Patent Application
20050067711
1. Field of Invention
The field of invention relates generally to vias and, more specifically, relates to a method and apparatus to provide a via with an increased via contact area.
2. Background Information
Semiconductor dies are typically encased in a shell or package prior to installation in microelectronic devices. The package makes the die easier to handle and protects the die from dust, dirt, and other contaminants. The package usually has leads or contact pads that are soldered to a printed circuit board (PCB). With its leads attached to the PCB, the package acts as an interface between the die and the PCB.
Generally, a die includes dielectric layers attached to a semiconductor support layer. Attached to the dielectric layers are metal layers. In some dies, a via is formed in the semiconductor support and dielectric layers to connect the metal layers to components outside of the die.
In constructing a die package, the diameter of the vias is usually kept to a minimum in order to help reduce electrical interconnect pitch. Electrical interconnect pitch (e.g., bump pitch) is the distance between the center of two electrical interconnects on a die package. In a die package, a via connects to an electrical interconnect which supplies electrical connection out of the package through bumps, pins, leads or other electrical connective items. Smaller diameter vias allow the vias to be placed closer together, and subsequently, reduce the electrical interconnect pitch. A smaller pitch leads to smaller die packages.
However, difficulties arise when a via with a small diameter is connected to a metal layer of a die. The small diameter of the via creates adhesion problems and may result in de-lamination of the via and the metal layer. Also, a connection with a small diameter via may result in undesired levels of electrical resistance in the connection between the via and the metal layer.
The present invention is illustrated by way of example and not by limitation in the accompanying figures.
Methods and apparatuses for providing a via with an increased via contact area are disclosed. In the following description numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one having ordinary skill in the art that the specific detail need not be employed to practice the present invention. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present invention.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. In addition, it is appreciated that the figures provided herewith are for explanation purposes to persons ordinarily skilled in the art and that the drawings are not necessarily drawn to scale.
Via 210 is shown passing through the semiconductor support layer 202 and the dielectric layer 204. The via 210 is attached to contact 206. In one embodiment, via 210 is a metal-filled via. The portion of via 210 that passes through the semiconductor support layer 202 includes a bottom end 212, a shaft 214, and an enlarged end 216. The enlarged end 216 allows for an increased via contact area 218 for connection of via 210 to contact 206. The bottom end 212 may be electrically coupled to a PCB or another die package.
In one embodiment, the diameter of the bottom end 212 and the shaft 214 are substantially the same. At the enlarged end 216, the via extends outward from the center of the via 210 to form a semi-cone or bowl shape. In one embodiment, the largest diameter of the via at the enlarged end 216 is twice the diameter of the bottom end 212. In an embodiment, the diameter of the bottom end 212 is 10 to 60 microns. In yet another embodiment, the diameter of the increased via contact area 218 is 15 to 100 microns.
The via 210 passes through the dielectric layer 204 to connect to the contact 206 at the increased contact area 218 of the via 210. In one embodiment, the diameter of the via 210 through the dielectric layer 204 is similar to the largest diameter of the via 210 at the enlarged end 216. In another embodiment, the semi-cone shape at the enlarged end 216 continues through the dielectric layer 204 to the contact 206.
It will be understood that the enlarged end 216 of the via 210 begins in the semiconductor support layer 202 and increases in diameter as the via 210 approaches the dielectric layer 204. This enlarged end 216 tapers outward from the center of the via 210 to create an increased via contact area 218 for connection to contact 206. An increased via contact area adheres better to the contact and decreases the possibilities of de-lamination of the surrounding layers. Also, the large contact area of the via against the contact decreases the electrical resistance in the connection. Additionally, a narrow via diameter may still by used in the die to keep electrical interconnect pitches small, yet gain the advantages of an increased via contact area at the contact 206. The increased via contact area 218 also ensures connectivity to the contact 206. The increased via contact area 218 provides more surface to create a connection with the contact 206.
Continuing to a block 304, the semiconductor support layer is dry etched to form an enlarged end of the via hole. The enlarged end forms a notch in the semiconductor support layer. The enlarged end will create a via with a large contact area to couple the via to a conductive layer within the die. In one embodiment, the dry etch process from block 302 is allowed to continue and creates a charge on the dielectric layer that repels the ions laterally forming the enlarged end in the semiconductor support layer. The shape of the enlarged end depends on how long the ions are allowed to etch in the semiconductor support layer. For example, the longer the ions are allowed to etch, the wider the enlarged end will be at the dielectric layer. In one embodiment, an anisotropic dry etch forms the via and the enlarged end in a single dry etch process.
In a block 306, the dielectric layer is etched to continue the via hole through the dielectric layer to a conductive layer. In one embodiment, the etch through the dielectric layer is conducted with a wet etch process. In another embodiment, the etch through the dielectric layer is conducted with the same dry etch process as was used to etch the via hole and the enlarged end. In another embodiment, the dielectric layer is etched so that the outward taper of the via hole continues from the semiconductor support layer, continues to taper outward through the dielectric layer, to the conductive layer.
Continuing in a block 308, the via hole is filled with a conductive material to create a via. In one embodiment, the via hole is filled with a metallized paste to form a metal-filled via. In another embodiment, a Chemical Vapor Deposition (CVD) process is used to fill the via hole.
In a block 310, the via is connected to the conductive layer. In one embodiment, a chemical reflow process is used to couple the enlarged end of the via to the conductive layer. In another embodiment, a thermal reflow process is used to connect the via to the conductive layer.
It will be appreciated that the via hole and the enlarged end in the semiconductor support layer may be completed in a single dry etch process. The diameter of the via is narrow along most of the depth of the via and increased at one end to increase the via contact area with the conductive layer. The etch of the semiconductor support layer, including the via hole and the enlarged end, can be completed in a single dry etch process; the use of build up layers is not required to create the enlarged end of the via. Thus, a large diameter via does not have to extend along the entire depth of the via, but only the diameter of the via at one end is increased to connect with the conductive layer.
In the foregoing detailed description, the method and apparatus of the present invention have been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the present invention. The present specification and figures are accordingly to be regarded as illustrative rather than restrictive.
