JP3967045B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and a manufacturing method thereof.
[0002]
[Prior art]
In the industrial power field, high-efficiency and large-capacity energy conversion elements are required for energy saving, and power converters such as inverters made of Si-based semiconductors have been used so far.
[0003]
Recently, it has been expected to realize a conversion device made of, for example, a SiC semiconductor that can be expected to operate with higher efficiency, but there are tens to hundreds of crystal defects called micropipes in the wafer. A large-area device having a wafer size level required as a power device could not be produced.
[0004]
Thus, in order to realize a high-power power converter, a wafer-size diode is required. Here, since the SiC semiconductor has physical properties such as a wide band gap, it is expected to realize a diode with low on-resistance.
[0005]
FIG. 2 is a perspective view of a conventional general SiC semiconductor wafer.
[0006]
As shown in this figure, on the surface of the SiC substrate 1, there are several tens to several hundreds of through-hole-like defects called micropipes 2 having a diameter of several microns to tens of microns and extending toward the inside of the substrate 1. .
[0007]
Here, a problem when a pn junction type diode is manufactured using such a SiC substrate will be described with reference to FIG.
[0008]
As shown in FIG. 3, the n-type substrate 11 is ion-implanted and annealed with Mg or the like to form a p-type layer 12 and then an upper electrode 13 is formed.
[0009]
Here, for example, at the locations indicated by the arrows 14 and 16 indicating the positions of the defects, in the ion implantation process, ions flying from above the wafer pass through the through holes and form the implantation layer 15 at a deep position in the substrate 11. . Even if the p-type layer is formed by diffusion, it is clear that the impurity diffuses through the through hole and the same problem occurs. A pn junction diode having an abnormal protrusion in the depth direction has a current Normal characteristics such as leakage and lack of diode breakdown voltage cannot be expected.
[0010]
Further, for example, the electrode material falls into a hole which is a larger defect as shown by the position of the arrow 16 to form a depressed portion 17 and adhere to the pn junction. At this time, the pn junction is short-circuited and does not exhibit diode characteristics.
[0011]
Further, when a pn junction type diode is formed using the SiC substrate 1, there are the following problems.
[0012]
(1) First, as shown in FIG. 4A, an n-type epi layer 18 is formed on an n-type substrate 11 including micropipes by an epitaxial growth method. At this time, a defective crystal region 19 having various crystal orientations and containing many crystal defects is formed in the vicinity of the micropipe. This is because the epitaxial growth depending on the crystal orientation of the side surface of the hole of the micropipe occurs, and when this also spreads in the lateral direction, it occurs because it is confronted with the growth layer epitaxially grown from the original substrate 11 surface. It is considered one.
[0013]
(2) Next, as shown in FIG. 4B, Mg or the like is ion-implanted and annealed to form the p-type layer 20.
[0014]
Here, in the annealing process after the ion implantation, the impurities implanted into the defective crystal region 19 diffuse abnormally deeply through the crystal grain boundaries and crystal defects that are present in the defect crystal region 19, and are jagged as shown in FIG. (Meaning that it is not flat) is formed. A diode having such a non-flat junction surface causes defects such as an increase in leakage current and a low breakdown voltage.
[0015]
Further, even when a metal is deposited on a semiconductor to form a Schottky diode as shown in FIG. 4A, a leakage current caused by poor crystallinity at the position of the defective crystal region 19 A breakdown voltage failure occurs and good diode characteristics cannot be obtained.
[0016]
[Problems to be solved by the invention]
As described above, even if an attempt is made to produce a large-area diode using a substrate having a micropipe, the occurrence of abnormal bonding, a drop in electrode material, or the position of a defective crystal region at the micropipe hole position. As a result, a leakage current and a breakdown voltage due to poor crystallinity occur, and there is a problem that a diode having normal characteristics cannot be realized.
[0017]
The present invention eliminates the above-mentioned problems and results from the occurrence of abnormal bonding, drop of electrode material, etc. occurring at the position of the micropipe hole in the semiconductor substrate, and poor crystallinity occurring at the position of the defective crystal region. It is an object of the present invention to provide a semiconductor element capable of preventing the occurrence of leakage current and breakdown voltage and a method for manufacturing the same.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides
[1] In the semi-conductor elements, concave n-type semiconductor substrate (21) including a defect is deposited from the surface side, filling the concave defect of an n-type semiconductor substrate (21) including the concave defects insulation The insulating film (23) is removed from the surface of the n-type semiconductor substrate (21) covered with the film (23) and the insulating film (23) until the surface of the n-type semiconductor substrate (21) is reached. The p-type layer (25) formed in the removed portion and the electrode (26) formed on the p-type layer (25) are provided.
[0019]
[2] In a semiconductor element, an insulating film is deposited from the surface side of an n-type semiconductor substrate (31) including a concave defect and embeds the concave defect of the n-type semiconductor substrate (31) including the concave defect. (33) and removing the insulating film (33) from the surface side of the n-type semiconductor substrate (31) covered with the insulating film (33) until reaching the surface of the n-type semiconductor substrate (31), The n-type epi layer (35) formed in the removed portion, the p-type conductive layer (36) formed on the n-type epi layer (35), and the p-type conductive layer (36) And an electrode (37) formed thereon.
[0020]
[3] The semiconductor element according to [1] or [2] , wherein the semiconductor substrate is silicon and the insulating film is a silicon oxide film.
[0021]
[4] The semiconductor element according to [1] or [2] , wherein the semiconductor substrate is SiC and the insulating film is a silicon nitride film.
[0022]
[5] The method of manufacturing a semi-conductor elements, deposited an n-type semiconductor substrate (21) surface side including the concave defects, the concave defect of an n-type semiconductor substrate (21) including the concave defects forming a write-free insulation Enmaku (23) filling said from the surface of the insulating film n-type semiconductor substrate covered with (23) (21) to reach the n-type semiconductor substrate (21) surface The step of removing the insulating film (23) , the step of forming a p-type layer (25) in the removed portion, and the step of forming an electrode (26) on the p-type layer (25) are performed. It is characterized by that.
[0023]
[6] In the method of manufacturing a semiconductor device, the n-type semiconductor substrate (31) including a concave defect is deposited from the surface side, and the concave defect of the n-type semiconductor substrate (31) including the concave defect is embedded. A step of forming an insulating film (33), and the insulating film (33) from the surface side of the n-type semiconductor substrate (31) covered with the insulating film (33) to the surface of the n-type semiconductor substrate (31). 33), a step of forming an n-type epi layer (35) at the removed portion, and a step of forming a p-type conductive layer (36) on the n-type epi layer (35). And a step of forming an electrode (37) on the p-type conductive layer (36).
[0024]
[7] The method of manufacturing a semi-conductor device, comprising the steps of forming only a thickness of the insulating film filling the concave defect in the semiconductor substrate (41) (42) comprising a concave defect, the semiconductor substrate (41) removing the surface of the insulating film (42), and wherein the applying and the step of forming a single crystal layer is epitaxially grown (43) on the surface of the semiconductor substrate (41).
[0025]
[ 8 ] The method for manufacturing a semiconductor device according to [ 7 ], wherein the epitaxial growth is performed so that a side surface of the concave defect is not exposed.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0027]
FIG. 1 is a cross-sectional view of a manufacturing process of a semiconductor device showing a first embodiment of the present invention. Here, a junction type large diode is manufactured.
[0028]
(1) First, as shown in FIG. 1A, a micropipe 22 is present in a semiconductor device (see steps (4) and (5) described later) of an n-type substrate 21 to be used.
[0029]
(2) Therefore, as shown in FIG. 1B, for example, a silicon oxide film 23 is grown to a thickness equal to or larger than the radius of the micropipe 22 by a CVD (chemical vapor deposition) method. At this time, the micropipe 22 (hole) has a structure embedded with the silicon oxide film 23.
[0030]
(3) Next, as shown in FIG. 1C, the silicon oxide film 23 is etched and removed from the surface side of the substrate 21, and the etching is stopped when the substrate 21 is reached. Then, a structure in which only the micropipes 22 (holes) are embedded with the silicon oxide film 24 is obtained.
[0031]
(4) Next, as shown in FIG. 1D, after p-type impurity ions are implanted, a p-type layer 25 is formed by heat treatment annealing.
[0032]
(5) Finally, as shown in FIG. 1 (e), an electrode 26 is formed to obtain a semiconductor element on which a large junction diode is formed.
[0033]
Thus, according to this embodiment, as shown in FIG. 1C, the defective portion (micropipe) 22 of the wafer is buried with the insulating silicon oxide film 23 (24). Therefore, in such a situation, even if ion implantation is performed as shown in FIG. 1D, ions flying into the micropipe 22 (hole) are blocked by the silicon oxide film 24 filling the hole. As a result, the micropipe 22 cannot penetrate deeply.
[0034]
As a result, the bottom surface (junction) of the p-type layer 25 formed inside the substrate 21 is flat without being affected by the micropipes 22. Here, the silicon oxide film 24 in which the hole is filled is thermally stable, and even if impurity ions are implanted therein, the impurities hardly reach the substrate 21 by diffusion.
[0035]
Here, for example, when the substrate 21 is made of SiC, it is preferable to use a silicon nitride film instead of the silicon oxide film used above. The reason is that since the densities of SiC and silicon nitride film are approximately the same, the impurity implantation depth is also approximately the same, and the bottom surface of the p-type layer 25 is flat.
[0036]
Of course, as shown in FIG. 1E, since the electrode 26 does not fall into the micropipe, there is no possibility of short-circuiting the pn junction.
[0037]
As described above, according to the first embodiment of the present invention, it is possible to produce a large diode even for a wafer including a concave defect such as a micropipe.
[0038]
In the embodiments of the present invention, a method of manufacturing a large diode by embedding micropipe defects peculiar to a SiC substrate with an insulating film to avoid abnormal junction formation and electrode drop is described. However, the present invention can make it possible to form a conductive layer and an electrode regardless of the presence of a defect, and a similar concave defect can be applied to a semiconductor substrate or an epitaxial substrate other than SiC. Thus, it is apparent that the embodiment of the present invention can be applied even when there is a factor that prevents the formation of uniform bonding and the formation of normal electrodes. Furthermore, in the present embodiment, a large junction diode at the wafer size level has been described, but it is obvious that the present invention can be applied to other field effect transistors and bipolar transistors.
[0039]
Next, a second embodiment of the present invention will be described.
[0040]
FIG. 5 is a cross-sectional view of a manufacturing process of a semiconductor device showing a second embodiment of the present invention.
[0041]
In this embodiment, an example of manufacturing a junction type large diode will be described.
[0042]
(1) First, as shown in FIG. 5A, the n-type substrate 31 to be used has, for example, a micropipe 32 which is a concave defect.
[0043]
(2) Therefore, as shown in FIG. 5B, for example, a silicon oxide film 33 is grown to a thickness equal to or larger than the radius of the micropipe 32 by a CVD (chemical vapor deposition) method. At this time, the micropipe 32 has a structure embedded with the silicon oxide film 33.
[0044]
(3) Next, as shown in FIG. 5C, the silicon oxide film 33 is removed by etching from the surface side of the substrate 31, and when the substrate 31 is reached, the etching is stopped. Then, a structure in which only the hole of the micropipe 32 is embedded with the silicon oxide film 34 is obtained.
[0045]
(4) Next, as shown in FIG. 5D, an n-type epi layer 35 is formed by an MBE (molecular beam epitaxy) method or an MOCVD (metal organic chemical deposition) method. At this time, no epitaxial growth is performed on the silicon oxide film 34 at the position of the micropipe 32, and a region 35A where no epitaxial growth is performed is formed as shown in an enlarged view in FIG. Bonding occurs above the epitaxially grown silicon oxide film 34 grown in the lateral direction. That is, the thickness of the epi layer 35 is set to a thickness larger than that at which the epi layer 35 is bonded above the silicon oxide film 34.
[0046]
(5) Next, as shown in FIG. 5E, p-type impurity ion implantation and p-type epi growth are performed to form a p-type conductive layer 36, and finally an electrode 37 is formed. The junction diode is obtained.
[0047]
As described above, according to the second embodiment of the present invention, as shown in FIG. 5D, since the defective portion (micropipe) of the wafer is buried with the insulating film, the epitaxial growth is not performed. Due to the lateral growth of epi from the region other than the insulating film, the defective portion of the wafer is also covered with the epi layer.
[0048]
That is, according to the present embodiment, it is possible to form an epi layer that does not include defects caused by those defects even on a wafer including a concave defect that is fatal to bonding and electrodes.
[0049]
As a result, a large-sized diode that does not have poor electrical characteristics due to crystal defects can be realized.
[0050]
Next, a third embodiment of the present invention will be described.
[0051]
In the step shown in FIG. 5C, if the silicon oxide film 33 is excessively removed by etching, the surface of the silicon oxide film 34 may be slightly recessed from the substrate 31. This is because, in the etching method of the silicon oxide film 33, when the etching rate of the silicon oxide film 33 is higher than the etching rate of the substrate 31 (for example, in the etching of the silicon oxide film 33, a plasma etching method using a general freon gas is used. In some cases). The state of this part is shown in FIG.
[0052]
That is, when the side surface exposed portion 31A occurs, a crystal orientation different from the surface of the substrate 31 appears, and epi-growth with a crystal orientation different from the surface of the substrate 31 occurs, which causes a crystal defect.
[0053]
Therefore, a method in which the side surface of the concave defect described above is not exposed will be described with reference to FIG.
[0054]
(1) First, as shown in FIG. 8A, the concave defects of the substrate 41 are filled with a silicon oxide film 42, as in FIG. 5C of the second embodiment. At this time, as shown in FIG. 7, the silicon oxide film is excessively etched, and the surface of the silicon oxide film 42 is lower than the surface of the substrate 41.
[0055]
(2) Therefore, as shown in FIG. 8B, the substrate 41 is selectively etched until the surface thereof is below the surface of the silicon oxide film. If the substrate 41 is made of SiC at this time, for example, if dry etching with chlorine gas or the like is performed, the etching rate of SiC is faster than that of the silicon oxide film, so that the above situation can be realized.
[0056]
(3) Next, as shown in FIG. 8C, when epitaxial growth is performed, growth is performed only in accordance with the crystal orientation of the surface of the substrate 41, and a single crystal layer 43 without crystal defects is obtained.
[0057]
Thus, according to the third embodiment of the present invention, as shown in FIG. 8A, even when the surface of the insulating film is slightly recessed from the substrate surface during etching, the substrate 41 side is etched. By reducing the thickness, a single crystal plane can be exposed on the substrate 41. As a result, an epitaxial growth layer having no defects can be realized on the entire surface of the substrate.
[0058]
In other words, according to the present embodiment, a method capable of reliably performing a defective portion insulating film embedding process that is actually difficult to perform is provided, and as a result, an epitaxial layer that does not include a defect. And a large diode having good characteristics can be manufactured.
[0059]
In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and they are not excluded from the scope of the present invention.
[0060]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
[0061]
(1) A large semiconductor device such as a diode can be manufactured even for a wafer including a concave defect such as a micropipe.
[0062]
(2) It is possible to form an epi layer that does not include defects caused by those defects even on wafers that include concave defects that are fatal to bonding and electrodes.
[0063]
(3) Even when the surface of the insulating film is slightly dented from the substrate surface during etching, a single crystal plane can be exposed on the substrate by etching and lowering the substrate side. An epitaxial growth layer having no defects can be realized on the entire surface of the substrate.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a manufacturing step of a semiconductor element showing a first embodiment of the invention.
FIG. 2 is a perspective view of a conventional general SiC semiconductor wafer.
FIG. 3 is an explanatory diagram of a problem when a pn junction type diode is manufactured using a conventional SiC substrate.
FIG. 4 is an explanatory diagram of another conventional problem.
FIG. 5 is a cross-sectional view of a manufacturing process of a semiconductor device showing a second embodiment of the invention.
6 is an enlarged cross-sectional view of a part A in the step of FIG. 5 (d).
FIG. 7 is a diagram showing problems in the process of FIG. 5 (c).
8 is a cross-sectional view of a manufacturing step of a semiconductor element showing a third embodiment of the invention. FIG.
[Explanation of symbols]
21, 31, 41 Substrate showing n-type conductivity 22, 32 Micropipe 23, 33, 42 Silicon oxide film 24, 34 Silicon oxide film filling hole 25 p-type layer 26, 37 Electrode 31A Side surface exposed portion 35 n-type epi layer 35A region where epi growth is not performed 36 p-type conductive layer 43 single crystal layer

Claims (8)

(A) an insulating film (23) deposited from the surface side of an n-type semiconductor substrate (21) including a concave defect and embedding the concave defect of the n-type semiconductor substrate (21) including the concave defect; ,
(B) The insulating film (23) is removed from the surface side of the n-type semiconductor substrate (21) covered with the insulating film (23) until reaching the surface of the n-type semiconductor substrate (21), and the removal A p-type layer (25) formed in the formed site;
( C ) A semiconductor device comprising an electrode (26) formed on the p-type layer (25) . (A) an insulating film (33) which is deposited from the surface side of an n-type semiconductor substrate (31) including a concave defect and embeds the concave defect of the n-type semiconductor substrate (31) including the concave defect; ,
(B) The insulating film (33) is removed from the surface side of the n-type semiconductor substrate (31) covered with the insulating film (33) until reaching the surface of the n-type semiconductor substrate (31), and the removal An n-type epi layer (35) formed in the formed region;
(C) a p-type conductive layer (36) formed on the n-type epi layer (35);
(D) A semiconductor device comprising an electrode (37) formed on the p-type conductive layer (36). The semiconductor device according to claim 1 or 2, wherein said semiconductor substrate is a silicon semiconductor device, wherein the insulating film is a silicon oxide film. The semiconductor device according to claim 1 or 2, wherein said semiconductor substrate is a SiC, a semiconductor device, wherein the insulating film is a silicon nitride film.
(A) depositing an n-type semiconductor substrate (21) surface side of including a concave defect, filling the concave defect of an n-type semiconductor substrate (21) including the concave defect write no absolute Enmaku (23 )
(B) removing the insulating film (23) from the surface side of the n-type semiconductor substrate (21) covered with the insulating film (23) until reaching the surface of the n-type semiconductor substrate (21) ;
(C) forming a p-type layer (25) at the removed site;
(D) a method of manufacturing a semiconductor device characterized by performing the step of forming an electrode (26) on the p-type layer (25) on. (A) An n-type semiconductor substrate (31) including a concave defect is deposited from the surface side, and an insulating film (33) for embedding the concave defect of the n-type semiconductor substrate (31) including the concave defect is formed. And the process of
(B) removing the insulating film (33) from the surface side of the n-type semiconductor substrate (31) covered with the insulating film (33) until reaching the surface of the n-type semiconductor substrate (31);
(C) forming an n-type epi layer (35) at the removed site;
(D) forming a p-type conductive layer (36) on the n-type epi layer (35);
(E) A process for forming an electrode (37) on the p-type conductive layer (36).
(A) forming an insulating film (42) having a thickness sufficient to embed the concave defects in the semiconductor substrate (41) including the concave defects;
(B) removing the insulating film (42) on the surface of the semiconductor substrate (41) ;
(C) a method of manufacturing a semiconductor device characterized by performing the steps of forming a single crystal layer (43) epitaxially grown on the surface of the semiconductor substrate (41). The method of manufacturing a semiconductor device according to claim 7, a method of manufacturing a semiconductor device characterized by causing the epitaxial growth so as not to expose the side surfaces of the concave defects.

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