AFM for Process Development / Control Applications

Atomic force microscopy can be a cost effect technique to evaluate samples for process development, and/or to control a process. The AFM measurements used for process control are typically routine and made repetitively. Accuracy and precision can be assured by using standard measurement protocols and qualified probe tips.

What follows are AFMWorkshop examples of measurements routinely made for process development and control.

Surface Texture

AFM images of processed silicon 40 µm x 40 µmLeft: 40 X 40 micrometer image of processed silicon.
Right: Surface roughness parameters for the processed silicon image.
Bottom: Line profile of silicon image, designated by red line.

 

Polished and machined surfaces of semiconductors, glass, and metals are readily scanned with the AFM. Traditional profiling methods such as the stylus profiler do not have the vertical resolution required and optical profilers do not have the horizontal resolution. AFM's offer vertical resolution of 0.1 nm and horizontal resolution as small as a nm.  

Step Height Measurements

Atomic force microscopes  accurately measure  the thickness of deposited films as well as the height of  features on patterned wafers. Step heights of 1 nm to 100 nm are measurable with an AFM.

AFM patterned wafer analysisLeft: AFM image of a section of a patterned wafer.
Right: Dimensions taken from the line profile.
Bottom: Line profile of features on the patterned wafer

 

Nano-Particle Size

Atomic force microscopes are ideal for measuring the size of nanoparticle mixtures when nanoparticles are between 1 and 50 nm.

AFM images of 2-20 nm Nanoparticles2-20 nm NanoParticles
Line profile analysis nanoparticlesLine profiles for the 3 nanoparticles identified in the image at left, used to calculate the size of each nanoparticle.
 

Phase Measurements on Polymers

20 µm x 20 µm AFM phase image of polymerThe phase signal measured with an AFM is  sensitive to variations in composition, adhesion, friction, and  viscoelasticity. Thus, this technique is ideal for establishing the number of phases in polymer samples. On the left is a phase image of a polymer sample. Contrast in this sample shows the distributions of the three different polymer phases.

Left: 20 micron X 20 micron Phase image of 3 component polymer

 

Visualization

Often, it is difficult to establish a numerical parameter that fully characterizes surface features, and it is helpful to visualize the topography of surface structure. Through visualization minor surface blemishes or irregularities can be detected. Below are two images of ruled diffraction gratings. At the left the grating has a pitch of 421.5 nm, and at the right the grating has a pitch of 1673.5nm. Small irregularities at the edges of the apex of the grating lines on the left are readily visualized.

AFM image of grating irregularities 4 µm x 4 µm4 µmX 4 µm
Grating irregularities measured by AFM 16 µm x 16 µm16µm X 16 µm