TWI467650B - Plasma etch methods and computer-readable memory media - Google Patents

Description

Plasma etching method and computer readable memory medium

The present invention relates to a plasma etching method for plasma etching an oxide film formed on a substrate through a mask layer, and a computer readable memory medium for memorizing a control program for performing the plasma etching method.

In the semiconductor device process, a photoresist pattern is formed on a semiconductor wafer of a substrate to be processed by a lithography imaging technique, and is etched as a mask.

In recent years, with the miniaturization of semiconductor devices, fine processing has been required for etching. Corresponding to the miniaturization, the film thickness of the photoresist used for the mask is thinned, and the photoresist used is also moved by the KrF photoresist (that is, the photoresist exposed by the laser light using the K rF gas as the light source) to An ArF photoresist having a pattern opening of about 0.13 μm or less (that is, a photoresist that is exposed by a shorter-wavelength laser light having an ArF gas as a light source) can be formed.

However, since the ArF photoresist has low etching resistance, surface roughness in the middle of etching in which the K rF photoresist hardly occurs is generated. Therefore, there is a problem that the vertical stripe is formed on the inner wall surface of the opening, and the opening portion is enlarged (the expansion of the CD), and the thickness of the photoresist film is thinned, resulting in a failure to form an etched via hole with a good etching selectivity. Happening.

To solve this problem, Patent Document 1 discloses a technique of forming an amorphous carbon film on an etched layer as a sacrificial hard mask, forming a patterned photoresist film thereon, and etching the amorphous film with a photoresist pattern as a mask. In the carbon film, at least the amorphous carbon film is used as an etching mask to etch the layer to be etched by a commonly used CF-based gas. The problem of etching selectivity and shape can be solved to some extent by this technique.

However, for example, in the capacity etching of a DRAM, a hole having an opening ratio of 80 nm and a depth of 2 μm is required to be formed in an oxide film, which requires 68 nm for the next generation and 58 nm for the next generation. In the section of the above-mentioned Patent Document 1, it is difficult for the through hole of such a size to have sufficient etching selectivity and to form a good shape such as bowing (shape abnormality). .

Patent Document 1: JP-A-2006-41486

The present invention has been made in view of the above conventional problems, and it is an object of the invention to provide a plasma etching method which can achieve both good etching selectivity and shape when etching an oxide film to form a fine via having a high aspect ratio.

Further, it is an object of the present invention to provide a computer readable memory medium having a program for performing the plasma etching method.

In order to solve the above problems, a plasma etching method according to a first aspect of the present invention provides a plasma etching method in which an oxide film formed on a substrate is plasma-etched through a hard mask using a plasma etching apparatus. The lower electrode is provided as a substrate mounting table in the vacuum evacuation processing container, and the upper electrode is formed opposite to the lower electrode, and a relatively high frequency high frequency power for generating plasma is applied to the upper electrode or the lower electrode. Applying a relatively low frequency high frequency power to the lower electrode, applying a DC voltage to the upper electrode, and plasma-treating the processing gas supplied into the processing container to perform plasma etching; In the processing container, a substrate in which an oxide film to be etched, a hard mask layer, and a patterned photoresist are sequentially placed in the processing container to be placed on the lower electrode, and the inside of the processing container is supplied C _x F _y (where x is an integer below 3, y is an integer less than 8), C ₄ F ₈ , rare gas, O 2 processing gas; A process of applying a high-frequency power to the lower electrode or a plasma of the processing gas; applying a high-frequency power for biasing to the lower electrode; and applying a DC voltage to the upper electrode.

According to a second aspect of the present invention, in a plasma etching method, a plasma etching apparatus is provided, wherein the plasma etching apparatus has a function of providing a lower electrode as a substrate mounting table in a processing chamber capable of evacuating inside, and a lower portion The electrode is formed to face the upper electrode, and the high-frequency electric power for generating plasma and bias is applied to the lower electrode, and a DC voltage is applied to the upper electrode to plasma the processing gas supplied into the processing container. In the plasma etching apparatus, the substrate is provided with a substrate in which an etching film, a hard mask layer, and a patterned photoresist are sequentially formed in the processing container, and is placed on the substrate. Engineering of the lower electrode; a process for supplying a processing gas containing C _x F _y (where x is an integer of 3 or less, y is an integer of 8 or less), C ₄ F ₈ , a rare gas, or O _{2 in} the processing container; The lower electrode applies a process of applying a bias voltage while generating a plasma of the processing gas as a plasma generating and high-frequency power for biasing, and applying a bias to the upper electrode. Project voltage.

In the first or second aspect, the hard mask layer is preferably an amorphous carbon film. The above C _x F _{y is} preferably C ₃ F ₈ or CF ₄ . Above using C _x F _y C ₃ F ₈ flow rate is better when the above-mentioned C ₄ F ₈ flow rate of the above. The absolute value of the above DC voltage is preferably 800 to 1200V. The above rare gas is preferably Ar or Xe.

The plasma etching method of the present invention is particularly effective when forming a via hole having a section opening of 70 to 90 nm and an aspect ratio of 1:15 to 1:25.

According to a third aspect of the present invention, a computer-readable memory medium is a memory control program, and the control program is controlled by a computer to control a plasma etching device, and the plasma etching device is internally vacuum-dischargeable. a lower electrode is provided in the gas processing container as a substrate mounting table, and an upper electrode is formed opposite to the lower electrode, and a relatively high frequency high frequency power for generating plasma is applied to the upper electrode or the lower electrode. Applying a relatively low-frequency high-frequency power for biasing the lower electrode or applying high-frequency power for plasma generation and biasing to the lower electrode, applying a DC voltage to the upper electrode, and supplying the same to the processing A plasma etching process is performed by plasma-treating a processing gas in the container; wherein the control program is executed, and the plasma etching method according to any one of claims 1 to 14 is performed to cause the computer to control the above Plasma etching device.

Specific embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is a schematic cross-sectional view showing an example of a plasma etching apparatus used in the practice of the present invention.

The plasma etching apparatus is configured as a capacity coupling type parallel plate plasma etching apparatus, and has, for example, a substantially cylindrical chamber (processing container) 10 made of aluminum surface-anodic-treated. The chamber (processing vessel) 10 is safely grounded.

At the bottom of the chamber 10, a cylindrical susceptor support 14 is disposed through an insulating plate 12 made of ceramic or the like. A susceptor 16 made of, for example, aluminum is placed above the susceptor support table 14. The susceptor 16 constitutes a lower electrode on which the semiconductor wafer W on which the substrate to be processed is placed.

An electrostatic chuck 18 is disposed on the top of the susceptor 16 to electrostatically attract and hold the semiconductor wafer W. The electrostatic chuck 18 has a structure in which the conductive film constituent electrode 20 is held by a pair of insulating layers or insulating sheets, and the electrode 20 is electrically connected to the DC power source 22. The semiconductor wafer W is adsorbed and held by the electrostatic chuck 18 by an electrostatic force such as a Coulomb force generated by a DC voltage of the DC power source 22.

A conductive magnetic collecting ring (correcting ring) 24 made of, for example, tantalum is provided around the electrostatic chuck (semiconductor wafer W) 18 on the upper surface of the susceptor 16 for correcting the uniformity of etching. A cylindrical inner wall member 26 made of, for example, quartz is provided on the side surface of the susceptor 16 and the susceptor support table 14.

A refrigerant chamber 28 is provided inside the susceptor support table 14, for example, on the circumference. In the refrigerant chamber 28, a cooling medium (not shown) provided outside is circulated to supply a specific temperature refrigerant such as cooling water through the pipes 30a and 30b, and the semiconductor wafer on the susceptor 16 can be controlled by the temperature of the refrigerant. W processing temperature.

Further, a heat transfer gas such as He gas from a heat transfer gas supply means (not shown) is supplied between the upper surface of the electrostatic chuck 18 and the back surface of the semiconductor wafer W via the gas supply pipe 32.

The upper electrode 34 is disposed in parallel with the susceptor 16 above the susceptor 16. The space between the upper electrode 34 and the lower electrode 16 becomes a plasma generating space. The upper electrode 34 is opposed to the semiconductor wafer W on the susceptor 16 of the lower electrode to form a surface in contact with the plasma, that is, the opposite surface.

The upper electrode 34 is supported by the insulating shielding member 42 on the upper portion of the chamber 10, and is configured to form an electrode plate 36 having a plurality of ejection holes 37 opposite to the opposing surface between the susceptor 16 and The electrode support 36 is detachably supported, and an electrode support 38 of a water-cooling structure composed of an electrically conductive material, for example, anodized aluminum is applied to the surface. The electrode plate 36 is preferably a low-resistance conductor or a semiconductor having less Joule heat, and as described later, it is preferably a ruthenium-containing substance from the viewpoint of resist reinforcement. From this point of view, the electrode plate 36 is preferably made of tantalum or SiC. A gas diffusion chamber 40 is provided inside the electrode support body 38, and the gas diffusion chamber 40 extends a plurality of gas flow holes 41 that communicate with the discharge holes 37 downward.

A gas introduction port 62 is formed in the electrode support body 38 for introducing a processing gas into the gas diffusion chamber 40, and a gas supply pipe 64 is connected to the gas introduction port 62. The gas supply pipe 64 is connected to the gas supply pipe 64. In the gas supply pipe 64, an MFC (mass flow controller) 68 and an on-off valve 70 are provided in order from the upstream side (the FFC can also be used instead of the MFC). The processing gas supply source 66 is a processing gas for etching, and contains a processing gas containing C _x F _y (where x is an integer of 3 or less, y is an integer of 8 or less), C ₄ F ₈ , a rare gas, and O ₂ . The gas supply pipe 64 to the gas diffusion chamber 40 are ejected into the plasma generation space in a jet shape through the gas circulation holes 41 and the discharge holes 37. That is, the upper electrode 34 functions as a jet head that supplies a process gas.

The first high frequency power source 48 is electrically connected to the upper electrode 34 via the matching unit 46 and the power supply rod 44. The first high-frequency power source 48 outputs a high-frequency power of a frequency of 10 MHz or more, for example, 60 MHz. The matching unit 46 is for integrating the internal (or output) impedance and the load impedance of the first high-frequency power source 48, and has a function of matching the output impedance of the first high-frequency power source 48 with the load impedance when plasma is generated in the chamber 10. . The output terminal of the matcher 46 is connected to the upper end of the power supply rod 44.

Further, the upper electrode 34 is electrically connected to the variable DC power source 50 in addition to the first high frequency power source 48. The variable DC power source 50 can also be a bipolar power source. Specifically, the variable DC power supply 50 is connected to the upper electrode 34 via the matching unit 46 and the power supply rod 44, and is powered by the ON/OFF switch 52. The polarity, current, voltage of the variable DC power supply timing generator 50 and ON/OFF of the ON/OFF switch 52 are controlled by the controller 51.

As shown in FIG. 2, the matching unit 46 has a first variable capacitor 54 branched from the power supply line 49 of the first high-frequency power source 48, and a second variable capacitor 56 provided on the downstream side of the branch point of the power supply line 49. By playing the above functions. The notch filter 58 is provided in the matching unit 46, so that a high frequency (for example, 60 MHz) from the first high-frequency power source 48 and a high frequency (for example, 2 MHz) from a second high-frequency power source to be described later are trapped, and DC is applied. A voltage current (hereinafter simply referred to as a direct current voltage) is effectively supplied to the upper electrode 34. That is, the direct current from the variable DC power source 50 is connected to the power supply line 49 via the filter 58. The filter 58 is composed of a coil 59 and a capacitor 60, and the high frequency from the first high-frequency power source 48 and the high-frequency power source from the second high-frequency power source described later are trapped.

The cylindrical ground conductor 10a is provided so as to extend from the side wall of the chamber 10 to a position higher than the height of the upper electrode 34, and the wall portion of the cylindrical ground conductor 10a is upper by the cylindrical insulating member 44a. Power supply rod 44.

The second high frequency power supply 90 is electrically connected to the susceptor 16 of the lower electrode via a matching unit 88. The second high-frequency power source 90 supplies high-frequency power to the susceptor 16 of the lower electrode to introduce ions into the semiconductor wafer W side. The second high-frequency power supply 90 outputs a high-frequency power of a frequency in the range of 300 kHz to 13.56 MHz, for example, 2 MHz. The matching unit 88 is for integrating the internal (or output) impedance and the load impedance of the second high-frequency power source 90, and has a function of matching the output impedance of the second high-frequency power source 90 with the load impedance when plasma is generated in the chamber 10. . The output terminal of the matcher 46 is connected to the upper end of the power supply rod 44.

Further, the upper electrode 34 is electrically connected to the low pass filter (LPF) 92, and the high frequency from the second high frequency power supply 90 can be made without passing through the high frequency (for example, 60 MHz) from the first high frequency power supply 48. (eg 2MHz) to ground. The low pass filter (LPF) 92 is preferably composed of an LR filter or an LC filter, but can provide a sufficiently large reactance to a high frequency (for example, 60 MHz) from the first high frequency power supply 48 by only one wire. Therefore, it can also be used. Further, the high-pass filter (HPF) 94 is electrically connected to the susceptor 16 of the lower electrode, so that the high frequency from the first high-frequency power source 48 can be grounded.

An exhaust port 80 is provided at the bottom of the chamber 10, and the exhaust port 84 is connected to the exhaust device 84 via the exhaust pipe 82. The venting device 84 has a vacuum pump such as a vortex molecular pump, and can depressurize the inside of the chamber 10 to a desired degree of vacuum. Further, a carry-out port 85 of the semiconductor wafer W is provided on the side wall of the chamber 10, and the carry-out port 85 can be opened/closed by the gate valve 86. Moreover, the deposit preventing member 11 is detachably provided along the inner wall of the chamber 10, and the etching by-product (deposit) can be prevented from adhering to the chamber 10. That is, the deposit preventing member 11 constitutes a chamber wall. Further, the deposit preventing member 11 is also provided on the outer circumference of the inner wall member 26. An exhaust plate 83 is provided between the deposit preventing member 11 on the chamber wall side of the bottom of the chamber 10 and the deposit preventing member 11 on the inner wall member 26 side. The deposit preventing member 11 and the exhaust plate 83 can be used for a ceramic member in which an aluminum member covers Y ₂ O ₃ or the like.

The portion of the wafer W constituting the inner wall of the chamber of the deposit preventing member 11 is disposed at substantially the same height, and is electrically connected to the grounded conductive member (GND block) 91 in a DC manner, thereby preventing abnormal discharge. effect.

Each component of the plasma processing apparatus is controlled by being connected to a control unit (all control unit) 95. The control unit 95 is connected to a user interface 96 including a keyboard that the engineering manager manages the plasma etching apparatus to input the command, and a display that visually displays the state of the plasma etching apparatus.

The control unit 95 is connected to the storage unit 97 for storing a control program, which can be implemented under the control of the control unit 95, or a program (recipe), which can be made according to processing conditions. Each component of the plasma processing apparatus performs processing. The program may be stored in a hard disk or a semiconductor memory, or may be set to a specific position of the memory unit 97 in a state of being stored in a portable medium readable by a portable computer such as a CDROM or a DVD.

If necessary, the memory unit 97 may call any program to be executed by the control unit 95 in accordance with the instruction of the user interface 96, and the processing of the plasma processing apparatus may be performed under the control of the control unit 95.

Hereinafter, a plasma etching method according to an embodiment of the embodiment of the plasma etching apparatus configured as described above will be described.

In the semiconductor wafer W as the object to be processed, the resist film 102, the oxide film 103 to be etched, the hard mask layer 104, and the anti-reflection film (BARC) are sequentially formed on the ruthenium substrate 101 as shown in FIG. After the photoresist film 106 is formed, a specific pattern is formed on the photoresist film 106. First, the hard mask layer 104 is etched by using the photoresist film 106 as a mask, and then the etching of the oxide film 103 to be etched is performed.

As the oxide film 103 to be etched in the present embodiment, for example, a film formed of TEOS or a glass film (BPSG or PSG) can be used. The thickness of the oxide film 103 can be appropriately set, and is about 1.5 to 3.0 μm when used as a capacitor for a DRAM.

As the hard mask layer 104, an amorphous carbon film can be used. The amorphous carbon film is equivalent to SiN or SiC which is generally used as a hard mask layer, and is inexpensive, and is inexpensive. It is also possible to use a material such as TiN or SiN which is usually used. The thickness of the hard mask layer 104 is about 500 to 900 nm.

The resist film 102 is made of a SiC-based material such as SiCN, and has a thickness of about 20 to 100 nm. The antireflection film 105 may be made of SiON or organic, and has a thickness of about 20 to 100 nm. The photoresist film 106, typically an ArF resist, has a thickness of about 100 to 400 nm.

At the time of the etching process, first, the gate valve 86 is set to be in an open state, and the wafer W having the above-described structure is carried into the chamber 10 via the carry-out port 85, and placed on the susceptor 16. Thereafter, the processing gas supply source 66 supplies the etching processing gas to the gas diffusion chamber 40 at a specific flow rate, and is supplied into the chamber 10 through the gas circulation hole 41 and the discharge hole 37, and the chamber is exhausted by the exhaust device 84. The exhaust gas in the chamber 10 is set to a set value in the range of, for example, 20 to 30 Pa. The temperature of the susceptor 16 is set to be about 20 to 50 °C.

The processing gas for etching the oxide film 103 is a processing gas containing C _x F _y (where x is an integer of 3 or less, y is an integer of 8 or less), C ₄ F ₈ , a rare gas, or O ₂ , and may contain Other gases are preferably composed of only four types of C _x F _y , C ₄ F ₈ , rare gases, and O ₂ . C ₄ F ₈ functions to make the shape of the mask vertical, and is an important gas for obtaining a good etching shape. However, when only C ₄ F ₈ is supplied at a flow rate at which a sufficient etching rate can be obtained, deposits are generated at the intervals, and subsequent etching causes a shape defect such as bowing degree. Here, the use of C _x F _y , wherein x is an integer of 3 or less, and y is an integer of 8 or less, which is less than C ₄ F ₈ and equivalent to 1 molecule of C, can reduce such deposits. In order to effectively reduce the deposit of the opening, it is preferred to additionally raise the temperature of the susceptor 16 of the lower electrode to about 50 °C.

C ₃ F ₈ or CF ₄ can be used for C _x F _y . Of these, C ₃ F ₈ is preferred. C ₃ F ₈ has the effect of increasing the etch rate. When C ₃ F ₈ is used, the flow rate is preferably more than the flow rate of C ₄ F ₈ . In this way, the deposit of the opening can be effectively eliminated. More preferably, the flow rate of C ₃ F ₈ : the flow rate of C ₄ F ₈ is about 1:1 to 1.5:1. The specific flow rate is preferably a flow rate of C ₃ F ₈ of 20 to 60 mL/min (converted to a standard flow rate (sccm)), and a flow rate of C ₄ F ₈ of 20 to 40 mL/min (sccm).

The addition of O ₂ gas is to ensure the hole penetration of the etched through hole, to obtain a wide bottom CD (Critical Dimention) of the etched through hole, and to add the balance of the processing gas, preferably by using a flow rate ratio as the processing gas. 2.5~3.5% of the total is added. The specific flow rate is preferably 20 to 30 mL/min (sccm).

The rare gas is to ensure the penetration of the through hole, and to dilute the CF system gas to obtain the balance of the processing gas, and to control the deposit or F to be added, preferably the flow ratio is 85 to 90% of the total processing gas. . The specific flow rate is preferably 600 to 900 mL/min (sccm). However, the flow rate of the rare gas varies depending on the material of the hard mask layer 104, and when the hard mask layer 104 is an amorphous carbon film, it is preferably 800 mL/min or more. When a Poly Mask (polysilicon mask) material is used, it is preferably set to 300 mL/min (sccm) or less.

The rare gas can use Ar and Xe, especially the Xe used by the rare gas, which can enhance the function as the carrier of C, can improve the linearity of the straight signal of the etching, and can form the etching shape and oxide film of the good hard mask layer 104. 103 etching shape.

In the etching of the hard mask layer 104 before the oxide film 103 is performed, etching is performed under normal conditions. For example, when the hard mask layer 104 is an amorphous carbon film, it may be an example of C ₄ F ₆ + rare gas (Ar) + O ₂ .

As described above, in the state where the etching processing gas is introduced into the chamber 10, the high-frequency power for generating plasma of a specific power is applied to the upper electrode 34 by the first high-frequency power source 48, and the second high-frequency power source 90 is provided. The ion of a specific power is introduced into the susceptor 16 of the lower electrode with a high frequency. Thereafter, a specific DC voltage is applied to the upper electrode 34 by the variable DC power source 50. Further, a DC voltage is applied from the DC power source 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 ejected from the gas ejection hole 37 formed on the electrode plate 36 of the upper electrode 34 is plasma-charged in a coulomb discharge between the upper electrode 34 and the lower electrode receiver 16 by high-frequency power generation. The radical or ion generated by the plasma, first, as shown in FIG. 4(a), the hard mask layer 104 is etched by using the photoresist film 106 as a mask, and the resist pattern is transferred, and then, as shown in FIG. As shown in FIG. 4(b), the oxide film 103 is etched by the hard mask layer 104 as a mask to form the via hole 107.

When the upper electrode 34 is supplied with high-frequency power in a high-frequency band (for example, 10 MHz or more), the plasma can be made into a high-density state in a good state, and a high-density plasma can be formed under a lower-pressure condition.

However, when only the high-frequency power is applied and the oxide film is etched using the processing gas, the shape of the etching can be ensured, but the etching selectivity of the hard mask layer 104 is low, as shown in FIG. 5, the etching of the oxide film 103 is performed. The hard mask layer 104 will disappear before the end.

Therefore, in the present embodiment, when the plasma is formed as described above, the variable DC power supply 50 applies a DC voltage of a specific polarity and magnitude to the upper electrode 34. By adjusting the DC voltage applied at this time, it is possible to set the etching selectivity ratio to the hard mask layer 104 to be in a good state. As shown in FIG. 6, the oxide film 103 can be etched in a good shape in the remaining state of the hard mask layer 104. At this time, the DC voltage is preferably 800 to 1200V.

More specific description below.

The upper electrode 34 is adhered to the polymer by a conventional etching process, particularly an etching process in which the high frequency power of the upper electrode 34 is small. When an etching process is performed, an appropriate DC voltage is applied to the upper electrode 34, and as shown in FIG. 7, the self-bias voltage Vdc of the upper electrode 34 can be deepened, and the absolute value of Vdc on the surface of the upper electrode 34 can be increased. Therefore, the polymer attached to the upper electrode 34 is supplied to the semiconductor wafer W by DC voltage sputtering applied thereto and adhered to the hard mask layer 104. As a result, the hard mask layer 104 is difficult to be etched, and the etching of the oxide film 103 can be performed at a high selectivity.

When the etching of the oxide film 103 is performed, as described above, when a DC voltage is applied to the upper electrode 34, electrons generated in the vicinity of the upper electrode 34 during plasma formation are accelerated in the vertical direction of the processing space, and are appropriately controlled at this time. The DC voltage or the like allows the electrons to reach the inside of the via, suppressing the shading effect, and making the shape of the via hole good.

Further, when a plasma is formed, when a DC voltage is applied to the upper electrode 34, the plasma density of the center portion for plasma diffusion can be increased, but the pressure in the chamber 10 is high, and the negative polarity of the CF-based gas is used. When the gas is used as the processing gas, the plasma density at the central portion in the chamber 10 tends to be low, and by applying a direct current voltage, a uniform plasma density can be obtained by raising the plasma density of the central portion.

Moreover, the condition of richer deposits is selected by the application of a DC voltage, and the etching selectivity can be ensured only by the photoresist film without using a hard mask layer. However, in this case, deposits may adhere to the section opening to form a bow shape. Poor degree or thinning of the front end. Therefore, a hard mask layer 104 must be used.

The experimental results of actually confirming the effects of the plasma etching method of the present invention will be described below.

(Experiment 1)

An SiN film having a thickness of 50 nm is formed on the germanium substrate as the resist film 102, and a two-layer film of a BPSG film (lower layer) having a thickness of 1500 nm and a TEOS film (upper layer) is formed thereon as an oxide film 103 to be etched. An amorphous carbon film having a thickness of 500 nm was formed as the hard mask layer 104, and a SiON film having a thickness of 60 nm was formed thereon as an anti-reflection film (BARC) 105, and an ArF resist having a thickness of 200 nm was formed thereon as a photoresist film 106. A sample having the structure of FIG. 3 is fabricated, and after the hard mask layer 104 is etched by the device as shown in FIG. 1, the remaining portion of the photoresist film 106 and the hard mask layer 104 are used as an etch mask, under various conditions. Etching of the oxide film 103 of the etching target. Here, etching of a circular via having a hole diameter of 90 nm was performed. When the oxide is etched, the chamber pressure is set to 2.7 Pa, the upper high frequency power is 1200 W, the lower high frequency power is 3800 W, the DC voltage is -1000 V, the temperature is the upper electrode: 95 ° C, the lower electrode: 10 ° C, the processing gas Etching is performed using C ₃ F ₈ , C ₄ F ₈ , Ar, O ₂ , and varying the flow rates thereof.

First, the flow rate of the fixed Ar was 800 mL/min (sccm), the flow rate of O ₂ was 250 mL/min (sccm), and etching was performed by changing C ₄ F ₈ /C ₃ F ₈ . The etching shape at this time is as shown in Fig. 8, and is set to C ₄ F ₈ : 35 mL/min (sccm) and C ₃ F ₈ : 30 mL/min (sccm) as shown in Fig. 8B, and is set to C as shown in Fig. 8B. ₄ F ₈ : 30 mL/min (sccm) and C ₃ F ₈ : 35 mL/min (sccm), as shown in Fig. 8C, C ₄ F ₈ : 25 mL/min (sccm) and C ₃ F ₈ : 40 mL/min (sccm), as shown in Fig. 8D, was set to C ₄ F ₈ : 20 mL/min (sccm) and C ₃ F ₈ : 45 mL/min (sccm). As shown in the figure, C is the shape of the shoulder portion of the opening which is the best.

Thereafter, C ₄ F ₈ /C ₃ F _{8 was} fixed to the composition of C described above, and the flow rates of Ar and O _{2 were} changed, and other conditions were etched in the same manner as in the above experiment. The etching shape at this time is as shown in Fig. 9, and is set to Ar: 500 mL/min (sccm) and O ₂ : 34 mL/min (sccm) as shown in Fig. 9E, and is set to Ar: 700 mL/min as shown in Fig. 9F ( Sccm) and O ₂ : 32 mL/min (sccm), as shown in Fig. 9G, Ar: 900 mL/min (sccm) and O ₂ : 30 mL/min (sccm), and Fig. 9H is set to Ar: 1100 mL/ Min (sccm) and O ₂ : 28 mL/min (sccm). Among them, G is an improvement in the shoulder portion of the opening, and the shape is the best. In addition, the process change is performed by changing the gas ratio to a larger number of centers. As a result, a good shape in which no bowing degree is generated as shown in FIG. 10 is obtained. At this time, the top CD, the CD in the middle of the bowlessness, and the bottom CD are 89 nm, 89 nm, and 74 nm in the center of the semiconductor wafer, respectively. 91 nm, 93 nm, and 75 nm, and the edges are good values of 85 nm, 87 nm, and 73 nm, respectively.

From the above, it was confirmed that the shape of etching under a specific condition in which C ₃ F _{8 is} large and Ar is large is good.

(Experiment 2)

A sample having the same structure as that of Experiment 1 was fabricated, and after the hard mask layer 104 was etched by the apparatus shown in FIG. 1, the remaining portion of the photoresist film 106 and the hard mask layer 104 were used as an etch mask to perform the oxide film 103. Etching. Here, the set pressure is 2.7 Pa, the temperature is the upper electrode: 95 ° C, and the lower electrode: 10 ° C is fixed. The condition I is set: the upper high frequency power is 1200 W, the lower high frequency power is 3800 W, and the direct current voltage is -1000 V. , C ₄ F ₈ : 40 mL/min (sccm), C ₃ F ₈ : 25 mL/min (sccm), Ar: 900 mL/min (sccm), O ₂ : 30 mL/min (sccm), set under Condition J: Upper The high frequency power is 1200W, the lower high frequency power is 3800W, the DC voltage is -1000V, C ₄ F ₈ :25mL/min (sccm), C ₃ F ₈ :40mL/min (sccm), Ar: 1000mL/min (sccm ), O ₂ : 28mL/min (sccm), set under condition K: upper high frequency power is 1500W, lower high frequency power is 4500W, DC voltage is -1100V, C ₄ F ₈ : 25mL/min (sccm), C ₃ F ₈ : 40 mL/min (sccm), Ar: 1000 mL/min (sccm), O ₂ : 25 mL/min (sccm), and etching was performed. The results are shown in Figure 11, as shown in the condition I → J conditions, with respect to the C ₄ F _8, C ₃ F ₈ with the amount of more shape becomes good condition as the condition J → K shown by increased The upper high-frequency power and the lower high-frequency power increase the DC voltage and reduce O ₂ , so that the CD shrinks more and a better etching shape can be obtained.

(Experiment 3)

A SiN film having a thickness of 40 nm is formed as a resist film 102 on the germanium substrate 101, and a PSG film having a thickness of 2.0 μm is formed thereon as an oxide film 103 to be etched, and an amorphous carbon film having a thickness of 400 nm is formed thereon as a hard mask. The cap layer 104 is formed with a SiON film having a thickness of 60 nm as an anti-reflection film (BARC) 105, and an ArF resist having a thickness of 200 nm is formed thereon as a photoresist film 106, and a sample having the structure of FIG. 3 is produced by, for example, After the hard mask layer 104 is etched by the device shown in FIG. 1, the remaining portion of the photoresist film 106 and the hard mask layer 104 are used as etching masks, and the etching of the oxide film 103 to be etched is performed under various conditions. Here, etching of an elliptical shape having a long diameter of 160 nm and a short diameter of 80 nm and a via having an aspect ratio of 25 was performed. When the oxide is etched, the chamber pressure is set to 3.3 Pa, the upper high frequency power is 1000 W, the lower high frequency power is 4500 W, the DC voltage is -500 V, the temperature is the upper electrode: 95 ° C, the lower electrode: 50 ° C, the processing gas The flow rate of C ₃ F ₈ , C ₄ F ₈ , Xe, O ₂ , and Xe was fixed to 400 mL/min (sccm), and the others were changed. Set under condition L: C ₄ F ₈ : 20 mL/min (sccm), C ₃ F ₈ : 20 mL/min (sccm), O ₂ : 12.5 mL/min (sccm) (C ₃ F ₈ /C ₄ F ₈ = 1), set under condition M: C ₄ F ₈ : 10 mL/min (sccm), C ₃ F ₈ : 30 mL/min (sccm), O ₂ : 10 mL/min (sccm) (C ₃ F ₈ /C ₄ F ₈ = 3), set under condition N: C ₄ F ₈ : 6.7 mL/min (sccm), C ₃ F ₈ : 33.3 mL/min (sccm), O ₂ : 7.5 mL/min (sccm) (C ₃ F ₈ / C ₄ F ₈ = 5), and etching is performed. The result is shown in Fig. 12. As C ₃ F ₈ / C ₄ F ₈ is shown by 1 to 3, the bowing degree at the edge side is remarkably improved, and the bowing degree at the edge side when C ₃ F ₈ / C ₄ F ₈ = 5 It almost disappeared, but the spread of the mouth of the center became a significant tendency. Further, it can be confirmed that the etching selectivity ratio is lowered by increasing the ratio of C ₃ F ₈ . As explained above, as the ratio of C ₃ F ₈ rises, there is a change in bowing degree → no bow angle → interval mouth diffusion. Considering the shape difference between the center and the edge and the selection ratio, it can be confirmed that C ₃ F ₈ /C ₄ F ₈ =3 is the most appropriate value. However, the C ₃ F ₈ /C ₄ F ₈ ratio which is improved in bowing degree differs depending on the thickness of the hard mask layer, the hardness, the hardness of the oxide film, and the short axis/long axis ratio of the through holes.

(Experiment 4)

Here, the etching uniformity caused by DC application was confirmed.

A SiN film having a thickness of 60 nm is formed as a resist film 102 on the germanium substrate 101, and a BPSG film having a thickness of 2000 nm is formed thereon as an oxide film 103 to be etched, and a SiON film having a thickness of 60 nm is formed thereon as an anti-reflection film (BARC). 105, further forming an ArF resist having a thickness of 650 nm as the photoresist film 106, and preparing a sample having a structure in which the hard mask layer 104 is removed from FIG. 3, and using the photoresist film 106 as a device as shown in FIG. The mask is etched, and etching of the oxide film 103 to be etched is performed under various conditions. The treatment gas used C ₄ F ₆ , CF ₄ , Ar, O ₂ , setting: C ₄ F ₆ : 40 mL/min (sccm), CF ₄ : 60 mL/min (sccm), Ar: 350 mL/min (sccm), O ₂ : 45 mL/min (sccm), the set pressure was 2.67 Pa (20 mTorr), the upper high frequency power and the direct current voltage were changed, and the etching rate and the selection ratio were calculated. As a result, as shown in FIG. 13, it can be seen from the figure that the through-hole etching rate of the center rises when the DC voltage is raised, and the via etching rate of the edge increases when the upper high-frequency power is raised. From this, it was confirmed that the in-plane etching rate can be controlled by the direct current voltage applied to the upper electrode or the upper high frequency power. In addition, the reversal of the center/edge etch rate is also easy.

Further, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, an amorphous carbon film is used as the hard mask layer, but other conventionally used hard mask materials may be used. Further, the oxide film is described by using TEOS as a raw material or BPSG or PSG as an example, but is not limited thereto.

Further, the device to which the present invention is applied is not limited to those shown in Fig. 1, and the following various types can be used. For example, the upper electrode 2 can be used to divide the center and the periphery to adjust the form of the high-frequency applied power. Further, as shown in FIG. 14, the receiver 16 of the lower electrode is applied with a high-frequency power of, for example, 40 MHz for plasma generation by the first high-frequency power source 48', and ion introduction is applied by the second high-frequency power source 90'. For example, a plasma etching apparatus of a lower 2 frequency application type of high frequency power of 2 MHz may be applied. As shown in the figure, a specific DC voltage is applied to the upper electrode 234 via the variable DC power supply 166, and the same effects as in the above embodiment can be obtained.

Further, as shown in FIG. 15, instead of the first high-frequency power source 48' and the second high-frequency power source 90' connected to the susceptor 16 of the lower electrode in FIG. 14, the high-frequency power source 170 is connected, and the high-frequency power source is connected. A plasma etching apparatus in which a high-frequency power of, for example, 40 MHz for plasma generation and bias formation is applied is also applied. Also in this case, similarly to Fig. 4, by applying a specific DC voltage to the upper DC electrode 234 via the variable DC power supply 166, the same effects as in the above embodiment can be obtained.

(effect of the invention)

According to the present invention, a substrate having an oxide film, a hard mask layer, and a patterned photoresist which are sequentially formed is used, and C _x F _y (where x is an integer of 3 or less, and y is an integer of 8 or less) is used. The processing gas of C ₄ F ₈ , rare gas and O ₂ is plasma-etched. Therefore, even a narrow-port, high aspect ratio through-hole can have a practical etching rate and no bowing. Etching is performed with good shape. Moreover, in such a gas system, a sufficient etching selectivity cannot be obtained in a usual process, and the mask layer may disappear before the end of etching. However, in the present invention, a high frequency for plasma generation is applied to either the upper electrode or the lower electrode. When electricity is generated and plasma is generated, a DC voltage is applied to the upper electrode. Therefore, the polymer can be supplied to the hard mask layer by the upper electrode, so that the resistance of the hard mask layer is increased, and the etching selectivity can be improved even in the above gas. The hard mask layer will not disappear and good etching can be performed.

10. . . Chamber (processing vessel)

16. . . Lower electrode receiver

34. . . Upper electrode

44. . . Power supply rod

46, 88. . . Matcher

48. . . First high frequency power supply

50. . . Variable DC power supply

51. . . Controller

52. . . ON/OFF switch

66. . . Process gas supply

84. . . Exhaust

90. . . Second high frequency power supply

91. . . GND block

101. . .矽 substrate

102. . . Corrosion film

103. . . Oxide film

104. . . Hard mask layer

105. . . Anti-reflective film (BARC)

106. . . Photoresist film

W. . . Semiconductor wafer (processed substrate)

Fig. 1 is a schematic cross-sectional view showing an example of a plasma etching apparatus used in the practice of the present invention.

Fig. 2 is a structural view showing a matching device connected to a first high-frequency power source in the plasma etching apparatus of Fig. 1;

Fig. 3 is a cross-sectional view showing the structure of a semiconductor wafer W used in an embodiment of the present invention.

Fig. 4 is a schematic view showing a state in which the structure of Fig. 3 is etched.

Fig. 5 is a schematic view showing a state in which the hard mask layer disappears in the middle of etching of the oxide film.

Fig. 6 is a schematic view showing a state in which an oxide film is etched by this embodiment.

Fig. 7 is a view showing the comparison of the state of the plasma when the upper electrode is applied and the DC voltage is not applied to the plasma processing apparatus of Fig. 1.

Figure 8 shows the results of Experiment 1.

Figure 9 shows the results of Experiment 1.

Figure 10 shows the results of Experiment 1.

Figure 11 shows the results of Experiment 2.

Figure 12 shows the results of Experiment 3.

Figure 13 shows the results of Experiment 4.

Fig. 14 is a schematic view showing an example of a plasma etching apparatus according to another embodiment of the present invention.

Fig. 15 is a schematic view showing an example of a plasma etching apparatus according to another embodiment of the present invention.

10. . . Chamber (processing vessel)

10a. . . Cylindrical ground conductor

11. . . Sediment prevention member

12. . . Insulation board

14. . . Receptor support

16. . . Lower electrode receiver

18. . . Electrostatic chuck

20. . . electrode

twenty two. . . DC power supply

twenty four. . . Polymagnetic ring

26. . . Inner wall member

28. . . Refrigerant room

30a: 30b. . . Piping

32. . . Gas supply pipe

34. . . Upper electrode

36. . . Electrode plate

37. . . Spout hole

38. . . Electrode support

40. . . Gas diffusion chamber

41. . . Gas circulation hole

42. . . Insulating shielding member

44. . . Power supply rod

46, 88. . . Matcher

48. . . First high frequency power supply

50. . . Variable DC power supply

51. . . Controller

52. . . ON/OFF switch

62. . . Gas inlet

64. . . Gas supply pipe

66. . . Process gas supply

70. . . Switch valve

80. . . exhaust vent

82. . . exhaust pipe

83. . . Exhaust plate

84. . . Exhaust

86. . . Gate valve

90. . . Second high frequency power supply

91. . . GND block

92. . . Low pass filter

94. . . High pass filter

95. . . Control department

96. . . user interface

97. . . Memory department

Claims (15)

A plasma etching method is a plasma etching method in which an oxide film formed on a substrate is plasma-etched through a hard mask layer, and the plasma etching device is provided with a lower portion in a processing chamber capable of vacuum evacuation inside. The electrode functions as a substrate mounting table, and an upper electrode is formed opposite to the lower electrode, and a relatively high frequency high frequency power for generating plasma is applied to the upper electrode or the lower electrode, and a bias voltage is applied to the lower electrode. The low-frequency high-frequency power is applied to the upper electrode to apply a DC voltage, and the processing gas supplied to the processing container is plasma-plasmaized and plasma-etched; and the present invention is characterized in that the processing is carried out in the processing container. a substrate on which an oxide film to be etched, a hard mask layer, and a patterned photoresist are formed to be placed on the lower electrode; and the inside of the processing container is supplied with C _x F _y (where x is 3 or less) An integer, y is an integer of 8 or less), a process of treating a gas of C ₄ F ₈ , a rare gas, or O ₂ ; applying high frequency power to the upper electrode or the lower electrode And a process of generating a plasma of the processing gas; applying a high-frequency power for biasing to the lower electrode; applying a DC voltage to the upper electrode; and applying the hard mask layer to the mask to the oxide film In the plasma etching process, the plasma etching of the oxide film is carried out using the plasma generated as described above, and the ratio of CxF _y / C ₄ F ₈ is in the range of 1 to 3. A plasma etching method is a plasma etching apparatus which is provided with a lower electrode as a substrate mounting table in a processing chamber capable of vacuum evacuation inside, and is formed in a direction opposite to the lower electrode. The upper electrode applies high-frequency power for plasma generation and biasing to the lower electrode, applies a DC voltage to the upper electrode, and plasma-treats the processing gas supplied into the processing container to perform plasma etching. The feature is that a substrate in which an oxide film, a hard mask layer, and a patterned photoresist are sequentially formed in the processing container is placed in the processing container, and the substrate is placed on the lower electrode; The processing container is supplied with a process gas containing C _x F _y (where x is an integer of 3 or less, y is an integer of 8 or less), C ₄ F ₈ , a rare gas, and O ₂ , and is applied to the lower electrode. The plasma generates a work for applying a bias voltage while generating a plasma of the processing gas with a high-frequency power for biasing; a process of applying a DC voltage to the upper electrode, and The mask is formed by plasma etching the oxide film using the hard mask layer, and the plasma etching of the oxide film is performed by using the plasma generated as described above, CxF _y / C ₄ F ₈ The ratio is in the range of 1 to 3. Such as the plasma etching method of claim 1 of the patent scope, wherein The hard mask layer is an amorphous carbon film. The plasma etching method of claim 2, wherein the hard mask layer is an amorphous carbon film. The plasma etching method of claim 1, wherein the C _x F _y is C ₃ F ₈ or CF ₄ . The plasma etching method of claim 2, wherein the C _x F _y is C ₃ F ₈ or CF ₄ . The plasma etching method according to claim 1, wherein the C _x F _y is C ₃ F ₈ and the flow rate is equal to or higher than the flow rate of the C ₄ F ₈ . The plasma etching method according to claim 2, wherein the C _x F _y is C ₃ F ₈ and the flow rate is equal to or higher than the flow rate of the C ₄ F ₈ . The plasma etching method of claim 1, wherein the absolute value of the DC voltage is 800 to 1200V. The plasma etching method of claim 2, wherein the absolute value of the DC voltage is 800 to 1200V. The plasma etching method of claim 1, wherein the rare gas is Ar or Xe. The plasma etching method of claim 2, wherein the rare gas is Ar or Xe. The plasma etching method according to claim 1, wherein the through-hole having a section opening of 70 to 90 nm and an aspect ratio of 1:15 to 1:25 is formed by the plasma etching. The plasma etching method of claim 2, wherein the plasma is etched to form a section of 70 to 90 nm in depth and width. The ratio is 1:15~1:25 through hole. A computer readable memory medium is a memory control program. The control program is controlled by a computer to control a plasma etching device. The plasma etching device is disposed in a processing chamber capable of vacuum evacuation inside. The lower electrode functions as a substrate mounting table, and forms an upper electrode opposite to the lower electrode, and applies high-frequency high-frequency power for plasma generation to the upper electrode or the lower electrode, and applies a bias to the lower electrode. a high-frequency electric power of a relatively low frequency for pressing or a high-frequency electric power for generating a plasma and a bias voltage is applied to the lower electrode, and a DC voltage is applied to the upper electrode to electrically supply the processing gas supplied into the processing container. The slurry is etched and subjected to plasma etching; and the control program is executed to cause the plasma etching method of any one of claims 1 to 14 to be performed to cause the computer to control the plasma etching apparatus.