JPH0786161A - Selective growing method for semiconductor - Google Patents

Abstract

PURPOSE:To grow a crystal selectively in a region not irradiated with laser light by irradiating an arbitrary region on a semiconductor substrate under growth with laser light and raising the substrate temperature at that region to a level for desorbing the group III element of semiconductor to be grown CONSTITUTION:A GaAs substrate 21 subjected to normal pretreatment is heated, at first, to a growing temperature. The GaAs substrate 21 is then irradiated, on the surface thereof, with Ar laser light through a pattern set by a pattern generator. The surface of the GaAs substrate 21 is separated into parts 22, 23 irradiated and not irradiated, respectively, with laser light according to a desired pattern. Laser output is regulated under that state to set the part 22 at a temperature for desorbing a group 11 element and the part 23 at a growing temperature. When growth is started under that state, GaAs is not grown in the part irradiated with laser light because the group III element impinging on the Gaps substrate 21 are evaporated again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor crystal growth method, and more particularly to a semiconductor crystal growth method capable of maskless selective growth and buried growth.

[0002]

2. Description of the Related Art In crystal growth of a III-V group compound semiconductor represented by GaAs or the like, a normal epitaxial film grows on the GaAs surface by the molecular beam epitaxy (MBE) method using a solid source. It was said that the polycrystal grew on the oxide film such as _2nd grade and selective growth could not be performed. However, in recent years, the substrate temperature during growth is increased by using a SiO ₂ mask, and selectivity is realized by the difference in the Ga attachment coefficient and migration distance between the GaAs surface and the SiO ₂ surface (Applied Physics).
Letter (Appl. Phys. Lett.) 51 (19), 9 198
7 P1512-1514).

As described above, the conventional selective growth technique is GaA.
An oxide film such as SiO ₂ is deposited on the s substrate, and the oxide film is selectively removed by photolithography using a resist, and the remaining oxide film is used as a mask for selective growth. In the method using these masks, the number of processes is large before growth, and damage to the substrate in each process (such as thermal stress at the time of SiO ₂ deposition) and surface contamination of the substrate cannot be avoided.

After the selective growth, the next process cannot be performed unless the mask is removed from the growth apparatus once. Therefore, it is impossible to perform the buried growth of the selective growth layer or the continuous growth in the same growth process such as the continuous hetero growth after the selective growth.

[0005]

When selective growth is carried out using a molecular beam epitaxy apparatus using a solid source, it is necessary to form a mask of an oxide film on the substrate. Therefore, surface contamination due to foreign matter contact, And physical damage such as heat distortion occurs. Further, since the mask removal process is required after the selective growth, continuous growth cannot be performed after the selective growth.

[0006]

Laser light is irradiated to an arbitrary place on a growing semiconductor substrate, and the substrate temperature of that portion is raised to a temperature at which a growing group III element of the semiconductor is desorbed, so that laser light is emitted. Does not grow at the place irradiated with, but selectively grows at other places.

[0007]

The laser light for irradiating the substrate surface is pulsed, and the laser irradiation time is shorter than the time at which the temperature of the boundary surface between the laser-irradiated portion and the non-irradiated portion becomes a temperature at which the semiconductor does not grow due to heat conduction. This suppresses heat conduction from the laser-irradiated portion to the non-irradiated portion and suppresses the temperature of the interface below the temperature at which the semiconductor does not grow, thereby making it possible to grow a selective growth layer without sagging on the interface without masking. .

[0008]

【Example】

(Embodiment 1) An embodiment of the present invention will be described with reference to FIGS. The configuration of the device is as follows. A liquid nitrogen shroud 2 is provided in the growth chamber 1, several molecular beam sources 3 are provided below, and a substrate heating mechanism 4 is provided above, and the inside is maintained in an ultrahigh vacuum. The semiconductor substrate 5 is installed below the substrate heating mechanism 4 with the growth surface facing down. A viewing port 6 is provided just below the substrate 5. An Ar laser is used as the laser light source 7, and the laser light generated by the Ar laser is applied to the surface of the substrate 5 from the viewing port 6 via the pattern generator 8. Further, below the growth chamber 1 is a pyrometer 9 for measuring the temperature of the substrate 5.

Next, the procedure of selective growth will be described with reference to FIG. First, the GaAs substrate 21 that has been subjected to normal pretreatment is set in the substrate heating mechanism 4, and the growth temperature (for example, GaAs) is set.
In the case of, the temperature is raised to about 540 ° C. Next, Ar laser light is introduced into the pattern generator 8, where the laser light is set to an arbitrary pattern and is irradiated onto the surface of the GaAs substrate 21 via the reflection mirror 10 and the viewing port 6. At this time, the surface of the GaAs substrate 21 is separated into a portion 22 where the laser light is applied and a portion 23 where the laser light is not applied according to a desired pattern. In this state, the laser output is adjusted while observing the value of the pyrometer 9 to partially raise the substrate temperature. At this time, the temperature of the GaAs substrate 21 is the growth temperature (for example, GaAs
Temperature is set to about 540 ° C.), and the place 22 exposed to the laser light is at a temperature (eg, GaA) at which the group III element is desorbed.
725 ° C. in the case of s). When the growth is started in this state, the GaAs substrate 2 is placed in the place where the laser beam is applied.
Since the group III element (Ga element here) incident on 1 is re-evaporated, GaAs does not grow, but GaAs2 does not grow in the place where the laser beam is not irradiated because it does not change from the growth temperature.
4 grows epitaxially. By the above method, maskless selective growth can be realized.

(Embodiment 2) When a fine pattern is formed by laser light irradiation, heat conduction is not a little at the interface between the high temperature portion and the low temperature portion, which causes a problem. An embodiment for solving this will be described with reference to FIG. From the thermal conductivity and specific heat of the GaAs substrate, the time required for the interface temperature to reach 600 ° C when the temperature of a part of the substrate is 800 ° C is calculated to be about 50n.
It becomes sec.

In this embodiment, the temperature of the boundary surface is separated by irradiating the laser beam in pulses. The laser for irradiating the substrate surface is a pulse having an irradiation time of 50 nsec and an off time of 100 nsec as shown in the figure. Here, the off time is set to 100 nsec, but it can be extended to the longest, that is, the time for the selectively grown semiconductor to grow to ½ monolayer. With this method, the laser can be turned off before the temperature of the boundary surface becomes the same as that of the laser irradiation portion after the laser light irradiation, and the temperature of the boundary surface can be naturally cooled during the laser off time. For this reason, the temperature of the boundary surface does not always rise to a temperature at which the growth rate becomes zero, and since the time for growing one atomic layer of GaAs is about 1 second, GaAs grows during the laser light off time. Instead, selective growth without boundary on the boundary surface is possible.

(Embodiment 3) FIG. 4 shows an embodiment in which selective growth and buried growth utilizing the present invention are continuously grown. First, set the GaAs substrate 41 before growth to the substrate heating mechanism 4,
After thermal cleaning, the InAs growth temperature (400 ° C.) is set. Next, the surface of the GaAs substrate 41 is irradiated with patterned laser light. The laser output is adjusted so that the laser irradiation surface 42 has a temperature (600 ° C.) at which InAs is re-evaporated. Next, the laser is pulsed, and the InAs layer 43 is grown to about 500 Å while being irradiated. At this time, the interface between the laser irradiation part and the non-irradiation part does not rise above 600 ° C. because the cooling time is provided by pulse irradiation. Therefore, In
As does not grow, and selective growth can be performed without a peripheral sag in the shape shown in the figure. Here, the size of the selective growth layer can be miniaturized by narrowing the interval between the laser irradiation portions. Next, the laser irradiation is stopped and the GaAs layer 44 is grown with the substrate temperature set to the GaAs growth temperature (500 ° C.).
The s selective growth layer 43 is embedded. By the above procedure, continuous growth can be performed in the same process from maskless selective growth to buried growth.

(Embodiment 4) FIG. 5 shows a ternary mixed crystal (here, A
An example is shown in which a binary mixed crystal (here, GaAs) is embedded and grown in (1GaAs). First, A on the GaAs substrate 51
The lGaAs buffer layer 52 is normally grown. Next, the growth surface is irradiated with laser light at an arbitrary position to adjust the surface temperature to Ga.
The temperature is set to a temperature (725 ° C.) at which As does not grow. The GaAs layer 53 is selectively grown while irradiating the laser beam as it is. Then, the laser light is turned off, and the AlGaAs buried layer 54 is normally grown. Through the above steps, the selective growth layer of the binary mixed crystal embedded in the ternary mixed crystal can be formed without a mask.

(Embodiment 5) FIG. 6 shows an embodiment in which electrons are confined in the selective growth layer. First, the GaAs substrate 61
An undoped GaAs buffer layer 62 is grown on it. Next, a laser beam is irradiated to an arbitrary place on the growth surface to set the surface temperature to a temperature (725 ° C.) at which GaAs does not grow.
In that state, while irradiating laser light, Si-doped GaAs
Layer 63 is selectively grown. Then, the laser light is turned off, and the undoped GaAs buried layer 64 is normally grown. Through the above steps, Si-doped GaAs can be embedded in undoped GaAs. Here, since Si is an n-type impurity with respect to GaAs, electrons are confined in the selective growth layer. Further, holes can be confined by doping a p-type impurity such as Be instead of Si.

(Embodiment 6) FIG. 7 shows an embodiment in which a different type of doped semiconductor is embedded. First, G
Undoped GaAs buffer layer 72 on aAs substrate 71
To grow. Next, laser light is irradiated to an arbitrary place on the growth surface to adjust the surface temperature to a temperature at which InAs does not grow (600
℃). While irradiating laser light in that state, B
The e-doped InAs layer 73 is selectively grown. Then, the laser light is turned off, and the undoped GaAs buried layer 74 is normally grown.
Through the above steps, Be-doped InAs can be embedded in undoped GaAs. Where Be is InA
Since it becomes a p-type impurity with respect to s, holes are trapped in the selective growth layer. Also, S instead of Be
Electrons can also be confined by doping an n-type impurity such as i.

(Embodiment 7) FIG. 8 shows an embodiment in which the selective growth layer has a superlattice structure. First, the GaAs substrate 81
A GaAs buffer layer 82 is grown on top. Next, the surface temperature is set to GaAs by irradiating laser light on any place on the growth surface.
Is set to a temperature (725 ° C.) at which no growth occurs. In this state, the GaAs layer 84 is selectively grown while irradiating laser light. Subsequently, the InAs thin film 85 and the GaAs layer 84 are sequentially grown. Since the temperature at which InAs does not grow is lower than that of GaAs, GaA can be adjusted without adjusting the laser output.
If the temperature is set so that s does not grow, continuous growth is possible. After that, the laser light is turned off, and the GaAs layer 85 is grown over the entire surface by normal growth, whereby the superlattice structure 83 is formed.
Can be embedded and grown.

[0017]

According to the present invention, the mask used for selective growth becomes unnecessary. This eliminates the need for mask formation and removal processes, significantly shortens the formation time of the selective growth layer, prevents damage and contamination of the substrate, and allows growth on the clean surface of the substrate. Can be reduced. In addition, by irradiating the laser beam in a pulsed manner, the boundary between the high temperature portion and the low temperature portion can be clearly distinguished, and selective growth of a minute area becomes possible.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a molecular beam epitaxy apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a procedure of maskless selective growth.

FIG. 3 is an explanatory view showing a measure for preventing a temperature rise of a boundary surface by laser pulse irradiation.

FIG. 4 is an explanatory diagram showing a buried growth procedure in the same process.

FIG. 5 is an explanatory view showing an example in which a binary mixed crystal is embedded in a ternary mixed crystal.

FIG. 6 is an explanatory view showing an embodiment in which a Si-GaAs layer is embedded in a GaAs growth layer.

FIG. 7 is an explanatory view showing an embodiment in which a Be—InAs layer is embedded in a GaAs growth layer.

FIG. 8 is an explanatory diagram showing a procedure of confining a superlattice structure by buried growth.

[Explanation of symbols]

1 ... Growth chamber, 2 ... Liquid nitrogen shroud, 3 ... Molecular beam source, 4 ... Substrate heating mechanism, 5 ... Semiconductor substrate, 6 ... Viewing port, 7 ... Laser light source, 8 ... Pattern generator, 9 ... Pyrometer, 10 ... Reflection mirror, 21 ... G
aAs substrate, 22 ... Laser irradiation part (high temperature part), 23 ... Laser non-irradiation part (low temperature part), 24 ... GaAs growth layer.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // C30B 23/04

Claims (9)

[Claims] 1. Crystal growth of a semiconductor using a molecular beam epitaxy apparatus having a plurality of molecular beam sources, a substrate holder and a liquid nitrogen shroud, the temperature of an arbitrary portion of a semiconductor substrate surface being grown during epitaxial growth. A method for crystal growth of a semiconductor, which comprises locally increasing the temperature to a temperature at which the growth rate becomes zero, not performing epitaxial growth on a portion where the temperature is raised, and selectively performing epitaxial growth on only the other portion. 2. The structure according to claim 1, wherein the growth surface of the molecular beam epitaxy apparatus can be irradiated with laser light perpendicularly to the growth surface from the outside through a viewing port. A crystal growth method for a compound semiconductor, in which a pattern generator is installed between epitaxy devices to change the laser optical path, irradiate a semiconductor surface with an arbitrary pattern, and selectively grow. 3. A laser according to claim 1, wherein only a desired portion of the surface of the substrate is irradiated with laser light, and a semiconductor of a different type from the substrate is selectively grown on the other portion, and then the laser is irradiated. By turning off the light, the temperature of the substrate is returned to the normal growth temperature, and a semiconductor of a different type from the selective growth layer is continuously grown on the substrate to continuously grow a compound semiconductor crystal on the selective growth layer. . 4. The laser irradiation according to claim 1 or 2, wherein the temperature of the interface between the laser-irradiated portion and the non-irradiated portion rises to a temperature at which a growing group III element is desorbed. Stop the laser irradiation before, and
A method for growing a crystal of a compound semiconductor in which a natural cooling time is provided before the next laser irradiation to suppress temperature diffusion from a laser-irradiated portion to a non-irradiated portion and to clarify the boundary between the grown portion and the non-grown portion. 5. The method for crystal growth of a semiconductor according to claim 4, wherein the time until natural growth of the compound semiconductor selectively grown is 1/2 monolayer is maximized. 6. The method according to claim 2, wherein the temperature of the substrate during growth, especially the temperature of the laser irradiation portion is detected by a pyrometer and the data is fed back to the laser source.
A semiconductor crystal growth method in which the laser output for irradiating a substrate is adjusted to selectively grow while constantly controlling the substrate temperature. 7. The semiconductor crystal growth method according to claim 1, wherein the quantum wires and quantum boxes are formed by setting the size of the selective growth layer to a quantum size. 8. A method for crystal growth of a semiconductor according to claim 1, 3 or 7, wherein electrons or holes are confined in the selective growth layer by doping the selective growth layer with n-type or p-type impurities. 9. The method for crystal growth of a semiconductor according to claim 1, wherein the selective growth layer has a superlattice structure to have a quantum structure in the selective growth layer.