nanolithography different types.ppt

(1)

(2)

Types of Lithography

• A. Photolithography (optical,

UV, EUV)

• B. E-beam/ion-beam/Neutral

atomic beam lithography

• C. X-ray lithography

• D. Interference lithography

• E. Scanning Probe

Voltage pulse

CVD

Local electrodeposition

Dip-pen

F. Step Growth

G. Soft Lithography

H. Nanoimprint

I. Shadow Mask

J. Self-Assembly

K. Nanotemplates

Diblock copolymer

Sphere

Alumina membrane

Nanochannel glass

(3)

II-A. Photolithography

• KrF λ=248nm

• ArF λ=193nm

(4)

II-B. Electron-Beam Lithography

• Exposure source: electron beam

• At acceleration voltage Vc=120kV, λ=0.0336Å

• Utilizes an electron column to generate focused

(5)

(6)

(7)

SEM Resolution

• Magnification x Resolution in (Å) = 107

for a 1mm feature on the image

• Collimation

• Wavelength

• Charging effect - coating

carbon, metal

thickness

• Escape depth

metal ~40 Å

(8)

(9)

E – Beam Writing

•

Advantages

Better resolution

Direct writing, no mask needed

Arbitrary size, shape, order

•

Disadvantages

Serial process

slow, small area

Compatibility

(10)

(11)

Sample E-beam Writing

Procedure

• Application of e-beam resist (PMMA) • Spin coating & soft bake

• Loading

Ag paint reference, position • Power on

• Tuning emission current • Stabilizing filament

• Gun alignment

• Adjust astigmatism • Referencing

• Focusing • Writing

• Shutting down SEM • Developing

(12)

II-C. X-ray Lithography

• Exposure source: x-ray (synchrotron)

• Resist: sensitive to x-ray (PMMA)

– IBM used resists developed for DUV and obtained successful

results

• Mask: SiC membrane covered by high Z metal; fabricated by e –

beam writer

• Advantages: High resolution

• Large area

(13)

X- Ray Lithography: Applications

• IC industry

– Proposed for fabricating Gigabit-level DRAM

– Not a mainstream technique for IC fabrication

• Nanoelectronics

• MEMS applications

• – LIGA

(14)

Conclusions

• Electron-beam lithography is currently the industry

standard for high-resolution, but has limited applications

due to its high cost and time-demanding process.

• X-ray lithography is an up-and-coming technology that

can be used in the same capacities as optical

(15)

References for E – Beam and X –

Ray Lithography

• C. Ngo and C. Rosilio, "Lithography for semiconductor technology," Nucl. Instr. and Meth. In Phys. Res. B, vol. 131, pp. 22-29, 1997.

• R. C. Jager, Introduction to Microelectronic Fabrication, vol. 5. Upper Saddle River, New Jersey: Prentice Hall, 2002.

• J. G. Chase and B. W. Smith, "Overview of Modern Lithography Techniques and a MEMS Based Approach to High Throughput Rate Electron Beam Lithography," J. Intell. Mater. Syst. Struct., vol. 12, pp. 807-817, 2002.

• J. N. Helbert, Handbook of VLSI Microlithography. Norwich, NY: Noyes Publications/ William Andrew Publishing, LLC., 2001.

• "Facility Procedures," in http://rlewb.mit.edu/sebl/facility_procedures.htm. • "Raith Nanolithography Products," in

http://www.raith.com/WWW_RAITH/nanolithography/nano_faqs2.html. • "Electron Beam Lithography," in http://www.shef.ac.uk/eee/research/ebl.

• K.-S. Chen, I.-K. Lin, and F.-H. Ko, "Fabrication of 3D Polymer Microstructures Using Electron Beam Lithography and Nanoimprinting Technologies," J. Micromech.

Microeng., vol. 15, 2005.

• • J. P. Silverman, "Challenges and Progress in X-ray Lithography," J. Vac. Sci. Technol. B, vol. 16, pp. 3137-3140, 1998.

(16)

Focused Ion Beam (FIB)

• Liquid ion source: Ga, Au-Si-Be alloys LMI sources due

to the long lifetime and high stability.

• Advantages:

• High exposure sensitivity: 2 or more orders of magnitude

higher than that of electron beam lithography

• Negligible ion scattering in the resist

• Low back scattering from the substrate

• Can be used as physical sputtering etch and chemical

assisted etch.

• Can also be used as direct deposition or chemical

assisted deposition, or doping .

• Disadvantages:

(17)

(18)

(19)

(20)

(21)

II-E. Scanning Probe Lithography

• Probe

STM, AFM

• Techniques

Voltage pulse

CVD

(22)

(23)

(24)

Two Different Modes of STM

(25)

(26)

Manipulation of Atoms

1. Parallel process

(27)

(28)

(29)

(30)

Nanolithography

• Local anodic oxidation, passivation,

localized chemical vapor deposition,

(31)

(32)

(33)

(34)

(35)

(36)

(37)

(38)

Diagram illustrating thermal dip pen nanolithography. When the cantilever is cold (left) no ink is deposited. When the cantilever is heated (right), the ink melts and is deposited onto the surface. (

Journal of the American Chemical Society, 128(21) pp 6774 - 6775 , 2006)

(39)

Thermal Dip Pen Lithography

• To perform the tDPN technique, the team employed a silicon cantilever that contained a resistive heater and had a radius of curvature at its tip of about 100 nm. As the ink they used octadecylphosphonic acid (OPA), a material that has a melting point of 99 °C and self-assembles into monolayers on mica, stainless steel, aluminium and oxides such as titania and alumina. Sheehan and colleagues coated the cantilever with OPA before heating it to 122 °C to melt the ink. Scanning the tip across a mica substrate laid down 98 nm wide lines of OPA.

• The scientists were able to stop depositing molecules from the cantilever by turning off the current supply to the resistive heater. That said, it took

around two minutes for the deposition process to stop, perhaps because of the low thermal conductivity of the mica substrate.

• The researchers believe that optimizing the technique, for example by

decreasing the radius of curvature of the cantilever tip, should enable them to deposit features around 10 nm in size. So tDPN could find applications in producing features too small to be formed by photolithography, as a

nanoscale soldering iron for repairing circuits on semiconductor chips, or for making bioanalytical arrays. (Paul Sheehan, Lloyd Whitman, Applied

(40)

Thermal Dip Pen Lithography –

Conducting Polymer

• Whitman and colleagues Minchul Yang, Paul Sheehan and Bill King

deposited layers of the conducting polymer

poly(3-dodecylthiophene) (PDDT) onto silicon oxide surfaces. They

produced nanostructures with lateral dimensions of less than 80 nm

and achieved monolayer-by-monolayer thickness control – a

monolayer of the molecules was around 2.6 nm thick. The

researchers were also able to control the orientation of the polymer

chains.

• PDDT has promise in the field of organic electronics and could have

applications in areas such as transistors, photovoltaic devices and

video displays. "The performance of these devices depends

critically on the degree of molecular ordering and orientation within

the polymer film, a property that has been difficult to control," said

Whitman. "We have succeeded in directly writing polymer

nanostructures with monolayer-by-monolayer thickness control

(41)

(42)

A dip-pen nanolithography that has an array of 55,000 pens

that can create 55,000 identical molecular patterns

The background shows some of the 55,000 miniature images of a 2005 US nickel made with dip-pen lithography. (Each circle is only twice the diameter of a red blood cell.) Each nickel image with Thomas Jefferson's profile (in red) is made of a series of 80 nm dots. The inset (right) is an electron microscope image of a portion of the 55,000-pen array (

Journal of the American Chemical Society,

Angewandte Chemie 45 1-4,