Patent ID: 9030675
Filing Date: 2015-05-12
Classification: B82Y,H01J

Abstract:
1. A method for determining a distance between two charged particle beamlets in a multi-beamlet exposure apparatus provided with a sensor comprising a converter element for converting the energy of charged particles into light and a light sensitive detector, the converter element being provided with a sensor surface area provided with a two-dimensional pattern of beamlet blocking and non-blocking regions, the method comprising: scanning a first beamlet over an area of the two-dimensional pattern; receiving light generated by the converter element in response to charged particles being part of the first beamlet transmitted through the two-dimensional pattern; converting the received light into a first signal by means of the light sensitive detector; wherein the method, after scanning the first beamlet over the two-dimensional pattern, further comprises: relatively moving the two-dimensional pattern and the first beamlet with respect to each other over a predetermined distance; scanning a second beamlet over the area of the two-dimensional pattern; receiving light generated by the converter element in response to charged particles being part of the second beamlet transmitted through the two-dimensional pattern; converting the received light into a second signal by means of the light sensitive detector; determining the distance between the first beamlet and second beamlet based on the first signal, the second signal and the predetermined distance.