JP2007073867A - Nitride semiconductor laser element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a ridge stripe structure, to proceed digging of a nitride semiconductor growth layer formed on a substrate in an arbitrary depth by etching with sufficient precision to an arbitrary depth without inclining by the crystallinity of the nitride semiconductor growth layer. <P>SOLUTION: Between a p-type GaN contact layer 27 comprising a nitride semiconductor layer 20 formed on an n-type GaN substrate 11 and a p-type Al<SB>0.05</SB>Ga<SB>0.95</SB>N clad layer 26, a p-type Al<SB>0.2</SB>Ga<SB>0.8</SB>N layer of the thickness 0.005 μm, and an etching marker layer 30 having a super lattice structure equipped with a portion of ten periodic structures whose one periodic structure is made of a p-type GaN layer of the thickness 0.02 μm is disposed. Based on the thickness of a portion of one period of the periodic structure of the etching marker layer 30 measured in advance and an etching rate calculated from the periods of plasma luminescence due to Al generated periodically in the digging by the etching, the etching time and the etching depth are controlled. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a nitride semiconductor laser device using a dry etching method and a nitride semiconductor laser device manufactured by the method.

  Nitride semiconductor laser elements that oscillate in the ultraviolet to visible region using nitride semiconductor materials typified by GaN, AlN, InN, and mixed crystals thereof have been energetically studied in each research institution.

  In general, an AlGaN-based crystal is a ridge having a current confinement structure in a nitride semiconductor layer by a dry etching method such as an RIE (Reactive Ion Etching) method or an ICP (Inductively Coupled Plasma) method. Digging is performed to form a stripe structure. However, since the AlGaN-based crystal is chemically stable, the digging depth varies greatly depending on the crystallinity of the digged portion and the slight difference such as the power input to the etching apparatus and the concentration of the reactive gas. For this reason, the digging depth of the ridge stripe tends to be different for each element, such as digging too much or not enough for the set digging depth.

  The horizontal shape of the FFP (Far Field Pattern) of the semiconductor laser element is roughly determined from the width of the ridge stripe and the digging depth. Therefore, if the shape of the formed ridge stripe is different, the horizontal shape of the FFP will be different, and if it is out of the standard, it will be a defective product. Therefore, in order to improve the yield, it is necessary to form a ridge stripe having a certain shape in order to obtain a semiconductor laser device in which the horizontal shape of the FFP satisfies the standard.

As a conventional example, a case where a ridge stripe is formed on a nitride semiconductor layer by an ICP method will be described. FIG. 7 is a schematic configuration diagram of a nitride semiconductor wafer obtained by growing a nitride semiconductor growth layer on a substrate by MOCVD (Metal Organic Chemical Vapor Deposition). The nitride semiconductor wafer 110 has a nitride semiconductor growth layer 120 formed on an n-type GaN substrate 111. The nitride semiconductor growth layer 120 includes an n-type GaN layer 121 having a thickness of 0.2 μm, an n-type Al _0.05 Ga _0.95 N cladding layer 122 having a thickness of 2.2 μm, an n-type GaN guide layer 123 having a thickness of 0.02 μm, InGaN / GaN-3 MQW (Multi Quantum Well) active layer 124 in which three layers of InGaN layers with a thickness of 4 nm and GaN layers with a thickness of 8 nm are alternately stacked, p-type Al _0.3 Ga _0.7 N with a thickness of 20 nm An evaporation preventing layer 125, a 0.55 μm p-type Al _0.05 Ga _0.95 N clad layer 126, and a 0.1 μm thick p-type GaN contact layer 127 are sequentially stacked.

  FIG. 8 is a plan view showing a state in which the nitride semiconductor wafer 110 and the monitor wafer 161 shown in FIG. 7 are placed in the ICP device 170, and FIG. 9 is a front view showing the etched depth or digging. The principle of measuring the depth of penetration is illustrated schematically. The monitor wafer 161 is for monitoring the etched amount, and a GaN layer is grown to 4 μm or more on the sapphire substrate.

A stripe mask (width 2 μm) for forming a ridge stripe is formed on the p-type GaN contact layer 127 of the nitride semiconductor wafer 110, and in this state, etching is performed by the ICP apparatus 170 to form a p-type GaN contact layer. 127 and a p-type Al _0.05 Ga _0.95 N clad layer 126 are dug. In the case of this example, 0.57 μm is set as the target of the digging depth from the surface of the p-type GaN contact layer 127, and based on the digging depth measured by the following method, p-type Al _0.3 Ga _0.7 N The target was stopped 0.08 μm above the evaporation preventing layer 125.

  The measurement of the digging depth at this time is realized by irradiating the monitor wafer 161 with the laser beam from the laser beam generator 181 and measuring the intensity of the reflected light with the detector 182 as shown in FIG. The In the case of this example, the reflected light on the surface of the sapphire substrate (that is, the interface with the GaN layer) of the monitor wafer 161 interferes with the reflected light on the GaN layer surface, so the thickness of the GaN layer is dug and changed. Accordingly, the intensity of the laser beam changes as shown in a graph showing the relationship between the digging depth and the high laser intensity shown in FIG. The dug thickness can be measured from the relationship between this period and the refractive index of the dug material.

Further, Patent Document 1 and Patent Document 2 propose a method of forming a ridge stripe dug to a predetermined depth by etching a nitride semiconductor growth layer by a wet etching method using an etchant. .
JP-A-9-232681 (page 4, FIG. 2) JP 2000-332290 A (page 4, FIG. 2)

  FIG. 11 shows the relationship between the actual digging depth and the set digging depth measured using a surface level gauge for nitride semiconductor wafers etched to various depths by the conventional method described above. It can be seen from the figure that the digging depth varies greatly with respect to the set digging depth. In the case of this example, the measurement sample and the excavation sample may be different, and the excavation depth varies due to the difference in crystallinity. Therefore, the wafer with the GaN layer grown on the sapphire substrate was finely divided and etched several times, and the reproducibility of the apparatus was examined. As a result, it was found that the reproducibility of the etching amount of the apparatus was also poor. For these reasons, even if the reproducibility of the etching amount of the apparatus is improved, a difference in the digging depth due to the crystallinity is generated, so that the control is considered to be very difficult.

  In addition, not all layers have been grown to the thickness as designed for all wafers, and there may be some variation from wafer to wafer, and the actual elements cut out from these wafers will vary in the depth of digging. There is a high possibility of doing. For this reason, in order to set the digging depth for each element, for example, it is necessary to cut out the edge of the wafer and measure the layer thickness with an SEM or the like. In this case, since the edge of the wafer is taken, the number of elements that can be taken from one wafer is reduced, which is not preferable. Further, since the edge of the wafer is a place where abnormal growth is likely to occur, there is a high possibility that a difference occurs in the layer thickness between the center and the edge in an actual wafer, and the difference is not necessarily constant. Therefore, this method also has a drawback that the depth setting itself is inaccurate.

  Further, in the methods proposed in Patent Document 1 and Patent Document 2, the side surface of the formed ridge stripe is difficult to be flat, and the entire semiconductor laser element is immersed in an etching solution, so that unnecessary portions are etched. Further, since an etching solution is required and a drying process is also required, the apparatus and process are complicated and complicated.

  Accordingly, an object of the present invention is to provide a nitride semiconductor laser device capable of producing a ridge stripe dug to a desired digging depth and a method for manufacturing the same.

  To achieve the above object, the present invention provides a first step of forming a nitride semiconductor growth layer by laminating a nitride semiconductor thin film on a nitride semiconductor substrate, and removing a part of the nitride semiconductor growth layer. In the method of manufacturing a nitride semiconductor laser device including the second step, in the first step, a periodic structure composed of at least two types of layers having different compositions is provided between the nitride semiconductor thin films in two or more periods. In the second step, the nitride semiconductor layer is removed by dry etching, and plasma emission of an element contained in the etching marker layer accompanying dry etching is detected in the second step. And measuring the time required for one cycle etching of the periodic structure of the etching marker layer, and after completing the measurement, Based on the measurement by the time the etching rate was calculated from the thickness of the one period of the periodic structure necessary for one cycle of the etching, and performing dry etching to a predetermined depth.

According to the present invention, in the method for manufacturing a nitride semiconductor laser device having the above-described structure, the etching marker layer includes Al _W Ga _{1 -W} N (0.05 ≦ W ≦ 1), In _X Ga _{1 -X} N (0 .05 ≦ X ≦ 1), Al Y in Z Ga 1-YZ N (0.05 ≦ Y ≦ 1,0.05 ≦ Z ≦ 1) and the cycle comprising at least two or more layers of GaN structure or their Among them, the composition W, X, Y or Z is characterized by comprising two or more periodic structures composed of layers containing two or more of the same type of layers different from each other by 0.05 or more.

  According to the present invention, in the method of manufacturing a nitride semiconductor laser device having the above-described configuration, the etching marker layer is a superlattice.

  According to the present invention, in the method for manufacturing a nitride semiconductor laser device having the above-described structure, the thickness of each layer constituting the etching marker layer is 0.001 μm or more.

  According to the present invention, in the method of manufacturing a nitride semiconductor laser device having the above-described structure, the thickness of each layer constituting the etching marker layer is 0.05 μm or less.

  The nitride semiconductor laser device of the present invention is manufactured using any one of the above-described methods for manufacturing a nitride semiconductor laser device.

  According to the present invention, plasma emission that appears when etching a nitride semiconductor growth layer is detected, and periodic when etching an etching marker layer having two or more periodic structures composed of at least two types of layers having different compositions from each other. The etching rate is calculated from the time required for one period of etching measured from the plasma emission appearing on the substrate and the thickness of one period of the periodic structure measured in advance by an XRD (X-ray Diffractometer). Based on this, the nitride semiconductor growth layer is etched to a predetermined depth. Therefore, the crystallinity of the nitride semiconductor growth layer tends to be different for each wafer on which the nitride semiconductor growth layer is grown on the substrate, but the etching rate is calculated while etching the nitride semiconductor growth layer, and the etching depth is calculated. In order to control the thickness, etching can be performed at a constant depth regardless of the crystallinity. Therefore, a ridge stripe dug to a predetermined depth can be easily created by this nitride semiconductor device manufacturing method.

Further, according to the present invention, the etching marker layer is made of Al _W Ga _1-W N (0.05 ≦ W ≦ 1), In _X Ga _1-X N (0.05 ≦ X ≦ 1), Al _Y In _Z. A periodic structure including at least two or more layers of Ga _1-YZ N (0.05 ≦ Y ≦ _1, 0.05 ≦ Z ≦ 1) and GaN, or among these, the compositions W, X, Y, or Z are mutually Since the periodic structure including two or more layers including two or more layers of the same type different by 0.05 or more is provided, at least one of the plasma emission spectra of Al and In can be detected without being buried in noise.

  Furthermore, the etching marker layer is a superlattice layer that can be thinned with a clearly different composition from the surrounding layers, so that plasma emission of elements such as Al and In that are targets for detection of plasma emission of the etching marker layer While making it possible to detect the spectrum clearly, the concentration of these elements does not become too high around the ridge stripe, and an increase in the resistance and power consumption of the nitride semiconductor laser device can be suppressed.

In the following, the meanings of terms will be clarified in advance in describing embodiments of the present invention. The “nitride semiconductor layer” described in the present specification is made of Al _x Ga _y In _z N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z ≦ 1; x + y + z = 1). However, about 10% or less of the nitrogen element in the nitride semiconductor layer may be replaced with an element of As, P, or Sb. The nitride semiconductor layer may be doped with Si, O, Cl, S, C, Ti, Ge, Zn, Cd, Mg, or Be. Among these doping materials, Si, O, and Cl are particularly preferable as the n-type nitride semiconductor.

  In the drawings of the present application, dimensional relationships such as length, width, thickness, and depth are appropriately changed for the sake of clarity and simplification of the drawings, and do not represent actual dimensional relationships.

FIG. 1 is a schematic configuration diagram showing the structure of a nitride semiconductor wafer 10 before forming a nitride semiconductor laser device according to an embodiment of the present invention. In the nitride semiconductor wafer 10, a nitride semiconductor growth layer 20 is formed on an n-type GaN substrate 11. The nitride semiconductor growth layer 20 includes an n-type GaN layer 21 having a thickness of 0.2 μm, an n-type Al _0.05 Ga _0.95 N clad layer 22 having a thickness of 2.2 μm, a thickness of 0.2 μm in order from the n-type GaN substrate 11 side. An n-type GaN guide layer 23 having a thickness of 02 μm, an InGaN / GaN-3 MQW (Multi Quantum Well) active layer 24 in which an InGaN layer having a thickness of 4 nm and a GaN layer having a thickness of 8 nm are alternately stacked three by three. A 20 nm p-type Al _0.3 Ga _0.7 N evaporation preventing layer 25, a 0.3 μm thick p-type Al _0.05 Ga _0.95 N cladding layer 26, and a 0.1 μm thick p-type GaN contact layer 27 are laminated.

An etching marker layer 30 is formed between the p-type Al _0.05 Ga _0.95 N cladding layer 26 and the p-type GaN contact layer 27. The etching marker layer 30 has a cycle in which a p-type Al _0.2 Ga _0.8 N layer having a thickness of 0.005 μm and a p-type GaN layer having a thickness of 0.02 μm are taken as one cycle in order from the p-type Al _0.05 Ga _0.95 N cladding layer 26 side. It has a superlattice structure with 10 periods of structure.

The composition, configuration, and thickness of each layer are examples, and may be changed as appropriate. In this embodiment, the n-type GaN substrate 11 is used as a nitride semiconductor substrate. However, the nitride semiconductor substrate is not limited to this material, and a p-type GaN substrate or a semi-insulating GaN substrate. An Al _1-x Ga _x N (0 ≦ x ≦ 1) substrate or the like may be used.

  Next, a method for manufacturing the above-described nitride semiconductor growth layer 20 will be described. In the following description, the case where the MOCVD method (Metal Organic Chemical Vapor Deposition) is used is shown, but the growth method is not limited to the MOCVD method as long as it is an epitaxial growth method. Other vapor phase growth methods such as a method (Molecular Beam Epitaxy; molecular beam epitaxy) and an HVPE method (Hydride Vapor Phase Epitaxy) may be used.

The n-type GaN substrate 11 is placed on a predetermined susceptor in the growth furnace of the MOCVD apparatus, and the susceptor temperature is raised to 1050 ° C. while flowing H ₂ and NH ₃ as carrier gases at a rate of 5 l / min. When the temperature rise is finished, trimethylgallium ((CH ₃ ) ₃ Ga; TMG) is supplied at 130 μmol / min and SiH ₄ is 70 nmol / min as a Ga raw material, and the n-type GaN layer 21 is 0.2 μm. Grow. Thereafter, TMG is reduced to 100 μmol / min, trimethylaluminum ((CH ₃ ) ₃ Al; TMA) is supplied as 5 μmol / min as an Al raw material into the growth reactor, and the n-type Al _0.05 Ga _0.95 N cladding layer 22 is supplied. Is grown to 2.2 μm. When the growth of the n-type Al _0.05 Ga _0.95 N clad layer 22 is completed, the supply of TMA is stopped, TMG is increased to 130 μmol / min, and the n-type GaN guide layer 23 is grown to 0.02 μm.

Thereafter, the supply of TMG and SiH ₄ is stopped, the carrier gas is changed from H ₂ to N ₂ , and the susceptor temperature is lowered to 800 ° C. First, 10 μmol / min of TMG is supplied into the growth furnace to grow a GaN layer having a thickness of 20 nm. Next, as a raw material for indium, trimethylindium ((CH ₃ ) ₃ In; TMI) is supplied at 5 μmol / min and TMG at 10 μmol / min in the growth furnace to grow an InGaN layer having a thickness of 4 nm. Next, the supply of TMI is stopped, and an 8 nm GaN layer is grown. Thereafter, TMI is again supplied to the growth furnace at 5 μmol / min, an InGaN layer having a thickness of 4 nm is grown, and the same operation is repeated, so that the InGaN / GaN-3 MQW active layer 24 becomes GaN / InGaN / GaN / InGaN / GaN. / InGaN / GaN in this order. In addition, the last GaN layer was grown by the structure of un-GaN / Si-GaN / un-GaN, and each layer thickness was 20 nm, 10 nm, and 40 nm.

When the InGaN / GaN-3MQW active layer 24 is formed, the supply of TMI and TMG is stopped, the susceptor temperature is raised to 1050 ° C., the carrier gas is changed from N ₂ to H ₂ , and TMG is 30 μmol / Min, TMA is 10 μmol / min, and bisethylcyclopentadienylmagnesium ((C ₂ H ₅ C ₅ H ₄ ) ₂ Mg; EtCp ₂ Mg) is grown at 0.2 μmol / min as a raw material for Mg which is a p-type dopant. The p-type Al _0.3 Ga _0.7 N evaporation preventing layer 25 is grown to 20 nm by supplying into the furnace. When the growth of the p-type Al _0.3 Ga _0.7 N evaporation preventing layer 25 is completed, the supply of TMG is reduced to 100 μmol / min, TMA is supplied into the growth furnace at 4 μmol / min, and the p-type Al _0.05 Ga _0.95 N cladding layer 26 is grown by 0.35 μm.

Next, the supply of TMA is increased to 15 μmol / min (or the supply of TMG is decreased to 50 μmol / min), and a p-type Al _0.2 Ga _0.8 N layer is grown to 0.005 μm. Subsequently, the supply of TMA is stopped, and a p-type GaN layer is grown to 0.015 μm. Thereafter, 15 μmol / min TMA is supplied again to grow a p-type Al _0.2 Ga _0.8 N layer by 0.005 μm, and the same operation is repeated to obtain a 0.005 μm-thick p-type Al _0.2 Ga _0.8 N layer and a thickness. An etching marker layer 30 having a superlattice structure having a periodic structure with one period of 0.015 μm p-type GaN layer as one period is formed.

Next, after the supply of TMA is stopped, the supply amount of EtCp ₂ Mg is increased to 1 μmol / min, the supply of TMG is maintained at 100 μmol / min, and the p-type GaN contact layer 27 is grown by 0.1 μm to form nitrides The semiconductor growth layer 20 is completed, and the growth of the semiconductor laminated film of the nitride semiconductor laser element is completed. Thereafter, the supply of TMG and EtCp ₂ Mg is stopped and the temperature is lowered. In this manner, the nitride semiconductor wafer 10 having the nitride semiconductor growth layer 20 formed on the surface is obtained. In addition, the thickness of each of these layers is a target value and may differ from an actual value.

First, the p-type GaN contact layer 27 and the etching marker layer 30 are removed by etching so as to form a ridge stripe structure having a width of about 2 μm using a normal photolithography technique and a dry etching technique. Subsequently, a part of the p-type Al _0.05 Ga _0.95 N cladding layer 26 is etched to stop the etching. In this embodiment, SiCl ₄ is used as a reactive gas used for dry etching, but the present invention is not limited to this, and other gases containing chlorine such as BCl ₃ may be used. .

  When etching is performed in this manner, the reaction of the dry etching apparatus can be performed by directly connecting the entrance of the spectroscope to the viewport portion for plasma emission observation provided in the dry etching apparatus such as an ICP apparatus or by using an optical fiber or the like. Light from plasma generated in the furnace (chamber) is introduced into the entrance of the spectrometer. It observes and detects changes in the intensity of light of a specific wavelength. By detecting the change in the intensity of the observation light, it is possible to know up to which layer is etched.

  FIG. 2 shows, as an example, a temporal change in the intensity of light having a spectroscopic wavelength when a sample in which a GaN layer, an InGaN layer, an AlGaN layer, and a GaN layer are sequentially stacked from the substrate side is etched from the front side. As shown in the figure, the curve indicating the emission intensity of light having a wavelength of 261.16 nm when the etching time is 176 seconds and light having a wavelength of 451.23 nm when the etching time is 185 seconds is convex, showing a unique change. ing. Light with a wavelength of 261.16 nm is due to Al, and light with a wavelength of 451.23 nm is due to In. In addition, although the observation wavelength in a present Example was mentioned above, it can actually observe in the wavelength of the range of +/- 2nm.

  Therefore, if the emission spectrum caused by Al is detected when the nitride semiconductor growth layer 20 is etched, the etching marker layer 30 has a periodic structure, and the emission spectrum also appears when the etching marker layer 30 is etched. Since it changes periodically, it is known what number cycle is being etched and the time required for etching for one cycle. By measuring in advance the thickness of one period of the periodic structure of the etching marker layer 30 with an XRD (X-ray Diffractometer; X-ray diffractometer) or the like, this and the time required for etching for one period From this, the etching rate can be calculated during etching.

FIG. 3 is a graph showing the results of XRD measurement of the p-type GaN contact layer 27 surface of the wafer 10. Peaks attributed to GaN and AlGaN are seen. The interval indicated as the periodic layer thickness in this graph is the thickness of one period of the periodic structure formed by the p-type Al _0.2 Ga _0.8 N layer and the p-type GaN layer of the etching marker layer 30. From this result, the thickness of one period of the periodic structure can be determined to be 0.020 μm.

Therefore, by controlling the etching time based on the etching rate calculated during etching, it is possible to etch up to a part of the p-type Al _0.05 Ga _0.95 N cladding layer 26 so as to form a ridge stripe having a predetermined shape. it can. In this way, the crystallinity of the nitride semiconductor growth layer 20 is controlled by controlling the etching time based on the etching rate measured during etching, rather than based on the digging depth of the monitoring wafer as in the prior art. Regardless of this, it is possible to accurately etch to a target digging depth, and to form a ridge stripe having an appropriate shape.

Next, a process of processing the nitride semiconductor wafer 10 on which the ridge stripe is formed into individual nitride semiconductor laser elements 50 is performed. Since the outline is general, the details are omitted, but an insulating film 41 for current confinement and p-electrode pads 42 and 43 are formed on the surface of the nitride semiconductor wafer 10 on which the ridge stripe is formed, and n The type GaN substrate 11 is ground and polished from the surface on which the nitride semiconductor growth layer 20 is not formed, and an n-electrode 44 is formed on the ground and polished surface, and then the nitride semiconductor wafer 10 is placed in the ridge stripe direction. The nitride semiconductor laser device 50 shown in the schematic configuration diagram of FIG. 4 was manufactured by dividing the state into bars so that the cavity length was in the range of 300 μm to 1200 μm. Each of the p electrode pads 42 and 43 is formed by vapor-depositing a metal, and is a multilayer film of a metal such as Mo / Au, Mo / Pt / Au, Mo / Pd / Au, or Mo / Pt / Al. Or it may be a single layer of Au only. The insulating film 41 is made of SiO ₂ , ZrO, TiO ₂ , Si ₂ N ₄ or the like.

  Twenty wafers having the same structure as that of the wafer 10 were manufactured, and the thickness of one etching marker layer for each wafer was measured, and while monitoring plasma emission, etching was performed using an ICP apparatus to prepare ridge stripes. . Measure the time required for one period of etching from the detection result of the emission spectrum due to Al appearing periodically, and determine the etching rate from the thickness of one period obtained by measuring in advance by XRD. Etching was stopped when etching was performed for a time corresponding to a total etching of 0.57 μm including the p-type GaN contact layer from the first time when the signal of the marker layer was detected. 100 nitride semiconductor laser elements were randomly taken out from each wafer, and the half-value width of the horizontal FFP of the 2000 nitride semiconductor laser elements in total was measured. At this time, the number of nitride semiconductor laser elements within ± 1 degree with respect to the horizontal FFP design value was 1910. The results are shown in a frequency distribution graph in FIG. 5 where the horizontal axis represents a deviation from the FFP design value and the vertical axis represents the number of corresponding nitride semiconductor laser elements.

  A nitride semiconductor laser element manufactured by controlling etching by a method of measuring an etching thickness using a monitoring wafer without inserting an etching marker layer, that is, a conventional example, which satisfies the above conditions, Since the number was 600 as shown in the graph of FIG. 6 created in the same manner as FIG. 5, the yield was greatly improved. This is because there is no variation in etching depth.

In the present embodiment, the etching marker layer 30 is made of Al _W Ga _1-W N (0.05 ≦ W ≦ 1), In _X Ga _1-X N (0.05 ≦ X ≦ 1), and Al _Y In _Z Ga. _1-YZ N (0.05 ≦ Y ≦ _1, 0.05 ≦ Z ≦ 1) and a periodic structure including at least two kinds of layers of GaN, or a composition W, X, Y, or Z of these layers is mutually What is necessary is just to provide the periodic structure which consists of a layer containing 2 or more layers of the same kind different 0.05 or more. If two or more periodic structures are provided, the thickness of the periodic structure can be detected by XRD. In addition, even if any layer is selected to form a periodic structure, for example, even if the periodic structure is formed of the same constituent element layer, the concentration of Al or In is different by 0.05 or more in adjacent layers. When the layer being etched changes to another layer, plasma emission clearly changes. Therefore, a change in plasma emission is easy to detect, and the etching time for one period of the periodic structure can be easily calculated. Furthermore, by forming the etching marker layer 30 as a superlattice, each constituent layer can be thinned while the composition is clearly different from the surrounding layers. This makes it possible to clearly detect the plasma emission spectrum of elements such as Al and In that are the targets of plasma emission detection of the etching marker layer, while the average concentration of these elements around the ridge stripe may become too high. Therefore, it is possible to suppress an increase in resistance and power consumption of the nitride semiconductor laser element.

  Further, when the thickness of each layer constituting the etching marker layer 30 is less than 0.001 μm or when X and Y are less than 0.05, the emission spectrum of Al and In plasma emission that appears during etching is buried in noise. It cannot be detected. Therefore, the thickness of each layer constituting the etching marker layer 30 is preferably 0.001 μm or more, and more preferably 0.005 μm or more in order to improve the detection signal intensity of the emission spectrum. Moreover, it is preferable that the thickness of each layer which comprises the etching marker layer 30 is 0.05 micrometer or less. This is because, when the thickness of each layer constituting the etching marker layer 30 is thicker than 0.05 μm, the average concentration of at least one of Al and In in the vicinity of the ridge stripe of the nitride semiconductor growth layer 20 becomes too high. This is because the p-type characteristics are deteriorated, the resistance of the nitride semiconductor laser element 20 obtained from the nitride semiconductor wafer 10 is increased, and the power consumption is increased. In particular, when AlGaN is included in the etching marker layer 30, the lattice constant difference from the surrounding layers is large, so cracks are likely to occur, and the manufacturing yield of the device is greatly reduced.

In the present embodiment, the etching rate is determined from the period of the emission spectrum of the element contained in the layer constituting the etching marker layer 30 that appears periodically and the thickness of one period of the etching marker layer 30 measured in advance. Since the calculation is performed on the spot, even after the etching marker layer 30 has been etched, the etching can be further deepened while calculating the digging depth based on the etching time. Therefore, the etching marker layer 30 may be provided at a position shallower than the digging depth. Therefore, the p-type Al _0.05 Ga _0.95 N clad layer 26 or the p-type GaN contact layer 27 is divided and provided therebetween. Alternatively, it may be provided on the surface of the p-type GaN contact layer 27.

  As described above, a desired digging depth can be obtained regardless of the position where the etching marker layer 30 is provided, and it is possible to easily cope with a design change of the digging depth.

  The etching marker layer 30 may be inserted at an etching stop position. Etching is stopped when the plasma emission of Al and In disappears. In this case, in order to make it easy to take the timing to stop etching, it is preferable to have a structure having three or more periodic structures.

Schematic configuration diagram of a nitride semiconductor wafer according to an embodiment of the present invention Example of measurement results of plasma emission intensity during etching of nitride semiconductor thin films containing Al and In XRD measurement result of nitride semiconductor wafer according to an embodiment of the present invention 1 is a schematic configuration diagram of a nitride semiconductor laser device according to an embodiment of the present invention. Frequency distribution of deviation from FFP design value of nitride semiconductor laser element produced by method according to embodiment of the present invention Frequency distribution of deviation from FFP design value of nitride semiconductor laser device produced by conventional method Schematic configuration diagram of conventional nitride semiconductor wafer Plan view of an ICP device with a conventional nitride semiconductor wafer Front view of an ICP device with a conventional nitride semiconductor wafer Graph showing the relationship between the digging depth of a conventional nitride semiconductor growth layer and the laser beam intensity Graph showing the relationship between the conventional setting depth and the actual measurement depth

Explanation of symbols

11 n-type GaN substrate 20 nitride semiconductor growth layer 21 n-type GaN layer 22 n-type Al _0.05 Ga _0.95 N clad layer 23 n-type GaN guide layer 23
24 InGaN / GaN-3 MQW active layer 25 p-type Al _0.3 Ga _0.7 N evaporation prevention layer 26 p-type Al _0.05 Ga _0.95 N clad layer 27 p-type GaN contact layer 30 etching marker layer 50 nitride semiconductor laser device

Claims (6)

A nitride semiconductor comprising: a first step of stacking a nitride semiconductor thin film on a nitride semiconductor substrate to form a nitride semiconductor growth layer; and a second step of removing a part of the nitride semiconductor growth layer. In the manufacturing method of the laser element,
In the first step, between the nitride semiconductor thin films, an etching marker layer comprising two or more periodic structures composed of at least two types of layers having different compositions is laminated,
In the second step, the nitride semiconductor layer is removed by dry etching, and plasma emission of an element included in the etching marker layer accompanying dry etching is detected, and one cycle of the periodic structure of the etching marker layer is detected. After measuring the time required for etching and completing the measurement, a predetermined depth is obtained based on the etching rate calculated from the measured time required for one period of etching and the thickness of one period of the periodic structure. A method of manufacturing a nitride semiconductor laser device, comprising performing dry etching. The etching marker layer is made of Al _W Ga _{1 -W} N (0.05 ≦ W ≦ 1), In _X Ga _{1 -X} N (0.05 ≦ X ≦ 1), Al _Y In _Z Ga _{1 -YZ} N ( 0.05 ≦ Y ≦ 1, 0.05 ≦ Z ≦ 1) and a periodic structure including at least two kinds of layers of GaN or the same among them, the compositions W, X, Y, or Z are different from each other by 0.05 or more. 2. The method for manufacturing a nitride semiconductor laser element according to claim 1, further comprising two or more periodic structures each including a layer including two or more types of layers.   3. The method of manufacturing a nitride semiconductor laser element according to claim 1, wherein the etching marker layer is a superlattice.   4. The method for manufacturing a nitride semiconductor laser element according to claim 2, wherein the thickness of each layer constituting the etching marker layer is 0.001 [mu] m or more.   4. The method for manufacturing a nitride semiconductor laser element according to claim 2, wherein the thickness of each layer constituting the etching marker layer is 0.05 [mu] m or less.   A nitride semiconductor laser device manufactured using the method for manufacturing a nitride semiconductor laser device according to claim 1.

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