Step distance measuring device based on femtosecond optical-frequency comb and measuring method thereof
A distance measurement and measurement method technology, applied in the field of step-type surface topography measurement devices, can solve the problems affecting measurement resolution and accuracy, measurement datum connection, measurement results inability, etc., to eliminate measurement errors, increase measurement range, Avoid the effects of mechanical movement
A distance measurement and measurement method technology, applied in the field of step-type surface topography measurement devices, can solve the problems affecting measurement resolution and accuracy, measurement datum connection, measurement results inability, etc., to eliminate measurement errors, increase measurement range, Avoid the effects of mechanical movement
CN102494615AInactive Publication Date: 2012-06-13TSINGHUA UNIV
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[0031] The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.
[0032] In the present invention, the femtosecond optical frequency comb whose repetition frequency and bias frequency have been locked to the microwave frequency reference is used as the measurement light source, and its outgoing light is divided into reference light and measurement light, wherein the reference light is expanded after a certain optical path delay, Incident to the CCD detector; after the beam expansion, the measuring light is directly incident on the stepped surface to be measured, and the reflected light is incident on the CCD detector.
[0033] The femtosecond optical frequency comb is used as a light source, which is a femtosecond pulse laser with equal time intervals in the time domain and a laser frequency comb with equal frequency intervals in the frequency domain. By changing the repetition frequency f in the frequency do...
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Abstract
Disclosed are a step surface topography measuring device based on a femtosecond optical-frequency comb and a measuring method thereof. The measuring method includes steps of utilizing the femtosecond optical-frequency comb with repetition frequency and offset frequency which are locked to reach the microwave frequency reference as a light source; interfering measuring light with reference light, which is delayed by a certain light path, of split light beam; scanning repetition frequency of the femtosecond optical-frequency comb and acquiring positions of coherent peak value of light strength received by corresponding pixels of each step surface; and working out the absolute distance of steps according to the corresponding repletion frequency and light path delay of the coherent peak value. The measuring method overcomes the defects that light path is difficult to be regulated and precision is limited by motion precision of piezoelectric ceramic machinery when in use of the conventional measuring method, and has the advantages of high longitudinal resolution ratio and wide measuring range. Besides, the repetition frequency and offset frequency of the femtosecond optical-frequency comb are locked to reach the microwave frequency reference so that measuring results are traceable.
Description
technical field [0001] The present invention relates to a step-type surface topography measuring device and method, in particular to a step distance measuring device and method based on a femtosecond optical frequency comb. Background technique [0002] In the field of precision metrology, it is often necessary to measure the step distance with high precision. At the same time, step-type absolute distance precision measurement also has important requirements in modern industry, such as the measurement requirements for the height of micro-nano steps in semiconductor technology. [0003] Traditional non-contact step measurement methods are usually based on the principle of white light interferometers. When white light is used as the light source for interference, because white light contains a wide spectral range, it can only obtain interference fringes with better contrast when the optical path difference is zero. Using this feature of white light interference, construct a ...
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Patent Timeline
13 Jun 2012
Publication
CN102494615A
- IPC
- G01B11/02
- Inventors
- 朱敏昊; 吴学健