Failure Analysis Zhao Gong Semiconductor Engineer 2022-07-24 09:50 Published in Beijing
DISCO is a Japanese company whose core competitiveness is to grind manufactured semiconductor silicon wafers into thinner silicon wafers, and then It is cut into dies and then assembled into electronic products. Their company motto is Kiru, Kezuru, Migaku, which means cutting, grinding and polishing. DISCO has a leading market share in the production of wafer grinding machines , grinding wheels , wafer dicing saws, laser saws and surface planarization.
These businesses enabled DISCO to earn nearly $2 billion in revenue in 2021. We will take an in-depth look at the major semiconductor process tools manufactured by DISCO.
Before we dive into these topics, let’s give a brief introduction to the company’s history and their unique culture. Before focusing on semiconductors, DISCO was known as Dai-Ichi Seitosho CO. They were only renamed for easier pronunciation after they began exporting to the United States. They are focused grinding wheels for a variety of products, but they really hit the mark when they produce a thin (1.2mm) high-precision blade for grinding C-shaped magnets. As they progressed, they invented resin blades that encapsulate hard materials within ultra-thin (0.13mm) resin. These are used to cut the pen nib .
DISCO continues to make thinner and thinner grinding wheels, using the 40 micron thick grinding wheel MICRON-CUT. Many equipment manufacturers and industrial companies began blaming DISCO for the damage because the tools could not accommodate these ultra-thin grinding wheels. Because of this, DISCO began designing its own equipment. DISCO tools were even used to cut moon rocks brought back by Apollo 11 !
In the 1970s, DISCO entered the semiconductor industry by producing automatic scribing machines and dicing saws. At the 1977 Semicon conference, DISCO developed and demonstrated their DAD-2H cutting saw. They had issues with the cutting wheel breaking when stopping and restarting the saw, so the DISCO team decided to have their saw and cutting wheel never shut down throughout the multi-day show. Apparently, DISCO was all the rage among semiconductor users at the 1977 show. Although
is an old Japanese company, the company culture is not. They are very efficient and focused on quality and throughput. They may have the most unique corporate culture in the world. Let's talk about how it came about.
DISCO: Everything Has a Price
DISCO faces many of the same problems faced by large and established companies. A lot of time is wasted in meeting after meeting. Every decision must involve dozens of employees. There is no room for innovation and employees waste a lot of time on unnecessary actions. Bureaucracy kills the lifeblood of companies. At the same time, there was poor communication throughout the organization, as employees became increasingly focused on their niche markets that they missed the overall strategy. There are so many layers between those who work on the nuts and bolts of product and management. The
solution is very strange and frankly cool. There is an internal virtual currency was created called "Will". This currency is used as a compensation system to track each person's and team's contribution to revenue. Workers receive a base salary and a bonus based on how much they earn for completing tasks. Groups pay each other to complete tasks. Sales teams pay factory workers to produce goods, who in turn pay engineers to design products. Once a sale is made, it generates a certain amount of intent and is passed on to everyone in the supply chain, including HR and IT support staff.
Ordinary employees are awarded virtual currency when the group boss allocates a portion of the group's budget to each task they have to complete. Team members then use the app to bid on these jobs. Tasks that don't attract any bids often turn out to be unnecessary work. Managers who abuse or abuse the system have been abandoned by their employees and are free to move on to other teams.
At DISCO, everything has a price, from meeting rooms, desks and PCs to space for umbrellas.It’s almost a one-person startup!
This freedom enables employees to shape their own day and focus on the value of their time and effort. The ruthlessness of the hardcore free-market approach is diluted in an environment where people work side by side.
In addition, they have a punishment system for inefficient behavior, including piling up unnecessary inventory and even working overtime. Since the penalties were imposed in 2015, overtime hours have decreased by 9%, in line with the Japanese government’s goal of improving work-life balance.
The success of this program cannot be underestimated. DISCO's operating margin rose to 36% in the latest year from 16% before implementation. Additionally, they gained some share.
DISCO: involves the entire process of chip manufacturing.
DISCO products are used in the entire process of chip manufacturing. Ingots are grown and cut and then ground down. Before the wafer is cut, the backside of the wafer is ground away. The wafers are diced, and the chips are packaged on large-format packages and cut into individual units. Each of these steps has more complexities.
As shown in the figure, the DISCO grinder lineup varies greatly depending on the production volume of silicon wafers. There are also different tools for special materials such as silicon carbide which are harder than diamond. Material handling is very important depending on the thickness of each material. After main grinding, some use cases require the use of a grinder/ polisher to make the surface more uniform. Additionally, there are surface planers. They usually use diamond drill bit to partially remove the part of the cinnamon. DISCO also sells CMP tools, but their share is very low compared to Applied Materials, which holds the majority of the market share, and EBARA, which holds the bulk of the remaining market.
With the rise of advanced packaging, especially hybrid bonding, the thinning application market is soaring.
Cutting saws and blades are another main business of DISCO. There are also various tools depending on the level of automation and throughput required. There are also a variety of blade types. Generally speaking, there are 4 main types of inserts that lie at different points in the curve in terms of stiffness, insert life, and cutting capabilities. Saws , like grinding wheels, wear out and must be replaced on a semi-regular basis. This is a good consumable business for DISCO.
In many cases you don't just grind with a physical blade and then saw. The slide above shows some advanced refinement techniques. It is common to cut into pieces before grinding. The war film shows it visually, but with the wafer partially cut before flipping and grinding. When wear-through occurs, it encounters a partial cut and the silicon wafer splits into die. The process includes a lifecycle of 5 DISCO tools + multiple consumables such as saws, grinding wheels and tape laminates.
cutting is not just done with a saw. It can also be done with a laser. This is called invisible cutting. Here we will introduce the concept of "street". Street is the area between dies. As chip size becomes smaller, the area occupied by street for processing silicon wafer will become disproportionately larger. The ultra-small chip size must cope with the consumption of cost budget . As a result, the saw becomes very inefficient. This is where stealth cutting comes in. The laser can handle streets of size almost 0. There will be some waste, but the width will be greatly reduced, so the number of die per wafer can be increased.
Stealth and plasma cutting are currently mainly used for special processes, especially MEMS, or with extremely small die sizes. With wafer costs soaring with the upcoming 3nm node and advanced packaging, we could see stealth cutting into leading-edge logic chips. The laser is typically focused on the portion of the wafer below the top layer. It can also be used to create grooves in wafers that are then plasma cut. There are some concerns about taking laser cutting into other processes as the laser can cause delamination and street related metal issues. There are other issues with saws, cutting chips can cause the metal to be dragged onto the street and cause damage.
Taiko craft is a very interesting innovation. Rather than grinding the entire silicon wafer and then having to use a temporary carrier as a structural support, the grinding wheel grinds only the inside, leaving a full-thickness outer ring. There are some etching processes used for stress relief.This is followed by advanced integration of through-hole, bump, discrete device, backside metallization and wafer-level probe card testing. The entire thickness of the ring is cut with a laser, and the final assembly is cut into a mold for packaging.
In principle, the laser lift-off tool looks very similar to what SOITEC does with its Smart Cut SiC technology. Laser lift-off is shown on sapphire substrate , but transfer of the individual epitaxial layers is similar. It could be that SOITEC used DISCO's tools, but they didn't mention the laser for liftoff in the PR.
DISCO has almost a lock on the power semiconductor market because the grinding and cutting here is more complex compared to silicon.
Source: Semiconductor Industry Alliance
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