Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-09-03
2001-10-02
Bowers, Charles (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S613000, C438S614000, C438S627000, C438S629000, C438S637000, C438S643000, C438S653000, C438S674000, C438S675000, C438S676000, C438S677000, C438S678000, C438S687000
Reexamination Certificate
active
06297140
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for plating a conductive material to a conductive feature in and/or on a substrate. More particularly, the present invention concerns electroplating a conductive material to a metal feature in and/or on a substrate using a highly conducting barrier film to conduct electrical current. In particular, the present invention provides methods for electroplating a solder ball utilized in a controlled collapse chip connection (C4) process to a metal feature provided in and/or on a substrate. Additionally, the present invention provides semiconductor structures prepared according to processes of the present invention.
BACKGROUND OF THE INVENTION
Various techniques have been investigated and utilized for attaching conductive material to semiconductor chips. These methods include the lift-off process, thru-mask methods, metal reactive ion etch (RIE) and metal and insulator damascene and various combinations of the above-listed methods. The lift-off and thru-mask methods are more valuable for large features, such as those typically encountered in chip packaging. Unlike the lift-off process and the thru-mask methods, the metal RIE and insulator damascene methods have been the process of choice for chip metallizations where the ground rules are typically below one micron.
In accordance with the damascene process, metal film may be deposited over the entire patterned substrate surfaces to fill trenches and vias. This metal deposition may then be followed by metal planarization to remove metal overburden and to isolate and define the wiring pattern. When metal deposition is by electroplating or by electroless plating processes, the plating may be preceded by the deposition of a plating base or seed layer over the entire surface of the patterned wafer or substrate. Also, layers that may improve adhesion, and/or prevent conductor-insulator interactions and/or interdiffusion may be deposited between the plating base or seed layer and the insulator.
In the metal RIE methods, blanket metal film is etched to define the conductor pattern. The gaps between the metal lines and vias are then filled with insulators. In high performance applications, the dielectric is planarized to define a flat metal level. One of the main advantages of the damascene process as compared to metal RIE is that it is often easier to etch an insulator as opposed to metal. Also, insulator gap fill and planarization may be more problematic.
In the metal damascene process, all the recesses in the insulator are first filled with metal before metal polishing. However, during the metal deposition into trenches and vias, all the narrower features become filled before their wider counterparts. Thus, all features with width less than 2 microns will be filled before those with width greater than 5 microns. Hence, to fill trenches or test pads with width of 50 microns, the smaller recesses typically with widths less than 5 microns are overplated. During metal chemical-mechanical polishing (CMP), the additional time needed to remove the excess metal overburden on the overplated smaller features causes dishing on the larger features. Also, because of the prolonged polishing times, insulator adjacent may severely erode. Severe dishing and insulator erosion in large metal features is a source of yield loss, especially when the occur at lower levels. Here they cause trapped metal defects at the next higher level. The longer time needed to remove the thicker metal overburden of the smallest metal lines and vias is one of the main culprits responsible for the low thruput and yield losses in the metal CMP process.
Moreover, this last metal wiring level, which may include Cu, Al, Au, Ni, W, &agr;-Ta, and/or other metals and/or alloys with low resistivity, typically contains very wide metal lines for power bussing and large pads for wirebonds or C4 solder balls. In the CMP process, these relatively large metal structures are sensitive to dishing because of the prolonged polishing times.
After formation of wiring according to the above-described processes, further processing may be carried out on the substrate. For example, conductive elements, such as solder balls may be attached to portions of the wiring. One example of conductive elements that may be attached include solder balls for a C4 process.
Typically, patterns for a C4 process are created utilizing standard lithography techniques. According to such processes, a seed layer may be patterned, followed by lead-tin plating.
SUMMARY OF INVENTION
Broadly, an object of the present invention is to provide a process for selectively plating metal utilizing more than one metal as an electrode. One of the metals serves as a seed layer for plating and may be patterned. Another metal may act as a current carrying conductor during plating.
According to a particular application, an object of the present invention is to provide a process that permits attaching C4 solder balls directly to a final metal level in and/or on a substrate without requiring the utilization of a mask typical of traditional processes.
An advantage of the present invention is that it provides a less expensive process that known process for producing similar results.
Another advantage of the present invention is that it may utilize a barrier metal to carry plating current.
A further advantage of the present invention is that it may eliminate plating of metal on pins.
An additional advantage of the present invention is that is may provide higher productivity as compared to known processes.
In accordance with these and other objects and advantages, the present invention provides a method for plating a second metal directly to a first without utilizing a mask. A semiconductor substrate is provided including at least one metal feature of a first metal and at least one insulating layer covering said metal feature and the substrate. At least one recess is formed in the at least one insulating layer, thereby exposing at least a portion of the metal feature. At least one conductive barrier layer is formed over the insulating layer and the exposed portion of the metal feature. A plating seed layer is formed over the at least one barrier layer. A photoresist layer is deposited over the plating seed layer. Portions of the photoresist layer and portions of the plating seed layer outside of the at least one recess are removed. Photoresist remaining in the at least one recess is removed. A second metal is plated to the plating seed layer in the recess.
Aspects of the present invention also provide a method for plating a second metal directly to a first metal without utilizing a mask. A semiconductor substrate is provided including at least one metal feature of a first metal and at least one insulating layer covering the metal feature and the substrate. At least one recess is formed in the at least one insulating layer, thereby exposing at least a portion of the metal feature. At least one conductive barrier layer is formed over the insulating layer and the exposed portion of the metal feature. A plating seed layer is formed over the at least one barrier layer. A pad is provided in the at least one recess for preventing removal of portions of the seed layer in the at least one recess. Portions of the photoresist layer and portions of the plating seed layer outside of the at least one recess are removed. The pad is removed. A second metal is electroplated to the plating seed layer in the recess.
Furthermore, aspects of the present invention provide a semiconductor structure including a semiconductor substrate. At least one metal feature of a first metal is provided in the substrate. At least one insulating layer at least partially covers the at least one metal feature. At least one recess is located in the at least one insulating layer over the at least one metal feature. At least one conductive barrier layer is located over the at least one electrical insulating layer and over a portion of the at least one metal feature under the at least one recess. At least one plating seed layer is loc
Edelstein Daniel C.
Uzoh Cyprian Emeka
Abate Joseph P.
Bowers Charles
Connolly Bove Lodge & Hutz
Gurley Lynne A.
International Business Machines - Corporation
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