Method of Manufacturing an Image Sensor and Image Sensor

• US 20080265348A1
• Filed: 05/12/2005
• Published: 10/30/2008
• Est. Priority Date: 06/09/2004
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van Veen, Nicolaas Johannes Anthonius, Van Grunsven, Eric Cornelis Egbertus, Verbugt, Daniel Wilhelmus Elisabeth, Maas, Joris, Reuvers, Gerardus Lubertus Jacobus, Groot, Erik Harold, De Bruin, Leendert
• Application Number:
  US11/570,248
• Publication Number:
  US 20080265348A1
• Time in Patent Office: Days
• US Class Current: 257/432
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14632 Wafer-level processed structures
• CPC Class Codes: H01L 27/14636 Interconnect structures
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H01L 31/02162 for filtering or shielding light, e.g. multicolour filters for photodetectors
• CPC Class Codes: H01L 31/02327 the optical elements being integrated or being directly associated to the device, e.g. back reflectors optical coatings H01L31/0216

Abstract

A method of manufacturing a back-side (14) illuminated image sensor (1) is disclosed, comprising the steps of: starting with a wafer (2) having a first (3) and a second surface (4), providing light sensitive pixel regions (5) extending into the wafer (2) from the first surface (3), securing the wafer (2) onto a protective substrate (7) such that the first surface (3) faces the protective substrate, the wafer comprising a substrate of a first material (8) with an optical transparent layer (9) and a layer of semiconductor material (10), wherein the substrate (8) is selectively removed from the layer of semiconductor material by using the optical transparent layer (9) as stopping layer. For back-side illuminated image sensors, light has to transmit through the semiconductor layer and enter into the light sensitive pixel regions (5). In order to reduce absorption losses, it is very advantageous that the semiconductor layer (10) can be made relatively thin with a good uniformity. Because of the reduced thickness of the semiconductor layer, more light can enter into the light sensitive regions, resulting in an improved efficiency of the image sensor.

Claims

1. Method of manufacturing a back-side (14) illuminated image sensor (1), comprising the steps of:

starting with a wafer (2) having a first (3) and a second (4) surface,

providing light sensitive pixel regions (5) extending into the wafer from the first surface (3),

securing the wafer onto a protective substrate (7) such that the first surface (3) faces the protective substrate (7),

characterized in that the wafer comprises a substrate (8) of a first material with an optical transparent layer (9) and a layer of semiconductor material (10), wherein the substrate (8) is selectively removed from the layer (10) of semiconductor material by using the optical transparent layer (9) as stopping layer.

2. Method as claimed in claim 1, characterized in that the optical transparent layer (9) is a buried oxide layer of an SOI wafer.

3. Method as claimed in claim 2, characterized in that an additional semiconductor layer (11) is epitaxially grown on the layer of semiconductor material, in which the total thickness of the semiconductor layer is less than 5 microns.

4. Method as claimed in claim 1, characterized in that a color filter (12) is provided on the optical transparent layer (9).

5. Method as claimed in claim 1, in which a metallization pattern (13) is provided on the first side (6) of the wafer before securing the wafer onto a protective substrate, characterized in that the metallization pattern is designed such that light entering from the back-side (14) is reflected by the metallization pattern into the light sensitive pixel regions (5).

6. Method as claimed in claim 5, characterized in that the metallization pattern (13) is a multilevel metallization, in which the metal levels (15) function as reflectors such that different colors are absorbed at different light sensitive pixel regions (5).

7. Method as claimed in claim 1, in which a metallization pattern (13) is provided on the first side (6) of the wafer before securing the wafer onto a protective substrate, characterized in that an opening (50) is formed from the back-side to the metallization pattern (13) for making an external electrical connection.

8. Method as claimed in claim 7, characterized in that an electrical conductive stud or a wire bond (51) is formed inside the opening (50).

9. Method as claimed in claim 1, characterized in that the metallization pattern (13) includes bond pad extensions (16) in which, seen in perpendicular projection, a first part (17) of the semiconductor layer having overlap with the bond pad extensions is electrically insulated from a second part (18) of the semiconductor layer having the light sensitive pixel regions.

10. Method as claimed in claim 1, characterized in that isolation between the first part (17) and the second part (18) of the semiconductor layer is formed by trench isolation (19) through the entire semiconductor layer.

11. Method as claimed in claim 1, characterized in that the isolation between the first part and the second part of the semiconductor layer is formed by junction isolation (20).

12. Method as claimed in claims 9, characterized in that the first part of the semiconductor layer is removed after the manufacture of the color filter (12).

13. Method as claimed in claim 9, characterized in that the first part of the semiconductor layer is removed after the manufacture of a microlens.

14. Image sensor, comprising a semiconducting layer (10) having a first (3) and a second (4) surface, the semiconductor layer comprising light sensitive regions (5) extending into the semiconductor layer from the first surface (6), the second surface of the semiconductor layer having an optical transparent layer (9) through which light enters through the semiconductor layer in the light sensitive pixel regions, the first surface of the semiconducting layer facing a protective substrate (7), characterized in that there is a color filter in direct contact with the optical transparent layer.

15. Image sensor as claimed in claim 14, characterized in that

part of the light being not absorbed in the semiconductor layer is re-directed into the light sensitive pixel regions by reflection of a metallization pattern (13).

16. Image sensor as claimed in claim 15, characterized in that the metallization pattern is a multilevel metallization pattern and different colors of light are reflected via different levels of the metal towards different light sensitive pixel regions.

17. Image sensor as claimed in claim 14, characterized in that a metallization pattern (13) provided on the first surface (3) of the semiconductor layer (10) is connected via an opening (50) through the semiconductor layer (10) and the protective layer (7), for making an external electrical connection.

18. Image sensor as claimed in claim 17, characterized in that an electrical conductive stud or a wire bond (51) is formed inside the opening (50).