JP2003092286A - Method and device for detecting plasma etching end point - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for end point detection which can accurately detect an etching end point for a gas-switching etching method. SOLUTION: The device comprises light emission intensity detecting means 31 and 32 which detect the light emission intensity of light with wavelength corresponding to a specific reaction seed in a chamber 2 and an etching end point detecting means 34 which extracts light emission intensity data detected in the intermediate time zone of an etching process by removing the light emission intensity data obtained at a certain intermediate time after the start of the etching process and a certain time prior to the end of the etching process from light emission intensity data in the etching process such that the light emission intensity detecting means 31 and 32 detect and decides the etching end point when the extracted light emission intensity data exceed a preset reference value. Thus, the etching end point can accurately be detected on the basis of the light emission intensity data in the intermediate time zone of the etching process, which accurately reflects the etching progress state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting an etching end point in a plasma etching process.

[0002]

2. Description of the Related Art In a method of etching a silicon substrate with a reactive species such as radicals or ions generated by converting an etching gas into plasma, a method selected from a plurality of reactive species has hitherto been selected as a method for detecting the etching end point. A method is known in which the emission intensity of a specific reactive species is measured and the etching end point is detected from the variation.

For example, when SF ₆ gas is used as an etching gas, when this gas is turned into plasma, F radicals (fluorine radicals) are generated as reactive species, but when the end point of etching is approached, the consumption amount (consumed for etching). Amount) decreases, the amount of F radicals in the plasma gradually increases. Therefore, it is possible to determine that the etching end point is reached when the variation in the emission intensity of the F radicals, which is correlated with the amount of F radicals in the plasma, is observed, and when this exceeds a predetermined level.

On the other hand, as a plasma etching method, a step of converting an etching gas into a plasma to etch an etching ground on a silicon substrate, and a protective film forming gas into a plasma, are formed on the silicon substrate by the etching. A method of etching a silicon substrate by alternately repeating at least two steps of forming a protective film (a film having etching resistance) on a structural surface (hereinafter, this etching method is referred to as "gas switching etching method"). )It has been known.

In this gas switching etching method, since the protective film is formed on the structure surface formed on the silicon substrate, even when the F radical having an isotropic property is used for the etching, the protective film is underexposed. Etching can be effectively prevented, and a trench (deep groove or hole) can be efficiently formed with a high etching rate.

[0006]

However, when the above-mentioned endpoint detection method is applied to this gas switching etching method, there are problems as described below.

FIG. 6 is a graph showing the results of measuring the emission intensity of F radicals in the gas switching etching method. As shown in FIG. 6, in the gas switching etching method, the F radicals in the etching process The emission intensity is not constant, and peaks occur in the emission intensity in the initial stage when the protective film forming process shifts to the etching process and the final stage when the etching process shifts to the protective film forming process.

This is because, for example, when the trench is formed by etching, in the initial stage when the etching process is started, the F radicals are removed until the protective film formed at the bottom of the trench in the previous protective film forming process is removed. It is considered that this phenomenon occurs because the consumption is suppressed, and in the final stage, the gas (for example, SiF ₄ ) generated by the etching stays at the bottom of the trench and the replacement with the F radical is not performed well. In particular, the deeper the depth of the trench in the high aspect ratio trench etching, the greater the above-mentioned replacement obstacle.

As described above, the emission intensity detected in the initial stage and the final stage does not reflect the accurate etching progress state in the etching process, and therefore the peak value of the emission intensity during the etching process is adopted. However, the accurate etching progress state in the etching process cannot be grasped by the method of adopting the above or using the average value thereof. Therefore, conventionally, there has been a problem that a desired structure cannot be obtained due to insufficient etching or, conversely, excessive over-etching.

In particular, as shown in FIG. 7, a wafer having a structure in which a silicon oxide film (SiO ₂ ) 101 is sandwiched between an upper silicon layer 103 and a lower silicon layer 104 (SOI (Silicon on Insulator)
r) When the upper silicon layer 103 of the wafer 100 is etched by the gas switching etching method, it is difficult to control the etching shape near the interface between the upper silicon layer 103 and the silicon oxide film 101, and the etching ground is the silicon oxide film. After reaching 101, if this is over-etched too much, as shown in FIG.
At the bottom of the groove (or hole) 105, the protective film on the side surface is broken, which causes a problem that the upper silicon layer 103 is etched into an abnormal shape. Therefore, in the trench etching of the SOI wafer, control of the etching time becomes a very important problem. Reference numeral 104 in FIG. 7 is a mask.

The present invention has been made in view of the above circumstances, and provides an end point detecting method and apparatus capable of accurately detecting an etching end point in a plasma etching method in which an etching step and a protective film forming step are repeated. With the goal.

[0012]

The invention described in claim 1 of the present invention for solving the above-mentioned problems comprises a step of etching an etching ground on a silicon substrate with a reactive species that are turned into plasma, A method of detecting an end point of the etching in a plasma etching process of etching the silicon substrate by alternately repeating at least two steps of forming a protective film on a structure surface formed on the substrate by the etching. Therefore, the emission intensity data of the specific reaction species during the etching process is acquired, and the emission intensity obtained from the acquired emission intensity data within a fixed time after the start of the etching process and within a fixed time before the end of the etching process. Excluding the data, the emission intensity data acquired during the intermediate time period of the etching process was extracted and extracted. When the emission intensity data exceeds a preset reference value, according to the plasma etching end point detection method is characterized in that so as to determine that the etching end point.

The etching end point detecting method can be suitably implemented by the apparatus invention according to the fifth aspect. That is, in the invention described in claim 5, a step of disposing a silicon substrate in a chamber and etching an etching ground on the silicon substrate with a reactive species plasmatized in the chamber; A device for detecting the end point of the etching in a plasma etching process for etching the silicon substrate by alternately repeating at least two steps of forming a protective film on the structure surface formed in From the emission intensity detection means for detecting the emission intensity of the specific reaction species of, and the emission intensity data during the etching step detected by the emission intensity detection means, within a fixed time after the start of the etching step and a fixed time before the end of the etching step Except for the emission intensity data obtained in the And a plasma etching end point detecting means for extracting the extracted emission intensity data and determining that the etching end point is reached when the extracted emission intensity data exceeds a preset reference value. Related to the device.

As described above, in the plasma etching method in which the etching process and the protective film forming process are repeated, in the initial stage of shifting from the protective film forming process to the etching process and in the final stage of shifting from the etching process to the protective film forming process. The emission intensity of light having a wavelength corresponding to the detected etching reaction species does not reflect the accurate etching progress state.

Therefore, in the present invention, based on the obtained emission intensity data, the emission intensity obtained within a fixed time after the start of the etching process (the initial stage) and within a fixed time before the end of the etching process (the final stage). Except the data
The emission intensity data acquired in the intermediate time zone of the etching process is extracted, that is, the emission intensity data in the time zone that accurately reflects the etching progress state is extracted, and the extracted emission intensity data is preset. When the standard value is exceeded,
It is determined that the end point of etching is reached.

This makes it possible to accurately detect the etching end point, and for example, even in the SOI wafer described above, it becomes possible to form an etching structure having a highly accurate shape.

The determination of the etching end point is performed when the extracted emission intensity data exceeds the reference value continuously for a preset number of times, as in the inventions described in claims 2 and 6. It is preferable to determine that it is the end point. If it is determined that the etching end point is reached when the value exceeds the reference value only once, if the extracted emission intensity data includes noise, an error occurs in the determination. According to the above, an accurate determination can be made without error.

Further, the method for determining the etching end point is not limited to the above-mentioned method, and as in the invention described in claims 3 and 7, based on the amount of change in the emission intensity data sequentially extracted for each etching step. Alternatively, the etching end point may be detected.

That is, according to the third aspect of the invention, the step of etching the etching ground on the silicon substrate with the reactive species turned into plasma, and forming the protective film on the structural surface formed on the substrate by the etching. The method of detecting the end point of the etching in the plasma etching process of etching the silicon substrate by alternately repeating at least two steps of the step of Then, the emission intensity data obtained is excluded from the emission intensity data obtained within a certain period of time after the start of the etching process and within a certain period of time before the end of the etching process. Intensity data is extracted, and the extracted emission intensity data sequentially extracted for each of the etching steps is extracted. Calculating a change amount of the motor, when the calculated amount of change exceeds a preset reference value, according to the plasma etching end point detection method is characterized in that so as to determine that the etching end point.

Further, according to the invention described in claim 7, a step of arranging a silicon substrate in a chamber and etching an etching ground on the silicon substrate by a reactive species plasmatized in the chamber, A device for detecting the end point of the etching in a plasma etching process for etching the silicon substrate by alternately repeating at least two steps, which is a step of forming a protective film on the structural surface formed on the substrate, Based on the emission intensity detection means for detecting the emission intensity of the specific reactive species in the chamber and the emission intensity data during the etching process detected by the emission intensity detection means, within a certain time after the start of the etching process and at the end of the etching process. During the etching process, except for the emission intensity data obtained within a certain period of time With sequentially extracted for each etching step the emission intensity data detected in a time zone,
Plasma etching characterized in that it comprises an etching end point detecting means for calculating a change amount of the extracted emission intensity data and determining that the etching end point is reached when the calculated change amount exceeds a preset reference value. This relates to an end point detection device.

Further, similarly to the inventions described in claims 2 and 6, the determination of the etching end point in the inventions described in claims 3 and 7 is performed as in the inventions described in claims 4 and 8. When the extracted emission intensity data continuously exceeds the reference value a preset number of times, it is preferable to determine that the etching end point is reached.

The plasma etching process according to the present invention includes an etching step of plasmaizing an etching gas to etch a silicon substrate and a plasma of a protective film forming gas to form a plasma on a structure surface formed on the silicon substrate. The protective film forming step of forming a protective film is performed by a gas switching etching method in which the protective film forming step is alternately repeated.In the plasma etching process, the etching gas and the protective film forming gas are completely switched and introduced. In addition to the process of repeatedly performing the etching step and the protective film forming step, an etching gas and a protective film forming gas are simultaneously introduced into the chamber,
By increasing or decreasing the amount of each introduction, a process in which an etching process mainly proceeds and a process in which the protective film formation mainly proceeds are alternately repeated.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a partial block diagram of a schematic configuration of the etching apparatus according to the present embodiment.

As shown in FIG. 1, this etching apparatus 1
Is a case-shaped etching chamber 2 in which an etching chamber 2a is formed, a base 3 arranged in a lower region in the etching chamber 2a and on which a silicon substrate S to be etched is placed, A gas supply unit 7 that supplies an etching gas and a protective film forming gas into the etching chamber 2a, a decompression unit 13 that decompresses the inside of the etching chamber 2a, and a plasma of the etching gas and the protective film forming gas that are supplied into the etching chamber 2a. It includes a plasma generating unit 15 that turns into a plasma, a high frequency power source 18 that applies high frequency power to the base, a control device 20 that controls the operation of each of these units, and an end point detection device 30 that detects the end point of etching.

The etching chamber 2 is made of ceramic, and a ceiling has a viewing window 2b made of a transparent material such as quartz glass. The inside of the etching chamber 2a can be observed from the outside through the viewing window 2b. You can do it.

A silicon substrate S is placed on the base 3 via a sealing member such as an O-ring 4. The base 3 is provided so that its base 3a is led out of the etching chamber 2a, and a communication passage communicating with a space 5a formed between the base 3 and the silicon substrate S is provided at the center thereof. 5
Is provided, and the helium gas is filled and sealed in the space 5a through the communication passage 5. Further, a cooling water circulation passage 6 is formed in the base 3, and the silicon substrate S is cooled by the cooling water (20 ° C.) circulating in the cooling water circulation passage 6 through the base 3 and helium gas. It is designed to be cooled. Further, the high frequency power source 1 is mounted on the base 3.
8. High frequency power of 13.56 MHz is applied by 8 and the base 3 and the silicon substrate S mounted on the base 3
A bias potential is generated at.

The gas supply unit 7 has a gas supply pipe 8 connected to the upper end of the etching chamber 2 and mass flow controllers 11 and 12 connected to the gas supply pipe 8, respectively.
The gas cylinders 9 and 10 connected through the gas cylinders 9 and 10 whose flow rates are adjusted by the mass flow controllers 11 and 12 are supplied from the gas cylinders 9 and 10 into the etching chamber 2a. In addition, SF for etching is used in the gas cylinder 9.
₆ gas is filled, and the gas cylinder 10 is filled with C ₅ F ₈ gas for forming a protective film. In addition to this, CF ₄ , CHF ₃ , C ₄ F ₈ and C ₃ F ₈ are used as etching gas. Other fluorocarbon gas (CxFy) can be used as the protective film forming gas.

The decompression section 13 includes an exhaust pipe 14 connected to the lower end of the etching chamber 2 and the exhaust pipe 1.
4 and a vacuum pump (not shown) connected to the etching chamber 2a by the vacuum pump (not shown).
The inside pressure is reduced to a predetermined low pressure (for example, 10 mTorr).

The plasma generating unit 15 has a coil 16 disposed along the outer periphery of the etching chamber 2 at a position higher than the base 3 and a coil 13.56.
A high-frequency power source 17 for applying a high-frequency power of MHz, and by applying the high-frequency power to the coil 16, a fluctuating magnetic field is formed in the space inside the etching chamber 2a, and the gas supplied into the etching chamber 2a changes the magnetic field It is turned into plasma by the electric field induced by the.

The controller 20 controls the mass flow controllers 11 and 12 to control the gas cylinders 9 and 1.
The flow rate of gas supplied from 0 to the etching chamber 2a is shown in FIG.
The gas flow rate control means 21 adjusted as shown in FIGS. 2A and 2B and the high frequency power applied to the coil 16 are shown in FIG.
Coil power control means 22 for controlling as shown in (c),
It comprises a base power control means 23 for controlling the high frequency power applied to the base 3 as shown in FIG. 2 (d).

Further, the end point detecting device 30 has one end facing the observation window 2b, and the etching chamber 2a from the same end.
An optical fiber 31 arranged to receive the light inside,
Connect to the other end of this optical fiber 31,
The spectrum meter 32 detects the emission intensity of the light received by, and the processing unit 33 that receives the emission intensity data detected by the spectrum meter 32 and detects the end point of etching based on the emission intensity data.
In the present example, the spectrum meter 32 uses an F radical (fluorine radical) as a main etching reaction species.
It is set to detect the emission intensity of the wavelength (about 704 nm).

Further, the processing device 33 performs the processing shown in FIGS. 3 and 4 based on the emission intensity data detected by the spectrum meter 32, detects the end point of etching, and outputs an etching end signal. The control device 20
And an end point detection processing section 34 for transmitting the light emission intensity data and a data storage section 35 for storing the emission intensity data and the like. The control device 20 transmits an etching process start signal and a process signal (a signal indicating whether the current processing process is an etching process or a protective film forming process) to the endpoint detection processing unit 34. It has become so.

Next, the operation of the etching apparatus 1 having the above structure will be described.

First, a mode of etching the silicon substrate S will be described.

First, an etching mask (for example, a resist film or SiO 2) having a desired shape is formed by using photolithography or the like.
After forming _two films) on the silicon substrate S, the silicon substrate S is loaded into the etching chamber 2 and placed on the base 3 via the O-ring 4. Then, after this, the space 5a is filled and filled with helium gas from the communication passage 5. The cooling water in the cooling water circulation path 6 is constantly circulated.

Next, SF _{6 is} discharged from the gas cylinders 9 and 10.
Gas and C ₅ F ₈ gas are respectively supplied into the etching chamber 2a, and high frequency power is applied to the coil 16,
High frequency power is applied to the base 3.

As shown in FIG. 2A, the flow rate of the SF ₆ gas supplied into the etching chamber 2a is from V _e2 to V _e2.
2b , the flow rate of the C ₅ F ₈ gas changes in the rectangular wave shape in the range of V _d2 to V _d1 , and the flow rate of the SF ₆ gas changes. Phase and C ₅
The gas flow rate control means 21 controls so that the phases of the F ₈ gas are opposite to each other.

Further, as shown in FIG. 2C, the high frequency power applied to the coil 16 changes into a rectangular wave in the range of W _{c 2} to W _c1 , and the high frequency power applied to the base 3 is As shown in FIG. 2D, the phase of the high frequency power applied to the coil 16 and the phase of the high frequency power applied to the base 3 change in a rectangular wave shape in the range of W _p2 to W _p1. Coil power control means 22, respectively so that they are in phase
It is controlled by the base power control means 23.

The SF ₆ gas and C ₅ F ₈ gas supplied into the etching chamber 2a become a plasma containing ions, electrons, F radicals, etc. in the fluctuating magnetic field generated by the coil 16, and the plasma has a fluctuating magnetic field. High density is maintained by the action. F radicals existing in plasma are S
chemically reacts with i to remove Si from the silicon substrate S, that is, to etch the silicon substrate S,
The ions are accelerated toward the base 3 and the silicon substrate S by the self-bias potential generated in the base 3 and the silicon substrate S, and collide with the silicon substrate S to etch them.
Thus, the surface of the silicon substrate S (etching ground) in the mask opening is etched by these F radicals and ions, and a groove or hole having a predetermined width and depth is formed.

On the other hand, the C ₅ F ₈ gas forms a polymer in the plasma, and this polymer is deposited on the side surface and the bottom surface (etching ground) to form a fluorocarbon film. This fluorocarbon film does not react with F radicals,
It acts as a protective film against radicals, and this protective film prevents side etching and undercut.

As described above, in the presence of plasma obtained by simultaneously supplying SF ₆ gas and C ₅ F ₈ gas into the etching chamber 2a, etching by F radical and ion irradiation and formation of a protective film by polymerization are performed. Opposing actions simultaneously proceed on the bottom and side surfaces of the groove (or hole). Specifically, on the bottom surface where a large amount of ion irradiation is applied, the exfoliation of the polymer due to the ion irradiation acts more strongly than the deposition of the polymer, and the etching by F radicals and ions is more likely to proceed, while the side surface where the ion irradiation is less Then, the deposition of the polymer acts more strongly than the peeling of the polymer by ion irradiation, and the formation of the protective film is likely to proceed.

In consideration of the above, in this embodiment, the flow rates of the SF ₆ gas and the C ₅ F ₈ gas, the high frequency power applied to the coil 16 and the high frequency power applied to the base 3 are set as described above. As described above, the respective controls are performed as shown in FIG.

Specifically, in FIG. 2, e (etching
For time zones shown in (Process), SF₆Gas supply
V_e1And C₅F₈Gas supply amount is V_d2And few
The high frequency power applied to the coil 16
W_c1And set the high frequency power applied to the base 3 to W
_p1It is high. SF₆Increase the amount of gas supply, C
₅F₈The amount of gas supplied is reduced and applied to the coil 16.
Required for etching by increasing the high frequency power
To generate a proper amount of various F radicals and ions
Side etching and undercutting of polymer generation
Can be suppressed to the minimum amount that can prevent
Wear. Also, the high frequency power applied to the base 3 is increased.
By doing so, the ion irradiation speed is increased and the etching speed is increased.
Can be increased.

As described above, with respect to the etching ground (bottom surface) having a large amount of ion irradiation, the exfoliation of the polymer by the ion irradiation acts rather strongly than the deposition of the polymer,
While etching by F radicals and ions proceeds,
On the side where the amount of ion irradiation is small, the deposition of the polymer acts more strongly than the exfoliation of the polymer due to ion irradiation, and the formation of the protective film progresses. To be covered.

On the other hand, in FIG. 2, d (protective film forming step)
For time zones indicated by, SF₆Gas supply amount is V_e2
And reduce C₅F₈Gas supply amount is V_d1And many
At the same time, the high frequency power applied to the coil 16 is W_c2
And lower the high frequency power applied to the base 3 to W_p2And low
Combing. SF₆Reduce the amount of gas supply, C₅F ₈
Necessary for forming a protective film by increasing the gas supply amount
While more polymer can be produced,
The generation of calcium and ions is deposited on the etching ground.
The minimum amount required to peel off the polymer
You can In addition, the high frequency power applied to the base 3 is reduced.
The weight of the etching ground.
Slow the ion irradiation speed to the extent necessary to peel the compound
The protective film deposited on the sidewall of the groove can be
It can be prevented from being peeled off by irradiation.

From the above, the etching ground (bottom surface)
With regard to (1), while the etching is suppressed to such an extent that the deposited polymer is peeled off by ion irradiation, on the side surface where the ion irradiation is small, more polymer is deposited and a strong protective film is formed.

Thus, by sequentially repeating the above steps e and d, a step in which etching mainly proceeds (etching step) and a step in which protective film formation mainly proceeds (protective film formation step) Alternating sideways, the side walls formed sequentially by etching are immediately covered with the protective film, and the protective film is formed more strongly in the subsequent steps, so that the side etching and undercut described above are performed. Can be reliably prevented, whereby a trench whose inner wall surface is vertical and the surface waviness in the vertical direction is 100 nm or less, and more preferably 40 nm or less is formed efficiently on the silicon substrate S. be able to.

The SF for achieving such an action₆
Gas flow rate V_e1Is in the range of 60 to 300 sccm
Is preferable, and the flow rate V_e2Is in the range of 0 to 80 sccm
Preferably. The flow rate V_e20sccm in the range of
Is including C₅F₈When the gas is turned into plasma
Ions are also generated, so they are deposited on the etching ground.
The amount of ions necessary to remove the polymerized product is₅F₈
Ions from gas can do enough
It is believed that Also, the C₅F ₈Of gas
Flow rate V_d1Is preferably in the range of 50-260 sccm
Flow rate V _d2Is in the range of 0 to 150 sccm
Is preferred.

The high frequency power W _c1 applied to the coil 16 is preferably in the range of 800 to 3000 W, and W _c2 is preferably in the range of 600 to 2500 W. Further, the high frequency power W _p1 applied to the base 3 is 3
Is preferably in the range of 50 W, and W _p2 is 5 to 15
It is preferably in the range of W.

Further, the execution time of the step e is preferably in the range of 3 to 45 seconds, and the execution time of the step d is preferably in the range of 3 to 30 seconds.

As described above, according to this example, the vertical surface waviness of the groove or hole side surface obtained by etching the silicon substrate S is 100 nm or less, and more preferably 40 nm.
Since it is possible to achieve the following, it is possible to achieve high integration and high density of the semiconductor integrated circuit, and when the trench capacitor is used, it is possible to prevent deterioration of its insulating property. Further, when a gear is formed, its transmission loss can be minimized.

Next, a mode for detecting the etching end point will be described.

As described above, the light in the etching chamber 2a is received by the spectrum meter 32 via the optical fiber 31, and the emission intensity of the F radical as the main etching reaction species is detected.

The light emission intensity data detected by the spectrum meter 32 is sequentially stored in the end point detection processing section 34.
And the processing shown in FIGS. 3 and 4 is executed in the end point detection processing unit 34, and the etching end point is detected.

Specifically, the endpoint detection processing unit 3
4 receives the signal for starting the etching process from the control device 20 and starts the process, and the spectrum meter 32
Reception of the emission intensity data detected by the spectrum meter 32 is started (step S1).

Next, after resetting the counter n (step S2), it is confirmed whether the process signal received from the controller 20 is the etching process or the protective film forming process (step S3), and the etching process is performed. If it is, the timer is turned on (step S4), and while the elapsed time T of the timer is t ₁ <T <t ₂ , the emission intensity data received from the spectrum meter 32 is stored in the data storage unit 35. Store (steps S5, S6, S7).

The time t ₂ is the time until the timer times out, and the time t ₂ and the time t ₁ are
It is arbitrarily set in advance and stored in the data storage unit 35. Thus, as shown in FIG. 6, a constant time after the start of the etching process (during time t ₁ ) (the initial stage of etching) and a constant time before the end of the etching process (the time t ₂ was subtracted from the etching process time). time left)
The emission intensity data in the intermediate time zone of the etching process excluding (the final stage of etching) is stored in the data storage unit 35.

Then, when the timer times out (step S6), the end point detection processing section 34 next reads the emission intensity data stored in step S7 from the data storage section 35 (step S8) and reads it. After calculating the average value I of the emission intensity data (step S9), it is confirmed whether or not the calculated average value I exceeds a preset reference value K (step S1).
0), if the average value I does not exceed the reference value K, the processing from step S3 onward is repeated. On the other hand, the average value I
If the average value I exceeds the reference value K, it is further confirmed whether or not the previous average value I exceeds the reference value K (step S11). If the previous average value I exceeds the reference value K, Then, the counter n is updated (step S12), and if the previous average value I does not exceed the reference value K, the processing from step S2 onward is repeated. The reference value K is preset and stored in the data storage section 35.

Next, it is confirmed whether or not the counter n updated in step S12 has reached the preset number N (step S13). If the counter n has not reached the preset number N, the above step is performed. While repeating the processes from S3 onward, when the set number of times N is reached, it is determined that etching is completed, and an etching end signal is transmitted to the control device 20 (step S14), and then the spectrum meter 32 is connected. The acquisition of the data from is ended (step S15), and the process is ended.

Then, the control device 20 receives the etching end signal from the end point detection processing section 34 and ends the etching processing.

As described above, according to the end point detection device 30 of this example, the emission intensity of the F radical in the intermediate time zone of the etching process excluding the fixed time after the start of the etching process and the fixed time before the end of the etching process. Based on the data
When this exceeds the reference value K for the set number of times N continuously, it is determined to be the etching end point.

As described above, in the plasma etching method in which the etching process and the protective film forming process are repeated, in the initial stage of shifting from the protective film forming process to the etching process and in the final stage of shifting from the etching process to the protective film forming process. The emission intensity of light having a wavelength corresponding to the detected F radical does not reflect the accurate etching progress state.

In the end point detection device 30 of the present example, from the emission intensity data acquired by the spectrum meter 32, within the fixed time after the start of the etching process (during time t ₁ ) and before the end of the etching process (etching). Since the emission intensity data obtained during the remaining time obtained by subtracting the time t ₂ from the process time) is excluded, the etching progress state is reflected by appropriately setting the times t ₁ and t _2. It is possible to effectively remove the emission intensity data in the initial stage and the final stage of the etching process, which is the time period when the etching process is not performed, and extract only the emission intensity data in the intermediate time period of the etching process that accurately reflects the etching progress state. can do.

By determining the etching end point based on the emission intensity data thus extracted, it is possible to detect the accurate etching end point. still,
In this sense, it is preferable that the time t ₁ is set to about 20 to 30% of the etching process time,
The time t ₂ is preferably set to about 70 to 80% of the etching process time.

As described above, according to the etching apparatus 1 of the present embodiment, the etching end point can be accurately detected as described above. Therefore, even in the SOI wafer, for example,
It becomes possible to form an etching structure having a highly precise shape.

In the end point detection device 30 of this example, when the emission intensity data continuously exceeds the reference value K by the set number N, it is determined that the etching end point is reached. The purpose is to prevent misjudgment that occurs when the emission intensity data contains noise.
When the emission intensity data is less likely to contain noise, the above configuration is not necessarily required, and if the average value I of the emission intensity data exceeds the reference value K even once, it is immediately determined to be the etching end point. Can be configured.

Although one embodiment of the present invention has been described above, the specific mode of the present invention is not limited to this.

For example, in the etching end point determination process of the above example, the change amount ΔI of the emission intensity data average value I sequentially extracted for each etching step is calculated, and the calculated change amount ΔI is set to a preset reference value. K'is set number of times N
It may be determined that the etching end point is reached when the number of times of continuous etching exceeds.

Specifically, the endpoint detection processing unit 34 is configured to execute the processing shown in FIG. 5 subsequent to the processing shown in FIG. That is, the endpoint detection processing unit 34, after the processing shown in FIG. 3, stores the emission intensity data stored in step S7 in the data storage unit 3.
5 (step S21), the average value I of the read emission intensity data is calculated (step S21).
22), after storing the calculated average value I in the data storage unit 35 (step S23), the average value I in the pre-etching process is read from the data storage unit 35 (step S24), and the average value I in the pre-etching process is used. The change amount ΔI is calculated by taking the difference from the average value I of the current etching process (step S25).

Then, the calculated variation ΔI
Confirms whether or not the preset reference value K ′ has been exceeded (step S26), and if the change amount ΔI does not exceed the reference value K ′, the processing from step S3 onward is repeated. On the other hand, when the change amount ΔI exceeds the reference value K, it is further confirmed whether or not the previous change amount ΔI exceeds the reference value K ′ (step S27), and the previous change amount ΔI
When I exceeds the reference value K ′, the counter n is updated (step S28), and when the previous change amount ΔI does not exceed the reference value K ′, the processing from step S2 onward is repeated. .

Next, the endpoint detection processing section 34
It is confirmed whether or not the counter n updated in step S28 has reached the preset number N (step S28).
29) If the counter n has not reached the set number N, the processing from step S3 is repeated, while if the set number N is reached, it is determined that the etching has been completed and the control is performed. After transmitting the etching end signal to the apparatus 20 (step S30), the spectrum meter 3
Data acquisition from step 2 is completed (step S3
1) and the process ends.

Even in this case, as in the above example,
When the emission intensity data does not easily include noise, the etching end point can be immediately determined when the variation ΔI exceeds the reference value K ′ even once.

In the etching process, the etching conditions such as the flow rates of the SF ₆ gas and the C ₅ F ₈ gas, the high frequency power applied to the coil 16 and the high frequency power applied to the base 3 are changed within the above ranges. By so doing, it is sufficient that the step of mainly performing the etching and the step of mainly performing the protective film formation are alternately and repeatedly performed, and the above-mentioned etching conditions to be changed can be appropriately combined and performed. .

That is, the applied power of the coil 16 and the base 3
With the applied power constant, SF₆Gas and C₅F₈Of gas
The flow rate may be changed within the above range, or
Application of the base 3 while keeping only the power applied to the coil 16 constant
Power and SF₆Gas and C ₅F₈Set the gas flow rate to the above range.
It may be changed in the surrounding area, or conversely, the base 3
With the applied power kept constant, the applied power of the coil 16 and S
F₆Gas and C₅F₈Change the gas flow rate within the above range
You may do it.

In this embodiment, the etching process is started from the e process and the e process and the d process are sequentially repeated. However, the present invention is not limited to this, and the d process is started from the d process. The step e and the step e may be sequentially repeated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a partial block diagram of a schematic configuration of an etching apparatus according to an embodiment of the present invention.

FIG. 2 is a timing chart showing the flow rates of SF ₆ gas and C ₅ F ₈ gas and the control state of the high-frequency power applied to the coil and the base in the present embodiment.

FIG. 3 is a flowchart showing a processing procedure of the end point detection device according to the present embodiment.

FIG. 4 is a flowchart showing a processing procedure of the end point detection device according to the present embodiment.

FIG. 5 is a flowchart showing an end point detection procedure according to another aspect of the present invention.

FIG. 6 is a graph showing the emission intensity of specific reaction species in the gas switching etching method.

FIG. 7 is an explanatory diagram for explaining trench etching of an SOI wafer.

[Explanation of symbols]

S Silicon substrate 1 Etching equipment 2 Etching chamber 2a Etching room 3 bases 7 gas supply section 8 gas supply pipes 9,10 gas cylinder 11, 12 Mass flow controller 13 Decompression section 14 Exhaust pipe 15 Plasma generator 16 coils 17, 18 High frequency power supply 20 Control device 21 Gas flow rate control means 22 Coil power control means 23 Base power control means 30 End point detection device 32 Spectrometer 33 processor 34 Endpoint detection processing unit 35 data storage

Claims (8)

[Claims] 1. A step of etching an etching ground on a silicon substrate with plasma-generated reactive species,
A method of detecting an end point of the etching in a plasma etching process of etching the silicon substrate by alternately repeating at least two steps of forming a protective film on a structural surface formed on the silicon substrate by the etching. The luminescence intensity data of a specific reactive species during the etching step is obtained, and the luminescence obtained from the obtained luminescence intensity data within a certain time after the start of the etching step and within a certain time before the end of the etching step. Excluding the intensity data, the emission intensity data acquired during the intermediate time period of the etching process is extracted, and when the extracted emission intensity data exceeds a preset reference value, it is determined that the etching end point is reached. A method for detecting the end point of plasma etching, characterized in that 2. The plasma etching end point according to claim 1, wherein when the extracted emission intensity data continuously exceeds the reference value a preset number of times, it is determined that the etching end point is reached. Detection method. 3. A step of etching an etching ground on a silicon substrate with a reactive species formed into plasma,
A method of detecting an end point of the etching in a plasma etching process of etching the silicon substrate by alternately repeating at least two steps of forming a protective film on a structural surface formed on the silicon substrate by the etching. The luminescence intensity data of a specific reactive species during the etching step is obtained, and the luminescence obtained from the obtained luminescence intensity data within a certain time after the start of the etching step and within a certain time before the end of the etching step. Excluding the intensity data, the emission intensity data acquired in the intermediate time zone of the etching process is extracted, and the change amount of the extracted emission intensity data that is sequentially extracted for each etching process is calculated. Is determined to be the etching end point when exceeds the preset reference value. A characteristic method of detecting the end point of plasma etching. 4. The plasma etching end point detecting method according to claim 3, wherein when the change amount exceeds the reference value continuously for a preset number of times, it is determined that the etching end point is reached. . 5. A silicon substrate is placed in the chamber,
Etching the etching ground on the silicon substrate with the reactive species plasmatized in the chamber;
An apparatus for detecting an end point of the etching in a plasma etching process for etching the silicon substrate by alternately repeating at least two steps of forming a protective film on a structural surface formed on the silicon substrate by the etching. Of the emission intensity detection means for detecting the emission intensity of a specific reactive species in the chamber, and from the emission intensity data during the etching process detected by the emission intensity detection means, within a certain time after the start of the etching process and Except for the emission intensity data obtained within a certain period of time before the end of the etching step, the emission intensity data detected in the intermediate time zone of the etching step is extracted, and the extracted emission intensity data is set to a preset reference value. When crossed,
A plasma etching end point detecting device comprising: an etching end point detecting means for determining the end point of etching. 6. The etching end point detecting means is configured to judge that the etching end point is reached when the extracted emission intensity data continuously exceeds the reference value a preset number of times. Item 5. A plasma etching end point detection device according to item 5. 7. A silicon substrate is placed in the chamber,
Etching the etching ground on the silicon substrate with the reactive species plasmatized in the chamber;
An apparatus for detecting an end point of the etching in a plasma etching process for etching the silicon substrate by alternately repeating at least two steps of forming a protective film on a structural surface formed on the silicon substrate by the etching. Of the emission intensity detection means for detecting the emission intensity of a specific reactive species in the chamber, and the emission intensity data during the etching process detected by the emission intensity detection means, within a certain time after the start of the etching process and Except for the emission intensity data obtained within a certain period of time before the end of the etching process, the emission intensity data detected during the intermediate time period of the etching process is sequentially extracted for each etching process, and changes in the extracted emission intensity data are performed. When the amount of change is calculated and the calculated amount of change exceeds a preset reference value Plasma etching endpoint detection apparatus characterized by being composed to be an etching end point as determined etching end point detection means. 8. The etching end point detecting means is configured to determine that the etching end point is reached when the change amount continuously exceeds the reference value a preset number of times. 7. The plasma etching end point detection device according to 7.