Substrate anchor for undercut silicon on insulator microstructures

A method of anchoring a semiconductor substrate to another semiconductor substrate during fabrication of a solid state instrument comprising the steps of:

• providing a first semiconductor substrate having a buried oxide layer, a front covered with an oxide layer, and a semiconductor handle on a back;
• removing the front oxide layer;
• depositing a silicon nitride layer on the front;
• depositing a silicon nitride cap and an oxide cap on the front;
• removing the silicon nitride cap and the front silicon nitride layer except for a silicon nitride patch underlying the oxide cap;
• providing a second semiconductor substrate having a front covered in an oxide layer, wherein the front oxide layer includes a slot covered with silicon nitride;
• bonding the first semiconductor substrate front to the second semiconductor substrate front, wherein the shallow well substantially aligns with the slot;
• removing the semiconductor handle of the first semiconductor substrate;
• forming a deep slot through the back of the first semiconductor substrate substantially overlying the silicon nitride patch and oxide cap;
• removing the oxide cap and partially removing the silicon nitride patch and forming a cavity with a ledge, wherein a remaining silicon nitride patch covers the ledge;
• removing the silicon nitride within the slot;
• and
• depositing silicon inside the cavity.

A method of anchoring two semiconductor substrates comprising the steps of:

• providing a first semiconductor substrate having a buried oxide layer and a front oxide layer covering a front of the first substrate;
• forming a deep slot through the buried oxide layer and into the first substrate;
• removing the front oxide layer;
• covering a portion of the deep slot with a silicon nitride layer;
• covering another portion of the deep slot with an oxide layer;
• removing the silicon nitride layer;
• and
• filling the deep trench with a semiconductor material so that said semiconductor material is anchored on a portion of a second substrate.