KR100274912B1 - Etching method of INP thin film using mixed gas - Google Patents

Abstract

The present invention relates to an etching method of an InP thin film used as a material of an optical device, in particular, the mixed gas injected through the gas inlet (1) to facilitate the etching of the InP thin film using a mixed gas is electrons emitted from the ground electrode The excited ions are excited in the form of ions, and these excited ions diffuse into the plasma and move rapidly toward the excitation electrode in the sheath layer between the plasma and the excitation electrode, which are subjected to a strong electric field. Reacts with InP samples to form a gas, and in performing the etching process by discharging the gas through a vacuum pump, the mixed gas is characterized in that CH ₄ / He, CH ₄ / Ar, CH ₄ / N ₂ An etching method of an InP thin film using a mixed gas is provided.

Description

Etching method of INP thin film using mixed gas

The present invention relates to an etching method of an InP thin film used as a material of an optical device, and more particularly to an etching method of an InP thin film using a mixed gas.

The gas used in the reactive ion etching process of the conventional lnP thin film was first used a mixture gas of CH ₄ / H ₂ based on hydrogen. An etching process was performed by adding He or Ar to the mixed gas to increase ion sputtering and generate simpler plasma. In order to improve the etched surface properties, N ₂ is added to remove the large amount of hydrogen atoms in the form of NH ₃ gas, and the etching process is performed to improve the cleanliness and flatness of the etched surface state. Efforts have been made to remove the organic matters generated during the process by adding oxygen, and efforts have been made to maintain a clean surface state. However, since such a composition basically uses hydrogen as a base, the etching atmosphere is rich in hydrogen. Therefore, on the surface of the lnP thin film, the formation of PH ₃ having a strong volatility is rapidly progressed by the reaction with the reactant and is easily removed by the vacuum pump. Thus, a P deficiency region appears on the surface of the lnP thin film. The atoms of ln and P are not in the crystal state of 1: 1, and the components of ln cause relatively many states. This surface condition may result in poor results in subsequent successive processes such as regrowth because the lattice structure of the atoms is incomplete, or adversely affect long term reliability, such as after device fabrication. In addition, since ln (CH ₃ ) _{3, which} is a relatively less volatile product, often remains on the surface, the surface is easily contaminated by these particles, and thus, it is very difficult to set the process conditions.

The second most commonly used gas composition is chlorine-based gas composition such as Cl ₂ , CCl ₄ , BCl ₄ , SiCl ₄ , CCl ₃ F, CCl ₂ F ₂ , but their composition is ultimately harmful to the environment. In addition to the difficulty, almost all chlorofluorocarbon residues are formed on the surface of the etching process, which affects the subsequent process.

In the reaction of etching ions based on hydrogen, reaction equations generated in the reactor are as follows.

Experimental formula 1

InP + CH ₄ + H ₂ → InP + CH ₃ ⁺ + 3H ⁺

3CH ₃ ⁺ + In → In (CH ₃ ) ₃

P + 3H ⁺ → PH ₃

Looking at this equation, if the gas injected from the gas inlet (1) of Figure 1 is a mixed gas of CH ₄ / H _{2 and} the number of molecules of 1: 1, and all the gas molecules with the electrons emitted from the ground electrode (2) Assuming that it is decomposed in the form of an ionic substance (CH ₃ ⁺ , H ⁺ ) that is excited by a reaction and directly participates in etching, and all of them are changed into a substance that participates in the reaction, the reaction with InP in a crystalline state is shown in Equation 1. As is, three CH ₃ ⁺ and H ⁺ are used. As a result, since there are six H ⁺ remaining in the reaction, the rich H ⁺ ions present in the reactor have a great influence on the etching process. In particular, these ions readily combine with P to form highly volatile PH ₃ , creating a P-deficient region in the InP thin film on the surface. This surface state is not perfect in the lattice structure of atoms, which may result in poor results in continuous processes such as regrowth or in bad long-term reliability after device fabrication.

Experimental formula 2

InP + CH ₄ → InP + CH ₃ ⁺ + H ⁺

3CH ₃ ⁺ + In → In (CH ₃ ) ₃

P + 3H ⁺ → PH ₃

However, when the etching is performed by the gas composition of the present invention, since the mixed gas based on He is used as shown in Equation 2, each of CH ₃ ⁺ and H ⁺ excited from three CH ₄ molecules is used for etching. Therefore, there are no H ⁺ ions present in the residue. Thus, the ratio of In and P on the surface of InP will remain quantitatively 1: 1.

The present invention has been made to solve the problems described above, by using a simple gas composition of CH ₄ / He lnP having a 1: 1 bond structure and three molecules of CH ₄ reacting relatively rich He By suppressing the formation of excess H atoms to eliminate the P-deficient state on the etch surface and induce complete chemical reaction conditions to maintain the lnP thin film in the initial crystal state after etching or to minimize the P-deficient region.

The advantage obtained in this case is that the thin film maintains the initial crystalline state, thereby minimizing the influence of crystal defects on the surface in processes such as continuous regrowth and regrowth, and supplying abundant He to provide lnP. It is possible to suppress the growth of organic thin films by removing ln (CH ₃ ) ₃ or hydrocarbons, which are less volatile produced by CH ₃ ⁺ ions on the surface.

In order to achieve the above object, in the present invention, the mixed gas injected through the gas inlet 1 is excited in the form of ions by collision with electrons emitted from the ground electrode 2, and the excited ions are plasma ( 3) In the diffusion movement inside, the sheath layer 10 between the plasma and the excitation electrode, which is subjected to a strong electric field, quickly moves toward the excitation electrode 4, where the ions and the InP sample 9 on the excitation electrode 4 Reacting to form a gas, and performing the etching process by discharging the gas through a vacuum pump, the mixed gas is a mixed gas, characterized in that CH ₄ / He, CH ₄ / Ar, CH ₄ / N ₂ It provides an etching method of the InP thin film used.

1 is a schematic diagram of a reactive ion etching apparatus

<Explanation of symbols for main parts of the drawings>

1 gas inlet 2 ground electrode

3: plasma 4: excitation electrode

5: discharge passage 6: condenser

7: RF generator 8: reactor ground terminal

9: InP sample 10: sheath layer

The present invention relates to a method of performing reactive ion etching of InP based on He, and the process thereof will be described as follows.

As shown in FIG. 1, the CH ₄ / He mixed gas injected through the gas injection port 1 is excited in the form of ions by collision with electrons emitted from the ground electrode 2. The excited ions diffuse in the plasma 3 and then quickly move toward the excitation electrode 4 in the sheath layer 10 between the plasma and the excitation electrode under a strong electric field. At this time, these ions react with the InP samples 9 on the excitation electrode 4 to form gases such as PH ₃ , In (CH ₃ ) ₃ , and the etching process is performed by discharging these gases through a vacuum pump.

At this time, unlike the conventional ion-based reaction ion etching, since hydrogen gas is not injected from the outside, CH ₃ ⁺ and H ⁺ excited in CH ₄ gas participate in the reaction so that excess H ⁺ does not occur. do. Here, He acts as a carrier gas of reactants with low generation of plasma and low volatility, thereby minimizing the distribution of hydrogen atoms in the reactor and reducing the P deficiency region due to the reaction of hydrogen and P on the surface of InP. . Such a concept may be performed by replacing the He gas with a valence such as N ₂ or Ar. In this case, the injected gas is used in the same function as He, but when N ₂ is used instead, the generated hydrogen atoms are removed again in the form of NH ₃ , which is expected to further reduce the influence of H atoms.

The reaction ion etching process was performed by the above method, and the process conditions and results are the same as in Example 1.

Example 1

variable Experiment range Pressure (mTorr) 100 RF power (W) 240 CH ₄ (sccm) 1.5 He (sccm) 30 Total gas flow (sccm) 31.5 Etch depth (μm) About 1㎛ Etch rate (Å / min) 160 Process time (min) 60

As a result of the above experiment, when the volume ratio of CH ₄ was about 5%, a small amount of He was injected, and it was found to have an etchant of about 160 μs / min, and the etched surface was kept very clean. Based on this result, reactive ion etching of InP thin film was effectively performed by using mixed base based on He.

Effect of the invention as described above, the thin film can be reduced in the process, such as re-growth is continuous because it maintains the initial state to a minimum the effects caused by the determination of the surface, by supplying a rich He at the surface CH ₃ ⁺ By suppressing the growth of In (CH ₃ ) ₃ and organic thin films generated by ions, micromasking (m−)

It can prevent things like icromasking phenomenon.

Claims (3)

The mixed gas injected through the gas inlet 1 is excited in the form of ions by collision with the electrons emitted from the ground electrode 2, and these excited ions diffuse in the plasma 3 and undergo a strong electric field. In the sheath layer 10 between the applied plasma and the excitation electrode, quickly moves toward the excitation electrode 4, where ions react with the InP samples 9 on the excitation electrode 4 to form a gas, In performing the etching process by discharging through the vacuum pump, The mixed gas is CH ₄ / He etching method of the InP thin film using the mixed gas, characterized in that. The method of claim 1, The mixed gas is CH ₄ / Ar etching method of the InP thin film using a mixed gas, characterized in that. The method of claim 1, The mixed gas is CH ₄ / N ₂ Etching method of the InP thin film using a mixed gas, characterized in that.