WO2013174579A1 - Method for producing an optoelectronic semiconductor chip, and optoelectronic semiconductor chip - Google Patents

Description

description

Process for producing an optoelectronic

Semiconductor chips and optoelectronic semiconductor chip

There will be a method of making a

optoelectronic semiconductor chip specified. In addition, an optoelectronic semiconductor chip is specified.

The document US 2006/0186417 AI relates to a

LED chip.

One problem to be solved is one

Optoelectronic semiconductor chip with a reduced

Specify contact voltage.

This object is achieved, inter alia, by a method and by an optoelectronic semiconductor chip with the

Characteristics of the independent claims solved. Preferred developments are the subject of the dependent claims.

In accordance with at least one embodiment, the method is used to produce an optoelectronic semiconductor chip. The semiconductor chip is, for example, a

Led. In particular, the semiconductor chip is for

Generation of radiation in the wavelength range between 420 nm and 600 nm furnished.

According to at least one embodiment, according to the

Method provided a semiconductor layer sequence. The semiconductor layer sequence comprises one or more active layers for generating electromagnetic radiation. The semiconductor layer sequence is preferably epitaxial grown. In particular, the semiconductor layer sequence is based, for example, on a nitride compound semiconductor material such as Al _n In _] __ _n _ _m Ga _m N where 0 ^ n <1, 0 ^ m <1 and n + m <1. In this case, the semiconductor layer sequence may have dopants and additional constituents.

According to at least one embodiment is on the

Semiconductor layer sequence an oxygen-containing silver mirror applied. The silver mirror is applied by sputtering. The sputtering may be DC sputtering, RF sputtering, ion beam sputtering, magnetron sputtering, or reactive sputtering.

In accordance with at least one embodiment, the silver mirror is applied in an oxygen-containing atmosphere. Oxygenated means in particular that in the

Atmosphere a non-vanishing partial pressure of

Oxygen is present. The oxygen can in this case

ionized form. Other gases in the atmosphere are preferably inert gases such as noble gases and / or nitrogen.

In accordance with at least one embodiment, this includes

Process the step of completing the semiconductor chip. This process step may include that on the

Silver mirror further layers, in particular to a

Sealing and electrical contact,

be applied. This step may also include that the semiconductor layer sequence to one of a

 Growth substrate is mounted on a different carrier substrate and that a growth substrate for the

Semiconductor layer sequence is removed from this. In at least one embodiment, the method is for producing an optoelectronic semiconductor chip

set up. The procedure includes at least the

following steps in the specified or in a different order:

 Providing a semiconductor layer sequence with at least one active layer for generating an electromagnetic radiation,

 - Applying an oxygen-containing silver mirror on the semiconductor layer sequence, wherein the application is carried out by sputtering in an oxygen-containing atmosphere, and

 - Completing the semiconductor chip.

In conventional light-emitting diode chips, to lower a contact resistance between the silver mirror and a nearest GaN-based semiconductor layer, a thin, further metal layer, for example of platinum, is applied. However, such metal layers between the silver mirror and the semiconductor layer sequence lead to an additional absorption of radiation generated in the semiconductor layer sequence.

By adding oxygen to the silver mirror, it is possible to dispense with such an absorbing, additional metallic intermediate layer. Furthermore, by the

Sputtering a particularly poor at impurities

Silver level generated, so that the silver mirror can have a high reflectivity.

According to at least one embodiment, the

Oxygen content of the atmosphere during sputtering at least 0.1% or at least 0.5% or at least 1%, or at least 5% or at least 10%. Alternatively or in addition, the oxygen content is at most 80% or at most 50% or at most 20% or at most 15%. The oxygen content is in particular on the

Partial pressure of, for example, added 02 ~ gas determined. Likewise, the oxygen content may be related to at% of the atmosphere. As an alternative or in addition to C 2 gas, it is also possible to add O 3, N _x O y, H 2 O and / or H 2 ^O 2.

In accordance with at least one embodiment, the silver mirror is produced directly on the semiconductor layer sequence. In other words, then the silver mirror and the semiconductor layer sequence touch in places or over the entire surface.

In particular, the silver of the silver mirror is in direct contact with GaN based material

Semiconductor layer sequence.

In accordance with at least one embodiment of the method, the silver mirror is produced with a plurality of partial regions. The

Subregions follow this along a growth direction of the silver mirror, which preferably parallel to a

Growth direction of the semiconductor layer is aligned and can have the same orientation, immediately

each other. For example, the silver level is grown between two and five inclusive, or between two and four portions inclusive.

In accordance with at least one embodiment, a first

Part of the silver mirror, which is the

Semiconductor layer sequence is the closest, without

Oxygen sputtered. That is, the generation of the first subregion is preferably carried out in an oxygen-free atmosphere. Oxygen-free can mean that an oxygen content is negligible and, for example, at not more than 0.1% or not more than 0.01%. In other words, oxygen is not specifically incorporated into the silver level when this first subregion is generated.

In accordance with at least one embodiment of the method, the first subregion follows in the direction away from the first subregion

Semiconductor layer sequence, a second portion of the

Silver mirror after. The second portion is particularly preferably under an oxygen-containing atmosphere

sputtered. It is then incorporated into the second subarea so targeted oxygen. The second portion preferably has a greater thickness than the first portion.

It is possible for the second subregion to be produced with a constant oxygen content in the atmosphere within the manufacturing tolerances. In the second subregion, no gradient with respect to the oxygen in the silver mirror is then set in a targeted manner. Alternatively, it is possible for the oxygen content in the direction away from the semiconductor layer sequence in the second part to be reduced or also increased in steps or continuously.

In accordance with at least one embodiment of the method, the second subarea, in the direction away from the second subarea, follows

Semiconductor layer sequence, a third portion of the

Silver mirror after. The third subregion is preferably sputtered without oxygen. In particular, the third subregion has a greater thickness than the first subregion

Subarea. The thickness of the third portion may be smaller or larger than the thickness of the second portion.

In accordance with at least one embodiment, the finished silver mirror has a total thickness of at least 50 nm or at least 70 nm or at least 90 nm. Alternatively or additionally, the total thickness of the silver level is at most 500 nm or at the highest 300 nm or at most 200 nm.

According to at least one embodiment, the first

Part of the silver mirror produced with an average thickness of at least 5 nm or at least 10 nm. The thickness of the first subarea is, for example, at most 25 nm or at most 20 nm or at most 15 nm. The thickness of the first subarea is, as with all other specified thicknesses, preferably an average thickness over the entire semiconductor layer sequence in such Areas in which the silver level is applied is averaged. As with all other thicknesses, a local deviation of the thickness of the first subregion, based on the average thickness, is preferably not more than 25% or not more than 10%.

According to at least one embodiment, the second

Partial area a thickness of at least 10 nm or from

at least 15 nm or at least 20 nm. In particular, the thickness of the second portion is at most 200 nm or at most 100 nm or at most 50 nm or at most 30 nm.

According to at least one embodiment, the thickness of the third portion is at least 50 nm or at least 100 nm. It is possible that the thickness of the third

Subrange is at most 300 nm or at most 150 nm. In accordance with at least one embodiment, a protective layer is applied directly to the silver mirror. The

Protective layer is preferably impermeable to gaseous oxygen and / or to silver ions. Impermeable

means that the intended use of the

Semiconductor layer sequence and the semiconductor chip and over a mean lifetime of the semiconductor chip across propagate significant amounts of silver and / or oxygen through the protective layer. In other words, the protective layer is preferably one

Barrier for silver and for oxygen.

In accordance with at least one embodiment, the protective layer is electrically conductive. In particular, by the

Protective layer and also through the silver mirror through an energization of the semiconductor layer sequence during operation of the semiconductor chip.

According to at least one embodiment, the

Protective layer or the protective layer consists of an oxide, a nitride or an oxynitride. In particular, the

Protective layer of ZnO, which may be doped shaped. It is also possible that the protective layer is formed from (111203)] __ _x (SnC> 2) _x , in particular 0.05 ^ x ^ 0.25 or 0.07 <x <0.15.

In accordance with at least one embodiment, the protective layer has an average thickness of at least 30 nm or at least 50 nm or at least 80 nm. Alternatively or

In addition, the average thickness of the protective layer is at most 500 nm or at most 200 nm or at most 250 nm. According to at least one embodiment of the method, the silver level becomes exactly two or exactly three

Applied partial areas. Likewise, it is possible that the silver mirror has only a single portion, which comprises the entire silver level and which preferably with a uniform, not deliberately varied

Oxygen content is generated.

In accordance with at least one embodiment of the method, no tempering of the silver mirror takes place during or immediately after the steps of applying the silver mirror and in particular also the application of the protective layer. In particular, annealing is a process in which there is an elevated temperature of, for example, at least 90 ° C, or at least 150 ° C, or at least 300 ° C, which process is arranged to cause oxygen diffusion within the silver mirror. A duration of such

Temperature increase is for example at least 5 minutes or at least 10 minutes. In other words, the introduction of oxygen into the silver mirror is not or not done

predominantly by means of thermally driven diffusion.

In accordance with at least one embodiment of the method, the oxygen content of the silver level, averaged over the entire silver level, is at least 0.002 at.% Or at least 0.02 at.% Or at least 0.1 at.%.

Alternatively or additionally, this oxygen content is at most 10 atomic% or at most 2.5 atomic% or at most 1 atomic%. In particular, the oxygen content is about 0.2 atomic%.

According to at least one embodiment, the

Silver mirror made of oxygen and silver. That is, except Silver and oxygen are in the silver mirror no further substances, in particular metals, specifically introduced and there is no significant change in physical properties of the silver mirror caused by additional substances. This can mean, for example, that

Contamination by other substances account for a proportion of the silver level of at most 500 ppm or at most 200 ppm or at most 50 ppm.

In accordance with at least one embodiment, the surface of the semiconductor layer sequence, to which the silver mirror is applied directly, has a square roughness, English rms roughness or root-mean-squared roughness, of at most 5 nm or at most 1 nm.

In accordance with at least one embodiment, the finished silver mirror has a reflectivity of at least 0.90 or at least 0.94 at a wavelength of 450 nm.

According to at least one embodiment of the method, the application of the silver mirror in an atmosphere having a pressure of at least 5 x 10 ^ mbar or at least 1 x 10 ^-3 mbar. The pressure is preferably at most 1 × 10 ^-2 mbar or at most 5 × 10 ^-2 mbar.

In accordance with at least one embodiment, the silver level is applied at a growth rate of at least 0.1 nm / s or at least 0.5 nm / s. Furthermore, the application may alternatively or additionally with a

Growth rate of at most 20 nm / s or at most 5 nm / s. According to at least one embodiment, the silver mirror is applied at a temperature of at least 0 ° C. Alternatively or additionally, the application is carried out at a temperature of at most 100 ° C or at most 80 ° C or at most 50 ° C. In particular, the application is carried out at room temperature, ie at about 25 ° C. The temperatures stated here relate in particular to the

Temperature of a surface of the semiconductor layer sequence on which the silver mirror is applied.

In addition, an optoelectronic semiconductor chip is specified. The semiconductor chip is preferably with a

Processes as described in connection with one or more of the above embodiments. Features of the semiconductor chip are therefore also for the

Method disclosed and vice versa.

In at least one embodiment, the

optoelectronic semiconductor chip one

 Semiconductor layer sequence with at least one active layer for generating electromagnetic radiation. An oxygen-containing silver mirror is located directly on the semiconductor layer sequence. An oxygen content of the

Silver level is between 0.02 atom% and 2.5 atom% inclusive. Other materials except silver and oxygen account for at most 100 ppm of the silver level. ppm stands for parts per million.

Hereinafter, a method described herein and an optoelectronic semiconductor chip described herein with reference to the drawings using exemplary embodiments will be explained in more detail. The same reference numerals indicate the same elements in the individual figures. There are, however no scale relationships shown, but individual elements may be exaggerated to better understand.

Show it:

Figure 1 is a schematic representation of a method for

 Production of one described here

 optoelectronic semiconductor chips, and

Figures 2 and 3 are schematic sectional views of

 Embodiments of optoelectronic semiconductor chips described here.

1 shows a schematic sectional view of a method for producing an optoelectronic

Semiconductor chips 1 illustrated. According to FIG. 1A, a

Semiconductor layer sequence 2 with an active layer 20 is provided. The semiconductor layer sequence 2 is based on AlInGaN or on InGaN. In operation, in the active

Layer 20 in particular produces blue light.

The semiconductor layer sequence 2 is grown on a growth substrate 9. A growth direction G points from the

Growth substrate 9 away and is perpendicular to a

Main extension direction of the semiconductor layer sequence 2 oriented.

In Figure 1B, the application of an oxygen-containing

Silver mirror 3 on the semiconductor layer sequence 2

illustrated. Along the growth direction G follows the

Silver mirror 3 directly on the semiconductor layer sequence. 2 The silver mirror 3 is generated by sputtering. The sputtering of silver, short Ag, takes place in one

oxygen-containing atmosphere with a noble gas such as Ar and with the addition of, for example, O2 · Ein

Oxygen partial pressure is in this atmosphere

for example, about 10% or about 20%.

It is possible that the entire silver mirror 3 is sputtered under the same atmospheric and temperature conditions. Optionally, it is possible for the silver mirror 3 to be produced with a plurality of partial regions. The subregions are symbolically separated from each other in FIG. 1B by a dot line. One of the semiconductor layer sequence 2 next partial portion of the silver mirror 3 is preferably free or grown substantially free of oxygen. This

Partial area has a thickness of, for example, about 10 nm. Oxygen-free can mean that

Oxygen concentration is at most 1 x ΙΟ ^ cm ^~ 3.

This oxygen-free subregion is followed, in the direction along the growth direction G, immediately by a second subregion, which can make up the remaining silver mirror 3. This second portion is grown in the presence of oxygen.

It is optionally possible for this second subregion to have a third subregion along the growth direction G,

follows, unlike drawn in Figure 1B. In this case, it may be that the oxygen-containing second portion has only a small thickness of about 20 nm and the remaining part of the silver mirror 3 through the

Oxygen generated generated, third portion is formed. In the case of such a thin, oxygen-containing portion, it is also possible that the oxygen in the silver mirror 3 is evenly distributed via annealing. Preferably, however, there is no annealing to one

enhanced oxygen diffusion. The uneven distribution of the oxygen in the silver mirror with respect to the various partial regions may be substantially retained after the completion of the semiconductor chip 1.

Alternatively, it is also possible that the

Semiconductor layer sequence 2 closest portion of the silver mirror 3 is generated with oxygen and a

further, immediately following subarea or the entire remaining silver mirror 3 is generated oxygen-free.

A silver mirror 3 nearest area of the

Semiconductor layer sequence 2 is preferably p-doped,

for example, with magnesium and at a concentration of between 1 x ₁₀ 19 cm ^J and 2 x ₁₀ 20 cm 3. Such a boundary layer of the semiconductor layer sequence 2 has, for example, a thickness between 2 nm and 20 nm inclusive.

In the semiconductor layer sequence 2 nearest

Boundary layer of the silver mirror 3 may be at a comparatively low concentration further substances from the semiconductor layer sequence 2, ie in particular gallium, nitrogen, aluminum, indium, silicon, germanium and / or magnesium. The boundary layer is special

preferably has a thickness of at most 5 nm or at most 2 nm and the other substances, ie all substances except silver and oxygen, make at this boundary layer preferably has a combined content of at most 100 ppm. In remaining areas of the silver level, impurities are preferably at most 10 ppm.

According to Figure IC is on the silver mirror 3 a

Protective layer 4 applied. The protective layer 4 is

for example, formed from doped ZnO or ITO and has a thickness of in particular about 100 nm. In the direction away from the semiconductor layer sequence 2, the protective layer 4 preferably follows a metal layer 5 after. The metal layer 5 is configured, for example, to expand the current and / or to make contact with the semiconductor layer sequence 2. For example, the metal layer 5 is formed of TiAu or PtAu. The metal layer 5 has, for example, a thickness of between 250 nm and 15 μm. Differently than illustrated, as in all other embodiments, the metal layer 5 can be composed of several partial layers with different material compositions.

In FIG. 1D, the finished semiconductor chip 1 is shown schematically in a sectional view. Compared to FIG. 1C, the growth substrate 9 is of the

 Semiconductor layer sequence 2 is removed and on the metal layer 5, a carrier substrate 6 is attached. For an attachment of the carrier substrate 6 may be between the metal layer 5 and the support substrate 6 optionally further, not

drawn layers, in particular solder layers are located.

Further, on the side facing away from the carrier substrate 6 side of the semiconductor layer sequence 2, a roughening to improve a radiation decoupling is generated. On this side of the semiconductor layer sequence 2 is further a first electrical Contact 7a attached. Of the first electrical contact 7a can not optionally in Figure 1D

drawn power distribution structures go out.

A second electrical contact 7b is through the

Metal layer 5, the protective layer 4 and the silver mirror 3 is formed.

Optionally, on the side facing away from the carrier substrate 6 side of the semiconductor layer sequence 2 further, not shown layers are applied. Such further layers may be wavelength conversion materials

Passivations and / or act on optic bodies.

FIG. 2 shows a further exemplary embodiment of the invention

Semiconductor chips 1 shown. The semiconductor layer sequence 2 in this case is not the entire surface in direct contact with the silver mirror 3, unlike in connection with Figure 1 shown. In places are between the

Silver mirror 3 and the semiconductor layer sequence 2 a plurality of regions 8 with a material having a low optical refractive index. The material 8 may be electrically conductive or electrically insulating.

A further exemplary embodiment of the semiconductor chip 1 can be seen in FIG. The first electrical contact 7 a is attached to the carrier substrate 6 and extends in the form of a particular truncated conical shaped protuberance through the metal layer 5, the protective layer 4 and the

Silver mirror 3 into the semiconductor layer sequence 2. The first electrical contact 7a also pierces the active layer 20th The protuberance of the first electrical contact 7 a is surrounded laterally and toward the metal layer 5 by an electrical insulation layer 75. An energization of the

In operation, semiconductor chips 1 are thus produced on the one hand by the second electrical contact 7b, formed by the silver mirror 3, the protective layer 4 and the metal layer 5, and on the other hand by the first electrical contact 7a penetrating the silver mirror 3.

Unlike in FIG. 3, the first electrical contact 7a preferably has a multiplicity of the active ones

Layer 20 penetrating protuberances on. Furthermore, between the first contact 7 a and the

Carrier substrate 6 not shown intermediate layers

be present to an attachment of the

Semiconductor layer sequence 2 to the support substrate 6 to

simplify.

The carrier substrate 6 is preferably located on the p-doped side of the semiconductor layer sequence 2 and follows, along the growth direction G, the silver mirror 3

preferably after. This is preferably the case in all other embodiments. Deviating from this, the silver mirror 3 but also on an n-side of the

Semiconductor layer sequence 2 may be arranged.

The invention described here is not by the

Description limited to the embodiments.

Rather, the invention encompasses any novel feature as well as any combination of features, including in particular any combination of features in the claims, even if this feature or combination itself is not explicit is specified in the claims or exemplary embodiments.

This patent application claims the priority of German Patent Application 10 2012 104 553.4, the disclosure of which is hereby incorporated by reference.

Claims

claims 1. A method for producing an optoelectronic  Semiconductor chips (1) with the steps:  Providing a semiconductor layer sequence (2) with at least one active layer (20) for generating electromagnetic radiation,  - Applying an oxygen-containing silver mirror (3) on the semiconductor layer sequence (2), and  Finishing the semiconductor chip (1),  wherein the application by sputtering in a  oxygen-containing atmosphere takes place. 2. Method according to the preceding claim,  in which an electrically conductive protective layer (4) is applied directly on the silver mirror (3),  wherein the protective layer (4) is formed with or of an oxide, a nitride or an oxynitride. 3. Method according to the preceding claim,  wherein the protective layer (4) of ZnO or of (ln ₂ 0 ₃ ) i- _x (SnO ₂ ) _{x is formed} to be 0.05 <x <0.25, wherein an average thickness of the protective layer (4) is between 30 nm and 200 nm inclusive. 4. The method according to any one of the preceding claims, wherein an oxygen content of the atmosphere Sputtering is at least temporarily between 0.1% and 20% and the oxygen is introduced during sputtering in the silver mirror (3). 5. The method according to any one of the preceding claims, wherein the silver mirror (3) directly on the semiconductor layer sequence (2) is generated. 6. The method according to any one of the preceding claims,  in which one of the semiconductor layer sequence (2)  nearest first subarea (31) of the  Sputtered silver (3) is sputtered without oxygen, with a total thickness of the silver level (3) between 70 nm and 300 nm inclusive. 7. Method according to the preceding claim,  where, in the direction away from the  Semiconductor layer sequence (2), to the first portion (31) connects a second portion (32) of the silver mirror (3),  wherein the second portion (32) is sputtered with oxygen. 8. Method according to the preceding claim,  where, in the direction away from the  Semiconductor layer sequence (2), to the second  Subregion (32) connects a third portion (33) of the silver mirror (3),  wherein the third portion (33) is sputtered without oxygen. 9. The method according to any one of the preceding claims,  wherein the first portion (31) has an average thickness between 5 nm and 25 nm inclusive, and / or wherein an average thickness of the second Subregion (32) is between 10 nm and 50 nm inclusive. 10. The method according to any one of the preceding claims, wherein during or immediately after the steps of applying the silver mirror (3) and the application of the protective layer (4) no annealing of the silver mirror (3) takes place at temperatures above 90 ° C. 11. The method according to any one of the preceding claims,  wherein an oxygen content of the silver level (3) averaged over the entire silver level (3) is between 0.02 atom% and 2.5 atom% inclusive. 12. The method according to any one of the preceding claims,  in which the silver mirror (3) consists of oxygen and silver,  wherein other substances make up a proportion of the silver level (3) of at most 100 ppm. 13. The method according to any one of the preceding claims,  in which the application of the silver mirror (3) - at a pressure of between 5 x 10 -4 mbar and 5 x 10 ^-2 mbar,  a growth rate of between 0.1 nm / s and 20 nm / s, and  - Is carried out at a temperature of the semiconductor layer sequence (2) between 0 ° C and 80 ° C inclusive. 14. Optoelectronic semiconductor chip (1) with  - A semiconductor layer sequence (2) with at least one active layer (20) for generating a  electromagnetic radiation, and  - an oxygen-containing silver mirror (3) directly on the semiconductor layer sequence (2), wherein - an oxygen content of the silver level (3) is between 0.02 atom% and 2.5 atom% inclusive, and - other substances than silver and oxygen account for at least 200 ppm of the silver level (3).