Lithographic apparatus

1. A substrate stage of an immersion type lithographic apparatus arranged to project a patterned radiation beam from a patterning device onto a substrate, the substrate stage being constructed to hold the substrate and comprising:

a sensor constructed and arranged to sense the patterned radiation beam, the sensor comprising:

a transmissive layer, at least partially transmissive to a wavelength of the radiation beam and having a front side facing the incoming radiation beam and a back side opposite the front side, wherein the transmissive layer is positioned and dimensioned to receive substantially all of an aerial image of the projected patterned radiation beam in at least a depth direction;

wherein the back side comprises a sensor mark positioned to receive at least a portion of the radiation beam transmitted through the front side of the layer.

2. A substrate stage according to claim 1 , wherein the transmissive layer comprises a first transmissive layer and a second transmissive layer.

3. A substrate stage according to claim 1 , wherein the sensor mark is arranged at least partially in a back side of the transmissive layer.

4. A substrate stage according to claim 1 , wherein the back side of the transmissive layer is provided with a substantially non-transmissive layer.

5. A substrate stage according to claim 4 , wherein the sensor mark is arranged at least partially in the non-transmissive layer.

6. A substrate stage according to claim 1 , wherein the front side of the transmissive layer comprises a coating selected to repel an immersion liquid to be used in the lithographic apparatus.

7. A substrate stage according to claim 6 wherein the coating is a hydrophobic coating.

8. A substrate stage according to claim 6 , wherein the coating has a refractive index between about 1.3 and 1.8, and a thickness between about 0.1 and 1.5 μm.

9. A substrate stage according to claim 1 , wherein an index of refraction of the transmissive layer is substantially the same as an index of refraction of an immersion fluid to be used with the lithographic apparatus.

10. A substrate stage according to claim 1 , wherein the transmissive layer is a transmissive plate and the mark comprises a grating.

11. A substrate stage according to claim 1 , wherein the transmissive layer comprises a hydrophilic material.

12. A substrate stage according to claim 1 , wherein the transmissive layer has a thickness between about 0.01 and 5 μm.

13. A substrate stage according to claim 12 , wherein the transmissive layer has a thickness between 1 and 3 μm.

14. A substrate stage according to claim 1 , wherein an index of refraction of the transmissive layer is between about 1.3 and 1.8.

15. A lithographic apparatus comprising:

a projection system configured to project a patterned radiation beam from a patterning device onto a substrate:

an immersion liquid system for providing an immersion liquid between the patterning device and the substrate;

a substrate stage constructed to hold the substrate;

a sensor, positioned in the substrate stage, and constructed and arranged to sense the patterned radiation beam, the sensor comprising:

a transmissive layer, at least partially transmissive to a wavelength of the radiation beam and having a front side facing the incoming radiation beam and a back side opposite the front side wherein the transmissive layer is positioned and dimensioned to receive substantially all of an aerial image of the projected patterned radiation beam, and

wherein the back side comprises a sensor mark positioned to receive at least a portion of the radiation beam transmitted through the front side of the layer.