Equipment used in the process

The backgrounding machine is the most common equipment used in the silicon wafer grinding process. This method is more cost-effective and faster than plasma etching but has several disadvantages.

It can result in mechanical stress, excessive heat, and scratches on the backside of the wafer. The size of the grit is directly proportional to the pressure applied to the wafer during the grinding process.

The multi-wafer grinding machine can grind multiple silicon wafers simultaneously. It can process up to 300mm diameter wafers and grind both faces at once.

Although this process requires various grinding steps, it can increase productivity. Depending on the type of silicon wafer, the equipment may vary in terms of the number of grinding spindles used, as well as the quality of the wafers.

The conventional grinding tool has several grinding modules that grind the backside of the semiconductor wafer. It also has multiple stages that scratch the surface of the semiconductor wafer.

The bottom of the silicon wafer is scraped using a coarse grind and a delicate grinding process. The movement between the stages of the grinding process can cause delays and misalignment. This will impact the cost and quality of the final product.

The growing need for thinner semiconductor devices drives the demand for thinning silicon wafers. The process was once reserved for exceptional circumstances, but now it is necessary for nearly all semiconductor applications.

It is also becoming more crucial in assembly processes as it can be difficult to reclaim wafers if the backgrounding method is used. For this reason, the latest technology for grinding and polishing silicon wafers is a significant step forward.

The wheel head is movable and may be positioned vertically or horizontally. It is fitted with a spinning wheel axis 102 driven by a motor. A control unit 105 controls the movement of the wheel head.

When the wheel head is lowered, the grinding wheel is simultaneously rotated. The grinding wheel is then fitted onto the wafer and ground. The entire process requires much time but is worth the effort.

The silicon wafer grinding process requires excellent surface and subsurface quality. The process has evolved over the decades, and most machining techniques are now used in wafer factories. The grinding process is crucial in developing a high-quality silicon wafer for chip fabrication.

This paper discusses the historical perspectives of grinding silicon wafers, the impact of the progression in the size of silicon wafers, and the interrelationship between grinding and two other processes of silicon wafer manufacturing. The paper is intended to provide a complete overview of the grinding of silicon wafers and may also prove to be instrumental in future research on grinding other materials.

The second method is laser grinding. It includes two steps. The first step consists of removing pollutants from the sawing process. During the second step, the surface oxide layer absorbs the laser beam, forming a plasma with high energy density.

The plasma then expands, creating a shock wave and fragmenting the pollutants. The laser grinding process also results in laser melting. Due to surface tension and the Marangoni effect, the laser-melted silicon wafer surfaces are redistributed inflow.

Effects of residual stress on the process

The effects of residual stress on silicon wafer grinding have been studied for several years, but it has only recently come to light that it is a fundamental factor that can influence the final result of the process.

To determine the extent to which residual stress affects the silicon wafer grinding process, we studied the interaction of key process variables. As a result, we have developed a methodology for determining the impact of various parameters on the final distortion.

A simple way to determine the impact of residual stress on silicon wafer grinding is to measure the curvature of the silicon wafer during the grinding process. We use the Twyman effect, which causes the curvature of the silicon wafer, to calculate the residual stress.

We then polish the silicon wafer using MRF to remove the residual stress. We found residual stresses are highest near the lapped surface, decreasing with characteristic lengths of 0.4-0.5 micrometers.

As we can see, the presence of residual stress can have a significant impact on the grinding process. Specifically, when a silicon wafer is subjected to a large amount of pressure during the grinding process, a sizeable hydrostatic pressure is generated on the silicon wafer.

This is particularly important for single crystal silicon, which undergoes a phase transition under pressure, and the crystal structure changes from a diamond structure to a b-sn phase or a close-packed hexagonal structure.

The presence of residual stresses during the grinding process is a result of phase transformations and plastic deformations that take place during the process. Residual stresses also depend on various grinding parameters, including the rotational speed and the amount of load applied to the component during the grinding process.

High rotational speed causes more tensile residual stresses, while higher friction rates lead to tremendous flexural residual stress. High grinding speeds also increase the heat created by the process.

As a result of residual stresses, microstructural changes may occur in the steel. There can also be elastic-plastic deformation or surface integrity changes. When the surface temperature of the workpiece increases above the customization range, the material will re-harden, a process known as re-hardening burn. In addition to being hardened, the heat also causes cracks and pitting of the surface.

To test the hypothesis that residual stress has an engineering-specific response, we investigated the geometry of a coupon. Using a coordinate measurement machine, we assessed the coupon geometry using three scans in the longitudinal and transverse directions.

The resultant tensile stress regimes were higher, and the distortion magnitudes were higher. The results of this study indicate that residual stress formation is a complex process requiring additional assessment.