Method and fine-control collimator for accurate collimation and precise parallel alignment of scanned ion beams

A method of improving ion beam collimation in a hybrid-scan ion implantation system which includes an ion source, an analyzer magnet, a beam scanner scanning the beam within a plane, a coarse collimation device for converting the scanned beam into an approximately-parallel scanned ribbon beam, and a mechanism for passing a workpiece through the scanned ribbon beam at a target plane in a direction generally orthogonal to the direction the beam is scanned and implanting a substantially uniform dose of ions into the workpiece held at that plane, said improved collimation method comprising the steps of:

• defining a reference axis of parallelism in a known orientation relative to the plane at which the workpiece is to be implanted with a dose of ions;
• measuring the error in the direction of the beam centroid with respect to said reference axis within the plane at which the beam is scanned;
• generating a controllable region of magnetic field and an adjustable magnetic field gradient profile in a direction substantially orthogonal to the plane at which the beam is scanned;
• and
• adjusting the magnetic field gradient profile in response to said error measurement of beam centroid direction;
• and
• applying said adjusted magnetic field gradient profile across the breadth of the beam such that said errors in the direction of the beam centroid are substantially eliminated relative to the plane at which the workpiece is to be implanted.

A method of improving the beam collimation and uniformity in a hybrid-scan ion implanter which includes an ion source, an analyzer magnet, a beam scanner scanning the beam within a plane, a coarse collimation device for converting the scanned beam into an approximately parallel-scanned ribbon beam, and a mechanism for passing a plane workpiece through the scanned ribbon beam in a direction generally orthogonal to the direction the beam is scanned, thereby implanting a substantially uniform dose of ions into the workpiece, said method comprising the steps of

• defining an axis in a known orientation to the workpiece to be implanted;
• measuring the error in the direction of the beam centroid with respect to said axis both within the plane and orthogonal to the plane within which the beam is scanned;
• providing a controllable region of magnetic field substantially orthogonal to the plane in which the beam is scanned;
• adjusting the field to vary along the long dimension of the beam envelope in response to the measurement so as to substantially eliminate the errors in direction of the beam centroid, both within said plane and orthogonal to said plane;
• measuring the profile in the dimension in which the beam is scanned of the dose rate provided by the ion beam;
• and
• modifying the waveform with which the scanner scans the ion beam so as to modify said dose rate profile and to cause said dose rate profile to conform more closely with a desired profile.