Method and apparatus for measuring a surface profile of a sample
View Patent ↗In order to measure a surface profile of a sample, an imprint of the surface profile to be examined is produced in a transfer material. The sample contains processed semiconductor material and is in particular a patterned semiconductor wafer or part of a patterned semiconductor wafer. The transfer material is deformable and curable under suitable ambient conditions. The transfer material may be a thermoplastic material or a material which is deformable as desired after application on a substrate and cures in one case by means of irradiation with photons having a suitable wavelength or alternatively heating. The transfer material may be configured in such a way that the imprint produced is the same size as or alternatively of smaller size than the surface profile. The imprint produced is subsequently measured by known methods.
1. A method of fabricating an integrated circuit comprising:
bringing at least a portion of a sample surface of a patterned semiconductor wafer comprising a surface profile into contact with a transfer material that is deformable and curable under suitable ambient conditions such that an imprint of the portion is transferred into the transfer material;
separating the sample surface and the transfer material wherein the imprint is uncovered;
measuring dimensions of the uncovered imprint; and
evaluating, from the dimensions of the uncovered imprint, dimensions of the surface profile of the semiconductor wafer.
2. The method of claim 1 , wherein the layer thickness of the transfer material corresponds to at least 1.5 times a maximum height difference Δz within the surface profile, the maximum height difference Δz corresponding to the distance between a highest projecting region and a deepest depression, said distance being determined perpendicularly to the sample surface.
3. The method of claim 1 , wherein the transfer material comprises a thermoplastic polymer.
4. The method of claim 3 , wherein the thermoplastic polymer is selected from the group comprising polymethyl methacrylate, polycarbonate, polyester and novolak-resin-based polymers.
5. The method of claim 1 , further comprising:
heating the transfer material to a temperature at which the transfer material becomes soft, prior to bringing the sample surface into contact with the transfer material; and
cooling the transfer material to a temperature at which the transfer material becomes hard, after bringing the sample surface into contact with the transfer material.
6. The method of claim 1 , wherein the transfer material is deformable during the process of bringing it into contact with the sample surface and is curable under the action of heat.
7. The method of claim 6 , further comprising heating the transfer material to a temperature at which the transfer material cures, after bringing the sample surface into contact with the transfer material.
8. The method of claim 1 , wherein the transfer material comprises a material which is deformable during the process of bringing it into contact with the sample surface and is curable under the action of photon radiation.
9. The method of claim 8 , wherein the transfer material comprises a material which is curable under the action of UV radiation.
10. The method of claim 8 , further comprising irradiating the transfer material with photons during the step of bringing the sample surface into contact with the transfer material so that the transfer material cures.
11. The method of claim 1 , further comprising:
providing a substrate; and
applying the layer made of the transfer material on the substrate, which are carried out before the step for bringing the sample surface into contact with the transfer material, wherein while bringing the sample surface into contact with the transfer material, the transfer material applied on the substrate is brought into contact with the sample surface.
12. The method of claim 11 , further comprising inserting a pressure on the semiconductor wafer and the substrate during the bringing-into-contact step.
13. The method of claim 11 , wherein the substrate is a silicon wafer.
14. The method of claim 11 , wherein the semiconductor wafer has the same size as the substrate.
15. The method of claim 11 , wherein the semiconductor wafer is larger than the substrate.
16. The method of claim 11 , further comprising removing the transfer material from the substrate after the measuring the imprint, so that the substrate can be used for a further method.
17. The method of claim 1 , wherein the semiconductor wafer is a patterned silicon wafer.
18. The method of claim 1 , wherein the step for measuring the imprint is effected by means of one of the group comprising a scanning probe method, a scattering method, an ellipsomectric method, scanning electron microscopy, and microscopy using focused ion beams.
19. The method of claim 1 , wherein the transfer material is configured in such a way that a horizontal and a vertical dimension within the surface profile are transferred with the same size into the imprint.
20. The method of claim 1 , wherein the transfer material is configured in such a way that a horizontal and a vertical dimension in the imprint is smaller than within the surface profile.
21. The method of claim 7 , wherein the transfer material is shrunk during curing.