RU2084988C1 - Method for producing resistive contacts on planar side of structure with local regions of low-alloyed semiconductors - Google Patents

Abstract

FIELD: laser diodes, light-emitting diodes, and other devices. SUBSTANCE: method involves coating semiconductor structure with insulating film of silicon dioxide, applying auxiliary insulating layer, forming local regions for contacts by means of resistive mask, depositing contact material of first level, forming local metal contacts using explosion photolithography by dissolving auxiliary insulating layer under unwanted metal regions. Auxiliary insulating layer is europium oxide film ((Eu₂O₃); first-level metal coating is composed of alloys ensuring formation of resistive contacts for low-alloyed semiconductors A³B⁵ of n or p type; (Au:Zn) (Be, Mn) for p type and (Au:Ge) (Te, Sn) for n-type, and selective etching relative to europium oxide film which are subjected to annealing; second-level metal coating is adhesive sublayer of vanadium (V) or chromium (Cr); these procedure are followed by application of one of contact metals: Au, Ni, and others. EFFECT: facilitated procedure. 3 cl, 1 dwg , 1 tbl

Description

The invention relates to the field of semiconductor electronics using semiconductor compounds of type A ³ B ⁵ , such as gallium arsenide, indium phosphide and solid solutions based on them; concerns the problem of the formation of ohmic contacts to the listed materials and can be used in the design and manufacture of laser diodes, LEDs and other devices.

A known method of obtaining an ohmic contact to the structure with local regions of low-alloy p-type semiconductor, including:
applying a dielectric film to the structure;
the formation of a resistive mask on a dielectric (SiO ₂ ) film;
the formation of a strip semiconductor region (opening the dielectric);
resistive mask removal;
conducting diffusion of zinc in the stripe region;
contacting the adhesive layer (Cr, Au) on a planar surface (App. Phys. Ltt. 41 (5), 1, September, 1982, pp. 485 487).

 The use of impurity diffusion (Zn) in the strip regions increases the concentration level of the main carriers in the semiconductor, which makes it possible to obtain a low ohmic contact using metallization from CrAu.

 The reasons that impede the achievement of the required technical result when using the known method include the difficult reproducibility of the diffusion process, i.e. obtaining a guaranteed depth of zinc.

Another analogue of obtaining an ohmic contact to a laser structure based on gallium arsenide is the method according to Japan patent N2-13944, class. H 01S 3/18, H01L 21/28, including:
contact layer deposition (AuZn, Au);
formation of a photoresist mask;
metallization etching to obtain local contacts of strip geometry;
removal of photoresist film;
heat treatment at contact formation temperature.

 This method makes it possible to use any contact materials, but etching distorts the shape and size of the work elements.

 Currently, explosive photolithography is widely used to create metallization with a specific configuration.

The following method is known for producing metallization to a semiconductor, including the deposition of silicon dioxide (on Si), the deposition of aluminum, the formation of micrograph elements on aluminum, the application of an auxiliary dielectric layer of Al ₂ O ₃ with a thickness of 0.1 μm, the deposition of a second layer of aluminum, removal of the dielectric layer of Al ₂ O ₃ with a layer of aluminum deposited on it, i.e. explosive photolithography by dissolving an auxiliary dielectric layer of Al ₂ O ₃ (Foreign electronic technology, 1987, May, 5 (312), p. 23 Japan patent N52-12546).

 The closest way to the claimed prototype is a technical solution, including applying a dielectric film of silicon dioxide to the semiconductor structure, forming local areas for contacts using a resistive mask, applying contact material, annealing (GHOlsen Laser diodes For the 1.5 μk-2, 0 μk Wave Length Rang J. of Optical Comnunications 2 (1981), pp. 11-19.

The reasons that impede the achievement of the required technical result when using the known method adopted for the prototype include the fact that it does not provide reliability of ohmic contacts to the planar side of the structure containing local regions of low-alloyed semiconductors of group A ³ B ⁵ formed in a dielectric film (SiO ₂ )

The invention is as follows. The problem to which the invention is directed, is to increase the reliability of ohmic contacts to the planar side of the structure containing local regions of low-alloyed semiconductors of group A ³ B ⁵ formed in a dielectric film (SiO ₂ ).

The specified technical result in the implementation of the invention is achieved by the fact that in the known method of manufacturing ohmic contacts, including applying a dielectric film of silicon dioxide to the semiconductor structure, forming local areas under the contacts using a resistive mask, applying contact material, annealing, characterized in that the film silicon dioxide is applied auxiliary dielectric film of europium oxide, metallization of the first level, providing the creation of ohmic contact a low alloy semiconductors A ³ B ⁵ p- or n-type (i.e., alloys of Au with a doping acceptor impurity Zn, Be, Mn for p-type semiconductors, alloys of Au with a doping donor impurity Ge, Te, Sn - semiconductors n -type) and etching selectivity with respect to the europium oxide film; local contact regions are formed by "explosive" photolithography by dissolving an auxiliary film of europium oxide under unnecessary metal regions, metallization of the second level with an adhesive sublayer (from vanadium or chromium) is applied, and then one of the contact materials (Au, Ni, Al and others).

The reliability of the contacts obtained by the proposed method is ensured through the use of two-level metallization. The first level metallization is gold-based alloys with alloying impurities that create low-resistance contacts to the semiconductor regions of compounds A ³ B ⁵ with a low concentration: Au with an acceptor impurity Zn, Be, Mn for p-type semiconductors;
Au with a Ge, Sn, Te donor impurity for n-type semiconductors.

 The desired configuration of local contacts is created by “explosive” photolithography using an auxiliary layer consisting of a dielectric film of europium oxide.

The choice of europium oxide as an auxiliary layer is due to the following reasons:
exceptional adhesion of this material to a semiconductor (GaAs, InP) and a silicon dioxide film without the use of high-temperature heating of the plates during the deposition of the film;
ease of dissolution of the film, for example, both in concentrated and highly diluted (1 10) hydrochloric acid. This ensures the selectivity of its etching relative to the semiconductors (above) of the film of silicon dioxide and metallization of the first level;
the presence of a mask of europium oxide (compared to a mask of photoresist) does not limit the temperature of heating the plates during the deposition of metallization of the first level, and also allows the operation of firing to form an ohmic contact in local semiconductor regions before removing the auxiliary layer, i.e. before the "explosive" photolithography. This ensures good adhesion of gold-based alloys to a semiconductor surface.

 As a result of this, after the operation of the "explosion", clear boundaries are formed of the local contact areas with a given configuration and size.

 Since gold-based alloys have poor wettability to dielectric coatings, tearing occurs in a metal film after burning, which facilitates the access of the etchant to the europium oxide film during the process of explosive photolithography. In this regard, the auxiliary film of the dielectric may be less than or equal to the thickness of the metallization of the first level.

 The application of metallization of the second level, containing the adhesive layer, provides reliable coatings with both local areas with metallization of the first level and a dielectric film of silicon dioxide.

The essence of the invention is illustrated by the description with examples and graphic material depicting the elements of the epitaxial mesa structure after the technological operations included in the proposed route for the manufacture of ohmic contacts to the planar side containing local regions of low-alloyed semiconductors of compounds A ³ B ⁵ p- or n-type, where in the figure:
1 semiconductor substrate A ³ B ⁵ p- or n-type;
2 epitaxial layer of low-alloyed semiconductor of group A ³ B ⁵ p- or n-type;
3 silicon dioxide film;
4 europium oxide film;
5 resistive mask;
6 metallization of the first level (alloy with an alloying impurity);
7 metallization of the second level.

Example 1. (Fabrication of an ohmic contact to the planar side of a structure containing local regions of a low-alloy p-type A ³ B ⁵ compound formed in a dielectric film).

On InP-based epitaxial structures with the upper low-alloyed epitaxial layer 2 (Fig. "A"), a 0.3 μm thick silicon dioxide film 3 was deposited from a gas mixture of monosilane with argon at a temperature of 450 ^° C (Fig. "A").

путем испарения в вакууме с помощью электронно-лучевого испарителя. Исходным материалом для получения пленок оксида европия служили специальные таблетки. Пластины перед напылением оксида европия прогревались до 100^oC.An auxiliary film of europium oxide 4 (Fig. “B”) was deposited on silicon dioxide.

by evaporation in a vacuum using an electron beam evaporator. Special tablets served as the starting material for the preparation of europium oxide films. The plates before deposition of europium oxide were heated to 100 ^o C.

Then, a resistive mask 5 was formed on the resulting structure (Fig. “C”) with strip windows 3 μm wide, with which etched dielectric films were etched. The europium oxide film was etched in an HCl solution of H ₂ O (1 10), and the silicon dioxide in the etchant was made of HF NH ₄ F (40%) (1 9). After etching, the structure took the form corresponding to FIG. "g". This is followed by the removal of the resistive mask in dimethylformamide with monoethanolamine and the structure takes the form shown in FIG. "d".

Next, metallization of the first level 6 of an alloy of gold with zinc AuZn (90 10) was applied, which creates an ohmic contact to the low-alloy p-type compound A ³ B ⁵ , which is reflected in FIG. "e". The film thickness of the alloy was 0.1 μm. After that, the operation was carried out annealing in a hydrogen medium at a temperature of 450 ^o C for 1 min. Then, “explosive” photolithography was carried out by dissolving the auxiliary layer of europium oxide in a solution of HCl H ₂ O (1 10). As a result of this, contacts were formed to the stripe regions formed in the silicon dioxide film, which is reflected in FIG. "w".

) и золота Au (0,5 мкм), при нагреве пластин до 200^oC, обеспечивающая надежное покрытие как к металлизации первого уровня (AuZn), так и к пленке двуокиси кремния. В готовом виде структура представлена на фиг. "з".The next operation was metallization of the second level 7, consisting of applying an adhesive sublayer of vanadium V (

) and gold Au (0.5 μm), when the plates are heated to 200 ^o C, providing a reliable coating for both metallization of the first level (AuZn) and a film of silicon dioxide. The finished structure is shown in FIG. "h".

Example 2. The manufacture of contacts to the planar side of the structure containing local regions of low-alloyed compounds A ³ B ⁵ n-type, formed in a dielectric film.

On InP-based epitaxial structures with an upper epitaxial layer 2 (Fig. "A"), a 0.3 μm thick silicon dioxide 3 film was applied from a gas mixture of monosilane with argon at a temperature of 450 ^° C. (Fig. "A"). A support film of europium oxide 4 with a thickness of about 0.1 μm was deposited on silicon dioxide by evaporation in a vacuum using an electron beam evaporator on plates heated to 100 ^° C (Fig. "B").

За металлизацией следовало вжигание контакта при T 450^oC в течение 1 мин в среде водорода. После этого осуществлялась "взрывная" фотолитография путем растворения вспомогательного слоя оксида европия в растворе (1 10), в результате чего формировались контакты к полосковым областям, образованным в пленке двуокиси кремния (фиг. "ж"). На полученную структуру наносилась металлизация второго уровня 7, состоящая из адгезионного подслоя ванадия

и золота 0,5 мкм при нагреве пластин до 200^oC, обеспечивающая надежное покрытие как к металлизации первого уровня (AuGeNi), так и к пленке двуокиси кремния (фиг. "з").Then, a resistive mask 5 was formed on the resulting structure with strip windows about 3 μm wide (Fig. "C"), with which dielectric films were etched. The europium oxide film was etched in an HCl solution of H ₂ O (1 10), and the silicon dioxide in the etchant was made of HF NH ₄ F (40%) (1 9). After etching, the structure takes the form corresponding to FIG. "g". This is followed by the removal of the resistive mask in dimethylformamide with monoethanolamine (Fig. “D”), after which the metallization of the first level 6 of AuGeNi alloy (80 10 10) was applied, which creates an ohmic contact to the low-alloyed compound A ³ B ⁵ n-type (Fig. "a"). The film thickness was 500

Metallization was followed by contact burning at T 450 ^° C for 1 min in a hydrogen medium. After that, “explosive” photolithography was carried out by dissolving the auxiliary layer of europium oxide in solution (1 10), as a result of which contacts were formed to the strip regions formed in the silicon dioxide film (Fig. “G”). The metallization of the second level 7, consisting of an adhesive sublayer of vanadium, was deposited on the resulting structure

and gold 0.5 μm when the plates are heated to 200 ^o C, which provides a reliable coating for both metallization of the first level (AuGeNi) and a film of silicon dioxide (Fig. "C").

 Example 3. The manufacture of contacts to the planar side of the structure containing local regions of low-alloyed compounds from p-type GaAs.

On the structure with the upper epitaxial layer of gallium arsenide 2 (Fig. "A") was deposited a film of silicon dioxide 3 with a thickness of 0.35 μm from a gas mixture of monosilane with argon at a temperature of 450 ^o C (Fig. "A"). A supporting film of europium oxide 4 with a thickness of ≃ 0.1 μm was deposited onto silicon dioxide by evaporation in a vacuum using an electron beam evaporator on plates heated to 100 ^° C (Fig. "B").

Далее следовал отжиг полученной системы при температуре 450^oC в течение 1 мин в среде водорода, после чего осуществлялась "взрывная" фотолитография путем растворения вспомогательного слоя оксида европия в растворе HCl H₂O (1 10), в результате чего формировались контакты к полосковым областям, образованным в пленке двуокиси кремния (фиг. "ж"). После этого на полученную структуру наносилась металлизация второго уровня 7, состоящая из адгезионного подслоя хрома толщиной

и пленки золота толщиной 0,4 мкм при нагреве пластин до 250^oC, обеспечивающая надежное покрытие как к металлизации первого уровня (AuZn), так и к пленке двуокиси кремния (фиг. "з").Then, a resistive mask 5 with strip-wide windows was formed on the resulting structure; 3 μm (Fig. "C"), with which etching of dielectric films was carried out. The europium oxide film was etched in an HCl solution of H ₂ O (1 10), and the silicon dioxide in the etchant was made of HF NH ₄ F (40%) (1 9). After etching, the structure takes the form corresponding to FIG. "g". Then, the resistive mask was removed in a mixture of dimethylformamide with monoethanolamine (Fig. E), after which the metallization of the first level 6, consisting of an alloy of AuZn (90 10), creating a low-resistance contact to gallium arsenide (Fig. "E"), was applied. The film thickness was

This was followed by annealing the obtained system at a temperature of 450 ^o C for 1 min in a hydrogen medium, followed by "explosive" photolithography by dissolving an auxiliary layer of europium oxide in a solution of HCl H ₂ O (1 10), resulting in the formation of contacts to strip regions formed in the film of silicon dioxide (Fig. "g"). After that, the metallization of the second level 7, consisting of an adhesive chromium sublayer with a thickness of

and gold films with a thickness of 0.4 μm when the plates are heated to 250 ^° C., which provides a reliable coating both to first-level metallization (AuZn) and to a silicon dioxide film (Fig. “h”).

 Example 4. The manufacture of contacts to the planar side of the structure containing local regions of low-alloyed n-type gallium arsenide.

создающая низкоомный контакт к арсениду галлия n-типа (фиг. "е"). Далее следовал отжиг системы при T 450^oC в течение 1 мин в среде водорода, после чего осуществлялась "взрывная" фотолитография путем растворения вспомогательного слоя оксида европия в растворе HCl H₂O (1 10). В результате этого формировались контакты к полосковым областям, образованным в пленке двуокиси кремния (фиг. "ж"). Затем на полученную структуру наносилась металлизация второго уровня 7, состоящая из подслоя ванадия толщиной

и пленки никеля толщиной 0,1 мкм при нагреве пластин до 250^oC, обеспечивающая надежное покрытие как к металлизации первого уровня (AuGe), так и к пленке двуокиси кремния.On the structure with the upper epitaxial layer of gallium arsenide n-type 2 (Fig. "A") was deposited a film of silicon dioxide 3 with a thickness of 0.35 μm from a gas mixture of monosilane with argon at a temperature of 450 ^o C (Fig. "A"). An auxiliary europium oxide film of 0.1 μm thickness was deposited onto silicon dioxide by evaporation in vacuum onto plates heated to 100 ^° C (Fig. "B"). Then, a resistive mask 5 with strip windows 3 μm wide (Fig. "C") was formed on the resulting structure, with the help of which etching of dielectric films was carried out. The europium oxide film was etched in an HCl solution of H ₂ O (1 10), and the silicon dioxide in the etchant was made of HF NH ₄ F (40%) (1 9). After etching, the structure takes the form corresponding to FIG. "g". After removing the resistive mask in a mixture of dimethylformamide with monoethanolamine (Fig. "D"), the metallization of the first level 6, consisting of an AuGe alloy (90 10) thick, was applied to the plates

creating a low-resistance contact with n-type gallium arsenide (Fig. "e"). This was followed by annealing the system at T 450 ^o C for 1 min in a hydrogen medium, followed by "explosive" photolithography by dissolving an auxiliary layer of europium oxide in a solution of HCl H ₂ O (1 10). As a result of this, contacts were formed to the stripe regions formed in the silicon dioxide film (Fig. "G"). Then, the metallization of the second level 7, consisting of a vanadium sublayer with a thickness of

and a nickel film with a thickness of 0.1 μm when the plates are heated to 250 ^° C., which provides a reliable coating both to first-level metallization (AuGe) and to a silicon dioxide film.

 The table shows comparative data on the yield of plates after the operation of manufacturing ohmic contacts according to the claimed method and the basic method (032.917 MK, 035.063 TC).

Claims (3)

1. A method of manufacturing ohmic contacts to the planar side of the structure with local regions of low-alloyed semiconductors of group A ³ B ⁵ from gallium arsenide or indium phosphide, comprising applying a dielectric film of silicon dioxide to the semiconductor structure, forming local regions under the contacts using a resistive mask, applying a contact material, annealing, characterized in that the silica film is deposited supporting dielectric film of europium oxide (Eu ₂ O _3), causing the contact ma Methods and material carried sequential formation of the first level metallization, form local contact areas "explosive" photolithography by dissolving auxiliary europium oxide film under the metal unnecessary areas, metallization of the second level is applied.  2. The method according to claim 1, characterized in that, as the metallization of the first level, alloys based on gold (Au) with a doping acceptor impurity from Zn, Be, Mn for p-type semiconductors are applied, alloys based on gold (Au) with a doping a donor impurity from Ge, Te, Sn for n-type semiconductors, providing etching selectivity relative to the europium oxide film.  3. The method according to claim 1, characterized in that as the metallization of the second level, an adhesive sublayer of V or Cr and one of the contact materials, for example, of Au, Ni, Al, are applied.

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