DE20320295U1 - A process for preparation of an electrical contact region on an n-conductive AlGaInP-based layer by the steps useful in semiconductor technology - Google Patents

Abstract

A process for preparation of an electrical contact region on an n-conductive AlGaInP-based layer by:application of an electrical contact material containng Au and at least one doping material, i.e. an element from the group Ge, Si, Sn, and Te, and of tempering the n-conductive AlGaInP-based layer. An independent claim is included for a structural element having an epitaxial semiconductor layer series with an electromagnetic radiation emitting active zone.

Description

The invention relates to a Component that has an epitaxial semiconductor layer sequence active zone emitting electromagnetic radiation, the semiconductor layer sequence on one side with an n-type AlGaInP-based Completes shift on which an electrical contact is applied.

An AlGaInP-based layer is to be understood as a layer which comprises at least one material with the composition Al _x Ga _y In _1-x-y P with 0 ≤ x ≤ 1, 0 ≤ y ≤ 1 and x + y ≤ 1.

For commercial, AlGaInP-based Semiconductor devices is the front, i.e. that of a growth substrate opposite side of a semiconductor layer sequence, usually doped in such a way that she is p-conductive. This is due in particular to the fact that commercial GaAs substrates are used in the required quality are only available as n-doped substrates, on which initially one n-doped epitaxial semiconductor structure is applied. Out this is why electrical contacts are based on AlGaInP So far, semiconductor layer sequences have been produced almost exclusively on p-doped layers.

Below are external semiconductor layers hereinafter, semiconductor layers of a semiconductor layer sequence to understand those on one side, at least in some areas are further subordinate semiconductor layers.

External n-type AlGaInP-based Semiconductor layers occur, for example, in thin-film light-emitting diodes. at their manufacture is like the epitaxial semiconductor layer sequence common practice finished with a p-type layer. Then on this a carrier substrate is applied and the growth substrate is at least partially covered by the semiconductor layer removed so that a n-type semiconductor layer, which started with the growth, is exposed.

Another way to have n-type exterior Get semiconductor layers when growing up with a p-type layer is completed, p-type layers on at least one Remove point until part of an n-type to be contacted Layer exposed. In this way you can, for example, at a Make the LED both electrical contacts on one side.

There are also technologies conceivable in which when growing an epitaxial AlGaInP-based Semiconductor layer sequence started with a p-type layer and is finished with an n-type layer, so that from the start an n-type semiconductor layer is on the outside.

In order to produce an electrical contact to an n-type AlGaInP-based semiconductor layer, an electrically conductive contact to a GaP intermediate substrate can be produced, for example by means of direct wafer bonding, to which an electrical connection contact is then applied (see, for example, FA Kish, FM Steranka et al., "Very high-efficiency semiconductor wafer-bonded transparent substrates (Al _x Ga _{1- x} ) _0.5 In _0.5 P / GaP light emitting diodes", 1994, Appl. Phys. Lett. 64 ( 21): 2839-2841) In contrast, the technology for producing an electrical connection contact applied directly to such an n-type semiconductor layer has not yet been sufficiently developed, and at the same time the need for possibilities for producing such electrical contacts is increasing.

The present invention has the Task to provide a device in which an electrical Contact area directly on an n-type AlGaInP-based semiconductor layer is arranged.

This task is performed using a component solved the features of claim 1.

Further refinements and training the invention result from the remaining claims.

A method of making a electrical contact area on an n-type AlGaInP-based Layer includes applying electrical contact material, which has Au and at least one dopant, the dopant has at least one element from the group Ge, Si, Sn and Te, and subsequent annealing. Annealing causes diffusion of Dopant from the contact material in the AlGaInP layer, whereby this is heavily n-doped in the edge region. This will make one Potential barrier between the AlGaInP based layer and the Contact material so narrow that it is effectively an ohmic electrical one Contact is created. The term dopant refers in this context, therefore, on the function of the respective substance in the AlGaInP-based layer, in which of these in particular diffused into it during tempering.

By applying an electrical contact structure directly on the n-type AlGaInP-based layer, compared to making an electrical contact via a Intermediate substrate, a significantly simplified process. With this let yourself about achieve a simple layer structure, so that both manufacturing costs as well as manufacturing time can be saved.

The proportion of dopants in the electrical contact material is with particular advantage between 0 and 5 percent by weight, preferably between 0 and inclusive 3 percent by weight, particularly preferably between 0.1 inclusive and including 1.5 percent by weight.

Au and dopants can be present together in an alloy, which is a possible embodiment. Alternatively, the electrical contact material can also be composed of several material layers, at least one of which consists essentially of Au and at least one further essentially consists of at least one of the dopants.

Also with a special advantage the electrical contact material has at least one alloy with Au and at least one of the dopants, the ratio of Au and dopant about the respective eutectic composition equivalent. This contains for Au-Ge about 12 weight percent Ge, for Au-Si about 3 weight percent Si, about 20% by weight Sn for Au-Sn and about 42% for Au-Te Te. Eutectic compositions have a lower melting point on, why such a contact material appropriately about then to choose if provided, annealing and soldering the chip with a bond wire to perform simultaneously or if a simple peeling of the electrical contact material is desired.

Before or after annealing the n-type AlGaInP-based Layer is preferably applied electrical connection material such that it has contact with the contact material. The contact should be from be of a kind that after performing all procedural steps there is electrical contact between the electrical connection and contact material.

Advantageously, the electrical connection material at least seen from the n-type AlGaInP-based layer a first and a second layer, the first layer represents a diffusion barrier and the second layer is an electrical one Forms pad.

Here, the first layer preferably at least one of the substances Ti, Pt, TiPt, TiW, TiN and TiW: N and the second layer on at least one of the substances Al and Au. It is also possible that the first layer has several such partial layers.

It is particularly preferred in the Method before applying the contact material at least one for the Electrical contact area provided area on the n-type AlGaInP-based layer cleaned. With this measure can one significant improvement in the reproducibility of the electrical contacts in terms of their conductivity achieve what an effective use of the method according to the invention in a series production is required.

Before contact material is applied with particular advantage applied a layer that at least one of the substances Ti, Cr, V and Ni and a thickness between 0.1 nm and 100 nm, preferably between 1 and 20 nm, the Limits are included. By placing the contact material under it with such substances the lowest temperature for tempering, in which there is still a sufficiently good electrical contact can be reduced. It also adds liability between the contact material and the n-type AlGaInP-based layer improved.

The electrical contact area will preferably generated by first applying a mask layer in one step the AlGaInP-based Layer is applied, in which at the places where electrical Contact areas are provided, windows are formed. To the application of the electrical connection material that on the mask layer located contact and connection material by removing the Mask layer lifted off. With such a method it is possible to To make contact area with only one lithography process, even if it has multiple layers.

In a particularly preferred embodiment of the method according to the invention, the n-conducting AlGaInP-based layer is doped with at least one of the substances Te, Si, Se, S, Ge and Sn, with a concentration which is greater than or equal to 5 · 10 ¹⁷ cm ^{. 3} and is preferably in the range greater than or equal to 8 x 10 ¹⁷ cm ^-3 and less than or equal to 5 x 10 ¹⁹ cm ^-3 .

The n-type AlGaInP-based layer is advantageously part of a growth substrate grown epitaxial semiconductor layer sequence, which with the n-type AlGaInP-based layer grew up starting. The n-type AlGaInP-based layer is exposed by the semiconductor layer sequence on the front on a carrier substrate is applied and subsequently the growth substrate and any Intermediate layers between the growth substrate and the epitaxial Semiconductor layer sequence are removed. Front means in this context on that facing away from the growth substrate Side of the semiconductor layer sequence. In this embodiment the process can be the carrier substrate significantly thinner chosen as the growth substrate become.

Such an epitaxial semiconductor layer sequence is preferred a light-emitting diode layer sequence, in particular for a thin-film light-emitting diode.

Before the annealing, between the carrier substrate and the epitaxial semiconductor layer sequence expediently a solder layer is formed. Below is at a temperature annealed, in which the solder layer essentially does not melt.

In a particularly advantageous embodiment of the process can be done before the tempering on that of the epitaxial Semiconductor layer sequence facing away from the carrier substrate an electrical Back contact muster. Thus, both the electrical contact area as well as the rear contact at the same time be annealed.

The carrier substrate expediently has a semiconductor material, in particular GaAs or Ge on and the back contact preferably has Au and at least one of the substances Ge, Zn and Be.

A component according to the invention has an epitaxial one Semiconductor layer sequence with electromagnetic radiation emitting active zone, with the semiconductor layer sequence on one side with an n-type AlGaInP-based layer an electrical contact is applied. The electrical contact comprises contact material, which Au and at least one dopant has, wherein the dopant at least one element from the group Contains Ge, Si, Sn and Te.

The electrical contact preferably has electrical connection material on.

The proportion of dopants in the electrical contact material is with particular advantage between 0 and 5 percent by weight, preferably between 0 and inclusive 3 percent by weight, particularly preferably between 0.1 inclusive and including 1.5 percent by weight.

Advantageously, the electrical connection material at least seen from the n-type AlGaInP-based layer a first and a second layer, the first layer represents a diffusion barrier and the second layer is an electrical one Forms pad.

Here, the first layer preferably at least one of the substances Ti, Pt, TiPt, TiW, TiN and TiW: N and the second layer on at least one of the substances Al and Au. In this context it is also possible that the first layer has several such sub-layers.

The contact material is advantageously with underlaid with a layer containing at least one of the substances Ti, Cr, V and Ni and a thickness between 0.1 nm and 100 nm, preferred has between 1 and 20 nm, the limits included in each case are. By underlaying the contact material with such substances among other things the liability between the contact material and the n-type AlGaInP-based Layer improved.

In a particularly preferred embodiment of the component according to the invention, the n-conducting AlGaInP-based layer is doped with at least one of the substances Te, Si, Se, S, Ge and Sn, with a concentration which is greater than or equal to 5 · 10 ¹⁷ cm ^{. 3} and is preferably in the range greater than or equal to 8 x 10 ¹⁷ cm ^-3 and less than or equal to 5 x 10 ¹⁹ cm ^-3 .

The epitaxial semiconductor layer sequence is preferred of the component a light-emitting diode layer sequence, in particular one Thin-film LED.

Further advantages and preferred embodiments result from the following in connection with the 1a to 2e described two embodiments. In a schematic representation:

the 1a and 1b different process stages of a first embodiment of the method according to the invention and

the 2a to 2e different process stages of a second embodiment of the method.

1a shows one on a growth substrate 17 grown epitaxial semiconductor layer sequence 8th , This is with an n-type AlGaInP-based layer 7 grown up and has an electromagnetic radiation emitting active zone (not shown). The AlGaInP-based layer 7 has at least one material of the composition Al _x Ga _y In _1-x-y P with 0 ≤ x ≤ 1, 0 ≤ y ≤ 1 and x + y ≤ 1. For example, it consists of GaP. The active zone has, for example, a radiation-generating pn junction or a radiation-generating single or multiple quantum structure. Such structures are known to the person skilled in the art and are therefore not explained in more detail. The growth substrate 17 can consist of n-doped GaAs, for example.

In 1b is the epitaxial semiconductor layer sequence 8th on the front, ie with that of the growth substrate 17 opposite side on a carrier substrate 14 applied and the growth substrate 17 from the epitaxial semiconductor layer sequence 8th away. On the exposed n-type AlGaInP-based layer 7 becomes an electrical contact 2 manufactured. This has an approximately 10 nm thick Ti layer 16 , a contact layer 3 from Au: Ge with about 1 percent by weight Ge, as well as connection material 6 on. The connection material 6 includes a barrier layer 4 , which consists of nitrogen-doped TiW, and a connection layer 5 made of aluminium. These different layers of material of electrical contact 2 can be applied, for example, by lithography using mask layers and vapor deposition. The surface of the connection layer 5 is suitable for connecting a bond wire.

Alternatively, the contact layer 3 consist of two sub-layers, one of which can be, for example, a 10 nm thick Ge layer and the other, for example a 200 nm thick Au layer. Both orders are possible. A contact layer is also possible, which consists of an alloy of, for example, 88 percent by weight Au and 12 percent by weight Ge, which is the eutectic composition for these materials.

The epitaxial semiconductor layer sequence 8th is by means of a solder layer 11 with the carrier substrate 14 connected. Between the solder layer 11 and the epitaxial semiconductor layer sequence 8th are from the solder layer 11 seen from a barrier layer 10 and an AuZn layer 9 applied. Between the solder layer 11 and the carrier substrate 14 are from the solder layer 11 seen from another barrier layer 12 as well as an electrical intermediate contact 13 applied. On that of the epitaxial semiconductor layer sequence 8th opposite side of the carrier sub strats 14 is an electrical back contact 15 applied.

The carrier substrate 14 can for example consist of GaAs, the intermediate contact 13 and the back contact 15 can consist of Au: Ge, for example, the solder layer 11 is for example from AuSn.

The n-type AlGaInP-based layer is doped with tellurium, with a concentration of approximately 1 · 10 ¹⁹ cm ^-3 . It is applied before the electrical contact area is applied 2 cleaned, which can happen, for example, with highly dilute HCl, cold phosphoric acid or a solution containing hydrofluoric acid.

Below is the thin film light emitting diode chip 1 annealed so that Ge from the contact layer 3 of the electrical contact area 2 , from the intermediate contact 13 as well as the back contact 15 can diffuse into the respective adjacent semiconductor layer, thus forming a highly conductive electrical contact which is practically ohmic. The annealing is carried out for a sufficiently long time and at a temperature at which the solder layer 11 essentially does not melt, which could otherwise lead to an unfavorable deformation of the solder layer when it re-solidifies and to an impairment of the properties of the thin-film light-emitting diode chip.

The application of the Ti layer 16 leads to a lower minimum temperature during tempering, at which a sufficiently good electrical contact is formed. This can be particularly in connection with the possible method step of annealing at a temperature at which the solder layer 11 essentially does not melt, be particularly advantageous for the process.

In 2a to 2e is an n-type AlGaInP-based layer 7 shown, to which an electrical contact area is applied by means of lifting technology. For this, a mask layer is first 18 upset what in 2a is shown. In the mask layer 18 a window is formed in such a way that the areas of the mask layer delimiting the window 18 an acute angle with the surface of the n-type AlGaInP-based layer 7 include so that the window is on its to the n-type AlGaInP-based layer 7 facing side has a larger cross section than on its opposite side (see 2 B ).

In 2c is a contact layer using a directional deposition process 3 applied. Subsequently, a barrier layer is created using an undirected, overmolding coating process 4 as well as a connection layer 5 upset as in 2d is shown. It should be pointed out here that the connection layer can in principle also be produced using non-overmolding processes. The mask layer can be removed using a solvent 18 subsequently removed and thus the material located thereon can be lifted off. A suitable material for the mask layer 18 and a suitable solvent for dissolving them are known to the person skilled in the art and are not explicitly stated here. What remains is as in 2e shown, only the electrical contact area 2 which can subsequently be annealed.

The description of the process and of the component using the exemplary embodiments is self-evident not as a limitation to view the invention on this. For example, the epitaxial Semiconductor layer sequence with an n-type AlGaInP-based layer finally have grown up so that she is exposed from the start and can be contacted directly electrically. In addition, the contact material must and / or the connection material not be applied in the form of a layer. Rather, it can electrical contact material also in any form and also on several, not connected Areas are applied distributed. Likewise, the connection material by no means all over be applied to the contact material, but it is sufficient if materials in one place, e.g. in a plane perpendicular to n-type AlGaInP-based layer, touch such that there is a sufficiently good electrical contact between can train them.

Claims (10)

Component that has an epitaxial semiconductor layer sequence active zone emitting with electromagnetic radiation, wherein the semiconductor layer sequence on one side with an n-type AlGaInP-based layer completes on which an electrical Contact is applied in which the electrical contact is electrical Comprises contact material which has Au and at least one dopant, wherein the dopant is at least one element from the group Ge, Contains Si, Sn and Te. Component according to Claim 1, in which the electrical Contact has electrical connection material. Component according to one of the preceding claims, which the proportion of dopants in the electrical contact material at the most 5 percent by weight, preferably at most 3 percent by weight, particularly preferably between 0.1 and including 1.5 percent by weight. Component according to one of the preceding claims, which is the electrical contact material from several layers of material composed, at least one of which consists essentially of Au and at least one other essentially of at least one Dopant exists. Building element according to claim 1 or 2, in which the electrical contact material has at least one Au dopant alloy in which the ratio of Au and dopant approximately corresponds to the respective eutectic composition. Component according to one of claims 2 to 5, wherein the electrical Connection material seen from the n-type AlGaInP-based layer at least has a first and a second layer, the first one Represents diffusion barrier and the second forms an electrical connection surface. The component of claim 6, wherein the first layer at least one of the substances Ti, Pt, TiPt, TiW, TiN and TiW: N and the second layer has at least one of the substances Al and Au. Component according to one of the preceding claims, which the contact material is underlaid with a layer that at least one of the substances Ti, Cr, V and Ni and which has a thickness between 0.1 nm and 100 nm, preferably between 1 and 20 nm, the Limits are included. Component according to one of the preceding claims, in which the n-conducting AlGaInP-based layer is doped with at least one of the substances tellurium, silicon, selenium, sulfur, germanium and tin, with a concentration greater than or equal to 5 · 10 ¹⁷ cm ^{- 3} and is preferably greater than or equal to 8 x 10 ¹⁷ cm ^-3 and less than or equal to 5 x 10 ¹⁹ cm ^-3 . Component according to one of the preceding claims, which the epitaxial semiconductor layer sequence is a light-emitting diode layer sequence, in particular for one Thin film light emitting diode.