Selective ionic implantation of fluoropolymer film to modify the sensitivity of underlying sensing capacitors

• US 20030104647A1
• Filed: 11/30/2001
• Published: 06/05/2003
• Est. Priority Date: 11/30/2001
• Status: Active Grant

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Evans, Richard P., Lane, Fred P., Siegel, Harry M.
• Granted Patent: US 6,707,093 B2
• Time in Patent Office: Days
• US Class Current: 438/50
• CPC Class Codes: G06V 40/1329 Protecting the fingerprint sensor against damage caused by the finger
• CPC Class Codes: H01L 23/3171 the coating being directly applied to the semiconductor body, e.g. passivation layer H01L23/3178 takes precedence
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/12044 OLED
• CPC Class Codes: H01L 2924/19041 being a capacitor
• CPC Class Codes: H01L 2924/3025 Electromagnetic shielding

Abstract

A touch-sensitive semiconductor chip having a physical interface to the environment, where the surface of the physical interface is coated with a fluorocarbon polymer. The polymer is highly scratch resistant and has a characteristic low dielectric constant for providing a low attenuation to electric fields. The polymer can be used instead of conventional passivation layers, thereby allowing a thin, low dielectric constant layer between the object touching the physical interface, and the capacitive sensing circuits underlying the polymer.

Claims

1. A method for fabricating a semiconductor device, comprising the steps of:

forming a transistor circuit in a semiconductor material of the device, said transistor circuit being responsive to an electric field;

forming a fluorocarbon polymer over at least a portion of said transistor circuit so that said electric field passes through said fluorocarbon polymer; and

embedding a particle in said fluorocarbon polymer to influence the electric field.

2. The method of claim 1, further including embedding a plurality of particles of a type for influencing the electric field.

3. The method of claim 1, further including embedding electrons in said fluorocarbon polymer.

4. The method of claim 1, further including embedding particles in said fluorocarbon polymer at desired locations, and in other locations of said fluorocarbon polymer embedding no particles.

5. The method of claim 4, further including using a mask to selective embed the particles in said fluorocarbon polymer.

6. The method of claim 1, further including embedding particles in said fluorocarbon polymer using implant techniques.

7. The method of claim 1, further including forming capacitor plates on said semiconductor material, and using said fluorocarbon polymer as a dielectric with a dielectric constant less than about 2.1.

8. The method of claim 1, wherein said transistor circuit includes a capacitor plate to which said electric field is coupled.

9. The method of claim 8, further including forming said fluorocarbon polymer over said capacitor plate.

10. The method of claim 8, further including embedding the particles in said fluorocarbon polymer at a location to influence the electric field coupled to said capacitor plate.

11. The method of claim 1, further including embedding particles of a type for gettering the fluorocarbon polymer to prevent deleterious ions from migrating to said sensor circuits.

12. A semiconductor device fabricated according to the method of claim 1.

13. A method for fabricating a semiconductor device, comprising the steps of:

forming in a semiconductor material a matrix of sensor circuits for processing signals generated by capacitive circuits;

forming a matrix of said capacitive circuits on said semiconductor material, each said capacitive circuit having at least one conductive plate, each said capacitive circuit coupled to a respective said sensor circuit;

forming a dielectric layer overlying said capacitive circuits by depositing a layer of a fluorocarbon polymer; and

embedding particles in said dielectric layer to influence an electric field coupled to ones of said capacitive circuits.

14. The method of claim 13, further including using a fluorocarbon polymer with a dielectric constant of less than about 2.1.

15. The method of claim 13, further including using a mask to selectively implant the particles in said fluorocarbon polymer.

16. The method of claim 13, further including forming said dielectric layer by spraying said fluorocarbon polymer on said semiconductor device.

17. The method of claim 13, further including forming said dielectric layer with a thickness of about 20 microns.

18. The method of claim 13, further including forming said capacitive circuits so as to be responsive to ridges and valleys of a fingerprint.

19. The method of claim 18, further including forming a physical interface in said semiconductor device for allowing a touch input to said capacitive circuits.

20. The method of claim 19, further including forming said dielectric layer with one surface thereof exposed to the environment.

21. A semiconductor device constructed according to the method of claim 13.