The invention relates to a microchip with processing circuits in the front side of a substrate. Moreover, it is related to a microchip assembly and a microfluidic device comprising such a microchip, and to a process for the production of said microchip assembly.
From the WO 2005/010543 A1 and WO 2005/010542 A2 a microchip is known which may for example be used in a microfluidic biosensor for the detection of biological molecules labeled with magnetic beads. The sensor chip is provided with coupling circuits comprising wires for the generation of a magnetic field and Giant Magneto Resistances (GMR) for the detection of stray fields generated by magnetized beads. The coupling circuits are fabricated at a “sensitive side” of the chip on a semiconductor substrate, and each sensor chip is attached behind a hole in the wall of a microfluidic channel with its sensitive side facing the channel. A disadvantage of these known devices is that the sample fluid has to dive into a recess to reach the sensitive chip surface. This may create regions of low or stagnant flow and generally impairs the measurement.
Based on this situation it was an object of the present invention to provide means that particularly allow the construction of an improved microfluidic device of the kind described above.
This object is achieved by a microchip according to claim 1, by a microchip assembly according to claim 7, by a microfluidic device according to claim 8, and by a process according to claim 9. Preferred embodiments are disclosed in the dependent claims.
According to its first aspect, the invention relates to a microelectronic chip or “microchip” comprising the following components:
The substrate on which the processing circuits are disposed or fabricated may particularly be one of the known semiconductor materials (like silicon Si or GaAs), glass, ceramic, and organic material or mixtures thereof. Typically, there is an intimate contact and junction between substrate and processing circuits, with the circuits for example being generated by doping in the surface layers of the substrate and/or by deposition of material on said surface.
As the terminal pads of the microchip are located in recesses, the corresponding connections to external lines or wires are shifted rearwards with respect to the front side of the substrate. The processing circuits in said front side therefore become better accessible, which makes the microchip suited for applications where the processing circuits are to be brought into the vicinity of another object.
The dimensions of the at least one recess on the microchip in connection with the intended bonding technique (for example wire bonding) determine how well the processing circuits will be accessible. According to a preferred embodiment, the at least one recess has a depth of more than 20 μm, preferably more than 30 μm (measured with respect to the front side of the substrate). Moreover, the at least one recess has preferably a width ranging from 100 to 1000 μm, most preferably from 200 to 400 μm. The recess may particularly be disposed at the border of the substrate, thus forming a stepped edge of the microchip.
According to a preferred embodiment, bumps (i.e. a raised contact-pads) are disposed on the terminal pads. As known in the state of the art, bumps may consist of a metal like gold or copper or a soldering material to which electrical tracks or wires can be bonded. Due to their arrangement in the recesses, the bumps extend correspondingly less far in forward direction of the microchip as they normally would. Preferably, the bumps are even completely retracted from the front side, i.e. they do not project beyond the front side. In this case it is possible to produce electrical connections to the bumps that do not extend beyond the front side either, thus providing a freely accessible, exposed position of the processing circuits in the front side.
The processing circuits may in principle have any design and may serve any purpose. Preferably, the processing circuits comprise coupling circuits that are adapted to perform and process a wireless physical interaction. Said physical interaction may particularly comprise the generation and/or detection of electromagnetic fields. It may however also involve other physical phenomena (e.g. thermal conduction). Typically, these interactions are limited to short distances in the order of the extensions of the microchip, particularly in the order the thickness of the chip or its components, which may range from zero up to 100 μm, preferably up to 10 μm. It should be noted that the coupling circuits are also capable to process the physical interactions. This shall quite generally mean that they have a controllable influence on these interactions and/or that they are influenced by the interactions in a controllable way. This distinguishes the coupling circuits from usual circuits of a microchip, which are of course also subject to physical interactions, but wherein said interactions are only (undesired) interferences and effectively without influence on the normal processing function of the circuits. In contrast to this, the coupling circuits are particularly designed to exploit the experienced wireless physical interactions.
The coupling circuits may particularly be designed in such a way that they implement a sensor, preferably a capacitive sensor, a light sensor, an electrical current sensor, a voltage sensor and/or a magneto-electric sensor. Moreover, the coupling circuits may be designed to provide temperature control (i.e. heating, cooling and/or measurement of temperature) in a nearby location, e.g. a (bio-) chemical reaction chamber. In the aforementioned applications, it is often necessary to bring the coupling circuits as close as possible to an object. The proposed microchip allows such close contacting as the access to its sensitive front side is not hindered by bulky external connections.
According to a particular embodiment of the invention, the coupling circuits comprise circuits for the generation of an electromagnetic field, for example wires through which (AC or DC) currents can be directed to generate (alternating or static) magnetic fields. Additionally or alternatively, the coupling circuits may comprise circuits for the detection of an electromagnetic field, particularly a magnetic sensor device like a Giant Magneto Resistance (GMR) for the detection of magnetic fields. If both circuits for the generation and the detection of electromagnetic fields are provided, the microchip is especially apt for biosensor applications of the kind referred to above.
The invention further relates to microchip assembly comprising the following components:
The microchip assembly described above has the advantage that the processing circuits in the front side of the microchip (being by definition identical to the front side of the substrate of the microchip) are very well accessible, because the electrical tracks that connect these circuits to external devices are located in or below said front side.
The invention further relates to a microfluidic device with at least one sample chamber in which liquid, gaseous or solid samples can be provided, particularly to a biosensor for the investigation of biological samples, which comprises a microchip of the kind described above. The microfluidic device may preferably comprise a microchip with coupling circuits for wireless physical interactions in the front side of a substrate. The free accessibility of the coupling circuits in the front side can be exploited in such a microfluidic device in various ways to improve the contact between the microchip and a sample in the sample chamber of the device.
The invention further relates to a process for the production of a microchip assembly of the kind described above, said process comprising the following steps:
The aforementioned process has the advantage that electrical tracks with a precise geometry can be bonded to the microchip because they are initially fixed to a carrier substrate. After embedding the microchip in the filling and the attachment of the electrical tracks to said filling, the carrier substrate can be removed to provide a free access to the front side of the microchip.
According to further development of the process, a recess is produced in the carrier substrate before step a), wherein the processing circuits of the microchip and the associated substrate material can protrude into said recess during and after the bonding step a). This allows the production of a microchip assembly in which the front side of the microchip with the processing circuits assumes an elevated, completely accessible position.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. Like reference numbers in the Figures (or numbers differing by ±10) refer to identical or similar components.
In the following the invention is described by way of example with the help of the accompanying drawings in which:
The devices described in the following may particularly be used for (magnetic) biosensors or biochips, though the invention is not limited thereto and can be applied to all sensors that require electrical connections, e.g. capacitive sensors, electronic light detectors, Ampere metric sensors, Volta metric sensors, magneto-electric sensors, etc. Moreover, such a device may be designed to provide temperature control in a sample space, for example if it is integrated into the (bottom) wall of a Polymerase Chain Reaction (PCR) chamber used for DNA amplification.
Magneto-resistive biochips have promising properties for bio-molecular diagnostics, in terms of sensitivity, specificity, integration, ease of use, and costs. Examples of such biochips are for example described in WO 2003/054566, WO 2003/054523, WO 2005/010542 A2, WO 2005/010543 A1 or Rife et al. (Sens. Act. A vol. 107, p. 209 (2003)), which are incorporated into the present application by reference. The known biosensors have however several drawbacks, namely:
The origin of these drawbacks is quite principally: the sensitive surface of the sensor and the sensor connections are located in the same plane. A solution for this problem is to contact the sensor at a plane, which is not its sensitive plane (“front side”). Several embodiments of this approach will be described in the following. These embodiments can particularly be used in a read-head device, which is brought in close contact to a carrier with magnetic beads. The carrier can for example be a foil, a microtiter well or a porous medium. Such a read-head sensor can be re-used several times on many different samples.
After dicing of the recesses 12, metallization or other processing steps known to a person skilled in the art may be performed to produce the required processing circuits 16 on the front side 13 of the substrate. As was already mentioned, the processing circuits 16 may particularly be coupling circuits with electrical tracks for generating magnetic fields and sensing devices like a GMR (Giant Magnetic Resonator) for sensing magnetic fields. An important feature of the processing circuits 16 is that their terminal pads are located on the bottom sides of the recesses 12.
In
The main difference to the first production process of
In the final step of
The sensor chip 10 of the embodiments described in the Figures has a typical area of 1.4×1.5 mm. It typically comprises 30 bondpads with a pitch of 150 μm, the thickness of the leads being about 10 μm, and the total thickness of the interconnection above the sensor surface being less than 30 μm.
Finally it is pointed out that in the present application the term “comprising” does not exclude other elements or steps, that “a” or “an” does not exclude a plurality, and that a single processor or other unit may fulfill the functions of several means. The invention resides in each and every novel characteristic feature and each and every combination of characteristic features. Moreover, reference signs in the claims shall not be construed as limiting their scope.
Number | Date | Country | Kind |
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05107309.6 | Aug 2005 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB06/52624 | 8/1/2006 | WO | 00 | 2/8/2008 |