Semiconductor Manufacturing Precision Measurement in Real Time to Improve Yield And Process Stability

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The increasing complexity of modern semiconductor manufacturing processes presents system manufacturers with new challenges in terms of precision, process control and quality assurance. Measurement and control concepts are becoming increasingly important, especially in heterogeneous 3D integration.

In the semiconductor industry, every nanometer counts, every defect costs thousands of euros and process stability is essential. From grinding to CMP and bonding to test procedures, manufacturers of semiconductor equipment are increasingly no longer viewing force, pressure and acceleration sensors as an optional additional function. In many applications, classic MEMS or strain gauge sensors reach their limits in terms of resolution, measuring range or service life. It can make sense to integrate high-precision piezoelectric sensors into semiconductor production systems in order to meet the increasing demands on yield, quality and efficiency.

Heterogeneous 3D integration is revolutionizing semiconductor manufacturing by combining logic, memory, radio frequency (RF) and chiplet components into compact, high-performance systems. This enables technological advances in artificial intelligence (AI), high performance computing (HPC) and 5G/6G. However, the complexity of the wafer bonding, die stacking and through-silicon via (TSV) processes also harbors considerable risks.

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As components become ever smaller and contain new materials, the tolerances for force, pressure, vibration and temperature are shrinking to a critical level. Yield is affected by specific risks at every step of the process: from sub-micron alignment during wafer-to-wafer bonding, to avoiding voids during TSV filling, to chip displacement during the die attach process or anomalies during encapsulation. At the same time, the economic consequences of defects are increasing rapidly. Each of these anomalies can multiply costs, often by several thousand euros. Production equipment with integrated monitoring and control can contribute significantly to process stability and yield to protect the substantial value of each wafer.

Semiconductor Suppliers Bear the Burden of Precision

The manufacturers of production systems for the semiconductor industry are at the center of technological change: they play a central role in precision, productivity and quality. This makes them key factors for the entire industry. While speed and mechanical precision used to be the decisive parameters for success, semiconductor manufacturers today have much higher requirements. Among other things, integrated sensor technology, closed-loop process control and traceable quality data that enable predictive maintenance are required. As a result, systems are evolving from purely mechanical precision tools to intelligent systems with integrated monitoring and adaptive control.

Failure Modes Put the Yield at Risk

3D integration is associated with a large number of complex and cost-intensive failure mechanisms. Defects such as cracks or misalignments can be identified by optical inline inspection, but additional risks arise during production that cannot be detected using these methods. Thermomechanical stresses due to different coefficients of thermal expansion (CTE) can lead to deformation or micro-cracking. TSV processes are prone to incomplete filling and voids, which compromises electrical integrity. Even minimal lateral displacements or tilts in the micrometer range during the die attach process can disrupt alignment and prevent precise contacting of the interconnect structures. Furthermore, a faulty print profile during encapsulation can cause mechanical damage to sensitive chips.

Precise Sensor Technology: the Foundation for Quality And Yield

High-resolution piezoelectric force sensors integrated directly into the bond heads monitor all bonding processes in real time and can reduce the risk of quality deviations. Suppliers such as Kistler offer sensor solutions that enable semiconductor equipment manufacturers to implement closed-loop control and support end-to-end process transparency. Thanks to their high resolution, signal stability and low drift, the sensors provide reliable measurement data for process optimization, quality assurance and complete traceability. Stable measurement results can also be achieved under demanding conditions such as high-temperature bonding and encapsulation. The sensors are also optimized for clean room and vacuum applications.

The compact, highly sensitive sensors detect forces from nanonewtons to kilonewtons and thus cover a wide measuring range and application spectrum—from precise grinding and chemical mechanical planarization (CMP) to bonding, chiplet placement and encapsulation. Thanks to the high-resolution real-time detection of even the smallest forces, they enable more precise process control and help to achieve stable quality even at high throughput rates.

During the acceleration and deceleration of linear drives, integrated acceleration sensors monitor micro-vibrations and shock events that can lead to micrometer displacements. In the subsequent process steps such as encapsulation, underfill or TSV filling, the latest generation of pressure sensors enable continuous real-time monitoring of the cavities. This allows errors to be reliably detected, homogeneous encapsulation to be ensured and stable process conditions to be supported.

In conjunction with industrial charge amplifiers, the sensors provide the control system of the semiconductor equipment with real-time data for force monitoring, which then enables precise control and monitoring. Furthermore, mobile diagnostic tools with integrated charge amplifiers are available for location-independent, in-process verification of relevant process parameters and quality-critical measured variables.

Sensor Placement Requires Individual Solutions

When developing devices for heterogeneous 3D integration, it is important to do more than just select the right sensor technology. It is also crucial that the sensors are placed exactly where they deliver meaningful measurement results. Kistler works with semiconductor manufacturing equipment manufacturers to optimize application and installation to ensure that force, pressure and acceleration sensors are optimally applied to capture important measurement data. Additional services such as calibration and system validation contribute to long-term accuracy and reliability.

Acting Innovatively to Realize Higher Performance And Competitive Advantages

The use of advanced sensor systems can provide an important basis for stable production processes, high efficiency and reproducible quality. At the same time, new product requirements such as miniaturization pose complex challenges and open up new opportunities for differentiation.

Retrofits in existing machines are often technically demanding and rarely achieve the performance of solutions that have already been integrated in the design phase. This is why forward-looking planning and early integration can pay off.

Looking to the future, the requirements continue to increase: new and innovative materials as well as more complex manufacturing processes require precise and sophisticated monitoring strategies. High-resolution sensors play an important role in ensuring quality, efficiency and competitiveness in the long term. Early investment in sensor technologies can create competitive advantages. (sb)

Robert Hillinger is Industry Lead Semiconductor at Kistler.

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