JP5203667B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device.

A technique for increasing the donor concentration of a semiconductor substrate by implanting hydrogen ions into the semiconductor substrate and then heating the semiconductor substrate is known. When the semiconductor substrate into which hydrogen ions have been implanted is heated, the concentration of the donor in the vicinity of the depth into which hydrogen ions have been implanted increases compared to before the heating. For example, in Patent Document 1, protons are injected into a semiconductor substrate (n ⁻ region) having a low donor concentration, and then the semiconductor substrate is heated, so that an n ⁺ region (a donor concentration is high in the vicinity of the proton implantation depth). Forming a region).
It has not yet been clarified how the implanted hydrogen ions behave in the semiconductor substrate, but there is a phenomenon that the donor concentration near the implantation depth of hydrogen ions increases by heating the semiconductor substrate after the implantation of hydrogen ions. can get. Hereinafter, an increase in donor concentration in the semiconductor substrate due to the behavior of hydrogen ions is referred to as activation of hydrogen ions. The temperature range in which hydrogen ions are activated is referred to as a hydrogen ion activation temperature range. Since hydrogen ions are activated at a lower temperature than other impurity atoms (phosphorus, arsenic, etc.), they can be used for various purposes.

JP 2001-160559 A

  When the semiconductor substrate after hydrogen ion implantation is heated, the donor concentration increases and the region with the high donor concentration expands. This is presumably because the implanted hydrogen ions are diffused in the semiconductor substrate by heat. Hydrogen is more easily diffused than phosphorus or arsenic. Since hydrogen ions diffuse in a wide range, the conventional method has a low rate of increase in donor concentration relative to the amount of hydrogen ions implanted. Therefore, in order to significantly increase the donor concentration, it is necessary to implant a large amount of hydrogen ions into the semiconductor substrate, and it takes a long time to implant the hydrogen ions. Further, since the region having a high donor concentration is enlarged, there is a problem that it is difficult to form a fine region pattern.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a method for manufacturing a semiconductor device that can activate hydrogen ions while suppressing diffusion of implanted hydrogen ions.

When the semiconductor substrate into which hydrogen ions have been implanted is heated, the donor concentration in the vicinity of the hydrogen ion implantation depth increases. The inventors of the present invention have a region in which the donor concentration is increased in a region shallower than the hydrogen ion implantation depth (hereinafter referred to as a surface side region) and a region on the side deeper than the hydrogen ion implantation depth (hereinafter referred to as a surface ion region). Then, we found that it is distributed more widely than the area on the anti-surface side. That is, it was discovered that the donor concentration distribution is asymmetric between the surface side region and the anti-surface side region.
The present inventors have found that the cause that the donor concentration is distributed as described above is due to the following phenomenon. When hydrogen ions are implanted into a semiconductor substrate, crystal defects are formed in the semiconductor substrate due to the movement of hydrogen ions. Therefore, in the semiconductor substrate after the implantation of hydrogen ions, a large number of crystal defects exist on the trajectory through which the hydrogen ions have passed. That is, in the semiconductor substrate after the implantation of hydrogen ions, a larger amount of crystal defects are present in the surface side region than in the anti-surface side region. As described above, if a large amount of crystal defects exist in the surface side region, the crystal defects serve as escape routes for hydrogen ions, so that hydrogen ions easily diffuse in the surface side region. Therefore, as described above, it is considered that the region where the donor concentration is increased after the semiconductor substrate is heated is widely distributed in the surface side region.
Hereinafter, the phenomenon in which the diffusion of hydrogen ions is promoted when the semiconductor substrate is heated by the crystal defects formed when hydrogen ions are implanted is referred to as outward diffusion of hydrogen ions. The present invention activates hydrogen ions while suppressing the outward diffusion of hydrogen ions.

The method for manufacturing a semiconductor device of the present invention includes an implantation step, a surface heating step, and an implantation depth heating step. In the implantation step, hydrogen ions are implanted into the surface of the semiconductor substrate with energy reaching a depth away from the surface. In the surface heating step, the temperature of the semiconductor substrate at the depth after the implantation step is maintained below the hydrogen ion outward diffusion temperature, and the temperature of the semiconductor substrate is increased until the temperature of the surface of the semiconductor substrate rises above the crystal defect extinction temperature. Heat the surface. In the implantation depth heating step, after the surface heating step, at least the semiconductor substrate having the depth is heated until it reaches a temperature not lower than the hydrogen ion outward diffusion temperature in the hydrogen ion activation temperature range.
The hydrogen ion outward diffusion temperature is a temperature at which outward diffusion of hydrogen ions occurs. That is, the hydrogen ion outward diffusion temperature means that when the implantation depth of hydrogen ions is heated, the donor concentration is reduced on the shallower side (surface side region) and deeper side (anti-surface side region) than the implantation depth of hydrogen ions. This is an asymmetrically distributed temperature. The hydrogen ion outward diffusion temperature varies according to the crystal defect density in the surface side region and the anti-surface side region.
The crystal defect extinction temperature is a temperature at which at least a part of crystal defects in the semiconductor substrate disappears. If the crystal defect density in the surface side region of the semiconductor substrate is lowered after the surface of the semiconductor substrate is heated, it can be said that the heating is performed at a temperature equal to or higher than the crystal defect extinction temperature.
In the manufacturing method of the present invention, the surface of the semiconductor substrate (the surface into which hydrogen ions are implanted) is heated to a temperature equal to or higher than the crystal defect extinction temperature in the surface heating step. Therefore, the crystal defect density in the surface side region of the semiconductor substrate is lowered. At this time, the hydrogen ion implantation depth is maintained below the hydrogen ion outdiffusion temperature, so that outdiffusion of hydrogen ions does not occur. Next, in the implantation depth heating step, the semiconductor substrate having the implantation depth of hydrogen ions is heated. This activates the hydrogen ions and diffuses the hydrogen ions. At this time, since the crystal defect density in the surface side region is low, outward diffusion of hydrogen ions is suppressed. Therefore, the donor concentration of the hydrogen ion implantation depth can be greatly increased. In addition, since the region where the donor concentration increases due to the suppression of outward diffusion becomes narrow, the region where the donor concentration increases can be formed with higher accuracy.

In the semiconductor device manufacturing method described above, in the surface heating step, it is preferable that the surface temperature of the semiconductor substrate is heated so as to be maintained at 800 ° C. or higher for 1 to 1000 msec.
Thus, by setting the heating time of the surface of the semiconductor substrate to a short time, the temperature of the semiconductor substrate at the hydrogen ion implantation depth can be maintained below the hydrogen ion outward diffusion temperature.

In the semiconductor device manufacturing method described above, it is preferable to irradiate the surface using any one of a flash lamp, an electron beam, and a laser in the surface heating step.
By heating the surface of the semiconductor substrate in this way, the above-described short-time heating can be realized.

  In the semiconductor device manufacturing method described above, the entire semiconductor substrate may be heated in the implantation depth heating step. As a result, the semiconductor substrate having a hydrogen ion implantation depth is heated.

Further, the diffusion distance of hydrogen ions varies not only with the crystal defect density but also with the heating time. That is, the longer the hydrogen ion implantation depth is heated, the longer the hydrogen ion diffusion distance. On the other hand, the heating time has little influence on the activation amount of hydrogen ions. That is, if you give a certain amount of heat to the semiconductor substrate of the implantation depth of the hydrogen ions, Ru can be briefly obtain sufficient activating amount.
Another method for manufacturing a semiconductor device disclosed in this specification includes an injection step and a heating step. In the implantation step, hydrogen ions are implanted into the surface of the semiconductor substrate. In the heating process, the surface of the semiconductor substrate after the implantation process is heated. In the heating step, heating is performed so that the temperature of the surface of the semiconductor substrate is maintained at a temperature in a temperature range of 300 to 600 ° C. for 50 to 1000 msec. In the implantation step, hydrogen ions are implanted to a depth that raises the temperature to 300 to 600 ° C. in the heating step.
In this method of manufacturing a semiconductor device, in the heating step, the semiconductor substrate having the hydrogen ion implantation depth is heated with substantially the same temperature profile as the surface of the semiconductor substrate. By heating the semiconductor substrate with the hydrogen ion implantation depth under the above conditions, a sufficient amount of heat can be applied to activate the hydrogen ions. In addition, by setting the heating time to 50 to 1000 msec, the diffusion distance of hydrogen ions is shortened, and the donor concentration in the vicinity of the hydrogen ion implantation depth can be increased to a higher concentration.

  According to the production method of the present invention, hydrogen ions can be activated while suppressing diffusion of implanted hydrogen ions. A semiconductor device including a region having a higher donor concentration can be manufactured. In addition, a region having a high donor concentration can be formed with higher accuracy.

The main features of the embodiments described in detail below are listed first.
(Feature 1) In the semiconductor substrate manufacturing method of the first embodiment, in the implantation step, hydrogen ions are implanted so that the peak of hydrogen ion concentration distribution is located at a depth of 1 to 1000 μm from the surface of the semiconductor substrate. To do.
(Characteristic 2) In the method of manufacturing the semiconductor device of the second embodiment, in the implantation step, hydrogen ions are implanted so that the peak of the hydrogen ion concentration distribution is located at a depth of 50 μm or less from the surface of the semiconductor substrate. .
(Characteristic 3) In the method of manufacturing the semiconductor device according to the second embodiment, in the implantation process, hydrogen ions are implanted at a depth shallower than the diffusion distance of hydrogen ions in the heating process.
(Characteristic 4) In the semiconductor device manufacturing method according to the first and second embodiments, any one of protons, dutrons and tritons is implanted into the semiconductor substrate in the implantation step.

(Diffusion and activation of hydrogen ions)
Before describing the examples, diffusion and activation of hydrogen ions will be described.
FIG. 1 shows the relationship between the heating temperature and the donor concentration in the semiconductor substrate when a semiconductor substrate (silicon substrate) implanted with a certain amount of hydrogen ions (protons) is heated at various temperatures. Curve A in FIG. 1 shows the donor concentration (vertical axis) of the semiconductor substrate after being heated at each heating temperature (horizontal axis). Note that the donor concentration on the vertical axis indicates the peak value in the donor concentration distribution in the hydrogen ion implantation direction (depth direction). A straight line B in FIG. 1 shows the donor concentration of the semiconductor substrate before hydrogen ion implantation. Therefore, the difference between the value on curve A and the value on line B indicates the amount of increase in donor concentration. As shown by the straight line B, in each heating temperature experiment, a semiconductor substrate having a donor concentration of about 4 × 10 ¹³ (cm ⁻³ ) was used as the semiconductor substrate before hydrogen ion implantation. Moreover, in the experiment of each heating temperature, conditions other than heating temperature were performed on the same conditions. That is, a certain amount of hydrogen ions was implanted at an energy of 17 MeV. In the heating process after hydrogen ion implantation, the entire semiconductor substrate was maintained at the temperature shown on the horizontal axis in FIG. 1 for about 30 minutes in an electric furnace.

As shown in FIG. 1, when the heating temperature is 300 to 600 ° C., a donor concentration clearly higher than the donor concentration (4 × 10 ¹³ (cm ⁻³ )) of the semiconductor substrate before hydrogen ion implantation is obtained. That is, when the heating temperature is 300 to 600 ° C., the implanted hydrogen ions are activated. On the other hand, when the heating temperature is less than 300 ° C. and when the heating temperature is higher than 600 ° C., the donor concentration hardly increases. When the heating temperature is less than 300 ° C., it is considered that the implanted hydrogen ions are hardly activated. In addition, when the heating temperature is higher than 600 ° C., it is considered that hydrogen ions activated once do not function as a donor for some reason. As shown in FIG. 1, particularly when the heating temperature is 350 to 550 ° C., the donor concentration is greatly increased (that is, more hydrogen ions are activated). However, as described above, the experiment of FIG. 1 is the donor concentration when the heating time is 30 minutes. Therefore, the implanted hydrogen ions are largely diffused in the semiconductor substrate. If the diffusion of hydrogen ions can be suppressed, a higher donor concentration can be obtained. In particular, in the graph of FIG. 1, the amount of increase in donor concentration decreases when the heating temperature is in the range of 450 to 600 ° C. This is considered to be mainly due to diffusion of hydrogen ions. If the diffusion of hydrogen ions is suppressed, a very large increase in donor concentration can be obtained when the heating temperature is 450 to 600 ° C.
In the experiment of FIG. 1, protons are implanted as hydrogen ions into the semiconductor substrate. However, substantially the same results can be obtained by injecting dutrons or tritons.

  FIG. 2 shows the concentration of hydrogen ions (dutron) in a semiconductor substrate when a semiconductor substrate (silicon substrate) into which hydrogen ions (dutron) has been implanted is heated at 450 ° C., 500 ° C., and 550 ° C., respectively. Distribution is shown. Curve C in FIG. 2 shows the concentration distribution when the heating temperature is 450 ° C., curve D in FIG. 2 shows the concentration distribution when the heating temperature is 500 ° C., and curve E in FIG. 2 shows that the heating temperature is 550 ° C. The density distribution is shown. The horizontal axis of FIG. 2 indicates the depth (position) from the surface of the semiconductor substrate (the surface into which hydrogen ions are implanted). The vertical axis in FIG. 2 indicates the donor concentration at each depth. In addition, the experiment of each heating temperature of FIG. 2 was performed on conditions other than heating temperature on the same conditions.

As shown in the figure, when the heating temperature is 450 ° C., the dutron concentration distribution is substantially symmetrical on both sides from the peak position. On the other hand, when the heating temperature is 500 ° C., the region closer to the surface than the peak position (the region closer to 0 than the peak position (horizontal axis): hereinafter referred to as the surface side region) A region having a higher dutron concentration than the region on the anti-surface side (region on the deeper side (horizontal axis) than the peak position: hereinafter, the region on the anti-surface side) is greatly expanded. When the heating temperature is 550 ° C., a region having a high dutron concentration spreads further in the surface side region. Thus, when the heating temperature is increased, a phenomenon occurs in which the region having a high dutron concentration is distributed more widely in the surface side region than in the anti-surface side region. Similar to the change in the distribution of the dutron concentration, the distribution of the carrier concentration in the semiconductor substrate (the carrier concentration during non-energization) also changes.
The cause of this phenomenon can be estimated as follows. When hydrogen ions are implanted into a semiconductor substrate, a large number of crystal defects are formed in the surface side region. Therefore, after the implantation of hydrogen ions, the density of crystal defects in the surface side region is higher than the density of crystal defects in the anti-surface side region. When the semiconductor substrate is heated, a large number of crystal defects in the surface-side region serve as escape routes for hydrogen ions, and it is considered that hydrogen ions are easily diffused in the surface-side region. Therefore, it is considered that the diffusion distance of hydrogen ions becomes longer in the surface side region, and the region having a high dutron concentration is widely distributed in the surface side region.
FIG. 2 shows that when the heating temperature exceeds 500 ° C., outward diffusion of hydrogen ions occurs. In the example of FIG. 2, outward diffusion occurs at about 500 ° C., but the outward diffusion temperature varies depending on the crystal defect density in the surface side region, the crystal defect density in the anti-surface side region, the implantation depth of hydrogen ions, and the like. .
In the experiment of FIG. 2, deuteron is implanted into the semiconductor substrate as hydrogen ions, but substantially the same result can be obtained by injecting proton or triton.

(First embodiment)
Next, a method for manufacturing the semiconductor device according to the first embodiment will be described. In the first embodiment, an IGBT manufacturing method will be described. FIG. 3 shows a schematic cross-sectional view of the IGBT 10 manufactured by the manufacturing method of the first embodiment. As shown in the figure, the IGBT 10 is a trench gate type IGBT. The IGBT 10 includes a semiconductor substrate 12, an emitter electrode 14 formed on the upper surface 12 a of the semiconductor substrate 12, and a collector electrode 16 formed on the lower surface 12 b of the semiconductor substrate 12. The semiconductor substrate 12 is mainly made of silicon. On the upper surface 12 a side of the semiconductor substrate 12, an upper surface side element structure 30 including an n ⁺ emitter region 20, a p ⁺ contact region 22, a p ⁻ body region 24, a gate electrode 26, and an insulating film 28 is formed. As shown in the drawing, since the upper surface side element structure 30 is a general IGBT trench gate structure, the description thereof is omitted. An n ⁻ drift region 32 having a low donor concentration is formed below the upper surface side element structure 30. An n ⁺ buffer region 34 having a high donor concentration is formed below the n ⁻ drift region 32. A p ⁺ collector region 36 is formed below the n ⁺ buffer region 34. The p ⁺ collector region 36 is in contact with the collector electrode 16.

The flowchart of FIG. 4 shows the manufacturing process of the IGBT 10. As shown in FIG. 5, the IGBT 10 is manufactured from a semiconductor substrate 12 whose entire region is an n ⁻ region (region having a low donor concentration).

In step S2, the upper surface side element structure 30 (that is, the n ⁺ emitter region 20, the p ⁺ contact region 22, the p ⁻ body region 24, the gate electrode 26, and the insulating film 28) is formed on the upper surface 12a side of the semiconductor substrate 12. The upper surface side element structure 30 is formed by ion implantation, heat treatment, etching, crystal growth, or the like. Since the formation method of the upper surface side element structure 30 is a conventionally known method, the detailed description thereof is omitted.

  In step S4, the emitter electrode 14 is formed on the upper surface 12a of the semiconductor substrate 12 by vapor deposition or the like.

In step S ^< b ^> 6, the p ⁺ collector region 36 is formed on the lower surface 12 b of the semiconductor substrate 12. That is, p-type impurities (B, Al, etc.) are implanted into the lower surface 12 b of the semiconductor substrate 12. The implantation of the p-type impurity is performed by adjusting the implantation energy of the p-type impurity so that the p-type impurity stops in the immediate vicinity of the lower surface 12b of the semiconductor substrate 12. Next, the lower surface 12b of the semiconductor substrate 12 is irradiated with an electron beam to locally heat the lower surface 12b. In heating by electron beam irradiation, the heating range is limited to the electron beam irradiation range, so the entire lower surface 12b is scanned by scanning the entire lower surface 12b. Then, the implanted p-type impurity is activated. As a result, a p ⁺ collector region 36 is formed on the lower surface 12b of the semiconductor substrate 12, as shown in FIG.

In step S8, hydrogen ions (protons in this embodiment) are implanted into the lower surface 12b of the semiconductor substrate 12. Implantation of hydrogen ions, hydrogen ions p ⁺ a top of the collector region 36 so as to stop in the vicinity of the p ⁺ collector region 36 (position 50 in FIG. 6) (more specifically, after injection of hydrogen ions This is performed by adjusting the implantation energy of hydrogen ions so that the peak of the concentration distribution is located at the position 50 in FIG. In this embodiment, the implantation energy is adjusted so that the implantation depth of hydrogen ions (the depth from the lower surface 12b) is about 250 μm.
Note that, when hydrogen ions are implanted, crystal defects are formed in the semiconductor substrate 12 due to the movement of hydrogen ions in the semiconductor substrate 12. That is, a large number of crystal defects are formed in the semiconductor substrate 12 in the region on the lower surface 12b side from the hydrogen ion implantation position 50 (region 52 in FIG. 6; hereinafter referred to as the lower surface region 52).

  In step S10, the lower surface 12b of the semiconductor substrate 12 is irradiated with an electron beam to locally heat the lower surface 12b. In heating by electron beam irradiation, the heating range is limited to the electron beam irradiation range, so the entire lower surface 12b is scanned by scanning the entire lower surface 12b. The heating in step S10 is performed so that the temperature of the lower surface 12b of the semiconductor substrate 12 is maintained at a temperature of 1000 ° C. or higher for about 1 msec. Since the lower surface 12b is heated by scanning the electron beam, the heating timing of each point on the lower surface 12b is slightly shifted, but each point on the lower surface 12b is maintained at a temperature of 1000 ° C. or higher for about 1 msec. As a result, most of the crystal defects in the lower surface region 52 in FIG. 6 disappear. Further, when the lower surface 12b of the semiconductor substrate 12 is heated under the above conditions, the temperature of the hydrogen ion implantation position 50 is maintained at a temperature lower than 500 ° C. The hydrogen ion outward diffusion temperature in the semiconductor substrate 12 of this example is about 500 ° C., similar to the experimental result of FIG. Therefore, the hydrogen ions implanted into the semiconductor substrate 12 do not diffuse outward by the heating in step S10.

In step S12, the entire semiconductor substrate 12 is heated in an electric furnace. At this time, the temperature of the semiconductor substrate 12 is maintained at 500 ° C. for 30 minutes. Thereby, the hydrogen ions in the semiconductor substrate 12 are activated. That is, the donor concentration near the hydrogen ion implantation position 50 increases. In step S <b> 12, the implanted hydrogen ions diffuse in the semiconductor substrate 12. However, most of the crystal defects in the lower surface region 52 in FIG. 6 have disappeared in step S10. That is, in step S12, the outward diffusion of hydrogen ions hardly occurs. Accordingly, in step S12, the diffusion distance of hydrogen ions becomes shorter than in the conventional case, and the donor concentration in the vicinity of the hydrogen ion implantation position 50 increases significantly. As a result, an n ⁺ buffer region 34 is formed in the vicinity of the hydrogen ion implantation position 50 as shown in FIG. The remaining n ⁻ region becomes the n ⁻ drift region 32.
Further, as described above, since the diffusion distance of hydrogen ions is short in step S12, the n ⁺ buffer region 34 is formed thin. When the n ⁺ buffer region 34 is formed thin, the n ⁻ drift region 32 can be kept thick. Therefore, the breakdown voltage of the IGBT 10 can be further increased.

In step S14, the collector electrode 16 is formed on the lower surface 12b of the semiconductor substrate 12 by vapor deposition or the like.
Through the above steps, the IGBT 10 shown in FIG. 1 is manufactured.

As described above, in the method of manufacturing the IGBT 10 of the first embodiment, after the crystal defects in the lower surface region 52 are eliminated by local heating of the lower surface 12b in step S10, the entire semiconductor substrate 12 (that is, in step S12) The hydrogen ion implantation position 50) is heated. Therefore, hydrogen ions can be activated while suppressing diffusion of hydrogen ions. The donor concentration in the vicinity of the hydrogen ion implantation position 50 can be significantly increased. Further, since the diffusion distance of hydrogen ions is shortened, the n ⁺ buffer region 34 can be formed thin. Thereby, the IGBT 10 having a higher breakdown voltage can be manufactured.

In the method for manufacturing the IGBT 10 described above, hydrogen ions were implanted to a depth of 250 μm from the lower surface 12b of the semiconductor substrate 12 in step S8. In step S10, the lower surface 12b was heated so that the lower surface 12b of the semiconductor substrate 12 was maintained at a temperature of 1000 ° C. or higher for about 1 msec. However, the implantation depth (that is, implantation energy) of hydrogen ions can be appropriately adjusted in consideration of the formation position of the n ⁺ buffer region 34, the diffusion distance of hydrogen ions, and the like. Further, the heating conditions (temperature, time) in step S10 can be appropriately adjusted in consideration of the thermal conductivity of the semiconductor substrate 12, the implantation depth of hydrogen ions, the crystal defect extinction temperature, and the like. In particular, it is preferable that the hydrogen ion implantation depth (the depth of the hydrogen ion concentration distribution peak) in step S8 be 1-1000 μm. Moreover, in step S10, it is preferable to maintain the lower surface 12b of the semiconductor substrate 12 at a temperature of 800 ° C. or higher for 1 to 1000 msec. According to this condition, the lower surface 12b can be heated while maintaining the temperature at the hydrogen ion implantation position 50 below 500 ° C. (hydrogen ion outward diffusion temperature in this embodiment). Furthermore, in order to minimize the influence of heat on the hydrogen ion implantation depth in step S10, the heating time in step S10 is more preferably 1 to 100 msec.

  Moreover, in the manufacturing method of IGBT10 mentioned above, the lower surface 12b of the semiconductor substrate 12 was heated by electron beam irradiation (scanning) in step S10. However, the lower surface 12b may be heated by laser irradiation (scanning). Alternatively, the entire lower surface 12b may be heated at a time by irradiating a flash lamp.

  Moreover, in the manufacturing method of IGBT10 mentioned above, in step S10, the temperature of the hydrogen ion implantation position 50 was maintained below 500 degreeC by making heating time into a short time (about 1 msec). However, the lower surface 12b may be heated while the semiconductor substrate 12 is cooled from the upper surface 12a side. According to such a configuration, the temperature of the hydrogen ion implantation position 50 can be maintained below 500 ° C. even if the heating time in step S10 is relatively long.

  Moreover, in the manufacturing method of IGBT10 mentioned above, the semiconductor substrate 12 whole was heated in step S12. However, in step S12, various heating methods can be used as long as at least the hydrogen ion implantation position 50 can be heated. For example, similarly to step S10, the lower surface 12b may be heated by electron beam irradiation. In this case, the temperature of the hydrogen ion implantation position 50 can be raised to 500 ° C. by extending the electron beam irradiation time (ie, heating time) from step S10.

  Moreover, in the manufacturing method of IGBT10 mentioned above, since the hydrogen ion outward diffusion temperature started at the temperature of 450 degreeC-500 degreeC, the semiconductor substrate 12 was heated to 500 degreeC in step S12. However, as described above, the hydrogen ion outward diffusion temperature varies depending on various conditions. Therefore, the heating temperature in step S12 can be set to an appropriate heating temperature corresponding to the hydrogen ion outward diffusion temperature.

  Moreover, in the manufacturing method of IGBT10 mentioned above, although the proton was injected as a hydrogen ion, you may inject a dutron or a triton. Even if Dutron or Triton is injected, the donor concentration can be increased greatly as in the first embodiment.

(Second embodiment)
Next, a method for manufacturing the semiconductor device of the second embodiment will be described. In the second embodiment, a method for manufacturing a diode will be described. FIG. 7 shows a schematic cross-sectional view of a diode 100 manufactured by the manufacturing method of the second embodiment. As illustrated, the diode 100 includes a semiconductor substrate 112, an anode electrode 114 formed on the upper surface 112 a of the semiconductor substrate 112, and a cathode electrode 116 formed on the lower surface 112 b of the semiconductor substrate 112. The semiconductor substrate 112 is mainly made of silicon. A p ⁺ region 120 having a high acceptor concentration is formed on the upper surface 112 a side of the semiconductor substrate 112. The p ⁺ region 120 is in contact with the anode electrode 114. A p ⁻ region 122 having a low acceptor concentration is formed below the p ⁺ region 120. An n ⁻ region 124 having a low donor concentration is formed below the p ⁻ region 122. An n ⁺ region 126 having a high donor concentration is formed below the n ⁻ region 124. The n ⁺ region 126 is in contact with the cathode electrode 116.

The flowchart of FIG. 8 shows the manufacturing process of the diode 100. Similarly to the semiconductor substrate 12 shown in FIG. 5, the diode 100 is manufactured from the semiconductor substrate 112 whose entire region is an n ⁻ region (region having a low donor concentration).

In step S ^< b ^> 22, ap ⁺ region 120 and ap ⁻ region 122 are formed on the semiconductor substrate 112. The p ⁺ region 120 and the p ⁻ region 122 are formed by implanting p-type impurities into the upper surface 112a of the semiconductor substrate 112, heat treatment of the semiconductor substrate 112, and the like. Since the method for forming the p ⁺ region 120 and the p ⁻ region 122 is a conventionally known method, a detailed description thereof will be omitted.

  In step S24, the anode electrode 114 is formed on the upper surface 112a of the semiconductor substrate 112 by vapor deposition or the like.

  In step S26, hydrogen ions (protons in this embodiment) are implanted into the lower surface 112b of the semiconductor substrate 112. The implantation of hydrogen ions is raised to substantially the same temperature as the lower surface 112b (for example, 90% or more of the temperature of the lower surface 112b) when the lower surface 112b of the semiconductor substrate 112 is locally heated in step S28 described later. The implantation energy is adjusted so that the hydrogen ions stop at the depth to be formed (that is, the position close to the lower surface 112b: the position 150 in FIG. 9). More specifically, hydrogen ions are implanted so that the peak depth of the concentration distribution of hydrogen ions after implantation is located at position 150 in FIG. In this embodiment, the hydrogen ion implantation position 150 is about 50 μm deep from the lower surface 112b.

In step S28, the lower surface 112b of the semiconductor substrate 112 is irradiated with an electron beam to locally heat the lower surface 112b. In the heating by electron beam irradiation, since the heating range is limited to the electron beam irradiation range, the entire lower surface 112b is scanned by scanning the entire lower surface 112b. FIG. 10 shows a temperature profile at one point on the lower surface 112b in the heating in step S28. As shown in the figure, in step S28, the maximum temperature reached on the lower surface 112b of the semiconductor substrate 112 is about 450 ° C. That is, the temperature of the lower surface 112b is raised to a temperature within a temperature range of 300 to 600 ° C. at which hydrogen ions are activated. Step S28 is performed so that the heating time (the time during which the temperature of the lower surface 112b is maintained within the temperature range of 300 to 600 ° C. as shown in the heating time Ta in FIG. 10) is about 100 msec. Since the lower surface 112b is heated by scanning the electron beam, the heating timing of each point on the lower surface 112b is slightly shifted, but each point on the lower surface 112b is heated with a temperature profile that substantially matches the temperature profile shown in FIG.
As described above, the hydrogen ion implantation position 150 is located at a depth at which the temperature is raised to substantially the same temperature as the lower surface 112b of the semiconductor substrate 112. That is, the hydrogen ion implantation position 150 is heated with a temperature profile substantially equal to the temperature profile shown in FIG. When the hydrogen ion implantation position 150 is heated to a temperature in the temperature range of 300 to 600 ° C., the hydrogen ions are activated and diffused. At this time, the activation amount of hydrogen ions hardly depends on the heating time Ta of the lower surface 112b (that is, the time during which the temperature of the hydrogen ion implantation position 150 is maintained within the temperature range of 300 to 600 ° C.). That is, the activation amount of hydrogen ions does not change so much even when heating is performed for a short time or for a long time. On the other hand, the diffusion distance of hydrogen ions greatly depends on the heating time Ta of the lower surface 112b. That is, the longer the heating time Ta of the lower surface 112b, the longer the hydrogen ion diffusion distance. As described above, in step S28, the heating time Ta of the lower surface 112b of the semiconductor substrate 112 is as short as 100 msec. Therefore, the diffusion distance of hydrogen ions is shortened. For this reason, the donor concentration in the vicinity of the hydrogen ion implantation position 150 is significantly increased. As a result, an n ⁺ region 126 is formed near the hydrogen ion implantation position 150 as shown in FIG. Further, the remaining n ⁻ region becomes the n ⁻ region 124.
Further, as described above, since the diffusion distance of hydrogen ions is short in step S28, the n ⁺ region 126 is formed thin. When the n ⁺ region 126 is formed thin, the n ⁻ region 124 can be kept thick. Therefore, the reverse breakdown voltage of the diode 100 can be further increased.

In step S30, the cathode electrode 116 is formed on the lower surface 112b of the semiconductor substrate 112 by vapor deposition or the like.
Through the above steps, the diode 100 shown in FIG. 7 is manufactured.

As described above, in the method of manufacturing the diode 100 of the second embodiment, hydrogen ions are implanted near the lower surface 112b of the semiconductor substrate 112, and the heating time Ta of the lower surface 112b is set to a short time (about 100 msec). , Activate the implanted hydrogen ions. Thus, the donor concentration in the vicinity of the hydrogen ion implantation position 150 can be significantly increased by shortening the heating time Ta of the lower surface 112b.
FIG. 11 shows the heating time Ta when the heating time Ta in Step S28 (the time during which the lower surface 112b is maintained at a temperature in the temperature range of 300 to 600 ° C.) is variously changed in the manufacturing method described above. The relationship with the increase amount of the donor concentration in the semiconductor substrate 112 is shown. That is, each point plotted in FIG. 11 indicates the amount of increase (vertical axis) of the donor concentration in the semiconductor substrate 112 when heated at the heating time Ta (horizontal axis). The increase amount of the donor concentration on the vertical axis indicates the increase amount at the peak position of the donor concentration in the donor concentration distribution (concentration distribution after heating) in the hydrogen ion implantation direction (depth direction). Each experiment (the experiment of each point plotted in FIG. 11) is performed under the same conditions except for the heating time.
As shown in FIG. 11, when the heating time is 1 to 60 sec (1000 to 60000 msec), the amount of increase in the donor concentration is about 3 × 10 ¹⁵ cm ⁻³ . Even if the heating time is increased to 60 seconds or more, the amount of increase in the donor concentration is hardly changed. That is, the increase amount of the donor concentration of 3 × 10 ¹⁵ cm ⁻³ is a value obtained by the conventional manufacturing method. On the other hand, when the heating time Ta is in the range of 50 to 1000 msec (0.05 to 1 sec), the amount of increase in donor concentration increases. In particular, when the heating time Ta is in the range of 67 to 200 msec (0.067 to 0.2 sec), the amount of increase in the donor concentration is significantly increased. Thus, the amount of increase in the donor concentration can be increased by setting the heating time Ta of the lower surface 112b of the semiconductor substrate 112 to 50 to 1000 msec (particularly 67 to 200 msec).

  In step S28, the lower surface 112b of the semiconductor substrate 112 (that is, the hydrogen ion implantation position 150) is heated to about 450 ° C., but the heating temperature (maximum temperature reached) in step S28 is appropriately within a temperature range of 300 to 600 ° C. You can choose. If the hydrogen ion implantation position 150 is heated to a temperature within the temperature range of 300 to 600 ° C., the hydrogen ions can be activated. The heating temperature (maximum temperature reached) in step S28 is particularly preferably a temperature within a temperature range of 350 to 550 ° C. (see FIG. 1).

  Moreover, in the manufacturing method of the diode 100 described above, the lower surface 112b of the semiconductor substrate 112 is heated by electron beam irradiation in step S28. However, the lower surface 112b may be heated by laser irradiation. Further, the lower surface 112b may be heated by irradiating a flash lamp. Also by these methods, the lower surface 112b of the semiconductor substrate 112 can be heated only for a short time.

  Moreover, in the manufacturing method of the diode 100 described above, hydrogen ions are implanted from the lower surface 112b to a depth of 50 μm in step S26. However, the implantation depth of hydrogen ions can be appropriately selected according to the implantation range of hydrogen ions (that is, the range that requires heating), the shape and thermal conductivity of the semiconductor substrate, the heating method of the semiconductor substrate, and the like. . Note that the implantation depth of hydrogen ions is preferably 50 μm or less. If hydrogen ions are implanted to such a depth, the temperature of the hydrogen ion implantation depth can be heated to a temperature substantially equal to the temperature of the lower surface 112b of the semiconductor substrate 112 in step S28.

  Moreover, in the manufacturing method of the diode 100 described above, protons are implanted as hydrogen ions, but dutrons or tritons may be implanted. Even if Dutron or Triton is injected, the donor concentration can be increased greatly as in the second embodiment.

In the second embodiment, the method for manufacturing the diode 100 has been described. However, the technique of the second embodiment can be applied to the manufacture of other types of semiconductor devices. For example, the present invention can be applied to the manufacture of the MOS-FET 200 shown in FIG. In this case, the n ⁺ collector region 202 of the MOS-FET 200 can be formed by hydrogen ion implantation and short-time heating at the hydrogen ion implantation position. As a result, the n ⁺ collector region 202 having a high donor concentration can be formed. In addition, since the n ⁺ collector region 202 is formed thin, the n − drift region 204 is formed thick. A MOS-FET 200 having a high breakdown voltage can be manufactured.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

The graph which shows the relationship between a heating time and donor concentration. The graph which illustrates the donor concentration distribution in a semiconductor substrate when a semiconductor substrate is heated with various heating time. A sectional view of IGBT10. The flowchart which shows the manufacturing process of IGBT10. Sectional drawing of the semiconductor substrate 12 which is the material of IGBT10. Sectional drawing of the semiconductor substrate 12 after step S6 implementation. 2 is a cross-sectional view of the diode 100. FIG. 3 is a flowchart showing a manufacturing process of the diode 100. Sectional drawing of the semiconductor substrate 112 after step S24 implementation. The graph which shows the temperature profile of the point on the lower surface 112b of the semiconductor substrate 112 in the heating of step S28. The graph which shows the relationship between the heating time of step S28, and the raise amount of the donor concentration of the hydrogen ion implantation position 150 after step S28 implementation. Sectional drawing of MOS-FET200.

Explanation of symbols

10: IGBT
12: Semiconductor substrate 14: Emitter electrode 16: Collector electrode 20: n ⁺ emitter region 22: p ⁺ contact region 24: p ⁻ body region 26: gate electrode 28: insulating film 32: n ⁻ drift region 34: n ⁺ buffer region 36: p ⁺ collector region 50: hydrogen ion implantation position 52: lower surface side region 100: diode 112: semiconductor substrate 114: anode electrode 116: cathode electrode 120: p ⁺ region 122: p ⁻ region 124: n ⁻ region 126: n ⁺ Region 150: hydrogen ion implantation position

Claims (4)

A method for manufacturing a semiconductor device, comprising:
An implantation step of implanting hydrogen ions into the surface of the semiconductor substrate with energy reaching a depth away from the surface;
While maintaining the temperature of the semiconductor substrate at the depth after the implantation step below the hydrogen ion outward diffusion temperature, the semiconductor substrate is heated until the temperature of the surface of the semiconductor substrate rises above the crystal defect extinction temperature. A surface heating step of heating the surface of
After the surface heating step, an implantation depth heating step of heating the semiconductor substrate at least at the depth until the semiconductor substrate reaches a temperature not lower than the hydrogen ion outward diffusion temperature within the hydrogen ion activation temperature range,
A method for manufacturing a semiconductor device, comprising:   2. The method of manufacturing a semiconductor device according to claim 1, wherein in the surface heating step, heating is performed so that a temperature of the surface of the semiconductor substrate is maintained at 800 ° C. or more for 1 to 1000 msec.   3. The method of manufacturing a semiconductor device according to claim 1, wherein in the surface heating step, the surface is irradiated using any one of a flash lamp, an electron beam, and a laser.   4. The method of manufacturing a semiconductor device according to claim 1, wherein, in the implantation depth heating step, the entire semiconductor substrate is heated.

Images