Patent Application
20100270868
1. Field of the Invention
The present invention relates to a semiconductor device capable of input and output of information by using electromagnetic waves. It is to be noted that the semiconductor device in this specification refers to all devices that can function by utilizing semiconductor characteristics, and electro-optic devices, semiconductor circuits, and electrical appliances, which have this function, are all semiconductor devices.
2. Description of the Related Art
In recent years, wireless chips for RFID (radio frequency identification system) have been researched and put into practical use as an information and communication technology utilizing electromagnetic waves.
RFID refers to a communication technology over electromagnetic waves between a reader/writer and a semiconductor device capable of wirelessly transmitting and receiving information (also called an RFID tag, an RF tag, an ID tag, an IC tag, a wireless tag, an electronic tag, a wireless chip, or an ID chip), so that data can be stored in or read out from the semiconductor device. Such a semiconductor device includes an antenna and an integrated circuit having a signal processing circuit provided with a memory circuit and the like.
A wireless chip used for RFID obtains an operating power by electromagnetic induction from electric waves that are received with a reader/writer, and exchanges data with the reader/writer by utilizing the electric waves. A wireless chip, in general, has an antenna which transmits and receives such electric waves and which is formed separately from an integrated circuit and connected to the integrated circuit.
In the case where an antenna and an integrated circuit are thus formed separately from each other and connected to each other, the both need to be electrically connected, which leads to low yield because of technical difficulty in connection between the antenna and a minute terminal of the integrated circuit. Moreover, stress applied at a connection point in the use of a wireless chip causes disconnection or poor connection. In particular, when a wireless chip is flexible, it is expected that poor connection is more likely to occur.
In order to solve the aforementioned problem of poor connection between an antenna and an integrated circuit, a wireless chip having an antenna coil formed over the same substrate has been suggested. For example, in a suggested wireless chip having an integrated circuit and an antenna coil formed over the same substrate, a conductor of the antenna coil is formed by a metal sputtering layer or a metal evaporation layer and by a copper plating layer formed over the metal sputtering layer or the metal evaporation layer. The metal sputtering layer and the metal evaporation layer include one of aluminum, nickel, copper, or chromium, or include an alloy of at least two of these metals (see Patent Document 1: Japanese Published Patent Application No. 2002-324890).
Accordingly, the conductor of the antenna coil has a stacked-layer structure of the metal sputtering layer or the metal evaporation layer, and the copper plating layer having lower electric resistance than the metal sputtering layer or the metal evaporation layer. Therefore, the loss of electromagnetic energy can be reduced as compared with a structure of only the metal sputtering layer or the metal evaporation layer, and communication distance to a reader/writer can be extended.
However, the present inventors found that the aforementioned conventional structure causes copper diffusion such as electromigration or stress migration, which adversely affects electrical characteristics of circuit elements in the integrated circuit formed over the same substrate as the antenna coil.
It is an object of the present invention to prevent, in a semiconductor device having an integrated circuit and an antenna formed over the same substrate which uses copper plating for the antenna, electrical characteristics of a circuit element from being adversely affected by copper diffusion such as electromigration or stress migration. It is another object of the present invention to prevent a defect of a semiconductor device having an integrated circuit and an antenna formed over the same substrate, which is caused by poor connection between the antenna and the integrated circuit.
In order to achieve the above objects, a semiconductor device of the present invention having an antenna and an integrated circuit formed over the same substrate uses a nitride film of a predetermined metal as a base layer of the antenna and also has a copper plating layer formed over the base layer.
In a semiconductor device of the present invention having an integrated circuit and an antenna formed over one substrate, which uses copper plating for the antenna, a nitride film is used as a base layer of the antenna. Therefore, copper diffusion to a circuit element by electromigration, stress migration, or the like can be prevented and an adverse effect on electrical characteristics of the circuit element due to copper diffusion can be decreased. Moreover, the use of nickel nitride as metal nitride of the base layer of the antenna can improve the adhesion between the copper plating layer and the base layer of the antenna and can decrease poor connection between the antenna and the integrated circuit
Embodiment modes of the present invention will hereinafter be described with reference to the accompanying drawings. However, the present invention is not limited to the following description and it is easily understood by those skilled in the art that modes and details of the present invention can be modified in various ways without departing from the purpose and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the following description of embodiment modes. Note that in all the drawings for explaining embodiment modes, the same portions are denoted by the same reference numerals.
In this specification, an integrated circuit refers to an electronic circuit having various functions, which is manufactured in such a way that circuit elements such as a transistor, a resistor, a capacitor, and a diode are collectively designed over one substrate and simultaneously the elements are connected by wirings. For example, the integrated circuit includes a transmission circuit, a reception circuit, a power supply circuit, a memory circuit, and a logic control circuit in order to operate as a wireless chip. A substrate supporting the integrated circuit (IC chip) is not limited to a silicon substrate and may be a glass substrate or a flexible substrate such as a polyimide substrate.
Embodiment Mode 1 of a semiconductor device of the present invention will hereinafter be described with reference to drawings.
In
Although a TFT (thin film transistor) 105 is shown as an example of a semiconductor element in the integrated circuit 100, the semiconductor element used in the integrated circuit 100 is not limited to the TFT. For example, a storage element, a diode, a photoelectric conversion element, a resistor, a coil, a capacitor, an inductor, or the like is used instead of the TFT.
An insulating layer 109 is formed between elements of the antenna 101, and the protection film 115 and the cover member 103 are formed over the antenna 101 and the insulating layer 109.
The nitride of titanium, tantalum, tungsten, or molybdenum of the antenna base layer 107 can prevent copper of the copper plating layer 108 from diffusing into the insulating layer 109. Since nickel nitride of the antenna base layer 107 has high adhesion to copper, the resulting copper plating can be fixed onto the antenna base layer 107. Such metal nitrides have conductivity; therefore, the nitride serves as a precipitation electrode of copper at electrolytic plating. Thus, Embodiment Mode 1 where the antenna base layer 107 is the nitride film of the alloy of nickel and any of titanium, tantalum, tungsten, or molybdenum has advantageous effects in that the antenna base layer 107 works as a seed layer at the formation of the copper plating layer 108 and also works as a barrier layer for preventing copper diffusion such as electromigration or stress migration.
It is preferable to form an inorganic insulating film with a high barrier property, such as silicon nitride oxide or silicon nitride, between the protection film 115 and the copper plating layer 108, because copper diffusion from above can also be prevented.
The cover member 103 can be formed of a dielectric material such as plastic, an organic resin, paper, fiber, prepreg, or a ceramic sheet, which is to be attached with an adhesive. Although an example is shown here in which the wireless chip has mechanical strength increased by the cover member 103 being attached with an adhesive, it is not always necessary that the cover member 103 of the wireless chip of the present invention be attached with an adhesive. For example, instead of attaching the cover member 103 with an adhesive, the integrated circuit 100 and the antenna 101 may be covered directly with a resin or the like to increase the mechanical strength of the wireless chip. Alternatively, the mechanical strength of the wireless chip may be increased by controlling the thickness of the insulating layer 109.
Next, a method of manufacturing a semiconductor device of this embodiment mode will be explained.
As shown in
First, a base film 110 is formed over the substrate 102, and the TFT 105 is formed over the base film 110 in accordance with a general process. Then, a first interlayer insulating film 111 and a second interlayer insulating film 112 are formed in order over the TFT 105. Contact holes are next formed by a general method in the first interlayer insulating film 111 and the second interlayer insulating film 112 at portions thereof to be provided with electrodes, such as a source region and a drain region of the TFT 105. Then, an electrode 113 is formed.
The base film 110 is provided in order to prevent alkaline-earth metal or alkali metal such as Na in the substrate 102 from diffusing into the semiconductor film, thereby preventing an adverse effect on characteristics of the semiconductor elements such as the TFT. The base film 110 may be either a single insulating film or stacked insulating films. For example, an insulating film which can prevent alkali metal and alkaline-earth metal from diffusing into the semiconductor film, such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film is used. It is to be noted in this specification that silicon oxynitride contains more oxygen than nitrogen, whereas silicon nitride oxide contains more nitrogen than oxygen.
In this embodiment mode, a 100-nm-thick silicon oxynitride film, a 50-nm-thick silicon nitride oxide film, and a 100-nm-thick silicon oxynitride film are stacked in order to form the base film 110; however, the material, thickness, and number of films are not limited to these as is clear from the above description. For example, even in the aforementioned case of the three-layer structure, the silicon oxynitride film as the lower layer may be replaced by a siloxane-based resin film with a thickness of 0.5 to 3 μm which is formed by a spin coating method, a slit coating method, a droplet discharging method, a printing method, or the like. The silicon nitride oxide film as the middle layer may be replaced by a silicon nitride (such as Si3N4) film. The silicon oxynitride film as the upper layer may be replaced by a silicon oxide film. The thickness of each film is preferably in the range of from 0.05 to 3 μm, and can be freely selected from that range.
Subsequently, as shown in
Next, as shown in
Next, as shown in
The first interlayer insulating film 111 can be formed of a heat-resistant organic resin such as polyimide, acrylic, or polyamide. Instead of the aforementioned organic resins, a low dielectric constant material (low-k material), a resin including a Si—O—Si bond (hereinafter also called a siloxane-based resin), or the like can also be used. Siloxane has a skeleton structure of a bond of silicon (Si) and oxygen (O). As a substituent, an organic group containing at least hydrogen (such as an alkyl group or aromatic hydrocarbon) is used. Alternatively, a fluoro group may be used as the substituent. Further alternatively, a fluoro group and an organic group containing at least hydrogen may be used as the substituent. The first interlayer insulating film 111 can be formed by spin coating, dipping, spray coating, a droplet discharging method (an ink jetting method, screen printing, offset printing, or the like), a doctor knife, a roll coater, a curtain coater, a knife coater, or the like, depending on the material thereof. Alternatively, the first interlayer insulating film 111 can be formed using an inorganic material such as silicon oxide, silicon nitride, silicon oxynitride, PSG (phosphosilicate glass), PBSG (phosphoborosilicate glass), BPSG (borophosphosilicate glass), or an alumina film. Insulating films of these may be stacked to form the first interlayer insulating film 111.
The second interlayer insulating film 112 may be a film including carbon such as DLC (diamond-like carbon) or carbon nitride (CN), a silicon oxide film, a silicon nitride film, a silicon nitride oxide film, or the like formed by a plasma CVD method, atmospheric pressure plasma, or the like. Alternatively, a photosensitive or nonphotosensitive organic material such as polyimide, acrylic, polyamide, resist, or benzocyclobutene; a siloxane-based resin; or the like may be used.
Filler may be mixed into the first interlayer insulating film 111 or the second interlayer insulating film 112 in order to prevent the first interlayer insulating film 111 or the second interlayer insulating film 112 from being peeled off or cracked due to stress generated by a difference in coefficient of thermal expansion between the first interlayer insulating film 111 or the second interlayer insulating film 112 and a conductive material of a wiring that is formed later, or the like.
The third interlayer insulating film 104 can be formed using an organic resin film, an inorganic insulating film, or a siloxane-based insulating film. The organic resin film may include, for example, acrylic, polyimide, polyamide, or the like, and the inorganic insulating film may include silicon oxide, silicon nitride oxide, or the like. A mask used for forming the contact hole can be formed by a droplet discharging method or a printing method. Moreover, the third interlayer insulating film 104 itself can be formed by a droplet discharging method or a printing method.
Although the example is explained in which the lower wiring 106 has a stacked-layer structure of the Al film 106a with high conductivity and the Ti film 106b for preventing generation of hillock and void of the Al film 106a, a titanium nitride film may be formed below the Al film 106a to prevent Al diffusion. The Al film 106a is preferably formed to a thickness of from 400 to 500 nm by using pure Al with a purity of 99.9% or more.
The lower wiring 106 is not always necessary. Even when the lower wiring 106 is not formed, the antenna 101 includes the antenna base layer 107 and the copper plating layer 108 in a similar manner to the case where the lower wiring 106 is formed.
The antenna base layer 107 including the alloy of nickel and any of titanium, tantalum, tungsten, or molybdenum can be formed by performing sputtering only once. Moreover, when the unnecessary part of the antenna base layer 107 is removed, only one kind of etchant is necessary. This can achieve improvement of throughput and cost reduction in manufacturing semiconductor devices.
An organic resin such as polyimide, epoxy, acrylic, or polyamide can be used for the insulating layer 109. Instead of the aforementioned organic resins, an inorganic resin such as a resin including a Si—O—Si bond formed by using a siloxane-based material (this resin is hereinafter referred to as a siloxane-based resin) as a starting material can be used. The siloxane-based resin may include as a substituent at least one of fluorine, an alkyl group, or aromatic hydrocarbon in addition to hydrogen.
If a soft magnetic material can be contained, an inorganic insulating film such as a film of silicon oxide, silicon nitride oxide, silicon nitride, or the like can also be used as the insulating layer 109.
The protection film 115 can be formed by, for example, applying on the entire surface an epoxy-based, acrylate-based, or silicon-based resin which is soluble in water or in alcohols by a spin coating method or the like.
Although this embodiment mode shows the example of forming the copper plating layer 108 by an electrolytic plating method, an electroless plating method may alternatively be employed. The top surface of the antenna may have a shape other than the rectangular and spiral shape.
Although the example is described in which the substrate 102 is a glass substrate in this example, the substrate 102 may be a flexible substrate such as a plastic substrate. In the case of using a flexible substrate, the antenna and the integrated circuit are first formed over a substrate made of glass or the like; then, the antenna and the integrated circuit are separated and attached to the flexible substrate.
Next, an example of a circuit configuration of the wireless chip of this embodiment mode is shown.
Although not particularly shown here, there may additionally be a data modulator/demodulator circuit, a sensor, an interface circuit, and the like. With such a structure, the wireless chip 400 can communicate information with the reader/writer 401 without contact.
In the above structure of the wireless chip, the portion other than the antenna portion 402 can be the integrated circuit, and the antenna and the integrated circuit can be formed over one substrate.
Although this embodiment mode explains the example of the wireless chip provided with the battery capacitor 410 as a wirelessly chargeable battery (radio frequency battery, or noncontact battery by radio frequency), the battery capacitor 410 is not always necessary. When the battery capacitor 410 is not provided, the backflow prevention diode 409 is also unnecessary.
Moreover, the capacitor is used as a charging element for accumulating charges (also called battery); however, the present invention is not limited to this. In this embodiment mode, the battery refers to a wirelessly chargeable battery of which continuous operation time can recover by being charged. Further, as the battery, a thin sheet-like battery or a roll-like battery with a small diameter is preferably used, although the type of battery used may differ depending on the intended use. For example, size reduction is possible with a lithium battery, preferably a lithium polymer battery using gel electrolyte, a lithium ion battery, or the like. The battery may be any kind of chargeable battery, such as a nickel metal hydride battery, a nickel cadmium battery, an organic radical battery, a lead-acid battery, an air secondary battery, a nickel-zinc battery, a silver-zinc battery, or a capacitor with high capacity.
Note that as the capacitor with high capacity that can be used as a battery of this embodiment mode, it is preferable to use a capacitor having electrodes whose opposed areas are large. In particular, it is preferable to use a double-layer electrolytic capacitor which is formed using an electrode material having a large specific surface area, such as activated carbon, fullerene, or a carbon nanotube. A capacitor has a simpler structure than a battery, and further, a capacitor can be easily formed to be thin and formed by stacking layers. A double-layer electrolytic capacitor has a function of storing power and will not deteriorate that much even after it is charged and discharged a number of times. Further, a double-layer electrolytic capacitor has an excellent property that it can be charged rapidly.
In the present invention, the antenna is disposed in the center of the wireless chip, which improves the capability of the power source produced in the wireless chip and therefore enhances the charging efficiency.
In this embodiment mode, the antenna portion, the rectifier circuit portion, and the booster circuit used in the wireless chip are also used as the antenna portion, the rectifier circuit portion, and the booster circuit portion in the wirelessly chargeable battery; therefore, the reader/writer 401 can be used as a signal generating source for charging the battery capacitor 410 at the same time as operating the wireless chip.
The wirelessly chargeable battery shown in this embodiment mode can charge an object without contact, and is very easy to be carried. When the battery is provided in the wireless chip, a memory which needs a power source, such as SRAM, can be mounted, which can contribute to sophistication of the wireless chip.
However, the present invention is not limited to this structure, and a part or all of the antenna portion, the rectifier circuit portion, and the booster circuit may be separated for RFID operation and for charge of the wirelessly chargeable battery. For example, when the antenna portion 402 is separated for the antenna portion for RFID operation and the antenna portion for charge of the wirelessly chargeable battery, the frequency of signals used for RFID operation and the frequency of signals for charge of the wirelessly chargeable battery can be different from each other. In this case, the signals generated from the reader/writer 401 and the signals generated from the signal generating source to the wirelessly chargeable battery are preferably in the frequency range where the both signals do not interfere with each other.
When the antenna portion, the rectifier circuit portion, and the booster circuit are used in common for RFID operation and for charge of the wirelessly chargeable battery, the structure may be that a switching element is disposed between the wirelessly chargeable battery and the booster circuit and the booster circuit and the wirelessly chargeable battery are disconnected from each other by turning off the switch during writing operation while they are connected to each other by turning on the switch during the time other than the writing operation. In this case, since the battery is not charged during the writing operation, voltage drop during the writing operation can be avoided. The switching element can have a known structure.
Another embodiment mode of a wireless chip as an example of a semiconductor device of the present invention will hereinafter be explained with reference to drawings.
Since
The first antenna base layer 107a is formed over the lower wiring 106, and the second antenna base layer 107b is formed over the first antenna base layer 107a. The copper plating layer 108 is formed over the second antenna base layer 107b.
The antenna 101 includes the lower wiring 106, the first antenna base layer 107a, the second antenna base layer 107b, and the copper plating layer 108.
The first antenna base layer 107a is a nitride film of any of titanium, tantalum, tungsten, or molybdenum, while the second antenna base layer 107b is a nickel nitride film. It is to be noted that any of titanium, tantalum, tungsten, or molybdenum means one of titanium, tantalum, tungsten, or molybdenum, or means two or more of these metals.
The nitride film of any of titanium, tantalum, tungsten, or molybdenum as the first antenna base layer 107a can prevent copper of the copper plating layer 108 from diffusing into the insulating layer 109. Since the nickel nitride film as the second antenna base layer 107b has high adhesion to copper, the resulting copper plating can be fixed onto the second antenna base layer 107b. The nitride films of such metals have conductivity, thereby serving as a precipitation electrode of copper at electrolytic plating. Thus, Embodiment Mode 2 where the first antenna base layer 107a is the nitride film of any of titanium, tantalum, tungsten, or molybdenum and the second antenna base layer 107b is the nickel nitride film has advantageous effects in that the first antenna base layer 107a works as a barrier layer for preventing copper diffusion such as electromigration or stress migration and the second antenna base layer 107b works as a seed layer at the formation of the copper plating layer 108. In this manner, stacking the antenna base layers can improve the function of the first antenna base layer 107a as a barrier layer and can stabilize the function of the second antenna base layer 107b as a seed layer.
It is to be noted that the same advantageous effect can be obtained even when the second antenna base layer 107b includes a metal selected from aluminum, nickel, copper, or chromium, or an alloy of two or more selected from these metals, and the first antenna base layer 107a includes a nitride film of an alloy of nickel and any of titanium, tantalum, tungsten, or molybdenum.
Next, a method of manufacturing a wireless chip of this embodiment mode will be explained. The method of manufacturing a wireless chip of this embodiment mode is the same as that of Embodiment Mode 1 except that the step of forming the antenna base layer 107 in the method of manufacturing a wireless chip in Embodiment Mode 1 is replaced by the step of forming the first antenna base layer 107a and the second antenna base layer 107b.
Therefore, description will hereinafter be made on only the step of forming the first antenna base layer 107a and the second antenna base layer 107b with reference to
In Embodiment Mode 2, the first antenna base layer 107a and the second antenna base layer 107b are formed in order by a sputtering method over the exposed portion of the lower wiring 106 and the insulating layer 109, instead of the antenna base layer 107 shown in the step of manufacturing a wireless chip in
Next, the copper plating layer 108 is formed by an electrolytic plating method as shown in
The steps other than the above steps are the same as those in the method of manufacturing a wireless chip in Embodiment Mode 1.
The description of the circuit configuration of the wireless chip in this embodiment mode is omitted because the configuration is the same as that of Embodiment Mode 1.
Next, a method of manufacturing a wireless chip of another embodiment mode of the present invention will be explained in detail. Although this embodiment mode shows a TFT as an example of a semiconductor element used for an integrated circuit of a wireless chip, a semiconductor element used for an integrated circuit is not limited to this, and any kind of semiconductor element can be used.
First, a release layer 501 is formed over a first substrate 500 having heat resistance as shown in
The release layer 501 can be formed by a sputtering method, a reduced-pressure CVD method, a plasma CVD method, or the like by using a layer containing silicon such as amorphous silicon, polycrystalline silicon, single-crystal silicon, or microcrystalline silicon (including semi-amorphous silicon) as its main component. In this embodiment mode, the release layer 501 is formed of amorphous silicon with a thickness of about 50 nm by a reduced-pressure CVD method. The material of the release layer 501 is not limited to silicon and may be of any kind as long as it can be selectively etched away. The thickness of the release layer 501 is preferable in the range of from 10 to 100 nm. When semi-amorphous silicon is used, the thickness may be in the range of from 30 to 50 nm.
Next, a base film 502 is formed over the release layer 501. The base film 502 is provided in order to prevent alkaline-earth metal or alkali metal such as Na in the first substrate 500 from diffusing into the semiconductor film, thereby preventing an adverse effect on characteristics of the semiconductor element such as a TFT. The base film 502 also works to protect the semiconductor element during a later step of separating the semiconductor elements. The base film 502 may be either a single insulating film or stacked insulating films. Therefore, an insulating film which can prevent alkali metal and alkaline-earth metal from diffusing into the semiconductor film, such as a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film is used.
In this embodiment mode, a 100-nm-thick silicon oxynitride film, a 50-nm-thick silicon nitride oxide film, and a 100-nm-thick silicon oxynitride film are stacked in order to form the base film 502; however, the material, thickness, and number of stacked films are not limited to these. For example, the silicon oxynitride film as the lower layer may be replaced by a siloxane-based resin film with a thickness of 0.5 to 3 μm which is formed by a spin coating method, a slit coating method, a droplet discharging method, a printing method, or the like. The silicon nitride oxide film as the middle layer may be replaced by a silicon nitride (such as Si3N4) film. The silicon oxynitride film as the upper layer may be replaced by a silicon oxide film. The thickness of each film is preferably in the range of from 0.05 to 3 μm, and can be freely selected from that range.
Alternatively, the base film 502 may be formed by sequentially stacking a silicon oxynitride film or a silicon oxide film, a siloxane-based resin film, and a silicon oxide film.
Here, the silicon oxide film can be formed by thermal CVD, plasma CVD, normal pressure CVD, bias ECRCVD, or the like with the use of a mixed gas of SiH4 and O2, a mixed gas of TEOS (tetraethoxysilane) and O2, or the like. The silicon nitride film can be formed typically by plasma CVD with the use of a mixed gas of SiH4 and NH3. The silicon oxynitride film and the silicon nitride oxide film can be formed typically by plasma CVD with the use of a mixed gas of SiH4 and N2O.
Next, a semiconductor film 503 is formed over the base film 502. It is preferable that the semiconductor film 503 be formed without being exposed to the air after the formation of the base film 502. The semiconductor film 503 has a thickness of 20 to 200 nm (preferably 40 to 170 nm, more preferably 50 to 150 nm). The semiconductor film 503 may be formed of an amorphous semiconductor, a semi-amorphous semiconductor, or a polycrystalline semiconductor. Instead of silicon, silicon germanium may be used as the semiconductor. In the case of using silicon germanium, the concentration of germanium is preferably in the range of from about 0.01 to 4.5 at. %.
The semiconductor film 503 may be crystallized by a known technique. Known crystallization methods include a laser crystallization method using laser light and a crystallization method using a catalytic element. Alternatively, a laser crystallization method using laser light and a crystallization method using a catalytic element may be used in combination. When the first substrate 500 is a heat-resistant substrate such as a quartz substrate, high-temperature annealing at about 950° C. may be combined with any of a thermal crystallization method using an electrically heated oven, a lamp annealing crystallization method using infrared light, or a crystallization method using a catalytic element.
For example, in the case of carrying out laser crystallization, the semiconductor film 503 is subjected to thermal annealing at 500° C. for an hour before laser crystallization. This thermal annealing can increase the resistance of the semiconductor film 503 against laser. Then, a continuous wave solid-state laser is used to irradiate the semiconductor film 503 with laser light of any of second to fourth harmonic waves of a fundamental wave; thus, crystals with large grain diameter can be obtained. For example, typically, a second harmonic (532 nm) or a third harmonic (355 nm) of a Nd:YVO4 laser (fundamental wave: 1064 nm) is preferably used. Specifically, laser light emitted from a continuous wave YVO4 laser is converted into a harmonic wave through a non-linear optical element, and thus laser light with a power of 10 W is obtained. Then, the laser light is preferably shaped into rectangular or elliptical laser light on an irradiated surface through an optical system, and is delivered onto the semiconductor film 503. The power density of the laser light at this time is necessary to range from about 0.01 to 100 MW/cm2 (preferably 0.1 to 10 MW/cm2). The irradiation is then performed by setting the scan speed in the range of from about 10 to 2000 cm/sec.
Alternatively, the laser crystallization may be performed by using a pulsed laser with a repetition rate of 10 MHz or more, which is extremely higher than generally used lasers having a repetition rate of several tens to several hundreds of hertzs. It is said that it takes several tens to several hundreds of nanoseconds to completely solidify a semiconductor film after the semiconductor film is irradiated with pulsed laser light. When the pulsed laser light has the above-described repetition rate, the semiconductor film can be irradiated with laser light before the semiconductor film melted by previous laser light is solidified. Therefore, a solid-liquid interface can be continuously moved in the semiconductor film so that crystal grains which have continuously grown in a scanning direction are formed in the semiconductor film. Specifically, it is possible to form an aggregation of crystal grains each having a width of approximately 10 to 30 μm in the scanning direction and a width of 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 a channel direction of the TFT by forming a crystal grain of a single crystal that is extended long along the scanning direction.
The laser crystallization may be performed by simultaneously delivering continuous wave laser light of a fundamental wave and continuous wave laser light of a harmonic wave, or simultaneously delivering continuous wave laser light of a fundamental wave and pulsed laser light of a harmonic wave.
The laser light may be delivered in an inert gas atmosphere such as noble gas or nitrogen. This can suppress the roughness of a semiconductor surface due to the laser irradiation and also suppress variation in threshold voltage caused by variation in interface state density.
By the aforementioned laser irradiation, the semiconductor film 503 with improved crystallinity is formed. Alternatively, a polycrystalline semiconductor may be formed in advance by a sputtering method, a plasma CVD method, a thermal CVD method, or the like.
Although the semiconductor film 503 is crystallized in this embodiment mode, the semiconductor film 503 may remain amorphous or microcrystalline without being crystallized and may be subjected to a later-described process. A TFT using an amorphous semiconductor or a microcrystalline semiconductor has advantages of low cost and high yield because the number of manufacturing steps is smaller than that of a TFT using a polycrystalline semiconductor.
An amorphous semiconductor can be obtained by glow discharge decomposition of a gas containing silicon. As a typical gas containing silicon, SiH4, and Si2H6 are given. This gas containing silicon may be diluted with hydrogen or with hydrogen and helium.
Note that a semi-amorphous semiconductor refers to a semiconductor with an intermediate structure between an amorphous semiconductor and a crystalline semiconductor (including a single-crystal semiconductor and a polycrystalline semiconductor). The semi-amorphous semiconductor is a semiconductor having a third condition that is stable in terms of free energy and is a crystal having a short-range order and lattice distortion which can be dispersed in a non-single-crystal semiconductor film with its grain diameter of 0.5 to 20 nm. The peak of the Raman spectrum of the semi-amorphous semiconductor shifts to the side of lower wavenumber than 520 cm−1. According to X-ray diffraction, diffraction peaks of a silicon crystal lattice are observed at (111) and (220). In order to terminate a dangling bond, hydrogen or halogen is added by at least 1 at. % or more. In this specification, such a semiconductor is referred to as a semi-amorphous semiconductor (SAS) for convenience. Moreover, a noble gas element such as helium, argon, krypton, or neon may be contained therein to further promote lattice distortion, so that stability is enhanced and a favorable semi-amorphous semiconductor film can be obtained.
In addition, SAS can be obtained by glow discharge decomposition of a gas containing silicon. As a typical gas containing silicon, SiH4 is given, and Si2H6, SiH2Cl2, SiHCl3, SiCl4, SiF4, or the like can be used as well as SiH4. The gas containing silicon may be diluted with hydrogen or with a gas in which one or more of noble gas elements selected from helium, argon, krypton, or neon are added to hydrogen; therefore, the SAS film can be easily formed. It is preferable that the gas containing silicon be diluted with a dilution ratio in the range of from 2 to 1000 times. Further, a carbide gas such as CH4 or C2H6, a germanium gas such as GeH4 or GeF4, F2, or the like may be mixed into the gas containing silicon so as to adjust the energy bandwidth within the range of from 1.5 to 2.4 eV or from 0.9 to 1.1 eV
For example, in the case of using a gas in which H2 is added to SiH4 or a gas in which F2 is added to SiH4, the subthreshold coefficient (subthreshold swing) of the TFT can be less than or equal to 0.35 V/dec, typically 0.25 to 0.09 V/dec, and the mobility of carriers can be 10 cm2/Vs when the TFT is manufactured using the formed semi-amorphous semiconductor. When a 19-stage ring oscillator is formed of the TFT using the above-described semi-amorphous semiconductor, for example, the oscillation frequency is greater than or equal to 1 MHz, preferably, greater than or equal to 100 MHz, at a power supply voltage of 3 to 5 V. In addition, at a power supply voltage of 3 to 5 V, delay time per one stage of an inverter can be 26 ns, preferably less than or equal to 0.26 ns.
Next, as shown in
Next, gate electrodes 510 to 512 are formed as shown in
The resist mask may be replaced by a mask of silicon oxide or the like. In this case, a step of patterning to form a mask of silicon oxide, silicon oxynitride, or the like (called a hard mask) is added; however, the gate electrodes 510 to 512 can have desired widths because the film thickness of the mask does not decrease at the time of etching compared with the resist. The gate electrodes 510 to 512 may be formed selectively by a droplet discharging method without using the resist 513.
As the conductive material, various materials can be selected depending on the function of a conductive film. When the gate electrodes and the antenna are formed at the same time, the material may be selected in consideration of their functions.
As an etching gas for etching the gate electrodes, a mixed gas of CF4, Cl2, and O2, or a Cl2 gas is employed, though the etching gas is not limited to this.
Next, as shown in
Next, as shown in
Next, as shown in
When the insulating film 520 is formed, the insulating film 520 may also be formed at a rear surface of the first substrate 500. In this case, the insulating film formed at the rear surface of the first substrate 500 may be selectively etched away by using a resist. Specifically, the insulating film formed at the rear surface may be etched away together with the insulating film 520 and the gate insulating film 507 at the time of forming the sidewalls 522 to 524 by the etchback method.
The sidewalls 522 and 524 will serve as masks in, subsequently, doping with an impurity imparting n-type conductivity at high concentration to form low-concentration impurity regions or non-doped off-set regions below the sidewalls 522 and 524. Therefore, in order to control the widths of the low-concentration impurity regions or the off-set regions, the size of the sidewalls 522 and 524 may be adjusted by changing, as appropriate, the film thickness of the insulating film 520 or the condition at the etchback method in forming the sidewalls 522 and 524.
Next, as shown in
After removing the resist 525 by ashing or the like, the impurity regions may be thermally activated. For example, after depositing a silicon oxynitride film in 50 nm thick, heat treatment may be performed at 550° C. for 4 hours in a nitrogen atmosphere.
After a silicon nitride film containing hydrogen is formed in 100 nm thick, heat treatment may be performed thereon at 410° C. for 1 hour in a nitrogen atmosphere for hydrogenation of the island-like semiconductor films 504 to 506. Alternatively, heat treatment may be performed at 300 to 450° C. for 1 to 12 hours in an atmosphere containing hydrogen for hydrogenation of the island-like semiconductor films 504 to 506. Moreover, plasma hydrogenation (using hydrogen excited in plasma) may be performed as another means of hydrogenation. This hydrogenation step can terminate dangling bonds with thermally excited hydrogen. After attaching the semiconductor element onto a second substrate 548 that is flexible in a later process, a defect may be formed in the semiconductor film by bending the second substrate 548. However, even in this case, the defect can be terminated by the hydrogen in the semiconductor film when the concentration of hydrogen in the semiconductor film is set in the range of from 1×1019 to 1×1022 atoms/cm3, preferably from 1×1019 to 5×1020 atoms/cm3, by the hydrogenation. Further, in order to terminate the defect, halogen may be included in the semiconductor film.
According to a series of the foregoing steps, an n-channel TFT 529, a p-channel TFT 530, and an n-channel TFT 531 are formed. When the size of the sidewall is adjusted by changing, as appropriate, the condition at the etchback method or the film thickness of the insulating film 520 in the manufacturing steps described above, the TFT can have a channel length of 0.2 to 2 μm. Although the TFTs 529 to 531 each have a top-gate structure in this embodiment mode, they may have a bottom-gate structure (inverted-staggered structure).
After that, a passivation film for protecting the TFTs 529 to 531 may be formed. It is preferable that the passivation film be made of silicon nitride, silicon nitride oxide, aluminum nitride, aluminum oxide, silicon oxide, or the like which can prevent the penetration of alkali metal or alkaline-earth metal into the TFTs 529 to 531. Specifically, for example, a silicon oxynitride film having a thickness of approximately 600 nm can be used as the passivation film. In this case, the hydrogenation step may be performed after forming the silicon oxynitride film. In this manner, three layers of insulating films of silicon oxynitride, silicon nitride, and silicon oxynitride are formed over the TFTs 529 to 531. However, the structures and the materials of these films are not limited thereto. With the above structure, since the TFTs 529 to 531 are covered with the base film 502 and the passivation film, it is possible to prevent alkali metal such as Na or alkaline-earth metal from diffusing into the semiconductor film used for the semiconductor element, thereby preventing an adverse effect on characteristics of the semiconductor element.
Next, as shown in
Further, a second interlayer insulating film 534 is formed over the first interlayer insulating film 533 in this embodiment mode. The second interlayer insulating film 534 may be a film including carbon such as DLC (diamond-like carbon) or carbon nitride (CN), a silicon oxide film, a silicon nitride film, a silicon nitride oxide film, or the like formed by a plasma CVD method, atmospheric-pressure plasma, or the like. Alternatively, the second interlayer insulating film 534 may be formed of a photosensitive or non-photosensitive organic material such as polyimide, acrylic, polyamide, resist, or benzocyclobutene, a siloxane-based resin, or the like.
Filler may be mixed into the first interlayer insulating film 533 or the second interlayer insulating film 534 in order to prevent the first interlayer insulating film 533 or the second interlayer insulating film 534 from being peeled off or cracked due to stress generated by a difference in coefficient of thermal expansion between the first interlayer insulating film 533 or the second interlayer insulating film 534 and a conductive material of a wiring that is formed later, or the like.
Next, as shown in
By mixing about 1 at. % of silicon into aluminum, it is possible to prevent generation of hillock at the time of baking the resist during patterning of the wirings. Copper may be mixed by approximately 0.5 at. % instead of silicon. When an aluminum-silicon alloy layer is sandwiched between titanium and titanium nitride, the resistance against the hillock is improved further. It is preferable to use the hard mask described above which is made of silicon oxynitride or the like in patterning. The material and the forming method of the wirings are not limited thereto, and the aforementioned material used for the gate electrode may be used.
The wirings 535 and 536 are connected to the high-concentration impurity regions 527 of the n-channel TFT 529. The wirings 536 and 537 are connected to the high-concentration impurity regions 519 of the p-channel TFT 530. The wirings 538 and 539 are connected to the high-concentration impurity regions 528 of the n-channel TFT 531.
Next, as shown in
Next, an antenna 541 and an insulating layer 544 are formed over the third interlayer insulating film 540. The antenna 541 can have a structure of lower wiring\antenna base layer\copper plating layer in a similar manner to the example shown in Embodiment Mode 1. In this case, a nitride film of an alloy of nickel and any of titanium, tantalum, tungsten, or molybdenum is used as the antenna base layer.
Alternatively, the antenna 541 may have a structure of lower wiring\first antenna base layer\second antenna base layer\copper plating layer in a similar manner to the example shown in Embodiment Mode 2. In this case, the first antenna base layer is a nitride film of any of titanium, tantalum, tungsten, or molybdenum, and the second antenna base layer is a nickel nitride film.
In either case, description is omitted because the antenna 541 and the insulating layer 544 are formed by a similar method to that described in Embodiment Mode 1 or 2.
After forming the antenna 541 and the insulating layer 544, a separation insulating film 542 is formed to cover the antenna 541 and the insulating layer 544, as shown in
Next, a protection layer 543 is formed to cover the separation insulating film 542, as shown in
In this embodiment mode, the protection layer 543 is formed in the following manner: a water-soluble resin (manufactured by Toagosei Co., Ltd.: VL-WSHL10) is applied so as to have a thickness of 30 μm by a spin coating method, and exposed to light for 2 minutes for temporary curing, and then, its rear surface is exposed to UV light for 2.5 minutes and its front surface is exposed to UV light for 10 minutes, 12.5 minutes in total, so that the resin is fully cured. When both the separation insulating film 542 and the protection layer 543 are formed of organic resins, the two films might be partly melted depending on a solvent to be used, at the time of application or baking, resulting in that the adhesion between them becomes too high. Therefore, in the case of forming both the separation insulating film 542 and the protection layer 543 using organic resins that are soluble in the same solvent, it is preferable to further form an inorganic insulating film (a silicon nitride film, a silicon nitride oxide film, an aluminum nitride film, or an aluminum nitride oxide film) over the separation insulating film 542 so as to smoothly remove the protection layer 543 in a later step.
Next, a groove 546 is formed to isolate the wireless chips from each other, as shown in
Next, the release layer 501 is etched away, as shown in
Subsequently, as shown in
The second substrate 548 may be, for example, a glass substrate including barium borosilicate glass, aluminoborosilicate glass, or the like, a flexible organic material such as paper or plastic. Alternatively, the second substrate 548 may be formed of a flexible inorganic material. ARTON (manufactured by JSR Corporation) formed of polynorbornene having a polar group can be used for a plastic substrate. In addition, polyester typified by polyethylene terephthalate (PET); polyether sulfone (PES); polyethylene naphthalate (PEN); polycarbonate (PC); nylon; polyetheretherketone (PEEK); polysulfone (PSF); polyetherimide (PEI); polyarylate (PAR); polybutylene terephthalate (PBT); polyimide; an acrylonitrile butadiene styrene resin; polyvinyl chloride; polypropylene; polyvinyl acetate; an acrylic resin; and the like can be given. It is preferable that the second substrate 548 have thermal conductivity as high as 2 to 30 W/mK in order to diffuse heat generated in an integrated circuit.
Then, the protection layer 543 is removed. Here, since the protection layer 543 is formed of a water-soluble resin, the protection layer 543 is removed by being dissolved in water. When the remaining part of the protection layer 543 leads to a defect, a surface of the remaining part of the protection layer 543 is preferably subjected to washing or O2 plasma treatment so that the remaining part of the protection layer 543 is partially removed.
Next, an insulating layer 549 is formed to cover the separation insulating film 542, as shown in
Next, an adhesive 552 is applied onto the insulating layer 549, and a cover member 553 is attached thereto. The cover member 553 can be formed of a similar material to the second substrate 548. The adhesive 552 may have a thickness of from, for example, 10 to 200 μm.
A material which can attach the cover member 553 and the insulating layer 549 to each other is used for the adhesive 552. As the adhesive 552, for example, various curable adhesives such as a reactive curable adhesive, a thermosetting adhesive, and a photo curable adhesive such as an ultraviolet curable adhesive, and an anaerobic adhesive can be used.
Although the cover member 553 is attached to the insulating layer 549 by using the adhesive 552 in this embodiment mode, the present invention is not limited to this structure. The insulating layer 549 and the cover member 553 can also be attached to each other directly when a resin that functions as an adhesive is used for an insulator 550 of the insulating layer 549.
Although this embodiment mode shows the example of using the cover member 553 as shown in
Through the aforementioned steps, the wireless chip is completed. By the above-described manufacturing method, a considerably-thin integrated circuit having a total thickness of greater than or equal to 0.3 μm and less than or equal to 3 μm, typically approximately 2 μm, can be formed between the second substrate 548 and the cover member 553. It is to be noted that the thickness of the integrated circuit includes the thicknesses of various insulating films and interlayer insulating films formed between the adhesive 547 and the adhesive 552 in addition to the thickness of the semiconductor element itself, but does not include the thickness of the antenna. In addition, the integrated circuit included in the wireless chip can be formed so as to occupy an area of less than or equal to 5 mm×5 mm (25 mm2), more preferably, approximately 0.3 mm×0.3 mm (0.09 mm2) to 4 mm×4 mm (16 mm2).
Further, when the integrated circuit is provided at a position that is closer to the center between the second substrate 548 and the cover member 553, mechanical strength of the wireless chip can be increased.
The wireless chip formed thus has an advantageous effect in that even when the copper plating layer is used as the antenna, the nitride film of the alloy of nickel and any of titanium, tantalum, tungsten, or molybdenum which is used as the antenna base layer works as a seed layer at the formation of the copper plating layer and also works as a barrier layer for preventing copper diffusion such as electromigration or stress migration.
Moreover, another advantageous effect is that when the nitride film of any of titanium, tantalum, tungsten, or molybdenum is used as the first antenna base layer 107a and the nickel nitride film is used as the second antenna base layer 107b, each antenna base layer works as a seed layer at the formation of the copper plating layer 108 and also works as a barrier layer for preventing copper diffusion such as electromigration or stress migration.
It is to be noted that the same advantageous effect can be obtained even when a metal selected from aluminum, nickel, copper, or chromium, or an alloy of two or more selected from these metals is used for the second antenna base layer 107b, and a nitride film of an alloy of nickel and any of titanium, tantalum, tungsten, or molybdenum is used for the first antenna base layer 107a.
Embodiment Mode 4 will explain application examples of a semiconductor device of the present invention. The application range of a semiconductor device of the present invention is so wide that it can be applied to any product in order that the information of an object such as the history is revealed without contact and utilized in production, management, and the like. For example, a semiconductor device of the present invention may be incorporated in bills, coins, securities, certificates, bearer bonds, containers for packaging, books, recording media, personal belongings, vehicles, foods, clothes, healthcare items, livingware, medicals, electronic appliances, and the like. These examples are explained with reference to
The bills and coins correspond to currency circulating in the market and include notes that are current as money in a specific area (cash voucher), memorial coins, and the like. The securities include a check, a certificate, a promissory note, and the like (
When a semiconductor device 80 of the present invention is incorporated in bank notes, coins, securities, bearer bonds, certificates, and the like, forgery can be prevented. When the semiconductor device 80 is incorporated in containers for packaging, books, recording media, personal belongings, foods, livingware, electronic appliances, and the like, the efficiency of an inspection system, a system used in a rental shop, or the like can be improved. When the semiconductor device 80 is incorporated in vehicles, healthcare items, medicals, and the like, forgery and theft of them can be prevented and medicines can be prevented from being taken in a wrong manner. The semiconductor device 80 may be attached to a surface of a product or incorporated into a product. Further, the semiconductor device 80 may be incorporated into paper of a book, or an organic resin of a package, for example.
In addition, when a semiconductor device is implanted into creatures such as animals, each creature can be identified easily. For example, when a semiconductor device provided with a sensor is implanted into creatures such as domestic animals, not only the year of birth, sex, breed, and the like but also the health condition such as the current body temperature can be easily managed. In particular, since the semiconductor device shown in the above embodiment mode includes the antenna base layer formed of a nitride of a nickel alloy that has high adhesion to copper, it is possible to prevent a defect of the semiconductor device due to poor connection between the antenna and the integrated circuit even when the semiconductor device is provided to a curved surface or the product is bent.
The semiconductor device shown in this embodiment mode can be applied to the semiconductor device in any of the other embodiment modes described in this specification.
This application is based on Japanese Patent Application serial no. 2007-105395 filed with Japan Patent Office on Apr. 13, 2007, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-105395 | Apr 2007 | JP | national |
This application is a continuation of U.S. application Ser. No. 12/055,918, filed Mar. 26, 2008, now allowed, which claims the benefit of a foreign priority application filed in Japan as Serial No. 2007-105395 on Apr. 13, 2007, both of which are incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12055918 | Mar 2008 | US |
| Child | 12830195 | US |
