KR0144491B1 - A method for manufacturing semiconductor laser diode - Google Patents

Abstract

The present invention relates to a method for manufacturing a semiconductor laser diode, wherein a first cladding layer of the same conductivity type, an intrinsic active layer, and a second cladding type second clad layer are grown on a compound semiconductor substrate of a first conductivity type. After forming an etch mask of a stripe-shaped insulating film pattern on the second clad layer, a semiconductor substrate is inserted into a groove of a holder having a groove into which the semiconductor substrate is inserted, and the holder is immersed in an etching solution. After mesa etching from the second cladding layer to the first cladding layer sequentially, the first and second current blocking layers were grown to form PBH-LD, and thus the degree of etching according to the position of the semiconductor substrate during the mesa etching process. Uniformity improves the operation characteristics and reproducibility of the device, prevents the loss of semiconductor substrates, improves the process yield, and reduces the manufacturing cost by eliminating photoresist coating and plasma etching processes. Can be.

Description

Manufacturing method of semiconductor laser diode

1A to 1D are manufacturing process diagrams of a semiconductor laser diode.

2 is a layout diagram after mesa etching of a semiconductor laser diode according to the prior art.

3 is a perspective view of a wafer holder used in the mesa etching process of a semiconductor laser diode according to the present invention.

4 is a schematic view for explaining a mesa etching process of a semiconductor laser diode according to the present invention.

5 is a layout diagram after mesa etching of a semiconductor laser diode according to the present invention.

* Explanation of symbols for main parts of the drawings

1: Semiconductor Substrate 2: First Clad Layer

3: active layer 4: second clad layer

5: etch mask 6: P type current blocking layer

7: N-type current blocking layer 10: wafer holder

11: groove of the wafer holder 15: support

20: etching solution tank 25: etching solution

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a light amplification by stimulated emission of radition diode (LD), in particular a planar buried hetero structure in which a linear active layer is embedded by a current blocking layer. In the LD (hereinafter referred to as PBH-LD), the wafer is placed in a holder having a groove into which the wafer is inserted during mesa etching of the active layer and the clad layer, followed by mesa etching to uniformly etch the wafer and etching the side surface of the wafer. The present invention relates to a method for manufacturing a semiconductor LD, which can prevent the occurrence of defects caused by the photosensitive film and improve process yield and reliability of device operation.

Recently, the necessity of information communication is increasing due to the rapid development of the entire semiconductor industry, and a single wavelength and a laser having excellent straightness are attracting attention as a transmission means for effective information communication. The laser is classified into gas, liquid, solid, semiconductor, and chemical laser according to the type of laser medium, among which semiconductor laser diode has a smaller driving current, smaller size, and light intensity and frequency according to the change of current. Can be directly modulated, the efficiency of the laser is usually very high, such as 70% or more, and has an advantage of having a wide wavelength range. Therefore, it is widely used as an optical signal generating device in office devices such as laser printers and bar code readers or optical communication devices. .

Also, a photo detector is a device that converts an optical signal generated from LD into an electrical signal when it enters a receiver through an optical fiber.

The semiconductor LD is a kind of light emitting diode. The semiconductor LD is formed of a group III-V or II-VI compound semiconductor and amplifies light having a single wavelength generated from a PN junction formed on a semiconductor substrate among materials having different refractive indices. It works.

Current semiconductor LDs typically use each compound semiconductor layer as a method of metal organic chemical vapor deposition (hereinafter referred to as MOCVD) or liquid phase epitaxy (hereinafter referred to as LPE). Although formed at a high temperature of about -650 ℃, there is a reliability problem, such as low production yield due to long-term exposure to air, such as deterioration of characteristics when using for a long time.

1A to 1D show the manufacturing process of LD according to the prior art, which is an example of PBH-LD, and an example using an N-type InP substrate.

First, on the N-type InP semiconductor substrate 1, the first cladding layer 2 made of N-type InP, the active layer 3 made of intrinsic InGaAsP, and the second cladding layer 4 made of P-type InP. Grow sequentially (see also Figure 1a).

Then, on the second clad layer 4, a rectangular etching mask 5 extending to one side in an oxide film pattern is formed (see also FIG. 1b).

Thereafter, mesa-etched sequentially from the second clad layer 4 to the first clad layer 2 exposed by the etching mask 5 to form a stripe shape. At this time, a portion of the upper side of the semiconductor substrate 1 is also etched, and the second cladding layer 4, the first active layer 3, and the first cladding layer 2 pattern have a lower portion of the etching mask 5. Undercut is lost (see also section 1c).

Then, the first current blocking layer 6 and the first conductive layer of P-type InP, which is the second degree, are formed on the sidewalls from the second cladding layer 4 pattern to the first cladding layer 2 pattern. The second current blocking layer 7 made of N-type InP is sequentially grown (see also FIG. 1d).

Then, although not shown, the etch mask is removed and a subsequent process is completed to complete the PBH-LD.

In the method of manufacturing PBH-LD according to the prior art as described above, during the mesa etching process from the second clad layer to the first clad layer, the semiconductor wafer on which the etch mask is formed is picked up with forceps and immersed in a tank filled with an etching solution. Perform oral mesa etching.

However, in this mesa etching method, as shown in FIG. 2, the etching speed of the center portion of the semiconductor substrate 1 is lower than that of the edge portion due to the diffusion of the etching solution and the reaction with the sample. The second cut layer 4 and the active layer 3 and the first clad layer 2 pattern undercut are formed to have an uneven width and depth of etching, so that the thickness of growth can be easily controlled during subsequent epitaxial growth. Without this, the area of the active layer 3 is not uniform, resulting in poor process yield and reproducibility of device characteristics, and since devices having different characteristics are formed on one substrate, operating characteristics of the device are inferior.

In addition, another mesa etching method for solving the above problems is a method of attaching the semiconductor wafer on a glass plate or other lipid substrate by using a porous film, and then immersing it in an etching bath to mesa etching.

However, this method requires a plasma etching process to remove the photoresist film after mesa etching, in which case the photoresist debris between the etching mask and the wafer is not easily removed. , The etching surface is damaged by the plasma, the regrowth interface is bad, there is a problem that the process yield and device operation reliability is inferior.

The present invention is to solve the above problems, an object of the present invention is to insert and fix the wafer in the holder having a groove into which the wafer is inserted during the mesa etching, the holder is immersed in an etching tank to mesa etching The uniformity of the etching is improved, and the plasma etching process is omitted because the photoresist film is not used, thereby preventing the etching surface damage caused by the plasma or the regrowth defect caused by the photoresist residue, thereby improving the process yield and the reliability of device operation. It is to provide a method for producing LD.

Features of the method for manufacturing a semiconductor LD according to the present invention for achieving the above object is a step of forming a first cladding layer of a compound semiconductor of the first conductivity type on a compound semiconductor substrate of the first conductivity type; Forming an active layer of an intrinsic compound semiconductor having a composition different from that of the first cladding layer on the first cladding layer, and a second conductivity type compound semiconductor having the same composition as the first cladding layer on the active layer Forming a second cladding layer; forming an etching mask of an insulating film pattern on the second cladding layer; and a semiconductor substrate in a groove of a holder having a groove into which the semiconductor substrate of the structure is inserted. And inserting the holder into an etching solution bath to mesa-etch sequentially from the second clad layer to the first clad layer exposed by the etching mask, and the mesa-etched first clad. Forming a first current blocking layer of a second conductive typical compound semiconductor on a sidewall of the second layer to the second cladding layer pattern, and a second first conductive semiconductor being formed on the first current blocking layer A process for forming a current blocking layer is provided.

Hereinafter, a method of manufacturing a semiconductor LD according to the present invention will be described in detail with reference to the accompanying drawings.

The method of manufacturing a semiconductor LD according to the present invention has a main point in the mesa etching process of PBH-LD, and other processes are the same as in the prior art, and thus, the method will be described with reference to FIGS. 1A to 1D.

First, a first clad layer of a compound semiconductor having the same composition as that of the semiconductor substrate 1, for example, an N-type InP, is formed on a first semiconductor compound semiconductor, for example, an N ⁺ type InP semiconductor substrate 1. An intrinsic compound semiconductor having a composition different from that of the first cladding layer 2 on the first cladding layer 2, for example, having a thickness of about 1 to 1.5 μm; An active layer 3 made of InGaAsP or multi quantum wells, for example, having a thickness of about 0.05 to 0.4 μm, and then the same as the first clad layer 2 on the active layer 3 The second clad layer 4 made of P-type InP, which is a compound semiconductor of the second degree typical composition, is formed to a thickness of about 0.1 to 0.5 탆. Here, the semiconductor substrate 1 has a rectangular shape of 2 inches or less, and the first cladding layer 2, the active layer 3, and the second cladding layer 4 are sequentially formed by MOCVD or LPE. (See also section 2a)

Then, an etching mask 5 having a rectangular stripe shape extending to one side of an insulating film, for example, an oxide film or a nitride film, is formed on the second clad layer 4 by a front coating and a photolithography method. For example, it is formed in a width of about 2 to 4 μm and a thickness of about 0.1 to 0.3 μm (see also FIG. 1b).

Thereafter, the semiconductor substrate 1 having the above structure is inserted into and fixed to the groove 11 of the holder 10 shown in FIG. 3, and as shown in FIG. 4, both sides of the holder 10 are supported. The second cladding layer 2 is immersed in the bath 20 containing the etching solution 25 for a predetermined time, and the first cladding layer 2 is exposed to the second cladding layer 4 exposed by the etching mask 5. ) Mesa-etched sequentially to form a stripe shape, and part of the upper side of the semiconductor substrate 1 is also etched. At this time, the second cladding layer 4, the active layer 3, and the first cladding layer 2 pattern have an undercut under the etching mask 5. The etching solution 25 contains, for example, HBr: H ₂ O ₂ : H ₂ O: HCI in the water tank 20.

Here, the holder 10 is a glass plate or a Teflon plate having a larger area than the semiconductor substrate 1, for example, 30 × 30 (± 10) mm ² , and the semiconductor substrate 1 is inserted into a central portion thereof. Grooves 15 are formed in a precision size, for example, 15 × 15 (± 5) mm ² area and a thickness in which the semiconductor substrate 1 is thick, for example, about 300 to 400 μm in depth.

Accordingly, the semiconductor substrate 1 is inserted into the groove 15 during the mesa etching process so that the semiconductor substrate 1 is not etched on the back or side surface of the semiconductor substrate 1, and the semiconductor substrate 1 does not slip during the etching process. As the thickness of the semiconductor substrate 1 is similar, the etching uniformity is improved by reducing the geometrical problem, the concentration gradient of the etching solution and the diffusion of the solution, and the etching uniformity is improved, as shown in FIG. The shape of the stripe from the first clad layer 2 to the second clad layer 4 is formed similarly to the shape of the etching mask 5, and the difference in etching speed between the center portion and the edge portion is reduced. See also 1c)

Next, a first current blocking layer of P-type InP, which is a second degree typical of the same composition as the cladding layers, is formed on the sidewalls from the second cladding layer 4 to the first cladding layer 2 pattern. 6) and the second current blocking layer 7 made of N-type InP, which is typical of FIG. 1, are sequentially regrown to fill the etched portion of the lower portion of the etch mask 5.

Thereafter, although not shown, the etch mask is removed and subsequent epiprocesses and electrodes are formed to complete the PBH-LD.

As described above, in the method of manufacturing a semiconductor LD according to the present invention, the first conductive layer of the same conductivity type, the intrinsic active layer, and the second conductive type second clad layer are formed on the compound semiconductor substrate of the first conductivity type. After the growth, and forming an etching mask of a stripe-shaped insulating film pattern on the second clad layer, a semiconductor substrate is inserted into a groove of a holder having a groove into which the semiconductor substrate is inserted, and the holder is placed in an etching solution. After immersing mesa-etched from the second cladding layer to the first cladding layer in succession, the first and second current blocking layers were grown to form PBH-LD, and thus, at the position of the semiconductor substrate during the mesa etching process. As the etching degree is uniform, the operation characteristics and reproducibility of the device are improved, the process yield is improved by preventing the loss of the semiconductor substrate, and the manufacturing cost is reduced by eliminating the photoresist coating or plasma etching process. There is an advantage in that.

Claims (15)

Forming a first clad layer of a first semiconductor compound semiconductor on a first semiconductor compound semiconductor substrate; and an intrinsic compound having a composition different from that of the first clad layer on the first clad layer Forming an active layer made of a semiconductor, forming a second cladding layer made of a second conductivity type compound semiconductor having the same composition as the first cladding layer on the active layer, and forming a second cladding layer on the second clad layer Forming an etching mask of an insulating film pattern, inserting a semiconductor substrate into a groove of a holder having a groove into which the semiconductor substrate of the structure is inserted, and dipping the holder in an etching solution bath to be exposed by the etching mask. Mesa-etching the second cladding layer from the second cladding layer to the first cladding layer sequentially; and a second semiconductor compound compound is formed on the sidewalls of the mesa-etched first cladding layer to the second cladding layer pattern. First war A method of manufacturing a semiconductor laser diode, comprising: forming a current blocking layer; and forming a second current blocking layer of a compound semiconductor of a first conductive type on the first current blocking layer. The method of manufacturing a semiconductor laser diode according to claim 1, wherein the first and second conductivity types are opposite conductivity types, and each is N or P type. The method of manufacturing a semiconductor laser diode according to claim 1, wherein the semiconductor substrate is an N ⁺ type InP substrate. The method of claim 1, wherein the first and second clad layers and the first and second current blocking layers are formed of InP. The method of claim 1, wherein the first cladding layer is formed to a thickness of 1 to 1.5 μm. The method of claim 1, wherein the active layer is formed of i-InGaAsP or multi quantum wells. The method of manufacturing a semiconductor laser diode according to claim 1, wherein the active layer is formed to a thickness of about 0.05 to 0.4 m. The method of manufacturing a semiconductor laser diode according to claim 1, wherein the second clad layer is formed to a thickness of 0.1 to 0.5 탆. The method of claim 1, wherein the first and second cladding layers, the active layer, and the first and second current blocking layers are grown by MOCVD or LPE. The method of claim 1, wherein the etching mask is formed of an oxide film or a nitride film. The method of claim 1, wherein the etching mask is formed in a rectangular stripe shape. The method of claim 11, wherein the etching mask is formed to have a width of 2 to 4 μm and a thickness of 0.1 to 0.3 μm. The method of manufacturing a semiconductor laser diode according to claim 1, wherein the holder is larger than the semiconductor substrate and is formed of a glass plate or a Teflon plate having a size of 30 × 30 (± 10) mm ² . The method of manufacturing a semiconductor laser diode according to claim 1, wherein the groove is formed to have a size of about 15 × 15 (± 5) mm ² and a depth of 300 to 400 μm. The method of claim 1, wherein the etching solution is a mixed solution of HBr: H ₂ O ₂ : H ₂ O: HCI.