JP2016046273A5 - - Google Patents

Description

Silicon carbide semiconductor device manufacturing method and silicon carbide semiconductor device

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

  Conventionally, semiconductor devices used as power devices include those using silicon (Si) as a semiconductor material and those using silicon carbide (SiC). SiC has physical properties of 3 times the thermal conductivity, 10 times the maximum electric field strength, and 2 times the electron drift velocity compared to Si. For this reason, a semiconductor device using SiC (SiC semiconductor device, that is, a silicon carbide semiconductor device) is called a wide gap semiconductor or the like, and has recently been applied as a power device having a high dielectric breakdown voltage, low loss, and capable of operating at high temperature. Has been studied.

Among silicon carbide semiconductor devices, in power MOSFETs and IGBTs, nickel silicide (Ni silicide, Ni ₂ Si) is generally used in order to obtain ohmic contact with the substrate on the front surface side. In forming the nickel silicide, for example, after forming a desired impurity layer on the front surface side of the SiC substrate, a gate oxide film is formed, and a polysilicon pattern is formed. Next, after an interlayer insulating film is formed, a portion requiring contact is opened by etching. Thereafter, a Ni film is formed by sputtering or vapor deposition, and nickel silicide is formed by performing a rapid heat treatment.

  FIG. 6 is an explanatory view schematically showing a cross section in a state where nickel silicide is formed by a conventional method when manufacturing a silicon carbide semiconductor device. As shown in FIG. 6, in order to provide a nickel silicide film 602 by a conventional method, when heat treatment is performed in a state where nickel (Ni, see reference numeral 602a in FIG. 6) is present on the interlayer insulating film 601 or on the side wall, There is a problem in that nickel diffuses into the interlayer insulating film 601 and a gate-source short-circuit failure occurs. Further, when heat treatment is performed with nickel on the interlayer insulating film 601 or on the side wall by a conventional method, metal contaminants, moisture, and the like (see reference numeral 603 in FIG. 6) enter the gate oxide film 604. There is a problem that the gate oxide film 604 deteriorates.

  In order to avoid problems caused by diffusion of nickel into the interlayer insulating film 601, it is conceivable to perform a process of leaving nickel only in the contact portion where the contact hole 605 is provided using photolithography. When implementing such a process, alignment and dimensional deviations must be taken into account. For this reason, in the manufacturing method which implements such a process, it is difficult to stably manufacture the silicon carbide semiconductor device, and the practicality is inferior. Further, even when a process of leaving nickel only at the contact portion using photolithography is performed, the deterioration of the gate oxide film 604 due to the entry of metal contaminants or moisture into the gate oxide film 604 is prevented. has no effect.

In FIG. 6, reference numeral 606 indicates a SiC substrate, and reference numeral 607 indicates a SiC epitaxial layer. In FIG. 6, reference numeral 608 indicates a p channel layer, reference numeral 609 indicates an n ⁺ source layer, and reference numeral 610 indicates a p ⁺ contact layer. In FIG. 6, reference numeral 611 denotes a doped polysilicon film.

  Conventionally, in order to solve these problems, there has been a technique of providing a shielding film that shields metal and moisture, such as a TiN film formed using titanium nitride (TiN). Specifically, for example, after opening the contact hole 605, a TiN film is formed on the entire surface of the SiC substrate with a thickness of about 100 nm by a method such as reactive sputtering, and only the portion to be silicided is dry etched. To open the window. Thereafter, nickel film formation and heat treatment are performed. Thereby, in addition to preventing nickel from diffusing into the interlayer insulating film 601, entry of metal contaminants and moisture into the gate oxide film 604 can be prevented.

  Conventionally, as a related technique, a second conductivity type body region in a first conductivity type first silicon carbide semiconductor layer on a first conductivity type semiconductor substrate, and a first conductivity type impurity region in the body region, A second conductivity type second silicon carbide semiconductor layer on the first silicon carbide semiconductor layer; a gate insulating film on the second silicon carbide semiconductor layer; a gate electrode on the gate insulating film; and an impurity region. In a semiconductor element including a first ohmic electrode and a second ohmic electrode on the back surface of the semiconductor substrate, the body region includes a first body region and a second body region, and the average impurity concentration of the first body region is the second body. There is a technique in which the average impurity concentration of the region is twice or more and the bottom surface of the impurity region is positioned deeper than the bottom surface of the first body region (see, for example, Patent Document 1 below).

Japanese Patent No. 5015361

  However, as described above, the conventional manufacturing method for manufacturing a silicon carbide semiconductor device provided with a shielding film that shields metal and moisture is effective only in an ideal case where a TiN film can be uniformly formed. The manufacturing method has a problem that it is inferior in feasibility. Specifically, there are the following problems.

  7 and 8 are explanatory views showing problems of the silicon carbide semiconductor device according to the conventional manufacturing method. 7 and 8, the same parts as those in FIG. 6 are denoted by the same reference numerals. FIG. 7 schematically shows a cross section of the silicon carbide semiconductor device in which TiN film 702 is formed when the silicon carbide semiconductor device is manufactured by the conventional manufacturing method.

  As shown in FIG. 7, in practice, there is a stepped portion 701 caused by the underlying step such as the doped polysilicon film 611 and the contact hole 605, and the thickness (film thickness) of the TiN film 702 is locally present. However, there will be insufficient parts. In order to secure a sufficient thickness of the TiN film 702 in the stepped portion 701, it is necessary to increase the thickness of the TiN film 702.

  FIG. 8 schematically shows a cross section of the silicon carbide semiconductor device in a state where the TiN film 702 is formed thick when the silicon carbide semiconductor device is manufactured by the conventional manufacturing method. As shown in FIG. 8, when the thickness of the entire TiN film 702 is increased in order to ensure a sufficient thickness of the TiN film 702 also in the stepped portion 701, the TiN film 702 in the removal target portion is removed by dry etching. In order to achieve this, it is necessary to etch more than the thin case because the thickness is increased.

  For this reason, the conventional method for manufacturing a silicon carbide semiconductor device has a problem in that the SiC substrate exposed through the contact hole 605, that is, the impurity layer, is also removed, resulting in etching damage. Further, the conventional method for manufacturing a silicon carbide semiconductor device has a problem that contact resistance increases due to etching damage.

  Thus, the conventional method for manufacturing a silicon carbide semiconductor device has a problem that it is difficult to suppress an increase in contact resistance and to prevent a short-circuit between the gate and the source and deterioration of characteristics of the gate oxide film.

In order to eliminate the above-described problems caused by the prior art, the present invention provides a method for manufacturing a silicon carbide semiconductor device capable of preventing a short circuit between the gate and the source and deterioration of characteristics of the gate oxide film without increasing the contact resistance. And it aims at providing a silicon carbide semiconductor device .

  In order to solve the above-described problems and achieve the object, a method for manufacturing a silicon carbide semiconductor device according to the present invention includes a step of forming a gate oxide film on a front surface side of a semiconductor substrate made of silicon carbide, Forming a gate electrode on a front surface side of the gate oxide film; and an insulating film on a front surface side of the gate electrode and a portion of the gate oxide film exposed without being covered by the gate electrode Forming a contact hole reaching the semiconductor substrate by opening the insulating film, and forming a titanium film formed using titanium on the entire front surface side of the semiconductor substrate A step of forming a shielding film for shielding metal and moisture on the front surface side of the titanium film, a step of removing the shielding film on the bottom surface of the contact hole by dry etching, Previous A step of removing the titanium film by wet etching, a step of forming a nickel film formed of nickel on the entire front surface side of the semiconductor substrate and the entire back surface side of the semiconductor substrate, and the nickel film And heating the entire semiconductor substrate on which the film is formed.

  In the method for manufacturing a silicon carbide semiconductor device according to the present invention as set forth in the invention described above, the shielding film is formed using titanium nitride.

  In the method for manufacturing a silicon carbide semiconductor device according to the present invention as set forth in the invention described above, the titanium film has a thickness of 50 nm to 150 nm.

  In the method for manufacturing a silicon carbide semiconductor device according to the present invention as set forth in the invention described above, the thickness of the shielding film is 150 nm to 1 μm.

  In the method for manufacturing a silicon carbide semiconductor device according to the present invention as set forth in the invention described above, the step of removing the shielding film by dry etching stops dry etching by detecting the end point.

  In the method for manufacturing a silicon carbide semiconductor device according to the present invention as set forth in the invention described above, the step of removing the shielding film by dry etching performs dry etching for a predetermined etching time.

  The method for manufacturing a silicon carbide semiconductor device according to the present invention is characterized in that, in the above invention, the step of removing the titanium film by wet etching uses a mixed solution of ammonia water and hydrogen peroxide solution.

In order to solve the above-described problems and achieve the object, a silicon carbide semiconductor device according to the present invention includes a gate oxide film and a gate electrode on a front surface side of a semiconductor substrate made of silicon carbide, and the gate electrode In a MOS type silicon carbide semiconductor device having an interlayer insulating film to cover, a titanium film and a titanium nitride film on the titanium film cover a top surface and a side surface of the interlayer insulating film, and a surface electrode formed on the titanium nitride film Is in contact with nickel silicide in the contact hole of the semiconductor substrate.

In the silicon carbide semiconductor device according to the present invention as set forth in the invention described above, the titanium film has a thickness of 50 nm to 150 nm.

In the silicon carbide semiconductor device according to the present invention as set forth in the invention described above, the titanium nitride film has a thickness of 150 nm to 1 μm.

According to the method for manufacturing a silicon carbide semiconductor device and the silicon carbide semiconductor device according to the present invention, a silicon carbide semiconductor capable of preventing a gate-source short-circuit failure and deterioration of characteristics of a gate oxide film without increasing contact resistance. There exists an effect that an apparatus can be provided .

It is explanatory drawing which shows the structure of the vertical MOSFET manufactured by the manufacturing method of the silicon carbide semiconductor device of embodiment concerning this invention. It is explanatory drawing (the 1) which shows a part of vertical MOSFET manufactured with the manufacturing method of the silicon carbide semiconductor device of embodiment concerning this invention. It is explanatory drawing (the 2) which shows a part of vertical MOSFET manufactured with the manufacturing method of the silicon carbide semiconductor device of embodiment concerning this invention. It is explanatory drawing (the 3) which shows a part of vertical MOSFET manufactured with the manufacturing method of the silicon carbide semiconductor device of embodiment concerning this invention. It is explanatory drawing (the 4) which shows a part of vertical MOSFET manufactured with the manufacturing method of the silicon carbide semiconductor device of embodiment concerning this invention. It is explanatory drawing which shows typically the cross section of the state in which the nickel silicide was formed by the conventional method at the time of manufacture of a silicon carbide semiconductor device. It is explanatory drawing (the 1) which shows the problem of the silicon carbide semiconductor device by the conventional manufacturing method. It is explanatory drawing (the 2) which shows the problem of the silicon carbide semiconductor device by the conventional manufacturing method.

With reference to the accompanying drawings, illustrating a preferred embodiment of the manufacturing method and silicon carbide semiconductor device of the silicon carbide semiconductor device according to the present invention in detail.

(Configuration of vertical MOSFET)
First, the structure of a vertical MOSFET that realizes a silicon carbide semiconductor device (SiC semiconductor device) manufactured by the method for manufacturing a silicon carbide semiconductor device according to the embodiment of the present invention will be described. FIG. 1 is an explanatory view showing a configuration of a vertical MOSFET manufactured by a method for manufacturing a silicon carbide semiconductor device according to an embodiment of the present invention. FIG. 1 schematically shows a cross section of a vertical MOSFET as a final form of a silicon carbide semiconductor device manufactured by the method for manufacturing a silicon carbide semiconductor device according to the embodiment of the present invention.

In FIG. 1, a vertical MOSFET 100 as a silicon carbide semiconductor device manufactured by the method for manufacturing a silicon carbide semiconductor device according to the embodiment of the present invention includes a front surface side of an n ⁺ type SiC substrate 101 (the paper surface in FIG. 1). An n ⁻ type SiC epitaxial layer 102 provided on the upper side) is provided. N ⁺ type SiC substrate 101 and n ⁻ type SiC epitaxial layer 102 form an epitaxial substrate 115.

In this embodiment, semiconductor substrate made of silicon carbide according to the embodiment of the present invention can be realized by epitaxial substrate 115 formed by n ⁺ type SiC substrate 101 and n ⁻ type SiC epitaxial layer 102. it can. The n ⁺ type SiC substrate 101 realizes the n ⁺ drain layer of the embodiment according to the present invention. The n ⁻ type SiC epitaxial layer 102 realizes the n ⁻ drift layer of the embodiment according to the present invention.

A p-channel layer 103 is provided on the front surface side of the epitaxial substrate 115, that is, on the front surface side of the n ⁻ -type SiC epitaxial layer 102. The p-channel layer 103 is provided in a predetermined pattern at a part of the front surface side of the n ⁻ -type SiC epitaxial layer 102 with a space therebetween.

An n ⁺ source layer 104 and a p ⁺ contact layer 105 are provided on the front surface side of the p channel layer 103. The n ⁺ source layer 104 and the p ⁺ contact layer 105 are provided adjacent to each other on the front surface side of the p channel layer 103. The n ⁺ source layer 104 and the p ⁺ contact layer 105 are provided so as to be exposed on the front surface side of the epitaxial substrate 115. The p channel layer 103 is provided in a state where a part thereof excluding the portion where the n ⁺ source layer 104 and the p ⁺ contact layer 105 are provided is exposed on the front surface side of the epitaxial substrate 115. The p channel layer 103, the n ⁺ source layer 104, and the p ⁺ contact layer 105 can be formed by ion implantation, for example.

A gate oxide film 106 is provided on the front surface side of the epitaxial substrate 115 on which the p channel layer 103, the n ⁺ source layer 104, and the p ⁺ contact layer 105 are formed. The gate oxide film 106 includes adjacent p channel layers 103 spaced apart from each other, n ⁻ -type SiC epitaxial layers 102 between the adjacent p channel layers 103, and the adjacent p channel layers 103. It is provided in contact with the n ⁺ source layer 104 provided in the p channel layer 103.

  On the front surface side of the gate oxide film 106, a doped polysilicon film 107 and an interlayer insulating film 108 are provided in this order from the gate oxide film 106 side. Interlayer insulating film 108 is provided on the front surface side of gate oxide film 106 so as to cover doped polysilicon film 107. The interlayer insulating film 108 realizes the insulating film according to the embodiment of the present invention.

A contact 109 is provided on the front surface side of the epitaxial substrate 115 on which the interlayer insulating film 108 is formed. The contact 109 is formed, for example, by etching the interlayer insulating film 108 formed on the front surface side of the n ⁺ type SiC substrate 101 to open a contact hole 110 and burying a metal material in the contact hole 110. be able to.

  A titanium film (Ti film) 111 and a titanium nitride film (TiN film) 112 are provided on the front surface side of the interlayer insulating film 108. The Ti film 111 is formed using titanium (Ti), and has a thickness of, for example, 100 nm. Further, the TiN film 112 is formed using titanium nitride (TiN), and has a thickness of, for example, 400 nm. The Ti film 111 and the TiN film 112 are not provided in the contact hole 110.

A nickel silicide layer 113 is provided on the front surface side of the epitaxial substrate 115. The nickel silicide layer 113 is provided so as to cover a portion of the n ⁺ source layer 104 that is not covered with the Ti film 111 and the TiN film 112 and the p ⁺ contact layer 105. Nickel silicide layer 113 is provided on the back side of epitaxial substrate 115, that is, on the back side of n ⁺ -type SiC substrate 101. Nickel silicide layer 113 is provided on the entire back surface side of n ⁺ -type SiC substrate 101.

Metal films 114 (114a and 114b) serving as electrodes are provided on the front surface side and the back surface of the epitaxial substrate 115 on which the nickel silicide layer 113 is provided. Metal film 114 (114a) provided on the front surface side of epitaxial substrate 115 (n ^- type SiC epitaxial layer 102) realizes a surface electrode. Metal film 114 (114b) provided on the back side of epitaxial substrate 115 (n ⁺ -type SiC substrate 101) realizes a back electrode.

(Method for manufacturing silicon carbide semiconductor device)
Next, a method for manufacturing the silicon carbide semiconductor device of the embodiment according to the present invention will be described. 2, 3, 4 and 5 are explanatory views showing a part of vertical MOSFET 100 manufactured by the method for manufacturing the silicon carbide semiconductor device according to the embodiment of the present invention.

In manufacturing vertical MOSFET 100 by the method for manufacturing a silicon carbide semiconductor device according to the embodiment of the present invention, first, n ⁻ type SiC epitaxial layer 102 is formed on the front surface side of n ⁺ type SiC substrate 101. Thus, the epitaxial substrate 115 is formed. The n ⁻ type SiC epitaxial layer 102 is formed by epitaxial growth, for example. The n ⁻ type SiC epitaxial layer 102 is formed with a thickness of 15 μm, for example. FIG. 2 shows a state in which an n ⁻ type SiC epitaxial layer 102 is formed on the front surface side of the n ⁺ type SiC substrate 101 and an epitaxial substrate 115 is formed.

Next, on the front surface side (n ⁻ type SiC epitaxial layer 102 side) of an epitaxial substrate 115 formed by depositing an n ⁻ type SiC epitaxial layer 102 on the n ⁺ type SiC substrate 101, a p channel layer 103, n ^{A +} source layer 104 and a p ⁺ contact layer 105 are formed. In FIG. 3, following the state shown in FIG. 2, a p channel layer 103, an n ⁺ source layer 104, and a p ⁺ contact are formed on the front surface side (n ⁻ type SiC epitaxial layer 102 side) of the epitaxial substrate 115. The state where the layer 105 is formed is shown.

p-channel layer 103, n ^- for the type SiC epitaxial layer 102, the the n ^- formed by adding an impurity from the front surface side of the mold SiC epitaxial layer 102 (doping). Specifically, p-channel layer 103, n ^- for the type SiC epitaxial layer 102, the n ^- from the front surface side of the mold SiC epitaxial layer 102, the p-type impurity is formed by ion implantation Can do. For example, boron (B) or the like can be used as the p-type impurity.

The n ⁺ source layer 104 and the p ⁺ contact layer 105 are formed by adding impurities to the p channel layer 103 from the front surface side of the p channel layer 103, respectively. Specifically, the n ⁺ source layer 104 can be formed by ion-implanting n-type impurities into the p channel layer 103 from the front surface side of the p channel layer 103. As the n-type impurity, for example, phosphorus (P), arsenic (As), antimony (Sb), or the like can be used.

Specifically, the p ⁺ contact layer 105 can be formed by ion-implanting p-type impurities into the p channel layer 103 from the front surface side of the p channel layer 103. As the p-type impurity, for example, boron (B) or the like can be used similarly to the p-channel layer 103.

In forming the p-channel layer 103, n ⁺ source layer 104 and the p ⁺ contact layer 105, after adding an impurity by ion implantation, the p-channel layer 103, n ⁺ source layer 104 and the p ⁺ contact layer 105 region A heat treatment is performed on the n ⁺ -type SiC substrate 101 to which impurities are added respectively. As a result, the impurities implanted into p channel layer 103, n ⁺ source layer 104 and p ⁺ contact layer 105 are activated. The heat treatment is performed at 1800 ° C., for example.

Next, a gate oxide film 106 is formed on the front surface side of the n ⁻ type SiC epitaxial layer 102 (epitaxial substrate 115) on which the p channel layer 103, the n ⁺ source layer 104 and the p ⁺ contact layer 105 are formed. . Then, a doped polysilicon film 107 is formed on the front surface side of the gate oxide film 106. For example, the gate oxide film 106 is formed to be wider than the doped polysilicon film 107. A method for forming the gate oxide film 106 and the doped polysilicon film 107 can be easily realized by using various known techniques, and thus description thereof is omitted.

Next, an interlayer insulating film 108 is formed on the front surface side of the n ⁻ type SiC epitaxial layer 102 (epitaxial substrate 115) on which the doped polysilicon film 107 is formed. The interlayer insulating film 108 is formed so that the end is in contact with the front surface side of the gate oxide film 106 outside the doped polysilicon film 107. In FIG. 4, following the state shown in FIG. 3, a gate oxide film 106, a doped polysilicon film are formed on the front surface side of the epitaxial substrate 115 (n ⁻ type SiC epitaxial layer 102) shown in FIG. 107 shows a state in which an interlayer insulating film 108 and a contact hole 110 are formed.

As a result, the doped polysilicon film 107 is covered with the gate oxide film 106 and the interlayer insulating film 108 and sealed. Thereafter, contact holes 110 are formed. A method for forming the interlayer insulating film 108 and the contact hole 110 can be easily realized by using various known techniques, and thus description thereof is omitted. By forming the contact hole 110, a part of the front surface side of the n ⁺ source layer 104 and the p ⁺ contact layer 105 are exposed in the contact hole 110.

  Next, a Ti film 111 is formed on the front surface side of the interlayer insulating film 108. The Ti film 111 is formed, for example, by depositing Ti on the front surface side of the interlayer insulating film 108 so as to have a thickness of 100 nm. Further, a TiN film 112 is formed on the front surface side of the Ti film 111. The TiN film 112 is formed, for example, by depositing TiN on the front surface side of the Ti film 111 so as to have a thickness of 400 nm.

  Next, the TiN film 112 and the Ti film 111 formed in the contact hole 110 by the formation of the Ti film 111 and the TiN film 112 are removed. In this embodiment, first, the TiN film 112 formed in the contact hole 110 is removed by dry etching, and then the Ti film 111 formed in the contact hole 110 is removed by wet etching. . FIG. 5 shows a state where the TiN film 112 and the Ti film 111 formed in the contact hole 110 are removed following the state shown in FIG.

By removing the TiN film 112 and the Ti film 111 formed in the contact hole 110, the front surface side of the p ⁺ contact layer 105 is exposed. Further, by removing the TiN film 112 and the Ti film 111 formed in the contact hole 110, a part of the front surface side of the n ⁺ source layer 104 is exposed.

That is, by removing the TiN film 112 and the Ti film 111 formed in the contact hole 110, the Ti film 111 forms the gate oxide film 106 and the interlayer insulating film 108 on the epitaxial substrate 115 (n ⁻ type SiC epitaxial layer). 102) is covered from the front surface side, and its end is in contact with the n ⁺ source layer 104 outside the gate oxide film 106. Further, by removing the TiN film 112 and the Ti film 111 formed in the contact hole 110, the TiN film 112 is formed only on the front surface side of the Ti film 111.

Specifically, the TiN film 112 formed in the contact hole 110 can be removed by performing dry etching with, for example, Cl ₂ / BCl ₃ gas. The dry etching is performed when the TiN film 112 formed in the contact hole 110 is removed and the Ti film 111 formed under the TiN film 112 is exposed (exposed). Is detected as the etching end point, and stops when the end point is detected.

  When removing the TiN film 112 formed in the contact hole 110, for example, based on the light emission waveform during etching (dry etching), the time when the light emission waveform indicating TiN disappears from the light emission waveform is etched. It can be detected as an end point. According to this method, at the time of etching, the end point of etching by dry etching can be determined based on the change in the intensity of the etching gas that emits light or the emission intensity of the reaction product that is generated.

  Specifically, the end point of the etching by dry etching is, for example, a dry etching process using the fact that the emission intensity of a specific wavelength in the plasma light used for dry etching changes with the progress of etching of the TiN film 112. It is possible to detect a change in emission intensity of a specific wavelength from the plasma light, and to detect the etching end point of the specific film (TiN film 112) based on the detection result.

  Further, when the TiN film 112 formed in the contact hole 110 is removed, the TiN film 112 may be removed by performing dry etching for a predetermined etching time, that is, so-called time-designated etching. . In time-designated etching, for example, a time point when a predetermined etching time specified in advance from a predetermined start time point such as a time point when dry etching is started is detected as an end point of etching by dry etching.

  Specifically, it is possible to measure the elapsed time since the start of the generation of plasma (discharge) in the chamber of the dry etching apparatus, and stop dry etching when the elapsed time reaches a predetermined etching time. it can. The predetermined etching time can be set, for example, by conducting an experiment in advance and examining the etching rate of TiN in advance. The start time is not limited to the time when the generation of plasma (discharge) is started, and can be appropriately set according to, for example, a TiN etching rate investigation method.

  The Ti film 111 serves as a stopper film during dry etching. By forming the Ti film 111 with a thickness of 50 nm to 150 nm, the Ti film 111 can sufficiently serve as a stopper film for dry etching. The TiN film 112 needs to be formed with a thickness of 150 nm to 1 μm in order to obtain a sufficient shielding effect even in a step portion with poor coverage.

Wet etching causes less damage to the base material to be etched (in this embodiment, the epitaxial substrate 115) than dry etching. Therefore, the Ti film 111 formed in the contact hole 110, that is, the n ⁻ type SiC epitaxial layer 102 (more specifically, the n ⁺ source layer 104 (one surface side of the n ⁺ source layer 104) And the Ti film 111 directly formed on the p ⁺ contact layer 105) is removed by wet etching, so that the epitaxial substrate 115 is removed by etching for removing the Ti film 111 formed in the contact hole 110. It can be prevented from being shaved.

When removing the Ti film 111 formed in the contact hole 110, for example, wet etching is performed using a mixed solution of ammonia water and hydrogen peroxide solution. The n ⁺ source layer 104 and the p ⁺ contact layer 105 are damaged by removing the Ti film 111 formed in the contact hole 110 by wet etching using a mixed solution of ammonia water and hydrogen peroxide solution. Therefore, the Ti film 111 formed in the contact hole 110 can be reliably removed.

  Next, after the Ti film 111 formed in the contact hole 110 is removed by wet etching, a nickel film is formed using nickel on the front surface side and the entire back surface of the epitaxial substrate 115. Then, high-speed heat treatment is performed on the epitaxial substrate 115 on which the nickel film is formed. Thereby, the nickel film is silicided, and the nickel silicide layer 113 can be formed. Thereafter, metal films 114 (114a and 114b) to be front and back electrodes are formed on the front and back surfaces of the epitaxial substrate 115, respectively. Thereby, the vertical MOSFET 100 shown in FIG. 1 is completed.

  The vertical MOSFET 100 manufactured by the method for manufacturing the silicon carbide semiconductor device according to the embodiment of the present invention, as described above, is obtained by etching to remove the Ti film 111 formed in the contact hole 110 (SiC substrate ( The epitaxial substrate 115) can be prevented from being scraped. Thereby, since the impurity layer is not scraped or damaged, good contact 109 characteristics can be obtained.

  In the above-described embodiment, the example in which the shielding film according to the present invention is realized by the TiN film 112 has been described. However, the shielding film according to the present invention is not limited to the TiN film 112 formed by TiN. The shielding film according to the present invention may be formed using a material other than TiN that functions to prevent nickel diffusion and prevent metal contaminants and moisture from entering.

  In the above-described embodiment, the silicon carbide semiconductor device manufactured by the method for manufacturing the silicon carbide semiconductor device according to the present invention is exemplified by the vertical MOSFET 100. However, the silicon carbide semiconductor device according to the present invention is illustrated. Is not limited to that realized by the vertical MOSFET 100. The silicon carbide semiconductor device according to the present invention may be applied to other silicon carbide semiconductor devices such as a vertical IGBT in place of vertical MOSFET 100.

  As described above, in the method for manufacturing a silicon carbide semiconductor device according to the embodiment of the present invention, gate oxide film 106 is formed on the front surface side of epitaxial substrate 115 that realizes a semiconductor substrate made of silicon carbide. Then, a doped polysilicon film 107 that realizes a gate electrode is formed on the front surface side of the gate oxide film 106. Next, an insulating film is realized on the front surface side of the doped polysilicon film 107 and on a portion of the gate oxide film 106 exposed to the front surface side without being covered by the doped polysilicon film 107. The interlayer insulating film 108 to be formed is formed, and the interlayer insulating film 108 is opened, and the contact hole 110 reaching the epitaxial substrate 115 is provided. Further, a Ti film 111 formed using Ti is formed on the entire front surface side of the epitaxial substrate 115, and a shielding film that shields metal and moisture on the front surface side of the Ti film 111. A TiN film 112 is formed.

  Then, after the TiN film 112 on the bottom surface of the contact hole 110 is removed by dry etching, the Ti film 111 on the bottom surface of the contact hole 110 is removed by wet etching. Thereafter, a nickel film formed of nickel is formed on the entire front surface side of the epitaxial substrate 115 and the entire back surface side of the epitaxial substrate 115, and the entire epitaxial substrate 115 on which the nickel film is formed is heated. A vertical MOSFET 100 that realizes a silicon carbide semiconductor device is manufactured by forming nickel silicide.

According to the method for manufacturing a silicon carbide semiconductor device of the embodiment of the present invention, interlayer insulating film 108 and gate oxide film 106 are protected by TiN film 112 to prevent Ni from diffusing into interlayer insulating film 108. At the same time, entry of metal contaminants and moisture into the gate oxide film 106 can be prevented. Prior to the formation of the TiN film 112, the Ti film 111 is formed on the entire front surface side of the epitaxial substrate 115, the TiN film 112 on the bottom surface of the contact hole 110 is removed by dry etching, and then the contact hole 110. By removing the Ti film 111 on the bottom surface by wet etching, the p ⁺ contact layer 105 can be exposed without damaging the n ⁺ source layer 104 and the p ⁺ contact layer 105.

That is, when the TiN film 112 on the bottom surface of the contact hole 110 is removed by dry etching in order to expose a part of the n ⁺ source layer 104 and the p ⁺ contact layer 105, the Ti film 111 serves as a stopper film. Only the TiN film 112 on the bottom surface of the contact hole 110 can be removed without damaging the n ⁺ source layer 104 and the p ⁺ contact layer 105, and Ti in the contact hole 110 is removed by wet etching. Thus, the n ⁺ source layer 104 and the p ⁺ contact layer 105 can be exposed without the n ⁺ type SiC substrate 101 being etched away. As a result, it is possible to prevent the n ⁺ source layer 104 and the p ⁺ contact layer 105 from being scraped, and the impurity layers such as the p ⁺ contact layer 105 and the n ⁺ source layer 104 from being damaged. Contact 109 (ohmic contact 109) characteristics can be obtained.

Thus, according to the method for manufacturing the silicon carbide semiconductor device of the embodiment of the present invention, the diffusion of Ni into interlayer insulating film 108 and the intrusion of metal contaminants and moisture into gate oxide film 106 are prevented. At the same time, part of the n ⁺ source layer 104 and the p ⁺ contact layer 105 can be exposed without deteriorating the impurity layer. Thus, according to the method for manufacturing the silicon carbide semiconductor device of the embodiment of the present invention, the short circuit failure between the gate and the source and the deterioration of the characteristics of the gate oxide film 106 can be achieved without increasing the contact 109 resistance. A silicon carbide semiconductor device that can be prevented can be manufactured.

  The method for manufacturing a silicon carbide semiconductor device according to the embodiment of the present invention is characterized in that the shielding film according to the present invention is realized by the TiN film 112 formed using TiN.

  According to the method for manufacturing a silicon carbide semiconductor device of the embodiment of the present invention, the shielding film is formed of TiN, thereby effectively preventing metal contaminants and moisture from entering the gate oxide film 106. be able to. Then, the gate oxide film 106 can be prevented from being deteriorated by preventing metal contaminants and moisture from entering the gate oxide film 106. Thereby, a silicon carbide semiconductor device that can prevent a short circuit failure between the gate and the source and deterioration of the characteristics of the gate oxide film 106 without increasing the resistance of the contact 109 can be manufactured.

  In addition, the method for manufacturing the silicon carbide semiconductor device according to the embodiment of the present invention is characterized in that the thickness of the Ti film 111 is 50 nm to 150 nm.

  According to the method for manufacturing a silicon carbide semiconductor device of the embodiment of the present invention, the thickness of the Ti film 111 is set to 50 nm to 150 nm, so that the TiN film 112 serving as a shielding film is uniformly (uniform thickness). Even when the film is not formed, it is possible to reliably play the role of the stopper film by the Ti film 111 in the process of removing the shielding film by dry etching, and to prevent the occurrence of etching damage. Thereby, a silicon carbide semiconductor device that can prevent a short circuit failure between the gate and the source and deterioration of the characteristics of the gate oxide film 106 without increasing the resistance of the contact 109 can be manufactured.

  In the method for manufacturing a silicon carbide semiconductor device according to the embodiment of the present invention, the thickness of the shielding film (for example, TiN film 112) is 150 nm to 1 μm.

  According to the method for manufacturing a silicon carbide semiconductor device of the embodiment of the present invention, by setting the thickness of the shielding film to 150 nm to 1 μm, a sufficient shielding effect can be exhibited even in a stepped portion with poor coverage. . Thereby, it is possible to reliably prevent metal contaminants and moisture from entering the gate oxide film 106.

  A method for manufacturing a silicon carbide semiconductor device according to an embodiment of the present invention is characterized in that dry etching is stopped by end point detection.

  According to the method for manufacturing a silicon carbide semiconductor device of the embodiment of the present invention, the dry etching is stopped by detecting the end point, so that the TiN film is formed according to the film formation state of the TiN film 112 to be dry etched. 112 can be reliably removed. In other words, when the actual silicon carbide semiconductor device (vertical MOSFET 100) is manufactured, the TiN film 112 in the contact hole 110 is formed even when the TiN film 112 is not completely formed in accordance with the silicon carbide semiconductor device. It can be removed reliably.

As a result, a part of the n ⁺ source layer 104 and the p ⁺ contact layer 105 can be reliably exposed, and the short circuit failure between the gate and the source and the characteristics of the gate oxide film 106 can be achieved without increasing the contact 109 resistance. A silicon carbide semiconductor device capable of preventing deterioration can be manufactured.

  In the method for manufacturing the silicon carbide semiconductor device according to the embodiment of the present invention, instead of the method of stopping the dry etching by detecting the end point, the dry etching is performed for a predetermined etching time, whereby the TiN film 112 is obtained. You may make it remove shielding films, such as.

  According to the method for manufacturing a silicon carbide semiconductor device of the embodiment of the present invention, it is easy to manage the manufacturing process by performing dry etching for a predetermined etching time. A silicon carbide semiconductor device such as the vertical MOSFET 100 can be stably mass-produced without being influenced.

  The method for manufacturing the silicon carbide semiconductor device according to the embodiment of the present invention is characterized in that the step of removing the Ti film 111 by wet etching uses a mixed solution of ammonia water and hydrogen peroxide solution.

According to the method for manufacturing a silicon carbide semiconductor device of the embodiment of the present invention, Ti formed in contact hole 110 is removed by wet etching using a mixed solution of ammonia water and hydrogen peroxide solution. Thus, the Ti film 111 formed in the contact hole 110 can be reliably removed without damaging the n ⁺ source layer 104 and the p ⁺ contact layer 105. As a result, a part of the n ⁺ source layer 104 and the p ⁺ contact layer 105 can be reliably exposed, and the short circuit failure between the gate and the source and the characteristics of the gate oxide film 106 can be achieved without increasing the contact 109 resistance. A silicon carbide semiconductor device capable of preventing deterioration can be manufactured.

As described above, the manufacturing method and silicon carbide semiconductor device according silicon carbide semiconductor device according to the present invention are useful in manufacturing method and silicon carbide semiconductor device of a semiconductor device in which a silicon carbide semiconductor device used as a power device, in particular In order to obtain ohmic contact with the substrate on the front surface side, it is suitable for a method of manufacturing a silicon carbide semiconductor device which is a semiconductor device such as a power MOSFET or IGBT using nickel silicide and a silicon carbide semiconductor device .

100 Vertical MOSFET
101 n ⁺ type SiC substrate 102 n ⁻ type SiC epitaxial layer 103 p channel layer 104 n ⁺ source layer 105 p ⁺ contact layer 106 gate oxide film 107 doped polysilicon film 108 interlayer insulating film 109 contact 110 contact hole 111 Ti film 112 TiN film 113 Nickel silicide layer 114, 114a Metal film (surface electrode)
114, 114b Metal film (back electrode)
115 Epitaxial substrate

Claims (10)

Forming a gate oxide film on a front surface side of a semiconductor substrate made of silicon carbide;
Forming a gate electrode on the front side of the gate oxide film;
Forming an insulating film on a front surface side of the gate electrode and a portion of the gate oxide film exposed without being covered by the gate electrode;
Providing a contact hole that opens the insulating film and reaches the semiconductor substrate;
Forming a titanium film formed using titanium on the entire front side of the semiconductor substrate;
Forming a shielding film for shielding metal and moisture on the front side of the titanium film;
Removing the shielding film on the bottom surface of the contact hole by dry etching;
Removing the titanium film on the bottom surface of the contact hole by wet etching;
Forming a nickel film formed of nickel on the entire front surface side of the semiconductor substrate and the entire back surface side of the semiconductor substrate;
Heating the entire semiconductor substrate on which the nickel film is formed;
The manufacturing method of the silicon carbide semiconductor device characterized by the above-mentioned.   The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the shielding film is formed using titanium nitride.   The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the titanium film has a thickness of 50 nm to 150 nm.   2. The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the shielding film has a thickness of 150 nm to 1 μm.   The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the step of removing the shielding film by dry etching stops the dry etching by detecting an end point.   2. The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the step of removing the shielding film by dry etching performs dry etching for a predetermined etching time.   The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein the step of removing the titanium film by wet etching uses a mixed solution of ammonia water and hydrogen peroxide solution. In a MOS type silicon carbide semiconductor device including a gate oxide film and a gate electrode on the front surface side of a semiconductor substrate made of silicon carbide, and an interlayer insulating film covering the gate electrode,
The upper surface and the side surface of the interlayer insulating film are covered with a titanium film and a titanium nitride film on the titanium film, and the surface electrode formed on the titanium nitride film is in contact with nickel silicide at the contact hole of the semiconductor substrate. A silicon carbide semiconductor device. The silicon carbide semiconductor device according to claim 8, wherein the titanium film has a thickness of 50 nm to 150 nm. The silicon carbide semiconductor device according to claim 8, wherein the titanium nitride film has a thickness of 150 nm to 1 μm.