This article will discuss the advantages and limitations of wafer backgrinding. We will look at the costs and productivity of this process as well as the environmental impacts of it. Let’s start by examining the limitations of backgrinding. First, let’s understand what a backgrinding pattern looks like. A backgrinding pattern consists of scratches on the backside of a silicon wafer. The depth of these scratches is dependent on the grit size and vertical pressure of grinding. Obviously, the finer the grit, the smaller the scratches are. Moreover, silicon strength is inversely proportional to its depth. As a result, a smooth surface minimizes the strength of silicon.
Limitations
While a number of advantages of this back grinding process are noted, this procedure has its limitations. In addition, a wafer with a thickness of 300 mm or more is at risk of being deeply deflected. When the grinding process is completed, the wafer grinding is usually turned upside down, making peeling the adhesive film a difficult task. In addition, the thickness of the adhesive film may result in decreased adhesion workability.
Thinner wafers are also more fragile than thick ones, which makes the next process more difficult. In addition, the wafer is also less resistant to external forces, making it more prone to warping and breaking. It also requires more complex technologies to accomplish this. Further, a thinner wafer may not be as strong as a thicker one, making it difficult to process it in any manner.
To reduce the risk of air bubbles, the substrate film must have good adhesion and no residue should remain on the surface after peeling. Backside grinding may also cause non-UV reduced tack films to fail, as their adhesive strength is weak and the film is prone to air bubbles. The non-UV reduction tack film treatment also results in the appearance of bump films, which are twice as thick as UV reduction films. This technique is expected to become more common in the future.
The technology used in back grinding is based on three processes: rough grinding, fine grinding, and polishing. In a typical wafer, a single back grinding process involves three steps: rough grinding, fine grinding, and polishing. The first two steps are similar to the steps used in Chemical Mechanical Polishing. The backside grinding process uses a thin blue tape for protection from ultraviolet light, which helps reduce friction between the wafer and the pad.
Costs
The back grinding process generates high-temperature thermo-mechanical stresses on the wafer. This can make it susceptible to cracking. The cost per semiconductor chip is determined by the thickness of the wafer, so the process order is critical. For this reason, back grinding is a critical step in the semiconductor manufacturing process. In addition, back grinding can help semiconductor manufacturers meet increasingly stringent production and reliability standards.
High costs may hinder the growth of the wafer backgrinding tape market in the near future. The growing semiconductor manufacturing industry in Asia-Pacific is creating lucrative opportunities for the market. In particular, India has fast-growing electronics systems design manufacturing.
Depending on the process, the cost of backgrinding a 300 mm wafer can range from a few hundred dollars to several thousands of dollars. However, the process does require highly accurate measurements, which is essential for the proper removal of material from semiconductor wafers.
The industry has experienced a booming market, with the average value of backgrinding tape growing at nearly 5% over the next four years. The COVID -19 pandemic has affected sales revenue of leading companies, followed by innovators and disruptors.
Productivity
The process of backgrinding a wafer starts with precise measurements. In a backgrinding process, the right amount of material is removed from a wafer to form the complex components needed for semiconductor packaging. A backgrinder can remove 100-um logic gates, 50-um DRAM memory, or 30um MEMS memory. The vendor of the wafer backgrinding equipment must perform high-resolution measurements before shipping the wafers. Some customers, however, perform their own measurements after receiving the wafers. In either case, MTI Instruments plays an important role.
Backgrinding can improve productivity, because it reduces the thickness of the wafer. Typically, a 200-mm wafer is 720-um thick, which is about ninety percent of the original thickness. The next step is a finer grit that polishes the wafer to the required thickness. A typical two-step backgrinding process uses grinding wheels mounted on two separate spindles.
As the size of portable devices decreases, the thickness of semiconductor wafers is also decreasing. Integrated circuits must be smaller and thinner to be compatible with smaller devices. Backgrinding a wafer can produce ultra-thin silicon wafers that are ideal for compact electronic devices. However, it can also compromise wafer strength, which makes the process more complex. In this case, wafer backgrinding is crucial.
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Environmental impact
In semiconductor device manufacturing, the process of weipeo (wafer backgrinding) involves a series of processes involving ultrapure water. It requires high amounts of water to operate and generates large quantities of wastewater. Furthermore, the process uses excessive amounts of ultrapure water.
This back grinding process uses a Disco Corp. DFG-860 grinding machine. The average warpage values of the silicon wafers after backgrinding were 1.8 mm, 0.5 mm, and 1.0 mm, respectively. Consequently, back grinding can cause significant environmental damage, but it does not compromise the functionality of the wafer.
These resins are less durable than other materials, but have the same chemical properties. Non-crystalline polyester reflects the chemical solution method, while polyethylene terephthalate is more resistant to chemical reaction. Poly(ether sulphone) can reduce the environmental impact of wafer backgrinding and improve its sustainability.
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