Confocal microscopic device

• US 6,674,572 B1
• Filed: 08/11/1999
• Issued: 01/06/2004
• Est. Priority Date: 03/29/1997
• Status: Expired due to Fees

• Current Assignee: CARL Zeiss JENA GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: CARL Zeiss JENA GmbH (Carl-Zeiss-Stiftung)
• Inventors: Czarnetzki, Norbert, Scheruebl, Thomas
• Primary Examiner(s): Robinson, Mark A.
• Assistant Examiner(s): FINEMAN, LEE A
• Application Number:
  US09/194,299
• Time in Patent Office: 1,609 Days
• Field of Search: 359/368, 359/385, 359/389, 356/600-624, 356/237--23, 356/391, 356/392, 356/393
• US Class Current: 359/368
• CPC Class Codes: G01B 2210/50 Using chromatic effects to achieve wavelength-dependent depth resolution
• CPC Class Codes: G02B 21/0024 Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
• CPC Class Codes: G02B 21/0044 moving apertures, e.g. Nipkow disks, rotating lens arrays
• CPC Class Codes: G02B 21/006 focusing arrangements; selection of the plane to be imaged
• CPC Class Codes: G02B 21/0064 multi-spectral or wavelength-selective arrangements, e.g. wavelength fan-out, chromatic profiling G02B21/0076 takes precedence
• CPC Class Codes: G02B 21/008 Details of detection or image processing, including general computer control

Abstract

An autofocus for a confocal microscope is realized by means of a confocal microscope arrangement comprising an illumination arrangement for illuminating an object in a raster pattern, first means for generating a first wavelength-selective splitting of the illumination light and second means for generating a second wavelength-selective splitting of the light coming from the object in a parallel manner for a plurality of points of the object, and detection means for detecting the light distribution generated by the second means, wherein an at least point-by-point spectral splitting and detection of an object image in a wavelength-selective manner is carried out and a control signal is generated from the determination of the frequency deviation and/or intensity deviation from a predetermined reference value corresponding to the object position in order to adjust the focal position by means of the vertical object position and/or the imaging system of the microscope. Further, a process is realized for determining deviations of at least a first height profile from at least one simultaneously or previously detected second height profile, preferably for detecting and/or monitoring defects in semiconductor structures, wherein a first object is illuminated in a wavelength-selective manner by a light source and the light originating from the first object is detected and is compared electronically with a previously or simultaneously detected second object.

Claims

1. An automatic inspection process for determining deviations of at least a first height profile from at least one simultaneously or previously detected second height profile, for detecting and/or monitoring defects in semiconductor wafers utilizing a confocal microscope comprising:

an illumination arrangement for illuminating an object in a confocal raster pattern;

first means for generating a first wavelength-selective splitting of the illumination light;

second means for generating a second wavelength-selective splitting of the light coming from the object in a simultaneous manner for a plurality of points at varying heights of the object, the light coming from the object containing spectrally coded height information for the plurality of points of the object; and

detection means for detecting the light distribution generated by the second means, said process including the steps of;

illuminating a first object in a wavelength-selective manner by the illumination arrangement; and

detecting the light originating from the first object with an array of detectors and comparing detected light electronically with a previously or simultaneously detected second object.

2. The process according to claim 1, wherein the step of comparing includes comparing adjacent areas of one and the same object.

3. The process according to claim 1, wherein the step of comparing includes comparing the detected light with a stored object.

4. The process according to claim 1, wherein the step of comparing includes averaging the detection of a plurality of object areas or objects and formation of a reference value.

5. The process according to at claim 1, wherein the step of comparing includes subtracting a detected image of the object from the image of the second object, or vice versa.

6. A method of determining a height deviation of a first semiconductor object in a wafer from a reference semiconductor object in a wafer utilizing a confocal microscope, the method comprising:

simultaneously illuminating with light from a light source a plurality of points at varying heights of a first semiconductor object in a wavelength selective manner using a confocal microscope;

simultaneously receiving the light coming from the plurality of points of the first object, the received light containing spectrally coded height information for the plurality of points of the first object; and

comparing the light distribution from the received light with the light distribution of a reference semiconductor object to determine a height deviation of the first object from the reference object.

7. The method according to claim 6, wherein the step of comparing includes detecting the light distribution using CCD lines or diode lines.

8. The method according to claim 6, prior to the step of comparing, further comprising dispersing the received light into a spectrum of wavelengths through a dispersive element.

9. The method according to claim 6, further comprising determining the difference between the light distribution from the received light and the light distribution of the reference object to obtain a height deviation of the first object from the reference object.

10. The method according to claim 9, further comprising determining the light distribution of the reference object by averaging a plurality of light distributions.

11. The method according to claim 6, wherein the step of simultaneously illuminating a plurality of points of a first object in a wavelength selective manner includes generating a longitudinal chromatic aberration in the light.

12. The method according to claim 11 wherein the step of simultaneously illuminating a plurality of points of a first object includes passing the light source through a Nipkow disk.