KR20110096990A - Method for forming pattern of semiconductor device - Google Patents

Abstract

A method of forming a pattern of a semiconductor device, the method comprising: preparing a substrate, forming a metal film on the substrate, oxidizing the metal film to deform the metal oxide film, and etching the substrate using the modified metal oxide film as a mask. Forming a fine pattern, and removing the remaining metal oxide film can be made.

Description

Method for forming pattern of semiconductor device

The present invention relates to a semiconductor device, and more particularly to a method of forming a pattern of the semiconductor device.

In general, laser light of semiconductor laser devices has been put to practical use in such places as optical communication, multiple communication, and space communication.

The semiconductor laser device is a means for transmitting, recording, and reading data in a communication field such as optical communication or a device such as a compact disk player (CDP) or a digital versatile disk player (DVDP). It is widely used.

Among them, the nitride semiconductor laser device is of particular interest because of its direct transition type with high laser oscillation probability and the possibility of blue laser oscillation.

Recently, active layers grown by organometallic chemical vapor deposition (MOCVD) using nonpolar and semipolar gallium nitride (GaN) substrates have improved efficiency and high performance, resulting in an improvement over conventional polar c-plane optical devices. Is bringing.

The laser device basically has a structure between an n-type nitride semiconductor layer and a p-type nitride semiconductor layer, having an active layer made of InGaN of a multi-quantum well structure (MQW: Multi-Quamtum-Well), and the increase or decrease in wavelength is an InGaN active layer. It is decided to increase or decrease the In composition ratio.

The laser device has a structure in which an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are sequentially formed on a sapphire or GaN substrate surface, and a ridge stripe is formed on a portion of the p-type nitride semiconductor layer. Have.

The condition of the material used for the film of each laser element is that the energy gap Eg of the semiconductor layer material must be larger than the energy gap of the active layer in order to trap carriers (electrons and holes) in the active layer to obtain an inversion distribution state. In order to trap light in the active layer, the refractive index of the material of the semiconductor layer can be made smaller than the refractive index of the active layer material.

The most widely used N-type semiconductor layer is composed of GaN or AlxGa1-xN implanted with Si impurities, and the active layer structure is repeatedly repeated several times with a quantum well (QW) layer and a quantum barrier (QB) layer. Multi-quantum well (MQW) layer formed by overlapping.

The material component of the quantum well layer is mainly InxGa1-xN (0 <x≤1), and the quantum barrier layer component is composed of InyGa1-yN (0≤y <1, x> y) having a lower In composition than the quantum well layer. .

The P-type semiconductor layer is composed of GaN or AlxGa1-xN implanted with Mg impurities, and each semiconductor layer is a superlattice structure that repeatedly grows GaN and AlxGa1-xN, or a bulk form of GaN or AlxGa1-xN. It consists of a single film.

SUMMARY OF THE INVENTION An object of the present invention is to form a fine pattern using a metal oxide film of a metal thin film, so that the surface shape of various structures can be simply and stably formed without being affected by the surface structure and the size of the wafer. To provide.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above are clearly understood by those skilled in the art from the following descriptions. Could be.

The method for forming a pattern of a semiconductor device according to the present invention comprises the steps of preparing a substrate, forming a metal film on the substrate, oxidizing the metal film to transform the metal oxide film, and using the modified metal oxide film as a mask Etching to form a fine pattern, and removing the remaining metal oxide film.

The metal film may be any one of Ti, Cr, Ni, Al, and Pd, and the metal film may have a thickness of 10 to 100 kPa.

In addition, the metal film may be oxidized using an oxygen plasma (O 2 plasma).

The step of oxidizing the metal film to transform it into a metal oxide film includes determining a shape and size of a pattern to be formed on the substrate, mounting a substrate having the metal film in a reactive ion etching chamber, and oxygen in the metal film. And applying the plasma, and adjusting the application time and power of the oxygen plasma according to the shape and size of the determined pattern.

Here, the etching of the substrate is dry etching, the metal oxide film may be removed with an acid or base solution.

The surface of the substrate on which the metal film is deposited is the m-plane of the substrate, and the surface of the substrate exposed by etching may be the c-plane or the a-plane of the substrate.

Other objects, features and advantages of the invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

The pattern forming method of the semiconductor device according to the present invention has the following effects.

According to the present invention, after depositing a thin metal thin film on a substrate and inducing a metal oxide film having a non-uniform thickness on the surface through oxygen plasma treatment, and then dry etching, a portion of the oxide film acts as an etching mask to produce a fine Since the pattern of size can be formed, the surface shape of various structures can be formed simply and stably without being influenced by the surface structure and the size of a wafer.

1A to 1E are cross-sectional views illustrating a process for forming a pattern of a semiconductor device according to the present invention.
2 is a view showing a top-down type semiconductor laser device having a fine pattern according to the present invention;

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Currently, III-V nitride-based semiconductors are used as basic materials for the fabrication of blue / green laser diodes and LEDs.

In particular, the development of high power light emitting diodes (LEDs) is attracting attention as a white light source foretelling the era of light emitting diodes (LEDs).

In the manufacture of high power light emitting diodes, the nitride semiconductor epitaxial region grown on sapphire is removed using a method such as laser lift-off (LLO), and then a vertical light emitting diode structure using the exposed surface as a light emitting surface of the light emitting diode is used. It is done.

Photon generated in the active layer region has a radiation angle and emerges to the surface portion, and some total reflection occurs due to the difference in refractive index between gallium nitride (GaN) and the atmosphere and enters into the inside again, thus extracting efficienccy. Will fall.

Therefore, in order to increase the light extraction efficiency, the surface portion is roughened at present, and the diffuse reflection induced light extraction efficiency is increased.

As such, as a method of making the surface rough, a dry etching method using KOH or photolithographic work is performed.

However, when using KOH, the surface of the crystallized group group {10-11} gallium nitride (GaN) having low surface energy is revealed and has a hexagonal pyramid shape.

Therefore, the hexagonal pyramid made using KOH is a crystal plane, and all pyramids on the surface are formed with a constant vertex angle of about 60 degrees and exist together in various sizes ranging from several tens of nm to several um.

Therefore, some of the photons made in the active layer are totally reflected back into the interior due to the limitation of the crystal plane angle.

In addition, when using photolithographic work, it is difficult to make a pattern of very small size uniformly over a large area due to the limitation of photo work, and when the surface is uneven, the limit of patterning becomes larger, which is a problem for large area work. In addition, the process becomes complicated.

Accordingly, the present invention intends to provide a method for stably and simply manufacturing the surface shape of various structures without being affected by the surface structure and the wafer size.

The present invention relates to a method of forming a fine pattern on the surface of the device, after depositing a thin metal thin film on the substrate, and then induced to form a metal oxide film of non-uniform thickness on the surface by oxygen plasma treatment, and then dry etching In this case, a portion of the oxide layer may serve as an etching mask to form a pattern having a fine size.

1A to 1E are cross-sectional views illustrating a process of forming a pattern of a semiconductor device according to the present invention.

First, as shown in FIG. 1A, a substrate 10 is prepared, and a metal film 20 is formed on the prepared substrate 10 in a thin thickness.

Here, the metal film may use a metal having particularly good cohesion characteristics among metals that are easily oxidized on the surface of the substrate 10.

In the present invention, the metal film 20 may be formed using any one of Ti, Cr, Ni, Al, and Pd.

In addition, the thickness of the metal film 20 is deposited using a thin E-beam (E-beam) equipment to be less than 100 Å in consideration of the pattern depth and the etching depth, the most preferred thickness is preferably about 10-100 Å.

If the thickness of the metal film 20 is about 100 GPa or more, the area of the exposed substrate is large so that formation of a fine pattern is difficult, and when the thickness of the metal film 20 is about 10 GPa or less, it can be used as an etching mask during dry etching. none.

Therefore, when the E-beam equipment for the deposition of the metal film 20 is repeated, the thickness uniformity of the metal film 20 is about ± 10%, thereby obtaining a pattern result of the same size each time. In order to be able to deposit a metal film of the same thickness.

Next, as shown in FIG. 1B, the metal film 20 is oxidized to be transformed into a metal oxide film.

Here, the oxidation treatment of the metal film 20 may be oxidation treatment using an oxygen plasma (O 2 plasma).

In the step of oxidizing the metal film 20 to a metal oxide film, first, a shape and a size of a pattern to be formed on the substrate 10 are determined.

Subsequently, the substrate 10 having the metal film 20 is mounted in the reactive ion etching chamber by using ICP-RIE equipment.

Next, an oxygen plasma is applied to the metal film 20, and the application time and power of the oxygen plasma are adjusted according to the shape and size of the determined pattern.

As such, when the metal film 20 is oxidized, the metal film 20 is deformed into a metal oxide film, and the oxidized metal film 20 formed on the surface of the substrate 10 becomes unevenly agglomerated. 20) surface becomes uneven.

For example, when a Ti metal film is deposited on a substrate and subjected to plasma treatment, the Ti metal film deforms into a TiO 2 metal oxide film, aggregates with each other, and has a non-uniform thickness.

Accordingly, the oxidized metal film 20 has a non-uniform thickness. The region where the metal oxide film is agglomerated among the entire thickness of the oxidized metal oxide film has a relatively high thickness, and the main surface area has a relatively low thickness.

At this time, by adjusting the processing time and power of the oxygen plasma, it is possible to deform the pattern shape of the metal oxide film.

Subsequently, as illustrated in FIG. 1C, the oxidized metal film 20 is dry etched to expose the substrate 10.

Here, since the oxidized metal film 20 having a non-uniform surface is also non-uniform in thickness, dry etching may expose a substrate in a region where a relatively low thickness is located.

That is, the thin portion of the oxidized metal film 20 is partially etched first to expose a part of the surface of the substrate 10.

Next, as shown in FIG. 1D, when the substrate 10 exposed with the remaining metal film 20 as a mask is dry etched, a fine pattern is formed by an etching selectivity.

Here, when performing dry etching, the depth of the pattern may be adjusted by adjusting the etching angle and the etching power.

And, as shown in Figure 1e, by removing the remaining metal film 20, it is possible to form a fine pattern having a determined shape and size.

Here, the oxidized metal film 20 may be removed using an acid or base solution.

Since the various crystal surfaces of the nitride semiconductor substrate can be exposed using the manufacturing process of the present invention, a nitride semiconductor substrate can be produced which is advantageous for growing a desired epi.

For example, a nitride semiconductor substrate having an m-plane exposed may be prepared, and a fine pattern may be formed in which the c-plane or a-plane of the nitride semiconductor substrate is exposed using the etching process of the present invention.

As described above, the present invention forms a metal oxide film having a non-uniform thickness by depositing a thin metal film having good cohesion characteristics, particularly good for cohesion, on the surface of the substrate to about 100 kPa or less, and then performing the oxygen plasma treatment. The substrate may be etched to form a fine pattern.

The present invention can control the size and depth of the fine pattern by changing the type, thickness and plasma treatment conditions of the metal film to be deposited.

In addition, the present invention can increase the exposed surface area by about 10-50% through the surface etching of the substrate using the metal oxide film as a mask.

Therefore, the present invention can uniformly form a pattern of minute size, which is difficult to make by the photolithographic method, even in a large area.

In addition, because the minute size of the curved surface of the substrate can be used in a process that requires an increase in the surface area.

FIG. 2 illustrates a top-down type semiconductor laser device having a fine pattern according to the present invention. As shown in FIG. 2, an n-type clad layer on an n-type gallium nitride substrate 1 is illustrated. (3), the n-type waveguide layer 5, the active layer 7, and the p-type waveguide layer 9 are sequentially formed, and the p-type cladding layer 11 and the p-type contact gallium nitride in the form of a ridge thereon. The layer 13 and the p-type contact metal layer 15 are sequentially formed, and blocking layers 17 are formed on both sides of the ridge, and the p-type electrode 19 is disposed on the p-type contact metal layer 15 including the blocking layer 17. ) Is formed.

An n-type electrode 21 is formed below the n-type gallium nitride substrate 1, and the n-type electrode 21 is formed below the n-type gallium nitride substrate 1 having a non-uniform surface with a fine pattern. As a result, the contact area is large, and ohmic contact is possible.

Therefore, using the micropattern forming process method of the present invention, when fabricating an n-type ohmic electrode of a semiconductor laser diode using a nonpolar m-plane gallium nitride substrate, the c-plane or a-plane of the substrate is exposed through dry etching. By forming a fine pattern to form and implement the n-type ohmic electrode thereon, it is possible to ensure a low contact resistance, and to improve heat resistance.

Here, the fine pattern formed on the substrate is composed of a plurality of protrusions, it may be formed in a stripe shape arranged in one direction.

Here, the stripe-shaped protrusion is located in the a-plane direction of the gallium nitride substrate in the longitudinal direction, and the side is exposed in the width direction, the exposed side may be the c-plane of the gallium nitride substrate.

Alternatively, the stripe-shaped protrusion may be formed such that its longitudinal direction is the c-plane direction of the gallium nitride substrate, and the side surface exposed in the width direction is the a-plane of the gallium nitride substrate.

In addition, the protrusion of the gallium nitride substrate, which is a non-polar m-plane, may have a trapezoidal shape having a wider area of the lower surface than the upper surface, and two sides having the same length or different sides meet at one point, and the angle between the two sides is 90 degrees. It may be a triangular shape having a smaller acute angle, but is not limited thereto.

Referring to FIG. 2, a method of forming a fine pattern of a gallium nitride semiconductor substrate on which a fine pattern is formed is as follows.

First, a gallium nitride substrate on which a semiconductor layer is formed is polished through lapping and polishing processes.

In the gallium nitride substrate having the lapping and polishing processes completed, a metal (Ti, Cr, Ni, Al, Pd, etc.) that is easy to be oxidized and has good cohesion characteristics on the substrate surface on which the n-type electrode is to be formed is thinly deposited to about 100 kPa or less. Deposition using a beam (E-beam) equipment.

Here, the thickness of the metal film may be adjusted to about 50-100 kPa in consideration of the size and etching depth of the pattern result.

When the E-beam equipment is repeated, the thickness uniformity is about ± 10%. Therefore, in order to obtain a pattern result of the same size each time, a metal film of the same thickness must be deposited.

Then, oxygen plasma (O2 plasma) treatment using the ICP-RIE equipment.

Here, when the oxygen plasma treatment is performed, the metal film is deformed into the metal oxide film, and the oxide films formed on the surface are uniformly agglomerated.

Therefore, the pattern shape of the metal oxide film may be modified while controlling the plasma treatment time and power.

Subsequently, when dry etching is performed, the thin portion of the metal oxide film is partially etched first to expose a part of the surface of the substrate.

Next, the substrate is etched by the etching selectivity using the remaining oxide film as an etching mask.

Here, the depth of the pattern can be adjusted by adjusting the etching gas and the power.

Finally, the metal oxide film used as a mask can be easily removed using an acid or base solution.

In this process, a pattern of minute size, which is difficult to make by the photolithographic method, can be formed uniformly over a large area, and the surface area of the substrate is increased by the occurrence of minute size bending.

An n-type electrode is formed on the gallium nitride substrate having the increased surface area by a fine pattern.

Here, the n-type electrode may be formed by sequentially depositing Al / Ti / Au using an electron beam equipment.

As described above, since the n-type electrode formed on the fine pattern has low contact resistance and heat resistance is improved, the reproducibility, yield and reliability of the laser are improved by lowering the threshold voltage and the operation voltage of the nitride semiconductor device. You can.

In addition, it is possible to produce a device having better electrical properties than exposing the c-plane or a-plane to form the electrode thereon rather than forming the electrode on the m-plane substrate.

Until now, the fine pattern manufacturing process has been used for the ohmic contact with the n-type electrode, but when the fine pattern is formed on the surface of the semiconductor layer on the active layer using the fine pattern forming process of the present invention, light scattered from the active layer is generated. By inducing the light extraction efficiency may be increased.

As described above, the present invention utilizes the principle that a metal oxide film is unevenly formed by performing oxygen plasma treatment on a thin metal film in order to produce a fine pattern that is limited in the photolithographic method. It can be produced uniformly regardless of planarization, and the surface area can be increased.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (9)

Preparing a substrate;
Forming a metal film on the substrate;
Oxidizing the metal film to transform the metal film into a metal oxide film;
Etching the substrate using the modified metal oxide layer as a mask to form a fine pattern; And,
And removing the remaining metal oxide film. The method of claim 1, wherein the metal film is any one of Ti, Cr, Ni, Al, and Pd. The method of forming a pattern of a semiconductor device according to claim 1, wherein the metal film has a thickness of 10-100 GPa. The method of claim 1, wherein the metal film is oxidized using an oxygen plasma (O 2 plasma). The method of claim 1, wherein the step of oxidizing the metal film to a metal oxide film,
Determining a shape and a size of a pattern to be formed on the substrate;
Mounting a substrate having the metal film in a reactive ion etching chamber;
Applying an oxygen plasma to the metal film;
And adjusting the application time and power of the oxygen plasma according to the shape and size of the determined pattern. The method of claim 1, wherein the forming of the fine pattern comprises:
Dry etching the metal oxide layer to expose the substrate;
And dry etching the exposed substrate using the remaining metal oxide film as a mask to form a fine pattern. The method of claim 6, wherein in the dry etching of the metal oxide layer to expose the substrate, a thickness of the metal oxide layer is non-uniform, and a region where a relatively low thickness is located by dry etching the metal oxide layer having the non-uniform thickness. The method of forming a pattern of a semiconductor device, characterized in that to expose the substrate. The method of claim 1, wherein the metal oxide layer is removed with an acid or a base solution. The semiconductor device of claim 1, wherein the surface of the substrate on which the metal film is deposited is an m-plane of the substrate, and the surface of the substrate exposed by the etching is a c-plane or a-plane of the substrate. Pattern formation method.

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