JP2005123369A - Dry etching method and dry etching apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dry etching method by which a sample substrate is processed or surface-treated, or resist is removed from the sample substrate, or other processes are performed on the sample substrate by dry etching, which allows many experiments to be done in a short time at a low cost; and also to provide a dry etching apparatus used for the same. <P>SOLUTION: This dry etching method makes it possible to process only an exposed portion of the sample substrate by covering the sample substrate with a focus ring formed with an opening in a part. Since the focus ring can be rotated by any angle of rotation, only a desired portion of the sample substrate can be processed. By repeating the rotation of the focus ring and dry etching process several times, a plurality of portions on one sample substrate can be processed under different etching conditions. The dry etching apparatus used for the method is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dry etching method and a dry etching apparatus in dry etching applied to a fine processing field such as a semiconductor process.

  In order to increase the density of semiconductor integrated circuits, miniaturization of dimensional width such as device wiring and a method for forming connection holes play a major role. A pattern with a size of 100 nm or less is being put into practical use for these dimensions, but the realization of such a fine pattern is largely due to the development of photolithography technology and dry etching technology.

  Dry etching uses a phenomenon that etching is performed when a material to be etched is placed in a reactive plasma or radical generated by applying a high frequency (RF) power source such as 13.56 MHz to an appropriate gas. In order to form a fine pattern, a photoresist or an electron beam resist pattern is usually used as a mask material. Recently, RIE (Reactive Ion Etching) or ICP (Inductive Coupled Plasma) dry etching, which performs reactive dry extraction from plasma using self-bias voltage (Vdc) and performs anisotropic dry etching, has become the mainstream. ing. The reason why 13.56 MHz is used as the frequency of the RF power supply is relatively high because it is a frequency allocated by the Radio Law, so there is no problem even if some radio waves leak, and the shield device can be simplified. is there.

  FIG. 6 is a schematic view showing a conventional general dry etching apparatus (parallel plate type RIE). Reactive gas is supplied into the vacuum chamber 1 through the supply port 2. Further, since the gas is exhausted through the exhaust port 3, the inside of the chamber is controlled to an appropriate pressure (about 0.1 to several hundreds mTorr). There are an anode (anode) 4 and a cathode (cathode) 5 at the top and bottom of the chamber, respectively. An impedance matching unit (MB) 6 and an RF power source (high frequency oscillator) 7 for generating plasma are connected to the anode, and electric power is supplied to the gas in the chamber to generate plasma. An RF power source (high frequency oscillator) 10 for RF bias control is connected to the cathode via a blocking capacitor 8 and an impedance matching unit (MB) 9 to control the incident energy of ions. A sample (such as a material to be etched with a resist pattern) 11 is chucked by a stage 12 on the cathode 5 capable of electrostatic chucking (or mechanical chucking).

When an RF power source is applied to the reactive gas in the chamber, a glow discharge is generated between the anode and the cathode, and electrons and ions are generated to generate plasma. At that time, the electrode area in contact with the glow discharge is larger on the anode because the sample is placed on the cathode. At the same time, the mobility of electrons and ions in the plasma is overwhelmingly larger than that of the latter. Electrons flow into and the blocking capacitor is negatively charged, thereby negatively biasing the cathode. This bias is called a self-bias voltage _Vdc . Plasma is divided into a bulk region where the potential is constant and a sheath region where the potential changes abruptly near the cathode electrode due to self-bias, and ions are mainly generated in the bulk region. Ions generated in the bulk region enter the sheath region from the boundary between the bulk and the sheath, and are accelerated by the negative voltage due to the self-bias of the sheath region, impacting the material to be etched and causing an etching reaction. can get. Further, if power is supplied from an RF power supply for RF bias, the bias in the sheath region is increased, that is, the ion bombardment energy is increased, so that anisotropic etching with higher directionality is possible.

Up to this point, the parallel plate RIE type dry etching apparatus in which the anode and cathode electrode plates are arranged in parallel has been described as an example, but inductive coupling type (ICP), ultrahigh frequency type ( Other types of dry etching apparatuses such as UHF), ECR type, microwave type, helicon wave type, and surface wave type have been developed. The feature of these systems is that high-density plasma (10 ¹¹ to 10 ¹³ cm ⁻³ ) can be obtained in a wider pressure range (0.1 to several tens of Pa) than the parallel plate type. These are different from each other only in the energy input method for generating the plasma, and in that the power source for controlling the plasma state and the power source for controlling the ion bombardment energy exist independently, the above-described parallel plate RIE of FIG. It is the same as the method.

  FIG. 7A shows a sample before etching. Normally, a mask material 14 patterned by photolithography or electron beam lithography is disposed on the material to be etched 13. In the etching process of a semiconductor integrated circuit, there are silicon, silicon oxide, silicon nitride, silicon carbide, metal (aluminum, copper, etc.) as an etching target material, and photoresist, electron beam resist, silicon, silicon oxide, nitriding as mask materials There are silicon, silicon carbide, metal and the like. As the etching gas, a gas composed of a halogen element such as F (fluorine atom), Cl (chlorine atom), Br (bromine atom), I (iodine atom), or a compound containing a halogen element is used. The degree of vacuum in the chamber is evacuated to 0.1 to several tens of Pa by a vacuum pump.

  Next, a method for performing isotropic and anisotropic etching using a dry etching apparatus will be described with reference to the drawings. FIG. 8 is a schematic diagram showing isotropic and anisotropic etching by dry etching, where (a) shows the state of the sample before etching, (b) shows the material to be etched by isotropic etching. (C) is a state in which the resist is removed after (b), (d) is a state in which the material to be etched is processed by anisotropic etching, and (e) is ( The resist is peeled after d).

  FIGS. 8B and 8C illustrate the case of isotropic etching. The RF power supply on the cathode side is turned off or the power is very small (several W), and the RF power on the anode side is shown. Turn on the power and turn on the power of tens to thousands of watts. At this time, the etching gas is ionized and dissociated, and is in a so-called plasma state in which ions having electrons and charges, neutral radicals having no charges, and the like exist. Since the RF power supply on the cathode side is turned off (or very small power of about several watts), there is almost no bias in the sheath region (between the bulk region and the cathode), and positive ions in the plasma are hardly accelerated. The ions 16 incident on the material to be etched 15 are incident at various angles, and isotropic etching occurs (see FIG. 8B). FIG. 8C shows a state after the mask is peeled after isotropic etching.

  On the other hand, in the case of anisotropic etching (FIGS. 8 (d) and 8 (e)), the RF power supply on the cathode side also applies tens to thousands of watts of power, so that a bias is generated in the sheath region and the plasma Since the positive ions 17 are accelerated perpendicularly to the sample direction and incident perpendicularly to the material 18 to be etched, anisotropic etching is realized (see FIG. 8D). FIG. 8E shows a state after the mask peeling after anisotropic etching (see Patent Document 1).

  Up to here, the dry etching process of only one layer has been described. However, an actual semiconductor device has a three-dimensional structure of several to several tens of layers, and photolithography, dry etching, film formation of an insulating layer and a conductive layer. In this process, each process such as impurity implantation and cleaning is repeated.

The known literature is described below.
JP-A-6-61182

  In recent years, with the progress of higher integration, miniaturization, and higher performance of semiconductor devices found in VLSI, ULSI, etc., there is an increasing technical demand for dry etching methods, which are the main processes of semiconductor device manufacturing. It is getting stricter. At the same time, the Si wafer substrate has become larger due to the expansion of the area of devices and chips for higher performance, so that the price of semiconductor manufacturing equipment has risen and the cost has increased due to the use of large amounts of materials such as wafers and resists. Have been forced. In other words, recent semiconductor devices have high technical hurdles, and in order to develop and manufacture a single device, many experiments and conditions are required, but the cost per wafer in experiments and conditions ( Material costs and time have become higher. More specifically, in a conventional dry etching apparatus, only one etching condition can be performed on one sample wafer prepared through each process for an etching experiment. For this reason, material costs such as wafer substrate, resist, film forming process gas, time required for sample preparation, etc. are enormous, which increases costs.

  The present invention solves the above-described problems of the prior art, and provides a dry etching method and a dry etching apparatus that can perform many experiments at a low cost and in a short time.

  In order to achieve the above object, according to a first aspect of the present invention, in a method of processing a sample by dry etching, the sample is exposed by covering the sample with a focus ring having a part of the opening. This is a dry etching method characterized by processing only those portions.

  The invention according to claim 2 of the present invention is characterized in that the focus ring can process only an arbitrary portion of the sample by rotating at an arbitrary rotation angle. This is a dry etching method.

  According to a third aspect of the present invention, there is provided a dry etching apparatus for processing a sample, comprising a focus ring having an opening partly provided therein.

  The invention according to claim 4 of the present invention is the dry etching apparatus according to claim 3, further comprising means for rotating the focus ring at an arbitrary rotation angle.

In a method of processing a substrate of a sample by dry etching, surface treatment, resist stripping, etc., the opening is covered by covering the target sample with a focus ring (hereinafter referred to as a special focus ring) that is partially opened. Provided is a method and apparatus for dry etching only a part of a sample exposed from a part. This special focus ring has a rotation mechanism, and dry etching under a plurality of conditions can be performed on one sample by repeating dry etching and rotation of the special focus ring.
It is.

According to the dry etching method and apparatus of the present invention, in dry etching that requires many experiments and conditions, different etching conditions are carried out at a plurality of locations on one wafer without removing the wafer from the etching reaction vessel. It is possible to reduce the time required for etching experiments, reduce the number of substrates of the sample to be used, reduce the material such as resist and gas in sample preparation, and reduce the time for sample preparation, Cost and time can be dramatically reduced. In addition, since the apparatus of the present invention simply attaches a rotating unit and a special focus ring to the cathode portion (wafer stage portion) of a conventional etching apparatus, it is suitable for general dry etching apparatuses at low cost and without changing the performance of the etching itself. Is possible.

  This will be described in detail below with reference to the drawings. Conventional and dry etching methods and apparatuses of the present invention will be described. FIG. 9 is a schematic view of a cathode portion of a conventional dry etching apparatus. FIG. 9A is a top view, and FIGS. 9B and 9C are cross-sectional views taken along the dotted line AA ′ in FIG. 9A. First, the sample 19 such as a Si wafer is transported onto the stage 21 on the upper surface portion of the cathode unit 20 (FIG. 9B). Next, the focus ring 23 is lowered by the upper and lower arms 22, and the sample 19 is fixed (FIG. 9C). Thereafter, dry etching is performed. In such a conventional method, the focus ring 23 has a structure that suppresses only the outer peripheral portion of the sample 19, and since almost the entire surface of the sample is etched, only one condition can be processed per sample.

  Next, a dry etching method and apparatus according to the present invention will be described. FIG. 1 is a schematic view of a cathode portion of a dry etching apparatus according to the present invention. FIG. 1A is a plan view seen from above, and FIGS. 1B and 1C are side cross-sectional views taken along the dotted line BB ′ in FIG. First, the sample 24 such as a Si wafer is transported onto the stage 26 on the upper surface portion of the cathode unit 25 (FIG. 1B). Next, the special focus ring 29 having the opening 28 is lowered by the upper and lower arms 27 to fix the sample 24 (FIG. 1C). In addition, the upper and lower arms 27 of the present invention are attached to the rotary unit 30, and the upper and lower arms 27 and the special focus ring 29 can be rotated at an arbitrary angle. Thereafter, dry etching is performed under certain conditions, but only the portion exposed by the opening 28 of the special focus ring 29 is etched. In the apparatus of the present invention, it is possible to etch one sample under a plurality of conditions by alternately repeating dry etching and rotation of the special focus ring 29. The size of the opening 28 is arbitrarily determined as necessary.

  In the method of the present invention, the material to be etched, the mask material, and the etching gas are not particularly limited as long as dry etching is possible. The plasma generation method of the etching apparatus includes parallel plate type, capacitive coupling type (CCP), inductive coupling type (ICP), ultra high frequency type (UHF), ECR type, microwave type, helicon wave type, surface wave type, These plasma generation methods can be used.

Embodiments of the present invention will be described below with reference to the drawings. First, a device in which a rotation unit and a special focus ring were mounted on a general ICP type dry etching device was manufactured. First, the apparatus of the present invention will be described with reference to FIGS. FIG. 2 is a schematic diagram of the entire apparatus, and FIG. 3 is a schematic diagram of only the cathode unit portion. 2 is a model number RF-20M (20 MHz, 2 kW) manufactured by PFPP, and a high frequency oscillator 32 for RF bias is a model number AGC-6B (13.56 MHz manufactured by ENI). , 60-600 W). The chamber 1 is a general vacuum chamber, which has a process gas supply port 2 and an exhaust port 3, an anode electrode coil 33 for generating ICP plasma at the upper part of the chamber, and an RF bias cathode at the lower part of the chamber. A cathode unit 34 incorporating an electrode is connected. A difference from a general ICP type dry etching apparatus is that a special focus ring 36 partially opened with a rotating unit 35 is attached to the cathode unit 34 (see FIG. 3 below). The special focus ring 36 in FIG.
The opening 38 was made into an isosceles triangle having an apex angle of 43 degrees.

From here, the example which dry-etched using this apparatus of FIG. 3 is shown. First, as shown in FIG. 4A, an EB resist pattern was formed on the Si substrate 41 by an EB lithography process. At this time, the thickness of the EB resist 42 was 500 nm, and the pattern was an isolated line having a line width of 200 nm. EB resist 42 using a ZEP-520 (manufactured by Nippon Zeon Co., Ltd.), was drawn by the EB drawing machine JBX-7000MV (dose 50μC / cm ^2).

  Next, dry etching was performed using the dry etching apparatus of the present invention. The direction of the special focus ring at this time is the position shown in FIG. Etching conditions are CF4: 22 sccm, CH4: 15 sccm, Ar: 150 sccm, pressure: 10 mTorr, RF bias electrode power: 85 W, ICP plasma electrode power: 500 W, etching time: 4 minutes, and shows a cross section after etching. Shown in 4 (b). After that, the special focus ring was rotated 45 ° counterclockwise (FIG. 5B), and dry etching was performed again under different conditions. Thereafter, 45 ° rotation of the special focus ring and dry etching with different conditions were repeated (FIG. 5C), and a total of eight conditions of dry etching were performed on the Si substrate 41 of one sample (FIGS. 5D and 5D). )reference).

  Thereafter, the sample is taken out from the dry etching apparatus of the present invention, and the resist is removed by the oxygen plasma ashing apparatus (see FIG. 4C), and the etching conditions are different in each of the eight regions of the sample (FIG. 5D). An isolated line pattern having a line width of 200 nm was formed on the Si substrate 41.

  As described above, in the conventional etching apparatus, an experiment in which eight samples were prepared and etched one by one could be completed with one wafer in the experiment using the apparatus of the present invention.

The schematic diagram which showed the cathode unit part of the dry etching apparatus of this invention system, (a) is the top view which looked at the cathode unit from the top, (b) is the side along the dotted line BB 'of (a). In the cross-sectional view, the special focus ring is raised, (c) is the cross-sectional view of (a), the special focus ring is lowered. The schematic diagram which showed the dry etching apparatus produced by this invention system. The schematic diagram which showed the cathode of the dry etching apparatus produced by this invention system, (a) is a perspective view, (b) is the top view seen from the top. The side sectional view showing the sample which etched Si substrate by the method of the present invention, (a) is the sample before etching, (b) is the sample after etching, (c) is the sample after resist stripping. The top view which shows the position of the special focus ring at the time of etching several places of Si substrate by different conditions by this invention system, respectively, (a) is the position of the special focus ring when etched on condition 1, (b) Is the position of the special focus ring when etching is performed under condition 2, (c) is the position of the special focus ring when etching is performed under condition 3, and (d) is the position of the Si substrate when etching is performed under conditions 1 to 8. The top view of all the etching areas. The schematic diagram which showed the dry etching apparatus (parallel plate type RIE) of the conventional system. A side sectional view showing the structure of a sample to be dry-etched, (a) is a state in which a mask material is coated on the material to be etched, and (b) is a state in which the mask material is patterned by photolithography or electron beam lithography. Side sectional view showing isotropic and anisotropic etching by dry etching, (a) is a state of a sample before etching, (b) is a state where a material to be etched is processed by isotropic etching. (C) is the state where the resist is peeled off after (b), (d) is the state where the material to be etched is processed by anisotropic etching, (e) is the state where the resist is peeled off after (d). State. The schematic diagram which showed the cathode unit part of the dry etching apparatus of a conventional system, (a) is the top view which looked at the cathode unit from the top, (b) is sectional drawing along the dotted line AA 'of (a). The focus ring is raised, (c) is the sectional view of (a), and the focus ring is lowered.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Chamber 2 ... Gas supply port 3 ... Gas exhaust port 4 ... Anode 5 ... Cathode 6 ... (impedance) matcher 7, 31 ... High frequency oscillator 8 (for plasma generation) ... Blocking capacitor 9 ... (impedance) ) Matching devices 10, 32... High-frequency oscillators 11, 19, 24 (for RF bias control) Sample 12... Stage 13, 15, 18 (for electrostatic chucking or mechanical chucking) 14. , 25, 34 ... Cathode units 21, 26 ... Stages 22, 27, 37 ... Upper and lower arms 23 ... Focus rings 28, 38 ... Openings 29, 36 ... Special focus rings 30, 35 ... Rotating unit 33 ... Coil 41 ... Si substrate 42 ... EB resist

Claims (4)

  In a method of processing a sample by dry etching, the dry etching method is characterized in that only the exposed portion of the sample is processed by covering the sample with a focus ring provided with an opening in a part thereof.   2. The dry etching method according to claim 1, wherein the focus ring can process only an arbitrary portion of the sample by rotating at an arbitrary rotation angle.   A dry etching apparatus for processing a sample, comprising a focus ring having an opening in a part thereof.   4. The dry etching apparatus according to claim 3, further comprising means for rotating the focus ring at an arbitrary rotation angle.

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