Keithley Launches Upgraded On-Wafer RF Measurement Capability

Cleveland -- Keithley Instruments has announced its third generation on-wafer RF measurement capability for semiconductor parametric production process control. New to Keithley's third-generation RF Option solution is the unique ability to offer continuous, automatic, real-time monitoring of measurement quality, providing high quality results with high throughput, low cost of operation, and easy use. According to the company, the RF Option measurement capability is the only test system qualified for parametric process control by 200 mm and 300 mm production fabs worldwide for applications involving high-performance logic and high-performance analog IC production.

Measurement integrity
Automatic continuous monitoring of measurement integrity works by having the tester automatically detect events that would invalidate the RF calibration, and automatically trigger corrective action such as an unattended recalibration. Changes in system configuration, such as a probe card change, can be set up to trigger an unattended recalibration. There are also time-based trigger events, such as time-expired RF calibration. The final class of trigger events is measurement based. For example, while the prober is indexing to the next site, in the background the tester automatically verifies the quality of probe contact and triggers automated probe cleaning if required.

Higher measurement integrity eliminates the need for an RF specialist to manually inspect raw data curves for anomalies that would suggest questionable RF measurements. It also eliminates the high cost of re-probe and rework, making it operationally compatible with highly efficient lights-out 300 mm fabs.

Throughput
The RF Option, with the Model S680 SimulTest option, and appropriately designed test structures and probe cards, is the only RF test system on the market that can make simultaneous DC and RF measurements in parallel within the same probe touchdown, Keithley claims. This yields higher throughput than similar methods that perform sequential DC measurements followed by RF measurements. Furthermore, RF parameters can be extracted and de-embedded in real time from measured s-parameters using an RF parametric extraction library without the need for post processing, saving time and increasing throughput.

In addition, combined with the Model S680 parametric test system, Keithley has a direct-dock capability for making measurements at 40 GHz. Competitive products require a manual probe card change by an RF specialist using a torque wrench followed by manual recalibration. Keithley's RF Option solution completes an automated RF probe card change in a fraction of the time it takes for a manual change, increasing overall throughput. Automated probe-card changes also increase measurement integrity by eliminating major variability, caused by human intervention, in system-to-system variation in RF measurement results. And because an RF specialist is no longer needed, it lowers the cost of operation. This automated probe card change capability is a new feature offered in Keithley's RF Option.

Cost of operation
The SofTouch option maximizes probe-card lifetime by minimizing probe overdrive while meeting measured quality criteria for probe contact. One fab's estimate was for a 100X lifetime increase for their RF probe card touchdown count, reducing probe-card costs by the same amount. Keithley's Probe Card Manager option integrates with RF probe cards for continuous, automatic monitoring of probe touchdowns and remaining probe card lifetime to further reduce probe-card costs.

Keithley's 40 GHz RF Option solution works with a fab's existing automated DC production probers. This reduces initial acquisition costs by as much as two-thirds and lowers maintenance and operator costs as compared to other offerings that require purchasing a specialized RF prober. Operational costs are also decreased significantly because DC and RF tests can be run in single-insertion mode on the same equipment, eliminating the need to move wafer lots between a DC-only tester and an RF-only tester. In addition, unlike competitive products that offer only a single RF probe-card supplier, Keithley now offers a choice of three suppliers. This minimizes probe card costs and offers a more predictable and stable supply chain for highest confidence during production ramp up.

Range of applications
Keithley's RF Option measurement capability includes an improved software suite that enables users to rapidly obtain large quantities of quality RF data, allowing its use in a wide range of applications. It also is built upon a field-proven, mature operational GUI.

For production parametric process control of high-k transistors, Keithley's RF-CV methodology replaces traditional CV or MFCV measurements, letting production fabs more tightly control electrical gate thickness on sub-65 nm high-performance logic ICs. For high-performance analog or RFICs, Keithley's RF Option cuts RF circuit-model verification times to two weeks or less. RFIC companies can also use Keithley's RF Option solution for parametric production process control of BiCMOS standard figures of merit such as ft or fmax. Also, companies making SOCs use Keithley's RF measurement capability for functional testing of benchmark circuits and figures of merit such as LNA and cell phone filters.

RF support
Keithley's RF measurement capabilities are supported by years of RF field implementation experience in fabs around the world. Keithley application engineers have experience in RF test structure design for production environments, including transistor gate capacitors for RF-CV measurements for high-performance logic, and inductors and filters for high-performance analog applications. In addition, Keithley's semiconductor physicists can help customers interpret their measurement results and apply them to better control their process.

Availability
Keithley's third generation RF Option measurement capability is available immediately for both new Model S680 and Model S470 systems shipping from the factory. It is also available as a field-retrofit option to existing Model S600 and Model S400 Series units already installed during the past 15 years.

Source: Keithley Instruments