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copper may contact and poison the very devices that they supply with energy and information; with barrier layers too thick, these wrapped stacks of two barrier metal films and an inner copper conductor can have a greater total resistance than the traditional aluminum interconnections would have, eliminating any benefit derived from the new metallization technology.
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diffusion barrier simultaneously, the bonding between layers needs to come from a chemical reaction of limited range at both boundaries. Materials providing good adhesion are not necessarily good diffusion barriers and vice versa. Consequently, there are cases where two or more separate layers must be used to provide a proper interface between substrates.
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in order to maintain a good electronic contact, while maintaining a low enough copper diffusivity to sufficiently chemically isolate these copper conductor films from underlying device silicon. The thickness of the barrier films is also quite important; with too thin a barrier layer, the inner
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between plate and substrate in order to work. The role of a diffusion barrier is to prevent or to retard the inter-diffusion of the two superposed metals. Therefore, to be effective, a good diffusion barrier requires inertness with respect to adjacent materials. To obtain good adhesion and a
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involves three diffusion barrier layers—copper, nickel, then chromium—to provide long term durability where there will be many large temperature changes. If chromium is plated directly onto the steel, then their different
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has excellent adhesion to many materials because of its reactivity. Its affinity for oxygen forms a thin stable oxide coat on the outer surface, creating a
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from soft metal interconnects, while maintaining an electrical connection between them. For instance, a layer of barrier metal must surround every
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which prevents further oxidation of the chromium, and of the underlying metal (if any), even in corrosive environments. Chromium plating on steel
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usually placed between two other metals. It is done to act as a barrier to protect either one of the metals from corrupting the other.
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are a few of the metal combinations used to form diffusion barriers for specific applications. Conductive
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metal combinations have been evaluated for their adhesion and diffusion barrier properties.
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52:, and service life, are critical parameters to select diffusion barrier materials. Many
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its virtue relies in its inertness, and ease of application; its problem is its cost.
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also easily reacts with oxygen but its oxides have poor adhesion properties. As for
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While the choice of diffusion barrier depends on the final function, anticipated
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layer to its substrate requires a physical interlocking, inter-
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Some materials that have been used as barrier metals include
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259:, vol. 1 (4th ed.), Elsevier, p. 1355,
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will cause the chrome plating to peel off the steel.
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As the name implies, a barrier metal must have high
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20:is a thin layer (usually micrometres thick) of
189:in modern integrated circuits, to prevent
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193:of copper into surrounding materials.
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236:, but "metals" in this context).
287:Semiconductor device fabrication
232:(the last four being conductive
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105:thermal expansion coefficients
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145:can be also used, such as
78:properties of its oxide.
253:Cahn, Robert W. (1996),
74:reactivity and the self-
198:electrical conductivity
181:to chemically isolate
177:is a material used in
50:operating temperature
68:thermal conductivity
35:of the deposit or a
256:Physical metallurgy
187:copper interconnect
179:integrated circuits
169:Integrated circuits
100:for automotive use
266:978-0-444-89875-3
96:passivation layer
18:diffusion barrier
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271:
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230:titanium nitride
226:tungsten nitride
218:tantalum nitride
163:titanium nitride
159:tungsten nitride
147:tantalum nitride
37:chemical bonding
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155:copper silicide
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183:semiconductors
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62:provides good
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27:Adhesion of a
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292:Metal plating
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222:indium oxide
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151:indium oxide
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29:plated metal
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76:passivation
281:Categories
240:References
64:electrical
210:ruthenium
191:diffusion
131:zirconium
54:thin film
44:Selection
33:diffusion
234:ceramics
214:tantalum
143:ceramics
139:tungsten
135:vanadium
119:tantalum
115:Nichrome
92:Chromium
60:Aluminum
127:niobium
123:hafnium
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228:, and
206:cobalt
161:, and
137:, and
111:Nickel
82:Copper
72:oxygen
22:metal
261:ISBN
86:gold
66:and
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