Integrated circuit device including tunable substrate capacitors

An integrated circuit device and method. A substrate having contacts has a plurality of capacitors thereon. A plurality of fusible links selectively connect the plurality of capacitors to one another and selected ones of the capacitors to the contacts. In this manner, for example, the capacitance value can be adjusted to tune an antenna mounted on the substrate during testing of the integrated circuit device.

BACKGROUND

With certain integrated circuit devices, such as radio frequency (RF) devices, impedance matching to an antenna is required to achieve the desired performance. For instance, a tuning process is required for RF identification devices (RFID) to achieve the desired operating distance. However, due to typical underlying manufacturing processes of semiconductor wafers, a certain variation and consequently a deviation in the RF-output impedance of the device is encountered. To match the antenna impedance, discrete passive components are required. During test processes for such RF devices, different results can be obtained depending on the variance of those discrete components. A further optimization to match the antenna impedance, such as would be required for RFID devices, does not take place during the component manufacturing processes.

With known processes, such RF components typically are not tuned until they are mounted on a printed circuit board (PCB) as part of a larger system. Tuning processes at a system or board level is difficult and expensive. For instance, in systems on PCBs a tunable capacitor (for example, cermet trimmer) is mounted on the PCB for this purpose. Alternatively, when manufacturing devices such as RF-IDs, the wafer manufacturing process is kept in a narrow process window to keep the variations as low as possible. Unfortunately, this also adds complexity and cost to manufacturing processes.

SUMMARY

An integrated circuit device includes a substrate having contacts with a plurality of capacitors on the substrate. A plurality of fusible links selectively connect the plurality of capacitors to one another and selected ones of the capacitors to the contacts. In this manner, for example, the capacitance value can be adjusted to tune an antenna mounted on the substrate during testing of the integrated circuit device.

DETAILED DESCRIPTION

FIG. 1conceptually illustrates portions of an integrated circuit device100in accordance with disclosed embodiments. The device100includes a substrate110with an integrated circuit chip112mounted thereon. A variable capacitor114is coupled to the integrated circuit chip112. In certain embodiments, the capacitor114is a tunable substrate capacitor that is integrated into a laminate package, allowing immediate antenna matching during a device test process, thereby enabling optimum performance. The integrated circuit device100mounted to a printed circuit board (PCB)102, along with other components as part of an electronic system. The terms coupled, connected, and similar terms and derivatives are used in this disclosure to indicate that two elements co-operate or interact with each other regardless of whether they are in direct physical or electrical contact.

Typically, antenna matching circuitry is required in RF and other types of devices. Reconfigurable capacitors as part of such tunable antenna matching are desirable for several reasons. For instance, fine-tuning of an antenna during manufacturing test procedures before the device is shipped out of the fabrication facility simplifies later assembly of the device into a system.

FIG. 2illustrates an example where the device100is an RF device used in an RFID, for example. The device112includes RF transmitter circuitry coupled to an antenna120that is tunable via a network of configurable capacitors114.

FIG. 3conceptually illustrates portions of an example of an embodiment of the capacitors114, which are integrated into the substrate110. The substrate110includes any suitable substrate material such as BT, FR4, etc. In one exemplary embodiment, an area of about 5×5 mm of the entire substrate110is used to implement the tunable capacitors114. The substrate110is a laminated structure, including first and second conductive layers130,132that are spaced apart from each other. The conductive layers130,132can be formed from copper, for example. Each of the layers130,132is connected to a respective contact134,136.

In the example illustrated inFIG. 3, the first layer130is a solid metal plane that may be connected to ground, depending on whether the capacitor is grounded or not. The second layer132includes a matrix of conductive strips situated above the first layer130such that a certain capacitance is defined based on the area of the conductive strips and the material and distance separating the first and second layers130,132.

For the example shown inFIG. 3, each of the strips132defines the same area. Thus, if all of the unit capacitors formed by respective strips132and the first layer are connected together, the resulting value is approximately five times higher than the value of one of the capacitors. The number and size of the conductive strips132can be adapted to the needs of the particular device, such as the main frequency of the RF device. In some embodiments where one of the terminals of the capacitor is grounded, the ground layer of the substrate110functions as the first layer130, thus eliminating the need for an extra conductive layer.

The conductive strips of the second layer132are connected to one another and the contact136by fusible links140. By opening selective ones of the links140, the desired strips of the second layer132are disconnected from the contact136(and from a device coupled to the contact132). In this manner, the value of the capacitor112can be changed as necessary to tune the antenna120. As shown inFIG. 3, the second layer132is positioned as either the top or bottom layer. This allows access to the fusible links140, enabling laser fusing and thereby disconnecting selected ones of the strips from the contact136to adjust the capacitance. In this manner, “on-the-go” optimization of the antenna matching process during testing is provided, without a need to disconnect or interrupt the test procedure.

FIG. 4conceptually illustrates portions of an embodiment of the capacitor112, where capacitors of different values are used to achieve the desired capacitance value. The capacitor112illustrated inFIG. 4includes five individual capacitors151,152,153,154,155on the substrate110. The particular arrangement of the capacitors151-155illustrated inFIG. 4is exemplary only—other arrangements are possible and would be a routine undertaking for one skilled in the art having the benefit of this disclosure. Each of the individual capacitors are electrically connected (at least initially) by corresponding fusible links161,162,163,164,165. The fusible links160are exposed such that a laser is able to break selected connections during a testing process, thereby RF-tuning in embodiments with an RF device and antenna connected to the capacitors.

In the illustrated example, the capacitors151-155have three different values, C1, C2and C3, due to the different sized (different area) of the second layer conductive strips with respect to the first layer conductive plane (which can be the substrate ground layer in embodiments where grounded capacitors are required). Several factors influence the capacitance value of the capacitors151-155, such as the distance between conductive layers, the dielectric material between the capacitor layers, the size (area) of the conductive strips, etc. With five individual capacitors151-155having three different capacitance values C1, C2and C3due to their different area with respect to the below lying conductive layer, the following capacitance values are possible.

FIG. 5illustrates a side view of an embodiment of the integrated circuit device100, in which an RF device112is connected to tunable capacitors114. The system100includes a substrate110upon which the RF device112and capacitors114(such as the capacitors151-155) are mounted, as well as the fusible links161-165. As noted above, the fusible links161-165are situated such that selected ones can be opened (by a laser, for example) during a testing or tuning process. In the embodiment illustrated inFIG. 5, substrate110is a redistribution layer (RDL)170. Once the desired capacitance value is achieved to tune the device, the device can be encapsulated in a mold compound172.

In one exemplary embodiment, the system100is a wafer level ball grid array (WLB), in which the RF device112and the capacitors114are embedded in the mold compound172and an array of solder balls174are attached to contact areas on the underside of the substrate110. The connections between the RF device112and the capacitors114, and from these devices to the contact areas and thus the solder balls174of the device100are provided by the RDL170.

In a process sometimes referred to as “reconfiguration,” a plurality of integrated circuit devices, such as the RF device112are spaced apart and the gaps between the devices112(and other devices situated on the RDL170) are subsequently filled with the mold material172. This process provides additional space around the active area of the integrated circuit devices for the fusible links161-165, among other things. The molding material172provides a relatively inexpensive placeholder for bearing additional interconnect elements.