How to Measure Wafer Thickness in the Semiconductor Industry?

In recent years, the demand for semiconductor wafers industry is increasing with the continuous development of 5G technology, IoT and technology. There are certain specifications for general wafer thickness, and wafer thickness has a significant impact on the performance and quality of semiconductor devices.wafer testing With the continuous development of integrated circuit manufacturing technology, the chip feature size has been gradually reduced, leading to the rise and development of wafer thinning process, and wafer thickness measurement has become one of the essential requirements for many wafer manufacturers.

Wafer preparation process

At present, the main processes of wafer preparation are: single crystal growth, slicing, polishing, deposition, circuit preparation, cleaning, testing, etc. The test is to assess the quality of the wafer.

Among them, testing is the key link to evaluate the quality of wafers, which helps to ensure the performance and reliability of wafers. Wafer inspection items include package inspection, contact resistance inspection, RF inspection, defect inspection, thickness inspection, roughness inspection and flatness inspection.

Wafer thickness for the development of inspection history process

In the early days (70's), the contact method was used to measure the thickness of wafers, such as micrometers, profilometers, etc., which could easily cause damage to the wafers and loss of materials.

And then with the development and progress of science and technology, non-contact measurement has become the mainstream method of wafer thickness inspection. Among them, there are mainly white light interferometer, ray fluorescence method, laser displacement sensor, spectral confocal displacement sensor and so on. These methods measure from the microscopic level, non-contact detection through the principle of optics, will not cause damage to the wafer,wafer probe and the measurement accuracy is high.

At present, the wafer thickness measurement technology has been developed to a higher level, and the emergence of various non-contact measurement technologies has provided reliable technical support for the semiconductor industry. However, with the gradual reduction of process nodes, the wafer thickness is also gradually reduced, and the requirements for wafer thickness detection are also getting higher and higher.

Example of Wafer Thickness Inspection

An electronics research institute wanted to detect the TTV thickness of wafers with an accuracy of 1μm, so as to realize automatic measurement on the production line and screen for defective products. UCOMETRIC received the customer's measurement requirements, selected the test and customized the solution for the customer:

UCOMETRIC engineers can first analyze and test six randomly selected points on the wafer to obtain the thickness of each point of the wafer.

Then, the platform's motion simulation automatically measures the wafer's thickness in real time.

In order to meet the requirements of different sizes/materials/thicknesses of the customer's vehicle, excellent measurable development customization requirements to meet the customer's needs for the vehicle to ensure the stability of the test. The surface of vacuum adsorbent is customized according to the characteristics of customer's products to ensure the high accuracy of products in the plane state. At the same time with script editing capabilities to provide customers with after-sales debugging and software development assistance.

After receiving the samples and the test results of the project design,probe holder the customer said: "I didn't expect this excellent and measurable point spectrum measurement to be so effective. In addition, the rack design of the whole machine meets our needs. Our automated measurements on the production line can finally be realized!"

Measurement Principle of the Excellent Measurable Spectral Confocal Displacement Sensor

The spectral confocal displacement sensor emits light from a white point light source, which is illuminated on the surface of the material by means of "optical fibers" and "mirrors". From top to bottom, light of different operating wavelengths is focused at different heights, forming an important measuring range of its own. When different characteristic wavelengths of light irradiation to other objects, only we focus on the surface of the measurement technology object structure of the reflected light can be developed to reach the "dispersive mirror group", through the lens group dispersion, dispersed into different detection wavelengths of monochromatic light, mapping to the "CMOS Spectral Imaging Terminal CMOS spectral imaging end". The final result analyzes the wavelength of the reflected light, which in turn affects the height of the surface that can be generated according to the object under test.

Confocal displacement sensor has three advantages

1, not affected by the material can be stabilized for measurement

Any material can achieve high precision measurement, transparent objects can also be recognized through the multi-layer transparent surface to accurately measure the displacement and thickness of transparent products, and even confocal method can be used to measure the narrow holes without dead ends.

2. High-precision measurement with 0 heat generated in the measuring unit.

Traditional laser displacement sensors are easy to develop is because of the company's own heat generation problems produce deformation, resulting in the deviation of the student measurement. You can measure the spectral confocal displacement sensor measurement control unit inside only one lens structure can be designed, no heat, coupled with low distortion mirror group, can realize the social ideal of high-precision measurement.

3, oversized angle characteristics

Excellent measurable spectral confocal displacement sensor's maximum angular characteristics of ± 48 °, the measurement of the arc is convenient.