JPH03181127A - Dry etching device - Google Patents

Abstract

PURPOSE:To normalize the etching and to decrease the cleaning frequency of a reaction chamber by detecting the luminous spectrum within the plasma of a reaction chamber, and controlling the inflow quantity of reaction gas so that this detected value may accord with the reference value. CONSTITUTION:When a wafer W is put in a reaction chamber 1 and reaction gas is introduced from a reaction gas introduction pipe 5 and high frequency is applied to a substrate holder 3, plasma P occurs. The luminous spectrum of reactive species within this plasma is detected with a band pass filter 10, and is converted to the voltage signal in accord with the intensity by a photoelectric transfer device 11, and is input into a comparator 12. And the input signal and the reference voltage value are compared in the comparator 12, and the differential signal is sent to a driving control circuit 13. The circuit 13 controls the reaction gas inflow quantity of a mass flow controller 7 so that the differential signal may be zero. Hereby, the etching is normalized, and also the cleaning frequency of the reaction chamber is made small.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a dry enching device.

<Prior art> A dryer etching device converts a reaction gas into plasma in a reaction chamber using high-frequency power, etc., and guides the ions in this plasma to the surface of a sample such as a wafer, thereby etching the wafer. It is configured to perform

In addition, in such a dry etching apparatus, the desired etching is generally achieved by appropriately setting etching conditions such as the flow rate of reactant gas introduced into the reaction chamber, high frequency power for generating plasma, and the degree of vacuum in the reaction chamber. is configured to do so.

<Problems to be Solved by the Invention> By the way, in a dry etching apparatus, as etching is repeated, reaction products may accumulate in the reaction chamber, and the reactive species in the plasma are consumed by the deposits. The amount of reactive species that is originally required may be reduced. For this reason, in conventional apparatuses, as the number of processed patches increases and the amount of deposits increases, the etching condition changes accordingly, and the period during which normal etching characteristics can be obtained is limited. Furthermore, it is necessary to frequently clean the inside of the reaction chamber every time the amount of deposited reaction products and the like reaches a certain level.

<Means for Solving the Problems> The present invention has been made to solve the above-mentioned conventional problems, and the configuration thereof will be explained with reference to FIG. 1 corresponding to an embodiment. Means for detecting the emission spectrum intensity of ion species that react with the sample (wafer) W of the plasma P generated in the reaction chamber 1 (for example, a bandpass filter 10 and a photoelectric conversion device 11, etc.) and the detection value thereof are set in advance. means (for example, voltage comparator 12) for successive comparison with the reference value determined, and etching conditions such that the detected value of the spectrum intensity matches the reference value based on the comparison result;
For example, means for changing the reaction gas introduction flow rate (mass flow controller 7 and its drive control circuit 13, etc.)
It is characterized by the establishment of

<Operation> Changes in the amount of reactive species in the plasma generated within the reaction chamber 1 correlate with changes in the emission spectrum intensity of the reactive species.

Therefore, by detecting the intensity of the emission spectrum of the reactive species in the plasma and controlling the enching conditions, such as the amount of reactive gas flowing into the reaction chamber 1, so that the detected value matches the reference value, The amount of reactive species can always be kept constant.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is an explanatory view of the configuration of an embodiment of the present invention, and is a front view showing a reaction chamber 1 cut vertically at the center thereof.

A ground electrode 2 and a substrate holder 3 are arranged facing each other in a reaction chamber 1, and a wafer W is mounted on the holder 3. A high frequency power source 4 is connected to this substrate holder 3.

A reaction gas introduction pipe 5 is inserted into the reaction chamber 1 to penetrate the wall and introduce the reaction gas into the interior thereof, and a number of nozzles n...n are formed at the tip thereof. A gas injection pipe 6 is attached.

A reaction gas supply source 8 is connected to the reaction gas introduction pipe 5 via a mass flow controller 7 .

The reaction chamber 1 is, for example, a glass bell jar, and is connected to an exhaust system (not shown) for evacuating the inside thereof.

A bandpass filter 10 is disposed on the side wall of the reaction chamber 1, and only the emission spectrum of the reactive species in the plasma P is guided by this filter 10 to the next stage photoelectric conversion device 1 via an optical fiber cable 14. , a voltage signal corresponding to its intensity is manually input to the voltage comparator 12.

The voltage comparator 12 successively compares the input signal from the photoelectric conversion device 11 and the pre-input reference voltage value, and outputs a signal corresponding to the difference between the two to the drive control circuit 13. The drive control circuit 13 controls the mass flow controller 7, that is, the flow rate of the reaction gas introduced into the reaction chamber 1, based on the comparison result of the voltage comparator 12, so that the output voltage of the photoelectric conversion device 11 becomes equal to the reference voltage value. It is configured like this.

In the above embodiments of the present invention, first, in the reaction chamber 1,
A high frequency voltage is applied to the substrate holder 3 while a predetermined amount of reaction gas is introduced from the reaction gas introduction tube 5 after the wafer W to be processed is mounted and vacuum is drawn. This results in
A discharge occurs between the ground electrode 2 and the substrate holder 3, and a plasma region P of reactive gas is formed therebetween, and ions in this plasma react with the surface of the wafer W, thereby etching the surface layer.

As etching is repeated, reaction chamber 1
Reaction products and the like may be deposited within the plasma, and the deposits may consume reactive species in the plasma, reducing the amount of reactive species originally required for etching. in this way,
When the amount of reactive species decreases, the intensity of the emission spectrum of the reactive species decreases, so by monitoring the intensity it is possible to know whether the etching situation is normal or not. Therefore, only the emission spectrum of the reactive species in the plasma is guided to the photoelectric conversion device 11 by the bandpass filter 10, and the flow rate of the reactive gas introduced into the reaction chamber 1 is adjusted so that the voltage signal based on the intensity becomes the reference voltage value. By increasing the amount of the reactive species, the emission spectrum intensity of the reactive species, that is, the amount of the reactive species can be kept constant.

Therefore, by investigating in advance the output value of the photoelectric conversion device 11 with respect to the emission spectrum intensity of the reactive species when performing the desired etching, and setting the resulting voltage value as the reference value of the comparator 12, the desired etching can be carried out. It becomes possible to perform the operations sequentially and continuously in a normal state at all times.

Next, an example will be described in which the above-described apparatus of the present invention is used to perform metal etching on the surface of the wafer W and then perform dry etching as an anticorrosion treatment. Note that anti-corrosion treatment after metal dry etching is carried out by various methods, but in this example, metal dry etching and dry etching as anti-corrosion treatment are carried out in the same reaction chamber 1, and the reaction gas is , 37 fluorinated methane (CH
Assume that plasma processing is performed using a mixed gas of F3) and oxygen (02).

First, in metal dry etching, since etching progresses while generating deposits to control the etching shape, reaction products are also deposited in the reaction chamber 1, and the deposits are used to stimulate the plasma during the next anticorrosion treatment. The reactive species inside are consumed. This consumption increases as the amount of deposits increases, that is, the number of processing batches increases, and eventually corrosion occurs as a result of not being able to obtain a sufficient anticorrosive effect.

Now, in the conventional apparatus, the etching conditions for each process are constant, and the probability of occurrence of corrosion increases rapidly when the number of process batches exceeds 100, as shown by the broken line in FIG. Here, the emission spectrum intensity of reactive species, oxygen active species, and fluorine active species for each treatment (○: lllnm
, F: 104nlI), it was found that as shown in FIG. 3, the corrosion probability decreased as the corrosion probability increased. In addition, in the figure, the solid line indicates oxygen active species, and the broken line indicates fluorine active species.

On the other hand, in the apparatus of the present invention, as shown in FIG. 4, the reaction gas (solid line: 02, broken line:
The introduced flow rate of CHF5) is changed, thereby keeping the amount of reactive species in the plasma constant, so that corrosion does not occur even when the number of processing batches exceeds 200, as shown by the solid line in FIG. 2.

Furthermore, if a function is added to the configuration of the above-described embodiment to store the reaction gas introduction flow rate during etching, that is, the etching conditions, and to use the stored contents as the initial conditions for the next etching for the same purpose. The amount of reactive species in the plasma is
Control to keep it constant becomes quick. For example, as shown in Figures 5 and 6, if the above functions are not provided (
In the case (broken line in the figure), it takes more than 4 minutes from the start of etching to adjust the reaction gas introduction flow rate to keep the emission spectrum intensity constant, whereas when it is provided (solid line in the figure),
Immediately after the start of etching, the intensity of the emission spectrum, that is, the amount of reactive species in the plasma becomes constant.

Furthermore, in addition to the above-mentioned memory function, when a predetermined external signal is input manually by an operator or the like, the conditions for the next etching are set to In other words, if a function is provided to set the conditions to the stored conditions when no reaction products have accumulated in the reaction chamber 1, then after the cleaning of the inside of the reaction chamber is completed, the operators can perform key manual operations, etc. Etching conditions can be set to suit the atmosphere in the reaction chamber. For example, as shown in Figures 7 and 8, in the case where only the memory function is provided (dashed line in the figure), when the atmosphere inside the reaction chamber changes significantly due to cleaning, a reaction is required to keep the emission spectrum intensity constant. While it takes more than 4 minutes from the start of etching to adjust the gas introduction flow rate, when this setting function is provided (solid line in the figure), the emission spectrum intensity, that is, the amount of reactive species in the plasma, changes immediately after the start of etching. becomes constant.

Therefore, even when cleaning is performed, control for keeping the amount of reactive species in the plasma constant can be performed quickly.

Note that the emission spectrum intensity on the vertical axis in the graphs shown in FIGS. 3, 6, and 8 is set to 1OO, which is the spectral intensity in a normal state of target etching.

In the embodiments of the present invention described above, the flow rate of the reactive gas introduced into the reaction chamber 1 is controlled in order to keep the amount of reactive species in the plasma constant, but the present invention is not limited to this. , high frequency power for generating plasma, degree of vacuum in the reaction chamber, and other etching conditions may be controlled, or conditions such as flow rate of reaction gas introduction, high frequency power, degree of vacuum, etc. may be controlled. The configuration may be such that the control is performed in an appropriate combination.

<Effects of the Invention> As explained above, according to the present invention, the emission spectrum intensity of reactive ion species in the plasma is monitored, and the etching conditions of the reactant gas introduction meteor etc. are adjusted in order to keep the emission spectrum intensity constant. Since it is configured to change, the star of reactive ion species in the plasma can be kept constant.

As a result, even if the number of processing batches is large, desired etching can always be repeated and continued in a normal state. Furthermore, the frequency of cleaning inside the reaction chamber can be reduced.

[Brief explanation of drawings]

FIG. 1 is an explanatory view of the configuration of an embodiment of the present invention, and is a front view showing a reaction chamber 1 cut vertically at the center thereof. 2 to 4 are explanatory diagrams of the operation of the embodiment of the present invention, and the second
The figure is a graph showing the probability of occurrence of corrosion as a function of the number of processing batches. Figure 3 is a graph showing the change in the emission spectrum intensity of reactive species as a function of the number of processing batches. Figure 4 is a graph showing the change in the flow rate of reactant gas introduced as a function of the number of processing batches. It is a graph. 5 to 8 are explanatory diagrams of the operation of a modified example of the embodiment of the present invention, and FIGS. 5 and 7 are graphs showing changes in the flow rate of reactant gas introduced with respect to etching elapsed time, and FIGS. FIG. 8 is a graph showing changes in emission spectrum intensity with respect to processing and notching elapsed times, respectively. 1...Reaction chamber 2...Ground electrode 3... - Base plate holder 4 ・ 5 ・ 6 ・ 7 ・ 8 ・ 10 ・ 11 ・ 12 ・ 13 ・ W ・ High frequency power supply Reaction gas introduction tube Gas injection tube Mass flow Controller Reaction gas supply source Bandpass filter Photoelectric conversion device Heavy pressure comparator Drive control circuit Wafer

Claims (1)

[Claims] In an apparatus that etches a sample such as a wafer placed in the reaction chamber by guiding ions in the plasma generated by electric discharge to the surface of the sample, ion species that react with the sample in the plasma are used. means for detecting the intensity of the emission spectrum, means for successively comparing the detected value with a preset reference value, and means for changing etching conditions so that the detected value matches the reference value based on the comparison result. A dry etching device characterized by comprising means.