Introduction to Silicon Wafers used in Electronics

Silicon wafers are actually semiconductor devices that are heavily used in todays electronics. To some, these micro devices may seem dismissible but they really have important uses in technology. Silicon wafers are primarily used in manufacturing computer chips. Every electronic device that you enjoy these days contains these tiny yet very significant wafers.

Generally, silicon is a good conductor of electricity. If you have it altered, not only will it conduct electricity, you can also make good use of it as an effective insulator. Whats amazing about these sophisticated wafers is that manufacturers only use regular beach sand particles as the main ingredient in the manufacturing process. Everyone knows that sand also acts as a lightning conductor, and the same technology is also utilized in both computer and electronic circuit boards.

The sand used in the wafer manufacturing process is being closely monitored. It must be kept clean at all times, free from any debris. Whenever the manufacturing process is contaminated due to foreign material inclusion, wafers with faulty connections are created. These bad wafers are costly mistakes, thus the manufacturing of silicon wafers must take place in a strictly regulated environment. It must be handled with extreme care by professional and experienced technicians.

Technically, the device can be described as a thin, circular disc mainly used in the semiconductor and integrated circuit manufacturing. There are also other recognized types in the industry like the Gallium Arsenide or the SOI, which is basically silicon on insulator. These are also utilized in electronics, requiring a careful and thorough manufacturing for efficient end products.

Specialized companies that operate a MEMS foundry create these devices. During the manufacturing process of the thin film, the wafers produced can come in various sizes and desired specifications. The composition can include so many components before the fabrication is completed. After this, the finished product is then packaged carefully for distribution.

A special compound is used to clean the finished product. It guarantees consistency so it will not be altered in any way. The cleaner material used is some weak acid adequate enough to remove impurities of any kind. It also takes care of the various issues within the sawing process.

The various sizes in the finished products make up for the different applications, though they are generally determined based on the components mechanical strengths. And even though the sizes vary, these wafers are manufactured in between 100 mm. to about 300 mm. in diameter. These parts and pieces vary in their costs and dependent of course on the size and usage.

The machinery involved in the manufacturing and cutting of these parts can cost a fortune, or likely that of a small factory. Manufacturing and perfecting such small but vital electronic components costs a great deal. There is no other way of going around the process just to save on the manufacturing costs at the least.

All these tiny yet important pieces are integrated in various electronic applications all over the world today. Computer systems are among the obvious benefactors, including mobile phone technology and digital appliances. There is a clear revolution in the world of electronics and silicon wafers are at the forefront, continuously doing wonders for this electronics-dependent world.

Advances In Silicon Technology Enables Replacement Of Quartz-based Oscillators

Introduction

With a market size estimated at more than $650M and more than 1.4B crystal oscillators supplied annually, quartz crystal oscillators have long been the preferred choice for clock generation in consumer, computing, and communication applications. Quartz oscillators are available in a wide
range of frequencies, package sizes, and stabilities. In addition to providing excellent jitter performance, quartz oscillators are available from a broad range of suppliers.

Quartz Resonator Based Oscillators

Crystal oscillators require a unique quartz resonator for each frequency. The crystal oscillator assembly process requires the quartz to be cut, x-rayed, lapped, mounted, and sealed into the
final package . Fabrication of these resonators becomes increasingly difficult at frequencies over 100 MHz because the resonator must be manufactured to very tight tolerances. The complexity of the manufacturing process is subject to poor yield at multiple steps within the
process forcing material restarts and overall production delays.

In addition to lead times, reliability is a chief concern with quartz oscillators. Quartz oscillators are susceptible to contamination which can affect both the center frequency and the ability of the XO to start up reliably. If an oscillator fails in the end application, often the entire system fails because the oscillator provides critical timing for the electronics.

MEMS Resonator Based Oscillators

The industry has long been searching for a technology that enables the replacement of quartz oscillators with a solution that addresses lead time and reliability concerns while providing performance on par with quartz oscillators. Over the last several years, micro-electromechanical
system (MEMS)-based oscillators have emerged as a possible replacement technology for quartz oscillators. MEMS-based oscillators provide an alternative solution to quartz by replacing the
quartz oscillator with a CMOS-based mechanical resonator.

Si500 Silicon Oscillator

Silicon Labs Si500 silicon oscillator leverages a standard IC manufacturing flow. The silicon oscillator is fabricated using standard submicron CMOS technology and standard low-cost
plastic packaging that does not require a hermetic seal. The silicon oscillator is factoryprogrammed at test to a specific frequency, signal format, and supply voltage.

Si500 Technology Overview

The heart of the architecture is a low phase noise, frequency flexible LC oscillator. Using innovative mixed-signal analog circuitry, the oscillator is compensated for frequency variation due to operating temperature range, aging, initial frequency accuracy, supply voltage change, and output load
change. The silicon oscillator supports a wide frequency range, generating any output clock frequency from 0.9 to 200 MHz. Selection of the frequency, output type, supply voltage, and output enable (OE) is stored in non-volatile memory (NVM). At power-on, the Si500 performs a
self-calibration using these stored parameters and configures itself for operation.

Temperature Stability

Temperature stability refers to how much the oscillator frequency varies over the operating temperature range of the device. For the Si500 silicon oscillator, tight temperature stability is achieved through dynamic temperature compensation. The device has an on-board temperature
sensor that, upon detection of a temperature change, dynamically adjusts the frequency of oscillation of the LC oscillator to maintain a stable output frequency.

Aging

All oscillators experience drift in the frequency over long periods of time. The effect is called aging and is an important specification in the overall frequency stability budget. Aging behavior is dependent on several aging mechanisms including the design of the resonator, the assembly of the oscillator, the contamination level surrounding the resonator, the design of the electronics, and the operating temperature. To determine an upper bound on aging performance, it is
necessary to control as many of the mechanisms as possible and to verify conformance through extensive aging studies.

Reliability

Quartz oscillators require hermetic packaging for the crystal. Package leaks or internal contamination can lead to long term frequency aging, or if severe enough, can even prevent oscillation. Consequently, oscillator manufacturers minimize contamination by using costly, hermetically sealed ceramic or metal packaging and special processing. Done properly, reliable operation can be achieved, but package and assembly costs will be considerably higher than with non-quartz CMOS only devices. Being a mechanical device, MEMS resonators are susceptible to the same contamination issues and also require hermeticity.

Shock and Vibration

Shock and vibration can also limit the reliability of quartz-based oscillators. Quartz crystals are mounted above the oscillation electronics using epoxy or metal clips supported on one side only. Attaching the crystal on one side places the crystals center of gravity far away from
the support point allowing the crystal to swing like a diving board when exposed to vibration.

Jitter Performance

Period jitter is a key specification for oscillators since it impacts the setup/hold time, noise margin, or bit-error rate of systems that require alignment between clock and data. Period jitter describes how much any period may deviate from the ideal clock period and is used to determine the setup/hold time margin within a digital system. The amount of margin required depends greatly on the how many timing violations (i.e., bit-errors) a system can handle. In most designs, no timing
violations are allowed over the lifetime of the product, so the amount of margin is quite large. Period jitter is related to phase noise[2] and is often dominated by phase noise at far offset frequencies up to half of the clock frequency.

Programmable Output Buffer

Because the Si500 can generate frequencies across a large range (0.9 to 200 MHz), the output buffer design must provide easy connectivity for the many common receiver formats and voltages used in this range. The Si500 employs a programmable output buffer with support for both
differential and single-ended formats while easing the design effort by incorporating common external components.

Conclusion

With advances in mixed-signal CMOS technologies, silicon oscillators like the Si500 are now competitive with oscillators that use traditional quartz or MEMS resonators. By eliminating the need for these mechanical resonators, the Si500 offers significantly improved reliability when
shock, vibration, and oscillator start up are considered. In addition, the Si500s simplified manufacturing flow reduces cost and enables short predictable lead times when compared to traditional quartz based oscillators.