Application recommendation | Application of SM200 and its series film thickness gauges in thin film detection

2024-01-31
thickness measurer

The thin film structure is a special form. Its size in the thickness direction is small and can only be measured microscopically. Due to the sudden change of the thin film structure at the interface, it has different properties from ordinary structures. Maxwell's "On Electricity and Magnetism" published in the 19th century laid the theoretical foundation for the thin film problem. In order to obtain excellent thin film performance, we need to accurately control the thickness parameters of the thin film so that the thin film device can work normally. Thin film detection technology has been widely developed in recent years, mainly including contact measurement methods, quartz crystal oscillation method, ellipsometry, reflection spectroscopy, white light spectroscopy, etc.

  1. Contact test

The probe method is a typical contact measurement method that uses the vertical offset generated when the probe moves on the film surface to measure the film thickness. The step meter is a typical application of this method. When using this method, steps must be made on the film. The substrate serves as the lower surface of the step and the film serves as the upper surface of the step. The probe contacts the surface of the film and completes the measurement according to the step. Under this measurement method, the film to be measured needs to be made steps first, have caused damage to many films, and scratches may be produced on the surface of the film during the contact process, resulting in slow measurement speed.

2. Quartz crystal oscillation method

The quartz crystal oscillation method mainly uses the piezoelectric effect and mass load effect of the quartz crystal to measure the film thickness by measuring the change in its natural resonant frequency. The resonant frequency of the quartz crystal piezoelectric effect is f=N/d, where f is the natural frequency of the quartz crystal, N is the frequency constant, and d is the crystal thickness. The quartz crystal oscillation method has matured after decades of development and is widely used in real-time online measurements.

3. Elliptical polarization method

The elliptical polarization method is based on the polarization phenomenon that occurs when polarized light is reflected on a film. When the component of polarized light is reflected by the sample surface, the polarization state will change. The elliptical polarization method uses the change of polarization state to calculate the optical constants of the film, mainly by calculating the reflection coefficient amplitude ratio and phase difference of the two components. The most widely used spectral ellipsometry system at present is a typical multi-wavelength solution. The measured ellipsometry parameters are inverted and optimized for fitting to obtain the film parameters. Ellipsometry has extremely high sensitivity and is especially suitable for measuring ultra-thin films and can measure quickly. However, due to excessive sensitivity, the non-uniformity of the film, sample surface, model differences, etc. will affect the accuracy of its measurement. The complexity, price, and computational complexity of the instrument also limit its widespread application.

4. Reflection spectroscopy

Reflection spectroscopy uses the reflectivity of the film to calculate the optical constants of the film, and is the most commonly used instrument for measuring films. The measurement principle is that light is incident on the film structure and reflected. A spectrometer is used to collect the reflection spectrum in a wide band, and the reflectance curve is calculated through a standard sample. Finally, the curve is optimized and fitted with the theoretical model to accurately solve the film parameters. Reflection spectroscopy has a wide measurement range and a simple testing process.

5. White light spectral interference method

This method mainly uses the interference principle of light and the principle of spectral splitting, and uses the interference intensity of light at different wavelengths to solve the problem. The light emitted from the light source is divided into two beams through the dichroic prism, one of which is incident on the reference mirror, and the other is incident on the surface of the measurement sample. Both beams of light are reflected and incident on the dichroic prism. At this time, the two beams of light will interfere. The interference light is collected by the spectrometer to obtain the white light spectrum interference signal. The film properties are obtained by analyzing its interference signal. The testing process is simple and has high accuracy.

As a leader in domestic spectroscopy companies, Optosky is committed to the development of domestic instruments. We also focus on launching optical film thickness instruments such as SM series, which are widely used in semiconductor coatings, photoresist films, nitride layers, polysilicon, etc. It is developed based on the principle of film reflected light interference. It uses light with a wavelength of 200-1700nm to be incident on the surface of the film. If the film has a certain degree of projection instrument, can calculate the thickness of the film based on the interference spectrum reflected back. The maximum thickness mapping range reaches 1nm-250um.

Instrument introduction

SM200 optical film thickness measurement mapping instrument

Non-contact, non-destructive testing.

Ultra-long life light source, higher luminous efficiency (light source can be customized).

Desktop distributed design, rich applicable scenarios.

Low maintenance cost and easy maintenance.

SM230 automatic optical film thickness scanning mapping instrument

Non-contact, non-destructive testing.

The surveying and mapping speed is fast and supports multi-point surveying and mapping point map drawing.

Supports drawing 2D/3D thickness distribution of samples.

High-precision, long-life 3-axis rotating platform.

SM280 microscope-based film thickness mapping instrument

Non-contact, non-destructive testing system.

Integrated live camera to monitor measurement points.

Equipped with a microscope objective to support detection of small-sized samples.

The software interface is intuitive, easy to operate and saves time.

Applications

  1. Application of film thickness measuring instrument in a certain crystal oscillator industry

The crystal oscillator industry generally uses the quartz oscillation method to test film thickness. For relatively thin films (a few microns and below), the accuracy usually does not meet the requirements.

A certain crystal oscillator industry used our instruments to conduct film thickness tests and obtained good results.

  1. Application of film thickness measuring instrument in silicon dioxide measurement

Silicon dioxide films have been widely used in the fields of semiconductors, microwaves, optoelectronics, optical devices, and thin film sensors due to their excellent properties. Therefore, it is very necessary to monitor and control their film thickness.

Test Results

Material

Sample 1 (nm)

Sample 2 (nm)

Sample 3 (nm)

Sample 4 (nm)

Sample 5 (nm)

Sample 6 (nm)

Truth value (nm)

120

69

45

35

12

110

Test 1

120.37

71.11

46

35

8.48

105.28

Test2

120.44

71.02

46

35

8.48

105.12

Test 3

120.3

71.19

46

35

8.36

105.22

Test4

120.42

71.06

46

35

8.36

105.19

Test 5

120.4

71

46

35

8.37

105.21

Repeatability

0.14

0.19

0

0

0.12

0.16

Average value

120.39

71.07

46

35

8.41

105.21

Accuracy

0.39

2.07

1

0

3.52

4.8

(3) Application of film thickness measuring instrument on parylene coating

Parylene coating is widely used in PCB boards and related electronic device coatings. It has excellent electrical insulation and protection properties and is the most effective moisture-proof, mildew-proof, anti-corrosion and anti-salt spray coating material in the world.

Test Results

Sample name

Film thickness (nm)

Sample name

Film thickness (nm)

Sample name

Film thickness (nm)

Sample name

Film thickness (nm)

1029-1

30.44

1035-1

31.49

1039-1

30.42

1049-1

30.47

1029-2

30.43

1035-2

32.54

1039-2

30.44

1049-2

30.48

1029-3

30.40

1035-3

31.49

1039-3

30.45

1049-3

30.41

1029-4

30.42

1035-4

32.56

1039-4

30.43

1049-4

30.45

(4)Testing of PET film

The characteristic of PET reflective film is that the film has excellent optical properties and can be used in high-end vacuum aluminum plating and other products to achieve good results. The PET film is now tested.

Test Results

Sample number

Number of measurements

A (um)

B (um)

C (um)

D (um)

E (um)

#1

1

24.71

24.5

25.59

25.45

25.53

2

24.97

24.52

25.07

24.93

25.79

3

24.44

24.52

25.59

25.19

25.52

4

24.97

24.5

25.59

25.71

25.79

5

24.45

24.58

25.33

25.45

25.52

Average value

24.71

24.51

25.44

25.35

25.63

#2

1

25.89

25.65

25.23

23.45

25.56

2

25.64

25.39

25.55

23.19

25.82

3

25.63

25.65

24.74

23.72

25.56

4

25.11

25.39

25.28

23.19

25.82

5

25.63

25.65

25.55

23.98

25.82

Average value

25.58

25.54

25.27

23.51

2572

#3

1

25.89

25.8

25.35

25.63

25.16

2

25.63

26.32

25.38

25.25

25.94

3

25.89

26.07

25.41

25.46

25.68

4

25.63

25.8

25.33

25.48

25.68

5

26.15

26.32

25.22

25.33

25.41

Average value

25.84

26.06

25.34

25.43

25.57

Using a film thickness measuring instrument to test the PET film, the stability is good and the difference with the customer's true value is small.

Instrument parameters

SM series optical film thickness measuring instrument

Model

SM-LUV

SM-HUV

SM

SM-NIR

General specifications

Spectral range

200nm-1000nm

200nm-1000nm

400nm-1000nm

900nm-1700nm

Light source

Deuterium-halogen combination lamp

Tungsten halogen lamp

Measurement specifications

Thickness range1

5nm-10um

5nm-30um

20nm-60um

100nm-250um

Accuracy2

±2nm or 0.2%

±3nm or 0.4%

Incidence angle

90°

Film thickness layers

1~3

Sample material

Transparent or translucent film

Measurement mode

Single-point measurement/multi-point measurement/automatic measurement

Spot size3

2mm

Sample size

Diameter from 1mm to 300mm or larger

Basic requirements

Operating system

Windows10/11

Indicator light

Deuterium lamp indication, halogen lamp indication

Halogen lamp indication

Button

Power button, deuterium lamp, halogen lamp

Power button, Halogen light switch

External interface

Power outlet, USB 2.0, RJ45

Movable stroke

150mm*360°

Material

Aluminum alloy

Power supply

100~240VAC, 50~60Hz

Packing list

Host, measurement platform, power cord, communication cable, optical probe, Y-shaped optical fiber

Remarks: 1. Depends on the material; 2. Whichever is larger depends on the material; 3. Optional to 20um

Summarize

The SM series film thickness measuring instrument adopts the principle of thin film reflected light interference and can be widely used in film thickness testing in semiconductor, photoresist, crystal oscillator, polysilicon, nitride layer and other industries. The test is non-destructive, fast, accurate and has a wide range of application scenarios. At the same time, customized measurements can be made according to user needs. If you are interested in the above solutions or have other film thickness application scenarios, or want to know more about the design details, please call us for consultation.