JP5128907B2 - Activity controlled nitrogen compound MBE film forming method and apparatus - Google Patents

Description

  The present invention relates to a nitrogen compound MBE film forming method and apparatus for controlling activity, and more particularly to a molecular beam epitaxial film forming method and apparatus for chemical activity controlled nitrogen compounds, typically group III nitrogen compounds.

Recently, for forming a group III nitrogen compound film such as GaN, InGaN, InN, InAlN on a substrate such as a sapphire substrate for an electronic device such as a blue light emitting diode, the film forming operation is relatively low. Since it is simple and the film thickness can be controlled at the atomic level, a molecular beam epitaxy (MBE) film forming apparatus that makes the film forming chamber a high vacuum of about 10 ⁻² to 10 ⁻⁹ Pa is provided. It is made using.

Conventionally, when a group III metal nitrogen compound film, for example, a GaN film, is epitaxially grown on a substrate held in a film forming chamber of an MBE film forming apparatus, the exit portion of a molecular beam cell for Ga (solid metal Ga source) at the start of film formation The substrate mounted on the substrate is opened to continuously irradiate the substrate with Ga atom beams, while an excited nitrogen molecular beam is emitted from an RF nitrogen excitation cell using radio frequency (RF) power to the exit portion of the nitrogen excitation cell. A method of effectively improving the flatness of the growth surface of the GaN film is known by irradiating the substrate while periodically opening and closing the shutter disposed on the substrate with a time width modulation duty (open / close period ratio). (For example, see Patent Document 1).

In addition, the metal (for example, Ga) atomic beam from the solid metal molecular beam cell and the excited nitrogen molecular beam from the nitrogen excitation cell are alternately opened and closed to open and close the shutter on the substrate surface. After suspending irradiation of the Ga atom beam (after closing the shutter for the Ga molecular beam cell) and opening the shutter for the nitrogen excitation cell while giving the time for Ga atoms to diffuse or move (Migration) in the lateral direction. A method for improving the flatness of the GaN growth surface is known by reacting nitrogen active species emitted from the nitrogen excitation cell with Ga atoms adsorbed on the substrate surface (see Non-Patent Document 1).

However, in principle, the methods described in Patent Document 1 and Non-Patent Document 1 have the following effect: Ga atoms irradiated on the substrate surface by intermittently opening and closing a mechanical shutter disposed at the exit portion of the nitrogen excitation cell. The flatness of the GaN film is improved by providing a grace period for dispersion or movement. For this reason, compared with the growth of the substrate surface by the normal method of irradiating the substrate with the metal flux and the nitrogen active species at the same time, it is not only very fast, but it is difficult to precisely control the growth amount. It was not taken into account to control the irradiation dose of nitrogen active species, and the utilization efficiency of the excited nitrogen flux was not so good.

Therefore, the inventors of the present invention replace the mechanical shutter disposed at the exit portion of the nitrogen excitation cell in the conventional type with the shutter disposed at the exit portion of the solid metal molecular beam cell (first molecular beam cell). The timing of RF power input to the excitation coil of the nitrogen excitation cell is switched in synchronization with the periodic switching operation, that is, the excitation state of the nitrogen excitation cell is switched between the LB excitation mode and the HB excitation mode, and the generated film is flattened. Have already been proposed (Japanese Patent Application No. 2006-252887), which is a method and apparatus for forming a nitrogen compound MBE that can switch the excitation mode and the crystallinity and the film formation rate effectively at the same time.

However, although the method and apparatus by the inventors of the present invention having the above-described configuration significantly improve the film formation flatness and the film formation speed, it is possible to manufacture under the relatively low temperature and ultrahigh vacuum manufacturing conditions in the normal MBE method. For example, it has been extremely difficult to stably and easily manufacture a cubic zinc blende-type nitrogen compound semiconductor film which is thermodynamically metastable. In practice, some conventional MBE systems can produce hexagonal wurtzite nitrogen compound semiconductor films that are thermodynamically stable under relatively high temperature production conditions, but their production costs are also very high. It was. In particular, when improving of the deposition rate, for example, when increasing the number of metal atoms from a solid metal cell, tends to become polycrystalline film, thermodynamically it is stable and crystalline covalent, thus There has been a problem that it is difficult to obtain a cubic or hexagonal nitrogen compound semiconductor film having good electrical characteristics.

  As a result of further earnest research, the inventors of the present invention, in the MBE film forming method according to the earlier application of the inventors of the present invention, from a nitrogen excitation cell in an HB excited state to a substrate fixed at a target position. Of the nitrogen active species irradiated, nitrogen molecular ions and electrons have been inferred to have an unfavorable effect on the crystallinity and physical properties of the film produced.

Therefore, based on the above inference, the inventors of the present invention periodically open and close the shutter (first shutter) for the first molecular beam arranged at the exit of the metal molecular beam cell (first molecular beam cell). In the open period of the first shutter, the nitrogen molecule ions and electrons released from the nitrogen excitation cell in the LB excited state toward the substrate held at the target position are excluded, and substantially only the excited nitrogen molecules are While supplying the substrate, the nitrogen excitation cell is maintained in the HB excitation state for a certain period during the closing period of the first shutter, and the chemical activity of the nitrogen active species emitted from the nitrogen excitation cell to the substrate is controlled. However, the inventors have devised a method and apparatus for obtaining a cubic or hexagonal nitrogen compound semiconductor film that is thermodynamically metastable or stable on a substrate.
JP-A-11-111617 Veeco Application Note March 2000 No.2 / 00, Veeco Instruments Company USA

The present invention, the conventional form of nitrogen compounds, typically, flat film forming than in the conventional method to completely solve the problems in the excitation mode switching type nitrogen compound MBE deposition method and device for the Group III nitrogen compound The activity-controlled nitrogen compound MBE can be produced stably and easily at low cost, and can effectively improve the crystallinity and the film formation rate and can stably produce a cubic or hexagonal nitrogen compound semiconductor film having good crystallinity. An object is to provide a membrane method and apparatus.

The activity controlled nitrogen compound MBE film forming method according to claim 1 of the present invention excludes nitrogen molecular ions and electrons emitted from the nitrogen excitation cell in each film forming preliminary step of the film forming cycle. While the substrate is irradiated with only excited nitrogen molecules with low chemical activity,
In each film formation step of the film formation cycle, the opening and closing operation of the second shutter disposed at the exit portion of the nitrogen excitation cell is controlled, and the power supplied to the nitrogen excitation cell is adjusted according to the target irradiation amount ( The substrate is irradiated with excited nitrogen atoms N ^* and basal nitrogen atoms N with high chemical activity while eliminating the nitrogen molecular ions and electrons emitted from the nitrogen excitation cell. consisting of a film forming process to be characterized and this is repeated plural times film formation cycle.

Activity controlled nitrogen compounds MBE film forming method according to claim 2 of the present invention, before starting the deposition cycle, on the substrate which is fixed from the nitrogen pumping cell and LB excited state to a target position, of the nitrogen active species of nitrogen molecular ions and electrons by eliminating released from or HB excited state was the nitrogen pumping cell supplying excitation nitrogen partial child excitation nitrogen with the exclusion of nitrogen molecular ions and electrons By supplying atoms and basal nitrogen atoms to the substrate at a low flow rate, a single crystal nitride film of the same system as the substrate is formed on the substrate surface.

Activity controlled nitrogen compounds MBE film forming method according to claim 3 of the present invention, the time predetermined according the open time t ₀ of the first shutter to repeat certain open period T ₁ of the first shutter α and it switches the LB excited state in a short delay time τ = (T ₁ -α) elapsed time t ₂ at the nitrogen pumping cell to HB excited state.

Time MBE method of forming activity controlled nitrogen compound according to claim 4 of the present invention, in the period T ₂ in which the first shutter is closed, that returned within the nitrogen pumping cell from the HB excited state into LB excited state during time period β than t ₃ to time t ₀ when said first shutter is opened again, the excitation of nitrogen molecules from the nitrogen pumping cell in LB excited state and removing the remaining first molecule on the substrate.

The activity controlled nitrogen compounds MBE film forming method according to claim 5 of the present invention, the opening period T ₁ of the said first shutter in accordance with the number of metal atoms epitaxially growing a 1 molecular layer below the membrane to the substrate defined, HB excited state holding period T ₃ is characterized in that determined according to the nitrogen active species atomic quantity required to react with the first shutter open period T metal atoms supplied to the substrate during ₁ .

MBE method of forming activity controlled nitrogen compound according to claim 6 of the present invention, open period T ₁ of the said first shutter is determined according to the number of metal atoms epitaxially growing a film of a plurality of molecular layers on the substrate is a feature that HB excited state holding period T ₃ is determined according to the nitrogen active species atomic quantity required to react with the metal atoms supplied to the substrate during the open period T ₁ of the said first shutter To do.

  According to a seventh aspect of the present invention, there is provided an activity-controlled nitrogen compound MBE film forming method in which the nitrogen excitation cell is irradiated with electromagnetic waves to maintain the LB excitation state.

The activity-controlled nitrogen compound MBE film forming apparatus according to claim 8 of the present invention,
Is arranged near outlet portion of the upper Symbol nitrogen excited cells, upper Symbol nitrogen excited cells activated nitrogen species eliminated to excite the nitrogen atom of nitrogen molecular ions and electrons of the emitted from the base nitrogen atoms and excited nitrogen molecules above a load conductive particles exclude means you irradiating the substrate,
First shutter driving means for periodically opening and closing the first shutter with a certain open period T ₁ ;
A second shutter driving means for disposing a second shutter at an outlet portion of the nitrogen excitation cell and driving the opening and closing of the second shutter in synchronization with the opening and closing operation of the first shutter;
Depending on the film formation target, at least the period T for opening / closing the first shutter, the open period T _1, and the high brightness (HB) excited state holding period T ₃ are set in advance, and these setting data (T, T ₁ , Setting data input means for inputting T ₃ );
A low brightness (LB) excitation state is established by supplying power to the excitation coil of the nitrogen excitation cell with power W _LB in synchronization with opening and closing operations of the first shutter and the second shutter , while the power W greater than _LB, one or, to establish the HB excited state by feeding with a power W _HB which changes according to the target dose of nitrogen active species, and a power supply control means for controlling switching of the excitation power ,
An epitaxial film of a nitrogen compound is generated by supplying the substrate while controlling the chemical activity of the nitrogen active species flux from the nitrogen excitation cell.

Charged particle exclusion means in activity control nitrogen compounds MBE deposition apparatus according to claim 9 of the present invention includes an electromagnetic charged particles deflection circuit, and the nitrogen molecular ions of nitrogen active species released from the nitrogen pumping cell It deflects the electrons excitation nitrogen atom, characterized by being configured to illuminate the base nitrogen atoms and excited nitrogen molecules on the substrate which is fixed to the target position.

Activity controlled nitrogen compounds MBE deposition apparatus according to claim 10 of the present invention, a plurality of nitrogen excited cells as the nitrogen pumping cell to the MBE deposition chamber arranged, the first shutter opening and closing operation and synchronization together control the opening and closing of each of the second shutter and the excitation power to power the excitation coil of the respective nitrogen pumping cell, by controlling switching through the power supply control unit, a target from the respective nitrogen pumping cell An epitaxial film of a nitrogen compound is formed on the substrate while controlling the activity of the nitrogen active species radiated to the substrate fixed at a position.

Power supply control means activity control nitrogen compounds MBE deposition apparatus according to claim 11 of the present invention includes a variable reactance circuit inserted matching between the RF (radio frequency) excitation coils of the power supply and the nitrogen pumping cell And a nitrogen beam flux detecting means for detecting the flow rate of the excited nitrogen beam flux emitted from the nitrogen excitation cell, and the value detected by the nitrogen beam flux detecting means is the variable reactance for matching during the HB excited state holding period T _3. The circuit is configured such that the reactance value of the circuit is adjusted to be a predetermined constant value, and RF power is _supplied to the excitation coil with a constant power W _HB for establishing the HB excitation state. .

Power supply control means activity control nitrogen compounds MBE deposition apparatus according to claim 12 of the present invention includes a variable reactance circuit inserted matching between the RF (radio frequency) excitation coils of the power supply and the nitrogen pumping cell , and a nitrogen beam flux detection means for detecting the excitation nitrogen beam flux flow emitted from the nitrogen pumping cell, the detected value is within HB excited state holding period T ₃ by the nitrogen beam flux detection means, a predetermined fixed value The RF power is supplied with the power W _HB for adjusting the oscillation frequency of the RF power supply so as to establish the HB excitation state in the excitation coil.

Activity controlled nitrogen compounds MBE deposition apparatus according to claim 13 of the present invention, using a computer which stores a control program for sequentially controlling the deposition cycle operation in accordance with the periodic opening and closing of the first shutter in the storage unit It is characterized by being configured.

According to the nitrogen compound MBE film forming method of the activity control type according to claim 1 of the present invention, the irradiation amount of the first (group III) molecular beam from the first molecular beam cell to the substrate through the first shutter is set. And controlling the chemistry of the nitrogen compound in the generated film among the nitrogen active species irradiated toward the substrate from the nitrogen excitation cell switched from the LB excitation state to the HB excitation state during the first shutter closing period T _2. Since the group III molecules attached to the substrate are covalently bonded while controlling the irradiation amount of excited nitrogen atoms and basal nitrogen atoms that are directly involved in (covalent) bonding, the conventional MBE film forming method can be used. In addition, it effectively increases the flatness and deposition rate of the nitrogen compound film, and effectively utilizes the energy held by the excited nitrogen molecules in the film deposition preliminary process, while maintaining the substrate temperature at a relatively low temperature. Excellent low temperature film formation, excellent thermodynamic stability, excellent crystallinity and stable electrical properties, cubic and hexagonal nitrogen compound films can be manufactured easily and inexpensively. Play.

According to the nitrogen compound MBE film forming method of the activity control type according to the second aspect of the present invention, the opening of the second shutter 32 disposed at the outlet of the nitrogen excitation cell 21 or the gap or opening degree of the periphery thereof is set. By controlling the number of dissociated nitrogen atoms that can be adjusted and leaked from it, it is possible to generate a buffer layer effective for initial growth quickly and inexpensively by slowly generating homogenous nitridation on the substrate surface. It has an excellent effect of being able to.

According to the activity controlled nitrogen compound MBE film forming method of the third aspect of the present invention, only the time α corresponding to the switching response delay time (dead time) from the LB excitation mode to the HB excitation mode of the nitrogen excitation cell. The start of irradiation of nitrogen active species from the nitrogen excitation cell that reacts with metal atoms on the substrate surface is advanced, and the film formation speed can be effectively increased by reducing the required film formation time per film formation cycle period T by α hours. Has the function and effect.

According to the activity controlled nitrogen compound MBE film forming method of claim 4 of the present invention, on the substrate that has not reacted with a predetermined amount of nitrogen active species supplied from the nitrogen excitation cell every film forming cycle. Since excess metal atoms are removed during the β period, the generation of nitrogen atom defects on the growth surface is suppressed, the flatness and crystallinity are effectively enhanced, and the high-temperature Ga atoms remaining on the substrate 5 are removed. By removing it, the substrate temperature can be kept at a low temperature, and an excellent effect of being able to ensure low temperature film formation of the epitaxial film is achieved.

According to the nitrogen compound MBE film formation method of the activity controlled nitrogen compound according to claim 5 of the present invention, the metal atom flux required for generating one atomic layer from the first molecular beam cell to the substrate surface every film formation cycle. And excited nitrogen atoms and basal nitrogen atoms in an amount that reacts with the metal atoms on the substrate surface without excess or deficiency from the nitrogen excitation cell. An excellent effect of being able to grow a nitrogen compound film having good crystallinity is obtained.

According to the activity-controlled nitrogen compound MBE film forming method according to claim 6 of the present invention, the metal atom flux required for generating a plurality of atomic layers from the first molecular beam cell to the substrate surface every film forming cycle. And excited nitrogen atoms and basal nitrogen atoms in an amount that reacts with the metal atoms on the substrate surface without excess or deficiency from the nitrogen excitation cell. Has an excellent effect of obtaining a very high nitrogen compound film.

  According to the nitrogen compound MBE film forming method of the activity control type according to claim 7 of the present invention, the discharge space of the nitrogen excitation cell is replenished with electromagnetic wave energy during the entire LB excitation mode period of the nitrogen excitation cell. Since the LB excited state is maintained without substantially affecting the distribution of dissociated nitrogen molecules therein, an excellent effect of being able to stably grow on the substrate surface over the entire film formation period is achieved.

  According to the activity-controlled nitrogen compound MBE film forming apparatus of claim 8 of the present invention, the opening / closing operation of the first shutter, the nitrogen molecular ion and electron exclusion operation of the charged particle exclusion means, and the nitrogen excitation of the power supply control means By sequentially controlling the power feeding operation to the coil, the irradiation amount of the first (Group III) molecular beam from the first molecular beam cell to the substrate through the first shutter is controlled, and the substrate from the nitrogen excitation cell to the substrate is controlled. Among the nitrogen active species irradiated toward the first, the first applied to the substrate while controlling the irradiation dose of excited nitrogen atoms and basal nitrogen atoms that are substantially involved in chemical (covalent) bonding of nitrogen compounds in the generated film Since it is covalently bonded to a molecule (group III molecule), the flatness and deposition rate of the nitrogen compound film can be effectively increased as compared with the conventional MBE film deposition apparatus, and nitrogen excitation in the LB excited state can be achieved. Effective use of the energy of the excited nitrogen molecules irradiated from the cell to the substrate allows low temperature deposition of the epitaxial (layer) film while keeping the substrate temperature relatively low, and is thermodynamically stable. A cubic or hexagonal nitrogen compound film that is high and has good shareability and stable electrical characteristics can be produced easily and inexpensively.

  According to the activity controlled nitrogen compound MBE film forming apparatus of claim 9 of the present invention, the electromagnetically charged particles arranged in the irradiation path region of the nitrogen active species from the nitrogen excitation cell to the substrate fixed at the target position The first molecule on the substrate is deflected by the deflection circuit by deflecting nitrogen molecular ions and electrons out of the nitrogen active species emitted toward the substrate from the nitrogen excitation cell that is in the HB excited state during the closed period of the first shutter. The substrate is irradiated with excited nitrogen atoms and basal nitrogen atoms that are substantially involved in the covalent bond with (Group III molecule), so that the thermodynamically stable and good covalent electrical characteristics Thus, it is possible to produce a stable cubic or hexagonal nitrogen compound film easily and inexpensively.

  According to the nitrogen compound MBE film forming apparatus of the activity control type according to claim 10 of the present invention, the opening and closing operations of the second shutters respectively disposed at the outlet portions of a plurality of, preferably two nitrogen excitation cells are individually performed. In this way, the supply mode of nitrogen excited atoms and ground nitrogen atoms from each nitrogen excitation cell to the substrate via the second shutter can be changed in various ways, and the chemical activity can be controlled more precisely. In addition, the cubic or hexagonal nitrogen compound semiconductor film can be manufactured more reliably and inexpensively.

  According to the activity-controlled nitrogen compound MBE film forming apparatus of the eleventh aspect of the present invention, the reactance value of the variable reactance circuit inserted between the RF power source and the excitation coil of the nitrogen excitation cell is calculated in the nitrogen excitation cell. By changing the impedance according to the switching between the LB excitation mode and the HB excitation mode, the nitrogen excitation cell is put into a desired nitrogen excitation state (LB or LB) by applying predetermined RF power to the excitation coil. There is an excellent effect of being able to quickly switch to the HB excited state.

  According to the activity-controlled nitrogen compound MBE film forming apparatus of the twelfth aspect of the present invention, the impedance matching of the variable impedance circuit can be performed quickly and easily by changing the oscillation frequency of the RF power source to instantaneously perform LB. And the outstanding effect that it can switch between HB excitation modes is produced.

  According to the activity controlled nitrogen compound MBE film forming apparatus of the thirteenth aspect of the present invention, the automatic control apparatus according to the first aspect of the present invention is fully automatic according to a control program configured based on a periodic opening / closing operation of the first shutter. By performing the film formation cycle, the first molecular beam (Group III molecular beam), the excited nitrogen molecular flux and the nitrogen active species flux can be efficiently used to keep the substrate temperature relatively low, enabling low temperature film formation. For example, it has an excellent effect of being able to mass-produce, for example, a cubic or hexagonal nitrogen compound semiconductor film which is flat (uniform growth) and thermodynamically stable, for example.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, the activity-controlled nitrogen compound MBE film forming apparatus 1 of the present invention is generally used for MBE (molecular beam epitaxy) film formation. For example, a VGSemicon (UK) VG80HMBE IRFS-501RF excited nitrogen manufactured by Arios Co., Ltd. (Tokyo, Japan), which is commercially available as a set of the excitation cell 21, the power supply control circuit 51 (matching variable reactance circuit 52 and automatic reactance adjustment circuit 54), and the RF power source 53. A source (device) is incorporated. The MBE film forming apparatus 1 will be described in detail with reference to FIG. 2 showing the basic configuration concept of the film forming apparatus of the present invention. In FIG. 2, parts equivalent to those of the MBE film forming apparatus of FIG.

In FIG. 1, a substrate 5 is detachably fixed to a substrate holder 3 disposed at a target position in the MBE film formation chamber 2 by a fixture (not shown), and the substrate 5 is placed at a predetermined temperature, for example, via a heater 4. By heating to 600 ° C., a group III nitrogen compound, for example, typically a Ga nitride semiconductor (GaN) film is grown on the surface of the substrate 5. A manipulator 7 is attached via an operating rod attached to the substrate holder 3. An operation of fixing the substrate 5 to the substrate holder 3 from the outside of the film forming chamber 2 by the manipulator 7 or an operation of rotating the substrate 5 fixed to the substrate holder 3 is possible. Reference ^numeral 8 denotes a vacuum mechanism, and, for example, the film forming chamber 2 is brought to an ultra vacuum of 10 ⁻⁵ to 10 ⁻⁹ Pa using a turbo molecular pump.

A plurality of, for example, four solid metal molecular beam cells 11 a to 11 d are arranged at the bottom of the film forming chamber 2 below the substrate holder 3. These solid metal molecular beam cells 11 (one of them is typically shown with the suffixes a to d omitted) are configured using, for example, a crucible 14 made of PBN (Pyrolytic Boron Nitride). A group III solid metal material charged in the crucible 14, typically Ga, is melted and evaporated by the melting heater 15, and is a shutter for a metal molecular beam cell attached to the outlet portion of each cell 11 (hereinafter referred to as this). (Referred to as the first shutter) 12 is opened, and the Ga atom beam is irradiated from the metal molecular beam cell 11 onto the surface of the substrate 5 fixed at the target position. Each first shutter 12 is driven to open and close by a shutter drive circuit 46 (see FIG. 2) of an opening / closing drive mechanism (not shown). When the first shutter 11 is opened by the opening / closing drive mechanism, the solid metal molecular beam cell corresponding to the first shutter 12 (hereinafter, this metal molecular beam cell is referred to as the first molecular beam cell) 11 is melted and evaporated. The substrate 5 is irradiated with a metal atom beam (Ga atom beam). Together with these solid metal molecular beam cells 11a to 11d, a so-called gas molecular beam cell 17 that generates a carbon molecular beam by decomposing acetylene gas for generating a gas source, for example, a carbon compound buffer layer or a film. Is installed. For example, acetylene gas, organometallic gas (MO gas), or the like is supplied to the gas molecular beam cell 17 through a gas supply pipe 19. It should be noted that the metal material to be deposited on the surface of the substrate 5 on the solid metal molecular beam cells 11a to 11d, for example, a solid metal material such as Al, In, or Tl other than Ga, or a metal nitrogen compound semiconductor that is deposited. It is possible to use an impurity material to be doped.

  A nitrogen excitation cell 21 is arranged together with the solid metal molecular beam cells 11 a to 11 d and the gas molecular beam cell 17. The nitrogen excitation cell 21 excites (discharges) nitrogen gas N2 supplied from a nitrogen gas cylinder 26 from a nitrogen gas supply pipe 29 connected to a mass flow controller 27 and a gas pressure gauge 28 with high-frequency power, and generates excited nitrogen molecules and free It generates a so-called nitrogen active species in which electrons, excited nitrogen atoms, and ground nitrogen atoms are mixed. An excitation coil 24 that also serves as a water-cooled pipe is coaxially wound around the outer periphery of the cylinder that forms the excitation chamber 22 of the nitrogen excitation cell 21. As will be described in detail later, the excitation coil 24 excites nitrogen gas in the excitation chamber 22 by applying RF power from an RF power source 43, and uses a so-called inductively coupled plasma (ICP) method. Nitrogen active species are generated, and the nitrogen active species are ejected from an orifice 25 provided at the outlet of the nitrogen excitation cell 21. The observation window formed at the rear end portion of the nitrogen excitation cell 21 measures a spectral spectrum during excitation (discharge) in the excitation chamber 22 via an optical fiber cable. For example, PMA-11 spectrum manufactured by Hamamatsu Photonics Co., Ltd. A spectroscopic spectrum measuring device 30 using the instrument is attached.

  A charged particle eliminator 34 is disposed in the vicinity of the outlet portion of the nitrogen excitation cell 21. The charged particle eliminator 34 is charged particles emitted from the nitrogen excitation cell 21, that is, nitrogen molecule ions and electrons other than neutral excitation nitrogen molecules emitted in the LB excitation state (discharge mode), and HB excitation. A neutral excited nitrogen atom, a ground nitrogen atom, a nitrogen molecular ion other than the excited nitrogen molecule, and an electron that are released in the state (discharge mode) deviate from orbits to the substrate 5 electromagnetically fixed to the target position or orbit It acts so as to deflect.

The charged particle eliminator 34 includes a pair of halved cylindrical electrode bodies 36 , a DC power source (not shown), and a magnetic field generator (not shown) including a magnetic field generating coil. The pair of halved cylindrical electrode bodies 36 are mounted in an upright manner facing each other on a ring-shaped ceramic insulator 35 fixed to the tip of the nitrogen excitation cell 21. Both halved cylindrical electrode bodies 36 , 36 are set to a positive potential and a negative potential by a DC power source, respectively, and an electric field having a strength corresponding to the voltage between both halved cylindrical electrode bodies 36 , 36 is formed. . The magnetic field generator is mounted at the tip of both halved cylindrical electrode bodies 36 , 36 , and the magnetic field generated in the axial direction of the excitation coil of the magnetic field generator and the space portion of the halved cylindrical electrode bodies 36 , 36 . It is attached so that the electric field formed in the crossing (substantially orthogonal).

  The voltage applied to each halved cylindrical electrode body 35 of the charged particle eliminator 34 is adjusted or controlled according to the vacuum pressure in the MBE film forming chamber 2, the operating conditions (excitation current) of the nitrogen excitation cell 21, and the like. The nitrogen molecular ions (+) and electrons (−) emitted from the nitrogen excitation cell 21 toward the substrate 5 are respectively half cylinders having a reverse potential (polarity) due to the electromagnetic force acting in the electric field and magnetic field. The electrode body 35 is attracted or adsorbed or deflected, thereby deviating from the trajectory toward the target position and excluded from the charged particle flux. In the MBE film forming apparatus 1 of the present embodiment, the electrode body of the charged particle eliminator 34 is configured using a pair of halved cylindrical electrode bodies 35, but is configured using a plurality of counter electrode pairs. You can also Further, the charged particle eliminator 34 may be configured by at least a pair of counter electrode bodies by omitting the magnetic field generator.

  The molecular quantity of the nitrogen active species (excited nitrogen beam flux) irradiated to the substrate 5 fixed to the substrate holder 3 from the nitrogen excitation cell 21 is, for example, the detection of the nitrogen beam flux mounted on the fixing member connected to the substrate holder 3. Detected by the instrument 44.

  An RHEED (Reflection High-energy Electron Diffraction) electron gun disposed on one side (left side in FIG. 1) of the outer wall of the deposition chamber 2 on the surface of the substrate 5 fixed at the target position in the MBE deposition chamber 2 The reflected fast electron beam incident at a shallow angle (1-2 °) from 41 is reflected and diffracted on the surface of the substrate 5 and projected onto the RHEED screen 42 disposed on the other side (right side in FIG. 1). Based on the image of the RHEED screen 42, the crystal state of the growth surface of the substrate 5 is observed. For example, the crystal growth mechanism can be clarified by analyzing the vibration of the RHEED reflected beam intensity by a known method. In addition, a quadrupole mass analyzer 43 is disposed on the outer wall portion of the MBE film forming chamber 2 so that the type and amount of residual gas in the film forming chamber 2 can be measured.

Next, the activity-controlled nitrogen compound MBE film forming method of the present invention will be described in the case of forming a GaN semiconductor film, for example, according to the time sequence shown in FIG.
The film formation cycle in accordance with the above time sequence is executed using the film formation control device 45 (shown in FIG. 2) of the MBE film formation apparatus 1 of the present invention shown in FIG. 2, as will be described in detail later. .

First, before starting the film formation cycle, that is, before the time point t ₀ , the nitrogen excitation cell 21 is activated, and excited nitrogen molecules having relatively low activity from the nitrogen excitation cell 21 to the film formation target substrate 5. A nitride film or a single crystal β-Si ₃ N ₄ film is formed on the surface of the substrate 5, for example, the Si substrate, by irradiating a line or irradiating a dissociated nitrogen atom beam having a relatively high activity.

  When the nitrogen excitation cell 21 is set to the LB excitation state, as will be described in detail later, the second shutter 32 for the excitation cell attached to the outlet of the nitrogen excitation cell 21 is opened, and the substrate to be deposited is formed. For example, a nitride film (buffer layer) is formed over about 20 minutes on a 3-inch (7.62 cm) Si substrate (Si wafer) in accordance with the material and diameter. On the other hand, when the nitrogen excitation cell 21 is set in the HB excitation state, the second shutter 32 is closed and nitriding is performed in about 20 seconds using the dissociated nitrogen atom beam leaking from the gap of the second shutter 32. A membrane can be produced. In this way, by effectively using the second shutter 32, a buffer layer effective for initial growth can be generated quickly and inexpensively.

A Ga mass is charged into the crucible 14 of the first molecular beam cell 11 and heated and melted by the heater 15 to generate Ga vapor. As will be described in detail later, the excitation coil 24 of the nitrogen excitation cell 21 is supplied with relatively small RF power from an RF power source 53, and the excitation chamber 22 is excited without reacting with Ga atoms irradiated on the substrate 5. It is held in a low-brightness excited state (LB excited state) in which molecular beams occur.

LB excited state of the nitrogen pumping cell 21, the excitation coil 24 of the nitrogen excitation cell 21, by feeding with a relatively small power W _LB, as shown in FIG. 4 (a), occurs in the excitation chamber 22 As shown in FIG. 4B, the orifice 25 of the nitrogen excitation cell 21 is in a relatively dark state. The spectrum (discharge spectrum) of the excited nitrogen molecular beam emitted from the nitrogen excitation cell 21 in the LB excited state was measured using a PMA-11 spectrometer manufactured by Hamamatsu Photonics Co., Ltd. and shown in FIG. As can be seen, a spectrum of only excited nitrogen molecules was observed. A relatively large first positive band and second positive band were also observed.

The first shutter 12 disposed at the outlet portion of the solid metal molecular beam cell 11 is periodically opened and closed with a predetermined constant period T and an open period T ₁ (T ₁ <period T). The period T is determined based on experimental data collected in advance so that the film thickness of GaN epitaxially grown on the AlN buffer layer of the substrate 5 is not more than one monolayer.

During time period T ₁ of the up time t ₁ to close from time t ₀ to the first shutter 12 is opened, a metal atom beam emitted from the first molecular beam cell 11, i.e., LB excited state irradiates the Ga flux to the substrate 5 A film formation preliminary step of irradiating the substrate 5 with excited nitrogen molecular beams emitted from the nitrogen excitation cell 21 is executed.

Among the nitrogen active species radiated from the nitrogen excitation cell 21 in the LB excited state in the film forming preliminary step, nitrogen molecular ions that are positive (+) charged particles and negative (−) charged particles. The electrons are effectively removed by the charged particle eliminator 34 disposed at the exit portion of the nitrogen excitation cell 21, and the substrate 5 is irradiated with an excited nitrogen molecular beam having energy corresponding to a relatively low excitation power _WLB. The

In the film forming preliminary step, Ga atoms corresponding to one molecular layer from the molecular beam cell for Ga (first molecular beam cell) 11 adsorbed on the surface of the substrate 5 are diffused or moved, and simultaneously irradiated from the nitrogen excitation cell 21. Energy is imparted or transferred from the excited nitrogen molecules to the Ga atoms, and the diffusion or movement of Ga atoms on the substrate 5 is effectively promoted. In addition, the activity of Ga atoms energized by nitrogen excited molecules is increased, the increase in the substrate temperature is suppressed, and the film forming step by the nitrogen active species emitted from the nitrogen excited cell 21 switched to the next HB excited state. The GaN film can be formed at a low temperature.

Next, at a time t ₂ when a predetermined time τ has elapsed or delayed since the opening time t ₀ of the first shutter, as will be described in detail later, the excitation coil 24 of the nitrogen excitation cell 21 is relatively connected from the RF power source 53. By switching on a large constant RF power, the LB excitation state is switched to the HB excitation state, and the HB mode is maintained for a predetermined period T ₃ from the excitation state switching time t ₂ to enter the nitrogen excitation cell 21. excited nitrogen atoms produced by HB excited state, the base nitrogen atoms and excited molecular nitrogen (that these nitrogen active species) have a certain molecular quantity irradiated to the substrate 5, Ga atoms adsorbed dispersed in the substrate 5 And the formation of an epitaxial film of the metal nitrogen compound GaN is started. The time τ is referred to as a delay time in this specification.

The HB excited state of the nitrogen excitation cell 21 is generated in the excitation chamber 22 as shown in FIG. 5A by supplying power to the excitation coil 24 of the nitrogen excitation cell 21 with a relatively large power W _HB . As shown in FIG. 5B, the orifice 25 of the nitrogen excitation cell 21 is brought into a very bright state. When the spectrum (discharge spectrum) of the excited nitrogen molecular beam emitted from the nitrogen excitation cell 21 in the HB excited state was measured using the PMA-11 spectrometer, as shown in FIG. An atomic spectrum of nitrogen atom of 747 nm, an atomic spectrum of excited nitrogen atoms of 822 nm, 868 nm, 940 nm, and the like were observed. In addition, a relatively weak first positive band and second positive band were observed.

The delay time τ is expressed as τ = T ₁ ± α with the opening period T ₁ of the first shutter 12 and a time α (α ≧ 0) predetermined according to the RF power supply switching condition to the excitation coil 24. . The delay time τ = T ₁ −α is a time corresponding to a period from the time point t ₀ to a time point a time α before the time point t ₁ when the opening period T ₁ of the first shutter 12 expires. = T ₁ + α is a time corresponding to a period from time t ₀ to time after time t ₁ when the opening period T ₁ of the first shutter 12 expires. The HB excited state holding period T ₃ is determined in advance according to the molecular quantity of the nitrogen active species necessary for the binding reaction with the Ga atoms supplied to the substrate 5 during the opening period T ₁ of the first shutter 12. It is done.

Next, at the time t ₃ when the HB mode duration T ₃ expires, the excited state of the nitrogen excitation cell 21 is returned to the LB excited state, and the first shutter 12 is opened again from the time t _3. During the period β up to t _0, Ga atoms remaining on the surface of the substrate 5 or inside the film forming chamber 2, that is, excess Ga atoms in forming one molecular layer are removed by a known cleaning means. In this way, by removing the high-temperature Ga atoms remaining on the substrate 5, holding the substrate temperature to a low temperature, from time t ₂ switch excited state up to the time t ₀ which is again the first shutter 12 is opened During the period (film formation process HB excited state holding period T ₃ + period β), the film formation process is executed while ensuring low temperature film formation of the epitaxial film.

  A film forming cycle including a film forming preliminary process and a film forming process during one cycle T of the opening / closing operation of the first shutter 12 is repeated a plurality of times according to the film thickness of the GaN semiconductor film to be formed on the substrate 5. .

As described above, the opening period T ₁ of the first shutter 12 is not limited to the number of metal atoms of one molecular layer or less, but is a period length corresponding to the number of metal atoms for a plurality of molecular layers so as to increase the film formation rate. It may be. In particular, at the initial stage of forming a metal nitrogen compound film having a predetermined thickness, metal atoms for a plurality of molecular layers are supplied to form a film at a relatively high speed. By performing the film formation preliminary process with a period T ₁ corresponding to the atomic quantity, the generation rate of the entire film formation operation can be effectively increased, and the flatness and crystallinity of the film surface should be improved. Can do.

  The film formation control device 45 is configured using, for example, a personal computer PC, and executes the above-described film formation cycle in a memory (not shown) of the computer PC according to the time sequence shown in FIG. A membrane control program is stored.

  As the control panel (control panel) of the film formation control device 45, as shown in FIG. 4, an image control panel that is visually displayed on a liquid crystal monitor screen for a computer PC is used.

  In the image control panel, 61 is a start button for a command to start control of the film formation control device 45, 62 is an operation mode setting switch, 63 is an operation mode setting switch, and 64 is a pulse (see FIG. 2) cycle switching. The switch 65 is an input current monitor in the power supply control circuit 51 to be described in detail later, 66 is an output voltage monitor corresponding to the input RF power applied to the excitation coil 24 of the nitrogen excitation cell 21, and 67 is the HB mode setting RF power. Target current setting dial for setting a current target value corresponding to W, 68 is an upper limit setting dial for making setting RF power, 69 is a lower limit setting dial for making setting RF power, and 70 is LB excitation state holding power setting It is a dial.

A user (user of the film formation control device 45) includes various setting data input switches that are preset according to the film formation work target, and 71 is a period T (sec) setting of the periodic opening / closing operation of the first shutter 12 The button 72 is an opening period T ₁ (sec) setting button of the first shutter 12, 73 is a time α (sec) setting button, 74 is an HB mode duration T ₃ (sec) setting button, and 75 is a time. This is a β (sec) setting button. The delay time τ = T ₁ ± α is set by the setting button 72 in an arithmetic logic unit (ALU) (not shown) of the film formation control device 45 when a timing signal t ₂ is output from a timer circuit described later. Calculation is performed based on the T ₁ value and the α value set by the setting button 63. In addition, 76 is an operation mode changeover switch of the reactance adjustment circuit 54, and 78 is an output voltage setting dial corresponding to the input setting RF power in the manual operation mode.

A timer circuit (not shown) is formed using the memory area of the film formation control device 45, and from the timer circuit, the first shutter 12 is operated in cooperation with the data input setting switches 71 to 75 arranged on the control panel. the above timing signal indicating an open time t _0, the timing signal and said time point t ₂ indicating the time t ₂ to switch with time delayed said time point t ₀ tau nitrogen excitation cell 21 from the LB excited state to the HB excitation state A timing signal indicating the time point t ₃ when the HB excited state holding period T ₃ has elapsed is output.

A feed control circuit 51 is connected to a high-frequency feed line that connects the RF power source 53 and the excitation coil 24 of the nitrogen excitation cell 21. The power supply control circuit 51 is a variable variable for matching connected between the excitation coil 24 constituting the known inductively coupled nitrogen gas excitation (discharge) circuit in the nitrogen excitation cell 21 and the RF power source (circuit) 53. A reactance circuit 52, a nitrogen beam flux detector 44 for detecting the molecular quantity of the excited nitrogen beam flux emitted from the nitrogen excitation cell 21, and the detected value of the nitrogen beam flux detector 44 are the target current setting dial 67 or The reactance value of the variable reactance circuit for matching 52 is feedback-controlled so as to be the target value set by the LB excitation state holding power setting dial 70, whereby a relatively large constant power W _HB or relatively small is applied to the excitation coil 24. automatic reactance adjustment so as to introduce the RF power with a constant power W _LB (own Constituted by an impedance matching circuit) 54.

With the above configuration, when the automatic reactance adjustment circuit 54 receives the timing signal t ₂ from the timer circuit of the film formation control device 45, the matching variable reactance circuit 52 during the HB excitation state holding period T ₃ set by the setting button 74. The RF power source 53 supplies power to the excitation coil 24 of the nitrogen excitation cell 21 with a relatively large constant power W _HB to establish an HB excitation state in the excitation chamber 22 of the nitrogen excitation cell 21. Similarly, when the automatic reactance adjustment circuit 54 receives the timing signal t ₃ from the timer circuit, the reactance value of the matching variable reactance circuit 52 is adjusted, and a relatively small power W _{LB is supplied} from the RF power source 53 to the excitation coil 24. The excitation chamber 22 of the nitrogen excitation cell 21 is switched to the LB excitation state. The excitation chamber 22 of the nitrogen excitation cell 21 is subjected to LB excitation during a period (= β + τ) after the time t ₃ until the automatic reactance adjustment circuit 54 receives the timing signal t ₂ from the timer circuit in the next film formation cycle. Kept in a state. In this period (= β + τ), the excitation chamber 22 can be irradiated with electromagnetic waves so that the excited state, that is, the discharge is not completely extinguished or extinguished. In this manner, the switching of the nitrogen excitation cell 21 from the LB mode to the HB mode can be made stable and reliable.

  Instead of the operation of adjusting the reactance value of the variable reactance circuit 52 for matching by the automatic reactance adjustment circuit 54, the impedance matching operation of the high-frequency power feeding circuit may be performed by changing the oscillation frequency of the RF power supply 53. . In this way, the responsiveness of the automatic matching operation can be effectively increased, and thus film growth can be controlled more precisely.

  In the MBE film forming apparatus 1 of the above embodiment, the case where the group III metal element Ga is used as the solid metal has been described. However, other group III metal elements Al, In or Tl nitrogen compounds AlN, InN or TlN and The present invention can also be applied when producing an alloy film containing them.

In the MBE film forming apparatus 1 of the above embodiment, a single nitrogen excitation cell 21 is mounted.
A plurality of, preferably a few, nitrogen excitation cells 21 may be mounted. As shown in FIG. 11 and FIG. 12, for example, two nitrogen excitation cells 21 are arranged at intervals, and the central axis of the outlet portion of each nitrogen excitation cell 21 is appropriately set on the substrate surface fixed at the target position. It can be configured to emit nitrogen active species flux from each nitrogen excitation cell 21 in accordance with two set aiming points (positions). With this configuration, the chemical activity of the film formation region in the substrate 5 fixed at the target position can be controlled more precisely, and a high-quality epitaxial film can be manufactured.

  Also, as shown in FIGS. 11 and 12, a ceramic insulator 35 and a charged particle eliminator 34 are attached to the tip of the outlet of the nitrogen excitation cell 21, and nitrogen excitation is performed in front of the charged particle eliminator 34. A cell shutter 32 (hereinafter referred to as a second shutter) is arranged, and the opening / closing operation of the second shutter 32 is controlled via the shutter drive circuit 33 in the same manner as the first shutter 12 for the first molecular beam cell. As a result, the chemical activity of the film formation region in the substrate 5 fixed at the target position can be controlled more precisely, and a high-quality epitaxial film can be manufactured.

Further, by arranging the second shutter 32 at the outlet of the nitrogen excitation cell 21, the opening of the second shutter 32 or the gap or opening degree of the periphery of the second shutter 32 is adjusted when the nitrogen excitation cell 21 is in the HB excitation state. It is possible to change the amount of dissociated nitrogen atoms leaking from there. As a result, the number of dissociated nitrogen atoms reaching the surface of the substrate 5 can be controlled, and the amount of film formation can be controlled by adjusting the number of Ga atoms or Al atoms so as to match the number of reactions. In the case of a substrate surface, for example, a Si substrate, a single crystal β-Si ₃ N ₄ film is formed as a buffer layer of the substrate in the film forming process by slowly causing nitridation of the homogeneous system (Si) on the surface. be able to. In this way, the initial growth immediately after the start of the film formation cycle can be controlled, and an epitaxial film with good crystallinity and flatness in the film formation region can be manufactured. In this case, the degree of tightness of the second shutter 32 can be adjusted while measuring or monitoring the nitrogen atom beam flux using the nitrogen atom beam flux measuring device 44.

Next, an AlN buffer layer was formed on a 3-inch (7.62 cm) Si (111) substrate (Sample 1 and Sample 2) using the MBE film forming apparatus of the present invention, and then both samples 1 3 and the sample 2, the Ga atom beam from the first molecular beam cell 11, the nitrogen active species from the nitrogen excitation cell 21 through the charged particle eliminator 34, and the same period T = 2. A GaN film was formed by repeated irradiation for 8 seconds, T ₁ = 1 second, and T ₂ = 1.8 seconds.
In the sample 1, the first shutter 12 is opened, the sample 1 is irradiated with the Ga atom beam, the second shutter 32 attached to the outlet of the nitrogen excitation cell 21 is opened, and the nitrogen excitation cell is brought into the LB excitation state. The substrate surface of the sample 1 is irradiated with an excited nitrogen molecular beam from 21 through the charged particle eliminator 34. Next, the first shutter 12 is closed, the irradiation of the Ga atom beam on the substrate surface is stopped, and the second shutter 32 opened from the nitrogen excitation cell 21 switched to the HB excitation state and the charged particle eliminator 34 are passed through. Then, a GaN film was formed by repeatedly executing a film formation cycle in which the substrate surface was irradiated with dissociated nitrogen atoms.
In the sample 2, the first shutter 12 is opened, the sample 1 is irradiated with the Ga atom beam, the second shutter 32 attached to the outlet of the nitrogen excitation cell 21 is closed, and the nitrogen excitation cell is brought into the LB excitation state. The irradiation of the excited nitrogen molecular beam is cut off from 21 to the substrate surface of the sample 1 through the charged particle eliminator 34. Next, the first shutter 12 is closed, the irradiation of the Ga atom beam on the substrate surface is stopped, and the second shutter 32 opened from the nitrogen excitation cell 21 switched to the HB excitation state and the charged particle eliminator 34 are passed through. Then, a GaN film was formed by repeatedly executing a film formation cycle in which the substrate surface was irradiated with dissociated nitrogen atoms.
Sample 1 and Sample 2 are both set to a substrate temperature of 610 ° C. without rotating the substrate holder 3 during film formation, and the temperature in the Ga molecular beam cell (first molecular beam cell) 11 is set to 1030 ° C. It was.

As can be seen from the interference photographs of the GaN surfaces of Sample 1 and Sample 2 (FIG. 9), Sample 1 shows concentric shading, while Sample 2 shows interference fringes arranged in one direction and is flat. Regarding the property, Sample 1 was better.
Regarding the film thickness distribution on the GaN surface of Sample 1 and Sample 2, as can be seen from the X-ray diffraction measurement data in FIG. 8, Sample 1 was better than Sample 2 in terms of flatness.
Further, regarding the film thickness distribution on the GaN surface of Sample 1 and Sample 2, as can be seen from the X-ray diffraction measurement data in FIG. 8, the X-ray diffraction half-value width of Sample 1 is narrower than the half-value width of Sample 2, and the flatness Sample 1 was better than Sample 2.

As is clear from the above embodiments, the film forming method of the present invention is not limited to the group III nitrogen compound semiconductor, but, for example, using an RF oxygen gas excitation cell (not shown) similar to the nitrogen gas excitation cell 21 described above. It can be applied to film formation of oxide semiconductors obtained by oxidizing metal elements such as tin (Sn) or zinc (Zn), such as TiO ₂ , ZnO, NiO, and SnO ₂ .

It is a schematic sectional drawing of the activity control type nitrogen compound MBE film-forming apparatus which can apply the film-forming method of this invention. It is the schematic which expands and shows the main components of the film-forming apparatus of this invention. It is a figure which shows the basic time sequence of the film-forming cycle of the film-forming method of this invention. It is explanatory drawing of the LB excitation state of the nitrogen excitation cell applied to this invention, (a) is a figure which shows the principle of LB excitation state generation | occurrence | production, (b) shows the brightness of the orifice part at the time of LB excitation state operation | movement. In the photograph shown, (c) shows a measurement graph of the spectrum (discharge spectrum) of the excited nitrogen molecular beam emitted from the nitrogen excited cell 21 in the LB excited state. It is explanatory drawing of the HB excitation state of the nitrogen excitation cell applied to this invention, (a) is a figure which shows the principle of HB excitation state generation | occurrence | production, (b) shows the brightness of the orifice part at the time of HB excitation state operation | movement. In the photograph shown, (c) shows a measurement graph of the spectrum (discharge spectrum) of the excited nitrogen molecular beam emitted from the nitrogen excitation cell 21 in the HB excited state. It is a front view of the control panel of the electric power feeding control apparatus in the film-forming apparatus of this invention. The comparison data of two flatness implemented by the different film-forming control system using the film-forming apparatus of this invention are shown. The flatness improvement comparison data of the GaN surface produced | generated by the said sample 1 and the sample 2 are shown. The comparison data of the film thickness distribution with respect to the position of the GaN surface produced | generated by the said sample 1 and the sample 2 are shown. It is the interference photograph of the GaN surface produced | generated by the said sample 1 and the sample 2. FIG. The conceptual diagram of the main components of the modification of the MBE film-forming apparatus of this invention is shown. The schematic of the main component part of the said modification is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 MBE film-forming apparatus 2 MBE film-forming chamber 3 Substrate holder 5 Substrate 8 Vacuum mechanism (turbo molecular pump)
9 Liquid nitrogen shroud 11 Solid metal molecular beam cell (first molecular beam cell)
11a to 11d Solid metal molecular beam cell (K cell)
12 First shutter (Shutter for metal molecular beam cell)
14 PBN crucible 15 Melting heater 21 Nitrogen excitation cell 22 Excitation chamber 24 Excitation coil 25 Orifice 26 Nitrogen gas cylinder 27 Mass flow controller 28 Pressure gauge 29 Nitrogen gas supply pipe 30 Spectral spectrum measuring instrument 32 Second shutter (shutter for nitrogen excitation cell)
33 Second shutter drive circuit 34 Charged particle eliminator 35 Ceramic insulator 36 Half cylindrical electrode body 41 RHEED electron gun 42 RHEED screen 43 Quadrupole mass analyzer 44 Nitrogen beam flux detector 45 Deposition control device (circuit)
46 Shutter drive circuit 47 Control panel 48 Start button 49 Data input setting button (data input setting device)
51 Power Supply Control Circuit 52 Matching Variable Reactance Circuit 53 RF (High Frequency) Power Supply 61 Start Button 67 Target Current (Excitation Power) Setting Dial 70 LB Mode Maintenance Power Setting Dial 71 Period T Setting Switch 72 Open Period T ₁ Setting Switch 73 Time α Setting switch 74 HB excitation state holding period T ₃ setting switch 75 Time β setting switch

Claims (13)

While supplying a first atomic beam (group III metal atomic beam) to a substrate fixed at a target position in a MBE (molecular beam epitaxy) deposition chamber via a first shutter disposed at an exit portion of the first molecular beam cell. Runisaishite to supply nitrogen active species flux from nitrogen exciting cell, the first shutter repeatedly opened and closed periodically, in open period T ₁ of the said first shutter, said first emitted from the first molecular beam cell the atomic beam as well as elevation irradiation, the inside of the nitrogen pumping cell low brightness (low brightness: LB) deposition of irradiating the low nitrogen active species flux from nitrogen excited cells in chemical activity in the substrate is maintained in an excited state During the preliminary process and a fixed period in the first shutter closing period T ₂ , the irradiation of the first atomic beam from the first molecular beam cell to the substrate is interrupted and the inside of the nitrogen excitation cell has high brightness (H igh Brightness: HB) to maintain the excited state comprising a film forming step of producing an epitaxial film of a nitrogen compound to the substrate by supplying a high nitrogen active species flux in chemical activity in the substrate, a plurality of deposition cycles Upon times repeatedly to produce an epitaxial film of nitrogen compounds,
In each film formation preliminary step of the film formation cycle, while irradiating the substrate with only excited nitrogen molecules having low chemical activity while eliminating nitrogen molecular ions and electrons emitted from the nitrogen excitation cell,
In each film formation step of the film formation cycle, the opening and closing operation of the second shutter disposed at the exit portion of the nitrogen excitation cell is controlled, and the power supplied to the nitrogen excitation cell is adjusted according to the target irradiation amount ( The substrate is irradiated with excited nitrogen atoms N ^* and basal nitrogen atoms N with high chemical activity while eliminating the nitrogen molecular ions and electrons emitted from the nitrogen excitation cell. film forming process consisting of the activity of control nitrogen compounds MBE deposition wherein that you repeated a plurality of times deposition cycles.   Before starting the film formation cycle, the nitrogen excited ions are supplied to the substrate fixed at the target position from the nitrogen excited cell in the LB excited state by removing nitrogen molecular ions and electrons, or in the HB excited state. Among the nitrogen active species released from the nitrogen excitation cell, by removing nitrogen molecular ions and electrons and supplying excited nitrogen atoms and basal nitrogen atoms to the substrate at a low flow rate, the substrate surface is the same as the substrate. 2. The activity-controlled nitrogen compound MBE film forming method according to claim 1, wherein an original single crystal nitride film is formed. The nitrogen at the time t ₂ when a delay time τ = (T ₁ −α), which is shorter than the first shutter opening time t _{0 by} a predetermined time α corresponding to the repeated constant opening period T ₁ of the first shutter, has elapsed. 3. The activity-controlled nitrogen compound MBE film forming method according to claim 1, wherein the LB excited state in the excitation cell is switched to the HB excited state. During the period T ₂ when the first shutter is closed, during the period β from the time t ₃ when the inside of the nitrogen excitation cell is returned from the HB excited state to the LB excited state until the time t ₀ when the first shutter is opened again, LB excitation is performed. 4. The activity-controlled nitrogen compound MBE film formation according to claim 1, wherein residual first molecules on the substrate are removed by excited nitrogen molecules from the nitrogen excited cell in a state. Method. The opening period T ₁ of the first shutter is determined according to the number of metal atoms for epitaxially growing a film of one molecular layer or less on the substrate, and the HB excited state holding period T ₃ is during the opening period T ₁ of the first shutter. The activity-controlled nitrogen compound MBE composition according to any one of claims 1 to 4, characterized in that it is determined according to the atomic quantity of nitrogen active species necessary for reacting with the metal atoms supplied to the substrate. Membrane method. The opening period T ₁ of the first shutter is determined according to the number of metal atoms for epitaxially growing a film of a plurality of molecular layers on the substrate, and the HB excited state holding period T ₃ is set during the opening period T ₁ of the first shutter. 6. The activity-controlled nitrogen compound MBE according to claim 1, wherein the activity-controlled nitrogen compound MBE is determined according to an atomic quantity of nitrogen active species necessary for reacting with the metal atom supplied to the substrate. Film forming method.   7. The activity-controlled nitrogen compound MBE film forming method according to claim 1, wherein the LB excited state is maintained by irradiating the nitrogen excited cell with electromagnetic waves. While irradiating a substrate fixed at a target position in an MBE (molecular beam epitaxy) deposition chamber with a first atomic beam via a first shutter that is arranged at the exit portion of the first molecular beam cell and periodically opens and closes. in nitrogen compound MBE deposition apparatus for generating an epitaxial film of a nitrogen compound by supplying nitrogen active species flux from the nitrogen pumping cell on the substrate,
It is arranged near outlet portion of the nitrogen pumping cell, eliminating the nitrogen molecular ions and electrons of the nitrogen activity is released from the top Symbol nitrogen excited cell species excited nitrogen atom, basal nitrogen atom and excited nitrogen molecules to the substrate a load conductive particles exclude means you irradiated to,
First shutter driving means for periodically opening and closing the first shutter with a certain open period T ₁ ;
A second shutter driving means for disposing a second shutter at an outlet portion of the nitrogen excitation cell and driving the opening and closing of the second shutter in synchronization with the opening and closing operation of the first shutter;
Depending on the film formation target, at least the period T for opening / closing the first shutter, the open period T _1, and the high brightness (HB) excited state holding period T ₃ are set in advance, and these setting data (T, T ₁ , Setting data input means for inputting T ₃ );
A low brightness (LB) excitation state is established by supplying power to the excitation coil of the nitrogen excitation cell with power W _LB in synchronization with opening and closing operations of the first shutter and the second shutter , while the power W to establish a HB excited state by feeding with a power W _HB which changes according to the target dose of greater or one nitrogen active species than _LB, and a power supply control means for controlling switching of the excitation power,
An activity-controlled nitrogen compound MBE film-forming apparatus, wherein an epitaxial film of nitrogen compound is generated by supplying to the substrate while controlling the chemical activity of nitrogen active species flux from the nitrogen excitation cell.   The charged particle exclusion means includes an electromagnetic charged particle deflection circuit, which deflects nitrogen molecular ions and electrons among the nitrogen active species released from the nitrogen excitation cell to target excited nitrogen atoms, basal nitrogen atoms and excited nitrogen molecules to target positions. 9. The activity-controlled nitrogen compound MBE film forming apparatus according to claim 8, wherein the substrate fixed to the substrate is irradiated. To the MBE deposition chamber by arranging a plurality of nitrogen excited cells as the nitrogen pumping cell, in synchronization with the opening and closing operation of the first shutter with control the opening and closing of each of the second shutter, the respective nitrogen pumping cell the excitation power for powering the excitation coil, by controlling switching through the power supply control unit, the substrate while controlling the nitrogen active species activity that radiates to the substrate which is fixed to a target location from each of the nitrogen pumping cell 10. The activity-controlled nitrogen compound MBE film forming apparatus according to claim 8, wherein an epitaxial film of a nitrogen compound is formed on the substrate. The power supply control means includes a variable reactance circuit for matching inserted between an RF (high frequency) power source and an excitation coil of the nitrogen excitation cell, and a nitrogen beam for detecting an excitation nitrogen beam flux flow rate emitted from the nitrogen excitation cell. A flux detection means, and the detected value by the nitrogen beam flux detection means is adjusted so that the reactance value of the variable reactance circuit for matching becomes a predetermined constant value during the HB excitation state holding period T _3. 11. The activity-controlled nitrogen compound according to claim 8, wherein RF power is applied to the coil with a constant power W _HB for establishing the HB excited state. 11. MBE deposition system. The power supply control means includes a variable reactance circuit for matching inserted between an RF (high frequency) power source and an excitation coil of the nitrogen excitation cell, and a nitrogen beam for detecting an excitation nitrogen beam flux flow rate emitted from the nitrogen excitation cell. Flux detecting means, and adjusting the oscillation frequency of the RF power source so that the detected value by the nitrogen beam flux detecting means becomes a predetermined constant value during the HB excited state holding period T ₃ , and 11. The activity-controlled nitrogen compound MBE film formation according to claim 8, wherein RF power is input with a constant power W _HB for establishing an HB excited state. apparatus.   The computer program according to any one of claims 8 to 12, wherein a control program for sequentially controlling the film forming cycle operation according to the periodic opening / closing operation of the first shutter is used. Activity controlled nitrogen compound MBE deposition system.