registration mark position signal values with said command position signal values to generates new error signals corresponding to deviations of said remeasured registration mark positions from said command signal value positions;
• and
• generating new control signals to adjust the phase of said clock signal in dependence on said new error signal magnitude.

An apparatus for use with an optical scanning system that has a curved platen for receiving a substrate having a surface and a raster scanning means responsive to control signals for advancing relative to said substrate an optical beam across said substrate surface in a first direction forming a scan line, said apparatus comprising:

• a mirror having a curved reflective surface defined by at least a portion of an off axis parabola;
• a positioning means for generating signals indicative of the angular position of said reflective surface for locating said mirror to optically communicate with said substrate surface;
• and
• a means for rotating said curved reflective surface about an axis within an included angle in response to said control signals.