JP2011253832A - Resist trimming method and trimming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resist trimming method capable of highly accurately controlling dimension by performing resist trimming at a low trimming speed.SOLUTION: The resist trimming method includes: a plasma generation step of generating plasma of a reaction gas; a removing step of removing ions and electrons from the generated plasma to selectively extract a radical; and a trimming step of trimming a resist pattern by irradiating the plasma, from which the ions and the electrons have been removed, to the resist pattern.

Description

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

  In recent years, with the high integration of semiconductors and the reduction in chip size, pattern size miniaturization has been promoted. Since the speed performance of a semiconductor device is mainly determined by the width dimension of a circuit pattern when the materials are the same, miniaturization has been promoted year by year, and a precise exposure process is required accordingly.

  Since the miniaturization capability of the exposure process mainly depends on the wavelength of the exposure light source, the development of resist materials sensitive to the wavelength from the I-line to the KrF laser, ArF laser, the shorter wavelength light source and the wavelength has been advanced. . However, in recent years, the shortening of the wavelength of the light source has not caught up with the progress of miniaturization, and the pattern transfer capability has reached its limit, and it is difficult to perform miniaturization in generations with a gate length of 32 nm or later.

  In view of this, developments have been made on techniques for finer patterns that cannot be formed by exposure.

  As such a technique, for example, a technique called resist trimming is disclosed in which an etching gas such as oxygen is introduced into a vacuum processing chamber, a plasma discharge is generated under reduced pressure, and plasma processing is performed to narrow the width of the resist pattern. (See Patent Document 1).

JP 2005-303088 A

  However, resist trimming using capacitively coupled plasma as disclosed in Patent Document 1 has the following problems.

First, because the plasma electron density is as high as 1 × 10 ⁺¹⁰ to 10 ⁺¹² cm ⁻³ , the resist etching rate, that is, the trimming rate is too high, from several hundred to several thousand nm / min. It is difficult to control the dimensions of several tens to several nanometers.

  Secondly, as described above, if the electron density or ion density of plasma is high, high-density plasma is directly irradiated onto the substrate, which may cause charge-up damage to the processing substrate.

  Third, if the ion density is high, it is difficult to perform isotropic etching due to ion bombardment. For example, when an intended pattern width is obtained, the pattern thickness may become too small.

  The present invention has been proposed in view of the above-described problems, and an object of the present invention is to provide a resist trimming method and a trimming apparatus capable of controlling dimensions with high accuracy by performing resist trimming at a low trimming speed. And

  The resist trimming method of the present invention includes the following steps in order to achieve the above-described object.

  The first step is a plasma generation step for generating plasma of a reactive gas. The second step is a removal step in which ions and electrons are removed from the generated plasma to selectively extract radicals. The third step is a trimming step for trimming the resist pattern by irradiating the resist pattern with plasma from which ions and electrons have been removed.

  According to the resist trimming method of the present invention, it is possible to perform resist trimming at a low trimming speed, so that the dimensions can be controlled with high accuracy.

  Hereinafter, embodiments of a resist trimming method and a trimming apparatus according to the present invention will be described with reference to the drawings.

[Configuration of trimming device]
A trimming apparatus according to an embodiment of the present invention includes a plasma generation space in which high-frequency electrodes are disposed, a trimming processing space in which an object to be processed can be disposed, a conductive member, a gas introduction unit, an exhaust unit, and a high-frequency power. Control means and a controller are provided. The conductive member is disposed between the plasma generation space and the trimming processing space, and has a plurality of through holes for communicating both spaces. The gas introduction means is a means for introducing a reaction gas into the plasma generation space. The exhaust means is means for exhausting the plasma generation space and the trimming processing space. The high frequency power control means is means for controlling power supply to the high frequency electrode. The controller controls the gas introduction unit, the exhaust unit, and the high frequency power control unit to introduce the plasma from which ions and electrons have been removed into the trimming process space and trim the resist pattern introduced into the trimming process space. It is means of.

  Hereinafter, a trimming apparatus according to an embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 is a schematic diagram showing a configuration of a trimming apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the trimming apparatus according to the embodiment of the present invention includes a vacuum container 11 capable of maintaining the inside in a vacuum state. Inside the vacuum vessel 11, a partition plate 1 made of a conductive member (SUS or aluminum) is provided in a horizontal state. The vacuum vessel 11 is grounded by the partition plate 1 and is divided into a plasma generation chamber 3 that forms a plasma discharge space that functions as a plasma generation space, and a trimming processing chamber 4 that functions as a trimming processing space. The partition plate 1 is formed with a plurality of through holes 5 penetrating the plasma generation chamber 3 and the trimming chamber 4 in the vertical direction, thereby blocking electrons and ions. Further, by introducing a trimming gas, which is a reactive gas, into the plasma generation chamber 3 and supplying high frequency power (for example, 13.56 MHz) to the high frequency electrode 2 from the high frequency power source 21 that functions as high frequency power control means, capacitively coupled plasma is obtained. Is born.

  In the trimming processing chamber 4, a substrate holding mechanism 6 capable of holding a substrate by an electrostatic adsorption action or the like is disposed. In addition, a heater 7 is provided inside the substrate holding mechanism 6, and it is possible to uniformly control the substrate temperature by this heater 7 and keep the trimming distribution uniform. It is possible to obtain a trimming shape with a good in-plane distribution by attaching a heater to the entire interior of the partition plate 1 and the vacuum container 11 to uniformly control the temperature of the entire vacuum container 11.

The gas introduction system 8 that functions as a gas introduction means introduces gas from a gas supply source to the plasma generation chamber 3, has a mass flow controller (not shown), and is based on a command from the controller 9. The flow rate introduced into the can be adjusted. The trimming gas introduced from the gas introduction system 8 includes O atoms, H atoms, and N as substances that can convert C, H, O, etc. into components such as CO ₂ by reaction with organic compounds that constitute the photoresist. A gas containing atoms or the like can be used. Radicals containing O atoms can be suitably used because of their high reactivity. For example, C atoms in a photoresist are converted into components such as carbon dioxide. Further, radicals containing H atoms react with C atoms in the photoresist and are converted into components such as CH _X. For example, O ₂ , O ₃ , N ₂ , NH ₃ , H ₂ , NO _X, C _X H _Y (X and Y are arbitrary numbers, for example, alkanes such as methane and ethane, alkynes such as ethylene), C _X H _Y O _Z (X, Y, Z are any number, for example, alcohols (CH ₃ OH, etc.), ketones (methyl ethyl ketone, isopropyl methyl ketone, methyl propyl ketone, etc.), aldehydes, carboxylic acids, ethers And gas containing esters) can be used.

When high frequency power is supplied to the high frequency electrode 2 in a state where the trimming gas is introduced into the plasma generation chamber 3, plasma serving as a radical generation source is generated in the plasma generation chamber 3. The plasma contains electrons, radicals, and ions, but the electrons and ions are blocked by the partition plate 1 charged by high-frequency discharge, and the radicals are selectively introduced into the trimming chamber 4 through the through-holes 5 to the substrate. Will be irradiated. For example, when high frequency power is supplied to the plasma generation chamber 3 in a state where oxygen is introduced into the plasma generation chamber 3, oxygen plasma is generated. Among them, only oxygen radicals pass through the through holes and are separated and introduced into the resist trimming chamber, and the oxygen radicals are irradiated onto the processing substrate. Oxygen radicals are combined with C atoms in the photoresist to become CO ₂ or CO, or are combined with H atoms and converted to H ₂ O or the like.

  In the case of the apparatus having the above configuration, if the gas flow rate in the through hole 5 of the partition plate 1 is u, the substantial length of the through hole 5 is L, and the mutual gas diffusion coefficient is D, uL / D> The length L of the through hole 5 and the gas flow rate u are set so as to satisfy the condition of 1. Thereby, the reverse diffusion of radicals from the partition plate 1 to the plasma generation chamber 3 is prevented. The diameter size of the through holes 5 and the number of the through holes 5 in the partition plate 1 are also related to the amount of electrons and ions blocked, and are set so that the electron density in the trimming processing chamber 4 is set to a target value. The

  The exhaust system 10 that functions as an exhaust means includes a turbo molecular pump (not shown) and the like, and exhausts the trimming processing chamber 4 at a predetermined exhaust speed based on a command from the controller 9.

  The controller 9 can control process conditions such as high-frequency power, gas flow rate, process pressure, processing time, and substrate temperature by sending commands to the high-frequency power source 21, the gas introduction system 8, the exhaust system 10, the heater 7, and the like. ing. In the present embodiment, the process pressure is set to a predetermined value by controlling at least one of the gas introduction system 8 and the exhaust system 10 based on an input from a pressure sensor (not shown). The controller 9 includes a general computer, a driver that can transmit commands to various devices, and the like, and executes trimming processing based on a program. The controller 9 having such a configuration functions as a control unit 91, a timer processing unit 92, a trimming speed information storage unit 93, and an end timing calculation unit 94. The control unit 91 is a functional unit that controls the timer controller 9 in an integrated manner. The timer processing unit 92 is a functional unit for ending the trimming process when the resist pattern is trimmed to a desired size. The trimming speed information storage unit 93 is a functional unit for storing trimming speed information related to the trimming speed. The end timing calculation unit 94 is a functional unit for determining the end timing of the trimming process based on the trimming speed information.

[Trimming method]
Next, a resist trimming method using the trimming apparatus having the above-described configuration will be described.

The resist trimming method according to the embodiment of the present invention has the following three steps as main steps. The first step is a plasma generation step for generating plasma of a reactive gas. The second step is a removal step in which ions and electrons are removed from the generated plasma to selectively extract radicals. The third step is a trimming step for trimming the resist pattern by irradiating the resist pattern with plasma from which ions and electrons have been removed. In the trimming step, plasma is generated by introducing a reactive gas into the plasma generation space, supplying high frequency power to the high frequency electrode, and causing high frequency discharge. Then, the generated plasma is introduced into the trimming processing space via a conductive member, so that the plasma from which ions and electrons are removed is irradiated. In this trimming step, it is preferable to irradiate plasma with an electron density of 1 × 10 ⁺⁷ cm ⁻³ or less.

  Hereinafter, a resist trimming method according to an embodiment of the present invention will be described in detail with reference to FIG. FIG. 2 is an explanatory view showing a resist trimming method according to the embodiment of the present invention.

First, as shown in FIG. 2A, in a state where the inside of the vacuum vessel 11 is maintained at a predetermined degree of vacuum, a substrate on which an etching target material 31 and a resist pattern are stacked (a substrate portion is not shown) is used as a trimming device. It is carried in and placed on the substrate holding mechanism 6. Then, a trimming gas is introduced into the plasma generation chamber 3 and high frequency power is applied to the high frequency electrode 2 to generate plasma. Plasma diffuses toward the trimming chamber 4, but ions and electrons are blocked by the partition plate 1, and only radicals of trimming gas molecules are introduced into the trimming chamber 4, and the electron density in the trimming chamber 4 is 1 ×. It is maintained at 10 ⁺⁷ cm ⁻³ or less.

  When exposed to radicals of trimming gas molecules, the surface of the photoresist 32 is oxidized and converted into gas molecules such as carbon dioxide, and the size of the resist pattern is reduced as shown in FIG.

  When the resist pattern has a desired size, the power supply to the high-frequency electrode 2 is stopped to end the trimming process. For example, when a predetermined processing time elapses, the processing is terminated assuming that the desired size is reached.

The predetermined processing time will be described with reference to FIG. FIG. 3 is a map showing the correspondence between the CD and the trimming time (in this example, the line width of the resist pattern). For example, as shown in FIG. 3, the predetermined processing time is a controller that maps a map showing the correspondence between the CD and the trimming time, corresponding to each process condition (trimming gas type, process pressure, substrate temperature, etc.) and each resist material. 9 and determine based on this. Specifically, the processing time Δt required to change from the line width CD ₀ before processing to the target line width CD ₁ is calculated based on the map, and the processing is terminated when the processing time Δt has elapsed. Of course, a predetermined processing time may be calculated based on an approximate expression instead of a map, or appropriate correction may be performed.

As described above, the electron density is 1 × 10 ⁺⁷ cm ⁻³ or less, and the resist trimming can be performed at a low trimming speed by trimming the resist pattern using the trimming gas. For this reason, it becomes possible to control the dimensions with high accuracy at a level of several tens of nanometers to several nanometers.

  In addition, by not directly irradiating the substrate with plasma, it is possible to eliminate charge-up damage due to electric charges on the substrate. Furthermore, it is possible to perform isotropic etching.

  The predetermined processing time described above is determined by calculation by the controller 9, but a predetermined value is inputted by the user, and only the timer processing (processing for sending an end signal when the predetermined time elapses) is performed by the controller. 9 may be executed. Further, although the end point is determined by timer processing, feedback control may be performed by detecting the actual value using a known film thickness detector or the like. However, in the case of the present invention, the trimming speed can be made very small by selectively using radicals, so that a desired dimension can be obtained with high accuracy even by a method of determining the processing time based on the trimming speed, and the end point. There are advantages that detection is easy and the apparatus configuration can be simplified.

  In addition, this invention is not limited to embodiment mentioned above. For example, although capacitively coupled plasma is generated in the above-described embodiment, an apparatus configuration that generates inductively coupled plasma may be used, or an apparatus configuration that generates ECR or helicon wave plasma may be used.

[Example 1]
Next, specific examples of the present invention will be described.

  As Example 1, in order to confirm that the trimming apparatus shown in FIG. 1 satisfies the requirements for electron density, an electron density measurement test of the trimming chamber 4 was performed. The electron density of the trimming processing chamber 4 was measured using a Langmuir probe to measure the saturation ion current density at a position 11 mm directly above the processing substrate.

  Oxygen 500 sccm was used as a trimming gas, and argon 50 sccm was used as a carrier gas. A power of 200 W was applied to the high-frequency electrode 2 provided in the plasma generation chamber 3. The process pressure was 20 Pa.

FIG. 4 is an electron density measurement result diagram of Example 1. As shown in FIG. 4, the electron density was kept at 1 × 10 ⁺⁷ cm ⁻³ or less, and it was confirmed that the electron density was lower by 3 digits or more than when the partition plate 1 was not used.

[Example 2]
Next, as Example 2, a test for confirming the effect of reducing the charge-up damage was performed.

  In Example 2, the MOS capacitor was processed using the same apparatus and process conditions as in Example 1.

  As a comparative example, a similar test was performed on a capacitive coupling type apparatus in which the partition plate 1 does not exist. The test was performed with the trimming gas as oxygen at 500 sccm, the pressure as 180 Pa, and the input power as 1000 W.

  The measurement was performed at 56 points on the 8 "wafer surface and the antenna ratio (area ratio of the upper electrode to the gate oxide film) was 700,000 times.

  5 to 8 are graphs showing the result of evaluating the charge-up damage by measuring the IV characteristics of the MOS capacitor. The numerical values in FIG. 5 (Example 2) and FIG. 7 (Comparative Example) indicate the leakage current (pA) at each point. When there is a charge-up damage, the absolute value of the leakage current value of the MOS capacitor is large. Become. Moreover, the numerical value in FIG. 6 (Example 2) and FIG. 8 (comparative example) has shown the breakdown voltage (V), and the absolute value of a breakdown voltage becomes small.

  In the comparative example, there was a region where the absolute value of the leak current was locally high as 1E + 6 pA in the wafer surface, and a region where the breakdown voltage was also locally small was measured (see FIGS. 7 and 8). From this, it was confirmed that charge up is induced by slight plasma non-uniformity due to the high electron density in the plasma. On the other hand, in Example 2, it was confirmed that the leakage current was uniformly 40 pA or less in the wafer surface, the dielectric breakdown voltage was uniform in the surface, and there was no charge-up damage (see FIGS. 5 and 6).

[Example 3]
Next, as Example 3, the trimming speed was measured.

  In Example 3, the substrate having a photoresist formed on the surface was processed and the trimming speed was measured using the same apparatus and process conditions as in Example 1. Further, as a comparative example, the substrate on which the photoresist was formed was processed under the same process conditions as in the comparative example in Example 1, and the trimming speed was measured.

  FIG. 9 is a measurement result diagram of the trimming speed. As shown in FIG. 9, in the comparative example, the resist trimming speed is very high, 100 to 1000 nm / min, but it was confirmed that the trimming speed was 10 nm / min or less in the resist trimming method using the radical of the present invention. It was.

[Example 4]
Next, as Example 4, the resist trimming speed and in-plane distribution were measured by changing the substrate temperature and the process pressure.

  Oxygen 500 sccm was used as a trimming gas, and argon 50 sccm was used as a carrier gas. A power of 200 W was applied to the high-frequency electrode provided in the plasma generation chamber.

  The process pressures in the plasma generation chamber 3 and the trimming chamber 4 are both 20 to 50 Pa, and the temperature of the processing substrate is 30 to 100 ° C., which is a low temperature region that does not affect the resist resistance.

  FIG. 10 is a measurement result diagram of the trimming speed and the temperature of the substrate holding mechanism.

  As shown in FIG. 10, in any temperature range from 30 to 100 ° C., it was confirmed that the resist trimming rate was 10 nm / min or less, and the trimming rate was kept low.

  FIG. 11 shows the process pressure and the in-plane distribution, and confirms the in-plane distribution on the 200 mm substrate.

  Measurement was performed with Edge exclusion 5 mm and 25 points in the plane.

  As shown in FIG. 11, the trimming distribution is 3σ and a maximum of 5% or less is realized.

[Example 5]
Next, as Example 5, a test for confirming dimensional controllability was performed.

  As Example 5, the process gas used was 500 sccm of oxygen and 50 sccm of argon as the carrier gas. The high-frequency electrode disposed in the plasma generation chamber was supplied with a power of 200W. The process pressure of the plasma generation chamber 3 and the trimming chamber 4 was 50 Pa, and the temperature of the processing substrate was 100 ° C.

  As a comparative example, CD measurement was performed on a trimming method using inductively coupled plasma in which plasma was irradiated as it was without selecting radicals. The process gas was oxygen 1 sccm, Ar 50 sccm, power 500 W, process pressure 1 Pa, and the processing substrate temperature was 80 ° C.

  FIG. 12 is a measurement result diagram of CD of the resist pattern.

  As shown in FIG. 12, as a result of performing the trimming in the comparative example, the 50 nm trimming is completed in only 30 seconds. On the other hand, it was shown that the trimming method of the present invention can perform resist trimming with a much higher accuracy of about 200 s to perform 50 nm trimming.

[Example 6]
Next, as Example 6, a test for confirming the isotropy of the trimming process was performed.

  The process conditions of Example 6 and Comparative Example were the same as those of Example 5.

  FIG. 13 is a measurement result diagram of the amount of change in the aspect ratio after resist trimming.

  The amount of change in the horizontal direction after resist trimming was A, and the amount of change in the vertical direction was B.

  As shown in FIG. 13, in the resist trimming method using radicals of the present invention, the aspect ratio is A: B = 1: 1, whereas in the conventional method, the aspect ratio is A: B = 1: 1.5. Met.

  In conventional methods, the aspect ratio of trimming tends to be anisotropic due to ion bombardment and the like, but the resist trimming method using the present invention can reduce ion bombardment and trim the aspect ratio isotropically. .

Schematic which shows the structure of the trimming apparatus which concerns on embodiment of this invention. Explanatory drawing which shows the resist trimming method which concerns on embodiment of this invention. Map showing correspondence between CD and trimming time. The electron density measurement result figure of Example 1. FIG. FIG. 6 is a diagram illustrating a result of evaluating charge-up damage by measuring the IV characteristics of a MOS capacitor (Example 2 / leakage current). The result figure which evaluated the charge-up damage by the measurement of the IV characteristic of a MOS capacitor (Example 2 / breakdown voltage). The result figure which evaluated the charge-up damage by the measurement of the IV characteristic of a MOS capacitor (comparative example / leakage current). The result figure which evaluated charge-up damage by measuring the IV characteristic of a MOS capacitor (comparative example / dielectric breakdown voltage). The measurement result figure of trimming speed. The measurement result figure of the trimming speed and the temperature of a board | substrate holding | maintenance mechanism. The figure which shows process pressure and in-plane distribution. The measurement result figure of CD of a resist pattern. The measurement result figure of the amount of change of the aspect ratio after resist trimming.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Partition plate 2 High frequency electrode 3 Plasma generation chamber 4 Trimming processing chamber 5 Through-hole 6 Substrate holding mechanism 7 Heater 8 Gas introduction system 9 Controller 91 Control unit 92 Timer processing unit 93 Trimming speed information storage unit 94 End timing calculation unit 10 Exhaust system 11 Vacuum container 21 High frequency power supply 31 Material to be etched 32 Photoresist

Claims (6)

A plasma generation step for generating a plasma of the reaction gas;
A removal step of selectively removing radicals by removing ions and electrons from the generated plasma;
A trimming step of trimming the resist pattern by irradiating the resist pattern with plasma from which the ions and electrons have been removed,
A resist trimming method comprising: A plasma generation space in which high-frequency electrodes are arranged; and
Trimming processing space in which an object to be processed on which a resist pattern is formed can be placed;
Using an apparatus provided with a conductive member disposed between the plasma generation space and the trimming processing space and having a plurality of through holes communicating with both spaces,
In the trimming step, plasma is generated by introducing a reactive gas into the plasma generation space, supplying high frequency power to a high frequency electrode, and performing high frequency discharge, and the generated plasma is subjected to the trimming process via the conductive member. The resist trimming method according to claim 1, wherein the resist trimming method is performed by irradiating the plasma from which ions and electrons are removed by introducing the plasma into the space. 3. The resist trimming method according to claim 1, wherein the trimming step irradiates plasma with an electron density of 1 × 10 ⁺⁷ cm ⁻³ or less. A plasma generation space in which high-frequency electrodes are arranged; and
Trimming processing space;
A conductive member disposed between the plasma generation space and the trimming processing space and having a plurality of through-holes communicating with both spaces;
Gas introduction means for introducing a reaction gas into the plasma generation space;
Exhaust means for exhausting the plasma generation space and the trimming processing space;
High-frequency power control means for controlling power supply to the high-frequency electrode;
By controlling the gas introduction unit, the exhaust unit, and the high-frequency power control unit, the plasma from which ions and electrons have been removed is introduced into the trimming processing space, and the resist pattern introduced into the trimming processing space is trimmed. A controller that performs the trimming process;
A trimming apparatus comprising:   The trimming apparatus according to claim 4, wherein the controller includes a timer processing unit that terminates the trimming process when the resist pattern is trimmed to a predetermined size. The controller is
A trimming speed information storage unit for storing trimming speed information related to the trimming speed;
An end timing calculator that determines the end timing of the trimming process based on the trimming speed information;
The trimming apparatus according to claim 5, further comprising:

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