Fabrication and characterisation of a double-clamped beam structure as a control gate for a high-speed non-volatile memory device

• A suspended double-clamped beam for a NV-Memory is fabricated and characterised.
• The recipe developed to suspend the beam structure shows a high selectivity rate.
• Once biased, the beam pulls-in but due to the short-range forces pull-out was missing.
• Short-range forces such as the van der Waals are stronger when in contact (Al/SiO2Al/SiO2).
• A relationship to overcome such forces is obtained through 2D-FEM analysis.

We report the fabrication and characterisation of a suspended double-clamped beam structure that is implemented as a movable control gate within a hybrid high-speed non-volatile memory device. This structure features a foundation of SiO2/Si layers over which a poly-Si layer (sacrificial) is deposited by using a low-pressure chemical vapour deposition (LPCVD) and as a movable control gate, an aluminium (Al) layer is deposited by using an e-beam evaporator. The Al layer is patterned with double-clamped beam structures by using photolithography and through a combination of wet and dry etching processes, the structures are successfully suspended and characterised by using a C–V meter. From the structure characterisation, the pull-in curve is successfully obtained and due to unexpected large short-range forces such as the van der Waals forces, the pull-out curve is not observed. In order to clarify this issue, a numerical analysis is performed in which the structural materials under test shown the influence of such short-range forces on the structure and a solution to override them is proposed.

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