JPH11126923A - Method for manufacturing gallium nitride compound semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a metal layer on the reverse side of a substrate. SOLUTION: After a separation groove 21 is formed at a depth of nearly 3/4 of the thickness of a substrate from the reverse side of a substrate 11 along a dicing line, where wafer in which semiconductor layer is formed on the substrate is set, a separating groove 22 is formed until the substrate appears at a position corresponding to the separation groove 21 from a semiconductor layer side. Then, a reverse side 11b is polished, the substrate 11 is thinned to an extent where the trace of the separation groove 22 remains, a metal layer 10 is formed due to the deposition of Al on the entire portion of the reverse side 11b, and the groove 23 corresponding to the separation groove 21 is formed. Then, an adhesive sheet 24 is applied onto an electrode pad 20, and scribing is made from the side of the metal layer 10 along the groove 23, thus forming a scribe line. Then, a load is applied to the wafer for braking, thus manufacturing a light-emitting element where the metal layer 10 is formed on the reverse side 11b. Light advancing towards the side of the substrate 11 is reflected by the metal layer 10 being formed on the reverse side 11b, and light take-out efficiency from the sides of electrodes 18A and 18B is improved, thus obtaining high emission intensity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gallium nitride (Ga) nitride.
The present invention relates to a method for manufacturing a N) -based compound semiconductor device, and more particularly to a method for forming a metal layer on the back surface of a substrate.

[0002]

2. Description of the Related Art Conventionally, a GaN-based compound semiconductor light emitting device has a configuration in which a semiconductor layer is laminated on an insulating sapphire substrate, and positive and negative electrodes are provided on the same side. FIG. 8 is a schematic cross-sectional view in which the light emitting element 30 is disposed on a lead frame 31. The light emitting element 30 has a light emitting layer 34 that emits light at a predetermined wavelength, and the positive and negative electrodes 35 and 36 are provided above the substrate 33. And the substrate 3
3 is die-bonded to the lead frame 31 using a paste 32 made of a resin material.
Although not shown, the electrodes 35 and 36 are electrically connected to predetermined portions by wire bonding.
Light is extracted from the sides 5 and 36. But,
In the configuration shown in FIG. 8, since there is no selectivity in the direction of light emission obtained from the light emitting layer 34, the reflected light on the back surface of the substrate 33 greatly contributes to the light extraction amount from the electrodes 35 and 36. In addition, since light is absorbed by the paste 32 provided on the back surface of the substrate 33, there is a problem that light reflection efficiency is not good and light emission intensity is low. Also paste 3
No. 2 deteriorates with time due to ambient temperature or heat generated by driving the element 30 (discoloration to yellow), so that there is a problem that reflected light decreases and luminous intensity deteriorates with time. Therefore, a method of increasing the light reflection efficiency by forming a metal layer on the back surface of the substrate 33 to obtain high emission intensity is considered.

[0003]

Normally, since the hardness of the substrate 33 is high, the substrate 33 is polished and thinned when the wafer is separated, and then scribed from the back surface of the substrate 33 for breaking. Is used to separate wafers. Therefore, the metal layer is formed after the polishing of the substrate, and if a metal layer for reflection is formed on the back surface of the substrate 33 before scribing, it becomes difficult to perform positioning during scribing. If the metal layer is formed after scribing, the wafer is in a state in which the adhesive sheet is stuck to the electrodes 35 and 36, so that it is difficult to clean the back surface of the wafer and it is not possible to heat the wafer when forming the metal layer. Therefore, adhesion between the metal layer and the back surface of the substrate 33 cannot be obtained. Further, a method of forming a reflection film using an oxide film is also conceivable, but there is difficulty in manufacturing such as control of the film thickness.

Accordingly, an object of the present invention is to provide a GaN-based compound semiconductor light-emitting device, in which it is possible to form a metal layer on the back surface of a substrate, to obtain good light reflection over time, The purpose is to improve the amount of light taken out from the electrode side.

[0005]

According to a first aspect of the present invention, there is provided a wafer having a gallium nitride-based compound semiconductor formed on a substrate in a first step. It is cut to a predetermined first depth from the back side to form a first groove. In the second step, the wafer is cut from the surface thereof to a predetermined second depth at a position substantially corresponding to the first groove to form a second groove.
Here, in the first step and the second step, either step may be performed first. Next, in a third step, the back surface of the substrate is polished to the extent that traces of the first groove remain, and thereafter, in a fourth step, a metal layer is formed on the back surface of the substrate. Next, in a fifth step, scribing is performed from the metal layer side along the first groove, and thereafter, in a sixth step, the wafer is broken and separated into individual elements. As described above, even if the metal layer is formed on the back surface of the substrate, since there is a trace of the first groove, positioning at the time of scribing can be easily performed from the metal layer side. In addition, since the metal layer is formed on the back surface of the substrate, light output from the element to the substrate side is reflected by the metal layer, so that high emission intensity can be obtained. In addition, since the light is not reflected by the resin material, stable light emission can be obtained over time.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. FIG. 1 shows a light emitting device 10 made of a GaN-based compound semiconductor formed on a sapphire substrate 11.
FIG. 2 is a schematic cross-sectional configuration diagram of No. On the substrate 11, a buffer layer 1 of aluminum nitride (AlN) having a thickness of about 25 nm
2 is provided thereon, and a high carrier concentration n ⁺ layer 13 of silicon (Si) doped GaN having a thickness of about 4.0 μm is formed thereon. On this high carrier concentration n ⁺ layer 13, a cladding layer 1 made of Si-doped n-type GaN having a thickness of about 0.5 μm is formed.
4 are formed. Then, on the cladding layer 14, a barrier layer 151 made of GaN having a thickness of about 35
The light emitting layer 15 has a multiple quantum well structure (MQW) in which well layers 152 made of Ga _0.8 In _0.2 N are alternately stacked. The barrier layer 151 has six layers, and the well layer 152 has five layers. On the light emitting layer 15, a cladding layer 16 of p-type Al _0.15 Ga _0.85 N with a thickness of about 50 nm is formed. further,
On the cladding layer 16, a film thickness of about 100 nm made of p-type GaN
Contact layer 17 is formed.

A light-transmissive electrode 18A formed by metal evaporation is formed on the contact layer 17, and the electrode 18A is formed on the n ⁺ layer 13.
B is formed. The translucent electrode 18A is made of about 15 ° of cobalt (Co) bonded to the contact layer 17 and about 60 ° of gold (Au) bonded to Co. The electrode 18B is made of vanadium (V) having a thickness of about 200
It is made of μm aluminum (Al) or Al alloy.
On a part of the electrode 18A, an electrode pad 20 made of Co or Ni and Au, Al, or an alloy thereof and having a thickness of about 1.5 μm is formed. On the back surface of the substrate 11, a metal layer 10 of aluminum (Al) having a thickness of about 200 nm is formed.

Next, a method of manufacturing the light emitting device 100 will be described. The light emitting device 100 was manufactured by vapor phase growth by metal organic chemical vapor deposition (hereinafter abbreviated as “MOVPE”). The gases used were ammonia (NH ₃ ), carrier gas (H ₂ , N ₂ ), trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”), and trimethylaluminum (Al (CH ₃ )).
₃ ) (hereinafter referred to as “TMA”), trimethylindium (In
(CH ₃ ) ₃ ) (hereinafter referred to as “TMI”), silane (SiH ₄ ) and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter “CP
₂ Mg ”). First, a single crystal substrate 11 having an a-plane as a main surface, which has been cleaned by organic cleaning and heat treatment, is subjected to MOVPE.
The susceptor is mounted on the reaction chamber of the apparatus. next,
The substrate 11 was baked at a temperature of 1100 ° C. while flowing H ₂ into the reaction chamber at normal pressure. Next, the temperature of the substrate 11 was lowered to 400 ° C., and H ₂ , NH ₃ and TMA were supplied to form the AlN buffer layer 12 to a thickness of about 25 nm.

Next, the temperature of the substrate 11 is maintained at 1150 ° C.
Supplying H ₂ , NH ₃ , TMG and silane, the film thickness is about 4.0 μm,
High carrier concentration n composed of GaN with electron concentration of 2 × 10 ¹⁸ / cm ^3
+ Layer 13 was formed. Next, the temperature of the substrate 11 is maintained at 1150 ° C., and N ₂ or H ₂ , NH ₃ , TMG, TMA and silane are supplied to form a GaN film having a thickness of about 0.5 μm and an electron concentration of 1 × 10 ¹⁸ / cm ³ . Was formed. The above cladding layer 1
After the formation of No. 4, N ₂ or H ₂ , NH ₃ and TMG were supplied to form a barrier layer 151 of GaN having a thickness of about 35 °. Next, N ₂ or H ₂ , NH ₃ , TMG and TMI were supplied to form a well layer 152 of Ga _0.8 In _0.2 N having a thickness of about 35 °. Furthermore, the barrier layer 151 and the well layer 152 were formed under the same conditions for four periods, and the barrier layer 151 made of GaN was formed thereon. Thus, the light emitting layer 15 having the MQW structure having five periods was formed.

Next, the temperature of the substrate 11 is maintained at 1100 ° C.
Supplying N ₂ or H ₂ , NH ₃ , TMG, TMA and CP ₂ Mg, a film thickness of about 50 nm, p-type Al _0.15 Ga doped with magnesium (Mg)
_A cladding layer 16 of _0.85 N was formed. Next, the temperature of the substrate 11 is maintained at 1100 ° C., and N ₂ or H ₂ , NH ₃ , TMG and CP ₂ Mg are supplied to form a p-layer doped with Mg with a thickness of about 100 nm.
A contact layer 17 made of type GaN was formed. Next, an etching mask is formed on the contact layer 17, the mask in a predetermined region is removed, and the contact layer 17, the cladding layer 16, the light emitting layer 15, the cladding layer 14, and the n ⁺ A part of the layer 13 is etched by reactive ion etching using a gas containing chlorine, and n ⁺
The surface of layer 13 was exposed. Next, in the following procedure, n ⁺
An electrode 18B for the layer 13 and a translucent electrode 18A for the contact layer 17 were formed.

(1) A photoresist is applied, a window is formed in a predetermined region on the exposed surface of the n ⁺ layer 13 by photolithography, and the window is evacuated to a high vacuum of the order of 10 ⁻⁶ Torr or less.
Vanadium (V) having a thickness of about 200 ° and Al having a thickness of about 1.8 μm were deposited. Next, the photoresist is removed. Thereby, electrode 18B is formed on the exposed surface of n ⁺ layer 13. (2) Next, apply photoresist uniformly on the surface,
By photolithography, the photoresist on the electrode formation portion on the contact layer 17 is removed to form a window. (3) After evacuation to a high vacuum of the order of 10 ⁻⁶ Torr or less on the photoresist and the exposed contact layer 17 using a vapor deposition apparatus, a Co film having a thickness of about 15 mm was formed. About 60
A film of Au is formed.

(4) Next, the sample is taken out of the vapor deposition device,
Co, Au deposited on photoresist by lift-off method
Is removed, and a translucent electrode 18A is formed on the contact layer 17. (5) Next, in order to form a bonding electrode pad 20 on a part of the translucent electrode 18A, a photoresist is uniformly applied, and a photoresist is applied to a portion of the electrode pad 20 where the photoresist is formed. Open the window. Next, Co or Ni and Au,
Al or an alloy thereof is deposited to a film thickness of about 1.5 μm by vapor deposition, and Co or Ni and Au, Au deposited on the photoresist by a lift-off method in the same manner as in the step (4).
The electrode pad 20 is formed by removing the film made of l or an alloy thereof. (6) Thereafter, the sample atmosphere is evacuated with a vacuum pump, and O ₂ gas is supplied to a pressure of 3 Pa.
The contact layer 17 and the cladding layer 16 are heated to 50 ° C. for about 3 minutes to reduce the resistance of the p-type contact layer 17 and the cladding layer 16.
7 and electrode 18A, n ⁺ layer 13 and electrode 18
Alloying with B was performed. Thus, the metal layer 1
A wafer without zeros is formed.

Next, the formation of the metal layer 10 and the separation of the wafer will be described with reference to FIGS. First, as shown in a schematic cross-sectional view of FIG. 2, the wafer formed as described above is cut from the back surface 11b side of the substrate 11 using a blade 40 along a set dicing line (not shown). A separation groove (first groove) 21 is formed at a depth (first depth) of about ／ of the thickness (first step). Next, in the wafer of FIG. 2, using the blade 40, the substrate is separated from the semiconductor side opposite to the substrate 11b by a depth of about 15 μm (second depth) corresponding to the separation groove 21 (second depth). 2 groove) 2
Form 2 Thereby, the cross-sectional configuration shown in FIG. 3 is obtained. Next, in the wafer of FIG. 3, the back surface 11b of the substrate 11 is polished using a lapping machine, and the substrate 11 is thinned to the extent that traces of the separation grooves 21 remain (third step). Thus, the cross-sectional configuration shown in FIG. 4 is obtained.

Next, a metal layer 10 having a thickness of about 200 nm is deposited on the entire back surface 11b of the substrate 11 by vapor deposition of aluminum (Al).
Is formed (fourth step). Thus, the cross-sectional configuration shown in FIG. 5 is obtained. As shown in this figure, a groove 23 is formed in the metal layer 10 corresponding to the separation groove 22. Next, an adhesive sheet 24 is stuck on the electrode pad 20 to obtain the configuration shown in FIG. Next, from the metal layer 10 side,
The groove 23 is scribed using a scriber to form a scribe line 25 (fifth step). FIG. 7 shows a cross-sectional configuration in this state. Next, the wafer is braked by applying a load to the wafer using a roller (sixth step), and the configuration shown in FIG. 1 is obtained.

As described above, the back surface 11b of the substrate 11
By forming the metal layer 10 in a state where the separation groove 21 is formed on the metal layer 10, the groove 23 corresponding to the separation groove 21 is formed on the metal layer 10.
Is formed, positioning at the time of scribing from the metal layer 10 side can be easily performed. Thereby, the substrate 11
Light emitting element 100 having metal layer 10 formed on back surface 11b
Can be manufactured. Further, since the metal layer 10 is formed before the adhesive sheet 24 is attached, the metal layer 10 can be formed by heating by vapor deposition, and can be formed in close contact with the back surface 11b of the substrate 11. Further, in the light emitting element 100, light traveling toward the substrate 11 is favorably reflected by the metal layer 10 formed on the back surface 11b, so that light extraction efficiency from the electrodes 18A and 18B is improved, and the light emission intensity is improved. Can be enhanced. In addition, since the metal layer 10 does not deteriorate with time, light can be stably emitted with time.

In the above embodiment, the separation groove 22 is formed from the semiconductor side of the substrate after the formation of the separation groove 21. However, the separation groove 21 may be formed after the formation of the separation groove 22. In the above embodiment, the metal layer 10 made of Al having a thickness of about 200 nm is provided by vapor deposition, but the metal constituting the metal layer 10 may be of any type, and has a film thickness enough to reflect light. I just need. Further, the metal layer 10 may be formed using a method other than the vapor deposition. Further, in the above embodiment, the depth of the separation groove 22 is about 15 nm, but may be in the range of 5 to 50 nm. or,
Although the depth of the separation groove 21 is set to approximately ／ of the plate thickness,
The range may be 5/6. The light emitting layer 15 of the light emitting element 100 has M
Although a QW structure is used, a single layer made of SQW, Ga _0.8 In _0.2 N, or the like, or a quaternary or ternary AlGaInN having an arbitrary mixed crystal ratio may be used. Although Mg is used as the p-type impurity, a Group 2 element such as beryllium (Be) and zinc (Zn) can be used. Further, the present invention can be used not only for light emitting elements but also for light receiving elements.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a structure of a GaN-based compound semiconductor light emitting device according to a specific example of the present invention.

FIG. 2 is a schematic view showing a first step in a method for forming a GaN-based compound semiconductor light emitting device according to a specific example of the present invention.

FIG. 3 is a schematic view showing a second step in a method for forming a GaN-based compound semiconductor light-emitting device according to a specific example of the present invention.

FIG. 4 is a schematic view showing a third step in the method for forming a GaN-based compound semiconductor light emitting device according to a specific example of the present invention.

FIG. 5 is a schematic view showing a fourth step in the method for forming a GaN-based compound semiconductor light-emitting device according to a specific example of the present invention.

FIG. 6 is a schematic view showing a state in which an adhesive sheet is stuck on an electrode pad in the method of forming a GaN-based compound semiconductor light emitting device according to a specific example of the present invention.

FIG. 7 is a schematic view showing a fifth step in the method for forming a GaN-based compound semiconductor light-emitting device according to a specific example of the present invention.

FIG. 8 is a schematic cross-sectional view showing a state in which a conventional GaN-based compound semiconductor light emitting device is fixed on a lead frame.

[Explanation of symbols]

Reference Signs List 10 metal layer 11 sapphire substrate 12 buffer layer 13 high carrier concentration n ⁺ layer 14, 16 clad layer 15 light emitting layer 17 contact layer 18A p electrode 18B n electrode 20 electrode pad 21, 22 separation groove 24 adhesive sheet 25 scribe line 100 light emitting element

Claims (1)

[Claims] 1. a first step of cutting a wafer having a gallium nitride-based compound semiconductor formed on a substrate to a predetermined first depth from a back side thereof to form a first groove; A second step of forming a second groove by cutting a second groove at a position substantially corresponding to the first groove from a surface side thereof, and a step of leaving a trace of the first groove. A third step of polishing the back surface of the substrate, a fourth step of forming a metal layer on the back surface of the substrate after the third step, and the metal layer side after the fourth step. And a fifth step of scribing the wafer along the first groove, and after the fifth step, a sixth step of breaking the wafer and separating the wafer into individual devices. A method for manufacturing a gallium nitride-based compound semiconductor device.