JP2010287731A - Method of manufacturing substrate product, substrate product, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a leakage current of a nitride-based compound semiconductor layer in a method of manufacturing the nitride-based compound semiconductor layer on a different substrate by removing part of a nitride-based compound semiconductor substrate laminated on the different substrate from the different substrate. <P>SOLUTION: The method of manufacturing a substrate product 1 having a gallium nitride layer 30 on a support substrate 20 such as a silicon substrate includes the steps of: implanting ions in a surface 10a of the gallium nitride substrate 10; cleaning the surface 10a; bonding the surface 10a and a surface 20a of the support substrate 20 to each other; and forming the gallium nitride layer 30 on the support substrate 20 by leaving the part of the gallium nitride substrate 10 including the surface 10a and removing the remainder. In the steps of cleaning the surface 10a, the total concentration of Fe, Cr, Ni, and Si of the surface 10a after the cleaning is ≤1×10<SP>18</SP>[cm<SP>-3</SP>]. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a substrate product, a substrate product, and a semiconductor device.

  Semiconductor devices using nitride compound semiconductors are formed by various methods. In general, molecular beam epitaxy (MBE) growth on a substrate made of a dissimilar material (Si, SiC, sapphire, etc.) whose thermal expansion coefficient is close to that of a nitride compound or a substrate (bulk substrate) made of a nitride compound semiconductor. Or metal organic chemical vapor deposition (MOCVD) method. However, when formed on a substrate made of a different material, stress is generated in the substrate due to a difference in thermal expansion coefficient between the substrate and the semiconductor device layer or a lattice mismatch, and the substrate and the semiconductor device layer are warped. As a result, undesired phenomena such as deterioration of device characteristics, peeling of the semiconductor device layer from the substrate, and increase of dislocation density in the semiconductor device layer occur. On the other hand, when it is formed on a substrate made of a nitride-based compound semiconductor, since the substrate is expensive, the cost ultimately increases the manufacturing cost of the semiconductor device.

  In order to manufacture a nitride-based compound semiconductor device having good properties at a low cost, for example, there is a method described in Patent Document 1. Patent Document 1 discloses a method for manufacturing a semiconductor substrate having a nitride semiconductor film on a heterogeneous substrate. In the method described in this document, ions are implanted near the surface of the GaN substrate to form an ion-implanted layer, and heat treatment is performed with the surface of the GaN substrate and the single crystal silicon substrate superimposed. The semiconductor substrate having the GaN thin film on the silicon substrate is fabricated by bonding them together and peeling off the main portion of the GaN substrate excluding the ion implantation layer from the single crystal silicon substrate. Then, various nitride semiconductor layers are grown on the GaN thin film of the semiconductor substrate to produce LEDs and transistors.

JP 2006-210660 A

  However, when ions are implanted into the nitride-based compound semiconductor substrate, impurities present in the ion generator or the chamber adhere to the substrate surface simultaneously with the ion implantation. Further, since the nitride-based compound is a piezoelectric crystal, it is particularly easy to attract impurities. Impurities (particles) present on the surfaces of the nitride compound semiconductor substrate and the dissimilar substrate serving as the bonding surface cause a leakage current in the nitride compound semiconductor layer.

  The present invention has been made in view of the above-described problems, and by bonding a surface of a nitride compound semiconductor substrate and a heterogeneous substrate, and removing a portion of the nitride compound semiconductor substrate from the heterogeneous substrate. Leakage current in a nitride-based compound semiconductor layer is reduced in a method for manufacturing a nitride-based compound semiconductor layer on a heterogeneous substrate, a substrate product manufactured by this method, and a semiconductor device including the substrate product. For the purpose.

In order to solve the above-described problems, a method for producing a substrate product according to the present invention is a method for producing a substrate product having a nitride compound semiconductor layer on a support substrate made of a material different from a nitride compound semiconductor. A step of performing ion implantation on the surface of the nitride compound semiconductor substrate, a step of cleaning the surface of the nitride compound semiconductor substrate, and a surface of the nitride compound semiconductor substrate and the surface of the support substrate. A step of bonding, and a step of forming a nitride-based compound semiconductor layer on a support substrate by removing the remaining portion of the nitride-based compound semiconductor substrate while leaving a portion including the surface in a layered form, and nitriding when the step of cleaning the surface of the object-based compound semiconductor substrate, Fe at the surface of the nitride compound semiconductor substrate after cleaning, Cr, Ni, and Si of 1 × density in total 10 18 ^{[cm 3],} characterized in that less.

The present inventor, when any one of Fe, Cr, Ni, and Si is attached as an impurity to the surface of the nitride compound semiconductor substrate which is a bonding surface, the nitride compound semiconductor layer and It has been found that current leakage is likely to occur between the supporting substrate (that is, the different substrate). Further, it has been found that when the total amount of these impurities is 1 × 10 ¹⁸ [cm ⁻³ ] or less, current leakage is remarkably reduced and pressure resistance is improved. That is, according to the manufacturing method of a substrate product described above, during the step of cleaning the surface of the nitride compound semiconductor substrate, Fe, Cr, Ni, and Si on the surface of the nitride compound semiconductor substrate after cleaning. By making the density of the total 1 × 10 ¹⁸ [cm ⁻³ ] or less, the leakage current flowing in the nitride-based compound semiconductor layer can be effectively reduced.

  In the method of manufacturing a substrate product, the step of cleaning the surface of the nitride-based compound semiconductor substrate includes a step of cleaning the surface of the nitride-based compound semiconductor substrate using a hydrogen peroxide solution containing ammonia. It may be a feature. Generally, when a semiconductor device layer is grown on a nitride-based compound semiconductor layer, a surface opposite to the nitrogen surface of the nitride-based compound semiconductor layer (for example, a gallium surface) is often used as a growth surface. In that case, the surface of the nitride-based compound semiconductor substrate that is to be bonded to the support substrate needs to be a nitrogen surface. However, for example, cleaning with a strong alkaline liquid such as KOH or NaOH causes the nitrogen surface to be etched, The flatness of the substrate is impaired, and it becomes difficult to bond to the support substrate. On the other hand, if the surface is cleaned using aqueous hydrogen peroxide containing ammonia, the nitrogen surface of the nitride-based compound semiconductor substrate is kept flat, and the impurity density on the nitrogen surface is suppressed to the above range by cleaning. Can do.

  The method for manufacturing a substrate product may be characterized in that the nitride compound semiconductor substrate is cleaned while being swung or vibrated during the step of cleaning the surface of the nitride compound semiconductor substrate. Thereby, the cleaning effect | action with respect to the surface of a nitride type compound semiconductor substrate can be improved.

In addition, the substrate product according to the present invention performs ion implantation on the surface of the nitride-based compound semiconductor substrate, and after cleaning the surface of the nitride-based compound semiconductor substrate, the surface of the nitride-based compound semiconductor substrate and the nitride-based compound semiconductor substrate Nitride-based compound formed by bonding surfaces of a support substrate made of a material different from a compound semiconductor to each other, and removing other portions of the nitride-based compound semiconductor substrate while leaving the portion including the surface in a layer form A semiconductor layer is provided on a support substrate, and the total density of Fe, Cr, Ni, and Si at the interface between the nitride-based compound semiconductor layer and the support substrate is 1 × 10 ¹⁸ [cm ⁻³ ] or less. And

According to the substrate product described above, the total density of Fe, Cr, Ni, and Si at the interface between the nitride-based compound semiconductor layer and the support substrate is 1 × 10 ¹⁸ [cm ⁻³ ] or less. Leakage current flowing in the nitride-based compound semiconductor layer can be effectively reduced.

  A semiconductor device according to the present invention includes the above-described substrate product and a semiconductor device layer made of a nitride-based compound semiconductor provided on the nitride-based compound semiconductor layer of the substrate product. According to this semiconductor device, the leakage current flowing through the nitride-based compound semiconductor layer can be effectively reduced by providing the substrate product described above.

  According to the method for manufacturing a substrate product, the substrate product, and the semiconductor device according to the present invention, it is possible to reduce the leakage current flowing in the nitride-based compound semiconductor layer.

FIG. 1A shows a gallium nitride substrate 10 used in the substrate product manufacturing method according to the present embodiment. FIG. 1B shows a step of implanting ions into the gallium nitride substrate 10. FIG. 1C shows a process of cleaning the surface of the gallium nitride substrate 10. FIG. 2A shows a process of bonding the gallium nitride substrate 10 and the support substrate 20 together. FIG. 2B shows a step of heating the substrate on which the gallium nitride substrate 10 and the support substrate 20 are bonded. FIG. 2C shows a state in which the gallium nitride substrate 10 is peeled from the support substrate 20 leaving the gallium nitride layer 30. FIG. 3A shows a substrate product 1 having a gallium nitride layer 30 on a support substrate 20. FIG. 3B shows a process of forming the epitaxial layer 60 on the gallium nitride layer 30. FIG. 3C shows a process of forming the semiconductor layers 70 to 78 on the epitaxial layer 60. FIG. 4A shows a step of mesa etching each of the semiconductor layers 70 to 78. FIG. 4B shows a process of forming the anode electrode 82 and the cathode electrode 84.

  Embodiments of a substrate product manufacturing method, a substrate product, and a semiconductor device according to the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  1 to 4 are diagrams showing each step in a method for manufacturing a substrate product, a substrate product, and a method for manufacturing a semiconductor device using the substrate product according to the present embodiment. In addition, the substrate product manufactured by the method of the present embodiment has a gallium nitride (GaN) layer as a nitride compound semiconductor layer on a support substrate.

<First step (ion implantation)>
First, as shown in FIG. 1A, a gallium nitride substrate 10 is prepared. The gallium nitride substrate 10 is a nitride-based compound semiconductor substrate in the present embodiment. The gallium nitride substrate 10 is produced by growing gallium nitride by, for example, hydride vapor phase epitaxy (HVPE), and may be doped with impurities such as oxygen atoms.

  Next, ions are implanted into the surface 10 a of the gallium nitride substrate 10. First, after polishing the surface 10 a of the gallium nitride substrate 10, the gallium nitride substrate 10 is placed in the ion implantation apparatus 100 as shown in FIG. Then, ions 12 of predetermined atoms (preferably hydrogen, helium, nitrogen, etc.) are implanted into the surface 10a of the gallium nitride substrate 10 to form the fragile layer 10b.

<Second step (cleaning)>
Subsequently, as shown in FIG. 1C, the surface 10 a of the gallium nitride substrate 10 is cleaned using a cleaning liquid 14. In the gallium nitride substrate 10, impurities are generated from an ion gun that generates ions 12, the outer wall of the chamber, and the like during the above-described ion implantation. Since gallium nitride is a piezoelectric crystal, impurities easily adhere to it, and the surface 10a needs to be sufficiently cleaned. Note that the impurities to be removed by cleaning are not limited, and in this embodiment, the impurities are limited to Fe, Cr, Ni, and Si. These are current leakage sources when an electronic device is manufactured using the substrate product of the present embodiment.

In the present embodiment, the surface of the gallium nitride substrate 10 is adjusted so that the total density of Fe, Cr, Ni, and Si on the surface 10a of the cleaned gallium nitride substrate 10 is 1 × 10 ¹⁸ [cm ⁻³ ] or less. Wash 10a.

  In order to remove these elements, it is preferable to use a cleaning solution 14 that can oxidize these elements at a redox potential. In addition, it is preferable to use a cleaning solution 14 that has extremely low etching properties with respect to the surface 10 a of the gallium nitride substrate 10. In particular, when the surface 10a to be cleaned is a nitrogen surface, cleaning with a strong alkaline liquid such as KOH or NaOH etches the nitrogen surface, and the flatness of the surface 10a is impaired, which will be described later. This will interfere with the bonding process. Therefore, it is preferable to use the acidic cleaning liquid 14.

  The acidic cleaning solution 14 will be further described. The higher the redox potential of the cleaning solution 14 is, the higher the effect of removing Fe, Cr, Ni, and Si. Examples of such cleaning solution 14 include hydrochloric acid, nitric acid, and hydrofluoric acid. Or sulfuric acid, a mixture of these with hydrogen peroxide, or a mixture thereof.

  On the other hand, it is possible to clean the nitrogen surface of the gallium nitride substrate 10 using the alkaline cleaning solution 14, but the flatness of the nitrogen surface is impaired in the strong alkaline cleaning solution 14 as described above. The nitrogen surface is preferably cleaned using a weakly alkaline cleaning solution 14 such as a hydrogen peroxide solution.

  The step of cleaning the nitrogen surface of the gallium nitride substrate 10 using the alkaline cleaning solution 14 is preferably performed after the cleaning step using the acidic cleaning solution 14. Unlike other semiconductor materials, gallium nitride has a positive zeta potential at neutral pH 7 and negative zeta potentials of other impurities (Fe, Cr, Ni, and Si). Even if it is washed with water, impurities adhere due to electrostatic force. Since the zeta potential of gallium nitride becomes negative at pH 7.1 or higher, it is necessary to perform the cleaning step with the alkaline cleaning solution 14 after the cleaning step with the acidic cleaning solution 14, otherwise impurities will increase. It is.

  Further, when cleaning the surface 10a of the gallium nitride substrate 10, it is preferable to clean the gallium nitride substrate 10 while oscillating or vibrating (for example, ultrasonic vibration). Thereby, the cleaning effect | action with respect to the surface 10a of the gallium nitride substrate 10 can be improved.

<Third Step (Lamination of Gallium Nitride Substrate and Support Substrate)>
Subsequently, as shown in FIG. 2A, a support substrate 20 made of a material different from the nitride compound semiconductor is prepared. Then, the surface 20a of the support substrate 20 and the surface 10a of the gallium nitride substrate 10 are bonded to each other and bonded. As long as the supporting substrate 20 has a strength (hardness or thickness) sufficient to hold a gallium nitride layer to be formed later, its constituent material is not particularly limited, but a semiconductor device layer is grown on the gallium nitride layer. In consideration of exposure to high temperatures and gas atmospheres such as ammonia and hydrogen, it is preferable to use a material system that can withstand such an environment. As such a support substrate 20, for example, a silicon substrate having an oxide layer 20b on the surface 20a is suitable.

  In addition, before bonding them, each bonding surface of the gallium nitride substrate 10 and the support substrate 20 is preferably cleaned in advance by plasma obtained by discharging in argon gas in a dry etching apparatus.

  There are various methods for bonding the gallium nitride substrate 10 and the support substrate 20 to each other. For example, the bonded surfaces of the gallium nitride substrate 10 and the support substrate 20 are polished to mirror surfaces, and bonded together, and then heated while applying a load. A method of bonding by exposing the gallium nitride substrate 10 and the support substrate 20 to plasma, or hitting the surfaces of the gallium nitride substrate 10 and the support substrate 20 with plasma, ions, neutral particles, or the like in a vacuum. There is a method in which the reaction of the surface is increased by, and then the gallium nitride substrate 10 and the support substrate 20 are bonded to each other and bonded. Moreover, it is also possible to join these through resin coating, an adhesive tape, etc. Further, a method in which a metal is interposed at the bonding interface between the gallium nitride substrate 10 and the support substrate 20 and heated to form eutectic bonding, or a material that easily moves ions is interposed between the gallium nitride substrate 10 and the support substrate 20. Any method may be used as long as it is a bonding method in which different substrates can maintain their characteristics in a region excluding the vicinity of the bonding interface, such as a bonding method.

<Fourth Step (Peeling of Gallium Nitride Substrate)>
Subsequently, as shown in FIG. 2B, the gallium nitride substrate 10 and the support substrate 20 bonded to each other are introduced into the annealing furnace 200, and the N ₂ atmosphere, the O ₂ atmosphere, or the N ₂ + O ₂ atmosphere is used. Annealing treatment is performed. The temperature at this time is, for example, 300 ° C. or higher. As a result, a crack occurs in the fragile layer 10b, and as shown in FIG. 2C, only the portion on the surface 10a side of the fragile layer 10b is left in a layered state, and the other part of the gallium nitride substrate 10 is peeled off from the support substrate 20. (Thinning the gallium nitride substrate 10). In this way, the other part of the gallium nitride substrate 10 is removed, and the fragile layer 10b remains on the surface 20a of the support substrate 20 as the gallium nitride layer 30.

  In this embodiment, a part of the gallium nitride substrate 10 is left on the support substrate 20 by heating after the ion implantation. However, other methods may be used for thinning the gallium nitride substrate 10, for example, gallium nitride. The fragile layer 10b may be peeled off by applying a force to the ion-implanted portion of the substrate 10, or the gallium nitride substrate 10 may be sliced or thinned by polishing or the like.

  Through the above steps, the substrate product 1 having the gallium nitride layer 30 on the support substrate 20 is produced as shown in FIG.

<Epitaxial layer formation process>
Subsequently, as shown in FIG. 3B, an epitaxial layer 60 made of a nitride compound semiconductor is grown on the gallium nitride layer 30. As a material constituting the epitaxial layer 60, a material whose lattice constant is the same as or close to that of the gallium nitride layer 30, for example, gallium nitride is suitable. Through this epitaxial layer forming step, a substrate product 2 having a high surface flatness and more suitable for device fabrication is produced.

<Device layer formation process>
Subsequently, the process proceeds to manufacture of a semiconductor device using the substrate product 2. First, as shown in FIG. 3C, a first conductivity type nitride-based compound semiconductor layer such as an n-type GaN layer 70 and an n-type AlGaN layer 72, a light emitting layer 74 on the epitaxial layer 60 of the substrate product 2. In addition, a second conductivity type nitride-based compound semiconductor layer such as a p-type AlGaN layer 76 and a p-type GaN layer 78 is grown. The light emitting layer 74 is a layer that generates light when a current (carrier) is injected, and has a multiple quantum well structure. Specifically, the light emitting layer 74 is configured by alternately laminating a plurality of barrier layers and well layers. Barrier layer and the well layer _is made of _{Al X3 In Y Ga 1-X3} -Y N (0 ≦ X3 <1,0 ≦ Y <1,0 <X3 + Y <1) such nitride-based compound semiconductor. The composition of the barrier layer and the well layer is adjusted so that the band gap of the barrier layer is larger than the band gap of the well layer. With this configuration, carriers injected into the light emitting layer 74 are efficiently confined in the well layer.

  Subsequently, as illustrated in FIG. 4A, a part of the surface of the n-type GaN layer 70 is exposed by etching (mesa etching) a part of each of the semiconductor layers 70 to 78. Then, as shown in FIG. 4B, the anode electrode 82 and the cathode electrode 84 are formed by a vacuum evaporation method or an electron beam evaporation method. At this time, the anode electrode 82 is provided over substantially the entire surface of the p-type GaN layer 78 on the surface opposite to the surface facing the light emitting layer 74. The anode electrode 82 is formed by sequentially laminating metals such as Ni / Au / Al / Au, and ohmic contact is realized between the anode electrode 82 and the p-type GaN layer 78.

  Further, the cathode electrode 84 has an n-type AlGaN layer 72, a light emitting layer 74, a p-type AlGaN layer 76, and a p-type GaN layer on the surface of the n-type GaN layer 70 opposite to the surface facing the epitaxial layer 60. It is provided on a region different from the region where 78 is provided. The cathode electrode 84 is formed by sequentially laminating metals such as Ti / Al / Au, and ohmic contact is realized between the cathode electrode 84 and the n-type GaN layer 70.

  Through the above steps, the semiconductor device layer 3 having a function of a light emitting diode is formed on the epitaxial layer 60. Thereby, a semiconductor device 4 having the semiconductor device layer 3 on the substrate product 2 is provided.

  As an example of the substrate product 1 according to the above embodiment, a change in characteristics of the substrate product 1 due to the density of impurities on the surface of the gallium nitride substrate 10 investigated by the inventors will be described.

First, six sheets of a 2-inch GaN wafer (corresponding to the gallium nitride substrate 10) having a thickness of 500 [μm] doped with oxygen and polished to have a mirror surface were prepared. These GaN wafers were hexagonal and had a (0001) plane. The specific resistance of these GaN wafers was 1 [Ω · cm] or less, and the carrier concentration was 1 × 10 ¹⁷ [cm ⁻³ ] or more.

Next, hydrogen ions were implanted into the nitrogen surface of these GaN wafers. At this time, the acceleration voltage of ions was set to 100 [keV], and the dose amount was set to 4 × 10 ¹⁷ [cm ⁻² ]. After ion implantation, one of these GaN wafers was subjected to total reflection X-ray fluorescence measurement. The results are shown in Table 1 below.

  Subsequently, the nitrogen surfaces of the remaining five GaN wafers were cleaned. At this time, one of the five GaN wafers is washed with acetone for 5 minutes, the other three are washed with hydrochloric acid for 1, 3, and 10 minutes, respectively, and the remaining one is washed with hydrochloric acid for 20 minutes. Washed with acid for 10 minutes.

Thereafter, five GaN wafers were set in a dry etching apparatus, and the nitrogen surface was cleaned with plasma obtained by discharging in an argon gas. Separately, five silicon wafers (corresponding to the support substrate 20) are prepared, and the surfaces of these silicon wafers are thermally oxidized to form a SiO ₂ layer having a thickness of 100 [nm] (corresponding to the oxide layer 20b). Formed. The surface of these silicon wafers was cleaned with plasma. The Ar gas conditions for cleaning the GaN wafer and the silicon wafer were RF power 100 [W], Ar flow rate 50 [sccm (standard cubic centimeter per minute)], and pressure 6.7 [Pa]. Thereafter, each of the five GaN wafers and the silicon wafer are bonded to each other in the air and bonded together by placing them in nitrogen and heating at 300 [° C.] for 2 hours, and at the same time leaving a fragile layer by ion implantation, leaving the GaN wafer. Was peeled from the silicon wafer to produce a silicon wafer (corresponding to the substrate product 1) having a GaN film on the surface.

Next, a GaN epitaxial layer was formed on the GaN film of each silicon wafer using the MOCVD method. An n-type dopant was added to the GaN epitaxial layer, and the impurity concentration was 7 × 10 ¹⁵ [cm ⁻³ ]. The thickness of the GaN epitaxial layer was 5 [μm]. Each of these five silicon wafers was divided into two parts, and the impurity density at the interface of the GaN film with silicon was measured for one of them by secondary ion mass spectrometry (SIMS analysis).

  Further, the surface of the GaN epitaxial layer of the other divided silicon wafer is subjected to a surface treatment for 1 minute at room temperature with an aqueous hydrochloric acid solution (hydrochloric acid: pure water = 1: 1), and then the GaN epitaxial layer is formed on the GaN epitaxial layer. Two Schottky electrodes made of Au film were formed by resistance heating vapor deposition. One Schottky electrode was a circular electrode having a diameter of 200 [μm]. The other Schottky electrode is an annular electrode provided around one Schottky electrode, the distance from the one Schottky electrode is 250 [μm], and the outer diameter is 300 [μm]. It was. The breakdown voltage between these Schottky electrodes was measured for each silicon wafer.

表２に示すように、不純物密度が３．７×１０^１８［ｃｍ^−３］から１．２×１２^１８［ｃｍ^−３］までおよそ７０％低下しても耐圧は５０［Ｖ］から９８［Ｖ］まで約２倍にしか増加しないが、不純物密度がそれより低くなると、１．２×１２^１８［ｃｍ^−３］から７．４×１０^１７［ｃｍ^−３］までおよそ４０％低下しただけで約２倍増加している。そして、不純物密度がこれより低くなるほど、耐圧が顕著に増加していることがわかる。このように、ＧａＮ膜のシリコンウェハとの界面における不純物密度が１×１０^１８［ｃｍ^−３］以下であれば、耐圧が顕著に増加する（すなわち、ＧａＮ膜におけるリーク電流が顕著に減少する）ことが判明した。 Table 2 below shows the cleaning method, the maximum amount of impurity density by SIMS analysis, and the pressure resistance value for each of the silicon wafers (1) to (5). The maximum amount of impurity density is considered to mean the impurity density at the interface of the GaN film with the silicon wafer.

As shown in Table 2, even if the impurity density is reduced by approximately 70% from 3.7 × 10 ¹⁸ [cm ⁻³ ] to 1.2 × 12 ¹⁸ [cm ⁻³ ], the breakdown voltage is from 50 [V] to 98 [98]. V] only increases about twice, but when the impurity density is lower than that, it is only about 40% lower from 1.2 × 12 ¹⁸ [cm ⁻³ ] to 7.4 × 10 ¹⁷ [cm ⁻³ ]. It has increased by about 2 times. It can be seen that the withstand voltage increases significantly as the impurity density becomes lower. Thus, if the impurity density at the interface between the GaN film and the silicon wafer is 1 × 10 ¹⁸ [cm ⁻³ ] or less, the breakdown voltage increases remarkably (that is, the leakage current in the GaN film significantly decreases). It has been found.

On-resistance and forward voltage were measured using the silicon wafers (1) and (5) provided with the Schottky electrode in Example 1 described above. In the case of the silicon wafer (1), when the applied voltage is 5V, only a current of 50 [A] can be flowed. In the case of the silicon wafer (5), a current of 100 [A] can be flowed, and the forward current density Of 470 [A · cm ⁻² ] and a forward voltage of 1.7 [V] were obtained. From this result, it was found that if the impurity density at the interface between the GaN film and the silicon wafer is 1 × 10 ¹⁸ [cm ⁻³ ] or less, a good Schottky barrier diode can be formed.

  As another example of the substrate product 1 according to the above-described embodiment, the results of examining the influence of the type of cleaning liquid on the manufacturing process when an alkaline cleaning liquid is used in the cleaning process will be described.

First, three sheets of a 2-inch GaN wafer (corresponding to the gallium nitride substrate 10) having a thickness of 500 [μm] doped with oxygen were polished to prepare three mirror surfaces. The surface roughness of the nitrogen surface after polishing was 1 [nm]. These GaN wafers were hexagonal and had a (0001) plane. The specific resistance of these GaN wafers was 1 [Ω · cm] or less, and the carrier concentration was 1 × 10 ¹⁷ [cm ⁻³ ] or more.

Next, hydrogen ions were implanted into the nitrogen surface of these GaN wafers. At this time, the acceleration voltage of ions was set to 100 [keV], and the dose amount was set to 4 × 10 ¹⁷ [cm ⁻² ]. After the ion implantation, the nitrogen surfaces of the three GaN wafers were ultrasonically cleaned with acetone for 5 minutes, and then cleaned with hydrochloric acid (HCl: water = 1: 1) for 10 minutes.

  Subsequently, KOH solution and NaOH solution each having a pH adjusted to 13 by diluting with water were prepared as cleaning solutions. Separately, as a cleaning solution, the ratio of ammonia water, hydrogen peroxide solution, and water was A mixed solution of 1: 1: 5 was prepared. And after immersing three GaN wafers in these three kinds of cleaning solutions, the surface roughness of these GaN wafers was measured.

表３に示すように、ＫＯＨ溶液で洗浄したＧａＮウェハ及びＮａＯＨ溶液で洗浄したＧａＮウェハはシリコンウェハと接合されず、アンモニア水と過酸化水素水と水の混合溶液で洗浄したＧａＮウェハのみシリコンウェハと接合できた。 In addition to the three GaN wafers, three silicon wafers (corresponding to the support substrate 20) are prepared, and the surfaces of these silicon wafers are thermally oxidized to form a SiO ₂ layer (oxidized) having a thickness of 100 nm. Corresponding to layer 20b). Thereafter, each of the three GaN wafers and the silicon wafer were bonded to each other. Table 3 shows the surface roughness of each GaN wafer cleaned with three types of cleaning liquids and whether or not bonding is possible.

As shown in Table 3, a GaN wafer cleaned with a KOH solution and a GaN wafer cleaned with an NaOH solution are not bonded to a silicon wafer, and only a GaN wafer cleaned with a mixed solution of ammonia water, hydrogen peroxide water, and water is a silicon wafer. We were able to join.

  The bonded silicon wafer and GaN wafer are heated, and the GaN wafer is peeled off from the silicon wafer leaving a fragile layer by ion implantation, whereby a silicon wafer having a GaN film on the surface (corresponding to the substrate product 1) is obtained. Produced. And when this board | substrate product was used and the Schottky barrier diode similar to Example 1 was produced, the proof pressure was 442 [V] and the favorable characteristic was acquired.

The manufacturing method of the substrate product 1 described above, the effects of the substrate product 1 and the semiconductor device 4 will be described. As described in the first embodiment, the inventor believes that any one of Fe, Cr, Ni, and Si is attached as an impurity to the surface 10a of the gallium nitride substrate 10 which is a joint surface with the support substrate 20. It has been found that current leakage is likely to occur in the gallium nitride layer 30 through the impurities. Further, it has been found that if these impurities are 1 × 10 ¹⁸ [cm ⁻³ ] or less in total, current leakage is significantly reduced and pressure resistance is improved. That is, according to the method of manufacturing the substrate product 1 according to the above embodiment, the density of Fe, Cr, Ni, and Si on the cleaned surface 10a is summed during the step of cleaning the surface 10a of the gallium nitride substrate 10. Therefore, the leakage current flowing in the gallium nitride layer 30 can be effectively reduced by setting the pressure to 1 × 10 ¹⁸ [cm ⁻³ ] or less. Further, according to the substrate product 1 and the semiconductor device 4 according to the above embodiment, the total density of Fe, Cr, Ni, and Si at the interface between the gallium nitride layer 30 and the support substrate 20 is 1 × 10 ¹⁸ [cm ^{−. 3} ] or less, the leakage current flowing in the gallium nitride layer 30 can be effectively reduced.

Further, as in the above embodiment, the step of cleaning the surface 10a of the gallium nitride substrate 10 may include the step of cleaning the surface 10a using a hydrogen peroxide solution containing ammonia. Generally, when the semiconductor device layer 3 (see FIG. 4B) is grown on the gallium nitride layer 30, a gallium surface opposite to the nitrogen surface of the gallium nitride layer 30 is used as the growth surface. Many. In that case, the surface of the gallium nitride substrate 10 to be bonded to the support substrate 20 needs to be a nitrogen surface. However, as shown in Example 3, for example, if cleaning is performed using a strongly alkaline liquid such as KOH or NaOH, The surface is etched, the flatness of the surface is impaired, and bonding with the support substrate 20 becomes difficult. On the other hand, if the surface 10a is cleaned using hydrogen peroxide containing ammonia, the impurity density of the nitrogen surface is maintained by cleaning while maintaining the flatness of the nitrogen surface of the gallium nitride substrate 10 as shown in Table 3. Can be suppressed to 1 × 10 ¹⁸ [cm ⁻³ ] or less.

  Further, as in the above embodiment, in the step of cleaning the surface 10a of the gallium nitride substrate 10, it is preferable to clean the gallium nitride substrate 10 while oscillating or vibrating (for example, ultrasonic vibration). Thereby, the cleaning effect | action with respect to the surface 10a of the gallium nitride substrate 10 can be improved.

  The substrate product manufacturing method, the substrate product, and the semiconductor device according to the present invention are not limited to the above-described embodiments, and various other modifications are possible. For example, although the gallium nitride substrate is exemplified as the nitride-based compound semiconductor substrate in the above-described embodiments and examples, the substrate may be made of other compounds as long as the substrate is made of a nitride-based compound.

  1, 2 ... substrate product, 3 ... semiconductor device layer, 4 ... semiconductor device, 10 ... gallium nitride substrate, 10a ... surface, 10b ... fragile layer, 12 ... ion, 14 ... cleaning solution, 20 ... support substrate, 20a ... surface 20b ... oxide layer, 30 ... gallium nitride layer, 60 ... epitaxial layer, 70 ... n-type GaN layer, 72 ... n-type AlGaN layer, 74 ... light-emitting layer, 76 ... p-type AlGaN layer, 78 ... p-type GaN layer, 82 ... Anode electrode, 84 ... Cathode electrode, 100 ... Ion implanter, 200 ... Annealing furnace.

Claims (5)

A method of manufacturing a substrate product having a nitride compound semiconductor layer on a support substrate made of a material different from a nitride compound semiconductor,
A step of performing ion implantation on the surface of the nitride-based compound semiconductor substrate;
Cleaning the surface of the nitride-based compound semiconductor substrate;
Bonding the surface of the nitride-based compound semiconductor substrate and the surface of the support substrate to each other;
Forming a nitride-based compound semiconductor layer on the support substrate by removing other portions of the nitride-based compound semiconductor substrate while leaving the portion including the surface in a layer shape,
In the step of cleaning the surface of the nitride-based compound semiconductor substrate, the total density of Fe, Cr, Ni, and Si on the surface of the nitride-based compound semiconductor substrate after cleaning is 1 × 10 ¹⁸ [cm ^{− 3} ] A method for producing a substrate product, characterized by:   The step of cleaning the surface of the nitride-based compound semiconductor substrate includes a step of cleaning the surface of the nitride-based compound semiconductor substrate using a hydrogen peroxide solution containing ammonia. A method for producing the described substrate product.   The substrate product according to claim 1, wherein the nitride compound semiconductor substrate is cleaned while being swung or vibrated during the step of cleaning the surface of the nitride compound semiconductor substrate. Manufacturing method. After the surface of the nitride compound semiconductor substrate is ion-implanted and the surface of the nitride compound semiconductor substrate is cleaned, the surface of the nitride compound semiconductor substrate and the nitride compound semiconductor are made of different materials. The nitride-based compound semiconductor layer formed by bonding the surfaces of the support substrate to each other and removing the other portion of the nitride-based compound semiconductor substrate while leaving the portion including the surface in a layer form on the support substrate. In preparation for
The substrate product, wherein the total density of Fe, Cr, Ni, and Si at the interface between the nitride-based compound semiconductor layer and the support substrate is 1 × 10 ¹⁸ [cm ⁻³ ] or less. A substrate product according to claim 4;
A semiconductor device layer comprising a nitride compound semiconductor provided on the nitride compound semiconductor layer of the substrate product.

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