A method of manufacturing a semiconductor light-emitting element

 

(57) Abstract:

The invention relates to semiconductor electronics and can be used in the production of semiconductor laser diodes and LEDs. To simplify the technological processes in the manufacture of semiconductor light-emitting element in ensuring its durability and reduced cost in a known method of manufacturing a semiconductor light-emitting element, comprising growing a semiconductor epitaxial substrate structure, drawing on the structure of a mask, etching the mask window, carrying out diffusion of dopants into the structure through the window in the mask, removing the mask, causing contacts, chipping plates on crystals, planting crystal on a heat sink, as the mask on the epitaxial structure put additional semiconductor layer from a material which is capable of selective etching, the thickness determined from the condition d2>d1(v2/v1), where d1- total thickness of epitaxial layers through which it is necessary to conduct the diffusion of dopants; d2the additional thickness of the semiconductor layer; v1- average schiraldi impurities in the additional semiconductor layer.

The invention relates to semiconductor electronics and can be used for the manufacture of light-emitting elements, in particular laser diodes or LEDs.

A known method of manufacturing a semiconductor laser (see UK patent N 2021307, CL H 01 S 3/19), which includes the cultivation on the semiconductor substrate with the epitaxial semiconductor structure, the etching in the structure of grooves ("window"), carrying out diffusion of dopants in the structure, causing the contacts, the shearing plate on the crystals, planting crystal on a heat sink. While the diffusion of dopants occurs in the contact layer. In the groove area of the diffusion front is deformed, forming a narrow conductive layer, supplying a pump current to a narrow section of the active region. The structure becomes similar to a laser with a very narrow strip contact, and this contact strip is located at a distance of less than or equal to 1 μm from the active region. In order to avoid adverse effects from the grooves and the ohmic contact to the active layer, the distance the bottom of the groove from the active area should be not less than 2 μm.

Singularity and lack dynasties in the design of the laser crystal. The presence of the indicated grooves in the contact layer in the immediate vicinity of the active region and located between the pumped area of the active region, where the main heat dissipation, and the heat sink, on which is mounted a laser crystal, affects the heat transfer from the active region in the copper heat sink. Therefore, the shape and dimensions of the said grooves in the contact layer must meet certain requirements. This way you can receive reliably working (without significant overheating of the active area) lasers with only a very narrow strip contact, so-called laser with a V-shaped groove, the width of the strip of contact which does not exceed 5 μm, resulting in a very narrow half-width values of the distribution of radiation in the near zone and the curvature of the wave front in the plane parallel to p-n junction. In this regard, the distribution of radiation in the far zone in a specified plane has a lobe (doggery) in nature and therefore severely limits the scope of V-shaped lasers (see G. Arnold et al., Long-Torm Behavior of V-Groove Lasers at Elevated Temperature; IEEE J. of Quant Electron, vol. QE-17, N 5, p. 759-762, 1981; M. Nakamura and STS JI, "Single-Mode saiconductor injection lasers for optical fiber communications", IEEE J. of Quant. Electron, vol. QE-17, No. 6, p. 994 100tω, in the structure of the laser crystal which has a potential germ defects. This refers to the bottom or corners of the groove, near where possible the birth and spread into the structure of the defect type dark lines and the formation of defects on the mirror faces when chipping on edges, which reduce radiative properties and eventually deduce the laser system. The disadvantage of this method is that the resulting lasers are minimal, usually no more than 5 mW with the same face due to the fundamental limitations of power density for durable lasers. Therefore, lasers manufactured by the above method, have limitations in application.

Lasers with planar contact layer devoid of these shortcomings are more preferable than lasers with a V-shaped groove, if it is possible to obtain the advantages that have V-shaped lasers.

There is a method of creating a laser diode with planar strip contact (N. Jonezu et al. "A GaAs-GaAlAs double heterostructure planar stripe laser", Japan Journal Appl. Phys., vol. 12, p. 1585-1592, 1973), in which the semiconductor substrate is grown epitaxial structure. Then on the structure put diffusione the participating impurities create the plot to summarize the pump current in the active region. After conducting a diffusion mask is removed by vacuum deposition causing contacts, chop off the plate on the crystals produce landing crystals on the heat sink.

The disadvantage of this method is the inevitable presence of abnormal lateral diffusion of dopants under the mask, which leads to an increase of the width of the strip of contact and as a consequence of the expansion of the pumped area active area and a wide distribution of radiation in the near zone. When the pump current becomes large, and the distribution of radiation in the near and far zones resistant to change of the pump current and temperature. Therefore, the light emitting elements, in particular laser diodes and LEDs, made this method unsuitable in applications where the stability of the radiation in a wide range of currents pumping and temperature. In addition, in many applications, such as fiber-optic systems, recording and reading information, requires limited the size of the emitting region (10-15 μm), which also limits the scope of application of lasers and LEDs manufactured by the above method. This method is time-consuming and includes a process that requires expensive oborudovaniya diffusion of dopants planar stripline lasers with a wide strip of contact within 3 to 10 microns (these sizes are most effective for applications in fiber-optic systems of recording and reading information) you can use the method of selective diffusion in semiconductors, described in the patent UK N 2168194, CL H 01 L 21/223, 21/302. This method is taken as a prototype of the present invention eliminates the abnormal lateral diffusion and to minimize the relation where Y is the width of the transverse diffusion, Z is the depth of the vertical diffusion. For conventional diffusion through the window specified relationship more than four ( 4).

A method of manufacturing a semiconductor light-emitting element by the method of selective diffusion in the United Kingdom patent includes the following operations: growing on a semiconductor substrate epitaxial structure; chemical treatment of the surface of the structure followed by washing in an ultrasonic bath (sequentially in water, acetone, trichloroethylene, acetone and alcohol); the application of plasma-chemical deposition (RSUD) dielectric film, which serves as a diffusion mask; etching a window in the mask; carrying out diffusion of dopants into the structure through the window in the mask; removing the mask; drawing pins; chipping on the crystals; landing crystals on the heat sinks.

The disadvantage of the prototype is that before plasma-chemical deposition of dielectric films require time-consuming updates tub consistently in multiple environments. In addition, the process of plasma-chemical deposition of dielectric films is labor-intensive and environmentally unclean, carried out in several stages with different modes and requires expensive equipment.

All the above mentioned disadvantages of the claimed technical solution eliminated.

The invention consists in the following. The task, which is aimed by the invention is the simplification of the technological processes in the manufacture of semiconductor light-emitting element in ensuring its durability and cost reduction.

This technical result in the implementation of the invention is achieved in that in the known method of manufacturing a semiconductor light-emitting element, comprising growing a semiconductor epitaxial substrate structure, drawing on the structure of a mask, etching the mask window, carrying out diffusion of dopants, the shearing plates on crystals, planting crystal on a heat sink, as the mask on the epitaxial structure put additional semiconductor layer from a material which is capable of selective etching, the thickness,bhodemon to spend the diffusion of dopants;

d2the additional thickness of the semiconductor layer;

v1- average speed of diffusion of dopants in the epitaxial layers through which it is necessary to conduct the diffusion of dopants;

v2- diffusion of dopants in the additional semiconductor layer.

Use as a diffusion mask additional semiconductor layer allows you to avoid time-consuming operation of chemical processing of the surface of the structure followed by washing in an ultrasonic bath and the operation of the plasma-chemical deposition of the dielectric film with the use of expensive and cumbersome equipment.

To improve the performance of the proposed method and to completely eliminate the appearance of anomalously high diffusion of dopants under the mask for the semiconductor layer is grown on the epitaxial layer structure in the same process epitaxy (e.g., liquid or gas phase), which eliminates the possibility of oxidation or contamination of the interface between the additional and the contact layers. The reason for the abnormally large lateral diffusion is the presence of diffusion between the mask and the peak in particular for GaAs this Ga2O3. Native oxide semiconductor is unstable and in the process of diffusion at high temperatures (~ 650oC) decomposes. Oxygen-containing semiconductor layer with a thickness of several tens of angstroms inevitably is formed in contact with the surface of a semiconductor with oxygen or air, and also in the process of depositing dielectric films containing oxygen (for example, SiO, SiO2, Al2O3and so on). As in the claimed method further semiconductor layer increasing in a single epitaxy process, the oxygen-containing semiconductor layer is not formed.

By conducting ordinary photolithography grown in the additional semiconductor layer to form a diffusion window, followed by the diffusion of dopants inside the epitaxial layers. Alloying impurity diffuses at the same time as in the epitaxial structure, and the additional semiconductor layer. Depending on the thickness of the epitaxial layer structure and the speed of diffusion in them dopant you can choose the thickness of the additional layer such that the boundary diffusion outside the window would remain in until the dykova layer only in the case if the thickness of the additional layer (d2) there will be more works v2t, where v2the diffusion rate in the additional layer, and t is the time of diffusion, defined by the depth of diffusion in the epitaxial layers (d1) and an average speed of diffusion in these layers (v1)

Thus, the condition under which the dopant remains in the additional layer, you can write:

< / BR>
After carrying out diffusion of dopants extra layer using selective to him the stain is removed. Together with the additional layer are removed and embedded dopant remains planar contact layer epitaxial structure formed in it use strip areas.

In the proposed method of manufacturing a semiconductor laser diodes and LEDs may appropriate selection of stain to form a diffusion window different cross-sectional shape that allows you to vary the width of the strip of contact for a given initial width of the photomask. Thus, by selecting, for example, a triangular cross-sectional shape of etching the additional layer, it is possible to manufacture the planar strip the width of the contact is already pervonachalnogo lasers with planar (non-recessed) contact layers.

Example. On a substrate of GaAs, Si alloy (~21018using the method of liquid-phase epitaxy is grown heterostructure, consists of the following layers (relative to substrate):

1st layer n-GaAs

2nd layer - n-Ga0,7Alfor 0.3As

3rd layer - p-Gaof 0.95Al0,05As

4th layer - p-Ga0,7Alfor 0.3As

5-th layer n-GaAs

6th layer (optional) - n-Ga1-xAlxAs

The composition of aluminum in the last layer (6) was chosen in the range from 50 to 80%, i.e. 0,5x0,8.

After growing heterostructures in the last layer method conventional photolithography was vytavlyali grooves (window) in the form of stripes along the crystallographic direction (100). Etching was carried out in hydrochloric acid, which poisons layer Ga1-xAlxAs at x0,4.

After etching of the window plate was placed in the reactor, which was in the process of diffusion of zinc in the presence of a carrier gas of hydrogen at a temperature of 650oC. At this time, the diffusion process was chosen based full front passes through the diffusion of the 5-th layer (n-GaAs). As the speed of diffusion layers with A content more than in the GaAs layers, and the thickness of the 5th layer was chosen in the range of 0.5-1.0 μm, the depth of diffusion in the 6th layer (optional) amounted to 1.5-3.0 microns is in the structure of the impurities remained in the last (6th) layer.

At the end of the diffusion process the last layer (Ga1-xAlxAs with 0,5x0,8) was removed by selective provide the Etchant - hot phosphoric or hydrochloric acid, and the planar layer of n-GaAS with the diffusion use strip areas deposited ohmic contact, including the consistent application of metallic layers of Pd, Va, Ni, Au.

By dividing the structure into separate crystals (laser or led, depending on the type of masks) and landing each crystal on a copper heat sink using solder made of laser diodes or edge LEDs depending on the type of crystal.

The width of the strip of contact, which sets the initial width of the photomask, shape etched in the additional layer of the grooves and the time of diffusion, in this case were selected from 5 to 20 μm. Traces of abnormal lateral diffusion in all manufactured structures were observed. The width of the transverse diffusion and the depth of the vertical diffusion layer of n-GaAs were equal to each other, i.e., the ratio was equal to 1, regardless of the width of the strip (The width of the transverse diffusion, Z is the depth of the vertical diffusion).

As the base object passed to the method described in patent Large is the sing expensive and energy-intensive equipment annual economic effect will be approximately 90 thousand rubles.

Presently claimed method laboratory tests gave a positive result, on the basis of which will be conducted production tests.

A method of manufacturing a semiconductor light-emitting element, comprising growing a semiconductor epitaxial substrate structure, drawing on the structure of a mask, etching the mask window, carrying out diffusion of dopants into the structure through the window in the mask, removing the mask, causing contacts, chipping plates on crystals, planting crystal on a heat sink, characterized in that as a mask on the epitaxial structure put additional semiconductor layer from a material which is capable of selective etching, the thickness determined from the condition

d2> d1(2/1)

where d1- total thickness of epitaxial layers through which it is necessary to conduct the diffusion of dopants;

d2the additional thickness of the semiconductor layer;

1- average speed of diffusion of dopants in the epitaxial layer structure;

2- average speed of diffusion of dopants in additional the

 

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