Variable pixel density imaging

#In some embodiments a method is provided for topographically characterizing a workpiece. The method includes steps of scanning the workpiece with a scanning probe along a first directional grid, thereby scanning a reference surface and an area of interest subportion of the reference surface, at a variable pixel density including a first pixel density outside the area of interest and a second pixel density inside the area of interest to derive a first digital file characterizing topography of the workpiece; scanning the reference surface and the area of interest with the scanning probe along a second directional grid, that is substantially orthogonal to the first directional grid, at a constant pixel density to derive a second digital file characterizing topography of the workpiece; and executing computer-readable instructions stored in memory that generate a topographical profile of the workpiece in relation to the first and second digital files.

#In some embodiments an apparatus is provided for topographically characterizing a workpiece. The apparatus has a scanning probe that obtains topographical data about the workpiece. A processor controls the scanning probe to scan the workpiece along a first directional grid, thereby scanning a reference surface and an area of interest subportion of the reference surface, at a variable pixel density including a first pixel density outside the area of interest and a second pixel density inside the area of interest to derive a first digital file characterizing topography of the workpiece, and to scan the workpiece along a second directional grid, that is substantially orthogonal to the first directional grid, at a constant pixel density to derive a second digital file characterizing topography of the workpiece. The apparatus further includes logic that generates a topographical profile of the workpiece in relation to the first and second digital files.

#In some embodiments a topography metrology apparatus is provided having a processor controlling a scanning probe to collect first data along a variable pixel density grid and to collect second data along a constant pixel density grid to obtain topographical data about a workpiece, and means for integrating the first and second data to generate a topographical profile for the workpiece.

#FIG. 1 is an isometric depiction of an atomic force microscope probe constructed and used in accordance with embodiments of the present invention.

#FIG. 2 is an isometric depiction of a cavity transition feature in a workpiece that is suited for measuring with atomic force microscopy (AFM) techniques of the present embodiments.

#FIG. 3 depicts a variable pixel density directional grid of the present embodiments.

#FIG. 1 is a perspective view an atomic force microscope 10 positioned over a surface of structure 12 (sometimes referred to herein as “workpiece”). Atomic force microscope 10 includes probe 11 having cantilever portion 14 and tip portion 16. Atomic force microscope 10 also includes light source 18, position sensitive detector 20, and processor 22. Light source 18 emits a beam 24 that is reflected by cantilever 14 and received by position sensitive detector 20. Processor 22 receives signals from position sensitive detector 20 and provides signals to control movement of probe 11 relative to structure 12.

#Structure 12 in these illustrative embodiments is the pole tip region of a magnetic recording system, including slider 26 carrying reader structure 28 and writer structure 30. The atomic force microscopy (AFM) techniques described herein are useful for measuring and imaging feature characteristics of structure 12, such as pole tip recession (PTR) features of reader structure 28 and writer structure 30. It should be noted that structure 12 is shown merely for purposes of illustration, and the AFM techniques described herein are also useful for measuring and imaging nanometer and micrometer scale surface features of other structures. For example, the AFM techniques may also be used to measure feature characteristics in other magnetic recording device structures, such as a cavity transition feature as shown in FIG. 2.

#Atomic force microscope 10 measures physical characteristics or properties of structure 12, such as feature dimensions and surface finish. Probe tip 16 is positioned in very close proximity (i.e., within picometers) to the surface of structure 12 to allow measurements of structure 12 over a small area. Probe tip 16 is moved relative to structure 12 using extremely precise positioning. For example, processor 22 may control motion of probe 11 such that probe tip moves along the surface of stationary structure 12. Alternatively, processor 22 may control a device such as a tube scanner to move structure 12 while probe 11 remains stationary. As probe tip 16 moves over the surface of structure 12, features on the surface of structure 12 cause cantilever 14 to bend in response to the force between probe tip 16 and structure 12.