Method of fabricating a monolithic sensor device from a layered structure
AssigneeThe University Court of the University of Glasgow
InventorsDavid Robert Sime Cumming, Chengzhi Xie, Vincenzo Pusino
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Abstract
A method of fabricating a field-effect transistor in which a native oxide layer is removed prior to etching a gate recess. The cleaning step ensures that the etch of the gate recess starts at the same time across an entire sample, such that a uniform gate recess depth and profile can be achieved across an array of field-effect transistors. This results in a highly uniform switch-off voltage for the field-effect transistors in the array.
Claims25
A method of fabricating a monolithic sensor unit comprising a sensor and field-effect transistor formed within a layered semiconductor stack, the layered semiconductor stack having a substrate, a first semiconductor device layer for forming the field-effect transistor deposited on the substrate and a second semiconductor device layer deposited on the first semiconductor device layer, the second semiconductor device layer providing an active region for the sensor, wherein the method comprises the steps of:
- selectively etching a portion of the second semiconductor device layer to expose a surface of the first semiconductor device layer;
- and
- performing a wet etch process on a portion of the first semiconductor device layer to form a gate recess in the first semiconductor device layer, wherein the wet etch process comprises:
- applying a native oxide removal solution to remove native oxide from the exposed surface of the first semiconductor device layer, and
- applying an etchant solution to remove material from the first semiconductor device layer and thereby form the gate recess.
A monolithic sensor unit having a sensor integrated with a field-effect transistor, the sensor unit having a layered semiconductor stack comprising:
- a substrate;
- a first semiconductor device layer forming the field-effect transistor deposited on the substrate;
- a second semiconductor device layer deposited on the first semiconductor device layer, the second semiconductor device layer providing an active region for the sensor;
- a common contact layer disposed between the first semiconductor device layer and the second semiconductor device layer;
- a first contact electrode deposited on a surface of the first semiconductor device layer;
- a second contact electrode deposited on a surface of the second semiconductor device layer;
- and
- a gate electrode for the field-effect transistor disposed in a gate recess formed in the first semiconductor device layer,
- wherein the field-effect transistor is arranged to control, based on a bias voltage applied to the gate electrode, a current flowing between the first contact electrode and the second contact electrode.
Dependencies are inferred from the claim text.