Method for maskless particle-beam exposure
For maskless irradiating a target with a beam of energetic electrically charged particles using a pattern definition means with a plurality of apertures and imaging the apertures in the pattern definition means onto a target which moves (v) relative to the pattern definition means laterally to the axis, the location of the image is moved along with the target, for a pixel exposure period within which a distance of relative movement of the target is covered which is at least a multiple of the width (w) of the aperture images as measured on the target, and after said pixel exposure period the location of the beam image is changed, which change of location generally compensates the overall movement of the location of the beam image.
1. A method to position a target using a beam of energetic electrically charged particles, comprising:
providing a pattern definition means having a plurality of apertures transparent to said particles,
illuminating said pattern definition means by means of said beam, which traverses the pattern definition means through said apertures thus forming a patterned beam (pb) consisting of a corresponding plurality of beamlets,
forming said patterned beam into an image on the location of the target, said image comprising the images of at least part of the plurality of apertures, said images of apertures having a first width (w), and at least part of the beam impinging on markers provided on the target which then produce secondary radiation,
moving the target relative to the pattern definition means along a path within an image plane in which the images of apertures are formed, wherein the relative movement of the target covers a distance of advance greater than the first width as measured on the target,
measuring said secondary radiation by a detection system with a suitably high sampling rate, and
adjusting the position of the target in a manner that the secondary radiation as measured obtains an extremal (maximum or minimum) value.
2. The method of claim 1 , wherein the substrate stage moves the target at a continuous speed equaling a speed at which the target is moving during a subsequent exposure process.
3. The method of claim 1 , wherein the markers comprise structures which are part of a multilayer structure, said structures having been formed on the target in at least one foregoing process step.
4. The method of claim 1 , wherein the markers comprise components adapted to produce secondary radiation comprising characteristic Auger electron radiation, and the detection system employs an energy selective detector adapted to detect said Auger radiation.
5. The method of claim 1 , wherein the markers comprise components having a characteristic backscattering yield.
6. The method of claim 1 , comprising a subsequent particle-beam exposure process performed on the target in which the same pattern definition means is used and the target moves relative to the pattern definition means in a corresponding manner.
7. The method of claim 1 , wherein said distance of advance is a multiple of a distance which is covered by the relative movement of the target during a typical pixel exposure period during a subsequent exposure process.