JP2005303088A - Plasma processing apparatus and resist trimming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform high-precision stable resist trimming by suppressing variations in resist pattern line width extremely small during processing of many substrates. <P>SOLUTION: A plasma processing apparatus for making a resist pattern on a substrate thin has a holder 104 which holds a substrate 101 in a chamber 102, a light source 110 which irradiates a surface of the substrate 101 with light, and a spectroscope 111 which obtains a reflected light distribution by spectrally diffusing reflected light from the substrate and is equipped with a film thickness detecting means of detecting a resist pattern film thickness based upon the reflected light distribution, a light emission intensity ratio arithmetic part 112c which computes the ratio of light emission intensity of an active species as an etching seed and the light emission intensity of a dissociation species from an etching product from light emission of plasma 109, and an end point control unit 112f which controls the end point of plasma etching processing based upon the light emission intensity ratio computed by the light emission intensity ratio arithmetic part 112c. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plasma processing apparatus and a resist trimming method for forming an ultrafine resist pattern below the resolution limit of an exposure apparatus.

  The speed of high integration and miniaturization of semiconductor devices is fast, and at present, ultrafine patterns that are below the resolution limit of an exposure apparatus are required. Introduction of a resist trimming process by plasma treatment is becoming common as one of means for obtaining an extremely fine pattern. On the other hand, in order to stably obtain a resist pattern with good line width accuracy in mass production, dimensional control for each wafer is indispensable. However, it is extremely difficult to directly measure the resist pattern line width dimension in the resist trimming process. Therefore, by detecting the amount of change in the resist pattern film thickness or optical constant that correlates with the line width dimension, the deformation amount of the resist pattern is obtained, and the end point of the plasma processing is controlled so that the desired line width dimension is obtained. A method has been proposed (see, for example, Patent Document 1).

  Further, a method for measuring the depth of a wiring groove formed in a transparent material film based on the intensity of a reflection interference spectral waveform in a predetermined wavelength region has been proposed (see, for example, Patent Document 2). Further, there is a method of calculating a characteristic parameter value indicating a film forming state, comparing the calculated value with a target value, determining the suitability of the film forming state, and changing the film forming time and the process parameters as necessary. It has been proposed (see, for example, Patent Document 3). Further, a method has been proposed in which the plasma emission state in the chamber is measured and the initialization state in the chamber is controlled based on the measured plasma emission state (see, for example, Patent Document 4).

JP 2002-64047 A (page 2-3, FIG. 1) Japanese Patent Laying-Open No. 2003-229424 (page 5-7, FIGS. 1 and 9) JP 2003-229362 A (page 8, FIG. 1) JP 2002-367958 (page 4-6, FIG. 6)

  However, only the method described in Patent Document 1 cannot satisfy the required accuracy for future miniaturization. This is because, for example, in the generation of a gate length of 32 nm required for a 65 nm node semiconductor device, if the tolerance of dimensional error is 5%, only dimensional variation of 1.6 nm or less is allowed. This is because it is a strict dimension that is difficult to realize even if the resist film thickness accuracy correlated with the line width dimension is controlled with high accuracy. This is because it is impossible to eliminate process variations even with a plasma device having excellent stability, and the correlation between resist line width and resist film thickness varies due to process variations of the plasma device. It is. As a result, even if the resist film thickness is controlled to be completely constant, variations in the resist line width cannot be suppressed to an allowable amount or less.

  In the first place, with the method described in Patent Document 1, it is impossible to accurately measure the resist pattern in the plasma apparatus from a practical viewpoint. Detection of a resist pattern film thickness with a normal optical film thickness meter requires a resist pattern larger than the spot size of the detection light, and cannot be detected with a circuit pattern of a fine semiconductor device. In addition, the substrate cross-sectional structure of an actual semiconductor device is very complicated, and it is difficult to detect the resist film thickness on this substrate. Furthermore, accurate measurement is difficult due to interference of plasma background light.

  The present invention has been made to solve the above-described conventional problems, and can perform highly accurate and stable resist trimming with extremely small variations in resist pattern line width when processing a large number of substrates. With the goal.

A plasma processing apparatus according to the present invention is a plasma processing apparatus for thinning a resist pattern formed on a substrate by plasma etching,
A processing chamber for generating plasma;
A holding unit that is provided in the processing chamber and holds the substrate;
A light source that irradiates light on the surface of the substrate; and a spectroscope that divides the reflected light from the substrate to obtain a reflected light spectral distribution, and detects a resist pattern film thickness based on the reflected light spectral distribution Film thickness detection means;
A light emission intensity ratio calculating unit that detects light emission of the plasma and calculates a light emission intensity ratio between a light emission intensity of an active species that is an etching species and a light emission intensity of a dissociated species from an etching product;
An end point control unit for controlling the end point of the plasma etching process based on the resist pattern film thickness detected by the film thickness detection unit and the emission intensity ratio calculated by the emission intensity ratio calculation unit; It is a feature.

In the plasma processing apparatus according to the present invention, the end point control unit includes:
First storage means for storing the relationship between the resist pattern film thickness and the corresponding resist pattern line width dimension;
Line width dimension predicting means for predicting a resist pattern line width dimension from the resist pattern film thickness detected by the film thickness detecting means based on the relationship stored in the first storage means;
Second storage means for storing the relationship between the emission intensity ratio and the variation amount of the resist pattern line width dimension corresponding thereto;
Line width dimension correcting means for correcting the resist line width dimension predicted by the line width dimension predicting means based on the relationship stored in the second storage means;
It is preferable to control the end point by comparing the resist line width dimension corrected by the line width dimension correcting unit with a desired resist line width dimension.

In the plasma processing apparatus according to the present invention, the film thickness detection means includes:
A third storage means for storing a plurality of reference spectral distributions corresponding to the film thickness of the resist pattern;
It is preferable that the resist pattern film thickness is detected by comparing the reflected light spectral distribution obtained by the spectroscope with the reference spectral distribution stored in the third storage means.

In the plasma processing apparatus according to the present invention, the film thickness detection means includes:
Fourth storage means for storing the relationship between the resist pattern coverage and the variation amount of the resist pattern film thickness;
It is preferable that the apparatus further includes a film thickness correcting unit that corrects the resist pattern film thickness based on the relationship stored in the fourth storage unit.

In the plasma processing apparatus according to the present invention, the plasma processing apparatus further comprises a temperature detector that is disposed in the vicinity of the substrate and detects a temperature equivalent to the surface temperature of the substrate.
The end point detection unit determines the end point based on the film thickness detected by the film thickness detection unit, the light emission intensity ratio calculated by the light emission intensity ratio calculation unit, and the temperature detected by the temperature detector. It is preferable to control.

A resist trimming method according to the present invention is a resist trimming method for thinning a resist pattern formed on a substrate by plasma etching,
Irradiating the surface of the substrate exposed to plasma with light, detecting reflected light from the surface, and obtaining a reflected light spectral distribution from the reflected light;
Detecting a resist pattern film thickness based on the reflected light spectral distribution;
Detecting the light emission of the plasma, and determining a light emission intensity ratio between the light emission intensity of the active species that is the etching species and the light emission intensity of the dissociated species from the etching product;
And a step of determining an end point of the plasma etching process based on the detected resist pattern film thickness and the obtained emission intensity ratio.

In the resist trimming method according to the present invention, the step of determining the end point is based on the relationship between the resist pattern film thickness and the corresponding resist pattern line width based on the detected resist pattern film thickness. Predicting
Correcting the predicted resist pattern line width dimension based on the relationship between the emission intensity ratio and the corresponding resist pattern line width dimension;
It is preferable to include a step of comparing the corrected resist pattern line width dimension with a desired resist line width dimension to determine the end point.

  In the resist trimming method according to the present invention, it is preferable to obtain the emission intensity ratio within 2 seconds from the start of the plasma etching process.

  As described above, according to the present invention, by determining the end point based on the resist pattern film thickness and the emission intensity ratio, the variation of the resist pattern line width when processing a large number of substrates is suppressed to be extremely small. Highly accurate and stable resist trimming can be performed.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof may be simplified or omitted.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram for explaining a plasma processing apparatus according to Embodiment 1 of the present invention.
As shown in FIG. 1, a lower electrode 104 serving as a holding portion on which a substrate 101 is placed is provided in a chamber (also referred to as a “plasma chamber”) 102 in which a resist pattern trimming process is performed. An electrostatic chuck 104a is provided on the upper surface of the lower electrode 104, and the substrate 101 is held on the electrostatic chuck 104a. He gas is sealed between the electrostatic chuck 104a and the substrate 101 in order to improve heat conduction. An upper electrode 103 is provided on the upper portion of the chamber 102 so as to face the lower electrode 104. A high frequency is applied to the lower electrode 104 and the upper electrode 102 from RF power supplies 116 and 117. A gas supply port (not shown) is provided in the upper part or side wall of the chamber 102, and the process gas is supplied into the chamber 102 from the gas supply port. An exhaust port 114 connected to an exhaust pump (not shown) via a conductance valve 115 is provided at the bottom of the chamber 102, and the pressure in the chamber 102 is controlled by the opening of the conductance valve 115. Although not shown, the temperature of the sidewall of the chamber 102, the lower electrode 104, and the upper electrode 103 is detected by a sensor or the like and is controlled to be constant by a heat exchanger or the like.

The plasma processing apparatus according to the first embodiment includes a light interference type resist pattern film thickness detection mechanism and a mechanism for detecting plasma emission and calculating a light emission intensity ratio. The resist pattern film thickness detection mechanism includes an Xe flash lamp as the light source 110, an optical fiber 106 that guides the lamp light and reflected light, an optical window 105 provided through the upper electrode 103, and reflected light from the substrate. And a control unit 112 that performs analysis, calculation, control, and the like of a reflected light spectral distribution, which will be described later.
The mechanism for detecting the plasma emission and calculating the emission intensity ratio is an optical window 107 provided through the side wall of the chamber 102, an optical fiber 108 for guiding the plasma light, a spectroscope 111 for splitting the plasma light, and will be described later. And a control unit 112 for calculating the emission intensity ratio.
The resist pattern film thickness detection mechanism and the plasma emission intensity ratio calculation mechanism are each connected by a signal line, and the light emission of the light source 110, the detection of the reflected light from the substrate 101, and the detection of the light emission of the plasma 109 are synchronized. It has been.

  The control unit 112 includes a film thickness detection unit 112a that determines the resist pattern film thickness based on the reflected light spectral distribution, and a film that corrects the resist pattern film thickness based on the relationship between the resist pattern coverage and the resist pattern film thickness variation. A thickness correcting unit 112b and a light emission intensity ratio calculating unit 112c that calculates a light emission intensity ratio between the light emission intensity of the active species and the light emission intensity of the dissociated species from the spectrum of the plasma light.

  Further, the control unit 112 predicts the resist pattern line width dimension from the resist pattern film thickness corrected by the film thickness correcting unit 112b based on the relationship between the resist pattern film thickness and the resist pattern line width dimension. A line width dimension correcting means 112e for correcting the resist pattern line width dimension predicted by the line width dimension predicting means 112d based on the relationship between the means 112d, the emission intensity ratio and the variation amount of the resist pattern line width dimension; And an end point control unit 112f that controls the end point of the plasma etching process by comparing the resist pattern line width dimension with a desired line width dimension. The end point control unit 112f controls the RF power sources 116 and 117 and performs process gas supply control and the like.

  In addition, the control unit 112 has a storage unit 113 inside or outside. The storage means 113 stores the relationship between the resist pattern film thickness and the resist pattern line width dimension (see FIG. 8), the relationship between the resist pattern coverage and the resist pattern film thickness fluctuation amount (see FIG. 6), the emission intensity ratio and the resist. The relationship with the pattern line width variation (see FIG. 11), the theoretical spectral distribution of reflected light (see FIG. 4), and the like are stored. The control unit 112 reads and uses the information stored in the storage unit 113 as necessary. Although a large amount of information is stored in one storage unit 113 in the first embodiment, a plurality of storage units may be provided for each piece of information.

In the first embodiment, the plasma light is obtained from the optical window 107, but the plasma light is obtained by separating the reflected light component of the Xe flash lamp light from the surface of the substrate 101 from the light obtained from the optical window 105. It is also possible. However, the thickness of the plasma 109 is larger when viewed from the optical window 107 disposed on the side surface, and the plasma light from the optical window 107 on the side wall of the chamber 102 can be detected with higher sensitivity without receiving interference from the substrate surface. It is better to get
In addition, the spectroscope for reflected light from the substrate and the spectroscope for plasma light are performed by one spectroscope 111. The spectroscope for spectroscopic reflection of light from the substrate and the spectroscope for spectroscopic plasma light are used. You may comprise separately. However, since a single spectroscope equipped with an area sensor can perform a plurality of spectrographs, it is desirable to use one spectroscope 111 in terms of cost and space.

Next, the operation of the plasma processing apparatus will be described.
First, detection of the resist pattern film thickness will be described.
FIG. 2 is a diagram showing a temporal change in the intensity of the reflected light reflected from the substrate surface. In the first embodiment, the Xe flash lamp, which is the light source 110 shown in FIG. 1, emits light repeatedly at a time interval of about 10 times per second, and the time modulation in which the spectroscope 111 detects the spectral distribution of the reflected light from the substrate surface. Measure. This time interval becomes the detection time resolution of the resist pattern film thickness. The intensity (a) of the detection light detected when the Xe lamp emits light includes not only the reflected light from the substrate 101 but also the light emission component from the plasma 109. On the other hand, the intensity (b) of the detection light detected when the Xe lamp is extinguished is the intensity of only the light emission component from the plasma 109. Therefore, by performing time modulation measurement and obtaining the difference (a)-(b), it is possible to measure the resist pattern film thickness with high accuracy without being affected by plasma emission.

FIG. 3 is a diagram showing an example of a cross-sectional structure of the substrate for detecting the resist pattern film thickness. The cross-sectional structure shown in FIG. 3 is a cross-sectional structure when a MOS LSI gate electrode is formed. An element isolation (STI: shallow trench isolation) 302 is formed in the Si substrate 301, and a gate insulating film 303 is formed on the Si substrate 301. A polysilicon film 304 as a gate electrode material, a TEOS oxide film 305 as an etching mask material for the polysilicon film 304, and an antireflection film 306 are sequentially stacked on the gate insulating film 303, and a resist pattern 307 is formed on the antireflection film 306. Is formed.
As can be seen from FIG. 3, the structure of the actual etching substrate is very complicated. For this reason, in order to accurately measure the film thickness of the resist pattern 307 on the substrate in the plasma processing apparatus, modeling of the substrate cross-sectional structure is indispensable (described later).
A substrate having a cross-sectional structure as shown in FIG. 3 is irradiated with Xe flash lamp light 308 from above the substrate. At this time, the areas of the incident light 308 and the reflected light 309 are sufficiently large as compared with the size of the pattern 307 formed on the substrate 301, and preferably the area is equal to or larger than the chip size of the device. Try to get average reflected light. Since the laminated structure differs depending on the location on the substrate, in the case of the cross-sectional structure as shown in FIG. 3, the sum of four different interference signals 309 a to 309 d is detected as reflected light 309. The above-described modeling of the substrate cross-sectional structure is performed by defining the laminated structure of each part from which different interference signals 309a to 309d are obtained and their area ratio.

FIG. 4 is a diagram for explaining a method of predicting the resist pattern film thickness.
In the film thickness detector 112a of FIG. 1, as shown in FIG. 4, the spectral distribution of the reflected light from the substrate obtained by the spectroscope 111 of FIG. 1, and the theoretical spectral distribution of the reflected light obtained from the defined cross-sectional structure model And the resist pattern film thickness is predicted. Here, the theoretical spectral distribution of the reflected light is obtained by using the optical constants (refractive index n and absorption coefficient k) of the material of each laminated film defined by the cross-sectional structure model and the film thickness of each laminated film as input parameters. The thickness is obtained by repeatedly calculating with the variable (t). The t at which the actually measured reflected light spectral distribution and the calculated reflected light theoretical spectral distribution are closest is the predicted resist pattern film thickness. As can be seen from FIG. 4, the theoretical spectral distribution in the case of defining a substrate structure in accordance with the actuality is in good agreement with the actual spectral distribution.

Next, a resist trimming method according to the first embodiment will be described with reference to FIGS.
FIG. 5 is a process cross-sectional view for explaining the resist trimming process in the first embodiment. Specific conditions and methods of the resist trimming process will be described with reference to FIGS. Note that FIG. 1 is simplified to the extent that the conditions and methods can be described, and the detailed mechanism section described in the following description is omitted.
FIG. 5A is a diagram showing a cross-sectional structure of the substrate before trimming. The cross-sectional structure of the substrate shown in FIG. 5A is substantially the same as the structure shown in FIG. 3 and will not be described in detail. However, an organic BARC material is used as the material of the antireflection film 306 and ArF is used as the material of the resist pattern 307. A lithography resist is used.
The substrate 301 is placed on the electrostatic chuck 104a of the lower electrode 104 of the chamber 102, and He gas is sealed at a pressure of 3 Torr between the back surface of the substrate 301 and the electrostatic chuck 104a. The temperatures of the lower electrode 104, the upper electrode 103, and the side wall of the chamber 102 are controlled to 40 ° C., 80 ° C., and 60 ° C., respectively. A mixed gas of O ₂ and CF ₄ is introduced into the chamber 102 at a flow rate ratio of 54:26 sccm, and the conductance valve 115 is controlled to open and close to adjust the pressure in the chamber 102 to 20 mTorr. Thereafter, by applying high frequency power of 60 MHz and 600 W from the RF power source 117 to the upper electrode 103 and applying high frequency power of 13.56 MHz and 100 W to the lower electrode 104 from the RF power source 116, the plasma 109 is excited in the chamber 102, Plasma etching processing of the organic BARC layer 306 on the substrate is started. Along with the etching of the organic BARC layer 306, the ArF resist pattern 307 having the height T1 and the line width dimension L1 is also etched, and as shown in FIG. 5B, the ArF resist pattern 307a having the height T2 and the line width dimension L2 is changed. To do.
When the plasma treatment is continuously performed under the same conditions after the etching of the organic BARC material 306 is finished, the ArF resist pattern 307a has a height T3 and a line width L3 as shown in FIG. The ArF resist pattern 307b is changed.

During the resist trimming process described above, the film thickness monitoring is continuously performed by the resist pattern film thickness detecting means described above, and the resist trimming process is terminated when the height T3 reaches a desired value. As a result of the diligent study, the following problems were found.
It was found that the absolute accuracy of resist pattern film thickness measurement is affected by the coverage of the resist pattern on the substrate, and the measurement error increases as the coverage decreases. FIG. 6 is a diagram showing the dependency of the resist pattern film thickness detection value on the resist pattern coverage. As shown in FIG. 6, when the resist pattern coverage is 94%, the error between the actual film thickness (measured film thickness T in the following equation (1)) and the detected film thickness t is as good as 1% or less. there were. However, it was found that the error increases as the resist pattern coverage decreases to 53% and 21%. However, since the resist pattern film thickness predicted by this method has good linearity, it is possible to easily correct the measurement accuracy by correcting the approximate value using a linear function.
T = at + b, (a and b are constants) ... Equation (1)
As shown in FIG. 7, by performing the approximate value correction by the film thickness correcting means 112b using the equation (1), it can be seen that the absolute accuracy is within 1% even when the resist pattern coverage is 21%. Therefore, in the first embodiment, the above approximate value correction is indispensable. The reason why the detection accuracy of the resist pattern film thickness deteriorates with a decrease in the pattern coverage is not well understood, but it is presumed that the optical constant of the thin film is changed during the process.

FIG. 8 is a diagram showing the relationship between the resist pattern film thickness and the resist pattern line width dimension when the trimming processing time is changed in the first embodiment. Specifically, the pattern deformation amount when the ArF resist pattern having a line width of 120 nm after ArF lithography is trimmed is shown. As shown in FIG. 8, the correlation between the line width dimension L of the resist pattern and the film thickness T is completely proportional, and is expressed by the following equation (2).
L = cT + d, where c and d are constants (2)
If the film thickness of the resist pattern is detected from the relationship of Expression (2), it can be seen that the line width dimension can be predicted by the line width dimension predicting unit 112d in FIG.

However, it has been found that the following problems occur in the actual process.
FIG. 9 is a diagram showing a variation in the resist pattern line width when a large number of substrates are continuously processed. More specifically, by using the relationship shown in FIG. 8 (the relationship of equation (2)), the trimming processing time is controlled so that the resist pattern line width dimension L is a film thickness T finished to 40 nm, and a large number of substrates are formed. The stability of the resist pattern line width dimension when continuously processed is shown. Although the variation in the film thickness T of the resist pattern was suppressed to within 2 nm, the variation in the line width dimension was about 3 nm. In the relationship of FIG. 8, the ratio of the line width variation / film thickness variation is 0.45, and the value of the dimensional variation expected from the variation in film thickness is 2 nm × 0.45 = 0.9 nm. However, the actual dimensional variation value (= 3 nm) is a value that is at least three times larger than the expected value. This is considered to be because the plasma state inevitably fluctuates in the plasma apparatus during continuous processing.

The present inventor has found that the emission spectrum from the plasma emission obtained by the spectroscope 111 of FIG. 1 is used as a method for detecting such a change in the plasma state. FIG. 10 is a diagram showing temporal changes in emission spectrum intensities of plasma O atoms and CO molecules during the BARC etching to trimming process. FIG. 10 shows the result of processing a large number of substrates (emission spectrum intensity) in an overlapping manner. Here, the O atom is one of active species for etching the BARC and the resist pattern, and the CO molecule is one of dissociated species from the etching product. As shown in FIG. 10, in the emission spectrum of O atoms, when the BARC etch is completed and the process proceeds to the trimming process, the area of the etching object is reduced and the consumption of O atoms is reduced, so that the emission intensity is increased. On the other hand, when the emission spectrum of the CO molecule shifts to the trimming process, the etching product decreases and the CO density as the dissociated species decreases, so the emission intensity decreases. Of these, the characteristic part is the CO emission intensity for 2 seconds immediately after the start of etching, and it can be seen that the variation is larger than the other parts.
FIG. 11 is a diagram showing the correlation between the O / CO emission spectrum intensity ratio at 0.5 seconds after the start of etching and the trimmed resist pattern line width when the trimming time is 22 seconds. A linear correlation was observed between the two, and it was found that fluctuations in the plasma that caused fluctuations in the resist pattern line width occurred in 2 seconds immediately after the start of etching. Further, from this result, it is possible to predict and correct the line width variation during continuous processing of a large number of substrates. The dimensional variation D expected from the emission intensity ratio R 0.5 seconds after the start of etching is expressed by the following equation (3).
D = eR + f (e and f are constants) Expression (3)
Accordingly, the relationship between the resist pattern film thickness T and the resist pattern line width dimension L is expressed by the following expression (4) in consideration of the dimension variation amount D due to the change of the plasma state in the relation of the expression (2).
L = cT + d−D = cT + d−eR−f (4)
Further, in consideration of the relationship between the resist pattern film thickness t detected by Equation (1) and the actual film thickness T, the relationship between the detected resist pattern film thickness t and the resist pattern line width dimension L is expressed by the following equation (5). It is represented by
L = c (at + b) + d−eR−f Formula (5)
From this relationship, the resist pattern line width dimension L is predicted based on the film thickness t detected by the resist pattern film thickness detecting means and the light emission intensity ratio R calculated by the light emission intensity ratio calculation unit 112c. The processing is stopped by the end point control unit 112f at the line width dimension. As a result, even when the substrate is continuously processed, the resist pattern line width dimension can be controlled with high accuracy. The result at this time is shown in FIG. The substrate was continuously processed by simultaneously monitoring the resist pattern film thickness and the O / CO emission spectrum intensity ratio 0.5 seconds after the start of etching during BARC etching, and controlling the end point of the trimming process based on this. Even in the case, the dimensional variation was remarkably suppressed.

  As described above, according to the first embodiment, time modulation measurement of the resist pattern film thickness is performed while blinking the light source 110 of the optical interference film thickness meter, and the reflected light theoretical spectral distribution based on the substrate structure model is performed. Then, the film thickness detection unit 112a predicts the resist pattern film thickness from the relationship between the detected reflected light spectral distribution. Based on the relationship between the resist coverage and the variation amount of the resist pattern film thickness, the film thickness correcting unit 112b corrects the resist pattern film thickness predicted by the film thickness detector 112a. Therefore, in the plasma processing apparatus that performs the resist trimming process, the resist pattern film thickness on the substrate in the plasma 109 can be accurately detected without being disturbed by the plasma 109.

  Further, in the first embodiment, the line width dimension predicting unit 112d predicts the resist pattern line width dimension based on the relationship between the thickness of the resist pattern and the line width dimension obtained in advance, and calculates the emission intensity ratio. The line width dimension correcting unit 112e corrects the resist pattern line width dimension based on the relationship between the emission intensity ratio calculated by the unit 112c and the resist pattern line width dimension variation amount, and based on the corrected resist pattern line width dimension. The end point of the trimming process is controlled by the end point control unit 112f. Accordingly, it is possible to suppress resist pattern line width variations when processing a large number of substrates to be extremely small, and to perform highly accurate and stable resist trimming.

  In the first embodiment, the parallel plate type plasma processing apparatus in which the upper electrode 103 and the lower electrode 104 are opposed to each other in the chamber 102 has been described. However, the present invention is applied to other plasma processing apparatuses. can do.

Embodiment 2. FIG.
In the first embodiment, when the resist pattern film thickness is detected using the optical interference type film thickness detection mechanism, the substrate structure is modeled differently in order to apply it to actual mass production. Must be done for each device. At this time, reflected light from a very large area compared to the device structure is detected on average, so it is difficult to accurately define it in the modeling of the substrate structure. Therefore, it is necessary to optimize by a certain amount of trial and error, and the procedure is complicated.

  In the second embodiment of the present invention, the resist pattern film thickness detection mechanism is different from the first embodiment. Hereinafter, a resist pattern film thickness detection mechanism that is different from the first embodiment will be described. The main apparatus configuration and method are the same as those in the first embodiment, and thus the description thereof is omitted.

  Although not shown, the plasma processing apparatus according to the second embodiment stores the reflected light spectral distribution (reference spectral distribution) at each processing time and the actually measured resist pattern film thickness obtained at that time in the storage means 113 ( In the film thickness detection unit 112a of the control unit 112, a spectral distribution collating unit that collates the reflected light spectral distribution detected during the processing with the stored reference spectral distribution.

FIG. 13 is a diagram showing a change with time in the spectral distribution of reflected light from the substrate in the second embodiment of the present invention. As shown in FIG. 13, when trimming a resist pattern of a certain type of device, the shape of the reflected light spectral distribution during the trimming process is, for example, 13 seconds, 16 seconds, 19 seconds, 22 seconds, and 25 seconds. It changes over time. That is, the shape of the reflected light spectral distribution detected during resist trimming changes with changes in the resist pattern film thickness.
If the relationship between the reflected light spectral distribution shape at each elapsed time of the trimming process and the resist pattern film thickness actually measured at that time is obtained, the film thickness of the resist pattern can be predicted by collating the reflected light spectral distribution. Therefore, the trimming process can be performed while the resist pattern film thickness is predicted in real time.

  As described above, in the second embodiment, a unique reflected light spectral distribution from substrates with different device types and pattern shapes is acquired in advance using an actual substrate, and a resist corresponding to the reflected light spectral distribution is obtained. The pattern film thickness was acquired and made into a database. The reflected light spectral distribution shape of the substrate detected during actual resist trimming is compared with the reference spectral distribution shape in the database to predict the resist pattern film thickness. Therefore, it is not necessary to define a substrate structure model and obtain a theoretical reflected light spectral distribution as in the first embodiment, and high-precision trimming control can be flexibly applied to processing of a plurality of types of substrates.

Embodiment 3 FIG.
In the first embodiment, the effect of improving the dimensional stability in the processing of a large number of wafers was recognized. However, as a result of intensive studies by the present inventor, it has been found that if processing of 100 wafers is continuously performed, the resist pattern size varies due to factors other than plasma variation. And it turned out that the cause of this dimensional variation is the temperature rise of the substrate surface. As described in the first embodiment, the temperatures of the upper and lower electrodes 103 and 104 and the side wall of the chamber 102 are controlled to be constant by a heat exchanger or the like. However, each surface temperature gradually increases when a large number of substrates are continuously processed. In particular, when the side walls of the upper electrode 103 and the chamber 102 are covered with an adhesion-preventing plate (liner) made of a material such as quartz or ceramics, the increase in surface temperature increases due to a decrease in heat conduction. Radiation heat from here also raises the temperature of the substrate surface. Such a rise in the substrate surface temperature causes a problem of variation in the line width dimension of the resist pattern.

FIG. 14 is a schematic diagram for explaining a plasma processing apparatus according to the third embodiment of the present invention. The main apparatus configuration and method are the same as those in the first embodiment, and thus the description thereof is omitted.
As shown in FIG. 14, a flat plate type temperature detector 118 is provided in the immediate vicinity of the substrate 104. The temperature detector 113 is, for example, a thermocouple embedded in a thin silicon plate having a thickness of 0.1 mm. The temperature detector 118 is placed on the electrostatic chuck 104 a together with the substrate 101. Although not shown, the temperature detector 118 and the thermocouple are electrically insulated from the lower electrode 104, and have a structure in which high-frequency noise of plasma is removed by a low-pass filter. The electromotive force from the thermocouple is converted into a signal by an analog-digital conversion unit (A / D conversion unit) 119, and the detected temperature is sent to the control unit 112. The end point control unit 112f of the control unit 112 further predicts the variation amount of the resist pattern line width dimension based on the detected temperature, and controls the end point of the resist trimming process.

  FIG. 15 is a diagram showing a tendency that the resist line width dimension is reduced due to the temperature rise of the substrate surface during continuous processing of a large number of substrates. In contrast, FIG. 16 shows the result of adjusting the resist trimming time by predicting the dimensional variation while monitoring the substrate surface temperature by the temperature detector 118. By controlling the processing time by an amount corresponding to the substrate surface temperature rise, the dimensional variation can be suppressed.

  As described above, in the third embodiment, in addition to the effects obtained in the first embodiment, a change in the resist pattern line width due to an increase in the substrate surface temperature is predicted by detecting a temperature close to the substrate surface temperature. This makes it possible to suppress variations in the line width when processing a large number of substrates, and to perform highly accurate and stable resist trimming.

  In the third embodiment, the temperature detection mechanism 118 is added to the first embodiment, but may be added to the second embodiment.

It is the schematic for demonstrating the plasma processing apparatus by Embodiment 1 of this invention. It is a figure which shows the time change of the intensity | strength of the reflected light reflected from the substrate surface. It is a figure which shows an example of the cross-sectional structure of the board | substrate which detects a resist pattern film thickness. It is a figure for demonstrating the prediction method of a resist pattern film thickness. It is process sectional drawing for demonstrating a resist trimming process. It is a figure which shows the resist pattern coverage rate dependence of the resist pattern film thickness detection value. It is a figure which shows the result of having corrected the resist pattern coverage dependency of the resist pattern film thickness detection value. It is a figure which shows the relationship between a resist pattern film thickness when a trimming process time is changed, and a resist pattern line width dimension. It is a figure which shows the fluctuation | variation of the resist pattern line | wire width dimension at the time of processing a lot of board | substrates continuously. It is a figure which shows the time change of the emission spectrum intensity | strength of the O atom and CO molecule | numerator of the plasma during a BARC etching-trimming process. It is the figure which showed the correlation with the O / CO emission spectrum intensity ratio in 0.5 second after an etching start, and the trimmed resist pattern line width dimension. In Embodiment 1 of this invention, it is a figure which shows the result by which the resist pattern line width dimension was controlled with high precision. In Embodiment 2 of this invention, it is a figure which shows the time-dependent change of the reflected light spectral distribution from a board | substrate. It is the schematic for demonstrating the plasma processing apparatus by Embodiment 3 of this invention. It is a figure which shows the fluctuation | variation of the resist pattern line width dimension by the temperature rise of a board | substrate surface. It is a figure which shows the result which correct | amended the fluctuation | variation of the resist pattern line | wire width dimension.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Substrate 102 Chamber 103 Upper electrode 104 Lower electrode 104a Electrostatic chuck 105 Optical window 106 Optical fiber 107 Optical window 108 Optical fiber 109 Plasma 110 Light source 111 Spectrometer 112 Control part 112a Film thickness detection part 112b Film thickness correction means 112c Light emission intensity ratio Arithmetic unit 112d Line width dimension predicting unit 112e Line width dimension correcting unit 112f End point control unit 113 Storage unit 114 Exhaust port 115 Conductance valve 116 RF power source for lower electrode 117 RF power source for upper electrode 118 Temperature detector 119 A / D converter

Claims (8)

A plasma processing apparatus for thinning a resist pattern formed on a substrate by plasma etching,
A processing chamber for generating plasma;
A holding unit that is provided in the processing chamber and holds the substrate;
A light source that irradiates light on the surface of the substrate; and a spectroscope that divides the reflected light from the substrate to obtain a reflected light spectral distribution, and detects a resist pattern film thickness based on the reflected light spectral distribution Film thickness detection means;
A light emission intensity ratio calculating unit that detects light emission of the plasma and calculates a light emission intensity ratio between a light emission intensity of an active species that is an etching species and a light emission intensity of a dissociated species from an etching product;
An end point control unit for controlling the end point of the plasma etching process based on the resist pattern film thickness detected by the film thickness detection unit and the emission intensity ratio calculated by the emission intensity ratio calculation unit; A plasma processing apparatus. The plasma processing apparatus according to claim 1,
The end point controller
First storage means for storing the relationship between the resist pattern film thickness and the corresponding resist pattern line width dimension;
Line width dimension predicting means for predicting a resist pattern line width dimension from the resist pattern film thickness detected by the film thickness detecting means based on the relationship stored in the first storage means;
Second storage means for storing the relationship between the emission intensity ratio and the variation amount of the resist pattern line width dimension corresponding thereto;
Line width dimension correcting means for correcting the resist line width dimension predicted by the line width dimension predicting means based on the relationship stored in the second storage means;
A plasma processing apparatus, wherein the end point is controlled by comparing a resist line width dimension corrected by the line width dimension correcting unit with a desired resist line width dimension. In the plasma processing apparatus according to claim 1 or 2,
The film thickness detecting means includes
A third storage means for storing a plurality of reference spectral distributions corresponding to the film thickness of the resist pattern;
A plasma processing apparatus for detecting the resist pattern film thickness by comparing a reflected light spectral distribution obtained by the spectroscope with a reference spectral distribution stored in the third storage means. In the plasma processing apparatus in any one of Claim 1 to 3,
The film thickness detecting means includes
Fourth storage means for storing the relationship between the resist pattern coverage and the variation amount of the resist pattern film thickness;
A plasma processing apparatus, further comprising: a film thickness correcting unit that corrects the resist pattern film thickness based on the relationship stored in the fourth storage unit. In the plasma processing apparatus according to any one of claims 1 to 4,
A temperature detector that is disposed in the vicinity of the substrate and detects a temperature equivalent to the surface temperature of the substrate;
The end point detection unit determines the end point based on the film thickness detected by the film thickness detection unit, the light emission intensity ratio calculated by the light emission intensity ratio calculation unit, and the temperature detected by the temperature detector. A plasma processing apparatus characterized by controlling. A resist trimming method for thinning a resist pattern formed on a substrate by plasma etching,
Irradiating the surface of the substrate exposed to plasma with light, detecting reflected light from the surface, and obtaining a reflected light spectral distribution from the reflected light;
Detecting a resist pattern film thickness based on the reflected light spectral distribution;
Detecting the light emission of the plasma, and determining a light emission intensity ratio between the light emission intensity of the active species that is the etching species and the light emission intensity of the dissociated species from the etching product;
A resist trimming method comprising: determining an end point of a plasma etching process based on the detected resist pattern film thickness and the obtained emission intensity ratio. The resist trimming method according to claim 6,
The step of determining the end point is a step of predicting a resist pattern line width dimension from the detected resist pattern film thickness based on the relationship between the resist pattern film thickness and the corresponding resist pattern line width;
Correcting the predicted resist pattern line width dimension based on the relationship between the emission intensity ratio and the corresponding resist pattern line width dimension;
A step of comparing the corrected resist pattern line width dimension with a desired resist line width dimension and determining the end point. The resist trimming method according to claim 6 or 7,
A resist trimming method characterized in that the emission intensity ratio within 2 seconds from the start of plasma etching is obtained.

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