JP7008474B2 - Plasma etching method - Google Patents

Description

Various aspects and embodiments of the present invention relate to plasma etching methods.

Conventionally, a plasma etching apparatus etches a film to be processed using, for example, a photoresist or a metal-containing mask as a mask. When the photoresist is used as a mask, there is a method of depositing a silicon-containing deposit as a protective film on the surface of the photoresist by plasma of a processing gas while applying a negative DC voltage to the upper electrode containing silicon.

Japanese Patent Application Laid-Open No. 2003-282539 Japanese Unexamined Patent Publication No. 2014-82228

However, in the plasma etching apparatus, when a metal-containing mask is used as a mask, it is not considered to avoid the etching stop caused by the material of the mask. That is, in the plasma etching apparatus, when the metal-containing mask is used as a mask, the metal scattered from the metal-containing mask adheres to the film to be treated as a metal compound, so that the etching of the film to be treated is hindered, and as a result, the etching of the film to be treated is hindered. There is a problem that etching stop occurs.

In the plasma etching method according to one aspect of the present invention, a deposit containing an element constituting the upper electrode is sputtered by the plasma of the first processing gas with respect to the metal-containing mask having a predetermined pattern. Includes a deposition step of depositing the metal-containing mask on which deposits containing elements constituting the upper electrode are deposited, and an etching step of etching the film to be treated with plasma of the second processing gas.

According to various aspects and embodiments of the present invention, when a metal-containing mask is used as a mask, a plasma etching method and a plasma etching apparatus capable of avoiding an etching stop caused by the material of the mask are realized.

FIG. 1 is a cross-sectional view schematically showing a simplified plasma etching apparatus according to the first embodiment. FIG. 2 is a schematic cross-sectional view showing the plasma etching apparatus according to the first embodiment. FIG. 3 is a flowchart showing an example of the flow of the plasma etching process in the first embodiment. FIG. 4 is a diagram showing a deposition step in the first embodiment. FIG. 5 is a diagram showing an example of a cross section of the wafer W after execution of each step when the deposition step and the etching step are repeated. FIG. 6 is a diagram showing another example of the cross section of the wafer W after the execution of each step when the deposition step and the etching step are repeated. FIG. 7 is a diagram showing an example of a cross section of the wafer W after the execution of each step when the oxidation step is executed between the deposition step and the etching step. FIG. 8 is a diagram showing the processing results in Comparative Example 1 and Example 1.

Hereinafter, embodiments of the disclosed plasma etching method will be described in detail with reference to the drawings. The invention disclosed by the present embodiment is not limited. Each embodiment can be appropriately combined as long as the processing contents do not contradict each other.

(Plasma etching apparatus in the first embodiment)
FIG. 1 is a cross-sectional view schematically showing a simplified plasma etching apparatus according to the first embodiment. As shown in FIG. 1, the plasma etching apparatus applies a high frequency (RF) power of, for example, 40 MHz for plasma generation from the first high frequency power supply 89 to the susceptor 16 which is a lower electrode, and also from the second high frequency power supply 90. A lower RF 2 frequency application type plasma etching apparatus that applies, for example, 2 MHz high frequency (RF) power for ion attraction, and a variable DC power supply 50 is connected to the upper electrode 34 as shown in the figure to obtain a predetermined DC (DC). It is a plasma etching apparatus to which a voltage is applied.

FIG. 2 is a schematic cross-sectional view showing the plasma etching apparatus according to the first embodiment. The plasma etching apparatus is configured as a capacitively coupled parallel plate plasma etching apparatus, and has, for example, a substantially cylindrical chamber (processing container) 10 made of aluminum whose surface has been anodized. The chamber 10 is grounded.

At the bottom of the chamber 10, a columnar susceptor support base 14 is arranged via an insulating plate 12 made of ceramics or the like. On the susceptor support base 14, for example, a susceptor 16 made of aluminum is provided. The susceptor 16 constitutes a lower electrode, and a semiconductor wafer (hereinafter referred to as “wafer”) W, which is an object to be processed, is placed on the susceptor 16.

An electrostatic chuck 18 that attracts and holds the wafer W by electrostatic force is provided on the upper surface of the susceptor 16. The electrostatic chuck 18 has a structure in which an electrode 20 made of a conductive film is sandwiched between a pair of insulating layers or insulating sheets, and a DC power supply 22 is electrically connected to the electrode 20. In the electrostatic chuck 18, the wafer W is adsorbed and held by an electrostatic force such as a Coulomb force generated by a DC voltage from the DC power supply 22.

A conductive focus ring (correction ring) 24 for improving etching uniformity is arranged on the upper surface of the susceptor 16 around the electrostatic chuck 18 (wafer W). The focus ring (correction ring) 24 is formed of, for example, silicon. On the side surfaces of the susceptor 16 and the susceptor support base 14, for example, a cylindrical inner wall member 26 made of quartz is provided.

Inside the susceptor support base 14, for example, a refrigerant chamber 28 is provided on the circumference. A refrigerant having a predetermined temperature is circulated and supplied to the refrigerant chamber 28 from an external chiller unit (not shown) via the pipes 30a and 30b. The processing temperature of the wafer W on the susceptor 16 is controlled by the temperature of the refrigerant.

Further, heat transfer gas from a heat transfer gas supply mechanism (not shown), for example, He gas, is supplied between the upper surface of the electrostatic chuck 18 and the back surface of the wafer W via the gas supply line 32.

Above the susceptor 16 which is a lower electrode, an upper electrode 34 is provided in parallel so as to face the susceptor 16. The space between the upper electrode 34 and the lower electrode 16 is the plasma generation space. The upper electrode 34 forms a surface facing the wafer W on the susceptor 16 which is a lower electrode and in contact with the plasma generation space, that is, a facing surface.

The upper electrode 34 is supported on the upper part of the chamber 10 via the insulating shielding member 42. The upper electrode 34 is an electrode plate 36 having a surface facing the susceptor 16 and having a large number of gas discharge holes 37, and an electrode support 38 having a water-cooled structure made of a conductive material by detachably supporting the electrode plate 36. It is composed of and. The conductive material forming the electrode support 38 is, for example, aluminum whose surface has been anodized. The electrode plate 36 is formed of a silicon-containing substance, for example, silicon. Silicon is an example of an element constituting the upper electrode 34. A gas diffusion chamber 40 is provided inside the electrode support 38. From the gas diffusion chamber 40, a large number of gas flow holes 41 communicating with the gas discharge holes 37 extend downward.

The electrode support 38 is formed with a gas introduction port 62 for guiding the processing gas to the gas diffusion chamber 40. A gas supply pipe 64 is connected to the gas introduction port 62, and a processing gas supply source 66 is connected to the gas supply pipe 64. The gas supply pipe 64 is provided with a mass flow controller (MFC) 68 and an on-off valve 70 in this order from the upstream side. From the processing gas supply source 66, fluorocarbon gas (CxFy) such as C4F8 gas reaches the gas diffusion chamber 40 from the gas supply pipe 64 as the processing gas for etching, and the gas flow hole 41 and the gas discharge hole 37 It is discharged into the plasma generation space like a shower through the gas. That is, the upper electrode 34 functions as a shower head for supplying the processing gas.

As will be described later, the processing gas supply source 66 supplies a processing gas used for depositing silicon-containing deposits, a processing gas used for etching, and the like. Details of the gas supplied by the treated gas supply source 66 will be described later.

A variable DC power supply 50 is electrically connected to the upper electrode 34 via a low-pass filter (LPF) 46a. The variable DC power supply 50 may be a bipolar power supply. The variable DC power supply 50 can be turned on / off by the on / off switch 52. The polarity and current / voltage of the variable DC power supply 50 and the on / off of the on / off switch 52 are controlled by the controller (control device) 51.

The low-pass filter (LPF) 46a is for trapping high frequencies from the first and second high-frequency power sources described later, and is preferably composed of an LR filter or an LC filter.

A cylindrical ground conductor 10a is provided so as to extend above the height position of the upper electrode 34 from the side wall of the chamber 10. The cylindrical ground conductor 10a has a top wall above it.

A first high frequency power supply 89 is electrically connected to the susceptor 16 which is a lower electrode via a matching unit 87. Further, the susceptor 16 is electrically connected to the second high frequency power supply 90 via the matching unit 88. The first high frequency power supply 89 outputs high frequency power having a frequency of 27 MHz or higher, for example, 40 MHz. The high-frequency power output from the first high-frequency power source 89 is high-frequency power for generating plasma, and is appropriately referred to as “high-frequency power for plasma generation” below. The second high frequency power supply 90 outputs a high frequency power of 13.56 MHz or less, for example, 2 MHz. The high-frequency power output from the second high-frequency power source 90 is high-frequency power for attracting ions in the plasma, and is appropriately referred to as “high-frequency power for attracting ions” below. The first high frequency power supply 89 may be electrically connected to the upper electrode 34 via the matching unit 87.

The matchers 87 and 88 are for matching the load impedance with the internal (or output) impedances of the first and second high frequency power supplies 89 and 90, respectively, and are the first when plasma is generated in the chamber 10. It functions so that the internal impedance and the load impedance of the first and second high frequency power supplies 89 and 90 seem to match.

An exhaust port 80 is provided at the bottom of the chamber 10, and an exhaust device 84 is connected to the exhaust port 80 via an exhaust pipe 82. The exhaust device 84 has a vacuum pump such as a turbo molecular pump, and the inside of the chamber 10 can be depressurized to a desired degree of vacuum. Further, a carry-in / outlet 85 for the wafer W is provided on the side wall of the chamber 10. The carry-in outlet 85 can be opened and closed by the gate valve 86. Further, a depot shield 11 is detachably provided along the inner wall of the chamber 10 to prevent etching by-products (depots) from adhering to the chamber 10. That is, the depot shield 11 constitutes the chamber wall. The depot shield 11 is also provided on the outer periphery of the inner wall member 26. An exhaust plate 83 is provided between the depot shield 11 on the chamber wall side at the bottom of the chamber 10 and the depot shield 11 on the inner wall member 26 side. As the depot shield 11 and the exhaust plate 83, those obtained by coating an aluminum material with ceramics such as Y2O3 can be preferably used.

A conductive member (GND block) 91 connected to the ground in a DC manner is provided at a portion having substantially the same height as the wafer W of the portion constituting the inner wall of the chamber 10 of the depot shield 11, which will be described later. It exerts such an abnormal discharge prevention effect.

Each component of the plasma etching apparatus is connected to and controlled by the control unit (overall control device) 95. Further, the control unit 95 includes a user interface 96 including a keyboard for the process manager to input commands for managing the plasma etching apparatus, a display for visualizing and displaying the operating status of the plasma processing apparatus, and the like. It is connected.

The control unit 95 has a control program for realizing various processes executed by the plasma etching apparatus under the control of the control unit 95, and for causing each component of the plasma etching apparatus to execute the processes according to the processing conditions. A storage unit 97 in which a program, that is, a recipe is stored is connected. The recipe may be stored in a hard disk or a semiconductor memory, or may be stored in a storage medium readable by a portable computer such as a CDROM or DVD, and set in a predetermined position in the storage unit 97. Is also good.

In the plasma etching apparatus, if necessary, an arbitrary recipe is called from the storage unit 97 by an instruction from the user interface 96 or the like and executed by the control unit 95, so that the plasma etching apparatus controls the control unit 95. The desired processing is performed.

For example, the control unit 95 controls each unit of the plasma etching apparatus so as to perform the plasma etching method described later. To give a detailed example, the control unit 95 contains an element constituting the upper electrode 34 while sputtering the upper electrode 34 with the plasma of the first processing gas with respect to the metal-containing mask provided on the object to be treated. Accumulate deposits. Then, the control unit 95 etches the film to be processed by the plasma of the second processing gas, using the metal-containing mask on which the deposits containing the elements constituting the upper electrode 34 are deposited as a mask. Here, the object to be processed is, for example, a wafer W.

When performing the etching process in the plasma etching apparatus configured as described above, first, the gate valve 86 is opened, the wafer W to be etched is carried into the chamber 10 through the carry-in outlet 85, and the susceptor 16 is carried out. Place on top. Then, the processing gas for etching is supplied from the processing gas supply source 66 to the gas diffusion chamber 40 at a predetermined flow rate, and is supplied into the chamber 10 through the gas flow hole 41 and the gas discharge hole 37, while being supplied to the exhaust device. The inside of the chamber 10 is exhausted by the 84, and the pressure in the chamber 10 is set to a set value in the range of, for example, 0.1 to 150 Pa.

With the etching gas introduced into the chamber 10 in this way, high-frequency power for plasma generation is applied from the first high-frequency power source 89 to the susceptor 16 which is the lower electrode with a predetermined power, and the second high-frequency power source 90 is used. High frequency power for drawing ions is applied at a predetermined power. Then, a predetermined DC voltage is applied to the upper electrode 34 from the variable DC power supply 50. Further, a DC voltage is applied from the DC power supply 22 for the electrostatic chuck 18 to the electrode 20 of the electrostatic chuck 18 to fix the wafer W to the susceptor 16.

The processing gas discharged from the gas discharge hole 37 formed in the electrode plate 36 of the upper electrode 34 is converted into plasma in the glow discharge between the upper electrode 34 and the susceptor 16 which is the lower electrode generated by high frequency power, and is generated by plasma. The surface to be treated of the wafer W is etched by the generated radicals and ions.

In the plasma etching apparatus, since the susceptor 16 which is the lower electrode is supplied with high frequency power in a high frequency region (for example, 27 MHz or more) from the first high frequency power supply 89, the plasma can be densified in a preferable state. , High density plasma can be formed even under lower pressure conditions.

(Plasma etching method in the first embodiment)
FIG. 3 is a flowchart showing an example of the flow of the plasma etching process in the first embodiment. As will be described in detail below, the plasma etching apparatus performs a series of processes on the wafer W in which the film to be processed and the metal-containing mask having a predetermined pattern are sequentially laminated. Further, in the following description, it is assumed that the upper electrode 34 is formed of a silicon-containing substance.

The film to be treated is, for example, a silicon-containing film. The silicon-containing film contains, for example, at least one of SiO2, SiOC, SiC and SiC. The metal-containing mask is, for example, a metal, a metal nitride, a metal oxide, a metal carbide, or a compound of a metal and silicon. The metal contains, for example, at least one of titanium (Ti), tantalum (Ta) and tungsten (W). The metal nitride contains, for example, at least one of titanium nitride (Ti3N4) and tantalum nitride (Ta3N5). The metal oxide is, for example, titanium oxide (TiO2). The metal carbide is, for example, tungsten carbide (WC). The compound of the metal and silicon is, for example, tungsten silicide (WSi2).

Returning to the description of FIG. As shown in FIG. 3, when the processing timing is reached (step S101), the plasma etching apparatus applies a negative DC voltage to the upper electrode 34 containing silicon while applying the plasma of the first processing gas to the surface of the metal-containing mask. On the other hand, a deposition step of depositing silicon-containing deposits is performed (step S102). The first processing gas contains a noble gas. The noble gas contains, for example, at least one of argon, helium, xenon and neon. The silicon-containing deposit is an example of a deposit containing an element constituting the upper electrode 34.

FIG. 4 is a diagram showing a deposition step in the first embodiment. The control unit 95 of the plasma etching apparatus applies high frequency power from the first high frequency power supply 89, and connects the variable direct current power supply 50 to the upper electrode 34 to apply a predetermined direct current (DC) voltage. At this time, the high frequency power for ion attraction is not applied from the second high frequency power supply 90. That is, as shown in FIG. 4 (1), the control unit 95 applies a predetermined negative DC voltage from the variable DC power supply 50 to the upper electrode 34 when the plasma is formed. More preferably, the plasma etching apparatus has a self-bias voltage Vdc on the surface of the electrode plate 36 to such an extent that a predetermined (moderate) sputtering effect can be obtained on the surface of the electrode plate 36 which is the surface of the upper electrode 34 which is an applied electrode. The voltage from the variable DC power supply 50 is applied so as to be deep, that is, so that the absolute value of Vdc on the surface of the upper electrode 34 becomes large. Then, the control unit 95 supplies, for example, argon as the first processing gas into the chamber 10.

As a result, as shown in FIG. 4 (1), for example, argon ions collide with the surface of the electrode plate 36, the silicon forming the electrode plate 36 is sputtered, and the sputtered silicon drops on the metal-containing mask 203. .. Then, as shown in FIG. 4 (2), the silicon-containing deposit 204 is deposited on the surface of the metal-containing mask 203. As a result, the plasma resistance of the metal-containing mask 203 is improved, so that the scattering of the metal from the metal-containing mask 203 is suppressed, and the etching of the film to be treated is not hindered by the metal compound. As a result, the etching stop caused by the material of the metal-containing mask 203 can be avoided.

Returning to the description of FIG. Subsequently, the plasma etching apparatus performs an etching step of etching the film to be processed by the plasma of the second processing gas using the metal-containing mask on which the silicon-containing deposits are deposited as a mask (step S103). The second processing gas includes, for example, a CF-based gas. The CF-based gas includes, for example, at least one of C4F6 gas, C5F8 gas, C4F8 gas, CF4 gas, CHF3 gas and CH2F2 gas.

(Effect in the first embodiment)
As described above, according to the first embodiment, the silicon-containing deposits are formed by the plasma of the first processing gas while applying a negative DC voltage to the upper electrode 34 with respect to the metal-containing mask provided on the object to be treated. The film to be treated is etched by the plasma of the second processing gas, using the metal-containing mask on which the silicon-containing deposits are deposited as a mask. As a result, the plasma resistance of the metal-containing mask is improved, so that the scattering of the metal from the metal-containing mask is suppressed, and the etching of the film to be treated is not hindered by the metal compound. As a result, the etching stop caused by the material of the metal-containing mask can be avoided.

(Other embodiments)
Although the plasma etching method and the plasma etching apparatus according to the first embodiment have been described above, the disclosed technique is not limited thereto. Hereinafter, other embodiments will be described.

In the above embodiment, a case where a silicon-containing deposit is deposited on a metal-containing mask by applying a negative DC voltage to the upper electrode 34 has been shown as an example, but the disclosed technique is not limited to this. .. For example, instead of applying a negative DC voltage to the upper electrode 34, high frequency power of 13.56 MHz or less, for example, 2 MHz may be applied to the upper electrode 34. Alternatively, high frequency power of 13.56 MHz or less, for example, 2 MHz may be applied to the lower electrode 16. Alternatively, high frequency power of 13.56 MHz or less, for example, 2 MHz may be applied to the upper electrode 34 and the lower electrode 16. When high frequency power in the above frequency range is applied to the upper electrode 34, the lower electrode 16, or both the upper electrode 34 and the lower electrode 16, the same sputtering effect as when a negative DC voltage is applied to the upper electrode 34 is obtained. can get. This causes silicon-containing deposits to deposit on the metal-containing mask.

Further, in the above embodiment, the case where the upper electrode 34 is formed of the silicon-containing substance has been described as an example, but the disclosed technique is not limited to this. For example, the upper electrode 34 may be formed of a metal-containing substance. The metal-containing substance contains, for example, ruthenium or the like as a metal. A metal such as ruthenium is an example of an element constituting the upper electrode 34. When the upper electrode 34 is formed of a metal-containing substance, the control unit 95 deposits the metal-containing substance on the metal-containing mask by applying a negative DC voltage to the upper electrode 34.

When the upper electrode 34 is formed of a silicon-containing substance or a metal-containing substance, it is considered that the following phenomenon occurs. That is, a region in which the atoms constituting the metal-containing mask and the atoms constituting the lowered upper electrode 34 are bonded is formed at the interface between the metal-containing mask and the deposit deposited on the metal-containing mask. The plasma resistance of the metal-containing mask is improved. For example, when the upper electrode 34 containing silicon is used, a region containing metal silicide is formed at the interface between the metal-containing mask and the deposit deposited on the metal-containing mask.

(Repeat of deposition process and etching process)
The plasma etching apparatus may alternately repeat the deposition process and the etching process. By repeating the deposition step and the etching step alternately, the plasma resistance of the metal-containing mask is further improved, so that the scattering of metal from the metal-containing mask is more reliably suppressed, and the etching of the film to be treated is a metal compound. Not hindered by. As a result, the etching stop caused by the material of the metal-containing mask can be more reliably avoided.

Further, when the plasma etching apparatus alternately repeats the deposition process and the etching process, the etching process is executed in a longer processing time as compared with the deposition process. As a result, even when the thickness of the silicon-containing deposits deposited on the film to be treated is relatively large in addition to the metal-containing mask in the deposition step, the film to be treated is on the film to be treated together with the film to be treated in the etching step. Silicon-containing deposits are also efficiently removed.

(Processing time in the deposition process)
In another embodiment, the plasma etching apparatus may increase the processing time in the deposition process as the predetermined pattern of the film to be processed becomes deeper according to the number of repetitions of the deposition process and the etching process. The predetermined pattern of the film to be treated includes holes and grooves. Hereinafter, the case of increasing the processing time in the deposition process will be further described with reference to FIG.

FIG. 5 is a diagram showing an example of a cross section of the wafer W after execution of each step when the deposition step and the etching step are repeated. Here, a case where the deposition process and the etching process are repeated three times will be described as an example. Further, the plasma etching apparatus executes a series of processes on the wafer W in which the film to be processed 301 and the metal-containing mask 302 having a predetermined pattern are laminated in order.

First, the plasma etching apparatus performs the first deposition step. The cross section of the wafer W after the execution of the first deposition step is, for example, the state shown in FIG. 5 (a-1). That is, by executing the first deposition step, the silicon-containing deposit 303a is deposited on the surface of the metal-containing mask 302.

Subsequently, the plasma etching apparatus executes the first etching step. The cross section of the wafer W after the execution of the first etching step is, for example, the state shown in FIG. 5 (b-1). That is, the predetermined pattern 304 is formed on the film 301 to be processed by executing the first etching step.

Subsequently, the plasma etching apparatus performs a second deposition step. The plasma etching apparatus performs the treatment so that the treatment time in the second deposition step is longer than the treatment time in the first deposition step. The cross section of the wafer W after the execution of the second deposition step is, for example, the state shown in FIG. 5 (a-2). That is, by performing the treatment so that the treatment time in the second deposition step is longer than the treatment time in the first deposition step, the silicon-containing deposit is thicker than the silicon-containing deposit 303a on the surface of the metal-containing mask 302. Object 303b is deposited.

Subsequently, the plasma etching apparatus performs a second etching step. The cross section of the wafer W after the execution of the second etching step is, for example, the state shown in FIG. 5 (b-2). That is, by executing the second etching step, the predetermined pattern 304 formed on the film 301 to be processed becomes deeper.

Subsequently, the plasma etching apparatus performs a third deposition step. At this time, the plasma etching apparatus performs the treatment so that the treatment time in the third deposition step is longer than the treatment time in the second deposition step. The cross section of the wafer W after the execution of the third deposition step is, for example, the state shown in FIG. 5 (a-3). That is, by performing the treatment so that the treatment time in the third deposition step is longer than the treatment time in the second deposition step, the silicon-containing deposit is thicker than the silicon-containing deposit 303b on the surface of the metal-containing mask 302. Object 303c is deposited.

Subsequently, the plasma etching apparatus executes a third etching step. The cross section of the wafer W after the execution of the third etching step is, for example, the state shown in FIG. 5 (b-3). That is, by executing the third etching step, the predetermined pattern 304 formed on the film 301 to be processed becomes deeper.

As described above, the deeper the holes or grooves formed in the film to be treated according to the number of repetitions between the deposition process and the etching process, the longer the processing time of the deposition process is increased, so that the silicon-containing deposits on the metal-containing mask are deposited. Can be formed thick. As a result, the plasma resistance of the metal-containing mask to the film to be treated is improved, so that the etching stop caused by the material of the metal-containing mask can be more reliably avoided. Further, as the predetermined pattern formed on the film to be treated becomes deeper, the amount of silicon-containing deposits that can reach the bottom of the predetermined pattern decreases, so that even if the treatment time in the deposition step is lengthened, the predetermined pattern can be easily removed. The decline is avoided.

(Negative DC voltage applied to the upper electrode in the deposition process)
In another embodiment, the plasma etching apparatus has a negative DC voltage applied to the upper electrode 34 in the deposition process as the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions of the deposition process and the etching process. The absolute value of may be increased. In this case, the ion energy colliding with the upper electrode 34 increases, the amount of sputtered silicon contained in the upper electrode 34 increases, and the amount of sputtered silicon falling onto the metal-containing mask surface increases. This allows the silicon deposits on the metal-containing mask to be gradually thickened. As a result, the plasma resistance of the metal-containing mask to the film to be treated is improved, so that the etching stop caused by the material of the metal-containing mask can be more reliably avoided.

(Pressure in the deposition process)
In another embodiment, the plasma etching apparatus may increase the pressure in the deposition step as the predetermined pattern formed on the film to be treated becomes deeper according to the number of repetitions of the deposition step and the etching step. In this case, the ion flux colliding with the upper electrode 34 increases as compared with the case where the pressure is not changed, the amount of sputtered silicon contained in the upper electrode 34 increases, and the sputtered silicon reaches the metal-containing mask surface. The amount of descent increases. This allows thickening of the silicon deposits on the metal-containing mask. As a result, the plasma resistance of the metal-containing mask to the film to be treated is improved, so that the etching stop caused by the material of the metal-containing mask can be more reliably avoided.

(High frequency power for ion attraction in the etching process)
In another embodiment, the plasma etching apparatus may increase the high frequency power for ion attraction in the etching process as the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions of the deposition process and the etching process. .. Hereinafter, an example of an increase in high frequency power for ion attraction in the etching process will be described with reference to FIG.

FIG. 6 is a diagram showing another example of the cross section of the wafer W after the execution of each step when the deposition step and the etching step are repeated. Here, a case where the deposition process and the etching process are repeated three times will be described as an example. Further, the plasma etching apparatus executes a series of processes on the wafer W in which the film to be processed 301 and the metal-containing mask 302 having a predetermined pattern are laminated in order.

First, the plasma etching apparatus performs the first deposition step. The cross section of the wafer W after the execution of the first deposition step is, for example, the state shown in FIG. 6 (a-1). That is, by executing the first deposition step, the silicon-containing deposit 303a is deposited on the surface of the metal-containing mask 302.

Subsequently, the plasma etching apparatus executes the first etching step. The cross section of the wafer W after the execution of the first etching step is, for example, the state shown in FIG. 6 (b-1). That is, the predetermined pattern 304 is formed on the film 301 to be processed by executing the first etching step.

Subsequently, the plasma etching apparatus performs a second deposition step. The plasma etching apparatus performs the treatment so that the treatment time in the second deposition step is longer than the treatment time in the first deposition step. The cross section of the wafer W after the execution of the second deposition step is, for example, the state shown in FIG. 6 (a-2). That is, by performing the treatment so that the treatment time in the second deposition step is longer than the treatment time in the first deposition step, the silicon-containing deposit is thicker than the silicon-containing deposit 303a on the surface of the metal-containing mask 302. Object 303b is deposited.

Subsequently, the plasma etching apparatus performs a second etching step. At this time, the plasma etching apparatus increases the high frequency power for ion attraction in the second etching step more than the high frequency power for ion attraction in the first etching step. The cross section of the wafer W after the execution of the second etching step is, for example, the state shown in FIG. 6 (b-2). That is, by executing the second etching step, the predetermined pattern 304 formed on the film 301 to be processed becomes deeper. Further, by increasing the high frequency power for ion attraction in the second etching step, the energy of the ions incident on the predetermined pattern 304 is increased. This improves the straightness of the ions incident on the predetermined pattern 304.

Subsequently, the plasma etching apparatus performs a third deposition step. At this time, the plasma etching apparatus performs the treatment so that the treatment time in the third deposition step is longer than the treatment time in the second deposition step. The cross section of the wafer W after the execution of the third deposition step is, for example, the state shown in FIG. 6 (a-3). That is, by performing the treatment so that the treatment time in the third deposition step is longer than the treatment time in the second deposition step, the silicon-containing deposit is thicker than the silicon-containing deposit 303b on the surface of the metal-containing mask 302. Object 303c is deposited.

Subsequently, the plasma etching apparatus executes a third etching step. At this time, the plasma etching apparatus increases the high frequency power for ion attraction in the third etching step as compared with the high frequency power for ion attraction in the second etching step. The cross section of the wafer W after the execution of the third etching step is, for example, the state shown in FIG. 6 (b-3). That is, by executing the third etching step, the predetermined pattern 304 of the film 301 to be processed becomes deeper. Further, by further increasing the high frequency power for ion attraction in the third etching step, the energy of the ions incident on the predetermined pattern 304 is further increased. This improves the straightness of the ions incident on the predetermined pattern 304.

As described above, the deeper the predetermined pattern formed on the film to be treated is, the higher the high-frequency power for attracting ions in the etching step is increased, so that the straightness of the ions incident on the predetermined pattern is improved. At this time, since the thickness of the silicon-containing deposits on the metal-containing mask is increased, the plasma resistance of the metal-containing mask to the film to be treated does not deteriorate, and the obliquely incident ions colliding with the side wall of the predetermined pattern are reduced. can do. As a result, while suppressing the scattering of metal from the metal-containing mask, it is possible to suppress the occurrence of Boeing in which the shape of the predetermined pattern becomes a barrel shape and bending in which the shape of the predetermined pattern is distorted in the middle.

(Frequency of high frequency power for ion attraction in etching process)
In another embodiment, the plasma etching apparatus lowers the frequency of the high frequency power for ion attraction in the etching process as the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions of the deposition process and the etching process. Is also good. In this case, the energy of the ions incident on the predetermined pattern formed on the film to be treated increases. This improves the straightness of the ions incident on the predetermined pattern. At this time, since the thickness of the silicon-containing deposits on the metal-containing mask is increased, the plasma resistance of the metal-containing mask to the film to be treated does not deteriorate, and the obliquely incident ions colliding with the side wall of the predetermined pattern are reduced. can do. As a result, while suppressing the scattering of metal from the metal-containing mask, it is possible to suppress the occurrence of Boeing in which the shape of the predetermined pattern becomes a barrel shape and bending in which the shape of the predetermined pattern is distorted in the middle.

(Pressure in etching process)
In another embodiment, the plasma etching apparatus may reduce the pressure in the etching process as the predetermined pattern of the film to be processed becomes deeper according to the number of repetitions of the deposition process and the etching process. This improves the straightness of the ions incident on the predetermined pattern. At this time, since the thickness of the silicon-containing deposits on the metal-containing mask is increased, the plasma resistance of the metal-containing mask to the film to be treated does not deteriorate, and the obliquely incident ions colliding with the side wall of the predetermined pattern are reduced. can do. As a result, as in the case of increasing the high-frequency power for ion attraction in the etching process, Boeing in which the shape of the predetermined pattern becomes barrel-shaped while suppressing the scattering of metal from the metal-containing mask, and the shape of the predetermined pattern are in the middle. It is possible to suppress the occurrence of bending that is distorted by.

(Oxidation process)
In another embodiment, the plasma etching apparatus oxidizes the surface of the silicon-containing deposit deposited on the metal-containing mask by the plasma of the oxygen-containing gas to form an oxidation region between the deposition step and the etching step. Further steps may be performed. In this case, the plasma etching apparatus etches the film to be processed by the plasma of the second processing gas and removes the oxidized region in the etching step. The oxygen-containing gas contains, for example, at least one of O2, CO2 and CO. Hereinafter, the case where the oxidation step is executed between the deposition step and the etching step will be further described with reference to FIG. 7.

FIG. 7 is a diagram showing an example of a cross section of the wafer W after the execution of each step when the oxidation step is executed between the deposition step and the etching step. Here, the plasma etching apparatus executes a series of processes on the wafer W in which the film to be processed 401 and the metal-containing mask 402 having a predetermined pattern are sequentially laminated. It is assumed that a predetermined pattern 404 is formed on the film to be treated 401.

First, the plasma etching apparatus performs a deposition step. The cross section of the wafer W after the execution of the deposition step is, for example, the state shown in FIG. 7A. That is, by executing the deposition step, the silicon-containing deposit 403 is deposited on the surface of the metal-containing mask 402. Further, a part of the silicon-containing deposit 403 adheres to the opening of the pattern of the metal-containing mask 402. Here, if the portion of the silicon-containing deposit 403 that adheres to the opening of the pattern of the metal-containing mask 402 is thick, there is a concern that the opening of the pattern of the metal-containing mask 402 may be blocked.

Subsequently, the plasma etching apparatus performs an oxidation step using the plasma of O2. The cross section of the wafer W after the execution of the oxidation step is, for example, the state shown in FIG. 7 (b). That is, the surface of the silicon-containing deposit 403 is oxidized to form the oxidation region 403a.

Subsequently, the plasma etching apparatus performs an etching step. The cross section of the wafer W after the etching step is executed is, for example, the state shown in FIG. 7 (c). That is, by executing the etching step, the predetermined pattern of the film 401 to be treated becomes deeper, and the oxidation region 403a is removed from the silicon-containing deposit 403. As a result, the portion of the silicon-containing deposit 403 that adheres to the opening of the pattern of the metal-containing mask 402 becomes thin.

In this way, the surface of the silicon-containing deposit on the metal-containing mask is oxidized to form an oxidized region, and the oxidized region is removed during etching of the film to be treated. The portion that adheres to the opening of the pattern can be thinned. As a result, the blockage of the opening of the pattern of the metal-containing mask can be suppressed.

(Repeat of deposition process, oxidation process and etching process)
In another embodiment, the plasma etching apparatus may repeat the deposition step, the oxidation step, and the etching step in order. In this case, etching is performed while thinning the portion of the silicon-containing deposit that adheres to the opening of the pattern of the metal-containing mask and improving the plasma resistance of the metal-containing mask. As a result, it is possible to more reliably avoid the etching stop caused by the material of the metal-containing mask while suppressing the blockage of the opening of the pattern of the metal-containing mask more stably.

(Processing time in the oxidation process)
In another embodiment, the plasma etching apparatus may lengthen the treatment time in the oxidation step as the predetermined pattern formed on the film to be treated becomes deeper according to the number of repetitions of the deposition step, the oxidation step, and the etching step. .. In this case, the oxidized region can be gradually thickened according to the thickness of the silicon-containing deposit on the metal-containing mask, and the oxidized region can be appropriately removed at the time of etching the film to be treated. As a result, even when the deposition step, the oxidation step, and the etching step are repeated in order, it is possible to suppress the blockage of the opening of the pattern of the metal-containing mask.

(Pressure in oxidation process)
In another embodiment, the plasma etching apparatus may increase the pressure in the oxidation step as the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions of the deposition step, the oxidation step, and the etching step. In this case, the oxidized region can be gradually thickened according to the thickness of the silicon-containing deposit on the metal-containing mask, and the oxidized region can be appropriately removed at the time of etching the film to be treated. As a result, even when the deposition step, the oxidation step, and the etching step are repeated in order, it is possible to suppress the blockage of the opening of the pattern of the metal-containing mask.

(High frequency power for plasma generation in the oxidation process)
In another embodiment, the plasma etching apparatus increases the high frequency power for plasma generation in the oxidation step as the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions of the deposition step, the oxidation step, and the etching step. May be. In this case, the oxidized region can be gradually thickened according to the thickness of the silicon-containing deposit on the metal-containing mask, and the oxidized region can be appropriately removed at the time of etching the film to be treated. As a result, even when the deposition step, the oxidation step, and the etching step are repeated in order, it is possible to suppress the blockage of the opening of the pattern of the metal-containing mask.

Hereinafter, the disclosed plasma etching method will be described in more detail with reference to examples. However, the disclosed plasma etching method is not limited to the following examples.

(Comparative Example 1)
In Comparative Example 1, an etching step was performed on the object to be treated. As the object to be treated, a test chip having the following structure was used. The etching step was performed using the following conditions.
(Processed object)
Film to be treated: SiO2 film Metal-containing mask: Titanium nitride (Ti3N4)
(Etching process)
Processing gas: C4F6 / Ar / O2 = 5/950/4 sccm
Pressure: 2.7Pa (20mTorr)
High frequency power from the first high frequency power supply: 100W
High frequency power from the second high frequency power supply: 150W
DC voltage to the upper electrode: -300V
Processing time: 600 seconds

(Example 1)
In Example 1, a deposition step of depositing a silicon-containing deposit was performed on the object to be treated, an etching step was performed, and the deposition step and the etching step were alternately repeated 50 times. As the object to be treated, one having the same structure as that of Comparative Example 1 was used. The deposition step was carried out under the following conditions. The etching step was performed under the same conditions as in Comparative Example 1 except that the treatment time shown below was used.
(Sedimentation process)
Processing gas: Ar = 800sccm
Pressure: 6.7Pa (50mTorr)
High frequency power from the first high frequency power supply: 300W
High frequency power from the second high frequency power supply: 0W
DC voltage to the upper electrode: -900V
Processing time: 5 seconds (etching process)
Processing time: 10 seconds

FIG. 8 is a diagram showing the processing results in Comparative Example 1 and Example 1. In FIG. 8, “Conv. Etch 600 seconds” indicates the object to be processed after the etching step in Comparative Example 1. Further, "Si cot + Conv. Etch 5 seconds + 10 seconds, 50 cycles" indicates the object to be treated after the deposition step and the etching step in Example 1 are alternately repeated 50 times. The "cross section" in the figure is a trace diagram of a photograph obtained by enlarging the cross section of the object to be processed.

Further, in FIG. 8, “SiO2 Depth” indicates the depth of the etching hole formed in the SiO2 film.

As shown in FIG. 8, in Comparative Example 1, the etching stop caused by the metal-containing mask occurred. On the other hand, in Example 1, the depth of the etching hole was "293 nm", which satisfied the predetermined allowable specifications.

Thus, as can be seen from the comparison between Example 1 and Comparative Example 1, in Example 1, by depositing the silicon-containing deposits, it is possible to avoid the etching stop caused by the material of the metal-containing mask. rice field.

When a plurality of objects to be processed are continuously processed, it is conceivable that the sputtered atoms are cumulatively attached to the inner wall of the chamber 10 by sputtering the upper electrode 34. Therefore, a cleaning process for removing deposits on the inner wall of the chamber 10 may be performed each time one object to be processed is processed or for each lot.

10 Chamber 32 Gas supply line 34 Upper electrode 36 Electrode plate 50 Variable DC power supply 51 Controller 87 Matcher 88 Matcher 89 First high frequency power supply 90 Second high frequency power supply 95 Control unit 96 User interface 97 Storage unit 203 Metal-containing mask 204 Silicon-containing deposits

Claims (20)

A step of providing a substrate having a film to be processed and a metal-containing mask having a predetermined pattern formed on the film to be processed in a plasma etching processing apparatus having an upper electrode and a lower electrode.
A deposition step in which the upper electrode is sputtered on the metal-containing mask by plasma of the first processing gas to deposit a deposit containing an element constituting the upper electrode.
An etching step of etching the film to be treated with plasma of a second processing gas using the metal-containing mask on which deposits containing elements constituting the upper electrode are deposited as a mask .
Including
In the etching step, high frequency power for plasma generation is supplied to the upper electrode or the lower electrode.
A plasma etching method in which high-frequency power for drawing ions is supplied to the lower electrode in the etching step . A step of providing a substrate having a film to be processed and a metal-containing mask having a predetermined pattern on the film to be processed in a plasma etching processing apparatus having an upper electrode and a lower electrode.
Before etching the film to be treated through the metal-containing mask, the upper electrode is sputtered by plasma of the first processing gas, and a deposit containing an element constituting the upper electrode is deposited on the metal-containing mask. And the deposition process
An etching step of etching the film to be treated with the plasma of the second treatment gas using the metal-containing mask on which deposits containing the elements constituting the upper electrode are deposited after the deposition step as a mask.
Plasma etching methods, including. In the deposition step, a negative DC voltage is applied to the upper electrode, a high frequency power of 13.56 MHz or less is applied to the upper electrode, or a high frequency power of 13.56 MHz or less is applied to the lower electrode. The plasma etching method according to claim 1 or 2 , wherein a deposit containing an element constituting the upper electrode is deposited on the metal-containing mask by applying the above. The plasma etching method according to any one of claims 1 to 3, wherein the deposition step and the etching step are alternately repeated . The plasma etching method according to claim 4 , wherein the deeper the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions between the deposition step and the etching step, the longer the processing time in the deposition step is. As the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions between the deposition step and the etching step, the absolute value of the negative DC voltage applied to the upper electrode in the deposition step is increased. , The plasma etching method according to claim 4 or 5 . According to any one of claims 4 to 6 , the pressure in the deposition step is increased as the predetermined pattern formed on the film to be treated becomes deeper according to the number of repetitions between the deposition step and the etching step. The plasma etching method described. The claim that the deeper the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions between the deposition step and the etching step, the higher the high frequency power for attracting ions in the plasma in the etching step. The plasma etching method according to any one of 4 to 7 . As the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions between the deposition step and the etching step, the frequency of high-frequency power for attracting ions in the plasma in the etching step is lowered . The plasma etching method according to any one of Items 4 to 8 . One of claims 3 to 8, wherein the pressure in the etching step is reduced as the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions between the deposition step and the etching step. The plasma etching method described. Between the deposition step and the etching step, an oxidation step of oxidizing the surface of the deposit deposited on the metal-containing mask with plasma of an oxygen-containing gas to form an oxidation region is further included.
The plasma etching method according to any one of claims 1 to 10 , wherein the etching step etches the film to be processed with the plasma of the second processing gas and removes the oxidized region. The plasma etching method according to claim 11 , wherein the deposition step, the oxidation step, and the etching step are repeated in order. 12. The process according to claim 12 , wherein the deeper the predetermined pattern formed on the film to be treated is, the longer the treatment time in the oxidation step is, depending on the number of repetitions of the deposition step, the oxidation step and the etching step. Plasma etching method. The 12th or 13th claim , wherein the pressure in the oxidation step is increased as the predetermined pattern formed on the film to be treated becomes deeper according to the number of repetitions of the deposition step, the oxidation step and the etching step. Plasma etching method. As the predetermined pattern formed on the film to be processed becomes deeper according to the number of repetitions of the deposition step, the oxidation step, and the etching step, the high frequency power for generating plasma in the oxidation step is increased . The plasma etching method according to any one of Items 12 to 14 . The plasma etching method according to any one of claims 1 to 15 , wherein the metal-containing mask is a metal, a metal nitride, a metal oxide, a metal carbide, or a compound of a metal and silicon. The plasma etching method according to claim 16, wherein the metal contains at least one of titanium (Ti), tantalum (Ta), and tungsten (W). The plasma etching method according to any one of claims 1 to 17 , wherein the film to be treated is a silicon-containing film. The plasma etching method according to any one of claims 1 to 18 , wherein the first processing gas contains a rare gas. The plasma etching method according to any one of claims 1 to 19 , wherein the second processing gas contains a CF-based gas.

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