Session A:

Nanoscale Measurement Technology/System

Technical Subject:

Development of a Nanometer Microwave Imager
Corresponding Applicant:Co-researcher:Prof. Michael Kelly, Stanford University
University

Prof. Zhi-Xun Shen, Stanford

The need:
Rapid submicron characterization of semiconductor devices, maps of protein distributions, and images of othermicrostructures are needed in many industries. The short-range forces involved in SPM systems make it
difficult to rapidly scan the larger areas needed, or to operate with robust sensing tips that are not easily
damaged.
Our Research:
Recently developed near-field microwave probes operate with a longer range force, and provide unique
1,2
information about the electrical properties of a material . Some examples of measurements made in ourlaboratory with a current microwave probe:
Below: A cross section of
an implanted semiconductor
device. Contrast comes fromdifferent electrical propertiesof dopants, dielectrics, metals

Quantitative Measurements
1098

F re qu en cy S hift (M Hz)

7

Bio imaging :Drosophila Chromosome

SiO 2 D ata

6Si3 N4 D ata

M odel R esu lts:

SiL K D ata

Semiconductor Imagingaging5SiO 2: ε = 4.5

4Si 3N 4: ε = 6.8

Si3 N4 Mo del3

SiLK : ε = 2.8

SiL K Mod el

SiO 2 Mode l2

Dopedregions

100

Above:0 .5

1F ilm T hick ne ss (m ic ro ns )

1.5

10µm

2

measurements of a variety

welldefectof

Above: an image of abiological specimen. Many
biomedical applications areenvisioned for the technology

Interconnect
layerslow-k dielectrics deposited on Si. A
model relates the measured change
in the frequency of a resonant cavity
to the dielectric constant

50µm

Our Proposal:
To develop a general-purpose imaging instrument, applicable to a wide range of applications, based uponcurrent near-field microwave technology. Specific improvements to the current capabilities are the following:•Develop a high sensitivity lightweight sensor with a protected tip•
Increase the scanning bandwidth so an image can be obtained in 1 -10 sec.
•Incorporate a "zoom" feature permitting a 100:1 change in viewing area

New Sensor~ 100µ~400µElectronics
hSampleHigh Scan Rates: The lightsensor can be rapidly scannedover the sample; the highbandwidth electronics provides
a high data rate.

Zoom capability

Large Area Scan

Zoom: smaller area;
improved resolution

Zoom: At a larger tip/sample spacing,a large area can be scanned rapidly; orat a closer spacing, a smaller area canbe scanned in the same time yielding ahigher resolution image.

Time to scan 100 x 100 pixels (sec)

New Sensor: A guarded tip with an
integrated amplifier interacts with thesample. The small size permits highsensitivity, high bandwidth response.
Spatial resolution is approximately
equal to the spacing between tip andsample

105

Higher bandwidth
Targetperformance

100
Current
speeds0.1

1103
Bandwidth (Hz)Shielded Tip

Invitation to collaborate: We would welcome colleagues interested in exploring applications for this newcapability, particularly in the biomedical field.

1. Anlage, S. M. et al. “Near-field Microwave Microscopy of Materials Properties” ArXiv: cond-mat/0001075, 7 Jan,2000
2. Wei, T. et al. "Scanning tip microwave near-field microscope" Appl.Phys. Lett., 1996. vol.68, no.24, p. 3506-8106