SJ 3247-1989 Infrared interferometry test method for thickness of homogeneous GaAs epitaxial layer SJ3247-1989 standard download decompression password: www.bzxz.net

Standard of the Ministry of Machinery and Electronics Industry of the People's Republic of China Infrared Interference Test Method for Thickness of Gallium Arsenide Epitaxial Layer Subject Content and Scope of Application
SJ3247-89
This standard specifies the infrared interferometer measurement principle, instrumentation, sample preparation measurement steps, result calculation and accuracy of the thickness of the same type of gallium arsenide epitaxial layer as the substrate.
This standard is applicable to the measurement of the thickness of the same type of gallium arsenide epitaxial layer as the substrate. The room temperature resistivity of the substrate and epitaxial layer should be less than 0.022cm and greater than 0.192.cm respectively, and the measurable thickness is greater than 2um2 Principle
The difference in the optical constants of the substrate and the epitaxial layer leads to the continuous maximum and minimum optical interference phenomenon in the sample reflection spectrum. The thickness of the epitaxial layer is calculated according to the extreme wavelength, the optical constants of the epitaxial layer and the substrate and the incident angle. 3 Instruments and Equipment
3.1 Infrared Spectrometer
a. Dispersive double-beam infrared spectrophotometer or Fourier transform infrared spectrometer with wavelength or wavenumber scanning. b. Wavelength range 2~50μm. The wavelength range commonly used in this method is 6~40μm. c. The wavelength repeatability defined by A1 in Appendix A is at least 0.05μm. d. The wavelength accuracy defined by A2 in Appendix A is at least ±0.05μm. 3.2 Instruments and accessories
a. The incident angle of the reflection accessories used is not greater than 30°b. The mask holes are made of non-reflective materials, and the aperture range is based on obtaining an excellent reflection spectrum. 4 Sample requirements
4.1 The conductive type of the substrate and epitaxial layer and the substrate resistivity should be known before measurement. 4.2 The sample should have a good optical surface to ensure high reflectivity. The epitaxial layer deposited by normal process does not require special treatment.
5 Measurement steps
5.1 If a dispersive infrared spectrophotometer is used, refer to the following steps to select the maximum scanning speed. 5.1.1 Select a sample with a substrate and epitaxial layer resistivity of 0.0089 cm and 0.12 Ω cm respectively, which can still show a minimum value after 25 μm.
5.1.2 Select an appropriate mask hole and record the minimum wavelength greater than 25 μm at the slowest scanning speed. 5.1.3 Increase the scanning speed step by step and record the corresponding minimum position each time: 5.1.4 The final allowed scanning speed is based on the deviation of the extreme wavelength recorded by the slowest scanning speed less than ±0.1 μm.
5.2 If an FT-1R spectrometer is used, a resolution of 4 cm-1 is generally used. Scan 64 times for measurement. 5.3 Place the clean sample on the mask hole and align the required measurement position with the beam. 5.4 Start the measurement instrument to automatically record the reflection spectrum, as shown in the figure. If the ratio of the interference peak amplitude to the noise amplitude is less than 5, it cannot be used to calculate the thickness.
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Wave number (um)
Figure Typical 5/5+monumentalized sample reflectance spectrum 19.64
5.5 In the peaks and valleys of each interference peak, draw a horizontal line parallel to the horizontal axis at 3% of the full scale of each extreme point, and intersect each interference peak at two points respectively. The wavelength corresponding to the two intersection points is the mean value, which is the extreme wavelength of each interference peak. 6 Result calculation
6.1 First, calculate the order corresponding to the extreme wavelength by the following formula: mλ1
P2=1A2+
Wherein: The order corresponding to P2-λ2
211-222
λ1-λ2
λ1-λ2 extreme wavelength (22<λ1) (μm): m-the difference in the orders corresponding to λ1 and λ2, m=P2-P: The phase shift corresponding to Φ21-λ1 (given in the attached table according to the wavelength and substrate resistivity); The phase shift corresponding to Φ22-λ2 (given in the attached table according to the wavelength and substrate resistivity) (1)
6.1.1 If λ2 is an extreme value, the calculated value of P is an integer; if λ2 is a minimum value, the calculated value of P3 is half an integer, and the difference in the orders of two adjacent extreme values ​​is 0.5.
6.2 Calculate the thickness reflected by each peak point using the following formula: Tn(Pn+ean)
2(ni—sin20)→
Where: Tn is the epitaxial thickness (μm) calculated using the nth extreme wavelength (λ): Pn is the order corresponding to λn, calculated by formula (1), n1 is the refractive index of the epitaxial layer relative to vacuum, which is a known value. (GaAs, n1=3.29) e is the incident angle used by the reflection accessory.
The meaning of other parameters is the same as that of formula (1). 6.3 Take the average value of the thickness reflected by each extreme point as the sample thickness, 2
午=Tn/m
SJ3247-89
6.4 Example of calculation of the thickness of a typical n/n+GaAs sample: 6.4.1 The R-λ curve obtained from the experiment is shown in the figure. In the spectrum extreme wavelength, input 1 is taken as 22.81μm and input 2 is taken as 14.05μm. 6.4.2 From the figure, we can find that the order difference between input 1 and input 2 is m=3.5; and knowing the resistivity of the substrate Rs=0.0005Q·cm, we can find 21 and Φ22 from Appendix A. 6.4.3 Substitute the above data into formula (1) to calculate P2=9.0; 6.4.4 Use formula (2) to calculate T3=17.85. 5 The relevant parameters and thickness averages corresponding to each extreme value are shown in the table below, 64.5
Table Calculation Results of Typical n/n+ GaO2 Samples Parameters
Extreme Value Number
Average Thickness (μm)
The report content is as follows:
an(μm)
Sample name, source and number,
b. Conductivity model of substrate and epitaxial layer;bZxz.net
substrate resistivity;
d, illustrated sample measurement position,
calculated thickness Tn corresponding to n,
f, average thickness,
measurement unit and date;
name of measurer;
8 precision
In (μm)
When the thickness of n-type arsenide epitaxial layer is greater than 2μm, the measurement accuracy is ±(0.116μm+0.0015T). 3
(μm）)0.0001
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Appendix A
n/n*GaAs phase shift (Φ2n)
(Supplement)
0-0010
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Appendix B
Definition of wavelength repeatability and accuracy
(Reference)
B.1 Wavelength repeatability: When a certain absorption band is repeatedly measured in a given wavelength range, it is expressed by the difference between each measurement value and the measurement average value, divided by the number of measurements, that is: n
E【λ-/n
Wavelength repeatability=（
Where: Yuan=（λ ：）/n, is the average value of n measurements, n is the number of measurements, and λ is the wavelength value of the ith measurement. i=1
B.2 Wavelength accuracy: It is expressed by the deviation between the average value of the wavelength position of a certain absorption band and the theoretical value of the band, that is: Wavelength accuracy = ±—λ11
Wherein: λ is the theoretical value of the absorption band wavelength. B.3 When measuring wavelength repeatability or accuracy, select a polystyrene film with a thickness of 300~500um as the standard sample, and use the 3.303μm peak as the measurement reference band, and the number of measurements is 10 times. Additional notes:
This standard was drafted by the 46th Institute of the Ministry of Machinery and Electronics Industry. The main drafters of this standard: Li Guangping, He Xiukun, Wang Qin, Zheng Ju, Jian Ping5
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