JP2011044529A - Metallic mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: an increase in high-temperature breakdown voltage leak, deterioration in characteristics due to a snap-back, etc., occur in life-time control by electron beam irradiation. <P>SOLUTION: A metallic mask 2 is used to manufacture a semiconductor device 1 including an emitter part 100 and a guard ring part 101 as an element formation part, and includes: a mask 6 corresponding to an emitter part, serving as a first mask part corresponding to the emitter part 100; and a mask 5 corresponding to a guard ring part, serving as a second mask part corresponding to the guard ring part 101. The mask 6 and the mask 5 are composed of a mesh structure, and have numerical apertures set independently of each other in accordance with a mesh numerical aperture (0-100%) of the mesh structure. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a metal mask, and more particularly to a metal mask used for electron beam irradiation of an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor).

  In an insulated gate bipolar transistor (IGBT), it is necessary to quickly remove carriers accumulated in the semiconductor chip in order to improve switching characteristics. As one of the methods, lifetime control that shortens the lifetime of carriers by generating defects by electron beam irradiation has been mainly used conventionally (see Patent Document 1).

JP 2008-91705 A

  Electron beam irradiation has a merit in terms of improving productivity, cost, and switching characteristics as a lifetime control method. However, there are also disadvantages such as an increase in high-temperature withstand pressure leakage and deterioration of characteristics due to snapback.

  The present invention has been made to solve the above-described problems, and obtains an IGBT that suppresses deterioration in characteristics due to high-temperature withstand pressure leakage and snapback without impairing merits such as productivity, cost, and switching characteristics. An object of the present invention is to provide a metal mask.

  The present invention is a metal mask used for manufacturing a semiconductor device including an element forming portion and a guard ring portion, and includes a first mask portion corresponding to the element forming portion and a second mask corresponding to the guard ring portion. The first and second mask parts are configured by a mesh structure, and the opening ratios of the first and second mask parts are set according to the mesh opening ratio (0% to 100%) of the mesh structure. Each is set independently.

  According to the present invention, there is provided a metal mask used for manufacturing a semiconductor device including an element formation portion and a guard ring portion, the first mask portion corresponding to the element formation portion, and the first mask corresponding to the guard ring portion. 2 mask portions, the first and second mask portions are configured by a mesh structure, and the openings of the first and second mask portions according to the mesh aperture ratio (0% to 100%) of the mesh structure. Since the rate is set independently, defects can be formed at a desired density for each region by electron beam irradiation, and the breakdown voltage can be stabilized while maintaining the switching characteristics, thereby improving yield and reliability. The improvement of sex can be expected. Moreover, reduction of manufacturing cost can be expected.

1 is a diagram illustrating a structure of a semiconductor device and a metal mask according to a first embodiment. It is a figure which shows the mesh structure of the metal mask concerning Embodiment 1. FIG. FIG. 3 is a diagram showing the arrangement of the metal mask and the defect density distribution with respect to the semiconductor device according to the first embodiment. FIG. 3 is a diagram showing the arrangement of the metal mask and the defect density distribution with respect to the semiconductor device according to the first embodiment. It is a figure which shows distribution of defect density by the conventional method.

<A. Embodiment 1>
<A-1. Configuration>
In the conventional electron beam irradiation, the defect density is generated by irradiating the entire surface of the semiconductor chip with an electron beam (see FIG. 5). Although switching characteristics can be improved as an advantage, high temperature breakdown voltage leakage increases as a disadvantage, and current sense characteristics deteriorate depending on conditions. Therefore, a metal mask 2 as shown in FIG. 1 is disposed at the time of electron beam irradiation.

  As shown in FIG. 1, the metal mask 2 used for manufacturing the semiconductor device 1 is arranged on the semiconductor device 1 as an irradiation mask in the electron beam irradiation process, and meshes corresponding to each region of the semiconductor chip of the semiconductor device 1. It has a structure. In the figure, illustration of each mesh of the mesh structure is omitted.

  FIG. 2 shows the mesh structure in detail. FIG. 2A corresponds to the emitter-corresponding mask 6 as the first mask part corresponding to the emitter part 100 as the element forming part provided in the semiconductor chip, and the guard ring part 101 provided in the semiconductor chip. A guard ring portion corresponding mask 5 as a second mask portion, and a peripheral portion of the guard ring portion 101 of the semiconductor chip, that is, an emitter portion 100 as an element forming portion and a metal plate mask portion 4 corresponding to the outside of the guard ring portion 101. The metal mask 2 provided is shown. The emitter portion correspondence mask 6 and the guard ring portion correspondence mask 5 have a mesh structure. Further, the metal plate mask portion 4 is formed of a plate metal.

  Further, in FIG. 2B, when the current sensing part 102 is further provided in the emitter part 100 as the element forming part, a current sensing part corresponding mask 7 as a third mask part corresponding thereto is further provided. A metal mask 2 is shown. The current sense portion corresponding mask 7 has a mesh structure.

  In accordance with the mesh aperture ratio (0% to 100%) of the mesh structure in FIGS. 2A and 2B, the emitter corresponding mask 6 which is the first to third mask portions, the guard ring corresponding mask 5 and the current sense portion. The aperture ratio of the corresponding mask 7 is set independently for desired electron beam irradiation control. In order to control electron beam irradiation in a single region, other mask portions except for any one of the first to third mask portions corresponding to the emitter portion corresponding mask 6, the guard ring portion corresponding mask 5, and the current sense portion corresponding mask 7 It is also possible to set the mesh aperture ratio to 0%.

  FIG. 3 is a cross-sectional view showing a state in which the metal mask 2 is disposed on the semiconductor device 1 in the electron beam irradiation process, and corresponds to a cross-sectional view taken along line A-A ′ in FIG.

  As shown in FIG. 3, the semiconductor device 1, which is an IGBT, has a P + diffusion layer 11 stacked on a P-type substrate 10 and an N-type layer 12 stacked thereon. In the region on the right side of FIG. 3, the P + diffusion layer 15 is disposed on the surface of the N-type layer 12, and the metal plate mask portion 4 of the metal mask 2 is disposed corresponding to the region. 3 is the guard ring portion 101, and the P-type guard ring layer 14 is disposed on the surface of the N-type layer 12 at a predetermined interval. An insulating film 17 is formed on the surface. Corresponding to the guard ring portion 101, the guard ring portion corresponding mask 5 of the metal mask 2 is arranged. The left region of FIG. 3 is an emitter section 100, and a P-type base layer 13 having an N-type emitter layer (not shown) disposed on the surface is disposed on the surface of the N-type layer 12. Corresponding to the emitter portion 100, the emitter portion corresponding mask 6 of the metal mask 2 is arranged. Note that an N-type emitter layer, a gate electrode, and the like exist on the surface of the P-type base layer 13, but the portions are not shown in FIG. 4.

  FIG. 4 is a cross-sectional view showing a state in which the metal mask 2 is disposed on the semiconductor device 1 in the electron beam irradiation process, and corresponds to a cross-sectional view taken along line B-B ′ in FIG.

  In addition to the case shown in FIG. 3, the case where the current sense layer 16 is formed on the surface of the P-type base layer 13 is shown. When the current sense portion 102 corresponding to the current sense layer 16 exists, the current sense portion corresponding mask 7 of the metal mask 2 is further disposed corresponding to the current sense portion 102. In this case as well, an N-type emitter layer, a gate electrode, and the like are present on the surface of the P-type base layer 13, but the portions are not shown in FIG.

  Stainless steel can be used as the material of the metal mask in order to improve the mask strength.

<A-2. Operation>
Conventionally, lattice defects are formed by controlling the lifetime by irradiating the entire surface of the semiconductor chip with an electron beam, so that lattice defects are uniformly formed in all regions of the semiconductor chip as shown in FIG. As a result, problems such as high-temperature pressure-resistant leakage and snapback have occurred. Here, the crosses shown in FIGS. 3, 4, and 5 indicate lattice defects.

  According to the present invention, as shown in FIGS. 3 and 4, the emitter-corresponding mask 6, the guard-ring-corresponding mask 5, and the current-sensing part corresponding to the emitter part 100, the guard-ring part 101, and the current-sensing part 102, respectively. By generating an aperture ratio of the mesh structure of the mask 7 independently and irradiating an electron beam in a state where the metal mask 2 provided with these is arranged, the density of lattice defect formation for each region is It becomes possible to obtain a desired density for each region.

  By selecting the aperture ratio of the mesh structure corresponding to the part that requires high defect density and the part that requires low defect density, it is necessary to irradiate the electron beam under different conditions to the part that requires different defect density In addition, a desired defect density can be formed in each part under one electron beam condition (see FIGS. 3 and 4). According to the present invention, it is possible to manufacture the semiconductor device 1 having a desired defect density by an existing process and one-time electron beam irradiation, and an improvement in manufacturing cost and productivity can be expected.

  Specifically, since the increase in the high-temperature withstand pressure leak is affected by the number of defects in the guard ring portion 101, it is necessary to suppress the irradiation of the electron beam to the guard ring portion 101 by setting the aperture ratio of the mesh structure. This can be realized by making the aperture ratio of the guard ring portion corresponding mask 5 as the second mask portion smaller than the aperture ratio of the emitter portion corresponding mask 6 as the first mask portion. By generating some defects in the guard ring portion 101 and stabilizing the elongation of the depletion layer, it becomes possible to stabilize the leakage current at normal temperature.

  Further, since the emitter section 100 requires a high defect density in order to improve the switching speed, it is necessary to increase the defect density by setting the aperture ratio of the mesh structure. By increasing the aperture ratio, the defect density increases, and the leakage current can be stabilized while improving the switching speed.

  In addition, the current sense unit 102 has a small area, and when electron beam irradiation equivalent to that of the emitter unit 100 is performed, the carrier injection efficiency is reduced and snapback occurs. Therefore, it is necessary to set the aperture ratio of the mesh structure so as to suppress the irradiation amount of the electron beam applied to the current sense unit 102 rather than the emitter unit 100. This can be realized by making the aperture ratio of the mask 7 corresponding to the current sense portion which is the third mask portion smaller than the aperture ratio of the mask 6 corresponding to the emitter portion which is the first mask portion.

<A-3. Effect>
According to the first embodiment of the present invention, the metal mask 2 used for manufacturing the semiconductor device 1 including the emitter portion 100 as the element forming portion and the guard ring portion 101, which corresponds to the emitter portion 100. A mask 6 corresponding to the emitter part, and a mask 5 corresponding to the guard ring part, which is a second mask part corresponding to the guard ring part 101. The emitter part corresponding mask 6 and the guard ring part corresponding mask 5 have a mesh structure. In accordance with the mesh aperture ratio (0% to 100%) of the mesh structure, the aperture ratios of the emitter corresponding mask 6 and the guard ring corresponding mask 5 are set independently, so that one electron Defects can be formed at a desired density for each region by beam irradiation, and withstand voltage leakage can be stabilized while maintaining switching characteristics Because, to improve the yield improvement and reliability can be expected. Moreover, reduction of manufacturing cost can be expected.

  Also, according to the first embodiment of the present invention, in the metal mask, the aperture ratio of the guard ring corresponding mask 5 that is the second mask section is the aperture ratio of the emitter corresponding mask 6 that is the first mask section. By being smaller, some defects are generated in the guard ring portion 101, the depletion layer can be elongated, and the leakage current at room temperature can be stabilized.

  According to the first embodiment of the present invention, in the metal mask, the emitter unit 100 as the element forming unit further includes the current sense unit 102 and is a third mask unit corresponding to the current sense unit 102. The current sense portion corresponding mask 7 is further provided. The current sense portion corresponding mask 7 is configured by a mesh structure, and the opening ratio of the current sense portion corresponding mask 7 is set according to the mesh opening ratio (0% to 100%) of the mesh structure. By setting independently the emitter corresponding mask 6 and the guard ring corresponding mask 5 which are the first and second mask portions, snapback of the current sense portion 102 can be suppressed, and an improvement in yield can be expected.

  According to the first embodiment of the present invention, in the metal mask, the aperture ratio of the current sense portion corresponding mask 7 which is the third mask portion is the aperture ratio of the emitter portion corresponding mask 6 which is the first mask portion. By being smaller, carrier injection efficiency can be maintained and snapback can be prevented.

  According to the first embodiment of the present invention, in the metal mask, any one of the first to third mask portions corresponding to the emitter portion corresponding mask 6, the guard ring portion corresponding mask 5, and the current sense portion corresponding mask 7 is used. By setting the mesh aperture ratio of the other mask portions except for one to 0%, it is possible to cope with all types by changing the aperture ratio based on the same mask design standard, thereby reducing the development cost.

Further, according to the first embodiment of the present invention, the use of stainless steel as the material of the metal mask can be expected to improve the mask strength and the processing accuracy.
Can do.

  Further, according to the first embodiment of the present invention, the metal mask further includes the emitter plate 100 as the element forming portion and the metal plate mask portion 4 corresponding to the outside of the guard ring portion 101, thereby increasing the mask strength. It is possible to improve and suppress characteristic variation, and as a result, yield improvement can be expected.

  DESCRIPTION OF SYMBOLS 1 Semiconductor device, 2 metal mask, 4 metal plate mask part, 5 guard ring corresponding mask, 6 emitter corresponding mask, 7 current sense part corresponding mask, 10 P type substrate, 11, 15 P + diffusion layer, 12 N type Layer, 13 P-type base layer, 14 P-type guard ring layer, 16 current sense layer, 17 insulating film, 100 emitter section, 101 guard ring section, 102 current sense section.

Claims (7)

A metal mask used for manufacturing a semiconductor device including an element forming portion and a guard ring portion,
A first mask portion corresponding to the element forming portion;
A second mask portion corresponding to the guard ring portion,
The first and second mask portions are configured by a mesh structure,
According to the mesh aperture ratio (0% to 100%) of the mesh structure, the aperture ratios of the first and second mask portions are set independently.
Metal mask. The aperture ratio of the second mask portion is smaller than the aperture ratio of the first mask portion;
The metal mask according to claim 1. The element formation unit further includes a current sense unit,
A third mask portion corresponding to the current sense portion;
The third mask portion is configured by a mesh structure,
According to the mesh aperture ratio (0% to 100%) of the mesh structure, the aperture ratio of the third mask portion is set independently of the first and second mask portions,
The metal mask according to claim 1 or 2. An aperture ratio of the third mask portion is smaller than an aperture ratio of the first mask portion;
The metal mask according to claim 3. The mesh aperture ratio of the other mask portions excluding any one of the first to third mask portions is set to 0%.
The metal mask in any one of Claims 1-4. Stainless steel was used as the material.
The metal mask in any one of Claims 1-5. Further comprising a metal plate mask portion corresponding to the outside of the element forming portion and the guard ring portion,
The metal mask in any one of Claims 1-6.

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