Thinning and Cutting of Chips

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Thinning and Cutting of Chips

Chip thinning and dicing In modern semiconductor manufacturing, the size of silicon wafers continues to increase, from 6 inches to 18 inches. The size of the silicon wafer is limited by its thickness, so its size increases, and the thickness needs to be increased accordingly to ensure the mechanical strength, which also brings challenges to the subsequent chip processing, the most significant of which is chip cutting and packaging.

This article mainly introduces the thinning and cutting of silicon wafers, which are described as follows:

Chip downsizing

Chip cutting

1 Chip downsizing

For example, for a TSOP package, the effective thickness of the circuit layer is only 300 μm, but the total thickness of the actual silicon wafer usually needs to be 900 μm. Therefore, after the relevant process of the circuit layer is completed, the back side of the processed silicon wafer will be thinned and then cut to form a thinned bare die.

There are various technologies for backside thinning of silicon wafers, mainly including:

Grinding & Grinding:

This method is a physical process, but it can lead to subtle damage to the surface of the silicon wafer and reduce the mechanical strength. The instrument used in this method is a grinding wheel, which is thinned with a medium such as abrasive paste and water.

 

Dry Polishing：

This method is different from the grinding and grinding described above, and does not need to be paired with excess media, and only uses specific instruments for polishing to remove stress and unevenness.

CMP：

Combined with chemical corrosion and physical grinding, the thinning and polishing of silicon wafers can be realized.

Other technologies use chemical or electrochemical methods in combination with physical means to downgauge silicon wafers, such as plasma-enhanced chemical corrosion. In order to improve the flexural strength of the thinned wafer, methods such as dry polishing or plasma corrosion are usually used to remove the stress.

2 Chip cutting

The silicon wafer after the chip thinning needs to be cut, and the cutting method is mainly divided into two categories: blade cutting and laser cutting.

Blade cutting:

This method is the most traditional cutting method, as the name suggests, the cutting tool used is the blade, but the hardness of the ordinary blade is not enough, and the diamond grinding wheel blade is generally used.

However, chipping can occur near the cutting location due to stress, which can be significantly reduced by using fine abrasive inserts.

Laser cutting:

The energy generated by laser focusing is used for cutting, and the following figure is a schematic diagram of the laser grooving cutting process