KR20040054104A - Anisotropic Dry Etching of ZnO for Optical and Electronic Devices Using BCl3 Based Plasmas - Google Patents

Abstract

PURPOSE: An anisotropic dry etching method of zinc oxide semiconductor for a photo device using BCl3 plasma gas is provided to be capable of increasing etching rate, obtaining an uniform surface, and improving anisotropic etching characteristics. CONSTITUTION: A zinc oxide layer is deposited on a semiconductor substrate. The resultant structure is stably loaded on a susceptor in a reaction chamber. Predetermined plasma is generated by supplying BCl3-containing gas into the reaction chamber. Then, a dry etching process is carried out on the resultant structure by using the predetermined plasma. Preferably, the BCl3-containing gas further contains Cl2. Preferably, the BCl3-containing gas further contains Ar. Preferably, the dry etching process is carried out at the pressure of 1 mTorr to 1 Torr.

Description

Anisotropic Dry Etching of ZnO for Optical and Electronic Devices Using BCl3 Based Plasmas}

The present invention relates to an anisotropic dry etching method of a zinc oxide semiconductor, and more particularly, to a dry etching method of a zinc oxide semiconductor for reactive ion etching of a zinc oxide semiconductor by making a gas containing BCl ₃ into a plasma state.

Background Art Conventionally, zinc oxide based semiconductors have been used in the field of optical devices such as [Zn (Mg, Cd) O] transparent electrodes, window materials of solar cells, and varistors. However, the direct transition band structure of zinc oxide semiconductor, wide bandgap (3.37 eV), large bonding force (1.89 eV), high melting point (2248 ℃), and large exciton binding energy (60 meV) Due to its advantages, many studies have been conducted around the world as materials that can be applied as optical devices such as light emitting diodes, laser diodes, and UV-receiving devices, and communication electronic devices such as film bulk accousitc resonatior (FBAR).

In order to manufacture high quality optical devices and communication devices using such zinc oxide semiconductors, an etching process is required. However, in the case of zinc oxide semiconductors, since the strength of chemical bonding between zinc and oxygen is relatively high, it is difficult to perform satisfactory etching by the wet etching method, and it is difficult to obtain a vertical sidewall even after etching. In particular, in order to fabricate high-quality light emitting devices (LEDs) or laser diodes (LDs), an etching process having a vertical side surface having high anisotropy, a high etching rate, a high selectivity, and a uniform etching side surface is essential. Therefore, in order to fabricate an optical device, an electronic device, and a communication device using a zinc oxide semiconductor, it must be etched by a dry etching method.

The basic structure of an optical device using a zinc oxide semiconductor is obtained by sequentially growing n-type and p-type zinc oxide semiconductors on a substrate and bonding them together. However, since a sapphire, which is a non-conductor, is mainly used as a substrate for growing a zinc oxide semiconductor, an upper semiconductor layer must be etched to expose an n-type zinc oxide semiconductor layer for ohmic contact. In this case, since the semiconductor layer to be etched usually has a thickness of several μm, not only the etch rate should be large, but a process capable of maximally suppressing the influence on ohmic characteristics should be selected. In particular, in order to realize a high quality laser diode LD, the anisotropic etching characteristic and the roughness of the sidewall of the etched zinc oxide semiconductor must be low so that the etch side is vertical.

Halogen gas plasmas such as chlorine (Cl ₂ ), bromine (Br ₂ ) and iodine (I ₂ ) are mainly used for dry etching of II-VI or III-V compound semiconductors. At this time, the halogen gas is combined with the Group II or III elements of the semiconductor constituents to generate a halogenated gas such as chloride, bromide, iodide, and the like, which are highly volatile, and Group V or VI. The group element is removed in the form of a dimolecule or a hydride bonded with hydrogen to dry dry the semiconductor. At this time, when the argon gas is further added, argon accelerates decomposition of the halogen gas or collides with the surface of the semiconductor in the form of ions to promote desorption of the etching product, thereby increasing the etching rate. Recently published in the American Electrochemical Society [JM Lee et al., Journal of Electrochemical Society, 148 , G1 (2001)] and the American Journal of Applied Physics (SJ Pearton et al., Applied Physics Letter, 81 , 3546 (2002)) CH ₄ / H ₂ / Although a method of etching zinc oxide semiconductors using Ar has been reported, there are no techniques for the etching process that can produce light emitting devices or laser diodes. However, the research on dry etching based on BCl ₃ plasma has not been reported. It has not been reported.

Accordingly, the technical problem to be achieved by the present invention is to induce a zinc oxide semiconductor in a plasma state by forming a gas containing BCl ₃ to exhibit a high etching rate, uniform surface, good anisotropic etching characteristics Inductively coupled plasma Reaactive ion etching (ICP-RIE) provides a dry etching method of a zinc oxide semiconductor that can be widely applied in the manufacture of optical devices and electronic devices and a method of manufacturing the same.

1 is a graph showing the etching rate of the zinc oxide semiconductor according to the present invention with respect to the increase in the BCl ₃ gas inflow in the BCl ₃ / Cl ₂ / Ar plasma;

2 is a graph showing the etching rate of the zinc oxide semiconductor according to the present invention with respect to the increase in the BCl ₃ gas inflow in the BCl ₃ / CH ₄ / H ₂ plasma;

3 is a graph showing the etching rate of the zinc oxide semiconductor according to the present invention with respect to the increase in the BCl ₃ gas inflow in the BCl ₃ / Ar plasma;

4 is a graph showing the etching rate of the zinc oxide semiconductor according to the present invention with respect to the substrate temperature increase;

5 is a graph showing the etching rate of the zinc oxide semiconductor according to the present invention with respect to the ICP output;

Figure 6 is a graph showing the etch rate of the zinc oxide semiconductor according to the present invention with respect to the RF output;

7 is a graph showing the etching rate of the zinc oxide semiconductor according to the present invention with respect to the process pressure;

8 shows an SEM image showing the anisotropy of the etched zinc oxide semiconductor according to the present invention ((a) is performed at 900W ICP output, 140W RF output, 5mtorr BCL ₃ 100% (20sccm) at room temperature, (b ) Is taken at 900W ICP output 100W RF output, 5mtorr BCL ₃ 100% (20sccm)].

In the dry etching method of a zinc oxide semiconductor according to an embodiment of the present invention for achieving the above technical problem, the zinc oxide deposited on the susceptor in the reactor is deposited on the substrate, and supplies a gas containing BCl ₃ in the reactor By forming a plasma, the zinc oxide semiconductor is dry-etched with the plasma.

In this case, the reason for using BCl _{3 is} that an organic metal gas such as BO ₂ , BOCl, (BOCl) ₃ having high volatility by combining oxygen component in zinc oxide semiconductor with B radical or BCl radical of BCl ₃ ( This is to increase the efficiency of reactive ion etching by being removed in the form of metalorganic gas. In addition, the Cl radical in the plasma is combined with the zinc component in the zinc oxide semiconductor to simultaneously form and etch an organometallic gas such as ZnCl and Zn ₂ Cl ₂ to achieve higher etching rates.

In addition, magnetic field enhanced magnetically enhanced reactive ion etch (MRIE) may be performed by appropriately applying a magnetic field near the zinc oxide semiconductor specimen.

On the other hand, the dry etching is preferably carried out in a state in which the pressure of the reactor is 1 mTorr-1 Torr, the plasma is inductively coupled method, capacitive coupled method, or electron resonance (elctron cyclotron) resonance) method.

In addition, the plasma may be formed by combining an inductive coupling method and a capacitive coupling method. In this case, an ICP coil antenna is installed around the reactor, the ICP coil antenna is supplied with ICP power having a frequency of 10-20 MHz to 1-3000 W, and the susceptor has a frequency of 10-20 MHz. The plasma is formed by applying RF power at 1-500 W.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to these examples.

<Example 1>

A monocrystalline zinc oxide semiconductor thin film was formed on a sapphire substrate by a high temperature RF magnetron reactive sputtering method.

<Example 2>

The specimen prepared in Example 1 was charged to an inductively coupled plasma (ICP) reactor. An ICP coil antenna is installed around the reactor to form an inductively coupled plasma, and the RF frequency can be applied to the susceptor on which the specimen is seated for efficient etching. After loading the specimen as described above, a plasma was formed by introducing BCl ₃ / Cl ₂ / Ar gas into the reactor, and the zinc oxide semiconductor film was etched using the plasma. At this time, the zinc oxide semiconductor was etched while increasing the BCl ₃ ratio in the reaction gas. The etching process was performed while the reactor pressure was about 5 mtorr and the substrate temperature was about 25 ° C. The ICP coil antenna was supplied with 900 W of ICP power at 13.56 MHz and the RF power at 13.56 MHz for the susceptor at 140 W. The etching rate at this time is as shown in FIG.

<Example 3>

In order to compare the etching rates of the BCl ₃ and CH ₄ plasma, BCl ₃ / CH ₄ / Ar gas was introduced into the reactor to form a plasma, and the zinc oxide semiconductor film was etched using the plasma. At this time, the zinc oxide semiconductor was etched while increasing the BCl ₃ ratio in the reaction gas. The etching process was performed while the reactor pressure was about 5 mtorr and the substrate temperature was about 25 ° C. The ICP coil antenna was supplied with 1400 W of ICP power of 13.56 MHz, and the RF power of 13.56 MHz was applied to 140 W of the susceptor. The etching rate at this time is as shown in FIG.

<Example 4>

In order to compare the etching rates of the BCl ₃ and Ar plasma, BCl ₃ / Ar gas was introduced into the reactor to form a plasma, and the zinc oxide semiconductor film was etched using the plasma. At this time, the zinc oxide semiconductor was etched while increasing the BCl ₃ ratio in the reaction gas. The etching process was performed while the reactor pressure was about 5 mtorr and the substrate temperature was about 25 ° C. The ICP coil antenna was supplied with 900 W of ICP power at 13.56 MHz and the RF power at 13.56 MHz at the susceptor. The etching rate at this time is as shown in FIG.

Example 5

In order to investigate the effect of susceptor temperature on the etching rate of zinc oxide semiconductor, 100% BCl ₃ (20 sccm) gas was introduced into the reactor to form a plasma, and the zinc oxide semiconductor film was etched using the plasma. At this time, the zinc oxide semiconductor was etched while increasing the susceptor temperature to 250 ° C. In the etching process, the reactor pressure was about 5 mtorr, the ICP coil antenna was supplied with 900 W of ICP power of 13.56 MHz, and the RF power of 13.56 MHz was applied to 140 W of the susceptor. The etching rate at this time is as shown in FIG.

<Example 6>

The zinc oxide semiconductor was etched under the same conditions as in Example 1 except that BCl ₃ gas was introduced in an optimized state, ie 100% BCl ₃ (20 sccm) was introduced into the reactor and the ICP output was changed to 150-900 W. In this case, the etching rate is presented as a graph in FIG. 5. As the ICP output increases, the magnetic voltage induced on the specimen decreases, but the etch rate increases and the etch rate becomes very high as 146 nm / min when the ICP output is 900 W. This is because as the ICP output increases, the density of reactive radicals present in the plasma increases, thereby increasing the chemical reaction on the surface of the specimen.

<Example 7>

Zinc oxide under the same conditions as in Example 1 except that BCl ₃ gas was optimized, that is, 100% BCl ₃ (20 sccm) was introduced into the reactor and the RF output to the susceptor was changed to 50-200 W. The semiconductor was etched, with the etch rate shown graphically in FIG. 6.

Referring to FIG. 6, it can be seen that as the RF output increases, the etch rate increases, resulting in an etching rate of up to 200 nm / min at the 200 W output. This is because as the RF output increases, the self-bias induced in the specimen increases, so that the ions present in the plasma strike the surface more strongly. Therefore, as the RF output increases, the anisotropic etching characteristic also increases. It can be seen from the graph that the magnetic voltage induced at the specimen when the RF output is 180 W is about -300 V.

<Example 8>

To determine the effect of working pressure on the etch rate of zinc oxide semiconductors, BCl ₃ gas was introduced into the reactor, ie 100% BCl ₃ (20 sccm), and the working pressure was reduced to 2-20 Torr. A zinc oxide semiconductor was etched under the same conditions as in Example 1 except that the etching was performed in the range of, wherein the etching rate is shown as a graph in FIG. 7.

Hereinafter, the dry etching characteristics of the embodiments according to the present invention will be described with reference to the accompanying drawings.

Referring to FIG. 1, it can be seen that the etching rate of zinc oxide increases rapidly as the amount of BCl ₃ gas inflow in the BCl ₃ / Cl ₂ / Ar plasma increases. That is, the oxygen component of the zinc oxide semiconductor reacts with BCl to form a highly volatile organometallic gas in the form of BOCl, BO or (BOCl) _2, and the zinc component is combined with the Cl component in the plasma to form Zn ₂ Cl ₂ , It can be indirectly confirmed to be removed in the form of an organometallic such as ZnCl ₂ . While the conventional dry etching method using methane removes only the zinc component in the zinc oxide semiconductor component in the form of Zn (CH ₃ ) ₂ organometallic type, the dry etching method using BCl ₃ is more effective by simultaneously removing the zinc component and oxygen component. An improved etching rate can be obtained.

2 shows the etching rate according to the increase of the BCl ₃ gas inflow in the BCl ₃ / CH ₄ / Ar plasma, it can be observed that the increase in the BCl ₃ gas inflow sharply improves the etching rate. This indicates that the BCl ₃ gas can etch the zinc oxide semiconductor more efficiently than the dry etching using the CH ₄ gas.

In addition, as shown in FIG. 3, the increase in the amount of BCl ₃ gas inflow in the BCl ₃ / Ar plasma also rapidly increases the etching rate of the zinc oxide semiconductor, so that the dry etching process of the zinc oxide semiconductor can be efficiently performed using the BCl ₃ gas. It can be seen that.

4 shows the change in the etch rate of the zinc oxide semiconductor as the substrate temperature increases. As the temperature of the substrate increases, the etch rate improves as the temperature increases because the reaction between the BCl ₃ and the zinc oxide semiconductor may occur better. Able to know.

Referring to FIG. 5, the increase in the ICP output indicates a sharp increase in the zinc oxide semiconductor etch rate because the increase in the ICP output increases the density of ionic radicals for etching the zinc oxide semiconductor.

Also, as shown in FIG. 6, the increase in RF power also increases the etching rate of the zinc oxide semiconductor. As the RF power increases, the self-bias induced in the specimen increases, so that the ions present in the plasma become stronger. Because it crashes. Therefore, as the RF output increases, the anisotropic etching characteristic also increases. It can be seen from the graph that the magnetic voltage induced at the specimen when the RF output is 180 W is about -300 V.

The dry etching characteristics of the zinc oxide semiconductor were also affected by the working pressure. Referring to FIG.

8A and 8B show SEM images of zinc oxide semiconductors etched in 100% BCl ₃ plasma. NiCr metal was used as an etch mask to fabricate zinc oxide semiconductors with anisotropic vertical sidewalls, and the ICP and RF outputs were fixed at 900 W and 100 W, respectively. Etched at 5 mTorr with% BCl ₃ . As can be seen from the SEM image, when etched using 100% BCl ₃ , zinc oxide semiconductor having high anisotropy and clean side surface can be obtained.

According to the dry etching method of the zinc oxide semiconductor according to the present invention as described above, not only can obtain a very high etching rate than the conventional dry etching process using wet etching and methane, but also excellent anisotropy and clean side wall Can be obtained. In particular, in order to manufacture high-quality light emitting devices (LEDs) or laser diodes (LDs), an etching process having a vertical side surface having high anisotropy, a high etching rate, a high selectivity, and a uniform etching side is essential. By using a plasma based on BCl ₃ can achieve this etching characteristics. Therefore, its application range is large, such as the development of optical devices and electronic devices.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (6)

Zinc oxide, characterized in that the zinc oxide is deposited on the susceptor in the reactor, the zinc oxide semiconductor is dry-etched into the plasma by supplying a gas containing BCl ₃ in the reactor to form a plasma Dry etching method of semiconductor. The method of claim 1, wherein the gas containing BCl ₃ further comprises Cl ₂ . The zinc oxide dry etching method according to claim 1, wherein the gas containing BCl ₃ further includes argon. The dry etching method of claim 1, wherein the dry etching is performed at a pressure of 1 mTorr − 1 Torr in the reactor. The zinc oxide dry etching method of claim 1, wherein the plasma is formed by an inductive coupling method, a capacitive coupling method, or an electron resonance method. According to claim 1, ICP coil antenna is installed around the reactor, the ICP coil antenna is applied to the ICP power having a frequency of 10-20 MHz to 1-3000 W, the susceptor of 10-20 MHz A method of dry etching a zinc oxide semiconductor, the method comprising: applying an RF power having a frequency of 1 to 500 W, thereby forming the plasma in a mixture of an inductive coupling method and a capacitive coupling method.