Optical measurement of step size and plated metal thickness

1. A method of generating three-dimensional (3-D) information of a sample using an optical microscope, the method comprising:

varying the distance between the sample and an objective lens of the optical microscope at pre-determined steps;

capturing an image at each pre-determined step, wherein a first surface of the sample and a second surface of the sample are within a field of view of each of the captured images;

determining a characteristic value of each pixel in each captured image, wherein the characteristic value is intensity, contrast or fringe contrast;

determining, for each captured image, the greatest characteristic value across all pixels in the captured image;

comparing the greatest characteristic value for each captured image to determine if a surface of the sample is present at each pre-determined step;

determining a first captured image that is focused on a first surface of the sample based on the characteristic value of each pixel in each captured image;

determining a second captured image that is focused on a second surface of the sample based on the characteristic value of each pixel in each captured image;

determining a first distance between the first surface and the second surface;

determining a thickness of a semi-transparent layer of the sample; and

determining a thickness of a metal layer of the sample based at least in part on the thickness of the semi-transparent layer wherein the optical microscope includes a stage, wherein the sample is supported by the stage, wherein the optical microscope is adapted to communicate with a computer system, wherein the computer system includes a memory device that is adapted to store each captured image, wherein the optical microscope one of: a confocal microscope, a structured illumination microscope, or an interferometer, and wherein the characteristic value of each pixel one of: intensity, contrast, or fringe contrast.

2. The method of claim 1 ,

wherein the thickness of the metal layer is equal to the difference between the thickness of the semi-transparent layer and the first distance, wherein the first surface is a top surface of a photoresist layer, and wherein the second surface is a top surface of a metal layer.

3. Wherein the thickness of the metal layer is equal to the sum of the thickness of the semi-transparent layer and the first distance, wherein the first surface is a top surface of a passivation layer, and wherein the second surface is a top surface of a metal layer.

4. The method of claim 2 , wherein only a portion of each captured image is used to determine the thickness of the semi-transparent layer of the sample.

5. The method of claim 4 , wherein the portion of each captured image is selectable by an user input.

6. The method of claim 1 , wherein the determining the thickness of the semi-transparent layer comprises:

determining a third captured image that is focused on light reflected from the bottom surface of the semi-transparent layer of the sample based on the characteristic value of each pixel in each captured image; and

determining the location of the bottom surface of the semi-transparent layer based on the location where the third image was captured and the index of refraction of the semi-transparent layer.

7. A method of generating three-dimensional (3-D) information of a sample using an optical microscope, the method comprising:

varying the distance between the sample and an objective lens of the optical microscope at pre-determined steps;

capturing an image at each pre-determined step, wherein a first surface of the sample and a second surface of the sample are within a field of view of each of the captured images;

determining a characteristic value of each pixel in each captured image;

determining, for each captured image, a count of pixels that have a characteristic value within a first range, wherein all pixels that do not have a characteristic value within the first range are not included in the count of pixels;

determining if a surface of the sample is present at each pre-determined step based on the count of pixels for each captured image;

determining a first captured image that is focused on a first surface of the sample based on the characteristic value of each pixel in each captured image;

determining a second captured image that is focused on a second surface of the sample based on the characteristic value of each pixel in each captured image;

determining a first distance between the first surface and the second surface;

determining a thickness of a semi-transparent layer of the sample; and

determining a thickness of a metal layer of the sample based at least in part on the thickness of the semi-transparent layer wherein the optical microscope includes a stage, wherein the sample is supported by the stage, wherein the optical microscope is adapted to communicate with a computer system, wherein the computer system includes a memory device that is adapted to store each captured image, wherein the optical microscope one of: a confocal microscope, a structured illumination microscope, or an interferometer, and wherein the characteristic value of each pixel one of: intensity, contrast, or fringe contrast.

8. The method of claim 7 ,

wherein the thickness of the metal layer is equal to the difference between the thickness of the semi-transparent layer and the first distance, wherein the first surface is a top surface of a photoresist layer, and wherein the second surface is a top surface of a metal layer.

9. The method of claim 7 ,

wherein the thickness of the metal layer is equal to the sum of the thickness of the semi-transparent layer and the first distance, wherein the first surface is a top surface of a passivation layer, and wherein the second surface is a top surface of a metal layer.

10. The method of claim 9 , wherein only a portion of each captured image is used to determine the thickness of the semi-transparent layer of the sample.

11. The method of claim 10 , wherein the portion of each captured image is selectable by an user input.

12. The method of claim 7 , wherein the determining the thickness of the semi-transparent layer comprises:

determining a third captured image that is focused on light reflected from the semi-transparent layer of the sample based on the characteristic value of each pixel in each captured image; and

determining the location of the bottom surface of the semi-transparent layer based on the location where the third image was captured and the index of refraction of the semi-transparent layer.

13. A three-dimensional (3-D) measurement system, comprising:

an optical microscope comprising an objective lens and a stage, wherein the optical microscope is adapted to vary the distance between a sample supported by the stage and the objective lens of the optical microscope at pre-determined steps; and

a computer system comprising a processor and a storage device, wherein the computer system is adapted to:

store an image captured at each pre-determined step, wherein a first surface of the sample and a second surface of the sample is within a field of view of each image;

determine a characteristic value of each pixel in each captured image, wherein the characteristic value is selected from the group consisting of: intensity, contrast, and fringe contrast;

determine a first captured image that is focused on a first surface of the sample based on the characteristic value of each pixel in each captured image;

determine a second captured image that is focused on a second surface of the sample based on the characteristic value of each pixel in each captured image; and

determine a first distance between the first surface and the second surface,

determine a thickness of a semi-transparent layer of the sample; and

determine a thickness of a metal layer of the sample based at least in part on the thickness of the semi-transparent layer wherein the optical microscope includes a stage, wherein the sample is supported by the stage, wherein the optical microscope is adapted to communicate with a computer system, wherein the computer system includes a memory device that is adapted to store each captured image, wherein the optical microscope one of: a confocal microscope, a structured illumination microscope, or an interferometer, and wherein the characteristic value of each pixel one of: intensity, contrast, or fringe contrast.

14. The three-dimensional (3-D) measurement system of claim 13 ,

wherein the thickness of the metal layer is equal to the difference between the thickness of the semi-transparent layer and the first distance.

15. The three-dimension (3-D) measurement system of claim 13 ,

wherein the thickness of the metal layer is equal to the sum of the thickness of the semi-transparent layer and the first distance.

16. The method of claim 13 , wherein only a portion of each captured image is used to determine the thickness of the semi-transparent layer of the sample, and wherein the portion of each captured image is selectable by an user input.

17. The method of claim 13 , wherein the computer is further adapted to:

receive a user input that identifies a portion of each captured image is to be analyzed.

18. The method of claim 14 , wherein only a portion of each captured image is used to determine the thickness of the semi-transparent layer of the sample.