Method for selectively incorporating dopant atoms into semiconductor surfaces

Abstract

The present invention relates to a method for embedding a defined number of dopant atoms in a surface portion of a Group IV semiconductor lattice. The method comprises the following steps: forming one or more lithography sites on the surface portion; dosing the surface portion with a gas having molecules containing dopant atoms and hydrogen atoms at a temperature below 100 K in a manner such that a portion of the molecules are bonded to the surface portion; and incorporating one or more dopant atoms into the respective lithography sites by transferring a defined amount of energy to the dopant atoms. The number of dopant atoms incorporated into the lithography site is defined and is related to the size of the lithography site.

Description

[0001] The present invention claims priority from Australian Provisional Patent Application No. 2018901480 filed on May 2, 2018, the entire contents of which are incorporated herein by cross-reference. Technical Field

[0002] The present invention relates to a method for incorporating dopant atoms into a semiconductor surface. In particular, the present invention relates to a method for deterministically incorporating a dopant from a gaseous source into a semiconductor crystal. Background Art

[0003] A promising path to building error-corrected quantum computing circuits requires exploiting the quantum properties of individual donor atoms embedded in a semiconductor lattice to produce qubits. This approach involves fabricating the donor structure atom by atom in silicon and requires atomic precision.

[0004] U.S. Patent No. 7,097,708, which is incorporated herein by cross-reference, describes a technique for incorporating atoms into silicon by growing silicon on a doped surface after desorption of the passivating hydrogen. A scanning tunneling microscope (STM) is used to locally remove hydrogen from a passivated Si (001) surface, followed by dosing of gaseous phosphine and subsequent packaging by silicon molecular beam epitaxy. After dosing and before packaging, a thermal anneal is performed to incorporate dopant atoms into the surface.

[0005] In order to fabricate large error-corrected quantum computing circuits using this method, it is important that the dopant incorporation process is reproducible and that the number of incorporated atoms can be deterministically decided for each lithography site. Although single-dopant devices have been demonstrated, the probabilistic nature of the phosphorus incorporation process has hampered scaling up of architectures with large numbers of single-donor qubits using current techniques. Summary of the invention

[0006] Embodiments of the present invention relate to scalable methods for fabricating large error-corrected quantum computing circuits that circumvent the probabilistic nature of dopant absorption and dissociation, allowing one or more dopant atoms at specific locations to be deterministically incorporated into silicon.

[0007] According to a first aspect, the present invention provides a method for embedding a determined number of dopant atoms in a surface portion of a Group IV semiconductor crystal lattice, the method comprising the steps of:

[0008] a) forming one or more lithography sites on a surface portion;

[0009] b) dosing the surface portion at a temperature below 100 K using a gas having molecules comprising dopant atoms and hydrogen atoms in such a way that a portion of the molecules are bonded to the surface portion; and

[0010] c) incorporating one or more dopant atoms into corresponding lithographic sites by transferring a certain amount of energy to the dopant atoms;

[0011] The number of dopant atoms incorporated into the lithography site is determined and is related to the size of the lithography site.

[0012] In an embodiment, although some dopant atoms are incorporated into their corresponding lithographic sites, unincorporated atoms are released from the surface portion. In an embodiment, the surface portion of the Group IV semiconductor lattice is a pure crystalline silicon portion.

[0013] In an embodiment, the molecules in the dosing gas contain phosphine (PH3), and the dosing process is performed in such a way that the surface moiety is saturated with PH3 molecules and only PH3 molecules are absorbed at the lithography sites and bonded to the surface moiety.

[0014] In some embodiments, the dosing process is performed at a temperature that prevents PH3 from dissociating into PH2 (e.g., below 40 K). In alternative embodiments, the dosing process is performed at a temperature that allows PH3 to dissociate into PH2 (e.g., 77 K).

[0015] The lithography site can have different configurations. For example, the site can be a 1×1 silicon atom site, a 2×1 silicon dimer residue, a 3×1 silicon dimer residue, a 4×1 silicon dimer residue, or a 5×1 silicon dimer residue. In some examples, the lithography site can be a 2×2 silicon dimer residue, a 3×2 silicon dimer residue, a 4×2 silicon dimer residue, or a 5×2 silicon dimer residue. The lithography site can also have other configurations.

[0016] By using the methods disclosed herein, the number of atoms incorporated into each lithography site depends only on the size and configuration of the lithography site and can be controlled in a deterministic manner.

[0017] In some embodiments, the lithography site is a 3×1 silicon dimer remnant, and the step of incorporating one or more dopant atoms into the corresponding lithography site includes the following steps: annealing the surface portion in a manner such that a single dopant atom from a first portion of the bonded molecule is incorporated into the corresponding lithography site in the surface portion; and a second portion of the bonded molecule is released from the surface portion.

[0018] Each 3×1 silicon dimer can bond with six PH3 molecules. During bonding, the bonded PH3 molecules may lose one hydrogen atom. During the annealing step, the PH2 molecule bonds with another hydrogen atom and is partially released from the surface.

[0019] In an embodiment, the step of partially annealing the surface is performed in two stages: a first stage during which the bonded PH3 molecules lose one hydrogen atom to form multiple PH2 molecules bonded to the surface; and a second stage during which the bonded PH2 molecules lose their two hydrogen atoms to other PH2 molecules and a single P atom is embedded in a single 3×1 silicon dimer remnant.

[0020] A surface configuration with multiple PH2 molecules bonded to the surface is energetically more favorable than a configuration with PH3 molecules bonded to the surface.

[0021] The bonding strength between the PH2 molecules and the silicon atoms of the surface portion may be higher than the bonding strength between the PH3 molecules and the silicon atoms of the surface portion.

[0022] The first annealing stage can be performed, for example, by removing the sample from the deposition environment for a period of time and exposing it to room temperature. The second annealing stage can be performed using rapid thermal annealing (RTA) at a temperature between 200°C and 400°C.

[0023] In an embodiment, instead of performing an annealing step, one or more dopant atoms are incorporated into the respective lithographic sites by positioning the tip of a scanning tunneling microscope over one of the molecules and transferring an amount of energy to the dopant atom via the tip.

[0024] In an embodiment, energy is provided to the dopant atoms by applying an electric current to the dopant atoms and the semiconductor surface through a scanning tunneling microscope tip while the tip is positioned near the dopant atoms.

[0025] In one embodiment, to apply current via the tip, the feedback control loop of the scanning tunneling microscope is disabled, and to increase the magnitude of the current, the tip is controlled to move closer to the dopant atom. The magnitude of the applied current can be monitored to detect a sharp change triggered by the incorporation of the dopant atom. The magnitude of the current can be between 0.1 nA and 10 nA.

[0026] In one embodiment, the method includes applying a voltage between the tip and the semiconductor surface, the voltage having a magnitude between 2V and 4V.

[0027] In an alternative embodiment, in order to transfer a certain amount of energy to the dopant atoms, a voltage or current is applied to the dopant atoms and the semiconductor surface via the tip when the feedback control loop of the scanning tunneling microscope is active. As the magnitude of the current increases, the distance between the tip and the dopant atoms can be monitored to detect the sharp change triggered by the incorporation of the dopant atoms. The initial distance between the tip and the atoms is between 0.1 nm and 10 nm.

[0028] In other embodiments, in order to transfer a certain amount of energy to the dopant atoms, a voltage pulse with a duration between 0.1s and 1s and a magnitude between 2V and 4V or a current pulse with a duration between 0.1s and 1s and a magnitude between 0.1nA and 1nA can be applied to the dopant atoms and the semiconductor surface via the tip.

[0029] Advantageously, according to embodiments of the present invention, a determined number of donor atoms are incorporated into the semiconductor surface by providing uniform quantitative dosing on the surface at low temperature. The donor atoms can be deterministically incorporated into the corresponding lithography sites, and the number of incorporated atoms is only related to the size and configuration of the lithography sites.

[0030] Additionally, dopant atoms can be incorporated into the semiconductor surface through a series of chemical reactions driven by temperature or scanning tunneling microscope tip-assisted incorporation.

[0031] For example, in the case of doping phosphorus atoms into silicon using phosphine (PH3), the absorbed PH3 molecules simultaneously dissociate into PH2, then into PH, and finally into P, and by applying low temperature dosing and using a 3×1 dimer residue.

[0032] In contrast, when dosing at room temperature, PH3 can dissociate uncontrollably into PH2 and then into PH because there is enough energy in the surrounding environment to overcome the associated energy barrier before the annealing process proceeds. This can lead to PH x The starting configuration of the (x=1, 2) molecule is random, resulting in a random number of incorporated donors. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Features and advantages of the present invention will become apparent from the following description of embodiments given by way of example only and with reference to the accompanying drawings, in which:

[0034] FIG1 shows a flow chart of the steps of performing a method for embedding dopant atoms into a surface portion of a Group IV semiconductor crystal lattice;

[0035] Figure 2 A series of images of lithography sites of different sizes and shapes before and after dosing are shown;

[0036] Figure 3 A schematic diagram showing hydrogen lithography and chemical reactions for deterministically incorporating single phosphorus atoms into a silicon crystalline surface;

[0037] Figure 4 is a top view of a hydrogen terminated silicon surface used to form a donor qubit having four donor atoms; and

[0038] Figure 5Scanning tunneling micrographs showing the various steps of low temperature PH3 dosing; and

[0039] FIG6 schematically illustrates scanning tunneling microscope tip-assisted donor atom incorporation. DETAILED DESCRIPTION

[0040] In the following description, a method for deterministically doping atoms such as dopant atoms, such as phosphorus, into a semiconductor crystal according to an embodiment is described.

[0041] As used herein, the term "annealing" refers to the process of increasing the temperature of a sample. In some cases, the temperature can be increased by actively heating using a heat source such as a lamp, an electric current, or a furnace. Annealing can also be performed by taking the sample out of a cooling environment (cryostat) to a room temperature environment for a period of time to allow the temperature of the sample to rise.

[0042] Referring now to FIG. 1 , there is shown a flow chart 100 having steps for deterministically incorporating one or more phosphorus atoms into corresponding lithographic sites of a surface portion of a pure crystalline silicon lattice.

[0043] For example, the surface can be a Si(100)2×1 reconstructed surface. Such a silicon surface initially displays a 1×1 square array of surface Si atoms. Each of these arrays has two dangling bonds retained in the diamond structure, forming a surface that can be reconstructed into a low energy structure. The observed reconstruction has a 2×1 periodicity, which can be explained by the formation of dimers, which are composed of pairs of surface atoms, reducing the number of dangling bonds to one-half, and leaving one dangling bond per surface Si atom. The Si(001)2×1 surface is terminated with hydrogen atoms, which are selectively removed using the lithographic properties of a scanning tunneling microscope (STM) to form a "lithographic mask" (step 102).

[0044] Then, phosphine (PH3) is dosed to the surface portion at a temperature below 100K (step 104). The dosing is performed so that the surface portion is saturated with PH3 molecules and a portion of the molecules are bonded to the Group IV atoms of the surface portion. Importantly, only PH3 molecules are absorbed and bonded to the silicon lattice at the exposed silicon lithography sites. Each 3×1 dimer residue can bond to 6 PH3 molecules.

[0045] The absorption of gaseous PH3 into the dimer site is not affected by low temperature because there is no energy barrier associated with this process. The terminal configuration (absorbed PH3) was found to be 0.62 eV more stable than gas phase PH3 and the bare silicon surface.

[0046] On the other hand, PH XThe other dissociation steps of the molecule are dominated by energy barriers and their reaction rates can be described using the Arrhenius equation, which means that when the temperature is low enough, the dissociation process is expected to slow down significantly and effectively stop.

[0047] According to the present invention, the inventors have designed a dosing process to prevent PH3 from dissociating during dosing by reducing the available energy in the surrounding environment, so as to provide a silicon surface completely terminated with PH2 before phosphorus incorporation.

[0048] Another advantage provided by the cryogenic dosing process described herein is that sub-nm-scale STM hydrogen lithography has been shown to be more reliable at cryogenic temperatures. Cryogenic temperatures allow for increased tip stability and reduced thermal drift.

[0049] Another advantage of using low temperatures during dosing is that the hydrogen desorption rate increases due to the increased vibrational lifetime of Si-H bonds and reduced tunneling current at low temperatures, which in turn further increases tip and lithography stability.

[0050] Fig. 1 (b) and Fig. 1 (c) show the flow chart that the dosing process under two different situations is summarized.In the process shown in Fig. 1 (b), dosing is carried out at a temperature lower than 40K, for example 20K.In this case, PH3 molecule is prevented from dissociating into PH2, because there is not enough heat energy to allow dissociation in the dosing environment.In order to allow PH3 molecule to dissociate, the first annealing step can be carried out to provide the heat energy required for PH3 molecule to dissociate into PH2.This can be accomplished by, for example, extracting the sample from the cooling deposition environment.At room temperature, there is enough heat energy for the first part of the bonded molecule to lose a hydrogen atom and dissociate into PH2 molecule bonded to the surface.PH2 molecule is prevented from further dissociating into PH or P, because bare silicon site is lacked at this point in the process.

[0051] In other cases, the dosing is performed at a temperature above 40 K, such as liquid nitrogen temperature (77 K). In this case, during the dosing step, the PH3 molecules have enough energy to dissociate into PH2, and after dosing, only PH2 molecules are bonded to available sites on the semiconductor surface.

[0052] Once the PH2 molecules are bonded to all open lithography sites, individual phosphorus atoms can be incorporated by transferring a certain amount of energy to dopant atoms near the lithography site, either by thermal annealing or STM tip-assisted incorporation, depending on the size and configuration of the site (step 106). Using this process, the number of dopant atoms incorporated into each lithography site is determined and related to the size of the lithography site.

[0053] Reference now Figure 2, shows several examples of lithography sites of different sizes and shapes before and after dosing at 77K. For example, Figure 2 (a) shows a lithography site with 3 available bonding positions, to which a single PH2 molecule is bonded during dosing. Single phosphorus atoms can be incorporated into the surface from a single module by STM tip-assisted incorporation.

[0054] Figure 2 (b) shows a lithographic site with two dimers that allows two PH2 molecules to bond. Two PH2 molecules can also bond to Figure 2 (c) site, and Figure 2 (d) 3×1 dimer site and Figure 2 The site (e) allows three PH2 molecules to bond. Four PH2 molecules can bond to Figure 2 (f) The site shown. Phosphorus atoms can be incorporated using a series of temperature-triggered chemical reactions. Figure 2 (df) The sites indicated are described below.

[0055] For example, in Figure 2 In case (d), the PH3 dosing silicon surface comprising a plurality of 3×1 lithographic sites is annealed in a manner such that a single phosphorus atom of a bound PH3 molecule is incorporated into each site. The remaining portion of phosphorus atoms (not incorporated) and the remaining PH3 molecules are subsequently desorbed from the surface.

[0056] Reference now Figure 3 (a) shows an example of a hydrogen-terminated silicon surface with 3×1 silicon dimer remnants 302 formed by STM lithography. Theoretical studies have shown that the incorporation of one phosphorus atom from an adsorbed PH3 molecule using an annealing technique requires at least three adjacent bare silicon dimer sites in the hydrogen shielding. Due to the strong anisotropy of atomic motion on the reconstructed Si(001) surface, three dimers need to be oriented along a dimer row, as shown in Figure 2. Figure 3 (a) shown.

[0057] Figure 3 (b) shows a PH2 molecule 304 bonded to the surface, whose configuration is more energetically favorable than the configuration of the PH3 molecule bonded to the surface. At room temperature, thermal energy is sufficient to overcome the dissociation reaction energy barrier.

[0058] Figure 3 (c) to Figure 3(f) shows the steps that occur during the second annealing stage. A PH2 molecule 304 bonds to another hydrogen atom and is partially released 306 from the surface as PH3 308. The free silicon site left behind by this desorption 310 enables PH2 to immediately dissociate 312 into PH 314. The remaining PH2 316 can then recombine with H and desorb as PH3 318 before PH 314 can dissociate into atomic phosphorus 320, creating another free site. Finally, phosphorus atoms 322 are incorporated into the silicon surface layer 324, ejecting silicon adatoms in process 326.

[0059] Through the above reference Figure 3 In the process described, a single phosphorus atom 328 is embedded in a single 3×1 silicon dimer residue.

[0060] The method devised by the inventors allows the preparation of patterned silicon surfaces deterministically terminated with PH2 molecules, since all PH3 molecules dissociate simultaneously into PH2. This surface then allows the deterministic incorporation of P atoms into the corresponding silicon 3×1 dimer residues.

[0061] In some embodiments, the above-described single donor incorporation process can be used to fabricate quantum dots containing multiple phosphorus atoms. Each of these quantum dots can be used as a qubit to encode quantum information.

[0062] Reference now Figure 4 , shows a silicon surface 400 containing a qubit 402 with four donor atoms embedded in four adjacent dimer remnants 406 using the methods described herein. The 3×1 dimer remnants 406 of bare silicon are separated by surface topology of dimers 408 of hydrogen terminated silicon along the dimer rows and a 2×1 surface reconstruction perpendicular to the dimer rows 410. In this way, the remnants 406 can be considered to be separated from each other, and each remnant will eventually accommodate a phosphorus atom. The distance between the remnants is small enough so that each phosphorus atom is in a substantial part of the same qubit. The technique can be extended to produce qubits including any predetermined number of donors.

[0063] Figure 5 Scanning tunneling micrographs of different stages of the PH3 dosing process performed at 20 K are shown. The bare Si (001) 2×1 reconstructed surface was first cooled to 20 K. Figure 5 (a) shows the initial silicon surface, dimer reconstruction, and some surface vacancies (dark depressions).

[0064] Figure 5 (b) shows an STM image of a PH3-saturated surface with dosing. A significant change in the image conditions was observed. The degradation in image quality is attributed to the adsorbed molecular PH3, which may have altered the electronic properties of the surface.

[0065] Figure 5(c) shows the sample surface after the sample has reached room temperature by removing it from the cold STM stage using a room temperature swing rod. After a few minutes, the sample is inserted back into the cold STM stage and allowed to cool to below 77 K. Figure 5 (c) shows that the image quality has recovered to the stable Si-PH X The expected degree of surface configuration. Except for PH2, no PH X Complete surface coverage of half a monolayer of PH2 was observed.

[0066] Figure 5 (d) Yes Figure 5 (c) A close-up. Figure 5 In (d), the p(2*2) surface reconstruction typically found on saturated dosing surfaces with high PH2 fraction can be observed.

[0067] Figure 5 (e) shows the surface of the sample after annealing at 350 °C to incorporate PH2 into the surface. Figure 5 (b) to Figure 5 (f) is the same as the steps shown in Figure 5 In (e), the expelled silicon is clearly visible as bright protrusions on the surface.

[0068] Referring now to FIG6 , there is shown a schematic diagram of an alternative technique that can be used to incorporate phosphorus atoms from a PH2 dosing surface. For example, in the case where the lithography site has a single PH2 bonded molecule, such as Figure 2 As shown in (a), a single phosphorus atom can be incorporated into this site by using the STM tip-assisted incorporation technique. Two H atoms are also separated from the P atom and then incorporated by forming a monohydride.

[0069] In Figure 6(a), the tip of an STM 602 is positioned over a phosphorus atom 604 to be doped near a lithography site 606. While the STM control feedback loop 610 remains active, a current 608 between 0.1 nA and 10 nA is sent through the tip 602. The energy transferred to the phosphorus atom by the current 608 causes the atom to break from the PH2 molecule and bond to the silicon surface.

[0070] The initial distance between the tip and the atom is between 0.1 nm and 10 nm. The STM computer system 612 monitors the distance between the tip and the dopant atom as the magnitude of the current increases to detect a sharp change triggered by the incorporation of the dopant atom 614. When a sharp change is detected, the system considers the atom incorporated and switches back to imaging mode.

[0071] 6( b) schematically illustrates an alternative technique which requires disabling the STM control feedback loop 610 and applying a current 658 between 0.1 nA and 10 nA via the tip 602. To increase the magnitude of the current, the tip is moved closer to the dopant atom 604, controlled by the STM computer system 612. The magnitude of the current can be monitored to detect a sharp change 654 triggered by the incorporation of the dopant atom. A voltage between 2 V and 4 V can be applied between the tip 602 and the silicon surface to facilitate incorporation.

[0072] The STM computer system 612 monitors the current level in the tip 602 to detect a sharp change triggered by the incorporation of dopant atoms. When a sharp change is detected, the system considers the atom to be incorporated and switches back to imaging mode.

[0073] In some cases, the system of FIG. 6 may use a voltage pulse with a duration between 0.1 s and 1 s and a magnitude between 2 V and 4 V or a current pulse with a duration between 0.1 s and 1 s and a magnitude between 0.1 nA and 1 nA to promote the incorporation of phosphorus atoms.

[0074] As used herein, the term "comprising" (and its grammatical variations) is used in the inclusive sense of "having" or "including," and not in the sense of "consisting only of.

[0075] It will be appreciated by those skilled in the art that many changes and / or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. Therefore, the present embodiments are to be considered in all aspects as illustrative and not restrictive.

Claims

1. A method for embedding a defined number of dopant atoms into a surface portion of a Group IV semiconductor crystal lattice, the method comprising the steps of: a) forming one or more lithography sites on the surface portion; b) dosing the surface portion at a temperature below 100 K using a gas having molecules comprising said dopant atoms and hydrogen atoms in such a way that a portion of said molecules are bonded to said surface portion; as well as c) incorporating one or more dopant atoms into the corresponding lithographic sites by transferring a certain amount of energy to the one or more dopant atoms; The number of dopant atoms introduced into the corresponding lithography site is determined and is related to the size of the corresponding lithography site.

2. The method of claim 1, wherein: The surface portion of the Group IV semiconductor lattice is a pure crystalline silicon portion or a pure crystalline germanium portion.

3. The method according to claim 1 or 2, wherein: During incorporation, atoms that were not incorporated into the corresponding lithographic sites are released from the surface portion.

4. The method according to any one of claims 1 or 2, wherein: The molecules in the dosing gas contain PH3 and the dosing process is performed in such a way that the surface portion is saturated with PH3 molecules.

5. The method of claim 4, wherein: The dosing process is performed in such a way that only PH3 molecules are absorbed at the lithography sites and bonded to the surface moieties.

6. The method according to any one of claims 1 or 2, wherein: The dosing process is carried out at a temperature that prevents PH3 from dissociating into PH2, wherein the temperature is below 40K.

7. The method according to any one of claims 1 or 2, wherein: The dosing process is carried out at a temperature that allows PH3 to spontaneously dissociate into PH2.

8. The method of claim 7, wherein: The dosing process is carried out at a temperature between 40K and 100K.

9. The method of claim 8, wherein: The dosing process was carried out at 77K.

10. The method according to any one of claims 1 or 2, wherein: The one or more lithography sites are: 1×1 silicon atom sites, 2×1 silicon dimer residues, 3×1 silicon dimer residues, 4×1 silicon dimer residues or 5×1 silicon dimer residues.

11. The method according to any one of claims 1 or 2, wherein: The one or more lithography sites are 3×1 silicon dimer remnants, and the step of incorporating one or more dopant atoms into the corresponding lithography sites includes the following steps: annealing the surface portion in a manner so that a single dopant atom from a first portion of the portion of the molecule bonded to the surface portion is incorporated into the corresponding lithography site in the surface portion; and a second portion of the portion of the molecule bonded to the surface portion is released from the surface portion.

12. The method of claim 11, wherein: Each dimer residue is bonded to 6 PH2 molecules.

13. The method of claim 11, wherein: The molecules in the dosing gas contain PH3, and the dosing process is performed in such a way that the surface portion is saturated with PH3 molecules, and wherein during the annealing step, the PH3 molecules bonded to the surface portion at the lithography site lose a hydrogen atom.

14. The method of claim 11, wherein: During the annealing step, the PH2 molecule bonds to another hydrogen atom and is partially released from the surface.

15. The method of claim 11, wherein: The step of partially annealing the surface is performed in two stages: i. a first annealing stage, during which the bonded PH3 molecules lose a hydrogen atom to form a plurality of PH2 molecules bonded to the surface portion; ii. A second annealing stage during which the bonded PH2 molecules lose their two hydrogen atoms to other PH2 molecules and a single P atom is embedded in a single 3×1 silicon dimer remnant.

16. The method of claim 15, wherein: The first annealing stage is performed by exposing the surface portion to room temperature.

17. The method of claim 15, wherein: The second annealing stage is performed at a temperature between 200°C and 400°C.

18. The method of claim 1, wherein: The step of incorporating one or more dopant atoms into the respective lithographic sites comprises the steps of positioning the tip of a scanning tunnelling microscope over one of the molecules and transferring an amount of energy to the dopant atom via the tip.

19. The method of claim 18, wherein: The step of transferring a certain amount of energy to the dopant atoms includes the following steps: when the tip is positioned near the dopant atoms, applying an electric current to the dopant atoms and the semiconductor surface through the tip.

20. The method of claim 19, wherein: To apply the current via the tip, the feedback control loop of the scanning tunneling microscope is disabled, and to increase the magnitude of the current, the tip is controlled to move closer to the dopant atoms.

21. The method of claim 19, further comprising the steps of: The magnitude of the applied current is monitored to detect abrupt changes triggered by the incorporation of dopant atoms.

22. The method of claim 19, wherein: The magnitude of the current is between 0.1 nA and 10 nA.

23. The method of claim 18, further comprising the steps of: A voltage is applied between the tip and the semiconductor surface, the voltage having a magnitude between 2V and 4V.

24. The method of claim 18, wherein: The step of transferring a certain amount of energy to the dopant atoms comprises the following steps: when a feedback control loop of the scanning tunneling microscope is effective, a voltage or a current is applied to the dopant atoms and the semiconductor surface via the tip.

25. The method of claim 24, comprising the steps of: The magnitude of the current is increased and the distance between the tip and the dopant atoms is monitored to detect a sharp change triggered by the incorporation of dopant atoms.

26. The method of claim 24, wherein: The step of transferring a certain amount of energy to the dopant atoms comprises the step of applying a voltage pulse having a duration between 0.1 s and 1 s and a magnitude between 2V and 4V.

27. The method of claim 24, wherein: The step of transferring a certain amount of energy to the dopant atoms comprises the step of applying a current pulse having a duration between 0.1 s and 1 s and a magnitude between 0.1 nA and 1 nA.

28. The method of claim 25, wherein: The distance between the tip and the atom is between 0.1 nm and 10 nm.

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