JP3096579B2 - Vapor phase growth method and vapor phase growth apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a first semiconductor layer made of a compound semiconductor composed of three or more elements on a semiconductor substrate, and a composition of the compound semiconductor and the constituent elements constituting the first semiconductor layer. A vapor phase growth method for laminating a second semiconductor layer made of a compound semiconductor having a different ratio by vapor phase growth in which each of the constituent elements is supplied from a separately provided source to a semiconductor substrate in a gaseous state, and The present invention relates to a phase growth apparatus.

[0002]

2. Description of the Related Art In such a vapor phase growth method and a vapor phase growth apparatus, a first semiconductor layer and a second semiconductor layer are formed on a semiconductor substrate in order to laminate a first semiconductor layer and a second semiconductor layer. A supply source is prepared for each of the elements, and the supply amount of the constituent element to the semiconductor substrate from each supply source is determined by the first amount.
The semiconductor layers and the second semiconductor layers are stacked differently. The different supply amounts of the constituent elements include the case where the supply amount is simply changed and the case where the composition ratio of the constituent elements is set to “0” in the case where the second semiconductor layer is laminated, that is, the supply amount is set to “0”. There are times when you do. In order to make the supply amounts of the constituent elements different as described above, conventionally, one supply source is provided for supplying one constituent element, and the composition ratio of the constituent elements is set to “0” in the second semiconductor layer. In the case where only the constituent element is performed, it is performed by switching between a supply state in which the constituent element is supplied to the semiconductor substrate and a non-supply state in which the element is not supplied.
Such switching between the supply state and the non-supply state can be quickly performed by blocking the passage of the constituent element in the gaseous state.

On the other hand, when a constituent element is supplied to both the first semiconductor layer and the second semiconductor layer and the supply amount is changed, conventionally, one supply source is provided for supplying one constituent element. Therefore, even when changing the flow rate of the constituent element supplied in the gaseous state, or when changing the generation amount of the constituent element gas, it is difficult to change quickly. The lamination is stopped after laminating one of the first semiconductor layer and the second semiconductor layer, and the lamination of the other is started after the supply amount of the supply source is changed so as to have the other composition ratio.

[0004]

However, according to the above-mentioned prior art, when the stacking is stopped while the supply amount of the supply source is changed, the quality of the stacked interface between the first semiconductor layer and the second semiconductor layer is reduced by the stop of the stacking. If the stacking does not need to be stopped as described above, the supply amount from the supply source that supplies the constituent elements to both the first semiconductor layer and the second semiconductor layer cannot be changed. Therefore, the setting of the lamination condition is restricted. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for accurately stacking layers while preventing the need to stop stacking between the first semiconductor layer and the second semiconductor layer. The point is to be able to set.

[0005]

According to the vapor phase growth method of the present invention, a first semiconductor layer made of a compound semiconductor composed of three or more elements and the first semiconductor layer are formed on a semiconductor substrate. A compound semiconductor and a second semiconductor layer made of a compound semiconductor having a different composition ratio of constituent elements are stacked by vapor phase growth in which each of the constituent elements is supplied from a separately provided source to a semiconductor substrate in a gaseous state. The first feature is that the supply amounts of a plurality of the supply sources provided for the same element are separately set, and when the first semiconductor layer is laminated, and when the second semiconductor layer is laminated. The point is that some of the plurality of supply sources are switched between a supply state and a non-supply state.

A second feature is that, in the first feature, the compound semiconductor is a III-V compound semiconductor. A third feature is that, in the second feature, the compound semiconductor contains Al and Ga as Group III elements, and
AlGaAs containing As as a group element, and the semiconductor substrate is a GaAs substrate having a (411) A plane as a stacked surface.

According to the present invention, there is provided a vapor-phase growth apparatus comprising: a first semiconductor layer made of a compound semiconductor composed of three or more elements on a semiconductor substrate; a compound semiconductor constituting the first semiconductor layer; A second semiconductor layer made of a compound semiconductor having a different composition ratio, and each of the constituent elements is laminated by vapor phase growth in which each of the constituent elements is supplied on a semiconductor substrate in a gaseous state from a separately provided source, its characteristic configuration, a plurality provided for the same elements of the source, and when laminating the first semiconductor layer, in the case of stacking the second semiconductor layer, a portion of said plurality sources A switching control unit for switching the supply source between the supply state and the non-supply state is provided.

[0008]

According to the first feature of the vapor phase growth method of the present invention, a part of a plurality of supply sources provided for the same element is switched between a supply state and a non-supply state to thereby provide a first semiconductor. Even when the constituent element is supplied to both the layer and the second semiconductor layer, the supply amount of the constituent element to the semiconductor substrate can be quickly switched. According to the second feature of the vapor phase growth method of the present invention, since the group III-V compound semiconductor generally has a high vapor pressure of the group V element, the group V element is maintained in an oversupply tendency, A method of defining the lamination conditions by the supply amount of the group III element is employed, but while rapidly changing the supply amount of the group III element, the pressure ratio V / II which is the pressure ratio of the group V element to the group III element is obtained.
Lamination conditions such as I ratio can be set accurately.

According to a third feature of the present invention, (411) A
Al, Ga, and GaAs semiconductor substrates
A compound semiconductor containing As as a constituent element is stacked as a first semiconductor layer and a second semiconductor layer with different composition ratios. (411) It has been reported that a flat stacking interface can be obtained on a GaAs semiconductor substrate having the A-plane as a stacking plane (see Japanese Patent Application No. Hei 5-238081). By applying, the flatness of the lamination interface can be further improved. According to a feature configuration of the vapor deposition apparatus of the present invention, the control of the switching control unit, some of the sources provided plurality by switching to the supply state and a non-supply state to the same elements, Even when the constituent elements are supplied to both the first semiconductor layer and the second semiconductor layer,
The supply amounts of the constituent elements to the semiconductor substrate can be quickly switched.

[0010]

According to the first aspect of the vapor phase growth method and the characteristic configuration of the vapor phase epitaxy apparatus, even when the constituent elements are supplied to both the first semiconductor layer and the second semiconductor layer, the structure for the semiconductor substrate can be improved. Since the supply amount of the element can be quickly switched, it is possible to accurately set the laminating conditions without having to stop the lamination between the lamination of the first semiconductor layer and the second semiconductor layer. Reached. According to the second aspect of the vapor phase growth method, in addition to the effect of the first aspect of the vapor phase growth method, the lamination conditions such as the V / III ratio can be accurately set, so that the first semiconductor layer and the The quality of the second semiconductor layer can be further improved. According to the third feature of the vapor phase growth method, the flatness of the lamination interface can be further improved. Therefore, by applying the present invention to various semiconductor devices, the performance of the semiconductor device can be further improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a case in which crystal growth is performed by an MBE apparatus shown in FIG. 1 will be described as an example of a vapor phase growth apparatus that performs crystal growth by a vapor phase growth method. As shown in FIG. 1, a substrate holder 2 for holding a GaAs substrate S which is a semiconductor substrate is provided inside a growth vessel 1 of the MBE apparatus.
Four evaporation cells 3A, 3B, 3C, 3D into which Ga, Al, and As, which are constituent elements of an AlGaAs-based compound semiconductor, are respectively placed, and a substrate holder 2 on the peripheral wall of the growth vessel 1.
An electron beam source 4 for irradiating a high-speed electron beam toward a GaAs substrate S attached to
A fluorescent screen 5 for detecting an electron beam diffracted and reflected by the As substrate S is provided.

Of the four evaporation cells 3A, 3B, 3C and 3D, Ga is supplied to the evaporation cells 3A and 3B, Al is supplied to the evaporation cell 3C, and As is supplied to the evaporation cell 3D. Two evaporation cells 3A and 3B are prepared for supplying Ga. Each of the evaporation cells 3A, 3B, 3C, and 3D functions as a supply source for supplying each of the constituent elements to the GaAs substrate S, and heats and evaporates each of the constituent elements with a heater for heating and evaporation (not shown) to form the GaAs substrate S. Each constituent element is supplied to S in a gaseous state. The inside of the growth vessel 1 is sucked by an unshown vacuum pump (for example, a turbo-molecular pump or the like) from the opening 1a provided in the peripheral wall of the growth vessel 1 while the valve 6 is open, to be in an ultra-high vacuum state. . The substrate holder 2 is provided with a substrate heater 7 for heating the GaAs substrate S attached to the substrate holder 2. Control of the substrate temperature by heating the substrate heater 7, the evaporation cell 3A,
Ga, Al, As charged in 3B, 3C, 3D
Control of a heater (not shown) for heating and evaporating the ink, and opening and closing control of shutters 3a, 3b, 3c, 3d provided in each of the evaporation cells 3A, 3B, 3C, 3D are performed by a control unit C.
O is executed.

Next, GaAs is formed by the above MBE apparatus.
The process of growing the / Al _x Ga _1-x As hetero thin film will be described. First, as shown in FIG. 2, the GaAs substrate S is cut out from a GaAs single crystal rod C formed by the Czochralski method. The plane perpendicular to the longitudinal direction of the single crystal rod C is the (100) plane, and the single crystal rod C is cut in a direction inclined about 19.5 ° (19 ° to 20 °) from the (100) plane. Then, the surface of the GaAs substrate S becomes (411)
A side.

The GaAs substrate S cut out as described above
Is degreased with an organic solvent, the surface of the GaAs substrate S is lightly etched with a sulfuric acid-based etchant, and then (411) the substrate holder 2 in the growth vessel 1 so that the A surface side becomes the crystal growth surface.
Set to. The inside of the growth vessel 1 is about 1
0 ^-9 Pa of has reached an ultra-high vacuum, in this state, while monitoring the substrate temperature by the temperature sensor, not shown, by heating the GaAs substrate S under the control of the controller CO, and the substrate temperature to a predetermined temperature Set to be.

The control unit CO controls the temperature of the substrate together with the shutters 3a of the four evaporation cells 3 in a closed state.
Each growth material is heated and evaporated. Four evaporation cells 3A, 3
B, 3C, 3D, the first semiconductor layer FL, AlG
In the lamination of the aAs layer, three evaporation cells 3A, 3C, 3D
And three evaporation cells 3A, 3B, 3D are used for laminating the GaAs layer as the second semiconductor layer SL.

Each of these evaporation cells 3A, 3B, 3C, 3D
Is set, for example, by setting the aluminum mixed crystal ratio x =
In the case of 0.7, as an example, the heating temperature of the As supply evaporation cell 3D is such that the As ₄ molecular beam intensity is 8 × 10 ⁻⁵ T.
orr, and the heating temperature of one of the evaporation cells 3A for supplying Ga and 3C for supplying Al is set to A.
In the case of vapor-phase growth of an lGaAs-based compound semiconductor, the growth rate is controlled by the supply of the group III element, so that the growth rate of the AlGaAs layer having an Al mixed crystal ratio x = 0.7 is set to 1 μm / h. And the other evaporation cell 3 for supplying Ga
As for the heating temperature of B, the growth rate of the GaAs layer is 1 μm / h when Ga is supplied by the evaporation cell 3B for supplying Ga while keeping the temperature setting of the evaporation cell 3A for supplying Ga as described above. Set so that Then, after stacking a suitable buffer layer, the control unit CO firstly releases the shutters 3a, 3a of the three evaporation cells 3A, 3B, 3D.
By opening b and 3d, a GaAs layer is grown on the GaAs substrate S.

After the growth of the GaAs layer, two Ga
One of the supply evaporation cells 3A and 3B
Of the shutter 3a and the evaporation cell 3D for supplying As.
The gates 3a and 3d are kept open and the other Ga is supplied.
At the same time as closing the shutter 3b of the evaporation cell 3B for
Open the shutter 3c of the evaporating cell 3C for supplying
_0.7Ga_0.3An As layer is grown and GaAs / Al_0.7G
a_0.3An As hetero thin film is formed. Therefore,
The control unit CO changes the supply state of the evaporation cell 3B for supplying Ga to the supply state.
It functions as a switching control unit SC for switching to the supply state.

The state of growth of each of these layers is a so-called RHEED pattern generated on the fluorescent screen 5 as a result of the irradiation of the GaAs substrate S from the electron beam source 4 with the electron beam diffracted and reflected by the GaAs substrate S incident on the fluorescent screen 5. Can be observed.

GaAs / Al prepared as described above
_The result of evaluating the _0.7 Ga _0.3 As hetero thin film by photoluminescence will be described below. In the evaluation by photoluminescence, GaAs / Al _0.7 Ga _0.3 As quantum wells having GaAs well layers of various thicknesses were prepared at three different substrate temperatures, and the half-values of the emission spectra at different wavelengths from each well layer were obtained. Full width (FWHM)
Is done by asking for

FIG. 3 shows the measurement results. For comparison with the measurement results of FIG. 3, GaAs / Al _0.7 Ga _0.3 As
FIG. 4 shows the measurement results of the full width at half maximum (FWHM) of the photoluminescence when the quantum well is manufactured by a single evaporation cell for supplying Ga. That is, GaAs / Al _0.7 Ga _{0.3 is} used without using the above-mentioned Ga supply evaporation cell 3B at all.
It is a measurement result in the case of producing an As quantum well. As is clear from the comparison between FIG. 3 and FIG.
By using the evaporating cells 3A and 3B for supplying a, the full width at half maximum (FWHM) of the emission spectrum of photoluminescence is generally narrowed, and is particularly remarkable when the substrate temperature is 580 ° C.

The narrow full width at half maximum (FWHM) of the emission spectrum indicates that a laminated film having better flatness of the laminated interface is obtained. The reason why the flatness of the lamination interface becomes better is that GaAs
It is considered that the V / III ratio can be reduced by supplying Ga using the evaporation cell 3B for supplying Ga when stacking the s layer. The thus-obtained semiconductor film having a flat stacked interface can obtain excellent device characteristics when applied to a semiconductor laser device having a quantum well structure and a quantum device such as a resonance tunnel transistor.

[Other Embodiments] Other embodiments will be listed below. In the above embodiment, the case where the crystal is grown by the MBE method is exemplified. For example, the MOCVD method or the gas source M
The present invention can also be applied to the case of crystal growth by the BE method.

In the above embodiment, the case where the present invention is applied to the vapor phase growth of an AlGaAs-based compound semiconductor is exemplified. However, the present invention may be applied to the vapor phase growth of another III-V compound semiconductor such as an InGaAsP-based semiconductor. . Further, the present invention may be applied to vapor phase growth of II-VI compound semiconductors. In the above embodiment, the evaporation cells 3A and 3B for supplying Ga are used.
Are provided, but three or more may be provided as necessary. Further, a plurality of evaporation cells of constituent elements other than Ga may be provided.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the structure shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an MBE apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for manufacturing a GaAs substrate according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram of a sample manufactured by applying the present invention.

FIG. 4 is a characteristic diagram of a sample manufactured by applying a conventional technique.

[Explanation of symbols]

 3A, 3B, 3C, 3D Source S Semiconductor substrate SC Switching controller FL First semiconductor layer SL Second semiconductor layer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sasumi Suzumi 4-8-3-506 Motoyamanakacho, Higashinada-ku, Kobe City, Hyogo Prefecture No. (72) Inventor Yasunori Okamoto 1-1-1, Hama, Amagasaki City, Hyogo Prefecture Inside Kubota Technology Development Laboratory Co., Ltd. (56) References JP-A-3-261130 (JP, A) JP-A-2-64093 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 H01L 21/365 H01L 21/31 C23C 16/00

Claims (4)

(57) [Claims] 1. A first semiconductor layer (F) made of a compound semiconductor composed of three or more elements on a semiconductor substrate (S).
L) and a second semiconductor layer (SL) made of a compound semiconductor having a different composition ratio of the constituent elements from the compound semiconductor forming the first semiconductor layer (FL). Sources (3A), (3B), (3C), (3
D) A vapor deposition method in which the layers are stacked by vapor deposition supplied in a gaseous state from D), wherein a plurality of the supply sources (3A) provided for the same element are provided.
The supply amount of (3B) is set separately for each of the first semiconductor layer (FL) and the second semiconductor layer (FL).
When the semiconductor layer (SL) is laminated, a part of the plurality of sources (3A) and (3B) is a part of the source (3B).
Vapor phase growth method for switching between a supply state and a non-supply state. 2. The vapor phase growth method according to claim 1, wherein said compound semiconductor is a group III-V compound semiconductor. 3. The method according to claim 1, wherein the compound semiconductor is a group III element
A containing l and Ga and containing As as a group V element
lGaAs and the semiconductor substrate (S) is (411)
3. The vapor phase growth method according to claim 2, wherein the GaAs substrate is a GaAs substrate having the A surface as a laminated surface. 4. A first semiconductor layer (F) made of a compound semiconductor composed of three or more elements on a semiconductor substrate (S).
L) and a second semiconductor layer (SL) made of a compound semiconductor having a different composition ratio of the constituent elements from the compound semiconductor forming the first semiconductor layer (FL). Sources (3A), (3B), (3C), (3
D) A vapor phase epitaxy apparatus for laminating by vapor phase epitaxy supplied in a gaseous state from D), wherein a plurality of the supply sources (3A) and (3B) are provided for the same element and the first semiconductor layer (FL) is When laminating, the second
When the semiconductor layer (SL) is laminated, a part of the plurality of sources (3A) and (3B) is a part of the source (3B).
Control unit (S) for switching the state between the supply state and the non-supply state.
A vapor phase growth apparatus provided with C).