JP2006278866A - Manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form crystal defective regions at specific depths in a semiconductor device. <P>SOLUTION: An unevenly thick metal film (2) is formed on one principal surface (1a) of a semiconductor substrate 1 by plating metal of one kind or two kinds or more selected from a group comprising aluminum (Al), copper (Cu), platinum (Pt), lead (Pb) or their alloys; and exposed surfaces (2a) of the metal film (2) are mechanically cut or polished to flatten the exposed surfaces (2a) of the metal film (2). Recesses (3) are subsequently formed by etching the exposed surfaces (2a) of the flattened metal film (2), and radiation (5) is irradiated to the semiconductor substrate (1) through the metal film (2) where the recesses (3) are formed to form the crystal defective regions (6) at almost even depths D<SB>1</SB>, D<SB>2</SB>in the semiconductor substrate (1). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor element such as a transistor or a diode, and more particularly to a method for manufacturing a semiconductor element including a step of forming a crystal defect region by irradiation with radiation such as an electron beam, γ-ray, neutron beam or ion beam.

  The lifetime control technology for semiconductor devices using radiation such as electron beam, gamma ray, neutron beam or ion beam is compared with the lifetime control technology using heavy metal diffusion such as gold (Au) or platinum (Pt). Thus, it is known that the lifetime is excellent in control and reproduction. In particular, in a lifetime control technology using irradiation of various ion beams such as protons, a region in which a crystal defect region formed by ion beam irradiation is limited to the thickness direction of the semiconductor substrate centering on the range of the ion beam Therefore, the lifetime can be controlled with high accuracy.

  By the way, when the crystal defect region is formed over the entire semiconductor substrate constituting the semiconductor element, the internal resistance of the semiconductor substrate increases due to the generation of the crystal defect region, and the operating resistance (for example, on-resistance) of the semiconductor element increases. Occurs. Therefore, a technique is known in which crystal defects are selectively deeply formed in a specific region in a direction along the main surface of the semiconductor substrate without forming the crystal defect region with a uniform depth over the entire semiconductor substrate. For example, in Patent Document 1 below, stainless steel in which a thin film (absorber) of a metal such as aluminum is brought into contact with one electrode (for example, collector electrode on the back surface) side of a semiconductor element, and a large number of fine holes are formed thereon. Provide a mask of metal such as helium (He) and irradiate the mask with a light ion beam toward the mask, and pass through the micropores rather than the range of the light ion beam that passes through other regions except the micropores There has been disclosed a method for manufacturing a semiconductor element in which the position of the crystal defect region formed in the semiconductor substrate in the depth direction is made different for each region by increasing the range of the light ion beam.

Japanese Laid-Open Patent Publication No. 4-214673 (page 6, FIG. 1)

  In order to perform the lifetime control of the semiconductor element described in Patent Document 1, as shown in FIG. 6, for example, several hundreds μm to several mm on one main surface (1a) of the semiconductor substrate (1) by metal plating or the like. Then, a metal film (2) such as aluminum (Al) is formed with a thickness of 2 mm, and then the exposed surface (2a) of the metal film (2) is partially etched to form a plurality of recesses as shown in FIG. A metal mask (4) provided with (3) is formed. Thereafter, as shown in FIG. 8, helium (He) is passed through a metal mask (4) having a relatively thick portion without the recess (3) and a relatively thin portion with the recess (3). The semiconductor substrate (1) is irradiated with a light ion beam (5) such as) to form a crystal defect region (6) in the semiconductor substrate (1). This crystal defect forming method is inexpensive in production and excellent in productivity.

  However, when a thick metal film (2) is formed on one main surface (1a) of the semiconductor substrate (1) by metal plating, the peripheral side (1b) and the center of the semiconductor substrate (1) are formed as shown in FIG. A difference occurs in the thickness of the metal film (2) on the side (1c), and the upper surface of the metal film (2) is often formed in a shallow mortar shape. This is because a larger amount of current flows in the peripheral part than the central part of the semiconductor substrate (1) in the plating solution in which the semiconductor substrate (1) is immersed, and a thicker plating layer is formed in the peripheral part than the central part of the semiconductor substrate (1). This is because it is formed. By selecting the plating solution composition, temperature, and stirring conditions, the plating thickness non-uniformity can be eliminated to some extent, but it is practically impossible to control the current value evenly in the entire plating area of the plating solution. Thus, it is not possible to form a plating layer having a completely uniform thickness over the entire surface of the semiconductor substrate (1).

As shown in FIG. 7, a recess (3) is provided on the exposed surface (2a) of the metal film (2) having different thicknesses on the peripheral side (1b) and the central side (1c) of the semiconductor substrate (1). When the semiconductor substrate (1) is irradiated with the light ion beam (5) through the mask (4), the peripheral side (1b) and the center side (1c) of the semiconductor substrate (1) are formed. And there is a difference in the range of the light ion wire (5). Therefore, as shown in FIG. 8, the depths D ₁ and D _{2 of the} crystal defect region (6) formed on the peripheral side (1b) of the semiconductor substrate (1) and the crystal formed on the central side (1c). Since there is a difference between the depths D ₃ and D ₄ of the defect region (6), the electrical characteristics of the semiconductor elements formed on the peripheral side (1b) and the central side (1c) of the semiconductor substrate (1) are different. Has occurred, and the yield of semiconductor elements has been reduced.

  Accordingly, an object of the present invention is to provide a method of manufacturing a semiconductor element that can obtain uniform electrical characteristics over the entire semiconductor substrate.

  A method of manufacturing a semiconductor device according to the present invention includes plating one or more metals selected from the group consisting of aluminum (Al), copper (Cu), platinum (Pt), lead (Pb), or alloys thereof. A step of forming a metal film (2) on at least one main surface (1a) of the semiconductor substrate (1), and mechanically cutting or polishing the exposed surface (2a) of the metal film (2) (2 ) Smoothing the exposed surface (2a), etching the exposed surface (2a) of the smoothed metal film (2) to form a plurality of recesses (3), and a plurality of recesses (3 And irradiating the semiconductor substrate (1) with radiation (5) through the metal film (2) on which the crystal defect region (6) is formed, and forming a crystal defect region (6) in the semiconductor substrate (1).

Even if the metal film (2) is formed with an uneven thickness on one main surface (1a) of the semiconductor substrate (1) by plating, the exposed surface (2a) of the metal film (2) is mechanically cut or By polishing, the thickness of the metal film (2) from one main surface (1a) of the semiconductor substrate (1) is uniformly smoothed throughout. Thereafter, when a plurality of recesses (3) are formed on the exposed surface (2a) of the metal film (2) by etching, the depth of the recess (3) formed on the exposed surface (2a) of the metal film (2). The thickness from the bottom surface (3a) of the recess (3) to one main surface (1a) of the semiconductor substrate (1) is substantially uniform over the entire main surface of the semiconductor substrate (1). Thereafter, when the semiconductor substrate (1) is irradiated with radiation (5) through the metal film (2) formed with the recess (3), the metal film (2) is exposed to the radiation (5) in the semiconductor substrate (1). The crystal defects are formed at substantially equal depths D ₁ and D ₂ at positions where the recesses (3) are formed over the entire surface of the semiconductor substrate (1) and positions where the recesses (3) are not formed. Region (6) can be formed. Therefore, substantially uniform electrical characteristics of the semiconductor element can be imparted to the entire surface of the semiconductor substrate (1), thereby improving the yield of the semiconductor element.

  According to the present invention, homogenization and stabilization of electrical characteristics of a plurality of semiconductor elements can be achieved, and the reliability of the quality of the semiconductor elements can be improved. In addition, since a metal film that controls the range of radiation in the semiconductor substrate can be formed by using each processing step including metal plating, cutting or polishing, and etching, productivity can be improved.

  Hereinafter, an embodiment of a method for manufacturing a semiconductor device according to the present invention will be described with reference to FIGS. In these drawings, parts that are substantially the same as those shown in FIGS. 6 to 8 are given the same reference numerals, and descriptions thereof are omitted.

  In the method of manufacturing a semiconductor element of this embodiment, first, a semiconductor substrate (1) on which a plurality of semiconductor elements are formed by impurity diffusion, epitaxial growth, or the like is prepared. In the present embodiment, the semiconductor element is, for example, an insulated gate bipolar transistor (IGBT), but is not limited thereto. Therefore, detailed illustration of the structure of the PN junction, the insulating film, various electrodes, and the like formed in the semiconductor substrate (1) is omitted.

  Subsequently, as shown in FIG. 6, a metal film (2) made of, for example, aluminum (Al) is formed on one main surface (1a) of the semiconductor substrate (1) to a thickness of, for example, about 500 μm by metal plating. . The thickness of the metal film (2) immediately after the formation is different between the peripheral side (1b) and the central side (1c) of the semiconductor substrate (1) as shown by a broken line in FIG. That is, the thickness of the metal film (2) is relatively large on the peripheral side (1b) of the semiconductor substrate (1), and the thickness of the metal film (2) is relatively large on the center side (1c) of the semiconductor substrate (1). Thinly formed. For example, when an insulated gate bipolar transistor (IGBT) is manufactured as a semiconductor element, the metal film (2) is formed on the exposed surface of the emitter electrode.

  Next, the exposed surface (2a) of the metal film (2) is subjected to mechanical cutting, polishing or cutting / polishing so that the exposed surface (2a) of the metal film (2) is formed as shown in FIG. Smoothing to make the thickness of the metal film (2) uniform. When smoothing the exposed surface (2a) of the metal film (2), as shown in FIG. 2, the rotation stop (7b) prevents relative rotation or relative movement with the support base (7), and The semiconductor substrate (1) is placed on the flat support surface (7a) of the support base (7). Thereafter, the cutting tool (8) or the polishing tool brought into contact with at least a part or the whole of the exposed surface (2a) of the metal film (2) is pressed against the exposed surface (2a) and relatively rotated or relatively rotated. Move to cut or polish the exposed surface (2a). For example, when the cutting tool (8) or the polishing tool is brought into contact with the metal film (2) and pressed, the cutting tool (8) or the polishing tool moves left and right, back and forth in the horizontal plane, or rotates, revolves or rotates. Perform a revolving movement. Thereby, the metal film (2) is cut or polished over the entire surface, and the thickness of the metal film (2) is made uniform over the entire one main surface (1a) of the semiconductor substrate (1). Cutting includes grinder grinding, lapping, honing, or machining by a grindstone. The polishing process is buffing. In order to smooth the exposed surface (2a) of the metal film (2), the difference in height of the metal film (2) between the central portion and the outer peripheral portion of the semiconductor substrate (1) is 20 μm or less, preferably 10 μm or less. More preferably, the thickness is 5 μm or less.

  Thereafter, as shown in FIG. 3, the exposed surface of the metal film (2) obtained by smoothing a mask (9) made of a material different from that of the metal film (2), for example, resin and having a large number of openings (9a). (2a) is deposited, and the metal film (2) is selectively etched through the opening (9a) of the mask (9). As a result, the metal film (2) is thinly etched at the exposed surface (2a) of the metal film (2) corresponding to the opening (9a) of the resin mask (9), and the uniform depth as shown in FIG. A plurality of concave portions (3) are formed, and a metal mask (4) having a relatively thick portion and a relatively thin portion is formed. The bottom surface (3a) of the recess (3) does not reach one main surface (1a) of the semiconductor substrate (1), and the bottom surface (3a) of the recess (3) and one main surface (1a) of the semiconductor substrate (1) ) To form a thin film portion (3b). In addition, the concave portion (3) has various cross-sectional shapes such as U-shape, U-shape, V-shape, etc., such as dents, depressions, grooves, grooves, grooves, dovetails, notches, notches, holes (mortises), etc. Includes recesses of various cross-sectional shapes, widths and lengths. In the present embodiment, the metal film (2) is etched so that at least one thick portion and thin portion face each other with respect to one semiconductor element.

After removing the resin mask (9) shown in FIG. 4, as shown in FIG. 5, protons or helium (as shown in FIG. 5) are applied to the semiconductor substrate (1) through the metal film (2) having a plurality of recesses (3). Irradiate a light ion beam (5) (radiation) such as He). Thereby, the relatively thick portion of the metal film (2), that is, the light ion beam (5) irradiated through the portion excluding the recess (3) reaches a relatively shallow position of the semiconductor substrate (1), The light ion beam (5) irradiated through the relatively thin portion of the metal film (2), that is, the recess (3), reaches a relatively deep position of the semiconductor substrate (1). As a result, a relatively shallow depth D ₁ from one main surface (1a) of the semiconductor substrate (1) corresponding to the portion of the metal film (2) excluding the recess (3), and the recess of the metal film (2) ( one main surface (1a) from a relatively deep depth D ₂ to the crystal defect region of the semiconductor substrate (1) corresponding to 3) (6) is formed. Further, by removing the metal film (2) and dividing the semiconductor substrate (1) into a plurality of parts, a plurality of semiconductor elements having the same electrical characteristics can be obtained.

In the present embodiment, one main surface (1a) of the semiconductor substrate (1) is metal-plated to form a metal film (2) made of aluminum (Al), and then the exposed surface (2a of the metal film (2)) ) Is subjected to mechanical cutting, so that the entire one main surface (1a) of the semiconductor substrate (1) is smoothed to make the thickness of the metal film (2) uniform. Then, etching the exposed surface (2a) of the metal film (2) with a uniform thickness to form the recess (3), the recess (3) formed on the exposed surface (2a) of the metal film (2) Are equal on the peripheral side (1b) and the central side (1c) of the semiconductor substrate (1). Further, by irradiating the semiconductor substrate (1) with a light ion beam (5) such as proton or helium (He) through the metal film (2) in which the recess (3) is formed, the metal film (2) Acts as a mask for controlling the range of the light ion beam (5) in the semiconductor substrate (1), and has a uniform depth D ₁ , D on the peripheral side (1b) and the central side (1c) of the semiconductor substrate (1). _Since a crystal defect region (6) can be formed in ₂ , a semiconductor element having uniform electrical characteristics is formed on the entire surface of the semiconductor substrate (1) including the peripheral side (1b) and the central side (1c) of the semiconductor substrate (1). Thus, the yield of semiconductor elements can be improved. Further, the metal mask (4) for controlling the range of the light ion beam (5) in the semiconductor substrate (1) can be formed at low cost by using a processing technique including metal plating, cutting or polishing and etching, and There is an advantage that productivity can be improved.

  Embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made. For example, in the above embodiment, the metal film (2) is formed on one main surface (1a) of the semiconductor substrate (1), but the metal film (2) is formed on the other main surface (1d). May be. In the above embodiment, aluminum (Al) is selected as the metal constituting the metal film (2), but aluminum (Al), copper (Cu), platinum (Pt), lead (Pb), or alloys thereof. You can choose from. Also, the exposed surface (2a) of the metal film (2) is smoothed by various mechanical polishing processes such as cutting, buffing, barreling, or CMP (Chemical Mechanical Polishing). You can also. Further, smoothing by mechanical cutting or polishing is also effective when irregularities, depressions, voids, and protrusions are formed on the exposed surface (2a) of the metal film (2) by plating. Further, a recess (3) of the metal film (2) reaching the semiconductor substrate (1) below the metal film (2) is formed, and a thin film is formed between the bottom surface of the metal film (2) and the semiconductor substrate (1). The part (3b) may not be formed.

  The present invention can be suitably applied to the manufacture of a semiconductor element having a crystal defect region in a semiconductor substrate or the control of the amount of electron beam radiation.

Sectional drawing which shows the state which smoothed the exposed surface of the metal film formed on the semiconductor substrate by cutting Sectional drawing which shows the state which mounted the semiconductor substrate on the support stand, and made the cutting tool contact the exposed surface of a metal film Sectional drawing which shows the state which adhered the resin-made mask which has many opening parts to the exposed surface of a metal film Sectional drawing which shows the state which formed the several recessed part in the exposed surface of the metal film shown in FIG. Sectional drawing which shows the state which irradiates a light ion beam to a semiconductor substrate through a metal film, and forms a several crystal defect area | region in a semiconductor substrate Cross-sectional view of a semiconductor substrate with a metal film with a non-uniform thickness Cross-sectional view of a semiconductor substrate with a plurality of recesses formed in a metal film with a non-uniform thickness Sectional drawing which shows the state which irradiates a light ion beam to a semiconductor substrate through the metal film of non-uniform thickness, and forms a crystal defect area | region in a semiconductor substrate

Explanation of symbols

  (1) ・ ・ Semiconductor substrate, (1a) ・ ・ One main surface, (1b) ・ ・ Rim, (1c) ・ ・ Center side, (1d) ・ ・ The other main surface, (2) ・ Metal Membrane, (2a) ·· Exposed surface, (3) ·· Concavity, (3a) ·· Bottom surface, (3b) ·· Thin film portion, (5) ·· Light ion beam (radiation), (6) ·· Crystal Defective area, (7) ・ ・ Support base, (7a) ・ ・ Support surface, (7b) ・ ・ Rotation stop, (8) ・ ・ Cutting tool, (9) ・ ・ Mask, (9a) ・ ・ Opening,

Claims (4)

At least one main surface of the semiconductor substrate is plated with one or more metals selected from the group consisting of aluminum (Al), copper (Cu), platinum (Pt), lead (Pb), or alloys thereof. Forming a metal film;
Smoothing the exposed surface of the metal film by mechanically cutting or polishing the exposed surface of the metal film;
Etching the exposed surface of the smoothed metal film to form a plurality of recesses in the metal film;
Irradiating the semiconductor substrate with radiation through the metal film in which a plurality of the recesses are formed to form a crystal defect region in the semiconductor substrate.   2. The method of manufacturing a semiconductor element according to claim 1, wherein a bottom surface of the concave portion does not reach the semiconductor substrate below the metal film, and a thin film portion is formed between the bottom surface and the semiconductor substrate.   3. The method of manufacturing a semiconductor element according to claim 1, wherein the step of smoothing the exposed surface of the metal film sets the difference in height depending on the location of the metal film from the semiconductor substrate to 20 μm or less.   The step of smoothing the exposed surface of the metal film is a step of disposing the semiconductor substrate on a flat support surface of the support base by preventing relative rotation or relative movement between the semiconductor substrate and the support base. And cutting or polishing the exposed surface by rotating or moving relatively while pressing a cutting tool or polishing tool brought into contact with at least a part of the exposed surface of the metal film against the metal film. The manufacturing method of the semiconductor element of any one of Claims 1-3 including the process of performing.

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