JPH04256832A - Apparatus and method for analizing crystal growing step and evaluating apparatus thereof - Google Patents

Abstract

PURPOSE:To obtain the data of the atomic layer of the outermost surface of a growing crystal by attaching an electron energy analyzer which can detect photoelectrons of the surface of solid at a specified angle so that a specified vacuum degree is maintained. CONSTITUTION:Emitted light 1 whose energy can be varied is introduced into a crystal growing device and cast on the surface of a solid sample 2 whose crystal is growing. A molecular beam is applied on the surface of the sample 2 from a crystal growing vapor deposition source 5, and the crystal growing in the order of an atomic layer is performed. Photoelectrons 6 discharged from the surface of the sample 2 are detected with an electron energy analyzer 8 having the angle decomposing function at an angle which is close to the surface. The detected spectral light is accumulated in a data memory device 11 through a photoelectron-measurement control device 10. After the end of the measurement, the spectra are overlapped and displayed on a CRT display 12. At this timer an orifice and a differential exhausting system are provided in order to maintain the difference in vacuum degrees in the analyzing chamber and the analyzer 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analysis device, an analysis method, and an evaluation device for the crystal growth process, which directly observes the semiconductor crystal growth process and enables higher quality crystal growth.

0002

[Prior Art] Conventionally, methods for evaluating the crystal growth process include: (1) extracting the grown crystal, performing X-ray diffraction, photoluminescence, SIMS analysis, etc., and inferring the growth process from the crystal growth results; MBE (Molecular Beam Epitaxy), a method in which the growth chamber and analysis chamber are combined in an ultra-high vacuum, and the surface after crystal growth is analyzed in the ultra-high vacuum using Auger electron spectroscopy or X-ray photoelectron spectroscopy, for example. RHEED (reflection high-speed electron diffraction), which irradiates a crystal growth surface in an ultra-high vacuum with a high-speed electron beam and detects the diffracted electron beam from the surface, and the Auger electrons and fluorescence emitted from the surface at that time. There was a way to detect X-rays. Of these, ■
In case 2, the surface is exposed to the atmosphere, so it is not possible to infer what happens during the growth process. Alternatively, atomic species may be desorbed, making it impossible to observe the growth process. Regarding this, as reported by Watanabe et al. at the 1990 Spring Applied Physics Conference 29a-T-2/I, the surface on which TMG (trimethyl gallium) was adsorbed on the GaAs surface using the gas source MBE method was There is an example in which most of the material comes off during transport. In addition, in the case of method (2), it is certainly possible to observe the growth process, but since it uses the diffraction phenomenon caused by electron beams, information about the crystal structure can be obtained, but information about the bonding state cannot be obtained. No information is available. Although information on the surface composition can be obtained by detecting Auger electrons or fluorescent X-rays from the crystal surface, it is difficult to obtain information on the bonding state, and there is also a risk that adsorbed molecules may be dissociated by the electron beam.

On the other hand, Horikoshi et al. (Applied Physics: Volume 59 (199
0 years) p. 27) has recently reported that the growth surface is G
Although it has been demonstrated that it can be used to distinguish between a-plane and As-plane and monitor atomic layer growth, direct observation of molecular species at the crystal growth surface does not reveal the growth process or surface reaction process. information cannot be obtained.

0004

[Problems to be Solved by the Invention] As described above, with the conventional techniques, it is not possible to observe or make analogies during the crystal growth process, or even if the state during crystal growth can be observed and information on the crystal structure can be obtained, It was not possible to obtain information on the binding status.

The purpose of the present invention is to obtain information on the outermost atomic layer of a growing crystal at high speed, to determine the bonding state and composition ratio of gas species during the crystal growth process, and to This enables photoelectron spectroscopy measurements.

[0006]

[Means for Solving the Problems] The above object is equipped with a device for heating a solid surface with heat or light, a vapor deposition source for crystal growth, and a synchrotron radiation irradiation device with energy appropriately selected depending on the element to be measured. In the crystal growth process analyzer in which the degree of vacuum of the synchrotron radiation beam line, the analysis chamber, and the crystal chamber are maintained at predetermined values, an electron energy analyzer capable of detecting photoelectrons at a specific angle on the solid surface is installed at a predetermined value. An orifice and a differential pump are installed to maintain the degree of vacuum between the synchrotron radiation irradiation device and the analysis chamber, and a vacuum between the analysis chamber and the electron energy analyzer. This is achieved by providing an orifice and a differential pump to maintain the degree difference.

[0007]

[Operation] In the crystal growth process analyzer of the present invention, in order to irradiate the solid surface undergoing crystal growth with synchrotron radiation, the synchrotron radiation beam line, the analysis chamber, the crystal growth chamber, and the electron energy analysis chamber are each operated at the required degree of vacuum. to avoid interfering with the ultra-high vacuum required by the synchrotron radiation beam line. In addition, in the crystal growth process evaluation apparatus, an orifice and a differential pumping device are used to maintain the above-mentioned degree of vacuum. After that, the surface of the solid sample is irradiated with synchrotron radiation of appropriate energy so that the kinetic energy of the photoelectrons becomes 10 eV, the escape depth of the photoelectrons is set to about 5 Å, and the angle at which the photoelectrons are extracted from the surface of the solid sample is made shallow. , and by extracting in a specific crystal direction, information on only the outermost atomic layer can be obtained. Furthermore, in order to measure the crystal growth process at high speed in real time, a two-dimensional detector is installed in the detection section of the angle-resolved photoelectron energy analyzer, and the photoelectron spectrum is repeatedly measured without performing an energy sweep.

[0008]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a crystal growth process analyzer according to the present invention, in which (a) is a side view of the main part viewed from a direction perpendicular to the synchrotron radiation incident axis, and (b) is a view from the synchrotron radiation incident direction. Figure 2 shows a method for detecting photoelectrons from the outermost surface of a crystal. (a) shows the kinetic energy dependence of the photoelectron escape depth in a solid, and (b) shows near-surface information. (c) is a diagram showing the relationship between the optimal synchrotron radiation incident angle and photoelectron extraction angle for the atomic arrangement on the outermost surface of the crystal, and FIG. 3 is the As3d photoelectron spectrum of the GaAs surface realized by the present invention. FIG. 4 is a diagram showing an embodiment of the crystal growth process evaluation apparatus of the present invention, and FIG. 5 is a measurement diagram of the Ga3d photoelectron spectrum of the GaAs surface realized by the present invention.

In the crystal growth process analyzer of the present invention, synchrotron radiation 1 whose energy can be varied is introduced into the crystal growth apparatus,
Although the surface of the solid sample 2 undergoing crystal growth is irradiated, the beam line of the synchrotron radiation 1 needs to be maintained at an ultra-high vacuum, so each of the crystal growth apparatuses must be maintained at a required degree of vacuum. The solid sample 2 is thermally or optically heated by a heating device 3 and irradiated with atomic beams or molecular beams from a crystal growth vapor deposition source 5, thereby performing crystal growth on the order of atomic layers. Photoelectrons excited by the synchrotron radiation 1 are emitted from the surface of the solid sample 2;
Usually, many photoelectrons are emitted in a direction perpendicular to the direction of the radiation 1. Therefore, an electron energy analyzer with an angular resolution function is installed in the mounting port 4 so that only the photoelectrons emitted at a grazing angle from the surface of the solid sample can be detected from a direction perpendicular to the incident direction of the synchrotron radiation 1. . The angular resolution in this case does not need to be the extraction angular resolution of 2 degrees or less, which is used for band structure analysis, and even around 10 degrees is sufficiently applicable for the purpose of this analysis. The detection sensitivity can be increased by widening the slit 7. However, although it is not suitable for an angle-integrating type analyzer such as a cylindrical mirror analyzer (CMA), it can be applied to the above-mentioned analysis method if a slit having an angle-resolving function is used. In this example, a hemispherical electron energy analyzer 8 is used, and a two-dimensional detector 9 such as a channel plate is used as the detection part, and a predetermined core level, for example, from a GaAs surface is detected without energy sweeping. It is possible to measure the Ga3d photoelectron spectrum in a few 100 ms by measuring a region approximately 10 eV wide. The above spectrum is transferred to the data storage device 11 via the photoelectronic measurement control device 10 and stored therein. After the measurement is completed, these spectra are superimposed to elucidate the reaction state on the crystal growth surface with a time resolution of several 100 ms. In order to increase the speed of this configuration, it is necessary to shorten the time required for data transfer and storage, and to shorten the measurement time.The latter requires increasing the brightness of the synchrotron radiation beam 1 and increasing the electron energy. The key is to increase the sensitivity of the analyzer 8.

FIG. 2 shows a method of obtaining information only from the outermost layer of the crystal growth surface in the present invention. In other words, electrons moving in a solid lose kinetic energy by interacting with solid atoms (electrons inside). In general, the higher the kinetic energy, the more difficult it is to interact. That is,
Since the inelastic scattering cross section becomes smaller, photoelectrons generated inside the solid also reach the surface and are detected. On the other hand, when the kinetic energy becomes 40 eV or less, the interaction decreases, and photoelectrons from the inside still reach the surface. Therefore, as shown in FIG. 2(a), there is a region where the interaction is maximum around several tens of eV (approximately 60 eV) and the escape depth of photoelectrons is minimal at 4 to 5 Å. Utilizing this property, in the case of Ga3d core level in GaAs, the binding energy is about 19 eV, so
About 8 to make the kinetic energy of photoelectrons about 60 eV
If the surface of a solid sample is irradiated with monochromatic synchrotron radiation having an energy of 0 eV, information about about 5 Å on the GaAs surface can be obtained. However, since this is the depth at which the signal intensity is 1/e, it is only average information from the surface to several atomic layers, and there is too much noise to elucidate the reaction process at the crystal growth surface. Therefore, by setting the photoelectron extraction angle to 10 degrees or less as shown in FIG. 2(b), the detection depth can be made to be sin 10 degrees or less. Note that when surface-sensitive measurements are performed as described above, the signal/noise ratio of the signal also depends on the atomic arrangement on the outermost surface. Therefore, as shown in FIG. 2(c), for example, GaAs(100)
Considering crystal growth on the surface, the angle-resolved photoelectron energy analyzer is installed in the direction in which the atoms on the outermost surface are connected, that is, the <110> direction, and the synchrotron radiation is incident in the <1￣10> direction. This enables measurements that are sensitive to crystal surfaces.

FIG. 3 shows GaA measured using this analyzer.
As3d (bonding energy =
41 eV) is shown. In this example, one atomic layer, that is, one Ga layer and one As layer, was grown in 2 seconds, and one spectrum was measured every 0.2 seconds. When we started the experiment from the As-terminated GaAs surface, very little Ga3d was seen at first, and G
As in the aAs state only appeared with a binding energy of about 41 eV, its intensity decreased as Ga was deposited on its surface, and As3d disappeared in about 1 second, indicating the end of the Ga layer growth. It was judged. Therefore, when the shutter of the Ga source is then closed and the vapor deposition source of As4 is opened, the signal strength of As3d gradually recovers. However, among the As3d peaks, a shoulder peak in the As elemental state (approximately 0.6 eV high binding energy side) is also clearly detected, indicating that direct observation of the reaction process is possible. It can be seen that when As vapor deposition is continued after the growth of one atomic layer is completed in about 2 seconds, the shoulder peak of the elemental As state increases. The results of this example are: ■ incorrect energy selection of synchrotron radiation or use of a normal X-ray source, ■ not using an angle-resolved electron energy analyzer, ■ setting a deep photoelectron extraction angle, and ■ setting the crystal orientation. Even if there is a mistake, etc., it cannot be obtained.

FIG. 4 is a diagram showing an embodiment of the crystal growth process evaluation apparatus of the present invention, and particularly shows an exhaust system to enable observation during crystal growth. In order to irradiate the surface of the growing sample with synchrotron radiation while coexisting the vacuum level of 10￣9 Torr or less in the synchrotron radiation beam line and the vacuum level of, for example, 10￣5 Torr during crystal growth, the following steps are required: It is necessary to install an orifice and a differential pumping system. Here, an example will be described in which GaAs crystal growth is performed using TMG (trimethyl gallium) gas by the gas source MBE method. The vacuum level 22 of the crystal growth chamber is 10￣5To
Since it is an RR unit, a two-stage differential exhaust system is constructed as shown in Figure 4. That is, the vacuum degree 20 of the synchrotron radiation beam line is 10￣9 Torr (P1), the vacuum degree 21 of the analysis chamber is 10￣7 Torr (P2), and the difference between the two vacuum degrees is determined by the orifice 14 (conductance; C1) and differential pumping. Maintain system 13 (effective pumping speed; S1). In addition, the difference between the vacuum degree 21 of the analysis chamber, 10￣7 Torr, and the vacuum degree 22, 10￣5 Torr (P3) of the crystal growth chamber, is determined between the orifice 16 (conductance; C2) and the differential pumping system 15 (effective pumping speed; S2). ). Vacuum degree of crystal growth chamber 2
2 to 10￣5 Torr, consider the vapor deposition source 5 for crystal growth, and in this case, an exhaust system (S3) that is suitable for the gas flow rate (Q) introduced into the crystal growth chamber from a gas source such as TMG. is necessary. On the other hand, the degree of vacuum (P4) of the electron energy analyzer 8 connected to the analysis room is 1.
In order to maintain the level at 0￣9 Torr, the orifice 19 (conductance; C3) and the differential pumping system 18 (effective pumping speed;
S4) is provided. There is a relationship between these as shown below. That is, it is expressed by the following four equations: S1×P1=C1×(P2-P1) S2×P2=C2×(P3-P2) S3×P3=Q S4×P4=C3×(P2-P4). If the orifice conductances C1, C2, C3, the effective pumping speeds S1, S2, S3, S4 of the vacuum pump, and the gas flow rate Q are optimized and determined according to this formula, the vacuum degree 20 of the beam line will be 10￣
It becomes possible to observe the crystal growth process at 10-5 Torr while maintaining 9 Torr, and contamination of the electron energy analyzer 8 by the growth gas is also reduced.

Next, an example in which the surface state during crystal growth was observed according to the present invention will be shown. Synchrotron radiation 1 whose energy can be varied is introduced into a crystal growth apparatus and irradiated onto the surface of a solid sample 2 during crystal growth. A vapor deposition source 5 for crystal growth is placed on the surface of the solid sample 2.
irradiates with molecular beams to grow crystals on the order of atomic layers. Photoelectrons 6 emitted from the surface of the solid sample 2 irradiated with synchrotron radiation are detected at an angle just below the surface by an electron energy analyzer 8 having an angular resolution function. In this example, a hemispherical electron energy analyzer is used, and the detection section includes a two-dimensional detector 9 such as a channel plate.
to obtain the Ga3d photoelectron spectrum from a given core level, e.g., a GaAs surface, without energy sweeping.
It is possible to measure in several 100 ms by measuring an area with a width of about 10 eV. This spectrum is transferred to the data storage device 11 via the photoelectronic measurement control device 10 and stored therein. After the measurement is completed, the above spectra are superimposed and displayed on a CRT.
By displaying the information on the display 12, it is possible to elucidate the state of the reaction on the crystal growth surface with a time resolution of several hundred milliseconds. In order to increase the speed of this system, two things are necessary: shortening the time required for data transfer and storage, and shortening measurement time.The latter requires increasing the brightness of the synchrotron radiation beam and analyzing electron energy. The key is to increase the sensitivity of the instrument. In the present invention, in order to obtain information only from the outermost layer of the crystal growth surface, the kinetic energy of photoelectrons must be set to approximately 60 eV.
In order to achieve this, at the Ga3d core level, the solid surface is irradiated with synchrotron monochromatic light with an energy of about 80 eV, and the detection depth is made less than sin 10 degrees by making the photoelectron extraction angle less than 10 degrees. ■The direction in which the atoms on the outermost surface are connected, that is, GaAs (10
0), it is important to install the angle-resolved photoelectron energy analyzer in the <110> direction, for example.

FIG. 5 shows the photoelectron spectra of Ga3d (binding energy=19 eV) from the surface of a solid sample during the GaAs crystal growth process measured using this evaluation apparatus. In this experiment, one atomic layer was formed in 2 seconds, that is, a Ga layer and an A layer.
The s-layer was grown one layer at a time, and one spectrum was measured every 0.2 seconds. When the experiment started from the As-terminated GaAs surface, almost no Ga3d was observed at first, indicating that the analysis of the first layer on the surface was achieved. As TMG is attached to the surface, Ga3
The photoelectron intensity of d increases, but at the early stage of growth
TMG deposited on s atoms immediately decomposes and becomes Ga.
While Ga is in an As-bonded state, as it grows to about 0.5 atomic layer, Ga becomes in a TMG state.
Shoulder peaks at 3d spectral positions start to become noticeable. The ratio of GaAs and TMG states depends on the substrate temperature during growth. It can be seen that as the deposition progresses further and becomes one atomic layer or more, the TMG state becomes predominant, and TMG deposited on Ga is difficult to decompose. As mentioned above, by combining the differential pumping system of the present invention, high-speed measurement system, synchrotron radiation energy, electron energy analyzer, and optimal setting of crystal orientation, which enable analysis of the extreme surface, It is possible to evaluate the surface condition during growth in real time.

[0015]

Effects of the Invention As described above, the crystal growth process analyzer according to the present invention includes a device that heats a solid surface with heat or light, a vapor deposition source for crystal growth, and a synchrotron radiation beam whose energy is appropriately selected depending on the element to be measured. irradiation device, and maintains the degree of vacuum of the synchrotron radiation beam line, the analysis chamber, and the crystallization chamber at predetermined values. By installing the energy analyzer to maintain a predetermined degree of vacuum, it is possible to obtain information on only the outermost atomic layer on the solid surface during crystal growth in real time and at high speed, and to analyze the crystal growth process. By determining the bonding state and composition ratio of gas species in the process, it is possible to discover the mechanism of crystal growth and the key points for realizing high-quality film formation. Furthermore, in order to maintain the vacuum difference between the synchrotron radiation irradiation device, the analysis chamber, and the electron energy analyzer, the crystal growth process evaluation device equipped with an orifice and differential pumping device uses a low vacuum of 10￣5 Torr. Photoelectron spectroscopy can be used to measure the surface bonding state even in the growth atmosphere, making it possible to discover key points for achieving high-quality crystal growth.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a crystal growth process analyzer according to the present invention, in which (a) is a side view of the main part viewed from a direction perpendicular to the synchrotron radiation incident axis, and (b) is a synchrotron radiation incident direction. This is a diagram seen from.

[Fig. 2] Diagrams showing a method for detecting photoelectrons from the outermost surface of a crystal. (a) is a diagram showing the kinetic energy dependence of the photoelectron escape depth in a solid, and (b) is a diagram showing a method for obtaining near-surface information. Photoelectron extraction explanatory diagram (c) is a diagram showing the relationship between the optimal synchrotron radiation incident angle and the photoelectron extraction angle with respect to the atomic arrangement on the outermost surface of the crystal.

FIG. 3 is an As3d photoelectron spectrum measurement diagram of a GaAs surface realized by the present invention.

FIG. 4 is a diagram showing an embodiment of the crystal growth process evaluation device of the present invention.

[Figure 5] Ga on the GaAs surface realized by the above example
It is a 3D photoelectron spectrum measurement diagram.

[Explanation of symbols]

1 Synchrotron radiation 2 Solid sample 3 Heating device 5 Vapor deposition source for crystal growth 6 Photoelectron 8 Electron energy analyzer 9 Two-dimensional detectors 13, 15, 18 Differential pumping device 14, 16, 1
9 Orifice 20 Beamline vacuum level 21 Analysis chamber vacuum level 22 Crystallization chamber vacuum level

Claims (5)

[Claims] Claim 1: A system comprising: a device for heating a solid surface with heat or light; a vapor deposition source for crystal growth; and a synchrotron radiation irradiation device with energy appropriately selected depending on the element to be measured; In a crystal growth process analyzer that maintains the degree of vacuum in the analysis chamber and the crystallization chamber at a predetermined value, an electron energy analyzer capable of detecting photoelectrons at a specific angle on the solid surface is installed to maintain the predetermined degree of vacuum. A crystal growth process analyzer characterized by: 2. A system comprising: a device for heating a solid surface with heat or light; a vapor deposition source for crystal growth; and a synchrotron radiation irradiation device with energy appropriately selected depending on the element to be measured; In a crystal growth process analysis method in which the degree of vacuum in the analysis chamber and the crystallization chamber are maintained at predetermined values, synchrotron radiation set so that the kinetic energy of photoelectrons emitted from the element to be measured is several tens of eV is used to analyze the crystal growth process. The photoelectrons are irradiated onto the solid surface inside the solid surface, so that the photoelectron escape depth from the solid surface is about 2 atomic layers, and the emitted photoelectrons are extracted at an extremely shallow angle, and the surface atomic density is maximized with respect to the orientation of the crystal plane. Crystal growth is characterized by attaching an electron energy analyzer with angular resolution performance to maintain a predetermined degree of vacuum, collecting information only from the outermost surface layer, and analyzing the surface state of growth on the order of atomic layers. Process analysis method. 3. The electron energy analyzer is equipped with a two-dimensional detector, measures a photoelectron spectrum without sweeping the energy of the energy analyzer, and transfers and stores the measurement data in a high-speed storage device. 3. The crystal growth process analysis method according to claim 2, wherein the reaction process on the crystal growth surface is analyzed at high speed. 4. A device for heating a solid surface with heat or light, a vapor deposition source for crystal growth, a synchrotron radiation irradiation device with energy appropriately selected depending on the element to be measured, and photoelectron detection at a specific angle on the solid surface. In a crystal growth process evaluation device having an analysis chamber and equipped with an electron energy analyzer having a function, an orifice and a differential pumping device for maintaining a degree of vacuum difference between the synchrotron radiation irradiation device and the analysis chamber; and a crystal growth process evaluation apparatus, comprising an orifice and a differential pumping device for maintaining a difference in degree of vacuum between the analysis chamber and the electron energy analyzer. 5. The electron energy analyzer is equipped with a two-dimensional detector, measures a photoelectron spectrum without sweeping the energy of the energy analyzer, and transfers and stores the measurement data in a high-speed storage device. 5. The crystal growth process evaluation apparatus according to claim 4, wherein a reaction process on a crystal growth surface is analyzed at high speed.