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
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
SUBSTANCE: in the boron diffusion method, the process is carried out using a gaseous source - diborane (B2H6) at temperature of 960°C for 35 minutes at the deposition step, with the following ratio of components: nitrogen N2=240 l/h, oxygen O2=120 l/h and hydrogen H2=7.5 l/h, at the distillation step at temperature of 1100°C for 2 hours. Surface resistance Rs=155±5 ohm/cm.
EFFECT: reduced spread of surface concentration values and obtaining trays that are uniformly doped on the length.
FIELD: semiconductor engineering; manufacture of extremely thin semiconductor structures and diaphragms.
SUBSTANCE: proposed method includes sticking of wafers and locking plates on faceplate using hold-down devices and separate mechanical treatment of plate and wafer surfaces to attain their desired definite thickness; faceplate is provided with at least two areas for sticking wafers and plates separated by blind slots; stuck to one of these areas are plates made of material whose hardness is greater than that of semiconductor wafer material; locking plates are mechanically finished and semiconductor wafers are stuck to free area of faceplate without changing position of pre-treated locking plates on faceplate. Adhesive used for sticking locking plates has melting point higher by at least 15 - 20 °C than that of adhesive employed for sticking semiconductor wafers. Locking plates are stuck using hold-down device independent of that used for semiconductor wafers.
EFFECT: enhanced quality and precision of treatment of semiconductor wafers.
3 cl, 4 dwg
FIELD: thermochemical etching.
SUBSTANCE: method comprises etching the surface of articles made of high-melting chemically stable materials by applying the layer of an agent interacting the article material and heating the surface by laser pulse irradiating. The surface of the article is simultaneously affected by the laser pulses and vapors of a volatile composition, which is subjected to the pyrolytic decomposition to produce the above mentioned material. The amplitude of the laser pulse should be sufficient to cause the evaporation of the material.
EFFECT: enhanced adaptability to shaping.
FIELD: machining semiconductor wafers.
SUBSTANCE: proposed machine tool designed for circular machining of semiconductor wafers to produce wafers having side surfaces of desired shape with minimal quantity of post-machining circular scratches and to execute great number of process operations without displacing wafers from one position to other has pair of supporting and driving rollers that function as supports for vertically disposed semiconductor wafers and are set in motion by means of drive belt connected to them. Machine tool also has two opposing movable wafer-machining units each incorporating first and second members designed for machining wafers when they are installed in first and second positions. Second design alternate of semiconductor wafer machine tool and self-aligning arbor fastening assembly is also proposed.
EFFECT: enlarged functional capabilities of machine tool, improved quality of post-machining side surfaces of wafers.
22 cl, 17 dwg
FIELD: treatment of semiconductor wafer surfaces, such as their chemical and mechanical polishing followed by washing them.
SUBSTANCE: proposed device has chemical-mechanical polishing mechanism, vertical displacement mechanism with magazine holder installed for step-by-step vertical displacement of magazines, robot-manipulator provided with wafer grip, two wafer transfer robots, and wafer washing plant. Magazine holder of vertical displacement mechanism is made in the form of hollow shaft mounted on top end of spline shaft for its turning through 360 deg. from drive; bottom end of hollow shaft mounts n magazine intake platforms, where 1 < n ≤ 4; axes of magazine intake platforms are spaced 90 deg. apart and bottom ends of intake platforms carry guides with slots similar to and coaxial with magazine slots. Magazine holder is installed in detergent tank; wafer grip of robot-manipulator is made in the form of removable ring whose top part is beveled to receive wafers and spring-loaded restricting pins. Wafer grip of robot-manipulator is provided with spray nozzles installed on top and below the ring.
EFFECT: reduced labor consumption for device manufacture due to its reduced size.
1 cl, 3 dwg
FIELD: electronic engineering; production of photomask blanks.
SUBSTANCE: proposed method for producing photomask blanks includes mechanical and chemical treatment of glass wafers, their placement in vacuum chamber, and coating with masking chromium layer by heating chromium-containing evaporator in nitrogen environment until desired optical density is attained, this being followed by wafer washing, covering with resist, and control. Chromium is cleaned prior to being applied to masking layer by remelting it at temperature of 2000 to 2100°C and residual pressure of 400 - 500 mm of mercury in argon environment; chamber is cooled down to room temperature, evaporator is heated at a rate of 500 - 700°C a minute to 1700 - 1850°C, exposed to this temperature for 25 - 35 minutes, then evaporator is heated to 1860 - 1950°C and chromium is evaporated at a rate of 140 - 160Å a minute until desired optical density is attained.
EFFECT: enhanced quality of varying-reflectance masking layer and environmental friendliness of method.
4 cl, 1 tbl
FIELD: optoelectronics; producing wafers from ingots or bullions of monocrystals, such as sapphires.
SUBSTANCE: ingots or bullions are subjected to X-ray analysis to determine direction of cutting and at least one oriented flat is made thereon by grinding at its faces (0001). Then deviation from desired position is measured by means of diffraction meter and grinding process is repeated until deviation shorter than 3 minutes is attained. Cylinder blank is cut from monocrystal ingot or bullion perpendicular to at least one flat with distinct face on its surface. Then ends of cylinders are ground at 3-minute precision of their deviation from desired value. After that cylinder diameters are calibrated and base cut is made on each cylinder. Cylinders are annealed at 1300-1500 °C for minimum 8 hours. Upon cutting cylinder blanks into wafers annealing is repeated. Wafers are thinned by grinding and annealed under same conditions as cylinders.
EFFECT: ability of producing thin sapphire wafers at high precision with respect to diameter and thickness.
10 cl, 6 dwg
FIELD: production of pieces of electronics, applicable, for example, in operations of cleaning of semiconductor plates with the aid of brushes and mega sound.
SUBSTANCE: the device has loading and unloading holders, mechanisms of their vertical motion, mechanism for extraction of the plate from the holder, mechanism for loading of the machined plate in the holder, mechanism of horizontal motion of the plates, machining unit actuating the centrifuge installed in the process bath, brush. The mechanism of vertical motion of the unloading holder is installed at an angle to the horizontal plane in the direction of the plates feed, and the mechanism for extraction of the plates from the holder and the mechanism for loading of machined plates in the holder are made in the form of a suction cup with a vacuum table installed on a carriage for longitudinal motion, the suction cup of the mechanism for extraction of the plates from the holder is installed for turning on the carriage through a preset angle, the carriage is fastened at the same angle to the horizontal plane as the mechanism of vertical motion of the unloading holder, besides, the mechanism of horizontal motion of plates is made in the form of two manipulators for turning in the horizontal plane, each manipulator is provided with a carrier in the form of a ring with an inner tapered surface.
EFFECT: enhanced reliability of device operation and quality of machining, simplified construction.
2 cl, 9 dwg
FIELD: electronic industry.
SUBSTANCE: proposed method for producing photomask blanks involves two-stage polishing; first stage includes pre-polishing using perforated polishing canvas based on synthetic fibers, 8- 10 μm in diameters, at cubic density of 0.25 g/cm3; perforated holes are staggered; perforated-to-non-perforated area ratio being 0.08 0.09: 1, with ultrasonic action at frequency of 20 - 50 kHz for 30 - 50 minutes, temperature of 20 - 40 °C, and glass removal speed of 0.6 - 1.0 μm/min, whereupon glass removal is checked up and wafer is washed out in three-step ultrasonic line using surface active materials; during second stage wafer is subjected to finishing polishing by removing 10 - 12 μm of glass for 10- 15 minutes using softer polishing canvas.
EFFECT: enhanced surface quality of glass wafers for photomasks.
1 cl, 1 tbl
FIELD: chemical industry; other industries; methods of polishing of the silver chloride crystals.
SUBSTANCE: the invention is pertaining to the field of manufacture of the optical elements and may be used in the infrared engineering. The method provides for the abrasive polishing of AgCl crystals with the sodium thiosulfate water solution and with the finishing washing of the treated article in 30-40 % solution of 2-methyl-2-aminopropane (СН3)3CNH2 in ethanol С2Н5ОН and the following dry final polishing. The method ensures the high-accuracy polishing of the articles made out of the silver chloride crystals and the high quality of the polished surfaces.
EFFECT: the invention ensures the high-accuracy polishing of the articles made out of the silver chloride crystals and the high quality of the polished surfaces.
FIELD: microelectronics, namely processes for preparing even-atom surfaces of semiconductors.
SUBSTANCE: method comprises steps of chemical-dynamic polishing of substrate surface in polishing etching agent containing sulfuric acid, hydrogen peroxide and water for 8 - 10 min; removing layer of natural oxide in aqueous solution of hydrochloric acid until achieving hydrophobic properties of purified surface of substrate; washing it in deionized water and drying in centrifuge. Then substrate is treated in vapor of selenium in chamber of quasi-closed volume while forming gallium selenide layer at temperature of substrate Ts = (310 -350)°C, temperature of chamber walls Tc = (230 - 250)°C, temperature of selenium Tsel = (280 - 300)°C for 3 - 10 min. After such procedure substrate is again placed in aqueous solution of hydrochloric acid in order to etch layer of gallium selenide. Invention allows produce even-atom surface of gallium arsenide at non-uniformity degree such as 3Å.
EFFECT: possibility for using substrates for constructing nano-objects with the aid of self-organization effects.