JP2014086709A - Method for manufacturing semiconductor device - Google Patents

Abstract

The reliability and yield of a semiconductor device using a SiC substrate are improved.
An SiC substrate is cleaned by performing ammonia / hydrogen peroxide solution cleaning (SC1) and hydrochloric acid / hydrogen peroxide solution cleaning (SC2) (RCA cleaning step S2). Next, ozone gas having a concentration of 80% by volume or more is supplied to the SiC substrate at 100 sccm and treated at 300 Pa and 1000 ° C. for 26 minutes (sacrificial oxidation step S3). The SiC substrate after completion of the sacrificial oxidation step S3 is treated with hydrofluoric acid to remove the oxide film formed on the surface of the SiC substrate (HF cleaning step S4).
[Selection] Figure 4

Description

  The present invention relates to a method for manufacturing a semiconductor device using a silicon carbide single crystal substrate.

  A silicon carbide (SiC) element is expected to realize a semiconductor device having a higher breakdown voltage and lower on-resistance than a silicon (Si) element. In recent years, the manufacturing technology of SiC elements has remarkably advanced, and the superiority of device characteristics of SiC elements is being established. In addition, the quality and size of silicon carbide single crystal substrates (SiC substrates) are increasing, and it is relatively easy to obtain SiC substrates necessary for manufacturing semiconductor devices. Against the background of these technological advances, full-scale development with a view to practical use of SiC elements is in full swing. In particular, the Schottky barrier diode (SBD) is one of the most developed SiC devices, and has reached the stage of process development for mass production, such as ensuring reliability and improving yield (ratio of good products). ing.

  In order to put the SiC element into practical use, further improvement in the degree of integration (power density) of the SiC element is required. In order to improve the integration degree of the SiC element, it is necessary to design an element using a larger size electrode. And when using a large-sized electrode, the SiC substrate surface treatment for keeping the yield of a SiC element high becomes important. In a SiC substrate, adhesion and mixing of metal impurities to the substrate generated by a high-temperature SiC element manufacturing process, and other surface roughness due to the formation of a carbon compound are considered to be one of the factors that reduce the yield of SiC elements.

  In the SiC element manufacturing process, a cleaning process of the SiC substrate surface with a chemical solution is performed. For example, RCA cleaning, which is a cleaning technique cultivated as a technique for manufacturing Si elements, is often used in the SiC element manufacturing process. The RCA cleaning is a Si substrate wet cleaning method based on cleaning with ammonia / hydrogen peroxide solution (SC1) and cleaning with hydrochloric acid / hydrogen peroxide solution (SC2).

  In the Si substrate, an oxide film is formed on the surface of the Si substrate by the SC1 process, and metal impurities are taken into this film. Then, by removing the oxide film formed by the SC1 process in the SC2 process, the metal impurities taken into the oxide film are also removed. On the other hand, with an SiC substrate, it is difficult to form an oxide film on the surface of the SiC substrate by the SC1 process, and an oxide film is formed like the SC1 process of the Si substrate, and metal impurities are taken into this oxide film. It is said that it is difficult to remove by. In addition, when etching a SiC substrate, etching is performed using a special chemical solution such as a potassium hydroxide melt, but it is difficult to control surface roughness because the etching rate has a large plane orientation dependency. Become.

  Therefore, in the cleaning of the SiC substrate, the surface of the SiC substrate is cleaned using both RCA cleaning and an oxide film forming process called sacrificial oxidation (for example, Patent Document 1). In normal sacrificial oxidation, an oxide film is formed on the substrate surface by oxygen.

JP 2009-194216 A JP 2008-283201 A JP 2008-53561 A JP 2001-244227 A JP 2001-244260 A

Ryoji Kosugi, 2 others, "Thermal oxidation of (0001) 4H-SiC at high temperatures in ozone-admixed oxygen gas ambient", Applied Physics Letters, American Institute of Physics, June 3, 2003, 83, Vol. 5, p. 884-886

  However, it is known that the metal impurity density on the surface of the SiC substrate after removal of the sacrificial oxide film becomes lower by changing the oxidation method (oxidation gas species) in the sacrificial oxidation process than when the sacrificial oxidation method using oxygen gas is used. (For example, Patent Document 1). It has been confirmed that the reliability and yield of SiC elements are improved by reducing the metal impurity density on the surface of the SiC substrate.

  In Patent Document 1, the use of oxygen plasma as an oxidizing agent on the surface of a SiC substrate tends to reduce the metal impurity density on the surface of the SiC substrate after removal of the sacrificial oxide film as compared with a sacrificial oxidation method using oxygen gas. It is shown that there is. From this fact, it is considered that metal impurities can be effectively incorporated into the oxide film by using stronger oxidizing species, and more metal impurities can be removed by removing this oxide film. It is done. Further, Patent Document 1 verifies the cleaning effect of the SiC substrate surface due to the difference in the oxidation method in the manufacturing process of various elements such as SBD and MOSFET, and improves the reliability and yield of the SiC element due to the difference in the oxidation method. It has been shown that it can.

  As described above, since the conventional Si substrate processing method is not necessarily applicable to the SiC substrate, a SiC substrate processing method for further improving the reliability and yield of the SiC element is required.

  In view of the above circumstances, an object of the present invention is to provide a technique that contributes to improvement in reliability and yield of a semiconductor device using a SiC substrate.

  In one embodiment of the semiconductor device manufacturing method of the present invention that achieves the above object, a silicon carbide single crystal substrate is oxidized in an ozone atmosphere of 80% by volume or more, and an oxide film is formed on the surface of the silicon carbide single crystal substrate. It has a sacrificial oxidation process.

  Another aspect of the semiconductor device manufacturing method of the present invention that achieves the above object is characterized in that, in the semiconductor device manufacturing method, the sacrificial oxidation step is performed after the silicon carbide single crystal substrate is subjected to RCA cleaning treatment. It is said.

  According to another aspect of the semiconductor device manufacturing method of the present invention that achieves the above object, in the semiconductor device manufacturing method, the sacrificial oxidation step is performed under a condition that a film formation rate of oxygen oxide film is 3 nm / h or less. It is characterized by doing.

  In another aspect of the semiconductor device manufacturing method of the present invention that achieves the above object, in the semiconductor device manufacturing method, the processing conditions of the sacrificial oxidation step are a processing pressure of 1000 Pa or lower and a processing temperature of 1200 ° C. or lower. It is characterized by being.

  According to another aspect of the semiconductor device manufacturing method of the present invention that achieves the above object, in the semiconductor device manufacturing method, an electrode forming step of forming an electrode layer on the silicon carbide single crystal substrate after the sacrificial oxidation step is performed. It is characterized by doing.

  Another aspect of the semiconductor device manufacturing method of the present invention that achieves the above object is characterized in that, in the semiconductor device manufacturing method, the oxide film has a thickness of 0.4 nm or more.

  Another aspect of the semiconductor device manufacturing method of the present invention that achieves the above object is characterized in that, in the above semiconductor device manufacturing method, an epitaxially grown layer is formed on the silicon carbide crystal substrate.

  According to another aspect of the semiconductor device manufacturing method of the present invention that achieves the above object, in the semiconductor device manufacturing method, after the sacrificial oxidation step, the silicon carbide single crystal substrate is placed under a vacuum of 10 Pa or less. It is characterized by cooling to room temperature at a temperature lowering rate of 100 ° C./min or more.

  According to another aspect of the semiconductor device manufacturing method of the present invention for achieving the above object, in the semiconductor device manufacturing method, the silicon carbide single crystal substrate is irradiated with ultraviolet light of 200 to 300 nm in the sacrificial oxidation step. Thus, an oxide film is formed.

  According to the above invention, it is possible to contribute to the improvement of the reliability and the yield of the semiconductor device using the SiC substrate.

It is the schematic of the oxide film formation apparatus used for the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is a schematic sectional drawing of the principal part of the oxide film formation apparatus used for the manufacturing method of the semiconductor device which concerns on embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is principal part sectional drawing of the semiconductor device which concerns on embodiment of this invention, (a) Explanatory drawing explaining reaction of ozone on the SiC substrate surface, (b) The circuit which evaluates the electrical property of a semiconductor device is demonstrated. It is explanatory drawing. (A) The flowchart explaining the manufacturing method of the semiconductor device of an Example, (b) The flowchart explaining the manufacturing method of the semiconductor device of a comparative example. (A) Characteristic diagram showing forward characteristic of semiconductor device of example, (b) Characteristic diagram showing reverse characteristic of semiconductor device of example, (c) Characteristic diagram showing forward characteristic of semiconductor device of comparative example (D) It is a characteristic view which shows the reverse direction characteristic of the semiconductor device of a comparative example.

  A semiconductor device manufacturing method according to an embodiment of the present invention will be described in detail with reference to the drawings. The silicon carbide single crystal substrate (SiC substrate) of the present invention refers to a substrate having a single crystal layer of silicon carbide or a silicon carbide substrate having a layer ion-implanted into a single crystal of silicon carbide.

  First, an oxide film forming apparatus 1 that forms an oxide film on the surface of a SiC substrate will be described with reference to FIGS. As processing apparatuses that perform surface treatment of SiC substrates, for example, processing apparatuses disclosed in Patent Documents 2 and 3 are known.

  As shown in FIG. 1, the oxide film forming apparatus 1 includes a processing furnace 2, an ozone generator 3, a light source 4 and a light source 5.

  The processing furnace 2 is a horizontal laminar pressure reduction type furnace. An ozone generator 3 is connected to the processing furnace 2 via a pipe 6, and an ozone removing device 8 is provided via a pipe 7. Residual ozone in the gas subjected to the reaction of the processing furnace 2 is decomposed and removed by the ozone removing device 8. The gas treated by the ozone removing device 8 is discharged out of the system by the vacuum pump 9. A susceptor 11 that holds the SiC substrate 10 is provided in the vicinity of the inner center of the processing furnace 2. The susceptor 11 is made of, for example, a material that absorbs infrared light (such as opaque quartz or SiC single crystal), and is irradiated with infrared light from a light source 5 provided outside the processing furnace 2 and heated.

  FIG. 2 is a diagram showing details of the processing furnace 2. As shown in FIG. 2, for example, a quartz glass tube 2 a is used as the processing furnace 2. A pipe 6 and a pipe 7 are provided at the end of the quartz glass tube 2a via O-rings 12 (or gaskets), respectively. The pipe 6 and the pipe 7 are vacuum-compatible pipes, and for example, a stainless steel (SUS material) pipe whose inner surface is surface-treated by electrolytic polishing is used. The connecting portion 6a (connecting portion 7a) between the piping 6 (pipe 7) and the processing furnace 2 (that is, the quartz glass tube 2a) is desirably water-cooled. The O-ring 12 is made of a heat-resistant material (for example, Kalrez manufactured by DuPont). The pipe 6 and the pipe 7 are respectively provided with variable flow valves 13 and 14, and by controlling the variable flow valves 13 and 14, the flow rate of ozone supplied to the processing furnace 2 and the pressure of the processing furnace 2 are controlled. Is done. In addition, the gas for cooling is supplied so that it may distribute | circulate the outer periphery vicinity of the processing furnace 2, and the processing furnace 2 is air-cooled. That is, the processing furnace 2 is a cold wall, and the thermal decomposition of ozone during gas transportation is suppressed.

  As shown in FIG. 1, the ozone generator 3 supplies ozone to the processing furnace 2. The ozone generator 3 cools gaseous ozone to liquid ozone, and vaporizes the liquid ozone again to generate almost 100% ozone gas. As such an ozone generator 3, for example, there is a pure ozone generator manufactured by Meidensha, and by diluting ozone generated from the ozone generator 3 with an inert gas (argon, helium, etc.), ozone having an arbitrary concentration Can be supplied to the processing furnace 2.

The light source 4 emits light in the ultraviolet region having an emission line having a continuous or discrete wavelength longer than a wavelength of 210 nm. The light from the light source 4 is irradiated, for example, toward the surface of the SiC substrate 10 perpendicular to the gas flow. The illuminance of light from the light source 4 is adjusted so that fluctuation of illuminance on the entire surface of the SiC substrate 10 is reduced. Ozone generates excited state atomic oxygen O ( ¹ D) by an ultraviolet dissociation reaction represented by the formula (1). In addition, ozone generates ground state atomic oxygen O ( ³ P) by a thermal decomposition reaction represented by the formula (2).
O ₃ + hν (λ <310 nm) → O ( ¹ D) + O ₂ (1)
O ₃ → O ( ³ P) + O ₂ (2)
The excited state atomic oxygen generated by the ultraviolet photodissociation reaction has a higher reactivity than the ground state atomic oxygen. Therefore, when ozone gas is supplied to the SiC substrate 10 by irradiating ultraviolet light from the light source 4, the SiC substrate 10 The surface cleaning effect is further improved. Since ground state atomic oxygen also has high reactivity, a good oxide film can be formed on SiC substrate 10. Therefore, when a sufficient cleaning effect can be obtained by the ground state atomic oxygen, it is not always necessary to irradiate ultraviolet light.

  The light source 5 is a lamp that outputs light in the infrared light region. Light from the light source 5 passes through the processing furnace 2 and is irradiated to the susceptor 11, and the temperature of the susceptor 11 is controlled so that the temperature of the SiC substrate 10 held by the susceptor 11 becomes a predetermined temperature. Therefore, the wavelength of the light emitted from the light source 5 may be any wavelength as long as the light is absorbed by the susceptor 11 or the SiC substrate 10.

[Example]
A semiconductor device manufacturing method according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 3A is a schematic cross-sectional view of a SiC substrate 10 used in the method for manufacturing a semiconductor device according to the embodiment of the present invention, and FIG. 3B is a semiconductor device configured using the SiC substrate 10. It is a figure which shows the outline of the electrical property evaluation circuit 16 which evaluates 15 properties. The SiC substrate 10 in FIG. 3A and the semiconductor device 15 in FIG. 3B schematically show the SiC substrate and the semiconductor device according to the embodiment of the present invention. And the actual dimensional ratio do not always coincide with each other.

  FIG. 4 is a diagram illustrating a flow of the manufacturing method of the semiconductor device 15 of the embodiment. With reference to FIG. 4, the manufacturing method of the semiconductor device 15 of an Example is demonstrated.

In the example, a simple PN diode was prepared using a 12 mm □ size 4H—SiC (0001) substrate (SiC substrate). Specifically, n-type doped n ⁺ layer substrate 10a with an off angle of 4 ° and 1.2 × 10 ¹⁸ cm ⁻³ manufactured by Cree was used.

First, in the previous step S1, an n ⁻ epi layer 10b (epicap growth layer) was formed on the n ⁺ layer substrate 10a. Specifically, an n ⁻ epi layer 10b having a thickness of about 4.7 μm was formed on the n ⁺ layer substrate 10a at a concentration of 1.2 × 10 ¹⁵ cm ⁻³ . Then, n ^- such as p layer 10c on the epitaxial layer 10b n ^- performs carrier distribution process of creating the epi layer 10b, creating the SiC substrate 10.

  Next, RCA cleaning step S2 was performed. The RCA cleaning step S2 is ammonia that is treated at 70 to 80 ° C. for 10 minutes with a cleaning solution of ammonia (28 wt%): hydrogen peroxide solution (30 to 35 wt%): water = 1: 1: 5 (volume ratio). -The hydrogen peroxide washing process (SC1) was performed. Then, hydrochloric acid / hydrogen peroxide treated at 70-80 ° C. for 10 minutes with a cleaning solution of hydrochloric acid (36% by weight): hydrogen peroxide (30-35% by weight): water = 1: 1: 5 (volume ratio) A water cleaning step (SC2) was performed to clean the SiC substrate 10.

  In the sacrificial oxidation step S3, the oxidation treatment of the SiC substrate 10 was performed using the oxide film forming apparatus 1 shown in FIGS. The SiC substrate 10 was held on the susceptor 11, ozone gas having a concentration of 80% by volume or more was supplied to the processing furnace 2 at 100 sccm and 300 Pa, and the SiC substrate 10 was subjected to ozone treatment at 1000 ° C. for 26 minutes. At this time, irradiation of ultraviolet light by the light source 4 was not performed. The oxide film formed in the sacrificial oxidation step S3 was about 10 nm. In the sacrificial oxidation step S3, annealing treatment (POA) of the SiC substrate 10 was not performed after the ozone oxidation. By performing POA, an oxide film / SiC interface with few interface states can be formed, but by not performing the POA process, the process time can be shortened.

  When the oxidation treatment of the SiC substrate 10 was completed, the ozone supply to the processing furnace 2 was stopped, and the inside of the processing furnace 2 was evacuated (10 Pa or less). In this state, heating of SiC substrate 10 was stopped, and SiC substrate 10 was cooled to room temperature. After the SiC substrate 10 was cooled to room temperature, the inert gas was purged, and the SiC substrate 10 was taken out of the processing furnace 2 and subjected to the HF cleaning step S4.

  In the HF cleaning step S4, the oxide film formed on the surface of the SiC substrate 10 in the sacrificial oxidation step S3 was removed using hydrofluoric acid (about 0.5 to 10% hydrogen fluoride aqueous solution).

  Further, in the metal electrode layer forming step S5, the metal electrode layer 18 was formed on the surface 17 of the SiC substrate 10 from which the oxide film was removed in the HF cleaning step S4. The metal electrode layer 18 was formed by alloying nickel at 1000 ° C., and this metal electrode layer 18 was used as an anode electrode. In the semiconductor device 15 of the example, 16 metal electrode layers 18 formed in a circle having a diameter of 1 mm were formed.

In the post-process S6, aluminum was alloyed on the metal electrode layer 18 at a temperature equal to or higher than the melting point, and the anode electrode pad 19 was provided on the metal electrode layer 18. Also, aluminum was alloyed on the surface opposite to the surface on which the anode electrode pad 19 of the SiC substrate 10 is provided (that is, the n ⁺ layer substrate 10a) by ohmic bonding to form the cathode electrode 20.

[Comparative example]
The flow of the semiconductor device manufacturing method of the comparative example is shown in FIG. As shown in FIG. 4B, the semiconductor device manufacturing method of the comparative example is the same as the semiconductor device manufacturing method of the embodiment except for the sacrificial oxidation step S7. Therefore, only the sacrificial oxidation step S7 will be described in detail, and in order to avoid duplication, the other steps are denoted by the same reference numerals and description thereof is omitted.

In the sacrificial oxidation step S7 of the semiconductor device manufacturing method of the comparative example, the SiC substrate after performing the pre-step S1 and the RCA cleaning step S2 is held in the susceptor 11 of the processing furnace 2, and the processing furnace 2 has 100 sccm, 1.015. A surface treatment of the SiC substrate was performed by supplying 100% oxygen gas at × 10 ⁶ Pa at 1200 ° C. for 50 minutes. The oxide film formed in the sacrificial oxidation step S7 was about 10 nm.

  After completion of the sacrificial oxidation step S7, an anode electrode and a cathode electrode were provided on the semiconductor device of the comparative example by the HF cleaning step S4, the metal electrode layer creation step S5, and the post-step S6, as in the semiconductor device manufacturing method of the example. . Sixteen electrodes formed into a circle having a diameter of 1 mm were formed.

  FIG. 5 shows measurement results obtained by measuring the forward characteristics and the reverse characteristics at the respective electrodes of the semiconductor devices of the example and the comparative example by the electrical characteristic evaluation circuit 16 shown in FIG.

  As shown in FIGS. 5 (a) and 5 (c), an ohmic VI relationship was established on the higher voltage side than the location indicated by the arrow in the figure for many electrodes. As shown in FIGS. 5A and 5B, in the semiconductor device of the example, there is one sample exhibiting defective characteristics in the forward characteristic and reverse characteristic tests, and the remaining 15 samples. The sample showed good properties. On the other hand, as shown in FIGS. 5C and 5D, in the semiconductor device of the comparative example, there are three samples showing defective characteristics in both the forward characteristic and reverse characteristic tests, and the remaining 13 samples. The sample showed good properties. That is, according to the semiconductor device manufacturing method of the example, the number of defective electrodes was reduced as compared with the semiconductor device manufacturing method of the comparative example.

  As described above, according to the method for manufacturing a semiconductor device of the present invention, a sacrificial oxidation process for forming a sacrificial oxide film using high-concentration (80% by volume or more) ozone for cleaning an SiC substrate, and the sacrificial oxidation By using the SiC substrate cleaning method including the HF cleaning process for removing the film, it is possible to effectively remove metal impurities and carbon-based compounds on the surface of the SiC substrate. Furthermore, not only the removal of impurities due to the strong oxidizing power of ozone, but also the roughness of the surface of the SiC substrate can be suppressed. As a result, the reliability of the SiC element can be improved and the yield of the SiC element can be improved.

  Moreover, it is possible to reduce the damage on the surface of the SiC substrate by irradiating the SiC substrate with light having a wavelength of 200 nm or longer, and generating excited state atomic oxygen by irradiating ozone with light having a wavelength of 300 nm or shorter. Can do. Therefore, when the surface of the SiC substrate is subjected to ozone treatment, the cleaning effect on the substrate surface is further improved by irradiating the SiC substrate surface with ultraviolet light (including light having a wavelength of 200 to 300 nm) necessary for ozone decomposition. (For example, cited reference 5).

  In addition, the method for manufacturing a semiconductor device of the present invention reduces the influence of oxidation by oxygen by performing sacrificial oxidation treatment under process conditions such that the deposition rate of the SiC substrate surface by oxygen is 3 nm / h or less. The SiC substrate can be cleaned. Specifically, as shown in Non-Patent Document 1, by setting the processing pressure to 1000 Pa or less and the processing temperature to 1200 ° C. or less, the deposition rate of the SiC substrate surface by oxygen becomes 3 nm / h or less. Thus, the surface of the SiC substrate can be oxidized. As a result, the progress of the oxidation reaction of the SiC substrate surface by oxygen gas can be suppressed, and the incomplete oxidation by oxygen can be locally performed to reduce the non-uniform cleaning state of the SiC substrate surface. . An oxide film can be formed on the surface of the SiC substrate by setting the processing pressure to 10 Pa or higher and the processing temperature to 800 ° C. or higher. Therefore, the processing conditions of the sacrificial oxidation step are not only removing the impurities on the surface of the SiC substrate by setting the supply amount of ozone gas: 50 to 300 sccm, the processing pressure: 10 to 1000 Pa, and the processing temperature: 800 to 1200 ° C. In addition, it is possible to perform cleaning of the SiC substrate with reduced surface roughness of the SiC substrate.

  Further, by using ozone with a high concentration (80% by volume or more) for the oxidation treatment of the SiC substrate in the sacrificial oxidation step, the SiC substrate can be oxidized in a short time at a low temperature. As a result, thermal distortion of the SiC substrate and contamination of impurities into the SiC substrate can be reduced. A good oxide film can be formed by subjecting ozone having a concentration of 80% by volume or more, more preferably 95% by volume or more to sacrificial oxidation treatment of the SiC substrate. In particular, when approximately 100% by volume of ozone is used, the SiC substrate can be oxidized in a few minutes. This processing time is 1.25 times the formation speed of forming an oxide film having the same film thickness with 80% by volume of ozone, and the throughput of the SiC substrate per unit time is improved. Since the manufacturing process of the semiconductor device is a single wafer process, the improvement in the oxide film formation rate greatly affects the production rate of the semiconductor device.

  Further, the SiC / electrode layer having high bonding reliability can be obtained by using the method for cleaning the surface of the SiC substrate used in the method for manufacturing a semiconductor device of the present invention in the substrate processing step before forming the anode contact electrode on the SiC substrate. A (for example, Ni) interface can be formed.

  In addition, by performing ozone treatment on the surface of the SiC substrate in a cold wall processing furnace, the ozone-treated SiC substrate can be cooled at a temperature lowering rate of 100 ° C./min or more. After completion of the sacrificial oxidation process, when the SiC substrate is cooled to room temperature at a temperature lowering speed of 100 ° C./min or higher under a vacuum of 10 Pa or lower, adhesion of particles to the substrate is prevented and contamination of impurities to the wafer is prevented. be able to.

  It is disclosed that the surface of the SiC substrate can be treated with ozone to reduce carbon impurities on the surface of the SiC substrate and to form a high quality oxide film (for example, Patent Documents 4 and 5). On the other hand, the semiconductor device manufacturing method of the present invention is characterized in that 80% or more of ozone is used for the oxidation treatment in the sacrificial oxidation step. In particular, by using ozone for the oxidation of the sacrificial oxidation process, which is a subsequent cleaning process of the SiC substrate, in the processing of the SiC substrate after the carrier distribution creation process in the epi layer, the junction of the SiC substrate and the electrode layer is formed. Reliability is improved. By forming the film thickness of the oxide film formed in this sacrificial oxidation step to be more than the thickness of one atomic layer (0.4 nm), particularly about 10 nm, a good junction between the SiC substrate and the electrode layer can be obtained. Can do.

  In addition, although the manufacturing method of the semiconductor device of this invention was demonstrated in detail, showing the specific example, the manufacturing method of the semiconductor device of this invention is not limited to embodiment mentioned above, The feature of this invention is shown. The design can be changed as appropriate within a range that is not impaired, and the modified form is also the method for manufacturing a semiconductor device of the present invention.

  For example, in the description of the embodiment, a SiC substrate made of 4H—SiC is used as the silicon carbide single crystal. However, as the silicon carbide single crystal, 2H—SiC and 6H—SiC are available in addition to 4H—SiC. Other crystal forms of silicon carbide single crystal such as 3C—SiC can also be used as the SiC substrate. In the examples, an epi layer, a metal electrode layer, and the like were formed on the (0001) plane of the single crystal substrate. However, in addition to the (0001) plane, the (000-1) plane and the (11-20) plane On the other hand, the semiconductor device manufacturing method of the present invention can be applied to a substrate on which an epi layer or the like is formed. In the embodiment, the SiC substrate having an off angle of 4 ° is used. However, the off angle is not limited to 4 °, and any other angle may be used as long as it is about 0 to 8 °.

Further, the SiC substrate cleaning method used in the method for manufacturing a semiconductor device of the present invention is not limited to the pretreatment when bonding the interface of the SiC substrate / electrode layer. It can be used as a pretreatment for the interface (for example, SiC substrate / SiO ₂ interface).

  In addition to Schottky barrier diodes (SBDs), semiconductor devices such as MOSFETs and IGBTs are also used for semiconductor devices when the electrodes are formed on the SiC surface by Schottky junctions or ohmic junctions. A cleaning method according to the manufacturing method can be applied.

DESCRIPTION OF SYMBOLS 1 ... Oxide film formation apparatus 2 ... Processing furnace 3 ... Ozone generator 4 ... Light source 5 ... Light source 6, 7 ... Pipe 8 ... Ozone removal apparatus 9 ... Vacuum pump 10 ... SiC substrate 10a ... n ⁺ layer substrate 10b ... n ^- epi Layer 10c ... p layer 11 ... susceptor 15 ... semiconductor device 16 ... electric characteristic evaluation circuit 17 ... surface of SiC substrate (SiC / Ni interface)
18 ... Metal electrode layer 19 ... Anode electrode pad 20 ... Cathode electrode 21 ... Protective film

Claims (9)

A sacrificial oxidation step of oxidizing the silicon carbide single crystal substrate in an ozone atmosphere of 80% by volume or more and forming an oxide film on the surface of the silicon carbide single crystal substrate,
A method for manufacturing a semiconductor device, comprising: The sacrificial oxidation step includes
The method of manufacturing a semiconductor device according to claim 1, wherein the method is performed after the silicon carbide single crystal substrate is subjected to an RCA cleaning process. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the sacrificial oxidation step is performed under a condition that a deposition rate of an oxide film with oxygen is 3 nm / h or less. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the processing conditions of the sacrificial oxidation step are a processing pressure of 1000 Pa or lower and a processing temperature of 1200 ° C. or lower. 5. The method of manufacturing a semiconductor device according to claim 1, wherein an electrode forming step of forming an electrode layer on the silicon carbide single crystal substrate is performed after the sacrificial oxidation step. 6. 6. The method of manufacturing a semiconductor device according to claim 1, wherein the oxide film has a thickness of 0.4 nm or more. The semiconductor device manufacturing method according to claim 1, wherein an epitaxial growth layer is formed on the silicon carbide crystal substrate. 8. The silicon carbide single crystal substrate is cooled to room temperature at a temperature lowering rate of 100 [deg.] C./min or higher under a vacuum of 10 Pa or less after the sacrificial oxidation step. 2. A method for manufacturing a semiconductor device according to claim 1. 9. The oxide film according to claim 1, wherein in the sacrificial oxidation step, the silicon carbide single crystal substrate is irradiated with ultraviolet light of 200 to 300 nm to form an oxide film. Semiconductor device manufacturing method.

Images