Complex three-dimensional (3D) micro-electro-mechanical system (MEMS) chips can have electrical contacts on either the top and bottom surface, or both. Such a MEMS chip can include interconnects to couple a contact on one side (e.g., the top) of the chip to the other (e.g., the bottom), or even to a contact on an edge. These interconnects can be used to couple the MEMS chip to one circuit element on one side (e.g., couple the MEMS chip to a circuit board or package) and couple the MEMS chip to another circuit element (e.g., an ASIC) on another side. These interconnects can be created using through-wafer vias (TWVs). TWVs consume die area, which is not always available. Accordingly, the interconnects can also be created using screen-printing and direct write methods to directly print leads on the edges of a die. Printing leads on the edges of a die uses almost no extra die area, and edge leads are printed on one die at a time.
In an example, a method of fabricating one or more vertical interconnects is provided. The method includes patterning and stacking a plurality of wafers to form a wafer stack. A plurality of apertures can be formed in the wafer stack within one or more saw streets of the wafer stack, and conductive material can be deposited on sidewalls of the plurality of apertures. The wafer stack can be diced along the one or more saw streets and through the plurality of apertures such that the conductive material on the sidewalls is exposed on an edge portion of resulting stacked dies.
Understanding that the drawings depict only exemplary embodiments and are not therefore to be considered limiting in scope, the exemplary embodiments will be described with additional specificity and detail through the use of the accompanying drawings, in which:
In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the exemplary embodiments.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments. However, it is to be understood that other embodiments may be utilized and that logical, mechanical, and electrical changes may be made. Furthermore, the method presented in the drawing figures and the specification is not to be construed as limiting the order in which the individual steps may be performed. The following detailed description is, therefore, not to be taken in a limiting sense.
The embodiments described below relate to a method of batch fabricating one or more vertical interconnects on one or more edges of a three-dimensional (3D) chip. In particular, the vertical interconnects can be fabricated at wafer-level. In an example, the vertical interconnects are formed by forming a plurality of apertures in one or more saw streets of a stack of wafers. Conductive material is then deposited on sidewalls of the plurality of apertures. The stack of wafers is then diced to split the plurality of apertures such that a portion of the vertically oriented conductive material in each aperture is on an edge of adjacent resulting stacked dies.
The chip 100 can include a plurality of sides including a top side 106, a bottom side 108, and a plurality of edges 110. The top side 106 and bottom side 108 are the sides that are oriented parallel to the conventional working planes or working surfaces of the wafers used to form the chip 100. The plurality of edges 110 are the sides that are oriented perpendicular to the top side 106 and the bottom side 108 and are thus oriented perpendicular to the conventional working planes or working surfaces of the wafers used to form the chip 100. It should be understood, however, that the chip 100 can be oriented in any manner and is not limited to the top side 106 being up and the bottom side 108 being down.
The chip 100 can include a plurality of interconnects 112 on one or more of the edges 110. An interconnect 112 can be oriented vertically (with respect to the conventional working planes or working surfaces of the wafers used to form the chip 100) and can be coupled to one or more traces 114 on the top side 106 and bottom side 108 of the chip 100. Accordingly, an interconnect 112 can electrically couple a trace 114 on the top side 106 of the chip 100 to a trace 114 on the bottom side 108 of the chip 100. In an example, the plurality of interconnects 112 are exposed on the edge 110 of the chip. In other examples, the plurality of interconnects 112 can be covered with a dielectric or other material. In some examples, a dielectric can be disposed between the interconnects 112 and the substrates of the layers 102, 104 to provide electrical isolation between the interconnects 112 and the substrates of layers 102, 104. The traces 114 can be coupled to a component fabricated in the chip 100 and/or to a pad (e.g., an input/output pad) for connecting the chip 100 to a mounting substrate such as a circuit board or application specific integrated circuit (ASIC). Accordingly, the pad can be configured to bond an ASIC and/or surface mount to a circuit board. Accordingly, as an example, a component in the first layer 102 of the chip 100 can be coupled to a pad on the bottom (e.g., opposite) surface 108 of the chip 100 using an interconnect 112. In another example, a component in the first layer 102 can be coupled to a component in the second layer 104 via an interconnect 112. The traces 114, and corresponding interconnects 112 can be coupled to one or more components in the chip 100 with a though substrate via (TSV) 116. In an example, an interconnect 112 extends from the top surface 106 to the bottom surface 108 of the chip 100. In an example, one or more interconnects 112 can be configured to connect to a circuit board and/or an ASIC. Accordingly, the chip 100 can be connected to a circuit board and/or an ASIC on an edge 110. This can enable the chip 100 to be mounted in different orientations.
An interconnect 112 can comprise a conductive material (e.g., a metal) disposed within a groove 118 in the edge 110 of the chip 100. The groove 118 can be formed in the substrate of each layer 102, 104 of the chip 100. In some examples, a dielectric material can be disposed in each groove 118 between the conductive material and the substrate. The dielectric material can be used to insulate the substrate and any conductive portions therein from the conductive material of the interconnect 112. Accordingly, the chip 100 can include a plurality of grooves 118 having conductive material forming a plurality of interconnects 112.
The method 200 begins by patterning a plurality of wafers 302 with components (e.g., MEMS devices) to be included in the 3D chip (block 202 of
As shown in
In an example, one or more traces (shown in
The wafer stack 306 can include a plurality of saw streets 308 between adjacent device areas 304. The saw streets 308 can provide the space for dicing the wafer stack 306 into a plurality of stacked dies. A plurality of apertures 310 can be formed such that the apertures 310 are partially within the saw streets 308 (block 206 of
An aperture 310 can include one or more sidewalls. The one or more sidewalls can be composed of substrate of the wafers 302. Accordingly, in an example, the one or more sidewalls can be composed of glass. The apertures 310 can be formed using one of ultrasonic drilling, sandblasting, laser drilling, mechanical drilling, or etching; however, any suitable method of forming the apertures 310 can be used.
Once the apertures 310 have been formed, the conductive material can be deposited on the sidewalls of the apertures 310 (block 208 of
In an example, a dielectric material can be deposited on the sidewalls of the apertures 310 prior to depositing the conductive material thereon. The dielectric material can insulate the substrates of the wafer stack 306 from the conductive material in the apertures 310, thereby reducing the likelihood of an unintended electrical coupling. Any suitable dielectric material can be used such as silicon dioxide (SiO2), polyimide, or parylene.
As mentioned above, one or more traces 316 can be formed on the top surface 312 and/or bottom surface 314. In an example, the one or more traces 316 and the conductive material in the apertures 310 can be deposited such that they are connected. That is, the conductive material in the apertures 310 can be connected to the one or more traces 316. The traces 316 can couple the conductive material in the apertures 310 to components in the device area 304 and/or to a pad (e.g., an input/output pad) for a resulting stacked die. In a particular example, the trace 316 on the top surface 312 can couple the conductive material in the aperture 310 to a through substrate via (TSV) which is electrically coupled to a component in of the device area 304. Additionally, a trace 316 on the bottom surface 314 can couple the conductive material in an aperture 310 to a pad for connection of the resulting stacked die to a mounting substrate (e.g., a circuit board). Accordingly, a component in a first wafer 302 can be coupled through a first trace 316 on the top surface 312 to a pad on the bottom surface 314 via conductive material in an aperture 310.
Once the conductive material has been deposited in the apertures 310, wafer stack 306 can be diced to form a plurality of stacked dies (block 210 of
Accordingly, vertical interconnects can be formed on an edge of a stacked die through batch processing at wafer-level. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiments shown. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.
This application claims the benefit of priority to U.S. Provisional Application No. 61/416,485, filed on Nov. 23, 2010, the disclosure of which is incorporated herein by reference.
Number | Date | Country | |
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61416485 | Nov 2010 | US |