One-chip integrated sensor process
AssigneeDelco Electronics Corporation
InventorDouglas Ray Sparks
Life of this patent
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Abstract
A method for concurrently forming a micromachine element and an integrated circuit device on the same substrate, such that fabrication of the micromachine element and the circuit device requires a minimal number of processing steps. The method is adapted for forming sensing devices, such as accelerometers and pressure sensors, which utilize a small micromachine element, such as a bridge, cantilevered beam, suspended mass, membrane or capacitive element that is supported over a cavity formed in the silicon substrate. Piezoresistors used to detect the deflection of the micromachine element are formed simultaneously with elements of the integrated circuit devices, such that a minimal number of processing steps are required.
Claims19
A method for forming a one-chip integrated sensor having a micromachined sensing structure which is concurrently formed with an integrated circuit device on a single substrate, the method comprising the steps of:
- forming an n-type epitaxial silicon layer on a first surface of the substrate, the epitaxial silicon layer forming an element of the integrated circuit device;
- growing a first field oxide layer on the epitaxial silicon layer and a second field oxide layer on a second surface of the substrate opposite the first surface;
- forming P+ regions in the epitaxial silicon layer so as to concurrently form at least one element of the integrated circuit device and a piezoresistor for the micromachined sensing structure;
- forming an N+ region in the epitaxial silicon layer so as to form a second element of the integrated circuit device and an ohmic contact to the epitaxial silicon layer;
- forming contacts and conductors for the micromachined sensing structure and the integrated circuit device through the first field oxide layer;
- and
- etching a cavity through the second field oxide and in the second surface of the substrate until the epitaxial silicon layer is exposed by the cavity, the micromachined sensing structure being a region of the epitaxial silicon layer that is free of metallization and buried layers.
A method for forming a one-chip integrated sensor having a micromachined sensing structure which is concurrently formed with an integrated circuit device on a single substrate, the method comprising the steps of:
- forming the substrate from a 100! p-type wafer having a first surface and an oppositely disposed second surface;
- forming an n-type epitaxial silicon layer on the first surface of the substrate, the epitaxial silicon layer forming an element of the integrated circuit device;
- growing a first field oxide layer on the epitaxial silicon layer and a second field oxide layer on the second surface of the substrate;
- forming P+ regions in the epitaxial silicon layer so as to concurrently form at least one element of the integrated circuit device and a piezoresistor for the micromachined sensing structure;
- forming an N+ region in the epitaxial silicon layer so as to form a second element of the integrated circuit device and an ohmic contact to the epitaxial silicon layer;
- forming contacts and conductors for the micromachined sensing structure and the integrated circuit device through the first field oxide layer;
- removing the first field oxide layer from the epitaxial silicon layer;
- forming a cavity through the second field oxide and in the second surface of the substrate until the epitaxial silicon layer is exposed by the cavity such that the micromachined sensing structure consists of a region of the epitaxial silicon layer that is free of buried layers and is adjacent the piezoresistor;
- and
- bonding a wafer to the second surface of the substrate.
A method for forming a one-chip integrated sensor having a micromachined sensing structure which is concurrently formed with a bipolar integrated circuit device on a single substrate, the method comprising the steps of:
- forming the substrate from a 100! p-type wafer having a first surface and an oppositely disposed second surface;
- forming an n-type epitaxial silicon layer on the first surface of the substrate and a P+ buried layer in the first surface of the substrate, the epitaxial silicon layer forming an element of the integrated circuit device;
- growing a first field oxide layer on the epitaxial silicon layer;
- forming an isolation diffusion in the epitaxial silicon layer and between the micromachined sensing structure and the integrated circuit device, and forming a second field oxide layer on the second surface of the substrate;
- ion implanting boron into the epitaxial silicon layer so as to concurrently form P+ regions in the epitaxial silicon layer, at least one of the P+ regions forming a first element of the bipolar integrated circuit device and a second of the P+ regions forming a piezoresistor for the micromachined sensing structure;
- forming an N+ region in the epitaxial silicon layer so as to form a second element of the integrated circuit device;
- forming contacts and conductors for the micromachined sensing structure and the integrated circuit device through the first field oxide layer;
- forming a passivation layer over the contacts and conductors;
- removing the first field oxide layer from the epitaxial silicon layer;
- electrochemical etching a cavity through the second field oxide and in the second surface of the substrate so as to remove the P+ buried layer, such that the epitaxial silicon layer alone forms the micromachined sensing structure;
- and
- bonding a wafer to the second surface of the substrate so as to enclose the cavity.
Dependencies are inferred from the claim text.