JP2000020665A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which is freely deformable, can be attached to merchandise of an arbitrary shape, is low in unit cost, does not require recovery after use and can prevent the erroneous operation of a circuit. SOLUTION: An LSI chip 12 formed into a thin film silicon and an antenna 13, which is formed of a vapor-deposited metal film and is connected to the LSI chip 12, are formed on a flexible film 11. When the antenna 13 receives electromagnetic waves, an electromotive force is generated by an electromagnetic induction, then the LSI chip 12 operates by being supplied with the force, and transmits the data held inside by way of the antenna 13. When the LSI chip 12 has not only a transmission circuit but also a reception circuit and a signal processing circuit, it is possible to receive a signal and process it by way of the antenna 13 and to transmits the signal in accordance with the result. Thus, the LSI chip 12, consisting of the film silicon and the antenna 13 consisting of the vapor deposited metal film, are formed on the flexible film 11, the device can be freely deformed and transformation is performed freely, and the film 11 can be affixed on a attached to merchandise of various shapes, and also made low in cost and reduced in power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, for example, a device suitable for use as a tag for managing goods in a distribution system.

[0002]

2. Description of the Related Art In recent years, with the progress of communication technology and the development of logistics-related business, a so-called wireless tag having a communication function of wirelessly transmitting information is attached to a product to perform sales management and inventory management of the product. Has been proposed by the following document 1.

Reference 1: Monthly Semiconductor World,
March 1998, pp. 22-33, “Fe to Electronic Commerce”
RAM will start in 1999, and fashion clothing will have a portable terminal. "FIG. 16 shows the appearance of a conventional wireless tag. LSI in which a circuit having a communication function is integrated in a resin case 141
(Large Scale Integrated circuit) chip 142,
An antenna 145 connected to the LSI chip 142;
LCD (Li) that displays the contents processed by SI chip 142
A display device 143 and a solar cell 144 for supplying power to the LSI chip 142 are mounted.

[0004] For example, a signal is sent from a register in a retail store to inquire about attribute data relating to the classification, name, selling price and the like of a product to which the wireless tag is attached,
The data is received by the LSI chip 142 via the antenna 145. The LSI chip 142 has a circuit formed on a bulk silicon substrate, displays attribute data of a product stored in a built-in memory on an LCD display device 143, and further registers a signal indicating the attribute data via an antenna 145 in a register. Send to.

FIG. 17 shows a schematic configuration of a circuit built in the LSI chip 142. This circuit uses RF (Radio Fr
equency) a signal modulation / demodulation unit 161 and a signal / data processing unit 152 are provided. The RF signal modulation / demodulation unit 161 performs processing such as modulation / demodulation necessary for transmitting / receiving a signal via the antenna 145. The modulation circuit 162 and the demodulation circuit 1
63, an antenna driver 164, and an R / F amplifier 165. The signal / data processing unit 152 performs processing necessary for displaying and transmitting built-in data based on the received signal, and a central processing unit (MPU) 155,
It has a ROM / RAM unit 154, an interface (I / F) unit 153, and an input / output (I / O) unit 156.

As described above, the conventional wireless tag includes the LSI chip 142 formed on the bulk silicon substrate and the LSI 1
A solar cell 144 for driving the LCD 42 and an LCD display 143 for an operator to visually check the processing status of the wireless tag.

However, since this wireless tag has many functions as described above, its size is 8.5 cm ×
It was quite large, 5.75 cm.

Also, an LSI formed on bulk silicon
A rigid resin case 141 has been used as a case for mounting the chip 142 and the like. For this reason, the wireless tag could be attached only to a relatively flat product with a relatively flat surface.

Further, the price per unit is as high as about 1,000 yen, and the products to which it is attached are limited to those of about 10,000 yen or more. Furthermore, there is a problem that the wireless tag must be collected after the sale because of its high price.

[0010] Among the above-mentioned problems of the large size and the high price of the wireless tag, one that slightly solves the problem of the size and the price is proposed by the following document 2 and shown in FIG. Wireless tag.

Reference 2: TRIGGER, July 1997
Monthly Issue, pages 32 to 33, "Small Non-Contact Label Achieving 100 Yen or Less per Sheet" This wireless tag does not include a display unit and a power supply by narrowing down its functions to wireless. In order to further reduce costs, this tag consists of a bare chip 172 of about 3 mm square formed on a bulk silicon substrate and an antenna 173.
Are directly mounted on the transparent resin 171, and transmission and reception are performed at a frequency of 2 GHz band in order to further reduce the size of the antenna 173.

According to this wireless tag, 6 cm × 1 cm ×
Can be downsized to the size of 0.1mm and the price is 1
It can be reduced to about 100 yen per piece.

However, this wireless tag is also fixed in shape, and can only be attached to a relatively flat product with a relatively flat surface. Also, since the price of the tag is still high, it was necessary to collect the tag. Furthermore, since it does not have a built-in battery, its function as a circuit is greatly limited as compared with the wireless tag shown in Document 1.

In the wireless tag disclosed in Document 2,
In order to reduce costs, a signal / data processing unit for processing digital signals and an RF modulation / demodulation unit for processing analog signals must be mounted on a bulk silicon substrate. As a result, noise generated by the signal / data processing unit affects the RF modulation / demodulation unit, which may cause a malfunction.

[0015]

As described above, the conventional wireless tag has a fixed shape, and is inflexible. Therefore, the number of products that can be attached is limited. Further, there is a problem that analog circuits malfunction due to noise generated by digital circuits mixedly mounted on the chip.

The present invention has been made in view of the above circumstances, and is freely deformable and can be attached to a product of any shape.
It is an object of the present invention to provide a semiconductor device whose unit price is sufficiently reduced, does not need to be collected after use, and can prevent malfunction of a circuit.

[0017]

According to the present invention, there is provided a semiconductor device comprising:
A flexible film, formed on the flexible film,
An antenna that receives an electromagnetic wave and is formed on thin-film silicon mounted on the flexible film, receives the electromagnetic wave, supplies power generated by electromagnetic induction to the antenna, operates and holds the antenna inside And a circuit for transmitting data via the antenna.

Here, the circuit receives the electromagnetic wave received by the antenna as a signal, performs predetermined processing, and, based on the result of the processing, stores the data held therein via the antenna. It may be transmitted.

Further, the circuit may further include a rewritable memory for storing the data.

The circuit has a plurality of transistors formed in the thin film silicon such that the bodies are electrically separated from each other. The other transistors are so arranged that the body potential in each transistor is equal to the gate potential. May be controlled independently of the body potential of the transistor.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the appearance of the semiconductor device according to the first embodiment of the present invention. An LSI chip 12 and an antenna 13 are mounted on the surface of a flexible film 11.

The flexible film 11 is made of a flexible material such as resin, rubber, and paper, and has a flat sheet shape. For example, a barcode seal may be used as the film 11.

The LSI chip 12 has an LSI formed not on a bulk silicon substrate but on thin film silicon, and has a size of, for example, about 2 mm square.

The antenna 13 is formed by depositing a metal film on the surface of the flexible film 11 and
Is electrically connected to Further, in the present apparatus, by using a signal having a frequency in the GHz band as a signal for transmission and reception, the length of the antenna 13 is reduced as much as possible, for example, to about 7 cm in total length. The rectangular flexible film 11 is arranged along the short side so that the antenna 13 is hardly deformed.

This apparatus does not have a power source such as a battery or an image display device such as an LCD. The LSI chip 12 operates by receiving an electromagnetic wave from the antenna 13 and supplying power generated by electromagnetic induction.

As described above, in the semiconductor device according to the present embodiment, since the LSI chip 12 and the antenna 13 of about 2 mm square are formed on the flexible film 11, the entire device is flexible and can be freely deformed. It is possible. Further, by applying an adhesive or attaching an adhesive sheet to the back surface side of the flexible film 11, the semiconductor device can be freely attached to various kinds of devices. For example, FIG.
The semiconductor device according to the present embodiment is attached to products of various shapes such as an apple 41 and a banana 43 shown in FIG.
2, 44 can be attached.

FIG. 2 shows a block configuration of a circuit mounted on the LSI chip 12. This circuit includes an RF signal modulation / demodulation unit 31 and a signal / data processing unit 21. RF
The signal modulation / demodulation unit 31 performs processing such as modulation / demodulation necessary for transmitting / receiving a signal via the antenna 13, and includes a modulation circuit 32, a demodulation circuit 33, an antenna driver 34,
An F amplifier 35 is provided. The signal / data processing unit 21 stores the built-in data based on the
Performs the processing required for transmission via
U24, ROM / RAM unit 23, I / F unit 22, I / O
It has a part 25.

As described above, in the present embodiment, the antenna 1
3, a signal is received by the RF signal modulation / demodulation unit 31 via
Based on the received signal, the signal / data processing unit 21 transmits data such as attribute data stored in the ROM / RAM unit 23 from the RF signal modulation / demodulation unit 31 via the antenna 13.

However, it is not always necessary to provide such a circuit configuration. For example, the reception function, built-in memory,
The MPU need not be provided. In this case, the electromagnetic wave is received by the antenna 13 and an electromotive force is generated by electromagnetic induction to start the operation of the circuit, whereby predetermined data is automatically transmitted. In this case, data held in a firmware state can be used instead of the built-in memory.

Next, a method of manufacturing the semiconductor device according to the present embodiment will be described with reference to FIGS. FIG.
As shown in FIG. 1, SOI (Silicon On Insulato) in which a buried oxide film 52 is formed on a surface of a silicon substrate 51 as thin film silicon for forming an LSI chip.
r) Use a substrate. This can reduce cost and power consumption, and furthermore, the buried oxide film 52
This is because it is easy to form the thin film silicon 53 thereon. Here, for example, the thickness of the silicon substrate 51 is about 500
μm, the buried oxide film 52 may have a thickness of 0.1 to 0.4 μm, and the thin film silicon 53 may have a thickness of 0.1 to 1.0 μm.

Using such a substrate, an LSI element and an antenna 13 are formed through the steps shown in FIGS. As shown in FIG. 5, an isolation layer 54 is formed on the periphery of the thin film silicon 53 by using, for example, the LOCOS method. The diffusion layers 55 and 56 are formed by implantation and diffusion of impurities. A gate electrode 5 is formed on the surface of the thin film silicon 53 on which the N @ + -type diffusion layers 55 and 56 are formed via a gate insulating film.
8 is formed. Further, an insulating film 57 is formed in a region where the gate electrode 58 is not formed. Further, a metal such as aluminum is vapor-deposited on the insulating film 57 by sputtering in a state where the N + type diffusion layer 56 is in contact with the N + type diffusion layer 56 to form a metal wiring 59 for antenna connection.

Then, as shown in FIG.
7 and substrate 51 on which metal wiring 59 for antenna connection is formed
The adhesive 60 is applied on the surface of. This is performed as preparation for separating the thin silicon 53 and the buried oxide film 52 from the silicon substrate 51 thereunder.

Next, as shown in FIG.
The film 61 is placed on the surface of the silicon substrate 51 in a state where the film 61 is interposed. As shown in FIG.
The silicon substrate 52 is turned upside down so that
Is separated by polishing.

The LSI chip 12 thus obtained
Is fixed on the surface of the flexible film 11 using an adhesive or the like as shown in FIG. Furthermore, the antenna connection metal wiring 59 exposed on the side surface of the LSI chip 12
The antenna 13 is formed by vapor-depositing a metal such as aluminum on the flexible film 11 by sputtering so that the antenna 13 is electrically connected to the antenna.

Here, the structure and the manufacturing process of each transistor in the LSI chip 12 using thin-film silicon in this embodiment and the LSI chip 142 using a bulk silicon substrate in a conventional wireless tag are compared. .

LSI using conventional bulk silicon substrate
In the chip 142, a MOS transistor whose vertical sectional structure is shown in FIG. 10 and a vertical bipolar transistor shown in FIG. 12 are formed by using a so-called bulk BiCMOS technology. The MOS transistor includes, on the surface of a bulk silicon substrate 81, impurity diffusion layers 82 and 83 as sources and drains, and a gate electrode 84. The bipolar transistor has a base 105 and an emitter 10 in a state where elements are separated by a shallow trench 04 and deep trenches 102 and 103 on a surface portion of a bulk silicon substrate 81.
6. The collector 107 is formed.

The MOS transistor formed on the thin film silicon in the present embodiment has a structure as shown in FIG. 11, and the lateral bipolar transistor has a structure as shown in FIG. MOS transistors
The thin film silicon 53 is located on the lower surface side of the buried oxide film 52. N + type diffusion layers 55 and 56 are formed on the thin film silicon 53 as a source and a drain, and a gate electrode 58 is formed via a gate oxide film. I have.

In the lateral bipolar transistor, an N + type diffusion layer 112 as a collector, a P type diffusion layer 113 as a base, and an N + type diffusion layer 114 as an emitter are formed in the thin film transistor 53 on the lower surface side of the buried oxide film 52. The electrode 1 is formed on each of the diffusion layers 112 to 114.
15 to 117 are formed.

In this embodiment, since the transistor is formed in thin silicon without using bulk silicon, the parasitic capacitance is small, which can contribute to high speed and low power consumption.

Further, as is apparent from FIG. 12, the vertical bipolar transistor formed on bulk silicon in the conventional wireless tag has a problem that the structure is extremely complicated, requires many steps, and is expensive to manufacture. is there.

On the other hand, the lateral bipolar transistor used in the present embodiment has a simple structure as shown in FIG. 13, and the number of manufacturing steps is smaller than that of the vertical bipolar transistor. For example, when the design rule of the LSI is 0.25 to 0.35 μm, the lateral bipolar transistor is about 520 and the vertical bipolar transistor is about 370. Therefore, according to the present embodiment, the number of steps can be reduced to about 2/3. When the number of steps is reduced, the yield is also improved. Therefore, the total cost of the LSI chip can be reduced to about ２〜 to よ り compared with the related art.

In consideration of the cost of the substrate on which the LSI chip is mounted, the flexible film according to the present embodiment is about 1/2 of the transparent resin used in the conventional apparatus.
Can be reduced. Assuming that the conventional wireless tag shown in FIG. 18 costs about 100 yen, the present embodiment costs about 30 yen, which can be reduced to about 1/3. Therefore, the device according to the present embodiment can be used as a wireless tag even for a low-priced product with a unit price of about 100 yen, for example, and collection is not required, so that the applicable market is greatly expanded.

Further, according to the present embodiment, an effect of reducing power consumption as compared with the conventional wireless tag can be obtained. FIG.
As shown in the figure, the space between the bodies 122 and 123 in each transistor formed on the thin film silicon 53 is
By being configured to be electrically isolated by the insulating film 124 connected to the buried oxide film 52, each body 12
2 and 123 can be controlled independently. Thus, for each transistor, the gate 58a and the body 122 can be electrically connected, and similarly, the gate 58b and the body 123 can be connected and operated.

For example, when 0.5 V is used as the power supply voltage, the body voltage of the transistor is 0.5 V, which is the same as the gate voltage, and the threshold voltage is almost 0 V, as shown in FIG. Therefore, high-speed operation can be performed even with a low power supply voltage of 0.5 V. When the transistor is off, both the body potential and the gate potential are 0.
V, and the threshold voltage increases to about 0.2 V, so that the off-state leakage current can be reduced. The conventional wireless tag selects 1.5 to 3.0 V as the power supply voltage. However, according to the present embodiment, it is possible to reduce the power consumption by one to two digits for the reasons described above.

By the way, in this embodiment, a power source such as a solar cell is not built in for cost reduction. Therefore, when data is transmitted using an internal memory such as the ROM / RAM section shown in FIG. 2, a nonvolatile storage device must be used. For example, a Ferro RAM operable at a lower power supply voltage may be used. Here, the Ferro RAM uses a ferroelectric material to hold data. The ferroelectric portion is formed above the transistor after the transistor is formed. Therefore, it can be formed even when the silicon substrate is finally deleted as in this embodiment.

It is desirable to minimize the capacity of the internal memory, such as 64 to 1 Kbit, in order to reduce the area of the LSI chip 12.

Further, by using a rewritable memory as the internal memory, it is possible to improve the security when a cryptographic system for preventing data reading by a third party is introduced. As a memory in this case, an E ² PROM can be used in addition to the above-described Ferro RAM.

Conventional wireless tags often use a standard DES (Data Encryption Standard) as an encryption system. In this embodiment, such a system may be used. However, in order to further enhance security, a rewritable memory is used to periodically perform RF communication.
The encryption of the U part may be reconstructed.

In the conventional wireless tag, since the analog circuit and the digital circuit are mixedly mounted on the bulk silicon substrate as described above, the analog circuit may malfunction due to noise generated by the digital circuit. On the other hand, in this embodiment mode, a circuit is formed using thin film silicon without using a bulk silicon substrate, so that malfunction due to noise can be prevented.

[0051]

As described above, according to the present invention, since the antenna and the circuit are formed on the flexible film,
It is deformable and can be attached to products of any shape, and because of its reduced cost, it does not need to be collected after use, and the applicable market is expanded.In addition, the circuit is driven by electromagnetic waves received by the antenna By doing so, power consumption can be reduced. Further, since the circuit is formed of thin film silicon, unlike the case where a bulk silicon substrate is used, the circuit is prevented from malfunctioning due to noise generated inside.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a layout diagram showing an internal configuration of an LSI chip included in the semiconductor device.

FIG. 3 is an explanatory diagram showing a state where the semiconductor device is attached to a product.

FIG. 4 is a longitudinal sectional view showing a section of thin-film silicon forming an LSI chip in the semiconductor device.

FIG. 5 is a longitudinal sectional view showing a step in the case of forming an element using the thin film silicon.

FIG. 6 is a longitudinal sectional view showing a step following FIG. 5 in the case where an element is formed using the thin film silicon.

FIG. 7 is a longitudinal sectional view showing a step following FIG. 6 in the case where an element is formed using the same thin film silicon.

FIG. 8 is a longitudinal sectional view showing a step following FIG. 7 in the case of forming an element using the thin film silicon.

FIG. 9 is a longitudinal sectional view showing a section when the LSI chip shown in FIG. 8 is mounted on a film to form an antenna.

FIG. 10 is a longitudinal sectional view showing a section of a MOS transistor formed on a bulk silicon substrate used in a conventional wireless tag.

FIG. 11 is a longitudinal sectional view showing a section of a MOS transistor formed on thin film silicon used in an embodiment of the present invention.

FIG. 12 is a longitudinal sectional view showing a cross section of a bipolar transistor formed on a bulk silicon substrate used in a conventional wireless tag.

FIG. 13 is a longitudinal sectional view showing a section of a bipolar transistor formed on thin film silicon used in the embodiment of the present invention.

FIG. 14 is a longitudinal sectional view showing a section of a plurality of MOS transistors formed on thin film silicon and separated from each other used in the embodiment.

15 is a graph showing a relationship between a threshold voltage and a body voltage of the MOS transistor shown in FIG.

FIG. 16 is a perspective view showing the appearance of a conventional wireless tag.

FIG. 17 is a layout diagram showing an internal configuration of an LSI chip included in the wireless tag.

FIG. 18 is a perspective view showing the appearance of another conventional wireless tag.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Flexible film 12 LSI chip 13 Antenna 21 Signal / data processing part 22 I / F part 23 ROM / RAM part 24 MPU 25 I / O part 31 RF modulation / demodulation part 32 Modulation circuit 33 Demodulation circuit 34 Antenna driver 35 RF amplifier 41 Apple 43 banana 42,44 wireless tag 51 silicon substrate 52 buried oxide film 53 thin silicon 54 separation layer 55,56,112 N + diffusion layer 57,124 insulating film 58,58a, 58b gate electrode 59 antenna connection metal wiring 60 bonding Agent 61 Film 115-117 Electrode 122, 123 Body

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Kameyama 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center Co., Ltd. Kuko Toshiba 1 F-term in Toshiba R & D Center (reference)

Claims (4)

[Claims] A flexible film; an antenna formed on the flexible film for receiving an electromagnetic wave; and a thin film silicon formed on the flexible film, wherein the electromagnetic wave is applied to the antenna. And a circuit that operates by being supplied with power generated by electromagnetic induction and that transmits data held therein via the antenna. 2. The circuit receives the electromagnetic wave received by the antenna as a signal, performs predetermined processing, and, based on a result of the processing, stores the data held therein via the antenna. The semiconductor device according to claim 1, wherein the transmission is performed. 3. The semiconductor device according to claim 1, wherein said circuit further comprises a rewritable memory for storing said data. 4. The circuit has a plurality of transistors formed in the thin film silicon such that bodies are electrically separated from each other, and a body potential of each transistor is equal to a gate potential. 4. The semiconductor device according to claim 1, wherein the semiconductor device is controlled independently of a body potential of another transistor.