PLASMA PROCESSING METHOD AND PLASMA PROCESSING APPARATUS

A target object processed by performing a plasma processing method includes a first layer made of silicon oxide and a second layer containing carbon. A processing sequence performed repeatedly includes: etching the target object with the second layer as a mask by forming plasma from a first gas; and etching, after the etching by forming the plasma from the first gas, the target object by forming plasma from a second gas. The first gas includes a gas containing a carbon atom and a fluorine atom. The second gas includes a gas containing a carbon atom, a fluorine atom and a hydrogen atom. High-order fluorocarbon is generated by the plasma from the first gas in the etching by forming the plasma from the first gas. Low-order fluorocarbon or low-order hydrofluorocarbon is generated by the plasma from the second gas in the etching by forming the plasma from the second gas.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No. 2019-043693 filed on Mar. 11, 2019, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The various aspects and embodiments described herein pertain generally to a plasma processing method and a plasma processing apparatus.

BACKGROUND

When etching a multilayered film by using a plasma processing apparatus, a plurality of holes having different depths may be formed in an oxide layer included in the multilayered film. A plasma processing method described in Patent Document 1 is directed to a method of forming multiple holes having different heights in a multilayered film. The multilayered film has an oxide layer, a plurality of etching stop layers and a mask layer. The etching stop layers are made of tungsten. In this method, by supplying a processing gas into a processing vessel and forming plasma from the processing gas, the multilayered film ranging from a top surface of the oxide layer to the plurality of etching stop layers is etched. The multiple holes having the different depths are formed in the oxide layer at the same time through this etching. The processing gas includes a fluorocarbon-based gas, a rare gas, oxygen and nitrogen.

SUMMARY

In an exemplary embodiment, there is provided a plasma processing method of processing a processing target object. The processing target object comprises a first layer and a second layer. The second layer is provided with multiple openings and is provided on a top surface of the first layer. The top surface is exposed through the multiple openings. The first layer is provided with multiple etching stop layers. Within the first layer, lengths from the multiple etching stop layers to the top surface are different. The first layer is made of silicon oxide. The second layer is made of a material containing carbon. The method comprises a processing sequence which is performed repeatedly within a chamber of a plasma processing apparatus in which the processing target object is accommodated. The processing sequence comprises: etching the processing target object through the multiple openings with the second layer as a mask by forming plasma from a first gas; and etching, after the etching by forming the plasma from the first gas, the processing target object by forming plasma from a second gas. The first gas includes a gas containing a carbon atom and a fluorine atom. The second gas includes a gas containing a carbon atom, a fluorine atom and a hydrogen atom. High-order fluorocarbon is generated by the plasma from the first gas in the etching performed by forming the plasma from the first gas. Low-order fluorocarbon or low-order hydrofluorocarbon is generated by the plasma from the second gas in the etching performed by forming the plasma from the second gas.

DETAILED DESCRIPTION

Hereinafter, various exemplary embodiments will be described. The exemplary embodiments provide a plasma processing method of processing a processing target object. The processing target object has a first layer and a second layer. The second layer is provided with a plurality of openings and is provided on a top surface of the first layer. Through the openings of the second layer, the top surface of the first layer is exposed. The first layer has a plurality of etching stop layers. Within the first layer, lengths from the respective etching stop layers to the top surface of the first layer are all different. The first layer is made of silicon oxide. The second layer contains carbon. In this plasma processing method, a processing sequence is repeatedly performed within a chamber of a plasma processing apparatus in which the processing target object is accommodated. The processing sequence includes etching the processing target object through the openings with the second layer as a mask by forming plasma from a first gas (sometimes referred to as process A). The processing sequence further includes etching, after etching the processing target object by the plasma from the first gas, the processing target object by forming plasma from a second gas (sometimes referred to as process B). The first gas includes a gas containing a carbon atom and a fluorine atom. The second gas includes a gas containing a carbon atom, a fluorine atom and a hydrogen atom. In the etching performed by forming the plasma from the first gas, high-order fluorocarbon is generated by the plasma from the first gas. In the etching performed by forming the plasma from the second gas, low-order fluorocarbon or low-order hydrofluorocarbon is generated by the plasma from the second gas.

In the process A, by the etching with the plasma from the first gas, the etching upon the first layer trough the openings of the second layer can be performed.

In the process A, however, the high-order fluorocarbon may be generated by the plasma from the first gas. The high-order fluorocarbon is polymer having a high attachment coefficient (hereinafter, sometimes referred to as first polymer). In the process A, this first polymer attaches on the second layer and a side surface of a hole formed by performing the process A. However, it is difficult for this first polymer to reach a bottom of the hole. If the process A is carried on, the first polymer keeps on attaching on a top surface of the second layer and side surfaces of the openings, clogging the openings. Accordingly, it may be difficult to carry on the etching upon the first layer.

Further, since it is difficult for the first polymer to reach the bottom of the hole, selectivity with respect to the etching stop layer is relatively low in the etching of the process A. Therefore, in case that the etching stop layer is exposed through the hole, this etching stop layer may not be protected by the first polymer, and, as a result, this etching stop layer may be etched.

Particularly, in the above-described method, a plurality of holes having different lengths from the top surface of the first layer to the etching stop layers are formed in parallel, not one by one. Therefore, the etching stop layer in a hole having a comparatively short length may be excessively etched by the etching of the process A.

In the process B following the process A, low-order fluorocarbon or low-order hydrofluorocarbon is generated by the plasma from the second gas. The low-order fluorocarbon or the low-order hydrofluorocarbon is polymer having a low attachment coefficient (hereinafter, sometimes referred to as second polymer). In the process B, though it is difficult for this second polymer to attach on the second layer and the side surface of the hole formed by the process A, the second polymer easily reaches the bottom of the hole. Meanwhile, in case that the etching stop layer is exposed through the hole, this second polymer may attach on the etching stop layer through the hole.

As stated above, the second polymer easily reaches the bottom of the hole. Accordingly, in case that the etching stop layer is exposed through the hole, the second polymer may be deposited on the etching stop layer (bottom of the hole), and, thus, the etching stop layer can be protected by the deposited second polymer.

As described above, in the etching performed in the process A, the selectivity with respect to the etching stop layer is relatively low. Further, in the etching performed in the process A, the opening of the second layer (mask) may be clogged, and it may be difficult to carry on the etching. As a resolution, by performing the process B after performing the process A appropriately, the opening of the second layer which is clogged in the process A can be enlarged. Further, in case that the etching stop layer is exposed through the hole formed by the process A, a protective film (second polymer) can be formed on the etching stop layer by performing the process B. Therefore, at the beginning of the process A performed after the process B, the opening of the second layer is already enlarged. At this time, in case that the etching stop layer is exposed through the hole in the etching of the process A, the protective film (second polymer) is already formed on the etching stop layer. Therefore, in the process A performed after the process B, the excessive etching upon the etching stop layer can be suppressed by the protective film (second polymer) while the opening of the second layer is suppressed from being clogged.

Furthermore, in this method, the above-stated processing sequence can be performed repeatedly. Accordingly, by performing the present method, the holes having the different lengths can be formed in parallel, not one by one. In this case, during a period until a hole having the longest length from the top surface of the first layer is formed, it is possible to avoid the clogging of the opening while suppressing the etching stop layer in the hole having the comparatively short length from being excessively etched.

In the plasma processing method according to the exemplary embodiment, the first gas may include at least one of a C4F6gas or a C4F8gas.

In the plasma processing method according to the exemplary embodiment, the second gas may include at least one of a CHF3gas, a CH2F2gas or a CH3F gas.

In the plasma processing method according to the exemplary embodiment, the second gas may further include at least one of a CO gas, a CO2gas, an O2gas, a N2gas, or a H2gas.

In the plasma processing method according to the exemplary embodiment, the etching stop layer may be made of tungsten.

In the plasma processing method according to the exemplary embodiment, in the etching performed by forming the plasma from the first gas, the high-order fluorocarbon mainly attaches on the second layer. In the etching performed by forming the plasma from the second gas, the low-order fluorocarbon or the low-order hydrofluorocarbon attaches on the etching stop layer through the hole formed by performing the processing sequence.

In the exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a placing table, a gas supply system, a high frequency power supply and a controller. The placing table is provided within the chamber. The gas supply system is configured to supply a first gas and a second gas into the chamber. The high frequency power supply is configured to supply a high frequency power to excite the first gas and the second gas. The controller is configured to control the gas supply system and the high frequency power supply. The controller controls the gas supply system and the high frequency power supply to perform a processing sequence repeatedly to etch a processing target object, which is placed on the placing table and provided with a first layer and a second layer, by forming plasma from the first gas and plasma from the second gas. The second layer is provided with multiple openings and is provided on a top surface of the first layer. The top surface is exposed through the multiple openings. The first layer is provided with multiple etching stop layers. Within the first layer, lengths from the multiple etching stop layers to the top surface are different. The first layer is made of silicon oxide. The second layer is made of a material containing carbon. The processing sequence comprises: etching the processing target object through the multiple openings with the second layer as a mask by forming plasma from the first gas; and etching, after the etching by forming the plasma from the first gas, the processing target object by forming plasma from the second gas. The first gas includes a gas containing a carbon atom and a fluorine atom. The second gas includes a gas containing a carbon atom, a fluorine atom and a hydrogen atom. High-order fluorocarbon is generated by the plasma from the first gas in the etching performed by forming the plasma from the first gas. Low-order fluorocarbon or low-order hydrofluorocarbon is generated by the plasma from the second gas in the etching performed by forming the plasma from the second gas.

In the plasma processing apparatus according to the exemplary embodiment, the first gas may include at least one of a C4F6gas or a C4F8gas.

In the plasma processing apparatus according to the exemplary embodiment, the second gas may include at least one of a CHF3gas, a CH2F2gas or a CH3F gas.

In the plasma processing apparatus according to the exemplary embodiment, the second gas may further include at least one of a CO gas, a CO2gas, an O2gas, a N2gas, or a H2gas.

In the plasma processing apparatus according to the exemplary embodiment, the high-order fluorocarbon attaches mainly on the second layer in the etching performed by forming the plasma from the first gas. In the etching performed by forming the plasma from the second gas, the low-order fluorocarbon or the low-order hydrofluorocarbon attaches on the etching stop layer through the hole formed by performing the processing sequence.

Now, various exemplary embodiments will be described in detail with reference to the accompanying drawings. In the various drawings, same or corresponding parts will be assigned same reference numerals.

FIG. 1is a flowchart illustrating a plasma processing method (hereinafter, referred to as “method MT”) according to an exemplary embodiment. The method MT shown inFIG. 1can be performed by using, for example, a plasma processing apparatus10shown inFIG. 2. First, referring toFIG. 2, a configuration of the plasma processing apparatus10will be explained.

FIG. 2is a diagram illustrating the plasma processing apparatus10according to the exemplary embodiment. The plasma processing apparatus10shown inFIG. 2is configured as a capacitively coupled parallel plate type plasma processing apparatus, and is equipped with a substantially cylindrical chamber12. The chamber12has, for example, an anodically oxidized aluminum surface. The chamber12is frame-grounded.

The plasma processing apparatus10is equipped with the chamber12, a grounding conductor12a,an exhaust port12e,a carry-in/out opening12g,a supporting member14, a placing table16, an electrostatic chuck18, an electrode20and a DC power supply22. The plasma processing apparatus10is also equipped with a coolant path24, a pipeline26a,a pipeline26b,a gas supply line28, an upper electrode30, an insulating shield member32, an electrode plate34, multiple gas discharge holes34aand an electrode supporting body36.

The plasma processing apparatus10is further equipped with a gas diffusion space36a,multiple gas through holes36b,a gas inlet opening36c,a gas supply line38, a gas supply system40, a splitter43, a deposition shield46, an exhaust plate48, an exhaust device50, an exhaust line52and a gate valve54.

The plasma processing apparatus10is also equipped with a conductive member56, a power feed rod58, a rod-shaped conductive member58a,a cylindrical conductive member58b,an insulating member58c,a DC power supply60, a first high frequency power supply62, a second high frequency power supply64, a matching device70, and a matching device71. The plasma processing apparatus10is further equipped with a controller Cnt, a focus ring FR and a processing space S.

The supporting member14is placed on a bottom of the chamber12. The supporting member14may have a cylindrical shape. The supporting member14may be made of an insulating material. The supporting member14supports the placing table16.

The placing table16is provided within the chamber12. The placing table16may be made of a metal such as aluminum. In the present exemplary embodiment, the placing table16constitutes a lower electrode.

The electrostatic chuck18is provided on a top surface of the placing table16. The electrostatic chuck18and the placing table16constitute a placing table of the exemplary embodiment. The electrostatic chuck18has a structure in which the electrode20is embedded in a pair of insulating layers or a pair of insulating sheets.

The electrode20may be a conductive film. The electrode20is electrically connected with the DC power supply22. The electrostatic chuck18attracts and holds a processing target object (for example, a processing target object W shown inFIG. 3) by an electrostatic force generated by a DC voltage applied from the DC power supply22.

The focus ring FR is disposed on the top surface of the placing table16to surround the electrostatic chuck18. The focus ring FR is configured to improve etching uniformity. The focus ring FR may be made of, by way of non-limiting example, silicon or quartz.

The coolant path24is provided within the placing table16. A coolant of a preset temperature, for example, cooling water from a chiller unit provided outside is supplied into and circulated in the coolant path24via the pipelines26aand26b.By controlling the temperature of the coolant circulated in the coolant path24, a temperature of the processing target object placed on the electrostatic chuck18can be controlled.

Through the gas supply line28, a heat transfer gas, for example, a He gas from a heat transfer gas supply mechanism (not shown) is supplied into a gap between a top surface of the electrostatic chuck18and a rear surface of the processing target object.

The upper electrode30is provided within the chamber12. The upper electrode30is disposed above the placing table16serving as the lower electrode, facing the placing table16. The placing table16and the upper electrode30are arranged to be substantially parallel to each other. Formed between the upper electrode30and the lower electrode is the processing space S in which plasma etching is performed on the processing target object.

The upper electrode30is supported at an upper portion of the chamber12with the insulating shield member32therebetween. The upper electrode30may include the electrode plate34and the electrode supporting body36. The electrode plate34is in direct contact with the processing space S, and is provided with the multiple gas discharge holes34a.The electrode plate34may be made of a conductor or semiconductor having low resistance and low Joule heat.

The electrode supporting body36is configured to support the electrode plate34in a detachable manner, and may be made of a conductive material such as, but not limited to, aluminum. The electrode supporting body36may have a water-cooling structure.

The gas diffusion space36ais formed within the electrode supporting body36. The gas diffusion space36acommunicates with the processing space S through the multiple gas through holes36band the multiple gas discharge holes34a.

The multiple gas through holes36bcommunicate with the multiple gas discharge holes34a,respectively. The gas through holes36bare formed at the electrode supporting body36, and the gas discharge holes34aare formed at the electrode plate34.

The gas inlet opening36cis connected with the gas supply line38. The gas inlet opening36cis formed at the electrode supporting body36. Various kinds of gases output from the gas supply system40can be introduced into the gas diffusion space36athrough the gas inlet opening36c.

The gas supply system40is configured to supply a first gas and a second gas for performing the method MT shown inFIG. 1into the chamber12. The gas supply system40is connected to the gas supply line38via the splitter43.

The first gas includes a gas composed of a carbon atom and a fluorine atom. The first gas may include at least one of, for example, a C4F6gas or a C4F8gas.

The second gas includes a gas composed of a carbon atom, a fluorine atom and a hydrogen atom. The second gas may include at least one of, for example, a CHF3gas, a CH2F2gas or a CH3F gas.

The second gas may further include at least one of, for example, a CO gas, a CO2gas, an O2gas, a N2gas, or a H2gas.

The grounding conductor12ais of a substantially cylindrical shape. The grounding conductor12aextends upward from a sidewall of the chamber12to be higher than a height position of the upper electrode30.

The deposition shield46is provided along an inner wall of the chamber12in a detachable manner. The deposition shield46is also provided on an outer side surface of the supporting member14. The deposition shield46is configured to suppress an etching byproduct (deposit) from adhering to the chamber12. The deposition shield46may be formed by coating, for example, an aluminum member with ceramics such as Y2O3.

At a bottom side of the chamber12, the exhaust plate48is disposed between the supporting member14and the inner wall of the chamber12. The exhaust plate48may be made of, for example, an aluminum member coated with ceramics such as Y2O3.

Within the chamber12, the exhaust opening12eis provided under the exhaust plate48. The exhaust opening12eis connected with the exhaust device50via the exhaust line52.

The exhaust device50includes a vacuum pump such as a turbo molecular pump, and is capable of decompressing the inside of the chamber12to a required vacuum level.

The carry-in/out opening12gis provided for the processing target object. The carry-in/out opening12gis provided at the sidewall of the processing vessel12. The carry-in/out opening12gis opened or closed by the gate valve54.

The conductive member56is provided at the inner wall of the chamber12. The conductive member56is fixed to the inner wall12to be located on a substantially level with the processing target object in a height direction. The conductive member56is DC-connected to the ground and has an effect of suppressing an abnormal discharge.

The location of the conductive member56is not limited to the example shown inFIG. 2as long as the conductive member56is provided in a plasma formation space. By way of example, the conductive member56may be provided near the placing table16, for example, around the placing table16. Alternatively, the conductive member56may be provided near the upper electrode30. For example, the conductive member56may be provided at an outside of the upper electrode30in a ring shape.

The power feed rod58supplies a high frequency power to the placing table16serving as the lower electrode. The power feed rod58has a coaxial double pipe structure. The power feed rod58includes the rod-shaped conductive member58aand the cylindrical conductive member58b.

The rod-shaped conductive member58aextends from an outside of the chamber12to an inside of the chamber12through the bottom of the chamber12in a substantially vertical direction. An upper end of the rod-shaped conductive member58ais connected to the placing table16.

The cylindrical conductive member58bis disposed to be coaxial with the rod-shaped conductive member58a,surrounding the rod-shaped conductive member58a. The cylindrical conductive member58bis supported at the bottom of the chamber12. Two sheets of substantially annular insulating members58care disposed between the rod-shaped conductive member58aand the cylindrical conductive member58b.Accordingly, the rod-shaped conductive member58aand the cylindrical conductive member58bare electrically insulated.

Lower ends of the rod-shaped conductive member58aand the cylindrical conductive member58bare connected to the matching devices70and71. The matching device70is connected to the first high frequency power supply62. The matching device71is connected to the second high frequency power supply64.

The first high frequency power supply62is configured to supply a high frequency power to excite the first gas and the second gas. The first high frequency power supply62generates a first high frequency power for plasma formation. A frequency of the first high frequency power is in a range from 27 MHz to 100 MHz, for example, 100 MHz.

The second high frequency power supply64is configured to generate a second high frequency power for ion attraction into the processing target object by applying a high frequency bias power to the placing table16. A frequency of the second high frequency power is in a range from 400 kHz to 13.56 MHz, and may be for example, 3 MHz.

The DC power supply60is connected to the upper electrode30. The DC power supply60is configured to apply a negative DC voltage to the upper electrode30. With the above-described configuration, the two different high frequency powers are applied to the placing table16serving as the lower electrode, and the DC voltage is applied to the upper electrode30.

The controller Cnt is a computer including a processor, a storage, an input device, a display device, and so forth. The controller Cnt controls the individual components of the plasma processing apparatus10, for example, the power supply system, the gas supply system, and the driving system. Particularly, the controller Cnt is capable of controlling the gas supply system40, the first high frequency power supply62and the second high frequency power supply64.

The storage of the controller Cnt stores therein a control program for implementing various processings performed in the plasma processing apparatus10by the processor. The control program that can be executed by the processor includes a computer program for allowing each component of the plasma processing apparatus10to perform a processing according to processing conditions, i.e., a processing recipe.

The control program stored in the storage of the controller Cnt may particularly include a computer program for implementing a processing described in the flowchart of the method MT ofFIG. 1. The controller Cnt executes the control program to etch the processing target object placed on the placing table16by forming the plasma from each of the first gas and the second gas supplied from the gas supply system40. The controller Cnt controls the gas supply system40and the first high frequency power supply62to repeat a processing sequence SQ of the method MT shown inFIG. 1.

To perform an etching processing by using the plasma processing apparatus10, the processing target object is placed on the electrostatic chuck18. By supplying various kinds of gases from the gas supply system40into the chamber12at preset flow rates while evacuating the chamber12by the exhaust device50, an internal pressure of the chamber12is set to be in a range from, e.g., 0.1 Pa to 50 Pa.

The first high frequency power is supplied to the lower electrode from the first high frequency power supply62, and the second high frequency power is supplied to the lower electrode from the second high frequency power supply64. The first DC voltage is applied to the upper electrode30from the DC power supply60. Accordingly, a high frequency electric field is formed between the upper electrode30and the lower electrode, and the plasma from the various processing gases supplied into the processing space S can be formed. The processing target object can be etched by various ions and radicals in the plasma.

The method MT shown inFIG. 1may be a method of etching the processing target object W having the structure shown inFIG. 3, for example. The processing target object W has a first layer LY1and a second layer LY2. The first layer LY1has a multiple number of etching stop layers (etching stop layers ML1to ML4, etc.).

The etching stop layer ML3is provided above the etching stop layer ML4. The etching stop layer ML2is provided above the etching stop layer ML3. The etching stop layer ML1is provided above the etching stop layer ML2. A top surface SF is provided above the etching stop layer ML1. By way of example, a film thickness of the etching stop layers ML1to ML4ranges from 30 nm to 80 nm.

Within the first layer LY1, lengths from the respective etching stop layers (the etching stop layers ML1to ML4) to the top surface SF are all different. In the present exemplary embodiment, a length L1from the etching stop layer ML1to the top surface SF is shorter than a length L2from the etching stop layer ML2to the top surface SF. The length L2is shorter than a length L3from the etching stop layer ML3to the top surface SF. The length L3is shorter than a length L4from the etching stop layer ML4to the top surface SF. By way of example, the length L1is in a range from 500 nm to 1000 nm, and the length L4is in a range from 7500 nm to 8000 nm.

As stated above, in the method MT, a multiple number of holes (openings) (holes HL1to HL4, etc.) having the different lengths from the top surface SF to the etching stop layers (the etching stop layer ML1, etc.) are formed in parallel, not one by one, as in the processing target object W shown inFIG. 3toFIG. 6.

The second layer LY2is provided on the top surface SF of the first layer LY1. The second layer LY2is provided with a multiple number of openings (openings OP1to OP4, etc.). The top surface SF is exposed through the openings (openings OP1to OP4, etc.). By way of example, the openings OP1to OP4have a diameter ranging from 120 nm to 140 nm.

In the present exemplary embodiment, the opening OP1is overlapped with the etching stop layer ML1in a stacking direction DL of the multiple number of etching stop layers (etching stop layers ML1to ML4, etc.) within the first layer LY1. The opening OP2is overlapped with the etching stop layer ML2in the stacking direction DL. The opening OP3is overlapped with the etching stop layer ML3in the stacking direction DL. The opening OP4is overlapped with the etching stop layer ML4in the stacking direction DL.

The first layer LY1is made of silicon oxide. By way of non-limiting example, the first layer LY1may be made of silicon dioxide (SiO2). The second layer LY2may be made of a material containing carbon. The second layer LY2may be a carbon layer formed by, for example, CVD (Chemical Vapor Deposition). The etching stop layers ML1to ML4may be made of tungsten.

In the present exemplary embodiment, the processing target object W further includes a third layer LY3. The first layer LY1is provided above this third layer LY3. To elaborate, the etching stop layer ML4is provided on the third layer LY3.

Referring back toFIG. 1, the method MT will be discussed. The method MT is an example of a plasma processing method of processing the processing target object. To be more specific, the method MT is a method of etching the processing target object W placed on the placing table16by forming the plasma from the first gas and the plasma from the second gas. In the method MT, the multiple number of holes (holes HL1to HL4, etc.) having the different lengths from the top surface SF to the etching stop layers (etching stop layers ML1to ML4, etc.) are formed in parallel, not one by one, as in the processing target object W shown inFIG. 3toFIG. 6.

The method MT includes the processing sequence SQ. The processing sequence SQ includes a process ST1and a process ST2. The process ST2is performed after the process ST1. The multiple number of holes (holes HL1to HL4, etc.) are formed by performing the processing sequence SQ.

The method MT also includes a process ST3. The process ST3is performed after the processing sequence SQ.

In the method MT, the processing sequence SQ is performed repeatedly (to be more specified, a preset number of times) in the chamber12of the plasma processing apparatus10in which the processing target object W shown inFIG. 3is accommodated (placed on the placing table16). The method MT can be performed under the control of the controller Cnt. In performing the etching according to the method MT, the controller Cnt particularly controls the gas supply system40and the first high frequency power supply62.

In the process ST1of the processing sequence SQ, the plasma from the first gas is formed, and the processing target object W is etched through the openings (opening OP1, etc.) of the second layer LY2by using the second layer LY2as a mask. Through the etching of the process ST1using the plasma from the first gas, the etching upon the first layer LY1through the multiple number of openings (openings OP1to OP4, etc.) of the second layer LY2can be performed.

As stated above, in the process ST1, the etching upon the first layer LY1is performed by the plasma from the first gas. In the process ST1, however, high-order fluorocarbon may be generated by the plasma from the first gas. The high-order fluorocarbon is first polymer mainly composed of CxFy(x is equal to or larger than 2) and has a high attachment coefficient. In the process ST1, the first polymer mainly attaches on the second layer LY2and may also attach to a side surface of the hole such as the hole HL1shown inFIG. 6which is formed through the process ST1. As shown inFIG. 4, due to the adhesion of the first polymer, a deposit film DP1of the first polymer is formed mainly on the second layer LY2and, also, on the side surface of the hole such as the hole HL1(particularly, at an upper portion of the corresponding side surface in the opening OP1or the like). Further, the first polymer may not reach a bottom of the hole such as the hole HL1.

Accordingly, if the process ST1is carried on over a relatively long period, the first polymer keeps on attaching on the top surface of the second layer LY2and on the side surface of the hole such as the hole HL1(particularly, at the upper portion of the corresponding side surface in the opening OP1or the like), so that a thickness of the deposit film DP1may be increased. In such a case, the opening such as the opening OP1may be clogged with the deposit film DP1, and it may be difficult to carry on the etching upon the first layer LY1. The process ST1may be continued for an appropriate time period unless the opening of the hole such as the hole HL1formed by the etching of the process ST1is clogged with the deposit film DP1.

Further, it is difficult for the first polymer to reach the bottom of the hole such as the hole HL1, and selectivity with respect to the etching stop layer such as the etching stop layer ML1is relatively low in the etching of the process ST1. Thus, in case that the etching stop layer such as the etching stop layer ML1is exposed through the hole such as the hole HL1, the corresponding etching stop layer is not protected by the first polymer, so that the corresponding etching stop layer may be etched.

Particularly, in the method MT, the multiple number of holes (corresponding to the hole HL1, etc.) having the different lengths from the top surface SF to the etching stop layers such as the etching stop layer ML1are formed in parallel, not one by one. Therefore, in the hole (corresponding to the hole HL1, etc.) having a relatively short length, the etching stop layer such as the etching stop layer ML1may be excessively etched by the etching of the process ST1.

The high frequency power for plasma formation from the first high frequency power supply62in the process ST1may be in a range from, e.g., 300 W to 1000 W. Further, if the high frequency power is larger than 1000 W, the deposit film DP1is formed at the upper portion and the sidewall of the second layer LY2and the sidewall and the bottom of the hole such as the hole HL1. As a result, it may be difficult to carry on the etching.

In the process ST2following the process ST1, the etching is performed on the processing target object W by forming the plasma from the second gas to remove the first polymer formed in the process ST1and to suppress the excessive etching upon the etching stop layer in the process ST1.

In the process ST2, low-order fluorocarbon or low-order hydrofluorocarbon is generated by the plasma from the second gas while the deposit film DP1formed in the opening such as the opening OP1in the process ST1is removed. The low-order fluorocarbon or the low-order hydrofluorocarbon is second polymer mainly composed of CF, CF2, CF3, CHF or CHF2, and has a low attachment coefficient. In the process ST2, though it is difficult for this second polymer to attach on the second layer LY2and the side surface of the hole such as the hole HL1formed by the process ST1, the second polymer easily reaches the bottom of the hole such as the hole HL1. Due to the adhesion of this second polymer, a deposit film DP2of the second polymer is formed at the bottom of the hole such as the hole HL1and a lower portion of the hole such as the hole HL1extending from the corresponding bottom.

Meanwhile, in case that the etching stop layer such as the etching stop layer ML1is exposed through the hole such as the hole HL1, the second polymer may attach on the etching stop layer such as the etching stop layer ML1through the corresponding hole. In such a case, the deposit film DP2of the second polymer is formed on the etching stop layer such as the etching stop layer ML1through the hole such as the hole HL1.

As stated above, the second polymer easily reaches the bottom of the hole such as the hole HL1. Accordingly, if the etching stop layer such as the etching stop layer ML1is exposed through the hole such as the hole HL1, the second polymer is deposited on the etching stop layer (bottom of the hole), so that the deposit film DP2is formed thereat. The etching stop layer can be protected by this deposit film DP2.

Further, if at least one of a CO gas, a CO2gas, an O2gas, a N2gas or a H2gas is added to the second gas, a width of the opening of the hole such as the hole HL1may be easily adjusted.

Particularly, if at least one of the CO gas or the CO2gas is added to the second gas, CO or CO2bonds with the fluorine atom of the second polymer, so that COF2is generated. In such a case, fluorine atoms in the second polymer and the first polymer are scavenged, so that carbon atoms deposited on the bottom of the hole such as the hole HL1may be relatively increased. Accordingly, in the process ST1performed after the process ST2, the excessive etching upon the etching stop layer such as the etching stop layer ML1can be effectively suppressed.

In the etching performed in the process ST1, selectivity with respect to the etching stop layer such as the etching stop layer ML1is comparatively low. Further, in the etching performed in the process ST1, the opening (opening OP1, etc.) of the second layer LY2(mask) may be clogged, and the etching may not be carried on. As a resolution, by performing the process ST2after carrying out the process ST1appropriately, the opening (opening OP1, etc.) of the second layer LY2clogged in the process ST1may be enlarged. Further, if the etching stop layer such as the etching stop layer ML1is exposed through the hole such as the hole HL1, the protective film (second polymer) can be formed on this etching stop layer as a result of performing the process ST2.

Therefore, at the beginning of the process ST1performed after the process ST2, the opening (opening OP1, etc.) of the second layer LY2is already enlarged. At this time, if the etching stop layer such as the etching stop layer ML1is exposed through the hole such as the hole HL1in the etching of the process ST1, the protective film (second polymer) is already formed on this etching stop layer. Therefore, in the process ST1performed after the process ST2, excessive etching upon the etching stop layer such as the etching stop layer ML1can be suppressed by the protective film (second polymer) while the opening (opening OP1, etc.) of the second layer LY2is suppressed from being clogged.

A processing time of the process ST2may be, for example, 5 seconds to 30 seconds, for example, 10 seconds to 25 seconds. If the processing time of the process ST2is relatively short (for example, shorter than 5 seconds), the deposit film DP2may not be formed at the bottom of the hole such as the hole HL1shown inFIG. 6. If the processing time of the process ST2is relatively long (for example, longer than 30 seconds), on the other hand, the thickness of the deposit film DP2may be excessively increased, and the etching upon the first layer LY1may not be carried on in the process ST1which may be performed after the process ST2through the process ST3to be described later. Further, if the processing time of the process ST2is relatively long, the opening such as the opening OP1may be excessively enlarged.

The high frequency power for plasma formation from the first high frequency power supply62in the process ST2may be equal to or higher than, e.g., 2000 W. If the high frequency power is less than 2000 W, the etching stop layer may be excessively etched.

In the method MT, by performing the process ST3, the above-described processing sequence SQ can be performed repeatedly a preset number of times. In a first cycle of the processing sequence SQ the processing target object W having the structure shown inFIG. 4is obtained from the processing target object W having the structure shown inFIG. 3by the process ST1, and the processing target object W having the structure shown inFIG. 5is obtained by the process ST2which is performed after the process ST1. Further, by performing the processing sequence SQ the multiple times, the processing target object W having the structure shown inFIG. 6can be obtained. Thus, by performing the method MT, the multiple number of holes (corresponding to the hole HL1, etc.) having the different lengths can be formed in parallel, not one by one. In such a case, during a period until the hole HL4having the largest length from the top surface SF is formed, the clogging of the openings (opening OP1, etc.) can be avoided and the excessive etching upon the etching stop layer in the hole having the relatively short length can be suppressed. Further, in the first cycle of the processing sequence SQ, the hole HL1of the opening OP1need not necessarily reach the etching stop layer ML1by the process ST1as in the case where the processing target object W having the structure shown inFIG. 4is obtained from the processing target object W having the structure shown inFIG. 3. Furthermore, the holes HL2to HL4of the openings OP2to OP4may etched deeper than a top surface of the etching stop layer ML1.

As stated above, by performing the method MT in which the processing sequence SQ is repeatedly performed the preset number of times, the holes (holes HL1to HL4, etc.) having the different lengths can be formed in the first layer LY1effectively, as shown inFIG. 6. As depicted inFIG. 6, by performing the method MT, the hole HL1is formed in the first layer LY1to reach the etching stop layer ML1through the opening OP1while the excessive etching upon the etching stop layer ML1is suppressed.

The hole HL2is formed in the first layer LY1to reach the etching stop layer ML2through the opening OP2while the excessive etching upon the etching stop layer ML2is suppressed. The hole HL3is formed in the first layer LY1to reach the etching stop layer ML3through the opening OP3while the excessive etching upon the etching stop layer ML3is suppressed. The hole HL4is formed in the first layer LY1to reach the etching stop layer ML4through the opening OP4.

According to the exemplary embodiment, it is possible to form a plurality of holes having different lengths effectively in parallel.

So far, the various exemplary embodiments have been described. However, the exemplary embodiments are not limiting, and various omissions, substitutions and changes may be made. Further, other exemplary embodiments may be created by combining elements in the various exemplary embodiments.