JP2007207798A - Semiconductor device and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device which can accurately and easily control the depth of etching without degrading element characteristic. <P>SOLUTION: In the step for manufacturing a nitride compound semiconductor laser, a p-type AlGaN etching marker layer 200 is placed under a p-type GaN cap layer 108 and a p-type AlGaN clad layer 107. When the ununiformity of etching quantity on a surface to be etched is B, the ununiformity of total film thickness of the cap layer 108 and the clad layer 107 is D, and the average film thickness of the marker layer 200 to the average value of the total film thickness is N; the relationships of 2B>D>0 and N>¾(B-D)¾ are satisfied. In addition, the total film thickness of the cap layer 108 and the clad layer 107 is changed according to the variation of the etching quantity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor device including an etching marker layer and a manufacturing method thereof.

  Nitride III-V compound semiconductors containing nitrides such as AlGaInN semiconductors are chemically stable and have high hardness. Therefore, chemical etching (specifically, wet etching) used in the manufacturing process of other III-V compound semiconductors such as gallium arsenide (GaAs) or indium phosphide (InP) cannot be used.

  For example, in an AlGaAs-based semiconductor, one AlGaAs layer can be selectively chemically etched by changing the composition ratio of Al and Ga in two AlGaAs layers. However, nitride-based III-V group compound semiconductors are hardly etched by chemical etching. Therefore, dry etching using plasma is used for etching a nitride III-V compound semiconductor.

  When manufacturing a ridge type compound semiconductor laser using a nitride III-V compound semiconductor, there are the following problems. That is, in the ridge type compound semiconductor laser, the oscillation characteristics of the laser greatly fluctuate when the depth of the ridge waveguide varies. Therefore, when the ridge waveguide is formed by etching, it is necessary to precisely control the etching depth.

  As described above, since chemical etching cannot be applied to nitride-based III-V compound semiconductors, dry etching is used for processing of nitride-based III-V compound semiconductors. However, dry etching has low etching selectivity. This is because, in dry etching, the etching depth is usually controlled by the etching time, and the etching depth control by the etching time has poor controllability of the etching amount. Therefore, it is difficult to precisely control the etching depth.

  In order to solve this problem, for example, there is a technique described in Patent Document 1 below. Patent Document 1 below discloses a method of stopping etching using a change in plasma emission spectrum when etching reaches an etching marker layer containing In.

JP 2001-244568 A

  In the above method in which etching is stopped using the etching marker layer, it is necessary that the emission spectrum change clearly. However, when dry etching is performed on the surface of a semiconductor substrate, it is difficult to keep the etching amount uniform at various locations on the surface to be etched. Therefore, due to the non-uniformity of the etching amount in the surface to be etched, the change in the emission spectrum becomes unclear and it may be difficult to detect the arrival of etching at the etching marker layer.

  In addition, even when the in-plane non-uniformity of the etching amount is zero, the distribution of the total thickness of each layer to be etched from the etching marker layer to the uppermost layer is non-uniform on the etching marker layer surface However, it may still be difficult to detect the arrival of etching at the etching marker layer.

  Further, the growth temperature of InGaN used as an etching marker layer in Patent Document 1 is lower than that of AlGaN. Usually, InGaN is formed at a growth temperature of about 800 ° C., and AlGaN is formed at a growth temperature of about 1000 ° C. Therefore, as shown in FIG. 4 of the above-mentioned Patent Document 1, in order to form the p-type AlGaN cladding layer 107 after the formation of the p-type InGaN etching marker layer 200, the p-type InGaN etching marker layer 200 is formed after the formation. It is necessary to raise the temperature in the chamber of the film forming apparatus to the growth temperature of the p-type AlGaN cladding layer 107 and wait until the temperature becomes stable.

  At this time, evaporation of In components and adhesion of residual gas components inside the film forming apparatus occur on the surface of the p-type InGaN etching marker layer 200. Therefore, the crystal quality of the p-type AlGaN cladding layer 107 on which crystal growth is performed on the p-type InGaN etching marker layer 200 is likely to deteriorate. When the crystal quality deteriorates, crystal defects increase, and light emitted from the strained quantum well layer is easily absorbed by the crystal defects, which causes a problem that the oscillation threshold current value increases.

  The forbidden band width of the p-type InGaN etching marker layer 200 is smaller than the forbidden band width of the p-type GaN light guide layer 106 and the p-type AlGaN cladding layer 107. Therefore, when the p-type InGaN etching marker layer 200 is inserted between the p-type GaN light guide layer 106 and the p-type AlGaN cladding layer 107, a part of the laser light is absorbed by the p-type InGaN etching marker layer 200 (laser light). There is also a problem that the oscillation threshold current value is further increased.

  Thus, when an InGaN etching marker layer is introduced to detect plasma emission, there is a problem that the performance of the light emitting device is degraded.

  This invention has been made in view of the above circumstances, and is a method of manufacturing a semiconductor device using an etching marker layer, which can accurately and easily control the etching depth without deteriorating element characteristics. And it aims at realizing the semiconductor device manufactured with the manufacturing method.

  The present invention includes (a) a step of forming an etching marker layer having a surface above the surface of a semiconductor substrate having a surface, and (b) a step of forming an etching target layer on the surface of the etching marker layer; (C) selectively etching the layer to be etched by dry etching using plasma, and in the step (c), a change in plasma emission intensity corresponding to the composition of the etching marker layer is achieved. Accordingly, in the method of manufacturing a semiconductor device in which the dry etching is stopped, in the step (b), the film thickness of the etched layer is increased at a location where the etching amount is large in the etched surface of the etched layer. , Forming a thin film thickness of the layer to be etched in a place where the etching amount is small within the surface to be etched of the layer to be etched, Using the maximum value, minimum value, and average value of the etching amount at various points in the etched surface of the etched layer, the value of (maximum value−minimum value) / average value × 100 [%] is used as the etching amount surface. (Maximum value−minimum value) / average value × 100, which is defined as non-uniformity B and uses the maximum value, the minimum value, and the average value of the film thickness of the layer to be etched at various points on the surface of the etching marker layer. The value of [%] is defined as non-uniformity D of the film thickness of the etched layer, the average value of the film thickness of the etched layer on the surface of the etching marker layer is L, and the average of the etching marker layer The film thickness is M, the value obtained by dividing M by L is the film thickness ratio N, and 2B> D> 0 and N> | (BD) | (“|” represents an absolute value symbol. ) And a semiconductor device manufacturing method that simultaneously satisfies the relational expressionFurther, the semiconductor device is manufactured by the manufacturing method.

  According to the present invention, the film thickness of the layer to be etched is thick at a location where the etching amount is large in the etched surface of the layer to be etched, and the film of the layer to be etched at a location where the etching amount is small in the etching surface of the layer to be etched. Form a thin thickness. Since the film thickness of the layer to be etched is large at the portion where the etching amount is large, and the film thickness of the layer to be etched is small at the portion where the etching amount is small, there is an effect of canceling the nonuniformity of the etching amount. The relational expression 2B> D> 0 and N = M / L> | (BD) | is simultaneously satisfied. Thereby, the thickness of the etching marker layer can be made thinner, and plasma emission can be monitored without reducing the maximum fluctuation amount of the emission intensity. And even in the case where in-plane non-uniformity of the etching amount exists, the uniformity of the etching residual thickness that is the distance from the predetermined position under the etching marker layer to the etched surface in the etching marker layer is improved. Can do. Therefore, it is possible to realize a method for manufacturing a semiconductor device using an etching marker layer in which the etching depth can be precisely and easily controlled without deteriorating element characteristics.

<A. Etching stop method using conventional plasma emission spectrum>
First, the etching stopping method using the plasma emission spectrum described in Patent Document 1 and its problem will be described in detail.

  FIG. 1 shows a structure in the course of manufacturing a semiconductor laser using a nitride-based III-V group compound semiconductor described in FIG. In FIG. 1, on a semiconductor substrate (sapphire substrate) 100, a GaN low temperature layer 101, an n-type GaN buffer layer 102, an n-type AlGaN cladding layer 103, an n-type GaN light guide layer 104, an InGaN strained quantum well layer 105, a p-type. The GaN light guide layer 106, the p-type InGaN etching marker layer 200, the p-type AlGaN cladding layer 107, the p-type GaN cap layer 108, and the oxide film layer 201 are laminated in this order. FIG. 1 shows a stage in which the p-type AlGaN cladding layer 107, the p-type GaN cap layer 108, and the oxide film layer 201 are dry etched to form a ridge portion of the semiconductor laser structure.

  Thereafter, a p-type electrode (not shown) is formed on the p-type GaN cap layer 108, and the stacked structure from the n-type AlGaN cladding layer 103 to the p-type InGaN etching marker layer 200 is changed to an n-type GaN buffer. Etching is performed halfway through the layer 102 to form an n-type electrode (not shown) on the exposed surface.

  The p-type GaN cap layer 108 and the p-type AlGaN cladding layer 107 are selectively subjected to plasma dry etching (for example, RIE: Reactive Ion Etching) using chlorine gas using the oxide film layer 201 as a mask. That is, the p-type GaN cap layer 108 and the p-type AlGaN cladding layer 107 together become a layer to be etched. By observing the plasma emission during the etching, the etching is stopped when an emission peak corresponding to the In plasma emission wavelength appears. That is, dry etching is stopped according to the change in the plasma emission intensity corresponding to the composition of the p-type InGaN etching marker layer 200.

  The cross sections of the p-type GaN layer cap layer 108 and the p-type AlGaN cladding layer 107 after etching constitute a mesa shape whose depth is defined by the etching marker layer. The mesa-shaped p-type GaN layer cap layer 108 and the p-type AlGaN cladding layer 107 function as a ridge waveguide of the semiconductor laser.

  When the etching depth of the AlGaN cladding layer 107 functioning as a ridge waveguide of a semiconductor laser varies, the laser oscillation characteristics greatly vary. Therefore, the etching depth during dry etching of the p-type GaN cap layer 108 and the p-type AlGaN cladding layer 107 must be precisely controlled. In Patent Document 1, InGaN is used as the material of the etching marker layer 200, and the etching depth is controlled by detecting the spectral change of plasma emission corresponding to In.

The inventors have a p-type In _0.1 Ga _0.9 N etching marker layer 200 with a thickness of 20 nm, a p-type Al _0.1 Ga _0.9 N cladding layer 107 with a thickness of 500 nm, and a p-type GaN cap layer 108 with a thickness of 20 nm. A plurality of structures shown in FIG. 1 were actually created and various measurements were performed. FIG. 2 shows one experimental result showing the normalized emission intensity of In at the time of etching the actually created structure together with the etching time. The etching rate is 200 nm / min.

Here, the “normalized emission intensity” of In refers to the emission intensity of In from the p-type In _0.1 Ga _0.9 N etching marker layer 200 with reference to the emission intensity of In when plasma etching is performed on p-type InN. The emission intensity is defined as a value divided by the emission intensity of In in p-type InN. That is, it is defined as In normalized emission intensity = (In plasma emission intensity in p-type In _x Ga _1-x N etching marker layer) / (In plasma emission intensity in p-type InN).

According to the experiments by the inventors of the present application, the surface to be etched on the semiconductor substrate 100 (of each layer such as the p-type GaN cap layer 108 and the p-type Al _0.1 Ga _0.9 N cladding layer 107 is etched by being in contact with the etching plasma). When the etching rate is almost constant at various points within the surface), the normalized emission intensity is expressed as x representing the composition ratio of In in the In _x Ga _1-x N composition formula of the p-type InGaN etching marker layer 200. It turns out that it becomes the same value.

With reference to FIG. 2, the normalized emission intensity of In from the start of etching of the p-type GaN cap layer 108 and the p-type Al _0.1 Ga _0.9 N cladding layer 107 to the end of etching of the p-type In _0.1 Ga _0.9 N etching marker layer 200 Will be described.

First, while the p-type GaN cap layer 108 and the p-type Al _0.1 Ga _0.9 N cladding layer 107 are etched, In is not contained in the film, so the normalized emission intensity of In is zero. When the etching progresses and the p-type In _0.1 Ga _0.9 N etching marker layer 200 is exposed, the normalized emission intensity becomes 0.10 (the same value as the In composition ratio). And while etching the etching marker layer 200 with a film thickness of 20 nm, it remains 0.1. Next, when the etching of the In _0.1 Ga _0.9 N etching marker layer 200 is completed, the p-type GaN light guide layer 106 not containing In is exposed, so that the normalized emission intensity becomes zero again.

In this way, if a change in the normalized emission intensity of In corresponding to the exposure of the etching marker layer 200 is detected, the etching may be stopped. In the above example, when the p-type In _0.1 Ga _0.9 N etching marker layer 200 is exposed after etching the p-type Al _0.1 Ga _0.9 N cladding layer 107, the normalized emission intensity of In increases by 0.10. .

Here, the difference in normalized emission intensity between the p-type In _0.1 Ga _0.9 N etching marker layer 200 and the p-type GaN cap layer 108 and the p-type Al _0.1 Ga _0.9 N cladding layer 107 formed thereon is expressed as follows: It is defined as the emission intensity change amount α. Then, it is determined that the etching from the surface of the p-type GaN cap layer 108 to the p-type In _0.1 Ga _0.9 N etching marker layer 200 can be performed when the In emission intensity change α is 0.10, and the etching is stopped. Thus, the etching depth can be controlled.

  Next, problems in the etching stopping method using the plasma emission spectrum described in Patent Document 1 will be described.

  In the etching stop method described in the above-mentioned Patent Document 1, it is assumed that the etching amount in each part of the surface to be etched is uniform, that is, the etching rate in each part in the surface to be etched is constant. However, in reality, there are differences in etching rates at various locations within the surface to be etched, and due to the differences, there is a distribution of an etching amount of about several percent in the surface to be etched.

Each layer from the p-type In _0.1 Ga _0.9 N etching marker layer 200 to the p-type GaN cap layer 108 (p-type In _0.1 Ga _0.9 N etching marker layer 200, p-type Al _0.1 Ga _0.9 N cladding layer 107 and p-type GaN). The total film thickness of the cap layer 108) may also differ at various places on the surface of the p-type In _0.1 Ga _0.9 N etching marker layer 200, and there may be a distribution of the total film thickness of these layers.

  As described above, the inventors of the present invention have found that the behavior of the normalized emission intensity with respect to the etching time greatly changes when the distribution of the etching amount or the distribution of the total film thickness on the etching marker layer exists.

FIG. 3 shows that the total film thickness of each layer from the p-type In _0.1 Ga _0.9 N etching marker layer 200 to the p-type GaN cap layer 108 is uniform at various points on the surface of the semiconductor substrate 100, and various points within the etched surface. Experimental results of plotting the normalized emission intensity of In against the etching time for in-plane non-uniformity of the etching amount at 0%, 3%, 6%, 10%, 15%, and 20% FIG.

  In the present application, the “in-plane nonuniformity of the etching amount” is expressed as (maximum value−minimum value) / average value × 100 [%] using the maximum value, the minimum value, and the average value of the etching amount at various points in the surface to be etched ] Defined. For example, “the in-plane non-uniformity of the etching amount is 0%” indicates that the etching amount is uniform and constant at various locations within the surface to be etched. "The property is 20%" means that the etching amount has a maximum deviation of 20% of the average etching amount at various points within the surface to be etched.

FIG. 3 shows that the maximum value of the normalized emission intensity and the amount of time variation vary depending on the in-plane nonuniformity value of the etching amount. When the in-plane nonuniformity is 3%, the maximum fluctuation amount of the normalized emission intensity is 0.10, which is the same as when the in-plane nonuniformity is 0%. However, the rate of change of the normalized emission intensity with respect to the etching time is different. The “maximum variation in normalized emission intensity” refers to the normalized emission intensity in the p-type Al _0.1 Ga _0.9 N cladding layer 107 from the maximum normalized emission intensity in the p-type In _0.1 Ga _0.9 N etching marker layer 200. The value defined as the difference minus the maximum value of.

  In the case of in-plane non-uniformity of 6% or more, the maximum fluctuation amount of the normalized emission intensity decreases as the in-plane non-uniformity increases. Furthermore, it was found that the rate of change of the normalized emission intensity with respect to the etching time also varies depending on the in-plane nonuniformity value. In other words, the maximum fluctuation amount of the normalized emission intensity and the etching time change rate of the normalized emission intensity depend on the in-plane nonuniformity of the etching amount, and when the in-plane nonuniformity increases, the maximum fluctuation amount of the normalized emission intensity And the rate of change over time decreases.

Although the case where the in-plane non-uniformity of the etching amount is not zero has been described here, the p-type In _0.1 Ga _0.9 N etching marker layer 200 is changed to the p-type even if the in-plane non-uniformity of the etching amount is zero. When the total film thickness of each layer up to the GaN cap layer 108 is non-uniformly distributed on the surface of the p-type In _0.1 Ga _0.9 N etching marker layer 200, the maximum variation of the normalized emission intensity and the normalized emission It has been found by experiments of the present inventors that the rate of change in strength etching time is reduced.

  That is, when there is an in-plane distribution of the etching amount or a distribution of the total film thickness of each layer above the etching marker layer, the normalized emission intensity is obtained by the etching stop method using plasma emission described in Patent Document 1. It has been found that there is a problem that it becomes difficult to detect the etching marker layer due to fluctuations in the etching time change rate of the maximum fluctuation amount and the normalized emission intensity.

Further, the control of the etching amount has been described so far, but in the semiconductor laser structure of FIG. 1, the p-type In _0.1 Ga _0.9 N etching marker layer 200 from the surface of the InGaN strained quantum well layer 105 serving as the active layer is included. When the distance to the surface to be etched is close to 0.05 μm to 0.3 μm, from the surface of the InGaN strained quantum well layer 105 to the surface to be etched in the p-type In _0.1 Ga _0.9 N etching marker layer 200. When the controllability of the distance (hereinafter referred to as the etching residual thickness) is deteriorated, the variation of the beam diameter divergence angle and the oscillation threshold current value increases, so that the uniformity of the etching residual thickness rather than the etching amount is improved. This is important for reducing variations in the beam divergence angle and oscillation threshold current value.

When there is no in-plane distribution of the etching amount or distribution of the total film thickness of each layer and uniform etching is performed, it can be said that the controllability of the etching amount is almost equal to the controllability of the remaining etching thickness. However, when there is an in-plane distribution of the etching amount and a distribution of the total film thickness of each layer, naturally, the distribution of the remaining etching thickness on the surface of the p-type In _0.1 Ga _0.9 N etching marker layer 200 also occurs. There is a problem in that light emitting elements having unetched thicknesses deviated from the design specifications are formed at various locations on the surface of the p-type In _0.1 Ga _0.9 N etching marker layer 200, resulting in a decrease in yield of the light emitting elements.

Further, when the p-type In _x Ga _1-x N etching marker layer 200 described in Patent Document 1 is inserted into a nitride-based III-V group compound semiconductor, the following problems occur.

When the p _- type In _x Ga _1-x N etching marker layer 200 is inserted between the p-type GaN optical guide layer 106 and the p-type Al _y Ga _1-y N cladding layer 107, the In _x Ga _1-x N is forbidden. Since the band width is narrower than the forbidden band width of GaN and Al _y Ga _1-y N, light absorption (light loss) in the p-type In _x Ga _1-x N etching marker layer 200 increases. As a result, there arises a problem that the oscillation threshold current value increases. As a matter of course, the light emitting element preferably has a lower oscillation threshold current value in order to suppress power consumption.

The crystal growth temperature of the p _- type Al _y Ga _1-y N cladding layer 107 is higher than the crystal growth temperature of the p-type In _x Ga _1-x N etching marker layer 200. Therefore, after the p-type In _x Ga _1-x N etching marker layer 200 is formed, the semiconductor laser structure is kept on standby in a film forming apparatus in which the crystal growth temperature of Al _y Ga _1-y N is stable. In evaporates from the surface of the p-type In _x Ga _1-x N etching marker layer 200, and the evaporation tends to cause defects and roughness on the surface of the p-type In _x Ga _1-x N etching marker layer 200. Therefore, the crystal quality of the p-type In _x Ga _1-x N etching on the marker layer 200 at the time of forming the p-type Al _y Ga _1-y N cladding layer 107, p-type Al _y Ga _1-y N cladding layer 107 As a result, the oscillation threshold current value increases.

  The present invention has been made on the basis of a detailed examination of the etching process in order to solve the above-mentioned problems.

<B. Regarding change in normalized emission intensity when there is an in-plane distribution of etching amount in the present invention>
Next, the change in the normalized emission intensity when there is an in-plane distribution of the etching amount in the present invention will be considered.

First, in the present invention, in place of the p-type In _x Ga _1-x N etching marker layer 200 of FIG. 1, a p-type Al _x Ga _1-x N etching marker layer 200 employing AlGaN instead of InGaN is employed. Other parts are the same as those of the semiconductor laser structure of FIG.

FIG. 4 shows a p _- type Al _0.05 Ga _0.95 N clad layer 107 that starts etching from the p-type GaN cap layer 108 in the semiconductor laser structure of the present invention employing the p-type Al _x Ga _1-x N etching marker layer 200. (When y = 0.05) and p-type Al _0.2 Ga _0.8 N etching marker layer 200 (when x = 0.2), the maximum variation of the normalized emission intensity with respect to Al is determined as the etching amount. In-plane non-uniformity of 0% (that is, when the etching amount is uniform in-plane) and 1%, 2%, 3%, 4%, 6%, 10%, 15%, and 20% It is a graph plotted against the case.

Here, the “normalized emission intensity” of Al refers to the emission intensity of Al from the p-type Al _0.2 Ga _0.8 N etching marker layer 200 on the basis of the emission intensity of Al when plasma etching is performed on p-type AlN. The emission intensity is defined as a value divided by the emission intensity of Al in p-type AlN. That is, the normalized emission intensity of Al = (Al plasma emission intensity of Al in the p-type Al _x Ga _1-x N etching marker layer) / (Al plasma emission intensity of p-type AlN).

Further, the “maximum fluctuation amount of the normalized emission intensity” refers to the maximum value of the normalized emission intensity in the p-type Al _x Ga _1-x N etching marker layer 200 in the p-type Al _y Ga _1-y N cladding layer 107. The value defined as the difference obtained by subtracting the maximum value of the normalized emission intensity. As described above, the definition of “in-plane non-uniformity of etching amount” is (maximum value−minimum value) / average value using the maximum value, the minimum value, and the average value of the etching amount at various points in the surface to be etched × 100 [%].

The graph of FIG. 4, _p-type Al _x Ga _1-x from the etching marker layer 200 of the total thickness of each layer of the p-type GaN cap layer 108, _p-type Al _x Ga _1-x surface of the etching marker layer 200 A semiconductor laser structure with a uniform distribution above was taken. The thickness of the p-type GaN cap layer 108 is 20 nm, the thickness of the p-type Al _0.05 Ga _0.95 N cladding layer 107 is 500 nm, and the thickness of the p-type Al _0.2 Ga _0.8 N etching marker layer 200 is 20 nm. The etching rate was 200 nm / min for all layers to be etched.

According to the experiments by the inventors of the present application, the surface to be etched on the semiconductor substrate 100 (of the p-type GaN cap layer 108, the p-type Al _y Ga _1-y N cladding layer 107, etc. is in contact with the etching plasma). In the p-type Al _x Ga _1-x N etching marker layer 200 and the p-type Al _y Ga _1-y N cladding layer 107, the Al standard It was found that the maximum value of the luminescence intensity becomes the same value as the Al composition ratio x or y. That is, when the in-plane non-uniformity of the etching amount is 0%, the maximum fluctuation amount of the normalized emission intensity is xy. In the above example, it is 0.15 (= 0.2-0.05).

As can be seen from FIG. 4, the maximum fluctuation amount of the normalized emission intensity is constant at 0.15 when the in-plane non-uniformity is about 0% to 3%, and the same maximum fluctuation amount as in the case of 0% is obtained. However, as the in-plane non-uniformity further increases, the maximum variation decreases. If the in-plane non-uniformity of the etching amount falls within about 3%, the same maximum fluctuation amount as that in the case of 0% can be obtained because the p-type is formed in all locations not protected by the etching mask on the semiconductor substrate 100. This is because the Al _x Ga _1-x N etching marker layer 200 remains, and even if the etching amount is non-uniform, sufficient light emission intensity can be secured in the p-type Al _x Ga _1-x N etching marker layer 200. It is believed that there is.

  As described above, the inventors of the present application set the conditions for obtaining the same maximum amount of variation in normalized emission intensity as in the case where the in-plane non-uniformity of the etching amount is 0% even when the in-plane non-uniformity of the etching amount exists. Empirically derived from various experiments as follows.

That is, the film thickness from the surface of the p-type Al _x Ga _1-x N etching marker layer 200 to the surface to be etched before etching, that is, in this embodiment, the p-type GaN cap layer 108 and the p-type Al _y Ga _1- The ratio N (= M / L × 100%) of the film thickness M of the p-type Al _x Ga _1-x N etching marker layer 200 with respect to the total film thickness L with the _y N cladding layer 107 (hereinafter, the ratio N) The condition is that the film thickness ratio is equal to the etching amount in-plane non-uniformity value or larger than the in-plane non-uniformity value. That is, when the relationship of the film thickness ratio N ≧ the in-plane non-uniformity of the etching amount is satisfied, the maximum fluctuation amount of the normalized emission intensity does not decrease.

Taking the case of this embodiment as an example, the film thickness ratio N = (film thickness of p-type Al _x Ga _1-x N etching marker layer 200 20 nm) / [(film thickness of p-type GaN cap layer 108 20 nm) + (Film thickness of p-type Al _0.05 Ga _0.95 N clad layer 107 500 nm)] × 100% = 20 / (20 + 500) × 100% = 3.8%. It is certainly shown in FIG. 4 that when the in-plane non-uniformity of the etching amount is 3%, which is smaller than the film thickness ratio N, the same maximum fluctuation amount as when the in-plane non-uniformity is 0%. Yes.

However, when the in-plane non-uniformity of the etching amount becomes larger than the film thickness ratio N, the deviation of the etching amount in the etched surface is larger than the film thickness M of the p-type Al _x Ga _1-x N etching marker layer 200. Become. Therefore, the exposed area of the p-type Al _x Ga _1-x N etching marker layer 200 is reduced. This is considered to be the cause of the decrease in the maximum fluctuation amount of the normalized emission intensity.

In a normal etching apparatus, there is an in-plane non-uniformity in the etching amount of about 6% to 10% in absolute value (± 3% to ± 5% from the average value of etching amount). In the case of etching the semiconductor laser structure using an etching apparatus having an in-plane non-uniformity of the etching amount of 6%, the maximum fluctuation amount does not decrease from the case where the in-plane non-uniformity is 0%. The minimum film thickness of the p-type Al _x Ga _1-x N etching marker layer 200 is 31.2 nm (= 6% × total film thickness L = 6% × 520 nm). When the film thickness M of the p-type Al _x Ga _1-x N etching marker layer 200 becomes thinner than this minimum film thickness, the maximum fluctuation amount of the normalized emission intensity decreases.

Further, the inventors of the present application have empirically derived from various experiments that there is a minimum film thickness of the p-type Al _x Ga _1-x N etching marker layer 200 in which the maximum fluctuation amount of the normalized emission intensity does not decrease. . In other words, etching a plane non-uniformity of the etching amount from the D%, p-type Al _x Ga _1-x N and the thickness M of the etching marker layer 200, p-type Al _x Ga _1-x N surface of the etching marker layer 200 When the total film thickness with the total film thickness L up to the previous surface to be etched is Enm, the minimum p-type Al _x Ga _1-x N etching marker layer 200 film that does not reduce the maximum variation in normalized emission intensity The thickness is D / 100 × E (nm).

If the film thickness B of the p-type Al _x Ga _1-x N etching marker layer 200 is increased, the relationship of film thickness ratio N ≧ (in-plane nonuniformity in etching amount) can be satisfied. However, when the thickness of the p-type Al _x Ga _1-x N film thickness M of the etching marker layer 200, since the lateral current spreading in the p-type Al _x Ga _1-x N etching marker layer 200 is increased, the laser active The current density in the layer decreases, causing an increase in the oscillation threshold current value. Therefore, the film thickness M of the p-type Al _x Ga _1-x N etching marker layer 200 is desirably 20 nm or less.

On the other hand, when the film thickness M of the p-type Al _x Ga _1-x N etching marker layer 200 is reduced, lateral current spreading in the p-type Al _x Ga _1-x N etching marker layer 200 is suppressed. However, the film thickness ratio N <(in-plane non-uniformity in the etching amount), and the maximum fluctuation amount of the normalized emission intensity decreases.

In the present invention, even when the film thickness M of the p-type Al _x Ga _1-x N etching marker layer 200 is reduced so that the film thickness ratio N <(in-plane nonuniformity in etching amount), It was made based on the result of considering the plasma emission detection method and its conditions without reducing the maximum intensity variation.

<C. In the present invention, regarding the change in normalized emission intensity when there is both the distribution of the total film thickness of each layer from the etching marker layer to the cap layer and the in-plane distribution of the etching amount>
B. Then, the total film thickness of each layer from the p _- type Al _x Ga _1-x etching marker layer 200 to the p-type GaN cap layer 108 (ie, the film thickness of the p-type Al _x Ga _1-x etching marker layer 200 and the p-type GaN). A semiconductor laser having a uniform distribution of the thickness of the cap layer 108 and the thickness of the p-type Al _y Ga _1-y N cladding layer 107 on the surface of the p-type Al _x Ga _1-x etching marker layer 200 The structure has been described. Here, on the surface of the p-type In _0.1 Ga _0.9 N etch marker layer 200, p-type In _0.1 Ga _0.9 N etch marker layer 200, p-type GaN cap layer 108, and the p-type Al _y Ga _1-y N cladding layer Even when the film thickness distribution 107 is non-uniform and the film thickness ratio N <(in-plane non-uniformity of the etching amount), the maximum fluctuation amount of the normalized emission intensity A method for preventing the deterioration and the conditions thereof will be described.

In order to consider the non-uniformity of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107, the film thickness ratio N is hereinafter referred to as the p-type GaN cap. P-type Al _x Ga _{1− with} respect to the average value L on the surface of the p-type Al _x Ga _1-x N etching marker layer 200 of the total thickness of the layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 _x Defined as the ratio of the average film thickness M of the N etching marker layer 200 (N = M / L).

When the non-uniformity of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 is brought close to the in-plane non-uniformity of the etching amount, the film thickness ratio N <( Even in the case of non-uniformity in the etching amount), it is possible to prevent the maximum fluctuation amount of the normalized emission intensity from being reduced.

Hereinafter, the conditions under which the maximum fluctuation amount of the normalized emission intensity does not decrease will be considered in more detail. _p-type Al _x Ga _1-x center of N etching marker layer 200 surface (corresponding to the center portion of the substrate surface of the semiconductor substrate 100) large etching amount, and p-type Al _x Ga _1-x N etching marker An etching apparatus having a convex etching amount distribution with a small etching amount in the peripheral part of the surface of the layer 200 (which also corresponds to the peripheral part of the semiconductor substrate 100), the p-type GaN cap layer 108 and the p-type Al _y Ga ₁ Etching having a convex total film thickness distribution in which the total film thickness with the _-y N cladding layer 107 is thick at the center of the surface of the p-type Al _x Ga _1-x N etching marker layer 200 and thin at the periphery Prepare the previous semiconductor laser structure. It is assumed that this semiconductor laser structure is etched using this etching apparatus.

Here, the average value of the etching amount in the etched surface is A (nm), the in-plane nonuniformity is B (%), the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107. (The p _- type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 at various locations on the surface of the p-type Al _x Ga _1-x N etching marker layer 200) D (%) is defined as (maximum value−minimum value) / average value × 100 [%] using the maximum value, minimum value, and average value of the total film thickness. Further, as described above, the average value of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 on the surface of the p-type Al _x Ga _1-x N etching marker layer 200. Is L, and M is the average film thickness of the p-type Al _x Ga _1-x N etching marker layer 200.

Conventionally, when the film thickness ratio N <(in-plane non-uniformity of etching amount), that is, when M / L <B, the maximum value of the normalized emission intensity has decreased. However, the in-plane non-uniformity B of the etching amount is normalized by compensating for the non-uniformity D of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107. It becomes possible not to reduce the maximum value of the emission intensity. That is, in a place where the etching amount is large in the etched surface, the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 is increased, and the etching amount is increased in the etched surface. In a few places, the film thickness may be reduced. By doing so, the total film thickness is large at a portion where the etching amount is large, so that there is an effect of canceling the nonuniformity of the etching amount.

As described above, the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 is increased at a location where the etching amount is large in the etched surface, and the etching amount is increased in the etched surface. When the total film thickness is reduced in a small area, the etching amount in-plane non-uniformity and the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 are non-uniform. It is defined that there is a “positive correlation” with gender.

On the other hand, in a place where the etching amount is large in the etched surface, the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 is reduced, and the etching amount is small in the etched surface. In the case where the total film thickness is increased, the in-plane non-uniformity of the etching amount and the non-uniformity of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 Is defined as “having a negative correlation”.

In the present invention, the in-plane non-uniformity B of the etching amount and the non-uniformity D of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 are positive. It is characterized by having a correlation of The inventors of the present application have empirically found that when there is a positive correlation between the two, the in-plane non-uniformity B of the etching amount and the non-uniformity D of the total film thickness are as follows. When the relationship was satisfied, it was derived that the maximum fluctuation amount of the normalized emission intensity did not decrease.

  That is, it is found that the maximum fluctuation amount of the normalized emission intensity does not decrease when the film thickness ratio N = M / L> | (BD) | (where “|” represents an absolute value symbol) is satisfied. ing. In order to reduce the thickness of the etching marker layer, B> | (BD) | (“|” represents an absolute value symbol) from the necessary condition B> M / L, that is, D is 2B> It is necessary to satisfy the relational expression of D> 0.

That is, the in-plane non-uniformity B of the etching amount and the non-uniformity D of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 have a positive correlation, The in-plane non-uniformity B of the etching amount and the non-uniformity D of the total film thickness simultaneously satisfy the relational expression 2B>D> 0 and the relational expression M / L> | (BD) | In this case, the p-type Al _x Ga _1-x N etching marker layer 200 can be made thinner, and the plasma emission can be monitored without reducing the maximum fluctuation amount of the normalized emission intensity. can get. When etching is performed while satisfying the above conditions, even if in-plane non-uniformity of the etching amount exists, the uniformity of the remaining etching thickness is improved.

Next, the effects of the present invention will be described in detail using specific examples. FIG. 5 shows a structure of a p-type GaN cap layer 108 and a p-type Al _y Ga _1-y N cladding layer 107 using a semiconductor laser structure of the present invention employing a p-type Al _x Ga _1-x N etching marker layer 200. It is a graph which shows the maximum variation | change_quantity of the normalized light emission intensity | strength of Al when the nonuniformity of a total film thickness is changed from 0% to 21%.

In FIG. 5, there is a positive difference between the in-plane non-uniformity of the etching amount and the non-uniformity of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107. Correlation is obtained. Further, the in-plane non-uniformity of the etching amount is 6%, the average film thickness of the p-type Al _y Ga _1-y N cladding layer 107 is 500 nm, the average film thickness of the p-type GaN cap layer 108 is 20 nm, and p-type Al _x The average film thickness of the Ga _1-x N etching marker layer 200 was 20 nm. The film thickness ratio N is 3.8%.

In FIG. 5, when the non-uniformity of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 is in the range of 3% to + 10%, the maximum fluctuation amount of the normalized emission intensity It can be seen that the same value as in the case where the in-plane non-uniformity of the etching amount is 0% is obtained. In other words, by controlling the non-uniformity of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107, the in-plane non-uniformity of the etching amount is more than the film thickness ratio N. Can be obtained, the maximum fluctuation amount corresponding to 0% in-plane non-uniformity of the etching amount can be obtained.

In other words, the thickness of the p-type Al _x Ga _1-x N etching marker layer 200 can be reduced without reducing the maximum fluctuation amount of the normalized emission intensity even when in-plane nonuniformity of the etching amount exists. It can be made thinner.

It is not required that the non-uniformity of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 be completely coincident with the in-plane non-uniformity of the etching amount. The nonuniformity of the total film thickness of the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer 107 is compensated for at least by the difference between the in-plane nonuniformity of the etching amount and the film thickness ratio N. That's fine.

That is, for example, in the case of FIG. 5 where the in-plane non-uniformity of the etching amount is 6% and the film thickness ratio N is 3.8%, the p-type GaN cap layer 108 and the p-type Al _y Ga _1-y N cladding layer. Even if the non-uniformity of the total film thickness with 107 is not 6%, the in-plane non-uniformity of the etching amount is 0 if the minimum is compensated for 2.2% (= 6% -3.8%). %, The maximum fluctuation amount of the normalized luminescence intensity is obtained.

<D. Etching stop method>
Next, a method for stopping etching using plasma emission in this embodiment will be described.

During the etching, the emission intensity of the Al plasma emission wavelength (for example, 396.2 nm) and the emission intensity of the Ga plasma emission wavelength (for example, 417.2 nm) are observed. Etching is stopped when a change in emission intensity corresponding to the etching reaching the p-type Al _x Ga _1-x N etching marker layer 200 is detected.

  The light emission intensity of Al and the light emission intensity of Ga begin to fluctuate when layers having different Al and Ga compositions are exposed as etching progresses. When all the etched surfaces have the same composition, the light emission intensity does not change and a constant light emission intensity is exhibited. That is, the etching is stopped using a change in emission intensity corresponding to a change in the composition of the film as a trigger.

  In this embodiment, the sum of the absolute value of the Al plasma emission intensity change and the absolute value of the Ga plasma emission intensity change is obtained to capture the emission intensity change. As a result, it is possible to detect light emission with less intensity change as compared with the case where etching is stopped by measuring the light emission intensity change of only one of Al and Ga.

When etching the p-type Al _y Ga _1-y N cladding layer 107 and stopping the etching at the p-type Al _x Ga _1-x N etching marker layer 200, the p-type Al _y Ga _1-y N cladding layer 107 The plasma emission intensity Pa of Al is Pa = αy, and the plasma emission intensity Pb of Ga is Pb = β (1-y). Further, the Al plasma emission intensity Pc of the p-type Al _x Ga _1-x N etching marker layer 200 is Pc = αx, and the Ga plasma emission intensity Pd is Pd = β (1-x). Here, α and β are constants determined by the element and the plasma state.

When etching proceeds from the p _- type Al _y Ga _1-y N clad layer 107 to the p-type Al _x Ga _1-x N etching marker layer 200, the change in Al emission intensity is αy−αx = α (y−x ), The Ga emission intensity change is β (1-y) −β (1-x) = − β (y−x). That is, the absolute values of the change in emission intensity of Al and Ga are α times and β times (y−x), respectively. On the other hand, the sum of the absolute values of the emission intensity changes of Al and Ga is (α + β) times (y−x), and a change larger than the emission intensity change of only one of Al and Ga can be obtained.

<E. Specific manufacturing method of semiconductor laser element>
The following is an application example of the principle of the present invention described above to actual manufacture of a nitride-based semiconductor laser device.

FIG. 6 is a cross-sectional view showing one step of the method for manufacturing the nitride semiconductor laser according to the present embodiment, and is a cross-sectional view perpendicular to the resonance direction of the resonator. First, an n-type GaN substrate 100 having a thickness of 400 μm, which is a semiconductor substrate, is prepared, and its surface is previously cleaned by thermal cleaning or the like. Thereafter, the n-type GaN buffer layer 20 is grown on the surface of the substrate 100 at a growth temperature of, for example, 1000 ° C. by MOCVD (Metal Organic Chemical Vapor Deposition). Thereafter, the n-type AlGaN cladding layer 21, the n-type GaN light guide layer 22, the undoped InGaN light guide layer 23, and the undoped In _z Ga ₁ -z N / In _w Ga _{1 -w} N multiple quantum well activity are also formed by MOCVD. Layer 24, undoped InGaN optical waveguide layer 25, p-type AlGaN electron barrier layer 26, p-type GaN light guide layer 27, 10-nm thick p-type Al _0.2 Ga _0.8 N etching marker layer 200, 500-nm thick p-type Al _0.05 A Ga _0.95 N clad layer 28 and a p-type GaN contact layer 29 having a thickness of 20 nm are sequentially formed.

  Here, the growth temperature of these layers is, for example, 1000 ° C. for the n-type AlGaN cladding 21 and the n-type GaN optical guide layer 22, 740 ° C. from the undoped InGaN optical guide layer 23 to the undoped InGaN optical waveguide layer 25, and p-type AlGaN electrons. The temperature from the barrier layer 26 to the p-type GaN contact layer 29 is set to 1000 ° C.

In addition, since InGaN which requires low temperature growth is not used as the etching marker layer 200, it is possible to grow from the p-type AlGaN electron barrier layer 26 to the p-type GaN contact layer 29 at the same temperature, and no growth interruption occurs. . Therefore, the high-quality p-type Al _0.05 Ga _0.95 N clad layer 28 and the p-type GaN contact layer 29 with few crystal defects can be formed.

  Next, a resist film PR is applied to the entire surface of the substrate after crystal growth, and a resist pattern having a predetermined shape corresponding to the ridge structure is formed by lithography. The resist pattern includes a ridge pattern PRa and a peripheral pattern PRb.

Next, using this resist film PR as a mask, the p-type GaN contact layer 29 and the p-type Al _0.05 Ga _0.95 N clad layer 28 are observed by RIE (Reactive ion etching), for example, while observing plasma emission, while FIG. Etching is performed as shown in FIG. That is, the p-type GaN contact layer 29 and the p-type Al _0.05 Ga _0.95 N cladding layer 28 are combined to be etched layers, and the plasma emission intensity changes corresponding to the composition of the p-type Al _0.2 Ga _0.8 N etching marker layer 200. Accordingly, dry etching is stopped. By this etching, the ridge 30 to be an optical waveguide structure is produced. As this RIE etching gas, for example, a chlorine-based gas is used.

In the etching apparatus used in this embodiment, the in-plane non-uniformity of the etching amount is 6%. Therefore, the nonuniformity of the total film thickness of the p-type Al _0.05 Ga _0.95 N clad layer 28 and the p-type GaN contact layer 29 was controlled in the range of 5% to 7%. Further, the non-uniformity of the total film thickness has a positive correlation with the in-plane non-uniformity of the etching amount.

With respect to the emission spectrum, the emission intensity of both the Al plasma emission wavelength and the Ga plasma emission wavelength is measured, and the difference between the Al plasma emission intensity change ΔA and the Ga plasma emission intensity change ΔG is used as an index. Etching was stopped when s reached the maximum value. After etching, the p-type GaN contact layer 29 and a part of the p-type Al _0.05 Ga _0.95 N cladding layer 28 are processed into a mesa shape with an etching depth defined by the p-type Al _0.2 Ga _0.8 N etching marker layer 200. It was.

In the present embodiment, the etching amount in the surface to be etched is not uniform, but the total film thickness of the p-type Al _0.05 Ga _0.95 N cladding layer 28 and the p-type GaN contact layer 29 is distributed, so that the p-type Etching could be stopped in the Al _0.2 Ga _0.8 N etching marker layer 200. Therefore, the etching residue, which is the distance from the surface of the undoped In _z Ga ₁ -z N / In _w Ga _{1 -w} N multiple quantum well active layer 24 to the surface to be etched in the p-type Al _0.2 Ga _0.8 N etching marker layer 200 The thickness was about 10 nm uniform and good accuracy was obtained.

This is because the uniformity of the remaining etching thickness is combined with the in-plane non-uniformity of the etching amount and the non-uniformity of the total film thickness of the p-type Al _0.05 Ga _0.95 N cladding layer 28 and the p-type GaN contact layer 29. It shows that it was able to improve by. When the distribution of the total film thickness of the p-type Al _0.05 Ga _0.95 N cladding layer 28 and the p-type GaN contact layer 29 is not controlled, even if the distribution of the total film thickness is zero, it is about 30 nm depending on the etching amount distribution. In-plane variation of the etching residual thickness occurs. In addition, the maximum fluctuation amount of the normalized emission intensity decreases, and it becomes difficult to detect emission. According to the etching method according to the present embodiment, the thickness of the p-type Al _x Ga _1-x N etching marker layer 200 can be reduced without reducing the maximum fluctuation amount of the normalized emission intensity, and the remaining etching thickness. It is possible to improve the in-plane uniformity.

Next, while leaving the resist pattern used as a mask, for example, a CVD method, a vacuum evaporation method, a sputtering method or the like is again applied to the entire surface of the substrate, as shown in FIG. 8, for example, a SiO ₂ film having a thickness of 0.2 μm. A film 31 is formed. Then, as shown in FIG. 9, so-called lift-off is performed to remove the SiO ₂ film on the ridge 30 simultaneously with the resist removal.

Further, as shown in FIG. 10, a resist pattern 33 is formed only on the ridge by lithography, and then an SiO ₂ film 32 as an insulating film is formed on the entire surface of the substrate. Then, as shown in FIG. 11, simultaneously with the removal of the resist pattern 33, the SiO ₂ film 32 on the ridge 30 is removed. As a result, an opening 32 a is formed on the ridge 30.

  Next, as shown in FIG. 12, the p-type electrode 34 is formed. The p-type electrode 34 has a structure in which, for example, Pt and Au films are sequentially stacked. After sequentially forming a Pt and Au film on the entire surface of the substrate of FIG. 11 by, for example, vacuum deposition, a pattern of the p-type electrode 34 is formed on the surface by resist coating and lithography and wet etching or dry etching. The p-type electrode 34 is in contact with the p-type GaN contact layer 29 on the ridge 30.

  Next, after the substrate back surface is ground and thinned, the n-type electrode 35 is formed. The n-type electrode 35 has a structure in which Ti and Al films are sequentially laminated. Ti and Al films are sequentially formed on the entire back surface of the substrate by vacuum deposition. Thereafter, an alloying process for bringing the n-type electrode 35 into ohmic contact is performed.

  Thereafter, the substrate is processed into a bar shape by cleaving or the like to form both end faces of the resonator, and end faces are coated on the end faces of the resonator, and then the bar is chipped by cleaving or the like. As described above, a nitride-based semiconductor laser is manufactured.

In the nitride-based semiconductor laser described in the present embodiment, the forbidden band width of the p _- type Al _x Ga _1-x N etching marker layer 200 is larger than the forbidden band width of the p-type Al _y Ga _1-y N cladding layer 28. Therefore, a p-type Al _x Ga _1-x N layer (x> y) is used as the etching marker layer 200. Thereby, the optical loss due to the insertion of the p-type Al _x Ga _1-x N etching marker layer 200 is suppressed as compared with the case of the p-type In _x Ga _1-x N etching marker layer. It becomes possible to oscillate. That is, the oscillation threshold current value can be reduced.

Further, the p-type Al _y Ga _1-y N cladding layer 28 and the p-type Al _x Ga _1-x N etching marker layer 200 can be crystal-grown at the same growth temperature, and p-type Al _y causing optical loss. Generation of crystal defects in the Ga _1-y N cladding layer 28 is suppressed. As a result, the oscillation threshold current value can be reduced.

In this embodiment, the p-type Al _0.2 Ga _0.8 N etching marker layer 200 is inserted between the p-type GaN light guide layer 27 and the p-type Al _0.05 Ga _0.95 N cladding layer 28. First, it is clear from the principle of the invention that the uniformity of the film thickness after etching, which is an effect of the present invention, can be obtained.

For example, when the p-type AlGaN electron barrier layer 26 is used as an etching marker layer, it is not necessary to insert the p-type Al _0.2 Ga _0.8 N etching marker layer 200. Therefore, compared to the case where the etching marker layer 200 is added, the substrate resistance is not increased, and the lateral spread of the current is not further increased.

According to the method of manufacturing a semiconductor device according to the present embodiment, the p-type GaN contact layer 29 and the p-type Al _0.05 Ga _0.95 N clad layer 28 that are to be etched are etched at a location where the etching amount is large. The film thickness of the layer to be etched is thin, and the film thickness of the layer to be etched is thinned at a location where the etching amount is small within the etching target surface of the layer to be etched. Since the film thickness of the layer to be etched is large at the portion where the etching amount is large, and the film thickness of the layer to be etched is small at the portion where the etching amount is small, there is an effect of canceling the nonuniformity of the etching amount. The relational expression 2B>D> 0 and N = M / L> | (BD) | is simultaneously satisfied. Thereby, the film thickness of the p-type Al _0.2 Ga _0.8 N etching marker layer 200 can be made thinner, and the plasma emission can be monitored without reducing the maximum fluctuation amount of the emission intensity. Even in the case where there is in-plane non-uniformity in the etching amount, the etching target in the p-type Al _0.2 Ga _0.8 N etching marker layer 200 is etched from a predetermined position under the p-type Al _0.2 Ga _0.8 N etching marker layer 200. It is possible to improve the uniformity of the remaining etching thickness that is the distance to the surface. Therefore, it is possible to realize a method for manufacturing a semiconductor device using an etching marker layer in which the etching depth can be precisely and easily controlled without deteriorating element characteristics.

Further, according to the method of manufacturing a semiconductor device according to the present embodiment, the etching marker layer is the p-type Al _x Ga _1-x N etching marker layer 200, and the etching target layer is formed on the etching marker layer. The p-type Al _y Ga _1-y N cladding layer 28 (x> y) is included. Therefore, the forbidden band width of the p-type Al _x Ga _1-x N etching marker layer 200 is wider than the forbidden band width of the p-type Al _y Ga _1-y N cladding layer 28 formed on the etching marker layer 200. The optical loss due to the insertion of the p-type Al _x Ga _1-x N etching marker layer 200 is suppressed as compared with the case of the p-type In _x Ga _1-x N etching marker layer. Therefore, it is possible to oscillate at a current value lower than that in the prior art. That is, the oscillation threshold current value can be reduced. Further, the p-type Al _x Ga _1-x N etching marker layer 200 and the p-type Al _y Ga _1-y N cladding layer 28 can be crystal-grown at the same growth temperature, and p-type Al _y causing optical loss. Generation of crystal defects in the Ga _1-y N cladding layer 28 is suppressed. As a result, the oscillation threshold current value can be reduced.

  By using the method for manufacturing a nitride-based III-V compound semiconductor device described in this embodiment, the etching depth can be easily controlled, and the laser oscillation threshold current value is reduced. A group V compound semiconductor light emitting device (semiconductor laser device) can be manufactured.

It is a figure which shows the structure in the middle of manufacture of the semiconductor laser using the nitride type III-V compound semiconductor. It is the figure which showed the normalized light emission intensity | strength of In at the time of an etching with etching time. It is a figure which shows the experimental result which plotted the normalized light emission intensity | strength of In with respect to the etching time according to the value of the in-plane nonuniformity of the etching amount in each place in the to-be-etched surface. A graph in which the maximum fluctuation amount of the normalized emission intensity of Al when the semiconductor laser structure employing the p-type Al _x Ga _1-x N etching marker layer is etched is plotted against the in-plane nonuniformity of the etching amount It is. Maximum fluctuation amount of normalized emission intensity of Al when the non-uniformity of the total film thickness of the cap layer and the cladding layer is changed for the semiconductor laser structure using the p-type Al _x Ga _1-x N etching marker layer It is a graph which shows. It is sectional drawing which shows 1 process of the manufacturing method of the semiconductor laser element concerning this invention. It is sectional drawing which shows 1 process of the manufacturing method of the semiconductor laser element concerning this invention. It is sectional drawing which shows 1 process of the manufacturing method of the semiconductor laser element concerning this invention. It is sectional drawing which shows 1 process of the manufacturing method of the semiconductor laser element concerning this invention. It is sectional drawing which shows 1 process of the manufacturing method of the semiconductor laser element concerning this invention. It is sectional drawing which shows 1 process of the manufacturing method of the semiconductor laser element concerning this invention. It is sectional drawing which shows 1 process of the manufacturing method of the semiconductor laser element concerning this invention.

Explanation of symbols

100 semiconductor substrate, 101 GaN low temperature layer, 102 n-type GaN buffer layer, 103 n-type AlGaN cladding layer, 104 n-type GaN light guide, 105 InGaN strained quantum well layer, 106 p-type GaN light guide layer, 107 p-type AlGaN cladding Layer, 108 p-type GaN cap layer, 200 p-type AlGaN etching marker layer, 201 oxide film layer, 20 n-type GaN buffer layer, 21 n-type AlGaN clad layer, 22 n-type GaN light guide layer, 23 and doped InGaN light guide layer , 24 Andopto In _z Ga ₁ -z N / In _w Ga _{1 -w} N multiple quantum well active layer, 25 Andopto InGaN optical waveguide layer, 26 p-type AlGaN electron barrier layer, 27 p-type GaN optical guide layer, 28 p-type AlGaN cladding layer, 29 p-type GaN contact layer, 30 ridge, 1,32 SiO ₂ film, 34 p-type electrode, 35 n-type electrode.

Claims (3)

(A) forming an etching marker layer having a surface above the surface of the semiconductor substrate having a surface;
(B) forming a layer to be etched on the surface of the etching marker layer;
(C) a step of selectively etching the layer to be etched by dry etching using plasma,
In the step (c), the dry etching is stopped according to a change in plasma emission intensity corresponding to the composition of the etching marker layer,
In the step (b), the thickness of the layer to be etched is thick at a place where the etching amount is large in the etched surface of the layer to be etched, and the area at the place where the etching amount is small in the etched surface of the layer to be etched. The thickness of the layer to be etched is made thin,
Using the maximum value, the minimum value, and the average value of the etching amount at various points in the etching target surface of the etching target layer, the value of (maximum value−minimum value) / average value × 100 [%] is set within the etching amount surface. Defined as non-uniformity B,
A value of (maximum value−minimum value) / average value × 100 [%] using the maximum value, the minimum value, and the average value of the film thickness of the layer to be etched at various points on the surface of the etching marker layer It is defined as the non-uniformity D of the thickness of the etching layer,
The average value of the thickness of the layer to be etched on the surface of the etching marker layer is L,
The average thickness of the etching marker layer is M,
A value obtained by dividing M by L is a film thickness ratio N,
2B>D> 0 and N> | (BD) | (where “|” represents an absolute value symbol). A method of manufacturing a semiconductor device according to claim 1,
The etching marker layer is a p-type Al _x Ga _1-x N etching marker layer,
The method for manufacturing a semiconductor device, wherein the layer to be etched includes at least a p-type Al _y Ga _1-y N layer (x> y) formed on the etching marker layer. A semiconductor device manufactured using the method for manufacturing a semiconductor device according to claim 1.

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