Maskless laser beam patterning ablation of multilayered structures with continuous monitoring of ablation

• US 6,696,008 B2
• Filed: 05/25/2001
• Issued: 02/24/2004
• Est. Priority Date: 05/25/2000
• Status: Expired due to Fees

• Current Assignee: Westar Photonics Incorporated
• Original Assignee: Westar Photonics Incorporated
• Inventors: Brandinger, Jay J.
• Primary Examiner(s): Staicovici, Stefan
• Application Number:
  US09/865,939
• Publication Number:
  US 20010045690A1
• Time in Patent Office: 1,005 Days
• Field of Search: 264/460, 264/482, 219/121.7, 219/121.71, 219/121.8, 219/121.81, 219/121.83, 219/121.23, 219/121.74, 219/121.75, 219/121.77
• US Class Current: 264/400
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/073 Shaping the laser spot
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G03F 7/70558 Dose control, i.e. achievement of a desired dose
• CPC Class Codes: G03F 9/70 for microlithography measuring printed patterns for monitoring overlay G03F7/70633 or focus G03F7/70641; projection system adjustment G03F7/70258; position control G03F7/70775

Abstract

A maskless patterning apparatus allows for laser beam ablation of one or more layers of material while not etching an underlying different material layer. A micromirror array produces the desired complex pattern on the workpiece and a continuous feature and end point detection system provides location and material parameter changes to accurately control the pattern position and depth of etching. End point detection includes monitoring energy reflected from a specially prepared replica of the material to be ablated, whose thickness and consistency match the active workpiece area. The process terminates when the proper amount of material is removed.

Claims

1. A process for machining a multi-layered work piece comprising at least a base layer, and a first layer of material of a dissimilar material on the surface of said base layer and preferably, a second layer of material of a dissimilar material to said first layer, said process consisting of the steps of:

(a) ablation etching a complex, three-dimensional pattern of openings into said work piece by directing radiant energy of a given energy against said composite work piece;

(b) generating, by using a computer, a maskless complex pattern and projecting said pattern onto said work piece using a Digital Micro Device (DMD) micromirror structure;

(c) continuously monitoring selected parameters from said work piece; and

,

(d) selectively terminating said ablation etching in at least one localized area, in accordance with said complex pattern, upon reaching the predetermined level of material removal in said localized area as detected in said monitoring step, thereby allowing said ablation etching to be selectively stopped upon reaching said predetermined level, independent of process conditions, while continuing ablation etching in at least another localized area to form said three-dimensional pattern of openings,

whereby said complex three-dimensional pattern of openings is etched into said work piece.

2. The process according to claim 1 wherein said monitoring step consists of:

detecting changes as a function of time, in a parameter selected from the group consisting of depth of layer, change in reflectivity of layer and quantity of material deposited on surrounding area.

3. The process according to claim 2 wherein said step of selectively terminating said ablation etching comprises the step of:

discontinuing the directing of radiant energy against the work piece within said at least one localized area.

4. The process according to claim 3 wherein said first layer material is selected from the group consisting of silicon dioxide and silicon nitride.

5. The process according to claim 4 wherein said second layer is a non-polymeric material.

6. A process for maskless, complex, pattern machining of a multi-layered work piece comprising at least a base layer, and a first layer of material of a dissimilar material on the surface of said base layer and preferably, a second layer of material of a dissimilar material to said first layer, said process consisting of the steps of:

(a) ablation etching a three-dimensional pattern of openings partway into said work piece by directing an ablation etch pattern of radiant energy of a first energy level against said multi-layered work piece, using a computer addressable micromirror array;

(b) providing a second beam of incident energy with an energy level sufficiently low so as to prevent ablation;

(e) continuously monitoring said work piece, using said second beam, with a detector located so as to determine the desired depth of ablation;

(f) calculating, using a computer, the differences between the measured depth of ablation and the desired ablation; and

(g) selectively stopping said ablation etching in at least one localized area upon reaching a desired depth of ablation in said localized area, by changing said ablation etch pattern using said addressable micromirror array, while continuing ablation etching in at least another localized area,

whereby said three-dimensional pattern of openings is etched in said surface of said work piece.

7. The process according to claim 6 wherein said first energy level of said first beam of radiant energy is sufficiently high for ablation etching of said base layer of said work piece.

8. The process according to claim 7 wherein said work piece is comprised of an additional layer overlying said first layer prior to said ablation etching and wherein said ablation etching creates openings through both said first layer and said overlying layer.

9. The process according to claim 6 wherein said step of directing an ablation etch pattern of radiant energy of a first energy level against said work piece, using a computer addressable micromirror array wherein said computer is programmable and said micromirror array mirrors are individually addressable and movable mirrors, programmed to produce the desired array pattern for ablation etching said composite work piece.

10. The process according to claim 9 wherein said directing said radiant energy against said composite work piece includes the use of a programmable modulating apparatus including a computer connected to a high resolution light valve or switch arrays having individually addressable elements, programmed to produce the desired array pattern for ablation etching said composite work piece.

11. The process according to claim 10 wherein said step of directing said radiant energy against said work piece further including the step of:

moving a said beam of radiant energy across said work piece in discrete steps.

12. A process for pattern machining a multi-layered work piece comprising at least a base layer, and a first layer of material of dissimilar material on the surface said base layer and preferably, a second layer of material of a dissimilar material to said first layer, said process consisting of the steps of:

(a) ablation etching a three-dimensional pattern of openings into said work by, directing a first beam of radiant energy having a first energy level and a first ablation pattern against said work piece;

(b) directing a second beam of radiant energy with a second wavelength different from than said wavelength of said first beam of radiant energy incident on said composite work piece and with a second energy level which is below the ablation threshold to monitor the quantity and rate of material removal from said work piece;

(c) monitoring the quantity of material removal from said work piece to ascertain when said ablation etching process reaches said first layer;

(d) monitoring the rate of material removal from said work piece to ascertain when said ablation etching process reaches said first layer;

(e) altering said first ablation pattern to a second ablation pattern upon reaching said first layer, wherein said second ablation pattern selectively stops further ablation etching within at least one region of said first ablation pattern;

(f) monitoring the quantity of material removal from said work piece to ascertain when said ablation etching process reaches said base layer;

(g) monitoring the rate of material removal from said work piece to ascertain when said ablation etching process reaches said base layer; and

,

(h) stopping said ablation etching upon reaching said base layer, while continuing ablation etching in at least another region,

whereby said three-dimensional pattern of openings is etched in said surface of said work piece.

13. A process for machining a multi-layered work piece comprising at least a base layer, and a first layer of material of a dissimilar material on the surface of said base layer and preferably, a second layer of material of a dissimilar material to said first layer, said process consisting of the steps of:

(a) monitoring selected parameters from said work piece;

(b) generating a working complex pattern of radiation, said working complex pattern of radiation being formed from a source of radiant energy by an addressable Digital Micro Device (DMD) micromirror structure under control of a computer using said monitoring selected parameters;

(c) ablation etching said working complex pattern of radiation into said work piece by projecting said working complex pattern of radiation onto said work piece; and

,

(d) repeating said steps of monitoring, generating and ablation etching, wherein said working pattern of radiation is generated such that said step of ablation etching is selectively terminated in at least one localized region of said desired pattern upon reaching a predetermined level of material removal in said localized region, as detected in said monitoring step, while continuing ablation etching in at least another localized region to another predetermined level of material removal until a desired three-dimensional pattern is etched into said work piece.