Patent Application
20060055014
1. Field of the Invention
The present invention relates to a wireless chip and a manufacturing method of the wireless chip.
2. Description of the Related Art
In recent years, a wireless chip for transmitting and receiving data has been actively developed and such a wireless chip is called, e.g., an IC tag, an ID tag, an RF (Radio Frequency) tag, a wireless tag, an electronic tag, a wireless processor, a wireless memory. For a transmission system of a wireless chip, there are three systems of an electromagnetic coupling system, an electromagnetic induction system and a radio wave system. The electromagnetic coupling system employs a mutual induction of electric coils by alternating magnetic field, and employs a frequency of 13.56 MHz. The electromagnetic induction system employs two frequencies with classifying broadly. One is 135 kHz or less and the other is 13.56 MHz. Communication having a range of maximum 1 m with a wireless chip can be conducted by the electromagnetic induction system depending on a shape and a size of a reader/writer. The radio wave method employs UHF and a frequency band of 2.45 GHz. The radio wave system has the greatest feature that a communication range is long. Such a wireless chip is used with the chip fixed to a product, e.g., attached on a surface of the product, or embedded in the product. For example, the chip is embedded in an organic resin constituting a package, or attached on the surface of the package.
However, it is complicated to fix the wireless chips that have been used recently to a product, e.g., to embed it in the product or attach it on the product. It is an object of the present invention to provide a new type wireless chip that can be used without being attached to a product. Specifically, it is another object to add a new function to a wireless chip by sealing. Further, it is another object of the present invention to manufacture a wireless chip by an easy method.
One feature of a wireless chip according to the present invention is to have a structure in which a thin film integrated circuit is sealed with a film. The wireless chip of the present invention can be obtained by sandwiching a thin film integrated circuit with two films and heating the parts of the films around the thin film integrated circuit to be melted so as to seal the thin film integrated circuit. In case that a plurality of thin film integrated circuits are sandwiched between two films, wireless chips according to the present invention can be obtained by heating and melting parts of the films between neighboring thin film integrated circuits so as to seal the plurality of the thin film integrated circuits.
One feature of a wireless chip according to the present invention is that the films sealing the thin film integrated circuit makes a hollow structure. In other words, a space is provided between the films and the thin film integrated circuit when the thin film integrated circuit is sealed.
By employing the hollow structure, an additional function can be added, which is not obtained in the case of not using the hollow structure.
A wireless chip with the hollow structure according to the present invention has a feature that an inert gas, an inert liquid, or an inert gel is encapsulated in the hollow portion. “To encapsulate an inert gas, an inert liquid, or an inert gel in a hollow portion” includes a case of filling a hollow portion with an inert gas, an inert liquid, an inert gel or the like.
One feature of a wireless chip according to the present invention is that a gas promoting degradation of a thin film integrated circuit (e.g., a gas including water) is encapsulated in a hollow portion in a wireless chip having the hollow structure.
In addition, in a wireless chip of the present invention, when the films sealing the thin film integrated circuit are broken, air or liquid outside the films enters the inside of the films sealing the thin film integrated circuit and is in contact with the thin film integrated circuit. In this case, degradation speed of the thin film integrated circuit is increased (the degradation speed is made greatly different in the case where the thin film integrated circuit is not exposed to the air outside the films sealing the thin film integrated circuit and the case where the thin film integrated circuit is exposed to the air outside the films sealing the thin film integrated circuit), which is one feature of the wireless chip according to the present invention. For example, one feature of the present invention is that a thin film integrated circuit is easy to deteriorate when it is exposed to the air.
In order that a thin film integrated circuit deteriorates easily when it is exposed to the air, for example, there is provided a method of shifting electric characteristics of a thin film transistor included in the thin film integrated circuit near an operation limit. In this manner, the thin film transistor stops operating due to an external factor. Here, the external factor means to break the films sealing the thin film integrated circuit. In order to shift the electric characteristics, a method of doping a channel forming region of a thin film transistor with an impurity element such as boron or phosphorus, or the like may be employed to obtain desired electric characteristics.
The method of shifting electric characteristics of a thin film transistor included in the thin film integrated circuit near an operation limit is described below with reference to
In addition, degradation speed of the thin film integrated circuit can be made faster by exposing the thin film integrated circuit sealed by the films to an external atmosphere of the films, as compared with a case where the thin film integrated circuit is sealed with the films. For example, a substance promoting degradation of a thin film transistor included in a thin film integrated circuit may be included in the external atmosphere outside the films sealing the thin film integrated circuit. As the substance promoting degradation of a thin film transistor, for example, Na, K, ammonia, monoethanolamine, H2O, SOx, NOx or the like are given.
When a thin film transistor is exposed to an atmosphere containing the substance promoting degradation at a certain concentration, an electric characteristic of the thin film transistor is shifted as shown in
In general, if thin film transistors are formed to have the same electric characteristics, there could be slight variation in electric characteristics of the respective thin film transistors as shown by 2900, 2901 and 2902 in
When the thin film transistor has the electric characteristic 2900, the electric characteristic 2900 may be shifted beyond the electric characteristic 2903 as the operation limit electric characteristic, so that the thin film transistor cannot operate at the time of Vg=Von, either. Herein, the shift amount of from the electric characteristic 2900 to the electric characteristic 2903 that is an operation limit electric characteristic is X+Y. Therefore, the electric characteristic may be shifted so that the shift amount thereof can be larger than X+Y in order to obtain a state in which the thin film transistor having the electric characteristic 2900 does not operate.
Then, the concentration of a substance promoting degradation included in the atmosphere outside films sealing the thin film integrated circuit is set so that the shift amount A in which an electric characteristic of a thin film transistor is shifted by being exposed to the atmosphere containing the substance promoting degradation of the thin film transistor is larger than X+Y, in which X is a range of variations on electric characteristics among the thin film transistors and Y is a shift amount of the operation limit electric characteristic. Then, by breaking the films sealing the thin film integrated circuit, an atmosphere outside the films sealing the thin film integrated circuit enters the inside of the films sealing the thin film integrated circuit. Thus, the thin film integrated circuit is exposed to the atmosphere containing the substance promoting degradation of the thin film transistor; therefore, the electric characteristic of the thin film transistor included in the thin film integrated circuit is shifted to the state as shown in
One feature of a manufacturing method of wireless chips according to the present invention is that a plurality of thin film integrated circuits, which are arranged regularly, are sandwiched with first and second films, and the parts of the first and second films around each of the plurality of thin film integrated circuits are melted by a heating means, thereby sealing each of the plurality of thin film integrated circuits.
One feature of a manufacturing method of wireless chips according to the present invention is that a plurality of thin film integrated circuits, which are arranged regularly, are sandwiched with first and second films, and the parts of the first and second films around each of the thin film integrated circuits are melted by a heating means, thereby simultaneously sealing and sectioning the plurality of thin film integrated circuits.
One feature of a manufacturing method of a wireless chip according to the present invention is that a plurality of thin film integrated circuits, which are arranged regularly, are sandwiched with first and second films, and the part of the first film around each of the plurality of thin film integrated circuits is irradiated with laser light from above the first film. The parts of the first and second films around each of the thin film integrated circuits are melted by the laser irradiation, thereby simultaneously sealing and sectioning the plurality of thin film integrated circuits.
Moreover, one feature of a manufacturing method of a wireless chip according to the present invention is that a plurality of thin film integrated circuits, which are arranged regularly, are sandwiched with first and second films, the part of the first film around each of the plurality of thin film integrated circuits is pressed from above the first film by a heated wire. The parts of the first and second films around each of the thin film integrated circuits are melted by being pressed with the heated wire, thereby simultaneously sealing and sectioning the plurality of thin film integrated circuits.
A wireless chip having a structure in which a thin film integrated circuit is sealed by films and a manufacturing method thereof are described above. However, a circuit sealed with films is not limited to a thin film integrated circuit, as long as it is an integrated circuit. For example, an integrated circuit formed on a semiconductor substrate or a thick film integrated circuit may be adopted. An integrated circuit in which an integrated circuit formed on a semiconductor substrate, a thick film integrated circuit and a thin film integrated circuit are mixed, may also be employed.
A wireless chip according to the present invention has a structure in which a thin film integrated circuit is sealed by films and thus, the wireless chip can be used with putting directly in a bag for package, like a desiccant put in a bag for package of food together with food. Therefore, there is no risk that a wireless chip is peeled off since it is not required to be fixed by attaching on a product. Thus, the step of fixing the wireless chip on a product can be omitted.
Degradation of a thin film integrated circuit can be prevented by sealing a desiccant together with the thin film integrated circuit when the thin film integrated circuit is sealed.
In addition to the above described advantageous effects, other advantageous effects 1 to 5 can be obtained by employing such a hollow structure.
1. External impacts to a thin film integrated circuit can be reduced, since films for sealing the thin film integrated circuit (sealing films) has the hollow structure.
2. Degradation of the thin film integrated circuit can be prevented by encapsulating inert gas such as nitrogen gas in the hollow portion.
3. The period when the wireless chip can be used can be limited to a short period only, by encapsulating a gas promoting degradation of the thin film integrated circuit (e.g., gas containing moisture) in the hollow portion. The wireless chip can be suitable for the use in a field in which security, privacy or the like is important, by limiting the period when the wireless chip can be used to a short period only. The correlation between a concentration of a gas to be sealed in (a composition of a gas to be encapsulated) and a use period for the thin film integrated circuit is measured in advance and the concentration of the gas to be encapsulated (a composition of a gas to be encapsulated) is varied; therefore, a use period of the wireless chip can be changed depending on an application thereof.
4. By employing the hollow structure, the wireless chip can float on water when it is thrown into water. Therefore, the wireless chip can be easily washed.
5. Heat from the outside is difficult to be conducted to the thin film integrated circuit because of the hollow structure. In particular, when a gas, a liquid or a gel to be encapsulated in the hollow portion has a low thermal conductivity, the heat from the outside is more difficult to be conducted.
Further, a structure can be employed, in which degradation speed of a thin film integrated circuit becomes faster in the case where gas or liquid outside the films sealing the thin film integrated circuit enters the inside of the films and the thin film integrated circuit is in contact with the gas or the liquid when the films sealing the thin film integrated circuit are broken. By the structure, the thin film integrated circuit deteriorates only by breaking the films sealing the thin film integrated circuit after the wireless chip is used, and thus the wireless chip cannot be used. Specifically, by employing such a structure that a thin film integrated circuit easily deteriorates by being exposed to an atmosphere (external air) (structure in which degradation speed is greatly different between the state in which it is exposed to the external air and the state in which it is not exposed to the external air), a state in which a thin film integrated circuit deteriorates and cannot be used can be obtained by exposing the thin film integrated circuit inside the films to the atmosphere (external air) by breaking the films sealing the thin film integrated circuit after the wireless chip is used. Therefore, since a state in which the wireless chip cannot be used can be obtained easily after it is used, the wireless chip can be suitable for the use in a field in which security, privacy or the like is important. By employing the hollow structure, the films sealing the wireless chip can be easily broken by breaking down the film having the hollow structure with a pressure, when the films sealing the thin film integrated circuit are broken after it is used.
In particular, in the case where a thin film integrated circuit is formed over a flexible substrate such as a resin substrate or the like, the thin film integrated circuit is difficult to be broken even when it is bent, since the substrate is flexible. Therefore, by employing the structure in which the thin film integrated circuit easily deteriorates when being exposed to the atmosphere (external air) (structure in which degradation speed is greatly different between the state in which it is exposed to the external air and the state in which it is not exposed to the external air), the method by which the wireless chip cannot be used by breaking the films sealing the thin film integrated circuit after the wireless chip is used is extremely effective.
The advantageous effects in the case of the thin film integrated circuit are described above; however, the same effects as described above can be obtained in circuits other than thin film integrated circuits.
In the accompanying drawings:
Embodiment mode according to the present invention will hereinafter be described with reference to the accompanying drawings. The present invention can be carried out in many different modes, and it is easily understood by those skilled in the art that modes and details herein disclosed can be modified in various ways without departing from the spirit and the scope of the present invention. It should be noted that the present invention should not be interpreted as being limited to the description of the embodiment mode to be given below. Note that the same reference numerals are used for the same portions through drawings in the structures of the present invention to be explained hereinafter.
A structure of a wireless chip according to the present invention is described with reference to
In the structure shown in
In the structure shown in
If a thin film integrated circuit of the wireless chip shown in
One feature of a wireless chip according to the present invention is that an inert gas such as a nitrogen gas, an inert liquid such as Fluorinert™ (this trademark is owned by 3M™), an inert gel or the like can be encapsulated in the hollow portion 103 or 105 in the wireless chip having a hollow structure. A known material can be used as the inert gas or the inert liquid, in addition to nitrogen gas or Fluorinert.
One aspect of a wireless chip according to the present invention is that a gas promoting degradation of a thin film integrated circuit (such as gas containing moisture) can be encapsulated in the hollow portion 103 or 105 in the wireless chip having a hollow structure. A state in which the hollow portion 103 or 105 is filled with a gas promoting degradation of a thin film integrated circuit can be obtained by sealing the thin film integrated circuit in an atmosphere containing the gas promoting degradation of the thin film integrated circuit.
A thermoplastic resin may be used for the first and second films. The thermoplastic resin used for the first and second films preferably has a low softening point. For example, polyolefin based resin such as polyethylene, polypropylene, or polymethylpentene; vinyl based copolymer such as vinyl chloride, vinyl acetate, polyvinyl chloride acetate copolymer, ethylene-vinyl acetate copolymer, vinylidene chloride, polyvinyl butyral, or polyvinyl alcohol; acrylic based resin; polyester based resin; urethane based resin; cellulosic based resin such as cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, or ethyl cellulose; styrene based resin such as polystyrene or acrylonitrile-styrene copolymer can be nominated. A film having a single layer or plural layers of the thermoplastic resin may be used for the first and second films. The film with plural layers has, for example, a structure in which, over a base 210 including a first thermoplastic resin, an adhesive layer 211 including a second thermoplastic resin having a softening point lower than the first thermoplastic resin is formed as shown in
Then, as shown in
When the first and second films are both planar, the cross-sectional shape as shown in
In
For example, a heated wire 208 is pressed onto the second film 204 as shown in
The case where each thin film integrated circuit 102 is sealed and sectioned simultaneously has been described above; however the sealing and sectioning are not necessarily conducted simultaneously and may be conducted in different steps. In this case, since sealing can be conducted so that the first and second films are bonded to each other with a larger area than an area used for sectioning, sealing can be done more surely as compared with the case where sealing and sectioning are conducted simultaneously. In addition, if sealing and sectioning are conducted in different steps, either sealing or sectioning may be conducted first.
As an example of conducting sealing and sectioning in different steps, for example, the following method can be given: irradiation of laser light having energy density capable of only sealing but not even sectioning is performed so as to seal thin film integrated circuits, and then irradiation of laser light having energy density capable of sectioning is preformed so as to section the thin film integrated circuits. In this case, the width of laser light used for sealing is made larger than that of laser light for sectioning. By making the width of laser light for sealing larger than that of laser light for sectioning, the area for bonding the first and second films can be made large. Thus, sealing can be more surely conducted, as compared with the case sealing and sectioning are conducted simultaneously.
As another example of conducting sealing and sectioning in different steps, there is also given a method by which a heated wire 208, which has a larger width than that of the heated wire 208, is pressed onto the second film 204 to conduct only sealing and then, sectioning is conducted by the heated wire 208 or laser light. By making the width of the wire for sealing larger than that of the wire or laser light for sectioning, sealing can be conducted in such a way that the area for bonding the first and second films can be made larger than the sectioned area.
This embodiment mode has described the wireless chip having the structure in which the thin film integrated circuit is sealed by the films, and the manufacturing method thereof. However, the circuit sealed by the films is not limited to a thin film integrated circuit, as long as it is an integrated circuit. For example, an integrated circuit formed on a semiconductor substrate or a thick thin film integrated circuit may be employed. Moreover, an integrated circuit in which an integrated circuit formed on a semiconductor substrate, a thick film integrated circuit and a thin film integrated circuit are mixed may also be employed.
In Embodiment 1, an embodiment of a process up to arranging regularly a plurality of thin film integrated circuits 102 over the first film 203 is described.
First, a substrate 400 is prepared and a release layer 401 is formed over the substrate 400 as shown in
The release layer 401 is formed with a metal film containing tungsten (W), molybdenum (Mo), niobium (Nb), titanium (Ti), silicon (Si) or the like. In this embodiment, a metal film containing W is used as the release layer 401. Note that a metal film including W can be formed by CVD, sputtering, electron beam, or the like; here, the metal film containing W is formed by the sputtering method. In the case where the thin film integrated circuit is physically peeled from the substrate in a subsequent step, a metal oxide (for example, WOx) film may be formed over the metal film (for example, W). Other than W, MoOx formed over a Mo film, NbOx formed over a Nb film, TiOx formed over a Ti film, or the like can be used as the combination in which a metal oxide film is formed over a metal film. Further, only WOx, MoOx, NbOx, TiOx or the like may be formed as a release layer 401.
Note that, in
Next, a layer including an integrated circuit formed with a thin film transistor (TFT) 402 (hereinafter, referred to as a TFT layer 402) is formed over the release layer 401 (
Note that a semiconductor film included in the TFT layer 402 has a thickness of 0.2 μm or less, typically, 40 to 170 nm, preferably, 50 to 150 nm. Since such an extremely thin semiconductor film is used, the integrated circuit can be further thinned, compared with a chip formed using a silicon wafer.
Subsequently, a layer for securing strength 403 is formed over the TFT layer 402 (
For the layer for securing strength 403, a resin material such as an epoxy resin, an acrylic resin, a phenol resin, a novolac resin, a melamine resin, a urethane resin, or silicone resin can be used. Alternatively, the layer for securing strength 403 may be formed of an organic material such as benzocyclobutene, parylene, flare, polyimide or a photosensitive resin; a compound material formed by polymerization of siloxane polymer; a composition material containing a water-soluble homopolymer and a water-soluble copolymer; an inorganic film such as a SiN film, a SiO2 film or a SiON film; or the like. In addition, the layer for securing strength 403 may be formed by stacking plural types of materials selected from the materials described above.
The layer for securing strength 403 can be formed by a screen printing method or a droplet discharge method. The droplet discharge method is a method for selectively discharging (spraying) a droplet of a composition including a material of a conductive film, an insulating film, or the like to form a film in an arbitrary position. The droplet discharge method includes as an inkjet method in some cases. An inorganic material may be used except the resin material when the inorganic material has a sufficient resistivity to an etching agent. As a method for forming the layer for securing strength 403, there is e.g., a method by which a photosensitive resin is applied by a spin coating method or the like, exposed to light and developed so that the photosensitive resin can remain in a necessary part, in addition to the screen printing method or the droplet discharge method described above.
Although
Then, the etching agent is introduced into the opening 404 to remove the release layer 401 as shown in
After removing the release layer 401, a thin film integrated circuit 408 including the TFT layer 402 and the layer for securing strength 403 is peeled from the substrate 400. In order to completely remove the release layer 401 in this embodiment, the thin film integrated circuit 408 can be peeled from the substrate 400 without using a physical means. The cross-sectional view of this state is shown in
The perspective view after removing the release layer 401 is shown in
Here, the case where the release layer 401 is removed completely is described; however, the release layer 401 may be removed such that a part of the release layer 401 remains as shown in
The method for transferring the thin film integrated circuit 408 on the substrate 400 onto the first film 203 is not limited to the above described method using the vacuum chuck 110, and another method may be employed. Another method for transferring the thin film integrated circuit 408 on the substrate 400 onto the first film 203 is described with reference to
After completely removing the release layer 401, the first film 203 is arranged over the thin film integrated circuits 408 which are arranged over the substrate 400 and have been detached from the substrate 400 (
Thereafter, sealing and sectioning of the thin film integrated circuits are conducted according to the method described in Embodiment Mode, thereby completing the wireless chip of the present invention.
The peeled substrate 400 can be reused. Accordingly, a thin film integrated circuit can be manufactured on such a substrate at low cost. Therefore, even in the case of using a quartz substrate, which is more expensive than a glass substrate, the thin film integrated circuit can be manufactured at low cost. Note that, in the case of reusing a substrate, the peeling step is preferably controlled so as not to damage the substrate. However, if the substrate is damaged, planarization process may be performed thereto by forming an organic or inorganic resin film on the substrate by a coating method or a droplet discharge method, or grinding or polishing the substrate.
In the case of thus manufacturing a wireless chip by forming a thin film integrated circuit over a substrate having an insulating surface, there is less limitation on the shape of the substrate, compared with the case of taking chips out of a circular silicon wafer. Therefore, the productivity of the wireless chips can be high, and mass production can be conducted. Moreover, cost can be reduced since the insulating substrate can be reused.
This embodiment has described the thin film integrated circuit formed on the substrate; however, the present invention is not limited thereto. An integrated circuit other than a thin film integrated circuit can be formed on a substrate. For example, a thick film integrated circuit may be formed on a substrate. In addition, a circuit in which a thick film integrated circuit and a thin film integrated circuit are mixed on a substrate may be employed.
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
In Embodiment 2, a method of using a film having an adhesive agent on one side thereof when the thin film integrated circuits 408 on the substrate 400 are transferred onto the first film 203 as shown in Embodiment 1, is described with reference to
A state in
The film 407 may have, specifically, a structure in which the adhesive layer 406 is provided on the base 405 formed of polyester, or the like. The adhesive layer 406 is formed of a material such as a resin material containing acrylic resin or the like, or a synthetic rubber material.
As shown in
Further, a film having weak adhesive force (preferably, 0.01 to 0.5 N, more preferably, 0.05 N to 0.35 N) is preferably used as the film 407 in order to bond the thin film integrated circuits 408 again to the first film 203 to be peeled from the film 407 after bonding the thin film integrated circuits 408 provided on the substrate 400 to the film 407. The thickness of the adhesive agent may be 1 to 100 μm, preferably, 1 to 30 μm. Preferably, the base 405 is formed to have a thickness of 10 μm to 1 mm for easy handling in processing.
By the method described above, the thin film integrated circuit 408 can be transferred onto the first film 203 from the substrate 400. Thereafter, sealing and the thin film integrated circuits and sectioning the films are conducted according to the method described in Embodiment Mode, thereby completing the wireless chip of the present invention.
This embodiment has described the case of transferring the thin film integrated circuits onto the first film 203; however, the present invention is not limited to a thin film integrated circuit as long as it is an integrated circuit. For example, an integrated circuit formed on a semiconductor substrate or a thick film integrated circuit may be used. In addition, an integrated circuit in which an integrated circuit formed on a semiconductor substrate, a thick film integrated circuit and a thin film integrated circuit are mixed, may be used.
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiment 3 describes a process up to a state in which a plurality of thin film integrated circuits are arranged over the first film 203 as shown in
A layer 901 including a plurality of thin film integrated circuits (hereinafter, a TFT layer 901) is formed over one surface of a substrate 900 having an insulating surface (
The TFT layer 901 includes at least a plurality of insulating films, a semiconductor layer and a conductive layer for constituting a plurality of elements, and a conductive layer serving as an antenna. Specifically, the TFT layer 901 includes a first insulating film serving as a base film, a plurality of elements provided over the first insulating film, a second insulating film covering the plurality of elements, a first conductive layer which is connected to the plurality of elements and is in contact with the second insulating film, a third insulating film covering the first conductive layer, a second conductive layer which serves as an antenna and is in contact with the third insulating film, and a fourth insulating film covering the second conductive layer. More specific structure is later described in Embodiment 4.
The example of forming the conductive layer functioning as an antenna in the TFT layer 901 is shown here; however, an antenna substrate in which an antenna has been provided may be bonded to the TFT layer 901 by an adhesive agent or the like as shown in
In
Next, a third film 902 is provided so as to cover the TFT layer 901 (or so as to cover the antenna substrate 235 in the case of bonding the antenna substrate 235 onto the TFT substrate as shown in
The third film 902 may be provided as necessary. The third film 902 is provided so as to protect the TFT layer 901. When the TFT layer 901 is not required to be protected, the fourth film 903 may be provided on the second film, without providing the third film 902.
Next, the surface opposite to the one surface of the substrate 900 on which the TFT layer 901 has been formed is ground by a grinding means 904 (
Next, the ground surface of the substrate 900 is polished by a polishing means 906 (refer to
The example where the substrate is ground to have a thickness of 100 μm or less and then polished to have a thickness of 20 μm or less is described here; however, the thickness of the substrate after the grinding and polishing steps is not limited to these values. In addition, the example of conducting both of grinding and polishing steps for thinning the substrate is described here; however, the substrate can be thinned by only one of the grinding and polishing steps.
Then, the substrate 900, the TFT layer 901, and the third film 902 are cut by a cutting means 907. As to the TFT layer 901, the boundary of integrated circuits are cut so as to separate the plurality of thin film integrated circuits apart. Elements provided in the TFT layer 901 are not cut but the insulating film provided in the TFT layer 901 is cut. Through this cutting step, a plurality of thin film integrated circuits 908 are formed (
Next, the fourth film 903 is expanded so as to form a space between the thin film integrated circuits 908 (
A pick-up means or a vacuum chuck may be employed as the physical means. When the pick-up means is adopted as the physical means, the fourth film 903 is irradiated with UV light and the thin film integrated circuit 908 is peeled from the fourth film 903 by the pick-up means 909 as shown in
When the vacuum chuck is adopted as the physical means, the fourth film 903 is irradiated with UV light and the vacuum chuck 910 is positioned over the thin film integrated circuits 908 as shown in
In the above process, the substrate 900 is cut (
The thin film integrated circuits completed through the above described steps have a thin thickness and is light in weight.
This embodiment has described the case where the thin film integrated circuits are formed on the substrate; however the present invention is not limited thereto. An integrated circuit other than a thin film integrated circuit can be formed on a substrate. For example, a thick film integrated circuit may be formed over a substrate. In addition, a circuit in which a thick film integrated circuit and a thin film integrated circuit are mixed on a substrate may be formed. An integrated circuit may be formed on a semiconductor substrate, instead of forming a thin film integrated circuit on the substrate.
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiment 4 describes an example of using the expand film (fourth film) 903, described in Embodiment 3, as the first film 203 for sealing a thin film integrated circuit.
A state shown in
Then, as shown in
Thereafter, sealing and sectioning of the thin film integrated circuits are conducted according to the method described in Embodiment Mode, thereby completing the wireless chip of the present invention.
This embodiment has described the thin film integrated circuit; however, the present invention is not limited to a thin film integrated circuit as long as it is an integrated circuit. For example, an integrated circuit formed on a semiconductor substrate or a thick film integrated circuit may be used. In addition, an integrated circuit in which an integrated circuit formed on a semiconductor substrate, a thick film integrated circuit and a thin film integrated circuit are mixed, may be employed.
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiments 1 to 4 have shown the example of using an element formed by peeling the TFT layer and the layer for securing strength from the substrate by removing at least a part of the release layer, or the example in which an element obtained by thinning the substrate on which the TFT layer is provided, as the thin film integrated circuit; however the present invention is not limited to the examples. A substrate provided with the TFT layer, which is not thinned, may be used as the thin film integrated circuit. In other words, the TFT layer may be formed on the substrate and may be sectioned into each unit circuit to be used as a thin film integrated circuit. In this case, for example, a thin film integrated circuit may be manufactured by omitting the process of thinning the substrate by grinding or polishing in Embodiment 3.
This embodiment has described the thin film integrated circuit; however, the present invention is not limited to a thin film integrated circuit as long as it is an integrated circuit. For example, an integrated circuit formed on a semiconductor substrate or a thick film integrated circuit may be used. In addition, an integrated circuit in which an integrated circuit formed on a semiconductor substrate, a thick film integrated circuit and a thin film integrated circuit are mixed, may be employed.
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiment 6 describes a structure of the TFT layer with reference to
Reference numeral 361 denotes an insulating film serving as a base film. The insulating film 361 includes a multilayer film including silicon nitride oxide and silicon oxynitride, a multilayer film including silicon oxynitride, silicon nitride oxide, and silicon oxynitride, or a multilayer film including silicon oxide, silicon nitride oxide, and silicon oxynitride or the like.
Next, a plurality of elements are formed over the insulating film 361. The plurality of elements correspond to, for example, a plurality of elements selected from a thin film transistor, a capacitor element, a resistor element, a diode, and the like.
An insulating film 366 is formed so as to cover the thin film transistors 362 to 365. Source or drain wirings 371 to 376 to be electrically connected to impurity regions of the thin film transistors 362 to 365 are formed over the insulating film 366. An insulating film 367 is formed so as to cover the source or drain wirings 371 to 376. Conductive layers 377 to 380 eclectically connected to the source or drain wirings 371 to 376 are formed over the insulating film 376. The conductive layers 377 to 380 serve as an antenna. An insulating film 368 is formed so as to cover the conductive layers 377 to 380.
This embodiment has described the example of forming the conductive layers serving as an antenna in the TFT layer; however, a structure may be employed, in which an antenna substrate provided with an antenna is bonded to the TFT layer to be electrically connected to each other, instead of forming the antenna in the TFT layer.
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiment 7 describes a structure of the TFT layer different from that in Embodiment 6 with reference to
A silicon nitride film 511 and a silicon oxide film 512 are each an insulating film serving as a base film. A plurality of elements are formed over the silicon oxide film 512. Herein, the silicon nitride film 511 and the silicon oxide film 512 serving as the base insulating films are not limited to these materials and the order for stacking the films. As the base insulating film, for example, a multilayer film including silicon nitride oxide and silicon oxynitride, a multilayer film including silicon oxynitride, silicon nitride oxide, and silicon oxynitride, or a multilayer film including silicon oxide, silicon nitride oxide, and silicon oxynitride or the like may be employed. The plurality of elements correspond to, for example, a plurality of elements selected from a thin film transistor, a capacitor element, a resistor element, a diode, and the like.
Hereinafter, a structure of the thin film transistor 523 is described. Insulating films 514 and 515 are formed over the lower electrode 513, and a semiconductor layer 521 is formed over the insulating film 515. Here, the lower electrode 513 can be formed from a polycrystalline semiconductor doped with a metal or an impurity having one conductivity type. W, Mo, Ti, Ta, Al or the like can be used as the metal.
The gate electrode 522 is formed over the semiconductor layer 521 with the gate insulating film 516 therebetween. In
An insulating film 517 is formed to cover the semiconductor layer 521 and the gate electrode 522. A source or drain wiring 518 to be electrically connected to the source or drain region in the semiconductor layer 521 is formed over the insulating film 517.
An insulating film 519 is formed over the source or drain wiring 518, and a conductive layer 524 is formed over the insulating film 519. The conductive layer 524 serves as an antenna. An insulating film 520 is formed to cover the conductive layer 524.
The insulating films 515, 517, 519 and 520 may be an inorganic insulating film or an organic insulating film. A silicon oxide film or a silicon oxynitride film formed by a CVD method, a silicon oxide film applied by an SOG (Spin On Glass) method, or the like may be used as the inorganic insulating film. A film of polyimide, polyamide, BCB (benzocyclobutene), acrylic, a positive photosensitive organic resin, a negative photosensitive organic resin, or the like may be used as the organic insulating film. Moreover, a stacked structure of films formed of different materials, e.g., a multilayer including an acrylic film and a silicon oxynitride film may be used.
The TFT having the lower electrode described above has an advantageous structure in reducing the size thereof. In general, when the size of a TFT is reduced and the clock frequency for driving a circuit is increased, power consumption of an integrated circuit is increased. Therefore, by applying a bias voltage to the lower electrode and varying the bias voltage, the threshold voltage of the TFT can be changed, and thus the increase of power consumption can be suppressed.
The application of a negative bias voltage to the lower electrode of an N-channel TFT increases threshold voltage and reduces leakage. On the contrary, the application of a positive bias voltage decreases threshold voltage to make current easily flow to the channel, and the TFT can operate at higher speed or at a low voltage. On the other hand, the application of a bias voltage to the lower electrode of a P-channel TFT exhibits the opposite effect. Thus, the characteristics of an integrated circuit can be drastically improved by controlling the bias voltage applied to the lower electrode.
By balancing the threshold voltage of the N-channel TFT with that of the P-channel TFT using the bias voltage, the characteristics of an integrated circuit can be improved. In this case, both a power source voltage and the bias voltage applied to the lower electrode may be controlled in order to reduce power consumption. When the circuit is in a standby mode, a large reverse bias voltage is applied to the lower electrode. In an operation mode, a small reverse bias voltage is applied to the lower electrode when load is light, whereas a small forward bias voltage is applied when the load is heavy. The application of the bias voltage may be made switchable depending on the operation state or load state of the circuit by providing a control circuit. By controlling power consumption or TFT performance in such a way, circuit performance can be maximized.
This embodiment has described the example in which the conductive layer serving as an antenna is formed in the TFT layer; however, a structure may be employed, in which an antenna substrate provided with an antenna is bonded to the TFT layer to be electrically connected to each other, instead of forming the antenna in the TFT layer.
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiment 8 describes a manufacturing method of the gate electrode of the thin film transistor included in the TFT layer in Embodiment 1 with reference to
A release layer 801 is formed over a substrate 800, and semiconductor films 811 and 812 are provided over the release layer 801 between insulating films 802 and 803 therebetween. The substrate 800 and the release layer 801 may be formed using the materials described in Embodiment 1. In addition, a gate insulating film 813 is formed over the semiconductor films 811 and 812. After that, a first conductive layer 821 and a second conductive layer 822 are stacked over the gate insulating film 813. In this embodiment, tantalum nitride (TaN) is used for the first conductive layer and tungsten (W) is used for the second conductive layer. The TaN film and the W film may be formed by a sputtering method. The TaN film may be formed by the sputtering method using a target of tantalum in a nitrogen atmosphere. The W film may be formed by the sputtering method using a target of tungsten.
In this embodiment, the first conductive layer 821 is made from TaN and the second conductive layer 822 is made from W. However, without being limited thereto, the first conductive layer 821 and the second conductive layer 822 may each be formed using an element selected from Ta, W, Ti, Mo, Al, Cu, Cr, and Nd; an alloy material or a compound material containing the element as its main component. Alternatively, a semiconductor film as typified by a polycrystalline silicon film, doped with an impurity element such as phosphorus, may be used. An AgPdCu alloy may be used. A combination thereof may also be appropriately selected. The first conductive layer 821 may be formed to have a thickness in the range of 20 to 100 nm. The second conductive layer 822 may be formed to have a thickness in the range of 100 to 400 nm. In this embodiment, the gate electrodes are formed to have a stacked structure of two layers. Alternatively, they may have a single-layer structure or a stacked structure of three or more layers.
Then, a resist 823 is selectively formed over the second conductive layer 822 by photolithography or a droplet discharge method (
A method for manufacturing a gate electrode, which is different from that shown in
As shown in
According to the manufacturing method described in this embodiment, a minute gate electrode that is finer than the finest one formed by patterning by a photolithography method or the like can be manufactured. Further, a minuter element structure can be provided by reducing the size of the gate electrode. Accordingly, more elements can be formed in a certain area, and a high-performance circuit can be formed. Thus, a smaller thin film integrated circuit (such as IC chip) can be obtained in the case where the thin film integrated circuit is formed with the same number of elements as the conventional one. The method shown in
This embodiment has described the manufacturing method of the gate electrode in the thin film transistor having the TFT layer in Embodiment 1; however the gate electrode may be formed by a method combining freely Embodiment Mode described above and the other embodiments, without being limited to the method in Embodiment 1.
Embodiment 9 explains a circuit diagram of a wireless chip according to the present invention as one example with reference to the drawings. The specification of the wireless chip explained here meets ISO (International Organization for Standardization) Standards 15693, which is a vicinity type and whose communication signal frequency is 13.56 MHz. In addition, the reception responds only to a data readout instruction, the data transmission rate of the transmission is approximately 13 kHz, and a Manchester code is used as data coding.
A wireless chip 715 roughly includes an antenna portion 721, a power supply portion 722, and a logic portion 723. The antenna portion 721 includes an antenna 701 for receiving an external signal and transmitting data (
A code recognized and determining by the circuit for recognizing and determining each code 706 is an end of frame (EOF), a start of frame (SOF), a flag, a command code, a mask length, a mask value, or the like. In addition, the circuit for recognizing and determining each code 706 also includes cyclic redundancy check (CRC) function that identifies a transmission error.
Next, one example of the layout of the wireless chip having the above configuration is explained with reference to
Subsequently, the layouts of the power supply portion 722 and the logic portion 723 are explained (
The mask ROM 711 forms memory content in a memory in the manufacturing process. Here, two power supply lines of a power supply line connected to a high-potential power supply (also referred to as VDD) and a power supply line connected to a low-potential power supply (also referred to as VSS) are provided, and the memory content stored by a memory cell is determined based on which of the above power supply lines a transistor included in each memory cell is connected to.
Then, one example of the circuit configuration of the rectifier circuit 702 is explained (
Then, the cross-sectional structure of a capacitor transistor included in the rectifier circuit 702 or the demodulation circuit 704 will be explained (
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiment 10 describes an example of using a crystalline semiconductor layer that is crystallized by laser irradiation, as the semiconductor layer of the thin film transistor included in the TFT layer.
A laser oscillator generating laser light is a continuous wave (CW) laser. The oscillator may employ one or plural types of CW lasers selected from a YAG laser, a YVO4 laser, a YLF laser, a YAlO3 laser, a glass laser, a ruby laser, an alexandrite laser, a Ti:sapphire laser, an excimer laser, an Ar laser, a Kr laser, and a CO2 laser.
With such a CW laser, it is possible to manufacture a transistor using the polycrystalline semiconductor having few crystal defects and having a large crystal grain. Therefore, a liquid crystal display device can be provided, in which the mobility and the response speed are high, thus, the operation speed can be high, and operation frequency of an element can be increased. The high reliability can be obtained, because variations on characteristics are few.
For increasing the operation frequency much more, the scanning direction of laser light is preferably the same as a channel length direction of a transistor. This is because the highest mobility can be obtained when the channel length direction of the transistor and the scanning direction of laser light with respect to a substrate are almost parallel (preferably, from −30° to 30°) in a step of laser crystallization by such a CW laser. The channel length direction is the same as a flowing direction of current in the channel forming region, in other words, a direction in which an electric charge moves. The thusly formed transistor has an active layer including a polycrystalline semiconductor in which crystal grains are extended in the channel length direction, and this means that crystal grain boundaries are formed almost along the channel length direction.
The laser crystallization using a CW laser is described; however, the present invention is not limited to the CW laser, and a pulsed laser may be used for the crystallization. Even when energy beam (pulsed beam) is output in a pulsed oscillation, crystal grains continuously grown in the scanning direction can be obtained by emitting laser light with a repetition rate sufficient to emit the next pulsed beam before the semiconductor film is solidified after it has been melted by the laser light. In other words, even when a pulsed laser is adopted, the same effect as that of a CW laser can be obtained.
Therefore, a pulsed beam having a determined lower limit of the pulse repetition rate may be used so that the pulse period becomes shorter than the period since the semiconductor film is melted until it is solidified. Specifically, the repetition rate of a pulsed laser is 10 MHz or more, preferably 60 to 100 MHz. The repetition rate is much higher repetition rate than that of several tens to several hundreds Hz of a typically used pulsed beam.
When the pulsed laser light has the repetition rate of 10 MHz or more, it is possible to irradiate the semiconductor film with pulsed laser light before the semiconductor film is solidified after it has been melted by the previous laser light. Therefore, unlike the case of using a pulsed laser having a conventional repetition rate, the interface between the solid phase and the liquid phase can be moved continuously in the semiconductor film, and the semiconductor film having crystal grains grown continuously in the scanning direction can be formed. Specifically, it is possible to form an aggregation of crystal grains each of which has a width from 10 to 30 μm in the scanning direction and a width from approximately 1 to 5 μm in a direction perpendicular to the scanning direction. It is also possible to form a semiconductor film having almost no crystal grain boundaries at least in the channel length direction of a TFT by forming single crystal grains long extended along the scanning direction.
As the pulsed laser, an Ar laser, a Kr laser, an excimer laser, a CO2 laser, a YAG laser, a Y2O3 laser, a YVO4 laser, a YLF laser, a YAlO3 laser, a glass laser, a ruby laser, an alexandrite laser, a Ti:sapphire laser, a copper vapor laser, or a gold vapor laser, which can oscillate in the above described repetition rate, can be used.
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiment 11 describes an example in which degradation speed of a thin film integrated circuit becomes faster when an atmosphere or a liquid outside films enters the inside of the films and is in contact with the thin film integrated circuit by breaking the films sealing the thin film integrated circuit, in a wireless chip having a hollow structure according to the present invention.
An insulating film 66 is formed to cover the thin film transistors 64 and 65, and source and drain wirings 74 to 76 electrically connected to impurity regions of the thin film transistors 64 and 65 are formed. An insulating film 67 is formed to cover the source and drain wirings 74 to 76. Conductive layers 79 and 80 electrically connected to the source and drain wirings 74 to 76 are formed over the insulating film 67. The conductive layers 79 and 80 function as an antenna. An insulating film 68 is formed to cover the conductive layers 79 and 80, and a third film 12 is formed over the insulating film 68. A portion from the insulating film 61 to the insulating film 68 corresponds to a TFT layer 11.
A hole 13 is formed in the substrate 10. One feature of the structure in
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiment 12 describes an example in which degradation speed of a thin film integrated circuit becomes faster when an atmosphere or a liquid outside films enters the inside of the films and is in contact with the thin film integrated circuit by breaking the films sealing the thin film integrated circuit, in a wireless chip having a hollow structure according to the present invention. The example is different from that in Embodiment 11.
As shown in
As the substance promoting degradation of a thin film transistor, Na, K, ammonia, monoethanolamine, H2O, SOX, NOx and the like are given. When a thin film transistor is exposed to a gas, a liquid or a gel containing the substance promoting degradation of the thin film transistor, the electric characteristic of the thin film transistor are shifted as shown in
In general, if thin film transistors are formed to have the same electric characteristics, slight variations in electric characteristics of the respective thin film transistors are generated as shown by 2900, 2901 and 2902 in
When the thin film transistor has the electric characteristic 2900, the electric characteristic 2900 may be shifted beyond the electric characteristic 2903 as the operation limit electric characteristic, so that the thin film transistor cannot operate at the time of Vg=Von, either. Herein, the shift amount of from the electric characteristic 2900 to the electric characteristic 2903 that is an operation limit electric characteristic is X+Y. Therefore, the electric characteristic may be shifted so that the shift amount thereof can be larger than X+Y in order to obtain a state in which the thin film transistor having the electric characteristic 2900 does not operate.
Thus, the concentration of a substance promoting degradation included in a gas, a liquid, or a gel existing in the space 121 between the first film and the second film is set so that the shift amount A in which the electric characteristic of the thin film transistor is shifted by being exposed to such a gas, a liquid, or a gel containing the substance promoting degradation of the thin film transistor is larger than X+Y, in which X is a range of variations on electric characteristics among the thin film transistors and Y is a shift amount of the operation limit electric characteristic. Then, by breaking the first film, the gas, the liquid, or the gel existing in the space 121 between the first film and the second film enters the inside of the first film. Thus, the thin film integrated circuit is exposed to the gas, the liquid, or the gel containing the substance promoting degradation of the thin film transistor; therefore, the electric characteristic of the thin film transistor included in the thin film integrated circuit is shifted to the state in
Embodiment has described the wireless chip having the structure in which a thin film integrated circuit is sealed by the first film and then the first film is surrounded by the second film. In other words, the wireless chip has the structure in which double films having a space therein are used to seal the thin film integrated circuit. However, triple or more films having a space therein may be used to seal the thin film integrated circuit.
Embodiment has described the wireless chip having the structure in which a thin film integrated circuit is sealed by the first film and then the first film is surrounded by the second film. However, the circuit sealed by the first film is not limited to only the thin film integrated circuit as long as it is an integrated circuit. For example, an integrated circuit formed on a semiconductor substrate or a thick film integrated circuit may be used. In addition, an integrated circuit in which an integrated circuit formed on a semiconductor substrate, a thick film integrated circuit and a thin film integrated circuit are mixed, may be used.
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
Embodiment 13 describes applications of a wireless chip according to the present invention. As shown in
This embodiment can be freely combined with the embodiment mode described above or the other embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-267415 | Sep 2004 | JP | national |
