Featured Research

from universities, journals, and other organizations

MIT Researcher's Test Can Save Millions Of Dollars For Microelectronics Industry

Date:
February 26, 1999
Source:
Massachusetts Institute Of Technology
Summary:
A Massachusetts Institute of Technology professor has come up with a quick and easy test which, with the pulse of a laser, can analyze the thin films used in microelectronics components. The same optical method may one day be used to provide an early-warning signal for eye disease or "optically switch" materials from one phase to another.

Technique may one day allow "optical switching" of material from one phase to another

CAMBRIDGE, Mass. --A Massachusetts Institute of Technology professor has come up with a quick and easy test which, with the pulse of a laser, can analyze the thin films used in microelectronics components. The same optical method may one day be used to provide an early-warning signal for eye disease or "optically switch" materials from one phase to another.

All this is part of a program developed by Keith A. Nelson, professor of chemistry at MIT, a member of the Institute's Materials Processing Center and the Center for Materials Science and Engineering. Nelson and his research group study how materials respond when they are irradiated by pulsed laser light.

Applications for this work range from adding to basic knowledge about complex materials to the practical test for thin films that may save the microelectronics industry millions of dollars annually in testing costs. Another far-off goal is the ability to "optically control" the structure and behavior of materials, with intriguing prospects including ultrafast optical signal processing and optical fabrication of unique material structures.

"Much of the 'art' in our efforts comes through understanding how light, especially in the form of short pulses, interacts with matter and how the interactions can be exploited to characterize or control materials," Nelson said.

In microelectronics manufacturing, a silicon base is coated with one thin layer after another. Copper, tungsten and other metal layers have precisely specified thicknesses that range from 100 angstroms, or about how much a fingernail grows in one second, to 10,000 angstroms, or one-thousandth of a millimeter. Variation in the thickness of the metal layers is a major cause of device failure and low microelectronics manufacturing yields.

To make sure that each film layer is the right thickness and is properly adhered to the layer below it, manufacturers have had to perform painstaking tests with expensive equipment. These tests destroy the sample, at huge cost to the industry. Nelson's nondestructive, noncontact optical test, which uses a laser device that fits into a briefcase, can measure film thickness to within about one layer of atoms (1-3 angstroms) in one second, and at the same time check for proper adhesion.

The device, which incorporates a mini-laser half a thumb's-length that was developed by MIT's Lincoln Laboratory, has been developed commercially in the past two years by a start-up company formed by Nelson and two of his former graduate students, John A. Rogers (MIT Ph.D. 1995) and Matt Banet (MIT Ph.D. 1993). Because of the device's promise and early industry acceptance, the company was wholly acquired last summer by Philips Analytical N.V. (part of the same Philips that makes CDs and CD players.) The instrument is now in use at locations around the world.

The instrument uses short laser pulses to generate ultrasonic waves--sound vibrations beyond the range of human hearing--in the thin film. Light from a second laser is used to monitor the acoustic waves and determine their velocity, which depends on the thickness and adhesion of the film.

"The device doesn't require difficult adjustments and you don't need a laser jock or a Ph.D. scientist to do the analysis or get the numbers out," Nelson said. In fact, the optical part of the instrument is entirely enclosed and out of view of the user, who simply pushes buttons to start the measurement.

By comparing the signal from a sample coming off the assembly line to that expected from a perfect component, the user can figure out if the sample is just right or if it was flawed in the manufacturing process. In addition to microelectronics materials, thin films that could be tested with Nelson's measurement method include optical elements like filters and mirrors, liquid-crystal displays and ultrahard coatings. Many kinds of polymer films, including biopolymers like the cornea of the eye, can also be examined. The main requirement is that the sample be smooth and shiny enough to reflect light without too much scatter.

In related work led by current graduate MIT students Timothy Crimmins and Richard Koehl, Nelson has experimented with ultrashort pulses of light to optically control the structure of crystalline solids by moving atoms from their initial positions along selected microscopic pathways toward the positions they would occupy in a new crystalline structure.

Although this objective is still far off, the technique may one day make it possible to "optically switch" a material from one structure to another even without any absorption of the light. Like an ice crystal, which can assume nine different forms (popularized in Kurt Vonnegut's sci-fi story in which a mad scientist tries to freeze the Earth by turning the oceans into "ice nine"), other crystals may be altered by re-arranging their structure from that of one phase to another.

This method may make it possible to "optically control" a material by changing the configuration of its molecular infrastructure, and even to create new states of existing materials by forcing their atoms into configurations they wouldn't normally assume, Nelson said.

Nelson's research group has recently succeeded in "shaping" a pulse of light less than one-quadrillionth of a second long into a timed sequence of pulses that can launch vibrational waves in a crystal with larger and larger amplitude. The pulses of light "push" at the crystal lattice framework much like a person pushing a child on a swing, causing ever-larger excursions from the original position. If sufficiently large motions can be induced, the material could enter a new crystalline phase.

Very recently, Nelson's group has been able to shape a single light pulse into not just one timed pulse sequence, but many pulse sequences that can reach different regions of a sample. In this manner, the researchers can continue to manipulate and amplify the vibrational wave as it travels through the crystal at light-like speed. This advance offers prospects for optical control over ultrafast signals and brings the dream of optical control over material structure one step closer to realization.

Nelson's work is supported by the National Science Foundation, the Office of Naval Research and the Army Research Office.


Story Source:

The above story is based on materials provided by Massachusetts Institute Of Technology. Note: Materials may be edited for content and length.


Cite This Page:

Massachusetts Institute Of Technology. "MIT Researcher's Test Can Save Millions Of Dollars For Microelectronics Industry." ScienceDaily. ScienceDaily, 26 February 1999. <www.sciencedaily.com/releases/1999/02/990226075644.htm>.
Massachusetts Institute Of Technology. (1999, February 26). MIT Researcher's Test Can Save Millions Of Dollars For Microelectronics Industry. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/1999/02/990226075644.htm
Massachusetts Institute Of Technology. "MIT Researcher's Test Can Save Millions Of Dollars For Microelectronics Industry." ScienceDaily. www.sciencedaily.com/releases/1999/02/990226075644.htm (accessed July 25, 2014).

Share This




More Matter & Energy News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Europe's Highest Train Turns 80 in French Pyrenees

Europe's Highest Train Turns 80 in French Pyrenees

AFP (July 25, 2014) Europe's highest train, the little train of Artouste in the French Pyrenees, celebrates its 80th birthday. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
TSA Administrator on Politics and Flight Bans

TSA Administrator on Politics and Flight Bans

AP (July 24, 2014) TSA administrator, John Pistole's took part in the Aspen Security Forum 2014, where he answered questions on lifting of the ban on flights into Israel's Tel Aviv airport and whether politics played a role in lifting the ban. (July 24) Video provided by AP
Powered by NewsLook.com
Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com
Algonquin Power Goes Activist on Its Target Gas Natural

Algonquin Power Goes Activist on Its Target Gas Natural

TheStreet (July 23, 2014) When The Deal's Amanda Levin exclusively reported that Gas Natural had been talking to potential suitors, the Ohio company responded with a flat denial, claiming its board had not talked to anyone about a possible sale. Lo and behold, Canadian utility Algonquin Power and Utilities not only had approached the company, but it did it three times. Its last offer was for $13 per share as Gas Natural's was trading at a 60-day moving average of about $12.50 per share. Now Algonquin, which has a 4.9% stake in Gas Natural, has taken its case to shareholders, calling on them to back its proposals or, possibly, a change in the target's board. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile: iPhone Android Web
          Follow: Facebook Twitter Google+
          Subscribe: RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins