Nano Science (Lec3 To-Down Nanofabrication)

Nano Science (Lec3 To-Down Nanofabrication) - MAE 287/EE...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
MAE 287/EE 257
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Nanofabrication is about how to make structures at nanoscale. There are two general strategies for nanofabrication, Top-down nanofabrication starts with large structures that are subsequently reduced to nano structure by physical, chemical, and mechanical, etc. processes. Bottom-up nanofabrication starts with atoms and molecules that react under physical, chemical, or biological environment to form nano structures.
Background image of page 2
Nano Science (MAE298)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Top down nanofabrication: Optical lithography Electron-beam lithography Scanning probe (AFM, STM) lithography Imprint lithography
Background image of page 4
Lithography is the workhorse of the computer chip industry. It is the most common top-down manufacturing process and it is one nanomanufacturing technique that is widespread. A target material is first applied to the surface of a substrate. Polymeric resist layer is then applied by spin coating. A light beam is shined through a mask that contains a predetermined pattern. Regions exposed to the light are sensitized (positive resist) or protected (negative) to the subsequent etch step. Following etching, the resist is removed, transferring the pattern inscribed by the mask to the target material.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Reactive ion etching (RIE) is an effective means of subtracting material from a substrate—hence, a top-down method. Molecules (usually oxygen, sulfur hexafluoride, fluorine, or other reactive species) are ionized to form chemically reactive plasmas by the action of an applied electromagnetic field (parallel plate configuration) under low-pressure conditions. Inductively coupled plasma (ICP) produced by RF magnetic fields is another mode of creating RIE plasmas. Since the trajectory of ions produced in RIE is mostly normal to the plane of a substrate, the process is capable of vertical etching—as opposed to chemical etching, which tends to act in an isotropic fashion.
Background image of page 6
Advantages: Low defect (no contact) Pattern size reduction from mask to substrate Disadvantages: Expensive optical system
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
d>λ d<<λ, diffraction will smear the patterns
Background image of page 8
Resolution for shadow lithography Where R is lowest width limit of parallel lines is the wavelength of light s is the gap between the mask and the photoresist h is the photo resist thickness h R 1.5 λ (s ) 2  Advantage: Higher resolution Disadvantages: Defect due to direct contact no pattern size reduction from mask to substrate Resolution limited by the wavelength
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
For projection lithography NA k R 1 Where R is the resolution is the wavelength of light k 1 is a constant related to resist NA is so-called numerical aperture, Sin n NA Where n is refraction index, is the maximum cone angle of the exposure light beam
Background image of page 10
In order to respond to shrinking circuit line widths of semiconductor devices, it is necessary to reduce the wavelength of the light source in exposure equipment or increase the numerical aperture (NA) of the projection lens. Because NA is proportional to the refraction index (n), when using ultrapure water (n = 1.44), for example, light at the same angle would yield an NA that is 1.44-times greater. Immersion exposure
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/17/2011 for the course MAE 287 taught by Professor Yongchen during the Winter '11 term at UCLA.

Page1 / 53

Nano Science (Lec3 To-Down Nanofabrication) - MAE 287/EE...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online