The Basics of Semiconductor Manufacturing and Examples of Chip ...

In this article, we’ll start with a simple overview of the processes and machines involved in making semiconductor chips and the products all around us that rely on them. We’ll then take a closer look at some of the challenges that arise in the semiconductor chip picking process, where chips are grabbed and lifted. After that, we’ll suggest methods for damage control using THK’s Pick and Place Robot (PPR) by sharing examples of user challenges and product applications.
We hope that young engineers just entering the semiconductor industry as well as veterans who are already grappling with the challenges of the chip picking and placing processes find this article useful.

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1 Other materials are also used.

2 A technique called “flip chip bonding” also exists at time of writing.

Among the various machines that are used in these processes are dicers for die singulation, die bonders for setting dies (chips), sorters for organizing dies prior to die bonding,* and wire bonders for wire bonding.

* Sorters can remove chips determined to be defective during testing.

Challenges in Picking Up Semiconductor Chips

Let’s return to the processes where wafers are broken into individual chips and these chips are picked up. During die singulation, wafers are stuck to adhesive tape to prevent chips from scattering when they are cut. Afterwards, the chips cut from the wafer are grabbed by a picking tool and removed from this tape. The physical properties of silicon make it easy to break or crack the material with even a small impact. This poses the risk of damaging chips that have already made it through pre-processing. To avoid this, the adhesive tape stuck to the wafer is expanded, and ejector pins are used to lift individual chips from below. This makes it easier for picking tools to then remove each chip from the adhesive tape.

Using ejector pins to lift chips makes it easier to remove them from the adhesive tape, but it requires highly advanced technology. Below are some factors that complicate this process.

1. Chips are very thin and very delicate
2. Ejector pins and picking tools must move in sync with each other
3. Wear can change the relative positions of ejector pins and collets* with respect to the chips

* In the semiconductor and electronic component industries, a suction nozzle is called a collet.

Let's look at each of these complicating factors more closely.

1. Chips are very thin and very delicate.

As mentioned above, ingots are sliced into thin pieces to produce semiconductor wafers. Making these wafers thin means that a single ingot can yield more of them, which drives down the cost of each. And the smaller and thinner semiconductor devices are, the less area and volume they require when mounted to a circuit board. All of this contributes to making the finished electrical device more compact and making the final product easier to use. While many chips are cut to a width of 0.5 mm to 1.0 mm for the sake of making them harder to break and thus easier to handle, some cutting-edge chips can be as thin as 20 μm.

3. Wear can change the relative positions of ejector pins and collets with respect to the chips.

Ejector pins and collets make contact with chips thousands if not tens of thousands of times each day, which can gradually wear them down. In order to prevent this wear, cemented carbides and even diamonds are used to make these components. All the same, the tips of these components can become warped such that their relative positions with respect to the chips are altered, which can cause ejection errors as well as damage to the chips being handled.

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Dicing: The wafer is cut with a diamond blade and separated into individual chips. In the dicing process, the wafer was attached to a dicing tape, and a rotating circular diamond blade was used to separate the semiconductors while spraying ultrapure water.

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In addition to the diamond blade method, there are other methods of dicing, such as the laser method, which cuts with a laser; the scribe method, which cuts by inserting scratch lines into the wafer to cause cracks; and the plasma dicing method, which uses etching with plasma to separate the wafer.

If dicing tape is used, the tape holding the wafer in place must not be cut. After cutting, the dicing tape was stretched to create a clearance between the chips to facilitate removal and other operations.

Wire bonding: The chip is fixed to the lead frame (die bonding). A lead frame is a thin metal support for a chip that serves as a terminal for mounting a semiconductor on a board.

Some lead frames can diffuse heat, and in some cases, such as in the manufacture of power semiconductors, they are mounted on heat sinks instead of lead frames. In die bonding, adhesives such as silver paste are used.

After die bonding, the wire-bonding process connects the chip to the lead frame with a thin gold wire. This allowed the chip to be wired through the lead frame.

Molding: Chips are very delicate products that can be affected by scratches, shocks, dust, and magnetism. Therefore, the chip is encased in epoxy resin to protect it from external factors. This is called molding or packaging.

However, in recent years, smaller semiconductors have been required as the products have become smaller. The answer is bare dies, which are semiconductors that have not yet been packaged. The advantage of bare dies is that they can be stacked on a substrate in three dimensions; however, their chip yield is poor.

Wire bonding: Lead frames that are bonded to chips via wire bonding are electroplated. This improves the bonding between the wire and the frame. In electroplating, the metal to be plated is immersed in a plating solution and electricity is applied to deposit the metal in the solution on the surface of the metal to be plated. Matsusada Precision provides power supplies for the electroplating of lead frames.

Evaluation testing: The pre-shipment inspection process for semiconductor products includes dielectric breakdown testing, electrostatic discharge testing, and non-destructive X-ray testing. In a dielectric breakdown test, a high voltage is applied to the insulator or other material covering the semiconductor, and the voltage at which it is destroyed is measured.

When a human touches a product and an electrostatic discharge occurs, the product's durability is assessed using the electrostatic discharge test. The capacitor was charged with voltage and produced a quick pulse current during the static discharge test. Matsusada Precision provides high-voltage power supplies for dielectric breakdown and electrostatic discharge testing.

X-ray nondestructive inspection is an inspection in which an object is irradiated with X-rays to check its internal state, and it offers a line of X-ray transmission inspection systems that can be used for X-ray nondestructive inspection of semiconductors.

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