JPH09306891A - Etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an etching method capable of keeping a high etching rate in a high density plasma atmosphere even if the number of works such as wafers increases. SOLUTION: A high frequency power from a second high frequency power source 47 is applied to an antenna 45 located around a treating vessel 3 to generate a plasma at a high density plasma of 10<10> cm<-3> or more in a treating chamber 3. At etching of a polysilicon film on a wafer W with a HBr gas, O2 is mixed as much as 3% or more of the total flow rate after the end of the etching and successively a plasma is generated for 1-5sec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method for etching a substrate to be processed in a high density plasma atmosphere using an etching gas.

[0002]

2. Description of the Related Art Conventionally, for example, in a semiconductor device manufacturing process, when etching a polysilicon film, tungsten silicide (WSix), silicon or the like on the surface of a semiconductor wafer (hereinafter referred to as “wafer”), HBr ( (Hydrogen bromide) gas is introduced into the processing container, plasma is generated in the processing container, and etching is performed by etchant ions or the like generated at that time.

Further, today, with the high integration of semiconductor devices, the etching process itself is required to be further miniaturized, and in order to further improve the throughput, a high-speed etching rate is emphasized. Therefore, when etching in the plasma atmosphere, for example, a high density plasma atmosphere of 1.0 × 10 ¹⁰ cm ⁻³ or more (5.0 × 10 ¹⁰ cm ⁻³ or more in the case of Ar (argon) gas plasma). It has been proposed to etch with a magnetron discharge or E as a plasma source.
An etching apparatus that generates high-density plasma using CR (Electron Cyclotron Resonance) or inductively coupled plasma may be used.

When the HBr gas is used to etch a polysilicon film on a wafer, the etching rate tends to gradually decrease as the number of wafers to be processed increases. This is because the carbon in the resist reacts with the ions in HBr, and C-Brx
It is considered that this is because a system-based or C-Hx-based compound floats or adheres to the inner wall of the processing container.

Therefore, conventionally, for example, every time a predetermined number of etchings are performed, the line is stopped, O ₂ gas is introduced into the processing container, and the inside of the processing container is cleaned with oxygen plasma. 1-24112
As disclosed in Japanese Patent No. 8, it has been proposed to add O ₂ gas to the etching gas from the beginning to perform etching.

[0006]

However, according to the experiments by the inventors, according to a method of introducing O ₂ gas into the processing container every time a predetermined number of processes are completed and cleaning the inside of the processing container with oxygen plasma. The plasma density is 10 ¹⁰ cm ⁻³ or more (in the case of Ar gas plasma, 5.
In the case of etching in a high density plasma atmosphere of 0 × 10 ¹⁰ cm ⁻³ or more), if an etching gas containing HBr gas as a main component is used, the tendency that the etching rate sharply decreases with each treatment is not improved. There was found.

It is considered that this is due to the following reasons. That is, unlike the case of low density plasma, the plasma density is 10 ¹⁰ cm ⁻³ or more (in the case of Ar gas plasma,
When it is etched in a high density plasma atmosphere of 5.0 × 10 ¹⁰ cm ⁻³ or more), red plasma emission generated by hydrogen atoms becomes strong. Then, it is considered that the dissociation progresses further and more multiple Br active principals are generated as compared with the case of the low density plasma. As a result, it is considered that the reaction product generated as a result of the reaction between Br and the resist or polysilicon floats in the processing container or adheres to the inner wall of the processing container.

Further, if O ₂ gas is added to the etching gas from the beginning of the etching process, or if it is added and etched during the etching process, the desired high-speed etching rate may not be obtained, or the flow rate may change slightly. However, the etching characteristics may vary.

The present invention has been made in view of the above points, and maintains a high etching rate even when the number of processed substrates such as wafers increases when etching is performed in the above-described high-density plasma atmosphere. An object of the present invention is to provide a possible etching method and solve the above problems.

[0010]

In order to achieve the above object, according to claim 1, an etching gas is introduced into the processing container so that the plasma density is 10 ¹⁰ cm ^-3 or more with respect to this etching gas. In the etching method of performing the etching process on the substrate to be processed in the processing container in the plasma atmosphere, the total flow rate including the etching gas is 3 immediately after the etching is finished (preferably at the same time as the etching is finished).
An etching method is provided, wherein O ₂ is mixed into the etching gas at a flow rate of not less than%, and plasma is subsequently generated for 1 to 5 seconds.
Here, the flow rate of O ₂ mixed with the etching gas is
The total flow rate including the etching gas is 3% or more, preferably 50% to 100%. The plasma generation time after completion of etching may be 1 to 5 seconds as described above, but more preferably 1 to 3 seconds. In addition, as an example of the etching gas that can obtain the intended function and effect of the present invention, in addition to the etching gas containing HBr gas as a main component, a gas containing HCl as a main component or Specifically, a gas containing Cl ₂ as a main component can be used.

Further, in this case, as described in claim 2, an etching gas containing HBr gas as a main component is substantially used as an etching gas, that is, a single HBr gas or HB gas.
The effect is particularly great in an etching process in which a gas containing 80% or more of r gas is introduced into a processing container for etching. Also, the amount of O ₂ mixed in the etching gas containing HBr gas as a main component is substantially
It is 3% or more, preferably 50% to 100%, of the total flow rate including the etching gas containing Br gas as a main component. The plasma generation time after completion of etching is preferably 1 to 5 seconds, more preferably 1 to 3 seconds.

Further, according to the third aspect, the first step of loading the substrate to be processed into the processing container and holding the substrate to be processed on the mounting table in the processing container, and substantially using HBr gas as a main component. A second step of introducing an etching gas as a component (that is, a single gas of HBr gas or a gas containing 80% or more of HBr gas) into the processing container, and a plasma density of 10 ¹⁰ cm ^{− with} respect to this etching gas. ^{A third} step of applying ^three or more plasmas in the processing container and applying a bias voltage to the substrate to be processed, a fourth step of stopping the application of the bias voltage immediately after the end of etching, A fifth step of stopping the generation of plasma and stopping the introduction of the etching gas, wherein a substantial amount of H is provided between the fourth step and the fifth step.
Provided is an etching method characterized by adding a step of introducing O ₂ into a processing container for 1 to 5 seconds at a flow rate of 3% or more of a total flow rate including an etching gas containing Br gas as a main component. It

Further, the amount of O ₂ mixed in the etching gas containing HBr gas as a main component is preferably HB.
50% to 100% of the total flow rate including the etching gas containing r gas as a main component is preferable. The time for introducing O ₂ is preferably 1 to 5 seconds, more preferably 1 to 5 seconds.
3 seconds is good. Then, after the lapse of the time of introducing O ₂ , the plasma is stopped (fifth step).
Therefore, the inside of the processing container is in a plasma atmosphere while O ₂ is being introduced.

According to the etching method of claims 1 to 3,
Oxygen radicals generated when O ₂ is introduced or a specific substance in the etching gas (for example, the etching gas is substantially H 2
In the case of Br gas, it occurs as a result of a reaction between Br oxide and Br oxide, floating in the chamber immediately after etching, or a deposit species or deposit (for example, Br and resist or polysilicon) accumulated on the inner surface of the processing container. It is considered that the reaction product) reacts with the reaction product and is directly discharged to the outside of the processing container through exhaust (in this type of etching process, the exhaust gas is constantly exhausted during the process). Therefore, even if the number of etching treatments is repeated under a high-density plasma atmosphere, a high-speed etching rate immediately after the so-called oxygen plasma cleaning, which is usually performed for each predetermined number, can be maintained. That is, the etching rate does not decrease even if the etching process is continuously performed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross section of an etching apparatus 1 used for carrying out an etching method according to the present embodiment. The processing chamber 2 in the etching apparatus 1 is formed in a cylindrical processing container 3 made of an insulating material such as a quartz material, and the processing chamber 2 is airtightly closed.

At the bottom of the processing chamber 2, a substantially columnar susceptor 4 for mounting a wafer W, which is a substrate to be processed, is housed. The susceptor 4 is made of, for example, aluminum that has been subjected to anodized alumite treatment. A refrigerant circulation path 5 through which the refrigerant flows is formed in the susceptor 4, and the refrigerant introduced from the refrigerant introduction pipe 6 circulates in the refrigerant circulation path 5 and flows from the refrigerant discharge pipe 7 to the processing container 3
It is designed to be discharged to the outside. With this configuration, the susceptor 4 and the wafer W can be cooled to a predetermined temperature. At the same time, a heating means such as a ceramic heater is separately provided in the susceptor 4, and the heating means is controlled by the control of an appropriate temperature sensor.
The wafer W may be controlled to a predetermined temperature. In this case, finer temperature adjustment is possible.

An electrostatic chuck 11 for attracting and holding the wafer W is provided on the susceptor 4. The electrostatic chuck 11 has a configuration in which, for example, a conductive thin film is sandwiched between polyimide resin films from above and below, and the high-voltage DC power supply 1 installed outside the processing container 3
When a predetermined DC voltage from 2, for example, a voltage of 1.5 kV to 2 kV is applied to the conductive thin film, the Coulomb force based on the charges generated on the resin film causes
The wafer W placed on the electrostatic chuck 11 is sucked and held on the upper surface of the electrostatic chuck 11.

In the susceptor 4, there is provided a heat transfer gas introducing pipe 13 penetrating the bottom of the processing container 3 and connected to a gas flow passage 14 opened on the upper surface of the electrostatic chuck 11. An appropriate heat transfer gas, such as He (helium) gas, supplied from the outside of the processing container 3 is transferred to the wafer W held on the electrostatic chuck 11 through the heat transfer gas introduction pipe 13 and the gas flow path 14. When supplied to the back surface, the heat transfer efficiency between the wafer W and the electrostatic chuck 11, that is, the susceptor 4 is improved.

If an annular focus ring having an insulating property is appropriately provided around the electrostatic chuck 11 on the outer peripheral edge of the upper surface of the susceptor 4 so as to surround the electrostatic chuck 11, etchant ions can be applied to the wafer W. It is possible to make the light incident efficiently.

A shower head 21 for introducing a gas such as an etching gas into the processing container 3 and uniformly supplying the gas to the wafer W is provided in the upper portion of the processing container 3. There is. This shower head 21
It has a hollow structure in which a baffle space S is formed,
A large number of diffusion holes 21b communicating with the baffle space S are formed on the lower surface 21a which is the surface facing the wafer W.

Further, a gas introducing pipe 22 is connected to the shower head 21, and the gas introducing pipe 22 is provided with corresponding valves 23, 24 and corresponding mass flow controllers 25, 26 for adjusting the flow rate, respectively. Is connected to the gas supply sources 27 and 28. Then, the etching gas from the gas supply source 27 is HBr gas, and the O ₂ gas from the gas supply source 28 is the shower head 21.
It is supplied to.

Next, regarding the exhaust system of the etching apparatus 1, an exhaust pipe 32 is connected to the bottom of the processing container 3, and the exhaust pipe 32 is connected to a vacuuming means 31 such as a turbo molecular pump. . A baffle plate 33 having a large number of small holes is provided around the susceptor 4. Therefore, the atmosphere in the processing container 3 is uniformly evacuated through the baffle plate 33 by the operation of the evacuation means 32, and the atmosphere can be evacuated to an arbitrary decompression degree of, for example, 10 mTorr and maintained. It is possible.

Next, the high-frequency power supply system of the etching apparatus 1 will be described. First, since a bias voltage is applied to the lower susceptor 4 with respect to the wafer W, a high-frequency power having a frequency of 13.56 MHz is supplied. The first high frequency power supply 41 for output is connected via a matching unit 42 having a blocking capacitor or the like.

On the other hand, the structure for generating plasma in the processing container 3 is as follows. First,
An electrostatic shield member 43 as shown in FIG. 2 is arranged on the outer periphery of the processing container 3. This electrostatic shield 43
The material of is made of aluminum, and the surface is made of Ag.
It is plated with (silver) to ensure high conductivity. The electrostatic shield member 43 is grounded by a ground wire 44.

The electrostatic shield member 43 has a cylindrical shape as a whole so as to surround the outer periphery of the processing container 3, and a slit formed in the longitudinal direction and penetrating the periphery of the electrostatic shield member 43. 43a is formed in the whole circumference under a predetermined interval. Therefore, it is possible to pass only an electric field perpendicular to the plasma generated by the antenna 45, and it is possible to prevent the slit 43a from generating an eddy current in the electrostatic shield member 43. As a result, the plasma generated in the processing container 3 by the antenna 45, which will be described later, is extremely stable without being biased or twisted.

An antenna 45 is spirally arranged on the outer periphery of the electrostatic shield member 43 at an appropriate distance. Further, this antenna 45 has a matching unit 46
A second high frequency power source 47 is connected via the second high frequency power source 47, and when a high frequency of 13.56 MHz, for example, is supplied from the second high frequency power source 47 to the antenna 45 with a predetermined power, the second high frequency power source 47 is supplied to the processing chamber 2 in the processing container 3. , HBr gas, high density plasma having an electron density of about 1.0 × 10 ¹¹ cm ⁻³ is generated. The other end of the antenna 45 is open.

Next, the control system of the etching apparatus 1 having the above-described structure will be described. The timing of gas introduction from the high-voltage DC power supply 12 for operating the electrostatic chuck 11 and the gas supply sources 27 and 28, and the flow rate at that time will be described. To carry, valve 2
3, 24, the mass flow controllers 25, 26, the vacuuming means 31 for reducing the pressure in the processing chamber 2, and the wafer W.
First high frequency power source 4 for applying a bias voltage to the
First, the second high frequency power source 47 for generating plasma in the processing container 3 and the like are all controlled by the control device 48.

The main part of the etching apparatus 1 used for carrying out the etching method according to the present embodiment is constructed as described above. On the side surface of the etching apparatus 1, for example, a gate valve (not shown) is provided. Load lock chambers (not shown) accommodating wafer transfer means such as transfer arms are arranged in parallel.

Next, using the etching apparatus 1 having the above-described structure, for example, a process for etching a polysilicon film on the wafer W will be described. First, the wafer W is processed from the load lock chamber (not shown). When the wafer W is loaded into the chamber 2 and placed on the electrostatic chuck 11, a predetermined voltage is applied from the high-voltage DC power supply 12 to the conductive thin film in the electrostatic chuck 11, and the wafer W is transferred to the electrostatic chuck 11. 1
1 is adsorbed and held on top.

Next, the inside of the processing chamber 2 is evacuated by the evacuation means 31, while the HBr gas as the etching gas from the gas supply source 27 has a predetermined flow rate (for example, 1).
Is supplied to the wafer W from the shower head 21 at a pressure of 00 sccm), and the pressure in the processing chamber 2 is reduced to a predetermined pressure reduction degree, for example, 40 m
Set and maintained at Torr.

Next, with respect to the antenna 45, the frequency is 13.56 MHz and the power is 3 from the second high frequency power source 47.
When high-frequency power of kW is supplied, plasma is generated in the processing chamber 2 inside the processing container 3. Further, the frequency from the first high frequency power supply 41 to the susceptor 4 is 13.56 MH.
When high frequency bias power having a power of 40 W is supplied, the etchant ions in the plasma etch the polysilicon film on the surface of the wafer W.

When the etching is completed, first, the supply of the bias high frequency power from the first high frequency power supply 41 is stopped. Next, O ₂ gas is supplied to the processing chamber 2 from the gas supply source 28 at a predetermined flow rate, for example, 100 sccm, that is, the same flow rate as the HBr gas. During this period, the second high frequency power source 47 continues to supply the high frequency power having the frequency of 13.56 MHz and the power of 3 kW to the antenna 45.

Then, after a lapse of a predetermined time, for example, 2 seconds, the supply of O ₂ gas and HBr gas is immediately stopped, and the supply of high frequency power from the second high frequency power supply 47 is also stopped. After that, the application of voltage from the high-voltage DC power supply 12 to the electrostatic chuck 11 is stopped, and the wafer W for which the etching process has been completed
Is transferred to the outside of the processing container 3 by the wafer transfer means. Electrostatic chuck 1 in the above process
1 operation, introduction of HBr gas, introduction of O ₂ gas, ON-OFF of first high frequency power supply 41, second high frequency power supply 47
The ON-OFF timing of is shown in the timing chart of FIG. 3 (note that in the timing chart of FIG. 3, the horizontal axis indicates the passage of time. The ratio with the introduction time of O ₂ gas is not the ratio of the actual time (that is, the timing chart of FIG. 3 shows only the timing).

After that, the unprocessed wafer W is again loaded into the processing chamber 3, and thereafter, the etching process is performed in the same procedure. Immediately after the etching is completed, the O ₂ gas is supplied again and the same process as the above process is performed. Carry out the process.

Immediately after the etching process on the wafer W is completed in this way, the process of mixing the O ₂ gas is successively added into the process container 3 under the plasma atmosphere, so that the process of the wafer W is continued. The etching rate does not decrease even if it is carried out.

This will be described with reference to the graph of FIG. In FIG. 4, the supply of HBr gas and the supply of high-frequency power from the first high-frequency power supply 41 and the second high-frequency power supply 47 are stopped immediately after the conventional process, that is, the etching process is completed, and then the electrostatic chuck is performed. Is turned off and the wafer W is unloaded, and the process according to the above-described embodiment, that is, the step of stopping only the first high-frequency power supply 41 at the end of etching and flowing O ₂ gas to HBr gas at the same flow rate for 2 seconds. The relationship between the number of wafers subjected to etching processing and the etching rate in each of the added processes immediately after cleaning the inside of the processing container 3 with oxygen plasma is shown. The etching conditions for each process are the same as those in the above-described embodiment, that is, the power of the first high-frequency power source 41 is 40 W, the power of the second high-frequency power source 47 is 3 kW, and H is H.
The flow rate of Br gas is 100 sccm.

According to this, according to the conventional method, the etching rate decreases as the wafers are repeatedly processed, whereas according to the present embodiment, the etching process is performed on 20 or more wafers. Even if it is performed, the etching rate immediately after oxygen plasma cleaning is 450 [nm
/ Min] is maintained. Therefore, it can be confirmed that the etching method according to the present embodiment maintains a high etching rate without lowering the etching rate.

Moreover, since the introduction time of O ₂ gas is as short as 2 seconds, the influence on the throughput is small. Rather, in view of the time of periodical oxygen plasma cleaning, in the present invention, the cleaning cycle can be lengthened in view of the characteristics of FIG. 4, so that the throughput is improved as a whole.

Etching apparatus 1 used in the above embodiment
Was an inductively coupled plasma source, but the present invention is not limited to this, and when the electron density is Ar (argon) plasma, a high density plasma of 5.0 × 10 ¹⁰ cm ⁻³ or more is used. Any etching device can be used.
Therefore, it can be implemented by an apparatus using magnetron discharge or ECR.

Although the above-described embodiment has been described as a process of etching polysilicon on a wafer, the present invention is not limited to this, and the present invention is not limited to tungsten silicide (W.
It is also effective when etching (Six) or silicon, and especially HBr (hydrogen bromide) is used as an etching gas.
The effect is great for an etching method that substantially uses gas.
Of course, the substrate to be processed is not limited to the wafer and may be an LCD substrate.

[0041]

According to the etching method of the first to third aspects, even if the number of etching treatments is repeated in a high-density plasma atmosphere, the high-speed etching rate immediately after oxygen plasma cleaning, which is usually performed for each predetermined number, is achieved. Can be maintained. Further, since the O ₂ gas is mixed in after the etching treatment, there is no possibility that the etching characteristics will vary and an unexpected situation will occur in the treatment.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of an etching apparatus used for carrying out an etching method according to an embodiment of the present invention.

FIG. 2 is a perspective view of an electrostatic shield member used in the etching apparatus of FIG.

FIG. 3 is an explanatory diagram of a timing chart of the etching method according to the embodiment of the present invention.

FIG. 4 is a graph showing the relationship between the number of processed wafers and the etching rate in the conventional etching method and the etching method according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Etching apparatus 2 Processing chamber 3 Processing container 4 Susceptor 11 Electrostatic chuck 12 High voltage DC power supply 21 Shower head 22 Gas introduction pipe 27, 28 Gas supply source 41 First high frequency power supply 43 Electrostatic shield member 45 Antenna 47 Second high frequency Power supply W wafer

Claims (3)

[Claims] 1. An etching method in which an etching gas is introduced into a processing container to perform etching on a substrate to be processed in the processing container in a plasma atmosphere having a plasma density of 10 ¹⁰ cm ⁻³ or more. Immediately after that, at a flow rate of 3% or more of the total flow rate including the etching gas,
O ₂ is mixed into the etching gas, and plasma is subsequently generated for 1 to 5 seconds,
Etching method. 2. An etching gas containing HBr gas as a main component is substantially introduced into the processing chamber to reduce the plasma density.
In an etching method for etching a substrate to be processed in a processing container in a plasma atmosphere of 10 ¹⁰ cm ⁻³ or more, 3% of the total flow rate including the etching gas containing HBr gas as a main component immediately after the etching is completed. With the above flow rate, the etching gas containing HBr gas as a main component is added to O
_An etching method, wherein ₂ is mixed and plasma is subsequently generated for 1 to 5 seconds. 3. A first step of loading a substrate to be processed into a processing container and holding the substrate to be processed on a mounting table in the processing container; and an etching gas substantially containing HBr gas as a main component. A second step of introducing into the processing container, and a third step of generating a plasma having a plasma density of 10 ¹⁰ cm ⁻³ or more in the processing container and applying a bias voltage to the substrate to be processed. A fourth step of stopping the application of the bias voltage after the etching, and a fifth step of stopping the generation of the plasma and stopping the introduction of the etching gas.
And a flow rate of 3% or more of the total flow rate including the etching gas containing HBr gas as a main component, between the fourth step and the fifth step. An etching method characterized by adding a step of introducing O ₂ into the processing container for 1 to 5 seconds.