JPH0633230B2 - Crystal growth method and crystal growth apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a crystal growth method and a crystal growth apparatus suitable for crystal growth requiring atomic layer control, particularly for epitaxial growth of compound semiconductors and the like.

(Conventional technology) Conventional technology is used for molecular beam epitaxial growth (molecular
Beam Epitaxy (hereinafter referred to as MBE), and Reflection of High Energy Electron Diffracti
on, hereinafter referred to as RHEED)
It will be described with reference to the drawings.

In the MBE growth, an element 4 supplied as a molecular beam 3 from a single or a plurality of Kunsen cells (hereinafter abbreviated as K cells) 2 is epitaxially grown on a substrate 5 in an ultrahigh vacuum chamber 1. For example, in the case of a compound semiconductor of GaAs / AlGaAs, the molecular beam 3 is formed by alternately opening and closing the shutter 6 of the K cell 2 of Ga, As and Al in the temperature range of 300 ° C to 700 ° C.
And epitaxial growth is performed. At this time, the growth process is evaluated by RHEED.

When the RHEED makes high-speed electrons of 10 kV to 40 kV incident on the substrate 5 during crystal growth from the electron beam source 7, the incident electrons 8 are scattered by reflecting the information on the surface of the substrate 5. When the scattered electrons 9 are received by the screen 10 coated with fluorescent paint, an electron diffraction image reflecting the information on the surface of the substrate is obtained. This diffraction image is particularly sensitive to the irregularities on the surface of the substrate 5, and a clear appearance of the surface can be known by focusing only on the intensity of the typical spots.

FIG. 7 is a diagram showing how the surface grows in response to changes in the intensity of a typical spot of a diffraction image. The intensity of the RHEED spot changes as the crystal growth progresses.
The period of this fluctuation corresponds to the speed at which the epitaxial film increases by one or two atomic layers. That is, since the intensity of the electron beam reflected from the crystal surface becomes stronger when the surface is flat, in the case of layer growth, the flatness is repeated every time one crystal plane is grown, and the spot intensity of RHEED is increased. Will be observed. By using such a method, it is possible to control while observing the state at the same time during crystal growth.

(Problems to be Solved by the Invention) However, the conventional growth method by MBE and RHEE
The evaluation method such as D has a problem that it is not possible to distinguish the type of the element 4 being grown on the surface of the substrate 5 or the element 4 formed on the surface. Further, although the intensity change reflected on the surface irregularities can be measured, there is also a problem that information on the structure of the irregularities, the initial growth process, the arrangement configuration in atomic size, and the like cannot be obtained. Therefore, when the atoms are crystallized one layer at a time, there is a problem that it is not possible to evaluate how or how many atomic layers the desired element has grown on the surface, and it is not possible to control it.

The present invention solves the above problems, and provides a crystal growth method and a crystal growth apparatus capable of obtaining information on the type of growing element and the growth process of an atomic layer.

(Means for Solving the Problems) In order to solve the above problems, the present invention irradiates ions and performs energy analysis of scattered ions.

(Operation) With the above configuration, the growth surface is irradiated with ions simultaneously with the growth of crystals, and energy analysis of scattered ions that differ depending on the type of atoms is performed, so that the type of atoms on the surface can be evaluated. Further, by measuring the angle dependence of the incident or scattering direction, it becomes possible to observe the atomic structure on the surface. Therefore, by the above evaluation method,
By measuring the coverage of each constituent atom on the surface and controlling the type and supply time of the supplied atoms, it becomes possible to perform complete crystal growth for each atomic layer.

(Embodiment) An embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view showing the structure of an MBE growth apparatus according to the present invention. Note that the same components as those of the conventional example shown in FIG.

In the figure, an MBE apparatus 11 according to the present invention is equipped with an ion scattering spectroscopy (Ion
Scatterring Spectroscopy (hereinafter referred to as ISS) Device 12
Is arranged.

The MBE device 11 is similar to the conventional example in the ultra-high vacuum chamber 1,
The K cell 2 and the substrate 5 are arranged, and the constituent element 4 necessary for crystal growth is supplied to the surface of the substrate 5 as the molecular beam 3. The growth conditions differ depending on the element 4, especially K cell 2
The temperature is determined in consideration of the vapor pressure of the element 4, the supply amount required for a desired crystal, the temperature of the substrate 5, and the like.

Next, the ISS device 12 will be described by taking the case of using helium (He) ions as an example. Helium ion 13
It is ionized by the helium ion source 14 and emitted as an ion beam 15. After that, it passes through two sets of deflection plates 16 and 17 for adjusting the traveling direction of the ion beam 15 and an electrostatic lens 18 for condensing. A DC voltage is applied to each of the deflection plates 16 and 17 and the electrostatic lens 18, and the voltage is adjusted by acceleration energy or the like to optimize the ion beam 15. Furthermore, the advanced ion beam
The deflecting plate 19 to which the pulse voltage is applied scans the slit 15, and the pulse 15 passes through the slit 20 to become a pulsed ion beam 21. The pulsed ion beam 21 passes through the through hole of the annular detector 22 and strikes the surface of the substrate 5. The colliding ions scatter as the scattered ions 23 at a velocity that depends on the type of atoms on the surface and the mass of the atoms. Among them, only scattered ions 23, which are scattered 180 degrees with respect to the incident, that is, backward, reach the detector 22.

Since the incident ion beam 21 is a pulsed ion beam 21, if the velocity of scattered ions 23 traveling a certain range 24 shown by the dimension line in the figure is different, the pulse beam will be slit 20.
Before passing the next pulsed beam through the detector
When the transit time of the scattered ions 23 that have reached and are detected is measured, the energy analysis of the scattered ions 23 becomes possible.

FIG. 2 is an energy distribution diagram showing an example of measurement of the ISS spectrum of the InP substrate surface measured with an acceleration voltage of 2 keV using the above method. Each of them corresponds to the number of scattered ions 23. The two peaks 25 and 26 observed here indicate ions scattered by colliding with indium (In) atoms and phosphorus (P) atoms near the surface, respectively.

By carrying out such measurement at the same time during actual MBE growth, in the case of InP, for example, the kind and amount of constituent atoms on the growth surface are simultaneously observed with the time difference and intensity of the scattered ions 23. be able to.

Further, the surface structure can be observed by changing the angle of the substrate and measuring the incident angle distribution. This principle will be described with reference to FIG. In the figure, the growth surface is formed by the first atomic layer 27, the second atomic layer 28, and subsequent atomic layers. Since the incident ions 29 are blocked by the collision cross section 30 of each atom, the shadow cone 31 of the atoms of the first atomic layer 27 spreads beyond the second atomic layer 28, and depending on the incident angle, the second atomic layer After 28, the second
In some cases, the peak is not observed in the ISS spectrum as shown in the figure but only the peak of the first atomic layer 27. In this way, by changing the angle of the substrate and measuring the incident angle dependence of the ISS spectrum, it is possible to observe the structure of the surface or constituent atoms from the surface to several atomic layers. In addition to the peak intensity of the scattered ions 23 described above, the coverage of constituent atoms on the surface can be known.

A method of growing a crystal while controlling the atomic layer by using the evaluation method by ISS simultaneously with such MBE growth will be described by taking InP as an example. InP by MBE
Growth of In while opening and closing the shutter 6 of the K cell 2.
And P are alternately supplied to form one layer at a time, and the growth surface is evaluated at the same time by ISS under the condition that the shadow cone 31 of the first atomic layer 27 covers the atomic layers after the second atomic layer 28.
This is done while observing the state of atoms supplied alternately.

FIG. 4 is a time-series state diagram showing the time change of the peak intensity of the ISS spectrum corresponding to each In and P atom.
Focusing on the change in the peak intensity of In and P in the ISS spectrum, the peak intensity corresponding to each atom is
The timing of opening and closing the shutter 6 of the K cell 2 of each atom is
It can be seen that it corresponds to the time change of the peak intensity like the time change of the spot intensity of RHEED. Therefore, if the shutter 6 of the K cell 2 for each atom is opened / closed in accordance with the temporal change of the peak intensity, it is possible to control the growth of each atom by one atomic layer.

FIG. 5 is a block diagram of an automatic control MBE apparatus adopting the crystal growth method according to the present invention, in which a data processor 32 and a peak intensity analysis system 33 are connected to an ISS apparatus 12 installed in the MBE apparatus 11, , K-cell 2 is connected to a shutter controller 34 for controlling the opening and closing of the shutter 6.

With such a configuration, the fourth data obtained by the data processor 32
The peak intensity of each atom is read by the peak intensity analysis system 33 from the signal as shown in the figure, and based on the data, the shutter 6 is turned on when the peak intensity of the growing atom in each atom becomes maximum. Sending a signal to the shutter controller 34 so as to switch enables MBE growth and evaluation by ISS in real time, thus enabling atomic layer control for a plurality of supply atoms.

(Effects of the Invention) As described above, according to the crystal growth method of the present invention,
By irradiating the growth surface with ions during crystal growth, energy analysis of scattered ions and measurement of the angle dependence of the incident or scattering direction make it possible to observe the type, coverage and structure of surface atoms. .

In addition, according to the crystal growth apparatus of the present invention which also uses the above-mentioned observation means, the coverage of each constituent atom on the surface is measured, and one atomic layer is a complete crystal layer while controlling the type and supply time of the supplied atoms. Will be able to grow.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an MBE device according to the present invention,
FIG. 2 is an energy distribution diagram showing a measurement example obtained by the crystal growth method of the present invention, FIG. 3 is a model diagram thereof, and FIG. 4 is a diagram showing time series peak intensity of the ISS data processor according to the present invention, FIG. 5 is a block diagram of an automatically controlled MBE device according to the present invention, and FIGS. 6 and 7 are diagrams showing a conventional MBE device and time-series peak intensity. 1 ... Ultra high vacuum chamber, 2 ... Kunsen cell, 3 ... Molecular beam, 4 ... Element, 5 ... Substrate, 6 ... Shutter, 7 ...
Electron beam source, 8 ... Incident electron, 9 ... Scattered electron, 10 ... Screen, 11 ... Molecular beam epitaxial growth (MBE)
Equipment, 12 …… Ion scattering spectroscopy (ISS) equipment, 13 …… Helium ion, 14 …… Helium ion source, 15 …… Ion beam, 16,17,19 …… Deflector, 18 …… Electrostatic lens, 20 …
… Slit, 21 …… pulsed ion beam, 22 …… detector, 23 …… scattered ion, 24 …… range, 25,26 …… peak, 27 …… first atomic layer, 28 …… second atom Layer, 29 ... Incident ion, 30 ... Collision cross section, 31 ... Shadow cone, 32
...... Data processor, 33 ...... Peak intensity analysis system, 34 ...... Shutter controller.

Claims (7)

[Claims] 1. In molecular beam crystal growth in ultra-high vacuum, at the same time as growing a crystal on a substrate, the surface of the substrate is irradiated with ions and energy analysis of scattered ions from the surface of the crystal is performed to perform crystal growth. Measuring the type of atoms on the surface of the substrate in units of one atomic layer, and changing the type of supply atoms supplied to the substrate after the growth of the number of crystalline atoms in units of one atomic layer, and changing another atom to one atom. And a step of growing the substrate on a layer-by-layer basis. 2. The crystal growth method according to claim 1, wherein the step of growing a crystal on the substrate and the step of irradiating the surface of the substrate with ions are not performed at the same time. 3. The crystal growth method according to claim 1, wherein the atomic coverage of the substrate surface is measured from the peak intensity of energy analysis of scattered ions. 4. The crystal growth method according to claim 1, wherein a shutter is opened / closed in accordance with the peak intensity of the constituent atoms on the substrate surface to control the crystal growth in units of one atomic layer. 5. The surface of the substrate is measured from the incident angle dependence of the scattered ions of the ion beam on the substrate, which is measured by changing the angle between the substrate and the ion beam while irradiating the substrate surface with the ion beam. 2. The crystal growth method according to claim 1, further comprising the step of measuring the structure of constituent atoms of the several atomic layers. 6. An MBE apparatus having a plurality of K cells, which is provided with a substrate inside and supplies a film to be grown on the substrate, and the surface of the substrate is irradiated with ions to remove the ions scattered by the substrate. An ISS device for detecting, a peak analyzer for analyzing the scattered ion peak intensity, and a shutter controller device for controlling the shutter of the K cell in the MBE device according to data from the peak analyzer. And crystal growth equipment. 7. The crystal growth apparatus according to claim 6, wherein the shutter of the K cell is switched when the scattered ion peak intensity reaches a predetermined peak intensity.