TW201707041A - Etching method and etching apparatus - Google Patents

Abstract

A method for etching a silicon film formed on a substrate includes supplying HBr gas, NF3 gas, and O2 gas into a chamber and performing a plurality of etching processes on the silicon film with a plasma generated by the supplied HBr gas, NF3 gas, and O2 gas, gradually reducing a flow rate of the HBr gas during the plurality of etching processes, and adjusting a flow rate of the O2 gas according to the reduction of the HBr gas.

Description

Etching method and etching device

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

There is proposed an etching method for etching an etched layer containing polysilicon by supplying hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas, and oxygen (O ₂ ) gas by plasma generated by the gases. (For example, refer to Patent Document 1).

[Previous Technical Literature]

[Patent Literature]

(Patent Document 1) Japanese Patent Laid-Open Publication No. 2013-258244

However, in the case where holes are formed in the tantalum film by etching, when the aspect ratio is as high as 15 or more, the end of the hole to be etched is distorted (hereinafter referred to as "twisting"), and the etching shape is deteriorated. In recent years, the problem of distortion has become increasingly prominent due to the need for etching of components and high aspect ratio etching.

In view of the above problems, the object of the present invention is to improve the etching shape.

In order to solve the above problems, an etching method is provided, which is an etching method for etching a tantalum film formed on a substrate, which comprises containing hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas, and a gas of oxygen (O ₂ ) gas is supplied into the chamber, and a plurality of steps of etching the tantalum film are performed by supplying plasma generated by the gas; in the plurality of steps, the flow rate of the hydrogen bromide gas is gradually reduced; The flow rate of oxygen is adjusted corresponding to the decrease in the hydrogen bromide gas.

The etching shape can be made good by one side.

1‧‧‧ etching device

10‧‧‧ chamber

11‧‧‧ mask

12‧‧‧ Polysilicon film

13‧‧‧ basement membrane

15‧‧‧ gas supply

20‧‧‧mounting table 20 (lower electrode)

25‧‧‧ gas shower head (upper electrode)

30‧‧‧Power supply unit

100‧‧‧Control Department

106‧‧‧Electrostatic fixture

Fig. 1 is a view showing a longitudinal section of an etching apparatus according to an embodiment.

Figure 2 is a diagram illustrating the distortion versus ideal etching.

Fig. 3 is a timing chart showing gas supply during etching in an embodiment and a comparative example.

Fig. 4 is a view showing the relationship between the aspect ratio and the distortion of an embodiment and a comparative example.

Fig. 5 is a view showing an etching shape of an embodiment and a comparative example.

Fig. 6 is a view showing an example of an etching method relating to an embodiment.

Fig. 7 is a view showing an example of the relationship between the bottom CD value and the twist value of the LF relating to a modification of the embodiment.

Fig. 8 is a view showing an example of a distortion value associated with a modification of the embodiment.

Fig. 9 is a view showing an example of an effect of an etching method according to a modification of the embodiment.

Hereinafter, the form of the present invention will be described with reference to the drawings. In the present specification and the drawings, the same components are denoted by the same reference numerals, and the description thereof will not be repeated.

[The overall composition of the etching device]

First, an example of an etching apparatus 1 according to an embodiment of the present invention will be described with reference to Fig. 1 . Fig. 1 is a view showing an example of a longitudinal section of an etching apparatus 1 according to the present embodiment. The etching apparatus 1 according to the present embodiment is a parallel plate type plasma processing apparatus (capacitive coupling type plasma processing apparatus) in which the mounting table 20 and the gas shower head 25 are disposed opposite to each other in the chamber 10. The mounting table 20 has a function of holding a substrate to be processed such as a semiconductor wafer (hereinafter simply referred to as "wafer W") and functions as a lower electrode. The gas shower head 25 has a gas shower-like supply to the cavity. The function inside chamber 10 functions as the upper electrode.

The chamber 10 is made of, for example, aluminum whose surface is treated with an alumite treatment (anodizing treatment) and has a cylindrical shape. The chamber 10 is electrically grounded. The mounting table 20 is attached to the bottom of the chamber 10 and mounts the wafer W. The wafer W is an example of a substrate to be etched, and the wafer W is formed with a mask on the polyimide film.

The mounting table 20 is a support body 104 formed of, for example, aluminum (Al), titanium (Ti), tantalum carbide (SiC), or the like, and an electrostatic chuck 106 formed on the upper surface of the mounting table 20 to electrostatically adsorb the wafer W. Composition. The electrostatic chuck 106 has a structure in which a clip electrode 106a is interposed between insulators 106b made of a dielectric material such as alumina (Al ₂ O ₃ ).

A DC voltage source 112 is connected to the clamp electrode 106a, and a DC current is supplied from the DC voltage source 112 to the clamp electrode 106a. Thereby, the wafer W is adsorbed to the surface of the electrostatic chuck 106 by Coulomb force.

A refrigerant flow path 104a is formed inside the support body 104. The refrigerant flow path 1044 is connected to the refrigerant inlet pipe 104b and the refrigerant outlet pipe 104c. From the cooler 107, for example, cooling water or The cooling medium such as brine is circulated through the refrigerant inlet pipe 104b, the refrigerant flow path 104a, and the refrigerant outlet pipe 104c. Thereby, the mounting table 20 and the electrostatic chuck 106 are cooled.

The heat transfer gas supply source 85 supplies a heat transfer gas such as helium (He) or argon (Ar) to the inner surface of the wafer W on the electrostatic chuck 106 through the gas supply line 130. With the related configuration, the electrostatic chuck 106 is temperature-controlled by the cooling medium circulating in the refrigerant flow path 104a and the heat transfer gas supplied to the inner surface of the wafer W. This result allows the wafer W to be controlled at a predetermined temperature. Further, it is also possible to form a structure for heating the wafer W by using a heat source.

The mounting table 20 is connected to a power supply device 30 that supplies dual-frequency overlapping power. The power supply device 30 includes a first high-frequency power supply 32 that supplies a high-frequency power HF (High Frequency) for generating plasma at a first frequency, and a high-frequency power LF for bias that supplies a second frequency that is lower than the first frequency. The second high frequency power source 34 of (Low Frequency). The first high-frequency power source 32 is electrically connected to the mounting table 20 through the first matching unit 33. The second high-frequency power source 34 is electrically connected to the mounting table 20 via the second matching unit 35. The first high-frequency power source 32 applies, for example, a high-frequency power HF for plasma excitation of 100 MHz to the mounting table 20. The second high-frequency power source 34 applies a bias high-frequency power LF of, for example, 13.56 MHz to the mounting table 20. Further, in the present embodiment, the high-frequency power HF is applied to the mounting table 20, but may be applied to the gas shower head 25.

The first matching unit 33 integrates the load impedance into the internal (or output) impedance of the first high-frequency power source 32. The second matcher 35 integrates the load impedance into the internal (or output) impedance of the second high frequency power source 34. When the first matching unit 33 generates plasma in the chamber 10, the internal impedance of the first high-frequency power source 32 and the load impedance appear to match each other. When the second matching unit 35 generates plasma in the chamber 10, the internal impedance of the second high-frequency power source 34 and the load impedance appear to match each other.

The gas shower head 25 is assembled by insulating the insulating member of the peripheral portion thereof to close the opening of the top of the chamber 10. The gas shower head 25 can also be electrically grounded as shown in FIG. Further, a variable direct current power source may be connected to apply a predetermined direct current (DC) voltage to the gas shower head 25.

The gas shower head 25 is formed with a conductor introduction port 45 into which a gas is introduced. Inside the gas shower head 25, a center side diffusion chamber 50a and an edge side diffusion chamber 50b which are branched from the gas introduction port 45 are provided. The gas output from the gas supply source 15 is supplied to the diffusion chambers 50a and 50b through the gas introduction port 45, and is diffused in the diffusion chambers 50a and 50b, respectively, and introduced from the plurality of gas supply holes 55 toward the mounting table 20.

An exhaust port 60 is formed on the bottom surface of the chamber 10, and the exhaust port 60 is connected through the exhaust pipe. The exhaust device 65 allows the chamber 10 to be vented. Thereby, the inside of the chamber 10 can be maintained at a predetermined degree of vacuum. A gate valve G is provided on the side wall of the chamber 10, and the wafer W can be carried in and out from the chamber 10 by opening and closing the gate valve G.

The etching apparatus 1 is provided with a control unit 100 that controls the overall operation of the apparatus. The control unit 100 includes a CPU (Central Processing Unit) 105, a ROM (Read Only Memory) 110, and a RAM (Random Access Memory) 115. The CPU 105 performs desired processing such as etching described later in accordance with various recipes stored in the memory areas. The formula describes the program time, pressure (gas exhaust), high frequency power or voltage, various gas flow rates, chamber temperature (upper electrode temperature, chamber sidewall temperature, electrostatic fixture temperature, etc.) for the control information of the program conditions. , cooler 107 temperature, etc. In addition, the programs or the recipes that display the processing conditions can also be stored in a hard disk or semiconductor memory. Further, the recipe may be set at a predetermined position in the memory area in a state of being stored in a memory medium readable by a computer such as a CD-ROM or a DVD.

During the etching process, the opening and closing of the gate valve G is controlled, and the wafer W is carried into the chamber 10 and placed on the mounting table 20. By supplying a direct current from the DC voltage source 112 to the clip electrode 106a, the wafer W can be adsorbed and held by the electrostatic chuck 106 by the Coulomb force.

Next, the etching gas, the plasma excitation high frequency power HF, and the bias high frequency power LF are supplied into the chamber 10 to generate plasma. The wafer W is subjected to a plasma etching process by the generated plasma.

After the etching process, the direct current voltage HV when the positive and negative electrodes are adsorbed against the wafer W from the DC voltage source 112 is applied to remove the electric charge of the wafer W, and the wafer W is peeled off from the electrostatic chuck 106. The opening and closing of the gate valve G is controlled to carry out the wafer W from the chamber 10.

[etching method]

The etching method in the same state of the present invention will be described. For example, as shown in FIG. 2(a), the poly (polycrystalline) ruthenium film 12 of the film to be etched is etched by using a tantalum oxide film (SiO ₂ ) as a mask 11. However, the film to be etched is not limited to the polysilicon film 12, and may be an amorphous germanium film or a single crystal layer. The film to be etched may also be a tantalum oxide film or a tantalum nitride film (SiN). The mask 11 may be an oxide film or a nitride film. The base film 13 of the polysilicon film 12 is exemplified by a tantalum oxide film, a tantalum nitride film, or the like.

2(a) shows an example of a film formation formed on a substrate before etching, and FIG. 2(b) shows an example of an etching shape profile of a hole formed in the polyimide film 12 after etching.

The aspect ratio is defined as the top CD (top CD) of the polysilicon film 12 and the depth D of the polysilicon film 12. ratio. For example, even if the aspect ratio is about 15 to 20, a good etching shape can be obtained as shown in Fig. 2(b). However, in recent years, the required aspect ratio of 25 to 30 does not provide a good etching shape. Especially at 30 or more, it is particularly remarkable. As a result, as shown in Fig. 2(c), the twisted (bending, flexing) phenomenon is twisted at the front end (the bottom side of the hole) of the etching hole. Hereinafter, the comparative example and the program conditions of the present embodiment will be compared, and the etching conditions for solving the problem of the distortion problem and the etching method according to the present invention based on the program condition will be described.

In the etching of the film structure of Fig. 2(a), main etching of the etching polysilicon film 12 and over etching of the etching base film 13 are performed. As the etching gas system, for example, hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas, and oxygen (O ₂ ) (first program condition) are used. In the first program condition, the plasma generated by the gases passes through the mask 11 to etch the polyimide film 12. Next, under etching of the underlying film 13 is performed under the first program condition. The etching method according to the present embodiment is suitable for manufacturing a three-dimensional stacked semiconductor memory such as a 3D NAND flash memory.

Further, in the etching method according to the present embodiment, a process of removing the natural oxide film on the polysilicon film 12 by the mask 11 by the plasma generated by the CF ₄ gas and the O ₂ gas is performed for about 10 seconds, and then The polysilicon film 12 is etched.

[Comparative method related etching method]

Hereinafter, the etching method related to the comparative example will be described. In the comparative example, the program conditions at the time of etching the polysilicon film 12 are as follows, for example.

‧pressure 80mT (10.7Pa)

‧High frequency power HF 400W

‧ High frequency power LF 2350W pulse wave (frequency 0.1kHz, Duty ratio 30%)

‧Gas HBr/NF ₃ /O ₂

‧ etching time 90 seconds

‧Tack 20 temperature 65 ° C

In the etching according to the comparative example, the overetching of the underlying film 13 is, for example, about 30% after the main etching of the polysilicon film 12. In the comparative example, HBr gas, NF ₃ gas, and O ₂ gas were supplied at a predetermined flow rate in both the main etching and the over etching as shown in FIG. 3( a ).

In the plasma etching of the above-described program conditions, when the aspect ratio is about 15, as shown in Fig. 2(b), the etching shape of the polysilicon film 12 is processed to be almost vertical. However, when the aspect ratio is as high as 20, distortion as shown in Fig. 2(c) is caused, so that the etching shape is deteriorated.

Fig. 4(a) shows an example of the etching result associated with the comparative example in the above-mentioned program conditions. As shown in Fig. 4(a), the aspect ratio is 15 or less, and the distortion is not a problem. However, when the aspect ratio exceeds 15, the distortion starts to occur, and when the aspect ratio reaches 25 or more, the distortion is obtained. It will be noticeable. In particular, with the miniaturization of elements in recent years, the problem of distortion in etching with a width ratio of 25 or more has become unacceptable.

One of the causes of the distortion is that the yttrium Si shown in the following reaction formula (1) and the SiBr _x O _y or SiOF _x of the reaction product generated in the etching process are excessively attached to the sidewall of the hole to hinder the directionality of the ion. And cause changes.

Si+HBr+O ₂ +NF ₃ →SiF _x Br _y ↑+SiF ₄ ↑+NH ₃ ↑+SiBr _x O _y ↓+SiOF _x ↓...(1)

According to the reaction formula (1), SiF _x Br _y , SiF ₄ , and NH ₃ are volatile substances, and are exhausted to the outside of the chamber 10. However, SiBr _x O _y and SiOF _x are deposition materials and adhere to the pore side. Department and so on.

In the above program conditions, the temperature of the mounting table 20 was 65 °C. On the other hand, when the temperature of the mounting table 20 is controlled to a high temperature of 100 ° C, and the main etching → over etching is performed without changing other conditions in the above-described program conditions, the amount of deposits adhering to the side walls of the holes or the like is reduced, so that the holes are small. The etching proceeds, resulting in a broadening of the side of the hole, which does not result in a good etched shape.

[Erosion method according to the embodiment]

Therefore, in the etching method according to the present embodiment, in addition to the above-described program conditions, the temperature of the mounting table 20 is controlled to 100 ° C, and as shown in Fig. 3 (b), the flow rate of the gas is changed in the etching step. Specifically, the flow rate of the NF ₃ gas is controlled to be fixed, and the flow rates of the HBr gas and the O ₂ gas are changed.

In the etching method of the present embodiment, as shown in FIG. 2(b), the main etching of the polysilicon film 12 is roughly divided into the first to third steps, and the overetching of the underlying film 13 is performed. Four steps of 4 steps to control the flow of each gas. The gas flow rate control is performed by the control unit 100.

Specifically, in the first step of FIG. 3(b), the flow rates of the HBr gas, the NF ₃ gas, and the O ₂ gas are set to initial values. The HBr gas is mainly used to promote etching, and is a main etching gas. The NF ₃ gas is mainly used to remove the gas adhering to the deposit of the mask 11. The O ₂ gas is mainly used to protect the gas of the side wall of the mask 11 or the pores of the polysilicon film 12.

The deflection is likely to occur when the flow rate of the HBr gas is increased, and when the flow ratio of the HBr gas to the O ₂ gas is increased, it is likely to occur. Therefore, in order to suppress the deflection in the etching of the polysilicon film 12, it is necessary to reduce not only the flow rate of the HBr gas but also the flow ratio of the O ₂ gas to the HBr gas.

Specifically, as shown in FIG. 3(b), the flow rate of the HBr gas in the first and second steps is controlled to be larger than the flow rate of the HBr gas in the third and fourth steps. Thereby, the etching in the first and second steps can be promoted. Further, the flow rate of the HBr gas is controlled to be reduced stepwise in the second to fourth steps. Thereby, the etching can be controlled stepwise to suppress the deflection formed by the holes. The flow rate of the HBr gas in the first step and the second step may be the same, or may be a stepwise decrease and increase.

Further, the second step in O ₂ gas flow rate to control the flow rate of the _gas than the first step is to increase the O, O ₂ gas will be able to increase the flow rate of HBr gas ratio relative to polyethylene protective film 12 formed of silicon The wall of the hole.

Further, the third and fourth step the flow rate of O ₂ gas flow rate of O ₂ gas will be slightly less than the second step. Further, the third and fourth step of O ₂ gas flow rate in the second step may be the same as the flow rate of O ₂ gas, may decrease stepwise, also increase. Here, in the second to fourth steps, the flow rate of the HBr gas is gradually reduced. Thereby, the flow ratio of the O ₂ gas to the HBr gas in the second to fourth steps is increased stepwise. Thereby, the deflection can be suppressed more effectively.

As a result, in the present embodiment, the flow rate of the O ₂ gas is changed in accordance with the flow rate of the HBr gas. Specifically, in order to suppress the deflection, it is controlled so as to gradually increase the flow ratio of the O ₂ gas to the HBr gas. Further, in FIG. 3(b), the O ₂ gas is controlled to the same flow rate in the third and fourth steps, but is not limited thereto. For example, as shown in FIG. 3(c), the flow ratio of the O ₂ gas to the HBr gas is increased stepwise from the first step to the fourth step to suppress the occurrence of deflection and to suppress the deflection. Preferably, the etching step is performed by etching at least two steps, and more preferably three or more steps. The flow ratio control of the HBr gas and the O ₂ gas changes depending on the temperature of the stage 20 and the structure of the sample.

Further, the flow rate of the NF ₃ gas is as shown in Fig. 3 (b), and can be controlled to be fixed in all steps. Further, the present invention is not limited thereto, and may be controlled to be fixed in, for example, the first and second steps, and controlled to gradually increase in the third and fourth steps. Alternatively, it may be controlled to increase the flow rate of the O ₂ gas corresponding to an increase in the flow rate of the NF ₃ gas. Thereby, the deposition portion attached to the mask 11 can be removed, and the formation of the protective film for protecting the sidewall of the hole can be promoted. Further, SF ₆ (sulfur hexafluoride) gas may be supplied instead of the NF ₃ gas.

An example of the etching result according to this embodiment is shown in Fig. 4(b). As shown in Fig. 3 (a), the flow rate of each gas was controlled to be constant, and the result of the comparative example in which the temperature of the mounting table 20 was controlled at 100 ° C was compared with the case of Fig. 4 (a), and it was found that the deflection was suppressed. occur. In particular, in Fig. 4(b), even if the aspect ratio is 25, the occurrence of deflection can be prevented.

As described above, according to the etching method according to the present embodiment, the stage temperature can be controlled to a high temperature of, for example, 100 ° C, and the flow rate of the etching gas can be changed in the plurality of etching steps (first to fourth steps). That is, the HBr gas is gradually reduced in the gas supplied into the chamber 10. Further, in the etching method, as the etching progresses, the flow rate of the O ₂ gas is controlled so as to increase the flow ratio of the O ₂ gas to the HBr gas. Furthermore, the flow rate of the NF ₃ gas is controlled to be fixed in all steps or increases as the O ₂ gas flow rate increases. Thereby, the occurrence of distortion during etching (refer to FIG. 2(c)) and the occurrence of deflection (refer to FIG. 5(a)) can be suppressed, and the holes of the polysilicon film 12 can be etched as shown in FIG. 5(b). The shape is formed to be substantially vertical.

The flow of the etching method according to the present embodiment will be briefly described with reference to Fig. 6 . At the start of the process, the control unit 100 supplies CF ₄ gas and O ₂ gas into the chamber 10, and removes the natural oxide film of the mask 10 on the substrate by the plasma generated by the CF ₄ gas and the O ₂ gas ( Step S10).

Next, the control unit 100 supplies the HBr gas, the NF ₃ gas, and the O ₂ gas into the chamber 10, and etches the polysilicon film 12 by the plasma generated by the HBr gas, the NF ₃ gas, and the O ₂ gas (step S12). ). However, other gases such as an inert gas may be added to the HBr gas, the NF ₃ gas, and the O ₂ gas.

Next, the control unit 100 determines whether or not the first step of etching is completed (step S14). When the control unit 100 determines that the first step is completed, the flow rate of the HBr gas is gradually reduced in the second to fourth steps (step S16). Next, in the second to fourth steps, the flow rate of the O gas with respect to the HBr gas is stepwise increased (step S18), and the present process is terminated. Thereby, the etching shape of the hole formed by the polysilicon film 12 can be improved.

[Modification]

Next, an etching method according to a modification of the above embodiment will be described. In the present modification, in order to improve the distortion, the control region of the bias high-frequency power LF is optimized.

Specifically, for example, the upper limit value of the control region of the conventional bias high-frequency power LF is less than 1500 W. On the other hand, in the present modification, the control unit 100 controls the bias high-frequency power LF to be in a range of 4000 W to 10000 W higher than the conventional one. For example, Fig. 7 shows an example of an etching method and a twisted state according to a modification of the embodiment.

The program conditions used in the etching method of this modification are as follows.

‧ Pressure 30mT (4.00Pa) ~ 90mT (12.0Pa)

‧High frequency power HF 300~700W

‧High frequency power LF 3000W, 4500W, 7000W (pulse wave (frequency 0.1kHz, Duty ratio) 20%))

‧Gas HBr/NF ₃ /O ₂

‧ etching time 90 seconds

‧Loading table 20 temperature 65 ° C ~ 100 ° C

Further, the pulse wave frequency of the bias high frequency power LF may be in the range of 0.1 kHz to 50 kHz. Also, the Duty ratio can range from 5% to 30%.

Fig. 7 shows the results of applying a bias wave high frequency power LF pulse wave at respective powers of 3000 W, 4500 W, and 7000 W. The horizontal axis of Fig. 7 is the bottom CD. As shown in FIG. 8, the bottom CD is the diameter of the bottom of the hole formed by the polysilicon film 12. The intermediate value is 12% smaller than the large value shown in the horizontal axis of Fig. 7, and the small value (Small) is 25% smaller.

The vertical axis of Figure 7 is the twist value. The distortion value shows the difference in the distance between the bottom shape (occupied area) of the hole shown in the example of Fig. 8 and the distance between the holes by the deviation (3σ). In the example of Fig. 8, in the case where the bias high-frequency power LF is low (Low Power), the distortion value becomes higher as compared with the case where the bias high-frequency power LF is higher (High Power). .

As a result of FIG. 7, when a high-frequency power LF pulse wave of 3000 W is applied, the closer the bottom CD is to "Small", the worse the distortion value is. This is because the smaller the bottom CD is, the more the ions in the plasma move in the small holes, it will be difficult to reach the bottom of the hole as shown in (1) of Fig. 9(a), and will be twisted before reaching the bottom of the hole. Therefore.

On the other hand, when the high frequency power LF pulse wave of the bias voltage of 4500 W and 7000 W is applied, the distortion value is hard to deteriorate even if the bottom CD becomes "Small" as compared with the case where the high frequency power LF pulse wave of the bias voltage of 3000 W is applied. . That is, it is possible to improve the distortion of ions caused by bending near the bottom of the hole. This is because the LF value of the high-frequency power for biasing is increased, and as shown in FIG. 9(b), the ion energy is increased, and the straightness of the ions is improved, and the number of ions reaching the vicinity of the bottom of the hole can be increased.

In addition, the bias high-frequency power LF is a pulse wave, and an ON period in which the bias high-frequency power LF is applied and an OFF period in which the bias high-frequency power LF is not applied are repeatedly applied. Thereby, etching is promoted while the bias high-frequency power LF is ON, and the gas in the hole can be exhausted to the outside of the hole while the bias high-frequency power LF is OFF. Thereby, it is possible to prevent clogging of the mask in which the gap between the mask films 11 shown in (2) of FIG. 9(a) is narrowed by the reaction product at the time of etching. Further, it is possible to prevent the side of the hole shown in (3) of Fig. 9(a) from adhering to the reaction product and narrowing the inner portion of the hole. By this, the ion It is easy to reach the bottom of the hole more easily.

As described above, according to the etching method according to the present modification, by applying a pulse wave of the high-frequency power LF of a bias voltage of 4000 W or more, the ion energy in the plasma can be increased, and the ions can easily reach the bottom of the hole. Thereby, the distortion can be improved, the etching shape is good, and the etching of the holes can be promoted. As a result, a good etching can be applied to the holes or grooves having a aspect ratio of 20 to 25, preferably 25 or more.

Further, as shown in FIG. 3(b), the etching method according to the present modification is performed by controlling the HBr gas, the NF ₃ gas, and the O ₂ gas in the above embodiment, and controlling the bias high frequency power LF. . Alternatively, as shown in Fig. 3 (a), the HBr gas, the NF ₃ gas, and the O ₂ gas of the above embodiment may be controlled to be fixed, and the bias high frequency power LF may be controlled.

Although the etching method and the etching apparatus have been described above by the above embodiments, the etching method and the etching apparatus according to the present invention are not limited to the above-described embodiments, and various modifications and improvements are possible within the scope of the invention. The matters described in the above embodiments can be combined in a range that does not contradict each other.

For example, the substrate temperature is preferably 100 ° C or higher, more preferably 100 ° C to 200 ° C. The substrate temperature may be the temperature of the mounting table 20 (surface temperature) or the temperature of the electrostatic chuck 106.

Further, an etching apparatus using the etching method according to the present invention is not limited to a capacitively coupled plasma (CCP) device, and other etching apparatuses can be applied. Other etching devices may be Inductively Coupled Plasma (ICP), plasma processing device using a slotted slot antenna, Hepwave Wave Plasma (HWP) device, and electron cyclotron resonance plasma. (ECR: Electron Cyclotron Resonance Plasma) device, etc.

Further, the substrate to be processed by the etching apparatus according to the present invention is not limited to a wafer, and may be, for example, a large substrate for a flat panel display, an EL element, or a substrate for a solar cell.

Claims (11)

An etching method for etching a tantalum film formed on a substrate by supplying a gas containing hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas, and oxygen (O ₂ ) gas to the chamber a plurality of steps of etching a ruthenium film by supplying a plasma generated by a gas; in the plurality of steps, a flow rate of the hydrogen bromide gas is gradually reduced; and a flow rate of the oxygen gas corresponds to the hydrogen bromide gas Reduce to adjust. The etching method according to claim 1, wherein the flow rate of the hydrogen bromide gas is stepwise reduced in two or more steps including the final step in the plurality of steps. The etching method of claim 1 or 2, which increases the flow rate of the oxygen stepwise. An etching method according to claim 1 or 2, which increases the flow ratio of oxygen to the hydrogen bromide gas stepwise. The etching method of claim 1 or 2, wherein the flow rate of the nitrogen trifluoride gas is fixed or increased; if the flow rate of the nitrogen trifluoride gas is increased, the flow rate of the oxygen is corresponding to The increase in the nitrogen trifluoride gas increases. An etching method according to claim 1 or 2, wherein the substrate temperature is adjusted to 100 ° C to 200 ° C. An etching apparatus having a control unit that etches a ruthenium film formed on a substrate, the control unit containing hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas, and oxygen (O) ₂ ) gas gas is supplied into the chamber, and the flow rate of the hydrogen bromide gas is stepwise reduced by a plurality of steps of etching the ruthenium film by the plasma generated by the gas; the flow rate of the oxygen corresponds to the bromination The reduction of hydrogen gas is adjusted. An etching method according to claim 1 or 2, wherein a pulse wave of the bias high-frequency power LF of 4000 W or more is applied in the plurality of steps. For example, in the etching method of claim 8, wherein the bias wave frequency of the high frequency power is 0.1 kHz to 50 kHz, and the duty ratio is 5% to 30%. An etching method for etching a tantalum film formed on a substrate by supplying a gas containing hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas, and oxygen (O ₂ ) gas to the chamber a plurality of steps of etching a ruthenium film by supplying a plasma generated by a gas; in the plurality of steps, a flow rate of the hydrogen bromide gas is gradually reduced, and a flow rate of the oxygen gas corresponds to the hydrogen bromide gas Reduce the pulse wave of the high frequency power LF by applying a bias voltage of 4000 W or more. An etching apparatus having a control unit that etches a ruthenium film formed on a substrate, the control unit having a hydrogen bromide (HBr) gas, a nitrogen trifluoride (NF ₃ ) gas, and oxygen (O) ₂ ) a gas gas is supplied into the chamber, and a plurality of steps of etching the tantalum film are performed by supplying plasma generated by the gas; in the plurality of steps, the flow rate of the hydrogen bromide gas is gradually reduced, and the flow rate of the oxygen gas is decreased. The pulse wave of the bias high-frequency power LF of 4000 W or more is applied in accordance with the decrease in the hydrogen bromide gas.