Lift-off technique for producing metal pattern using single photoresist processing and oblique angle metal deposition

• US 4,687,730 A
• Filed: 10/30/1985
• Issued: 08/18/1987
• Est. Priority Date: 10/30/1985
• Status: Expired due to Term

• Current Assignee: Intersil Corporation (Renesas Electronics Corporation)
• Original Assignee: RCA Corporation
• Inventors: Eron, Murat
• Primary Examiner(s): Bowers, Jr., Charles L.
• Application Number:
  US06/792,790
• Time in Patent Office: 657 Days
• Field of Search: 430/324, 430/312, 430/313, 430/314, 430/315, 430/328, 430/326
• US Class Current: 430/324
• CPC Class Codes: G03F 7/2022 Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal; corrective exposure
• CPC Class Codes: G03F 7/40 Treatment after imagewise removal, e.g. baking

Abstract

A process of forming sub-micrometer metallization structures on a substrate is provided. A layer of a photoresist on the structure is pattern irradiated with a reduced dosage of actinic radiation so that, upon development, recesses are formed therein which extend only partially through the photoresist layer. A first layer of metallization is deposited onto the structure at an oblique angle such that it does not completely coat the photoresist in the recesses. The structure is then flood irradiated with actinic light and developed to form openings to the substrate where the photoresist layer is not covered in the recesses. A second layer of metallization is then deposited at normal incidence. The second metallization breaks off and deposits isolated structures on the substrate through the openings. The photoresist layer and overlying layers of metallization are then removed by conventional lift-off technique.

Claims

1. A process for forming on a substrate a patern of metallization significantly finer than the resolution capability of a photoresist material utilizing a single layer of photoresist comprising:

(a) forming a single layer of a positive photoresist on the substrate;

(b) pattern irradiating the photoresist layer with a dosage of actinic radiation such that, upon development, the irradiated pattern of the photoresist layer will be only partially removed;

(c) developing the irradiated photoresist layer, thus forming recesses which extend only partially through the thickness of the photoresist layer;

(d) depositing a first layer of metallization onto the irradiated and developed photoresist layer at an oblique angle such that it does not completely cover said recesses;

(e) flood irradiating the portion of the photoresist layer not covered by the first layer of metallization, said portion lying within the recesses with actinic radiation and developing by removing said portion of the photoresist layer whereby openings are formed in the recesses of the photoresist layer which extend to the substrate;

(f) depositing a second layer of metallization over the substrate and first layer of metallization, wherein the metallization deposited on the substrate through said openings separates from that deposited on the first layer of metallization;

(g) contacting the photoresist layer with an organic solvent capable of separating the irradiated, developed and metallized photoresist layer from the substrate; and

(h) removing the layer of photoresist and metallization deposited thereover from the substrate leaving the second layer of metallization deposited in the openings.

2. A process in accordance with claim 1, wherein the substrate is gallium arsenide.

3. A process in accordance with claim 1, wherein the photoresist is a novolac resin/diazoquinone sensitizer-based photoresist.

4. A process in accordance with claim 1, wherein a photoresist composition is spin-coated onto the substrate, dried and soft-baked to form the layer in step (a).

5. A process in accordance with claim 1, wherein development in step (c) removes from about 25 to 50 percent of the thickness of the photoresist layer.

6. A process in accordance with claim 5, wherein development in step (c) removes about 30 percent of the thickness of the photoresist layer.

7. A process in accordance with claim 1, said process additionally including the step of treating the surface of the photoresist layer with a fluorocarbon plasma prior to deposition of the first layer of metallization.

8. A process in accordance with claim 1, wherein the first layer of metallization is nickel.

9. A process in accordance with claim 1, wherein the first layer of metallization is titanium.

10. A process in accordance with claim 1, wherein the second layer of metallization is aluminum or an alloy thereof.