# Patent

## Title
Via/contact and damascene structures

## Abstract

A semiconductor structure is provided and includes a dielectric layer disposed over a substrate. A first non-conductive barrier layer is formed over the dielectric layer. At least one opening is formed through the first non-conductive barrier layer and within the dielectric layer. A second non-conductive barrier layer is formed over the first non-conductive barrier layer and within the opening. At least a portion of the second non-conductive barrier layer is removed, thereby at least partially exposing a top surface of the first non-conductive barrier layer and a bottom surface of the opening, with the second non-conductive barrier layer remaining on sidewalls of the opening. A seed layer and conductive layer is disposed in the opening.

## Background
RELATED APPLICATION(S)
The application is a divisional application of U.S. patent application Ser. No. 11/680,981, filed on Mar. 1, 2007, the contents of which are hereby incorporated by reference as if set forth in their entirety.


FIELD OF THE INVENTION
The present invention relates, most generally, to semiconductor device manufacturing, and more particularly to via/contact and/or damascene structures and manufacturing methods for forming the same.
DESCRIPTION OF THE RELATED ART
With advances associated with electronic products, semiconductor technology has been widely applied in manufacturing memories, central processing units (CPUs), liquid crystal displays (LCDs), light emission diodes (LEDs), laser diodes and other devices or chipsets. In order to achieve high-integration and high-speed goals and keep up with the advances in electronic products, dimensions of semiconductor integrated circuits continue to shrink. In addition, low-k dielectric materials and low-resistance metallic materials are used for reducing parasitic capacitances and resistance-capacitance (RC) time delays in order to enhance speeds of integrated circuits.
FIG. 1 is a cross-sectional view of a prior art semiconductor structure for forming a via structure.
Referring to FIG. 1, metal lines 110 are formed over a substrate 100. A dielectric layer 120 is formed on the substrate 100 and the metal lines 110. Holes (not labeled) are formed within the dielectric layer 120 and are via holes but may alternatively represent contact holes or trenches within which damascene leads are to be formed. A conductive diffusion barrier layer 130, e.g., a tantalum/tantalum nitride (Ta/TaN) diffusion barrier layer, is formed on the dielectric layer 120 and within the via holes. A copper seed layer 140 is formed on the Ta/TaN diffusion barrier layer 130. A copper layer 150 is formed on the copper seed layer 140 and fills in the via holes.
In order to isolate via structures formed in adjacent via holes, a chemical-mechanical polishing (CMP) process is used to remove the copper layer 150, the copper seed layer 140 and the Ta/TaN diffusion barrier layer 130 formed over the surface 121 of the dielectric layer 120. Since the material property of copper is different from that of Ta/TaN or other materials which may be used as the barrier layer 130, different recipes, slurries, polishing forces, pads or other factors of CMP process must be selected for individually removing the copper layer 150, the copper seed layer 140 and the Ta/TaN diffusion barrier layer 130 formed over the surface 121 of the dielectric layer 120.
Based on the foregoing, improved methods and structures for forming contact/via and/or damascene structures are desired.
SUMMARY
In accordance with some exemplary embodiments, a semiconductor structure comprises a dielectric layer formed over a substrate. A plurality of openings are formed within the dielectric layer. A first non-conductive barrier layer is formed over the dielectric layer, wherein the first non-conductive barrier layer extends from an edge of a first one of the openings to an edge of a second one of the openings adjacent thereto. A second non-conductive barrier layer is formed on sidewalls of the openings. A conductive layer is formed within the openings.
In accordance with some exemplary embodiments, a semiconductor structure comprises: a lower composite film structure including a first non-conductive barrier layer disposed over a low-k dielectric layer, disposed over a substrate; a plurality of openings extending through the first non-conductive barrier layer and into the low-k dielectric layer; a second non-conductive barrier layer disposed within the openings but not completely covering bottoms of said openings; and a conductive material formed within the openings.
The above and other features will be better understood from the following detailed description of the preferred embodiments of the invention that is provided in connection with the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
Following are brief descriptions of exemplary drawings. They are mere exemplary embodiments and the scope of the present invention should not be limited thereto. The description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus/device be constructed or operated in a particular orientation.
FIG. 1 is a side, cross-sectional view of an exemplary prior art via structure.
FIGS. 2A-2H are schematic cross-sectional views showing a sequence of operations in an exemplary method for forming a single damascene structure according to an embodiment of the invention.



DETAILED DESCRIPTION
In accordance with some exemplary embodiments, a method for forming a semiconductor structure includes forming a dielectric layer over a substrate. A first non-conductive barrier layer is formed over the dielectric layer. At least one opening is formed through the first non-conductive barrier layer and within the dielectric layer. A second non-conductive barrier layer is formed over the first non-conductive barrier layer and within the opening. At least a portion of the second non-conductive barrier layer is removed, thereby at least partially exposing a top surface of the first non-conductive barrier layer and a bottom surface of the opening.
FIGS. 2A-2H are schematic cross-sectional views showing a sequence of processing operations in an exemplary method for forming a single damascene structure.
Referring to FIG. 2A, conductive structures 210 are formed over a substrate 200, and a dielectric layer 220 is formed over the conductive structures 210 and the substrate 200. The substrate 200 can be a silicon substrate, a III-V compound substrate, a display substrate such as a liquid crystal display (LCD), plasma display, electro luminescence (EL) lamp display, or a light emitting diode (LED) substrate (collectively referred to as, substrate 200), for example. In some embodiments, the substrate 200 may include at least one of diodes, devices, transistors, circuits or combinations thereof (not shown) formed in and/or on the substrate 200.
The conductive structures 210 are formed and electrically coupled to at least one of diodes, devices, transistors, circuits or combinations thereof which may be formed in and/or on the substrate 200. The conductive structure 210 may comprise, for example, metal-containing lines such as aluminum lines, aluminum copper lines, aluminum silicon copper lines, copper lines, polysilicon lines, combinations thereof, or other suitable conductive materials.
Referring again to FIG. 2A, the dielectric layer 220 is formed over the conductive structures 210 and the substrate 200. The dielectric layer 220 may comprise, for example, a low-k dielectric layer (e.g., having a dielectric constant of about 3 or less, such as fluorinated amorphous carbon, fluorinated polyimides, and methyl-silsesquioxane, a carbon-containing material layer, a nitrogen-containing material layer, a porous low-k dielectric layer, an oxide layer, a nitride layer, an oxynitride layer, or combinations thereof. The dielectric layer 220 may be formed by, for example, a chemical vapor deposition (CVD) processing step, a spin-on processing step, or combination thereof. The dielectric layer 220 is provided to isolate conductive structures formed on different and/or the same layers. In some embodiments using 45-nm technology, the dielectric layer 220 may have a thickness between about 1000 Å and about 3000 Å, but other suitable thicknesses may be used in other exemplary embodiments.
Referring to FIG. 2B, a non-conductive barrier layer 230 is formed over the top surface 221 of the dielectric layer 220. In some embodiments, the non-conductive barrier layer 230 may comprise a dielectric layer which may have, for example, a dielectric constant of about 7.0 or less, such as SixCy, SixNy, SixOyCz or SixOyNz. In some embodiments, the non-conductive barrier layer 230 may comprise at least one silicon-based material layer that includes at least one of nitrogen, oxygen and carbon. The silicon based material layer may comprise, for example, a carbon-containing silicon material layer, a silicon carbide layer, a carbon-doped silicon oxide layer, a silicon oxide layer, a silicon nitride layer, a silicon oxynitride layer, or combinations thereof. The non-conductive barrier layer 230 may be formed by a CVD processing step or other suitable deposition operations using a precursor comprising a silicon-containing gas such as silane (SiH4), tetraethyl-ortho-silicate oxide (TEOS), methylsilane (1MS), trimethylsilane (3MS), or tetramethylsilane (4MS) and a gas including a component selected from the group consisting of nitrogen, oxygen and carbon. In some embodiments, the gas may be NH3, N2, CO, CO2, O2 or the like, or combinations thereof. In some embodiments, the non-conductive barrier layer 230 may have a thickness between about 10 Å and about 200 Å.
Referring to FIG. 2C, at least one opening e.g., openings 240a, 240b, are formed through the non-conductive barrier layer 230 and within the dielectric layer 220, thereby forming the non-conductive barrier layer 230a and the dielectric layer 220a. The openings 240a, 240b have sidewalls 241a, 241b and bottom surfaces 211a, 211b (i.e., the top surfaces of the conductive structures 210), respectively. The openings 240a, 240b may be, for example, contact openings, via openings, single damascene openings, dual damascene openings, or combinations thereof. In some exemplary embodiments and at other cross-sectional locations, openings 240a, 240b may terminate within the dielectric layer 220. In some embodiments using 45-nm technology, the openings 240a, 240b have an opening width between about 500 Å and about 800 Å. In some embodiments using 45-nm technology for forming a dual damascene, a dual damascene opening has a via opening width of about 65 nanometer (nm) or less and a trench opening width of about 90 nm or less. Openings having other widths may be used in other exemplary embodiments.
The openings 240a, 240b may be formed, for example, by forming a patterned photoresist layer (not shown) over the non-conductive barrier layer 230 and using a dry-etch processing step to remove portions of the non-conductive barrier layer 230 and the dielectric layer 220 to define the openings 240a, 240b by using the patterned photoresist layer (not shown) as a mask. Various suitable dry etch processes may be used. After the dry-etch processing step, the patterned photoresist layer (not shown) is removed by, for example, a photolithographic removal process.
Referring to FIG. 2D, a non-conductive barrier layer 250 is formed substantially conformally over the structure of FIG. 2C. In some embodiments, the non-conductive barrier layer 250 may be a dielectric layer with a dielectric constant of about 7.0 or less, such as SixCy, SixNy, SixOyCz or SixOyNz. In some embodiments, the non-conductive barrier layer 250 may comprise at least one silicon-based material layer including at least one of nitrogen, oxygen and carbon. The silicon based material layer may comprise, for, example, a carbon-containing silicon material layer, a silicon carbide layer, a carbon-doped silicon oxide layer, a silicon oxide layer, a silicon nitride layer, a silicon oxynitride layer, or combinations thereof. The substantially conformal non-conductive barrier layer 250 may be formed using CVD or other suitable processing operations. In some embodiments, the non-conductive barrier layer 250 may have a thickness between about 10 Å and about 200 Å but may be formed to other thicknesses in other exemplary embodiments.
In some embodiments, the non-conductive barrier layers 230 and 250 may be formed of the same material. In some embodiments, the non-conductive barrier layers 230 and 250 may have substantially the same thickness.
Referring to FIG. 2E, at least a portion of the non-conductive barrier layer 250 is removed, thereby at least partially exposing a top surface 231 of the non-conductive barrier layer 230a and the bottom surfaces 211a, 211b of the openings 240a, 240b (i.e., the top surfaces of the conductive structures 210). The step of partially removing the non-conductive barrier layer 250 may comprise, for example, a dry-etch processing step. The dry etch processing step may be substantially anisotropic and may use a precursor comprising a fluorine-containing gas. In some embodiments, the fluorine-containing gas may comprise, for example, CxFy, CxFyHz, NF3, or CxFyOz, where x ranges from 0 to 9, y ranges from 0 to 9 and z ranges from 0 to 9. After the dry etch processing step, the non-conductive barrier layers 250a remain on the sidewalls 241a, 241b of the openings 240a, 240b, and the top surfaces of the conductive structures 210 are exposed for electrical connection with other conductive structures (not shown).
In some embodiments, the non-conductive barrier layers 230 and 250 have substantially the same thickness. After the dry-etch processing step, the thickness of the non-conductive barrier layer 250a on the sidewalls 241a, 241b may be substantially equal to that of the non-conductive barrier layer 230a over the surface 221 of the dielectric layer 220a. In other embodiments, the thickness of the non-conductive barrier layer 250a may be larger or smaller than that of the non-conductive barrier layer 230a, as long as the non-conductive barrier layer 250 at the bottom surfaces 211a, 211b of the openings 240a, 240b is removed to expose the top surfaces of the conductive structures 210.
Referring to FIG. 2F, a substantially conformal seed layer 260 is formed over the structure of FIG. 2E. The seed layer 260 is over the top surfaces 231 of the non-conductive barrier layer 230a and the bottom surfaces 211a, 211b of the openings 240a, 240b. The seed layer 260 may be, for example, a metal-containing seed layer such as a copper seed layer. The seed layer 260 is formed to serve as a seed for the chemical electroplating of a subsequent conductive layer 270 (shown in FIG. 2G) over the seed layer 260. The seed layer 260 may be formed by, for example, a physical vapor deposition (PVD) processing step, a CVD processing step, an atomic layer deposition (ALD) processing step, a chemical electroplating step, a chemical electroless plating step, or various combinations thereof. In some embodiments using 45-nm technology, the seed layer 260 on the sidewalls 241a, 241b of the openings 240a, 240b has a thickness between about 100 Å and about 200 Å, and the seed layer 260 on the bottom surfaces 211a, 211b of the openings 240a, 240b has a thickness between about 400 Å and about 700 Å.
Referring to FIG. 2G, a conductive layer 270 is formed over the seed layer 260. The conductive layer 270 also fills the openings 240a, 240b. The conductive layer 270 may be formed, for example, by a PVD processing step, a CVD processing step, an ALD processing step, a chemical electroplating step, a chemical electroless plating step, or various combinations thereof. The conductive layer 270 may comprise a metal-containing layer such as a copper layer, a copper alloy layer, an aluminum layer, an aluminum alloy layer, an aluminum copper layer, an aluminum silicon copper layer or the combinations thereof.
In some embodiments, the step of forming the seed layer 260 may be omitted if the formation of the conductive layer 270 within the openings 240a, 240b and/or over the top surface 231 of the non-conductive barrier layer 230a can be desirably achieved without a seed layer.
Referring to FIG. 2H, the conductive layer 270 and the seed layer 260 are partially removed, thereby at least partially exposing the top surfaces 231 of the non-conductive barrier layer 230a and forming the conductive layers 270a, 270b within the openings 240a, 240b. The step of partially removing the conductive layer 270 and the seed layer 260 may comprise, for example, a chemical-mechanical (CMP) processing step, an electropolishing step, a dry etch step, or combinations thereof.
If a conductive barrier layer (e.g., a Ta/TaN layer) is formed between the surface 221 of the dielectric layer 220a and the conductive layer 270 such as in conventional processing, a multi-step CMP process is required to remove the conductive layer 270, the seed layer 260 and the Ta/TaN barrier layer formed over the surface 221 of the dielectric layer 220a. In short, a separate CMP step is used to remove the Ta/TaN barrier layer formed over the dielectric layer 220a for isolating two adjacent contacts, vias and/or damascenes. However, if the dielectric layer 220a is a low-k dielectric layer, the CMP step for removing the Ta/TaN barrier layer may damage the low-k dielectric layer thereunder due to its porous and weak mechanical properties. For example, CMP forces may degrade electrical properties and/or reliabilities of the dielectric layer 220a. 
According to the exemplary methods described in FIGS. 2A-2H, no conductive barrier layer (e.g., tantalum/tantalum nitride (Ta/TaN) layer) is formed between the top surface 221 of the dielectric layer 220a and the conductive layer 270. Accordingly, a single CMP process may remove the conductive layer 270 and the seed layer 260 formed over the top surfaces 231 of the non-conductive barrier layers 230a without an additional CMP step for removing the conductive barrier layer. In this manner, changing recipes, slurries, chemicals, or combinations thereof for removing a conductive barrier layer can be avoided. After polishing, top surfaces 231 remain and the underlying dielectric layer 220a is less susceptible to being damaged.
In some embodiments, the conductive layer 270 and the seed layer 260 are the same material. A single chemical electropolishing step may be used to remove the conductive layer 270 and the seed layer 260 formed over the top surfaces 231 of the non-conductive barrier layers 230a. By the exemplary methods set forth above in connection with FIGS. 2A-2H, no additional CMP step or electropolishing is needed for removing a conductive barrier layer formed between the top surface 221 of the dielectric layer 220a and the conductive layer 270. Accordingly, damage to the dielectric layer 220a caused by the CMP step for removing a conductive barrier layer is prevented or reduced.
Referring again to FIG. 2F, the non-conductive barrier layer 230a is formed over the dielectric layer 220a, extending from the sidewall 241a of the opening 240a to the sidewall 241b of the adjacent opening 240b. The non-conductive barrier layers 250a are formed along the sidewalls 241a, 241b from the top to the bottom of the openings 240a, 240b, respectively. The non-conductive barrier layers 230a, 250a are formed of materials that desirably prevent metallic diffusion from the seed layer 260a and/or the conductive layers 270a, 270b. 
Although the present invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly to include other variants and embodiments of the invention which may be made by those skilled in the field of this art without departing from the scope and range of equivalents of the invention.

## Claims

1. A semiconductor structure, comprising:
a dielectric layer formed over a substrate;
a plurality of openings formed within the dielectric layer;
a first non-conductive barrier layer formed over the dielectric layer, wherein the first non-conductive barrier layer extends from an edge of a first one of the openings to an edge of a second one of the openings adjacent thereto;
a second non-conductive barrier layer formed on sidewalls of the openings;
a conductive seed layer with a conductive lower surface directly on and contacting the first non-conductive barrier layer and bottom surfaces of the openings; and
a composite conductive material formed within the openings and directly on the conductive seed layer.

2. The semiconductor structure of claim 1, wherein the first non-conductive barrier layer and the second non-conductive barrier layer have a substantially same thickness.

3. The semiconductor structure of claim 1, wherein at least one of the first non-conductive barrier layer and the second non-conductive barrier layer is a silicon-based material layer including at least one of nitrogen, oxygen and carbon.

4. The semiconductor structure of claim 1, wherein the dielectric layer is a low-k dielectric layer and the openings extend downwardly from an upper surface of the dielectric layer.

5. The semiconductor structure as in claim 1, wherein the composite conductive material comprises a combination of at least two of a copper layer, a copper alloy layer, an aluminum layer, an aluminum alloy layer, an aluminum copper layer and an aluminum silicon copper layer.

6. The semiconductor structure of claim 1, wherein the conductive seed layer comprises one of a copper layer, a copper alloy layer, an aluminum layer, an aluminum alloy layer, an aluminum copper layer, and an aluminum silicon copper layer.

7. The semiconductor structure as in claim 1, wherein the composite conductive material includes a lower portion thereof comprising one of a copper layer and a copper alloy layer.

8. The semiconductor structure as in claim 1, wherein the composite conductive material includes a lower portion thereof comprising one of a copper layer, an aluminum layer, an aluminum alloy layer, an aluminum copper layer, and an aluminum silicon copper layer.

9. The semiconductor structure as in claim 1, wherein the first non-conductive barrier layer is a carbon-containing material layer.

10. The semiconductor structure of claim 9, wherein the carbon-containing material layer comprises one of a carbon-containing silicon material layer, a silicon carbide layer and a carbon-doped silicon oxide layer.

11. The semiconductor structure of claim 1, wherein the second non-conductive barrier layer comprises one of a carbon-containing silicon material layer, a silicon carbide layer, a carbon-doped silicon oxide layer, a silicon oxide layer, a silicon nitride layer, and a silicon oxynitride layer.

12. A semiconductor structure comprising:
a lower composite film structure including a first non-conductive barrier layer disposed over a low-k dielectric layer, disposed over a substrate;
a plurality of openings extending through the first non-conductive barrier layer and into the low-k dielectric layer and the openings including bottom surfaces comprising aluminum lines;
a second non-conductive barrier layer disposed within the openings but not completely covering the bottom surfaces of the openings;
a conductive seed layer with a conductive lower surface directly on and contacting the bottom surfaces of the openings and top surface of the first non-conductive barrier layer; and
a composite conductive material formed within the openings and directly on and contacting the conductive seed layer.

13. The semiconductor structure of claim 12, wherein the composite conductive material fills the openings.

14. The semiconductor structure of claim 12, wherein the conductive seed layer comprises one of a copper layer, a copper alloy layer, an aluminum layer, an aluminum alloy layer, an aluminum copper layer, and an aluminum silicon copper layer.

15. The semiconductor structure of claim 12, wherein at least one of the first non-conductive barrier layer and the second non-conductive barrier layer is a carbon-containing material layer.

16. The semiconductor structure of claim 15, wherein the carbon-containing material layer comprises one of a carbon-containing silicon material layer, a silicon carbide layer and a carbon-doped silicon oxide layer.

17. The semiconductor structure of claim 12, wherein the second non-conductive barrier layer is disposed on sidewalls of the openings and at least one of the first non-conductive barrier layer and is second non-conductive barrier layer is a silicon based material including at least one of nitrogen, oxygen and carbon.

18. A semiconductor structure comprising:
a low-k dielectric layer, disposed over a substrate;
a first non-conductive barrier layer disposed over the low-k dielectric layer;
a plurality of openings extending through the first non-conductive barrier layer and into the low-k dielectric layer;
a second non-conductive barrier layer disposed along sidewalls of the openings, at least one of the first non-conductive barrier layer and the second non-conductive barrier layer being a carbon-containing material layer; and
conductive material filling the openings and including a conductive seed layer disposed directly on and contacting bottom surfaces of the openings, the conductive seed layer consisting of one of a copper layer, a copper alloy layer, an aluminum layer, an aluminum alloy layer, an aluminum copper layer, and an aluminum silicon copper layer seed layer, and a metal-containing layer disposed over and directly contacting the conductive seed layer.

19. The semiconductor structure of claim 18, wherein at least one of the first non-conductive barrier layer and the second non-conductive barrier layer is a silicon-based material layer including at least one of nitrogen, oxygen and carbon.