Image sensor having large micro-lenses at the peripheral regions

• US 6,638,786 B2
• Filed: 10/25/2002
• Issued: 10/28/2003
• Est. Priority Date: 10/25/2002
• Status: Expired due to Term

• Current Assignee: Omnivision International Holding Ltd. (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: Hua Wei Semiconductor (Shanghai) Co., Ltd.
• Inventors: Yamamoto, Katsumi
• Primary Examiner(s): Mulpuri, Savitri
• Application Number:
  US10/280,854
• Publication Number:
  US 20030042490A1
• Time in Patent Office: 368 Days
• Field of Search: 348/272, 359/620, 430/273.1, 430/5, 430/7, 430/321, 430/322, 430/323, 430/324, 438/57, 438/60, 438/69, 438/73, 438/75, 438/65, 438/66, 438/725, 438/734
• US Class Current: 438/57
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements

Abstract

An image sensor includes an array of pixels formed in a semiconductor substrate. The pixels are grouped as a center portion of pixels and an outer portion of pixels. A first set of micro-lenses is formed over each of the pixels in the center portion of pixels. A second set of micro-lenses is formed over each of the pixels in the outer portion of pixels. The second set of micro-lenses differ from said first set of micro-lenses. In one embodiment, the second set of micro-lenses are taller than the first set of micro-lenses.

Claims

1. A method for forming an image sensor comprising:

forming a plurality of pixels in a semiconductor substrate, each pixel including a light sensitive element, said pixels grouped as a center portion of pixels and an outer portion of pixels;

forming a micro-lens material over said plurality of pixels, wherein said micro-lens material is a photoresist;

exposing said micro-lens material with a first reticle mask to generate gap sections in said micro-lens material;

exposing said micro-lens material with a second reticle mask to generate top portions in said micro-lens material located in said center portion of pixels;

developing said micro-lens material to remove said top portions and said gap sections;

reflowing said micro-lens material to form a first set of micro-lenses over each of said pixels in said center portion of pixels and a second set of micro-lenses over each of said pixels in said outer portion of said pixels,

wherein said second set of micro-lenses differ from said first set of micro-lenses.

2. The method of claim 1 further including forming a color filter over each pixel, said color filter formed between said micro-lens and said light sensitive element.

3. The method of claim 1 further including forming a color filter over each pixel, said color filter formed over said micro-lens.

4. The method of claim 1 wherein the second set of micro-lenses are taller than said first set of micro-lenses.

5. The method of claim 1 wherein the second set of micro-lenses are larger than said first set of micro-lenses.

6. The method of claim 1 wherein said micro-lens material is either polymethylmethacrylate (PMMA) or polyglycidylmethacrylate (PGMA).