Method for reducing photolithographic steps in a semiconductor interconnect process

• US 5,972,569 A
• Filed: 10/07/1997
• Issued: 10/26/1999
• Est. Priority Date: 02/13/1996
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Pierrat, Christophe, Jeng, Nanseng
• Primary Examiner(s): Duda, Kathleen
• Application Number:
  US08/946,462
• Time in Patent Office: 749 Days
• Field of Search: 431/312, 431/313, 431/394, 431/396, 431/314
• US Class Current: 430/312
• CPC Class Codes: G03F 1/26 Phase shift masks [PSM]; PSM blanks; Preparation thereof
• CPC Class Codes: G03F 1/29 Rim PSM or outrigger PSM; Preparation thereof
• CPC Class Codes: G03F 1/32 Attenuating PSM [att-PSM], e.g. halftone PSM or PSM having semi-transparent phase shift portion,; Preparation thereof
• 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: H01L 21/0274 Photolithographic processes
• CPC Class Codes: H01L 21/31144 using masks
• CPC Class Codes: H01L 21/76813 involving a partial via etch
• CPC Class Codes: H01L 2221/1021 Pre-forming the dual damascene structure in a resist layer

Abstract

A semiconductor wafer having a first layer and overlying insulating layer receives a photoresist layer. A first photoresist area is exposed to light having a first dosage, while a second, adjacent photoresist area is concurrently exposed to light having a second dosage. The first area and second area then are concurrently developed to partially expose the photoresist layer. The partial exposure removes photoresist within the first area to one depth and within the second area to a second depth. The second depth differs from the first depth. In one embodiment the second depth extends through the photoresist down to the insulating layer. After subsequently performing a contact and/or trench etch through the exposed insulating layer and removing excess photoresist above the insulating layer, conductive material is deposited in the contact/trench opening and over the insulating layer. The result is an upper conductive layer coupled to the first layer via a contact or other conductive connection.

Claims

1. A method of at least partially developing a layer of photoresist, comprising:

exposing a first area of the layer of photoresist to radiation of a first dosage while concurrently exposing a second area of the layer of photoresist to radiation of a second dosage; and

developing the first area and the second area to remove photoresist within the first area to a first, partial depth of the layer of photoresist and to remove photoresist within the second area to a second depth.

2. The method of claim 1 in which the exposing comprises employing a mask having a first region of first transmissivity and a second region of second transmissivity, and in which radiation of a first dosage exits the mask at the first region to expose the first area, and in which radiation of a second dosage exits the mask at the second region to expose the second area.

3. The method of claim 1 in which the first area and the second area are adjacent.

4. A method of at least partially developing a layer of photoresist, comprising:

passing radiation through a first region of a mask having a first transmissivity and through a second region of the mask having a second transmissivity, wherein radiation of a first dosage exits the first region of the mask and radiation of a second dosage exits the second region of the mask concurrently with the radiation of a first dosage;

exposing a first area of the layer of photoresist to the radiation of the first dosage while concurrently exposing a second area of the layer of photoresist to the radiation of the second dosage; and

developing a portion of photoresist in the first area and photoresist in the second area to remove photoresist within the first area to a first, partial depth and to remove photoresist within the second area to a second depth.

5. The method of claim 4, in which the radiation of the first dosage is phase-shifted relative to the radiation of the second dosage.

6. A method of forming a conductive path electrically connecting multiple layers of a region of a semiconductor wafer, the region of the semiconductor wafer having a first layer and an insulating layer, the method comprising:

applying a layer of photoresist onto the insulating layer;

exposing a first area of the layer of photoresist to a first dosage of radiation while concurrently exposing a second area of the layer of photoresist to a second dosage of radiation;

developing the first area and the second area to remove photoresist within the first area to a first, partial depth of the layer of photoresist so as to define a first opening in the layer of photoresist and to remove photoresist within the second area so as to define a second opening in the layer of photoresist;

etching a region of the insulating layer exposed through the second opening to extend the second opening through the insulating layer to the first layer; and

depositing a conductive material into the second opening into contact with the first layer.

7. The method of claim 6 in which the first layer comprises a conductive material.

8. The method of claim 7 in which the first layer comprises a semiconductive material.

9. The method of claim 6, in which the developing comprises concurrently developing the first area and second area.

10. The method of claim 6, in which the second area is adjacent to the first area.

11. The method of claim 6, wherein the depositing comprises depositing the conductive material into the second opening, wherein at least a portion of the conductive material comprises a contact.

12. The method of claim 6, wherein the depositing comprises depositing the conductive material into the second opening, wherein at least a portion of the conductive material comprises a contact.

13. A method of interconnecting a wiring line and a conductive area of a semiconductor wafer, wherein the wiring line and the conductive area are separated by at least an insulating region, the method comprising:

applying photoresist to the insulating region;

exposing a first area of the photoresist to a first dosage of radiation while concurrently exposing a second area of the photoresist to a second dosage of radiation, wherein the first area is adjacent to the second area;

developing the first area and the second area to remove photoresist within the first area to a first, partial depth of the photoresist so as to define a first opening in the photoresist and to remove photoresist within the second area so as to define a second opening in the photoresist;

etching the insulating region exposed through the second opening to extend the second opening through the insulating region to the conductive area; and

depositing a quantity of a conductive material into the second opening in electrical communication with the conductive area and into the first area to define at least a portion of the wiring line.

14. The method of claim 13, wherein the exposing comprises passing radiation through a mask having a first region of first transmissivity and a second region of second transmissivity, wherein the first dosage of radiation exits the mask from the first region and the second dosage of-radiation exits the mask from the second region, and wherein the first dosage of radiation is phase-shifted by less than about 180°

relative to the second dosage of radiation.

15. The method of claim 13, in which the developing comprises concurrently developing the first area and the second area.

16. A method of forming a contact to a doped region of a semiconductor wafer, wherein an insulating layer overlays at least a portion of the doped region, the method comprising:

applying photoresist to the insulating layer;

exposing a first area of the photoresist to radiation of a first dosage while simultaneously exposing a second area to radiation of a second dosage;

developing the first area and the second area to remove photoresist within the first area to a first, partial depth of the photoresist so as to define a first opening in the first area and to remove all the photoresist from the second area so as to define a second opening in the second area;

etching the insulating layer exposed through the second openings to extend the second opening through the insulating layer to the doped region; and

depositing a conductive material into the second opening in electrical contact with the doped region, wherein at least a portion of the conductive material comprises at least a portion of the contact.

17. The method of claim 16, in which the developing comprises simultaneously developing the first area and the second area.