Microlens forming method

• US 5,324,623 A
• Filed: 06/03/1992
• Issued: 06/28/1994
• Est. Priority Date: 06/04/1991
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Tsumori, Toshiro
• Primary Examiner(s): LUSIGNAN, MICHAEL R
• Application Number:
  US07/892,985
• Time in Patent Office: 755 Days
• Field of Search: 427/162, 430/321, 430/323, 430/324, 430/330, 430/394
• US Class Current: 430/321
• CPC Class Codes: G02B 3/0018 Reflow, i.e. characterized by the step of melting microstructures to form curved surfaces, e.g. manufacturing of moulds and surfaces for transfer etching
• CPC Class Codes: G03F 7/0005 Production of optical devices or components in so far as characterised by the lithographic processes or materials used therefor
• CPC Class Codes: G03F 7/001 Phase modulating patterns, e.g. refractive index patterns

Abstract

A method of forming a microlens made of a thermoplastic resin on a solid-state imaging device, including the steps of forming a resist pattern having an opening as a microlens forming portion on the solid-state imaging device; filling the opening with the thermoplastic resin; removing the resist pattern; and thermally deforming the thermoplastic resin on the opening. Accordingly, a microlens having a desired shape can be formed with a fine lens pattern of 0.5 μm or less uniformly and highly accurately.

Claims

1. A method of forming a microlens on a solid-state imaging device, comprising the steps of:

coating a positive photoresist film on said solid-state imaging device;

patterning said photoresist film to form an opening therein;

filling said opening with a thermoplastic resin;

then removing said photoresist film; and

then heating said thermoplastic resin left in said opening to deform said thermoplastic resin into said microlens.

2. A method according to claim 1, wherein said step of filling said opening with said thermoplastic resin comprises the steps of applying a coating of said thermoplastic resin of a thickness to fill the openings and to cover said photoresist film formed with said opening and then etching back a portion of said coating of said thermoplastic resin until said photoresist film is exposed.

3. The method as defined in claim 1, wherein a negative resist is employed for said thermoplastic resin.

4. The method as defined in claim 1, wherein said step of removing said photoresist film comprises the steps of exposing a whole surface of said photoresist film to light and developing said exposed photoresist film to thereby remove said positive photoresist.

5. A method of forming a microlens on a surface of a solid-state imaging device, said method comprising the steps of:

applying a positive photoresist film on the surface of the solid-state imaging device;

patterning the positive photoresist film to form an opening therein;

applying a second coat of a negative resist on the photoresist film to fill the opening and to cover the film;

etching a portion of the coating of negative resist to uncover the photoresist film;

then exposing the device to light to transform the positive photoresist film into an exposed photoresist film;

then removing the exposed photoresist film by developing to leave the negative resist filling the opening; and

then heating the negative resist to deform the negative resist into a microlens.

6. A method according to claim 5, wherein the negative resist is a thermoplastic resin.