JP3875184B2 - Schottky diode and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a Schottky diode using a Schottky barrier generated by joining a semiconductor and a metal, and a method for manufacturing the same.
[0002]
[Prior art]
A Schottky diode is a two-terminal element that obtains a rectifying effect by a Schottky barrier generated when a semiconductor and a metal are brought into contact with each other. As shown in FIG. 1, a typical Schottky diode has an insulator layer 2 formed on a semiconductor substrate 1 made of silicon single crystal, and through an opening 7 provided in the insulator layer 2. The upper electrode layer 3 made of a metal such as aluminum or various silicides and the semiconductor substrate 1 are in contact with each other. A Schottky barrier is formed at a contact portion between the semiconductor substrate 1 and the upper electrode layer 3, and the upper electrode layer 3 and the semiconductor substrate 1 are connected to different connection terminals (not shown) (see, for example, Patent Document 1). .
[0003]
Schottky diodes with such a structure have superior characteristics such as faster switching speed and smaller forward voltage drop than PN junction diodes, especially high-frequency operation as an element constituting individual parts and integrated circuits. Is used in the necessary circuit.
[0004]
The Schottky diode having the structure of FIG. 1 is manufactured by a manufacturing method as shown in FIG.
[0005]
First, as shown in FIG. 2A, the insulator layer 2 is formed on the semiconductor substrate 1. Thereafter, a photoresist is applied on the insulator layer 2 to form a photoresist film 6, and exposure and development are performed to open a part of the photoresist film 6. Using this photoresist film 6 as a mask, the insulator layer 2 is etched to form an opening 7 through which a part of the semiconductor substrate 11 is exposed as shown in FIG. Next, the surface of the semiconductor substrate 1 exposed from the opening 7 is cleaned as necessary. Thereafter, as shown in FIG. 2C, a metal film is formed on the entire upper surface of the semiconductor substrate 1, and the metal film is patterned by a photolithography method, whereby the upper portion in contact with the semiconductor substrate 1 through the opening 7 is formed. The electrode layer 3 is formed. Thereby, a Schottky diode is completed.
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 09-246573
[Problems to be solved by the invention]
The conventional Schottky diode has the following problems due to the manufacturing method described above.
[0008]
Schottky diodes require atomic level flatness on the Schottky barrier surface. However, although the surface of the semiconductor substrate 1 is flattened by mirror polishing, there are many irregularities at the atomic level.
[0009]
In addition, when the insulating layer 2 is etched to form the opening 7, an anisotropic etching method is usually used because fine processing is possible. Therefore, when the insulator layer 2 is etched, the semiconductor substrate 1 exposed through the opening 7 is also irradiated with radical atoms and ions. As a result, as shown in FIG. 3A, a crystal defect portion 4 having a large number of crystal defects is generated in the vicinity of the surface layer of the semiconductor substrate 1.
[0010]
Furthermore, the exposed surface of the semiconductor substrate 1 is exposed to the atmosphere when transported from the etching apparatus to the film forming apparatus. As a result, the exposed surface of the semiconductor substrate 1 is contaminated by natural oxidation, diffusion of pollutant particles in the atmosphere, or reaction with the pollutant particles, and a contaminated portion 5 is formed as shown in FIG. Cleaning is performed to remove the crystal defect portion 4 and the contaminated portion 5, but it is difficult to completely remove the crystal defect portion 4 and the contaminated portion 5.
[0011]
After such a cleaning process is performed, the semiconductor substrate 1 is placed in a film forming apparatus such as sputtering or CVD in order to form the upper electrode layer 3. Is present.
[0012]
That is, in the Schottky diode manufactured by the conventional manufacturing method described above, the lattice defect part 4 and the contaminated part 5 are actually present at the Schottky interface as shown in FIG.
[0013]
Therefore, sufficient characteristics cannot be obtained with the conventional Schottky diode, and in particular, it cannot be applied to the production of a next-generation Schottky diode that requires a reduction in leakage current.
[0014]
In view of the above, an object of the present invention is to provide a Schottky diode having a clean Schottky interface that does not sandwich crystal defects and contaminants and exhibiting good diode characteristics, and a method for manufacturing the same.
[0015]
[Means for Solving the Problems]
In order to solve the above-described problems, a Schottky diode according to the present invention includes a semiconductor substrate having a first crystal orientation plane and metal atoms that have penetrated from the surface of the semiconductor substrate. }, And a metal part forming a Schottky barrier on the second crystal orientation plane.
[0016]
According to the above Schottky diode, the metal portion made of metal atoms that have penetrated from the surface of the semiconductor substrate forms a Schottky barrier in the second crystal orientation plane that is the {111} plane inside the semiconductor substrate. A Schottky interface without unevenness can be formed even at a level. In addition, this Schottky interface is not a semiconductor surface where lattice defects or contaminant particles are present, but is formed at a position where it enters a semiconductor substrate where lattice defects or contaminant particles are not present, so that a clean Schottky interface can be obtained. it can. Thereby, a Schottky diode having good characteristics can be obtained.
[0017]
The method for manufacturing a Schottky diode according to the present invention includes a step of forming a metal film on a semiconductor substrate whose surface is a first crystal orientation plane, and a second crystal that is a {111} plane of the semiconductor substrate. A step of intruding metal atoms in the metal film along the azimuth plane; and a step of replacing atoms constituting the semiconductor substrate with the intruded metal atoms.
[0018]
According to the above Schottky diode manufacturing method, the metal atoms in the metal film penetrate into the semiconductor substrate along the second crystal orientation plane which is the {111} plane of the semiconductor substrate to constitute the semiconductor substrate. Since it is replaced with an atom, a Schottky interface without unevenness can be formed even at the atomic level. In addition, even if the semiconductor substrate is exposed to various atmospheres and causes instructor defects or contamination, the lattice defects disappear during the substitution process with metal atoms in the metal film, and the contaminants are dispersed during the service. Does not remain on the Schottky interface. Thereby, a clean Schottky interface can be obtained.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
(First embodiment)
FIG. 4 is a cross-sectional view showing the Schottky diode according to the first embodiment of the present invention. In the Schottky diode of this embodiment, a Schottky barrier is formed between the semiconductor substrate 11 made of silicon (Si) single crystal connected to one connection terminal (not shown) and the semiconductor substrate 11, and the other connection terminal ( An upper electrode layer 13 made of aluminum (Al) connected to a not-shown) and an insulator film 12 made of silicon oxide for defining a current path are constituted.
[0020]
Since FIG. 4 is a cross-sectional view, the interface between the upper electrode layer 13 and the semiconductor substrate 11 is depicted in a V shape, but in reality, it has a three-dimensionally inverted quadrangular pyramid shape. That is, the upper electrode layer 13 is in contact with the semiconductor substrate 11 on four surfaces forming a cone.
[0021]
The upper electrode layer 13 is in contact with the {111} plane of the semiconductor substrate 11. As described above, when the aluminum atoms are in contact with only the {111} plane, the interface between the upper electrode layer 13 and the semiconductor substrate 11 becomes a surface having no unevenness even at the atomic level. Furthermore, since the Schottky interface can be formed three-dimensionally, the device can be downsized as compared with a conventional Schottky diode in which the Schottky interface is two-dimensional.
[0022]
5A to 5D are cross-sectional views showing a method for manufacturing the Schottky diode of the present embodiment in the order of steps.
[0023]
First, as shown in FIG. 5A, an insulating layer 12 made of silicon oxide is formed on a silicon semiconductor substrate 11 having a {100} surface by a CVD method to a thickness of 3,000 mm. A photoresist is applied to the insulator layer 12 to form a photoresist film 16, and exposure and development treatment are performed to provide an opening 17 having a 0.5 μm square in the photoresist film 16.
[0024]
Next, as shown in FIG. 5B, anisotropic etching is performed using the photoresist film 16 as a mask to form an opening 17 in the insulator layer 12 to expose a part of the surface of the semiconductor substrate 11. At this time, since the surface of the semiconductor substrate 11 is irradiated with radical atoms and ions by anisotropic etching, the lattice defect portion 101 is generated. In addition, as described in the related art, a natural oxide film or contaminants adhere to the exposed portion of the semiconductor substrate 11 until the upper electrode layer is formed, resulting in a contaminated portion 102.
[0025]
Next, aluminum is deposited on the entire upper surface of the semiconductor substrate 11 by sputtering or CVD to form an aluminum film having a thickness of 5,000 mm, and then the aluminum film is patterned by photolithography, as shown in FIG. As described above, the upper electrode layer 13 in contact with the semiconductor substrate 11 is formed through the opening 17 of the insulator layer 12.
[0026]
Next, annealing is performed in a nitrogen atmosphere at a temperature of 300 to 500 ° C., preferably 425 ° C. or less for 30 minutes. By this annealing, the aluminum atoms forming the upper electrode layer 13 and the silicon atoms forming the semiconductor substrate 11 are interdiffused. In the above temperature range, aluminum atoms preferentially diffuse in the <111> direction of single crystal silicon, so that aluminum enters the semiconductor substrate 11 with the {111} plane of silicon serving as an interface, and silicon atoms and aluminum Atom is replaced. At the same time, the lattice defects of the lattice defect portion 101 present in the exposed portion disappear, and the contaminating particles are dispersed in the aluminum. In this manner, a V-shaped Schottky interface having the {111} plane of silicon with an atomic arrangement as shown in FIG. 5D is obtained. Here, the reason for setting the annealing temperature to 300 to 500 ° C. is as follows. When the annealing temperature is less than 300 ° C., the mutual diffusion between the aluminum atom and the silicon atom is hardly performed, or the mutual diffusion rate is extremely slow, and the annealing process takes time. On the other hand, when the annealing temperature exceeds 500 ° C., aluminum atoms and silicon atoms can be interdiffused even in crystal orientation planes other than the {111} plane of the silicon crystal. Therefore, the temperature during the annealing treatment needs to be 300 to 500 ° C. However, in order to more reliably prevent aluminum atoms from passing through the {111} plane of the silicon crystal, the annealing temperature is preferably 350 to 450 ° C. or less, and more preferably 425 ° C. or less.
When the upper electrode layer 13 is formed, a second upper electrode layer (not shown) made of, for example, titanium may be formed on aluminum. Titanium forms a compound with silicon diffused in aluminum, and thus serves to reduce silicon remaining dispersed in aluminum. Moreover, since this compound has electroconductivity, it can also be used as a part of an electrode as it is. Metals having such characteristics include tungsten, cobalt, nickel, and tantalum in addition to titanium.
Here, since titanium and its silicide have a higher electrical resistance value than aluminum, when using the method as described above, the resistance is increased compared to the case where the upper electrode layer is formed only from aluminum. To do. For this reason, when the lower resistance of the upper electrode layer is required, the second upper electrode layer may be removed by a CMP method or the like. Further, in order to make the thickness of the upper electrode layer 13 reduced by the removal of the second upper electrode layer a predetermined thickness, aluminum may be further deposited after removing the second metal layer.
[0027]
According to the manufacturing process as described above, the Schottky diode has no Schottky interface even at the atomic level because the Schottky interface is formed from the {111} plane of silicon. In addition, lattice defects generated during etching of the insulator layer 12 disappear when silicon and aluminum are replaced, and contaminant particles are dispersed in the aluminum, so that the Schottky interface between the upper electrode layer 13 and the semiconductor substrate 11 is present. There are no lattice defects or contaminating particles. Therefore, a Schottky diode with good electrical characteristics can be obtained.
[0028]
Next, electrical characteristics of the Schottky diode of the present invention will be described with reference to FIG.
[0029]
FIG. 6 is a graph showing current-voltage characteristics (hereinafter referred to as IV characteristics) of the Schottky diode of the present invention. The horizontal axis represents the voltage V applied to the Schottky diode, and the vertical axis represents the current I flowing through the Schottky diode on a logarithmic scale. The dotted line shows the IV characteristic of the conventional Schottky diode expressed by (Equation 1), the solid line shows the IV characteristic of the Schottky diode having an ideal Schottky interface expressed by (Equation 2), and the one-dot chain line shows ( The IV characteristics of the parallel resistance Rp expressed by Equation 3) are shown respectively.
[0030]
The circuit shown in FIG. 6 is an equivalent circuit of a conventional Schottky diode, and has a resistance Rs in series with the Schottky diode and a resistance Rp in parallel with the Schottky diode due to lattice defects and contaminants existing at the Schottky interface. It is a connected structure.
[0031]
Such resistances Rs and Rp cause the following problems in the conventional Schottky diode.
[0032]
When the current V and the voltage I are small, the Schottky diode exhibits almost the same IV characteristics as the parallel resistance Rp, and the current I flows through the parallel resistance Rp. That is, as compared with an ideal Schottky diode that does not have a parallel resistor Rp, a larger amount of current flows through the parallel resistor Vd / Rp. The current flowing through the parallel resistor Rp causes a leak current to increase.
[0033]
On the other hand, as the current I increases, the voltage drop across the series resistor Rs increases, and in order to obtain a desired current value, the voltage applied to the series resistor compared to an ideal Schottky diode without the series resistor Rs. An extra voltage must be applied by RsI. That is, power consumption increases.
[0034]
Thus, the conventional Schottky diode cannot obtain the ideal current-voltage characteristics of the Schottky diode.
[0035]
On the other hand, in the Schottky diode of the present invention, since there are no lattice defects or contaminants at the Schottky interface, parasitic resistances Rs and Rp do not occur. Therefore, the Schottky diode of the present invention can obtain the ideal current-voltage characteristic of the Schottky diode indicated by the solid line in FIG.
(Second embodiment)
FIG. 7 is a cross-sectional view showing the Schottky diode of the present embodiment. Unlike the first embodiment, the Schottky diode of the present embodiment has an inverted V-shape spreading downward, unlike the first embodiment.
[0036]
For example, as shown in FIG. 8 (a), when the semiconductor substrate 11 is etched when the insulating layer 12 is anisotropically etched to form the opening 17, the metal layer 13 in the next annealing step is etched. When aluminum atoms intrude into the silicon semiconductor substrate 11, the aluminum atoms intrude along the plane indicated by A in FIG. 8B and are replaced with silicon atoms, as well as along the plane indicated by B. However, aluminum atoms enter and are replaced with silicon atoms. As a result, a Schottky interface having a shape as shown in FIG. 7 is formed.
[0037]
Also in this embodiment, the same effect as that of the first embodiment can be obtained.
(Third embodiment)
In the first and second embodiments, the case where a Schottky diode is manufactured using a silicon single crystal semiconductor substrate having a {100} surface has been described. However, when a semiconductor substrate other than the {100} surface is used. Can also be applied. In this case, a characteristic Schottky interface shape can be obtained according to the crystal orientation plane of the surface of each semiconductor substrate.
[0038]
FIG. 9 is a cross-sectional view of a Schottky diode shown for the third embodiment of the present invention. In the present embodiment, the Schottky interface formed by the semiconductor substrate 11 on the {110} surface and the upper electrode layer 13 is formed in a rectangular shape. The point that the Schottky interface is the {111} plane of the semiconductor substrate 11 is the same as in the first and second embodiments.
[0039]
Since the Schottky diode of the third embodiment is the same as that of the first embodiment except that the crystal orientation plane of the surface of the semiconductor substrate 11 is {110}, description of the manufacturing method is omitted here.
[0040]
The present invention is not limited to the first, second and third embodiments described above. For example, in the above embodiment, a silicon single crystal wafer is assumed as the semiconductor substrate, but the present invention is based on silicon compounds such as silicon germanium (SiGe) and silicon carbide (SiC), carbon (C), and gallium arsenide (GaAs). , Indium phosphide (InP), gallium nitride (GaN), and other single crystal wafers.
[0041]
Moreover, although aluminum (Al) was assumed as a metal which penetrate | invades a semiconductor substrate, this invention is cobalt (Co), nickel (Ni), titanium (Ti), platinum (Pt), palladium (Pd), ruthenium (Ru). , Gold (Au), silver (Ag), copper (Cu), chromium (Cr) and niobium (Nb).
[0042]
Further, in each of the above-described embodiments, the case where the {111} plane of the semiconductor substrate is the Schottky interface has been described, but the Schottky interface may be formed by a plane other than the {111} plane. In order to form a Schottky interface including a surface other than the {111} plane of the semiconductor substrate, the annealing temperature, the annealing time, and the shape of the semiconductor substrate exposed from the opening of the insulator layer may be changed.
(Supplementary note 1) a semiconductor substrate whose surface is a first crystal orientation plane;
A Schottky diode comprising a metal portion made of metal atoms entering from the surface of the semiconductor substrate and forming a Schottky barrier on a second crystal orientation plane of the semiconductor substrate.
(Appendix 2) The semiconductor substrate is made of a single crystal of any one of Si, SiGe, SiC and C,
The Schottky diode according to appendix 1, wherein the metal atom is a substituted metal.
(Supplementary note 3) The Schottky diode according to supplementary note 2, wherein the first crystal orientation plane is a {100} plane and the second crystal orientation plane is a {111} plane.
(Supplementary note 4) The Schottky diode according to supplementary note 3, wherein the second crystal orientation plane is formed in a quadrangular pyramid shape.
(Supplementary note 5) The Schottky diode according to supplementary note 1, wherein the first crystal orientation plane is a {110} plane and the second crystal orientation plane is a {111} plane.
(Appendix 6) A step of forming a metal film on a semiconductor substrate;
And a step of replacing a partial region of the semiconductor substrate with metal atoms in the metal film that have penetrated along a specific crystal orientation plane of the semiconductor substrate.
(Supplementary note 7) The method for manufacturing a Schottky diode according to supplementary note 6, wherein the specific crystal orientation plane is a {111} plane.
(Appendix 8) The shot according to appendix 6, wherein the metal film is made of any one of Al, Co, Ni, Ti, Pt, Pd, Ru, Au, Ag, Cu, Cr, and Nb. A manufacturing method of a key diode.
(Supplementary note 9) The Schottky diode manufacturing method according to supplementary note 6, wherein in the replacing step, the semiconductor substrate is annealed at a temperature of 300 to 500 ° C. (Additional remark 10) The manufacturing method of the Schottky diode of Additional remark 6 characterized by annealing the said semiconductor substrate at the temperature of 350 thru | or 425 degreeC at the said substitution process.
[0043]
【The invention's effect】
As described above, according to the Schottky diode of the present invention, since the Schottky interface is formed by the replacement process of the semiconductor substrate and the upper electrode layer, it is possible to form a Schottky interface without unevenness even at the atomic level.
[0044]
In addition, even if the exposed portion of the semiconductor substrate is exposed to various atmospheres during the manufacturing process to cause lattice defects or become contaminated, the lattice defects disappear during the replacement process of the semiconductor substrate and the upper electrode layer, Since contaminants are dispersed in the upper electrode and do not remain on the Schottky interface, a clean Schottky interface can be obtained.
[0045]
Such a Schottky diode can improve electrical characteristics.
[0046]
Furthermore, since the Schottky diode of the present invention forms the Schottky interface three-dimensionally, the area required per element is reduced and the degree of integration can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the structure of a conventional Schottky diode.
2 (a) to 2 (c) are cross-sectional views showing a conventional method for manufacturing a Schottky diode.
FIGS. 3A to 3C are cross-sectional views showing problems in a conventional Schottky diode manufacturing method.
FIG. 4 is a cross-sectional view showing the structure of a Schottky diode according to the first embodiment of the present invention.
FIGS. 5A to 5D are cross-sectional views illustrating a method for manufacturing a Schottky diode according to the first embodiment of the present invention.
FIG. 6 is a graph showing current-voltage characteristics of a Schottky diode according to the present invention.
FIG. 7 is a cross-sectional view showing the structure of a Schottky diode according to a second embodiment of the present invention.
FIG. 8 is a cross-sectional view showing an insulator layer etching step according to the first and second embodiments of the present invention.
FIG. 9 is a cross-sectional view showing the structure of a Schottky diode according to a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Insulator layer, 3 ... Upper electrode layer,
4 ... lattice defect part, 5 ... contaminated part, 6 ... photoresist,
7 ... opening, 11 ... semiconductor substrate, 12 ... insulator layer,
13 ... upper electrode layer, 14 ... lattice defect, 16 ... photoresist,
17 ... Opening part, 18 ... Exposed part, 101 ... Lattice defect part,
102 ... Contaminated part

Claims (7)

A semiconductor substrate whose surface is a first crystal orientation plane;
A Schottky diode comprising a metal portion that is made of metal atoms entering from the surface of the semiconductor substrate and forms a Schottky barrier on a second crystal orientation plane that is the {111} plane of the semiconductor substrate. 2. The Schottky diode according to claim 1, wherein the semiconductor substrate is made of a single crystal of any one of Si, SiGe, SiC, C , GaAs , InP , and GaN . The metal atom is Al, Co, Ni, Ti, Pt, Pd, Ru, Au, Ag, Cu, Cr as well as Nb The Schottky diode according to claim 1, wherein the Schottky diode is made of any one of the above. Forming a metal film on a semiconductor substrate having a first crystal orientation surface ;
Intruding metal atoms in the metal film along a second crystal orientation plane which is the {111} plane of the semiconductor substrate ;
And a step of replacing the atoms constituting the semiconductor substrate with the invading metal atoms. The semiconductor substrate is Si, SiGe, SiC , C , GaAs , InP ,as well as GaN 5. The method of manufacturing a Schottky diode according to claim 4, comprising any one of the single crystals. The metal atom, Al, Co, Ni, Ti , Pt, Pd, Ru, Au, Ag, Cu, any one of claims 4 or 5, characterized in that consists of any one of Cr and Nb method of manufacturing a Schottky diode according to. In the step of the replacement method of the Schottky diode according to claim 6, characterized in that annealing in the temperature of the semiconductor substrate 300 to 500 ° C..

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