JP2005317914A - Semiconductor element and manufacturing method of semiconductor laser chip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor element, capable of simply and stably forming an opening to a material film, such as a dielectric film. <P>SOLUTION: The manufacturing method of the semiconductor element includes a step (1) of covering a substrate 3, including a pair of grooves 7 extended substantially in parallel and a projection 9 demarcated by the pair of the grooves 7 with the material film 13, a step (3) of forming a first photo resist layer 17 made of a first photo resist onto the obtained substrate so as to fill the groove parts 7, a step (4) of covering the obtained substrate with a second photoresist layer 19 made of a second photoresist, a step (5) of removing part of the first resist layer 17 and the second photoresist layers 19 so as to expose part of the material film 13 on an upper face of the projection 9 to form a mask layer, and a step (6) of using the mask layer, to remove the exposed part of the material film 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor device and a method for manufacturing a semiconductor laser chip.

  FIG. 5 is a cross-sectional view showing the structure of a conventional semiconductor laser chip 51. The semiconductor laser chip 51 includes a substrate 53 having a laminated film including an active layer. The substrate 53 is formed with a pair of groove portions (extending in the direction perpendicular to the paper surface) 57 extending substantially in parallel. On the substrate 53, a dielectric film 63 having an opening 61 is formed above the convex portion 59 defined by these groove portions 57. Furthermore, an electrode 65 is formed on the entire surface of the obtained substrate. The current from the electrode 65 flows into the active layer through the opening 61 and the protrusion 59. Further, the portion 66 other than the groove portion and the convex portion protects the convex portion 59 from mechanical damage and the like.

  In such a semiconductor laser chip manufacturing process, the opening 61 of the dielectric film 63 is formed as follows (see, for example, Patent Document 1).

  First, the dielectric film 63 is formed on the entire surface of the substrate 53 having a pair of grooves 57 extending substantially in parallel.

  Next, a photoresist layer 67 made of a photoresist is formed on the entire surface of the obtained substrate by spin coating, and the obtained substrate is prebaked to obtain the structure shown in FIG. Here, in order to completely fill the groove portion 57, a photoresist having a low viscosity is usually used. When a low-viscosity photoresist is used, a thin photoresist layer 67 is formed on the surface of the substrate 53 other than the grooves 57.

  Next, the photoresist layer 67 is exposed to an upper portion of the projection 59, and the photoresist layer 67 is developed to obtain the structure shown in FIG. 6B. Here, the exposure of the photoresist layer 67 is usually performed over a range slightly wider than the convex portion 59 (indicated by an arrow in FIGS. 6A and 6B). This is because it is necessary to consider misalignment of the photomask or variation in the position of the convex portion 59 in the wafer surface.

Next, using the photoresist layer 67 as a mask, the dielectric film 63 is etched to remove the photoresist 67, and an electrode 65 is formed on the entire surface of the obtained substrate, thereby obtaining the structure shown in FIG.
JP 2002-217493 A

  However, the range in which the photoresist layer 67 is removed in the development process of the photoresist layer 67 strongly depends on the intensity or time of exposure or the time of development. In addition, the intensity or time of exposure or the development time usually varies, and it is difficult to eliminate this variation.

  For example, when the development time becomes longer than a predetermined value due to variations, the photoresist layer is removed in a wider range than usual and deeply. Therefore, a portion (hereinafter referred to as a “corner portion of the dielectric film”) 63a on the edge of the groove portion 57 and facing the convex portion 59 of the dielectric film 63 may be exposed. This state is shown in FIG. FIG. 7 corresponds to FIG.

  In this state, when the dielectric film 63 is etched using the photoresist layer 67 as a mask, the etching of the dielectric film 63 also proceeds from the corner portion 63a of the dielectric film 63, and the dielectric film 63 in that portion. Is removed. Thereafter, the state after further removing the photoresist layer 67 is shown in FIG.

  In this state, when the electrode 65 is formed and a current is passed, the current flows not only from the convex portion 59 but also from the edge 57a of the groove portion 57 that faces the convex portion 59 (dotted arrow in FIG. 8). This leads to variations in the characteristics of the semiconductor laser chip.

  The present invention has been made in view of such circumstances, and provides a method for manufacturing a semiconductor element capable of forming an opening in a material film such as a dielectric film easily and stably. is there.

  According to a first aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising: (1) covering a substrate having a pair of grooves extending substantially in parallel and a convex section defined between the pair of grooves with a material film; A) forming a first photoresist layer made of a first photoresist on the obtained substrate so as to fill the groove; and (3) making the obtained substrate a second photoresist layer made of a second photoresist. (4) removing a part of the first and second photoresist layers to expose a portion of the material film on the upper surface of the convex portion to form a mask layer; and (5) the mask. A step of removing the exposed portion of the material film using the layer;

  According to a second aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising: (1) covering a substrate having a pair of grooves extending substantially in parallel and a convex section defined between the pair of grooves with a material film; (2) The obtained substrate is covered with a third photoresist layer made of a third photoresist, and (3) a portion of the material film on the top surface of the convex portion and a portion on the side surface of the convex portion are exposed. And removing a part of the third photoresist layer so as to cover the portion of the material film on the edge of the groove and facing the convex portion, and (4) obtaining the obtained substrate by Cover with a fourth photoresist layer made of photoresist, and (5) remove a portion of the fourth photoresist layer to expose a portion of the material film on the upper surface of the convex portion to form a mask layer (6) The mask layer is used to remove the exposed portion of the material film. Comprising the step of.

  According to the first invention, the groove portion is filled with the first photoresist, and the obtained substrate is covered with the second photoresist layer made of the second photoresist. Since the photoresist layer has a two-layer structure, the first photoresist layer need not be formed thick. Therefore, the first photoresist having a relatively low viscosity can be used, and the groove can be reliably filled. In addition, since the groove is filled with the first photoresist layer, the second photoresist layer can be formed using a photoresist having a relatively high viscosity. As a result, the second photoresist layer is It can be formed thick. According to the first invention, a thick photoresist layer can be formed while reliably filling the groove portion. A portion (corner portion of the material film) that is on the edge of the groove and faces the convex portion is not exposed (or is less likely to be exposed than in the past). Therefore, according to the first invention, the opening can be formed in the material film such as the dielectric film easily and stably.

  According to the second invention, first, a third photoresist layer is formed with a third photoresist. As the third photoresist, one having a high viscosity can be used. If a resist having a high viscosity is used, the surface of the third photoresist layer may be uneven due to the influence of the groove. In the conventional method, if there is unevenness, there is a problem that variation in the development process of the photoresist becomes large. However, in the method of the present invention, there is no problem even if there is unevenness. Next, for example, the upper portion of the convex portion is exposed strongly and long. When exposed in this way, the development of the third photoresist layer proceeds selectively in the direction perpendicular to the substrate, and the portion of the material film on the top surface of the convex portion and the portion on the side surface of the convex portion are exposed. In addition, a part of the third photoresist layer can be removed so as to cover the corner portion of the material film. Next, a fourth photoresist layer made of a fourth photoresist is formed so as to cover the exposed protrusion. Since the corner portion of the material film is protected by the third photoresist layer, the fourth photoresist layer does not need to be formed thick, and the fourth photoresist can use a relatively low viscosity. . In this case, the fourth photoresist layer can be formed thin, and the space between the convex portion and the third photoresist layer can be reliably filled. In this state, for example, by developing the fourth photoresist layer, the fourth photoresist layer can be removed so that a portion of the material film on the upper surface of the convex portion is exposed. According to the second invention, since the corner portion of the material film is protected by the third photoresist layer, the corner portion of the material film is not exposed (or is less likely to be exposed than before). Therefore, according to the second invention, an opening can be formed in a material film such as a dielectric film easily and stably.

1. First Embodiment A method for manufacturing a semiconductor device according to a first embodiment is as follows: (1) A substrate having a pair of grooves extending substantially in parallel and a convex section defined between the pair of grooves. (2) A first photoresist layer made of the first photoresist is formed on the obtained substrate so as to fill the groove, and (3) the obtained substrate is made of the second photoresist. (4) A mask layer is formed by removing a part of the first and second photoresist layers so that a portion of the material film on the upper surface of the convex portion is exposed. (5) A step of removing the exposed portion of the material film using the mask layer is provided.

1-1. A process of covering a substrate having a pair of grooves extending substantially in parallel and a convex section defined between the pair of grooves with a material film (that is, forming a material film covering the substrate). A single layer semiconductor substrate such as a compound semiconductor substrate or an elemental semiconductor substrate such as Si, or a laminated semiconductor substrate in which these are laminated. The laminated semiconductor substrate includes, for example, a compound semiconductor substrate in which a lower clad layer, an active layer, and an upper clad layer are laminated. Such a substrate is used, for example, for manufacturing a semiconductor laser chip (hereinafter referred to as a “semiconductor laser chip substrate”).

  A pair of grooves extending substantially in parallel are formed in the substrate. In the semiconductor laser chip substrate, for example, an upper clad layer is formed. The shape of the groove may be rectangular or V-shaped in cross section. At the edge of the groove, the width of the groove is preferably about 5 to 30 μm. This is because within this range, it is possible to reduce mechanical damage to the convex portion defined between the pair of grooves when the substrate is divided. The depth of the groove is preferably about 2 to 4 μm. Within this range, good laser characteristics can be obtained. The substrate has a convex portion that is partitioned between the pair of grooves. The width of the convex portion is preferably about 2 to 3 μm μm. Within this range, good laser characteristics can be obtained. The groove can be formed by patterning the substrate using, for example, photolithography and etching techniques.

  The material film is preferably formed on the entire surface of the obtained substrate. Further, the material film covers at least the protrusions and the inside and the edge of each groove. The material film is made of a dielectric material or the like. The dielectric is made of silicon oxide or silicon nitride. The material film may be a semiconductor film that blocks current. For example, when the substrate is p-type and the ridge portion is an n-type semiconductor, the material film can be a p-type semiconductor film, and vice versa. In such a case as well, the material film functions so as to allow current to flow only through the convex portion sandwiched between the pair of groove portions. The material film can be formed by a CVD method or the like. The material film preferably has a thickness of about 200 to 400 nm. This is because the convex portion can be sufficiently covered within this range, and the role as a light confinement layer can be achieved.

1-2. A step of forming a first photoresist layer made of a first photoresist so as to fill the groove on the obtained substrate. The first photoresist preferably has a viscosity of 4 to 7 mm ² / s. It is because a groove part can be reliably filled if it is this range. Here, “viscosity” is measured by the Canon Fuenske viscometer method. The first photoresist is preferably a positive type. The first photoresist is spin-coated, for example, to form a first photoresist layer. The rotation speed in spin coating is preferably 2500 to 3500 rpm. This is because the groove portion can be reliably filled and the first photoresist layer can be formed flat within this range. Specifically, for example, Rohm and Haas Electronic Materials Co., Ltd. MICROPOSIT S1805 can be used for the first photoresist. It is preferable to pre-bake the first photoresist layer after forming the first photoresist layer. In this case, the shape of the first photoresist layer is stabilized.

1-3. Step of covering the obtained substrate with a second photoresist layer made of a second photoresist The second photoresist preferably covers the entire surface of the obtained substrate. The second photoresist preferably has a higher viscosity than the first photoresist. In this case, the second photoresist layer is easily formed thick. However, the viscosity of the second photoresist may be equal to or lower than that of the first photoresist, and the same second photoresist as the first photoresist may be used. Even in this case, the effect of the present invention can be obtained by, for example, pre-paying the first photoresist layer after filling the groove with the first photoresist and forming the second photoresist layer thereon. Because. Further, a photoresist layer composed of one or more layers may be formed on the second photoresist layer. Pre-baking may be performed each time each photoresist layer is formed. In this case, the photoresist layer can be formed to be thicker. The second photoresist preferably has a viscosity of 70 to 100 mm ² / s. This is because within this range, the second photoresist layer can be formed with a sufficient thickness and flatness. The second photoresist layer preferably has a thickness of 2 to 4 μm. This is because the outer edge of the groove can be reliably covered within this range. The second photoresist is preferably a positive type. The second photoresist is spin-coated, for example, to form a second photoresist layer. The rotation speed in spin coating is preferably 2500 to 3500 rpm. This is because within this range, the second photoresist layer can be formed with a sufficient thickness and flatness. Specifically, for example, Rohm and Haas Electronic Materials Co., Ltd. MICROPOSIT S1830 can be used for the second photoresist. It is preferable to pre-bake the second photoresist layer after forming the second photoresist layer. In this case, the shape of the second photoresist layer is stabilized.

  Conventionally, when a photoresist layer is formed on a substrate having a groove, if a photoresist having a high viscosity is used, the photoresist layer is not formed flat. According to the present invention, first, the groove portion is filled with the first photoresist, and then the second photoresist layer made of the second photoresist is formed. As a result, the second photoresist layer can be formed thick.

1-4. A step of forming a mask layer by removing a part of the first and second photoresist layers to expose a portion of the material film on the upper surface of the convex portion. The two photoresist layers can be formed by exposing the upper part of the convex portion and developing the first and second photoresist layers (when the photoresist is a positive type). The exposure is preferably performed at an intensity of 25 to 50 mJ / cm ² and a time of ² to 4 seconds. In this range, only the upper portions of the first and second photoresist layers are exposed, and the lower layers are not exposed. The exposure is preferably performed on the upper part of the first and second photoresist layers and the vicinity thereof. In this case, only the vicinity of the convex portion is developed and the outer edge portion of the groove portion is not developed. When development is performed after such exposure, the exposed portions of the first and second photoresist layers are dissolved, and the portion of the material film on the upper surface of the convex portion is exposed. According to the present invention, since the second photoresist layer can be formed thick and flat, even if the intensity or time of exposure or the time of development varies, the corner portion of the material film is It is not exposed (or it is harder to be exposed than before). It is preferable to post-bake the first and second photoresist layers after the exposure of the first and second photoresist layers. In this case, the shape of the first and second photoresist layers is stabilized.

  The mask layer may be formed by exposing portions of the first and second photoresist layers other than above the convex portions and developing the first and second photoresist layers (the photoresist is negative). Type).

1-5. Step of removing the exposed portion of the material film using the mask layer The step of removing the exposed portion of the material film can be performed, for example, by dry etching or wet etching. Dry etching can be performed with an RIE (reactive ion etching) apparatus, and wet etching can be performed with a hydrofluoric acid-based solution. As described above, even when the intensity or time of exposure or the time of development varies, the corner portion of the material film is not exposed (or is less likely to be exposed than before), so the material of that portion The film is not removed. Therefore, according to the present invention, the portion of the material film on the upper surface of the convex portion can be easily and easily removed.

  Further, when the method of the present invention is used, the opening of the ridge portion of the semiconductor laser chip can be easily and easily formed, so that the yield of manufacturing the semiconductor laser chip can be improved and the reliability thereof can be improved.

2. Second Embodiment A method of manufacturing a semiconductor device according to a second embodiment is as follows: (1) A substrate having a pair of grooves extending substantially in parallel and a convex section defined between the pair of grooves is used. (2) The obtained substrate is covered with a third photoresist layer made of a third photoresist, and (3) a portion of the material film on the upper surface of the convex portion and a side surface of the convex portion. A part of the third photoresist layer is removed so as to cover a part which is exposed on the edge of the groove and faces the convex part, and (4) the obtained substrate is used as a fourth photo. Cover with a fourth photoresist layer made of resist, and (5) remove a part of the fourth photoresist layer to expose a portion of the material film on the upper surface of the convex portion to form a mask layer. (6) Using the mask layer, the exposed portion of the material film is removed. The process is provided.

  The description of the first embodiment is basically applicable to the second embodiment. Moreover, the said process (1) and (6) is the same as that of 1st Embodiment.

2-1. Step (2) Step of Covering the Obtained Substrate with a Third Photoresist Layer Comprising a Third Photoresist Preferably, the third photoresist covers the entire surface of the obtained substrate. The third photoresist covers at least the protrusions and the inside and edge of each groove. As the third photoresist, one having a high viscosity is preferably used. When a resist having a high viscosity is used, unevenness may occur on the surface of the third photoresist layer due to the influence of the groove. In the conventional method, if there is unevenness, there is a problem that variation in the development process of the photoresist becomes large. However, in the method of the present invention, there is no problem even if unevenness exists. Because, in the method of the present invention, first, a part of the third photoresist layer is removed so that a part of the material film on the upper surface of the convex part and a part on the side surface of the convex part are exposed, and then This is because a process for forming the fourth photoresist layer covering the convex portion is provided, and therefore, there is no problem even if the variation in the development process of the third photoresist layer becomes large.

The third photoresist preferably has a viscosity of 70 to 100 mm ² / s. This is because within this range, the third photoresist layer can be formed with a sufficient thickness. The third photoresist layer preferably has a thickness (distance from the upper surface of the convex portion to the upper surface of the third photoresist layer) of 2 to 4 μm. This is because the protrusion can be sufficiently covered within this range. The third photoresist is preferably a positive type. The third photoresist is spin-coated, for example, to form a third photoresist layer. The rotation speed in spin coating is preferably 2500 to 3500 rpm. This is because within this range, the third photoresist layer can be formed with a sufficient thickness. Specifically, for example, Rohm and Haas Electronic Materials Co., Ltd. MICROPOSIT S1830 can be used for the third photoresist. It is preferable to pre-bake the third photoresist layer after forming the third photoresist layer. In this case, the shape of the third photoresist layer is stable.

2-2. Step (3) Of the material film, a portion on the upper surface of the convex portion and a portion on the side surface of the convex portion are exposed, and on the edge portion of the groove portion of the material film, facing the convex portion. The step of removing a part of the third photoresist layer so as to cover the portion (the corner portion of the material film) This step is performed by, for example, exposing the upper portion of the third photoresist layer above the convex portion and the vicinity thereof, This can be done by developing the 3 photoresist layer (when the photoresist is positive). The exposure is preferably performed at a strength of 180 to 400 mJ / cm ² and a time of 15 to 30 seconds. This is because within this range, it is possible to reliably expose the upper part of the convex part and the lower part of the third photoresist layer in the vicinity thereof. The exposure here is stronger and longer than usual. When exposed in this way, the development of the third photoresist layer proceeds selectively in the direction perpendicular to the substrate, and the portion of the material film on the top surface of the convex portion and the portion on the side surface of the convex portion are exposed. In addition, a part of the third photoresist layer can be removed so as to cover the corner portion of the material film.

  The mask layer may be formed by exposing a portion of the third photoresist layer other than the upper portion of the convex portion and the vicinity thereof and developing the third photoresist layer (when the photoresist is a negative type). ).

2-3. Step (4) Step of Covering the Obtained Substrate with a Fourth Photoresist Layer Consisting of a Fourth Photoresist Preferably, the fourth photoresist layer covers the entire surface of the obtained substrate. The fourth photoresist layer fills a space between the convex portion and the fourth photoresist layer and covers at least the convex portion. The fourth photoresist layer is preferably formed thin. Specifically, the fourth photoresist layer is preferably formed with a thickness (distance from the upper surface of the convex portion to the upper surface of the fourth photoresist layer) of 0.2 to 0.5 μm. This is because, in this case, it is easy to remove by only development (without exposure) in a later step.
The fourth photoresist preferably has a lower viscosity than the third photoresist. In this case, the fourth photoresist layer is easily formed thin. However, the viscosity of the fourth photoresist may be equal to or higher than that of the third photoresist, and the fourth photoresist may be the same as the third photoresist. Even in this case, the effect of the present invention can be obtained by reliably protecting the corner portion of the material film with the third photoresist layer. The fourth photoresist preferably has a viscosity of 4 to 7 mm ² / s. This is because the space between the convex portion and the third photoresist layer can be reliably filled within this range. For example, the fourth photoresist is spin-coated to form a fourth photoresist layer. The rotation speed in spin coating is preferably 2500 to 3500 rpm. This is because within this range, the fourth photoresist layer can be formed thin, and the space between the convex portion and the third photoresist layer can be reliably filled. Specifically, for example, Rohm and Haas Electronic Materials Co., Ltd. MICROPOSIT S1805 can be used for the fourth photoresist.
Further, the solvent contained in the fourth photoresist is preferably less soluble in the third photoresist than the solvent contained in the third photoresist, and more preferably does not substantially dissolve the third photoresist. When the solvent contained in the fourth photoresist easily dissolves the third photoresist, there may be a problem that the third photoresist dissolves when the fourth photoresist is applied. When a photoresist is used, the above problem can be avoided. Therefore, in this case, the corner portion of the material film can be more reliably protected. For example, a deep recess 73 for element isolation between adjacent light emitting portions 71a and 71b, such as a monolithic two-wavelength laser shown in FIG. Even in the case of manufacturing a laser having the above, it is possible to reliably protect the corner portion of the material film (particularly the entrance portion 73a of the deep recess).
The fourth photoresist may be the same photosensitive type as the third photoresist (for example, either positive type or negative type), but a different photosensitive type (for example, the third photoresist is positive type and fourth type). It is preferred that the photoresist be negative or vice versa. This is because a positive type photoresist and a negative type photoresist usually use different solvents, and it is easy to configure so that the solvent contained in one photoresist does not dissolve the other photoresist.
It is preferable to pre-bake the fourth photoresist layer after forming the fourth photoresist layer. In this case, the shape of the fourth photoresist layer is stabilized.

2-4. Step (5) Step of forming a mask layer by removing a part of the fourth photoresist layer to expose a portion of the material film on the upper surface of the convex portion. The fourth photoresist layer is formed of the material The film is removed so that a portion on the upper surface of the convex portion is exposed. The mask layer thus formed can be used to remove a portion of the material film on the upper surface of the convex portion in a later step. According to the present invention, since the corner portion of the material film is reliably protected by the third photoresist layer, the corner portion of the material film is not exposed (or is less likely to be exposed than before). Therefore, according to the present invention, an opening can be formed in a material film such as a dielectric film easily and stably.

  A portion of the fourth photoresist layer is preferably removed by development of the fourth photoresist layer. In this case, since a photomask is not necessary, problems caused by misalignment can be prevented. Further, the entire surface of the fourth photoresist layer may be exposed in advance. In this case, a photomask is not necessary. When the fourth photoresist is a positive type, the removal of the fourth photoresist is facilitated by this method.

  FIG. 1 is a cross-sectional view illustrating the structure of the semiconductor laser chip 1 according to the first embodiment. The semiconductor laser chip 1 includes a substrate 3 having a laminated film including an active layer. In addition, the substrate 3 is formed with a pair of grooves (extending in the direction perpendicular to the paper surface) 7 extending substantially in parallel. On the substrate 3, a dielectric film 13 having an opening 11 is formed above the convex portion 9 partitioned by these groove portions 7. Furthermore, an electrode 15 is formed on the entire surface of the obtained substrate. The current from the electrode 15 flows into the active layer through the opening 11 and the protrusion 9. Further, the portion 16 other than the groove portion and the convex portion protects the convex portion 9 from mechanical damage and the like.

  Hereinafter, the manufacturing process of the semiconductor laser chip 1 according to the first embodiment will be described with reference to FIGS. 2 and 3 are cross-sectional views illustrating the manufacturing process of the semiconductor laser chip 1 according to the first embodiment.

  First, the board | substrate 3 provided with a pair of groove part 7 extended in parallel substantially and the convex part 9 divided by a pair of groove part 7 is prepared. The substrate 3 has a laminated film including an active layer. The groove section has a rectangular cross section. The width of the groove is 20 μm. The depth of the groove is 2 μm. The width of the convex portion is 3 μm. The groove is formed by patterning the substrate using photolithography and etching techniques.

  Next, the dielectric film 13 covering the obtained substrate is formed. The dielectric film 13 is made of silicon oxide and has a thickness of 300 nm. The dielectric film 13 is formed by a CVD method.

Next, a first photoresist layer 17 made of a first photoresist is formed on the obtained substrate so as to fill the groove portion 7, and the first photoresist layer 17 is pre-baked to obtain the structure shown in FIG. Get the structure shown. Rohm and Haas Electronic Material Co., Ltd. MICROPOSIT S1805 is used for the first photoresist. The first photoresist is positive and has a viscosity of 4.8 to 5.8 mm ² / s. The first photoresist layer 17 is formed by spin-coating the first photoresist. The rotation speed in the spin coat is 3000 rpm. Since the first photoresist layer 17 is formed to fill the groove, it is not necessary to form the first photoresist layer 17 thick on the surface 16 of the substrate 3 other than the groove 7. Therefore, the first photoresist layer 17 having a low viscosity can be used. The first photoresist layer 17 surely fills the groove, and the surface of the first photoresist layer 17 becomes flat.

Next, the obtained substrate is covered with a second photoresist layer 19 made of a second photoresist having a viscosity higher than that of the first photoresist, and the second photoresist layer 19 is pre-baked, as shown in FIG. Get the structure. Rohm and Haas Electronic Materials Co., Ltd. MICROPOSIT S1830 is used for the second photoresist. The second photoresist is a positive type and has a viscosity of 79 to 89 mm ² / s. The second photoresist layer 19 is formed by spin coating a second photoresist. The rotation speed in the spin coat is 3000 rpm. At this time, the second photoresist layer 19 has a thickness of about 3.5 μm. Since the groove portion 7 of the substrate 3 is already filled with the first photoresist layer 17 and flattened, the second photo resist is affected by the groove portion 7 of the substrate 3 even if a high viscosity is used for the second photoresist. Unevenness is not formed on the surface of the resist layer 19 (or the unevenness becomes smaller than that of the conventional one).

Next, as shown by the arrows in FIG. 2B, the first and second photoresist layers 17 and 19 are exposed above the projection 9 and in the vicinity thereof to expose the first and second photoresist layers 17. 19 is developed, and the first and second photoresist layers 17 and 19 are post-baked to obtain the structure shown in FIG. The exposure is performed at an intensity of 37 mJ / cm ² and a time of 3 seconds. When development is performed after such exposure, the exposed portions of the first and second photoresist layers 17 and 19 are dissolved, and the portion of the dielectric film 13 on the upper surface of the convex portion 9 is exposed. To do. In this embodiment, since the second photoresist layer 19 is formed to be thick and flat, even if the intensity or time of exposure or the time of development varies, the dielectric film 13 has the groove 7. The portion 13a (the corner portion 13a of the dielectric film 13) that is on the edge and faces the convex portion 9 is not exposed (or is less likely to be exposed than in the prior art) (see FIG. 3).

  Next, using the mask layer obtained by the development step, the exposed portion of the dielectric film 13 is removed, and the first and second photoresist layers 17 and 19 are completely removed. The electrode 15 is formed on the substrate, and the structure shown in FIG. 1 is obtained to complete the manufacture of the semiconductor laser chip of this example. The dielectric film 13 is removed by dry etching using an RIE (reactive ion etching) apparatus. As described above, even when the intensity or time of exposure or the time of development varies, the corner portion 13a of the dielectric film 13 is not exposed (or is less likely to be exposed than before). The portion of the dielectric film 13 is not removed (or harder to remove than in the prior art). Therefore, according to the present embodiment, a portion of the dielectric film 13 on the upper surface of the convex portion 9 can be easily and easily removed.

  Further, when the method of this embodiment is used, the opening 11 of the convex portion 9 of the semiconductor laser chip 1 can be easily and easily formed, so that the yield of manufacturing the semiconductor laser chip is improved and its reliability is improved. be able to.

  A method of manufacturing a semiconductor laser chip according to the second embodiment will be described with reference to FIG. FIG. 4 is a cross-sectional view showing the manufacturing process of the semiconductor laser chip of this example. Further, according to this embodiment, a semiconductor laser chip (see FIG. 1) having the same structure as that of Embodiment 1 can be manufactured.

  First, the board | substrate 3 provided with a pair of groove part 7 extended in parallel substantially and the convex part 9 divided by a pair of groove part 7 is prepared. The substrate 3 has a laminated film including an active layer. The groove section has a rectangular cross section. The width of the groove is 20 μm. The depth of the groove is 2 μm. The width of the convex portion is 3 μm. The groove is formed by patterning the substrate using photolithography and etching techniques.

  Next, the dielectric film 13 covering the obtained substrate is formed. The dielectric film 13 is made of silicon oxide. The dielectric film 13 has a thickness of 300 nm. The dielectric film 13 is formed by a CVD method.

Next, the obtained substrate is covered with a third photoresist layer 27 made of a third photoresist, and the third photoresist layer 27 is prebaked to obtain the structure shown in FIG. Rohm and Haas Electronic Materials Co., Ltd. MICROPOSIT S1830 is used for the third photoresist. The third photoresist is a positive type and has a viscosity of 79 to 89 mm ² / s. As described above, when the third photoresist layer 27 is formed using the third photoresist having a high viscosity, irregularities 27 a may be generated on the surface of the third photoresist layer 27. In the conventional method, if there is unevenness, there is a problem that variation in the developing process of the photoresist becomes large. However, in the method of this embodiment, even if the unevenness 27a is present, there is no problem. This is because in the method of this embodiment, first, the third photoresist layer 27 of the dielectric film 13 is exposed so that the portion 13b on the upper surface of the convex portion 9 and the portion 13c on the side surface of the convex portion 9 are exposed. Since there is a step of forming a fourth photoresist layer 29 that covers part of the convex portion 9 after removing a part thereof, there is no problem even if the variation in the development process of the third photoresist layer 27 increases. is there.

  The third photoresist layer 27 is formed by spin-coating a third photoresist. The rotation speed in the spin coat is 3000 rpm. At this time, the third photoresist layer 27 has a thickness of about 3.5 μm.

Next, the upper portion of the third photoresist layer 27 and the vicinity thereof are exposed, and the third photoresist layer 27 is developed so that the dielectric film 13 has an upper surface on the convex portion 9. A portion 13b and a portion 13c on the side surface of the convex portion 9 are exposed, and a part of the third photoresist layer 27 is removed so as to cover the corner portion 13a of the dielectric film 13, and post-baking is performed. The structure shown in 4 (b) is obtained. The exposure is performed with an intensity of 250 mJ / cm ² and a time of 20 seconds. The exposure here is stronger and longer than usual. When exposed in this way, development of the third photoresist layer 27 proceeds selectively in the direction perpendicular to the substrate 3.

Next, the obtained substrate is covered with a fourth photoresist layer 29 made of a fourth photoresist having a viscosity lower than that of the third photoresist, and the fourth photoresist layer 29 is pre-baked, as shown in FIG. Get the structure shown. Rohm and Haas Electronic Materials Co., Ltd. MICROPOSIT S1805 is used for the fourth photoresist. Its viscosity is 4.8-5.8 mm ² / s. The fourth photoresist layer 29 is formed by spin-coating a fourth photoresist. The rotation speed in the spin coat is 3000 rpm. As described above, when the fourth photoresist layer 29 is formed using the fourth photoresist having a low viscosity, the fourth photoresist layer 29 can be formed thinly, and between the convex portion 9 and the third photoresist layer 27. It is possible to reliably fill the space.

  Next, by developing the fourth photoresist layer 29, a part of the fourth photoresist layer 29 is removed, and the portion 13b of the dielectric film 13 on the upper surface of the convex portion 9 is exposed, so that FIG. The structure shown in 4 (d) is obtained. Since the fourth photoresist layer 29 is made of a negative photoresist and is not exposed before development, the thickness of the fourth photoresist layer 29 is reduced. By adjusting the development time, the development is completed in a time that the portion 13b of the dielectric film 13 on the upper surface of the convex portion 9 is exposed. According to the present embodiment, the corner portion 13a of the dielectric film 13 is surely protected by the third photoresist layer 27, so that the corner portion 13a of the dielectric film 13 is not exposed (or more than conventional). Difficult to expose.) Therefore, according to the present embodiment, the opening 11 can be formed in the dielectric film 13 easily and stably.

  Further, when the method of this embodiment is used, the opening 11 of the convex portion 9 of the semiconductor laser chip 1 can be formed easily and easily, so that the yield of manufacturing the semiconductor laser chip is improved and its reliability is improved. be able to.

  A method for manufacturing a semiconductor laser chip according to the third embodiment will be described with reference to FIG. 4A. FIG. 4A is a cross-sectional view showing the manufacturing process of the semiconductor laser chip of this example. Further, this example is similar to Example 2 and mainly differs in the type of photoresist used.

First, a pair of grooves 7 and a dielectric film 13 are formed by the same method as in the second embodiment.
Next, the obtained substrate is covered with a third photoresist layer 27 made of a third photoresist by spin coating to obtain a structure shown in FIG. 4A (a). The third photoresist is a negative type, contains xylene as a solvent, and has a high viscosity (for example, 79 to 89 mm ² / s). Since the third photoresist layer 27 is formed using a high-viscosity photoresist, it can be formed sufficiently thick. After the third photoresist layer 27 is formed, the third photoresist layer 27 is pre-baked at about 120 ° C. in order to stabilize the shape of the third photoresist layer 27.

  Next, portions of the third photoresist layer 27 other than those above and near the protrusions 9 are exposed, and the third photoresist layer 27 is developed to obtain the structure shown in FIG. 4A (b). When exposed in this manner, the development of the first photoresist layer selectively proceeds in the direction perpendicular to the substrate, and the dielectric film 13 has a portion 13b on the top surface of the convex portion 9 and a side surface of the convex portion 9. A portion of the third photoresist layer 27 can be removed so that the upper portion 13c is exposed and the corner portion 13a of the dielectric film 13 is covered.

Next, the obtained substrate is covered with a fourth photoresist layer 29 made of a fourth photoresist by spin coating to obtain a structure shown in FIG. 4A (c). As the fourth photoresist, a positive type one containing 1-methoxy-2-propyl acetate as a solvent and having a low viscosity (for example, 4.8 to 5.8 mm ² / s) is used. When the fourth photoresist layer 29 is formed using the fourth photoresist having a low viscosity, the fourth photoresist layer 29 can be formed thin, and the space between the convex portion 9 and the third photoresist layer 27 is ensured. Can be filled.
The solvent (1-methoxy-2-propyl acetate) contained in the fourth photoresist is different from the solvent (xylene) contained in the third photoresist. Further, as the third photoresist, a material that is difficult to dissolve in the solvent contained in the fourth photoresist is used. With this configuration, it is possible to prevent the third photoresist from being melted when the fourth photoresist is applied.
After the formation of the fourth photoresist layer 29, the fourth photoresist layer 29 is pre-baked at about 90 ° C. in order to stabilize the shape of the fourth photoresist layer 29.

Next, by developing the fourth photoresist layer 29, a part of the fourth photoresist layer 29 is removed, and the portion 13b of the dielectric film 13 on the upper surface of the convex portion 9 is exposed, and FIG. The structure shown in 4 (d) is obtained. The exposure is not performed, and the development time is adjusted, and the development is completed in such a time that the portion 13b of the dielectric film 13 on the upper surface of the convex portion 9 is exposed.
According to the present embodiment, the corner portion 13a of the dielectric film 13 is reliably protected by the third photoresist layer 27, so that the portion 13a is not exposed (or is less likely to be exposed than in the prior art). . Therefore, according to the present embodiment, the opening 11 can be formed in the dielectric film 13 easily and stably.

It is sectional drawing which shows the structure of the semiconductor laser chip based on Example 1 and 2 of this invention. It is sectional drawing which shows the manufacturing process of the semiconductor laser chip concerning Example 1 of this invention. It is sectional drawing which shows the manufacturing process of the semiconductor laser chip concerning Example 1 of this invention. It is sectional drawing which shows the manufacturing process of the semiconductor laser chip concerning Example 2 of this invention. It is sectional drawing which shows the manufacturing process of the semiconductor laser chip concerning Example 3 of this invention. It is sectional drawing which shows the structure of the conventional semiconductor laser chip. It is sectional drawing which shows the manufacturing process of the conventional semiconductor laser chip. It is sectional drawing which shows the manufacturing process of the conventional semiconductor laser chip. It is sectional drawing which shows the manufacturing process of the conventional semiconductor laser chip. It is sectional drawing which shows the structure of a common monolithic two wavelength laser.

Explanation of symbols

1, 51 Semiconductor laser chip 3, 53 Substrate 7, 57 Groove 9, 59 Protrusion 11, 61 Opening 13, 63 Dielectric film 15, 65 Electrode 16, 66 Portions other than groove and convex 17 First photoresist layer 19 Second photoresist layer 27 Third photoresist layer 29 Fourth photoresist layer 67 Photoresist layer

Claims (16)

(1) A substrate having a pair of grooves extending substantially in parallel and a convex portion defined between the pair of grooves is covered with a material film, and (2) the grooves are filled on the obtained substrate. Forming a first photoresist layer made of a first photoresist; (3) covering the obtained substrate with a second photoresist layer made of a second photoresist; and (4) first and second photoresist layers. A portion of the material film on the upper surface of the convex portion is exposed to form a mask layer, and (5) the exposed portion of the material film is removed using the mask layer. A method for manufacturing a semiconductor element, comprising a step of removing. The manufacturing method according to claim 1, further comprising a step of pre-baking the first photoresist layer after the step (2) and before the step (3). The manufacturing method according to claim 1, wherein the second photoresist has a higher viscosity than the first photoresist. The manufacturing method according to claim 1, wherein the first photoresist has a viscosity of 4 to 7 mm ² / s, and the second photoresist has a viscosity of 70 to 100 mm ² / s. The manufacturing method according to claim 1, wherein the second photoresist layer is formed to have a thickness of 2 to 4 μm. 2. The manufacturing method according to claim 1, wherein the mask layer is formed by exposing an upper portion of the convex portion of the first and second photoresist layers and developing the first and second photoresist layers. (1) A substrate having a pair of grooves extending substantially in parallel and convex portions defined between the pair of grooves is covered with a material film, and (2) the obtained substrate is made of a third photoresist. Covering with a third photoresist layer; (3) a portion of the material film on the top surface of the convex portion and a portion on the side surface of the convex portion are exposed, and on the edge portion of the groove portion of the material film. A part of the third photoresist layer is removed so as to cover the portion facing the convex portion, and (4) the obtained substrate is covered with a fourth photoresist layer made of the fourth photoresist, (5) By removing a part of the fourth photoresist layer, a portion of the material film on the upper surface of the convex portion is exposed to form a mask layer. (6) Using the mask layer, The manufacturing method of a semiconductor element provided with the process of removing the said exposed part. The manufacturing method according to claim 7, wherein the viscosity of the fourth photoresist is lower than that of the third photoresist. The manufacturing method according to claim 7, wherein the solvent contained in the fourth photoresist is less likely to dissolve the third photoresist than the solvent contained in the third photoresist. The manufacturing method according to claim 7, wherein the fourth photoresist is a photosensitive type different from the third photoresist. The manufacturing method according to claim 7, wherein the third photoresist has a viscosity of 70 to 100 mm ² / s, and the fourth photoresist has a viscosity of 4 to 7 mm ² / s. The manufacturing method according to claim 7, wherein the third photoresist layer is formed to have a thickness of 2 to 4 μm. The manufacturing method according to claim 7, wherein the fourth photoresist layer is formed to have a thickness of 0.2 to 0.5 μm. In step (3), the upper portion of the third photoresist layer and the vicinity thereof are exposed, and the third photoresist layer is developed, whereby the portion of the material film on the upper surface of the protrusion is A step of removing a part of the third photoresist layer so that a portion on the side surface of the convex portion is exposed and a portion of the material film on the edge of the groove portion and facing the convex portion is covered; The manufacturing method according to claim 7. The manufacturing method according to claim 7, wherein in the step (5), a part of the fourth photoresist layer is removed by development of the fourth photoresist layer. A method for manufacturing a semiconductor laser chip, comprising the manufacturing method according to claim 1.

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