Last summer, the semiconductor industry reached a significant milestone: one of the world’s top-tier fabs had begun production of the first 3D NAND chip with more than 200 layers. The announcement was significant but not a shock. Several other fabs had been progressing toward breaking the 200-layer barrier, so reaching the milestone was not a matter of if but when.
As significant as this advance is, the high-volume manufacturing challenges of producing high-aspect ratio (HAR) 3D NAND chips are considerable. One challenge is the ability to measure the tungsten (W) recess to the bottom of a 3D NAND device following the replacement gate process. Presently, there is no in-line process control solution that can accomplish this. The reason for this is known: beyond just a few layers in the stack, the W recess becomes opaque in the ultraviolet/visible/ near-infrared region, the realm of many OCD systems, after just a few layers in the HAR stack. Additionally, increased wordline slit pitch scaling further reduces the already minimal optical signal from the top of the 3D NAND structure to the bottom.
For decades, Moore’s Law has been a way to measure performance gains in the semiconductor industry, but the ability to double the density of transistors on a chip every twoyears is becoming increasingly challenging. With scaling reaching its limit, manufacturers are looking to advanced packaging innovations to extend the performance gains that the industry, and the world at large, have grown to depend on. Cu-to-Cu hybrid bonding is one way the industry is looking to extend ever-increasing I/O density and faster connections, all while using less energy.
Not so long ago, Blu-ray was hailed as a technological advancement in the world of digital video. But in the streaming era, Blu-ray’s luster has faded. However, the technology responsible for the blue laser diode that gave the Blu-ray player its name – gallium nitride (GaN) – is emerging as one of a number of exciting new developments in the semiconductor industry.
Today, GaN is used by the military for radar systems, consumer and automotive electronics as a super-fast power charger and the telecommunications industry in base stations and data servers. GaN offers several advantages over silicon. For starters, GaN offers a significant increase in electron mobility over silicon – 1,000 times more electron mobility, according to various articles – a benefit that leads to other advantages. In addition, GaN is resistant to heat, consumes less energy than other semiconductors, operates at a lower voltage, enables increased miniaturization, offers wider bandwidth and allows for increased electron mobility.
Abstract
Ultrafast pump-probe measurements are used to characterize various samples, such as biological cells, bulk, and thin-film structures. However, typical implementations of the pump-probe apparatus are either slow or complex and costly hindering wide deployment. Here we combine a single-cavity dual-comb laser with a simple experimental setup to obtain pump-probe measurements with ultra-high sensitivity, fast acquisition, and high timing precision over long optical delay scan ranges of 12.5 ns that would correspond to a mechanical delay of about 3.75 m. We employ digital signal balancing to obtain shot-noise-limited detection compatible with pump-probe microscopy deployment. Here we demonstrate ultrafast photoacoustics for thin-film sample characterization. We measured a tungsten layer thickness of (700 ± 4) Å with shot-noise-limited detection. Such single-cavity dual-comb lasers can be used for any pump-probe measurements and are especially well-suited for ultrafast photoacoustic studies such as involving ultrasonic echoes, Brillouin oscillations, surface acoustic waves and thermal dynamics.
A mother steps on the brakes, bringing her car to a stop as she drops her kids off for dance lessons. At the time, she doesn’t notice anything wrong, but when she takes her car in for its regular service appointment, the mechanic conducts a diagnostic check and discovers that the primary brake system on the car had failed because of a faulty braking controller without anyone realizing it. Fortunately, the car was able to stop successfully due to the vehicle’s system redundancies, and the dealer’s diagnostic test confirms that since that first chip failure, another one has not occurred. The braking systems are behaving normally.
Following that, the dealership sends the information about the braking failure to the manufacturer, where an analyst notes that over the last 60 days, and around the country, six other brake failures traced back to the same controller system have been reported for the same make and model. In each of these situations, the backup system successfully brought each car to a complete stop. And, as in the case with the mother who dropped her kids off at dance class, the analyst looks at the reporting samples for these six other failures and determines that each is isolated and non-recurring.
A recent study shows the radio frequency (RF) filter market growing steadily by nearly $16 billion from 2019 to 2024 at a compound annual growth rate (CAGR) of approximately 20%, according to Technavio. The strong growth in the RF filter market is driven by the increased adoption of 5G technology, the surge in smartphones using 5G, and commercial and consumer devices dependent on internet of things (IoT) applications. Together, these factors are some of the most significant players driving society’s digital transformation.
However, the RF filter market is faced with many of the same challenges the semiconductor industry as a whole is experiencing, including the need to pack more into increasingly smaller spaces. In each successive generation of RF filters, the number of filters has not only steadily increased, the rising number of filters has led to a need for more stringent process monitoring and control. A frequency accuracy, 3σ of 0.1%, requires film thickness control within the same accuracy or better.
Let’s look at one RF filter component, a bulk acoustic wave (BAW) resonator. A BAW is a piezoelectric structure sandwiched between the top and bottom electrodes. The resonant frequency depends on the acoustic velocity and the thickness of the piezoelectric film, and the thickness of the electrode. The thickness of the top electrode as a mass loading layer can be dialed in to generate a frequency shift, which is often used to form a filter passband.
Since the RF filter process is directly correlated to thickness, extremely uniform films (~0.1% or better) need to be deposited. With the additional requirements of 5G to support higher frequencies and increased bandwidth, RF filter device manufacturers employ several different process knobs to tune the devices. For example, we see an increasing trend toward thinner layers to support higher frequencies, the adoption of Sc-doped piezoelectric materials to improve piezoelectric coupling and the addition of temperature compensation SiO2 layers to the stack to improve the temperature coefficient of the resonator.