Microelectronic interconnect material with adhesion...

Details Microelectronic interconnect material with adhesion... Microelectronic interconnect material with adhesion...

2002-01-30

2003-11-11

Nelms, David (Department: 2818)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S687000

Reexamination Certificate

active

06645847

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This invention relates in general to the field of semiconductor electronic devices, and more particularly to an improved microelectronic interconnect copper metallization structure having a cobalt-based or ruthenium-based adhesion promotion layer between diffusion barrier and copper layers and method of fabricating the same.
BACKGROUND OF THE INVENTION
Microelectronic semiconductor integrated circuit chip fabrication technology has focused on techniques and materials to produce smaller and faster devices with increasing packing densities for higher performance chips. This trend towards miniaturization has led to demand for improved semiconductor integrated circuit (IC) interconnect performance and improved manufacturability, resulting in a shift from conventional Al/SiO
2
interconnect architectures to copper-based metallization in conjunction with low-permitivity (or low-k) dielectrics. Compared to aluminum, Copper metallization reduces interconnect propagation delays, reduces cross-talk, and enables higher interconnect current densities with extended electro migration lifetime. When combined with low-k dielectrics, copper metallization can also decrease the number of metallization levels, resulting in reduced chip manufacturing costs. For instance, the superior electro migration performance and lower resistivity of copper compared to aluminum, permits a reduction in metal stack height that results in reduced signal cross-talk and improved interconnect speed.
A number of deposition methods, such as chemical-vapor deposition (CVD), physical-vapor deposition (PVD), and electrochemical deposition (ECD) or plating can be used for deposition of uniform thin-film copper layers. Chemical-vapor deposition, in particular, provides a number of advantages over other deposition techniques, including the capability for fully vacuum cluster integrated deposition of the diffusion barrier and copper layers through cluster tool equipment. Metal-organic CVD (MOCVD) is a particularly desirable means for deposition of copper due to its excellent gap-fill characteristics, such as is desirable for high-aspect ratio via holes and trenches, its excellent step coverage, its compatibility with single/dual damascene processing, and its relatively low thermal budget, such as less than 250° C. deposition process temperature, which helps ensure compatibility with low-k polymer dielectrics. Due to these advantages, as device dimensions shrink, MOCVD technology is likely to replace other deposition techniques as the preferred solution for deposition of uniform high-conductivity copper layers.
Although copper provides a number of advantages for microelectronic semiconductor chip performance, significant difficulties exist in depositing and reliably integrating copper layers on a substrate. One difficulty relates to rapid diffusion of copper atoms through many materials, including both metals and dielectrics. Copper tends to diffuse through device materials during the thermal cycling that a semiconductor substrate experiences during the multi-level interconnect fabrication process flow, as well as during actual chip operation under applied electric fields. Copper diffusion into and/or through the inter-metal dielectric (IMD) results in current leakage between adjacent metal lines, known as line-to-line leakage. Copper diffusion through the IMD and pre-metal dielectric (PMD) or inter-level dielectric (ILD) and into the transistor regions results in degraded device characteristics such as accelerated aging and, potentially, non-functional transistor and chips.
Another difficulty associated with copper in microelectronic device fabrication, such as semiconductor IC fabrication, is the sufficient adhesion of the copper to the underlying barrier to prevent copper delamination during subsequent chemical-mechanical polishing (CMP). Moreover, copper is prone to corrosion and must be passivated. Non-conducting diffusion barriers, such as Si
3
N
4
, are ideal for passivation and prevention of copper diffusion between metallization layers. However, for many applications, a conducting barrier is necessary. For instance, a conducting barrier is necessary to enable electrical current flow between via plugs and lower level metal lines. To reduce copper diffusion and corrosion, a number of advanced diffusion barriers have been developed to supplant traditional barriers used with aluminum and tungsten metallization, such as TiN and TiW barriers. For instance, some barrier materials proposed for use with copper metallization include Ta, TaN, WN
x
, and ternary barrier materials such as TiSiN, TaSiN, WSiN, and WBN. Although these barriers improve reliability of copper metallization in microelectronic devices, these conventional barriers have some significant difficulties including poor adhesion with as deposited copper and sometimes with other adjacent layers, such as low-K dielectrics.
Other potential problems associated with copper metallization include difficulties associated with the deposition process for depositing copper and barrier layers onto the substrate. The deposition of a barrier layer using conventional barrier materials and deposition techniques may have difficulty achieving a good nucleation surface to promote <111> texture in an overlying copper layer for improved electro migration lifetime, and good step coverage in high-aspect-ratio features so that barrier thickness on the sidewall and bottom of trenches and via holes is comparable to barrier thickness in the field. In addition, conventional barrier materials and deposition techniques tend to have increased resistivity, especially as deposition temperatures are lowered to below 380° C.
The adhesion and uniform nucleation of CVD Cu on commonly used PVD and CVD barriers is problematic. Organometallic precursors used for CVD Cu tend to prematurely decompose on the barrier surface at the initiation of the deposition, which results in non-uniform nucleation with long nucleation delays as well as poor adhesion. This problem is exacerbated as the CVD Cu thickness is scaled to 100-250 Å. For applications as a seed layer for subsequent electroplating, the CVD Cu thickness cannot exceed 15-20% of the feature size to be electroplated. For example, 0.1 m structures correspond to 150-200 Å CVD Cu thin film. For such thin seed films, long and variable nucleation delays (typically 30-60 s) lead to poor process repeatability as well as to discontinuous films within the high aspect ratio features. Adhesion of these films to the underlying barrier is also marginal leading to adhesion failure during electroplating or subsequent CMP process steps used to form the inlaid metal line and via plugs.
SUMMARY OF THE INVENTION
Therefore, a need has arisen for a barrier material and method for deposition of the barrier which reduces or suppresses copper diffusion through device layers.
A further need exists for a barrier material and method of deposition that improves adhesion of metallization layers, including adhesion of the barrier to underlying layers and adhesion of copper metallization to the barrier layer.
A further need exists for a barrier material and method of deposition that provides low resistance of the barrier layer to electrical current flow.
A further need exists for a barrier material and method of deposition that provides improved step coverage of microelectronic device features, such as a semiconductor chip interconnect structure, having high-aspect-ratio features.
A further need exists for a barrier material and method of deposition that supports deposition of low resistivity films at relatively low deposition temperatures.
A further need exists for a barrier material and method of deposition that reduces or eliminates copper corrosion.
In accordance with the present invention, a barrier material and method for deposition of the barrier are provided that substantially eliminate or reduce disadvantages and problems associated with previously developed diffusion barriers and methods of deposition. The barrier mater

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