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What is MEMS?
MEMS is an acronym for Micro Electro Mechanical Systems, and is pronounced MEMS.
It is also called a micro electromechanical system, andoften refers to a general micro device that integrates various functions such as mechanical, electronic, optical, and chemical.
In this article, I think it will be easier to imagine if you read it as a “device” instead of crystal.
Comparison between MEMS products and general crystal products
1. substance
Crystal products (oscillators), as the name suggests, use crystals and use the piezoelectric phenomenon to generate a certain frequency.
SiTime's MEMS products, on the other hand, are made from single crystal silicon, which is 15 times stronger than titanium.Since the mass is about 1/1000 to 3000 times that of a crystal oscillator, it is less susceptible to vibration.
2.Manufacturing process
Manufactured using the patented MEMS First™ and EpiSeal™ manufacturing processes and annealed at 1100°C.
This high-temperature manufacturing process allows us to produce high-quality contaminant-free, hermetically sealed crystals.
Manufacturing crystal products is much more complicated and less clean than MEMS products.
3. Number of processes
The flow of the general crystal manufacturing process consists of 23 processes.
The point is that the crystal manufacturing process is...
(1) Significantly more than the silicon MEMS process
(2) In the case of crystal, the four processes of fixing the crystal piece, grounding by wire bonding, mounting and hardening, and adjusting the frequency are performed with the lid of the package open.
In particular, in the process indicated by ②, crystal products are particularly susceptible to contaminants.
Naturally, countermeasures have been taken, but it is difficult to completely remove them, leading to accelerated aging and reliability problems.
In the case of an oscillator product that is integrated with an oscillator circuit, after a while, organic gas is generated from the adhesive that secures the oscillator, and it adheres to the oscillator and changes its mass, which may cause an abnormality.
In the case of MEMS products, there are about 12 main manufacturing processes, and the oscillator is manufactured in the semiconductor wafer cleaning process.
Cleanliness is controlled to ppb level and the crystals are sealed at the wafer with the EpiSeal™ process. This process achieves the highest quality and reliability in the industry.
So far, there have been no problems caused by the vibrator.
Click here for details → Manufacturer's white paper "Comparison of Crystal Oscillators and Si-MEMS Oscillators"
Advantages of clocks using MEMS technology
The main advantages of SiTime clocks over general crystal products are as follows.
・Strength against surrounding environment such as vibration and impact (environmental performance)
・Defect rate
・ Aging characteristics
・Change in oscillation frequency due to temperature change
・Programmable performance
·supply chain
These factors include the differences in materials, internal structures, and production processes due to the use of silicon MEMS.
Of course, new crystal products are released year by year, and programmable products are also on sale, but there seems to be still a gap in specifications from conventional products.
Although the internal PLL provides programmable performance, MEMS still has problems such as power consumption due to the complexity of the internal circuit.
SiTime also has a product lineup that overturns the recognition of such issues so far.
Configuration of SiTime MEMS oscillators
We provide an oscillator by combining the leftmost MEMS resonator and the central oscillation circuit.
Using the decimal point PLL described in the oscillation circuit (any frequency can be set below the decimal point) and OTP,
We have realized a programmable product that can handle sudden changes in specifications and rare frequencies that would otherwise be treated as custom products.
At the end
What did you think.
Whether you have used MEMS oscillators or not, I hope that you will be interested in them.
If you have any questions, please contact us below.