Self-aligned edge control in silicon on insulator
First Claim
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1. A method for isolating an active region of a semiconductor layer from another region of the semiconductor layer comprising the steps of:
- providing a layer of silicon on an insulating substrate;
forming a pad oxide layer on the layer of silicon;
providing a layer of silicon nitride on the pad oxide layer;
providing a photoresist layer over a portion of the layer of silicon nitride such that the photoresist layer is adapted to define the active region in the silicon layer wherein the active region is adapted for forming a transistor;
removing selected portions of the silicon nitride layer as defined by the photoresist layer;
removing the photoresist layer to expose a silicon nitride mask that covers portions of the active region;
oxidizing portions of the silicon layer as allowed by the silicon nitride mask to form a field oxide such that the silicon layer is oxidized at least in part through to the insulating substrate and such that an edge of the active region extends between the field oxide and the insulating substrate; and
implanting ions of a conductivity determining material in the edge of the active region after the portions of the silicon layer have been oxidized such that the ions are blocked by the silicon nitride mask from the portions of the active region that are covered by the silicon nitride mask and such that the ions are self-aligned in the edge of the active region by the silicon nitride mask.
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Abstract
An improved process and structure for channel stop in silicon on insulator using LOCOS isolation are disclosed. Advantages include decreased ion dose requirements; reduced processing time; smaller ΔW characteristics, thus, small transistor size and more precise process control over the edge of a MOSFET. The process also makes possible a wide range of transistor design capabilities and improved transistor operating parameters.
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Citations
16 Claims
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1. A method for isolating an active region of a semiconductor layer from another region of the semiconductor layer comprising the steps of:
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providing a layer of silicon on an insulating substrate; forming a pad oxide layer on the layer of silicon; providing a layer of silicon nitride on the pad oxide layer; providing a photoresist layer over a portion of the layer of silicon nitride such that the photoresist layer is adapted to define the active region in the silicon layer wherein the active region is adapted for forming a transistor; removing selected portions of the silicon nitride layer as defined by the photoresist layer; removing the photoresist layer to expose a silicon nitride mask that covers portions of the active region; oxidizing portions of the silicon layer as allowed by the silicon nitride mask to form a field oxide such that the silicon layer is oxidized at least in part through to the insulating substrate and such that an edge of the active region extends between the field oxide and the insulating substrate; and implanting ions of a conductivity determining material in the edge of the active region after the portions of the silicon layer have been oxidized such that the ions are blocked by the silicon nitride mask from the portions of the active region that are covered by the silicon nitride mask and such that the ions are self-aligned in the edge of the active region by the silicon nitride mask. - View Dependent Claims (2, 3, 4, 5, 6, 7, 14)
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8. A method for making a MOSFET characterized by a small Δ
- W characteristic comprising the steps of;
providing a substrate; providing a semiconductor layer having a thickness of about 1,500 Å
or less on the substrate,providing an oxidized layer having a thickness of at least about 100 Å
on a portion of the semiconductor layer;providing a silicon nitride layer having a thickness of at least about 750 Å
on the oxidized layer;defining an active region for the MOSFET transistor in the semiconductor layer by oxidizing portions of the semiconductor layer where the active region is not desired; oxidizing the semiconductor layer to grow a field oxide through to the substrate at locations not covered by the silicon nitride layer wherein the field oxide is grown such that an edge of the active region extends between the field oxide and the insulating substrate; and implanting ions of a conductivity determining material through the field oxide into the edge of the active region such that the ions are self-aligned by the silicon nitride layer. - View Dependent Claims (9, 10, 11, 15)
- W characteristic comprising the steps of;
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12. A method for isolating an active region in a semiconductor layer on an insulating substrate wherein the active region is adapted for use in a MOSFET, the method comprising:
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providing the insulating substrate wherein the substrate has a major surface; providing the semiconductor layer on the major surface of the insulating substrate; providing the active region in the semiconductor layer; providing a nitride mask that covers a portion of the active region and that defines an area of the active region for receiving ions of a conductivity determining material; providing a field oxide adjacent to the defined area of the active region; removing a portion of the field oxide layer; after the step of removing the portion of the field oxide layer, implanting ions from the group consisting of boron, arsenic and phosphorus through the field oxide and into the defined area of the active region such that the implanted ions are self-aligned by the nitride mask. - View Dependent Claims (13, 16)
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Specification