KR20240017273A - RF biased reactive ion beam etching apparatus and the method thereof - Google Patents

Abstract

In one embodiment of the present invention, after forming a high-density plasma 40 on the upper part of the ion source part in an etching chamber and forming a low-density plasma 40 on the lower part of the ion source part, the negative bias applied to the substrate is RF biased reactive ion etching device and RF biased reactive ion to solve problems affecting the etching profile that occur during ion beam etching or reactive ion beam etching by controlling the density of the low density plasma 40 by adjusting its size. RF biased reactive ion etching method using an etching device

Description

RF biased reactive ion beam etching apparatus and the method thereof}

The present invention relates to a reactive ion etching device, and more specifically, to an RF biased reactive ion etching device and an RF biased reactive ion etching device for solving problems affecting the etching profile that occur during ion beam etching or reactive ion beam etching. This relates to an RF biased reactive ion etching method using a device.

Generally, a magnetic tunnel junction cell (MTJ cell) is used to drive magnetoresistive memory (MRAM: Magnetic Random Access Memory).

1 is a perspective view of a magnetoresistive memory cell 1 having a magnetic tunnel junction cell 10.

The magnetic tunnel junction cell 10 includes a ferromagnetic free layer 11 whose magnetization direction is adjustable, a ferromagnetic free layer 13 whose magnetization direction is fixed, and a tunnel barrier layer that insulates the two magnetic layers. It consists of a (barrier layer) (15). The ferromagnetic free layer 11 and the ferromagnetic pinned layer 13 are metal layers such as CoFeB and CoPt based on magnetic materials Co, Fe, and Pt. MgO is mainly used for the tunnel barrier layer. If the magnetization directions of the two magnetic layers 11 and 13 of the magnetic tunnel junction cell 10 are the same, current flows, and if the magnetization directions are different, current does not flow.

Magnetoresistive memory with these magnetoresistive memory cells (1) is a next-generation memory device with characteristics such as non-volatility, high integration, fast operation speed, and low power operation. For commercialization, research has been conducted by many domestic and foreign semiconductor companies such as Samsung, Intel, and IBM. I'm losing.

To form a magnetic tunnel junction cell, ion beam etching (IBE) or reactive ion beam etching (RIBE) methods are generally used among dry etching methods using plasma.

The ion beam etching performs physical etching by extracting and accelerating ions within the plasma and out of the plasma region.

The reactive ion etching simultaneously performs physical etching using ions in plasma and chemical etching using reactive radicals.

This ion beam etching (IBE) or reactive ion beam etching (RIBE) method causes the problem of redeposition on the sidewall of the magnetic tunnel junction cell due to low volatility of the magnetic material during the etching process. This problem short-circuits the ferromagnetic free layer and the ferromagnetic fixed layer, making it impossible to turn the device on or off.

Additionally, because the etch selectivity between the magnetic material and the mask material is very low, a thick hard mask is required. This acts as a limitation in removing the metal layer redeposited on the sidewall by later tilting the substrate.

Some studies have been reported to remove magnetic materials by forming volatile compounds. However, when magnetic materials are removed by forming volatile compounds, residues remain due to insufficient chemical reaction on the side walls of the magnetic tunnel junction cell, or the etching profile ( Problems such as affecting the etch profile may occur.

When performing reactive ion etching, the charging problem can be solved, but problems such as excessive chemical reaction damaging the magnetic tunnel junction cell layer or some isotropic etching affecting the etching profile occur.

Registered Patent KR 1080604 (announced on October 31, 2011)

In order to solve the problems of the prior art described above, the present invention forms a high-density plasma on the upper part of the ion source part in an etching chamber, forms a low-density plasma 40 on the lower part of the ion source part, and then generates a negative sound applied to the substrate. By adjusting the density of the low-density plasma 40 by adjusting the size of the bias (negative bias), redeposition problems, residue problems, charging problems, and etching profiles that occur in ion beam etching or reactive ion etching methods are affected. The goal is to provide an RF biased reactive ion etching device and an RF biased reactive ion etching method that can solve the problem.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

In order to achieve the above technical problem, an embodiment of the present invention includes an etch chamber 110; A plasma source unit 120 installed on the upper part of the etching chamber 110 to generate high-density plasma 30 in the upper inner area of the etching chamber 110; an ion source unit 130 installed inside the etching chamber 110 at a lower portion of the area where the high-density plasma 30 is formed; A base 140 formed below the ion source unit 130 inside the etching chamber 110 and on which the substrate 141 is seated; A first RF power unit 150 that supplies RF power for generating the high-density plasma 30 to the plasma source unit 120; A second RF power unit 160 that supplies RF power to the base 140 to generate low-density plasma 40 in an area between the ion source unit 130 and the base 140; and a control unit 170 that controls the first RF power unit 150 and the second RF power unit 160.

The etching chamber 110 includes a gas injection unit 111 that supplies gas for generating the high-density plasma 30 or the low-density plasma 40 into the interior of the etching chamber 110; And it may further include an exhaust unit 112 that discharges reaction products generated inside the etching chamber 110 to the outside.

The ion source unit 130 includes a first grid 131 to which +DC is applied, which is lower than the voltage (V _PO ) when an RF bias with a negative potential is not applied to the base 140; a second grid 132 to which -DC is applied, which is the same as when an RF bias with a negative potential is not applied to the base 140; and a third grid 133 that is grounded.

The control unit 170 applies an RF bias having the negative potential (V _PR ) to the base 140 and applies an RF bias having a negative potential to the base 140 to the first grid 131. It may be configured to perform ion source voltage control by applying a +DC voltage lowered by the negative RF bias voltage (V _PR ) compared to the voltage when not applied.

After the high-density plasma 30 and the low-density plasma 40 are formed in the upper and lower portions of the ion source unit 130, the control unit 170 controls the voltage and It may be configured to perform low-density plasma density control in which the density of the low-density plasma 40 is adjusted by controlling the voltage of the RF power applied from the second RF power unit 160 to the base 140.

One embodiment of the present invention for solving the technical problem of the present invention described above includes an etch chamber 110, a plasma source unit 120, a first grid 131 to which a positive voltage is applied, and a negative potential to which a negative potential is applied. An ion source unit 130 having a second grid 132 and a third grid 133 that is grounded, a base 140, a first RF power unit 150, a second RF power unit 160, and a control unit ( In the reactive ion etching method using an RF biased reactive ion etching device including 170), the first RF power unit 150 supplies RF power to the plasma source unit 120 to irradiate the ion source unit 130. ) a high-density plasma forming step (S10) of forming high-density plasma 30 on the upper part of the; The voltage difference between the first grid 131 of the ion source unit 130 and the base 140 causes ions generated in the high-density plasma 30 to contact the substrate 141 seated on the upper part of the base 140 and the base 140. The ion source unit voltage that adjusts the voltage applied to the first grid 131 in response to the RF bias having the negative potential (V _PR ) so as to have a voltage difference (Vp) for performing reactive ion etching by collision. Control step (S20); And the second RF power unit 160 supplies RF power with an RF bias having a negative potential to the base 140 to form a low-density plasma 40 in the lower part of the ion source unit 130. An RF biased reactive ion etching method is provided, comprising a plasma forming step (S30).

The ion source voltage control step (S20) applies an RF bias having the negative potential (V _PR ) to the base 140 and the first grid 131 and the first grid 131. + lowered compared to the voltage (V _Po ) when an RF bias with a negative potential is not applied to the base 140 so that a voltage difference (V _P ) for reactive ion etching is generated between the bases 140. This may be a step of performing voltage control of the ion source unit that applies DC voltage.

In the RF biased reactive ion etching method, after performing the low-density plasma forming step (S30), the voltage of the first grid 131 and the second RF power unit 160 are applied to the base 140. It may further include a low-density plasma density control step (S40) of controlling the density of the low-density plasma 40 by controlling the voltage of the RF power.

The RF biased reactive ion etching device and the method of forming a magnetoresistive memory pattern using the RF biased reactive ion etching device of an embodiment of the present invention include an ion beam etching or reactive ion etching method for forming a magnetic tunnel junction cell of a magnetoresistive memory. It provides the effect of solving redeposition problems, residue problems, charging problems, and problems affecting the etching profile that occur in the process.

The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a perspective view of a magnetoresistive memory cell having a magnetic tunnel junction cell 10.
Figure 2 is a configuration diagram of an RF biased reactive ion etching device 100 according to an embodiment of the present invention.
Figure 3 is a flowchart showing the processing of an RF biased reactive ion etching method for forming a low-resistance memory pattern according to an embodiment of the present invention.
Figure 4 is a diagram showing ion beam or reactive ion etching in the prior art.
Figure 5 is a diagram showing RF biased reactive ion etching in one embodiment of the present invention.
Figure 6 is a graph evaluating the etch selectivity during reactive ion etching for manufacturing a magnetic tunnel junction cell using RF biased reactive ion etching according to an embodiment of the present invention.
FIG. 7 is a graph showing the results of measuring the electron density of the low-density plasma 40 when RF biased reactive ion etching according to an embodiment of the present invention is applied.
Figure 8 is a TEM image for evaluating sidewall redeposition of a magnetic tunnel junction cell after etching for manufacturing a magnetic tunnel junction cell using RF biased reactive ion etching according to an embodiment of the present invention.
Figure 9 is a graph evaluating the improvement of the charging effect during etching using RF biased reactive ion etching according to an embodiment of the present invention.
Figure 10 is a diagram showing the schematic configuration and operating principle of the ion source unit of the reactive ion etching device of the prior art.
FIG. 11 is a diagram showing the schematic configuration and operating principle of the ion source unit of an RF biased reactive ion etching device according to an embodiment of the present invention.

Hereinafter, the present invention will be described with reference to the attached drawings. However, the present invention may be implemented in various different forms and, therefore, is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, combined)" with another part, this means not only "directly connected" but also "indirectly connected" with another member in between. "Includes cases where it is. Additionally, when a part is said to “include” a certain component, this does not mean that other components are excluded, but that other components can be added, unless specifically stated to the contrary.

The terms used herein are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

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

The RF biased reactive ion etching device and method of an embodiment of the present invention can be applied to various reactive ion etchings including magnetic tunnel junction cells of magnetoresistive memory cells.

Figure 2 is a configuration diagram of an RF biased reactive ion etching device 100 according to an embodiment of the present invention.

As shown in FIG. 2, the RF biased reactive ion etching device 100 includes an etching chamber 110, a plasma source unit 120, a first grid 131 to which a positive voltage (or potential) is applied, and a negative voltage (or potential) applied thereto. An ion source unit 130 having a second grid 132 to which voltage (or potential) is applied and a third grid 133 to ground, and a base 140 to which RF power with a negative voltage (or potential) is biased. , may be configured to include a first RF power unit 150, a second RF power unit 160, and a control unit 170.

The etching chamber 110 may be configured to include a gas injection unit 111 and an exhaust unit 112.

The gas injection unit 111 may be formed to communicate with the interior of the etching chamber 110 to supply gas for generating the high-density plasma 30 or the low-density plasma 40 into the interior of the etching chamber 110. there is.

The exhaust unit 112 is configured to discharge reaction products such as radicals or volatile reactants generated in the high-density plasma 30 or low-density plasma 40 generated inside the etching chamber 110 and the substrate to the outside. It may be formed to communicate with the interior of the etching chamber 110.

The plasma source unit 120 may be installed at the top of the etching chamber 110 and configured to generate high-density plasma 30 in the upper inner region of the etching chamber 110. The plasma source unit 120 may be configured in various ways, such as ICP (Inductive Coupled Plasma), TCP (transformer Coupled Plasma), etc.

The ion source unit 130 may be installed at a location below the area where the high-density plasma 30 is formed and above the area where the low-density plasma 40 is formed inside the etching chamber 110. .

The ion source unit 130 includes a first grid 131 to which a positive voltage is applied and a second grid to which a negative voltage is applied, which are sequentially arranged in the direction from the plasma source unit 120 to the base 140. It may be configured to include a grid 132 and a third grid 133 that is grounded. When a negative RF bias voltage is applied to the base 140, the first grid 131 is between the high-density plasma and the RF biased base 140 with a negative voltage in response to the negative RF bias voltage. A voltage difference Vp for reactive ion etching must be applied. Accordingly, a +DC voltage lowered compared to the voltage (V _PO ) when the RF bias with a negative voltage is not applied to the base 140 is applied to the first grid 131, and the second grid ( 132), the same -DC voltage as when the RF bias with a negative voltage is not applied to the base 140 is applied, and the third grid 133 is grounded.

The base 140 is formed below the ion source unit 130 inside the etching chamber 110 to seat the substrate 141 on it.

The first RF power unit 150 is configured to supply RF power for generating the high-density plasma 30 to the plasma source unit 120.

The second RF power unit 160 applies an RF bias with a negative voltage to the base 140 to generate a low-density plasma 40 in the area between the ion source unit 130 and the base 140. It is configured to supply applied RF power.

The control unit 170 is configured to control the first RF power unit 150 and the second RF power unit 160.

Specifically, the control unit 170 determines that the voltage difference between the first grid 131 of the ion source unit 130 and the base 140 causes ions generated in the high-density plasma 30 to be generated in the base 140. ) has the negative voltage (V _PR) to have a voltage difference Vp for performing reactive ion etching to form a magnetoresistive memory pattern having a magnetic tunnel junction cell by colliding with the substrate 141 placed on the top of the It may be configured to perform ion source voltage control to adjust the voltage applied to the first grid 131 of the ion source unit 130 in response to the RF bias. That is, the control unit 170 applies an RF bias having the negative voltage (V _PR ) to the base 140, and the first grid 131 and the base 140 are applied to the first grid 131. A +DC voltage lowered compared to the voltage (V _PO ) when an RF bias with a negative voltage is not applied to the base 140 is applied so that a voltage difference (V _P ) for reactive ion etching occurs between the bases 140. It can be configured to do so.

In addition, the control unit 170 controls the first grid 131 of the ion source unit 130 after the high-density plasma 30 and the low-density plasma 40 are formed in the upper and lower parts of the ion source unit 130. To perform low-density plasma density control to adjust the density of the low-density plasma 40 by controlling the voltage of the RF power and the voltage (V _PR ) of the RF power applied from the second RF power unit 160 to the base 140. It can be configured.

Figure 3 is a flowchart showing the processing of an RF biased reactive ion etching method for forming a low-resistance memory pattern according to an embodiment of the present invention.

As shown in FIG. 3, the RF biased reactive ion etching method includes an etching chamber 110, a plasma source unit 120, a first grid 131 to which a positive voltage is applied, and a second grid to which a negative voltage is applied. (132) and an ion source unit 130 having a grounded third grid 133, a base 140, a first RF power unit 150, a second RF power unit 160, and a control unit 170. A reactive ion etching method using an RF biased reactive ion etching device may include a high-density plasma forming step (S10), an ion source voltage control step (S20), and a low-density plasma forming step (S30).

In the high-density plasma forming step (S10), the first RF power unit 150 supplies RF power to the plasma source unit 120 to form a high-density plasma 30 on the upper part of the ion source unit 130. It may be a step.

The ion source voltage control step (S20) is a voltage difference between the first grid 131 of the ion source unit 130 and the base 140 so that ions generated in the high-density plasma 30 are connected to the base 140. ) is applied to the first grid 131 in response to an RF bias having the negative voltage (V _PR ) so as to have a voltage difference Vp for performing reactive ion etching by colliding with the substrate 141 placed on top of the This may be a step to adjust the voltage.

In the low-density plasma forming step (S30), the second RF power unit 160 supplies RF power with an RF bias with a negative voltage to the base 140 to create low-density plasma at the bottom of the ion source unit 130. This may be a step of forming plasma 40.

In the RF biased reactive ion etching method, after performing the low-density plasma forming step (S30), the voltage of the first grid 131 and the second RF power unit 160 are applied to the base 140. It may further include a low-density plasma density control step (S40) of controlling the density of the low-density plasma 40 by controlling the voltage of the RF power.

FIG. 4 is a diagram showing ion beam or reactive ion etching of the prior art, and FIG. 5 is a diagram showing RF biased reactive ion etching according to an embodiment of the present invention.

4 and 5, the RF biased reactive ion etching device 100 and the RF biased reactive ion etching method using the same according to an embodiment of the present invention are performed in the high-density plasma 30 above the ion source unit 130. Due to the extracted ion beam 50 and the low-density plasma 40 discharged from the base 140, more chemical reactions occur compared to the reactive ion etching of the prior art, thereby enabling anisotropic etching.

In addition, due to the increase in chemical reaction, the etch selectivity with the hard mask 20 increases, thereby improving the redeposition problem occurring on the sidewall of the magnetic tunnel junction cell 10, as shown in FIG. 5.

In addition, electrons are continuously supplied from the low-density plasma due to the plasma discharged by the base 140, making it possible to solve the charging effect without using a neutralizer of the prior art. The reactive ion etching device of the prior art used a separate neutralizer to solve the charging effect, but had problems such as requiring periodic replacement due to contamination.

Figure 6 is a graph evaluating the etch selectivity during reactive ion etching for manufacturing a magnetic tunnel junction cell using RF biased reactive ion etching according to an embodiment of the present invention.

Figure 6 compares the etch selectivity of CoFeB and MgO, which are the constituent materials of the magnetic tunnel junction cell 10, and TiN and SiO ₂ , which are the materials of the hard mask 20.

The voltage of the first grid 131 and the negative RF bias voltage of the base 140 are maintained at 250 V for the total voltage for reactive ion etching to have the same energy as the commonly used reactive ion etching (RIBE 250 V). The specific voltage ratio of (V _PR ) was gradually increased. As a result, as shown in FIG. 6, it was confirmed that when a weak negative RF bias voltage (V _PR = -V) was applied to the base 140, the TiN and etch selectivity greatly increased. And as the ratio of applied voltage to the substrate increases, the etch selectivity decreases again, and it was confirmed that an appropriate ratio of RF bias with negative voltage exists to increase the etch selectivity.

FIG. 7 is a graph showing the results of measuring the electron density of the low-density plasma 40 when RF biased reactive ion etching according to an embodiment of the present invention is applied.

The voltage of the first grid 131 and the negative RF bias voltage of the base 140 are maintained at 250 V for the total voltage for reactive ion etching to have the same energy as the commonly used reactive ion etching (RIBE 250 V). The specific voltage ratio of (V _PR ) was gradually increased. As a result. As shown in Figure 7, as the voltage ratio increases, the electron density of the low-density plasma 40 generated by the discharge of the base 140 increases. This means that the plasma density increases. Therefore, it was confirmed that low-density plasma is needed in the area adjacent to the base 140 to improve the etch selectivity.

Figure 8 is a TEM image for evaluating sidewall redeposition of a magnetic tunnel junction cell after etching for manufacturing a magnetic tunnel junction cell using RF biased reactive ion etching according to an embodiment of the present invention.

Figure 8 (a) is a TEM image of the side wall of a magnetic tunnel junction cell after reactive ion etching using a conventional reactive ion etching device (RIBE). Figure 8 (b) is a TEM image (RF-biased RIBE) of the side wall of the magnetic tunnel junction cell after reactive ion etching using the RF biased reactive ion etching device 100 of an embodiment of the present invention.

8 (a) and (b), in the case of reactive ion etching of the prior art, redeposition 60 existed on the side wall of the magnetic tunnel junction cell 10, but in the case of the RF biased reactive ion etching of the embodiment of the present invention, there was redeposition 60. After etching, it was confirmed that there was almost no redeposition on the side walls of the magnetic tunnel junction cell 10.

Figure 9 is a graph evaluating the improvement of the charging effect during etching using RF biased reactive ion etching according to an embodiment of the present invention.

To evaluate the charging effect, CoFeB and MgO, which are constituent materials of a magnetic tunnel junction cell, were subjected to conventional reactive ion etching and RF biased reactive ion etching according to an embodiment of the present invention on ceramic. In the reactive ion etching of the prior art, almost no etching occurred. However, it was confirmed that the etch rate increased in the RF biased reactive ion etching of the embodiment of the present invention.

Figure 10 is a diagram showing the schematic configuration and operating principle of the ion source unit of the reactive ion etching device of the prior art.

Figure 10(a) shows reactive ion etching using a conventional reactive ion etching device. Figure 10(b) is a graph showing the voltage application state and voltage difference between the ion source unit 130 and the base 140.

As shown in Figure 10, the reactive ion etching device of the prior art has a plasma source such as an ICP source at the top of the chamber, and generates plasma by injecting gas and applying RF power to the plasma source.

Afterwards, the first to third grids (can be changed to 1 to 4 grids) of the ion source unit 130 are used to block the plasma from passing to the bottom of the chamber, and the ions inside the plasma are extracted and accelerated toward the substrate. do. At this time, +DC and -DC are applied sequentially from above to the first and second grids, and the third grid is grounded. The energy of the ions extracted by the first grid is controlled, and the flux of ions is controlled by the second grid. At this time, the substrate from which ions are extracted and finally reached is fixed in a grounded state.

At this time, the potential difference (Vp, energy) of the ions extracted to the substrate is higher than 0 by applying +DC to the first grid, and the plasma also has a slightly higher potential than the first grid. The second grid has a -DC potential, and at this time, the ions are extracted from the plasma and accelerated until they reach the second grid. Afterwards, the extracted ions pass through the second grid and are decelerated as they pass through the second grid. The energy of the ions that finally reach the substrate moves to the substrate with an energy of Vp, which is equal to the potential difference between the potential of the plasma and the potential of the base 140 (or the substrate 141) and performs etching.

FIG. 11 is a diagram showing the schematic configuration and operating principle of the ion source unit of an RF biased reactive ion etching device according to an embodiment of the present invention.

Figure 11 (a) shows RF biased reactive ion etching by the RF biased reactive ion etching device of an embodiment of the present invention. Figure 11 (b) shows the voltage application state and voltage difference between the ion source unit 130 and the base 140 during RF biased reactive ion etching by the RF biased reactive ion etching device of an embodiment of the present invention. This is a graph that represents

RF biased reactive ion etching by the RF biased reactive ion etching device of an embodiment of the present invention uses the same method of extracting ions as the prior art reactive ion etching device of FIG. 10 . However, a second RF power unit 160 that applies an RF bias having a negative voltage rather than ground is connected to the base 140. Low-density plasma 40 is generated in the lower area of the etching chamber 110 using the second power unit 160. At this time, when the base 140DP RF is applied, a negative bias is formed in the substrate 141. This negative bias allows the density of the low-density plasma 40 formed between the ion source unit 130 and the base 140 to be adjusted depending on the size.

That is, like the general prior art reactive ion etching device of FIG. 10, the ion beam must reach the substrate with an energy of Vp, which is equal to the difference in potential of the base 140 (or substrate 141) from the potential of the plasma. To this end, as shown in (b) of FIG. 11, the +DC potential of the first grid 131 must be lowered by the potential of the RF bias having a negative voltage (V _PR ) on the base 140. At this time, the total energy of the ion beam 50 accelerated to the substrate 141 of the base 140 is the same, but as the voltage ratio of the negative RF bias of the substrate 141 to the voltage of the first grid 131 gradually increases. The density of the low-density plasma 40 gradually increases due to the RF power supplied to the base 140. In the present invention, the low-density plasma 40 generated by the base 140 is a plasma of relatively low density compared to the high-density plasma 30 generated at the top. In general, the upper high-density plasma 30 is discharged from the plasma source unit 120, so it has a higher density than the plasma generated on the substrate. Therefore, in most cases, the lower density plasma 40 has a lower density than the upper high density plasma 30.

The description of the present invention described above is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. will be. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as unitary may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the patent claims described below, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.

1: Magnetoresistive memory cell
10: Subtunnel junction cell
11: Ferromagnetic free layer
13: Ferromagnetic fixed layer
15: Tunnel barrier layer
20: Hardmask
25: lower electrode
30: High-density plasma
40: Low-density plasma
50: Ion beam
60: redeposition
100: RF biased reactive ion etch device
110: Etching chamber
111: Gas injection part
112: exhaust part
120: Plasma source unit
130: Ion source unit
131: first grid
132: second grid
133: Third grid
VPO: Voltage difference to perform reactive ion etching
VPR: Negative RF bias voltage (voltage of applied RF power as expected (140))

Claims (9)

Etching chamber 110;
A plasma source unit 120 installed on the upper part of the etching chamber 110 to generate high-density plasma 30 in the upper inner area of the etching chamber 110;
an ion source unit 130 installed inside the etching chamber 110 at a lower portion of the area where the high-density plasma 30 is formed;
A base 140 formed below the ion source unit 130 inside the etching chamber 110 and on which the substrate 141 is seated;
A first RF power unit 150 that supplies RF power for generating the high-density plasma 30 to the plasma source unit 120;
A second RF power unit 160 that supplies RF power to the base 140 to generate low-density plasma 40 in an area between the ion source unit 130 and the base 140; and
An RF biased reactive ion etching device comprising a control unit 170 that controls the first RF power unit 150 and the second RF power unit 160. The method of claim 1, wherein the etch chamber 110 is
a gas injection unit 111 that supplies gas for generating the high-density plasma 30 or the low-density plasma 40 into the interior of the etching chamber 110; and
RF biased reactive ion etching device, characterized in that it further includes an exhaust unit 112 that discharges reaction products generated inside the etching chamber 110 to the outside. The method of claim 1, wherein the ion source unit 130 is,
A first grid 131 to which +DC is applied, which is lower than the voltage (V _PO ) when the RF bias having a negative voltage is not applied to the base 140;
a second grid 132 to which -DC is applied, which is the same as when an RF bias with a negative voltage is not applied to the base 140; and
An RF biased reactive ion etching device comprising a third grid (133) that is grounded. The method of claim 3, wherein the control unit 170,
When an RF bias with a negative voltage (V _PR ) is applied to the base 140 and an RF bias with a negative voltage is not applied to the first grid 131, the voltage is applied to the base 140. An RF biased reactive ion etching device, characterized in that it is configured to perform ion source voltage control by applying a +DC voltage lowered by the negative RF bias voltage (V _PR ). The method of claim 1, wherein the control unit 170
After the high-density plasma 30 and the low-density plasma 40 are formed in the upper and lower parts of the ion source unit 130, the voltage of the ion source unit 130 and the base ( 140) An RF biased reactive ion etching device characterized in that it is configured to perform low-density plasma density control to adjust the density of the low-density plasma 40 by controlling the voltage of the RF power applied to the RF power. Ions having an etch chamber 110, a plasma source unit 120, a first grid 131 to which a positive voltage is applied, a second grid 132 to which a negative voltage is applied, and a third grid 133 to which a ground is applied. A reactive ion etching method using an RF biased reactive ion etching device including a source unit 130, a base 140, a first RF power unit 150, a second RF power unit 160, and a control unit 170. Because,
A high-density plasma forming step (S10) in which the first RF power unit 150 supplies RF power to the plasma source unit 120 to form a high-density plasma 30 on the upper part of the ion source unit 130;
The voltage difference between the first grid 131 of the ion source unit 130 and the base 140 causes ions generated in the high-density plasma 30 to contact the substrate 141 seated on the upper part of the base 140 and the base 140. The ion source unit voltage that adjusts the voltage applied to the first grid 131 in response to the RF bias having the negative voltage (V _PR ) so as to have a voltage difference (Vp) for performing reactive ion etching by collision. Control step (S20); and
A low-density plasma in which the second RF power unit 160 supplies RF power with an RF bias with a negative voltage to the base 140 to form a low-density plasma 40 in the lower part of the ion source unit 130. RF biased reactive ion etching method comprising a forming step (S30). The method of claim 6, wherein the ion source voltage control step (S20),
An RF bias having the negative voltage (V _PR ) is applied to the base 140 and an RF bias is applied to the first grid 131 for reactive ion etching between the first grid 131 and the base 140. Perform ion source voltage control to apply a +DC voltage lower than the voltage (V _Po ) when the RF bias with a negative voltage is not applied to the base 140 so that a voltage difference (V _P ) is generated. RF biased reactive ion etching method characterized in that the step of. According to clause 6,
After performing the low-density plasma forming step (S30), the voltage of the first grid 131 and the voltage of the RF power applied from the second RF power unit 160 to the base 140 are controlled to form the low-density plasma. RF biased reactive ion etching method, characterized in that it further comprises a low-density plasma density control step (S40) for controlling the density of the plasma (40). According to clause 6,
An RF biased reactive ion etching method characterized by etching the magnetic tunnel junction cell of a magnetoresistive memory cell.

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