JP3380846B2 - 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 method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device including a dry etching process for a silicon oxide film.

[0002]

2. Description of the Related Art As the size of semiconductor devices has been reduced, the contact dimensions have been reduced, but the thickness of an interlayer insulating film has not been reduced. Therefore, the ratio of the insulating film thickness to the contact size (aspect ratio) has been significantly increased. For this reason, it is important to establish a technique for forming a high aspect ratio contact hole by etching.

In order to etch a contact hole having a high aspect ratio, a dry etching technique by plasma using a fluorocarbon gas in which the ratio of fluorine to carbon contained in one molecule is relatively small has been actively researched and developed.

[0004]

However, when the contact hole is formed by using the plasma of fluorocarbon gas as described above, if the selection ratio with respect to the photoresist is increased, carbon and fluorine are mainly contained in the bottom of the contact hole. A polymer film is deposited. If a contact is formed by embedding a conductive member in the contact hole without removing the polymer film, a good contact cannot be formed. Therefore, a method of removing the polymer film using oxygen plasma has been proposed. However, the inventor of the present application has found that when the treatment with oxygen plasma is performed to remove the polymer film from the bottom of the contact hole, the contact resistance rather increases because of that.

The present invention has been made to solve the above problems, and an object of the present invention is to remove a polymer film deposited at the bottom of a contact hole while preventing an increase in contact resistance. It is to provide a method of manufacturing a semiconductor device including the above.

[0006]

[0007]

Manufacturing of the semiconductor device of the present invention
The manufacturing method is a substrate having a silicon region on at least the surface.
A step of sequentially forming an oxide film and a resist pattern thereon,
On the electrode provided in the reaction chamber of the plasma etching system
The substrate is placed in a gas containing fluorocarbon gas
Etch the oxide film using plasma generated from
To form a contact hole, and a bias voltage is applied to the substrate.
Oxygen plasma is generated in the reaction chamber without applying pressure.
And substantially eliminates the fluorine present in the oxygen plasma.
A fluorine removing treatment step of removing oxygen, and after the fluorine removing treatment step, oxygen plasma is generated in the reaction chamber while applying a bias voltage to the substrate, thereby removing the polymer film remaining on the substrate. a plasma treatment step for packaging free.

The switching from the fluorine removing treatment step to the oxygen plasma treatment step is preferably performed by applying a bias voltage to the electrodes while generating the oxygen plasma.

It is preferable that the step of removing fluorine further includes the step of supplying oxygen gas into the reaction chamber to control the pressure of the oxygen gas.

In the fluorine removing treatment step, oxygen gas may be supplied into the reaction chamber while being increased stepwise.

The emission spectrum intensity of specific atoms or molecules contained in the oxygen plasma may be measured, and the application timing of the bias voltage may be determined based on the measured emission spectrum intensity.

After the measured emission spectrum intensity becomes equal to or lower than a predetermined value, a high frequency voltage may be applied to the electrode, and thereby the bias voltage may be applied to the substrate.

The specific atom is fluorine, carbon, oxygen,
It is preferably carbon monoxide or carbon dioxide.

The emission spectrum intensity may be an emission from a fluorine atom having a wavelength of 685.6 nm.

It is also possible to measure the opening of a valve that controls the gas pressure in the reaction chamber and determine the application timing of the bias voltage based on the opening.

A high-frequency voltage may be applied to the electrode when the opening becomes constant, whereby the bias voltage may be applied to the substrate.

The voltage of the electrode may be measured, and the application timing of the bias voltage may be determined based on the measured voltage.

A high frequency voltage may be applied to the electrodes when the voltage drops to a certain level, thereby applying the bias voltage to the substrate.

When a bias voltage is applied to the substrate,
Indicia power density 8kW / m ² of the following high-frequency power to the electrode
It is preferable to add .

The plasma etching apparatus is preferably any one of an inductively coupled plasma etching apparatus, a helicon wave plasma etching apparatus, an electron cyclotron resonance plasma etching apparatus source and a dual frequency capacitively coupled plasma etching apparatus.

The fluorocarbon gas is CH ₂ F ₂ ,
The gas is preferably selected from the group consisting of CH ₃ F, C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ and C ₅ F ₈ .

The substrate may be a silicon substrate.

The step of etching the oxide film may be a step of forming a contact hole in the oxide film that reaches a silicon side layer formed in the silicon substrate.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The inventor of the present application has found that the cause of the increase in contact resistance is excessive etching of the diffusion layer, and the excessive etching causes fluorine remaining in the reaction chamber to reach the silicon substrate during oxygen plasma treatment. I found it going on. The inventors of the present application have also found that fluorine in oxygen plasma is supplied from a polymer film deposited on the inner wall of the reaction chamber.

This phenomenon will be described below with reference to FIGS. 1 (a) to 1 (d). 1A to 1D are model diagrams showing the reason why the diffusion layer is etched by fluorine in oxygen plasma.

FIG. 1A shows a cross section of the silicon substrate 4 in which the contact holes 5 are formed in the silicon oxide film 2 by dry etching. A resist pattern 1 is formed on the silicon oxide film 2, and polymer films 6 and 7 are deposited on the surface of the resist pattern 1 and the bottom of the contact hole 5, respectively. The polymer films 6 and 7 are formed in the process of etching the silicon oxide film. In order to remove the polymer film 6 from the bottom of the contact hole 5, oxygen plasma is generated in the reaction chamber of the etching device and a bias voltage is applied to the silicon substrate 4. Figure 1 (a)
The figure shows a state immediately after starting the discharge of oxygen plasma in order to remove the polymer film 6.

As shown in FIG. 1A, in addition to oxygen 8 and oxygen ions 9, fluorine 1 is contained in the oxygen plasma.
There are 0 and fluoride ion 11. Fluorine 10 is
It is considered that the fluorine adhering to the inner wall of the reaction chamber during the contact etching has separated from the inner wall.

[0028] When a bias voltage is applied to the silicon substrate 4, a polymer film 6 and 7 me by the oxygen 8 and the oxygen ions 9 starts to be etched. As shown in FIG. 1B, when the polymer film 6 at the bottom of the contact hole 5 is completely removed, fluorine 10 and fluorine ion 1
The etching of the diffusion layer 3 by 1 is started.

While the oxygen plasma is being generated, the oxygen gas is continuously supplied to the reaction chamber of the etching apparatus and the gas is continuously exhausted from the reaction chamber. for that reason,
The fluorine in the reaction chamber gradually decreases.

As shown in FIG. 1C, when fluorine is removed from the oxygen plasma, the etching of the diffusion layer is stopped and only the etching of the polymer film 7 is advanced by oxygen 8 and oxygen ions 9. In this way, as shown in FIG. 1D, the polymer film 7 is also completely removed.

As described above, accompanying the step of removing the polymer film 6 at the bottom of the contact hole 5 using oxygen plasma, fluorine 10 and fluorine ions 11 in oxygen plasma deeply etch the diffusion layer 3. . Therefore, the contact resistance is significantly increased.

FIG. 2 shows the relationship between the etching amount of the diffusion layer and the discharge time of oxygen plasma. The negative value on the vertical axis indicates the thickness of the polymer film at the bottom of the contact hole, and the positive value indicates the etching amount of the diffusion layer.
As is clear from FIG. 2, the diffusion layer is rapidly etched for a while after the discharge of oxygen plasma is started.

In the present invention, fluorine is removed from the oxygen plasma to prevent an increase in contact resistance.

An embodiment of the method for manufacturing a semiconductor device of the present invention will be described below.

(First Embodiment) First, a dry etching apparatus used for carrying out the present invention will be described with reference to FIG. The device shown in FIG.
It is an etching apparatus using inductively coupled plasma. The inductively coupled plasma device has recently attracted attention as a device that can generate high density plasma with a relatively low gas pressure.

The apparatus of FIG. 3 includes a reaction chamber (reaction chamber) 37 in which a dry etching process is performed.
The outer wall of the reaction chamber 37 is surrounded by an induction coil 31 for forming plasma in the reaction chamber 37. The induction coil 31 is connected to a high frequency power supply 32 and receives high frequency power from the high frequency power supply 32.

A lower electrode 33 supporting a substrate to be processed (silicon substrate 36) is provided below the reaction chamber 37, and the lower electrode 33 is provided with a high frequency power source 3 via a matcher (not shown).
4 and is supplied with high frequency power from the high frequency power supply 34. In this dry etching apparatus, the plasma generating power source 32 and the silicon substrate voltage applying power source 34 can be controlled independently.

A quartz ring (not shown) is arranged in the peripheral region of the upper surface of the lower electrode 33. An upper electrode 35 made of, for example, silicon is provided above the reaction chamber 37. The upper electrode 35 is grounded.

A pressure control valve 38, a turbo molecular pump 39 and a dry pump 40 are inserted between the exhaust port of the reaction chamber 37 and the outside. The pressure control valve 38 is
The pressure in the reaction chamber 37 may be, for example, 1 mTorr to 100
It operates to maintain a constant value within the range up to mTorr.

Gas to be turned into plasma (etching gas)
Various gas cylinders 41 through a mass flow (not shown).
Is supplied into the reaction chamber 37. When a sufficient amount of etching gas is supplied to the reaction chamber 37, the induction coil 31 disposed on the outer wall of the reaction chamber 37 is connected to the induction coil high-frequency power source 3.
High frequency power is applied from 2 to generate plasma in the reaction chamber 37. In this embodiment, the induction coil 31 has 1000
High-frequency power of W to 3000 W is applied and the density is 10 ¹¹ cm.
^-High density plasma of ³ or more can be formed.

After the plasma is stably formed, high frequency power is applied from the high frequency power source 34 to the lower electrode 33 to apply a self-bias voltage to the silicon substrate 36,
Thereby, the silicon substrate 36 is irradiated with positively charged ions from the plasma. In this way, the reactive plasma etching process proceeds and the film to be etched formed on the silicon substrate 36 is etched. The power density of the high frequency power is preferably 8 kW / m ² or less.

Next, in addition to FIG. 3, FIG. 4 and FIG.
The method for manufacturing the semiconductor device according to the present embodiment will be described with reference to (a) and (b).

First, as shown in FIG. 5A, BPSG (BoroPh) is formed on a silicon substrate 54 (reference numeral "36" in FIG. 3) by chemical vapor deposition.
After depositing the osphoSilicate Glass) film 52, a photoresist pattern 51 is formed on the BPSG film 52 by a known lithography technique. The photoresist pattern 51 is formed to have an opening 51a that defines the shape and position of the contact hole to be formed. The opening 51a is formed so as to be located above the impurity diffusion region 53 provided on the surface of the silicon substrate 54. The surface of the impurity diffusion region 53 may be formed of a silicide layer.

Next, after the silicon substrate 36 is placed on the lower electrode 33 provided in the reaction chamber 37 of the plasma etching apparatus of FIG. 3, a contact etching step (step S1 of FIG. 4) is performed. Referring to FIG.
The contact etching process will be described in detail. First, before starting the etching, an etching gas containing a fluorocarbon gas as a main component is supplied from the gas cylinder 41 to the reaction chamber 3
7 is introduced into the coil 7, and high frequency power is applied to the coil 31 by the high frequency power supply 32. As the etching gas, for example, C
_A mixed gas of ₄ F ₈ / CH ₂ F ₂ / Ar / CO / O ₂ is used. By applying the high frequency power, plasma is generated in the reaction chamber 37. After that, a high frequency power is applied to the lower electrode 33 by the high frequency power supply 34, and thereby a self-bias voltage is applied to the silicon substrate 36. Silicon substrate 3
Since 6 is charged to a negative potential with respect to the plasma, positively charged ions in the plasma irradiate the silicon substrate.

Referring again to FIG. Sheet of the BPSG film 52 on the silicon substrate 54, a photoresist pattern 51
The portion not covered with (the portion exposed through the opening 51a) is etched, and as shown in FIG.
A contact hole 55 is formed in the PSG film 52.
The contact hole 55 reaches the impurity diffusion region 53 of the silicon substrate 54. Immediately after the contact hole 55 is opened, a polymer film 56 containing carbon and fluorine as main components is formed on the bottom of the contact hole 55. The thickness of the polymer film 56 is considered to be about 10 to 200 nm.

Next, step S2 of FIG. 4 is executed. That is, the oxygen gas is introduced into the reaction chamber 37 from the gas cylinder 41 into the oxygen gas reaction chamber 37. Then, the oxygen gas pressure in the reaction chamber 37 is controlled by adjusting the opening degree of the pressure control valve 38 (step S3 in FIG. 4).

In step S4, the high frequency power source 32 is applied to the coil 31 while the high frequency power source 34 does not apply the high frequency power to the lower electrode 33 on which the silicon substrate 36 is installed.
By applying high frequency power, oxygen plasma is generated in the reaction chamber 37.

Using this oxygen plasma, the polymer film deposited on the bottom of the contact hole is removed, and fluorine attached to the side wall of the reaction chamber is removed (step S5). In this embodiment, this fluorine removal step is continued for 40 seconds.

In step S6, a high frequency power source 34 applies high frequency power to the lower electrode 33 on which the silicon substrate 36 is placed. Then, a self-bias voltage is applied to the silicon substrate 36, and the silicon substrate 36 attracts oxygen ions from oxygen plasma. Thus, the polymer film deposited on the surface of the photoresist pattern is completely removed (step S7).

As described above, according to this embodiment, the bias voltage is not applied to the silicon substrate for 40 seconds immediately after the start of oxygen plasma generation, and the bias voltage is applied to the silicon substrate after 40 seconds have elapsed. The reason for doing this will be described in detail below.

The graph of FIG. 6 shows the relationship between the discharge time of oxygen plasma formed for the fluorine removal step and the emission intensity of fluorine contained in the oxygen plasma (emission wavelength: 685.6 nm). As you can see from the graph in Figure 6,
The emission intensity of fluorine decays with the passage of time after the start of discharge, and the emission intensity becomes zero (below the measurement limit) 40 seconds after the start of discharge. That is, it can be seen that fluorine in the oxygen plasma was substantially removed 40 seconds after the start of discharge.

The graph of FIG. 7 shows the relationship between the etching amount of the diffusion layer 53 and the discharge time of oxygen plasma. In this graph, the negative value on the vertical axis indicates the thickness of the polymer film at the bottom of the contact hole, and the positive value indicates the diffusion layer 5.
The etching amount of 3 is shown. From FIG. 7, it can be seen that the polymer film is almost completely removed 40 seconds after the start of the oxygen plasma discharge.

From the above, it can be seen that the polymer film is removed about 40 seconds after the oxygen plasma is generated, and the fluorine in the reaction chamber is also removed at the same time.
After this time, even if a bias voltage is applied to the silicon substrate, the diffusion layer 53 is not etched by fluorine and fluorine ions. In this embodiment, the substrate bias is applied 40 seconds after the start of the oxygen plasma discharge, but as can be seen from FIG. 7, the etching amount of the diffusion layer is suppressed to about 10 nm even 80 seconds after the start of the discharge. Has been.

The graph of FIG. 8 shows the relationship between the contact resistance and the etching amount of the diffusion layer 53. When the etching amount of the diffusion layer 53 is suppressed to about 10 nm as in this embodiment, no increase in contact resistance is observed. On the other hand, when the bias voltage is applied to the substrate immediately after the start of the oxygen plasma discharge, the diffusion layer becomes 4 times when the treatment necessary for removing the polymer film (about 40 seconds) is performed.
It can be seen from FIG. 8 that the contact resistance increases remarkably because the film is etched by about 0 nm (FIG. 2).

Thus, it is understood that the etching of the diffusion layer is suppressed by interrupting the application of the bias power to the electrode on the substrate side until the fluorine in the oxygen plasma is removed. Below, the reason is shown in FIG.
It will be described in detail with reference to (d).

FIG. 9A shows a cross section of the silicon substrate 54 in a state where the contact hole 55 is formed in the silicon oxide film 52 by dry etching. A photoresist pattern 51 is formed on the silicon oxide film 52, and polymer films 56 and 57 are deposited on the bottom of the contact hole 55 and on the resist pattern 51, respectively. Oxygen plasma is generated in the reaction chamber in order to decompose the polymer film, which is a fluorine supply source on the inner wall of the reaction chamber, and remove fluorine from the reaction chamber. As described above, the bias voltage is not applied to the silicon substrate 54 for a while after the generation of oxygen plasma.

As shown in FIG. 9A, fluorine 60 exists in addition to oxygen 58 in the oxygen plasma. Since no bias voltage is applied to the silicon substrate 54, oxygen 58 etches the polymer film 57 on the substrate surface and the polymer film 56 on the bottom of the contact hole (0 to 35 seconds after the start of discharge).

As shown in FIG. 9B, when the polymer film 56 at the bottom of the contact hole 55 is completely removed by the oxygen 58 in the oxygen plasma, the slightly remaining fluorine 10 etches the diffusion layer 3. Start (3 after starting discharge)
5 to 40 seconds).

Even after the polymer film 56 at the bottom of the contact hole 55 is removed, the polymer film 57 deposited on the resist pattern 51 is not yet completely removed. A bias voltage is applied to the silicon substrate 54 in order to quickly remove the polymer film 57. If no bias voltage is applied, it takes a very long time to remove the polymer film 57. When a bias voltage is applied to the silicon substrate 54, the polymer film 57 is quickly removed by oxygen 58 and oxygen ions 59. At this time, since the fluorine 10 in the oxygen plasma has been exhausted and has already disappeared, the diffusion layer 53 is not etched by the fluorine 10 and fluorine ions.

In the case of the present embodiment, when 80 seconds have elapsed from the start of oxygen plasma discharge, the polymer film 57 and the resist pattern 51 are completely removed, but the diffusion layer 53 is removed, as shown in FIG. 9D. Only 10 nm is etched.

As described above, according to the present embodiment, the silicon substrate 54 is maintained while fluorine is present in the oxygen plasma.
No bias voltage is applied to the substrate (fluorine removal treatment step), and after the fluorine is exhausted, the bias voltage is applied to the silicon substrate 54. In this way, the etching of the diffusion layer 53 due to fluorine and fluorine ions can be suppressed, and an increase in contact resistance can be prevented. Further, the polymer film 57 on the resist pattern 51 and the resist pattern 51 can also be removed in a short time.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The dry etching process of this embodiment is also performed using the apparatus shown in FIG.

First, a processing procedure diagram in this embodiment will be described with reference to FIG.

In step S101, contact holes are formed.

In step S102, oxygen gas is introduced into the reaction chamber 37.

In step S103, the oxygen gas pressure is controlled by adjusting the opening of the pressure control valve 38.

In step S104, the high frequency power is applied to the coil 31 by the high frequency power source without applying the high frequency power to the lower electrode 33 on which the silicon substrate 36 is installed, and oxygen plasma is generated.

In step S105, the flow rate of oxygen gas is increased stepwise.

In step S106, the fluorine attached to the inner wall of the reaction chamber 37 and the polymer film deposited on the bottom of the contact hole are removed.

In step S107, high frequency power is applied to the lower electrode 33 supporting the silicon substrate 36, and thereby a bias voltage is applied to the silicon substrate 36. As a result, the oxygen ions of the oxygen plasma are transferred to the silicon substrate 36.
To irradiate.

In step S108, the polymer film deposited on the photoresist surface is completely removed.

Next, the method of generating oxygen plasma in this embodiment will be described in detail.

FIG. 11 shows changes in the flow rate of oxygen gas and changes in reflected power with respect to the discharge time of oxygen plasma. The reflected power is 25 in the induction coil 31 of the device of FIG.
This is a value when a high frequency power of 00 W is applied. Figure 11
Indicates the data when the flow rate of the oxygen gas was kept constant at 300 sccm from the beginning with a black circle, and the data when the flow rate of the oxygen gas was increased stepwise from 150 sccm with a white circle.

When high frequency power is applied while introducing oxygen gas with a flow rate of 300 sccm into the reaction chamber, the reflected power becomes 100 W and no matching can be obtained. For this reason, the oxygen plasma cannot be maintained, and the discharge ends about 10 seconds after the start of the discharge. On the other hand, 150 scc
High-frequency power was applied at the same time when oxygen gas with a low flow rate of m was introduced, and the oxygen gas flow rate was gradually increased to 300 sccm.
When a high flow rate of oxygen gas is introduced (this embodiment), matching is achieved, and the reflected power is reduced to 5 W or less. Therefore, oxygen plasma is stably generated and maintained.

FIG. 12 shows changes in the emission intensity of fluorine with respect to the discharge time of oxygen plasma. The data shown in FIG. 12 is obtained by installing an emission analyzer in the dry etching apparatus shown in FIG. 3 and measuring the wavelength of fluorine (685.6n) in oxygen plasma.
It was obtained by measuring the emission intensity of m). As can be seen from FIG. 12, when the oxygen gas flow rate is 200 sccm, it takes 50 seconds for the fluorine to decrease after the start of discharge. The strength is sufficiently attenuated. That is, when the oxygen gas flow rate is 300 sccm,
Fluorine in the oxygen plasma is removed 40 seconds after the start of discharge. From this, it is understood that the fluorine on the side wall of the reaction chamber can be removed faster by performing the discharge while supplying a larger flow rate of oxygen gas into the reaction chamber.

FIG. 13 shows changes in the etching amount of the diffusion layer with respect to the discharge time of oxygen plasma. In the graph of FIG. 13, the negative value on the vertical axis indicates the thickness of the polymer film, and the positive value indicates the etching amount of the diffusion layer.

When the flow rate of oxygen gas is 200 sccm, fluorine on the inner wall of the reaction chamber disappears 50 seconds after the start of discharge, so that bias power is not applied for 35 to 50 seconds after the start of discharge. However, even in this case, the diffusion layer is etched by 18 nm by fluorine. 50 after the start of discharge
After a lapse of seconds, a bias power is applied to remove the polymer film on the substrate surface.

When the oxygen gas flow rate is 300 sccm, the fluorine on the inner wall of the reaction chamber disappears 40 seconds after the start of discharge, so that the bias power is not applied for 35 to 40 seconds after the start of discharge. In this case, the diffusion layer is 5n
m etched. After 40 seconds have passed from the start of discharge, the bias film is applied to remove the polymer film on the substrate surface.

From the above, it is understood that when the flow rate of oxygen gas is large, the fluorine on the side wall of the reaction chamber is removed in a short time, and the post-treatment time by oxygen plasma after contact hole etching can be shortened. As a result, etching of the diffusion layer can be suppressed, and an increase in contact resistance can be suppressed.

According to the present embodiment, by gradually increasing the flow rate of oxygen gas, the reflected wave of the high frequency power applied to the coil 31 is suppressed, and stable generation and maintenance of plasma is performed with high flow rate oxygen gas. it can. Further, by using the high flow rate oxygen gas, fluorine on the side wall in the reaction chamber 37 can be removed with a large amount of oxygen in a short time, so that the oxygen plasma treatment time after contact etching can be shortened. As a result, etching of the diffusion layer can be suppressed and the contact resistance can be reduced.

(Third Embodiment) A dry etching apparatus used in this embodiment will be described with reference to FIG. The apparatus of FIG. 14 has basically the same structure as the dry etching apparatus of FIG. 3, except that the apparatus of FIG. 14 has an optical fiber 72, an optical emission analyzer 73, a signal line 74, and a central processing unit. The device 75 is further provided.

The optical fiber 72 has a function of extracting the light emitted from the plasma in the reaction chamber 37 to the outside.
The emission analyzer 73 can receive the light emitted from the plasma via the optical fiber 72 and measure the emission intensity of the spectrum in a specific wavelength range. The central processing unit 75 performs a calculation based on the output of the emission analysis device 73, and when the emission intensity within the specific wavelength range changes to a predetermined range, provides a necessary signal to the high frequency power supply 34 via the signal line 74. .

In this embodiment, after contact etching is performed by the apparatus shown in FIG. 14, first, oxygen gas is introduced into the reaction chamber 37 from the gas cylinder 41, and high frequency power is applied to the coil 31 by the high frequency power source 32 to generate plasma. To generate.
Next, the light collected by the optical fiber 72 is analyzed by the emission analyzer 7
The spectrum is measured at 3 and the emission intensity of fluorine is measured. The central processing unit 75 determines the time when the emission intensity of fluorine drops below the measurement limit, and at that time sends a signal for starting the operation of the high frequency power supply 34 to the high frequency power supply 34 via the signal line 74. Thus, the high frequency power supply 34 starts operating and applies high frequency power to the lower electrode 33. As a result, the etching species in the plasma are drawn into the silicon substrate 36, and the polymer film on the silicon substrate 36 is etched. The central processing unit 75 is programmed to keep the high frequency power supply 34 off while the emission of fluorine is detected.

The processing procedure in this embodiment will be described with reference to FIG.

First, in step S151, contact holes are formed.

In step S152, oxygen gas is introduced into the reaction chamber 37.

In step S153, the oxygen gas pressure is controlled by adjusting the opening of the pressure control valve 38.

In step S154, the high frequency power is applied to the coil 31 by the high frequency power supply without applying the high frequency power to the lower electrode 33 on which the silicon substrate 36 is installed to generate oxygen plasma.

In step S155, the fluorine (eg, wavelength 685.6 nm) in the oxygen plasma is monitored by the emission analyzer 73 while removing the fluorine attached to the inner wall of the reaction chamber 37 and the polymer film deposited on the bottom of the contact hole. To do.

[0090] In step S156, if not detect the emission intensity of fluorine, in step S157, the lower electrode 33 for supporting the silicon substrate 36 by applying a high frequency power, thereby a bias voltage to the silicon substrate 36 mark
Add As a result, the silicon substrate 36 is irradiated with oxygen ions of oxygen plasma.

In step S158, the polymer film deposited on the photoresist surface is completely removed.

FIG. 16 shows the relationship between the discharge time of oxygen plasma, the emission intensity of fluorine (wavelength 685.6 nm) and the amount of diffusion layer etching. In the lower part of FIG. 16, the negative value on the vertical axis indicates the thickness of the polymer film, and the positive value indicates the etching amount of the diffusion layer.

According to this embodiment, after confirming that the emission intensity of fluorine is sufficiently attenuated, the bias voltage is applied to the silicon substrate thereafter. In this case, it can be seen from FIG. 16 that the diffusion layer is hardly etched. Further, since the bias power supply is turned on / off by the signal of the emission intensity of fluorine, the substrate processing by oxygen plasma can be started at the optimum timing even when the time required for removing fluorine changes.

As described above, according to this embodiment, the start timing of the bias voltage applied to the substrate is adjusted based on the emission intensity of fluorine, so that fluorine can be removed efficiently and reliably.

In this embodiment, the emission spectrum of fluorine is used as the emission spectrum to be measured, but the emission spectrum of carbon and carbon monoxide may be used. During the contact etching, a polymer film is deposited on the side wall of the reaction chamber in a combined state of C _x and C _x F _y.
(4) to (4) and then exhausted.

XO + C _X F _Y → XCO + YF (1) XO + C _X F _Y → XCO + YF → XC + XO + YF (2) O + C _X → CO + C _X-1 (3) O ₂ + C _X → CO ₂ + C _X-1 (4) Here, X and Y are natural numbers.

By measuring the emission spectrum of any one of fluorine, carbon, oxygen, carbon monoxide and carbon dioxide, it can be determined whether the polymer film deposited on the side wall of the reaction chamber has been removed. If the polymer film deposited on the side wall of the reaction chamber is removed and the carbon, oxygen, carbon monoxide, carbon dioxide, etc. that compose the polymer film are reduced from the reaction chamber to below the measurement limit, then fluorine is also removed from the reaction chamber. It can be determined that it has been done.

Since the emission at the wavelength of 685.6 nm has the highest intensity in the emission spectrum of fluorine, the emission at the wavelength of 685.6 nm was measured in this embodiment. It goes without saying that you can measure. Fourth Embodiment A dry etching apparatus used in this embodiment will be described with reference to FIG. The apparatus of FIG. 17 has basically the same structure as the dry etching apparatus of FIG. 3 except that the apparatus of FIG. 17 further includes a signal line 82 and a central processing unit 83. is there.

In this embodiment, after performing contact etching with the apparatus shown in FIG. 17, first, oxygen gas is introduced into the reaction chamber 37 from the gas cylinder 41, and high frequency power is applied to the coil 31 by the high frequency power supply 32 to generate plasma. To generate.
Next, the opening degree of the pressure control valve 38 is measured, and the time point when the opening degree of the pressure control valve 38 becomes constant is determined by the central processing unit 83, and the operation start signal of the high frequency power supply 34 is sent at that time point. It is sent to the high frequency power supply 34. Thus, the high frequency power supply 34 starts operating and applies high frequency power to the lower electrode 33. As a result, the etching species (positively charged ions) in the plasma are drawn into the silicon substrate 36, and the polymer film on the silicon substrate 36 is quickly etched.

The processing procedure in this embodiment will be described with reference to FIG.

First, in step S181, contact holes are formed.

In step S182, oxygen gas is introduced into the reaction chamber 37.

In step S183, the oxygen gas pressure is controlled by adjusting the opening of the pressure control valve 38.

In step S184, the high frequency power is applied to the coil 31 by the high frequency power supply 32 without applying the high frequency power to the lower electrode 33 on which the silicon substrate 36 is installed to generate oxygen plasma.

In step S185, the opening of the pressure control valve 38 is monitored while removing the fluorine attached to the inner wall of the reaction chamber 37 and the polymer film deposited on the bottom of the contact hole.

[0106] In step S186, if detecting that the opening became constant, at step S187, the lower electrode 33 for supporting the silicon substrate 36 by applying a high frequency power, thereby a bias voltage to the silicon substrate 36 mark
Add As a result, the silicon substrate 36 is irradiated with oxygen ions of oxygen plasma.

In step S188, the polymer film deposited on the photoresist surface is completely removed.

FIG. 19 shows the relationship between the discharge time of oxygen plasma, the opening of the pressure control valve 38, and the diffusion layer etching amount. In the lower part of FIG. 19, the negative value on the vertical axis indicates the thickness of the polymer film, and the positive value indicates the etching amount of the diffusion layer.

In this embodiment, a bias voltage is applied to the silicon substrate 36 after the opening of the pressure control valve 38 becomes constant. As will be described later, the pressure control valve 3
The time when the opening degree of 8 becomes constant corresponds to the time when there is no fluorine in the reaction chamber 37. It can be seen from FIG. 19 that according to the present embodiment, the diffusion layer is hardly etched.

Next, the reason why the constant opening of the pressure control valve 38 corresponds to the exhaustion of fluorine in the reaction chamber will be explained.

When oxygen plasma is generated after the contact etching, fluorine attached to the sidewall of the reaction chamber 37 is released into the oxygen plasma. As a result, the pressure inside the reaction chamber 37 increases. Then, in order to control the pressure to be constant, the opening degree of the pressure control valve 38 becomes large. afterwards,
When the amount of fluorine gradually decreases, the pressure in the reaction chamber 37 gradually decreases. Along with this, the opening degree of the pressure control valve 38 gradually decreases and becomes constant over time. From this, it is understood that the change in the amount of fluorine can be monitored by the opening degree of the pressure control valve 38.

In this embodiment, the change in the amount of fluorine is monitored by the opening of the pressure control valve 38, and the bias voltage is detected when the central processing unit 83 detects that the opening of the pressure control valve 38 has become constant. Since fluorine is started to be applied to the silicon substrate, fluorine can be removed efficiently. Further, since the ON / OFF of the bias voltage high frequency power source is controlled based on the opening degree of the pressure control valve 38, the substrate processing by oxygen plasma can be started at an optimum timing even when the time required for fluorine removal fluctuates.

(Fifth Embodiment) A dry etching apparatus used in this embodiment will be described with reference to FIG. The device of FIG. 20 has basically the same structure as the dry etching device of FIG. 3, except that the device of FIG.
3 and the central processing unit 94 are further provided.

In this embodiment, after performing contact etching with the apparatus shown in FIG. 20, first, oxygen gas is introduced into the reaction chamber 37 from the gas cylinder 41, and high frequency power is applied to the coil 31 by the high frequency power source 32 to generate plasma. To generate.
Next, the voltage of the lower electrode 33 is measured by the voltmeter 92, and the central processing unit 83 determines when the measured voltage becomes constant. It is sent to the high frequency power source 34 via. Thus
The high frequency power supply 34 starts operating and applies high frequency power to the lower electrode 33. As a result, the etching species (positively charged ions) in the plasma are drawn into the silicon substrate 36, and the polymer film on the silicon substrate 36 is etched.

The processing procedure in this embodiment will be described with reference to FIG.

First, in step S211, contact holes are formed.

In step S212, oxygen gas is introduced into the reaction chamber 37.

In step S213, the oxygen gas pressure is controlled by adjusting the opening of the pressure control valve 38.

In step S214, the high frequency power is applied to the coil 31 by the high frequency power supply 32 without applying the high frequency power to the lower electrode 33 on which the silicon substrate 36 is installed to generate oxygen plasma.

In step S215, the voltage of the lower electrode 33 is monitored while removing the fluorine attached to the inner wall of the reaction chamber 37 and the polymer film deposited on the bottom of the contact hole.

When the voltage of the lower electrode 33 becomes constant in step S216, high-frequency power is applied to the lower electrode 33 in step S217, thereby applying a bias voltage to the silicon substrate 36. As a result, the silicon substrate 36 is irradiated with oxygen ions of oxygen plasma.

In step S218, the polymer film deposited on the photoresist surface is completely removed.

Next, the measurement result of the etching amount of the diffusion layer when the dry etching method according to the present embodiment is performed will be shown.

FIG. 22 shows the relationship between the discharge time of oxygen plasma and the voltage of the lower electrode 33 and the etching amount of the diffusion layer.

In the lower part of FIG. 22, the negative value on the vertical axis indicates the thickness of the polymer film, and the positive value indicates the etching amount of the diffusion layer. In this embodiment, a bias voltage is applied to the silicon substrate 36 after the voltage of the lower electrode 33 becomes constant. As will be described later, the time when the voltage of the lower electrode 33 becomes constant coincides with the time when fluorine in the reaction chamber 37 disappears. It can be seen from FIG. 22 that according to the present embodiment, the diffusion layer is hardly etched.

Next, the reason why the case where the voltage of the lower electrode 33 becomes constant corresponds to the case where the fluorine in the reaction chamber 37 disappears will be explained.

When oxygen plasma is generated after the contact etching, fluorine attached to the side wall inside the reaction chamber 37 is released into the oxygen plasma. As a result, the pressure of the plasma in the reaction chamber 37 increases and the plasma density increases. The higher the plasma density, the lower the plasma resistance.
Assuming that the upper electrode 35 is ground and the plasma is a resistor and the current flowing into and out of the lower electrode 33 is constant, the voltage applied from the high frequency power source 34 to the plasma increases as the resistance of the plasma decreases. On the contrary,
When the fluorine is exhausted and the pressure of the plasma is lowered, the plasma density is reduced and the voltage applied to the plasma is lowered. Therefore, the voltage of the lower electrode 33 shows a high value immediately after the fluorine is released into the oxygen plasma, and then decreases as the fluorine is exhausted. When the fluorine is completely exhausted from the reaction chamber 37, the voltage of the lower electrode 33 becomes constant. From this, it is understood that the change in the amount of fluorine can be monitored by the voltage of the lower electrode 33. When detecting that the voltage of the lower electrode 33 has become constant, the central processing unit 94 of the present embodiment starts the operation of the high frequency power supply 34 and starts the application of the bias voltage to the silicon substrate 36.

As described above, according to this embodiment, the voltage of the lower electrode 33 is measured, and the operation of the high frequency power supply 34 is started in response to the signal that the voltage becomes constant, whereby the bias voltage to the silicon substrate is set. To start applying.
For this reason, fluorine can be removed efficiently, and even if the time required for fluorine removal fluctuates, the ion irradiation treatment of the substrate with oxygen plasma can be started at the optimum timing.

Although the silicon substrate is used as the substrate to be processed in each of the above embodiments, the application of the present invention is not limited to this. The manufacturing method of the present invention is also effective when manufacturing a semiconductor device using an insulating substrate having a silicon layer formed on its surface, for example, a glass substrate having a polycrystalline silicon film formed thereon. "Semiconductor device" in the present specification
Are not limited to those having a semiconductor substrate as an indispensable element.

[0130]

According to the present invention, a substrate is placed on an electrode provided in a reaction chamber of a plasma etching apparatus, and a plasma is generated from a gas containing a fluorocarbon gas while applying a bias voltage to the substrate. Since it includes a film etching step and a fluorine removal treatment step of removing fluorine from the reaction chamber by generating oxygen plasma in the reaction chamber without applying a bias voltage to the substrate, oxide film etching is performed. During the process, the polymer adhering to the inner wall of the reaction chamber can be decomposed and the fluorine contained therein can be removed from the reaction chamber. As a result, the silicon surface exposed by the etching of the oxide film is not likely to be excessively etched by the fluorine supplied from the polymer on the inner wall of the reaction chamber. Therefore, after the oxide film is etched, it is possible to perform the substrate surface treatment with oxygen plasma while applying a bias voltage to the substrate. Therefore, if the contact holes are formed by the oxide film etching of the present invention, it is possible to form fine contacts with low resistance with good reproducibility.

The electrode for supporting the substrate while generating oxygen plasma is switched from the fluorine removing process for removing the fluorine from the reaction chamber to the oxygen plasma treating process for removing the polymer remaining on the substrate. If the bias voltage is applied to the both steps, both steps can be continuously and swiftly executed while maintaining stable oxygen plasma.

Fluorine is removed from the reaction chamber by measuring the emission spectrum intensity of a specific atom or molecule contained in oxygen plasma and determining the bias voltage application timing based on the measured emission spectrum intensity. Efficient processing can be performed in accordance with the timing of the execution.

The opening of the valve for controlling the gas pressure in the reaction chamber was measured, the application timing of the bias voltage was determined based on the opening, and the voltage of the electrode supporting the substrate was measured. Also, by determining the application timing of the bias voltage based on the voltage applied, it is possible to perform efficient processing in accordance with the timing when fluorine is removed from the reaction chamber.

[Brief description of drawings]

FIG. 1A to FIG. 1D are views for explaining the principle of etching a diffusion layer with fluorine.

FIG. 2 is a graph showing the relationship between the discharge time of oxygen plasma and the etching amount of the diffusion layer.

FIG. 3 is a schematic view of a plasma etching apparatus used in the first and second embodiments of the present invention.

FIG. 4 is a diagram illustrating processing steps of the method for manufacturing a semiconductor device according to the first embodiment of the present invention.

5A and 5B are cross-sectional views showing an etching process for forming a contact hole.

FIG. 6 is a graph showing the relationship between the discharge time of oxygen plasma and the emission intensity of fluorine.

FIG. 7 is a graph showing the relationship between the discharge time of oxygen plasma and the etching amount of the diffusion layer.

FIG. 8 is a graph showing the relationship between the etching amount of the diffusion layer and the contact resistance.

9A to 9D are views for explaining the principle that the diffusion layer is not etched in the first embodiment of the present invention.

FIG. 10 is a diagram illustrating the processing steps of the method for manufacturing the semiconductor device according to the second embodiment of the present invention.

FIG. 11 is a graph showing the relationship between the discharge time of oxygen plasma, the oxygen gas flow rate, and the reflected power.

FIG. 12 is a graph showing the relationship between the discharge time of oxygen plasma and the emission intensity of fluorine.

FIG. 13 is a graph illustrating the relationship between the discharge time of oxygen plasma and the etching amount of the diffusion layer.

FIG. 14 is a schematic diagram of an etching apparatus used in a third embodiment of the present invention.

FIG. 15 is a diagram illustrating processing steps of a method for manufacturing a semiconductor device according to a third embodiment of the present invention.

FIG. 16 is a graph showing the relationship between the discharge time of oxygen plasma and the emission intensity of fluorine and the etching amount of the diffusion layer.

FIG. 17 is a schematic view of an etching apparatus used in the fourth embodiment of the present invention.

FIG. 18 is a view for explaining processing steps of the method for manufacturing the semiconductor device according to the fourth embodiment of the present invention.

FIG. 19 is a graph showing the relationship between the discharge time of oxygen plasma, the opening degree of the pressure control valve, and the etching amount of the diffusion layer.

FIG. 20 is a schematic diagram of an etching apparatus used in a fifth embodiment of the present invention.

FIG. 21 is a view for explaining processing steps of the method for manufacturing the semiconductor device according to the fifth embodiment of the present invention.

FIG. 22 is a graph showing the relationship between the discharge time of oxygen plasma, the voltage of the lower electrode, and the etching amount of the diffusion layer.

[Explanation of symbols]

1 photoresist 2 BPSG film 3 diffusion layer 4 Silicon substrate 5 contact holes 6 Polymer film on bottom of contact hole 7 Polymer film on the substrate surface 8 oxygen 9 oxygen ions 10 Fluorine 11 Fluorine ion 31 coils 32 high frequency power supply 33 Lower electrode 34 High frequency power supply 35 Upper electrode 36 Silicon substrate 37 Reaction Chamber 38 Pressure control valve 39 Turbo molecular pump 40 dry pump 41 gas cylinder 51 photoresist pattern 52 BPSG film 53 Impurity diffusion layer 54 Silicon substrate 55 contact holes 56 polymer membrane 57 Polymer membrane 58 oxygen 60 fluorine 72 optical fiber 73 Optical emission analyzer 74 signal line 75 Central processing unit 82 signal line 83 Central processing unit 92 Voltmeter 93 signal line 94 Central processing unit

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-6-275581 (JP, A) JP-A-9-50986 (JP, A) JP-A-6-177092 (JP, A) JP-A-2- 135731 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065

Claims (17)

(57) [Claims] 1. A silicon region is provided on at least the surface.
Step of sequentially forming an oxide film and a resist pattern on the substrate
And on the electrode provided in the reaction chamber of the plasma etching device.
The substrate is placed in a gas containing fluorocarbon gas
Etch the oxide film using plasma generated from
To form a contact hole, and a bias voltage is applied to the substrate.
Oxygen plasma is generated in the reaction chamber without applying pressure.
And substantially eliminates the fluorine present in the oxygen plasma.
A fluorine removing treatment step of removing oxygen, and after the fluorine removing treatment step, oxygen plasma is generated in the reaction chamber while applying a bias voltage to the substrate, thereby removing the polymer film remaining on the substrate. method of manufacturing a semi-conductor device you <br/> characterized in that the plasma treatment step to wrap free. 2. The switching from the fluorine removal treatment step to the oxygen plasma treatment step is performed by applying a bias voltage to the electrode after the oxygen plasma is generated. A method for manufacturing a semiconductor device as described above. 3. The method of manufacturing a semiconductor device according to claim 1, further comprising the step of supplying oxygen gas into the reaction chamber and controlling the pressure of the oxygen gas in the fluorine removal treatment step. Method. 4. The method of manufacturing a semiconductor device according to claim 1 , wherein oxygen gas is supplied into the reaction chamber while being increased stepwise in the fluorine removal treatment step. 5. The emission spectrum intensity of a specific atom or molecule contained in the oxygen plasma is measured, and the application timing of the bias voltage is determined based on the measured emission spectrum intensity. 2. The method for manufacturing a semiconductor device according to 2 . 6. A high-frequency voltage is applied to the electrode after the measured emission spectrum intensity is below a predetermined value,
The method of manufacturing a semiconductor device according to claim 5 , wherein the bias voltage is applied to the substrate thereby. 7. The specific atom or molecule is fluorine,
Carbon, oxygen, a method of manufacturing a semiconductor device according to claim 5 or 6, characterized in that carbon monoxide or carbon dioxide. Wherein said emission spectrum intensity, a method of manufacturing a semiconductor device according to claim 5 or 6, characterized in that an emission wavelength 685.6nm from fluorine atoms. 9. The semiconductor according to claim 2 , wherein an opening of a valve that controls the gas pressure in the reaction chamber is measured, and the application timing of the bias voltage is determined based on the opening. Device manufacturing method. 10. The manufacturing of a semiconductor device according to claim 9 , wherein when the opening is constant, a high frequency voltage is applied to the electrode, and thereby the bias voltage is applied to the substrate. Method. 11. The method of manufacturing a semiconductor device according to claim 2 , wherein the voltage of the electrode is measured, and the application timing of the bias voltage is determined based on the measured voltage. 12. When the voltage drops to a certain level, the high frequency voltage is applied to the electrodes, whereby the semiconductor device according to claim 1 1, wherein applying the bias voltage to the substrate Production method. When 13. applying a bias voltage to the substrate, a semiconductor according to claim 1 1 2 of the power density in the electrodes and applying a high frequency power of 8kW / m ² or less Device manufacturing method. 14. The plasma etching apparatus is any one of an inductively coupled plasma etching apparatus, a helicon wave plasma etching apparatus, an electron cyclotron resonance plasma etching apparatus source, and a dual frequency capacitively coupled plasma etching apparatus. the method of manufacturing a semiconductor device according to any one of claim 1 1 2. 15. The fluorocarbon gas is CH ₂
F ₂ , CH ₃ F, C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ and C ₅ F ₈
The method of manufacturing a semiconductor device according to claim 1 1 2, characterized in that a gas selected from the group consisting of. 16. The substrate manufacturing method of a semiconductor device according to claim 1 1 2, characterized in that a silicon substrate. 17. The step of etching the oxide film comprises:
The method of manufacturing a semiconductor device according to claim 16 , which is a step of forming a contact hole in the oxide film, the contact hole reaching a silicon side layer formed in the silicon substrate.