Method and device for determining information relating to the mass of a semiconductor wafer

1. A method of determining information relating to the mass of a semiconductor wafer comprising:

loading the semiconductor wafer on to a measurement area of a weighing device having weight compensation means arranged to compensate for a predetermined weight loaded on to the measurement area;

loading a reference mass on to the measurement area of the weighing device;

generating measurement output indicative of a difference between the weight of the semiconductor wafer and the predetermined weight; and

using the measurement output to determine information relating to the mass of the semiconductor wafer;

wherein the density of the reference mass is within ±20%, or within ±10%, or within ±5% of the density of a semiconductor substrate of the semiconductor wafer.

2. The method according to claim 1 , wherein:

the weight compensation means is arranged to compensate for part of the weight of the semiconductor wafer; and

the measurement output is indicative of an amount by which the weight of the semiconductor wafer exceeds the compensated part of the weight of the semiconductor wafer.

3. The method according to claim 1 , wherein:

the weighing device comprises a pre-loaded weighing device; and

the measurement output is indicative of a difference between the weight force of the semiconductor wafer and the pre-loading force.

4. The method according to claim 3 , wherein the weighing device is pre-loaded by a reference mass.

5. The method according to claim 4 , wherein the method comprises determining the mass of the semiconductor wafer based on the measurement output and on the known mass of the reference mass.

6. The method according to claim 1 , wherein the measurement output is used to determine the mass of the semiconductor wafer.

7. The method according to claim 1 , wherein the method further comprises:

generating measurement output indicative of a difference between the weight of the reference mass and the predetermined weight.

8. The method according to claim 7 , wherein the method comprises using the known mass of the reference mass and the measurement outputs for the semiconductor wafer and for the reference mass to determine the mass of the semiconductor wafer.

9. The method according to claim 7 , wherein the method comprises monitoring an evolution of the measurement output for the reference mass over time.

10. The method according to claim 7 , wherein the method comprises:

performing a measurement on the semiconductor wafer at a time t=t W ;

performing one or more measurements on the reference mass at a time or times other than t=t W ; and

calculating an estimate of a measurement on the reference mass at the time t=t W based on the one or more measurements on the reference mass at the time or times other than t=t W .

11. The method according to claim 1 , wherein the method comprises determining the mass of the semiconductor wafer based on the measurement output and on the known predetermined weight.

12. The method according to claim 1 , wherein the method comprises carrying out a measurement on the semiconductor wafer after the semiconductor wafer has been processed and wherein the measurement output is used to determine a change in the mass of the semiconductor wafer caused by the processing.

13. The method according to claim 12 , wherein the method further comprises carrying out a measurement on the semiconductor wafer before it has been processed and wherein the measurement outputs from the before and after measurements are used to determine the change in the mass of the semiconductor wafer caused by the processing.

14. The method according to claim 1 , wherein the weighing device comprises a balance having a counterweight arranged to pre-load the balance.

15. The method according to claim 1 , wherein the weight compensation means compensates for at least 80%, or at least 90%, or at least 95% of the weight of the semiconductor wafer.

16. The method according to claim 1 , wherein:

the semiconductor wafer is one of a plurality of semiconductor wafers having weights within a weight range; and

a weighing range of the weighing device is set based on the weight range.

17. The method according to claim 1 , wherein a correction is made for the buoyancy exerted on the semiconductor wafer by the atmosphere.

18. The method according to claim 1 , wherein a correction is made for the buoyancy exerted on part of the weighing device by the atmosphere.

19. The method according to claim 1 , wherein the method comprises calibrating the weighing device based on the measurement outputs for two known masses.

20. A method of determining information relating to the mass of a semiconductor wafer comprising:

loading the semiconductor wafer on to a measurement area of a weighing device having weight compensation means arranged to compensate for a predetermined weight loaded on to the measurement area;

loading a reference mass on to the measurement area of the weighing device;

generating measurement output indicative of a difference between the weight of the semiconductor wafer and the predetermined weight; and

using the measurement output to determine information relating to the mass of the semiconductor wafer; wherein the reference mass is made of the same material as a semiconductor substrate of the semiconductor wafer.

21. A method of determining information relating to the mass of a semiconductor wafer comprising:

loading the semiconductor wafer on to a measurement area of a weighing device having weight compensation means arranged to compensate for a predetermined weight loaded on to the measurement area;

loading a reference mass on to the measurement area of the weighing device;

generating measurement output indicative of a difference between the weight of the semiconductor wafer and the predetermined weight; and

using the measurement output to determine information relating to the mass of the semiconductor wafer; wherein the reference mass is a semiconductor wafer.

22. A method of determining information relating to the mass of a semiconductor wafer comprising:

loading the semiconductor wafer on to a measurement area of a weighing device having weight compensation means arranged to compensate for a predetermined weight loaded on to the measurement area;

loading a reference mass on to the measurement area of the weighing device;

generating measurement output indicative of a difference between the weight of the semiconductor wafer and the predetermined weight; and

using the measurement output to determine information relating to the mass of the semiconductor wafer; wherein:

the reference mass comprises a first material having a first density and a second material having a second density; and

the combined density of the reference mass is chosen based on the density of a semiconductor substrate of the semiconductor wafer.

23. A weighing device for determining information relating to the mass of a semiconductor wafer, the weighing device comprising:

a support for loading the semiconductor wafer on to;

weight compensation means arranged to compensate for a predetermined weight loaded on to the support;

a measurement device arranged to generate measurement output indicative of a difference between the weight of the semiconductor wafer and the predetermined weight;

a reference mass; and

the support including a reference mass support onto which the reference mass can be loaded and unloaded;

wherein the reference mass is a semiconductor wafer.

24. The weighing device according to claim 23 , wherein:

the weight compensation means is arranged to compensate for part of the weight of the semiconductor wafer; and

the measurement device is arranged to generate measurement output indicative of an amount by which the weight of the semiconductor wafer exceeds the compensated part of the weight of the semiconductor wafer.

25. The weighing device according to claim 23 , wherein:

the weight compensation means comprises pre-loading means for applying a pre-loading force to the measurement device; and

the measurement device is arranged to generate measurement output indicative of a difference between the weight of the semiconductor wafer and the pre-loading force.

26. The weighing device according to claim 23 , wherein the weighing device comprises a balance having a counterweight arranged to pre-load the measurement device.

27. The weighing device according to claim 23 , wherein the weight compensation means is arranged to compensate for at least 80%, or at least 90%, or at least 95% of the weight force of the semiconductor wafer.

28. The weighing device according to claim 23 , wherein the support has a wafer-receiving surface for loading the semiconductor wafer onto and wherein the support and/or the reference mass are configured so that the reference mass can be loaded and unloaded onto the support without interfering with the wafer-receiving surface.

29. A weighing device for determining information relating to the mass of a semiconductor wafer, the weighing device comprising:

a support for loading the semiconductor wafer on to;

weight compensation means arranged to compensate for a predetermined weight loaded on to the support;

a measurement device arranged to generate measurement output indicative of a difference between the weight of the semiconductor wafer and the predetermined weight;

a reference mass; and

the support including a reference mass support onto which the reference mass can be loaded and unloaded; wherein the reference mass is made of a semiconductor material.

30. A weighing device for determining information relating to the mass of a semiconductor wafer, the weighing device comprising:

a support for loading the semiconductor wafer on to;

weight compensation means arranged to compensate for a predetermined weight loaded on to the support;

a measurement device arranged to generate measurement output indicative of a difference between the weight of the semiconductor wafer and the predetermined weight;

a reference mass; and

the support including a reference mass support onto which the reference mass can be loaded and unloaded; wherein the reference mass comprises a first material having a first density and a second material having a second density.

31. A weighing device for determining information relating to the mass of a semiconductor wafer, the weighing device comprising:

a support for loading the semiconductor wafer on to;

weight compensation means arranged to compensate for a predetermined weight loaded on to the support;

a measurement device arranged to generate measurement output indicative of a difference between the weight of the semiconductor wafer and the predetermined weight;

a reference mass; and

the support including a reference mass support onto which the reference mass can be loaded and unloaded; wherein the reference mass has a through-hole in which the support is received so that the reference mass is positioned around the support.