JP5614810B2 - Injection method - Google Patents

Description

  The present invention relates to an implantation method for implanting impurity atoms in order to manufacture a light emitting element using an indirect transition type semiconductor.

  Various forms have been proposed for elements using indirect semiconductors typified by silicon, but recently, elements utilizing impurities in the semiconductor have been proposed (see Patent Document 1). In addition, a light-emitting element that emits light by utilizing impurities in the semiconductor has been proposed. These devices utilize the fact that impurity atoms have the same function as quantum dots due to the attractive potential of atomic nuclei. This element enables efficient light emission even using silicon which is an indirect semiconductor. Also, single photons can be generated by reducing the number of impurities in the device.

  A light-emitting element using impurities in the semiconductor described above will be described with reference to FIGS. As shown in FIG. 3, the light-emitting element includes a semiconductor layer 301 made of, for example, silicon, a p-type region 302 formed in the semiconductor layer 301, an n-type region 303 formed in the semiconductor layer 301, and a p-type region. A gate electrode 305 is provided on the semiconductor layer 301 in a region sandwiched between 302 and the n-type region 303 with a gate insulating layer 304 interposed therebetween.

  In addition, this light-emitting element includes a donor-acceptor pair including a donor atom 306 and an acceptor atom 307 introduced into the semiconductor layer 301 in a region sandwiched between the p-type region 302 and the n-type region 303. The donor-acceptor pair is arranged in a region (channel region) sandwiched between the p-type region 302 and the n-type region 303. The donor atom 306 and the acceptor atom 307 are introduced in a range of 30 nm from the interface on the gate electrode 305 side of the channel region. Note that the gate electrode 305 is coupled (capacitively coupled) to the channel region into which the donor atom 306 and the acceptor atom 307 are introduced.

  The donor atom 306 forms a donor level in the channel region, and the acceptor atom 307 forms an acceptor level in the channel region. The donor atom 306 and the acceptor atom 307 constituting the donor-acceptor pair are formed. Is within the range of the spread of the wave functions of each other. The spread degree of the wave function of each of the donor atom 306 and the acceptor atom 307 is 10 nm, and the distance between the donor atom 306 and the acceptor atom 307 is less than 10 nm.

  In the present light emitting device, single photons can be generated by the donor-acceptor pair described above. In a device having a large number of donor-acceptor pairs, a large number of photons can be generated.

  Next, the operation (driving method) of the light-emitting element described above will be described with reference to FIG. FIG. 4 is a potential diagram showing a potential in the vicinity of the surface of the semiconductor layer 301 in the semiconductor layer 301 (channel region) sandwiched between the p-type region 302 and the n-type region 303.

First, in the initial state, a gate voltage (for example, about 0 V) between the threshold value V _TH-n of the electron channel and the threshold value V _TH-p of the hole channel is applied to the gate electrode 305. Leave it in the state. Note that V _TH-n > V _TH-p . In this state, as shown in FIG. 4A, neither the electron channel nor the hole channel is open, and no electrons are trapped in the donor atom 306, and the acceptor atom 307 is not captured. , Holes are not trapped.

Following the initial state, a gate voltage having a magnitude exceeding the threshold V _TH-n of the electron channel is applied to the gate electrode 305. By applying the gate voltage, as shown in FIG. 4B, electrons are supplied from the n-type region 303 to the channel region below the gate electrode 305, and an electron channel 331 is formed. The electron channel 331 is formed in the conduction band of the semiconductor constituting the semiconductor layer 301. As a result, one electron is captured by the donor atom 306 from the formed electron channel 331. The electrons captured in this process lose energy corresponding to the ionization energy of the donor atom 306, but this energy is absorbed by the phonons. For this reason, this process does not contribute to light emission.

  Next, as described above, when one electron is captured by the donor atom 306 and the gate voltage similar to the initial state is applied to the gate electrode 305, the electron channel 331 is closed and the electron channel 331 is closed. The electrons supplied as (electrons in the conductor) are collected in the n-type region 303. However, as shown in FIG. 4C, the electrons trapped in the donor atoms 306 do not return to the n-type region 303 due to the finite ionization energy, and remain trapped in the donor atoms 306. Is done.

Next, a gate voltage (negative voltage) lower than the threshold value V _TH-p of the hole channel is applied to the gate electrode 305 in a state where electrons are captured by the donor atoms 306 as described above. . By applying this gate voltage, holes are supplied from the p-type region 302 to the channel region below the gate electrode 305 to form a hole channel 321 as shown in FIG. The hole channel 321 is formed in the valence band of the semiconductor constituting the semiconductor layer 301. Due to the formation of the hole channel 321, first, holes are captured by the acceptor atoms 307. Holes captured in this process lose energy corresponding to the ionization energy of the acceptor atom 307, but this energy is absorbed by phonons. For this reason, this process does not contribute to light emission.

  Next, when a gate voltage similar to the initial state is applied to the gate electrode 305 in a state where electrons are captured by the donor atom 306 and holes are captured by the acceptor atom 307 as described above, the hole channel 321 is obtained. Are closed, and holes in the valence band are collected in the p-type region 302. However, as shown in FIG. 4E, the holes trapped in the acceptor atom 307 do not return to the p-type region 302 due to finite ionization energy, and the state captured by the acceptor atom 307 is Maintained.

  Thus, electron-hole pairs are formed in the channel region in a state where electrons are captured by the donor atoms 306 and holes are captured by the acceptor atoms 307. Moreover, a single photon is generated by recombination of the formed electron-hole pair. In this state, there are no electrons and holes in the conduction band and the valence band, respectively, so there is no Auger process when the above electron-hole pairs recombine. Therefore, photons can be generated efficiently.

  In addition, since one electron-hole pair disappears in the above-described steps (a) to (e), one electron disappears from the n-type region 303 and one hole from the p-type region 302. It will disappear. The disappearance of one hole from the p-type region 302 corresponds to the generation of one electron. As a result, a single charge (one electron) is transferred from the n-type region 303 to the p-type region 302. It has been transferred.

  In the light-emitting element described above, the position of impurity atoms in the semiconductor is restricted in the depth direction, and the distance from the semiconductor interface needs to be within 30 nm. This is because in order to capture electrons or holes between the channel formed at the interface, the wave function of the channel electrons or holes and the charge of the impurity needs to overlap. The spread of the wave function of the charges trapped by the impurities is about 10 nm. The spread of the wave function of channel electrons and channel holes is about 5 nm. Therefore, sufficient capture does not occur unless the distance in the depth direction is less than twice the sum of these.

  Further, the distance between the donor and the acceptor needs to be about the extent of the mutual wave function, that is, 10 nm or less. As the distance increases, the probability of recombination decreases. In addition, when it is desired to generate two (or n) photons in one cycle, it is necessary to introduce two (n) donor-acceptor pairs. In this case, each donor-acceptor pair must be independent of each other. In other words, the distance between the two adjacent donor-acceptor pairs must be 10 nm or more. When other donor-acceptor pairs are present in close proximity, the energy generated by the recombination is received by another pair of donors or acceptors in the process of recombination in one pair. In this state, the Auger process is dominant and light emission does not occur.

  As can be seen from the above operating principle, in order to operate a light-emitting element using a donor-acceptor pair, the impurity of the donor or acceptor of the donor-acceptor pair must be within a distance of 30 nm from the semiconductor interface. In addition, it is necessary to form a donor-acceptor pair that is close to each other within 10 nm with a distance from another donor-acceptor pair of 10 nm or more.

JP 2006-332097 A

  However, when a general-purpose ion implantation apparatus is used, it has been difficult to form a donor-acceptor pair due to the above-described relationship. First, when a general-purpose ion implantation apparatus is used, atoms (for example, phosphorus) serving as donors and atoms (for example, boron) serving as acceptors are separately implanted. In this case, the implantation position of each atom is controlled within the depth direction by controlling the implantation energy so that the distance from the interface is within 30 nm, and the depth position is also made the same with two impurities. it can. However, a donor-acceptor pair cannot be formed because it is completely random in the horizontal direction at the interface.

  If the dose at the time of implantation is increased, the average distance between the donor and the acceptor can be reduced to 10 nm or less, but each impurity atom is paired with a plurality of other atoms (for example, two donors and one acceptor). In such a case, the Auger process is dominant and the light emission is not efficient.

  On the other hand, if a single ion implantation technique is used, a donor-acceptor pair independent of each other can be formed. However, in the current single ion implantation technique, the accuracy of the ion implantation location is not high, and thus the following complicated process is required. First, in order to inject an impurity into a desired location, an ion implantation mask having a fine hole of 10 nm level is prepared, and a single ion implantation apparatus is used to selectively apply a single ion to the hole region of the produced mask. Implant donor (or acceptor) atoms.

  At this time, since the position accuracy of the single ion implantation is not high, the implantation is not always performed by hitting the hole by one implantation. Therefore, an electrode is prepared, a minute current generated only when the injection is successful is detected, and the injection is repeated until this current is detected. When the current is detected, the injection is terminated.

  Next, the acceleration energy is set so that the depth of penetration of the acceptor (or donor) is the same as that of the first implanted donor (or acceptor), and the same process described above is repeated.

  As described above, even if a single ion implantation apparatus is used, the donor-acceptor pair serving as the nucleus of the light-emitting element cannot be efficiently formed. As described above, the conventional technique has a problem that a light-emitting element that generates a single photon by transferring a single electron using an indirect transition semiconductor cannot be easily manufactured.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to easily manufacture a light-emitting element using an indirect transition type semiconductor.

An implantation method according to the present invention includes a first step of generating an atomic cluster composed of one group III atom and one group V atom having the same cycle number, and a first step of injecting the atomic cluster into a semiconductor layer made of an indirect semiconductor. A group III atom having at least two steps , wherein any one of the group III atom and the group V atom has a distance of 30 nm or less from the interface of the semiconductor layer and is within the range of the spread of the wave function of each other and the impurity atom pair composed of group V atoms, formed a distance between other impurities atoms to the above range of spread of the wave function. The atomic cluster may be ionized.

  In the above implantation method, the semiconductor layer is made of silicon, and in the first step, a group III atom selected from boron, aluminum, gallium, indium, and thallium and nitrogen, phosphorus, arsenic, antimony, and bismuth. An atomic cluster is generated from the selected group V atoms. In the second step, an atomic cluster composed of boron and nitrogen has an energy of 5 keV or less, an atomic cluster composed of aluminum and phosphorus has an implantation energy of 22 keV or less, gallium And arsenic atom clusters have an implantation energy of 38 keV or less, atom clusters composed of indium and antimony have an implantation energy of 50 keV or less, and atom clusters composed of thallium and bismuth have an implantation energy of 70 keV or less. It may be injected into the semiconductor layer made of the atomic clusters from indirect semiconductor by any one of injection conditions of the chromatography.

  As described above, according to the present invention, since an atomic cluster composed of a group III atom and one group V atom is injected, a light emitting element using an indirect transition type semiconductor can be easily manufactured. An excellent effect of being able to do so is obtained.

FIG. 1 is a flowchart for explaining an injection method according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing a process of injecting an atomic cluster 202 composed of gallium atoms 221 and arsenic atoms 222 into the surface of the silicon layer 201. FIG. 3 is a configuration diagram illustrating a configuration of a light emitting element using impurities. FIG. 4 is a potential diagram showing the potential in the vicinity of the surface of the semiconductor layer 301 in the semiconductor layer 301 sandwiched between the p-type region 302 and the n-type region 303.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining an injection method according to an embodiment of the present invention. First, in step S101, an atomic cluster composed of one group III atom and one group V atom having the same cycle number is generated (first step). Next, in step S102, atomic clusters are implanted into a semiconductor layer made of an indirect semiconductor (second step). Here, the atom clusters may be ionized. In addition, the group III atom is a 13 group atom in the notation in which the genus number is divided into 18, and the group V atom is a 15 group atom in the notation in which the genus number is divided into 18.

  According to the present embodiment described above, an atomic cluster is formed from one group III atom and one group V atom, and this is implanted by, for example, ion implantation, so that the group III atom and the group V atom are mutually connected. It is easy to form an impurity atom pair by being arranged within the range of the spread of the wave function and to be arranged in a range of 30 nm in the depth direction from the interface of the semiconductor layer. As a result, according to the present embodiment, a light emitting element that generates a single photon by transferring a single electron using an indirect transition type semiconductor can be easily manufactured.

  In the implantation method in the present embodiment, as described above, the group III atom and the group V atom are arranged within the range of the spread of the wave function of each other to form an impurity atom pair, and the interface of the semiconductor layer The object is to be placed in a range of 30 nm in the depth direction. Therefore, for example, the injection conditions such as the injection energy are such that the group III atom and the group V atom are arranged within the range of the spread of the wave function of each other to form the impurity atom pair, and the depth from the interface of the semiconductor layer. What is necessary is just to set it as the conditions arrange | positioned in the range of 30 nm in a direction.

  Hereinafter, it demonstrates in detail using an Example.

[Example 1]
First, Example 1 will be described with reference to FIG. In Example 1, a case where the group III atom is gallium and the group V atom is arsenic will be described. FIG. 2 is an explanatory diagram showing a process in which an atomic cluster 202 composed of gallium atoms 221 and arsenic atoms 222 is implanted into the surface of the silicon layer 201.

  As shown in FIG. 2A, the atomic cluster 202 is composed of one gallium atom 221 and one arsenic atom 222, and these bonds are governed by ionic bonds. In the process of injecting such atomic clusters 202, first, as shown in FIG. 2B, when the atomic clusters 202 collide with the surface of the silicon layer 201, they are decomposed (dissociated) simultaneously with the collision, and FIG. As shown in (c) of the figure, each becomes a single gallium atom 221 and an arsenic atom 222 and penetrates into the silicon layer 201.

During the dissociation and intrusion described above, the kinetic energy of the flying atom clusters 202 is distributed to each atom in proportion to the mass of the atoms in the process of decomposition. Gallium has two isotopes ⁶⁹ Ga and ⁷¹ Ga, and As is 100% ⁷⁵ As. Therefore, regardless of the mass number of gallium, energy is distributed to the gallium atoms 221 and the arsenic atoms 222 at a ratio of about 1: 1.

  Further, the gallium atom 221 and the arsenic atom 222 each repeatedly collide with the silicon nucleus, enter the inside of the silicon layer 201 while changing the direction of movement at random, and eventually lose energy and stop. The penetration depth from the surface of the silicon layer 201 is determined by the magnitude of energy distributed by each atom at the time of surface collision. The greater the energy, the deeper the penetration depth. Since the collision described above is a random process, the depth of penetration also varies, and this distribution is a Gaussian distribution. The depth that gives the center of the Gaussian distribution is called the projected range (Rp), which is nothing but the average value of the penetration depth. Further, the spread of the Gaussian distribution (ΔRp) indicates the degree of variation in the penetration depth, which is about 1/3 of Rp.

For example, by ion implantation, when the atomic clusters consisting of ⁷¹ Ga atoms and ⁷⁵ As atoms were implanted at 38KeV, by degradation of the surface of the silicon layer, ⁷¹ Ga atoms 18 keV, ⁷⁵ As atom gains energy 20keV . The Rp of ⁷¹ Ga atoms obtained with an energy of 18 keV is 19 nm, and the Rp of ⁷⁵ As atoms obtained with an energy of 20 keV is 20 nm. Therefore, both atoms remain in the surface layer within 30 nm from the surface. Moreover, since the mass numbers of both atoms are almost the same, Rp is also almost the same, which is suitable for forming an atomic pair close to each other.

However, since the implantation is a random process, even if Rp is equal, both atoms are located at a certain interval. When Rp is equal, the average interval L between two atoms can be estimated by “(√3 / √2) ΔRp = 1.2ΔRp” using ΔRp. In the case of the above gallium atom and arsenic atom, both atoms have ΔRp = 7 nm, and therefore L = 9 nm. When the difference in Rp is 1 nm, L = 10 nm. The above situation hardly changes even when ⁶⁹ Ga is used instead of ⁷¹ Ga.

  If the implantation energy of the atomic cluster 202 is 38 keV or less, the average distance between the two atoms is further reduced, and the distance from the surface of both atoms is also reduced, resulting in a more desirable structure for efficient light emission. Can be formed. On the other hand, if the implantation energy of the atomic cluster 202 is set to 38 keV or more, as a result, the average interval between the two atoms becomes large, and it becomes difficult to obtain the target donor-acceptor pair structure. Therefore, when an atomic cluster composed of gallium atoms and arsenic atoms is used, the implantation energy may be set to 38 keV or less in order to make the average interval L 10 nm or less. At this time, the condition that it should be within 30 nm from the surface is also automatically satisfied.

  In the state immediately after the implantation, each atom is still in the silicon interstitial position and is not electrically active. In order to electrically activate the ion-implanted atoms, it is necessary to perform heat treatment to move the atoms at the interstitial positions to the lattice substitution positions. By moving to the lattice substitution position, gallium acts as an acceptor and arsenic acts as a donor. Here, the activation process by heat treatment is accompanied by atomic diffusion. For example, by suppressing the heat treatment temperature to 600 ° C. or less, the activation can be performed with a sufficiently small diffusion distance. Therefore, the effect of increasing the interatomic distance due to diffusion during heat treatment can be avoided by optimizing the heat treatment conditions.

If the implantation dose of the atomic cluster is sufficiently small, for example, 1 × 10 ¹¹ cm ⁻² , the average distance between another atomic pair consisting of one gallium atom and one arsenic atom is 33 nm. It becomes. By suppressing the dose amount in this way, it is possible to sufficiently reduce the probability that the distance between atom pairs will be 10 nm or less, and it is possible to create a situation in which atom pairs are independent of each other. Alternatively, by using the single ion implantation technique and implanting atom clusters one by one and making the position of the implanted atom pairs sufficiently wide, it is possible to form atom pairs independent of each other (donor-acceptor pairs). It is.

  The light-emitting element described with reference to FIG. 3 is manufactured under the above conditions, and the element operation described with reference to FIG. 4 is performed, so that photons can be efficiently generated in silicon. Become.

[Example 2]
Next, Example 2 will be described. The configuration of the first embodiment described above can be similarly applied to other periodic groups in the periodic table. In other words, an atomic cluster may be generated from a group III atom selected from boron, aluminum, indium, and thallium, and a group V atom selected from nitrogen, phosphorus, antimony, and bismuth. The atomic clusters satisfying this are boron nitride (boron nitride, BN), aluminum phosphide (AlP), indium antimony (InSb), and thallium bismuth (TlBi).

  However, the implantation energies for forming atom pairs with an average interval of 10 nm or less are different. In order to obtain the same Rp, or the same ΔRp, atoms with a higher mass number require more energy. The critical energy satisfying the condition in each atomic cluster is as follows.

BN: 5 keV
AlP: 22 keV
InSb: 50 keV
TlBi: 70 keV

  In either case, Rp is 30 nm or less, and the conditions regarding the distance from the interface are automatically satisfied.

  In the implantation method of the present invention, the method for extracting the atomic cluster from the ion source is not particularly limited. For example, to generate an atomic cluster composed of gallium atoms and arsenic atoms, a GaAs crystal substrate is sputtered with atoms such as argon, and an atomic cluster having a desired mass is selected from the generated atomic cluster group. Use it. Alternatively, a GaAs cluster may be generated and injected by forming an ion beam with a liquid metal such as Ga or PdAs and selecting it with a mass separator.

  In the case of a cluster composed of boron atoms and nitrogen atoms, there is a method in which boron is vaporized and ionized, nitrogen gas is ionized, and an ion beam is generated and implanted. In addition, aluminum, phosphorus, indium, antimony, thallium, and bismuth can be alloyed with other elements to form a liquid metal ion source to form an ion beam of each atomic cluster, which can be selected and injected by a mass separator. .

  Further, a coating layer such as a thin metal layer or an insulating layer may be formed on the surface of silicon to be implanted. However, when the thickness of the coating layer is 20 nm or more, the atomic clusters are injected into the coating layer without being injected into the silicon. Therefore, it is important to keep the coating layer sufficiently thin.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, the semiconductor layer made of an indirect semiconductor to be implanted is not limited to crystalline silicon, and the same applies to polycrystalline silicon. The same applies to germanium, which is the same group IV semiconductor as silicon. However, when injecting into the germanium layer, the value of critical injection energy is different from that in the case of silicon and needs to be set appropriately.

  201 ... silicon layer, 202 ... atomic cluster, 221 ... gallium atom, 222 ... arsenic atom.

Claims (3)

A first step of generating an atomic cluster composed of one group III atom and one group V atom having the same period number;
And at least a second step of injecting the atomic cluster into a semiconductor layer made of an indirect semiconductor ,
Any one of the group III atom and the group V atom has a distance of 30 nm or less from the interface of the semiconductor layer, and the group III atom and the V group arranged within the range of the wave function of each other. injection wherein the impurity atom pair composed of families atom, you formed a distance between other impurities atoms to the above range of the spread of the wave function. The injection method according to claim 1, wherein
The implantation method, wherein the atomic clusters are ionized. The injection method according to claim 1 or 2,
The semiconductor layer is made of silicon,
In the first step,
Generating the atomic cluster from a group III atom selected from boron, aluminum, gallium, indium, thallium, and the group V atom selected from nitrogen, phosphorus, arsenic, antimony, bismuth;
In the second step,
An atomic cluster composed of boron and nitrogen has an energy of 5 keV or less,
An atomic cluster composed of aluminum and phosphorus has an implantation energy of 22 keV or less,
An atomic cluster composed of gallium and arsenic has an implantation energy of 38 keV or less,
An atomic cluster composed of indium and antimony has an implantation energy of 50 keV or less,
An atomic cluster composed of thallium and bismuth is injected into the semiconductor layer made of the indirect semiconductor by injecting the atomic cluster under any injection condition of an injection energy of 70 keV or less.

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