JP2001176853A - Plasma processing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing system, having the function for predicting modification of plasma generating conditions by detecting variation in the molecular density of dissociated active species. SOLUTION: Emission of light from dissociated active species in plasma is measured, using means for measuring the emission intensity of plasma, an index indicative of dissociation of projected gas is determined from emission intensity and plasma generating conditions are controlled based on the index. Extended concept of temperature in an equilibrium system or the results of multiplication or division of the emission intensity for three or more wavelengths is employed as the index.

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 using plasma (plasma processing method) and an apparatus for manufacturing a semiconductor device by plasma processing (semiconductor manufacturing apparatus). It is used in a step of removing the surface (dry etching) and a step of forming a film on the substrate surface (film formation).

[0002]

2. Description of the Related Art Some dissociated active species molecules in plasma emit light at a specific wavelength. Therefore, Japanese Patent Laid-Open No. 5-972
In Japanese Patent Publication No. 8, during the thin film forming process, the quality of the film is predicted by observing the emitted light from the plasma in situ. In addition, Japanese Patent Application Laid-Open No. 8-330278 discloses a method of performing dry etching by adjusting the plasma generation conditions so that the emission intensity ratio between CF ₂ and F becomes constant.

On the other hand, there is a control method based on the electrical characteristics of plasma. In Japanese Patent Application Laid-Open No. H10-125660, a preliminary experiment is performed in advance, a model formula that associates an electric signal with plasma processing characteristics is obtained and stored, and the value of the electric signal is substituted into the model formula during etching to perform plasma processing. A method for predicting characteristics and controlling plasma generation conditions is shown.

[0004]

In the method disclosed in Japanese Patent Application Laid-Open No. Hei 5-9728, the film quality can be predicted, but how to control the plasma generation conditions (input power and gas flow rate) in order to obtain a film having a predetermined film quality. Is not shown. JP-A-8-33027
No. 8 also discloses that the ratio of the luminous intensity from CF ₂ and F is kept constant, but does not describe how to control the plasma generation conditions when the luminous intensity ratio changes. These known examples indicate that a change in the plasma processing characteristics is detected and the changed amount is returned based on the detected amount.

However, it does not describe how to change the conditions for generating plasma. In addition, control is only performed based on the amount directly observed. For example, the CF ₂ / F emission intensity ratio is measured to control the CF ₂ / F emission intensity ratio. However, since many kinds of dissociation active species molecules that cannot be observed by light emission exist in the plasma, control based on them cannot be performed by the above method.

Japanese Patent Application Laid-Open No. 10-125660 discloses a control based on an electric signal, not a method based on dissociated active species molecules in plasma or light emission thereof. Therefore, it is not possible to know how the density of the dissociation active species molecules has changed.

It is an object of the present invention to detect a change in the density of dissociated active species molecules in the plasma and predict how to change the conditions for generating the plasma. .

[0008]

In order to solve the above-mentioned problems, the emission intensity from plasma is measured, an index indicating the dissociation of the source gas in the plasma is obtained, and the plasma generation is performed based on the index indicating the dissociation of the gas. Control conditions.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the plasma generation conditions are controlled using an index indicating the dissociation of the input gas in the plasma. As an index indicating the dissociation of the input gas, an index (reaction temperature) obtained by expanding the concept of temperature defined in a normal reaction gas, or a product or quotient of the emission temperature corresponding to the reaction temperature is used. Further, the index is used to control the plasma generation conditions.

First, a method of calculating a reaction temperature in plasma will be described. In normal hot gases, the law of mass action holds between temperature and the density of molecules in the gas phase (Vincent
i, Introduction to Physical Gas Dynamics). The following reaction,

[0011]

A + B + C +... ⇒P + Q + R +... (Chem. 1)

[0012]

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## EQU1 ## Where [A], [B],
[C],. . . , [P], [Q], [R],. . . Represents each of the molecules A, B, C,. . . , P, Q, R,. . . , Q _A , Q _B , QC _,. . . , Q _P , Q _Q ,
QR _,. . . Are A, B, C,. . . , P,
Q, R,. . . Is the molecular partition function of. Also, -ΔE
(A + B + C + ... ⇒P + Q + R + ...) is the reaction energy of this reaction. Also, _Tr (A + B + C
+. . . ⇒P + Q + R +. . . ) Is the temperature for this reaction and is referred to as the reaction temperature in this application. Further, k is a Boltzmann constant.

Not only the plasma but also the molecules in the gas undergo translational, rotational and oscillatory movements, and the temperature can be determined for each movement. In a normal high-temperature gas, the translation temperature (T _x ^trans ), rotation temperature (T _x ^rot ),
The vibration temperature (T _x ^vib ) and the reaction temperature (T _r ) of each reaction can be regarded as the same.

However, all reactions occur in non-equilibrium due to the presence of a large number of extremely hot electrons in the plasma, and the above-mentioned temperatures do not always coincide. Therefore, the translation temperature (T _X
^trans), rotational temperature (T _X ^rot), vibrational temperature (T _X ^vib), reaction temperature (T _r) is handled as having different values. In particular, each reaction containing dissociated active species molecules in the plasma has a unique reaction temperature. However, some of these temperatures may be treated as the same temperature.

For example, as shown in FIG.
uum Science and Technology A, vol. 14, 2343 (1996)
In the CF ₄ ECR plasma described in the above, all the reaction temperatures can be kept the same. FIG. 1 shows _Tr (CF ₄
⇒CF ₃ + F) and _Tr (CF ₃ ⇒CF ₂ + F) are plotted against input power. In some cases, a relational expression may be obtained between the respective reaction temperatures. For example, Journal of Plasma and Fusion Society, Vol. 75, No. 7, July 1999
In the C ₄ F ₈ plasma shown on page 785, _Tr (CF ₃ ⇒CF ₂ + F) and _Tr (CF ₂ ⇒C
F + F)

[0017]

[Formula 3] _Tr (CF ₂ ＣＦCF + F) = 0.349 _Tr (CF ₃ ＣＦCF ₂ + F) +0.000071 (The unit of temperature is eV). . FIG. 2 shows _Tr (CF ₃
It is plotted against ⇒CF ₂ + F) and _{T r (CF 2 ⇒CF + F} ). In ^{_{addition, T X trans = 0.03eV, Q}} CF4
^rot = is set to ^{_{Q CF3 rot = Q CF2 rot =}} Q CF rot. All the reaction energies are set to 5 eV.

A first embodiment of the present invention will be described. When etching the oxide film, since CF ₂ etches oxide film, it may be desired to maximize the CF ₂ density. However, CF ₂ density because with respect to the input power, not or monotonically increasing or decreasing, it is difficult to control the CF ₂ density. For example, as shown in FIG. 3, CF ₂
When density is plotted against input power, it may be convex upward. This is because if the input power is insufficient, the generation of CF ₂ is small, and if the input power is too large, the generated CF ₂ is decomposed and reduced (CF ₂ ⇒CF + F).

When a large number of wafers are processed by the plasma processing apparatus, various things adhere to the inside of the chamber. For example, a CF-based film is generated by CF-based plasma. Therefore, the relationship between the plasma generation conditions such as the input power and the dissociated active species molecular density changes (changes with time). In the case of an apparatus equipped with another control mechanism, the numerical value representing the state of the plasma other than the molecular density of the dissociated active species changed, so that the control mechanism changed the plasma generation conditions. The relationship of CF ₂ density may change. For example, in order to maintain the uniformity of plasma distribution, the control mechanism may change the current of the coil for generating the magnetic field, and the relationship between the input power and the CF ₂ density may change.

Consider a case in which a large number of wafers are etched with an input power that maximizes the CF ₂ density. When a large number of wafers are processed, the input power and
The relationship of CF ₂ density changes. If the relationship between the CF ₂ / F emission intensity ratio and the density ratio is checked in advance, a change in the CF ₂ / F density ratio can be detected. However, the density of CF ₂ is unknown. Further, when plotting the CF ₂ density with respect to the input power, the projection power is upwardly convex. Even though it is known that the CF ₂ density has decreased, the input power for maximizing the CF ₂ density is shown in FIG. As shown in Fig. 4
As shown in (b), it cannot be distinguished whether the power has shifted to low power.
In other words, if the relationship between the input power and the CF ₂ density changes, it is impossible to determine whether the input power should be increased or decreased even if the decrease in the CF ₂ density is detected.

As an input gas (etching gas) for etching the oxide film, a mixed gas containing C ₄ F ₈ , C ₅ F ₈ , CF _{4 and the} like is used. For example, Ar / C ₄ F ₈
/ O ₂ mixed gas. In this embodiment, a mixed gas of CF ₄ and Ar is used as an etching gas to simplify the description.
The dissociated active species molecules in CF ₄ plasma include CF ₃ and C
Consider F ₂ , CF, C, F.

[0022] When etching the oxide film, since CF ₂ etches oxide film, it may be desirable to maintain the CF ₂ density maximum value. Conditions for generating plasma (plasma generation conditions) include input power, total pressure, and gas flow rates. Here, a case where input power is controlled will be considered. As a control method, there is a method of increasing or decreasing the input power at intervals of 10 W when the density of CF ₂ is out of the maximum value within 5%.

FIG. 5 shows an oxide film plasma etching apparatus to which the present invention is applied.

A vacuum chamber 1 for performing plasma etching is provided with a valve 2 for adjusting the pressure in the chamber.
Is connected to a vacuum pump 3 for exhausting air. Further, at a constant flow rate through the flow rate controller 4, C
Etching gas 5 containing F ₄ (also described as input gas)
Is supplied into the vacuum chamber 1.

The vacuum chamber 1 has a coil 6 for generating a magnetic field.
Is provided, and a DC current is supplied to the coil 6 from a DC power supply 7. In order to generate the plasma 8, high frequency power is applied to the antenna 9 from the high frequency power supply 11 through the matching unit 10. In the vacuum chamber 1, a lower electrode 13 for placing a wafer 12 is provided. The lower electrode 13 is connected to a bias power supply 15 through a bias matching unit 14, and a bias voltage is applied.

In the vacuum chamber 1, a quartz window 16 and an emission analyzer 17 for analyzing light emission are connected to a reaction temperature calculation computer 18 for calculating a reaction temperature from an emission spectrum and emission intensity. The reaction temperature calculation computer 18 is connected to a control computer 19, and the control computer 19 controls the high frequency power supply 11, the flow controller 4, and the valve 2. Computer for reaction temperature calculation 1
The control computer 8 and the control computer 19 may be integrated. In addition, it may be integrated with another computer 21 for performing control based on a signal from another measuring instrument 20 together. An infrared semiconductor laser 22 and an infrared spectroscope 23 used in a preliminary experiment are also attached.

First, in a preliminary experiment, the relationship between the density ratio of the dissociated active species molecules CF ₂ , CF, and F and the emission intensity ratio is determined. To this end, the emission intensity and density of CF ₂ , CF, and F are measured under a plurality of plasma generation conditions close to the plasma generation conditions of actual etching, and K ₁ and K ₂ in the following equations are obtained.

[0028]

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Here, I (X) is the emission intensity at a wavelength unique to the dissociated active species molecule X, and is measured with a spectrometer. Note that C
The wavelengths specific to F ₂ are 271.1 nm and 280.0 nm.
for CF, 207.9 nm and 2 for CF.
At 30.5 nm, 685.6 nm and 690.3 n for F
m. Here, typical wavelengths are listed among the wavelengths specific to each dissociation active species molecule.However, there are many wavelengths specific to each dissociation active species molecule, and wavelengths that can specify which dissociation active species molecule emits light can be specified. Other wavelengths can be substituted. The density of CF ₂ and CF ((CF ₂ ), (CF)) is measured by an infrared semiconductor laser absorption spectrum (IRLAS), and the density of F is determined by actinometry from the ratio of the emission intensity of F to Ar. . For the actinometry method, see Plasma Source Science and
Technology, vol. 3, p. 1554 (1994).

Before starting the etching, the relationship between the density of the dissociated active species molecules in the plasma and the reaction temperature is determined. CF ₄
CF ₃ , CF ₂ ,
When considering CF and F, the relationship between the sum of the densities of all molecules in the plasma and the total pressure is

[0031]

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## EQU1 ## Here, (X) represents the density of the molecule X when the plasma is generated. The number of ions is ignored because it is smaller than the number of neutral molecules.

Assuming that the number of each element in the plasma per unit volume is proportional to the ratio of the amounts of the elements in the input gas,

[0034]

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Is as follows.

The following equation is established based on the law of mass action.

[0037]

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[0038]

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[0039]

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[0040]

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Assuming the reaction temperature, the following formulas (5) to (1)
By solving 0) as a simultaneous equation, the density of dissociated active species molecules can be obtained. When the densities of the dissociated active species molecules are determined for a plurality of reaction temperatures, the relationship between the reaction temperature and the density of the dissociated active species molecules is determined (temperature density relationship). The temperature density relationship in this case is as shown in FIG. In FIG. 6, each reaction temperature is treated as being different, and the reaction temperature on the horizontal axis of the graph is _Tr (CF ₂ ⇒CF + F).

After starting the actual etching, the dissociation active species molecules in the plasma and the molecules of the input gas are determined based on the emission intensity of the dissociation active species molecules in the plasma and the wavelength specific to the input gas using an emission analyzer. Of which, based on the formula (Chem. 4)
_2. Calculate the density ratio of CF, F.

Here, a case is considered in which the CF ₂ density falls below an allowable range, for example, within 5%, due to control over time or other feedback loops, even though the input power is kept constant.

[0044] If the CF ₂ / F density ratio determined from the emission intensity ratio using equation (Formula 4) it is out of the allowable range, CF ₂ /
In addition to the F density ratio, the CF ₂ / CF density ratio is also determined from equation (4). A reaction temperature at which the density ratio of CF ₂ / CF / F obtained from the emission intensity ratio matches the density ratio calculated in advance is obtained from the temperature density relationship. If a reaction temperature with the same density ratio is not found, the temperature at which the density ratio becomes closest may be obtained.

Since the temperature density relationship is determined by the total pressure and the gas flow rate, it is not affected by aging or other control mechanisms. The reaction temperature at which the CF ₂ density is maximized is compared with the reaction temperature at that time. If the reaction temperature is lowered as shown in FIG. 4 (a), the input power can be increased to raise the reaction temperature. I just need. Conversely, when the reaction temperature is rising as shown in FIG. 4B, the input power may be reduced.

As described above, in this embodiment, the input power and CF
Whichever the relationship between the _two densities changes, control can be performed so that the CF ₂ density is maximized.

FIG. 7 summarizes the first embodiment. The relationship between the emission intensity ratio with CF ₂ / CF and the density ratio is determined by a preliminary experiment. Further, the relationship of the CF ₂ / F emission intensity ratio is also determined. Then, a temperature density relationship is obtained from the total pressure and the gas flow rate before starting the etching.

During the etching, the emission intensities of CF ₂ , CF, and F are measured (S1), and the emission intensity ratio is calculated (S1).
2). Then, a reaction temperature is determined using the temperature density relationship (S3).

Further, the CF ₂ density is determined again from the reaction temperature using the temperature density relationship (S 4).

If the CF ₂ density is within the allowable range, there is no need to change the plasma generation conditions. However, if the CF ₂ density falls out of the allowable range, the input power is increased or decreased. At this time, if the reaction temperature is lower, the input power is increased (S5a), and if the reaction temperature is higher, the input power is reduced (S5b).

A modification of the first embodiment is shown. These modifications can be applied to the embodiments described later.

In determining the relationship between the density ratio and the emission intensity in a preliminary experiment, infrared semiconductor laser-induced spectroscopy (IRLAS)
An example is shown in which the density of CF ₂ and CF is obtained by using the formula, and the density ratio is obtained from the density. However, only the density ratio may be obtained.
In this case, there is no need to determine the absolute value of the density of CF ₂ and CF.

In determining the relationship between the density ratio and the emission intensity in a preliminary experiment, infrared semiconductor laser-induced spectroscopy (IRLAS)
And the actinometry method, but the method of obtaining the density and the density ratio may be another method. For example, laser-induced fluorescence (LIF), mass spectrometry (MS), and appearance mass spectrometry (APMS) may be used.

Although an example using the reaction temperature as an index indicating the dissociation of the input gas has been described, I (CF) I (F) / I (CF ₂ ) I
In some cases, (Ar) can be used as an index of dissociation.
This is the case when the emission intensity ratio of CF ₂ / F is proportional to the density ratio, and the change in the density of argon can be ignored. In this case, I (CF) I (F) / I (CF ₂ ) I (Ar) is (CF) (F)
/ (CF ₂ ), and as shown in the formula (9), (CF)
This is because (F) / (CF ₂ ) corresponds to the reaction temperature.
A large value of I (CF) I (F) / I (CF ₂ ) I (Ar) indicates that the reaction temperature is high.

Although an example in which the relationship between the emission intensity ratio and the density ratio is obtained in a preliminary experiment is shown, when a plurality of plasma processing apparatuses of the same type are used, it is not necessary to perform the preliminary experiment in all apparatuses. . In this case, a device for performing the density and the density ratio, for example, the infrared semiconductor laser 22 is unnecessary in the device without performing the preliminary experiment. Further, if the relationship between the light emission intensity ratio and the density ratio is stored in a computer as a database, a preliminary experiment is unnecessary.

The relationship between the emission intensity ratio of CF ₂ / F and the density ratio can be determined by a preliminary experiment, and the density of F can be determined from the emission intensity ratio of Ar and F by the actinometry method (literature). Therefore, during etching, CF ₂ , CF, F, A
The emission intensity of r was observed, and C ₂ / CF emission intensity ratio
When the F ₂ / CF density ratio (CF ₂ ) / (CF) is obtained and the F density (F) is obtained by the actinometry method, the reaction temperature can be obtained by using the formula (Formula 9). As described above, the reaction temperature can be determined from the emission intensity of CF ₂ , CF, F, and Ar during the etching. In this case, there is no need to determine the temperature density relationship before etching.

From the emission intensity ratio of CF ₂ / CF / F, CF
Seeking ₂ / CF / F density ratio, an example of obtaining the reaction temperature, there is a case where the light emission intensity ratio of CF ₂ / CF obtained a reaction temperature from CF ₂ / CF density ratio. The range in which the reaction temperature changes depends on the plasma processing apparatus and the plasma processing method to be controlled. Within that range, CF ₂ / C
If the F density ratio and the reaction temperature correspond one to one, CF ₂ /
The reaction temperature can be determined only by the CF emission intensity ratio.

Further, when the reaction temperature is determined only by the CF ₂ / CF density ratio, the effect of the surface reaction on the F density can be evaluated. The reaction temperature can be determined from the emission intensity ratio of CF ₂ / CF, and the F density can be determined from the reaction temperature. Here, a plasma etching apparatus having a means for controlling a surface reaction is considered. For example, consider an apparatus having a means for exposing the silicon surface in the chamber 1 and applying a bias voltage to the silicon to reduce F in the plasma. During the etching, the CF ₂ / CF emission intensity ratio is observed, the CF ₂ / CF density ratio is determined using the formula (4), and the reaction temperature is determined. Further, the F density (predicted value) is determined from the reaction temperature. In addition, F /
The F density (actually measured value) is determined from the Ar emission intensity ratio. Then, the predicted value and the actually measured value of the F density are compared. If F is consumed by the surface reaction, the measured / predicted value of the F density becomes smaller, so that the surface reaction can be evaluated by the measured / predicted value of the F density.

Further, this method can be simplified. Keep seeking relationship of the emission intensity of CF ₂ and CF and F can also be evaluated consumption of F due to surface reaction. In this case, in the preliminary experiment, a table for calculating the emission intensity of F from the emission intensity of CF ₂ and CF is created without operating the means for controlling the surface reaction. During etching, CF ₂ and CF are used.
And the emission intensity of F are measured, and the CF ₂ / CF emission intensity ratio is determined. The emission intensity of F is predicted using the relationship between the CF ₂ / CF emission intensity ratio and the emission intensity of F obtained by a preliminary experiment (predicted value). The effect of the surface reaction is evaluated by comparing with the measured value of the emission intensity of F. That is, if the measured value / predicted value is small, it can be detected that F is consumed by the surface reaction.

[0060]

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Although an example has been described in which the temperature density relationship is obtained before etching, it is not necessary to obtain the temperature density relationship first. In this case, the density ratio is obtained from the emission intensity ratio during the etching. After that, the formulas (Formula 4) and the formulas (Formula 5) to (Formula 10) may be solved simultaneously. In this case, there is no need to store the temperature density relationship in the computer.

In determining the temperature density relationship, an example has been described in which the ratio of each element is the same as the ratio of the input gas. However, the ratio of each element may be determined based on a preliminary experiment.

In addition, there is a dimensionless expression in the mass action equation, and the density ratio used in the equation can be related to the emission intensity ratio. The reaction temperature can be determined. For example, the reaction formula is

[0064]

[Formula 11] A + B⇒P + Q (Formula 11), and the equation of mass action is

[0065]

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Dimensionless as in the form of

[0067]

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In the case where it is determined from the light emission intensity ratio. In such a case, it is not necessary to determine the temperature density relationship before etching.

Although the example in which the input power is increased in order to raise the reaction temperature has been described, the residence time of the gas may be extended. To extend the stay time, the flow rate may be reduced or the volume of the chamber may be increased. Conversely, to lower the reaction temperature, the residence time may be reduced by increasing the flow rate or reducing the volume of the chamber.

FIG. 7 shows the flow of the first embodiment. However, even if the input power is changed (S5a or S5
b) If the reaction temperature does not fall within the allowable range, steps S1 to S4 may be repeated. Further, if the reaction temperature does not change as expected when the input power is changed, the plasma processing may be stopped. For example, the plasma processing may be stopped when the reaction temperature decreases despite the fact that the input power is increased in order to increase the reaction temperature.

Although the modifications of the first embodiment have been described, these modifications can be applied to the embodiments described later.

Next, a second embodiment of the present invention will be described. In a first embodiment, an example to maximize CF ₂ density, CF ₂
The density may be too high and the etching rate may decrease. Therefore, it may be desirable to maintain the CF ₂ density at a predetermined value. However, CF ₂
Density does not increase monotonically. Therefore, CF ₂
When the density changes, it cannot be determined whether the input power should be increased or decreased. Therefore, a case where the CF ₂ density is kept constant will be described as a second embodiment.

First, a preliminary experiment similar to that of the first embodiment is performed, and the relationship between the density ratio of CF ₂ , CF, and F, which are dissociation active species molecules, and the emission intensity ratio is determined. Before etching, equation (10) is solved from equation (5) to determine the temperature density relationship.
Further, during the etching, the density ratio is obtained from the emission intensity ratio using the formula (Formula 4), the reaction temperature is obtained using the temperature density relationship, and the CF ₂ density is obtained again using the temperature density relationship.

If the CF ₂ density falls outside the allowable range, it is determined whether the reaction temperature has risen or fallen. When the reaction temperature rises, the input power may be decreased to lower the reaction temperature, and when the reaction temperature decreases, the input power may be increased to raise the reaction temperature.

The first embodiment shows an example in which the density of a specific dissociated active species molecule is maintained at a maximum value, and the second embodiment shows an example in which the density of a specific dissociated active species molecule is maintained at a predetermined value. Indicated. In any case, the reaction temperature may be controlled to be constant. Therefore, the method of maintaining the specific value at the maximum can be applied to the case where the specific value is maintained at the predetermined value. This is the same in the following embodiments.

In the first and second embodiments, the example in which the CF ₂ density is controlled to the maximum or a predetermined value has been described. However, this method can be applied to other dissociated active species molecules. For example, when etching a nitride film, CF ₃ etches the nitride film (K. Miyata, H. Arai, T. Kuno, M. Hori, T. Goto, P.
roceeding of Symposium on Dry Process, p. 129). In some cases, it is desired to control the CF ₃ density, but the CF ₃ can be controlled by the method described in the first and second embodiments. As described above, by applying the present invention, control can be performed based on the CF ₃ density that cannot be directly observed during etching.

A method for maintaining the CF ₂ / F density ratio at a maximum will be described as a third embodiment. As already mentioned, CF ₂ /
The method of maintaining the F density ratio at the maximum can be applied to the case where the CF ₂ / F density ratio is kept constant. In this embodiment, CF ₂ /
A method for maintaining the F density ratio at the maximum will be described.

When etching an oxide film having silicon as a base, it is desirable to etch the oxide film without etching silicon. CF ₂ etches the oxide film and F etches the underlying silicon. Therefore,
In order to selectively etch only an oxide film without etching silicon (etching with a high selectivity ratio of an oxide film to silicon), it is desirable to perform etching under plasma generation conditions having a large CF ₂ density and a small F density. Sometimes. However, as shown in FIG. 7, since the CF ₂ density is upwardly convex with respect to the applied power, the CF ₂ / F density ratio is also upwardly convex with respect to the applied power. Therefore, CF ₂ / F
Be able to detect the decrease in CF ₂ / F density ratio from emission intensity ratio, should reduce should increase the input power in order to increase the CF ₂ / F density ratio, it can not be determined.

A preliminary experiment is performed in the same manner as in the first and second embodiments to determine the relationship between the emission intensity ratio and the density ratio. Then, a temperature density relationship is obtained before etching.

[0080] From CF ₂ / F emission intensity ratio during etching, obtaining the CF ₂ / F density ratio.

If the CF ₂ / F density ratio is out of the allowable range, the reaction temperature is determined from the emission intensity ratio of CF ₂ / CF / F.

If the reaction temperature is increasing, the input power is decreased to lower the reaction temperature, and if the reaction temperature is decreasing, the input power is increased to increase the reaction temperature.

FIG. 8 summarizes the third embodiment. In the third embodiment, compared to the first and second embodiments,
Only when the CF ₂ / F density ratio is out of the allowable range, the reaction temperature may be calculated.

In the first to third embodiments, an example in which the density and density ratio of specific dissociated active species molecules are controlled has been described. However, if the reaction temperature under the optimum plasma generation conditions is known, the reaction temperature is maintained. Control may be performed. Further, I (CF)
If I (F) / I (CF ₂ ) I (Ar) is used as an index indicating dissociation, I (CF) I (F) / I (CF ₂ ) I ( Ar) may be determined.

Although the example of controlling the fluorocarbon-based plasma has been described, other types of plasma may be used. For example, a CVD process or a chamber cleaning process may be used. In the silicon cleaning process, it is useful to control the density of silicon atoms and the density ratio between silicon atoms and other dissociation active species molecules.

The oxide film and the input gas for etching the oxide film are described as examples, but the object to be etched is not limited to the oxide film.
Silicon, metals such as aluminum and copper, alloys such as BST, and organic substances such as polyaryl ethers may be used. In addition, a cleaning process using Cl ₂ , BCl ₃ , SF _6, or the like may be used as long as it uses dissociated active species molecules in plasma.

Although an etching process has been described as an example of the plasma processing, a film forming process such as CVD may be used. For example, a CVD process for forming a polysilicon thin film. Si atoms in the plasma become dissociation active species molecules. Therefore, in the polysilicon deposition process, if the density of Si atoms is associated with the reaction temperature, the plasma generation conditions can be controlled based on the reaction temperature.

[0088]

When the present invention is applied, the change in the density or the density ratio of the dissociated active species molecules in the plasma is detected, how to change the plasma generation conditions is predicted, and the plasma generation conditions are changed. Can do things. Also, C
The density of dissociated active species molecules that cannot be directly observed by light emission, such as F ₃ , can be predicted from the light emission of the plasma, and the plasma generation conditions can be controlled based on the density.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a reaction temperature of CF ₄ plasma.

FIG. 2 is a characteristic diagram showing an example of a relationship between reaction temperatures in C ₄ F ₈ plasma.

FIG. 3 is a characteristic diagram showing a relationship between CF ₂ density and input power.

FIG. 4 is a characteristic diagram showing a relationship between CF ₂ density and input power.

FIG. 5 is a diagram showing an example of a plasma processing apparatus to which the present invention is applied.

FIG. 6 is a characteristic diagram showing an example of a temperature density relationship (in the case of CF ₄ plasma).

FIG. 7 is a flowchart illustrating an increase / decrease of input power according to the first embodiment;

FIG. 8 is a flowchart illustrating an increase / decrease of input power according to a third embodiment.

[Explanation of symbols]

1. Vacuum chamber, 2. Valve, 3. Vacuum pump, 4.
Flow controller, 5 etching gas, 6 coil, 7 DC power supply, 8 plasma, 9 antenna, 10 matching device,
11: High frequency power supply, 12: Wafer, 13: Lower electrode, 1
4 ... Bias matching device, 15 ... Bias power supply, 16 ...
Quartz window, 17: emission analyzer, 18: computer for calculating reaction temperature, 19: computer for control, 20: other measuring instrument, 21: other computer, 22: infrared semiconductor laser, 23: infrared spectroscope.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 BA29 FA01 HA16 JA16 KA39 KA41 LA15 5F004 AA16 BA04 BB18 BD04 CB02 DA00 DA01 DA23 DA26 DB03 5F045 EH19 GB08 GB17

Claims (1)

[Claims] 1. An apparatus for controlling the processing of a semiconductor thin film using plasma, comprising means for measuring the emission intensity of plasma, obtaining an index representing the dissociation of the input gas using the output of said measuring means, A plasma processing apparatus characterized in that plasma generation conditions are controlled based on the condition.