JP2004342865A - Plasma processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out high-aspect-ratio etching of a test piece with a thin mask thickness with high accuracy. <P>SOLUTION: The test piece consists of an antireflection film 202 formed on the insulation film 203 of an oxide film, and an oxide film etching mask 201 formed of a photoresist film generated on the antireflection film 202. In this plasma etching method, an etching gas is supplied to the test piece to generate plasmas and then high-frequency voltage is applied to etch the insulation film. In this processing method, (a) the insulation film 203 is etched using the etching gas formed of a mixed gas of Ar, O<SB>2</SB>, and C<SB>x</SB>F<SB>y</SB>, and (b) when the aspect ratio of a hole 204 becomes 4 or above, (c) the test piece is exposed to the plasma with CO added, and with an added amount of oxygen reduced to such one as to stop etching for a prescribed period of time to deposit depository films of C and C<SB>2</SB>on the mask 201, and thereafter, (d) a hole 204 having a high aspect ratio is formed in the oxide film 203 using the etching gas wherein the added amount of oxygen is increased again to such a level as to allow etching. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing method suitable for performing a surface treatment of a semiconductor element or the like using plasma.
[0002]
[Prior art]
When etching is performed using a plasma processing apparatus, the processing gas is accelerated by ionizing and activating the processing gas, and high-frequency bias power is supplied to the material to be processed so that ions are incident perpendicularly to the material to be processed. High-precision etching processing for isotropic shapes and the like is realized. The conventional plasma processing method uses an etching gas Ar, O ₂ , C _x F _y (for example, C ₄ F ₈ , C ₅ F ₈ , C ₄ F ₆ ), and CO, particularly when performing a hole processing with a high aspect ratio. (See, for example, Non-Patent Document 1).
[0003]
With the miniaturization of devices, the exposure of the resist mask also shifts to shorter wavelengths, which reduces the thickness of the resist, and requires a high mask selectivity when performing an etching process. However, further miniaturization in the future has a limit in securing a high mask selectivity in the etching process. Although a new technology such as a resist mask pattern transfer technology has been proposed for processing a hole having a higher aspect ratio, there has been a problem that the number of steps is increased.
[0004]
Conventionally, when a contact hole is formed in a thin film of SiO ₂ , etching is performed on Ar, O ₂ , C _x F _y (for example, C ₄ F) as an etching gas in order to selectively etch a photoresist (PR) as a mask. etching is performed using an _{8, C 5 F 8, C} 3 F 6, C 4 F 6 , etc.) and CO. In this etching process, when a hole having a high aspect ratio such as a contact hole is formed, a radical having a low adhesion coefficient, for example, CF ₂ reaches the bottom of the hole, but C or C ₂ having a high adhesion coefficient is selectively deposited on a mask. (For example, see Non-Patent Document 2).
[0005]
[Non-patent document 1]
H. Hayashi et. al. : 1996 DPS (DRY PROCESS SYMPOSIUM) p135
[Non-patent document 2]
M. Izawa et. al. : 1999 DPS (DRY PROCESS SYMPOSIUM) p291
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide processing conditions capable of realizing highly accurate etching with a high aspect ratio in etching with a thin mask film and a high aspect ratio in a plasma processing apparatus.
[0007]
[Means for Solving the Problems]
In the plasma processing method of the present invention, an etch stop is generated once during an etching process in a plasma processing apparatus, and a mask is formed on a consumed mask by depositing a deposition film on the mask, thereby performing etching with a high aspect ratio. It is possible to realize.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a longitudinal sectional view of an etching apparatus which is an example of a plasma processing apparatus to which the present invention is applied. At the upper opening of the vacuum vessel 101, a cylindrical processing vessel 102 is hermetically provided with a flat antenna electrode 103 made of a conductor and a dielectric window 104 capable of transmitting electromagnetic waves, and a processing chamber is formed therein. ing. A magnetic field generating coil 105 is provided on an outer peripheral portion of the processing container 102. The antenna electrode 103 has a porous structure for flowing an etching gas, and is connected to a gas supply device 107. In addition, a vacuum exhaust device (not shown) is connected to a lower portion of the vacuum vessel 101 via a vacuum exhaust port 106.
[0009]
A coaxial line 108 is provided above the antenna electrode 103, and a high-frequency power supply 111 (for example, a frequency of 450 MHz) for plasma generation is connected via a filter 109 and a matching unit 110. Further, an antenna bias power supply 114 (for example, a frequency of 800 kHz) is connected to the antenna antenna electrode 103 via a coaxial line 108, a filter 112, and a matching unit 113. Here, the filter 109 allows the high-frequency power from the high-frequency power supply 111 to pass, and effectively cuts the bias power from the antenna bias power supply 114. The filter 112 allows the bias power from the antenna bias power supply 114 to pass, and effectively cuts the high-frequency power from the high-frequency power supply 111.
[0010]
A substrate electrode 115 on which a processing target material 116 can be arranged is provided at a lower portion in the vacuum chamber 101. A substrate bias power supply 119 (for example, a frequency of 800 kHz) is connected to the substrate electrode 115 via a filter 117 and a matching unit 118. The substrate electrode 115 is connected to an electrostatic chuck power supply 121 for electrostatically adsorbing the processing target material 116 via a filter 120. Here, the filter 117 allows the bias power from the substrate bias power supply 119 to pass, and effectively cuts the high-frequency power from the high-frequency power supply 111. Normally, high-frequency power does not flow to the substrate electrode 115 side because it is absorbed in plasma, but a filter 117 is provided for safety of power supply operation. The filter 120 allows DC power from the electrostatic chuck power supply 121 to pass therethrough, and effectively cuts power from the high-frequency power supply 111, the antenna bias power supply 114, and the substrate bias power supply 119.
[0011]
The antenna bias power supply 114 and the substrate bias power supply 119 are connected to a phase controller 122 so that the phase of the high frequency output from the antenna bias power supply 114 and the substrate bias power supply 119 can be controlled. In this case, the frequencies of the antenna bias power supply 114 and the substrate bias power supply 119 were the same.
[0012]
The phase controller 122 takes in voltage waveforms from between the filter 112 and the matching unit 113 on the antenna bias power supply 114 side and between the filter 117 and the matching unit 118 on the substrate bias power supply 119 side, and adjusts the phase of each voltage waveform. Are output to the antenna bias power supply 114 and the substrate bias power supply 119 with a small amplitude so that the phase difference becomes a desired phase difference within 180 ° ± 45 °. In this case, the antenna bias power supply 114 and the substrate bias power supply 119 need only have an amplifier function.
[0013]
In the plasma processing apparatus configured as described above, the inside of the processing chamber is depressurized by a vacuum exhaust device (not shown), and then the etching gas is introduced into the processing chamber by the gas supply device 107 and adjusted to a desired pressure. High-frequency power having a frequency of 450 MHz, for example, oscillated from the high-frequency power supply 111 propagates through the coaxial line 108 and is introduced into the processing chamber via the upper electrode 103 and the dielectric window 104. The electric field generated by the high-frequency power introduced into the processing chamber generates high-density plasma in the processing chamber by interaction with a magnetic field generated in the processing chamber by the magnetic field generating coil 105 (for example, a solenoid coil). Further, high frequency power (for example, a frequency of 800 kHz) is supplied from the antenna bias power supply 114 to the antenna electrode 103 via the coaxial line 108. The workpiece 116 placed on the substrate electrode 115 is supplied with high-frequency power (for example, a frequency of 800 kHz) from a substrate bias power supply 119, and is subjected to a surface treatment (for example, an etching process). In this case, the phase difference between the antenna bias power supply and the substrate bias power supply was 180 °.
[0014]
When a high-frequency voltage is applied to the antenna electrode 103 by the antenna bias power supply 114, when a desired material is used for the antenna electrode, the material reacts with radicals in the plasma, and the composition of the generated plasma can be controlled. For example, in the case of oxide film etching, by using Si for the material of the antenna electrode 103, the amount of F radicals in the plasma that affects the etching characteristics of the oxide film, particularly the SiO ₂ / PR (photoresist) selectivity, etc., is reduced. It becomes possible.
[0015]
In the plasma processing apparatus having the above configuration, plasma is generated mainly by the high-frequency power supply 111 of 450 MHz, the plasma composition is controlled by the antenna bias power supply 114, and the incident energy of ions in the plasma to the processing target material 116 is controlled by the substrate bias power supply 119. Controlling. Such a plasma processing apparatus has an advantage that the plasma generation (ion amount) and the plasma composition (radical concentration ratio) can be controlled independently.
[0016]
By adding CO to the etching gas, it is possible to supply these C and C _2, form a selectively protective film on the mask, it is possible to reduce the etch rate of the photoresist. However, in order for etching to proceed without etching stop at the bottom of the contact hole, it is necessary to add a certain amount of O ₂ and the mask is gradually removed. There is a limit to the hole processing in terms of the mask residual film amount.
[0017]
The etching method of the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram in which the vertical scale and the horizontal scale are different from each other, and the vertical direction is shown in a compressed state in a portion indicating a hole. A sample in which an antireflection film (BARC) 202 and a resist mask 201 are provided on an insulating film (for example, an oxide film: SiO ₂ ) 203 formed on the conductive wiring layer 205 is obtained by using Ar, O ₂ , and C _x F _y. The etching process is performed by using the amount of oxygen added to the etching gas composed of the mixed gas of (1) as the amount of oxygen that does not cause an etch stop (FIG. 2A).
[0018]
Due to the thickness of the deposition film deposited on the bottom of the hole, the etching stops when the ion energy of the incident ions is small and the ion range is short. (FIG. 2 (b)). The state where the etching is stopped by this processing is referred to as an etch stop in this specification.
[0019]
Next, C or C having a high adhesion coefficient is discharged on the mask 201 by discharging for a certain period of time using an etching gas composed of a mixed gas of Ar, O ₂ , C _x F _y , and CO with an oxygen amount at which an etch stop occurs. ₂ is formed (FIG. 2C). As mentioned earlier, at the time of etch stop, because high C and C ₂ of sticking coefficient at the bottom of the aspect ratio of 4 or more holes 204 are not incident, a deposit film is not grown on the bottom of the hole, on the mask 201 A deposition film is selectively formed.
[0020]
After the deposition film is sufficiently formed, the etching target film is etched to a desired depth by increasing the amount of oxygen in the etching gas composed of the mixed gas of Ar, O ₂ , and C _x F _y again to progress the etching. (FIG. 2D).
[0021]
Next, unlike the case of FIG. 2, FIG. 3 shows a hole processing shape when the amount of oxygen in the etching gas is reduced to such an extent that an etch stop is not generated and a deposit is deposited on the mask. If the amount of oxygen in the etching gas is reduced while the etching is in progress, the hole diameter decreases. Even if the amount of oxygen is subsequently increased, the etching proceeds along the reduced hole diameter. A hole with a small diameter is formed. In a contact hole, the area at the bottom of the hole is important for the electrical characteristics, and reducing the hole diameter is a problem.
[0022]
If a deposition film is deposited on the mask 201 without first etching to an aspect ratio of 4 or more, there is no sufficient aspect ratio difference between the upper surface of the mask 201 and the bottom of the hole 204. A deposit film is also formed on the bottom of the hole, making subsequent hole processing difficult.
[0023]
With reference to FIG. 4, a change over time of the oxide film remaining amount, the resist remaining film amount, and the oxygen addition amount when the oxygen step is used and when it is not used will be described. Here, the oxygen step refers to a process for performing an etch step. In the figure, time T1 is the time when the amount of the oxide film shaved becomes aspect 4, and the time (T2-T1) is determined by the deposition on the mask and the deposited film thickness to be deposited.
[0024]
As shown by the dashed line, when the oxygen step is not used, the amount of the resist mask necessary for etching the desired oxide film thickness is insufficient, so that an accurate hole cannot be generated. A desired oxide film thickness can be etched by depositing a deposition film on the mask using an oxygen step.
According to the present invention, holes having an aspect ratio of 15 or more can be processed.
[0025]
In the above embodiment, the case where the antenna bias power supply 114 (for example, a frequency of 800 kHz) and the substrate bias power supply 119 (for example, a frequency of 800 kHz) are controlled in phase, which is a method of highly attracting ions to the substrate, has been described. A similar effect is obtained even when the phase control of the upper and lower bias power supplies is not performed and the frequency of the antenna bias power supply 114 is 13.56 MHz, for example.
[0026]
In the above embodiment, the UHF-ECR etching apparatus has been described. However, other plasma processing such as dual frequency discharge, magnetron discharge, inductively coupled discharge (ICP, TCP), magnetic neutral discharge (NLD), and RIE. The same effect can be obtained in the apparatus.
[0027]
【The invention's effect】
According to the present invention, in a hole forming process with a high aspect ratio of a thin film mask, an etching process is performed once to an aspect ratio of 4 or more, and then a deposition film is selectively formed on the mask, thereby achieving a highly accurate etching process. The effect is that it is possible.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an etching apparatus according to a first embodiment to which the present invention is applied.
FIG. 2 is a conceptual diagram showing the etching method of the present invention.
FIG. 3 is a conceptual diagram showing an etching method when the present invention is not applied.
FIG. 4 is a characteristic diagram showing a time change of an oxide film remaining film amount and a resist remaining film amount when the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... vacuum container, 102 ... processing container, 103 ... antenna electrode, 104 ... dielectric window, 105 ... magnetic field generating coil, 106 ... vacuum exhaust port, 107 ... gas supply device, 108 ... coaxial line, 109, 112, 117, Reference numerals 120: filters, 110, 113, 118: matching unit, 111: high-frequency power supply, 114: antenna bias power supply, 115: substrate electrode, 116: workpiece, 119: substrate bias power supply, 121: electrostatic chuck power supply, 122: Phase controller, 201: photoresist film, 202: BARC film, 203: oxide film, 204: hole, 205: conductive wiring layer

Claims (8)

In an apparatus for generating plasma and etching an insulating film by applying a high-frequency voltage to a sample,
A plasma processing method, wherein an etch stop is generated once, a deposition film is deposited on a mask, and etching is performed again. The plasma processing method according to claim 1,
A plasma processing method, wherein the insulating film is an oxide film. The plasma processing method according to claim 1 or 2,
A plasma processing method characterized in that an oxide film etching mask of a material to be processed is a photoresist. The plasma processing method according to any one of claims 1 to 3,
A plasma processing method comprising: generating an etch stop at a location having an aspect ratio of 4 or more, exposing the film to plasma for a certain period of time, and performing etching again under conditions in which etching proceeds. The plasma processing method according to claim 4,
A plasma processing method, wherein an etch stop is controlled by increasing or decreasing the amount of added oxygen in a stepwise manner. The plasma processing method according to claim 5,
Plasma processing method, wherein the etching gas is a mixed gas of _{Ar, O 2, C x F} y. The plasma processing method according to claim 5, a plasma processing method, wherein the etching gas during the etch-stop is a mixed gas of _{Ar, O 2, C x F} y, CO. The plasma processing method according to claim 5, wherein a mixture gas of the etching gas during the etch stop _{Ar, O 2, C x F} y, CO, characterized in that the amount of oxygen etching reduces the amount of stopping Plasma treatment method.

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