JP2016213427A - Etching method and etching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a good etching shape.SOLUTION: An etching method for etching a silicon film formed on a substrate comprises the steps of: supplying a gas including a hydrogen bromide (HBr) gas, a nitrogen trifluoride (NF) gas and an oxygen (O) gas into a chamber; and etching the silicon film by plasma produced from the supplied gas. In the steps, the flow rate of the hydrogen bromide gas is decreased stepwise, and the flow rate of the oxygen gas is regulated according to the decrease in the hydrogen bromide gas.SELECTED DRAWING: Figure 3

Description

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

Etching that supplies a hydrogen bromide (HBr) gas, a nitrogen trifluoride (NF ₃ ) gas, and an oxygen (O ₂ ) gas, and etches a layer to be etched containing polycrystalline silicon by plasma generated from the gases. A method has been proposed (see, for example, Patent Document 1).

JP 2013-258244 A

  However, when holes are formed in a silicon film by etching, when the aspect ratio is increased to, for example, 15 or more, a phenomenon in which the etched holes are pointed (hereinafter referred to as “twisting”) occurs. Etching shape is deteriorated. In recent years, twisting issues have become increasingly apparent, especially due to the demand for device miniaturization and high aspect ratio etching.

  With respect to the above-described problem, in one aspect, the present invention aims to improve the etching shape.

In order to solve the above problems, according to one aspect, an etching method for etching a silicon film formed on a substrate, comprising hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas, and A plurality of steps of supplying a gas containing oxygen (O ₂ ) gas into the chamber and etching the silicon film by plasma generated from the supplied gas; and the flow rate of the hydrogen bromide gas in the plurality of steps. An etching method is provided in which the flow rate of the oxygen gas is adjusted stepwise and the flow rate of the oxygen gas is adjusted according to the decrease in the hydrogen bromide gas.

  According to one aspect, the etching shape can be improved.

The figure which shows the longitudinal cross-section of the etching apparatus concerning one Embodiment. The figure for demonstrating the twisting with respect to an ideal etching. The time chart which shows supply of the gas at the time of the etching in one Embodiment and a comparative example. The figure which shows the relationship between the aspect-ratio and twisting in one Embodiment and a comparative example. The figure which shows the etching shape in one Embodiment and a comparative example. The figure which shows an example of the etching method concerning one Embodiment. The figure which shows an example of the relationship between the bottom CD value of LF and the twisting value concerning the modification of one Embodiment. The figure which shows an example of the twisting value concerning the modification of one Embodiment. The figure which shows an example of the effect of the etching method concerning the modification of one Embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, in this specification and drawing, about the substantially same structure, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[Overall configuration of etching apparatus]
First, an example of an etching apparatus 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of a longitudinal section of an etching apparatus 1 according to this 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 a mounting table 20 and a gas shower head 25 are disposed in a chamber 10 so as to face each other. 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 also functions as a lower electrode. The gas shower head 25 has a function of supplying gas into the chamber 10 in a shower shape and also functions as an upper electrode.

  The chamber 10 is made of, for example, aluminum whose surface is anodized (anodized) and has a cylindrical shape. The chamber 10 is electrically grounded. The mounting table 20 is installed at the bottom of the chamber 10 and mounts the wafer W thereon. The wafer W is an example of a substrate to be etched, and a mask is formed on the wafer W on the polysilicon film.

The mounting table 20 is formed of, for example, a support 104 formed of aluminum (Al), titanium (Ti), silicon carbide (SiC), or the like, and an upper surface of the mounting table 20 to statically attract a wafer. The electric chuck 106 is provided. The electrostatic chuck 106 has a structure in which a chuck electrode 106a is sandwiched between insulators 106b made of a dielectric material such as alumina (Al ₂ O ₃ ).

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

  A coolant channel 104 a is formed inside the support body 104. A refrigerant inlet pipe 104b and a refrigerant outlet pipe 104c are connected to the refrigerant flow path 104a. A cooling medium such as cooling water or brine output from the chiller 107 circulates 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 gas (He) or argon gas (Ar) to the back surface of the wafer W on the electrostatic chuck 106 through the gas supply line 130. With this configuration, the temperature of the electrostatic chuck 106 is controlled by the cooling medium that is circulated through the refrigerant flow path 104 a and the heat transfer gas that is supplied to the back surface of the wafer W. As a result, the wafer can be controlled to a predetermined temperature. Alternatively, the wafer W may be heated by using a heating source.

  A power supply device 30 that supplies two-frequency superimposed power is connected to the mounting table 20. The power supply device 30 includes a first high-frequency power source 32 that supplies high-frequency power HF (High Frequency) for generating plasma at a first frequency, and a high-frequency power LF (Low Frequency for bias) having a second frequency lower than the first frequency. And a second high-frequency power supply 34 for supplying the power. The first high frequency power supply 32 is electrically connected to the mounting table 20 via the first matching unit 33. The second high frequency power supply 34 is electrically connected to the mounting table 20 via the second matching unit 35. For example, the first high frequency power supply 32 applies high frequency power HF for plasma excitation of 100 MHz to the mounting table 20. For example, the second high frequency power supply 34 applies a high frequency power LF for bias of 13.56 MHz to the mounting table 20. 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 matches the load impedance to the internal (or output) impedance of the first high frequency power supply 32. The second matching unit 35 matches the load impedance to the internal (or output) impedance of the second high frequency power supply 34. The first matching unit 33 functions so that the internal impedance of the first high-frequency power source 32 and the load impedance seem to coincide when plasma is generated in the chamber 10. The second matching unit 35 functions so that the internal impedance of the second high-frequency power source 34 and the load impedance seem to coincide when plasma is generated in the chamber 10.

  The gas shower head 25 is attached so as to close the opening of the ceiling portion of the chamber 10 through an insulating member that insulates the peripheral edge portion thereof. The gas shower head 25 may be electrically grounded as shown in FIG. A predetermined direct current (DC) voltage may be applied to the gas shower head 25 by connecting a variable direct current power source.

  The gas shower head 25 is formed with a gas inlet 45 for introducing gas. Inside the gas shower head 25, there are provided a center side diffusion chamber 50 a and an edge side diffusion chamber 50 b branched from the gas inlet 45. The gas output from the gas supply source 15 is supplied to the diffusion chambers 50a and 50b via the gas introduction port 45, diffused in the respective diffusion chambers 50a and 50b, and then transferred from the multiple gas supply holes 55 to the mounting table 20. Introduced towards.

  An exhaust port 60 is formed in the bottom surface of the chamber 10, and the inside of the chamber 10 is exhausted by an exhaust device 65 connected to the exhaust port 60 via an exhaust pipe. 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. The wafer W is loaded and unloaded 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 operation of the entire 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 executes desired processing such as etching, which will be described later, according to various recipes stored in these storage areas. The recipe includes process time, pressure (gas exhaust), high-frequency power and voltage, various gas flow rates, chamber temperature (upper electrode temperature, chamber side wall temperature, electrostatic chuck temperature, etc.), which are device control information for process conditions. The temperature of the chiller 107 is described. Note that recipes indicating these programs and processing conditions may be stored in a hard disk or a semiconductor memory. Further, the recipe may be set at a predetermined position in the storage area while being stored in a storage medium readable by a portable computer such as a CD-ROM or DVD.

  During the etching process, the opening and closing of the gate valve G is controlled, and the wafer W is loaded into the chamber 10 and placed on the mounting table 20. When a DC current is supplied from the DC voltage source 112 to the chuck electrode 106a, the wafer W is attracted to and held by the electrostatic chuck 106 by the Coulomb force.

  Next, an etching gas, high frequency power HF for plasma excitation, and high frequency power LF for bias are supplied into the chamber 10 to generate plasma. Plasma etching is performed on the wafer W by the generated plasma.

  After the etching process, a DC voltage HV having a polarity opposite to that at the time of adsorption of the wafer W is applied from the DC voltage source 112 to the chuck electrode 106 a to remove the 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, and the wafer W is unloaded from the chamber 10.

[Etching method]
An etching method of one embodiment of the present invention is described. For example, as shown in FIG. 2 (a), to etch the poly (polycrystalline) silicon film 12 which is an object to be etched film silicon oxide film (Si0 ₂₎ as a mask 11. However, the film to be etched is not limited to the polysilicon film 12 and may be, for example, an amorphous silicon film or a single crystal layer. The film to be etched may be a silicon oxide film or a silicon nitride film (SiN). The mask 11 may be an oxide film or a nitride film. Examples of the base film 13 of the polysilicon film 12 include a silicon oxide film and a silicon nitride film.

  FIG. 2A shows an example of the structure of the film formed on the substrate before etching, and FIG. 2B shows an example of the cross section of the etched shape of the hole formed in the polysilicon film 12 after etching. Show.

  The aspect ratio is defined as the ratio between the top CD (top CD) of the polysilicon film 12 and the depth D of the polysilicon film 12. For example, when the aspect ratio is about 15 to 20, even if a good etching shape is obtained as shown in FIG. 2B, a good etching shape can be obtained with the recently required aspect ratio of 25 to 30. There may not be. In particular, it is remarkable at 30 or more. As a result, as shown in FIG. 2C, twisting, which is a phenomenon in which the tip of the etched hole (bottom side of the hole) is bent (bent or bent), occurs. The process conditions for solving the twisting problem and the etching method of one embodiment of the present invention based on the process conditions will be described below while comparing the process conditions of the comparative example and the present embodiment.

2A, main etching for etching the polysilicon film 12 and over-etching for etching the base film 13 are performed. For example, hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas, and oxygen gas (O ₂ ) are used as the etching gas (first process condition). The polysilicon film 12 is etched through the mask 11 by the plasma generated from these gases under the first process condition. Subsequently, overetching is performed to etch the base film 13 under the first process 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.

In the etching method according to the present embodiment, the step of removing the natural oxide film on the polysilicon film 12 through the mask 11 by plasma generated from CF ₄ gas and O ₂ gas is performed for about 10 seconds. Subsequently, the polysilicon film 12 is etched.

[Etching method according to comparative example]
Below, the etching method concerning a comparative example is demonstrated. An example of process conditions for etching the polysilicon film 12 in the comparative example is shown below.
・ 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 ・ Temperature 20 temperature 65 ℃
In the etching according to the comparative example, after the polysilicon film 12 is main etched, the base film 13 is over-etched by about 30%, for example. In the comparative example, as shown in FIG. 3A, HBr gas, NF ₃ gas, and O ₂ gas are all supplied at a constant flow rate in the main etching and over etching.

  In plasma etching under the above process conditions, when the aspect ratio is about 15, the etching shape of the polysilicon film 12 is processed substantially vertically as shown in FIG. However, when the aspect ratio is as high as 20, for example, twisting as shown in FIG.

  FIG. 4A shows an example of the etching result according to the comparative example under the above process conditions. As shown in FIG. 4A, twisting does not cause a problem when the aspect ratio is 15 or less, but when the aspect ratio exceeds 15, twisting starts to occur, and when the aspect ratio becomes 25 or more, twisting starts. Sting becomes obvious. In particular, with the recent miniaturization of devices, the twisting problem in etching with an aspect ratio of 25 or more has become unacceptable.

One of the causes of twisting is that silicon Si represented by the following reaction formula (1) and reaction products generated during the etching process, such as SiBr _x O _y and SiOF _x, are excessively attached to the sidewall of the hole. This is thought to be due to the fact that the directionality of ions is hindered and changed.

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 out of the chamber 10, but SiBr _x O _y and SiOF _x are sedimentary substances. Yes, it adheres to the side of the hole.

  Under the above process 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 main etching → overetching is performed without changing the other conditions among the above process conditions, it adheres to the wall of the hole. The amount of deposits decreased, the etching of the holes progressed, and bowing that expanded the side of the holes occurred, and a good etching shape could not be obtained.

[Etching Method According to this Embodiment]
Therefore, in the etching method according to the present embodiment, in addition to controlling the temperature of the mounting table 20 to 100 ° C. among the above process conditions, as shown in FIG. Fluctuate. Specifically, the flow rates of HBr gas and O ₂ gas are varied while the flow rate of NF ₃ gas is controlled to be constant.

  In the etching method of the present embodiment, as shown in FIG. 2B, the first to third steps in which the main etching of the polysilicon film 12 is roughly divided into three equal parts, and the fourth step of overetching the base film 13 Each gas flow rate is controlled in four steps. The control of the gas flow rate is performed by the control unit 100.

Specifically, in the first step of FIG. 3B, the flow rates of HBr gas, NF ₃ gas, and O ₂ gas are set to initial values. The HBr gas is a gas mainly for promoting etching and is a main etching gas. The NF ₃ gas is a gas for mainly removing deposits adhering to the mask 11. The O ₂ gas is a gas mainly for protecting the mask 11 and the hole walls of the polysilicon film 12.

Boeing is likely to occur when the flow rate of HBr gas is increased, and is likely to be generated when the flow rate ratio of HBr gas to O ₂ gas is increased. Therefore, in order to suppress bowing in the etching of the polysilicon film 12, it is preferable not only to reduce the flow rate of the HBr gas but also to increase the flow rate ratio of the O ₂ gas to the HBr gas.

  Specifically, as shown in FIG. 3B, the flow rate of HBr gas in the first and second steps is controlled to be higher than the flow rate of HBr gas in the third and fourth steps. This promotes etching in the first and second steps. Further, the flow rate of the HBr gas is controlled so as to decrease stepwise in the second step to the fourth step. This suppresses etching step by step and suppresses bowing formed in the holes. The flow rate of the HBr gas in the first and second steps may be the same, and may be decreased and increased in stages.

Further, the flow rate of the O ₂ gas in the second step is controlled to be higher than the flow rate of the O ₂ gas in the first step, so that the flow rate ratio of the O ₂ gas to the HBr gas is increased. The wall of the formed hole is protected.

Furthermore, the flow rate of O ₂ gas in the third and fourth steps is slightly less than the flow rate of O ₂ gas in the second step. Further, the flow rate of O ₂ gas in the third and fourth steps may be the same as the flow rate of O ₂ gas in the second step, or may be decreased stepwise or increased. good. Here, in the second step to the fourth step, the flow rate of the HBr gas is decreased stepwise. Accordingly, the flow ratio of O ₂ gas to the HBr gas in the second step to the fourth step is stepwise increased. Thereby, a bowing can be suppressed more effectively.

Thus, in this embodiment, the flow rate of O ₂ gas is changed according to the flow rate of HBr. Specifically, in order to suppress bowing, control is performed so that the flow rate ratio of O ₂ gas to HBr gas is gradually increased. In FIG. 3B, the O ₂ gas is controlled to have the same flow rate in the third and fourth steps, but is not limited thereto. For example, as shown in FIG. 3C, by increasing the flow rate ratio of O ₂ gas to HBr gas step by step from the first step to the fourth step, the occurrence of twisting is suppressed and the bowing is also suppressed. I can do it. The etching step is preferably performed with at least two steps or more, and more preferably with three steps or more. The control of the flow rate ratio between the HBr gas and the O ₂ gas varies depending on the temperature of the mounting table 20 and the structure of the sample.

Further, the flow rate of the NF ₃ gas may be controlled to be constant in all steps as shown in FIG. In addition, the present invention is not limited to this, and for example, it may be controlled to be constant in the first and second steps and gradually increased in the third and fourth steps. Further, the flow rate of the O ₂ gas may be controlled to increase in accordance with the increase of the flow rate of the NF ₃ gas. Thereby, formation of the protective film which protects the side wall of a hole can be accelerated | stimulated, removing the deposit adhering to the mask 11. FIG. Further, SF ₆ (sulfur hexafluoride) gas may be supplied instead of NF ₃ gas.

  An example of the etching result according to this embodiment is shown in FIG. As shown in FIG. 3 (a), the twisting is compared with the case of FIG. 4 (a) as a result of the comparative example in which the flow rate of each gas is controlled to be constant and the temperature of the mounting table 20 is controlled to 100.degree. It turns out that generation | occurrence | production of is suppressed. In particular, in FIG. 4B, even when the aspect ratio is 25, the occurrence of twisting can be prevented.

As described above, according to the etching method according to the present embodiment, the temperature of the mounting table 20 is controlled to a high temperature of, for example, 100 ° C., and the flow rate of the etching gas in a plurality of etching steps (first to fourth steps). Fluctuate. That is, the HBr gas among the gases supplied into the chamber 10 is decreased stepwise. Further, in this etching method, as the etching proceeds, the flow rate of O ₂ gas is controlled so that the flow rate ratio of O ₂ gas to HBr gas becomes higher. Further, the flow rate of the NF ₃ gas is controlled to be constant in all steps, or is increased as the flow rate of the O ₂ gas is increased. This suppresses the occurrence of twisting in etching (see FIG. 2C) and bowing (see FIG. 5A), and as shown in FIG. 5B, the holes in the polysilicon film 12 are formed. The etching shape can be formed substantially vertically.

The flow of the etching method according to this embodiment will be briefly described with reference to FIG. When this process is started, the control unit 100 supplies CF ₄ gas and O ₂ gas into the chamber 10, and a natural oxide film of the mask 11 on the substrate is generated by plasma generated from the CF ₄ gas and O ₂ gas. Is removed (step S10).

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

Next, the control unit 100 determines whether or not the first step of etching has been completed (step S14). When it is determined that the first step is finished, the control unit 100 decreases the flow rate of the HBr gas step by step in the second to fourth steps (step S16). Next, the control unit 100 increases the flow rate of the O ₂ gas with respect to the HBr gas stepwise in the second to fourth steps (step S18), and ends this process. Thereby, the etching shape of the hole formed in the polysilicon film 12 can be made favorable.

[Modification]
Next, an etching method according to a modification of the above embodiment will be described. In this modification, in order to improve twisting, the control region of the high frequency power LF for bias is optimized.

Specifically, for example, the upper limit value of the control region of the conventional high frequency power LF for bias is less than 1500 W. On the other hand, in this modification, the control unit 100 controls the high frequency power LF for bias in the range of 4000 W to 10000 W, which is higher than the conventional one. For example, FIG. 7 shows an example of an etching method and a twisting state according to a modification of the present embodiment. The process conditions used for 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 0.1 kHz, duty ratio 20%))
・ Gas HBr / NF ₃ / O ₂
・ Etching time 90 seconds ・ Temperature 20 temperature 65 ℃ -100 ℃
The frequency of the pulse wave of the high frequency power LF for bias may be in the range of 0.1 kHz to 50 kHz. The duty ratio may be in the range of 5% to 30%.

  FIG. 7 shows a result when a pulse wave of the high frequency power LF for bias is applied at each power of 3000 W, 4500 W, and 7000 W. The horizontal axis in FIG. 7 is the bottom CD. As shown in FIG. 8, the bottom CD is the diameter of the bottom of the hole formed in the polysilicon film 12. The middle is 12% smaller and the small is 25% smaller than the Large shown on the horizontal axis in FIG.

  The vertical axis in FIG. 7 is the twisting value. The twisting value is a deviation (3σ) indicating the variation in the distance between the holes from the shape (footprint) of the bottom of the hole shown in FIG. In the example of FIG. 8, the twisting value is higher when the bias high frequency power LF is low (Low Power) than when the bias high frequency power LF is higher (High Power).

  According to the result of FIG. 7, when the pulse wave of the high frequency power LF for bias of 3000 W is applied, the twisting value becomes worse as the bottom CD becomes closer to “Small”. This is because, as the bottom CD is smaller, ions in the plasma are less likely to reach the bottom of the hole and reach the bottom of the hole as shown in (1) of FIG. This is because twisting occurs by bending forward.

  On the other hand, when the pulse wave of the high frequency power LF for bias of 4500 W and 7000 W is applied, the bottom CD becomes “Small” compared to the case of applying the pulse wave of the high frequency power LF for bias of 3000 W. However, the twisting value is hard to get worse. In other words, twisting caused by the bending of ions near the bottom of the hole is improved. This is because by increasing the value of the high frequency power LF for biasing, as shown in FIG. 9B, the ion energy is increased, the straightness of the ions is improved, and the number of ions reaching the bottom of the hole is reduced. This is because it could be increased.

  Note that the bias high-frequency power LF is a pulse wave, and is repeated between the time when the bias high-frequency power LF is applied and the time when it is not applied. This facilitates etching while the bias high-frequency power LF is on, and allows the gas in the hole to be exhausted out of the hole while the bias high-frequency power LF is off. Thereby, mask clogging in which the opening of the mask film 11 shown in (2) of FIG. 9A is narrowed by a reaction product during etching can be prevented. Further, necking in which a reaction product adheres to the side surface of the hole shown in (3) of FIG. This makes it easier for ions to reach the bottom of the hole.

  As described above, according to the etching method according to this modification, by applying a pulse wave of a high frequency power LF for bias of 4000 W or more, the ion energy in the plasma is increased, and the ions are placed at the bottom of the hole. Make it easy to reach. Thereby, twisting can be improved, the etching shape can be improved, and the etching of holes can be promoted. As a result, good etching can be performed on holes and grooves having an aspect ratio of 20 to 25, preferably 25 or more.

As shown in FIG. 3B, the etching method according to this modification controls the bias high frequency power LF while controlling the HBr gas, NF ₃ gas, and O ₂ gas of the above embodiment. You may go. Alternatively, as shown in FIG. 3A, the high frequency power LF for bias may be controlled while the HBr gas, NF ₃ gas, and O ₂ gas of the above embodiment are controlled to be constant.

  Although the etching method and the etching apparatus have been described in the above embodiment, the etching method and the etching apparatus according to the present invention are not limited to the above embodiment, and various modifications and improvements can be made within the scope of the present invention. It is. The matters described in the above embodiments can be combined within a consistent range.

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

  Moreover, the etching apparatus using the etching method according to the present invention is applicable not only to a capacitively coupled plasma (CCP) apparatus but also to other etching apparatuses. Other etching apparatuses include an inductively coupled plasma (ICP), a plasma processing apparatus using a radial line slot antenna, a helicon wave excited plasma (HWP) apparatus, an electron cyclotron resonance plasma (ECR). : Electron Cyclotron Resonance Plasma) apparatus or the like.

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

1: Etching apparatus 10: Chamber 11: Mask 12: Polysilicon film 13: Base film 15: Gas supply source 20: Mounting table 20 (lower electrode)
25: Gas shower head (upper electrode)
30: Power supply device 100: Control unit 106: Electrostatic chuck

Claims (11)

An etching method for etching a silicon film formed on a substrate,
A gas containing hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas and oxygen (O ₂ ) gas is supplied into the chamber, and a plurality of silicon films are etched by plasma generated from the supplied gas. Having a process,
Reducing the flow rate of the hydrogen bromide gas stepwise in the plurality of steps;
Adjusting the flow rate of the oxygen gas according to the decrease in the hydrogen bromide gas;
Etching method. Reducing the flow rate of the hydrogen bromide gas stepwise in two or more steps including the last step of the plurality of steps;
The etching method according to claim 1. Increasing the flow rate of the oxygen gas stepwise,
The etching method according to claim 1 or 2. Increasing the flow ratio of oxygen gas to hydrogen bromide gas stepwise.
The etching method as described in any one of Claims 1-3. Making the nitrogen trifluoride gas flow rate constant or increasing;
When the flow rate of the nitrogen trifluoride gas is increased, the flow rate of the oxygen gas is increased according to the increase of the nitrogen trifluoride gas.
The etching method as described in any one of Claims 1-4. Adjusting the temperature of the substrate to 100 ° C. to 200 ° C .;
The etching method as described in any one of Claims 1-5. An etching apparatus having a controller and etching a silicon film formed on a substrate,
The controller is
A gas containing hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas and oxygen (O ₂ ) gas is supplied into the chamber, and a plurality of silicon films are etched by plasma generated from the supplied gas. In the process, the flow rate of the hydrogen bromide gas is decreased stepwise,
Adjusting the flow rate of the oxygen gas according to the decrease in the hydrogen bromide gas;
Etching equipment. In the plurality of steps, a pulse wave of a high frequency power LF for bias of 4000 W or more is applied.
The etching method as described in any one of Claims 1-6. The frequency of the pulse wave of the high frequency power for bias is 0.1 kHz to 50 kHz, and the duty ratio is 5% to 30%.
The etching method according to claim 8. An etching method for etching a silicon film formed on a substrate,
A gas containing hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas and oxygen (O ₂ ) gas is supplied into the chamber, and a plurality of silicon films are etched by plasma generated from the supplied gas. Having a process,
In the plurality of steps, the flow rate of the hydrogen bromide gas is decreased stepwise, the flow rate of the oxygen gas is adjusted according to the decrease of the hydrogen bromide gas, and a pulse of high frequency power LF for bias of 4000 W or more is applied. Applying a wave,
Etching method. An etching apparatus having a controller and etching a silicon film formed on a substrate,
The controller is
A gas containing hydrogen bromide (HBr) gas, nitrogen trifluoride (NF ₃ ) gas and oxygen (O ₂ ) gas is supplied into the chamber, and a plurality of silicon films are etched by plasma generated from the supplied gas. Having a process,
In the plurality of steps, the flow rate of the hydrogen bromide gas is decreased stepwise, the flow rate of the oxygen gas is adjusted according to the decrease of the hydrogen bromide gas, and a pulse of high frequency power LF for bias of 4000 W or more is applied. Applying a wave,
Etching equipment.

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