Pellicle and pellicle assembly
A pellicle suitable for use with a patterning device for a lithographic apparatus. The pellicle comprising at least one breakage region which is configured to preferentially break, during normal use in a lithographic apparatus, prior to breakage of remaining regions of the pellicle. At least one breakage region comprises a region of the pellicle which has a reduced thickness when compared to surrounding regions of the pellicle.
1. A pellicle failure detection apparatus comprising a sensor assembly arranged to detect an electrical property associated with a pellicle situated on a pellicle frame, wherein the electrical property associated with the pellicle is indicative of actual or imminent damage to the pellicle.
2. The pellicle failure detection apparatus of claim 1 , wherein the sensor assembly is configured to detect a change in the electrical property and the change in the electrical property is indicative of actual or imminent damage to the pellicle.
3. The pellicle failure detection apparatus of claim 1 , wherein the electrical property is electrical resistance.
4. The pellicle failure detection apparatus of claim 1 , wherein the sensor assembly is further configured to detect a change in optical transmission or optical reflection of radiation by the pellicle.
5. The pellicle failure detection apparatus of claim 1 , wherein the sensor assembly is further configured to detect a change in acoustic transmission or acoustic reflection of sound waves by the pellicle.
6. The pellicle failure detection apparatus of claim 1 , wherein the sensor assembly comprises a strain gauge configured to measure strain which a pellicle undergoes.
7. The pellicle failure detection apparatus of claim 1 , further comprising a pellicle suitable for use with a patterning device for a lithographic apparatus, the pellicle comprising:
at least one electrically conductive layer; and
a plurality of electrical contacts at which an electrical connection to the electrically conductive layer can be established, thereby allowing electrical resistance of the electrically conductive layer between contacts to be measured.
8. The pellicle failure detection apparatus of claim 7 , further comprising a sensor connected to at least two of the electrical contacts on the pellicle, the sensor configured to measure the electrical resistance between the electrical contacts.
9. A pellicle suitable for use with a patterning device for a lithographic apparatus, the pellicle comprising:
at least one electrically conductive layer; and
a plurality of electrical contacts at which an electrical connection to the electrically conductive layer can be established, thereby allowing the electrical resistance of the electrically conductive layer between contacts to be measured.
10. The pellicle of claim 9 , wherein the at least one electrically conductive layer is a substantially transmissive of electromagnetic radiation.
11. The pellicle of claim 9 , wherein the contacts are located at a perimeter portion of the pellicle which lies within an exposure field but which does not overlie a patterned region produced by the patterning device.
12. The pellicle of claim 9 , wherein at two electrical contacts are located at opposite sides of the pellicle to measure resistance across a portion of an exposure field.
13. The pellicle of claim 9 , wherein electrical pathways between electrical contacts are electrically isolated from other parts of the pellicle.
14. The pellicle of claim 9 , further comprising at least one breakage region in a transmissive portion of the pellicle, the at least breakage region configured to preferentially break, during normal use in a lithographic apparatus, prior to breakage of a remaining region of the pellicle.
15. The pellicle of claim 9 , comprising a first layer having a first ductility; a second layer having a second ductility; and a third layer having a third ductility, wherein the third layer is situated in between the first and second layers and wherein the third ductility is less than the first ductility and less than the second ductility.
16. A pellicle failure detection apparatus comprising:
the pellicle of claim 9 ; and
a sensor connected to at least two of the electrical contacts on the pellicle, the sensor being configured to measure the resistance between the electrical contacts.
17. The pellicle failure detection apparatus of claim 16 , further comprising a sensor assembly configured to detect a change in optical transmission or optical reflection of radiation by the pellicle.
18. A pellicle assembly suitable for use with a patterning device for a lithographic apparatus, the pellicle assembly comprising:
a frame configured to support a pellicle;
a pellicle attached to the frame, wherein the pellicle comprises at least one electrically conductive layer; and
a current source connected across the at least one electrically conductive layer and configured to generate an electrical current through the at least one electrically conductive layer, wherein the current source is configured to generate a current which heats the pellicle through resistive heating such that the temperature of the pellicle is greater than a threshold temperature.
19. The pellicle assembly of claim 18 , wherein the threshold temperature is about 120 degrees Celsius.
20. The pellicle assembly of claim 18 , wherein the current source is configured to generate a substantially continuous current through the at least one electrically conductive layer.