JP2007266103A - Manufacturing method for semiconductor device and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a semiconductor device having low operation resistance and switching loss and excellent switching characteristics. <P>SOLUTION: An oxygen-rich layer (4) having an oxygen concentration higher than the other depth regions (16 and 17) of a semiconductor substrate (1) is formed to the specified depth region (15) of the semiconductor substrate (1), and the semiconductor substrate (1) is irradiated with a radiation and a recombination region (5) is formed to the oxygen-rich layer (4). When the oxygen-rich layer (4) is formed, the semiconductor substrate (1) is irradiated with the radiation and atomic vacancies are formed among the crystal lattices of the semiconductor substrate (1), the recombination region (5) is formed to the oxygen-rich layer (4) by composite faults formed by bonding oxygen and the atomic vacancies. The recombination region (5) functions as a carrier capture region controlling the lifetime of carriers in the specified depth region (15) of the semiconductor substrate (1). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a semiconductor device and a semiconductor device, and more particularly to a method of manufacturing a semiconductor device that controls the lifetime of a semiconductor device by irradiating a semiconductor substrate with radiation such as an electron beam and a semiconductor device formed by the manufacturing method.

  A semiconductor substrate is irradiated with radiation such as an electron beam, γ-ray, neutron beam, or ion beam, and a crystal defect (“recombination center” or “lifetime control region”) can be caused by radiation in a predetermined region of the semiconductor substrate. The lifetime control technology for controlling the lifetime of the semiconductor substrate carrier is known. By controlling the lifetime of the carrier of the semiconductor substrate, the response characteristics of the semiconductor device can be improved. The lifetime control technology for irradiating a semiconductor substrate with radiation is superior in lifetime controllability and reproducibility compared to lifetime control in which heavy metal atoms such as gold or platinum are introduced into a semiconductor substrate.

  In particular, in lifetime control technology that irradiates various ions such as protons, crystal defects are formed intensively by ion beams in a limited area in the thickness direction of the semiconductor substrate centering on the range of the ion beam. Highly effective lifetime control. On the other hand, in the lifetime control technology for irradiating an electron beam, since an electron beam having a long range is transmitted through the entire thickness direction of the semiconductor substrate, generally, crystal defects are formed in the entire thickness direction of the semiconductor substrate. It was used as a lifetime control.

  FIG. 6 shows a semiconductor substrate (1), an N − type semiconductor region (11) formed on one main surface (1a) side of the semiconductor substrate (1), and an N − type semiconductor region (11). An N + type semiconductor region (12) formed on the other main surface (1b) side of the semiconductor substrate (1), and one main surface (1a) of the semiconductor substrate (1) in the N− type semiconductor region (11). ) Side P + type semiconductor region (13), and a diode device forming a PN junction with the P + type semiconductor region (13), the N− type semiconductor region (11) and the N + type semiconductor region (12) (20) is illustrated. An insulating film (2) having an opening (2a) formed adjacent to the P + type semiconductor region (13) is formed on one main surface (1a) of the semiconductor substrate (1), and is made of a metal film. The upper electrode (emitter electrode) (3) is fixed to a part of the insulating film (2) and the P + type semiconductor region (13) through the opening (2a) of the insulating film (2). A lower electrode (collector electrode) (6) is fixed to the other main surface (1b) of the semiconductor substrate (1) adjacent to the N + type semiconductor region (12). In this type of semiconductor device, for example, a dynamitron accelerator (not shown) is used, and as shown in FIG. 7, the semiconductor substrate (1) is irradiated with an electron beam (25) accelerated at an acceleration voltage of about 2.0 MeV. Thus, crystal defects can be appropriately formed over the entire thickness direction of the semiconductor substrate (1).

  As described above, when crystal defects are formed over the entire thickness direction of the semiconductor substrate (1), the carrier lifetime can be shortened and the switching characteristics of the semiconductor device can be improved, but the internal resistance of the semiconductor substrate increases. As a result, there arises a problem that the operating resistance (ON resistance) of the semiconductor device (20) increases. Therefore, in recent years, there has been an attempt to form a crystal defect in a specific region in the thickness direction without forming the crystal defect in the entire thickness direction of the semiconductor substrate (1). If crystal defects are locally formed in the thickness direction of the semiconductor substrate (1), a semiconductor device having excellent electrical characteristics with relatively low operating resistance and improved switching characteristics can be formed.

  A method for manufacturing a semiconductor device having crystal defects in a specific region in the thickness direction of the semiconductor substrate is disclosed in, for example, Patent Document 1 below. According to Patent Document 1, a metal mask made of aluminum having a thickness of 30 μm and stainless steel having a thickness of 50 μm is arranged on the main surface of a semiconductor substrate, and a light ion beam accelerated by an acceleration voltage of 20.0 MeV is used. By irradiating the semiconductor substrate through the metal mask, crystal defects can be formed in a specific region in the thickness direction of the semiconductor substrate.

Japanese Patent Laid-Open No. 4-214673

However, in the manufacturing method of the semiconductor device of Patent Document 1, when irradiating an electron beam, electrons with a light mass easily pass through the metal mask, so that a crystal defect cannot be formed in a specific region in the thickness direction of the semiconductor substrate. It was. Even when other radiation is used, in order to control the depth of crystal defects to be formed, the thickness of the metal mask must be controlled, which is not practical.
Accordingly, an object of the present invention is to provide a method for manufacturing a semiconductor device capable of easily and reproducibly forming crystal defects in a desired specific region in the thickness direction of a semiconductor substrate, and a semiconductor device formed by the manufacturing method. And

The manufacturing method of a semiconductor device according to the present invention is a method for producing an oxygen-rich layer (4) having a higher oxygen concentration in a predetermined depth region (15) of a semiconductor substrate (1) than in other depth regions (16, 17) of the semiconductor substrate (1). ) And a process of irradiating the semiconductor substrate (1) with radiation to form a recombination region (5) in the oxygen-rich layer (4). After forming the oxygen-rich layer (4), the semiconductor substrate (1) is irradiated with radiation to form atomic vacancies between the crystal lattices of the semiconductor substrate (1). A recombination region (5) is formed in the oxygen-rich layer (4) by the composite defect. The recombination region (5) serves as a carrier capture region that controls the lifetime of carriers in a predetermined depth region (15) of the semiconductor substrate (1). Therefore, it is possible to obtain a semiconductor device having a relatively low operating resistance and excellent switching characteristics. By forming the oxygen rich layer (4) in the desired and predetermined depth region (15) of the semiconductor substrate (1), the depth and thickness of the recombination region (5) formed in the semiconductor substrate (1) can be reduced. Can be controlled.
A semiconductor device according to the present invention includes a semiconductor substrate (1) on which at least one PN junction is formed. The semiconductor substrate (1) has atomic vacancies in a predetermined depth region (15) of the semiconductor substrate (1). It has a recombination region (5) formed by a composite defect formed by bonding with oxygen. The lifetime of carriers in the semiconductor substrate (1) can be controlled by the recombination region (5) formed by a composite defect formed by combining atomic vacancies and oxygen.

  According to the present invention, it is possible to provide a semiconductor device having excellent electrical characteristics in which a recombination region is favorably formed in a specific region in the thickness direction of a semiconductor substrate, low operating resistance, and improved switching characteristics. .

  A semiconductor device manufacturing method and an embodiment in which the semiconductor device is applied to a diode device and the manufacturing method thereof will be described below with reference to FIGS. In this embodiment mode, the lifetime of the carrier of the semiconductor device is controlled by irradiation with an electron beam. However, in these drawings, parts that are substantially the same as those shown in FIGS. 6 and 7 are given the same reference numerals, and descriptions thereof are omitted.

  When the diode device (10) of the present embodiment shown in FIG. 1 is formed, a semiconductor substrate (1) shown in FIG. 2 formed of a single crystal silicon wafer is prepared. The semiconductor substrate (1) has an N− type semiconductor region (11), an N + type semiconductor region (12), and a P + type semiconductor region (13). For convenience, the illustrated semiconductor substrate (1) represents a single semiconductor chip having a single P + type semiconductor region (13), but the actual semiconductor substrate (1) is the X-axis direction of the semiconductor substrate (1). And a structure in which the semiconductor chip is repeatedly formed in the Y-axis direction. In this embodiment, together with the well-known semiconductor substrate manufacturing method, the illustration of the semiconductor substrate in which a large number of semiconductor chips are aligned is omitted.

  Next, as shown in FIG. 3, oxygen is introduced into the predetermined depth region (15) of the semiconductor substrate (1) from the entire surface of one main surface (1a) of the semiconductor substrate (1). That is, oxygen is not introduced throughout the thickness direction of the semiconductor substrate (1), but is locally introduced from one main surface (1a) of the semiconductor substrate (1) into the region (15) having a predetermined depth. . By this step, the oxygen rich layer (4) having a higher oxygen concentration than the other depth regions (16, 17) of the semiconductor substrate (1) is formed in the predetermined depth region (15) of the semiconductor substrate (1). . In the present embodiment, a region adjacent to one main surface (1a) of the semiconductor substrate (1) not included in the predetermined depth region (15) is set as one other depth region (16), and the other The region adjacent to the main surface (1b) is the other depth region (17). The P + type semiconductor region (13) is formed in one other depth region (16) of the semiconductor substrate (1).

For example, a well-known cyclotron accelerator (not shown) irradiates the semiconductor substrate (1) with oxygen ions (24), and introduces interstitial oxygen atoms or molecules into a predetermined depth region (15) of the semiconductor substrate (1). can do. If oxygen ions (24) are implanted with an acceleration voltage of about 1.0 MeV to 50.0 MeV by a cyclotron accelerator or a vandegraph accelerator, a depth of about 15 μm to 20 μm from one main surface (1a) of the semiconductor substrate (1). An oxygen rich layer (4) having a higher oxygen concentration than the other depth regions (16, 17) can be formed in the thickness region (15) with a thickness of about 5 μm. The semiconductor substrate (1) may contain oxygen atoms or molecules in the silicon during the production of the silicon ingot or wafer for reasons such as increasing the strength of the substrate. Therefore, the oxygen rich layer (4) formed in the region (15) of a predetermined depth is 1.2 times or more, preferably 2.0 times or more compared with other depth regions (16, 17). Having an oxygen concentration of For example, if the oxygen concentration in the other depth regions (16, 17) is about 1.0 × 10 ¹⁵ atoms / cm ³ , the oxygen concentration in the oxygen rich layer (4) is 1.2 × 10 ¹⁵ atoms / cm ^3. cm ³ or more, preferably 2.0 × 10 ¹⁵ atoms / cm ³ or more. If the oxygen concentration in the oxygen rich layer (4) is less than 1.2 times that in the other depth regions (16, 17), the semiconductor substrate (1) is irradiated with an electron beam (25) in the next step. However, complex defects that function well as a carrier trapping region cannot be locally formed only in the oxygen-rich layer (4). In this embodiment, since the P + type semiconductor region 13 is formed at a depth of about 13 μm from one main surface 1a of the semiconductor substrate 1, the P + type semiconductor region 13 and the N− type semiconductor are formed. The oxygen rich layer (4) can be formed at a position slightly deeper than the PN junction formed at the interface with the region (11).

  Subsequently, as shown in FIG. 4, the semiconductor substrate (1) is irradiated with an electron beam (25) to form a recombination region (5) in the oxygen rich layer (4) as shown in FIG. The electron beam (25) is irradiated to the entire surface of one main surface (1a) of the semiconductor substrate (1) to form atomic vacancies between crystal lattices of the semiconductor substrate (1). The electron beam (25) is introduced into the entire thickness direction of the semiconductor substrate (1) as in the prior art, but in the oxygen-rich layer (4), oxygen introduced into the silicon crystal lattice and the electron beam ( 25) bonds with the atomic vacancies formed in the silicon to form a composite defect. The composite defect functions well as a carrier trapping region and can form a recombination region (5) in the oxygen-rich layer (4). As mentioned above, since the electron beam (25) is introduced to the entire thickness direction of the semiconductor substrate (1), the electron beam (16, 17) other than the oxygen-rich layer (4) ( 25) Atomic vacancies are formed. However, since the oxygen density of the other depth regions (16, 17) is lower than that of the oxygen-rich layer (4), the atomic vacancies formed in the other depth regions (16, 17) And does not form a composite defect that functions well as a carrier trapping region.

  For example, a compound defect can be formed in the oxygen-rich layer (4) of the semiconductor substrate (1) by irradiating the electron beam (25) to the semiconductor substrate (1) with a well-known dynamitron accelerator (not shown). When an electron beam (25) is injected at an acceleration voltage of about 0.5 MeV to 5.0 MeV by a dynamitron accelerator, the electron beam (25) is irradiated to the entire thickness direction of the semiconductor substrate (1), and the semiconductor substrate Combines oxygen atoms or molecules in the oxygen-rich layer (4) of (1) with atomic vacancies formed by irradiation of the electron beam (25), and functions well as a carrier trapping region in the oxygen-rich layer (4) Composite defects can be formed. In the present embodiment, since the irradiation density of the electron beam (25) is set to about 1/2 to 1/4 of the manufacturing method of the conventional semiconductor device (20), other depth regions of the semiconductor substrate (1) ( 16, 17) are formed with few atomic vacancies as compared with the conventional semiconductor device (20). Therefore, the other depth regions (16, 17) of the semiconductor substrate (1) hardly function as the recombination region (5). As a result, by this method, a recombination center is formed from one main surface (1a) of the semiconductor substrate (1) to a depth region (15) of about 15 μm to 20 μm compared to the other depth regions (16, 17). A high-density recombination region (5) can be formed. Since the oxygen-rich layer (4) can be formed relatively easily with a predetermined thickness in the desired depth region (15) of the semiconductor substrate (1), the electron beam (25) is used to form the semiconductor substrate (1). The recombination region (5) can be formed with a predetermined thickness in the desired depth region (15).

  Next, the semiconductor substrate (1) in which the recombination region (5) is formed is annealed (heated) to stabilize crystal defects formed in the region (15) of a predetermined depth of the semiconductor substrate (1). Make it. In addition, this annealing treatment can remove or reduce crystal defects or lattice defects formed in other depth regions (16, 17) of the semiconductor substrate (1). The annealing process is, for example, a heating process of 200 ° C. to 400 ° C., preferably 300 ° C. for 1 hour. When heated at a temperature lower than 200 ° C., crystal defects formed in other depth regions (16, 17) cannot be removed satisfactorily. Further, heating at a temperature exceeding 400 ° C. is not preferable because composite defects that form the recombination region (5) are also reduced.

Finally, the insulating film (2) and the upper electrode (3) are formed on one main surface (1a) of the semiconductor substrate (1), and the lower electrode (1b) is formed on the other main surface (1b) of the semiconductor substrate (1). 6) is formed to complete the diode device (fast recovery diode) (10) shown in FIG. For example, the insulating film (2) is formed of a silicon oxide film (SiO ₂ ). The upper electrode (3) is formed by vapor-depositing aluminum, and the lower electrode (6) is formed by fixing a laminated electrode of aluminum, titanium and nickel.

  According to the manufacturing method of the semiconductor device, an oxygen-rich layer (4) is formed in a desired and predetermined depth region (15) of the semiconductor substrate (1), and the recombination region (5) is formed in the semiconductor substrate (1). The depth and thickness of the film can be controlled. As a result, the semiconductor device (10) having a relatively low operating resistance and excellent switching characteristics can be easily manufactured. The diode device (10) formed by the above manufacturing method has a recombination region (5) formed by a composite defect formed by combining atomic vacancies and oxygen in a predetermined depth region (15) of the semiconductor substrate (1). ). A composite defect functions well as a carrier trapping region as compared with a simple isolated defect such as an atomic vacancy or an interstitial atom.

  The present invention is not limited to the embodiment described above, and various modifications can be made. You may apply this invention to the manufacturing method of other semiconductor devices, such as IGBT or a thyristor. Further, the present invention is not limited to the lifetime control of the semiconductor device (10) by the electron beam (25), and the present invention may be applied to the lifetime control by other radiation that forms atomic vacancies in silicon. You may change the order of the manufacturing process of a semiconductor device suitably. In this embodiment, after forming the recombination region (5) in the semiconductor substrate (1), the insulating film (2), the upper electrode (3), and the lower electrode (6) are formed in the semiconductor substrate (1). However, after forming any or all of the insulating film (2), the upper electrode (3) and the lower electrode (6) on the semiconductor substrate (1), the oxygen-rich layer (4) or recombination on the semiconductor substrate (1) Region (5) may be formed. Further, the oxygen-rich layer (4) is formed over the entire planar direction of the semiconductor substrate (1). Only oxygen may be introduced to form the oxygen rich layer (4) and the recombination region (5).

  The manufacturing method of the semiconductor device described in this embodiment mode is merely an example, and unless otherwise specified in the claims, the present invention relates to an oxygen concentration, an irradiation rate of oxygen and radiation, an annealing temperature and time, a semiconductor substrate ( It is not limited by 1) and various set values such as the dimensions of the depth regions (15, 16, 17) and the type of each device that emits oxygen or radiation.

  The present invention can be favorably applied to a semiconductor device such as a diode, a transistor such as an IGBT, a thyristor, or an IC, and a manufacturing method thereof.

Sectional drawing which shows the manufacturing method of the semiconductor device by this invention, and embodiment of a semiconductor device Sectional view of the semiconductor substrate of FIG. Cross section of FIG. 2 irradiated with oxygen ions Cross-sectional view of FIG. 3 irradiated with an electron beam 4 is a cross-sectional view of FIG. 4 where a recombination region is formed. Sectional view showing a conventional semiconductor device Sectional view of FIG. 6 irradiated with an electron beam

Explanation of symbols

  (1) ・ ・ Semiconductor substrate, (4) ・ ・ Oxygen rich layer, (5) ・ ・ Recombination region, (15) ・ ・ Predetermined depth region, (16,17) ・ ・ Other depth regions, (24) ... Oxygen ions, (25) ... Electron beams (radiation),

Claims (4)

Forming an oxygen-rich layer having a higher oxygen concentration than other depth regions of the semiconductor substrate in a predetermined depth region of the semiconductor substrate;
Irradiating the semiconductor substrate with radiation to form a recombination region in the oxygen-rich layer. The process of forming the oxygen rich layer is:
The method for manufacturing a semiconductor device according to claim 1, comprising a step of irradiating the semiconductor substrate with oxygen ions and introducing oxygen into a predetermined depth region of the semiconductor substrate. The process of forming the recombination region includes:
The semiconductor substrate on which the oxygen-rich layer is formed is irradiated with an electron beam to form atomic vacancies in the semiconductor substrate, and a composite defect formed by combining oxygen and the atomic vacancies in the oxygen-rich layer. The manufacturing method of the semiconductor device of Claim 1 or 2 including the process to form. Comprising the semiconductor substrate on which at least one PN junction is formed;
The semiconductor device according to claim 1, wherein the semiconductor substrate has a recombination region formed by a composite defect formed by combining atomic vacancies and oxygen in a predetermined depth region of the semiconductor substrate.

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