Device with differential field isolation thicknesses and related methods

• US 20010001490A1
• Filed: 12/29/2000
• Published: 05/24/2001
• Est. Priority Date: 06/08/1998
• Status: Abandoned Application

• Current Assignee: Kuo-Tung Sung, Yuru Chu
• Original Assignee: Kuo-Tung Sung, Yuru Chu
• Inventors: Sung, Kuo-Tung, Chu, Yuru
• Application Number:
  US09/751,089
• Publication Number:
  US 20010001490A1
• Time in Patent Office: Days
• US Class Current: 257/316
• CPC Class Codes: H01L 21/76213 introducing electrical inactive or active impurities in the local oxidation region, e.g. to alter LOCOS oxide growth characteristics or for additional isolation purpose

Abstract

A semiconductor device structure with differential field oxide thicknesses. A single field oxidation step produces a nitrided field oxide region (322) that is thinner than a non-nitrided field oxide region (324). The bird'"'"'s beak (326) of the nitrided field oxide (322) encroaches less into the active cell region than the bird'"'"'s beak (328) of the thicker non-nitrided field oxide (324). The differential field oxide thicknesses allow isolation of multi-voltage integrated circuit devices, such as flash memory devices, while increasing available active cell area for a given design rule.

Claims

1. A method for producing an intermediate semi-conductor device structure, the method comprising:

(a) patterning an oxidation mask layer disposed on a substrate to create a first window region and a second window region, then;

(b) forming a layer of resist on the oxidation mask layer,

(c) patterning the layer of resist to cover the second window region and not the first window region, then;

(d) nitridizing the first window region, the second window region remaining non-nitridized, then;

(e) stripping the layer of resist from the oxide layer;

(f) oxidizing the substrate to form a nitridized field oxide in the first window region and a non-nitridized field oxide in the second window region, the nitridized field oxide being thinner than the non-nitridized field oxide; and

(g) stripping the oxidation mask from the substrate.

2. The method of

claim 1

wherein the step (d) of nitridizing is performed by an implantation process.

3. The method of

claim 1

wherein the step (d) of nitridizing is performed by applying a nitrogen source to at least the first window region.

4. The method of

claim 1

where the step (f) of oxidizing the substrate is a single field oxidation step.

5. The method of

claim 4

where the step (f) produces a non-nitridized field oxide thickness of between about 3,000-8,000 Å

and a nitridized field oxide thickness of between about 1,000-3,000 Å

.

6. The method of

claim 5

wherein the non-nitridized field oxide thickness is at least about 1.5 times the nitridized field oxide thickness.

7. A method for producing an intermediate flash memory semiconductor device structure, the method comprising:

(a) patterning an oxidation mask layer disposed on a substrate to create a first window region and a second window region, the first window region adjoining a low-voltage active cell and the second window region adjoining a high-voltage active cell, then;

(b) forming a layer of resist on the oxidation mask layer,

(c) patterning the layer of resist to cover the second window region and not the first window region, then;

(d) implanting nitrogen to nitridize the first window region, the second window region remaining non-nitridized, then;

(e) stripping the layer of resist from the oxide layer;

(f) oxidizing the substrate to form a nitridized field oxide in the first window region and a non-nitridized field oxide in the second window region, the nitridized field oxide being at least about 20% thinner than the non-nitridized field oxide; and

(g) stripping the oxidation mask from the substrate.

8. A method for producing an intermediate semi-conductor device structure, the method comprising:

(a) patterning an oxidation mask layer disposed on a substrate to create a first window region, then;

(b) nitridizing at least the first window region;

(c) patterning the oxidation mask layer to create a second window region, then;

(d) oxidizing the substrate to form a nitridized field oxide in the first window region and a non-nitridized field oxide in the second window region, the non-nitridized field oxide being at least about 1.5 times thicker than the nitridized field oxide; and

(e) stripping the oxidation mask from the substrate.

9. The method of

claim 8

wherein the step (b) of nitridizing is performed by an implantation process.

10. The method of

claim 8

wherein the step (b) of nitridizing is performed by applying a nitrogen source to at least the first window region.

11. A semiconductor device comprising:

a nitrided field oxide region having a nitrided field oxide thickness;

a non-nitrided field oxide region having a non-nitrided field oxide thickness, the nitrided field oxide thickness being less than the non-nitrided field oxide thickness.

12. The semiconductor device of

claim 11

wherein the nitrided field oxide region and the non-nitrided field oxide region result from a single field oxidation process.

13. The semiconductor device of

claim 12

wherein the nitrided field oxide region has a nitrided oxide thickness of between about 1,000-3,000 Å

and the non-nitrided field oxide region has a non-nitrided oxide thickness of between about 3,000-8,000 Å

.

14. The semiconductor device of

claim 12

wherein the non-nitrided oxide thickness is at least about 1.5 times the nitrided oxide thickness.

15. The semiconductor device of

claim 12

wherein the non-nitrided oxide thickness is at least about 2 times the nitrided oxide thickness.

16. The semiconductor device of

claim 12

wherein the non-nitrided oxide thickness is at least about 3 times the nitrided oxide thickness.

17. The semiconductor device of

claim 12

wherein the non-nitrided oxide thickness is at least about 4.5 times the nitrided oxide thickness.

18. The semiconductor device of

claim 12

wherein the non-nitrided oxide thickness is at least about 6 times the nitrided oxide thickness.

19. The semiconductor device of

claim 11

wherein the semiconductor device is a multi-voltage semiconductor device designed to operate at a first voltage and a second voltage, the second voltage being greater than the first voltage.

20. The semiconductor device of

claim 19

wherein the second voltage is at least about 1.5 times greater than the first voltage.

21. The semiconductor device of

claim 19

wherein the second voltage is at least about 2 times greater than the first voltage.

22. The semiconductor device of

claim 19

wherein the second voltage is at least about 3 times greater than the first voltage.

23. The semiconductor device of

claim 19

wherein the second voltage is at least about 4.5 times greater than the first voltage.

24. The semiconductor device of

claim 19

wherein the second voltage is at least about 6 times greater than the first voltage.

25. The semiconductor device of

claim 19

wherein the semiconductor device is a flash memory device.

26. The semiconductor device of

claim 19

further comprising a low-voltage cell and a high-voltage cell, the nitrided field oxide providing isolation to the low-voltage cell and the non-nitrided field oxide providing isolation to the high-voltage cell.

27. The semiconductor device of

claim 19

wherein the second voltage is at least about twice the first voltage.

28. The semiconductor device of

claim 11

wherein the non-nitrided field oxide thickness is at least about 20% greater than the nitrided field oxide thickness.

29. A flash-memory semiconductor device comprising:

a low-voltage active cell configured to operate at a first voltage;

a high-voltage active cell configured to operate at a second voltage, the second voltage being at least about twice the first voltage;

a nitrided field oxide region adjoining the low-voltage active cell, the nitrided field oxide having a nitrided field oxide thickness;

a non-nitrided field oxide region adjoining the high-voltage active cell, the non-nitrided field oxide having a non-nitrided field oxide thickness, the non-nitrided field oxide thickness being at least about 20% thicker than the nitrided field oxide thickness.