Semiconductor device and position detection system using semiconductor device

A position detection system is formed by network connection of a plurality of interrogators and a server. An RFID and the interrogators communicate wirelessly, whereby a distance from each interrogator to the RFID is searched to search a position of the RFID from the distance. In order to calculate the distance from the interrogator to the RFID, a signal is oscillated with a frequency corresponding to amplitude of a signal received in the RFID from the interrogator. A frequency of a signal oscillated in the RFID is detected in the RFID or by the interrogator, whereby a distance from the interrogator to the RFID is detected.

TECHNICAL FIELD

The present invention relates to a semiconductor device and a position detection system using the semiconductor device. The present invention particularly relates to a position detection system using a semiconductor device that performs position detection by a wireless signal from a plurality of interrogators.

BACKGROUND ART

In recent years, an individual identification technology using wireless communication through an electromagnetic field, an electric wave, or the like has attracted attention. In particular, as a semiconductor device that communicates data by wireless communication, an individual identification technology using an RFID (Radio Frequency Identification) tag has attracted attention. An RFID tag (hereinafter, simply referred to as an RFID) is also referred to as an IC (Integrated Circuit) tag, an IC chip, an RF tag, a wireless tag, or an electronic tag. The individual identification technology using an RFID has started to help production, management, or the like of an individual object and has been expected to be applied to personal authentication.

RFIDs can be divided into two types: an active-type RFID and a passive-type RFID, depending on whether it incorporates a power supply or it is supplied with electric power externally. An active-type RFID is disclosed in Reference 1, and a passive-type RFID is disclosed in Reference 2. An active-type RFID incorporates a power supply for driving the RFID and includes a cell as the power supply. In a passive-type RFID, an electric power for driving the RFID is made using an electric wave or electromagnetic wave (carrier wave) externally, and a structure in which a cell is not provided is realized.

FIG. 26is a block diagram showing a specific structure of an active-type RFID. In an active-type RFID1400ofFIG. 26, a communication signal received by an antenna circuit1401is input to a demodulation circuit1405and an amplifier1406in a signal processing circuit1402. The communication signal is normally transmitted after processing such as ASK modulation or PSK modulation is performed on carriers of 13.56 MHz, 915 MHz, or the like. Here inFIG. 26, an example of a case of 13.56 MHz as a communication signal is shown.

InFIG. 26, a clock signal as a reference is needed in order to process signals. Here, the carrier of 13.56 MHz is used as a clock. The carrier of 13.56 MHz is amplified by the amplifier1406and then supplied to a logic circuit1407as a clock. Further, the communication signal that is ASK modulated or PSK modulated is demodulated in the demodulation circuit1405. The demodulated signal is also transmitted to the logic circuit1407and analyzed. The signal analyzed in the logic circuit1407is transmitted to a memory control circuit1408, and based on the signal, the memory control circuit1408controls a memory circuit1409and retrieves data stored in the memory circuit1409to transmit the data to a logic circuit1410. The data transmitted from the memory circuit1409is encoded by the logic circuit1410, and subsequently amplified by an amplifier1411. A modulation circuit1412modulates the carrier in accordance with the signal.

An electric power inFIG. 26is supplied by a cell1403provided outside the signal processing circuit1402through a power supply circuit1404. The power supply circuit1404supplies an electric power to the amplifier1406, the demodulation circuit1405, the logic circuit1407, the memory control circuit1408, the memory circuit1409, the logic circuit1410, the amplifier1411, the modulation circuit1412, and the like. In such a manner, the active type RFID operates.

FIG. 27shows a block diagram showing a specific structure of a passive-type RFID. In a passive-type RFID1500ofFIG. 27, a communication signal received by an antenna circuit1501is input to a demodulation circuit1505and an amplifier1506in a signal processing circuit1502. The communication signal is normally transmitted after processing such as ASK modulation or PSK modulation is performed on carriers of 13.56 MHz, 915 MHz, or the like. InFIG. 27, an example of a case of using 13.56 MHz as a communication signal is shown.

InFIG. 27, a clock signal as a reference is needed in order to process a signal. Here, the carrier of 13.56 MHz is used as a clock. The carrier of 13.56 MHz is amplified by the amplifier1506and then supplied to a logic circuit1507as a clock. Further, the communication signal that is ASK modulated or PSK modulated is demodulated in the demodulation circuit1505. The demodulated signal is also transmitted to the logic circuit1507and analyzed. The signal analyzed in the logic circuit1507is transmitted to a memory control circuit1508, and based on the signal, the memory control circuit1508controls a memory circuit1509and retrieves data stored in the memory circuit1509to transmit the data to a logic circuit1510. The data transmitted from the memory circuit1509is encoded by the logic circuit1510, and subsequently amplified by an amplifier1511. A modulation circuit1512modulates the carrier in accordance with the signal. On the other hand, the communication signal in a rectifier circuit1503is rectified and input to a power supply circuit1504. The power supply circuit1504supplies an electric power to the amplifier1506, the demodulation circuit1505, the logic circuit1507, the memory control circuit1508, the memory circuit1509, the logic circuit1510, the amplifier1511, the modulation circuit1512, and the like. In such a manner, the passive-type RFID operates.

Japanese Published Patent Application No. 2005-316724
[Reference 2]Japanese Translation of PCT International Application No. 2006-503376

DISCLOSURE OF INVENTION

The above conventional semiconductor device having an RFID can obtain information such on whether or not the semiconductor device having an RFID exists in a predetermined space or can obtain information on ID or the like possessed in the RFID in a case where the semiconductor device exists in the predetermined space. However, the conventional semiconductor device having an RFID has a problem in that a position of the semiconductor device having an RFID can not be found in the predetermined space.

Thus, it is an object of the present invention to provide a semiconductor device that communicates data by wireless communication and can detect a distance between the semiconductor device and another device for wireless communication. Further, it is also an object of the present invention to provide a system for detecting a position of a semiconductor device with the use of such a semiconductor device.

In order to solve the foregoing problem, it is a feature of a semiconductor device relating to the present invention to communicate data by wireless communication, to generate a signal showing information on a distance from a source to a destination of a received signal, and to transmit the signal.

For detecting information on a distance, the present invention is implemented by focusing the following event: while a signal is transmitted in a space, electric field intensity is lowered depending on the transmitting distance. A semiconductor device of the present invention has means for oscillating a signal with a frequency corresponding to electric field intensity (a size of amplitude of a signal) of a received signal. When the frequency of the signal that is oscillated by this means is found, a distance between the source of the signal and the semiconductor device can be detected.

Thus, an aspect of the present invention is a semiconductor device including an antenna circuit for transmitting and receiving a signal, a signal oscillating portion for oscillating a signal with a frequency corresponding to electric field intensity of a signal received by the antenna circuit, and a signal processing portion for processing a signal oscillated in the signal oscillating portion, where the antenna circuit transmits a signal that is generated in the signal processing portion.

The signal processing portion has means for counting the number of oscillations of a signal that is oscillated in the signal oscillating portion. Further, the signal processing portion can have means for measuring a time period that is needed for counting, that is, an oscillation time period as well as means for counting the number of oscillations of a signal that is oscillated in the signal oscillating portion.

Another aspect of the present invention is a semiconductor device including an antenna circuit for transmitting and receiving a signal and a signal oscillating portion for oscillating a signal with a frequency corresponding to electric field intensity of a signal received by the antenna circuit, where the antenna circuit transmits a signal that is oscillated in the signal oscillating portion. When the signal transmitted from the antenna circuit is received and a frequency is detected, a distance between the semiconductor device and the source of the signal can be found.

Further, in a semiconductor device of the present invention, the signal oscillating portion includes power supply means for changing a signal received by the antenna circuit into a direct-current voltage and a ring oscillator using an output of the power supply means as power source. According to this structure, a pulse signal can be generated in the signal oscillating portion, which is oscillated with a frequency corresponding to electric field intensity (amplitude) of a signal received by the antenna circuit.

Further, a semiconductor device of the present invention may include an amplifier circuit for amplifying a signal that is transmitted and received by the antenna circuit.

A position detection system can be constituted by a semiconductor device relating to the present invention and a plurality of interrogators that communicate with the semiconductor device wirelessly. The position detection system relating to the present invention has a feature in that means for measuring the number of oscillations of a signal (pulse) and means for measuring an oscillation time period of a signal are provided in order to detect a frequency of a signal that is oscillated in a signal oscillating portion of the semiconductor device.

An aspect of the present invention is a position detection system including a semiconductor device and a plurality of interrogators which communicate with each other wirelessly, where the semiconductor device oscillates a signal with a frequency corresponding to electric field intensity of a received signal. In order to detect a frequency of a signal that is oscillated in the semiconductor device, means for measuring the number of oscillations of a signal is provided for the semiconductor device, and means for measuring an oscillation time period is provided for the interrogator.

More specifically, the semiconductor device is provided with an antenna circuit for transmitting and receiving a signal, a signal oscillating portion for oscillating a signal with a frequency corresponding to electric field intensity of a signal received by the antenna circuit, and a signal processing portion for processing a signal oscillated in a signal oscillating portion. Any one of the plurality of the interrogators transmits a signal for detecting a distance to the semiconductor device. In the semiconductor device, when the signal for detecting a distance is received by the antenna circuit, the signal for detecting a distance is output to the signal oscillating portion and the signal processing portion. In the signal oscillating portion, a signal is generated, which is oscillated with a frequency corresponding to electric field intensity of the signal for detecting a distance, and in the signal processing portion, count of the number of oscillations of a signal oscillated in the signal oscillating portion is started. When a count value reaches a predetermined value, a response signal showing completion of the count is generated in the signal processing portion, and the response signal is transmitted from the antenna circuit. In the interrogator transmitting the signal for detecting a distance, when the response signal is received, a time period from transmission of the signal for detecting a distance to reception of the response signal is detected.

Another aspect of the present invention is a position detection system including a semiconductor device and a plurality of interrogators which communicate wirelessly, where the semiconductor device oscillates a signal with a frequency corresponding to electric field intensity of a received signal. In order to detect a frequency of the signal oscillated in the semiconductor device, both means for measuring the number of oscillations of the signal and means for measuring an oscillating time period of the signal are provided for the semiconductor device.

More specifically, in the position detection system relating to the present invention, the semiconductor device is provided with an antenna circuit for transmitting and receiving a signal, a signal oscillating portion for oscillating a signal with a frequency corresponding to electric field intensity of a signal received by the antenna circuit, and a signal processing portion for processing a signal oscillated in the signal oscillating portion. Any one of the plurality of the interrogators transmits a signal for detecting a distance to the semiconductor device. In the semiconductor device, when the signal for detecting a distance is received by the antenna circuit, the signal for detecting a distance is output to the signal oscillating portion. In the signal oscillating portion, a signal is oscillated with a frequency corresponding to electric field intensity of the signal for detecting a distance. In the signal processing portion, an oscillation frequency and an oscillation time period of a signal oscillated in the signal oscillating portion are measured, a distance between the interrogator and the semiconductor device is detected by the number of oscillations and the oscillation time period, and the detected distance is transmitted to the interrogator.

Another aspect of the present invention is a position detection system including a semiconductor device and a plurality of interrogators which communicate wirelessly, where the semiconductor device oscillates a signal with a frequency corresponding to electric field intensity of a received signal. The semiconductor device has a feature in that the oscillated signal is transmitted to the interrogator so that the frequency is detected by the interrogator.

More specifically, the position detection system relating to the present invention is provided with a plurality of interrogators and a semiconductor device, and the semiconductor device has an antenna circuit for transmitting and receiving a signal and a signal oscillating portion for oscillating a signal with a frequency corresponding to electric field intensity of a signal received by the antenna circuit. Any one of the plurality of the interrogators transmits a signal for detecting a distance. In the semiconductor device, when the signal for detecting a distance is received by the antenna circuit, the signal for detecting a distance is input to the signal oscillating portion. In the signal oscillating portion, a signal is oscillated with a frequency corresponding to electric field intensity of the signal for detecting a distance. The antenna circuit transmits a signal oscillated in the signal oscillating portion. When the interrogator receives a signal from the antenna circuit, the interrogator detects a frequency of the received signal. The interrogator is provided with both means for measuring the number of oscillations of a signal and means for measuring an oscillation time period. Thus, a frequency can be detected.

It is to be noted that the term “connected” means “electrically connected” in the present invention. Therefore, in addition to a predetermined relation of connection, another element (for example, a switch, a transistor, a capacitor element, an inductor, a resistance element, a diode, or the like) which is capable of electrically connection may be provided in the connection, in a structure disclosed in the present invention.

It is to be noted that a semiconductor device in the present specification indicates general devices capable of functioning with the use of semiconductor characteristics.

According to the present invention, a semiconductor device capable of measuring a communication distance by wireless communication can be provided. Therefore, a position detection system can be formed, which detects information on a position where a semiconductor device is located in a space (for example, space coordinates), with the use of the semiconductor device relating to the present invention. A semiconductor device relating to the present invention is attached to equipment, and position information (space coordinates) of the semiconductor device is regularly detected by wireless communication, whereby a track of the equipment can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiment modes of the present invention will be explained with reference to drawings. However, the present invention is easily understood by those skilled in the art that various changes and modifications are possible, unless such changes and modifications depart from the content and the scope of the invention. Therefore, the present invention is not construed as being limited to the description of the following embodiment modes. It is to be noted that the same portion or a portion having the same function is denoted by the same reference numeral in all the drawings for explaining embodiment modes, and the explanation thereof is omitted.

The present invention is to detect a distance between an RFID and an interrogator and a position of the RFID by utilizing reduction in electric field intensity in accordance with a transmitting distance of a signal in transmitting the signal in a space. Hereinafter, the present invention will be explained on the conduction such that electric field intensity of a signal output from an interrogator is spherically spread by regarding the interrogator as a center and the electric field intensity is reduced as the distance from the interrogator is increased in the present specification.

In this embodiment mode, a structure of a semiconductor device of the present invention and a structure of a position detection system of the present invention using the semiconductor device will be explained.

A position detection system of the present invention is to detect a position of a semiconductor device that has an RFID by communication of an interrogator and the semiconductor device.FIG. 1is a block diagram for explaining a structure of a position detection system of the present invention and transmission and reception of a signal in the system. The system ofFIG. 1is for detecting a position of a semiconductor device that has an RFID in a space130. The semiconductor device that has an RFID performs wireless communication, and hereinafter, is referred to as an “RFID”.

As shown inFIG. 1, an RFID100is located to be surrounded by an interrogator121, an interrogator122, an interrogator123, and an interrogator124. As a matter of course, the number of the interrogators is not limited to 4 in the present invention. In order to detect a position of the RFID100in a three-dimensional space, at least four interrogators are necessary. This point is described later. When a two-dimensional coordinate is desired to be detected for detecting a position of the RFID100, at least three interrogators are necessary. Further, when only a distance between the RFID100and the interrogator is measured, at least one interrogator is necessary.

The interrogator121, the interrogator122, the interrogator123, and the interrogator124are connected to a server140with a LAN (local area network) or the like. The server140is a control portion of the system for controlling the interrogators121to124or for detecting a position of an RFID based on a signal from the interrogators121to124. A connection of the server140with the interrogators121to124and a connection between the interrogators121to124can be constituted by a wired network or a wireless network.

In the present specification, the interrogator (also referred to as a reader/writer device or a R/W device) outputs a signal which is being placed on a carrier and has a function for transmitting and receiving a signal to/from the RFID wirelessly. Here, a frequency of the carrier is not limited to a specific frequency.

The interrogator121, the interrogator122, the interrogator123, and the interrogator124each outputs a signal for detecting a distance having equivalent electric field intensity. Hereinafter, these signals are described as a signal F1, a signal F2, a signal F3, or a signal F4(seeFIG. 1). When a distance between the RFID100and the specific interrogator or a position of the RFID100is measured, the interrogator121, the interrogator122, the interrogator123, and the interrogator124sequentially transmit the signal F1, the signal F2, the signal F3, and the signal F4, respectively, so that the signals F1to F4are not received in the RFID at the same time from a plurality of interrogators. Timing for transmitting the signals F1to F4from the interrogators121to124is controlled by the server140.

The RFID100has a function in which the signals F1to F4transmitted from the interrogators121to124are received and signals S1to S4that are generated by reception of the signals F1to F4are transmitted.FIG. 2is a block diagram showing a basic structure of the RFID100relating to the present invention. A semiconductor device that has an RFID (hereinafter, referred to as an “RFID”) inFIG. 2includes an antenna circuit101, a signal oscillating portion102, and a signal processing portion103.

As shown inFIG. 2, a signal is input and output to/from the antenna circuit101and the signal oscillating portion102, and a signal is input and output between the signal oscillating portion102and the signal processing portion103. The antenna circuit101receives a signal from the outside or transmits a signal to the outside. That is, the signals F1to F4from the interrogators121to124shown inFIG. 1are received by the antenna circuit101, and the signals S1to S4are transmitted from the antenna circuit101.

The signal oscillating portion102has a function for oscillating a pulse signal to be output based on the signal received by the antenna circuit101. Therefore, the signal oscillating portion102has a pulse oscillating circuit. The pulse oscillating circuit has a function in which pulse signals with different frequencies from each other can be oscillated depending on a voltage of the input signal. Such a pulse oscillating circuit can be constituted by, for example, a rectifier circuit and a ring oscillating circuit in which a signal from the rectifier circuit is input.

It is to be noted that the pulse signal in the present specification indicates a signal in which a voltage is periodically changed. A pulse signal is illustrated by examples inFIG. 4. For example, the pulse signal indicates a wave in which a voltage swings periodically to have such a shape as a rectangular wave001(a), a rectangular wave001(b), a triangular wave002, a sawtooth wave003, or a sine wave004shown inFIG. 4.

The signal processing portion103has a function for counting a pulse of the pulse signal output from the signal oscillating portion102. Therefore, the signal processing portion103is provided with a counter for counting a pulse of the output pulse signal from the signal oscillating portion102.

A shape of the antenna in the antenna circuit101is not particularly limited. That is, as a transmission system of a signal that is applied to the antenna circuit101in the RFID100, an electromagnetic coupling system, an electromagnetic induction system, a micro-wave system, or the like can be used. The transmission system may be selected by a practitioner appropriately in consideration of usage, and an antenna having an optimal length and shape may be provided in accordance with the transmission system.

For example, in a case where an electromagnetic coupling system or an electromagnetic induction system (for example, 13.56 MHz band) is applied as a transmission system, electromagnetic induction by change of the electric field density is utilized; therefore, a conductive film serving as an antenna is formed into a circular shape (such as a loop antenna) or a spiral shape (such as a spiral antenna).

In a case where a micro-wave system (for example, UHF band (860 to 960 MHz band), 2.45 GHz band, or the like) is applied as the transmission system, a length or a shape of a conductive film serving as an antenna may be selected as appropriate in consideration of a wavelength of an electric wave used for signal transmission. For example, the conductive film serving as an antenna can be formed into a linear shape (such as a dipole antenna), a flat shape (such as a patch antenna), or the like. Further, a shape of the conductive film serving as an antenna is not limited to the linear shape, and the conductive film may be formed into a curve, a meandering shape, or a combined shape thereof in consideration of a wavelength of an electromagnetic wave.

The RFID100may be provided with an amplifier circuit for amplifying a signal transmitted and received in the antenna circuit101. The RFID100may have a structure of either of an active type or a passive type. For example, in a case of an active-type structure, as similar to a conventional example ofFIG. 26, the RFID is further provided with a cell, and a power supply circuit is provided in the signal oscillating portion102. In a case of a passive-type structure, as similar to a conventional example ofFIG. 27, a rectifier circuit and a power supply circuit may be provided in the signal oscillating portion102because the power supply is generated from the signal received by the antenna circuit101.

The present invention is to detect a distance between the RFID and the interrogator and a position of the RFID by utilizing reduction in electric field intensity in accordance with the transmission distance of a signal in transmitting the signal in the space.

Operation of the position detection system shown inFIG. 1is explained with the use of a flow chart shown inFIG. 3. Although the number of interrogators is not limited to 4 in the present invention, the number of the interrogators is limited to 4 for convenience of explanation, and flow of the position detection system of the present invention is explained. This point is similar to the other embodiment modes.

First, in order to detect a distance between the RFID100and the first interrogator121, the first interrogator121outputs the signal F1(step ST01). The RFID100receives the signal F1from the interrogator121by the antenna circuit101(step ST02).

The signal F1received by the antenna circuit101is output to the signal oscillating portion102. In the signal oscillating portion102, a pulse signal is generated, which is oscillated with a frequency corresponding to electric filed intensity of the input signal F1(step ST03). The signal F1received by the antenna circuit101is rectified and then smoothed to generate a direct-current voltage, and the pulse signal is oscillated by an oscillating circuit using this direct-current voltage as a power source, whereby such a pulse signal can be generated.

The pulse signal oscillated in the signal oscillating portion102is input to the signal processing portion103. In the signal processing portion103, the pulse number of the pulse signal is counted until a predetermined value is obtained (step ST04).

When the count number reaches a predetermined value, a signal (a response signal S1) showing completion of the count of the pulse is generated in the signal processing portion103(step ST05). The response signal S1is output from the signal processing portion103to the antenna circuit101. The response signal S1is transmitted from the antenna circuit101(step ST06). The interrogator121receives the response signal S1from the RFID100(step ST07). When the response signal S1is received, the interrogator121detects a time period T1from the transmission of the signal F1to reception of the response signal S1(step ST08). Here, this time period T1is referred to as a response time period T1.

It is to be noted that the response time period T1is determined by the oscillation frequency of the pulse signal that is oscillated in the signal oscillating portion102of the RFID100. Further, the oscillation frequency of the pulse signal is determined depending on electric field intensity of the signal F1at the time of being received in the RFID100. The electric field intensity of the signal F1at the time of being received in the RFID100is determined depending on the distance between the RFID100and the first interrogator121. As the distance between the RFID100and the interrogator121increases, the electric field intensity of the signal F1at the time of being received in the RFID100becomes lower; therefore, the oscillation frequency of the pulse signal is reduced. As a result, the time period needed for counting the pulse in the signal oscillating portion102is extended, and the response time period T1that is measured by the interrogator121becomes longer. Thus, the response time period T1that is measured by the interrogator121corresponds to the frequency of the pulse signal that is oscillated in the signal oscillating portion102; therefore, a distance between the RFID100and the interrogator121can be detected from the response time period T1.

Operation from the step ST01to the step ST08are sequentially performed in each case of the second interrogator122, the third interrogator123, and the fourth interrogator124, and a response time period T2, a response time period T3, and a response time period T4are detected in the case of the interrogator122, the interrogator123, and the interrogator124, respectively. Selection of the interrogator for communicating with the RFID100is controlled by an instruction from the server140. For specifying a position of the RFID100with the three-dimensional coordinate, the response time period may be measured by at least four interrogators; therefore, in a case where five or more interrogators are set in the space130, all interrogators are not necessary to be used for measuring the response time period.

The interrogator121, the interrogator122, the interrogator123, and the interrogator124, which are provided in the space130, transmit the measured response time periods T1, T2, T3, and T4to the server140through the LAN (local area network) or the like. The server140calculates a distance D1, a distance D2, a distance D3, and a distance D4between each interrogator121to124and the RFID100based on the response time periods T1to T4that are transmitted from the interrogators121to124. A position (space coordinates) of the RFID100can be specified by the distances D1to D4and the position information (space coordinates, more specifically, a relative coordinate) of the interrogators121to124.

Explanation that a position of the RFID can be specified using at least four interrogators is performed with reference toFIG. 5. In the space130, there are four spheres of each radius which corresponds to the distance D1, the distance D2, the distance D3, or the distance D4, by regarding each coordinate of the interrogators121to124as a center. An intersection point of the four spheres is determined at one point, and the intersection point becomes a coordinate of the RFID100.

As described above, the distance between the interrogator and the RFID100is measured, whereby the position of the RFID100in the space130can be detected. A manager can find a position where the RFID100is located by access to the server140.

When the above structure of the present invention is employed, information on a position where the RFID is located in the space can be obtained as well as individual information such as ID included in the RFID. Further, the position information of the RFID is regularly detected, whereby information on following a track (also referred to as a flow line) of movement of equipment provided with the RFID can be obtained.

In Embodiment Mode 1, in order to detect the oscillation frequency of a signal that is oscillated in the signal oscillating portion102, only count of a pulse of a pulse signal that is oscillated in the signal oscillating portion102is performed in the signal processing portion103, and a time period needed for counting a pulse is detected by the interrogator. A position detection system in this embodiment mode has a feature in that the number of oscillations of a pulse signal is counted and an oscillation time period is detected in a signal processing portion. It is to be noted that a structure of a position detection system and an RFID100is similar to those of Embodiment Mode 1 (seeFIG. 1andFIG. 2). Therefore, portions different from those of Embodiment Mode 1 will be explained, and the explanation in Embodiment mode 1 is applied for the similar portions.

FIG. 6shows a flow chart for explaining operation of the position detection system of this embodiment mode. First, a distance between an RFID100and a first interrogator121is detected. Therefore, communication is performed between the first interrogator121and the RFID100. Steps ST21to ST24are similar to the steps ST01to ST04(seeFIG. 3) in Embodiment Mode 1.

First, the first interrogator121outputs a signal F1(the step ST21). The signal F1from the interrogator121is received in an antenna circuit101of the RFID100(the step ST22). The signal F1is input from the antenna circuit101to a signal oscillating portion102. In the signal oscillating portion102, a pulse signal is generated, which is oscillated with a frequency corresponding to electric field intensity of the input signal F1(the step ST23). In a signal processing portion103, a pulse of the pulse signal that is oscillated in the signal oscillating portion102is counted until a predetermined value is obtained (the step ST24).

In this embodiment mode, means for measuring a time period is provided for the signal processing portion103. As the means for measuring a time period, for example, means for generating a reference clock signal and counting means for counting a reference clock signal can be used. A time period can be measured from the count number of the reference clock.

In the signal processing portion103, after the number of oscillations of the pulse signal that is oscillated in the signal oscillating portion102starts to be counted, a time period is measured until the count number reaches a predetermined value. As described in Embodiment Mode 1, the time period that is needed for count in the step ST24reflects a frequency of the pulse signal that is oscillated in the signal oscillating portion102and also reflects a distance between the RFID100and the interrogator121that is a source of the signal F1. In the signal processing portion103, a distance between the RFID100and the interrogator121is detected based on the time period that is needed for counting the pulse in the step ST24(a step ST25).

A data of the distance detected in the signal processing portion103is transmitted as a signal S1from the antenna circuit101(step ST26). The first interrogator121receives a signal S1(step ST27).

Operation from the step ST21to the step ST27is sequentially performed in each case of a second interrogator122, a third interrogator123, and a fourth interrogator124. A signal S2, a signal S3, and a signal S4, which show a distance, are received by the interrogator122, the interrogator123, and the interrogator124, respectively. The interrogator121, the interrogator122, the interrogator123, and the interrogator124, which are located in a space130, transmit the data of the distance to a server140. The server140specifies a position (space coordinates) of the RFID100from the distance data that is received from the interrogators121to124and position information (space coordinates, more specifically, a relative coordinate) of the interrogators121to124. A manager can find a position where the RFID100is located by access to the server140.

When the above structure of the present invention is employed, information on a position where the RFID is located in the space can be obtained as well as individual information such as ID included in the RFID. Further, the position information of the RFID is regularly detected, whereby information on following a track (also referred to as a flow line) of movement of equipment provided with the RFID can be obtained.

In this embodiment mode, another structure of a semiconductor device that has the RFID shown in Embodiment Mode 1 will be explained. In the drawings used in this embodiment mode, the same reference numerals as those of Embodiment Mode 1 denote the same portions. Explanation in Embodiment Mode 1 is applied for details of such portions in this embodiment mode.

FIG. 7is a block diagram showing a structure of a semiconductor device that has an RFID of this embodiment mode (hereinafter, referred to as “RFID”). An RFID200of this embodiment mode has such a structure in which the signal processing portion103is removed from the RFID100ofFIG. 2. The RFID200includes an antenna circuit101and a signal oscillating portion102.

As the result of removing the signal processing portion103, a circuit size of the entire RFID200can be reduced, and then low power consumption of the entire RFID200can be achieved. As a distance between an interrogator and the semiconductor device that has an RFID becomes larger, attenuation of a signal transmitted from the interrogator to the semiconductor device occurs. In such a case, power consumption of the entire RFID200is reduced, whereby stable oscillation can be performed in the signal oscillating portion102.

FIG. 8is a block diagram for explaining a structure of a position detection system of this embodiment mode and transmission and reception of a signal. As shown inFIG. 8, the RFID200of this embodiment mode can form a position detection system similarly to the RFID100of Embodiment Mode 1. In the RFID200of this embodiment mode, pulse signals PS1to PS4oscillated in the signal oscillating portion102are transmitted with respect to signals F1to F4from interrogators, which is a different point from the RFID100of Embodiment Modes 1 and 2.

Next, operation of a position detection system of this embodiment mode will be explained with reference toFIG. 9.FIG. 9is a flow chart for explaining communication of the RFID200and a first interrogator121. Steps ST31to ST33by oscillating a pulse signal in the RFID200are similar to the steps ST01to ST03(seeFIG. 3) of Embodiment Mode 1.

First, in order to measure a distance between the RFID200and the first interrogator121, the first interrogator121outputs a signal F1(the step ST31). The signal F1from the interrogator121is received by the antenna circuit101of the RFID200(the step ST32). The signal F1is input from the antenna circuit101to the signal oscillating portion102. In the signal oscillating portion102, the pulse signal PS1is generated, which is oscillated with a frequency corresponding to electric field intensity (amplitude) of the input signal F1(the step ST33).

Next, the pulse signal PS1that is oscillated in the signal oscillating portion102of the RFID200is output to the antenna circuit101, and then the pulse signal PS1is transmitted from the antenna circuit101(step ST34). The pulse signal PS1is received by the first interrogator121(step ST35). In the interrogator121, a frequency of the received pulse signal PS1is detected (step ST36).

Operation from the step ST31to the step ST36is similarly performed in each case of a second interrogator122, a third interrogator123, and a fourth interrogator124. A pulses signal PS2, a pulse signal PS3, and a pulse signal PS4are received, which correspond to signals transmitted by the interrogator122, the interrogator123, and the interrogator124, respectively, and each frequency thereof is detected.

Data corresponding to each frequency detected from the interrogators121to124is transmitted to a server140. As described in Embodiment Mode 1, the frequency of the pule signal PS that is oscillated in the signal oscillating portion102reflects a distance between the interrogator and the RFID200. Therefore, the server140can calculate distances between the RFID200and each interrogator121to124based on the data received from each interrogator121to124, and can detect a position (space coordinates) of the RFID based on the calculated distances and position information (space coordinates, more specifically, a relative coordinate) of the interrogators121to124. A manager can find a position where the RFID200is located by access to the server140.

An example of a method for detecting the oscillation frequency of a pulse signal PS by an interrogator is explained. The pulse number of the pulse signal PS is counted by the interrogator until a predetermined value is obtained, and a time period that is needed for counting the pulse is measured. As described in Embodiment Mode 1, since the time period that is needed for counting the pulse corresponds to a frequency, a frequency of the pulse signal PS can be detected by the interrogator by this method. The interrogator transmits the measured time period to the server140as data of the oscillation frequency.

When the above structure of the present invention is employed, information on a position where the RFID is located in the space can be obtained as well as individual information such as ID included in the RFID. Further, the position information of the RFID is regularly detected, whereby information on following a track (also referred to as a flow line) of movement of equipment provided with the RFID can be obtained.

In this embodiment mode, a more specific structure of the RFID100that is applied to the position detection system of Embodiment Mode 1 will be explained. It is to be noted that the similar structure to Embodiment Mode 1 is explained briefly, and explanation of Embodiment Mode 1 is applied for the details of the structure in this embodiment mode.

FIG. 10is a block diagram of an RFID of this embodiment mode. As shown inFIG. 10, the RFID100mainly includes an antenna circuit101, a signal oscillating portion102, and a signal processing portion103similarly toFIG. 2.

The signal oscillating portion102has a rectifier circuit809to which a received signal of the antenna circuit101is input, a power supply circuit820to which an output signal of the rectifier circuit is input, and an oscillation circuit806that is connected to an output of the power supply circuit820. In addition, the signal oscillating portion102has a modulation circuit814that modulates a signal from the signal processing portion103and outputs the modulated signal to the antenna circuit101.

The oscillating circuit806includes a ring oscillator in which a plurality of inverters are connected in a circular manner. In the rectifier circuit809, the output signal from the antenna circuit101is half-wave rectified. The direct-current signal by rectification is smoothed in the power supply circuit820, and a direct-current voltage corresponding to amplitude of the output signal from the antenna circuit101is generated. In the oscillating circuit806, a pulse signal is oscillated with a frequency corresponding to a voltage value of the direct-current voltage generated in the power supply circuit820, which is used as a power source. In such a manner, in the signal oscillating portion102, a pulse signal can be generated, which is oscillated with a frequency corresponding to electric field intensity (amplitude) of the output signal from the antenna circuit101.

The signal processing portion103has a demodulation circuit813, a logic circuit812, and a pulse counter815. After the output signal from the antenna circuit101is demodulated in the demodulation circuit813, the demodulated signal is input to the logic circuit812. The output signal from the logic circuit812is modulated in the modulation circuit814, and then the modulated signal is input to the antenna circuit101. The pulse counter815is a circuit for measuring pulses (number of oscillations) of a pulse signal that is oscillated in the oscillating circuit806.

The logic circuit812is for decoding the signal from the interrogator, which is input through the demodulation circuit813, and for making a decision as the RFID100.FIG. 11shows a block diagram of the logic circuit812. As shown inFIG. 11, the logic circuit812has a controller900. The controller900controls the pulse counter815or decodes a signal920to output a predetermined signal921to the modulation circuit814, based on the signal920demodulated in the demodulation circuit813.

It is to be noted that the logic circuit812of this embodiment mode can be provided with a CPU. The CPU may be provided so that an input and output thereof is connected to the controller900. When the CPU is provided, the program can be executed. As a result, the RFID100can be applied to various use application in addition to position detection.

Hereinafter, operation of a position detection system using a semiconductor device of this embodiment mode will be explained. Operation of the position detection system in this embodiment mode is similar to that of Embodiment Mode 1 (seeFIG. 3).

First, in order to search a distance between a first interrogator121and the RFID100, the first interrogator121transmits a signal F1to the RFID100. The signal F1includes an instruction for starting signal process in the signal processing portion103. When the RFID100receives the signal F1transmitted from the first interrogator in the antenna circuit101, the signal F1received by the antenna circuit101is input to the rectifier circuit809in the signal oscillating portion102and the demodulation circuit813in the signal processing portion103.

The signal F1is rectified in the rectifier circuit809to be smoothed in the power supply circuit820. As a result, a direct-current voltage corresponding to electric field intensity (amplitude) of the signal F1is generated. A pulse is oscillated in the oscillating circuit806using this direct-current voltage as a power source.

On the other hand, the demodulation circuit813demodulates the modulated signal F1, and the demodulated signal920is input to the controller900. The controller900controls the pulse counter815based on an instruction of the signal920, and the number of pulses of the pulse signal that is oscillated in the oscillating circuit806is counted by the pulse counter815until the number of the pulses reaches a certain value. In the controller900, the certain value that is counted by the pulse counter815can be changed. In this case, this certain value may be appropriately changed in accordance with a frequency of a transmit signal from the interrogator. When the logic circuit812is provided with the CPU, the certain value that is counted by the pulse counter815may be changed in the CPU or by the controller900.

The controller900generates a signal921for showing completion of the count when the count value reaches the certain value, and outputs the signal to the modulation circuit814. The signal921is modulated in the modulation circuit814and transmitted from the antenna circuit101as a response signal S1. When the first interrogator121receives the response signal S1, the first interrogator121detects a response time period T1from transmission of the signal F1to reception of the response signal S1. As the distance between the interrogator121and the antenna circuit101is closer, the electric field intensity of the signal F1becomes stronger when the signal is received by the antenna circuit101, and amplitude of the output signal of the antenna circuit becomes increased. Therefore, since a high direct-current voltage is generated in the power supply circuit820, a pulse signal is oscillated with a high frequency in the oscillating circuit806, and the count in the pulse counter815is completed in a short time period. In other words, the distance between the interrogator121and the antenna circuit reflects the count time period of the pulse counter815. Therefore, the distance can be measured based on the time period T1that is needed for response by the RFID100with respect to the signal F1of the interrogator121.

Similarly, in each case of a second interrogator122, a third interrogator123, and a fourth interrogator124, a response time period T2, a response time period T3, and a response time period T4are detected. As described in Embodiment Mode 1, the server140calculates distances between the RFID100and each interrogator121to124based on the data received from the interrogators121to124, and can detect a position (space coordinates) of the RFID based on calculated distances and position information (space coordinates, more specifically, a relative coordinate) of the interrogators121to124. A manager can find a position where the RFID100is located by access to the server140.

When the above structure of the present invention is employed, information on a position where the RFID is located in the space can be obtained as well as individual information such as ID included in the RFID. Further, the position information of the RFID is regularly detected, whereby information on following a track (also referred to as a flow line) of movement of equipment provided with the RFID can be obtained.

In this embodiment mode, a specific structure of the RFID100that is applied to the position detection system in Embodiment Mode 2 will be explained.

FIG. 12is a block diagram of an RFID100of this embodiment mode. This embodiment mode is a modification example of the RFID100of Embodiment Mode 4. In this embodiment mode, a signal processing portion103has a rectifier circuit829, a power supply circuit830provided with a regulator, and a reference clock generation circuit831, which is a different point from the RFID100of Embodiment Mode 4. A structure and operation of the signal oscillating portion102is similar to that of Embodiment Mode 4.

In the signal processing portion103, the rectifier circuit829half-waved rectifies an output signal from an antenna circuit101. A direct-current signal by rectification is smoothed in the power supply circuit830to generate a direct-current voltage. Since the power supply circuit830is provided with a regulator, power supply with a certain voltage value can be supplied, which does not depend on electric field intensity of the received signal in the antenna circuit101. The reference clock generation circuit831generates a reference clock that is to be a time standard, using the direct-current voltage as power source. In this embodiment mode, it is a feature in that the time period is measured using the reference clock in the logic circuit812.

FIG. 13shows a block diagram of the logic circuit812of this embodiment mode. The logic circuit812of this embodiment mode has not only a controller900but also a pulse counter910for counting pulses of a reference clock signal generated in the reference clock generation circuit831and a CPU for controlling the controller900. The pulse counter910is controlled by a signal of the controller900. In the CPU901, a distance is calculated based on the count value of the pulse counter815and the pulse counter910. Since the CPU901is provided, the program can be executed. Therefore, the RFID100can be applied to various use applications in addition to the position detection.

Hereinafter, operation of a position detection system to which a semiconductor device of this embodiment mode is applied will be explained. A structure of the position detection system is similar to that of Embodiment Mode 1 (seeFIG. 2), and operation thereof is similar to that of Embodiment Mode 2 (seeFIG. 6).

First, in order to search a distance between a first interrogator121and the RFID100, the first interrogator121transmits a signal F1to the RFID100. The signal F1includes an instruction for starting signal process in the signal processing portion103. When the RFID100receives the signal F1transmitted from the first interrogator by an antenna circuit101, the signal F1received by the antenna circuit101is input to the signal oscillating portion102and the signal processing portion103.

Operation of the signal oscillating portion102is similar to that of Embodiment Mode 5. In the oscillating circuit806, a pulse signal is generated, which is oscillated with a frequency corresponding to electric field intensity of the signal F1.

In the signal processing portion103, a direct-current voltage of a constant voltage is generated from the signal F1received by the antenna circuit101, by the rectifier circuit829and the power supply circuit830. A reference clock is generated in the reference clock generation circuit831by the direct-current voltage.

Furthermore, an output of the antenna circuit101is input to the demodulation circuit813, and the demodulation circuit813demodulates a modulated signal to output the signal to the controller900. When a signal920from the interrogator is received through the demodulation circuit813, the pulse of the oscillating circuit806is counted by the pulse counter815until the pulse reaches a certain value. Also, the controller900controls the pulse counter910to start the count of the reference clock. The count value of the pulse counter815corresponds to the number of oscillations of the pulse that is oscillated in the oscillating circuit806, and the count value of the pulse counter910corresponds to an oscillation time period thereof. It is to be noted that the value (a certain value) of the pulse counted in the pulse counter815can be changed as appropriate in the controller900and the CPU901. In this case, the certain value of the pulse counted by the pulse counter815may be changed in accordance with a frequency of the transmit signal of the interrogator.

Then, when the count value of the pulse counter815becomes a certain value, the controller900stops the count of the reference clock in the pulse counter910and search the count value of the pulse counter910. The count value of the pulse counter815and the count value of the pulse counter910are output to the CPU910through the controller900. The CPU901calculates a distance based on the two count values. The data of the distance calculated in the CPU901is output to the modulation circuit814as a signal921from the controller900. The modulation circuit814modulates a signal to output the signal to the antenna circuit101. The antenna circuit101transmits the modulated signal921as a response signal S1to the first interrogator121.

Similar operation is sequentially performed in each case of a second interrogator122, a third interrogator123, and a fourth interrogator124, and a signal S2, a signal S3, and a signal S4, which show distances, are received by the second interrogator122, the third interrogator123, and the fourth interrogator124, respectively. The interrogators121to124, each of which is located in the space130, transmit the data of the distances to the server140. The server140specifies a position (space coordinates) of the RFID100based on the data of the distances received from the interrogators121to124and position information (space coordinates) of the interrogators121to124. A manager can find where the RFID100is located by access to the server140.

In this embodiment mode, a more specific structure of the RFID200that is applied to the position detection system of Embodiment Mode 3 will be explained. It is to be noted that the similar structure to that of Embodiment Mode 3 is just explained briefly, and explanation of Embodiment Modes 3 to 5 is applied for the detail of the structure in this embodiment mode.

FIG. 14is a block diagram of an RFID200of this embodiment mode. As shown inFIG. 14, the RFID200mainly includes an antenna circuit101and a signal oscillating portion102similarly toFIG. 2. The portions with the same reference numeral inFIG. 14andFIG. 10denote the same components; therefore, explanation of Embodiment Mode 4 is applied for the explanation of the components in this embodiment mode.

The signal oscillating portion102has a rectifier circuit809to which a received signal from the antenna circuit101is input, a power supply circuit820to which an output signal from the rectifier circuit is input, an oscillating circuit806that is connected to an output of the power supply circuit820, and a modulation circuit814that modulates an input signal from the oscillating circuit806and outputs the modulated signal to the antenna circuit101. In this embodiment mode, an output of the oscillating circuit806is connected to the modulation circuit814, which is a different point from that of Embodiment Mode 4. In such a structure, a pulse signal that is oscillated in the oscillating circuit806can be modulated in the modulation circuit814to be transmitted from the antenna circuit101.

Operation for oscillating a pulse signal in the signal oscillating portion102is similar to that of Embodiment Mode 4. The oscillating circuit806includes a ring oscillator in which a plurality of inverters are connected in a circular manner. In the rectifier circuit809, an output signal from the antenna circuit101is half-wave rectified. A direct-current signal by rectification is smoothed in the power supply circuit820, and a direct-current voltage is generated, which corresponds to electric field intensity (amplitude) of an output signal from the antenna circuit101. With the use of the direct-current voltage generated in the power supply circuit820as power source, in the oscillating circuit806, a pulse signal is oscillated with a frequency depending on a voltage value of the direct-current voltage. As described above, in the signal oscillating portion102of this embodiment mode, a pulse signal can be generated, which is oscillated with a frequency corresponding to electric field intensity (amplitude) of the output signal from the antenna circuit101.

In this embodiment, a ring oscillator (a ring oscillating circuit) was formed using a thin film transistor, and then it was examined that a frequency of an oscillated signal was changed depending on an input voltage by the ring oscillator.

As shown inFIG. 15, a probe1002brought into contact with an evaluation element substrate1001provided with a ring oscillating circuit, and a signal is output to an oscilloscope connected to the probe1002. A frequency was measured with the oscilloscope while changing a power supply voltage of the ring oscillator. It is to be noted that the evaluation element substrate1001is provided with a 19-stage ring oscillator. A channel width of an n-type thin film transistor and a channel width of a p-type thin film transistor were set to be 20 μm and 10 μm, respectively. A channel length of both thin film transistors was set to be 4.5 μm, and a film thickness of a gate insulating film thereof was set to be 110 nm. The n-type thin film transistor had an LDD structure, and the p-type thin film transistor had a single drain structure.

As shown inFIG. 16, the evaluation element substrate1001has a size of 5-inch (12.7 centimeters) long×5-inch (12.7 centimeters) wide. A ring oscillator1003was manufactured in each of 10×10 sections, and the number of oscillations of the ring oscillators1003was measured in twelve measurement points1004that are shown by x (a cross mark) ofFIG. 16.

Moreover, relation of an input voltage and a frequency was simulated by a Smart SPICE model, of the above 19-stage ring oscillator which is formed using the thin film transistor.

The SPICE model (Simulation Program with Integrated Circuit Emphasis) is a model that reproduces response of an input and output of an element on SPICE-type circuit simulator that is normally used for circuit simulation. As a model for showing electric characteristics of a thin film transistor (hereinafter, referred to as a TFT), there are a various models which are approximated according to a physical phenomenon of which effect is considered. As such a model, there is a classical model called gradual channel approximation or depletion layer approximation, or a high-level and complicated model such as an RPI model. In the Smart Spice model, a LEVEL number is given for each model. A model having a larger LEVEL number tends to have higher physical precision and a larger number of parameters. However, parameter extraction based on a non-linear least square method is needed, and the calculation amount is definitely enormous. In this embodiment, LEVEL2was adopted, and the simulation was performed. In LEVEL2, the depletion layer approximation is improved, and the non-linear portions are not included so much; therefore, calculation can be conducted at high speed.

FIG. 17shows a measurement result of the number of oscillations of a ring oscillator by an oscilloscope and a simulation result by a Smart SPICE model. InFIG. 17, a horizontal axis indicates a power supply voltage of a ring oscillator and a vertical axis indicates the number of oscillations measured by the oscilloscope. A measurement result by the oscilloscope shows a solid line. The simulation result by the Smart SPICE model is plotted by triangular marks (a minimum value), square marks (a maximum value), circular marks (a median value).

As shown inFIG. 17, it is found that the number of oscillations of a ring oscillator is changed approximately in proportion to the power supply voltage V. From the measurement result of this embodiment, it was found that a ring oscillator (a ring oscillating circuit) can be applied to an oscillating circuit in a signal oscillating portion. Further, it was found that a ring oscillator formed using a thin film transistor can be applied. Therefore, if the entire RFIDs100and200of the present invention are manufactured using a thin film transistor by this embodiment, it was verified that a semiconductor device for wireless communication can be realized, which is capable of detecting a distance and a position.

Furthermore, measurement results at each measurement points1004ofFIG. 16are fitted within a range of the simulation result. It was found that operation simulation of a ring oscillator using a thin film transistor, with the use of the Smart SPICE model, is effective for means for estimating the measurement result.

In this embodiment, a manufacturing method of an RFID100and an RFID200will be explained. Each circuit included in the RFID100and200relating to the present invention can be manufactured using a thin film transistor. In this embodiment, a method for manufacturing a flexible RFID100and RFID200is shown, in which a circuit included in the RFID100or the RFID200is formed using a thin film transistor, and the circuit is transferred from a substrate used for manufacturing the thin film transistor to a flexible substrate.

FIG. 18Ashows an example of a top-view structure of the RFID100or200.FIG. 18Bshows an example of a cross-sectional structure.

As shown inFIG. 18A, in the RFID100or200, an antenna210provided in an antenna circuit101and an integrated circuit portion240are provided. It is to be noted that the integrated circuit portion240corresponds to a circuit other than the antenna210.

The RFIDs100and200of the present invention are a flexible device that can be bent and flexed. As shown inFIG. 18B, in the RFID100or200, a base insulating layer249and an element formation layer250formed over the base insulating layer249are sealed with a flexible substrate251and a flexible substrate252. The element formation layer250corresponds to the antenna210and the integrated circuit portion240. One of surfaces (corresponding to a surface on the upper side of a substrate in manufacture) of the element formation layer250is provided with a protect insulating layer253for protecting the antenna210.

A resin material is preferably used for the protect insulating layer253. This is because the resin material can be formed at a low temperature; in addition, the protect insulating layer253is formed for reducing concavity and convexity of the antenna210, and the resin material can be formed through drying and baking after application of a composition by a coating method. As the protect insulating layer253, an epoxy resin layer is used. The flexible substrate251is bonded to the base insulating layer249with an adhesive255. The flexible substrate252is bonded to the protect insulating layer253with an adhesive256.

As described below, the element formation layer250is provided with a diode, a TFT, a capacitor, a resistance element, a memory element, or the like, which compose the integrated circuit portion240, and an antenna210. Such elements are formed over the same substrate as described below.

FIG. 23Bshows a schematic cross-sectional structure of the element formation layer250. As part of a cross-section of the antenna circuit101, the signal oscillating portion102, and the signal processing portion103, a p-channel TFT (also referred to as a “Pch-TFT”)104and an n-channel TFT (also referred to as an “Nch-TFT”)105, which are included in an inverter or the like, a capacitor106, and a high withstand voltage-type Nch-TFT107provided in a power supply circuit are shown.

A substrate260is used when manufacturing the element formation layer250. In this embodiment, a glass substrate is used. Over the substrate260, a peeling layer261is formed, which is used for removing the substrate260from the element formation layer250. After the peeling layer261is formed over the substrate260, the base insulating layer249is formed, and then the element formation layer250including a TFT or the like is formed over the base insulating layer249. Hereinafter, a forming method of the element formation layer250will be explained with the use of cross-sectional views shown inFIGS. 19A to 23B.

A glass substrate is used for the substrate260. As shown inFIG. 19A, a peeling layer261is formed over the substrate260, which is made of three layers of a first layer261a, a second layer261b, and a third layer261c. As the first layer261a, a silicon oxynitride (SiOxNy, x>y) film is formed to have a thickness of 100 nm using SiH4and N2O for a material gas with the use of a parallel plate-type plasma CVD device. As the second layer261b, a tungsten film is formed to have a thickness of 30 nm with the use of a sputtering device. As the third layer261c, a silicon oxide film is formed to have a thickness of 200 nm with the use of a sputtering device.

When the third layer261c(silicon oxide) is formed, a surface of the second layer261b(tungsten) is oxidized, and tungsten oxide is formed at an interface thereof. Forming tungsten oxide makes it easy to separate the substrate260in transferring the element formation layer250to another substrate. The first layer261aholds adhesiveness of the second layer261bwhile manufacturing the element formation layer250.

For the second layer261b, in addition to tungsten (W), a metal film of molybdenum (Mo), titanium (Ti), tantalum (Ta), niobium (Nb), nickel (Ni), cobalt (Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), or iridium (Ir), or a metal compound thereof is preferable. The second layer261bcan have a thickness of greater than or equal to 20 nm and less than or equal to 40 nm.

As shown inFIG. 19B, a base insulating layer249having a two-layer structure is formed over the peeling layer261. As a first layer249a, a silicon oxynitride (SiOxNy, x<y) film is formed to have a thickness of 50 nm using SiH4, N2O, NH3, and H2for a material gas with the use of a plasma CVD device. The composition ratio of nitrogen in the first layer249ais made to be 40% or more, and a barrier property is enhanced. As the second layer249b, a silicon oxynitride (SiOxNy, x>y) film is formed to have a thickness of 100 nm using SiH4and N2O for a material gas with the use of a plasma CVD device. The composition ratio of nitrogen in the second layer249bis 0.5% or less.

As shown inFIG. 19C, a crystalline silicon film271is formed over the base insulating layer249. The crystalline silicon film271is formed by the following method. An amorphous silicon film having a thickness of 66 nm is formed using SiH4and H2for a material gas with the use of a plasma CVD device. The amorphous silicon film is irradiated with a laser to be crystallized, whereby the crystalline silicon film271is formed. An example of a laser irradiation method is shown. Irradiation of the second harmonic (a wavelength of 532 nm) of a YVO4laser of LD (laser diode) excitation is performed. A laser is not necessary to be limited to the second harmonic; however, the second harmonic is superior to third or higher harmonic in energy efficiency. At an irradiation surface, a shape of a beam is made to have a linear shape of which length is about 500 μm and of which width is about 20 μm by an optical system. Also, the beam is made to have intensity of 10 to 20 W. Further, the beam is moved at speed of 10 to 50 cm/sec relatively the substrate.

After the crystalline silicon film271is formed, a p-type impurity is added to the crystalline silicon film271. Here, diborane (B2H6) that is diluted with hydrogen is used for a doping gas in an ion doping device, and boron is added to the entire crystalline silicon film271. Since the crystalline silicon in which the amorphous silicon is crystallized has an unpaired bond, ideal intrinsic silicon is not obtained, but weak n-type conductivity is observed. Therefore, by addition of a minute amount of p-type impurity, there is an effect that the crystalline silicon film271is to be intrinsic silicon. This step may be performed as needed.

As shown inFIG. 19D, the crystalline silicon film271is divided for each element to form semiconductor layers273to276. In each of the semiconductor layers273to275, a channel formation region, a source region, and a drain region of a TFT are formed. The semiconductor layer276is included in an electrode of an MIS-type capacitor. An example of a method for processing the crystalline silicon film271is shown. A resist is formed over the crystalline silicon film271by a photolithography step. Then, using the resist as a mask, the crystalline silicon film271is etched using SF6and O2for an etchant with the use of a dry etching device, whereby the semiconductor layers273to276having a predetermined shape can be formed.

As shown inFIG. 20A, resists R31are formed by a photolithography step, and a minute amount of p-type impurity is added to the semiconductor layers274and275of an n-channel TFT. Here, diborane (B2H6) that is diluted with hydrogen is used for a doping gas, and the semiconductor layers274and275are doped with boron with the use of an ion doping device. After doping, the resists R31are removed.

A step ofFIG. 20Ais performed for the purpose that a threshold voltage of the n-channel TFT is not turned into a negative voltage. Boron may be added to the semiconductor layers274and275of the n-channel TFT at concentration of greater than or equal to 5×1015atoms/cm3and less than or equal to 1×1017atoms/cm3. The step ofFIG. 20Amay be performed as needed.

As shown inFIG. 20B, an insulating film277is formed over the entire substrate260. The insulating film277becomes a gate insulating film of a TFT or a dielectric of a capacitor. Here, a silicon oxynitride (SiOxNy, x>y) film is formed to have a thickness of 20 to 40 nm using SiH4and N2O for a material gas with the use of a plasma CVD device.

As shown inFIG. 20C, resists R32are formed by a photolithography step, and an n-type impurity is added to the semiconductor layer276of a capacitor. The semiconductor layer276is doped with phosphorus using phosphine (PH3) that is diluted with hydrogen for a doping gas, and an n-type impurity region279is formed. After a doping step, the resists R32are removed.

As shown inFIG. 20D, a conductive film281is formed over the insulating film277. The conductive film281is included in a gate electrode of a TFT. Here, the conductive film281has a multi-layer structure of two layers. As a first layer, a tantalum nitride (TaN) film having a thickness of 30 nm is formed, and as a second layer, a tungsten (W) film having a thickness of 370 nm is formed. The tantalum nitride film and the tungsten film are each formed with the use of a sputtering device.

A resist is formed over the conductive film281by a photolithography step, and the conductive film281is etched using an etching device to form first conductive films283to286as shown inFIG. 21Aover the semiconductor layers273to276. The first conductive films283to286become a gate electrode or a gate wiring of a TFT. In the n-channel TFT that is a high withstand voltage type, the first conductive film285is formed so that a gate width (a channel length) can be wider than that of other TFTs. The first conductive film286is included in one of electrodes of the capacitor.

The conductive film281is etched by a dry etching method. An ICP (Inductively Coupled Plasma) etching device method is used for an etching device. As etchant, first, a mixed gas of Cl2, SF6, and O2is used for etching tungsten. Next, an etchant introduced to a treatment chamber is changed to only a Cl2gas, and tantalum nitride is etched.

As shown inFIG. 21B, resists R33are formed by a photolithography step. An n-type impurity is added to the semiconductor layers274and275of the n-channel TFT. N-type low concentration impurity regions288and289are formed in the semiconductor layer274in a self-alignment manner, using the first conductive film284as a mask. N-type low concentration impurity regions290and291are formed in the semiconductor layer275in a self-alignment manner, using the first conductive film285as a mask. Phosphine (PH3) that is diluted with hydrogen is used for a doping gas, and phosphorus is added to the semiconductor layers274and275with the use of an ion doping device. The step ofFIG. 21Bis a step for forming an LDD region in the n-channel TFT. The n-type impurity is contained in the n-type low concentration impurity regions288and289within the range of greater than or equal to 1×1016atoms/cm3and less than or equal to 5×1018atoms/cm3.

As shown inFIG. 21C, resists R34are formed by a photolithography step, and a p-type impurity is added to the semiconductor layer273of a p-channel TFT. P-type high concentration impurity regions273aand273bare formed in the semiconductor layer273in a self-alignment manner, using the first conductive film283as a mask. Further, a region covered with the first conductive film283becomes a channel formation region273cthat is formed in a self-alignment manner. For addition to the p-type impurity region, diborane (B2H6) that is diluted with hydrogen is used for a doping gas. After doping, the resists R34are removed.

As shown inFIG. 21D, insulating layers293to296are formed around the first conductive films283to286. The insulating layers293to296are referred to as a sidewall or a side wall. First, a silicon oxynitride (SiOxNy, x>y) film is formed to have a thickness of 100 nm, using SiH4and N2O for a material gas with the use of a plasma CVD device. Next, a silicon oxide film is formed to have a thickness of 200 nm using SiH4and N2O for a material gas with the use of an LPCVD device. A resist is formed by a photolithography step. With the use of this resist, an upper side of the oxide silicon film is subjected to wet etching treatment using Buffered Hydrogen Fluoride. Then, the resist is removed, and a lower side of the silicon oxynitride film is subjected to dry etching treatment, whereby the insulating layers293to296are formed. Through a series of steps, the insulating film277made from silicon oxynitride is also etched, and the insulating film277is left at only a bottom of the first conductive films283to286and the insulating layers293to296.

As shown inFIG. 22A, resists R35are formed by a photolithography step. An n-type impurity is added to the semiconductor layers274and275of the n-channel TFT and the semiconductor layer276of the capacitor to form n-type concentration impurity regions. In the semiconductor layer274, an n-type impurity is further added to the n-type low concentration regions288and289using the first conductive film284and the insulating layer294as a mask to form n-type high concentration impurity regions274aand274bin a self-alignment manner. A region that is overlapped with the first conductive film284is set as a channel formation region274cin a self-alignment manner. Regions that are overlapped with the insulating layer294in the n-type low concentration impurity regions288and289are set as n-type low concentration impurity regions274eand274dwithout change.

Similarly to the semiconductor layer274, n-type high concentration impurity regions275aand275b, a channel formation region275c, and n-type low concentration impurity regions275eand275dare formed in the semiconductor layer275.

At this time, the n-type impurity region279is formed in the entire semiconductor layer276(seeFIG. 20C). An n-type impurity is further added to the n-type impurity region279using the first conductive film286and the insulating layer296as a mask to form n-type high concentration impurity regions276aand276bin a self-alignment manner. A region in the semiconductor layer276, which is overlapped with the first conductive film286and the insulating layer296are set as an n-type impurity region276c.

In an addition step of the n-type impurity, phosphine (PH3) that is diluted with hydrogen is used for a doping gas with the use of an ion doping device as described above. The n-type high concentration impurity regions274a,274b,275a, and275bof the n-channel TFT are doped with phosphorus at concentration of greater than or equal to 1×1020atoms/cm3and less than or equal to 2×1021atoms/cm3.

The resists R35are removed, and then a cap insulating film298is formed as shown inFIG. 22B). As the cap insulating film298, a silicon oxynitride (SiOxNy, x>y) film is formed to have a thickness of 50 nm with the use of a plasma CVD device. As for a material gas of the silicon oxynitride film, SiH4and N2O are used. After the cap insulating film298is formed, heating treatment is performed at 550° C. in an nitrogen atmosphere, and the n-type impurity and the p-type impurity added to the semiconductor layers273to276are activated.

As shown inFIG. 22C, a first interlayer insulating film300is formed. The first interlayer insulating film300has a two-layer structure. As a first insulating film, a silicon oxynitride (SiOxNy, x<y) film is formed to have a thickness of 100 nm using SiH4and N2O for a material gas with the use of a plasma CVD device. As a second insulating film, a silicon oxynitride (SiOxNy, x>y) film is formed to have a thickness of 600 nm using SiH4, N2O, NH3, and H2for a material gas with the use of a plasma CVD device.

The first interlayer insulating film300and the cap insulating film298are removed through a photolithography step and a dry etching step to form contact holes. A conductive film is formed over the first interlayer insulating film300. Here, the conductive film has a four-layer structure. From the bottom, a Ti film, a TiN film, a pure aluminum film, and a TiN film are sequentially stacked having a thickness of 60 nm, 40 nm, 500 nm, and 100 nm, respectively. Each film is formed with the use of a sputtering device. The conductive film is processed into a predetermined shape through a photolithography step and a dry etching step, whereby second conductive films303to314are formed.

In order to explain that the second conductive films and the first conductive films are connected to each other, the drawings show that the second conductive films and the first conductive films are connected to each other over the semiconductor layer. However, contact portions of the second conductive films and the first conductive films are avoided to be formed over the semiconductor layer usually.

The n-type high concentration impurity regions276aand276bare connected by the second conductive film312. Accordingly, an MIS-type capacitor having a stacked structure is formed, which includes the n-type impurity region276c, the insulating film277, and the first conductive film286. The second conductive film314is a terminal of the antenna circuit101, and an antenna210is connected thereto.

As shown inFIG. 23A, a second interlayer insulating film316is formed. A contact hole reaching the second conductive film314is formed in the second interlayer insulating film316. An example in which the second interlayer insulating film316is formed using photosensitive polyimide is shown. Polyimide is applied to have a thickness of 1.5 μm using a spinner. The polyimide is exposed through a photolithography step and developed, whereby polyimide provided with a contact hole is formed. After development, the polyimide is baked.

Furthermore, a conductive film is formed over the second interlayer insulating film316. This conductive film is processed into a predetermined shape through a photolithography step and an etching step to form a third conductive film320. As a conductive film forming the third conductive film320, a 100 nm thick Ti film is formed with the use of a sputtering device. The third conductive film320is a bump of an antenna for connecting the antenna210with the terminal (the second conductive film314) of the antenna circuit101.

As shown inFIG. 23B, a third interlayer insulating film321provided with an opening is formed. Here, the third interlayer insulating film321is formed using photosensitive polyamide by the similar method for forming the second interlayer insulating film316. The opening is formed in a region where the antenna210is formed.

As shown inFIG. 23B, the antenna210is formed. Aluminum is evaporated using a metal mask with the use of an evaporation device to form the antenna210having a predetermined shape is formed in the opening.

Through the steps shown inFIGS. 19A to 23B, the element formation layer250is formed over the substrate260. Next, as shown inFIG. 18B, a step for sealing the element formation layer250with the flexible substrate251and the flexible substrate252will be explained.

A protect insulating layer253for protecting the antenna210is formed. A photolithography step and an etching step are performed, or irradiation of laser light is performed, whereby an insulating film stacked over the element formation layer250are removed together with the protect insulating layer253, and an opening that reaches the peeling layer261is formed. Over the substrate260, a plurality of element formation layers250are formed. The opening is formed to divide the element formation layer250one by one.

Next, after a substrate for transfer is temporarily fixed over an upper surface of the protect insulating layer253, the substrate260is peeled. Since junction at an interface between the second layer261band the third layer261cof the peeling layer261is weak, peeling from an end portion of the opening proceeds by addition of force physically, and the substrate260can be peeled from the element formation layer250. The flexible substrate251is bonded with an adhesive255to the base insulating layer249from which the substrate260is peeled. Then, the substrate for transfer is removed. The flexible substrate252is bonded with an adhesive256to the protect insulating layer253. Heat treatment is performed while pressure is given from an outside of the flexible substrate251and the flexible substrate252, whereby the element formation layer250is sealed with the flexible substrate251and the flexible substrate252.

Although an example in which the antenna210is formed together with the integrated circuit portion240is shown in this embodiment, formation of the antenna210can be omitted. In this case, an antenna is provided for the flexible substrate, and attachment may be performed so that the antenna is electrically connected to the integrated circuit portion240of the element formation layer250.

Further, although an example in which the substrate used in manufacture is peeled from the element formation layer250is shown in this embodiment, the substrate used in manufacture can be left. In that case, the substrate may be thinned by grinding or polishing so that the substrate can be bent.

When a circuit is formed using a thin film transistor, the thin and lightweight RFIDs100and200capable of being bent can be manufactured.

In this embodiment, as an example of utilizing a semiconductor device and a position detection system relating to the present invention, a product management system and a management system of a moving object in an indoor or the like will be explained with reference toFIG. 24.

First, a case where a customer purchases a product in a store is explained with reference toFIG. 24. The semiconductor device of the present invention as well as an ID label or an ID tag incorporating information such as product-specific information or production history are attached to products displayed in the store.

A customer1201having a product1203provided with the semiconductor device of the present invention moves in the store surrounded by interrogators1202for position detection, which are placed in the store. As shown in the above embodiment modes, a manager can manage a flow line of the customer1201moving around display cabinets1204by detecting a position of the semiconductor device of the present invention by the interrogators1202placed in the store. It is preferable to record and manage the flow line of the customer because marketing such as a location for providing a product and product management can be performed efficiently.

As shown in this embodiment, a flow line of the product in the store is observed in real time by a plurality of interrogators placed in the store, so that theft can be prevented without the customer going through a gate of an interrogator for preventing theft from the display cabinets. Further, since the flow line of the product can be observed in real time, the manager can forecast information on move of a thief in advance with use of a computer or the like, and take measures such as blocking the passage, and thus, theft of the product can be prevented from occurring. Accordingly, the manager can capture the thief without directly catching the thief, whereby the thief can be easily caught.

In this embodiment, the manager can manage position information of the product in real time without providing a gate-shaped interrogator at a doorway and without the customer noticing an interrogator, if the interrogator is placed in a part of tiles of a floor, a part of pillars, a ceiling, or the like. By the position detection system using the semiconductor device of the present invention, a flow line of the product in a small area, which is difficult for a GPS or the like to trace, can be easily traced. Further, the semiconductor device of the present invention can cover a range of several m when an antenna for the UHF band is used. Further, it is preferable that the semiconductor device of the present invention have an anti-collision function because a plurality of moving objects can also be managed.

A position detection system using the semiconductor device of the present invention is effective in preventing theft by using together with a surveillance camera or the like. The manager can perform management from a remote place more certainly and easily.

In addition, it is preferable that an accurate flow line of a moving object provided with the RFID can be observed easily even in a large space by increase in the number of the plurality of interrogators in the present invention.

In this embodiment, as an example of utilizing the semiconductor device and the position detection system relating to the present invention, a management system of a moving object in a passage or the like will be explained with reference toFIG. 25.

First, an example where a manager manages a flow line of the moving object in the passage is explained with reference toFIG. 25. The moving object is provided with the semiconductor device of the present invention as well as an ID label or an ID tag incorporating specific information.

Hereinafter, an example of a management system of a moving object in a passage or the like will be explained with reference toFIG. 25.

A moving object1301having a semiconductor device1303of the present invention moves in a space surrounded by interrogators1302for position detection, which are placed in a passage. As a matter of course, a mode is similar to this embodiment, in which the moving object1301having equipment provided with the semiconductor device1303of the present invention moves. As shown in the above embodiment modes, a manager can manage flow line of the semiconductor device1303on the passage separated by obstructions1304by detecting a position of the semiconductor device1303of the present invention using the interrogators1302placed in the passage. Further, speed and a tendency of the moving object can be observed. InFIG. 25, a case where the moving object1301reaches a destination1306through a path shown by slanted lines1305is shown, and for example, move of the moving object following another path without following the path shown in the slanted lines can be easily observed in real time. The flow line of the moving object can be managed and recorded. Therefore, it is preferable that marketing such as product management can be performed efficiently when the moving object is a customer having a product provided with the semiconductor device. In the present invention, when an RFID is provided for an object person among an unspecified number of moving objects, move of the only moving object can be managed. Thus, when the semiconductor device is attached to a small child, move of the child in a crowd can be managed successively.

InFIG. 25, as an object of the moving object1301to which the RFID is attached, a criminal in prison, a person in need of care in a nursing home, and the like are considered. It is particularly effective that a flow line of a criminal in prison or a person in need of care in a nursing home can be managed, for example, when the RFID of the present invention is attached to the criminal in prison or the person in need of care in the nursing home, and the position detection system of the present invention is used for management. By the position detection system using the semiconductor device of the present invention, with respect to the criminal in prison, suspicious movement can be observed in advance. Further, in the nursing home, it is preferable to observe a wandering tendency for the person in need of care and to take appropriate measures.

As a management method for a moving object in an indoor space such as a passage, there are a method where cameras are located and a method where interrogators are provided at regular intervals to detect a position in one moving object by one interrogator for each other; however, it is difficult to follow a flow line in real time and to observe tendency of the flow line. A position of an RFID can be regularly detected by a position detection system of the present invention, in which a position of one moving object is detected by the plurality of the interrogators with the use of the semiconductor device of the present invention and a plurality of interrogators. Therefore, move of a moving object can be managed and recorded successively in real time. It is preferable that the manager can observe tendency of the flow line by recording the flow line, and storing and analyzing the records; and can redesign layout of a room in which the flow line is observed.

This application is based on Japanese Patent Application serial no. 2006-141841 filed in Japan Patent Office on May 22 in 2006, the entire contents of which are hereby incorporated by reference.

EXPLANATION OF REFERENCE