Semiconductor manufacturers need the flexibility of a wafer-cutting machine that supports various wafer sizes and cuts them without the mechanical and thermal damage often seen with traditional cutting methods, including the mechanical stress that occurs with conventional sawing, or the contamination and/or ablated material caused by laser cutting. Employing a dicing process that makes the wafers less prone to breakage would allow manufacturers to introduce thinner wafers into the production line, thereby increasing the number of functions on a given device. A machine that cuts lasers without a heat-affected zone would also offer efficiency advantages to manufacturers.
A number of major semiconductor companies in North America, Europe, and Japan are using Synova S.A.’s (Lausanne, Switzerland) water-guided lasers to eliminate the typical problems inherent in the semiconductor manufacturing industry.
Strengths and Weaknesses
Bernold Richerzhagen, an engineer at the Federal Institute of Technology (EPFL) in Lausanne, Switzerland, thought combining water jets and laser cutting would overcome the limitations of each individual technique.
Traditional water cutting breaks the target material under the pressure of a high-powered water jet. Soft materials such as wood, cardboard, and foodstuffs are well-suited for water jet cutting; adding microscopic particles to the jet stream widens the range of materials to include metal, stone, ceramics, and glass. While water jets require less investment capital and do not emit gas when cutting, water jet cutting imposes a drying step on the manufacturing process, and can mechanically damage the material.
Dry laser cutting happens when the material absorbs the energy of the laser and melts or vaporizes. Any residual material left from the cut is expelled by an assist gas. The two drawbacks of laser cutting are thermal damage to the material and contamination when the assist gas does not sufficiently remove the ablated material. In the latter case, a protective coating can be applied to the surface prior to cutting, but this increases costs. Although lasers fit quite well into today’s manufacturing processes, they incur higher initial costs than water jet cutting equipment.
To improve both systems, the engineers at the EPFL focused the laser beam into a water nozzle while simultaneously passing the beam through a pressurized water chamber. The low-pressure water jet (lower pressure than the standard water cutting jet) that is emitted from the nozzle guides the laser beam by means of total internal reflection at the water/air interface. Today, the semiconductor field is the primary beneficiary of this innovative technology; however, the water jet-guided laser is also used in an increasing number of other fields, including medical, tooling, and energy.
Best of Both Worlds
The Laser Micro-Jet technology has a number of advantages over the two traditional methods. In conventional laser cutting, the laser beam is divergent and the working distance is short; focus-distance control is required. This is in addition to the debris concerns and additional protective coating requirements mentioned earlier.