JP2012190829A - Manufacturing method of semiconductor device and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-resistance electrode with high reliability on SiC at a low cost using a Ni silicide.SOLUTION: A Ni layer 12 is formed on an n-type SiC layer 11 (Fig. 1(a)). A Ni silicide layer 13 is formed by performing heat treatment to react Ni of the Ni layer 12 and Si of the n-type SiC layer 11 (Fig. 1(b)). In this state, the heat treatment is performed in an oxidative atmosphere (Fig. 1(d)). In a reduction atmosphere, for example, the heat treatment is performed at 300 to 400°C (Fig. 1(f): reduction processing step). Thereby, an oxide layer 15 is reduced to serve as a reduction layer 16 composed of Ni, etc. This reduction layer 16 can be removed by wet etching (Fig. 1(g): etching step). Then, a Ti/Al layer 30 which serves as a wiring layer is formed on the Ni silicide layer 13 (Fig. 1 (h)).

Description

  The present invention relates to a method for manufacturing a semiconductor device using silicon carbide (SiC), and more particularly to a method for forming an electrode. The present invention also relates to a semiconductor device manufactured by this manufacturing method.

  Silicon carbide (SiC) is very promising as a material for power elements and the like because its forbidden band width is wider than that of silicon or the like. Using this, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a Schottky diode (SBD) using the Schottky junction, and the like are realized.

  In forming such an element, a current can be passed through SiC via an electrode formed on SiC, which is a semiconductor material. In this case, there are two types of electrodes: a Schottky electrode having a current-voltage characteristic (IV characteristic) between SiC and a rectifying property, and an ohmic electrode having no rectifying property and low contact resistance. In general, these electrodes are made of a metal material, and it is known that various materials can be used for each of n-type SiC and p-type SiC.

Of these, ohmic electrodes for n-type SiC are widely used as electrodes for MOSFETs, SBDs, and the like. As an electrode material having good ohmic characteristics with respect to n-type SiC (IV characteristics have no rectifying property and low contact resistance), for example, as disclosed in Patent Document 1, nickel (Ni) is known. It has been. However, it is not between Ni and n-type SiC that has good ohmic characteristics, but precisely between Ni silicide (Ni _x Si _y ), which is a compound of Ni and Si, and n-type SiC. Ni silicide is formed by a chemical reaction between Ni and SiC by performing heat treatment after forming Ni on the SiC surface. This chemical reaction formula is represented by formula (1).

Here, (x, y) = (1, 1), (x, y) = (1, 2), etc. In this case, Ni _x Si _y is formed, and at the same time, C (carbon) simple substance is liberated from SiC. This C moves in Ni silicide, aggregates on the surface and inside thereof, and precipitates as graphite. On the other hand, although Ni silicide functions as an ohmic electrode, in reality, it is necessary to form another metal material (Au, Al, etc.) to be a wiring thereon. For this reason, for example, a wiring material such as Ti / Al is further laminated thereon. 5A to 5D are process cross-sectional views schematically showing the above process.

  First, the Ni layer 12 is formed on the clean surface of the n-type SiC layer 11 by vapor deposition or sputtering (FIG. 5A). Thereafter, by performing a heat treatment at about 1000 ° C. in this state, the Ni silicide layer 13 is formed by the reaction of the formula (1) (FIG. 5B). In this figure, it is described that the entire Ni layer 12 is the Ni silicide layer 13, but actually, the vicinity of the outermost surface of the Ni layer 12 is not silicided but is in a pure Ni state. In some cases. In this case, the remaining pure Ni layer can be selectively removed by wet etching or the like, and finally the configuration shown in FIG.

  Here, in the state shown in FIG. 5B, as shown by the equation (1), the graphite 14 is also formed at the same time. This graphite 14 is distributed inside and on the surface of the Ni silicide layer 13. Next, in the same way as when the Ni layer 12 is formed, a Ti / Al layer 30 (wiring layer: titanium (Ti) in the lower layer and aluminum (Al) in the upper layer) is formed thereon as a wiring material. As a result, a final electrode structure is obtained (FIG. 5C). At this time, the adhesion between Ti of the Ti / Al layer 30 and the Ni silicide layer 13 is good, but the adhesion between Ti and the graphite 14 is low. For this reason, as shown in FIG. 5D, peeling may occur between the Ti / Al layer 30 and the Ni silicide layer 13 in the subsequent steps or during the operation of the semiconductor element.

In order to suppress such peeling, in Patent Document 1, the surface of the Ni silicide layer 13 is removed by plasma etching after the heat treatment, thereby removing the surface graphite 14. In Patent Document 2, (1) non-oxidizing heat treatment is performed to move the graphite 14 inside the Ni silicide layer 13 to the surface, and then this is removed by etching. (2) oxidizing It describes that the graphite 14 (C) moved to the surface is oxidized and removed as a gas in the state of CO and CO ₂ by performing heat treatment in an atmosphere. Among these methods, the method (2) is extremely effective because not only the surface but also the graphite 14 inside the Ni silicide layer 13 can be efficiently removed.

  Using such a manufacturing method, an ohmic electrode for SiC can be obtained using Ni (Ni silicide).

JP 2003-243323 A JP 2007-184571 A

  With the method described in Patent Document 1, it is possible to remove the graphite 14 on the outermost surface of the Ni silicide layer 13. However, it is difficult to remove the graphite 14 inside the Ni silicide layer 13. Since the mechanical strength of the Ni silicide layer 13 is lowered by the graphite 14 inside, it also causes a decrease in the reliability of the electrode.

  On the other hand, in the method described in Patent Document 2, the graphite 14 is effectively removed both on the surface and inside of the Ni silicide layer 13. However, in the heat treatment for oxidizing and gasifying this, not only the graphite 14 but also the Ni silicide layer 13 are oxidized at the same time. Therefore, an oxide layer containing Ni oxide as a main component and also containing oxides such as Si and C is formed on the outermost surface of the Ni silicide layer 13. This main component, Ni oxide (NiO), is insulative, which causes an increase in electrode resistance. Further, like the graphite 14, the oxide layer itself may cause peeling of the Ti / Al layer 30 and the like thereon. Furthermore, for example, NiO cannot be etched by a strong acid such as sulfuric acid, and it is difficult to etch NiO or the like with high selectivity from other materials by either wet etching or dry etching. For this reason, in order to remove the oxide layer on the surface, it is necessary to perform an etching process after covering a portion other than the portion where the oxide layer is to be removed with a mask such as a photoresist. This complicates the process.

  Thus, it has been difficult to obtain a highly reliable low-resistance electrode on SiC using Ni silicide at a low cost.

  The present invention has been made in view of such problems, and an object thereof is to provide an invention that solves the above problems.

In order to solve the above problems, the present invention has the following configurations.
A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device having a configuration in which an electrode using nickel (Ni) silicide is connected to a silicon carbide (SiC) layer, and a Ni layer is formed on the surface of the SiC layer. Forming a Ni silicide layer by forming a Ni silicide layer by reacting the Ni layer and the SiC layer by performing a heat treatment, and performing a heat treatment in an oxidizing atmosphere after the formation of the Ni silicide layer. An oxidation atmosphere heat treatment step to be performed; a reduction treatment step in which heat treatment is performed at a temperature lower than a temperature of the heat treatment in the silicide formation step in the reduction atmosphere after the oxidation atmosphere heat treatment step; and an etching step to perform an etching treatment on Ni It is characterized by comprising.
The method of manufacturing a semiconductor device according to the present invention includes a wiring formation step of forming a wiring layer in contact with the Ni silicide layer after the etching step.
The method for manufacturing a semiconductor device according to the present invention is characterized in that the temperature of the heat treatment in the reduction treatment step is in the range of 300 to 400 ° C.
The semiconductor device manufacturing method of the present invention is a non-oxidizing atmosphere heat treatment in which a heat treatment is performed between the silicide formation step and the oxidizing atmosphere heat treatment step in a non-oxidizing atmosphere at a temperature lower than the temperature of the heat treatment in the silicide forming step. It comprises the process.
The method for manufacturing a semiconductor device according to the present invention is characterized in that an ultrasonic cleaning process is performed in the etching step.
The method of manufacturing a semiconductor device according to the present invention is characterized in that an insulating layer is formed on the surface of the SiC layer, and the Ni forming step is performed after an opening is formed in the insulating layer.
In the method of manufacturing a semiconductor device according to the present invention, the semiconductor device includes a Schottky electrode for the SiC layer formed on one main surface side of the SiC layer, and an ohmic electrode for the SiC layer is the other main surface of the SiC layer. SBD (Schottky Barrier Diode) formed on the surface side, the Ni layer in the Ni forming step is formed on the other main surface side, and between the heat treatment step in the oxidizing atmosphere and the reduction treatment step, A Schottky electrode forming step of forming the Schottky electrode on one main surface side is provided.
The semiconductor device of the present invention is manufactured by the method for manufacturing a semiconductor device.

  Since the present invention is configured as described above, a highly reliable low-resistance electrode on SiC can be obtained at low cost using Ni silicide.

It is process sectional drawing of the manufacturing method of the semiconductor device which concerns on the 1st Embodiment of this invention. It is a figure which shows the reduction process temperature dependence of the IV characteristic between the electrode and SiC which used Ni silicide. It is process sectional drawing of the manufacturing method of the semiconductor device which concerns on the 2nd Embodiment of this invention. It is process sectional drawing of the manufacturing method of the semiconductor device which concerns on the 3rd Embodiment of this invention. It is a figure which shows an example of the manufacturing method of the conventional semiconductor device which uses Ni silicide for an electrode.

  Hereinafter, a method for manufacturing a semiconductor device according to an embodiment of the present invention will be described. The material constituting the semiconductor device used here is silicon carbide (SiC), and this manufacturing method is a method of forming electrodes on the surface thereof. This structure is used for all semiconductor devices using SiC, such as MOSFETs, SBDs, MESFETs, and the like.

(First embodiment)
This manufacturing method according to the first embodiment is a method of forming an ohmic electrode using Ni silicide on the entire surface of an n-type SiC wafer. 1A to 1H are process cross-sectional views illustrating a method for manufacturing this semiconductor device. Here, a low-resistance ohmic electrode using Ni silicide is formed on n-type SiC. In general, it is difficult to directly bond Ni silicide or the like, and thus another electrode material to be a wiring layer is further laminated thereon. In the following, this step will be particularly described.

  First, the Ni layer 12 is formed on the n-type SiC layer 11 (FIG. 1A: Ni forming step). The Ni layer 12 can be formed by a known film formation method such as vapor deposition (electron beam heating vapor deposition) or sputtering.

Next, Ni of the Ni layer 12 and Si of the n-type SiC layer 11 are reacted by heat treatment to form the Ni silicide layer 13 (FIG. 1B: silicide formation step). This heat treatment temperature is about 900 to 1200 ° C., whereby the reaction of the formula (1) occurs, and the Ni silicide layer 13 made of Ni _x Si _y is formed. At the same time, graphite 14 is formed and deposited on the surface or inside of the Ni silicide layer 13. FIG. 1B shows the case where the entire Ni layer 12 is silicided. However, when the Ni layer 12 is thick, unreacted Ni may remain in the vicinity of the uppermost portion. In this case, the unreacted Ni is removed by wet etching, whereby the configuration shown in FIG. 1B is obtained.

  In this state, a non-oxidizing atmosphere heat treatment at a low temperature is performed (FIG. 1C: non-oxidizing atmosphere heat treatment step). This process is the same as that described in Patent Document 2. That is, as described in paragraph No. 0055 of Patent Document 2, heat treatment is performed at a temperature of 100 to 600 ° C. in a non-oxidizing gas atmosphere. Thereby, the carbon component (graphite 14) inside the Ni silicide layer 13 moves to the surface. In this step, in order not to cause the silicide reaction, the temperature is set lower than the temperature of the heat treatment in the silicide formation step.

Next, heat treatment is performed in an oxidizing atmosphere in this state (FIG. 1D: heat treatment step in oxidizing atmosphere). This process is also the same as that described in Patent Document 2. That is, the carbon component (graphite 14) on the surface becomes CO and CO ₂ and is removed as a gas. Therefore, the carbon component is removed by this step.

  About the above process, it is the same as that of the conventional manufacturing method described in patent document 2. FIG.

In this state, as shown in FIG. 1E, the surface of the Ni silicide layer 13 is oxidized simultaneously with the oxidation of the graphite 14, and an oxide layer 15 is formed on the outermost surface. The oxide layer 15 is a solid containing NiO as a main component and containing SiO ₂ or C. Since NiO as the main component is an insulator, when the Ni silicide layer 13 is used as an electrode, it causes an increase in electrode resistance and peeling. NiO is a material that is difficult to remove by chemical reaction. In particular, it is difficult to chemically remove the oxide layer 15 with high selectivity from other materials.

In the manufacturing method according to the embodiment of the present invention, in this state, heat treatment is performed at, for example, 300 to 400 ° C. in a reducing atmosphere (for example, an Ar, N ₂ atmosphere to which 0.1 to 10% of H ₂ is added). Perform (FIG. 1 (f): reduction process). As a result, the oxide layer 15 is reduced to become a reduced layer 16 made of Ni or the like. When this heat treatment temperature is high, the silicide reaction occurs again and carbon deposition occurs again. Therefore, this heat treatment temperature is sufficiently lower than the above-described silicide formation step. As a specific example, FIG. 2 shows the results of measuring the contact resistance (IV characteristics) of the Ni silicide layer 13 when this reduction treatment step is not performed and when it is performed at 750 ° C. In the case of 750 ° C., it can be confirmed that the contact resistance is increased. On the other hand, when the temperature is lower than 300 ° C., the reduction effect is reduced. For this reason, it is preferable that this heat processing temperature shall be the range of 300-400 degreeC.

The reduction layer 16 can be removed by wet etching (FIG. 1 (g): etching process). In this case, sulfuric acid, SPM (mixture of sulfuric acid and hydrogen peroxide solution), or the like that can etch pure Ni with a high selectivity relative to other substances can be used. SiO ₂ , C, and the like are not etched by sulfuric acid, but they are in the form of fine particles and can be removed by a cleaning process after this wet etching such as ultrasonic cleaning. In addition, since the carbon fine particles present at this time are not dissolved in the acid, the ultrasonic cleaning treatment is particularly effective. In this wet etching, masking with a photoresist or the like is not necessary since high selectivity to Ni is obtained among Ni, SiC, and Ni silicide. Thereby, the Ni silicide layer 13 from which the oxide layer 15 has been removed from the surface is obtained.

  In this step, the remaining outermost surface of the Ni silicide layer 13 may also be oxidized by sulfuric acid or the like. However, since the oxide film formed in this case is very thin as compared with the oxide layer 15, it can be easily removed by dilute hydrofluoric acid treatment, plasma treatment or the like in order to remove it.

  Thereafter, a Ti / Al layer 30 to be a wiring layer is formed on the Ni silicide layer 13 (FIG. 1 (h): wiring formation step). At this time, the graphite 14 is removed, and good adhesion is obtained between the Ni silicide layer 13 and the Ti / Al layer 30 (particularly Ti), so that peeling is unlikely to occur. That is, a highly reliable low-resistance electrode can be obtained.

  In the above manufacturing method, the oxide layer 15 is removed by performing a reduction treatment step and an etching step. In this step, a photoresist mask or the like as in the case where the oxide layer 15 is removed by dry etching, for example, is unnecessary. Therefore, it is possible to obtain a semiconductor device using a highly reliable low-resistance electrode that does not cause peeling on the substrate at low cost.

(Second Embodiment)
In the first embodiment, the example in which the ohmic electrode using the Ni silicide layer is formed on the entire upper surface of the SiC wafer has been described. However, in practice, it is often necessary to form SiO _{2 serving} as an insulating layer and locally establish ohmic connection in the opening. In this case, a wiring layer is formed separately, and the wiring layer is in contact with the Ni silicide layer in the opening. The wiring layer is appropriately patterned so as to be a wiring connected to other elements on the wafer or to be a bonding pad or the like. Below, it describes about the manufacturing method in that case. 3A to 3G are process cross-sectional views illustrating this manufacturing method.

First, the SiO ₂ layer 41 is formed on the upper surface of the n-type SiC layer 11, and an opening is provided therein (FIG. 3A). This opening corresponds to a region where ohmic connection is made to n-type SiC layer 11. The SiO ₂ layer 41 can be formed by a CVD method or the like. Thereafter, the opening can be formed by performing photolithography and etching (wet etching, dry etching).

  Next, the Ni layer 12 is formed on the entire upper surface including the opening of this structure (FIG. 3B: Ni forming step). This is the same as in the first embodiment. The thickness of the Ni layer 12 is, for example, about 50 to 200 nm.

Next, heat treatment is performed to form the Ni silicide layer 13 (FIG. 3C: silicide formation step). This process is also the same as in the first embodiment. However, since the silicidation occurs only at the place where the Ni layer 12 and the n-type SiC layer 11 are in direct contact, the Ni silicide layer 13 is formed only in the opening as shown in FIG. Ni in other places (on the SiO ₂ layer 41) remains unreacted as it is. As in the first embodiment, the graphite 14 is also formed at the place where the Ni silicide layer 13 is formed.

Next, heat treatment is performed in an oxidizing atmosphere in this state (FIG. 3D: heat treatment step in oxidizing atmosphere). This process is also the same as in the first embodiment. That is, as a result, the graphite 14 is removed and the oxide layer 15 is formed on the surface of the Ni silicide layer 13. Further, the Ni layer 12 on the SiO ₂ layer 41 is also oxidized and becomes an oxide layer 15.

Next, heat treatment is performed in a reducing atmosphere (FIG. 3 (e): reduction treatment step). This process is also the same as in the first embodiment. As a result, the reduced layer 16 mainly containing reduced Ni remains on the Ni silicide layer 13 and the SiO ₂ layer 41.

Next, the reducing layer 16 is removed by wet etching (FIG. 3F: etching process). As a result, the Ni silicide layer 13 is exposed in the opening, and the reducing layer 16 on the SiO ₂ layer 41 is also removed. In the oxidizing atmosphere heat treatment process, even when the entire Ni layer 12 on the SiO ₂ layer 41 is not oxidized, for example, only the upper part thereof is oxidized, by performing the reduction treatment process and the oxidizing atmosphere heat treatment process, the SiO ₂ layer 41 is eventually oxidized. All the Ni on the _second layer 41 is removed. Thereby, since conductive Ni does not remain on the SiO ₂ layer 41, a wiring pattern can be formed thereon.

Next, a Ti / Al layer 30 to be a wiring layer is formed so as to be connected to the Ni silicide layer 13 in the opening (FIG. 3G: wiring formation step). At this time, the Ti / Al layer 30 is patterned to be a wiring on the SiO ₂ layer 41. This is performed by performing photolithography and etching after the Ti / Al layer 30 is formed on the entire surface. Alternatively, this patterning can be performed by forming a Ti / Al layer 30 after forming a photoresist mask by photolithography and performing lift-off.

  By the above manufacturing method, it is possible to locally form ohmic junction using Ni silicide in the SiC wafer. On this, a patterned wiring layer can be formed via an insulating layer. Also in this case, the adhesion between the Ni silicide layer and the wiring layer thereon can be increased, and a highly reliable semiconductor device can be obtained at low cost.

(Third embodiment)
In the first and second embodiments, only the process of forming an ohmic electrode using Ni silicide for n-type SiC is shown. On the other hand, below, the manufacturing method of SBD (Schottky Barrier Diode) using this manufacturing method is demonstrated. In this SBD, a Schottky electrode is formed on the upper surface (one main surface) side of the SiC wafer, and an ohmic electrode using the Ni silicide is formed on the lower surface (the other main surface) side. In this manufacturing method, an oxide layer having high etching resistance formed on the surface of the Ni silicide layer can be positively used as a protective film. 4A to 4I are process cross-sectional views illustrating this manufacturing method.

First, the SiO ₂ layer 41 is formed on the upper surface side of the n-type SiC layer 11 (SiC wafer), and the Ni layer 12 is formed on the lower surface side (FIG. 4A: Ni forming step). The SiO ₂ layer 41 can be formed by a CVD method or the like, and the Ni layer 12 is the same as described above.

Next, the silicide formation step is performed (FIG. 4B). The temperature at this time is about 900 to 1200 ° C. as described above. However, in this case, a small amount of O ₂ is mixed in the atmosphere. Thereby, in the vicinity of the n-type SiC layer 11, the silicide reaction proceeds and the Ni silicide layer 13 is formed, and at the same time, the surface (the lower surface in the figure) is oxidized. At this time, surplus carbon is vaporized as CO and CO ₂ . Therefore, as in FIG. 1E, the oxide layer 14 is formed on the surface of the Ni silicide layer 13 on the lower surface side.

Next, an opening is formed in the upper SiO ₂ layer 41 (FIG. 4C: opening forming step). This opening defines the Schottky junction surface of the SBD. In addition, insulation is achieved between the Schottky junction side electrode and the n-type SiC layer 11 at locations other than the opening. This opening can be performed by wet etching or dry etching for SiO ₂ using a photoresist as a mask.

Next, the Schottky electrode 42 is formed in a region including the opening (FIG. 4D: Schottky electrode forming step). The Schottky electrode 42 uses a material that forms a Schottky junction with the n-type SiC layer 11, or a silicide of this material forms a Schottky junction with the n-type SiC, for example, Ti. . Actually, like the ohmic electrode, a laminated structure in which Al or the like is laminated thereon is used. The Schottky electrode 42 can be patterned by forming it on the entire upper surface side and then performing etching using a photoresist as a mask, or by using a lift-off method. In order to obtain good Schottky characteristics, heat treatment can be performed at a lower temperature than the heat treatment in the silicide formation step. Further, a wiring layer connected to the Schottky electrode 42 may be formed on the SiO ₂ layer 41.

  A Schottky barrier is formed at the interface between the Schottky electrode 42 and the n-type SiC layer 11 so as to be able to operate as an SBD. This Schottky barrier depends on the state of this interface, particularly the reaction at the interface. Change. In order to maintain this Schottky characteristic satisfactorily, it is necessary to keep the temperature after the formation of the Schottky electrode 42 at 400 ° C. or lower. For this reason, it is necessary to perform a silicide formation process that requires a high temperature for the silicidation reaction before this.

  In the above process, photolithography (formation of a photoresist pattern) and etching are performed a plurality of times in the opening forming process and the Schottky electrode forming process. In this case, the process is often performed in direct contact with the lower surface side of the SiC wafer. Since the oxide layer 14 containing NiO as a main component is a chemically stable material, it becomes a protective film for the Ni silicide layer 13 on the lower surface side in such a process. That is, by performing the Schottky electrode formation step between the oxidizing atmosphere heat treatment step and the reduction treatment step, the oxide layer 14 can be left as it is in the Schottky electrode formation step. At this time, the Ni silicide layer 13 serving as a material for the ohmic electrode is mechanically and chemically protected.

  Next, the reduction process is performed in this state (FIG. 4 (e)). As a result, the oxide layer 14 on the lower surface becomes a reduction layer 15 containing Ni as a main component. Moreover, since this temperature is 300-400 degreeC as above-mentioned, it is a temperature range which does not have a bad influence with respect to the Schottky junction of an upper surface side.

  Next, in order to protect especially the Schottky electrode 42 and the like in this structure, a photoresist layer 50 is formed on the entire upper surface (FIG. 4F).

  In this state, by performing wet etching using dilute hydrofluoric acid or the like, the reducing layer 15 containing Ni as a main component is removed, and the Ni silicide layer 13 is exposed on the lower surface side (FIG. 4G: etching step). ). Since there is the photoresist layer 50, the SiO2 layer 41 on the upper surface side, the Schottky electrode 42, etc. are not affected by this. They are also mechanically protected by the photoresist layer 50. In this case, instead of dilute hydrofluoric acid, Ni can be etched, and another etching solution with which the photoresist layer 50 is resistant can also be used.

  Next, a Ti / Ni / Au layer 43 serving as a wiring layer is formed on the exposed surface of the Ni silicide layer 13 (FIG. 4H: wiring formation step).

  Next, the photoresist layer 50 is removed by wet processing, ashing processing, or the like (FIG. 4I). As a result, an SBD having a configuration in which the Schottky junction side is taken out on the upper surface side and the n-type SiC side electrode is taken out on the lower surface side is obtained. When manufacturing this SBD, the oxide layer 14 formed on the lower surface side serves as a protective film for the Ni silicide layer 13, particularly when forming the structure on the upper surface side (Schottky electrode 42 and the like). For this reason, this SBD can be manufactured easily with a high yield. Further, the adhesiveness between the Ni silicide layer 13 and the Ti / Ni / Au layer 43 can be improved, as in the first and second embodiments.

Note that also in the third embodiment, an SiO ₂ layer is formed on the lower surface of the n-type SiC layer 11 and an opening is provided in the SiO ₂ layer, so that the same process as in the second embodiment can be performed. Accordingly, it is possible to locally form an ohmic junction on the lower surface and form a wiring layer connected to the ohmic junction. In this case, an oxide layer can also be used as a protective film.

  In the above example, the case where an ohmic electrode using Ni silicide is formed on n-type SiC is described. However, Ni silicide is used on SiC other than n-type (p-type, semi-insulating). Even when an electrode is formed, it is clear that the above manufacturing method is effective. That is, the electrode having this structure is effective for all semiconductor devices that require electrical connection to SiC, such as SBD using SiC, MOSFET, MESFET, and pn junction diode. Therefore, the above manufacturing method is also effective when manufacturing all these semiconductor devices.

11 n-type SiC layer 12 Ni layer 13 Ni silicide layer 14 Graphite 15 Oxidation layer 16 Reduction layer 30 Ti / Al layer (wiring layer)
41 SiO ₂ layer 42 Schottky electrode 43 Ti / Ni / Au layer (wiring layer)
50 photoresist layers

Claims (8)

A method of manufacturing a semiconductor device comprising a configuration in which an electrode using nickel (Ni) silicide is connected to a silicon carbide (SiC) layer,
A Ni forming step of forming a Ni layer on the surface of the SiC layer;
A silicide forming step of forming a Ni silicide layer by reacting the Ni layer and the SiC layer by applying a heat treatment;
An oxidizing atmosphere heat treatment step of performing a heat treatment in an oxidizing atmosphere after the formation of the Ni silicide layer;
After the oxidation atmosphere heat treatment step, a reduction treatment step in which heat treatment is performed in a reducing atmosphere at a temperature lower than the temperature of the heat treatment in the silicide formation step;
An etching process for performing an etching process on Ni;
A method for manufacturing a semiconductor device, comprising: After the etching process,
2. The method of manufacturing a semiconductor device according to claim 1, further comprising a wiring forming step of forming a wiring layer so as to be in contact with the Ni silicide layer.   The method of manufacturing a semiconductor device according to claim 1, wherein the temperature of the heat treatment in the reduction treatment step is in a range of 300 to 400 ° C. 3. Between the silicide formation step and the oxidizing atmosphere heat treatment step,
The non-oxidizing atmosphere heat treatment step of performing heat treatment at a temperature lower than the temperature of the heat treatment in the silicide forming step in a non-oxidizing atmosphere is provided. A method for manufacturing a semiconductor device.   The method for manufacturing a semiconductor device according to claim 1, wherein an ultrasonic cleaning process is performed in the etching step.   6. The semiconductor device according to claim 1, wherein an insulating layer is formed on the surface of the SiC layer, and the Ni forming step is performed after forming an opening in the insulating layer. 6. Manufacturing method. The semiconductor device includes an SBD (Schottky Barrier) in which a Schottky electrode for the SiC layer is formed on one main surface side of the SiC layer, and an ohmic electrode for the SiC layer is formed on the other main surface side of the SiC layer. Diode),
The Ni layer in the Ni forming step is formed on the other main surface side,
Between the oxidizing atmosphere heat treatment step and the reduction treatment step,
7. The method of manufacturing a semiconductor device according to claim 1, further comprising a Schottky electrode forming step of forming the Schottky electrode on the one main surface side.   A semiconductor device manufactured by the method for manufacturing a semiconductor device according to claim 1.

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