Abstract
We present a cost-effective approach to produce silicon strain gauges that can withstand very high voltage without using any complex package design and without sacrificing any sensor performance. This is achieved by a special silicon strain gauge structure created on an alkali-free glass substrate that has a high breakdown voltage. A half-bridge silicon strain gauge is designed, fabricated, and then tested to measure its output characteristics. The device has a glass layer that is only 25–55 µm thick; it shows it is able to withstand a voltage of over 2000 V while maintaining a high degree of linearity with correlation coefficients higher than 0.9990 and an average sensitivity of 104.13. Due to their unique electrical properties, silicon strain gauges-on-glass chips hold much promise for use in advanced force and pressure sensors.
Highlights
Since the discovery of the piezoresistive effect in silicon (Si) and germanium in 1954 [1], there were continuous and challenging obstacles to overcome in the field of measuring basic mechanical quantities, such as stress, pressure, touch, acceleration, and weight
The finished Si gauge chip is glass-frit bonded onto a metal diaphragm. This results in a product with reliable glass–glass frit bonding that, unlike the Si–glass frit bonding in existing technology, provides high bond strength and quality, while the coefficient of thermal expansion (CTE)-matched Si–glass system can withstand very high voltages and has good electrical characteristics. The combination of these factors results in extremely high-performance Si strain gauges that are significantly better than any competitor
The backside glass was thinned down to about 25–55 μm by chemical mechanical polishing (CMP), and the whole wafer was diced into strain gauge chips using a sawing machine (Figure 3f)
Summary
Since the discovery of the piezoresistive effect in silicon (Si) and germanium in 1954 [1], there were continuous and challenging obstacles to overcome in the field of measuring basic mechanical quantities, such as stress, pressure, touch, acceleration, and weight. The vast majority of commercial force and pressure sensors today use Si piezoresistive strain gauges. These are made from p-type Si and are either manufactured as separate elements for bonding to the surface of a sensing diaphragm [5,6,7,8,9] or embedded into an Si sensing membrane [10,11,12,13]. Another example incudes medical pressure sensors in oxygen concentrator devices that need to have both a high degree of accuracy and a high degree of repeatability; on top of this, they should be able to measure oxygen tank pressure levels of about 2000 psi (136 bar) [15]
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