PASSIVATION LAYER FOR AN INTEGRATED CIRCUIT DEVICE THAT PROVIDES A MOISTURE AND PROTON BARRIER

Abstract

An integrated circuit device includes a metal contact and a passivation layer extending on a sidewall of the metal contact and on first and second surface portions of a top surface of the metal contact. The passivation layer is format by a stack of layers including: a tetraethyl orthosilicate (TEOS) layer; a Phosphorus doped TEOS (PTEOS) layer on top of the TEOS layer; and a Silicon-rich Nitride layer on top of the PTEOS layer. The TEOS and PTEOS layers extend over the first surface portion, but not the second surface portion, of the top surface of the metal contact. The Silicon-rich Nitride layer extends over both the first and second surface portions, and is in contact with the second surface portion.

Claims

1. An integrated circuit device, comprising: a metal contact having a top surface, the top surface of the metal contact including a first surface portion, a second surface portion and a third surface portion; and a passivation layer extending on the first and second surface portions of the top surface of the metal contact; wherein the passivation layer comprises a stack of layers including: a tetraethyl orthosilicate (TEOS) layer; a Phosphorus doped TEOS (PTEOS) layer on top of the TEOS layer; and a high-density Silicon-rich Nitride layer on top of the PTEOS layer; wherein the TEOS and PTEOS layers extend over the first surface portion of the top surface of the metal contact, but not over the second and third surface portions of the top surface of the metal contact; and wherein the high-density Silicon-rich Nitride layer extends over the first and second surface portions of the top surface of the metal contact, but not over the third surface portion of the top surface of the metal contact.

2. The integrated circuit device of claim 1, wherein the high-density Silicon-rich Nitride layer is in contact with the second surface portion of the top surface of the metal contact.

3. The integrated circuit device of claim 1, wherein the high-density Silicon-rich Nitride layer is in contact with side edge surfaces of the TEOS and PTEOS layers at a transition from the first surface portion to the second surface portion.

4. The integrated circuit device of claim 1, wherein the TEOS layer is in contact with the first surface portion of the top surface of the metal contact.

5. The integrated circuit device of claim 1, further comprising a Silicon flash layer in the stack of layers for the passivation layer, wherein said Silicon flash layer is positioned between the PTEOS layer and the high-density Silicon-rich Nitride layer.

6. The integrated circuit device of claim 5, wherein the Silicon flash layer has a thickness of less than 100 Å.

7. The integrated circuit device of claim 5, wherein the Silicon flash layer is in contact with the second surface portion of the top surface of the metal contact.

8. The integrated circuit device of claim 5, wherein the Silicon flash layer is in contact with side edge surfaces of the TEOS and PTEOS layers at a transition from the first surface portion to the second surface portion.

9. The integrated circuit device of claim 5, wherein the high-density Silicon-rich Nitride layer is in contact with the Silicon flash layer.

10. The integrated circuit device of claim 1, wherein the TEOS layer has a thickness in a range of about 12,000-16,000 Å.

11. The integrated circuit device of claim 1, wherein the PTEOS layer has a thickness in a range of about 4,000-6,000 Å.

12. The integrated circuit device of claim 1, wherein the high-density Silicon-rich Nitride layer has a thickness in a range of about 8,000-12,000 Å.

13. The integrated circuit device of claim 1, wherein the high-density Silicon-rich Nitride layer has a ratio of N/Si that is less than about 1.3 and the high-density Silicon-rich Nitride layer has a refractive index greater than 2.

14. The integrated circuit device of claim 1, wherein a stoichiometry of the high-density Silicon-rich Nitride layer comprises Si.sub.xN.sub.y where x:y is greater than or equal to 3:4 and the high-density Silicon-rich Nitride layer has a refractive index greater than 2.

15. The integrated circuit device of claim 1, wherein the metal contact extends over a premetallization dielectric layer.

16. The integrated circuit device of claim 12, wherein the premetallization dielectric layer is formed solely of TEOS.

17. The integrated circuit device of claim 1, wherein the metal contact is a gate contact of a discrete transistor.

18. The integrated circuit device of claim 1, wherein the metal contact is a source contact of a discrete transistor.

19. The integrated circuit device of claim 1, wherein the metal contact includes a sidewall, and wherein the passivation layer further extends on the sidewall of the metal contact.

20. The integrated circuit device of claim 1, wherein the metal contact is a contact for a transistor source or gate terminal.

21. The integrated circuit device of claim 1, wherein the metal contact is a contact for a transistor emitter or base terminal.

22. The integrated circuit device of claim 1, wherein the metal contact is a contact for an anode or cathode terminal of a diode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a better understanding of the embodiments, reference will now be made by way of example only to the accompanying figures in which:

[0023] FIG. 1 shows a cross-section of a portion of an integrated circuit device;

[0024] FIG. 2 shows detail of a passivation layer configuration at a source electrical contact and a gate electrical contact of the integrated circuit device of FIG. 1;

[0025] FIG. 3 shows detail of a passivation layer configuration at the source electrical contact and the gate electrical contact of the integrated circuit device of FIG. 1;

[0026] FIG. 4 shows a scanning electron micrograph of an example of the passivation layer configuration;

[0027] FIGS. 5A-5E show steps of a fabrication process for making the passivation layer configuration of FIGS. 3 and 4;

[0028] FIG. 6 shows detail of a passivation layer configuration at the source electrical contact and the gate electrical contact of the integrated circuit device of FIG. 1;

[0029] FIG. 7 illustrates a relationship between N/Si ratio and refractive index for Si-rich silicon nitride material; and

[0030] FIGS. 8A-8C show cross-sections of other integrated circuit devices utilizing the passivation layer configuration.

DETAILED DESCRIPTION

[0031] Reference is now made to FIGS. 3 and 6 which show detail of a passivation layer 50′ configuration at the source electrical contact 46 and the gate electrical contact 48 of the integrated circuit device of FIG. 1. In this embodiment, the passivation layer 50′ comprises a stack of layers including: a TEOS layer 50a′, a Phosphorus doped TEOS (PTEOS) layer 50b′ covering the TEOS layer 50a′, and a Silicon Nitride (SiN) layer 50c′. The TEOS layer 50a′ may, for example, have a thickness in a range of about 12,000-16,000 Å, the PTEOS layer 50b′ may, for example, have a thickness in a range of about 4,000-6,000 Å, and the SiN layer 50c′ may, for example, have a thickness in a range of about 8,000-12,000 Å. In the implementation as shown in FIG. 6, adhesion of the SiN layer 50c′ on the metal layer 44 may be enhanced by the use of a thin Silicon flash layer 70 between the PTEOS layer 50b′ and the SiN layer 50c′. The Silicon flash layer 70 may, for example, have a thickness of less than 100 Å. The passivation layer 50′ is lithographically patterned to form openings exposing an upper surface of the source (S) electrical contact 46 and gate (G) electrical contact 48.

[0032] The TEOS layer 50a′ provides a layer made of a material that is softer than Silicon Nitride to provide a stress relieving structure and also presents a good adhesion property with respect to the Aluminum material of the second metal layer 44. The TEOS layer 50a′ also provides a diffusion barrier that inhibits the diffusion of Phosphorus from the PTEOS layer 50b′. The PTEOS layer 50b′ functions as a gettering layer presenting a proton H+ gettering center. The SiN layer 50c′ is preferably implemented as a high-density Silicon-rich Nitride (referred to in the art as a “Yellow Nitride”) and functions as a moisture resistant barrier which inhibits penetration of contaminants such as proton H+ and moisture.

[0033] FIG. 4 shows a scanning electron micrograph of an example of the passivation layer 50′ configuration relative to a contact (C) made of Aluminum.

[0034] All three layers 50a′, 50b′ and 50c′ of the stack for the passivation layer 50′ extend over the exposed upper surface of the premetallization dielectric layer 32 in areas where the source (S) electrical contact 46 and gate (G) electrical contact 48 are not present (see, right side). All three layers 50a′, 50b′ and 50c′ of the stack for the passivation layer 50′ further extend over sidewalls (S) of the contact C (i.e., on the side edge surfaces of the lithographically patterned layers 42 and 44). The three layers 50a′, 50b′ and 50c′ of the stack for the passivation layer 50′ further extend over a first surface portion 52 of the top surface of the contact C (i.e., on the top surface of the lithographically patterned layer 44). However, only the SiN layer 50c′ extends over a second surface portion 54 of the top surface of the contact C. The SiN layer 50c′ (along with flash layer 70, when present) extends on side edge surfaces of the layers 50a′, 50b′ at a transition from the first surface portion 52 to the second surface portion 54. A third surface portion 56 of the top surface of the contact C is not covered by any of the passivation layer 50′. Additionally, the SiN layer 50c′ extends over sidewalls S1 of the layers 50a′, 50b′.

[0035] Fabrication of the passivation layer 50′ requires the use of two masks in lithographically patterning the three layers 50a′, 50b′ and 50c′ (plus layer 70, if present) of the stack. The steps of the fabrication process are shown by FIGS. 5A-5E. In FIG. 5A, the layers 50a′, 50b′ are deposited over the metal contact C (44). The layers 50a′ and 50b′ may, for example, be deposited using plasma-enhanced chemical vapor deposition (PECVD). In FIG. 5B, a first mask 60 is formed from a developed photoresist. The first mask 60 covers the first surface portion 52 of the top surface of the metal contact. An etch is then performed to remove portions of the layers 50a′, 50b′ which are not covered by the first mask 60. The first mask 60 is then removed. In FIG. 5C, the layer 50c′ (with interposed Silicon flash layer 70, see FIG. 6, if desired) is conformally deposited to cover the patterned layers 50a′, 50b′ as well as the second and third surface portions 54 and 56 of the top surface of the metal contact. The layer 50c′ and may, for example, be deposited using SiH.sub.4-based plasma-enhanced chemical vapor deposition (PECVD). The stoichiometry of the SiN layer 50c′ may, for example, comprise Si.sub.xN.sub.y where the bond ratio x:y, for example, determinable by analysis techniques such as R-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIS) or Rutherford backscattering (RBS) showing a N/Si ratio that is less than about 1.3 (or x:y greater than 3:4) and a refractive index, for example measured by the optical ellipsometry method, that is greater than 2 (see, FIG. 7). In FIG. 5D, a second mask 62 is formed from a developed photoresist. The second mask 62 covers the first and second surface portions 52 and 54 of the top surface of the metal contact. An etch is then performed to remove portions of the layer 50c′ which is not covered by the second mask 62 so as to provide a contact opening 64 over the third surface portion 56 of the top surface of the metal contact. The second mask 62 is then removed. The result is shown in FIG. 5E.

[0036] Although FIGS. 3 and 6 show use of the passivation layer 50′ in connection with a power MOSFET transistor, it will be understood that the passivation layer 50′ may be used in connection with the metal contact/bonding pad of any suitable integrated circuit device. Examples of such devices include, but are not limited to, a shielded gate trench power MOSFET (FIG. 8A) where the passivation is provided at a source and/or a gate contact, a trench gate field stop IGBT (FIG. 8B) where the passivation is provided at an emitter and/or gate contact, a superjunction MOSFET (FIG. 8C) where the passivation is provided at a source and/or gate contact, and a power diode where the passivation is provided at an anode and/or cathode contact.

[0037] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.