JP5026144B2 - Memory element - Google Patents

Description

  The present invention relates to a memory element used as an information processing element.

  In information processing devices, storage devices (hereinafter referred to as “memory”) that store bit information are widely used for civilian appliances and communication elements. Memory is divided into two types: one that retains the stored data when it is turned off (volatile memory) and one that retains the stored data even when the power is turned off (nonvolatile memory). be able to. Among them, the nonvolatile memory has recently become more important in many information processing apparatuses such as mobile phones and portable music players.

  As such a non-volatile memory, there is a flash memory provided with a floating gate (see Patent Document 1). FIG. 8 is a cross-sectional view schematically showing a configuration of a memory cell (memory element) of a typical flash memory conventionally used. This flash memory includes, for example, a floating gate 803 formed on a p-type silicon substrate 801 via a tunnel oxide film 802, and a control gate 805 formed on the floating gate 803 via a gate oxide film 804. And a source 806 and a drain 807 made of an n-type silicon layer formed on the silicon substrate 801 with the floating gate 803 interposed therebetween.

  In the memory cell configured in this manner, as is well known, first, bit information is stored by accumulating charges in the floating gate 803, and “0” state and “1” are determined depending on the state of accumulated charges. Distinguishes from the state. The memory cell constitutes an n-channel MOSFET, and the threshold value of the MOSFET differs depending on whether or not electric charge is accumulated in the floating gate 803, so that the memory state is read by the source / drain current. . In writing and erasing, by applying a voltage to the control gate 805, the source 806, and the drain 807, electrons are induced to the floating gate 803 through the tunnel oxide film 802, and electrons are emitted from the floating gate 803. To do. The floating gate 803 is normally insulated and separated, and electrons (charges) accumulated in the floating gate 803 do not leak even when the power is turned off. Thereby, a function as a rewritable nonvolatile memory in which information is not erased even when the power is turned off can be provided.

JP-A-5-335656

  However, in the flash memory using the floating gate structure as described above, a voltage is applied to the tunnel oxide film to forcibly move electrons to perform writing and erasing. Since the oxide film deteriorates, there is a problem that the lifetime of the element is not so long. This problem is caused by causing the tunnel oxide film to have two contradictory functions: the function of electrically insulating the floating gate for maintaining information and the function of allowing electrons to enter and exit for writing and erasing. It comes from being. Therefore, this problem is not limited to the flash memory, and is a problem common to all other nonvolatile memories using electrically isolated islands.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a new memory element having a longer element lifetime.

A memory element according to the present invention includes a support layer formed on a substrate and partially provided with a recess, and an opening region formed in contact with the support layer and partially open to correspond to the recess. And a storage layer comprising a buckled beam structure erected inside the open area, the storage layer having a compressive strain with respect to the support layer in a region in contact with the support layer, The beam structure can be displaced into two buckling states that are convex in at least two different directions in the plane direction of the substrate perpendicular to the extending direction of the beam structure. The state is bit information to be stored. According to this storage element, bit information is stored not by an electrical or magnetic state but by the shape of a buckled beam structure.

In the memory element, the memory layer is formed by crystal growth of a crystal material having a lattice constant different from that of the support layer on the support layer. Further, at least one supporting region layer and the storage layer is comprised of two made of a material mixed crystal having a lattice constant different, that is controlled the state of buckling of the beam structure by mole fraction mixed . The two materials with different lattice constants, GaAs, AlAs, InAs, GaP , AlP, InP, GaSb, AlSb, InSb, GaN, AlN, InN, and as long as it is selected from among a mixed crystal thereof Good. Two materials having different lattice constants may be selected from Si, Ge, C, and mixed crystals thereof.

  In the memory element, the memory layer may be made of a material having a piezoelectric effect, and the memory layer may be made of a material having a piezoresistive effect. Further, the storage layer may be made of a material having a magnetostrictive effect. Moreover, you may make it provide the ferromagnetic layer comprised on the beam structure and comprised from the ferromagnetic material. The storage layer may be composed of a material having a photodistortion effect.

The storage element may include a buckling state detection unit that detects two buckling states of the beam structure as stored bit information. Moreover, you may make it provide the buckling state control means which controls two buckling states of a beam structure as bit information to memorize | store. For example, buckled state detecting means, Ru includes a beam portion electrode formed on the beam structure, and a fixed electrode formed on the memory layer of the side of the beam structure. Incidentally, the beam structure, the thickness in the normal direction to the plane of the substrate, in parallel to buckle largely formed by the plane of the substrate to the plane direction of the width of the substrate.

As described above, according to the present invention, the beam structure in which the region in contact with the support layer is buckled by being built in the opening region on the storage layer having compressive strain with respect to the support layer. comprising a body, since the two-bit information stored buckling state of the beam structure, excellent effect that device lifetime of the memory element can be more lengthened is obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Embodiment 1]
First, Embodiment 1 of the present invention will be described. 1A and 1B are perspective views schematically showing a configuration example of the memory element in the first embodiment of the present invention. The memory element includes a substrate 101, a support layer 102 formed on the substrate 101, and a memory layer 103 formed on the support layer 102. The memory layer 103 has a compressive strain with respect to the support layer 102 in a region in contact with the lower support layer 102.

For example, the substrate 101 is made of GaAs, the support layer 102 is made of single crystal Al _0.7 Ga _0.3 As formed by crystal growth on the substrate 101, and the memory layer 103 is In _x Ga _1-x As. It should just be comprised from. x is a value from 0 to 1. Since In _x Ga _1-x As has a lattice constant that is approximately 7x% larger than Al _0.7 Ga _0.3 As, the above configuration allows the support layer 102 of the memory layer 103 formed on the support layer 102 to have the above structure. In the contact area, a compressive strain of about 7x% is provided. In this manner, when the storage layer 103 is formed by crystal growth of a crystal material having a lattice constant different from that of the support layer 102 on the support layer 102, the storage layer 103 is formed in a region in contact with the support layer 102. Is provided with a compressive strain with respect to the support layer 102.

  In addition, the memory layer 103 includes an opening region 132, and includes a beam structure 131 provided between the opposing sides of the opening region 132 (inside the opening region 132) and provided (built). ing. The beam structure 131 is buckled so as to protrude in a direction perpendicular to the direction in which the beam structure 131 extends. As will be described later, the beam structure 131 has two buckled states that are convex in at least two different directions, and can be displaced in these two states. In addition, an opening 121 is formed in the support layer 102 corresponding to the opening region 132 so that the substrate 101 side of the beam structure 131 is separated from the lower layer.

  In the example shown in FIGS. 1A and 1B, the support layer 102 has an opening 121 that passes therethrough, and the beam structure 131 is separated from the substrate 101. As a result, the beam structure 131 is formed apart from the surroundings except for both ends connected to the inside of the opening region 132 and can be displaced (buckled). In addition, it is good also as a state which can displace the beam structure 131 as the state spaced apart from the circumference | surroundings by providing a recessed part in the support layer 102 corresponding to the beam structure 131 instead of the opening part penetrated.

  A beam electrode 104 is formed on the beam structure 131, and a fixed electrode 105 and a fixed electrode 106 are formed on the memory layer 103 on the side of the beam structure 131. One end of the beam electrode 104 is connected to a terminal 107 formed on the memory layer 103.

Next, a method for manufacturing the memory element will be briefly described. First, an Al _0.7 Ga _0.3 As film serving as the support layer 102 is crystal-grown on the substrate 101 by a well-known crystal growth method such as metal organic vapor phase epitaxy. Next, an In _x Ga _1-x As film to be the memory layer 103 is formed on the Al _0.7 Ga _0.3 As film by a well-known crystal growth method. Next, the In _x Ga _1-x As film is processed by a known lithography technique and etching, and the memory layer 103 including the opening region 132 and the beam structure 131 installed in the opening region 132 is formed. To do. At this stage, since the beam structure 131 is formed in contact with the Al _0.7 Ga _0.3 As film, the beam structure 131 is fixed and not buckled, and is formed linearly.

Next, the electrodes such as the beam electrode 104, the fixed electrode 105, the fixed electrode 106, and the terminal 107 are formed on the memory layer 103 by a well-known lift-off method. Thereafter, the underlying Al _0.7 Ga _0.3 As film is selectively removed through the opening region 132 of the memory layer 103 by wet etching using hydrofluoric acid, and the support layer 102 having the opening 121 is formed. State. By forming the opening 121, the already formed beam structure 131 of the memory layer 103 is in a buckled state.

  For example, when the thickness of the beam structure 131 in the normal direction relative to the plane of the substrate 101 is larger than the width of the substrate 101 in the plane direction, the beam structure 131 is buckled in the plane direction of the substrate 101. Become. This embodiment exemplifies this case, and as shown in FIGS. 1 (a) and 2 (a), the beam structure 131 is in a state of buckling in a convex state on the fixed electrode 105 side, As shown in FIG. 1B and FIG. 2B, there are two states: a state in which the fixed electrode 106 is buckled in a convex state. 2A and 2B are plan views. In the memory element of the present embodiment, these two buckling states are made to correspond to “0” and “1” of the memory state.

  Writing and erasing of the memory element are performed by applying a voltage between the fixed electrode 105 or the fixed electrode 106 and the beam portion electrode 104 (terminal 107). For example, by applying a voltage between the fixed electrode 105 and the beam portion electrode 104, as shown in FIG. 2A, the beam structure 131 is made to buckle in a convex state toward the fixed electrode 105. What is necessary is just to delete bit information. On the other hand, a voltage is applied between the fixed electrode 106 and the beam electrode 104, and the beam structure 131 is buckled in a convex state toward the fixed electrode 106 as shown in FIG. Thus, the bit information “1” may be written. In this example, two buckling states of the beam structure 131 are controlled as stored bit information by an electrostatic force generated by applying a voltage to each electrode.

  In addition, reading of bit information may be performed by measuring the capacitance between the fixed electrode 105 or the fixed electrode 106 and the beam electrode 104. For example, a “0” state is read if the capacitance between the beam electrode 104 and the fixed electrode 105 is large, and a “1” state is read if the capacitance between the beam electrode 104 and the fixed electrode 105 is small. In the present embodiment, two buckling states of the beam structure are detected as stored bit information based on the measured capacitance.

  According to the memory element in the present embodiment described above, the memory layer formed so that the region in contact with the support layer has a compressive strain with respect to the support layer is erected in the opening region and buckled. A beam structure is provided, and two buckling states of the beam structure are stored as bit information. According to this storage element, bit information is stored not by an electrical and magnetic state but by the shape of the buckled beam structure, and unless the buckling state of the beam structure is changed, the stored state is Retained. As described above, since the information storage operation is performed by changing the shape of the beam structure, the storage element of this embodiment does not need to supply power for storing and holding. In addition, the deterioration of the tunnel oxide film in other storage elements using electrically isolated charge islands such as a well-known flash memory does not occur, and a longer element lifetime can be obtained.

  Moreover, in this memory element, the beam holding state is changed by displacing the beam structure and switching between the two buckling states, but the beam structure does not change in any state including the switching. , Except for both connected end portions, they are formed apart from the surrounding structure. For this reason, the beam structure does not have a problem such as sticking in which the side part contacts and fuses with the surrounding structure when writing or erasing bit information.

  By the way, the size of the buckling of the beam structure 131 is determined by the size of the residual strain in the memory layer 103. If the buckling amount is large, the stability of each of the “0” state and the “1” state increases. On the other hand, a high application is required to change the bit state from the “0” state to the “1” state or vice versa. A voltage is required. On the other hand, if the buckling amount is small, the bit state can be changed with a small voltage, but the stability of each state is lowered.

One of the most significant features of the memory element in this embodiment is that the value of the composition x in the In _x Ga _1-x As thin film constituting the memory layer 103 can be adjusted very accurately through control of the composition in crystal growth. is there. As described above, since the magnitude of the residual strain (compression strain) changes depending on the value of the composition x, according to the present embodiment, it is possible to control the magnitude of the compression strain extremely accurately. By using the advantage, the buckling state in the beam structure 131 can be controlled with high accuracy. In summary, at least one of the support layer and the storage layer is composed of a mixed crystal composed of two compounds (materials) having different lattice constants, and the buckling state of the beam structure can be controlled by this mixed crystal ratio. It becomes. As a result, according to the memory element of the present embodiment, a memory element having excellent bit information retention (memory) stability and a low driving voltage can be realized.

  In order to enable high-precision control as described above, materials (compounds) for which precise composition control technology has been established by crystal growth methods such as molecular beam epitaxy and metal organic vapor phase epitaxy are stored. What is necessary is just to use for a layer and a support layer. As such a compound, GaAs, AlAs, InAs, GaP, AlP, InP, GaSb, AlSb, InSb, GaN, AlN, InN, and mixed crystals thereof can be applied. Moreover, Si, Ge, C, and these mixed crystals are applicable as said material.

  In addition to controlling the buckling amount of the beam structure 131 and reducing the distance between the fixed electrode 105 or the fixed electrode 106 and the beam electrode 104, the drive voltage can be further reduced and the bit state can be easily read. It goes without saying that it becomes. In addition, when the interval is small as described above, the bit state can be read by detecting a tunnel current flowing between the fixed electrode 105 or the fixed electrode 106 and the beam electrode 104.

  Next, a memory device in which the above-described memory elements are arranged will be described with reference to the configuration diagram of FIG. First, the memory device includes a plurality of memory cells 301 including the memory elements described with reference to FIGS. 1A and 1B. The plurality of memory cells 301 are arranged in a square array. In addition, a bit line 302 is connected in common to the terminals 107 of each row of the plurality of memory cells 301 arranged in a square array, and each of the fixed electrode 105 and the fixed electrode 106 in each column of the plurality of memory cells 301 arranged in a square array In common, the word line 303 is connected. For example, if a film of an insulating material such as silicon oxide is formed at an intersection between each bit line 302 and the word line 303 by vapor deposition or CVD, insulation between the bit line 302 and the word line 303 can be achieved. Yes.

  Each bit line 302 is connected to a bit line selection unit 304 so that a positive potential can be selectively applied. Each word line 303 is connected to a word line selection unit 305, and a read AC power source 306 can be selectively connected thereto. Further, by switching the changeover switch 307, a negative potential that triggers writing can be selectively applied to each bit line 302. In addition, a differential amplifier 308 is connected to each column of the memory cells 301 so that reading is performed by a bridge output.

  For example, in the case of reading, the changeover switch 307 is turned off, one of the bit lines 302 is selected by the bit line selection unit 304, and the state of the memory cell 301 connected to the selected bit line 302 is changed to differential. Read by the amplifier 308. Here, a capacitor connected to the word line 303 with respect to the electrostatic capacitance between the beam structure 131 (beam electrode 104) buckled in any direction and the fixed electrode 105 and the fixed electrode 106. By forming a bridge with (or resistance), a small change in the beam structure 131 can be read out. Therefore, the beam electrode 104, the fixed electrode 105, the fixed electrode 106, and the above-described configuration (voltage applying means) for applying a voltage to these are the buckling state detecting means.

  Next, in the case of writing, first, one of the bit lines 302 is selected by the bit line selection unit 304, and one of the word line selection units 305 is selected by the word line selection unit 305, and one of the memory cells is selected. It is assumed that a positive potential is applied to the fixed electrode 106 of 301. In this state, the changeover switch 307 is turned on, a negative potential is applied to the terminal 107 (beam electrode 104) of the selected memory cell 301, and the beam structure 131 is buckled convexly toward the fixed electrode 106. Then, the bit information “1” can be written by changing the buckling direction. Therefore, these structures become the buckling state control means.

  By the way, although the case where the beam structure 131 buckled in the planar direction of the board | substrate 101 was demonstrated above, it does not restrict to this. For example, when the thickness of the beam structure 131 in the normal direction relative to the plane of the substrate 101 is smaller than the width of the substrate 101 in the plane direction, the beam structure 131 buckles in the normal direction of the plane of the substrate 101. It will be in the state. This buckling state also includes two states, a state in which it is convex toward the substrate 101 and a state in which it is convex on the side opposite to the substrate 101. Therefore, even if these two buckling states correspond to “0” and “1” of the memory state, the same as described above. In this case, a fixed electrode is provided on the opposite surface of the beam structure 131 on the substrate 101 side, and the two buckling states are controlled by the polarity of the potential applied between the fixed electrode and the beam electrode 104. That's fine.

[Embodiment 2]
Next, a second embodiment of the present invention will be described. FIG. 4 is a perspective view schematically showing a configuration example of the memory element in the second embodiment of the present invention. The memory element includes a substrate 101, a support layer 102 formed on the substrate 101, and a memory layer 103 formed on the support layer 102. The memory layer 103 has a compressive strain with respect to the support layer 102 in a region in contact with the lower support layer 102.

  In addition, the memory layer 103 includes an opening region 132 and includes a beam structure 131 that is provided between opposing sides of the opening region 132 (inside the opening region 132). In addition, an opening 121 is formed in the support layer 102 corresponding to the opening region 132 so that the substrate 101 side of the beam structure 131 is separated from the lower layer. The support layer 102 is provided with an opening 121 that penetrates, and the beam structure 131 is formed apart from the substrate 101 and apart from both ends except for the connected ends, and the beam structure 131 is displaced (seat). Bend) is possible. In addition, it is good also as a state which can displace the beam structure 131 as the state spaced apart from the circumference | surroundings by providing a recessed part in the support layer 102 corresponding to the beam structure 131 instead of the opening part penetrated.

  A beam electrode 104 is formed on the beam structure 131, and a fixed electrode 105 and a fixed electrode 106 are formed on the memory layer 103 on the side of the beam structure 131. One end of the beam electrode 104 is connected to a terminal 107 formed on the memory layer 103. The above is the same as that of the memory element of Embodiment 1 described above.

  In the memory element according to the second embodiment, the ferromagnetic layer 401 made of a ferromagnetic material is provided on the beam structure 131 (beam electrode 104). For example, the ferromagnetic layer 401 may be provided at the center of the beam structure 131. In the storage element according to the second embodiment configured as described above, by applying a magnetic field to the ferromagnetic layer 401, the two buckling states of the beam structure 131 are controlled as stored bit information. In the memory element in the second embodiment, two buckling states of the beam structure are stored by the capacitance measured using each electrode, as in the first embodiment. Is detected as bit information. Therefore, in this embodiment, a mechanism (not shown) for applying a magnetic field to the ferromagnetic layer 401 serves as a buckling state control means.

[Embodiment 3]
Next, a third embodiment of the present invention will be described. FIG. 5A and FIG. 5B are plan views schematically showing a configuration example of the memory element in the third embodiment. This memory element includes a substrate 501, a support layer 502 formed on the substrate 501, and a memory layer 503 formed on the support layer 502. The memory layer 503 has a compressive strain with respect to the support layer 502 in a region in contact with the lower support layer 502.

  Further, the memory layer 503 includes an opening region 532 and includes a beam structure 531 provided between opposing sides of the opening region 532 (inside the opening region 532). In addition, an opening 521 is formed in the support layer 502 corresponding to the opening region 532, the substrate 501 side of the beam structure 531 is separated from the lower layer, and other than both connected end portions are separated from the surroundings. It is said that it was in the state. In this embodiment mode, an opening 521 that penetrates is formed in the support layer 502, the beam structure 531 is separated from the substrate 501, and the beam structure 531 can be displaced (buckled).

  In addition, an electrode 505 and an electrode 506 formed so as to sandwich the beam structure 531 are provided. Note that the electrode 505 is connected to the terminal 508, and the electrode 506 is connected to the terminal 509. In this element, the memory layer 503 (beam structure 531) is made of a material having a piezoelectric effect typified by a compound semiconductor such as AlInN. In this case, the support layer 502 may be made of AlN, for example. Further, the memory layer 503 may be made of a material having a piezoresistance effect.

  According to the storage element configured as described above, by applying a predetermined voltage between the electrode 505 and the electrode 506, the two buckling states of the beam structure 531 are controlled as stored bit information. Further, two buckling states of the beam structure 531 are detected as stored bit information by a resistance (piezoresistance) measured between the electrodes 505 and 506. For example, by applying a positive voltage to the terminal 508 and applying a negative voltage to the terminal 509, the beam structure 531 is buckled convexly toward the electrode 506 as shown in FIG. State. Further, by applying a negative voltage to the terminal 508 and applying a positive voltage to the terminal 509, the beam structure 531 is buckled convexly toward the electrode 505 as shown in FIG. 5B. State. Therefore, in this embodiment, the electrode 505 and the electrode 506 constitute a buckling state detection unit, and the electrode 505, the electrode 506, and a mechanism for applying a voltage to them serve as the buckling state control unit.

[Embodiment 4]
Next, a fourth embodiment of the present invention will be described. FIG. 6 is a perspective view schematically showing a configuration example of the memory element in the fourth embodiment. The memory element includes a substrate 601, a support layer 602 formed on the substrate 601, and a memory layer 603 formed on the support layer 602. The memory layer 603 has a compressive strain with respect to the support layer 602 in a region in contact with the lower support layer 602. The memory layer 603 has a compressive strain with respect to the support memory layer 603 in a region in contact with the lower support memory layer 603.

  Further, as shown in FIG. 6, the memory layer 603 includes an opening region, and includes a beam structure 631 provided between opposing sides of the opening region (inside the opening region). In the present embodiment, a plurality of beam structures 631 are provided in one opening region. In addition, an opening is formed in the support memory layer 603 corresponding to the opening region, the substrate 601 side of the beam structure 631 is separated from the lower layer, and other than the two connected end portions are separated from the surroundings. The beam structure 631 can be displaced (buckled).

  In this embodiment, the plurality of beam structures 631 are arranged in a matrix. In other words, in this embodiment, a memory device is provided with a plurality of memory cells each including a memory element formed by the beam structure 631. In this embodiment mode, the beam structure 631 is formed so that the thickness in the normal direction with respect to the plane of the substrate 601 is smaller than the width in the plane direction of the substrate 101, and the beam structure 631 is formed of the substrate 601. It is in a state of being buckled in a direction perpendicular to the plane.

  In addition, in this embodiment, a ferromagnetic layer 604 made of a ferromagnetic material is provided on each beam structure 631, and a magnetic head 609 is provided. The magnetic head 609 can scan a plurality of beam structures 631 arranged in a matrix in the arrangement direction, and measure (detect) a magnetic field according to the distance from the ferromagnetic layer 604. Thus, the two buckling states of the beam structure 631 are detected as stored bit information. Further, the magnetic field applied from the magnetic head 609 is applied (applied) to the ferromagnetic layer 604 to control the two buckling states as stored bit information. In addition, since the magnetic head 609 can scan, bit information can be detected and controlled by selecting any one of the memory cells including the beam structure 601. In this case, the magnetic head 609 serves as a buckling state detection unit and a buckling state control unit.

  Note that if the memory layer 603 (beam structure 631) is made of a material having a magnetostrictive effect, the ferromagnetic layer 604 is not necessarily provided. In this case, for example, the storage layer 603 may be made of MnAs, and the support layer 602 may be made of GaAs. With this configuration, as described above, by detecting the magnetic field generated from the beam structure, two buckling states of the beam structure can be detected as stored bit information. By applying a magnetic field to the structure, two buckling states of the beam structure can be controlled as stored bit information. Further, as described above, when two buckling states are detected and controlled by a magnetic field, the two buckling states are controlled by simultaneously applying a magnetic field to a plurality of beam structures, for example, a plurality of memories. It is also possible to erase the stored state at once across the cell.

[Embodiment 5]
By the way, the memory layer may be made of a material having a photodistortion effect. For example, in the structure shown in FIG. 6, the memory layer 603 may be made of a material having a photodistortion effect. In this case, the ferromagnetic layer 604 is not necessary. In this case, a laser light source equipped with a condensing optical system may be used instead of the magnetic head 609. For example, the storage layer may be composed of AlInN and the support layer may be composed of AlN. With this configuration, the storage layer has a compressive strain with respect to the support layer. For example, the buckling state of the beam structure can be controlled by irradiating the beam structure with light having a light intensity that is strong enough to produce a photodistortion effect with a light source that can change the amount of light. In addition, a light detection mechanism is combined with such a light source to detect the buckling state by detecting the state of the optical characteristics of the beam structure measured as a result of irradiation with a light intensity that is weak enough not to produce the light distortion effect. Is possible. In this case, the light source serves as a buckling state control unit, and the light detection mechanism serves as a buckling state detection unit.

  By the way, in the above description, the storage layer is composed of a single layer, but the storage layer is not limited to this. , A piezoresistive effect, a magnetostrictive effect, and an optical strain effect, etc. For example, as shown in the perspective view of FIG. 7, a substrate 701, a support layer 702 formed on the substrate 701, a compression strain layer 703 formed on the support layer 702, and a compression strain layer 703 The memory layer 704 is formed. The compressive strain layer 703 has compressive strain with respect to the support layer 702 in the region in contact with the lower support layer 702. The memory layer 704 is made of a material having a piezoelectric effect, for example. The memory layer 704 may be made of a material having a piezoresistance effect.

  In addition, first, the compressive strain layer 703 includes an opening region 732 and includes a lower beam structure 731 bridged between opposing sides of the opening region 702. The memory layer 704 also includes an opening region 742 and an upper beam structure 741 provided between opposing sides of the opening region 742. An opening 721 is also formed in the support layer 702 corresponding to the opening region 703 and the opening region 742, and the substrate 701 side of the lower beam structure 731 is separated from the lower layer. In the example shown in FIG. 7, an opening 721 that penetrates is formed in the support layer 702, and the lower beam structure 731 is separated from the substrate 701. As a result, the beam structure having a laminated structure of the lower beam structure 731 and the upper beam structure 741 is formed apart from the surroundings except for the connected ends, and can be displaced (buckled). It is said that. In addition, it is good also as a state which can be displaced as the state which separated the lower beam structure 731 from the circumference | surroundings by providing a recessed part in the support layer 702. FIG.

  In addition, an electrode 705 and an electrode 706 are provided on one end side of the upper beam structure 741 so as to sandwich the upper beam structure 741 from the side. Note that the electrode 705 is connected to the terminal 708, and the electrode 706 is connected to the terminal 709. According to the memory element configured in this manner, the bending state (buckling state) of the upper beam structure 741 can be changed by applying a predetermined voltage between the electrode 705 and the electrode 706. Since the upper beam structure 741 is formed integrally with the lower beam structure 731, the lower beam structure 731 is displaced along with the displacement of the upper beam structure 741, and both change the buckling state at the same time. . As described above, in this memory element, two buckling states are controlled as stored bit information by applying a voltage to the upper beam structure 741.

  Further, two buckling states of the upper beam structure 741 are detected as stored bit information by a resistance (piezoresistance) measured between the electrodes 705 and 706. For example, by applying a positive voltage to the terminal 708 and applying a negative voltage to the terminal 709, the beam structure composed of the lower beam structure 731 and the upper beam structure 741 is changed to the electrode 706 side. It can be set as the state which buckled convexly. Further, by applying a negative voltage to the terminal 708 and applying a positive voltage to the terminal 709, the beam structure is in a state of being buckled convexly toward the electrode 705 as shown in FIG. be able to. Therefore, in the present embodiment, the electrode 705 and the electrode 706 constitute a buckling state detection unit, and the electrode 705, the electrode 706, and a mechanism for applying a voltage to them serve as the buckling state control unit.

  According to this memory element, a memory layer (upper beam structure) having a function of switching between two buckling states of the beam structure, and a compressive strain layer (lower beam) for forming the beam structure in a buckled state The beam structure was constructed from the structure. For this reason, according to the present memory element, the buckling state formation and the buckling state switching in the beam structure can be individually controlled and designed.

  In the above description, the cross-sectional shape of the beam structure is a rectangle, but is not limited thereto. For example, the cross section may be triangular. When a crystal material is used as the material constituting the memory layer, as is well known, a beam structure having a triangular cross section can be formed by utilizing the difference in etching rate on the crystal plane. In the case of such a triangular cross-section beam structure, the number of buckling directions is three or more, the size of the cross-sectional shape is controlled to control the buckling direction, and any two directions (buckling state) are stored. Bit information may be used.

It is a perspective view which shows typically the structural example of the memory element in Embodiment 1 of this invention. FIG. 3 is a plan view schematically showing a configuration example of a memory element in the first embodiment of the present invention. It is a block diagram which shows the structural example of the memory | storage device which arranged the several memory element in Embodiment 1 of this invention. It is a perspective view which shows typically the structural example of the memory element in Embodiment 2 of this invention. It is a top view which shows typically the structural example of the memory element in Embodiment 3 of this invention. It is a perspective view which shows typically the structural example of the memory element in Embodiment 4 of this invention. It is a perspective view which shows typically the structural example of the memory element in other embodiment of this invention. 1 is a cross-sectional view schematically showing a configuration of a memory cell of a flash memory.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Board | substrate, 102 ... Support layer, 103 ... Memory layer, 104 ... Beam part electrode, 105 ... Fixed electrode, 106 ... Fixed electrode, 107 ... Terminal, 121 ... Opening part, 131 ... Beam structure, 132 ... Opening area | region.

Claims (11)

A support layer formed on the substrate and partially provided with a recess;
A storage layer comprising an opening region formed in contact with a part of the support layer and opening corresponding to the recess, and a buckled beam structure erected inside the opening region; Prepared,
In the storage layer, a region in contact with the support layer has a compressive strain with respect to the support layer,
The storage layer is formed by crystal growth of a crystal material having a lattice constant different from that of the support layer on the support layer,
The beam structure has a thickness in a normal direction with respect to a plane of the substrate that is formed larger than a width in the plane direction of the substrate and buckles in parallel to the plane of the substrate,
The beam structure is displaceable in two buckled states that are convex in at least two different directions in the plane direction of the substrate perpendicular to the direction in which the beam structure extends,
At least one of the support layer and the storage layer is composed of a mixed crystal composed of two materials having different lattice constants,
The state of buckling of the beam structure is controlled by the mixed crystal ratio of the mixed crystal,
The memory element, wherein the two buckled states of the beam structure are stored as bit information. The storage element according to claim 1 .
The two materials having different lattice constants are selected from GaAs, AlAs, InAs, GaP, AlP, InP, GaSb, AlSb, InSb, GaN, AlN, InN, and mixed crystals thereof. A memory element. The storage element according to claim 1 .
The two materials having the different lattice constants are selected from Si, Ge, C, and mixed crystals thereof. The memory element according to any one of claims 1 to 3 ,
The memory element, wherein the memory layer is made of a material having a piezoelectric effect. The memory element according to any one of claims 1 to 3 ,
The memory element is composed of a material having a piezoresistive effect. The memory element according to any one of claims 1 to 3 ,
The storage element is made of a material having a magnetostrictive effect. The memory element according to any one of claims 1 to 3 ,
A memory element comprising a ferromagnetic layer formed on the beam structure and made of a ferromagnetic material. The memory element according to any one of claims 1 to 3 ,
The memory element, wherein the memory layer is made of a material having a photodistortion effect. The memory element according to any one of claims 1 to 3 ,
A storage element comprising a buckling state detecting means for detecting two buckling states of the beam structure as stored bit information. The storage element according to claim 9 , wherein
A storage element comprising a buckling state control means for controlling two buckling states of the beam structure as stored bit information. The memory element according to claim 9 or 10 ,
The buckling state detecting means includes
A memory element, comprising: a beam electrode formed on the beam structure; and a fixed electrode formed on the memory layer on a side of the beam structure.

Images