Self-leveling membrane probe

Abstract

A self-leveling membrane probe [10] is disclosed. A carrier [12] supports a translation stage [18] through radial flexure pivots [14]. A flexible membrane [22] having a first and second side is stretched over the translation stage [28] and held in high tension across its central portion compared to the tension maintained in its outer portion. The membrane's [22] center of the first side faces a device under test (DUT) (not shown) and carries contact bumps [34] that relay electric signals in and out of the DUT. The second side opposite the contact bumps [34] is occupied by a receptacle [32] including a rotation plate [30] and a conical well [32b] designed to receive a pivot pin [26] enbedded in a reference plate [24] suspended from above by the translation stage [18]. The pin [26] and well [32b] function together as a bearing and provide an automatic compensating rotation in response to an alignment mismatch between the probe [10] and a device under test. When the contact bumps [34] encounter uneven test pads, one end of the rotation plate [30] is pushed upwards away from the test wafer. Since the pivot pin [26] is held in a constant vertical position by the fixed reference plate [24], the rotation plate [30] reacts to the imbalanced force applied from below by rotating about the pointed end [26a] of the pivot pin [26] which is seated at the bottom of the conical well [32b]. The resulting angular deflection of the rotation plate [30] aligns the contact bumps [34] on the membrane [22] to the inclined plane of the input-output pads.