JP3523460B2 - Method for manufacturing semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing apparatus and a manufacturing method of a semiconductor device using plasma, and more particularly to a dry etching apparatus and a dry etching method.

[0002]

2. Description of the Related Art In recent years, there have been remarkable improvements in the degree of integration of semiconductor devices. The improvement in device integration was realized as a result of the progress of process technology. In particular, photolithography technology for forming a photoresist pattern and etching technology for transferring the formed photoresist pattern onto a substrate. Advances make a big contribution to its realization.

Nowadays, the dry etching technique has a tendency to positively utilize low gas pressure and high density plasma, and an apparatus using electron cyclotron resonance plasma, inductively coupled plasma or helicon wave excited plasma has been proposed. Being developed.

However, in order to stably generate plasma at a low gas pressure, various measures are required. Less than,
A general technique for generating a high-density plasma using an inductively coupled plasma device will be described with reference to the drawings.

FIG. 1 is a schematic view of a general semiconductor device manufacturing apparatus using plasma, which is an etching apparatus using inductively coupled plasma.

In the figure, 1 is an induction coil, 2 is a high frequency power source applied to the induction coil 1, 3 is a lower electrode, 4 is a high frequency power source for applying high frequency power to the lower electrode 3, 5
Is an upper silicon electrode, 6 is a silicon substrate, 7 is a reaction chamber,
8 is a pressure control valve for controlling the pressure in the reaction chamber 7, 9 is an exhaust pump, 10 is a mass flow controller for controlling the flow rate of gas supplied to the reaction chamber 7, 11
Is a gas supply unit for supplying gas into the reaction chamber 7,
Is a heater for heating the upper silicon electrode 5, 13
Is a matcher for matching the high frequency power supplied to the induction coil 1, 14 is a matcher for matching the high frequency power supplied to the lower electrode 3, and 15 is a quartz electrode collar for supporting the silicon substrate 6. Show.

Then, the conventional high-density plasma discharge process is performed by the following procedure using the apparatus shown in FIG.

First, 100 sc of argon gas is supplied to the reaction chamber 7.
Introduced at a flow rate of cm, high frequency power 16
00 W is applied, and plasma is generated without applying high frequency power to the lower electrode 3. Here, a gas that easily emits electrons in a plasma state is called an electron positive gas, and a gas that hardly emits electrons is called an electron negative gas. After that, after holding that state for a few seconds,
The flow rate of argon gas is set to 0 sccm, and at the same time, C2 F6
The gas is introduced at a flow rate of 30 sccm, and the high frequency power applied to the induction coil 1 is increased to 2600W. After that, high frequency power is applied to the lower electrode 3 to draw ions from the plasma into the silicon substrate 6 to etch the silicon substrate 6.

[0009]

However, in the above-mentioned conventional manufacturing method, the plasma disappears at the moment of switching from the electron positive gas, argon gas, to the electron negative gas, fluorocarbon gas, and an apparatus error occurs, and further processing is performed. I couldn't do it.

The present invention has been made in view of the above circumstances, and an object thereof is to provide means for preventing extinction of plasma at a moment when a gas filling a reaction chamber is switched from an electron positive gas to an electron negative gas. An object of the present invention is to provide a semiconductor device manufacturing apparatus and a manufacturing method thereof, which can stably maintain a plasma generation state.

[0011]

According to a first method of manufacturing a semiconductor device of the present invention, a first step of placing a workpiece on an electrode in a reaction chamber and supplying an electron positive gas to the reaction chamber. And a third step of generating plasma in the reaction chamber, a fourth step of stopping the supply of electron positive gas to the reaction chamber while reducing the supply amount thereof, and the electron Before stopping the positive gas supply, supply the electron negative gas while increasing the supply amount ,
A fifth step of maintaining a high plasma density at the time of switching of, and a sixth step of applying a bias voltage to said workpiece, said as electron negative gas, chemical formula C _x F _y ( x and y are natural numbers, 2 ≦
A fluorocarbon gas represented by x ≦ y, 6 ≦ y ≦ 8) is used.

Accordingly, in the process of executing the sequence, the electron negative gas is introduced after the plasma is generated by the electron positive gas and before the supply of the electron positive gas is stopped. That is, even if electrons are attached to the electron negative gas where electrons are likely to be attached at the moment when the electron negative gas is introduced, the remaining electron positive gas compensates for the decrease in electron density. The electron density can be maintained high. Therefore, the plasma discharge is stably maintained without interruption.

A second method of manufacturing a semiconductor device according to the present invention is
A first step of placing the work piece on the electrode in the reaction chamber;
A second step of supplying an electron positive gas to the reaction chamber, a third step of generating plasma in the reaction chamber, and a fourth step of increasing the plasma density
A fifth step of stopping the supply of the electron positive gas to the reaction chamber while the plasma density is increased.
And step comprises a sixth step of supplying electrons negative gas into the reaction chamber, as the electron negative gas, chemical formula C _x F _{y (x, y} is
Flora represented by natural number, 2 ≦ x ≦ y, 6 ≦ y ≦ 8)
Carbon gas is used.

Thus, in the process of executing the sequence, after the plasma is generated with the electron positive gas, the electron negative gas is introduced with the plasma density further increased. That is, even if electrons are attached to the electron-negative gas, the decrease in electron density is compensated by the increase in electron density before that, so that the electron density in the plasma can be kept high. Therefore, the plasma discharge is stably maintained without interruption.

A third method of manufacturing a semiconductor device according to the present invention is
A first step of placing a work piece on a monopolar electrostatic chuck type electrode in the reaction chamber, a second step of supplying an electron positive gas to the reaction chamber, and a plasma generation in the reaction chamber. And a fourth step of electrically fixing the work piece on the electrode after the third step, and for cooling the work piece after the third step. A fifth step of supplying a gas, a sixth step of increasing the plasma density after the third step, and a step of supplying the electron positive gas to the reaction chamber with the plasma density increased. a seventh step of stopping the comprises an eighth step of supplying the electron negative gas into the reaction chamber, as the electron negative gas, chemical formula C _x F _{y (x, y} are natural
Number, 2 ≦ x ≦ y, 6 ≦ y ≦ 8)
Gas is used.

As a result, in the process of executing the sequence, after the plasma is generated by the electron positive gas, the workpiece is electrically fixed on the electrode, and then the cooling gas for the workpiece is supplied. Electron-negative gas is introduced with the plasma density increased. That is, even if electrons are attached to the electron-negative gas, the decrease in electron density is compensated by the increase in electron density before that, so that the electron density in the plasma can be kept high. Therefore, the plasma discharge is stably maintained without interruption. Further, it is possible to prevent problems such as thermal destruction of the resist pattern while using the electrodes of the monopolar type electrostatic chuck system.

[0017] than especially using inductive coupled plasma,
Utilizing the characteristics of the inductively coupled plasma, it becomes easy to generate high density plasma in the reaction chamber.

[0018] upper Symbol Electron positive gas, Ar gas, it is preferable to use at least any one of He gas and Xe gas.

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment of the method for manufacturing a semiconductor device of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a general semiconductor device manufacturing apparatus using plasma used in this embodiment, which is an etching apparatus using inductively coupled plasma.

In the figure, 1 is an induction coil, 2 is a high frequency power source applied to the induction coil 1, 3 is a lower electrode, 4 is a high frequency power source for applying high frequency power to the lower electrode 3, 5
Is an upper silicon electrode, 6 is a silicon substrate, 7 is a reaction chamber,
8 is a pressure control valve for controlling the pressure in the reaction chamber 7, 9 is an exhaust pump, 10 is a mass flow controller for controlling the flow rate of gas supplied to the reaction chamber 7, 11
Is a gas supply unit for supplying gas into the reaction chamber 7,
Is a heater for heating the upper silicon electrode 5, 13
Is a matcher for matching the high frequency power supplied to the induction coil 1, 14 is a matcher for matching the high frequency power supplied to the lower electrode 3, and 15 is a quartz electrode collar for supporting the silicon substrate 6. Show.

Then, the high-density plasma discharge process of this embodiment is performed by the following procedure using the apparatus shown in FIG.

FIG. 2 is a timing chart showing the sequence of the semiconductor device manufacturing apparatus of the present invention. That is, the hardware configuration of the semiconductor device manufacturing apparatus according to this embodiment is the same as the conventional configuration, but the software sequence for operating the apparatus is different. Generally, the electron negative gas has a larger electron attachment coefficient than the electron positive gas, and therefore the electron negative gas is less likely to generate plasma.Therefore, by proceeding with the manufacturing process in the sequence described below, the reaction Plasma can be stably generated in the chamber 7.

First, at time t1, the mass flow controller 10 controls the gas supply unit 11 to introduce argon gas as an electron positive gas at a flow rate of 100 sccm, and the gas pressure in the reaction chamber 7 is set to 5 m.
Keep at Torr. At the same time, 1600 in induction coil 1
A high frequency power of W is applied to generate plasma Plz in the reaction chamber 7.

Next, at time t2, the mass flow controller 10 changes the flow rate of the argon gas to, for example, 20 sccm.
/ Min. Gradually begins to decrease. At the same time, C _{2 is} supplied as an electron negative gas from the gas supply unit 11.
F ₆ gas (etching gas) is gradually increased from 0 sccm to 30 sccm at a rate of 6 sccm / min. On the other hand, the high frequency power applied to the induction coil 1 is also increased to 2600W.

Next, at time t3, 1300 is applied to the lower electrode 3.
A high frequency power of W is applied to start etching.

In this embodiment, after the plasma is generated with the electron positive gas, the electron negative gas is introduced before the supply of the electron positive gas is stopped. That is, even if electrons are easily attached to the electron negative gas at the moment when the electron negative gas is introduced, the electron density decrease is compensated by the remaining electron positive gas. Can be kept high. Therefore, the plasma discharge can be maintained without interruption.

However, in the present embodiment, C ₂ F ₆ gas was used as the electron negative gas, but the present invention is not limited to this embodiment, and SF ₆ gas or other electron negative gas may be used. A halogen gas such as Cl ₂ gas or O ₂ gas can be used. These gases are preferable for maintaining a high electron density because the mean free path is small.

FIG. 3 shows the relationship between the discharge electric field strength and the mean free path of various gases (Source: Electrostatic Handbook, p. 219, Table 8.10). As can be seen from this figure, if the type of gas is different, there is a difference in discharge electric field strength even for gases containing gas molecules having the same mean free path. Further, when the number of halogen atoms Cl to be replaced with hydrogen atoms in CH ₄ is increased, the electric field strength of discharge is increased. Therefore, as in the present embodiment, by using C ₂ F ₆ gas or the like having a large number of substitution atoms of hydrogen groups and halogen groups as the electron negative gas, the mean free path is small, that is, the discharge electric field strength is high. A high plasma can be generated. That is, the electron density in the plasma can be maintained higher.

(Second Embodiment) Next, a second embodiment will be described with reference to the drawings. However, also in this embodiment, since the etching apparatus using the inductively coupled plasma shown in FIG. 1 is used, the description of the hardware of the apparatus is omitted.

FIG. 4 is a timing chart showing a sequence of plasma processing (etching) in the second embodiment.

First, at time t11, argon gas as an electron positive gas is introduced at a flow rate of 100 sccm to maintain the gas pressure in the reaction chamber 7 at 5 mTorr. After that, a high frequency power of 1600 W was applied to the induction coil 1,
Plasma Plz is generated in the reaction chamber 7.

Next, at time t12, the high frequency power applied to the induction coil 1 is increased to 2200 W to increase the electron density in the plasma Plz.

Next, at time t13, the flow rate of the argon gas is set to 0 sccm / min. That is, the supply is stopped, and at the same time, C ₂ F ₆ gas (etching gas) is introduced as an electron negative gas at a flow rate of 30 sccm, Induction coil 1
The high-frequency power supplied to is further increased to 2600W.

Next, at time t14, 1300 is applied to the lower electrode 3.
A high frequency power of W is applied to start etching.

The following effects can be exhibited by the process of this embodiment.

FIG. 5 is a diagram showing changes in the electron density with respect to the high frequency power applied to the induction coil when argon gas is used as the electron positive gas. As can be seen from the figure, by increasing the high frequency power supplied to the induction coil 1 before changing the atmosphere in the reaction chamber 7 from the electron positive gas to the electron negative gas, it is possible to increase the electron density in the plasma. You can Therefore, it is possible to reliably prevent the plasma from disappearing when the gas is switched, and it is possible to stably maintain the plasma state without interruption.

As shown in FIG. 6, the electron density can also be increased by increasing the gas pressure in the reaction chamber 7. Therefore, in the above embodiment, the electron density in the plasma is increased by increasing the high frequency power applied to the induction coil 1 before switching the atmosphere in the reaction chamber 7 from the electron positive gas to the electron negative gas. Instead of increasing the high frequency power, the gas pressure in the reaction chamber 7 may be increased.

Further, it is not always necessary to stop the supply of the electron positive gas and then start the supply of the electron negative gas, and even if the supply periods of both gases overlap each other as in the first embodiment. Let's be good.

(Third Embodiment) Next, a third embodiment will be described with reference to the drawings.

FIG. 7 is a schematic diagram of a plasma etching apparatus using a monopolar electrostatic chuck electrode according to this embodiment.

In the figure, 1 is an induction coil, 2 is a high frequency power source applied to the induction coil 1, 3 is a lower electrode, 4 is a high frequency power source for applying high frequency power to the lower electrode 3, 5
Is an upper silicon electrode, 6 is a silicon substrate, 7 is a reaction chamber,
8 is a pressure control valve for controlling the pressure in the reaction chamber 7, 9 is an exhaust pump, 10 is a mass flow controller for controlling the flow rate of gas supplied to the reaction chamber 7, 11
Is a gas supply unit for supplying gas into the reaction chamber 7,
Is a heater for heating the upper silicon electrode 5, 13
Is a matcher for matching the high frequency power supplied to the induction coil 1, 14 is a matcher for matching the high frequency power supplied to the lower electrode 3, 15 is a quartz electrode collar for supporting the silicon substrate 6, 17 Is a DC power supply for supplying DC power for chucking the substrate 6 to the lower electrode 3, and 20 is a dielectric plate such as Al ₂ O ₃ , AlN, or polyimide. That is, the apparatus of this embodiment is configured to hold the substrate 6 by the static electricity generated between the plasma and the dielectric plate 30. As described above, the monopolar electrostatic chuck is configured to fix the silicon substrate 6 by utilizing the electrons generated from the plasma, and thus does not operate until the plasma is generated.

FIG. 8 is a timing chart of the sequence of the semiconductor device manufacturing apparatus according to the third embodiment of the present invention. The present embodiment relates to a sequence of plasma generation and timing of electrostatic chucking of the silicon substrate 6 when an apparatus using a monopolar electrostatic chuck electrode is used.

First, at time t21, argon gas as an electron positive gas is introduced at a flow rate of 100 sccm, and the gas pressure is maintained at 5 mTorr. After that, a high frequency power of 1600 W is applied to the induction coil 1 to generate plasma Plz.
To generate.

Next, at time t22, the high frequency power applied to the induction coil 1 is increased to 2200 W, the electron density is increased, the DC power source 17 of the electrostatic chuck is activated, and the helium gas for cooling the substrate is supplied. It is introduced at a pressure of 12 Torr. At this time, the order of each operation may be slightly changed.

Next, at time t23, the flow rate of the argon gas is set to 0 sccm / min., And at the same time, 30 sc of C ₂ F ₆ gas (etching gas) is used as an electron negative gas.
It is introduced at a flow rate of cm, and the high frequency power is further increased to 2600W.

Next, at time t24, high frequency power of 1300 W is applied from the high frequency power source 4 to the lower electrode 3 to start etching.

In the present embodiment, since the plasma is generated, the substrate 6 is electrically fixed by the DC power source 17 and then the cooling helium gas is caused to flow, and then the plasma density is increased. While effectively preventing a defect such as thermal destruction of the resist pattern formed on the substrate 6, it is possible to prevent the disappearance of plasma by the same operation as that of the second embodiment.

Also in this embodiment, as in the second embodiment, the electron density is increased by increasing the high frequency power applied to the induction coil 1, but the electron density is also increased by increasing the gas pressure. be able to.

Further, it is not always necessary to stop the supply of the electron positive gas and then start the supply of the electron negative gas, and even if the supply periods of both gases overlap to each other as in the first embodiment. Let's be good.

In the second and third embodiments, the high frequency power applied to the induction coil 1 is, for example, 16 in order to increase the plasma density of the electron positive gas.
Although the voltage is increased by one step from 00W to 2200W, it goes without saying that the same effect can be exhibited even when the voltage is increased in multiple steps.

Further, in each of the above-mentioned embodiments, only the case where the inductively coupled plasma is used has been described, but the present invention is not limited to such an embodiment, and an electron positive gas and an electron negative gas are used. This is applicable to general plasmas using

Further, it is not always necessary to stop the supply of the electron positive gas and then start the supply of the electron negative gas, and even if the supply periods of both gases are slightly overlapped as in the first embodiment. Let's be good.

[0060]

EFFECT OF THE INVENTION Semiconductor device manufacturing apparatus or manufacturing of the present invention
According to the method, it is possible to prevent the plasma discharge from being stopped.
Wear.

[Brief description of drawings]

FIG. 1 is a block diagram partially showing in cross section the configuration of a general plasma etching apparatus that can be used in the first and second embodiments.

FIG. 2 is a timing chart diagram of a sequence of the semiconductor device manufacturing apparatus according to the first embodiment.

FIG. 3 is a diagram showing the relationship between the discharge electric field strength and the mean free path of various gases.

FIG. 4 is a timing chart diagram of a sequence of the semiconductor device manufacturing apparatus according to the second embodiment.

FIG. 5 is a diagram showing changes in electron density with respect to high-frequency power applied to an induction coil in plasma using argon gas.

FIG. 6 is a diagram showing changes in electron density with respect to gas pressure in plasma using argon gas.

FIG. 7 is a block diagram showing a partial cross-sectional view of the configuration of a monopolar electrostatic chuck type plasma etching apparatus that can be used in the third embodiment.

FIG. 8 is a timing chart diagram of the sequence of the semiconductor device manufacturing apparatus according to the third embodiment.

[Explanation of symbols]

1 induction coil 2 high frequency power supply 3 Lower electrode 4 high frequency power supply 5 Upper silicon electrode 6 Silicon substrate 7 Reaction chamber 8 Pressure control valve 9 Exhaust pump 10 Mass flow controller 11 Gas supply section 12 heater 13 Matcher 14 Matcher 15 Quartz electrode color 17 DC power supply 20 Dielectric plate

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065

Claims (5)

(57) [Claims] 1. A first step of placing a workpiece on an electrode in a reaction chamber, a second step of supplying an electron positive gas to the reaction chamber, and a third step of generating plasma in the reaction chamber. And a fourth step of stopping the supply of the electron positive gas to the reaction chamber while reducing the supply amount thereof, and supplying the electron negative gas before the supply of the electron positive gas is stopped. Supply the gas while increasing the amount, and
The method includes a fifth step of maintaining a high Zuma density and a sixth step of applying a bias voltage to the workpiece, and the chemical formula of the electron negative gas is C
_{Expressed as x} F _y (x and y are natural numbers, 2 ≦ x ≦ y, 6 ≦ y ≦ 8)
A method for manufacturing a semiconductor device, characterized in that a fluorocarbon gas is used. 2. A first step of placing a workpiece on an electrode in a reaction chamber, a second step of supplying an electron positive gas to the reaction chamber, and a third step of generating plasma in the reaction chamber. And a fourth step of increasing the plasma density, and a fifth step of stopping the supply of the electron positive gas to the reaction chamber with the plasma density increased.
And a sixth step of supplying an electron negative gas to the reaction chamber, wherein the chemical formula is C as the electron negative gas.
_{Expressed as x} F _y (x and y are natural numbers, 2 ≦ x ≦ y, 6 ≦ y ≦ 8)
A method for manufacturing a semiconductor device, characterized in that a fluorocarbon gas is used. 3. A first step of placing a workpiece on a monopolar electrostatic chuck type electrode in a reaction chamber, a second step of supplying an electron positive gas to the reaction chamber, and the reaction. A third step of generating plasma in the chamber, a fourth step of electrically fixing the workpiece on the electrode after the third step, and a step of the third step after the third step. A fifth step of supplying a cooling gas for the workpiece, a sixth step of increasing the plasma density after the third step, and an electron to the reaction chamber with the plasma density increased. Seventh, stopping the supply of positive gas
And an eighth step of supplying an electron negative gas to the reaction chamber, wherein the chemical formula is C as the electron negative gas.
_{Expressed as x} F _y (x and y are natural numbers, 2 ≦ x ≦ y, 6 ≦ y ≦ 8)
A method for manufacturing a semiconductor device, characterized in that a fluorocarbon gas is used. 4. The method for manufacturing a semiconductor device according to claim 1, wherein inductively coupled plasma is used. 5. The method of manufacturing a semiconductor device according to claim 1 , wherein the electron positive gas is Ar gas,
A method of manufacturing a semiconductor device, wherein at least one of He gas and Xe gas is used.