JP2010177281A - Gallium nitride-based compound semiconductor substrate and method of manufacturing the same, and semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GaN-based compound semiconductor substrate which has excellent quality as a semiconductor substrate and has its surface made high in resistance. <P>SOLUTION: The GaN substrate 1 has a main surface 10a where a semiconductor crystal is to be epitaxially grown, wherein predetermined ions such as H, He or Ar ions, are implanted in at least a partial region 12 of the main surface 10a, at least the partial region 12 is ≥70% of the entire main surface 10a, and the surface of the region 12 has an average sheet resistance value of 1×10<SP>4</SP>Ω/square or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gallium nitride compound semiconductor substrate, a method for manufacturing the same, and a semiconductor element using the gallium nitride compound semiconductor substrate.

  Gallium nitride (GaN) compound semiconductors are expected as materials for light-emitting devices and electronic devices because of their large band gaps compared to conventional semiconductors such as silicon.

  When manufacturing these devices, it may be necessary to increase the resistance of the GaN-based compound semiconductor. For example, Patent Document 1 discloses a method of manufacturing a high-resistance GaN crystal layer when manufacturing a GaN-based FET. In the method described in this document, a high-resistance GaN compound is grown by doping a p-type impurity such as C, Mg, and Zn on an insulating substrate such as a sapphire substrate to grow a high-resistance GaN crystal layer. A substrate having a surface made of a semiconductor is manufactured.

  Patent Document 2 discloses a method of forming a nitride semiconductor film on a silicon substrate. In the method described in this document, ions are implanted into the surface of a nitride semiconductor substrate, a silicon substrate is superimposed on the surface of the nitride semiconductor substrate, heat-treated, and then peeled off to nitride the silicon substrate. A physical semiconductor film is formed.

JP 2001-247399 A JP 2006-210660 A

  Generally, when manufacturing a substrate made of a GaN-based compound semiconductor, impurities are easily taken in during the growth process. Therefore, the resistivity of the manufactured GaN-based compound semiconductor substrate tends to be low. However, when manufacturing a light-emitting device or an electronic device, it may be desirable that the substrate surface has a high resistivity. When increasing the resistance of a GaN-based compound semiconductor substrate, there is a report that the resistance can be increased by doping a specific impurity such as Fe or C at the time of growth. However, when the doping amount of these impurities is increased, other impurities also increase at the same time, resulting in a problem that the resistivity on the surface of the substrate is lowered or cracks are generated and the substrate is easily broken. Therefore, with such a method, it has been difficult to increase the resistance of the surface while having good quality as a semiconductor substrate.

  The present invention has been made in view of the above-described problems, and has a good quality as a semiconductor substrate and has a surface with high resistance, a method for manufacturing the same, and the GaN-based compound. An object is to provide a semiconductor element using a semiconductor substrate.

In order to solve the above problems, a gallium nitride compound semiconductor substrate according to the present invention is a gallium nitride compound semiconductor substrate having a main surface for epitaxially growing a semiconductor crystal, and is formed in at least a part of the main surface. given ion are implanted, said at least part of the region accounts for 70% or more of the principal surface throughout the average sheet resistance value at the surface of the region is 1 × 10 ⁴ Ω / □ or more It is characterized by.

A method for manufacturing a gallium nitride-based compound semiconductor substrate according to the present invention is a method for manufacturing a gallium nitride-based compound semiconductor substrate having a main surface for epitaxially growing a semiconductor crystal, in at least a part of the main surface. In this case, predetermined ions are implanted into a region that occupies 70% or more of the entire main surface, whereby the average sheet resistance value on the surface of the region is set to 1 × 10 ⁴ Ω / □ or more.

  Ion implantation is generally used in many silicon-based semiconductor processes. For example, by implanting a desired impurity as ions into a desired region of a silicon-based semiconductor, the region can be an n-type semiconductor or a p-type semiconductor, and the resistivity of the region can be reduced. However, contrary to such common technical knowledge, the inventor has found that GaN-based compound semiconductors are more likely to be damaged by ion implantation than silicon, and that the resistivity tends to increase as the dose increases. I found it. Since ion implantation can be performed on a GaN-based compound semiconductor substrate that has already been formed, it is possible to stably produce a semiconductor substrate that is difficult to crack compared to the above-described increase in resistance by doping impurities. I found out that I can.

That is, according to the GaN-based compound semiconductor substrate and the manufacturing method thereof according to the present invention, when predetermined ions are implanted into at least a part of the main surface, the region occupies 70% or more of the entire main surface, In addition, even when the sheet resistance value on the surface of the region is as high as 1 × 10 ⁴ Ω / □ or more, the semiconductor substrate can have good quality.

  Further, the gallium nitride compound semiconductor substrate and the manufacturing method thereof may be characterized in that the predetermined ions are ions of atoms having an atomic weight of Ar or less. According to the experiments by the present inventors, it was found that when the atomic weight of ions is Ar or less, the damage on the surface of the GaN-based compound semiconductor substrate can be suppressed sufficiently low, and the recovery of crystallinity becomes extremely easy. . That is, by setting the atomic weight of ions to Ar or less in this way, it is possible to have a better quality as a semiconductor substrate and to increase the resistance of the surface.

In addition, the gallium nitride compound semiconductor substrate and the manufacturing method thereof may be characterized in that an average value of the ion implantation amount in the region is 1 × 10 ¹⁴ cm ⁻² or more and 2 × 10 ¹⁷ cm ⁻² or less. According to the experiment of the present inventor, when the ion implantation amount is within the above range, the surface resistance of the GaN-based compound semiconductor substrate can be sufficiently increased and the surface peeling can be suitably prevented.

The semiconductor device according to the present invention has a main surface for epitaxially growing a semiconductor crystal, predetermined ions are implanted into the main surface, and the average sheet resistance value on the surface of the region is 1 × 10 ⁴ Ω. It is characterized by comprising a gallium nitride-based compound semiconductor substrate that is / □ or more and a semiconductor layer formed on the main surface of the gallium nitride-based compound semiconductor substrate. According to this semiconductor element, a predetermined ion is implanted into the main surface of the GaN-based compound semiconductor substrate, so that the sheet resistance value on the substrate surface can be as high as 1 × 10 ⁴ Ω / □ or more. It becomes possible to have good quality. Therefore, a light emitting device or an electronic device having a high resistance substrate surface can be suitably realized.

  According to the gallium nitride compound semiconductor substrate and the method of manufacturing the same according to the present invention, it is possible to increase the resistance of the surface of the semiconductor substrate while having good quality as a semiconductor substrate. In addition, according to the semiconductor element of the present invention, a light emitting device, an electronic device, and the like using the gallium nitride compound semiconductor substrate can be suitably realized.

FIG. 1 is a view showing a GaN substrate 1 as a first embodiment of a GaN-based compound semiconductor substrate according to the present invention. (A) is a perspective view which shows the external appearance of the GaN substrate 1, (b) is a sectional side view of the GaN substrate 1 along the II line | wire of Fig.1 (a). FIG. 2 is a view for explaining the method for manufacturing the GaN substrate 1 according to the first embodiment. FIG. 3 is a side sectional view showing a configuration of a light emitting diode 20 as a second embodiment of the semiconductor element according to the present invention.

  Embodiments of a gallium nitride-based compound semiconductor substrate, a manufacturing method thereof, 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.

(First embodiment)
As shown in FIG. 1, the GaN substrate 1 according to the first embodiment of the present invention has a substantially disk shape having a main surface 10a, and is made of gallium nitride. The main surface 10a is a surface for epitaxially growing a GaN-based compound semiconductor crystal, and maintains a certain crystallinity.

Further, the whole or at least a part of the main surface 10a of the GaN substrate 1 is a region in which a predetermined ion is implanted and the resistance is increased. The area of the high resistance region 12 viewed from the direction perpendicular to the main surface 10a occupies 70% or more of the total area of the main surface 10a, and the high resistance region 12 constitutes a main part of the main surface 10a. ing. The average sheet resistance value on the surface of the high resistance region 12 is 1 × 10 ⁴ Ω / □ or more, and there are no particular restrictions on the atoms to be ion-implanted. Ions of atoms having an atomic weight are preferred. Moreover, it is preferable that the average value of the ion implantation amount in the high resistance region 12 is 1 × 10 ¹⁴ cm ⁻² or more and 2 × 10 ¹⁷ cm ⁻² or less. The thickness of the high resistance region 12, that is, the ion implantation depth based on the main surface 10 a is, for example, about 30 μm. This implantation depth is set to a desired depth depending on the type of ions and the acceleration voltage.

Here, a method for manufacturing the GaN substrate 1 according to the present embodiment will be described. As shown in FIG. 2, the GaN substrate 1 is first placed in the ion implantation apparatus 100. Then, ions 14 of predetermined atoms (atoms having an atomic weight equal to or less than Ar, such as H, He, and Ar) are implanted into the main surface 10a of the GaN substrate 1 to form the high resistance region 12. At this time, the area of the high resistance region 12 viewed from the direction perpendicular to the main surface 10a is set to 70% or more of the entire area of the main surface 10a, and the average sheet resistance value on the surface of the high resistance region 12 is 1 ×. Ion implantation is performed so as to be 10 ⁴ Ω / □ or more. Moreover, it is preferable that the average value of the ion implantation amount (dose amount) in the high resistance region 12 is 1 × 10 ¹⁴ cm ⁻² or more and 2 × 10 ¹⁷ cm ⁻² or less. Then, after the ion implantation, a heat treatment is performed on the GaN substrate 1.

  In the above-described manufacturing method, the larger the ion implantation amount, the better. The excessive amount of ion implantation may cause the surface of the GaN substrate 1 to peel off, and this will be shown in the examples described later. The element implanted as ions is not particularly limited as long as it can damage the main surface 10a of the GaN substrate 1 and increase the resistance. However, when heavy metals such as Au are implanted as ions, crater-like irregularities are formed on the main surface 10a of the GaN substrate 1, and the crystallinity recovery of the main surface 10a after ion implantation is compared to the case of light elements. There is a problem that it is difficult. Therefore, as described above, it is preferable to ion-implant a light element having an atomic weight of Ar or less. In particular, H, He, and the like are more preferable because crystallinity recovery after ion implantation is easy. Further, the number of elements implanted as ions into one GaN substrate 1 is not limited to one, and a plurality of elements can be ion-implanted.

(Second Embodiment)
FIG. 3 is a side sectional view showing a configuration of a light emitting diode 20 as a second embodiment of the semiconductor element according to the present invention. Referring to FIG. 3, the light emitting diode 20 includes a GaN substrate 10 formed by cutting the GaN substrate 1 of the first embodiment into a chip shape. The entire surface of the main surface 10a of the GaN substrate 10 is a high resistance region 12.

In addition, the light emitting diode 20 includes a thin film GaN buffer layer 21 sequentially stacked on the main surface 10 a of the GaN substrate 10, and a first conductivity type nitride semiconductor layer such as an n-type GaN layer 22 and an n-type AlGaN layer 23. ing. The n-type GaN layer 22 is made of GaN doped with an n-type impurity such as Si, and the n-type AlGaN layer 23 is Al _X1 Ga _1-X1 N (0 <X1 <1) doped with an n-type impurity. Consists of. The light emitting diode 20 includes an active layer 24 provided on the n-type AlGaN layer 23. The light emitting diode 20 includes a second conductivity type nitride semiconductor layer such as a p-type AlGaN layer 25 and a p-type GaN layer 26 that are sequentially stacked on the active layer 24. p-type AlGaN layer 25 is formed of p-type impurities such as Mg-doped _{Al X2 Ga 1-X2 N (} 0 <X2 <1), p -type GaN layer 26, p-type impurities are doped GaN Consists of.

The active layer 24 is a layer that generates light when a current (carrier) is injected. The active layer 24 is formed on the n-type AlGaN layer 23 and has a multiple quantum well structure. Specifically, the active layer 24 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 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 active layer 24 are efficiently confined in the well layer.

  The light emitting diode 20 further includes an anode electrode 27 and a cathode electrode 28 in addition to the above configuration. The anode electrode 27 is provided on the surface of the p-type GaN layer 26 opposite to the surface facing the active layer 24. In the present embodiment, the anode electrode 27 is provided over almost the entire surface of the p-type GaN layer 26. The anode electrode 27 is formed by sequentially laminating metals such as Ni / Au / Al / Au, and ohmic contact is realized between the anode electrode 27 and the p-type GaN layer 26.

  The cathode electrode 28 includes an n-type AlGaN layer 23, an active layer 24, a p-type AlGaN layer 25, and a p-type GaN layer 26 on the surface of the n-type GaN layer 22 opposite to the surface facing the GaN substrate 10. It is provided on a different area from the provided area. The cathode electrode 28 is formed by sequentially laminating, for example, metals such as Ti / Al / Au, and ohmic contact is realized between the cathode electrode 28 and the n-type GaN layer 22.

(Example)
Examples of GaN-based compound semiconductor substrates and semiconductor elements according to the present invention will be described below.

表１に示すように、イオン注入量が１×１０^１４ｃｍ^−２以上であれば、１Ω・ｃｍ以上の高い抵抗率が得られることがわかった。 <Example 1>
First, seven wafer-shaped GaN substrates (thickness 500 μm) made of a disk-shaped GaN crystal having a diameter of 2 inches doped with oxygen atoms and having a mirror-polished main surface were prepared. These GaN substrates are composed of hexagonal crystals, and the (0001) Ga surface is the main surface. The sheet resistance value on the main surface of these GaN substrates was 0.2Ω / □ or less. The main surface was implanted with hydrogen ions at an accelerating voltage of 90 keV, and the amount of hydrogen ions implanted was changed for each substrate to evaluate the sheet resistance value on the main surface of each substrate. The results are shown in Table 1.

As shown in Table 1, it was found that when the ion implantation amount was 1 × 10 ¹⁴ cm ⁻² or more, a high resistivity of 1 Ω · cm or more was obtained.

表２に示すように、イオン注入量が２×１０^１７ｃｍ^−２以下であれば、ＧａＮ基板の主面が剥離しないことがわかった。 <Example 2>
Next, each GaN substrate fabricated in Example 1 was heated at 800 ° C. for 30 minutes. Then, it was examined whether or not peeling occurred on the main surface of the GaN substrate after heating. The results are shown in Table 2.

As shown in Table 2, it was found that when the ion implantation amount was 2 × 10 ¹⁷ cm ⁻² or less, the main surface of the GaN substrate was not peeled off.

<Example 3>
Subsequently, ion implantation of He, Ar, and Au was performed on the main surface (Ga surface) of the same three GaN substrates used in Example 1 instead of hydrogen. At this time, the acceleration voltage was 90 keV, and the ion implantation amount was 5 × 10 ¹⁶ cm ⁻² . And the sheet resistance value in the main surface of each board | substrate was evaluated. The results are shown in Table 3. All the substrates had high sheet resistance values and exceeded the measurement range.

表４に示すように、ＨｅまたはＡｒがイオン注入されたＧａＮ基板は、Ａｕがイオン注入されたＧａＮ基板と比較して、アニールによる結晶性の回復が容易であることがわかった。 <Example 4>
Subsequently, each GaN substrate produced in Example 3 was placed in a heating furnace into which a mixed gas composed of N ₂ and NH ₃ was introduced, and annealed. At this time, the partial pressure of N ₂ and NH ₃ was NH ₃ / (N ₂ + NH ₃ ) = 0.4, and the temperature in the furnace was 1100 ° C. Further, the temperature was raised from room temperature to the above temperature at a heating rate of 20 ° C. or less per minute, and held at the above temperature for 1 hour. Table 4 shows the results of evaluating the half-value width difference between before and after annealing by performing X-ray measurement of the main surface of the GaN substrate to measure the rocking curve of the (0002) plane before and after annealing.

As shown in Table 4, it was found that the GaN substrate into which He or Ar was ion-implanted was easier to recover the crystallinity by annealing than the GaN substrate into which Au was ion-implanted.

<Example 5>
Hydrogen atoms are ion-implanted into the main surface (Ga surface) with an ion implantation amount of 1 × 10 ¹⁷ cm ⁻² to the same GaN substrate used in Example 1, and 1000 ° C. for 30 minutes in an N ₂ atmosphere. Annealing was performed. Separately, a sapphire substrate was prepared. Then, light emitting diode elements having the structure shown in FIG. 3 were formed on the main surfaces of the GaN substrate and the sapphire substrate by MOCVD. Specifically, n-type GaN layer on each substrate, _{an In} 0.2 _{Ga 0.8} N layer as an active _layer, Al 0.2 _{Ga 0.8} N layer, and a p-type GaN layer are sequentially grown . Then, the n-type GaN layer was exposed by dry etching, an anode electrode was formed on the exposed portion, and a cathode electrode was formed on the p-type GaN layer.

  When comparing the two light-emitting diode devices fabricated in this way, the device using a GaN substrate into which hydrogen atoms were ion-implanted had an emission spectrum intensity at a peak wavelength of 450 nm of 1.4 times that of a device using a sapphire substrate. became. From this, it was found that the light emitting diode element using the GaN substrate into which hydrogen atoms were ion-implanted had higher luminous efficiency than the element using the sapphire substrate.

  The operation and effect obtained by the GaN substrate 1 described above and the manufacturing method thereof will be described. As described above, ion implantation is generally used in many silicon-based semiconductor processes, and the resistivity of the region can be lowered by ion implantation of a desired impurity. However, the present inventor found that, contrary to such common technical knowledge, the GaN substrate is more likely to be damaged by ion implantation than silicon, and the resistivity tends to increase as the dose increases. . Since ion implantation can be performed on a GaN substrate that has already been formed, it is possible to stably produce a GaN substrate 1 that is difficult to crack compared to the above-described increase in resistance by doping impurities. I found.

That is, according to the GaN substrate 1 and the manufacturing method thereof according to the present embodiment, predetermined ions are implanted into at least a partial region 12 of the main surface 10a, so that the high-resistance region 12 extends over the entire main surface 10a. Even if the sheet resistance value on the surface of the region 12 occupies 70% or more and has a high resistance of 1 × 10 ⁴ Ω / □ or more, the GaN substrate can have good quality.

  Further, as shown in Example 4, the predetermined ion is preferably an ion of an atom having an atomic weight of Ar or less. That is, when the atomic weight of ions is Ar or less, damage to the main surface 10a of the GaN substrate 1 can be suppressed to a sufficiently low level, and crystallinity recovery becomes extremely easy. And by making the atomic weight of ion below Ar in this way, it becomes possible to have a better quality as a GaN substrate and to increase the resistance of the surface.

Moreover, as shown in Examples 1 and 2, the average value of the ion implantation amount in the high resistance region 12 is preferably 1 × 10 ¹⁴ cm ⁻² or more and 2 × 10 ¹⁷ cm ⁻² or less. That is, when the ion implantation amount is within the above range, the surface resistance of the GaN substrate 1 can be sufficiently increased (Example 1), and surface peeling can be suitably prevented (Example 2).

  The GaN-based compound semiconductor substrate, the manufacturing method thereof, and the semiconductor element according to the present invention are not limited to the above-described embodiments, and various other modifications are possible. For example, although the GaN substrate is exemplified as the GaN-based compound semiconductor substrate to be ion-implanted in the embodiment and each example, the present invention further includes a group III element or a group V element other than Ga and N as a composition. Even so, the same effect can be obtained.

  Moreover, although the light emitting diode was shown as an example of a semiconductor element in the said embodiment and Example, the semiconductor element which concerns on this invention is not restricted to this, For example, electronic devices, such as FET, and other devices are used for this invention. Applicable.

  DESCRIPTION OF SYMBOLS 1,10 ... GaN substrate, 10a ... Main surface, 12 ... High resistance region, 14 ... Ion, 20 ... Light emitting diode, 21 ... Buffer layer, 22 ... n-type GaN layer, 23 ... n-type AlGaN layer, 24 ... Active 25, p-type AlGaN layer, 26 ... p-type GaN layer, 27 ... anode electrode, 28 ... cathode electrode.

Claims (7)

A gallium nitride compound semiconductor substrate having a main surface for epitaxially growing a semiconductor crystal,
Predetermined ions are implanted into at least a part of the main surface, and the at least part of the region occupies 70% or more of the entire main surface, and the average sheet resistance value on the surface of the region is A gallium nitride-based compound semiconductor substrate, which is 1 × 10 ⁴ Ω / □ or more.   The gallium nitride compound semiconductor substrate according to claim 1, wherein the predetermined ion is an ion of an atom having an atomic weight of Ar or less. 3. The gallium nitride compound semiconductor substrate according to claim 1, wherein an average value of an ion implantation amount in the region is 1 × 10 ¹⁴ cm ⁻² or more and 2 × 10 ¹⁷ cm ⁻² or less. A gallium nitride system having a main surface for epitaxially growing a semiconductor crystal, in which predetermined ions are implanted into the main surface, and an average sheet resistance value on the surface of the region is 1 × 10 ⁴ Ω / □ or more A compound semiconductor substrate;
And a semiconductor layer formed on the main surface of the gallium nitride compound semiconductor substrate. A method for producing a gallium nitride compound semiconductor substrate having a main surface for epitaxially growing a semiconductor crystal,
By implanting predetermined ions into a region that is at least a part of the main surface and occupies 70% or more of the entire main surface, the average sheet resistance value on the surface of the region is 1 × 10 ⁴ Ω / A method for producing a gallium nitride-based compound semiconductor substrate, characterized by being □ or more.   6. The method for manufacturing a gallium nitride-based compound semiconductor substrate according to claim 5, wherein the predetermined ion is an ion of an atom having an atomic weight of Ar or less. The average value of the ion implantation amount in the region is 1 × 10 ¹⁴ cm ⁻² or more and 2 × 10 ¹⁷ cm ⁻² or less, and the gallium nitride compound semiconductor substrate according to claim 5 or 6 is manufactured. Method.

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