Market Watch

iSuppli Corp. has been tracking the first startup—Baolab Microsystems—for five years, starting when it focused on Radio Frequency (RF) MEMS switches. At the direction of the new man at the helm, Dave Doyle, the company has concentrated its efforts on building a truly CMOS-compatible MEMS process in order to meet cost requirements for cell-phone applications. The key competency of the Spanish startup now involves the process itself—which is why in addition to switches, the company has demonstrated accelerometers and magnetometers.

This resembles the company InvenSense with its “Nasiri” process, named after the inventor and company CEO, which was not initially developed for gyroscopes but instead for optical MEMS. Another firm, Akustica, which also claims a 100 percent CMOS-compatible process, hasn’t limited itself to microphones but includes accelerometers on its roadmap as well.

MEMS within CMOS
Specifically, Baolab’s approach is to construct MEMS structures within the CMOS wafer itself using standard, high-volume CMOS mask techniques, which is much easier and quicker with fewer process steps compared to existing MEMS fabrication techniques that build the MEMS on the surface of the wafer. This significantly reduces the cost, especially if several different MEMS structures are created together on the same chip.

Baolab engineers use existing metal layers in a CMOS wafer to form the MEMS structure; an Inter Metal Dielectric (IMD) is then etched away through the pad openings in the passivation layer using vapor HF. The etching uses equipment that is already available for volume production and takes less than an hour, which is insignificant compared to the overall production time. The holes are then sealed and the chip packaged as required. The advantage of CMOS processes are that MEMS can be directly integrated with active circuitry as required.

The 6-Degree Of Freedom (DOF) electronic compass chipset prototype is worth mentioning, too, with its very small dimension: For a combination involving a 3-axis accelerometer, 3-axis magnetic sensor and electronics, circuitry is squeezed into an area of only 2 x 2 millimeters. Integrating a gyroscope onto the same surface is on the roadmap as well. As to the magnetic sensor technology, Baolab indicated to iSuppli that it is not Hall, AMR or GMR technology, but the company can’t disclose more at this stage.

What’s next? Baolab has still a long way to go from introducing a prototype to demonstrating a breakthrough process and to unfolding a serial product. Also, while the performance of the RF MEMS switches that Baolab shared with iSuppli seems good, nothing has been disclosed yet on the performance of the sensors. Given that the sensing structures are very small, noise and sensitivity might prove to be issues. As such, iSuppli is very curious about the first samples scheduled for late 2010.

DelfMEMS Comes Clean
The second startup making waves is DelfMEMS, a French company created in 2005 that recently broke its silence to communicate its first achievement: a wafer-level-package RF MEMS device with a less than 1 microsecond switching time and low actuation voltage of 8 to 12 volts, integrated above passive devices, capable of hot switching and 26.5GHz broadband switching. The fabless company is targeting automated test equipment as well as cell-phone applications.

iSuppli has followed RF MEMS for many years and notes with continued amazement the enthusiasm that this field continues to generate despite the failure of so many promising companies, such as Magfusion, Teravicta, Siverta and Panasonic. Nonetheless, new companies bravely press on and at least two more startups—Protron and MultusMEMS—are also currently active.

DelfMEMS’ specs look good. A switching speed of less than 1 microsecond sounds excellent for cell-phone applications as it supports T/R switching applications. In addition, an actuation voltage of 8 to 12 volts sounds suitable for cell phones, even though a charge pump is still required.

Care is needed with specifications. On further digging, it appears that a 1-microsecond switching speed is actually obtained at 27 volts. At 10 volts, the switching speed increases to 20 microseconds—still an excellent rate but too slow for T/R switching. Also, the high-frequency capability of up to 26.5GHz is measured without the package; with the package, the frequency drops to 18GHz—still enough for ATE but too low for many RF test applications.

In particular, two items in DelfMEMS’ technology have caught iSuppli’s attention:

• The capability to integrate MEMS above integrated passive devices is an especially cost-competitive approach for cell phones. However, while the MEMS switch can be added as another passive at almost no cost, the main cost is related to its encapsulation. NXP was working on such an integration scheme for its MEMS capacitive switch before its RF MEMS group was acquired by EPCOS in 2008.
• The “hot switching/pull out system” capability is interesting as well. For switching on, the actuation is done using two internal electrodes, while the switching off employs two external electrodes. This avoids issues with stiction, the enemy of MEMS structures.

For mobile phones, DelfMEMS has developed an RF MEMS switch that holds great promise. 

Read the Latest MEMS Report, Consumer MEMS: Downturn? What Downturn?