Kodak reports to laboratories on:some information we hope you'll use and some we hope you won't ... how to

carve a fancy design on a microscopic bit of semi-conductor

Data for the timesAs a kind of a public service, we feel we ought to print the following table:

We have three reasons for print-ing it, in decreasing order of impor-tance.

1) In the event of nuclear disaster,pieces of film that survive lighttightmight serve as fortuitous dosimeters.Few American population centersof 10,000 souls or more wouldn'tcontain at least a box or two of sucha popular product as Kodak RoyalPan Film. Giving it the above-indi-cated processing normally recom-mended for that film would providea radiological survey party with aquick and rough estimate of theamount of prompt radiation thathit where the film was stored. Thetable neglects the possibility of so-larization, but perhaps this is anexcessively lugubrious thought.

2) In these nuclear times, thequestion often arises of how muchradiation it takes to spoil film for itsintended purpose. Here is a guide totolerance judgments, since the sen-sitivity of a particular photographicmaterial is essentially the same forall radiations harder than 1,000-kvpx-rays.

3) It's an excuse to tick off a fewfilm names you might like to knowabout. No. 2 is one of the mainthreads for Hollywood's loom ofglamour and glory. No. 3 is sheetfilm with good tone rendition formonochrome subjects, slow enoughfor processing by inspection under arelatively bright Series 1 Safelight.No. 4 is the basic sheet film forblack-and-white photomicrography.No. 5 has sensitivity out to nearly

10,000A and comes in widths up to91' and lengths up to 390 feet. No.6 is 16mm and 35mm film for re-cording repetitive patterns fromgreen-emitting c-r tubes, unaffectedby reddish cathode glow. No. 7 isthe world's No. 1 film for aerial pho-tography. No. 8 is a sheet film thatgives either inky blackness or diaph-anous clarity and nothing much be-tween. And No. 9 provides 16mm or35mm sanctuary for records by thebillions.For more detailed information on the

radiation sensitivity ofmore Kodakfilms,write Eastman Kodak Company, X-rayDivision, Rochester 4, N. Y., who hopethat the only film ever given an oppor-tunity to soak up roentgens will beKodak X-ray Film.

Here's how

Here is how to carve a microscopicbit of a semi-conductor like ger-manium or silicon into as intricate astructure as you need to beat acomplex vacuum tube at its owngame:Draw up the pattern nice and big

with India ink. Photograph it down

This is one of a series of reports on the many products

and services with which the Eastman Kodak Company and

Its divisions are... serving laboratories everywhere

to a stencil of desired size with agood lens (like a Kodak ProcessEktar Lens) on a virtually grainless,all-or-none material (like KodalithOrtho Film or, for really tiny work,a Kodak High Resolution Plate).Saw out a blank of the semi-

conductor crystal. Lap and polishit, finishing up with 0.5, grid-sizediamond paste. Etch off the remain-ing few microns of work-strainedlayer. Wash in trichloroethylene,rinse in distilled water, and dry.

Avoiding daylight or ultraviolet,filter a little Kodak Photo Resist.With it, coat the polished semi-conductor surface thinly. Dry undera heat lamp. Hold the stencil tightagainst the semi-conductor by vac-uum. Expose to an arc lamp. Im-merse in Kodak Photo Resist De-veloper. Take out. Put on a fewdrops of Kodak Photo Resist Dye tomake the developed image visible.Hold under a stream of tepid dis-tilled water to wash away the resistwhere the dark portions of thestencil shielded it. Pull up thewindow shades. Blot off the surfacemoisture. Inspect the pattern with amicroscope. If OK, bake for a fewminutes to harden the resist. Letan etchant suitable to the specificsemi-conductor remove it to anyrequired depth in those areas wherethere is no resist left to resist.Over the whole, deposit a metal

electrically, chemically, or by evap-oration. Immerse in 2-EthoxyethylAcetate* for 10 minutes and gentlyswab. This solvent, undeterred bythe overlying metal film, removesthe remaining resist.

There's your little triumph inapplied solid state physics, com-plete with electrodes.

This is basically Bell Telephone Lab-oratories' idea, not ours. All we did wasto suggest Kodak Photo Resist. Ap-parently it was a good suggestion. Any-body else who wants any suggestionsabout the Kodak products involved canwrite Eastman Kodak Company, GraphicReproduction Division, Rochester 4,N. Y.

*Available as Eastman Organic Chemi-cal No. P2378 at $2.05 for 1 kg. fromour division, Distillation Products In-dustries, Rochester 3, N. Y.

Price quoted is subject tochange without notice.

__.

1,000-KVP X-rays-KODAK FILM Kodak Time Roentgens for desby of

Developer (min.) 0.3t 1.0 2.0.____ net grow gros

1. Kodak Royal Pon Film DK-60a 4 1.2 13.2 440

2. Eastman Plus-X PanchromatlcNegative Film D-76 a 3.7 19 450

3. Kodak Commercial Film DK-50 5 4.3 47 305

4. Kodak Contrst ProcessPanchromac Fim D-1 1 5 I 1.5 36 95

S. Kodak Infraroed Arographic Film D-19 9.6 1.2 4.0 18

6. Kodak Unagraph Ortho Film D-19 7 1.1 3.2 12

7. Kodak Super-XX Aerographk Flm D-19 9.6 1.2 3.8 17

S. KodaUth Ortho Film, Type 2 Kodalith 2.25 - 1400 1700

9. Recordak Micro-File Panchromanc Film Kodagraph 5 90i 220 560

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SCIENCE is ptublished weekly by the AAAS, 1515Massachusetts Ave., NW, Washington 5, D.C. Entered at the Lancaster, Pa., Post Office

as second classmatter unider

act of 3 March 1879. Annual subscriptions; $7.50; foreign postage, $1; Canadian postage, 50¢.10 FEBRUARY 1956 203

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