Method of manufacturing a MEMS device and MEMS device

1. A method of manufacturing an electronic device comprising a micro-electromechanical systems (MEMS) element, which MEMS element comprises a first and a second electrode, which second electrode is movable towards and from the first electrode, which method comprises the steps of:

providing an etch stop layer of electrically insulating material at a first side of a substrate, the substrate being etchable by dry etching using fluorine chemistry;

providing a base layer of an electrically conductive material on the etch stop layer at the first side of the substrate, the first electrode being defined in the base layer;

providing a sacrificial layer which at least covers the first electrode in the base layer;

providing a mechanical layer of an electrically conductive material on top of the sacrificial layer, said mechanical layer being mechanically connected to the substrate;

providing the second electrode by defining same in the mechanical layer or as a separate layer in or on the sacrificial layer;

providing a mask on top of the mechanical layer, the mask including at least one window to the sacrificial layer; and

removing selective areas of said sacrificial layer by means of dry chemical etching, such that the second electrode is made movable towards and from the first electrode, wherein said dry chemical etching is performed using a fluorine-containing plasma, and the etch stop layer comprises a substantially non-conducting, fluorine chemistry inert material.

2. A method as claimed in claim 1 , wherein the sacrificial layer comprises inorganic material.

3. A method as claimed in claim 2 , further comprising forming a thin-film capacitor on the substrate, the thin-film capacitor having a first and a second capacitor electrode and an intermediate dielectric, wherein the first capacitor electrode is defined in the base layer parallel to defining the first electrode of the MEMS element and wherein the intermediate dielectric is defined in the sacrificial layer and the second capacitor electrode is defined in the same layer as the second electrode of the MEMS element, the part of the sacrificial layer defining said intermediate dielectric not being removed by said dry chemical etching.

4. A method as claimed in claim 1 , wherein the etch stop layer is provided at the first side of the substrate before provision of the base layer.

5. A method as claimed in claim 1 , wherein said fluorine-containing plasma is a CF y plasma.

6. A method as claimed in claim 1 , further comprising the steps of:

providing an intermediate layer of an electrically conductive material on the sacrificial layer, the second electrode being defined in the intermediate layer; and

providing a second sacrificial layer which covers the second electrode at least partially, said second sacrificial layer being removed in the same step as the sacrificial layer.

7. A method as claimed in claim 6 , wherein the base layer is provided with a contact pad, at least one window in the sacrificial layer and the second sacrificial layer leaving the contact pad exposed until filling of the window during provision of the mechanical layer and wherein the window in the sacrificial layer is provided after deposition of the second sacrificial layer.

8. A method as claimed in claim 1 , wherein said etch stop layer comprises a Group IV n-oxide.

9. A method as claimed in claim 8 , wherein said etch stop layer comprises HfO 2 , ZrO 2 , Al 2 O 3 or TiO 2 .

10. A method as claimed in claim 1 , wherein the substrate is a silicon substrate.

11. A method as claimed in claim 1 , wherein the etch stop layer comprises a material selected from an oxide of a group IV material, TiN, AlN, diamond and a perovskite material.

12. A method as claimed in claim 11 , wherein the etch stop layer comprises Al 2 O 3 .