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Method for measuring thickness of chromium film on photomask

A technology for photolithographic mask plate and thickness measurement, which is applied in the direction of measuring devices, optical devices, instruments, etc., can solve the problems of inability to measure the thickness of metal thin films and cannot expand, and achieve the effects of convenient operation, low cost, and simple device structure

Active Publication Date: 2015-02-18
SHANGHAI OPTICAL LITHOGRAPHY ENG
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, these methods can only measure the thickness of the most dielectric film, and cannot measure the thickness of the metal film
Using the dual-wavelength method of surface plasmon waves, although the thickness of noble metal (gold, silver, copper, etc.) films of about 50 nanometers can be measured, it is powerless for chromium films, and the measurement range of this method is only in the range of 40nm to 60nm. Cannot be extended to several nanometers and 100nm range

Method used

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  • Method for measuring thickness of chromium film on photomask
  • Method for measuring thickness of chromium film on photomask
  • Method for measuring thickness of chromium film on photomask

Examples

Experimental program
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Embodiment 1

[0020] Suppose the wavelength of the incident laser light λ=3.391um, the refractive index of the glass prism n 1 =1.70, the refractive index n of matching liquid and quartz glass 2 =n 4 =1.45, the thickness h of matching liquid 2 =8.5um, the dielectric coefficient ε of the chromium film 3 =-120+i68, the measuring range of chromium film thickness is 5nm~20nm. When the incident light changes within 58.45°~59.15°, the curve obtained according to the computer simulation is as follows picture 2. Depend on picture It can be seen that using the mid-infrared laser to excite the long-range surface plasmon resonance, since the angular position of the ATR absorption peak of the long-range surface plasmon resonance is a sensitive function of the thickness of the chromium film, the thickness of the chromium film can be accurately measured by this method, and the resolution of the measurement is greater than 0.003° / nm.

Embodiment 2

[0022] Suppose the wavelength of the incident laser light λ=3.391um, the refractive index of the glass prism n 1 =1.70, the refractive index n of matching liquid and quartz glass 2 =n 4 =1.45, the thickness h of matching liquid 2 =40um, the dielectric coefficient ε of the chromium film 3 =-120+i68, the measuring range of chromium film thickness is 20nm~100nm. When the incident light changes within 58.534°~58.567°, the curve obtained according to the computer simulation is as follows picture 3. Depend on picture It can be seen that using the mid-infrared laser to excite the long-range surface plasmon resonance, since the angular position of the ATR absorption peak of the long-range surface plasmon resonance is a sensitive function of the thickness of the chromium film, the thickness of the chromium film can be accurately measured by this method, and the resolution of the measurement is greater than 0.001° / nm.

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Abstract

The invention belongs to the field of physical measurement and relates to a method for measuring thickness of a chromium film on a photomask. The method is characterized in that a prism-coupled long-range surface plasmon resonance sensor is provided and used for measuring the thickness of the chromium film on a quartz substrate, under the two ranges, from 5nm to 20nm and from 20nm to 100nm; a mid-infrared He-Ne laser transmit parallel beams which become TM (transverse magnetic) polarized light after passing a polarizer; the TM polarized light enters the prism-coupled long-range surface plasmon resonance sensor; reflected light, carrying the thickness information of the chromium film, projects to a thermal radiation detector. The method has the advantages that mid-infrared He-Ne laser Lambada, being 3.391 micrometers, is used to trigger resonance of the chromium film and long-range surface plasmon on a dielectric interface, ATR (attenuated total reflection) absorption peaks are generated, the angle positions of the ATR absorption peaks are functions sensitive to the thickness of the chromium film, and thus, the thickness of the chromium film can be determined according to the angle positions of the ATR absorption peaks of a reflectivity-incident angle curve; the two measuring ranges, from 5nm to 20nm and from 20nm to 100nm, are available, and resolutions, 0.001 DEG / nm and 0.003 DEG / nm, are available; measuring equipment is simple in structure, convenient to operate and low in cost.

Description

technical field [0001] The invention relates to a measurement method, in particular to a method for measuring the thickness of a chromium film of a photolithography mask, belonging to the field of physical measurement. Background technique [0002] Chromium is a silver-white metal with high hardness and extremely stable chemical properties. It will not rust when placed in the air or immersed in water at room temperature. The best choice for photolithography. In the past thirty years, with the development of microelectronics technology, especially integrated circuits, the research and application of thin film thickness and critical dimension line width measurement have made great progress. The growth, characterization and non-contact and non-destructive precise measurement of nanoscale metal thin films are particularly important. At present, the usual methods for measuring the thickness of metal thin films include four-point probe method, eddy current method, X-ray absorpti...

Claims

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Application Information

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IPC IPC(8): G01B11/06
Inventor 陈开盛曹庄琪沈益翰
Owner SHANGHAI OPTICAL LITHOGRAPHY ENG
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