Automated sectioning tomographic measurement system

Abstract

A tomographic system includes a reporting device colocated and juxtaposed an object so that both are ground through grinding to various sectioning depths as the reporting device is ground down exposing a reporting marker along a length of the reporting device for indicating the depth of sectioning for accurate precise depth of grinding well suited for precise sectioned tomographic imaging.

Description

FIELD OF THE INVENTION[0001]The invention relates to the field of tomography. More particularly, the present invention relates to grinding, polishing, and imaging of objects in sliced sections.BACKGROUND OF THE INVENTION[0002]There is frequently a need to image the internal, three-dimensional structure of objects, in order to analyze internal structures or mechanism of failure, particularly at the scale from 200 nm to 10 mm. Imaging methods based on the transmission of a probe beam through a material can be used to generate a tilt series of data for three dimensional reconstruction, but such methods are typically insensitive to structure parameters, and are limited in the resolution that can be provided. A potentially more informative and higher spatial resolution approach to the collection of tomographic data sets can be to physically section an object in many slices while collecting images at incremental sectioning steps through the object. This sectioning approach also enables th...

AI Technical Summary

Benefits of technology

The invention is a tomographic system that can accurately section an object in slices using grinding processes. The system includes a reporting device that can provide accurate depth information during imaging of the object. The reporting device is integrated with a grinding and polishing, rinsing and washing, and imaging station for automated acquisition of depth values of images taken at various depths in a sectioning operation. The system can provide a means of straightforward automated depth sensing for accurate grinding control. The reporting device can be used to stop the automated serial sectioning of objects at target depths. The reporting device is a planar film that is ground in depth as is the object, revealing a reporting line that is a line across the planar film. The reporting device can provide within the image a reference to the precise depth of the ground surface of the object. The depth resolution of systems using the device can be as fine as 2.5 nm, two orders of magnitude greater than any other automated system commercially available. The invention covers a reporting device that can measure the depth and control grinding of every image in a series of images, including but not limited to the end point depth of the sectioning operation.

Problems solved by technology

Imaging methods based on the transmission of a probe beam through a material can be used to generate a tilt series of data for three dimensional reconstruction, but such methods are typically insensitive to structure parameters, and are limited in the resolution that can be provided.

A major problem exists with the sectioning approach.

For the mechanical sectioning approach, however, it is very difficult to accurately measure the depth of any particular step of material removal at small length scales.

This is in part caused by the difficulty in maintaining a reference plane for an object being sectioned in a planar manner.

Mechanical measurement systems that do not rely on a reference plane on the object being measured are limited to a resolution of one micron at best, rendering the sectioning only useful for objects with detail on the scale of at least twenty microns.

The profilometry method is not practical when sectioning an object in a planar manner.

The accuracy of these removal methods is severely limited to five microns in resolution.

As such, the interferometry methods suffer from the need to have external references.

Additionally, incorporation of an interferometry system into an automated sectioning or tomography system would add significant complexity and cost.

Such automated systems and methods reduce labor but are limited in resolution accuracy while sectioning through material.

In some cases, the feature of interest will have an appearance that is characteristic enough to allow for the robotic sectioning apparatus to stop automatically, but with most objects, such is not the case.

Sectioning machines are available that are capable of accurately sectioning material, but with a precision of only five microns, which is too coarse for many applications.

This offers an improvement over the measurement of only the depth of material removed, but is limited because such compensation requires calibration runs and to generate data sets related to tool wear and material grinding rates.

Also, replacement of consumables such as the sectioning head requires recalibration.

The frequent need for recalibration severely limits the use of such sectioning machines for sectioning objects and necessitates a thorough and complicated set of calibration data retention and labeling.

Its precision is five microns, which is insufficient for tomography of objects less than 1000 microns in size.

U.S. Pat. No. 6,121,147 discloses a reporting substance for detecting a polishing depth, but suffers from two major limitations.

First, the reporting substance marks only an end point in the grinding and polishing procedure.

Second, the method describes the use of spectroscopy in detection, which leads to the use of overly complicated spectroscopy devices than are necessary for this application.

This method requires the building of a complicated reporting device as well.

Prior sectioning and tomography systems and methods suffer from complicated and limited collateral reporting and sensing devices, and used the sectioned material as a sectioning object for measurement during grinding and polishing.

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