JP2006108440A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device in which a quantum structure can be manufactured only with a crystal growth technique without specially processing it at a pre-stage of crystal growth, and which can be controlled so as to be arranged to a desirable place on a semiconductor substrate; and to provide its manufacturing method. <P>SOLUTION: The semiconductor device 1 has the semiconductor substrate 10, a buffer layer 20 which is formed on the semiconductor substrate 10 and made of the same material as the semiconductor substrate 10, a semiconductor growth layer 30 formed on the buffer layer 20, and the quantum structure 50 formed on the semiconductor growth layer 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a semiconductor device capable of controlling the arrangement of quantum structures such as quantum dots and quantum wires on a substrate only by crystal growth technology and a manufacturing method thereof.

  Semiconductor performance has progressed in inverse proportion to device size. That is, pursuing a reduction in the size of the element (a fine structure such as a quantum structure such as a quantum dot, a quantum wire, or a quantum box) means that the performance of the element is improved. However, in recent years, there has been a limit to the miniaturization of elements. This is because the pattern transfer capability of lithography has been greatly involved in the determination of the element size so far.

  The pattern transfer capability here means how much minute pattern size can be drawn on the substrate. At present, methods using X-ray exposure, electron beam exposure, excimer laser, etc. have been developed, and it has become possible to draw a pattern size of around 100 nm. However, it is considered that these methods will eventually reach the same limits as ultraviolet exposure.

  In the first place, the greatest purpose of reducing the size of the device, that is, producing a fine structure called a quantum structure, is to transport carriers through them through quantum mechanical effects. In this case, as a pre-stage for operating the quantum structure as an actual device (quantum effect device), the quantum structure using the quantum effect device as an element, particularly quantum dots and quantum wires, are processed particularly at the pre-stage of crystal growth. It is considered ideal that it can be produced only by the crystal growth technique without applying it (for example, without taking the labor of lithography). Furthermore, if quantum structures such as quantum dots and quantum wires can be arranged and controlled at desired locations on the semiconductor substrate, it is considered that the practicality of the quantum structures will increase dramatically.

  Therefore, as a method for producing a quantum structure using only the crystal growth technique, there is a technique for growing a material having a larger lattice constant on a material having a relatively smaller lattice constant. For example, the reason why a quantum dot having a typical quantum structure is formed is as follows.

  First, on the buffer layer made of the same material as the substrate or the substrate, a growth layer made of a material having a lattice constant that is about 3 to 10% larger than the lattice constant of the material of the substrate or buffer layer is formed in two to three molecular layers. Grow. Then, the material forming the growth layer tries to grow so as to match the lattice constant of the buffer layer having a relatively smaller lattice constant.

  However, in actuality, the lattice constant of the growth layer is different from the lattice constant of the buffer layer, so that it undergoes compressive strain as it grows. As growth proceeds further, the material deposited on the substrate tends to mitigate this accumulated strain energy. Quantum dots are formed in the process of relaxation, and the growth in which quantum dots are formed in this way is called a Strance-Krastanov (SK) growth mode.

  III-V group compound semiconductors, particularly GaAs and InGaAs-based materials are currently known for the formation of high-quality quantum dots. Furthermore, GaAs and InGaAs materials can be grown by metal organic vapor phase epitaxy (MOVPE), which is currently used to fabricate HEMT and HBT epitaxial wafers used in GaAs devices. It is thought that the current mass production technology can be applied.

  Next, as an alternative to lithography, research has also been attempted to fabricate nanometer-order microstructures from another perspective. For example, by using a scanning tunneling microscope (STM), a high electric field is applied to the probe and a metal or semiconductor material is blown from the tip of the probe toward the substrate, and a fine structure is deposited. In the method using the single crystal growth technology, a method of combining a regular fine structure pattern on the order of several hundred nanometers with a fine tilt angle originally possessed by the substrate and the single crystal growth technology, Various techniques have been developed for producing fine pores in the pores, and producing fine structures on the order of several tens of nanometers in the pores in units of one unit (see, for example, Patent Document 1).

  In addition, focusing on quantum dots, which are the ultimate material that uses quantum mechanical effects, with the recognition that energy control of quantum dots is indispensable for applying quantum dots to devices. A technology capable of controlling the emission wavelength has been invented (see Patent Document 2).

As shown in FIG. 4, the technique described in Patent Document 1 is obtained by etching the semiconductor device 200 by etching the mask 220 on the surface of the substrate 210 to prepare the opening 230 on the substrate in advance. It includes a step of growing a mixed crystal semiconductor in a recess and a quantum effect layer growth step of growing a continuous mixed crystal semiconductor having a different energy band structure in the step, thereby forming a quantum dot with less damage at a desired position. It is what you want to make. Further, as shown in FIG. 5, in the technique described in Patent Document 2, the semiconductor device 300 has an InGaAs buffer layer 320 formed on the surface of a GaAs substrate 310, and the In composition of the InGaAs buffer layer 320 is realized as means for realizing a light emitting device. In response to the change, the emission wavelength of the quantum dot 330 is controlled by changing the size of the InAs quantum dot 330 grown thereon.
JP 09-127612 A JP 2000-196193 A

  However, according to the SK growth mode described first, it is difficult to control the arrangement of quantum structures such as quantum dots and quantum wires at desired locations on the semiconductor substrate. There is also a problem that the size of the quantum dots cannot be made uniform. Next, according to the technique described in Patent Document 1, not only process conditions for producing a uniform structure on a substrate are required, but also in-plane uniformity during growth becomes important. The processing process in the previous stage is indispensable. Further, according to the technique described in Patent Document 2, the focus is on the light emitting device, and it is not intended to control the arrangement of quantum dots and quantum wires. Therefore, according to the present invention, the ideal quantum structure, particularly quantum dots and quantum wires can be produced only by the crystal growth technique without any particular processing in the previous stage of crystal growth, and the desired quantum structure on the semiconductor substrate can be obtained. An object of the present invention is to provide a semiconductor device capable of controlling the arrangement of quantum structures such as quantum dots and quantum wires at a place, and a method for manufacturing the same.

  In order to achieve the above object, a semiconductor device of the present invention includes a semiconductor substrate, a buffer layer formed on the semiconductor substrate and made of the same material as the semiconductor substrate, and a semiconductor growth layer formed on the buffer layer. And a quantum structure formed on the semiconductor growth layer.

  Preferably, the semiconductor substrate is a GaAs substrate, the buffer layer is made of single crystal GaAs, the semiconductor growth layer is made of InGaAs, and the quantum structure is made of InAs.

  The semiconductor growth layer is preferably composed of an In-rich growth layer and a Ga-rich growth layer due to an In surface segregation phenomenon.

  The quantum structure is preferably formed selectively on the surface of the In-rich growth layer.

  The quantum structure has a band in which the distribution of In segregated on the surface of the In-rich growth layer due to the In surface segregation phenomenon is about 1 to 2 μm in [110] or [1-10] of the crystal plane orientation of the semiconductor substrate. It is preferable to grow in a region having a width.

  The method of manufacturing a semiconductor device of the present invention includes a first step of growing a buffer layer made of the same material as the semiconductor substrate on a semiconductor substrate, a second step of growing a semiconductor growth layer on the buffer layer, and the semiconductor And a third step of growing a quantum structure comprising quantum dots or quantum wires on the growth layer.

  Preferably, the semiconductor substrate is a GaAs substrate, the buffer layer is made of single crystal GaAs, the semiconductor growth layer is made of InGaAs, and the quantum structure is made of InAs.

  In the second step, an In surface segregation phenomenon is used to grow the semiconductor growth layer into an In-rich growth layer and a Ga-rich growth layer, and in the third step, a quantum structure is formed on the In-rich growth layer. It is preferable to grow it selectively.

  The quantum structure has a band in which the distribution of In segregated on the surface of the In-rich growth layer due to the In surface segregation phenomenon is about 1 to 2 μm in [110] or [1-10] of the crystal plane orientation of the semiconductor substrate. It is preferable to grow in a region having a width.

  The buffer layer, the semiconductor growth layer, and the quantum structure in the first to third steps are preferably grown by metal organic vapor phase epitaxy (MOVPE method).

  According to the present invention, the quantum structure that has been randomly formed on the substrate so far can be arranged on the substrate only by the crystal technique. That is, an ultrafine structure of nanometer order, particularly a quantum structure such as a quantum dot having a diameter of 10 to 50 nm and a height of 5 to 15 nm, or a quantum wire having a width of 50 nm can be formed at a desired location. Also, the contrast between the In-rich surface layer formed on the surface of the InGaAs growth layer and the Ga-rich surface layer due to the In surface segregation phenomenon inside the InGaAs growth layer generated during or after the growth of the InGaAs growth layer. Since (In composition distribution) can be used, the growth of the quantum structure can be controlled.

  Next, the best mode for carrying out the semiconductor device and the manufacturing method thereof of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of the structure of a semiconductor device according to the present invention, FIG. 2 is a plan view when an InAs layer is grown on a InGaAs growth layer corresponding to three molecular layers, and FIG. 3 is a band width of InAs dots and an InGaAs growth layer. It is a related figure of In composition.

  First, the basic principle of the present invention will be described. A single-crystal GaAs buffer layer is formed on the GaAs (001) just substrate. An InGaAs growth layer composed of an In-rich InGaAs growth layer and a Ga-rich InGaAs growth layer is formed on the single-crystal GaAs buffer layer. An InAs layer made of InAs dots or InAs thin wires is formed on the In-rich InGaAs growth layer.

  That is, a single crystal GaAs buffer layer made of the same material is grown on a compound semiconductor substrate GaAs (001) just substrate, and an InGaAs growth layer is grown thereon, whereby an InGaAs growth layer is formed. Contrast between In-rich InGaAs growth layer and Ga-rich InGaAs growth layer on the surface of InGaAs growth layer (In composition distribution) Is used to produce a fine structure (quantum dot or quantum wire) of InAs.

  Here, the In surface segregation phenomenon is a phenomenon in which In atoms in the InGaAs epitaxial layer mainly move to the growth layer surface side during or after the growth, and thus the surface of the InGaAs growth layer has an In concentration of In concentration. A high region is formed. At this time, the In concentration on the surface side is distributed in the plane. That is, a region with a high In concentration and a region with a low In concentration are formed on the surface of the InGaAs growth layer.

  This factor is distributed with the probability that there is an In-rich InGaAs growth layer and a Ga-rich InGaAs growth layer immediately after the start of growth of the InGaAs growth layer, and this distribution is mainly in the [110] and [1-10] directions. It is presumed to grow. Among them, the In-rich InGaAs growth layer has a large amount of In segregated to the surface side. As a result, the surface of the InGaAs growth layer has a distribution of In-rich InGaAs growth layer and Ga-rich InGaAs growth layer. Will be formed.

  For example, when InAs is epitaxially grown on an InGaAs growth layer having such a distribution, InAs is selectively grown at a place where the growth of the surface of the InGaAs growth layer is easy. That is, since the lattice mismatch of the GaAs crystal to the InAs crystal is as large as 7.3%, the growth of the InAs crystal to the In-rich InGaAs growth layer is promoted more than the Ga-rich InGaAs growth layer, which is difficult to grow. The Therefore, InAs can be selectively grown on the In-rich InGaAs growth layer.

  This principle will be described more specifically with reference to the drawings. As shown in FIG. 1, a single-crystal GaAs buffer layer is grown on a GaAs (001) just substrate, and an InGaAs growth layer is further grown. At this time, a distribution of an In-rich InGaAs growth layer and a Ga-rich InGaAs growth layer is formed at the initial stage of the InGaAs growth layer. When an InGaAs growth layer is further grown, In atoms therein move to the surface of the InGaAs growth layer due to a segregation phenomenon, and the surface of the In-rich InGaAs growth layer becomes a more In-rich surface.

  Here, for example, when an InAs layer is grown, the lattice constant of the InAs crystal is larger than that of the GaAs crystal. Therefore, when considered on the InGaAs growth layer, the In-rich InGaAs growth layer surface closer to the lattice constant of the InAs layer is preferred. Growth is expected to occur. Therefore, the InAs layer is selectively formed on the surface of the In-rich InGaAs growth layer by controlling the growth amount.

  Further, the In concentration distribution is easily formed linearly in the [110] and [1-10] directions. Further, the contrast of the concentration distribution of In and Ga on the surface of the InGaAs growth layer is promoted by the segregation phenomenon of In on the InGaAs surface.

  Next, when an InAs layer is actually grown on a GaAs (001) just substrate, the InAs layer grows along the In-rich region of the InGaAs growth layer. By controlling the growth amount of the InAs layer, it is possible to grow InAs quantum wires and quantum dots.

  Next, examples of the present invention will be described.

The GaAs (001) just substrate was carried into a MOVPE growth furnace, and first, the substrate temperature was raised to 640 ° C. and thermal cleaning was performed for 10 minutes while flowing arsine gas (AsH ₃ ). The purpose of this thermal cleaning is to remove the oxide film and impurities on the substrate surface. Thereafter, while maintaining the substrate temperature, trimethylgallium (TMG) diluted with hydrogen was flowed into the reaction furnace, and a GaAs buffer layer was grown to about 500 nm. Next, arsine gas (AsH ₃ ), trimethylgallium (TMG), and trimethylindium (TMI) were simultaneously flowed to grow an In _0.2 Ga _0.8 As layer of about 100 nm. At this time, 50 nm on the GaAs buffer layer side was an inclined layer having an In mixture ratio of 0 to 0.2. This is to prevent dislocation from occurring at the interface between the GaAs buffer layer and the In _0.2 Ga _0.8 As layer. Finally, only arsine gas (AsH ₃ ) and trimethylindium (TMI) were flowed to grow an InAs layer corresponding to three molecular layers. After the growth is completed, all the gas lines other than arsine gas (AsH ₃ ) are sealed, and after waiting for the substrate temperature to drop below 400 ° C., the arsine gas (AsH ₃ ) gas line is also sealed, and the substrate temperature is lowered to about 100 ° C. I took it out after waiting.

  When the surface of this sample was observed with a scanning electron microscope (SEM), a fine structure considered to be InAs dots or InAs fine wires was confirmed in the arrangement as shown in FIG. These microstructures grew in a bundle in a region having a width of 1 μm.

  In addition, when the sample which does not grow an InAs layer was produced on the said conditions and observed with the scanning electron microscope (SEM), since the three-dimensional structure considered to be such a fine structure was not confirmed, the fine observed above The structure may be considered as a three-dimensional structure made of InAs.

  Next, the InGaAs growth layer grown in Example 1 was grown with the In composition set to 0, 0.6, and 0.8. As the In composition was increased to 0.4 and 0.6, as shown in FIG. 3, the growth area of the dots considered to be InAs layers tended to narrow. This is thought to be because the absolute amount of In segregated increased as the In composition increased. However, with an In composition of 0.8, the surface of the InGaAs growth layer showed a rugged morphology. This is because the In composition of the InGaAs growth layer is increased, the amount of lattice mismatch with the GaAs crystal is increased, and this is regarded as a growth mode that has shifted to the three-dimensional growth mode (SK growth mode) instead of the two-dimensional growth mode. be able to. Therefore, it is considered optimal to control the In composition of the InGaAs growth layer grown in Example 1 to about 0.1 to 0.6.

As described above, according to the present invention, the InAs quantum structure that has been randomly formed on the GaAs (001) substrate so far can be arranged on the substrate by the crystal growth technique. In addition, this arrangement is made possible only by the crystal growth technique without taking time and effort such as lithography. In addition, it has become possible to grow InAs quantum wires and quantum dots by controlling the growth amount of the InAs layer. Furthermore, it is a desirable structural condition when a carrier is confined in a zero-dimensional space such as a quantum dot in the production of a fine structure, the size of which is on the order of 10 to 50 nm, the arrangement interval is about 10 to 20 nm, and a quantum wire In the case of a structure in which carriers are confined in such a one-dimensional space, it is possible to satisfy that the width of the thin line is 50 nm or less. Further, in the production by the SK growth mode, the non-uniformity of the size of the quantum dots was pointed out as a big problem, but the uniformization was promoted.
As the semiconductor device of the present invention can provide a semiconductor device capable of operating at a higher speed than the currently used device, it is expected that the utility value of the industry will be further increased.

It is a structure sectional view of a semiconductor device of the present invention. FIG. 6 is a plan view when an InAs layer is grown on a InGaAs growth layer corresponding to a trimolecular layer. FIG. 6 is a relationship diagram of the band width of InAs dots and the In composition of an InGaAs growth layer. It is a perspective view of the semiconductor device of a prior art (patent document 1). It is structure sectional drawing of the semiconductor device of a prior art (patent document 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor device 10 GaAs (001) just substrate 20 Single crystal GaAs buffer layer 30 InGaAs growth layer 40 In-rich InGaAs growth layer 50 Ga-rich InGaAs growth layer 60 InAs layer (InAs quantum dot or InAs quantum wire)
90 InAs layer (InAs quantum dots or InAs quantum wires)
100 InGaAs growth layer surface

Claims (10)

A semiconductor substrate; a buffer layer formed on the semiconductor substrate and made of the same material as the semiconductor substrate; a semiconductor growth layer formed on the buffer layer; and a quantum structure formed on the semiconductor growth layer A semiconductor device. 2. The semiconductor device according to claim 1, wherein the semiconductor substrate is a GaAs substrate, the buffer layer is made of single crystal GaAs, the semiconductor growth layer is made of InGaAs, and the quantum structure is made of InAs. 2. The semiconductor device according to claim 1, wherein the semiconductor growth layer includes an In-rich growth layer and a Ga-rich growth layer due to an In surface segregation phenomenon. The semiconductor device according to claim 1, wherein the quantum structure is formed of quantum dots or quantum wires selectively formed on a surface of the In-rich growth layer. The quantum structure has a band in which the distribution of In segregated on the surface of the In-rich growth layer due to the In surface segregation phenomenon is about 1 to 2 μm in [110] or [1-10] of the crystal plane orientation of the semiconductor substrate. 5. The semiconductor device according to claim 4, wherein the semiconductor device is grown in a region having a width. A first step of growing a buffer layer made of the same material as the semiconductor substrate on a semiconductor substrate, a second step of growing a semiconductor growth layer on the buffer layer, and a quantum dot or quantum wire on the semiconductor growth layer And a third step of growing a quantum structure. 7. The method of manufacturing a semiconductor device according to claim 6, wherein the semiconductor substrate is a GaAs substrate, the buffer layer is made of single crystal GaAs, the semiconductor growth layer is made of InGaAs, and the quantum structure is made of InAs. In the second step, an In surface segregation phenomenon is used to grow the semiconductor growth layer into an In-rich growth layer and a Ga-rich growth layer, and in the third step, a quantum structure is formed on the In-rich growth layer. The method of manufacturing a semiconductor device according to claim 6, wherein the semiconductor device is selectively grown. The quantum structure has a band in which the distribution of In segregated on the surface of the In-rich growth layer due to the In surface segregation phenomenon is about 1 to 2 μm in [110] or [1-10] of the crystal plane orientation of the semiconductor substrate. 9. The method of manufacturing a semiconductor device according to claim 8, wherein the semiconductor device is grown in a region having a width. 7. The method of manufacturing a semiconductor device according to claim 6, wherein the growth of the buffer layer, the semiconductor growth layer, and the quantum structure in the first to third steps is performed by a metal organic chemical vapor deposition method.

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