Patent Description:
The disclosure may hence relate to the technical field of RF, in particular RFID and NFC, communication applications.

RF communication devices such as radio-frequency identification (RFID) tags, commonly referred as RFID inlays, labels or transponders, are widely used to identify an object, to which the tag is attached. The most common application examples of the RFID tags are retail, supply chain management, shipping services, airline luggage tracking, laundry services, etc..

RFID tags are hereby part of RFID systems, which typically include an RFID reader and one or more tags which are associated to one or more objects. The RFID reader is composed by a transmitter section, to transmit the RF signals to the tag, and by a receiver, to receive the modulated information of the tag. The standard communication between a reader and a tag, and vice versa, are specified in protocols.

An RFID tag is generally developed over a planar inlay and includes two antenna segments which form a dipole. The RFID tag comprises an RFID chip which is connected to said antenna segments. <FIG> shows a diagram of a conventional RFID chip <NUM>. The RFID chip <NUM> contains two RF antenna pads <NUM> (RF1 and RF2), and an antenna (related) functionality comprising an RF front-end and PMU, a data demodulator, a data modulator, a digital control, and a memory. The RF pads <NUM> are connected to the antenna terminals (not shown) and receive e.g. an RF field from a reader. The RF front-end and PMU section harvest the incoming energy from the RF pads <NUM> and generate supply voltage for the circuits of the RFID chip <NUM>. The data demodulator receives the data from the reader and deliver it to the digital control. The data modulator transmits the data back to the reader. The digital control processes both the demodulated data and the protocol commands and handles communication with the memory. The memory stores the identification data. The chip <NUM> further contains two test pads (TP1 and TP2) <NUM> which are respectively connected to tester circuitry <NUM> by temporary connection lines <NUM> that are arranged partially external of the RFID chip <NUM>. The test pads <NUM> are used to run the functional test of all chips of a wafer during manufacturing (see <FIG> below).

The described conventional RFID chips <NUM> are semiconductor devices and are manufactured on semiconductor wafers. <FIG> shows a semiconductor wafer <NUM> containing many similar chips (RFID chip preforms). Each square inside the wafer <NUM> represents a single chip. It is shown in the enlargement that each RFID chip preform has two RF antenna pads <NUM> and two (non-antenna) test pads <NUM>. The separation of the chips <NUM> on the wafer <NUM> is done through scribe lines. The final separation of the chips <NUM> is done by dicing the wafer <NUM> through said scribe lines. The test pads <NUM> are used to run the functional test of all chips <NUM> of the wafer <NUM> before dicing. In the scribe lines, there are temporary electrical connection lines (commonly referred to as "sawbow connection") <NUM>, which connect the test pads <NUM> to the test circuity (internal circuits) of the chip <NUM>. The tester circuitry <NUM> interfaces with the external tester in order to run the functional test of the chip <NUM>. The final separation of the chips <NUM> is done by dicing the wafer <NUM> through the scribe lines, such that the chips <NUM> are separated and the (partially chip external) temporary connection lines <NUM> are broken.

<FIG> shows a detailed block diagram of a conventional RFID chip <NUM>. The block diagram shows the test pad <NUM>, the temporary connection line <NUM>, and a test circuity <NUM>. The border between chip <NUM> and scribe line is denoted by <NUM>. The test pad <NUM> is used to run the functional test of the chip <NUM>. The temporary connection line <NUM> connects the test pad <NUM> to the test circuitry <NUM>.

Conventionally, the antenna associated with the RFID chip <NUM> is formed as a slit antenna (with two diploes) having two segments (on both sides of the slit), wherein each antenna segment is connected to an RF antenna pad <NUM> and a test pad <NUM>. Hereby, the RF antenna pad <NUM> and the test pad <NUM> are short-circuited with each other. However, there is conventionally no risk for the RFID tag functionality because the test pads <NUM> are electrically disconnected from the tester circuitry <NUM> during the dicing of the wafer (by cutting the temporary connection line <NUM>). This separation is considered necessary, because otherwise, after the antenna assembly phase, the tester circuitry <NUM> will be connected to the RF antenna pads <NUM> (due to the short-circuit). This may cause a negative impact over the performance of the RFID tag because more circuitry is then connected to the RF antenna pads <NUM>. Since more circuits are connected to the RF antenna pads <NUM>, the load at these pads (capacitive and resistive) is increased such that a part of the total power available in the RF antenna pads <NUM> is dissipated by this additional load introduced by the tester circuity <NUM>.

However, with increasing miniaturization and further development of chip manufacturing techniques, it may be desirable to remove the temporary connection lines.

<CIT> describes an RFID tag and a test method for sequentially activating a plurality of RFID tags by applying a test signal and a power voltage directly to the RFID tag on a wafer and performing a test.

<CIT> describes over the air or radiated testing of an RF microelectronic or integrated circuit device under test (DUT) that has an integrated millimeter wave (mmw) antenna structure. The antenna structure may have multiple elements in an array design that may be driven and/or sensed by integrated RF transmitter and/or receiver circuitry. An interface printed wiring board has formed in it a mmw radiation passage that is positioned to pass mmw radiation to and/or from the integrated antenna of the DUT. Test equipment may be conductively coupled to contact points of the interface board, to transmit and/or receive signals for testing of the DUT and/or provide dc power to the DUT. A test antenna is designed and positioned to receive and/or transmit mmw radiation through the passage, from and/or to the integrated DUT antenna.

There may be a need to provide an efficient and reliable RF communication device without using a temporary connection line.

An RF communication device, a method of manufacturing the RF communication device, and a method of using according to the independent claims are provided.

According to an aspect of the present disclosure, there is described an RF communication device (e.g. an RFID tag, an RFID IC, etc.), as defined in claim <NUM>.

According to a further aspect of the present disclosure, there is described a method of manufacturing an RF communication device (e.g. as described above), as defined in claim <NUM>.

In the context of the present disclosure, the term "RF communication device" may in particular refer to a device that is enabled to interact with communication via radio frequency RF, in particular using ultra high frequency (UHF). The term "RF communication device" may for example refer to an RF(ID) IC or to an RF(ID) tag (IC and antenna).

In the context of the present disclosure, the term "RF antenna functionality" may in particular refer to a device (or a plurality of devices) that is (are) directly related with an antenna associated to the RF IC, in other words: an antenna-related device. For example, the RF antenna functionality may comprise at least one of a data modulator, a data demodulator, an RF front-end, a digital control. In an embodiment, the RF antenna functionality includes the RF antenna. In another embodiment, the RF antenna functionality refers only to a device related to said RF antenna.

In the context of the present disclosure, the term "further functionality" may in particular refer to a device (or a plurality of devices) that is (are) not directly related with an antenna associated to the RF IC, in other words: a non-antenna-related device. For example, the further functionality may be a test functionality (test circuit) used during manufacturing (and/or during operation) of the RF communication device. Such a test circuit may e.g. comprise an IO buffer and an analog multiplexer (MUX). In an embodiment, said test functionality is not connected to the antenna functionality.

In the context of the present disclosure, the term "RFID" (radio-frequency identification) may refer to a technique that uses electromagnetic fields (RF field) to communicate via short distances, in particular <NUM> meter or less. The term "RFID device" may refer to any device that has an RFID functionality. An RFID device may include an antenna and an integrated circuit with a transmitter and a receiver. A typical RFID system may include an RFID reader and one or more RFID tags which are associated to one or more objects. In an example, a first RFID device comprises a transmitter to transmit the RF signals to a second RFID device, and a receiver, to receive the modulated information of the second RFID device. The standard communication between RFID devices are specified in protocols. An RFID functionality may for example be implemented in a tag, a smart card, a card reader, or a mobile phone.

In the context of the present application, the term "NFC" may refer to Near Field Communication which may be a short-range wireless technology (distances measured in centimeters). In order to make two NFC devices communicate, users may bring them close together or even make them touch. NFC may be considered as an established standard. In the present document, the NFC standard may be considered as a special form of RFID. In the context of the present document, the term "NFC device" may refer to any device that has an NFC functionality as described above. An NFC functionality may for example be implemented in a tag, a smart card, a card reader, or a mobile phone.

In the context of the present disclosure, the term "connection line within the RF communication device" may refer to the circumstance that an electric connection (line) between the non-antenna pad and the further functionality is completely (exclusively) within the RF communication device. This is in contrast to conventional approaches, wherein a test pad and a test circuit are connected by a temporary connection line that is partially external of the RF chip, so that it will be cut during wafer separation.

According to an exemplary embodiment, the present disclosure may be based on the idea that an RF communication device can be provided without a partially chip-external temporary connection line, while still being efficient, reliable, and design flexible, when a connection line between a non-antenna pad and a further (non-antenna) functionality is provided completely within the RF communication device. In this manner, the temporary connection line can be removed which circumstance may enable new approaches of manufacturing. For example, the miniaturization (smaller scribe lines) may be improved or next generation developments of dicing techniques (e.g. plasma dicing) may be applied.

While conventionally, the temporary connection line has been mandatory for proper testing and functioning, it has now been found by the Inventors that an efficient and reliable testing is still enabled, while the connection line does not have to be temporary, thereby opening a new field of manufacturing options. Even though the antenna pad and the non-antenna pad are short-circuited, the RF communication by the antenna pad may not be negatively influenced, since the non-antenna pad can be electrically isolated from the further functionality, for example by providing an electric control element between the non-antenna pad and the further functionality.

According to an embodiment, the electrical connection between the non-antenna pad and the further functionality is free of a (partially external) temporary connection line. This may enable the application of a new generation of manufacturing techniques and/or further miniaturization.

According to a further embodiment, the non-antenna pad comprises a test pad, and the further functionality comprises a test circuit device. Even though the temporary connection line is omitted, a reliable test functionality may still be enabled.

According to a further embodiment, the RF communication device is one of the group which consists of an RFID device, a tag, an IC, a smart card, a smart phone. In particular, the device is a passive device. The device may be an RFID and/or an NFC device.

According to a further embodiment, the second mode is an RF communication mode, and, during the RF communication mode, the non-antenna pad is electrically isolated from the further functionality. Thus, a reliable and robust RF communication is enabled (see e.g. <FIG>), even though antenna pad and non-antenna pad are short-circuited with each other.

According to a further embodiment, the control element comprises a transmission gate, in particular an inverter. Thereby, the control element may be implemented in a straightforward manner using established measures.

According to a further embodiment, the control element comprises at least two transistors, in particular an NMOS transistor and a PMOS transistor. Also hereby, the control element may be implemented in a straightforward manner using established measures.

According to a further embodiment, the RF communication device further comprises: a peak detector arranged between the non-antenna pad and the control element, in particular wherein the peak detector comprises a positive peak detector element and a negative peak detector element. The application of the peak detector may decrease an undesired negative voltage at the further functionality (e.g. the analog-multiplexer).

According to a further embodiment, the device further comprises a charge pump. The charge pump may be connected to the control element. The application of the charge pump may decrease an undesired negative voltage at the further functionality (e.g. the analog-multiplexer).

According to a further embodiment, the RF communication device further comprises: an antenna that is configured as a slit, in particular single-slit, antenna with at least two segments, wherein the antenna pad and the non-antenna pad (form a common pad that is) are connected to the same antenna segment.

According to a further embodiment of the method, the wafer is free of a temporary connection line, which temporary connection line is disconnected during the separating, between the non-antenna pad and the further functionality. In this manner, smaller scribe lines can be provided and/or new dicing methods may be applied.

Before, referring to the drawings, an exemplary embodiment will be described in further detail, and some basic considerations will be summarized based on which embodiments of the disclosure have been developed.

According to an exemplary embodiment, there is described a single-slit antenna solution is an RFID assembly technology which can enable easier and low cost antenna designs. In this assembly solution, one or more non-antenna pads of the RFID chip (RF communication device) are shorted-circuited to the RF pads (antenna pads). In the state-of-the-art single-slit antenna solution implementation, the non-antenna pads short-circuited to the RF pads are electrically disconnected and therefore can be safely short-circuited to the RF pads. The connection from the non-antenna pads to the internal nodes (test circuitry) of the chip is done via the scribe lines (separation between adjacent chips) of the semiconductor wafer and broken after the dicing step. This connection is referred here as "saw bow connection" (temporary connection line). The present disclosure is about an electrical circuitry that allows the removal of the saw bow but keeping its functionality. In addition, it may enable smaller scribe lines being beneficial for next generation dicing techniques. This novel approach is isolating the RF signals to the internal nodes through the non-antenna pads allowing them to be short-circuited to the RF pads safely. A challenge of passive RFID tags may be seen in blocking the RF signal before being powered. It may be desirable to electrically isolate RF signals from a pad to an internal node, controlled by a passive device.

<FIG> illustrates an RF communication device <NUM> (in this example an RFID IC of an RFID tag) according to an exemplary embodiment of the present disclosure. The RF communication device <NUM> comprises an RF antenna functionality <NUM> with an RF front-end, a data modulator, a data demodulator, a digital control, and a memory. Two antenna pads <NUM> are connected to the RF antenna functionality <NUM>. The RF communication device <NUM> further comprises a further functionality <NUM> (in the example shown a test circuit) which is not an RF antenna functionality. Two non-antenna pads <NUM> (test pads) are electrically connected to the further functionality <NUM>. The antenna pad <NUM> and the non-antenna pad <NUM> are arranged to be short-circuited with each other (not shown, see <FIG> below). The non-antenna pads <NUM> are electrically connected via a connection line <NUM> to the further functionality <NUM>, respectively, within the RF communication device <NUM>. It can be seen that the electrical connection <NUM> between the non-antenna pads <NUM> and the further functionality <NUM> is free of a partially (chip-) external temporary connection line <NUM> (compare the conventional examples in <FIG> above).

<FIG> illustrates an RF communication device <NUM> with a single slit antenna design according to an exemplary embodiment of the present disclosure. The RF communication device <NUM> further comprises an antenna <NUM> with two antenna segments 116a, 116b which are divided by a slit. The segments 116a, 116b hereby form diploes of the antenna <NUM>. A first antenna pad <NUM> and a first non-antenna pad <NUM> are short-circuited within a common pad that is coupled to the first antenna segment 116a. A second antenna pad <NUM> and a second non-antenna pad <NUM> are short-circuited in a further common pad that is coupled to the second antenna segment 116b.

<FIG> illustrates an RF communication device <NUM> with a control element <NUM> according to the present disclosure. The control element <NUM> is implement with two transistors <NUM>, <NUM>, being an NMOS <NUM> and a PMOS <NUM> transistor, that implement an inverter function. If a control signal is "<NUM>", the non-antenna pad <NUM> is bypassed through the PMOS <NUM> and connected to the test circuitry <NUM>. If the control signal is "<NUM>", the test circuitry <NUM> is isolated from the non-antenna pad <NUM> and the node is pulled-down. Control signal being "<NUM>" would be an isolated mode (isolating TP2/circuitry) and "<NUM>" a connection (test) mode.

Connected mode: control signal starts "<NUM>" and later is moved to "<NUM>", connecting the non-antenna pad <NUM> and the test circuitry <NUM>. The supply voltage, which sets "<NUM>" of control signal, is generated from a stimulus at the non-antenna pad <NUM>. There is a voltage drop between the non-antenna pad <NUM> voltage and supply voltage, which is caused by the PMOS Vth, in a way the supply voltage and control, if "<NUM>" logic, can be increased by increasing the non-antenna pad <NUM> voltage. If the non-antenna pad <NUM> voltage is increased, the voltage also increases and once it achieves the control circuit threshold, the control signal is de-asserted "<NUM>", thereby connecting the non-antenna pad <NUM> to the test circuit <NUM>, thus allowing testability.

Isolated mode (RF communication mode): the control signal starts "<NUM>" and it keeps "<NUM>". Supply voltage is generated through the RF front-end and the supply voltage is high enough to block the RF signal present at the non-antenna pad <NUM>. In other words, the control signal, which is defined by the supply voltage being higher than the RF signal at the non-antenna pad <NUM>, is applied in a way that the RF signal can be isolated by the PMOS <NUM>.

In other words, according to the present disclosure the control element <NUM> is configured to electrically connect the non-antenna pad <NUM> and the further functionality <NUM> in a first mode, and the control element <NUM> is configured to electrically disconnect the non-antenna pad <NUM> and the further functionality <NUM> in a second mode. In particular, the first mode may be a test mode (connection mode), and the second mode may be a non-test mode (isolated mode). More specifically, the second mode may be an RF communication mode, such that, during the RF communication mode, the non-antenna pad <NUM> is electrically isolated from the further functionality <NUM>.

<FIG> illustrates an RF communication device <NUM> with a control element <NUM> according to an exemplary embodiment of the present disclosure. The control element <NUM> is implemented as a transmission gate between the non-antenna pad <NUM> and the test circuit <NUM>, including IO buffer <NUM> and analog-multiplexer (mux) block <NUM>. Reference sign <NUM> denotes the border between device <NUM> and scribe line. In test mode, the control element <NUM> is enabled and the test circuit <NUM> is connected to the non-antenna pad <NUM>. After the antenna assembly, since the chip is no more tested, the control element <NUM> is disabled, thereby isolating the test circuit <NUM> from the non-antenna pad <NUM>, and consequently, also isolating the test circuit <NUM> from the antenna pad <NUM>.

Once the control element <NUM> circuit has less load (capacitive and resistive) compared with the test circuit <NUM>, the introduction of the control element <NUM> contributes to minimize the impact of the removal of the temporary connection line <NUM> over chip parameters like impedance and power.

<FIG> illustrates an RF communication device <NUM> with a control element <NUM> according to an exemplary embodiment of the present disclosure. The design is similar to the one showed in <FIG>, the difference being that the IO buffer block <NUM> is omitted by simplicity and the analog-mux <NUM> is shown in more detail.

<FIG> illustrates an RF communication device <NUM> with a charge pump <NUM> according to an exemplary embodiment of the present disclosure. The design is very similar to the one shown in <FIG> with the difference being that a charge pump <NUM> is connected to the transmission gate <NUM>. The application of the charge pump <NUM> is to provide a proper bias voltage to the bulk terminals of the devices of the transmission gate, in a way the parasitic devices inherent to the MOS transistors (<NUM> and <NUM> in <FIG>), like diodes and bipolar transistors, are prevented to be triggered.

<FIG> illustrates an RF communication device <NUM> with an additional peak detector <NUM>, between the non-antenna pad <NUM> and the control element <NUM>, according to an exemplary embodiment of the present disclosure. The application of the peak detector <NUM> can also decrease an undesired negative voltage at the test circuit <NUM>, in particular the analog-mux <NUM>.

<FIG> illustrates an RF communication device <NUM> with a positive peak detector element <NUM> and a negative peak detector element <NUM> according to an exemplary embodiment of the present disclosure. The design is very similar to the one shown in <FIG> with the difference being that the peak detector <NUM> comprises a positive peak detector element <NUM> and a negative peak detector element <NUM>.

<FIG> illustrates a waveform (voltage vs. time) at power-up, for example according to the embodiment described in <FIG> above. The voltage at the RF antenna pads <NUM> starts to grow, and then stabilizes. This is the typical power-up behavior when a reader is turned-on and RFID tags in the same region of the reader are energized. It can be seen that, even though the antenna pad <NUM> and the non-antenna pad <NUM> are short-circuited, the waveform is as expected and desired (no negative impact from the non-antenna pad <NUM> to further functionality <NUM> connection <NUM>).

Claim 1:
An RF communication device (<NUM>), comprising:
an RF antenna functionality (<NUM>);
at least one antenna pad (<NUM>) connected to the RF antenna functionality (<NUM>);
a further functionality (<NUM>) which is not an RF antenna functionality, wherein the further functionality (<NUM>) comprises a test circuit device; and
at least one non-antenna pad (<NUM>), wherein the at least one non-antenna pad (<NUM>) comprises a test pad;
wherein the at least one antenna pad (<NUM>) and the at least one non-antenna pad (<NUM>) are arranged to be short-circuited with each other; and
wherein the at least one non-antenna pad (<NUM>) is electrically connected via a connection line (<NUM>) to the further functionality (<NUM>) within the RF communication device (<NUM>);
characterized in that the RF communication device (<NUM>) further comprises a control element (<NUM>) arranged at the connection line (<NUM>) between the at least one non-antenna pad (<NUM>) and the further functionality (<NUM>),
wherein the control element (<NUM>) is configured to electrically connect the at least one non-antenna pad (<NUM>) and the further functionality (<NUM>) in a first mode, and
wherein the control element (<NUM>) is configured to electrically disconnect the at least one non-antenna pad (<NUM>) and the further functionality (<NUM>) in a second mode.