WO2014156999A1 - Irradiation control method and irradiation controller - Google Patents

Abstract

An irradiation control method according to one embodiment includes a heating step for irradiating germanium placed on a surface of a substrate with a laser to heat the germanium to a temperature lower than the melding point thereof. The irradiation control method according to one embodiment also includes a control step for controlling so that laser irradiation is repeated. The irradiation control method according to one embodiment, for example, heats the germanium by irradiating the geranium with the laser while heating the substrate to a temperature in the range from room temperature to 500°C.

Description

Irradiation control method and irradiation control apparatus

Various aspects and embodiments of the present invention relate to an irradiation control method and an irradiation control apparatus.

In recent years, optical communication technology that has been used for long-distance communication has recently begun to be used for data communication between servers and communication between a baseband unit and an RF unit of a base station. As the amount of communication increases, power consumption increases in communication using electrical signals, and 80% of the power consumption of the entire data center is used for cooling. Communication technology with low power consumption is required. This is why optical communication technology is used. Another reason for using optical communication technology is that the use of optical communication increases the transmission bandwidth and solves the latency problem.

Furthermore, the configuration of multi-core, many-core and CPU (Central Processing Unit) becomes complicated, and the communication speed with the memory becomes faster. Due to physical limitations of I / O pins and latency problems, inter-chip communication is expected in the near future. However, optical communication technology is expected to be used.

Conventional optical communication devices are based on quartz-based materials, and the bend radius of optical circuits is on the order of mm to cm, and are not suitable for inter-chip communication. However, if the optical circuit is based on Si having a large refractive index, the bending radius can be reduced to the order of μm, so that optical communication between chips becomes possible. Here, a technique for making an optical circuit based on Si is called silicon photonics. Since it is based on Si, the manufacturing process is highly compatible with the CMOS device manufacturing process, and cost reduction by mass production can be expected at the same time.

Here, in the manufacture of CMOS (Complementary Metal Oxide Semiconductor) devices and field effect transistors, heating and recrystallization at a temperature at which germanium, silicon germanium is completely dissolved, There are techniques for forming crystalline germanium or silicon germanium in a trench. There is also a method of reducing the density of threading dislocations by heating germanium on silicon.

JP2011-146684A

However, the above-described technique has a problem that threading dislocations existing in germanium cannot be efficiently reduced.

In one embodiment, the disclosed irradiation control method and the irradiation control apparatus are configured to heat a germanium provided on an arbitrary surface of a substrate with a laser to heat it to an arbitrary temperature lower than the melting point of germanium, and And a control step for controlling the laser irradiation to be repeated.

According to one aspect of the disclosed irradiation control method and irradiation control device, there is an effect that threading dislocations existing in germanium can be efficiently reduced.

FIG. 1 is a diagram illustrating an example of a processing flow according to the first embodiment. FIG. 2 is a diagram illustrating an example of a configuration example of a laser irradiation apparatus that performs laser annealing. FIG. 3 is a diagram illustrating an example of a configuration example of a laser irradiation apparatus that performs laser annealing. FIG. 4 is a diagram illustrating an example of a configuration example of a laser irradiation apparatus that performs laser annealing. FIG. 5 is a diagram illustrating an example of a configuration example of a laser irradiation apparatus that performs laser annealing. FIG. 6 is a graph showing the absorption efficiency when laser annealing is performed on germanium, crystalline silicon, and SiO 2 using lasers of various wavelengths. FIG. 7 is a table showing values when a wavelength of 1070 nm is used, when a wavelength of 970 nm is used, and when a wavelength of 800 nm is used. FIG. 8 is a diagram showing the points where laser annealing is repeatedly performed. FIG. 9 is a diagram showing the results of Examples 1 to 6. FIG. 10 is a diagram showing the results of Examples 1 to 6. FIG. 11A is a diagram illustrating a result of the seventh example. FIG. 11-2 is a diagram illustrating the results of Example 7. FIG. 11C is a diagram illustrating a result of the seventh example. FIG. 11-4 is a diagram illustrating the results of Example 7. FIG. 12A is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. FIG. 12-2 is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. FIG. 13 is a diagram for showing results for Comparative Example 1 and Comparative Example 2. FIG. FIG. 14A is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. FIG. 14-2 is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. 14-3 is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. FIG. FIG. 15A is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. FIG. 15-2 is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. 15-3 is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. FIG. FIG. 16A is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. FIG. 16-2 is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2. FIG. 16C is a diagram for illustrating the results of Comparative Example 1 and Comparative Example 2.

Hereinafter, embodiments of the disclosed irradiation control method and irradiation control apparatus will be described in detail based on the drawings. The invention disclosed by this embodiment is not limited. Each embodiment can be appropriately combined as long as the processing contents do not contradict each other.

(First embodiment)
In one embodiment, the irradiation control method according to the first embodiment is a heating step of heating to an arbitrary temperature lower than the melting point of germanium by irradiating germanium provided on an arbitrary surface of the substrate with a laser. And a control step for controlling the laser irradiation to be repeated.

In the irradiation control method according to the first embodiment, for example, in one embodiment, the heating step heats germanium by irradiating germanium with a laser while heating the substrate to a temperature of room temperature to 500 ° C. To do.

In addition, in the irradiation control method according to the first embodiment, for example, in one embodiment, an arbitrary device or wiring is provided at a location where germanium is not provided on an arbitrary surface of the substrate. Further, in the heating step, a laser is selectively irradiated to a portion where germanium is provided on an arbitrary surface of the substrate.

In the irradiation control method according to the first embodiment, for example, in one embodiment, the wavelength of the laser is 700 nm or more and 1600 nm or less.

In the irradiation control method according to the first embodiment, for example, in one embodiment, the heating step irradiates the laser once for 10 nsec or more and 1 second or less.

In addition, in one embodiment, the irradiation control device according to the first embodiment irradiates a germanium provided on an arbitrary surface of a substrate with a laser to heat it to an arbitrary temperature lower than the melting point of germanium. The laser irradiation apparatus is controlled so that the laser irradiation is repeated.

(Irradiation control method according to the first embodiment)
FIG. 1 is a diagram illustrating an example of a processing flow according to the first embodiment. Of (1) to (4) in FIG. 1, (1) to (3) in FIG. 1 are performed prior to the irradiation control method according to the first embodiment. The irradiation control method according to the first embodiment is executed in (4) of FIG. In the following, the processes of (1) to (3) in FIG. 1 may be performed using a conventionally known method.
Briefly described.

As shown in FIG. 1 (1), a mask layer 20 having a predetermined pattern is provided on the silicon substrate 10. The mask layer 20 is, for example, SiO2. For example, a mask layer having a predetermined pattern is formed by forming a mask layer on the entire surface of the silicon substrate 10 and exposing the silicon substrate 10 by etching a portion where germanium is provided. In other words, the mask layer 20 that exposes a predetermined pattern portion of the surface of the silicon substrate 10 is formed. As a result, as will be described later, a germanium layer 50 containing germanium is provided in a portion of the surface of the silicon substrate 10 where the mask layer 20 is not provided. Hereinafter, the groove or hole formed by the silicon substrate 10 and the mask layer 20 and indicated by the arrow 30 in FIG. 1A is also referred to as “trench” or “hole”.

Then, as shown in FIG. 1B, a buffer layer 40 is formed on the exposed surface of the silicon substrate 10. In other words, the buffer layer 40 is formed at the bottom of the trench. Then, as shown in (3) of FIG. 1, a germanium layer 50 is formed in the trench. For example, the germanium layer 50 is formed in trenches or holes using chemical vapor deposition (CVD) or physical vapor deposition (PVD) techniques. For example, an additive such as tin may be included between the silicon substrate 10 and the germanium layer 50, and an additive such as tin may be added inside the silicon substrate 10. Further, the buffer layer 40 may be omitted.

Then, as shown in (4) of FIG. 1, germanium is heated to an arbitrary temperature lower than the melting point by irradiating laser on germanium provided on an arbitrary surface of the silicon substrate 10. For example, the temperature of the germanium layer 50 is heated by laser annealing until the temperature becomes lower than 938.2 ° C. which is the melting point of germanium.

For example, selective heat treatment of the germanium layer 50 with near infrared laser light is repeated. A more detailed example will be described. When a germanium device is manufactured on a silicon wafer or an SOI wafer, after depositing a germanium thin film, the photon energy is in the range of 0.77 to 1.8 eV (wavelength 700 to 1600 nm). The germanium thin film is irradiated with a laser beam oscillating at a time of 10 ns to 1 second, and the irradiation process is repeated.

In addition, for example, in a technique for producing a silicon / germanium / tin device on a silicon wafer or SOI wafer, after growing a silicon / germanium / tin thin film, the photon energy is larger than the band gap of the silicon / germanium / tin thin film, In addition, the silicon / germanium / tin thin film is irradiated with a laser beam oscillating in a range of 1.8 eV or less (wavelength 700 nm or more) with a small light absorption by silicon in a time range of 10 nsec to 1 sec, and the irradiation process is repeated.

Thus, by performing laser annealing, threading dislocations in germanium move by heating and disappear due to interaction between threading dislocations. Therefore, the threading dislocation density can be reduced. If there are many threading dislocations, for example, the dark current increases, the S / N ratio deteriorates, and the standby power increases. In other words, according to the first embodiment, for example, it is possible to suppress an increase in dark current, improve an S / N ratio, and reduce standby power.

In recent years, silicon photonics that monolithically integrates optical and electronic circuits using a silicon-on-insulator (SOI) wafer in which a silicon thin film is formed on an insulator such as a silicon wafer or a silicon oxide film has been used as an optical component for communication. It is attracting attention from the viewpoint of lowering the price, lowering power, and increasing the information processing speed of LSI. Since silicon is a transparent material that does not absorb light at 1.3 to 1.6 μm in the optical communication wavelength region, it can be used as an optical waveguide material that propagates optical signals on the chip. Germanium is the same group IV semiconductor as silicon. Since it absorbs near-infrared light of 1.3 to 1.6 μm in the optical communication wavelength region, it can be used as a light receiving element material in this wavelength region. A germanium crystal thin film is formed on silicon using an epitaxial growth technique such as a chemical vapor deposition method, and a diode having a pin structure or the like is manufactured, thereby functioning as a near-infrared light receiver on the silicon. A part of the light receiver integrated with the silicon optical waveguide is commercially available. However, in order to receive a weak optical signal, it is necessary to realize a light receiver with a small dark current. Germanium has a larger lattice constant than silicon, and lattice defects occur in the growth process of germanium crystals, which hinders the reduction of dark current in the photoreceiver. In addition, germanium is expected to be used as an optical active device such as an optical modulator or laser light source operating in the optical communication wavelength range, but reducing lattice defects in germanium is a common issue for improving device performance. Yes. Conventionally, defects have been reduced by high-temperature heat treatment using an electric furnace or lamp furnace after crystal growth. However, silicon electronic / optical devices integrated with germanium devices cause malfunctions and performance degradation due to high-temperature heat treatment. Therefore, it is necessary to selectively heat only germanium.

Under such circumstances, according to the first embodiment, it is possible to avoid a high temperature other than germanium and to realize a heat treatment that effectively reduces lattice defects in the germanium crystal layer.

Further, since it is difficult to form a germanium crystal layer having a low threading dislocation density on a silicon wafer or SOI wafer at a low temperature, a high temperature heat treatment after germanium growth is essential. By repeating the process of irradiating the near-infrared laser light for 10 ns to 1 second, germanium can be selectively and repeatedly heat treated, and threading dislocations and crystal defects in germanium can be obtained without causing thermal damage to silicon. Can be reduced. According to the first embodiment, it is possible to manufacture a germanium optical device after the silicon device is formed without deteriorating the silicon device. Therefore, it is possible to clear the problem in industrial application.

Here, when laser annealing is performed, a laser having an arbitrary wavelength may be used as long as it can be heated to an arbitrary temperature lower than the melting point of germanium. For example, a laser with a wavelength of 650 nm to 1650 nm may be used, and a laser with a wavelength of 700 nm to 1600 nm is more preferably used.

When laser annealing is performed, an arbitrary laser source may be used, for example, YB fiber, YVO4 (Yttrium Vanadate), YAG (Yttrium Aluminum Garnet), or the like may be used. In the case of performing laser annealing, for example, the laser is irradiated for 5 ns to 2 seconds per time, and more preferably, the laser is irradiated for 10 ns to 1 second per time. Here, the temperature of germanium can be rapidly increased and decreased by limiting the irradiation time of the laser light to, for example, a range of 10 ns to 1 second. Moreover, it is considered that the movement of threading dislocations is promoted and the reduction of threading dislocation density is promoted by the stress applied to germanium during the temperature rise and fall. As a result, for example, by repeating laser light irradiation limited to a time range of 10 ns to 1 second, heat treatment can be easily repeated, and the threading dislocation density can be effectively reduced.

In addition, any device or wiring is provided in a portion of the arbitrary surface of the silicon substrate 10 where the germanium layer 50 is not provided. Based on this, laser annealing is used to selectively irradiate a portion of the silicon substrate 10 where germanium is provided with a laser. In other words, it is possible to heat the germanium layer 50 without affecting any device or wiring by selectively heating the germanium layer 50 without heating any device or wiring. Further, since the heating of silicon can be suppressed only by the influence of heat conduction from germanium, the influence on other devices can be reduced.

Further, when performing laser annealing, the silicon substrate 10 may be heated together. Specifically, for example, while heating the silicon substrate 10 to a temperature not lower than room temperature (22 ° C.) and not higher than 500 ° C. while heating to a temperature that does not affect any device or wiring mounted on the silicon substrate 10. Alternatively, germanium may be heated by irradiating the germanium layer 50 with a laser. As a result, by heating the silicon substrate 10, the temperature of the germanium layer 50 before laser annealing can be made higher than room temperature, and the time for heating the germanium layer 50 can be shortened. The case where the germanium layer 50 is heated to “900 ° C.” will be described as an example. In this case, when the silicon substrate 10 is not heated, it is heated from room temperature to “900 ° C.”, whereas by heating the silicon substrate 10 to 500 ° C., the germanium layer 50 is also “ It will be heated to about “500 ° C.”, and it should be heated from “500 ° C.” to “900 ° C.”. As a result, the heating time can be shortened, and even when heating is repeated, the time required for heating can be shortened as compared with a method in which the silicon substrate 10 is not heated.

FIG. 2 is a diagram illustrating an example of a configuration example of a laser irradiation apparatus that performs laser annealing. In the example illustrated in FIG. 2, the laser irradiation apparatus 100 includes a laser unit 110 that generates a laser, and an optical system unit 120 that performs laser annealing using the laser generated in the laser unit 110. The laser unit 110 and the optical system unit 120 are connected by a laser transmission fiber 140 that transmits the laser generated by the laser unit 110 to the optical system unit 120. The optical system unit 120 uses a beam forming unit 121 that receives the laser generated by the laser unit 110, a monitor unit 122 that controls the laser output, the number of irradiation pulses, the irradiation position, and the like, and one or more mirrors. The galvano scanner 123 for operating the laser and the Fθ lens 124 serving as a lens for laser operation are provided. In the example shown in FIG. 2, the case where the wafer 210 is provided on the heater stage 200 is shown as an example, but the present invention is not limited to this. For example, a stage having no heater function may be used without using the heater stage 200. Further, the heater stage 200 may be an apparatus different from the laser irradiation apparatus 100, or may be a part of the laser irradiation apparatus 100.

In the laser irradiation apparatus 100 shown in FIG. 2, laser annealing is performed on the wafer 210 by moving the optical system unit 120 or the heater stage 200 on the XY plane. The wafer 210 corresponds to the above-described silicon substrate 10 or the like. The laser unit 110 and the optical system unit 120 may be controlled by software. The laser unit 110 and the optical system unit 120 may be a single unit.

In the laser irradiation apparatus 100 shown in FIG. 2, by irradiating germanium provided on an arbitrary surface of the substrate with laser, the laser irradiation is repeated when heating to an arbitrary temperature lower than the melting point of germanium. The laser irradiation apparatus is controlled. For example, the optical system unit 120 irradiates germanium provided on an arbitrary surface of the wafer 210 with a laser, thereby heating the germanium to an arbitrary temperature lower than the melting point of germanium. At this time, the laser irradiation is repeated. Control. Note that the laser irradiation device and the device that controls laser irradiation by the laser irradiation device may be separate devices.

FIG. 3 is a diagram illustrating an example of a configuration example of a laser irradiation apparatus that performs laser annealing. In the laser irradiation apparatus 100a shown in FIG. 3, unlike the optical system unit 120 of the laser irradiation apparatus 100 shown in FIG. 2, the optical system unit 120a includes an optical path folding unit 125, an exposure pattern creation unit 126, and a reduction optical unit 127. And have. The exposure pattern creation unit 126 is, for example, a DMD (Digital Micromirror Device) or LCOS-SLM (optical phase modulation).

In the optical system unit 120 a shown in FIG. 3, the optical path turning unit 125 receives the laser from the monitor unit 122 and sends it to the exposure pattern creation unit 126. Then, the exposure pattern creation unit 126 forms a laser on the pattern to be irradiated with laser and returns it to the optical path folding unit 125. Then, the optical path folding unit 125 sends the laser from the exposure pattern creation unit 126 to the reduction optical unit 127, and the reduction optical unit 127 irradiates the wafer 210 with the laser formed in a predetermined pattern.

FIG. 4 is a diagram illustrating an example of a configuration example of a laser irradiation apparatus that performs laser annealing. In the example shown in FIG. 4, in the laser irradiation apparatus 100 b, unlike the optical system unit 120 of the laser irradiation apparatus 100 shown in FIG. 2, the optical system unit 120 b includes an optical mask 128 and a reduction optical unit 127.

In the laser irradiation apparatus 100 b shown in FIG. 4, the laser from the monitor unit 122 becomes a laser having a predetermined pattern by the optical mask 128, and the laser formed in the predetermined pattern by the reduction optical unit 127 by the optical mask 128 is applied to the wafer 210. Irradiate.

FIG. 5 is a diagram illustrating an example of a configuration example of a laser irradiation apparatus that performs laser annealing. In the example shown in FIG. 5, the laser irradiation apparatus 100c has a metal mask 129, unlike the optical system unit 120 of the laser irradiation apparatus 100 shown in FIG.

In the laser irradiation apparatus 100 c shown in FIG. 5, the laser from the monitor unit 122 of the optical system unit 120 c is irradiated on the wafer 210 through the metal mask 129, so that the wafer 210 is formed on the metal mask 129. A laser is selectively irradiated to a position corresponding to a predetermined pattern.

FIG. 6 is a diagram showing the absorption efficiency when laser annealing is performed on germanium, crystalline silicon, and SiO 2 using lasers of various wavelengths. The data shown in FIG. 6 was obtained from “Palik, Edward D. Handbook of the Optical Constants of Solids. Academic Press, 1985”. In FIG. 6, “Ge” indicates the result performed on germanium, “c-Si” indicates the result performed on crystalline silicon, and “SiO 2” indicates the result performed on SiO 2. That is, “Ge”, “c-Si”, and “SiO 2” correspond to the germanium layer 50, the silicon substrate 10, and the mask layer 20, respectively, in FIG. FIG. 7 is a table showing values when a wavelength of 1070 nm is used, when a wavelength of 970 nm is used, and when a wavelength of 800 nm is used.

As shown in FIG. 6, when SiO2 uses a wavelength of 500 nm or more and 2000 nm or less, the absorption efficiency when laser annealing is performed shows a value close to “0”. Crystalline silicon exhibits a value close to “0” when a wavelength of about 700 nm to 2000 nm is used. On the other hand, germanium exhibits a higher absorption efficiency than “c-Si” and “SiO 2” by using a wavelength of 1600 nm or less.

That is, silicon absorbs near-infrared light having a wavelength longer than 0.7 um, but germanium absorbs near-infrared light not less than 0.7 nm and not more than 1.6 um well. As a result, by using laser light that oscillates between wavelengths of 0.7 μm and 1.6 μm, it is possible to selectively generate light absorption with germanium. Here, as a result of the energy of the absorbed laser light being changed to thermal energy, germanium can be selectively heated.

As a result, as described above, for example, by using a laser with a wavelength of 650 nm or more and 1650 nm, more preferably, by using a laser with a wavelength of 700 nm or more and 1600 nm or less, without heating the silicon substrate or the mask layer, Germanium can be selectively heated.

Hereinafter, the disclosed irradiation control method will be described in more detail with reference to examples. However, the disclosed irradiation control method is not limited to the following examples.

(Example 1) to (Example 6)
Laser annealing for heating the silicon substrate on which the germanium layer was formed to an arbitrary temperature lower than the melting point of germanium was repeatedly performed under the following conditions. Thereafter, the density of threading dislocations was measured at a portion 200 nm below the surface of germanium.

Laser power
Example 1 to Example 3: 150 W
Examples 4 to 6: 65 W

Laser spot: 1.5mm
Substrate temperature: 400 ° C
Atmosphere: N2 15 Torr

Irradiation time (Pulse Length)
Example 1: 9 ms Example 2 and Example 3: 8 ms Example 4: 45 ms Example 5 and Example 6: 40 ms

Repeat count (Cycle)
Example 1 and Example 2: 5 times Example 3: 50 times Example 4 and Example 5: 5 times Example 6: 50 times

Suppose here that laser annealing is repeated. FIG. 8 is a diagram showing the points where laser annealing is repeatedly performed. In the example shown in FIG. 8, the horizontal axis represents the time axis, and the vertical axis represents the temperature. For convenience of explanation, a line indicating 938 ° C. which is the melting point of germanium is also shown. As shown in FIG. 8, in Examples 1 to 6, by performing laser annealing for heating time, the temperature of germanium is heated to a temperature lower than the melting point of germanium, and then the laser annealing is stopped. Returns to the temperature before laser annealing. In Example 1 to Example 6, the subsequent cooling with heating by laser annealing is repeated. In the example shown in FIG. 8, the case where the temperature of germanium is 400 ° C. as a result of heating the substrate to 400 ° C. is shown as an example, but the present invention is not limited to this.

FIG. 9 is a diagram showing the results of Example 1 to Example 6. In FIG. 9, for the convenience of explanation, among the experimental conditions, the density of threading dislocations is shown in association with the combination of the laser power, the irradiation time, and the number of repetitions. Further, as shown in “As grown” in FIG. 9, the density of threading dislocations before laser annealing is also shown. As shown in FIG. 9, the density of threading dislocations was reduced by repeating laser annealing.

FIG. 10 is a diagram showing the results of Examples 1 to 6. FIG. 10 is a TEM (Transmission Electron Microscope; Transmission Electron Microscope;) photograph in which the cross section of germanium subjected to laser annealing is 38000 times. In FIG. 10, the lines seen in the germanium layer indicate threading dislocations. In the example shown in FIG. 10, for convenience of explanation, as shown in “As grown” in FIG. 10, a photograph before laser annealing is also shown.

As shown in FIG. 10, it was found that the density of threading dislocations was decreased by performing laser annealing as compared with the case where laser annealing was not performed. In particular, germanium provided on a silicon substrate is often used at a portion 150 nm to 200 nm below the upper surface of germanium. Here, as shown in FIG. 10, it was found that the density of threading dislocations decreased particularly near the upper surface of germanium. In addition, as described above, germanium can be selectively heated to reduce the threading dislocation density, and the low threading density can be reduced by increasing the number of repetitions. Can be implemented.

(Example 7)
The density of threading dislocations is measured in a portion under 200 nm before laser annealing for heating the silicon substrate on which the germanium layer is formed to an arbitrary temperature lower than the melting point of germanium. Thereafter, the following conditions are used. Then, laser annealing was repeated, and the density of threading dislocations was measured. Laser annealing was performed until the temperature of germanium reached 850 degrees.

Laser wavelength: 1070 nm
Laser power: 270W
Laser spot: 2mm
Substrate temperature: 25 ° C
Atmosphere: Air exposure time: 40 ms Repeat count: 50 times

11-1 to 11-4 are diagrams showing the results of Example 7. FIG. 11-1 to 11-4 are TEM (transmission electron microscope, Transmission Electron Microscope) photographs obtained by magnifying the germanium section subjected to laser annealing according to Example 7 at 38000 times. Further, in FIGS. 11-1 to 11-4, arrows are shown at positions where threading dislocations exist in a portion 150 nm to 200 nm below the upper surface of germanium. 11-1 and 11-2 show before laser annealing, and FIGS. 11-3 and 11-4 show after laser annealing, respectively. As shown in FIG. 11, by performing laser annealing, the density of threading dislocations was reduced by repeating laser annealing.

(Comparative Example 1) and (Comparative Example 2)
Laser annealing for heating the silicon substrate on which the germanium layer was formed to a temperature equal to or higher than the melting point of germanium was performed under the following conditions. Specifically, germanium was heated to 980 ° C. in Comparative Example 1 by laser annealing, and germanium was heated to 1500 ° C. in Comparative Example 2.

Laser power comparison example 1: 14 W
Comparative Example 2: 23W

Laser spot: 0.35mm
Substrate temperature: 25 ° C
Atmosphere: Air

Irradiation time comparison example 1: 50 ns Comparison example 2: 50 ns

Repeat number comparison example 1: 10 times Comparative example 2: 10 times

Pulse energy comparison example 1: 0.48 mJ
Comparative Example 2: 0.77 mJ

12 to 16 are diagrams for showing the results of Comparative Example 1 and Comparative Example 2. FIG. In FIGS. 12 to 16, for convenience of explanation, the case where laser annealing is not performed is also shown as “As grown”.

FIG. 12-1 shows an overall view of “As grown”, and FIG. 12-2 shows an overall view of Comparative Example 1 and Comparative Example 2. As shown by the arrows, it can be seen that germanium flows out on SiO2. FIG. 13 shows the results of EDX (Energy Dispersive X-ray Spectroscopy) for Comparative Example 1 and Comparative Example 2. In FIG. 13, for convenience of explanation, an SEM photograph is also shown. As shown in “Ge” in FIG. 13, in Comparative Example 1 and Comparative Example 2, germanium dissolved and flowed out onto SiO 2. Further, as shown in the SEM photograph shown in “SEM” of FIG. 13 and “Si” and “Ge”, in Comparative Example 2, the interface between germanium and the silicon substrate was gelled. 14 to 16 are TEMs having a cross section of 9900 times. FIGS. 14-1, 15-1, and 16-1 are for “As grown”, and FIGS. 14-2, 15-2, and 16-2 are for Comparative Example 1, and FIG. 14-3, FIGS. 15-3, and 16-3 are those of Comparative Example 2. FIG. As shown in FIGS. 14 to 16, in Comparative Example 1 and Comparative Example 2, the shape of germanium was changed as a result of the dissolution of germanium as compared with “As grown”.

10 Silicon substrate 20 Mask layer 40 Buffer layer 50 Germanium layer

Claims (6)

1. A heating process of heating to an arbitrary temperature lower than the melting point of germanium by irradiating germanium provided on an arbitrary surface of the substrate with a laser,
   And a control step of controlling the laser irradiation to be repeated.
2. The irradiation control method according to claim 1, wherein the heating step heats the germanium by irradiating the germanium with the laser while heating the substrate to a temperature of room temperature to 500 ° C.
3. Of the arbitrary surface of the substrate, an arbitrary device or wiring is provided in a location where the germanium is not provided,
   2. The irradiation control method according to claim 1, wherein, in the heating step, a laser is selectively irradiated to a portion where the germanium is provided in an arbitrary surface of the substrate.
4. The irradiation control method according to claim 1, wherein the wavelength of the laser is 700 nm or more and 1600 nm or less.
5. 2. The irradiation control method according to claim 1, wherein the heating step irradiates the laser once for 10 ns to 1 second.
6. A control unit that controls the laser irradiation device so that the laser irradiation is repeated when heating to an arbitrary temperature lower than the melting point of germanium by irradiating germanium provided on an arbitrary surface of the substrate with a laser. An irradiation control device comprising:

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