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Controlling Deposition of Polymeric Coatings

IP.com Disclosure Number: IPCOM000080864D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Gambino, RJ: AUTHOR [+4]

Abstract

There is described herein a method of continuously monitoring the deposition of antireflecting (AR) coatings, such as parylene, on any substrate surface. In the method, there is utilized a monochromatic beam from an He-Ne laser of relatively low power, which is reflected from the surface of the material as it is deposited. The reflected beam is sensed by a solid-state detector, and the intensity thereof is monitored on a chart recorder. As the antireflecting material, such as the parylene, grows in thickness in the deposition process, the reflectivity of the beam changes in a periodic manner between two extreme values.

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Controlling Deposition of Polymeric Coatings

There is described herein a method of continuously monitoring the deposition of antireflecting (AR) coatings, such as parylene, on any substrate surface. In the method, there is utilized a monochromatic beam from an He-Ne laser of relatively low power, which is reflected from the surface of the material as it is deposited. The reflected beam is sensed by a solid-state detector, and the intensity thereof is monitored on a chart recorder. As the antireflecting material, such as the parylene, grows in thickness in the deposition process, the reflectivity of the beam changes in a periodic manner between two extreme values.

Adjacent maxima and minima correspond to the thicknesses of the antireflecting material, such as the parylene, which differ by lambda/4n, where n is the refractive index of the parylene and lambda = 6943A (He=Ne). Such difference in the value of reflectivity between adjacent maxima and minima depends in the first instance upon the respective indexes of refraction, as is known. The larger this difference, the greater is the "swing." However, the actual variation of the value of the maxima and minima, as the film grows in thickness during deposition, will also depend upon the quality (uniformity and smoothness) of the film, and the monitoring of the value with the laser monitor is effected in the adjusting of the optimum deposition rates for the material.

In addition, the technique described herein can be employed to deposit antireflecting material such as parylene on substrates such as quartz which have, for example, substantially the same index as parylene. To effect the latter deposition, it is monitored by having a dummy sample of high index such as a semiconductor, for example, lying adjacent to the material being coated.

The conditions for deposition of high-quality films of parylene are as follows: source temperature 125-140 degrees C, cracking zone temperature about 700 degrees C, and deposition temperature, about room temperature. It has been found that when the deposition rate is too rapid, there result cloudy films which can immediately be detected from the reflectivity intensity, as shown on the recorder. In carrying out the method, it has been found important that the source material be under vacuum before its temperature is raised. Otherwise poor films result. By observing the reflectivity trace on the recorder, and turning off the source heater at the appropriate time, the film thickness can be controlled to within 100 angstroms. It has also been found important to employ a substantial excess of source material, in order to maintain a uniform deposition rate.

The method has been sucessfully employed to deposit parylene films on Gd- Co, the latter deposited films yielding a greatly enhanced contrast ratio for observing bub...