Method of forming a capacitor in semiconductor wafer processing

• US 5,202,278 A
• Filed: 09/10/1991
• Issued: 04/13/1993
• Est. Priority Date: 09/10/1991
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Yu, Chang, Doan, Trung T., Tuttle, Mark E., Mathews, Viju K.
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): TRINH, LOC
• Application Number:
  US07/757,197
• Time in Patent Office: 581 Days
• Field of Search: 437/19, 437/173, 437/20, 437/977, 437/942, 437/47, 437/60, 437/52, 437/919, 357/23.6, 365/149, 365/51
• US Class Current: 438/398
• CPC Class Codes: H01L 28/82 with an enlarged surface, e.g. formed by texturisation
• CPC Class Codes: Y10S 438/964 Roughened surface

Abstract

A method of forming a capacitor in semiconductor water processing comprising the following steps: a) providing a conductively doped first layer of polysilicon atop a silicon wafer to a first thickness; b) depositing an undoped second layer of polysilicon over the conductively doped first layer of polysilicon to a second thickness, the layer of undoped polysilicon being deposited at a deposition temperature of at least 590° and having an upper surface; c) impinging laser energy onto the upper surface of the second polysilicon layer at a laser fluence of 0.3 J/cm² or greater to roughen the upper surface and thereby increase the capacitance of the second polysilicon layer; d) patterning and etching the first and second polysilicon layers to define a lower capacitor plate; e) providing a layer of capacitor dielectric atop the roughened second polysilicon layer upper surface; and f) providing a layer of conductive material atop the capacitor dielectric to define an upper capacitor plate.

Claims

1. A method of forming a capacitor in semiconductor wafer processing comprising the following steps:

providing a conductively doped first layer of polysilicon atop a silicon wafer to a first thickness;

depositing an undoped second layer of polysilicon over the conductively doped first layer of polysilicon to a second thickness, the layer of undoped polysilicon being deposited at a deposition temperature of at least 590° and

having a smooth upper surface, said upper surface being smoother than upper surfaces of polysilicon layers deposited at temperatures less than 590°

C.;

impinging laser energy onto the upper surface of the second polysilicon layer at a laser fluence of 0.3 J/cm² or greater to roughen the smooth upper surface and thereby increase the capacitance of the second polysilicon layer;

patterning and etching the first and second polysilicon layers to define a lower capacitor plate;

providing a layer of capacitor dielectric atop the roughened second polysilicon layer upper surface; and

providing a layer of conductive material atop the capacitor dielectric to define an upper capacitor plate.

2. The method of forming a capacitor of claim 1 wherein the first thickness is from about 100 Angstroms to about 1000 Angstroms.

3. The method of forming a capacitor of claim 1 wherein the second thickness is from about 500 Angstroms to about 1500 Angstroms.

4. The method of forming a capacitor of claim 1 wherein the first thickness is from about 100 Angstroms to about 1000 Angstroms and the second thickness is from about 500 Angstroms to about 1500 Angstroms.

5. The method of forming a capacitor of claim 1 wherein,

the first thickness is from about 100 Angstroms to about 1000 Angstroms and the second thickness is from about 500 Angstroms to about 1500 Angstroms;

and

the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted using an excimer laser.

6. The method of forming a capacitor of claim 1 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted using an excimer laser.

7. The method of forming a capacitor of claim 6 wherein the excimer laser comprises a XeCl laser.

8. The method of forming a capacitor of claim 1 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer comprises impinging laser energy in pulsed bursts of about 25 nanoseconds duration.

9. The method of forming a capacitor of claim 1 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted at a laser fluence of 0.5 J/cm² or greater.

10. The method of forming a capacitor of claim 9 wherein the first thickness is from about 100 Angstroms to about 1000 Angstroms and the second thickness is from about 500 Angstroms to about 1500 Angstroms.

11. The method of forming a capacitor of claim 1 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted at a laser fluence of from 0.5 J/cm² to 0.8 J/cm².

12. The method of forming a capacitor of claim 1 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted using an excimer laser in pulsed bursts of about 25 nanoseconds duration.

13. The method of forming a capacitor of claim 12 wherein the excimer laser comprises a XeCl laser.

14. The method of forming a capacitor of claim 1 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted using an excimer laser at a laser fluence of 0.5 J/cm² or greater.

15. The method of forming a capacitor of claim 14 wherein the excimer laser comprises a XeCl laser.

16. The method of forming a capacitor of claim 14 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer comprises impinging laser energy in pulsed bursts of about 25 nanoseconds duration.

17. The method of forming a capacitor of claim 14 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted at a laser fluence of from 0.5 J/cm² to 0.8 J/cm².

18. A method of forming a capacitor in semiconductor wafer processing comprising the following steps:

providing a conductively doped first layer of polysilicon atop a semiconductor wafer to a thickness from 100 Angstroms to 1000 Angstroms;

depositing an undoped second layer of polysilicon over the conductively doped first layer of polysilicon to a thickness of from 500 Angstroms to 1500 Angstroms, the layer of undoped polysilicon being deposited at a deposition temperature of at least 590° and

having a smooth upper surface, said upper surface being smoother than upper surfaces of polysilicon deposited at temperatures less than 590°

C.;

impinging laser energy onto the smooth upper surface of the second polysilicon layer with a XeCl excimer laser at a laser fluence of 0.5 J/cm² or greater and with pulsed bursts of about 25 nanoseconds duration to roughen the smooth upper surface and thereby increase the capacitance of the second polysilicon layer;

patterning and etching the first and second polysilicon layers to define a lower capacitor plate;

providing a layer of capacitor dielectric atop the roughened second polysilicon layer upper surface; and

providing a layer of conductive material atop the capacitor dielectric to define an upper capacitor plate.

19. A method of forming a capacitor in semiconductor wafer processing comprising the following steps:

depositing a layer of polysilicon atop a wafer to a thickness from 500 Angstroms to 1000 Angstroms and at a deposition temperature of at least 590°

C., the layer of polysilicon having a smooth upper surface, said upper surface being smoother than upper surfaces of polysilicon deposited at temperatures less than 590°

C.;

impinging laser energy onto the smooth upper surface of polysilicon at a laser fluence of 0.3 J/cm² or greater to roughen the smooth upper surface and thereby increase the capacitance of the polysilicon layer;

ion implanting a conductivity enhancing material through the roughened upper polysilicon surface to impart conductivity to the polysilicon layer;

patterning and etching the polysilicon layer to define a lower capacitor plate;

providing a layer of capacitor dielectric atop the roughened polysilicon layer upper surface; and

providing a layer of conductive material atop the capacitor dielectric to define an upper capacitor plates.

20. The method of forming a capacitor of claim 19 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted using an excimer laser.

21. The method of forming a capacitor of claim 20 wherein the excimer laser comprises a XeCl laser.

22. The method of forming a capacitor of claim 19 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer comprises impinging laser energy in pulsed bursts of about 25 nanoseconds duration.

23. The method of forming a capacitor of claim 19 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted at a laser fluence of 0.5 J/cm² or greater.

24. The method of forming a capacitor of claim 19 wherein the step of impinging laser energy onto the upper surface of the second polysilicon layer is conducted using an excimer laser in pulsed bursts of about 25 nanoseconds duration.