JPH11135831A - Gallium nitride group compound semiconductor wafer and compound semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer for which a gallium nitride group compound semiconductor crystal of high carrier density is grown on the surface. SOLUTION: On the surface of this gallium nitride group compound semiconductor wafer W1 grown through an MOCVD method with good uniformity, a (p)-type GaN layer 8 is grown by a liquid phase growth method with easily producing high carriers. In particular, it is effective for obtaining the gallium nitride group compound semiconductor wafer of a structure provided with a high carrier (p)-type layer on the surface which is difficult to constitute by the MOCVD method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride compound semiconductor wafer and a gallium nitride compound semiconductor device.

[0002]

2. Description of the Related Art As a method for growing a gallium nitride-based compound semiconductor crystal, a metal organic chemical vapor deposition (MOC) method is generally used.
VD method) is known. This crystal growth method uses a group III raw material such as trimethyl gallium (TMG), trimethyl aluminum (TMA), trimethyl indium (TMI) and ammonia (NH ₃ ) on a crystal substrate heated in a reaction furnace. Is fed by a carrier gas such as hydrogen gas, and these source gases are thermally decomposed on a crystal substrate to grow crystals. The MOCVD method has the advantages of good controllability of the grown film thickness, and easy growth of crystals of different conductivity types or mixed crystal. The MOCVD method is currently used to grow gallium nitride based compound semiconductor crystals. Stack growth is performed, and a light emitting element and the like are manufactured.

[0003]

However, when a gallium nitride-based compound semiconductor crystal is grown by a conventional MOCVD method, a problem arises in the growth of a p-type crystal. MOC
When growing a p-type crystal by the VD method, p-type crystals such as Mg and Zn are used.
Although a p-type is achieved by doping with a type impurity, it does not actually become a p-type crystal but an i-type crystal having a very low carrier concentration and close to an insulator. When grown by MOCVD, it is inevitable that hydrogen enters the crystal as an impurity, and this causes a problem that it is difficult to increase the carrier of the p-type crystal. Therefore, when a p-type crystal is manufactured by the MOCVD method, a step such as a thermal annealing treatment or an electron beam irradiation treatment must be performed after the growth in order to make the grown crystal p-type. However, even if these steps are performed, the carrier concentration of the obtained p-type crystal does not increase so much. Therefore, when a device such as a light-emitting element for forming an electrode is formed, the contact resistance between the electrode and the semiconductor layer is large. Problems such as difficulty in dispersing current in the layer
It adversely affects the light emission characteristics.

Accordingly, the present invention solves the above-mentioned problems of the prior art, and provides a wafer on which a gallium nitride-based compound semiconductor crystal having a high carrier concentration is grown on the surface and a gallium nitride-based compound semiconductor device using the same. Is to do.

[0005]

To achieve the above object, a gallium nitride-based compound semiconductor wafer of the present invention is configured as follows.

[0006] (1) at least n-type and p-type formula impurity was doped Al _x Ga _y In _lxy N (where,
To 0 ≦ x ≦ 1,0 <y ≦ 1, x + y ≦ 1) with expressed surface of the gallium nitride-based compound semiconductor wafer formed by laminating growing a gallium nitride-based compound semiconductor, and further, the general formula Al _a
Ga _b In _lab N (0 ≦ a ≦ 1, 0 <b ≦ 1, a + b
≦ 1) has a structure in which gallium nitride-based compound semiconductor layers represented by ≦ 1) are stacked by a liquid phase growth method.

[0007] (2) at least n-type and p-type formula impurity was doped Al _x Ga _y In _lxy N (where,
0 ≦ x ≦ 1, 0 <y ≦ 1, x + y ≦ 1) On the surface of a gallium nitride-based compound semiconductor wafer formed by stacking gallium nitride-based compound semiconductors, and further, the same conductivity type as the surface layer of the wafer. Having the general formula Al _a Ga _b In
_lab N has a structure in which gallium nitride-based compound semiconductor layers represented by N (0 ≦ a ≦ 1, 0 <b ≦ 1, a + b ≦ 1) are stacked by a liquid phase growth method.

[0008] (3) at least n-type and p-type formula impurity was doped Al _x Ga _y In _lxy N (where,
0 ≦ x ≦ 1, 0 <y ≦ 1, x + y ≦ 1) The surface of a gallium nitride-based compound semiconductor wafer formed by stacking gallium nitride-based compound semiconductors, and further doped into the surface layer of the wafer the same impurity as are impurity doped, the general formula _{Al a Ga b In lab N (} 0 ≦ a ≦ 1,0
It has a structure in which gallium nitride-based compound semiconductor layers represented by <b ≦ 1, a + b ≦ 1) are stacked by a liquid phase growth method.

[0009] (4) at least n-type and p-type formula impurity was doped Al _x Ga _y In _lxy N (where,
A gallium nitride-based compound semiconductor wafer formed by laminating gallium nitride-based compound semiconductors represented by 0 ≦ x ≦ 1, 0 <y ≦ 1, x + y ≦ 1), and the outermost surface layer of which has a p-type conductivity. On the surface, further having a p-type conductivity type,
General formula Al _a Ga _b In _lab N (0 ≦ a ≦ 1, 0 <b
≦ 1, a + b ≦ 1) has a structure in which gallium nitride-based compound semiconductor layers are stacked by a liquid phase growth method.

[0010] (5) at least n-type and p-type formula impurity was doped Al _x Ga _y In _lxy N (where,
A gallium nitride-based compound semiconductor formed by stacking and growing a gallium nitride-based compound semiconductor represented by 0 ≦ x ≦ 1, 0 <y ≦ 1, x + y ≦ 1), and doping a p-type impurity in the outermost surface layer After subjecting the wafer to a heat treatment or an electron beam irradiation treatment to convert the conductivity type of the outermost surface of the wafer to p-type, the surface further has a p-type conductivity type, a general formula Al _a Ga
_b In _lab N (0 ≦ a ≦ 1, 0 <b ≦ 1, a + b ≦
It has a structure in which gallium nitride-based compound semiconductor layers represented by 1) are stacked by a liquid phase growth method.

(6) In the gallium nitride compound semiconductor wafer according to the fourth or fifth aspect, the gallium nitride compound semiconductor layer having the p-type conductivity is a layer doped with at least Mg as an impurity.

(7) In the gallium nitride-based compound semiconductor wafer according to any one of claims 1 to 5, the layers other than the gallium nitride-based compound semiconductor layer grown on the outermost surface of the wafer by a liquid phase growth method are formed by a metal organic chemical vapor deposition method. MOCVD).

[0013] (8) grown by metal organic chemical vapor deposition, at least n-type and p-type formula impurity was doped Al _x Ga _y In _lxy N (where, 0 ≦ x ≦ 1, 0
A heat treatment or electron beam irradiation is performed on a gallium nitride-based compound semiconductor wafer formed by laminating a gallium nitride-based compound semiconductor represented by <y ≦ 1, x + y ≦ 1), and the outermost surface layer of which is made of a GaN layer doped with Mg. After the treatment, the conductivity type of the outermost surface of the wafer is changed to p-type, and a GaN layer doped with Mg is further laminated on the surface by a liquid phase growth method.

(9) In the gallium nitride compound semiconductor wafer according to any one of claims 1 to 8, the gallium nitride compound semiconductor grown on the outermost surface of the wafer by a liquid phase growth method is polycrystalline.

(10) In the gallium nitride-based compound semiconductor wafer according to any one of claims 1 to 9, the gallium nitride-based compound semiconductor layer is grown on an insulating substrate.

(11) An electrode is formed in contact with at least the outermost surface of the gallium nitride-based compound semiconductor wafer according to any one of the first to tenth aspects to provide a manufactured gallium nitride-based compound semiconductor device.

The gist of the present invention is that MOCVD with good uniformity is achieved.
The gallium nitride-based compound semiconductor crystal is grown on the surface of the gallium nitride-based compound semiconductor crystal grown by the method using a liquid phase growth method that can easily increase the number of carriers. In particular, MO
This is effective for a gallium nitride-based compound semiconductor crystal having a structure having a high carrier p-type layer on the surface, which is difficult by the CVD method.

The liquid phase growth method is different from the MOCVD method.
Since a gallium nitride-based compound semiconductor crystal can be grown without using a hydride as a raw material, hydrogen is not taken into the grown crystal. Accordingly, since the incorporation of hydrogen, which has hindered the increase in the carrier of the p-type crystal, is eliminated, the p-type crystal can be obtained without performing thermal annealing or electron beam irradiation after growth. Further, when the carrier concentration is M
Since it is higher than that grown by the OCVD method, there are advantages in that when a device such as a light-emitting element in which an electrode is formed in this layer is manufactured, the contact resistance between the electrode and the semiconductor layer is small and the current is easily dispersed in the p-layer.

The purpose of growing the high carrier layer on the surface by the liquid phase method is to reduce the contact resistance between the gallium nitride-based compound semiconductor crystal and the metal electrode and to efficiently disperse the current in the surface layer. Therefore, it is not always necessary to use a single crystal film.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the illustrated embodiments.

(Conventional Example) A gallium nitride based compound semiconductor wafer having a double hetero (DH) structure as shown in FIG. 2 is formed on a sapphire substrate 1 by using a conventional technique of metal organic chemical vapor deposition (MOCVD). W1 was grown in layers. On this wafer W1, a sapphire c-plane is used as a substrate. On the sapphire substrate 1, an AlN buffer layer 2 is grown at 400 ° C. at 600 ° C., and at 1000 ° C., a Si-doped n-type GaN layer 3 is formed at 4 μm. Si-doped n-type Al
_{A 0.3} Ga _0.7 N layer 4 is grown to a thickness of 0.2 μm, and
After growing a Zn-doped In _0.1 Ga _0.9 N layer 5 at 200 ° C. at 200 ° C., at 1000 ° C., Mg-doped Al _0.3 Ga _0.7
The N layer 6 is 0.2 μm, and the Mg-doped GaN layer 7 is 0.5 μm.
It was grown by μm. In addition, this wafer has
A thermal annealing process was performed at 400 ° C. for 30 minutes in a nitrogen atmosphere to convert the Mg-doped layer into a p-type.

The carrier concentration of the p-type GaN layer 7 of the outermost surface, and growing a p-type GaN layer on only one layer on a sapphire substrate, estimated from the results measured by Pau method is 5 × 10 ¹⁷ cm ^-3 Is done.

A nickel (Ni) 5 is formed on the surface layer of the substrate.
When a dot electrode having a laminated structure of 00 ° and gold (Au) 1 μm was deposited and heat-treated at 500 ° C. for 5 minutes, the resistance between the electrodes was measured, and the contact resistance between the outermost surface layer and the electrode was determined. It was 1 × 10 ⁻⁴ Ω · cm ² .

Next, in order to attach an ohmic electrode, a part of the surface of the wafer W1 is subjected to reactive ion etching (RI).
After etching away by the method E) to expose the n-type GaN layer 3, as shown in FIG. 4, the surface of the n-type GaN layer 3 has a laminated structure of titanium (Ti) and aluminum (Al). An n-type electrode 10 and a p-type electrode 9 having a laminated structure of nickel (Ni) and gold (Au) are attached to a part of the surface of the p-type layer, and an LED chip (gallium nitride-based compound semiconductor element) 12 is formed. Produced.

When the LED chip 12 was energized and the light emission was observed, the light was emitted immediately below the p-type electrode 9.
It was only around it. Put this LED in the integrating sphere,
The emission output was measured to be 0.02 at 20 mA
mW.

(Embodiment 1) A first embodiment of the present invention will be described. FIG. 1 shows a cross-sectional structure of a wafer W2 manufactured in this embodiment.

The sapphire substrate 1
From the p-type GaN layer 7 to the p-type GaN layer 7 by the same MOCVD method as in the above-described conventional example, and a Mg-doped GaN layer 8 is further formed on the surface of the manufactured wafer W1 by a slide boat type liquid phase growth. The structure is 1 μm grown in a furnace.

First, a portion of the wafer W1, that is, a wafer grown by the MOCVD method shown in FIG. 2 was prepared and heat-treated.

More specifically, a gallium nitride-based compound semiconductor wafer W1 having the same double hetero (DH) structure as shown in FIG. 2 was first grown on a sapphire substrate 1 by using a conventional MOCVD method. . This wafer W1 uses the sapphire c-plane as a substrate, and the sapphire substrate 1
An AlN buffer layer 2 is grown at 400 ° C. at 600 ° C., and a Si-doped n-type GaN layer 3 is
The thickness of the n-type Al _0.3 Ga _0.7 N layer 4 doped with Si
Grown at 2 μm, and further doped with Zn-doped In _0.1 at 800 ° C.
After growing a Ga _0.9 N layer 5 at 200 °, M
The g-doped Al _0.3 Ga _0.7 N layer 6 is 0.2 μm
The doped GaN layer 7 is grown by 0.5 μm. Further, the wafer is placed in a nitrogen atmosphere at 400
A thermal annealing treatment was performed at 30 ° C. for 30 minutes to make the Mg-doped layer p-type.

After the heat treatment, an Mg-doped GaN layer 8 was further grown on the surface of the wafer W1 by 1 μm in a slide boat type liquid phase growth furnace. FIG. 1 shows a cross-sectional structure of the wafer W2 after the Mg-doped GaN layer 8 is grown by the liquid phase growth method.

The growth procedure in this liquid phase growth method is as follows.

First, the structure shown in FIG. 1 was grown by MOCVD, and the heat-treated wafer W1 was placed in a slide boat type liquid phase growth furnace. The solution in the slide boat was charged in advance with 50 g of Ga melt to which 1 g of GaN powder and 5 mg of Mg serving as a p-type impurity were added.

FIG. 5 shows a growth concentration program. First, nitrogen as an atmosphere gas was flowed at 2 L / min / min to purge the inside of the furnace with nitrogen. Next, the furnace was heated to 1000 ° C. while flowing nitrogen at a rate of 1 L / min.
At the time when 80 minutes had elapsed, the temperature was lowered at a rate of 0.5 ° C./min. When the supercooling was performed at 5 ° C., the melt was brought into contact with the wafer, and the temperature was lowered to 950 ° C. When the temperature reached 950 ° C., the contact between the wafer and the melt was cut off. Thereafter, the wafer was cooled to near room temperature and the wafer was taken out.

Mg-doped GaN prepared by liquid phase epitaxy
The carrier concentration of the layer 8 was found to be 4 × 10 ¹⁸ cm ⁻³ from the result of growing only one Mg-doped GaN layer on a sapphire substrate and measuring the electrical characteristics by the Pau method. However, it shows a p-type with a high carrier concentration.

With respect to the epi-wafer W2 manufactured by the above-described method, the same evaluation as that described in the conventional example was performed. That is,
On the surface layer of the substrate, nickel (Ni) 500 ° and gold (A)
u) A dot electrode is deposited on a 1 μm laminated structure,
For 5 minutes, the resistance between the electrodes was measured, and the contact resistance between the outermost surface layer and the electrodes was determined. As a result, the contact resistance between the electrode and the Mg-doped GaN layer 8 grown in the liquid phase becomes 2
× 10 ⁻⁵ Ω · cm ² , which was ５ of the conventional example.

Next, a part of the surface of the wafer W2 is removed by etching by reactive ion etching (RIE) to expose the n-type GaN layer 3, and then, as shown in FIG. An n-type electrode 10 having a laminated structure of titanium (Ti) and aluminum (Al) is provided on the surface of the GaN layer 3.
Nickel (Ni) is provided on a part of the surface of the p-type GaN layer 8.
And a p-type electrode 9 having a layered structure of gold (Au),
An LED chip (light emitting diode) 11 was produced.

When the LED chip 11 was energized and light emission was observed, it was observed that light was emitted over the entire surface of the InGaN layer (active layer) 5, and the light emission output was 2 mW when a current of 20 mA was applied, which is the conventional output. The output was 100 times.

(Example 2) A nitride semiconductor wafer W1 having a double hetero structure shown in FIG.
Lamination growth was performed by the OCVD method, and heat treatment was performed.

Next, the wafer W1 was set in a liquid phase growth furnace as shown in FIG. 6, and a Mg-doped p-type GaN layer 8 was grown on the surface by a liquid phase growth method. The procedure of liquid phase growth is described below.

First, 5 g of GaN powder was placed in quartz crucible 21.
And 300 g of Ga melt 22 to which 0.2 g of Mg serving as a p-type impurity was added. Next, the quartz crucible 21
The inside is sufficiently purged with nitrogen gas at 0.5 L / min, and then nitrogen is introduced at a flow rate of 0.2 L / min from a nitrogen gas introduction pipe 25 and exhausted through an exhaust pipe 26.
Ga melt 22 was heated to 1200 ° C. 1200 ° C
After holding for 60 minutes at -100 ° C / hr, 90
The temperature was lowered to 0 ° C. Thereafter, the heating by the heater 24 was stopped and the temperature was cooled to room temperature, and the wafer W1 was taken out from the Ga melt 22.

The surface of the taken-out wafer W1 showed a p-type conductivity without heat treatment or the like. Further, using the taken-out wafer, an LED is formed in the same manner as in the first embodiment.
The chip 11 was manufactured, and the light emission output was measured. As a result, the LED chip 11 obtained an output about 20 times higher than that of the light emitting diode shown in Conventional Example 1.

[0042]

As described above, according to the present invention, the following excellent effects can be obtained.

According to the first to tenth aspects of the present invention, the gallium nitride-based compound semiconductor crystal grown by MOCVD with good uniformity is formed on the surface of the gallium nitride-based compound semiconductor crystal by a liquid phase growth method that can easily increase the carrier. Since it has a structure in which a compound semiconductor crystal is grown, a gallium nitride-based compound semiconductor crystal having p-type conductivity with a high carrier concentration on the surface can be obtained easily and with good reproducibility. As a result, when an element is manufactured using such a crystal, the contact resistance between the p-type layer and the electrode is significantly reduced, and the current distribution in the p-type layer is sufficiently performed.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a gallium nitride based compound semiconductor wafer according to one embodiment of the present invention.

FIG. 2 shows an MOCV according to the prior art on which the present invention is based.
1 is a cross-sectional structural view of a gallium nitride-based compound semiconductor wafer grown by a D method.

FIG. 3 is a sectional structural view of a gallium nitride-based compound semiconductor device according to one embodiment of the present invention.

FIG. 4 is a cross-sectional structural view of a gallium nitride-based compound semiconductor device using a wafer grown by MOCVD according to the prior art.

FIG. 5 is a diagram showing a concentration program in a liquid phase epitaxy method for producing a gallium nitride based compound semiconductor wafer according to one embodiment of the present invention.

FIG. 6 is a configuration diagram of a liquid phase growth furnace used for producing a gallium nitride-based compound semiconductor wafer according to another embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 Sapphire substrate 2 AlN buffer layer 3 n-type GaN layer 4 n-type AlGaN layer 5 InGaN layer 6 p-type AlGaN layer 7 p-type GaN layer 8 p-type GaN layer grown by liquid phase growth 9 p Type electrode 10 n-type electrode 11, 12 LED chip (light-emitting diode) 21 quartz crucible 22 Ga melt 23 crystal substrate grown by MOCVD 24 heater 25 nitrogen gas introduction pipe 26 exhaust pipe W1, W2 wafer

Claims (11)

[Claims] 1. A compound of the general formula Al _x doped with at least n-type and p-type impurities. Ga _y In _lxy N (where, 0 ≦ x
A ≦ 1,0 <y ≦ 1, x + y ≦ 1) with expressed surface of the gallium nitride-based compound semiconductor wafer formed by laminating growing a gallium nitride-based compound semiconductor, and further, the general formula Al _a Ga _b
In _lab N (0 ≦ a ≦ 1, 0 <b ≦ 1, a + b ≦ 1)
A gallium nitride-based compound semiconductor wafer having a structure in which gallium nitride-based compound semiconductor layers represented by the following formulas are laminated by a liquid phase growth method. Wherein at least n-type and doped with p-type impurity formula Al _x Ga _y In _lxy N (where, 0 ≦ x
≦ 1, 0 <y ≦ 1, x + y ≦ 1) The surface of a gallium nitride-based compound semiconductor wafer formed by layer-growing gallium nitride-based compound semiconductors having the same conductivity type as the surface layer of the wafer The general formula Al _a Ga _b In _lab N
A gallium nitride based compound semiconductor wafer having a structure in which gallium nitride based compound semiconductor layers represented by (0 ≦ a ≦ 1, 0 <b ≦ 1, a + b ≦ 1) are stacked by a liquid phase growth method. Wherein at least n-type and p-type formula impurity was doped Al _x Ga _y In _lxy N (where, 0 ≦ x
.Ltoreq.1, 0 <y.ltoreq.1, x + y.ltoreq.1) The surface of a gallium nitride-based compound semiconductor wafer formed by laminating and growing gallium nitride-based compound semiconductors is further doped with impurities doped in the surface layer of the wafer. the same impurity doped, the general formula _{Al a Ga b In lab N (} 0 ≦ a ≦ 1,0 <b ≦
1. A gallium nitride-based compound semiconductor wafer having a structure in which gallium nitride-based compound semiconductor layers represented by a + b ≦ 1) are stacked by a liquid phase growth method. Wherein at least n-type and p-type formula impurity was doped Al _x Ga _y In _lxy N (where, 0 ≦ x
.Ltoreq.1, 0 <y.ltoreq.1, x + y.ltoreq.1), the surface of the gallium nitride based compound semiconductor wafer having a p-type conductivity is formed on the surface of the gallium nitride based compound semiconductor wafer. Furthermore, having p-type conductivity, the general formula _{1 a Ga b in lab N (} 0 ≦ a ≦ 1,0 <b ≦ 1, a
A gallium nitride-based compound semiconductor wafer having a structure in which gallium nitride-based compound semiconductor layers represented by + b ≦ 1) are stacked by a liquid phase growth method. 5. The at least n-type and doped with p-type impurity formula Al _x Ga _y In _lxy N (where, 0 ≦ x
≦ 1, 0 <y ≦ 1, x + y ≦ 1). A gallium nitride-based compound semiconductor wafer formed by laminating and growing a gallium nitride-based compound semiconductor represented by the following formula: After performing heat treatment or electron beam irradiation treatment to make the conductivity type of the outermost surface of the wafer p-type, the surface further has a p-type conductivity type, a general formula Al _a Ga _b
In _lab N (0 ≦ a ≦ 1, 0 <b ≦ 1, a + b ≦ 1)
A gallium nitride-based compound semiconductor wafer having a structure in which gallium nitride-based compound semiconductor layers represented by the following formulas are laminated by a liquid phase growth method. 6. The gallium nitride-based compound semiconductor wafer according to claim 4, wherein the p-type gallium nitride-based compound semiconductor layer is a layer doped with at least Mg as an impurity. 7. The gallium nitride-based compound semiconductor wafer, wherein layers other than the gallium nitride-based compound semiconductor layer grown on the outermost surface of the wafer by a liquid phase growth method are grown by a metal organic chemical vapor deposition method. Claims 1, 2,
6. The gallium nitride-based compound semiconductor wafer according to 3, 4, or 5. 8. A compound of the general formula Al doped with at least n-type and p-type impurities grown by metal organic chemical vapor deposition.
_x Ga _y In _lxy N (where, 0 ≦ x ≦ 1,0 <y ≦
A gallium nitride-based compound semiconductor wafer formed by laminating a gallium nitride-based compound semiconductor represented by (1, x + y ≦ 1), and the outermost surface layer of which is made of a GaN layer doped with Mg, is subjected to a heat treatment or an electron beam irradiation treatment. Then, after the conductivity type on the outermost surface of the wafer has been changed to p-type,
Gallium nitride-based compound semiconductor wafer having a structure in which GaN layers doped with GaN are stacked by a liquid phase growth method. 9. The gallium nitride-based compound semiconductor wafer, wherein the gallium nitride-based compound semiconductor grown on the outermost surface of the wafer by a liquid phase growth method is polycrystalline. 9. The gallium nitride-based compound semiconductor wafer according to 5, 6, 7, or 8. 10. The gallium nitride-based compound semiconductor layer,
10. The gallium nitride-based compound semiconductor wafer according to claim 1, wherein the gallium nitride-based compound semiconductor wafer is grown on an insulating substrate. 11. The method of claim 1, 2, 3, 4, 5, 6, 7,
11. A gallium nitride-based compound semiconductor device produced by forming an electrode in contact with at least the outermost surface of the gallium nitride-based compound semiconductor wafer according to 8, 9, or 10.