JPWO2018088532A1 - Etching apparatus and etching method - Google Patents

Abstract

In the etching method of irradiating plasma having reactive radicals, the processing gas used for plasma formation is an etching gas containing H2 gas and at least one gas selected from the group consisting of N2, NH3, H2O and CO2. The surface modification gas is contained, so that the etching rate can be improved and the increase in the surface roughness during the etching can be suppressed.

Description

  The present invention relates to an etching apparatus and an etching method using plasma.

  Conventionally, various etching methods have been studied for forming metal wiring such as Cu. In general, other than a chemical mechanical polishing (CMP) method, a method of dry etching Cu using a halogen gas such as chlorine is known (see Patent Document 1). In dry etching of a semiconductor material such as silicon having a covalent bond and germanium, etching may be possible by using hydrogen without using a perfluorocarbon gas having a high global warming potential or a halogen gas. Are known. The etching method using hydrogen has excellent advantages such as a low gas unit price, no global warming effect, and no toxicity compared to etching methods using perfluorocarbon gas or halogen gas. In particular, by setting the pressure in the vicinity of atmospheric pressure, a high-density plasma can be formed in the narrow gap, and volatile products generated by the reaction with the plasma can be efficiently removed.

JP-A-7-161687 JP 2014-63874 A

  In metal etching, it is simultaneously expected to use an inexpensive etching gas with a small environmental load, increase the etching rate, and reduce the roughness of the etched metal surface. The present invention has been made in view of the above problems, and provides an etching apparatus and an etching method capable of performing high-speed etching using an etching gas having a small environmental load and reducing the roughness of the resulting metal surface. The purpose is to provide.

In order to solve the above-described problem, an etching apparatus according to a first aspect includes a processing container, a sample holder disposed in the processing container, and a position facing the sample holder in the etching apparatus for a sample containing metal. A plasma generation electrode provided to generate plasma and supply a processing gas directly into the plasma; a high-frequency power source connected to the plasma generation electrode; and a process of supplying the processing gas to the plasma generation electrode comprising a gas inlet, wherein the processing gas, surface modification comprising at least one gas selected and etching gas containing _{H 2 gas,} from the group consisting of _{N 2, NH 3, H 2} O and CO ₂ Quality gas.

  In the etching apparatus according to the second aspect, the plasma generation electrode includes a gas discharge passage communicating with the processing gas introduction port, and plasma can be generated at a tip portion of the gas discharge passage.

  In the etching apparatus according to the third aspect, the metal may contain Cu.

An etching method according to a fourth aspect is an etching method in which a plasma having reactive radicals is irradiated. A processing gas used for plasma formation includes an etching gas containing H ₂ gas, N ₂ , NH ₃ , H ₂ O, and And a surface modifying gas containing at least one gas selected from the group consisting of CO ₂ .

  According to the present invention, it is possible to improve the etching rate and reduce the roughness of the etched metal surface by using an inexpensive and low environmental load etching gas.

It is a figure for demonstrating the principle of an etching. It is a figure which shows a sample board | substrate. It is a graph which shows improvement results, such as surface roughness. It is a graph which shows the relationship between a hydrogen concentration and an etching rate. It is a graph which shows the relationship between the power of the high frequency electric power from a high frequency power supply, and an etching rate. It is a figure which shows the structure of a 1st etching apparatus. It is a longitudinal cross-sectional view for demonstrating the state of the vicinity of a plasma generation area | region. It is a figure which shows the structure of a 2nd etching apparatus. It is a longitudinal cross-sectional view for demonstrating the state of the vicinity of a plasma generation area | region. It is a figure which shows the structure of a 3rd etching apparatus. It is a figure which shows the structure of a 4th etching apparatus. It is a figure which shows the structure of the 5th etching apparatus. It is a figure which shows the structure of the 6th etching apparatus. It is a figure which shows the detailed structure of a drum. It is a figure which shows the structure of the 7th etching apparatus. It is a figure which shows the structure of the 8th etching apparatus. It is a figure which shows the structure of the 9th etching apparatus. It is a figure which shows the structure of the 10th etching apparatus.

  Hereinafter, an etching apparatus and an etching method according to embodiments will be described. Note that the same reference numerals are used for the same elements, and redundant description is omitted.

  FIG. 1 is a diagram for explaining the principle of etching.

In this etching method, in the etching method in which plasma having reactive radicals is irradiated, a processing gas used for plasma formation uses a surface modification gas (N ₂ gas) in addition to an etching gas (H ₂ gas). Yes. The object to be etched is a metal, preferably copper.

  According to the study by the inventors of the present application, it was observed that the copper surface becomes rough when etching is performed by irradiating copper with only hydrogen plasma. The cause of this was found by observation with a transmission electron microscope or the like that hydrogen radicals (hydrogen atoms) penetrated into the copper and formed voids in the crystal grains or in the crystal grain boundaries. .

  Therefore, in this etching method, nitrogen gas is mixed as a surface modifying gas into the etchant hydrogen gas. When a nitrogen mixed hydrogen plasma is formed on the copper sample, a copper nitride (nitride layer) is formed on the surface of the copper metal. At the top of the copper sample, hydrogen and nitrogen atoms are present as radicals (FIG. 1A).

  When a nitride layer is formed on the metal copper surface, diffusion of hydrogen radicals (hydrogen atoms) in the hydrogen plasma to the deep portion is prevented, and the nitride layer on the surface is first scraped (FIG. 1B). Further, copper as a processing object is very convenient. The melting point of the nitride layer is lower than that of the metal copper before nitriding, and the nitride layer can be etched very quickly. This also means that the bond energy of nitride-copper-nitrogen is lower than that of metallic copper.

  Specifically, in this etching method, when the metal to be etched reacts with the surface modification gas that has become a reactive radical, the melting point of these compounds may be lower than that of the original metal. Hydrogen dissolves excessively in the molten compound and promotes transpiration of the compound. Here, in the case of etching using only hydrogen radicals (hydrogen atoms), a clean metal surface is always exposed on the metal surface, so that the hydrogen atoms dissolve very easily into the metal. Since the hydrogen atom has a very small particle diameter, it easily diffuses to the deep part of the metal, and these excessively dissolved hydrogens generate the cause of the increase in surface roughness such as voids in the metal crystal and grain boundaries. In this method, a reaction product of the target metal and the surface modification gas is formed on the surface layer of the substrate. This reaction product (nitride layer) on the surface layer is not a metal bond, but has a covalent bond or ionic bond, and is a layer containing many defects such as localized dangling bonds. By being trapped by these defects, it becomes slower than diffusion in metal. Since this layer functions as a barrier that suppresses the diffusion of hydrogen radicals (hydrogen atoms), the above-described diffusion of excessive hydrogen atoms into the metal is suppressed, resulting in the prevention of voids in the metal bulk, resulting in surface roughness. Can be suppressed.

Moreover, for example, in a device in which an Cu insulating film such as SiO ₂ is formed on the same substrate, this etching method can be used to etch only Cu with a very high selectivity.

In the case of using Cu as the metal, as a surface modifying gas, in addition to the _{N 2,} even with NH 3, _{H 2} O or CO _2, the surface roughness is improved. This is because the metal surface is converted into a covalent bond or ion bond substance by nitrogen, oxygen, and hydroxyl radicals generated from these gases.

  Furthermore, the present method is considered to be effective even when a metal other than Cu, for example, Al, Ni, In, Ag, Ga, Cr, or Mn is etched. This is because these metals form a relatively unstable hydride by reaction with a hydrogen atom, and can be reformed into a non-metal bonded substance by a nitrogen radical, an oxygen radical, or the like.

Note that the plasma generates high-density atomic hydrogen (10 ¹⁶ to 10 ¹⁹ atoms / cc). In addition, the nitride layer that is a compound of Cu and N is Cu ₃ N in terms of stoichiometric composition and has a lower melting point than Cu. By non-metallization by nitriding, a layer including many defects composed of dangling bonds is formed, whereby the nitride layer functions as a hydrogen barrier layer.

  FIG. 2 is a diagram showing a sample substrate (sample).

In the sample substrate, a SiO ₂ layer is formed on a Si substrate, and a Cu layer is embedded between the SiO ₂ layers. The etching described above was applied to this sample substrate.

  FIG. 3 is a chart showing improvement results such as surface roughness.

In the comparative example, the etching gas is only hydrogen (hydrogen concentration: 100%), and in the examples, hydrogen and surface modified gas (N ₂ ) are used (hydrogen concentration: 90%, nitrogen concentration: 10%). ). In addition, these density | concentrations are the ratio of the mass flow rate of each gas supplied to the inside of a processing container in normal pressure.

  The power of the high frequency power applied to the plasma generating electrode for generating plasma is 100 W, the pressure in the processing container is 13.3 kPa, the temperature in the processing container is room temperature, the distance between the plasma generating electrode and the sample substrate is 0.7 mm, The flow rate of the gas emitted from the plasma generating electrode is 10 SLM. The etching apparatus shown in FIG. 6 was used.

As is clear from these experimental results, the surface roughness is remarkably improved when the etching gas mixed with N ₂ is used as compared with the etching using only hydrogen, and the selective etching ratio with Cu (190 of SiO ₂ is 190 nm). It can be seen that the etching rate of Cu is also significantly increased.

  FIG. 4 is a graph showing the relationship between the hydrogen concentration and the etching rate.

  This hydrogen concentration is the ratio of the mass flow rate of each gas supplied into the processing container. It can be seen that the etching rate is highest when the hydrogen concentration is 90% (nitrogen concentration = 10%).

  FIG. 5 is a graph showing the relationship between the power (W) of the high frequency power from the high frequency power supply and the etching rate (μm / min).

As the power increases, the etching rate increases. However, the etching rate when nitrogen is mixed (N ₂ = 10% added hydrogen) is higher than etching with hydrogen only (pure hydrogen). This also shows that the addition of nitrogen is effective in increasing the etching rate.

  Next, an etching apparatus will be described.

  FIG. 6 is a diagram showing a configuration of the first etching apparatus.

  This etching apparatus is an etching apparatus for a sample substrate containing metal (Cu), and is provided at a position facing the processing container 1, a substrate holder 2 disposed in the processing container 1, and the substrate holder 2. A plasma generation electrode 5 to be generated, a high-frequency power source 6 electrically connected to the plasma generation electrode 5, and a processing gas inlet 4 for supplying a processing gas to the plasma generation electrode 5 are provided. The plasma generation electrode 5 has a function of supplying a gas directly into the plasma 8 and a function of forming a flow for forcibly transporting a reaction product generated by the reaction between the sample substrate (S, F) and the plasma 8. Have.

Here, the process gas contains the etching gas containing H ₂ gas, the surface modifying gas containing at least one gas selected from N _2, NH 3, the group consisting of _H 2 _O and CO _2.

As described above, when etching a metal, in addition to H ₂ gas, a surface modifying gas such as N ₂ is converted into plasma, thereby increasing the etching rate, improving the etching selectivity, and roughening the metal surface. Can be greatly reduced.

  The plasma generating electrode 5 includes a gas discharge passage 5P communicating with the processing gas introduction port 4, and plasma 8 is generated between the tip of the gas discharge passage 5P and the sample substrate (F, S). Since the plasma 8 is generated between the vicinity of the front end of the gas discharge passage 5P and the sample substrate (F, S), the process gas is efficiently supplied into the plasma 8, and the plasma 8 is supplied in accordance with the flow of this gas. Etching reaction products generated by the reaction between the sample substrate (F, S) and the sample substrate surface can be suitably removed.

  Since this apparatus can form high-pressure plasma in a narrow gap and gas can be directly supplied into the narrow gap, reaction products generated on the sample substrate can be efficiently removed and transported from the sample substrate surface. .

  This apparatus includes a plasma generation electrode holder 3 disposed at a position facing the substrate holder 2 in the processing container 1, a processing gas inlet 4 for introducing a processing gas into the processing container 1, and a plasma generation electrode holder. 3 is provided with a high frequency power source 6 connected to the plasma generating electrode 5 arranged in 3 and a control device 7 for controlling the high frequency power source 6 and the pressure in the container.

  An exhaust pump EX communicates with the internal space of the processing container 1 via a valve V. By driving the exhaust pump EX, the pressure in the internal space can be reduced. The exhaust amount of the exhaust pump EX can be controlled by adjusting the valve V. The pressure in the processing container 1 is measured by a pressure gauge PS.

A sample substrate S on which a metal to be etched and a metal film F are formed is held on a substrate holder 2 in the processing container 1, and a pipe-shaped plasma generation electrode 5 is disposed above the sample substrate S. The upper end of the plasma generation electrode 5 is held by the plasma generation electrode holder 3. The plasma generating electrode holder 3 can be fixed to the inner wall of the processing container 1. The internal space of the pipe-shaped plasma generation electrode 5 is connected to a plurality of process gas storage tanks (not shown) via piping and a flow rate controller MFC. In this example, these tanks are filled with hydrogen and nitrogen, and by controlling the flow rate controller MFC, the inside of the processing container 1 is passed through the processing gas inlet 4 provided on the outer wall of the processing container 1. Hydrogen gas (H ₂ ) and nitrogen gas (N ₂ ) can be introduced into the gas. The flow rate controller can also be provided to control the respective gas flow rates.

  The hydrogen introduced from the processing gas inlet 4 via the flow rate controller MFC passes through the internal space of the pipe-shaped plasma generation electrode 5 and is discharged from the lower end thereof. In the vicinity of the discharge destination, a high-frequency electric field of high electric field is formed by the high-frequency power source 6, and plasma is formed in the vicinity of the tip of the pipe by the discharged hydrogen and nitrogen (plasma generation region 8).

  The plasma generation electrode 5 is electrically connected to a high-frequency power source 6, and the substrate S, the substrate holder 2, and the outer wall of the processing container 1 are connected to a ground potential.

  The control device 7 is connected with a pressure gauge PS, a valve V, a high-frequency power source 6, and a flow rate controller MFC, and monitors the internal pressure with the pressure gauge PS so that the inside of the processing container 1 becomes a desired pressure. The opening degree of the flow rate controller MFC and the valve V is adjusted. The control device 7 can control the output power of the high-frequency power source 6, and by supplying an appropriate high-frequency power to the plasma generation electrode 5 in the case of a desired internal pressure, the periphery of the tip of the plasma generation electrode 5 Plasma can be generated.

Here, the control device 7 controls the high-frequency power source 6 when hydrogen and nitrogen are introduced into the processing container 1 from the processing gas inlet 4, and a plasma of hydrogen / nitrogen gas mixed around the plasma generation electrode 5. Is generated. The density A of the high frequency power applied per unit area in the plasma generation region 8 of the plasma generation electrode 5 by the high frequency power source 6, the distance B between the plasma generation electrode 5 and the sample substrate S, the plasma generation electrode 5 in the processing chamber 1 Is set so as to satisfy the following relationship.
A ≧ 130 (W / cm ² )
・ 0.1 (mm) ≦ B ≦ 15 (mm)
・ 80 (Pa) ≦ C ≦ 0.2 (MPa)

  The unit area in the plasma generation region 8 of the raw metal is the unit area on the contact surface between the plasma generation electrode 5 and the plasma. Since the plasma density is high in the vicinity of the pipe tip portion formed of the plasma generation electrode 5, the plasma generation region 8 shows a relatively high density plasma region in FIG. This plasma generation region extends in the direction of the substrate and touches the substrate.

That is, the distance B (gap) between the sample substrate S and the tip of the pipe-shaped plasma generation electrode 5 is very narrow, set to 0.1 (mm) or more and 15 (mm) or less, and the pressure C Is relatively high, such as 80 (Pa) or more and 0.2 (MPa) or less, and the density A of high-frequency power is 130 (W / cm ² ) or more, which is very high.

When nitrogen mixed hydrogen plasma is generated in this state, the plasma acts on the surface of the metal film F and etching is performed. The material of the plasma generating electrode 5 is made of a substance that is less reactive than hydrogen or the like with respect to hydrogen plasma, such as iron or stainless steel. Even a normal metal can be used for the plasma generating electrode 5 if the surface is coated with an insulator such as Al ₂ O _{3 having} low reactivity with hydrogen. The reaction product of plasma and metal moves to the outside of the plasma generation electrode by the gas flow.

  FIG. 7 is a longitudinal sectional view for explaining a plasma generation region around the plasma generation electrode 5.

  In the metal film F on the substrate surface, due to the influence of the gas flow discharged from the plasma generation electrode, a region slightly outside the region immediately below is etched as an etching region ER, and the etching product is released to the outside of the plasma.

The shape of the plasma generation electrode 5 is a pipe shape (circular tube), and has an outer diameter D _OUT and an inner diameter D _IN , and the length is longer than the dimension H in the longitudinal direction of the pipe in contact with the plasma generation region 8. That's fine. In one example, the dimension H of the pipe in contact with the plasma generation region 8 is not less than 2.7 mm and not more than 6.57 mm.
The surface area SP of the plasma generation electrode 5 in contact with the plasma generation region 8 is given by the following equation.
SP = π × D _OUT × H + (D _OUT / 2) ² × π− (D _in / 2) ² × π

The dimension H when the outer diameter D _{OUT is} 1.06 mm, the inner diameter D _{IN is} 0.7 mm, and the input power is 30 to 100 W is as follows.
・ At 30W: H = 2.7mm
・ At 40W: H = 3.5mm
・ At 50W: H = 4.1mm
・ At 60W: H = 4.5mm
・ At 70W: H = 5.4mm
・ At 80W: H = 5.8mm
・ At 100W: H = 6.6mm

  Therefore, if the input power is divided by the surface area SP of the plasma generation electrode 5 in contact with the plasma generation region 8, the density A of the high frequency power can be obtained.

  As described above, in this apparatus, the reformed gas and hydrogen are simultaneously supplied from the pipe-shaped plasma generation electrode (electrode). In addition, the horizontal cross section is not a circular or square pipe shape, but the vertical cross sectional shape is the same slit shape as this, and the horizontal cross section may be a plasma generating electrode having a rectangular shape.

  FIG. 8 is a diagram showing the configuration of the second etching apparatus, and FIG. 9 is a longitudinal section for explaining the state in the vicinity of the plasma generation region.

  The difference between the second etching apparatus and the first etching apparatus is that the direction of gas flow is opposite, and the other configurations, functions and effects are the same. The processing gas inlet 4 described above functions as a gas outlet. By controlling the inflow amount of the processing gas with the flow rate controller MFC and controlling the conductance of the exhaust valve V2, the gas flow velocity around the metal film can be controlled while controlling the pressure in the processing container. Further, since the gas inlet 4 is used as a gas outlet, a processing gas inlet 4 ′ for introducing a processing gas is newly provided on the outer wall of the processing container 1. A flow rate controller MFC is attached to the processing gas inlet 4 'to control the inflow amount.

An etching gas (H ₂ ) and a surface modification gas (N ₂ ) are introduced into the processing vessel 1 from the processing gas inlet 4 ′, and the plasma is generated while sucking these atmospheres with the pipe-shaped plasma generation electrode 5. Is generated.

  According to this structure, it can suppress that the reaction product by metal etching adheres again to the inner wall etc. of the processing container 1. FIG.

  FIG. 10 is a diagram showing the configuration of the third etching apparatus.

  This apparatus is different from the above-described etching apparatus only in that an XY stage 11 is provided, and the other structures are the same. The XY stage 11 includes an actuator inside, and can move two-dimensionally in a plane parallel to the substrate surface by a control signal from the control device 7. With this configuration, a metal film having a large area can be etched even by using localized plasma by two-dimensional scanning.

  FIG. 11 is a diagram showing the configuration of the fourth etching apparatus.

  The difference between the fourth etching apparatus and the first etching apparatus is that the periphery of the pipe-shaped plasma generation electrode 5 is covered with a gas shield cylinder 20 made of an insulator such as glass, and the gas between these is covered. It is the point which made it the structure discharged | emitted outside, and the other structure and effect are the same. The gas shield cylinder 20 communicates with a pipe outside the processing container 1, and the presence or absence of exhaust can be controlled by a valve V2 provided in the pipe.

  Also with this configuration, it is possible to suppress the reattachment of the reaction product as in the above suction type device. In addition, there is an advantage that the processed gas can be easily sucked by supplying the processing gas from the central pipe and exhausting the processed gas through the surrounding gas shield cylinder 20. By balancing the amount of gas supply and the amount of gas exhausted by the shield cylinder 20, etching can be performed even if the atmosphere in the container is a component other than process gas such as air. Also in this configuration, scanning can be performed as in the third etching apparatus.

  FIG. 12 is a diagram showing the configuration of the fifth etching apparatus.

  The difference between the fifth etching apparatus and the first etching apparatus is that the shape of the plasma generation electrode 5 is a drum shape, and the drum-type plasma generation electrode 51 is used. Are the same. When the drum-type plasma generation electrode 51 rotates about a horizontal axis, gas motion due to gas viscosity is induced in the vicinity of the drum electrode surface, and a viscous gas flow parallel to the sample substrate surface is generated. Etching is performed in the same manner as described above. A processing gas is introduced into the processing container 1 in advance.

  According to this structure, there is an advantage that continuous gas supply from the processing gas storage tank is not always necessary. Moreover, since a fresh gas is provided to the metal film surface by rotation, continuous processing is facilitated, and high-frequency power can be increased by an electrode cooling effect by rotation.

  FIG. 13 is a diagram showing the configuration of the sixth etching apparatus, and FIG. 14 is a side view showing the detailed configuration of the drum.

  The difference between the sixth etching apparatus and the fifth etching apparatus is that a plate having a plurality of holes is wound around the outer peripheral surface of the drum-type plasma generation electrode 51, and each hole is formed at the center of the drum. It is the point which was made to communicate with the space which is located, and the other structure and operation effects are the same. A space located at the center of the drum communicates with the inside of the processing container 1.

  Since the passage extending radially from the center of the drum is connected to the hole on the outer surface, when the drum rotates, the processing gas is discharged from the hole to the outside by centrifugal force. Along with this, processing gas is introduced into the center space of the drum from the openings provided at both ends in the horizontal direction (see FIG. 14). Further, a gas flow is generated not only from the hole but also from the metal film F due to the viscosity in the tangential direction of the rotating drum, and the plasma flow in the presence of these gas flows is also generated. Etching is performed in the same manner as described above. This apparatus also has the advantage that a continuous gas supply from the storage tank for the processing gas is not always necessary.

  FIG. 15 is a diagram showing the configuration of the seventh etching apparatus.

  The difference between the seventh etching apparatus and the sixth etching apparatus is that, instead of the drum-type plasma generation electrode 51, a plasma generation electrode 52 having a rotation axis as a vertical axis is used. -The effect is the same. This apparatus also has the advantage that a continuous gas supply from the storage tank for the processing gas is not always necessary.

The plasma generation electrode 52 includes a cylindrical portion 521 extending in the vertical direction, and a plurality of fine holes are provided on a side surface thereof. A discharge pipe 522 extending in the radial direction communicates with each hole, and when the cylindrical portion 521 is rotated, a gas flow induced by centrifugal force flows inside the discharge pipe 522 toward the outside. The atmospheric pressure inside the cylinder part 521 decreases, and suction of the surrounding processing gas (H ₂ + N ₂ ) occurs at the tip part of the cylinder part 521. Other functions and effects are the same as those of the sixth etching apparatus.

  FIG. 16 is a diagram showing the configuration of the eighth etching apparatus.

  The difference between the eighth etching apparatus and the first or fourth etching apparatus is that a plurality of sets including the plasma generation electrode 5 are arranged to correspond to etching of a large area. Are the same. The reaction product is exhausted and discharged to the outside through the gap between the plasma generation electrodes 5.

  FIG. 17 is a diagram showing the configuration of the ninth etching apparatus.

  The difference between the ninth etching apparatus and the second etching apparatus is that a plurality of sets including the plasma generation electrodes 5 are arranged to correspond to etching of a large area, and the other configurations, functions and effects are the same. is there. The reaction product passes through the space in the plasma generation electrode 5 and is exhausted and discharged to the outside.

  FIG. 18 is a diagram showing the configuration of the tenth etching apparatus.

The difference between the tenth etching apparatus and the first etching apparatus is that the function of the plasma generation electrode 5 is separated into processing gases (H ₂ , N ₂ ) and arranged in plural, and other configurations -The effect is the same. Note that the substrate can be moved by scanning. With this configuration, since hydrogen plasma and reformed gas plasma can be generated separately, more precise control can be expected.

  As described above, according to the etching apparatus and method described above, when the metal surface is etched with the plasma of the processing gas, the etching rate can be improved and the roughness of the etched metal surface can be reduced.

The etching apparatus according to the above-described embodiment is provided in a processing container 1, a sample holder (substrate holder 2) disposed in the processing container 1, and a position facing the sample holder in the etching apparatus for a sample containing metal. The plasma generating electrode 5 that can generate plasma and supply the processing gas directly into the plasma, the high-frequency power source 6 connected to the plasma generating electrode 5, and the processing for supplying the processing gas to the plasma generating electrode 5 A surface reforming process including an etching gas containing H ₂ gas and at least one gas selected from the group consisting of N ₂ , NH ₃ , H ₂ O and CO _2. Including gas.

The plasma generation electrode 5 forms a gas flow that quickly transports reaction products generated by the reaction between the plasma and the substrate to the outside of the plasma. In the case of etching a metal, in addition to H ₂ gas, a surface modifying gas such as N ₂ is made into plasma, so that an inexpensive etching gas with a small environmental load is used, and an etching rate is increased, and the surface of the metal is roughened. It was possible to greatly reduce the thickness.

  Further, in the etching apparatus according to the above-described embodiment, the plasma generation electrode 5 includes the gas discharge passage 5P that communicates with the processing gas introduction port, and plasma can be generated at the tip of the gas discharge passage 5P. The gas discharge passage 5P can be a gas suction passage. In this case, since plasma is generated at the tip of the gas suction passage, the metal etched by the plasma is preferably quickly removed from the sample according to the flow of the gas, leading to an improvement in the etching rate and from the metal sample. The etching product can be prevented from adhering to the raw surface, and the increase in roughness can be further improved.

In the etching apparatus according to the above-described embodiment, the metal can include Cu. In the case where the metal contains Cu, it was confirmed that the surface roughness can be significantly reduced when H ₂ and N ₂ are used at the same time.

Further, the etching method according to the above-described embodiment is an etching method in which plasma having reactive radicals is irradiated. The processing gas used for plasma formation is an etching gas containing H ₂ gas, N ₂ , NH ₃ , H _And a surface modification gas containing at least one gas selected from the group consisting of ₂ O and CO _2, and exhibit the above-described effects.

When Cu is used as the metal, the surface roughness can be improved by using NH ₃ , H ₂ O or CO ₂ in addition to N ₂ as the surface modification gas. This is because metal copper is nitrided, oxidized, and hydroxylated by nitrogen radicals, oxygen radicals, and hydroxyl radicals contained therein, and modified into a covalent bond or ionic bond surface layer. This is because these radical surface modified layers suppress the diffusion of hydrogen and prevent the introduction of excessive hydrogen into the metal as compared with the diffusion of hydrogen atoms in the metal. In addition, in such a surface-modified layer using radicals, hydrogen does not easily move, so that the concentration of hydrogen atoms in the layer is increased, and the reaction probability with the element group constituting the layer is increased. This leads to an increase in the etching rate.

  Furthermore, the present method is considered to be effective when a metal other than Cu, for example, Al, Ni, In, Ag, Ga, Cr, or Mn is etched. This is because these metals form a relatively unstable hydride by reaction with a hydrogen atom, and can be reformed into a non-metal bonded substance by a nitrogen radical, an oxygen radical, or the like.

  In the above etching method, when the metal to be etched reacts with the surface modification gas that has become a reactive radical, the melting point of these compounds may be significantly lower than that of the original metal. By setting the temperature above the melting point of this compound, the hydrogen plasma etches the molten compound at a significant rate. Here, in the case of etching using only hydrogen radicals (hydrogen atoms), a fresh metal surface is always exposed on the metal surface to be processed. In this case, hydrogen dissolves very easily from the plasma exposed surface into the metal binding material.

  Since the radius of hydrogen atoms is very small and light, it diffuses relatively easily to the deep part of the metal, causing voids in the bulk and gas bubbles at the grain boundaries. At the same time, exposure as an etched surface causes an increase in surface roughness. That is, voids, gas bubbles, and the like formed by hydrogen excessively dissolved in the metal before the etching proceeds cause surface roughness. On the other hand, in the present invention, a compound layer (modified layer) of the target metal and the surface modified gas is formed on the surface layer of the substrate. This surface compound layer (modified layer) contains many defects due to localized dangling bonds, which trap hydrogen and function as a barrier to suppress the diffusion of hydrogen radicals (hydrogen atoms). It is possible to suppress the increase in surface roughness. In addition, since hydrogen is easily stored in the barrier layer, the hydrogen concentration in the reformed layer is increased and the residence time is increased, thereby increasing the reaction rate between the elements constituting the reformed layer and hydrogen atoms. There is. Thereby, the improvement of an etching rate can be achieved.

  DESCRIPTION OF SYMBOLS 1 ... Processing container, 3 ... Plasma generation electrode holder, 4 ... Processing gas inlet, 5 ... Plasma generation electrode, 6 ... High frequency power supply, 7 ... Control apparatus.

Claims (4)

In an etching apparatus for a sample containing metal,
A processing vessel;
A sample holder disposed in the processing vessel;
A plasma generating electrode provided at a position facing the sample holder, which generates plasma and allows a processing gas to be supplied directly into the plasma;
A high-frequency power source connected to the plasma generating electrode;
A processing gas inlet for supplying a processing gas to the plasma generating electrode;
With
The processing gas is
An etching gas containing H ₂ gas;
A surface modifying gas comprising at least one gas selected from the group consisting of N ₂ , NH ₃ , H ₂ O and CO ₂ ;
including,
Etching equipment. The plasma generating electrode is
A gas discharge passage communicating with the processing gas introduction port;
Plasma is generated at the tip of the gas discharge passage.
The etching apparatus according to claim 1.   The etching apparatus according to claim 1, wherein the metal includes Cu. In the etching method of irradiating plasma having reactive radicals,
The processing gas used for plasma formation is
An etching gas containing H ₂ gas;
A surface modifying gas comprising at least one gas selected from the group consisting of N ₂ , NH ₃ , H ₂ O and CO ₂ ;
including,
Etching method.