On-wafer Absolute Calibration

May 2009

© NMDG NV 2009 2

Outline

● Introduction

● Absolute calibration for on-wafer setup

● On-wafer calibration in ICE 2009A

● Conclusions

© NMDG NV 2009 3

Introduction● Calibration of a Large-Signal Network Analyser requires:

● A relative “VNA-like” calibration, using calibration standards● A power calibration, using a power meter● A phase calibration, using a phase reference such as the NMDG NM200 HPR

● Calibration reference planes for on-wafer are defined at RF probe tips:● Relative calibration is done using calibration standards on substrate● Absolute (power and phase) calibration is not directly possible as absolute

calibration standards are connectorised elements (e.g. power sensor, HPR)

● One solution is:● Perform absolute calibration at connectorised reference planes● Characterise / model the S-parameters of each component between

connectorised planes and probe tips ● Use de-embedding techniques to transfer reference planes to probe tips● Disavantages:

● S-parameters characterisation of each component is cumbersome● Accumulation of errors when cascading S-parameters

● NMDG developed an in-situ on-wafer absolute calibration technique

© NMDG NV 2009 4

On-wafer calibration: Relative calibration

[a1b1a2b2] f =K f [1 M 12 M 13 M 14

M 21 M 22 M 23 M 24

M 31 M 32 M 33 M 34

M 41 M 42 M 43 M 44] f [a1

M

b1M

a2M

b2M ] f

● Standard on-wafer relative calibration is used to relate ratios between travelling waves at Port 1 and 2 and measured quantities.

© NMDG NV 2009 5

On-wafer calibration: Auxiliary SOL relative calibration

[a1b1a2b2] f =K f [1 M 12 M 13 M 14

M 21 M 22 M 23 M 24

M 31 M 32 M 33 M 34

M 41 M 42 M 43 M 44] f [a1

M

b1M

a2M

b2M ] f

● An auxiliary SOL relative calibration is performed at termination side of Port 2, connecting a line at probe tips and using Source at Port 1.

● Combining on-wafer relative and auxiliary calibrations and using reciprocity principle, it is possible to extract in-situ the S-parameters of the passive output block between Port 2 and Auxiliary reference planes.

© NMDG NV 2009 6

On-wafer calibration: Power calibration

[a1b1a2b2] f =K f [1 M 12 M 13 M 14

M 21 M 22 M 23 M 24

M 31 M 32 M 33 M 34

M 41 M 42 M 43 M 44] f [a1

M

b1M

a2M

b2M ] f

● Power calibration is then performed by connecting a power sensor (and power meter) at auxiliary reference plane.

● Using the S-parameters of the output block, one can then extract the power distortion (magnitude of K(f)) of the measurement system at probe tips reference planes.

Abs

© NMDG NV 2009 7

Phase

On wafer: Phase calibration

[a1b1a2b2] f =K f [1 M 12 M 13 M 14

M 21 M 22 M 23 M 24

M 31 M 32 M 33 M 34

M 41 M 42 M 43 M 44] f [a1

M

b1M

a2M

b2M ] f

● Phase calibration is finally performed by connecting a phase reference standard at auxiliary reference plane.

● Using S-parameters of the output block, one can then extract the phase distortion (phase of K(f)) of the measurement system at probe tips reference planes.

© NMDG NV 2009 8

On-wafer calibration in NMDG ICE 2009A

● A step-by-step on-wafer absolute calibration wizard is integrated in NMDG ICE 2009A

© NMDG NV 2009 9

Conclusions

● A on-wafer absolute calibration technique for LSNA has been explained

● Advantages compared to de-embedding techniques:● In-situ calibration: no need to disconnect/reconnect and characterise each

component in-between measurement system and probe tips● Reduction of errors caused by cascading S-parameters blocks

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