JP2002530844A - Method for anisotropically etching aluminum and its alloys without leaving a residue - Google Patents

Abstract

(57) Abstract: The present invention provides a method for anisotropically etching aluminum or an aluminum alloy using a plasma generated from a source gas containing a chlorine-containing gas and a hydrocarbon-containing gas without leaving any residue. This is the method. The etching is performed in a processing apparatus provided with separate power controls for the plasma source and the substrate biasing means. Etching is performed using a high-density plasma (at least 10 ¹¹ e ⁻ / cm ³ ) and a low substrate bias (less than about 200 V). The method of the present invention prolongs the life of the masking layer while providing an acceptable etch rate and good etch profile. The method of the present invention is particularly useful for etching aluminum alloys having a high (ie, greater than about 0.5%) alloy content. Also, the method of the present invention etches an aluminum or aluminum alloy layer deposited on a substrate having a large open area (i.e., an open area greater than about 65% of the surface area of the wafer) essentially without residue. Especially useful for:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a method for anisotropically etching aluminum and its alloys without leaving any residue.

[0002] Various methods for etching aluminum and aluminum alloys are disclosed in the art. Some of these methods are described below.

US Pat. No. 4,618,398 to Nawata et al., Issued Oct. 21, 1986, discloses a dry etching method for converting an etchant source gas mixture of boron trichloride, chlorine and hydrocarbons into a plasma and etching aluminum or its alloys. Is disclosed. According to the present invention, aluminum or its alloy can be anisotropically etched at high speed using low plasma RF power density.

US Pat. No. 5,277,750 to Frank, Jan. 11, 1994, discloses a method for anisotropically dry etching a metallized layer containing aluminum or aluminum alloy in a semiconductor integrated circuit using an etching mask. are doing. The etching is performed using a strictly anisotropically aggressive etching gas mixture containing an iodine compound that is volatile under normal conditions, resulting in the formation of a precisely defined vertical profile of the conductor lines.

US Pat. No. 5,298,112 to Hayasaka et al., Mar. 29, 1994, uses a gas containing a halogen element and a gas containing a hydrogen element in a reaction chamber containing materials used to manufacture semiconductor devices. Disclosed are methods and apparatus for removing composite materials processed by dry ashing using a gas containing fluorine, a gas containing oxygen, and a gas containing chlorine.

US Pat. No. 5,779,926 to Ma et al., Jul. 14, 1998, discloses a method for etching a multi-component aluminum alloy on a substrate without forming etchant residues on the substrate. In this method, a substrate is placed in a processing chamber with a plasma generator and a plasma electrode. The process gas comprises (i) an ionizable chlorine-containing gas for forming dissociated Cl ⁺ plasma ions and non-dissociated Cl ₂ ⁺ plasma ions, and (ii) an inert gas capable of enhancing the dissociation of the chlorine-containing gas. Gases are introduced into the processing chamber such that their volume flow ratio is _Vr . The process gas is ionized to form plasma ions, wherein the plasma ions (i) apply an RF current at a first power level to a plasma generator;
By applying an RF current at a power level to the plasma electrode, it is actively bombarded on the substrate. The combination of power ratio P _r of the volume flow ratio V _r of the process gas, and a first power level and the second power level, a chlorine-containing etchant gas at least about by ionizing 0.6: dissociation of 1 number ratio It is selected to form Cl ⁺ plasma ions and undissociated Cl ₂ ⁺ plasma ions. Increasing the amount of dissociation Cl ⁺ ions to non-dissociated Cl ₂ ⁺ ions, without forming etchant residue on the substrate, multi-component alloy on the substrate is etched at least about 500 nm / min etch rate.

In the art, when etching aluminum or its alloys, the sidewalls to be etched are passivated to obtain an acceptable etching profile, and the features are continuously exposed through a mask during vertical etching. It is known that it is important to protect the feature wall being etched from being further etched by incident reactive species. The film for passivation is
As feature sidewalls are formed by etching, they are formed by gaseous compounds (ie, sidewall passivating materials) that react to form a protective film thereon. Nitrogen (N ₂ ) gas is a widely used material for sidewall passivation. Nitrogen passivation provides an acceptable etch profile, but the use of nitrogen gas can create undesirable residues such as silicon nitride or copper nitride (when etching aluminum-copper alloys) that are difficult to remove. . If left in place, these residues bridge the metal interconnect lines and cause electrical problems (eg, short circuits) in the device.

[0008] Hydrocarbons (such as CH ₄ ) have been used as sidewall passivation materials. However, in typical plasma etch chambers, the use of hydrocarbons as passivating materials slows the aluminum etch rate to unacceptable levels (ie, less than about 5,000 ° / min). The use of high power densities (ie, about 5 mW / cm ² , or about 1 mA / cm ² ) during etching to improve the etch rate of aluminum in a capacitively or inductively coupled etching chamber may result in ions being deposited on the surface of the substrate. A rapid etching of the mask layer as well as the aluminum layer is achieved. If the thickness of the mask layer is increased to compensate for this, it becomes difficult to bring the features to be etched into the desired profile.

A desired etched profile is achieved by providing an acceptable selectivity for aluminum over the masking layer and achieving an acceptable aluminum etch rate while leaving essentially no residue on the etched surface. It would be desirable to provide a method for etching aluminum and aluminum alloys as described.

SUMMARY OF THE INVENTION In a typical plasma processing apparatus, the power for the plasma source is under common control with the power for the substrate biasing means. For example, in a parallel plate plasma chamber, increasing the plasma source power automatically increases the power to the substrate pedestal, which biases the substrate.

[0011] We have provided a plasma source power isolated from power control to a substrate bias device to provide higher selectivity to aluminum over the surrounding etch masking material while avoiding damage to the substrate device during the etching process. A plasma generator with control was used. In addition, we have discovered that using a separate power control as described above, hydrocarbon-containing materials can be added into the etching process while satisfying the etch rate for aluminum.

We use a separate power controller for the device used to bias the plasma source and the substrate, and carbonize either the plasma source gas or the processing chamber for substrate etching (or both). By combining with the addition of hydrogen,
It has been discovered that the etch selectivity for aluminum over the adjacent masking material and the protection of the sidewall of the etched aluminum feature (ie, passivating the sidewall) can be improved simultaneously. The polymer formed on the feature sidewalls to be etched as a result of the presence of the hydrocarbon material is sufficient to protect the aluminum sidewalls etched under anisotropic etching conditions.

By increasing the power to the plasma source, the number of reactive species present on the feature surface can be significantly increased. By separately controlling the substrate bias, the bias can be set to produce an anisotropic etch without causing heavy ion bombardment on all horizontal feature surfaces. The result is that the etchant seed compound (other than ion bombardment) controls the selectivity for aluminum over the adjacent masking material and achieves sufficient substrate bias to generate an anisotropic etch. By simultaneously adding hydrocarbons to the plasma species at the feature surface, a thin layer of polymer is deposited on the sidewalls and within the bottom of the feature. During the anisotropic etch, the sidewalls of the features are not exposed to the etchant species, thus helping to protect the thin polymer layer from etching the sidewall surface, while removing the polymer layer at the bottom of the feature (horizontal surface, That is, the thin polymer layer deposited on the field surface and within the bottom of the feature is removed during the anisotropic etch).

The method of the present invention involves anisotropically etching aluminum or an aluminum alloy using a plasma generated from a plasma source gas comprising a chlorine-containing gas and a hydrocarbon-containing gas. The etching is performed in a processing apparatus having separate power controls for the plasma source and the substrate biasing means.

Preferably, the chlorine containing gas is Cl ₂ , HCl, BCl ₃ , CCl ₄ , SiCl ₄ , CH
_{Cl 3, CCl 2 F 2,} CHCl 2 F, and is selected from the group consisting of combinations. More preferably, the chlorine containing gas does not contain fluorine. Most preferably, the chlorine-containing gas is Cl _2.

Preferably, the hydrocarbon-containing gas has a chemical formula of C _x H _y . Where y
When is in the range of about 1 to 12, x typically ranges from about 1 to about 5. More preferably, x ranges from 1 to 3 and y ranges from 1 to 6. Most preferably, the hydrocarbon-containing gas is CH _4.

The chlorine: carbon atomic ratio in the plasma source gas is preferably from about 5: 1 to about 200:
1, and more preferably in the range of about 10: 1 to 20: 1. The atomic ratio of hydrogen to carbon in the hydrocarbon preferably ranges from about 1: 1 to about 4: 1.

[0018] The plasma source gas may further include an additive gas that assists in controlling the etching profile. The additive gas is preferably BCl ₃ , N ₂ , CF ₄ , C ₂ F ₆ , C ₄
F ₈ , CHF ₃ , CH ₂ F ₂ , CHCl ₃ , CHCl ₂ F, CCl ₂ F ₂ , C ₂ Cl ₂ F ₄ , C
It is selected from the group consisting of BrF ₃ , CBr ₂ F ₂ , O ₂ , and combinations thereof. However, other similar additive gases can be used for profile control. More preferably, the additive gas does not contain oxygen. Most preferably, the additive gas is BCl _3.

The plasma source gas typically includes a non-reactive diluent gas selected from the group consisting of argon, helium, xenon, krypton, and combinations thereof, but because of its low cost, argon is preferable.

The electron density of the plasma is preferably at least 10 ¹¹ e ⁻ / cm ³ , and most preferably about 10 ¹² e ⁻ / cm ³ . The substrate bias is preferably below about -200V. Most preferably, the substrate bias ranges from about -50V to about -150V.

The method of the present invention is particularly useful for etching aluminum alloys, such as aluminum-copper and aluminum-copper-silicon alloys, which tend to generate more undesirable residues than pure aluminum.

The method of the present invention removes an aluminum or aluminum alloy layer deposited on a substrate having a large open area (ie, such that the open area is greater than about 65% of the surface area of the wafer) by essentially removing residue. It is particularly useful for etching without leaving any residue.

Embodiments We have discovered an improved residue-free method for etching aluminum and aluminum alloys, including interconnect structures and contacts, in semiconductor devices. The method itself and preferred processing parameters for performing the method of the present invention are described in detail below.

I. Before defining detailed description, the singular forms used in this specification and claims, should be understood to include a plurality of referents unless the can clearly understood from the context.

Certain terms that are particularly important in describing the present invention are defined below.

The term “aluminum alloy” is an alloy of aluminum of the type typically used in the semiconductor industry. These alloys include, but are not limited to, for example, aluminum-copper alloys and aluminum-copper-silicon alloys. Typically, the aluminum content of the alloy is 90% or higher.

The term “anisotropic etching” refers to etching that does not proceed in all directions at the same rate. If the etching proceeds in only one direction (eg, only in the vertical direction), the etching process is said to be completely anisotropic.

The term “aspect ratio” generally refers to the ratio of the height dimension to the width dimension of a particular feature. If a feature has more than one width,
The aspect ratio is calculated using the minimum width.

The term “bias power” refers to the power applied to a substrate support platen to generate a negative voltage on the substrate surface. Typically, this negative voltage is used to control the ion bombardment energy and the directivity of the ions towards the substrate.

The term “chlorine” as used herein is intended to include Cl ₂ as well as other chlorine-containing compounds capable of generating a reactive etchant species.

The term “separated (decoupled) plasma source” refers to a plasma generator having separate control for plasma source generation and power input to a substrate biasing device. Typically, the plasma source power controller controls the supply of inductively coupled RF power used to generate the plasma and determine the plasma density, and the bias power controller controls the direct current on the semiconductor substrate surface. Controls the supply of RF power used to generate the bias voltage. The bias voltage affects the ion bombardment energy on the substrate surface. Separate plasma sources typically incorporate strategies to separate the effects of the source and bias on each other. Applied Materials in Santa Clara, California
The ENDURA® metal deposition and CENTURA® metal etching systems available from the company, including a separate plasma source and bias power control, are referred to as “DPS” systems. Similar devices available from other manufacturers can be referred to by different nomenclature.

The term “etch profile” generally, but not exclusively, refers to the cross-sectional profile of the sidewalls of an etched aluminum line. Often, the etch profile is described by the angle between the sidewall and the underlying substrate. If the angle is 90 °, the sidewall is perpendicular to the substrate. This is generally preferred. If the angle is greater than 90 ° (positive), the side wall of the line is tapered (ie, the line is wider at its base where it contacts the substrate). If the angle is less than 90 ° (negative), the side wall of the line is said to be retrograde or undercut (ie, the line is narrower at its base than at its top surface). .
FIG. 3 shows the positive and negative angle line sidewall profiles.

The term “etch profile microloading” refers to the difference between the average etch profile angle of an array of dense lines on the same substrate and the average etch profile angle of an isolated line. For example, if the average etch profile angle of an array of dense lines is 90 ° and the average etch profile angle of an isolated line on the same substrate is 85 °, the etch profile microloading is 5 ° (ie, 90 °). ° -85 ° = 5 °).

The term “feature” refers to, but is not limited to, interconnects, contacts, vias, trenches, and other structures forming a topography in a substrate surface.

The term “feature size” refers to the smallest dimension of a feature.

The term “dense plasma” includes, but is not limited to, at least 10 ¹¹ e ⁻ /
Plasma having an electron density of cm ³ .

The term “hydrocarbon” refers to hydrogen and carbon containing compounds having the general formula C _x H _y . Here, x preferably ranges from about 1 to about 5, and y preferably ranges from about 1 to 12.

The term “ion bombardment” refers to, but is not limited to, the physical bombardment of a substrate surface by ions (and other excited atomic species present with the ions).
Ion bombardment is often used to remove atoms from a substrate surface, and physical momentum transfer is used to achieve atom removal.

The term “open area” refers to the area of a substrate in which an opening is formed (eg, the substrate is patterned and etched to form contacts, vias, trenches, etc.). A substrate having a large open area is one in which the openings are formed over a high percentage of the substrate surface (ie, greater than about 65%).

The term “oxide loss” is the disappearance of a silicon oxide layer that is typically sandwiched between a substrate and a diffusion barrier layer.

The term “plasma” refers to a partially ionized gas that contains essentially the same number of positive and negative charges and a different number of non-ionized gas particles.

The term “sidewall passivation” refers to protecting the sidewalls of a feature to be etched from further etching by incident reactive species during continuous vertical etching of the feature through a mask.

The term “source power” refers to plasma ions and neutrals, whether directly in the etch chamber or remotely, as in a microwave plasma generator. It is the power used to generate.

II. Apparatus for Realizing the Present Invention An apparatus with separate control for power to the plasma source and substrate bias means has been included in the minutes of the 11th International Plasma Processing Symposium (May 7, 1996).
n Ye et al., Electrochemical Society Bulletin (Vol. 96-12,
pp. 222-233, 1996).

FIG. 1 shows an etching apparatus, Applied Mate, which can be used to realize the present invention.
1 is a schematic cross-sectional view of rials' CENTURA® etching system (Applied Materials, Inc. of Santa Clara, CA). The CENTURA etching system is a fully automated semiconductor manufacturing system that uses a single wafer, multi-chamber design designed to process 200 mm wafers. As shown in FIG. 1, the CENTURA etching system includes a separate plasma source (DPS) chamber 102, an advanced strip and passivation (ASP) chamber 104, a wafer orientation chamber 106, a cooling chamber 108, and an independently operating load lock chamber. 110. The experiments described in Examples 1 and 2 below were performed using a System 2982 CENTURA etching system. The System 2982 is different from the general-purpose CENTURA shown in Figure 1 in that it contains only one ASP chamber.
It is different from the etching system.

FIG. 2 a is a detailed view of an individual metal etch DPS chamber 102 of the type used in a CENTURA etch system. Metal etching DPS chamber 1
02 includes a ceramic dome 202, a standard monopolar electrostatic chuck (ESC) 204, and a 1.0 inch focus ring 206. The dome 202 is maintained at a constant temperature during processing to control particle formation. Gas is introduced into the chamber via four ceramic gas injection nozzles 208 to evenly distribute the gas. Chamber pressure is controlled by a closed loop pressure control system 210 having a unique plunger-type throttle valve 212.

The DPS etch chamber 102 uses an inductive plasma source using a frequency tuned to about 2 MHz to generate and maintain a high density plasma (ie, having an electron density of at least 10 ¹¹ e ⁻ / cm ³ ). I do. The wafer is biased using a 11.56 MHz RF power supply. Separating the plasma source allows independent control of ion energy and ion density, and a highly uniform plasma (<<1>) with a wide processing window for changes in source and bias power, pressure, and metal etch gas material. 5% variation).

FIG. 2 b is a longitudinal sectional view of an individual metal etching DPS chamber 102. During the etching process, the substrate 225 is placed in the processing chamber 102 and is held in place by the electrostatic chuck 273. The electrostatic chuck 273 is located on a cathode plasma electrode 257 that is connected to an independently controlled plasma electrode (RF) power supply 270. Chamber wall 263 is electrically grounded to form anode plasma electrode 258. The plasma source gas is supplied to the processing chamber 102 by a gas distributor 265 located on the periphery of the substrate 225.
Distributed throughout. The plasma ions are independently controlled by a plasma generator (R
F) formed from a plasma source gas by applying an RF current to an induction coil plasma generator 255 connected to a power supply 268; The cathode electrode 257 is connected to the anode electrode 257 by applying an RF voltage to the cathode electrode 257 via the power supply 270.
Being electrically biased with respect to 58, plasma ions formed within chamber 102 are attracted toward substrate 225 and actively bombard substrate 225. Spent process gas and etchant by-products are pumped into the exhaust system 274
Exhausted from the processing chamber 102 through the A throttle valve 276 is provided in the exhaust system to control the pressure in the chamber 102. For details of the metal etch DPS chamber 102, see Ma et al., U.S. Pat.
See 779,926.

The experiments described in Examples 3, 4, and 5 described below were performed by Applied Materials' Sys.
Performed using a tem 5084 basic etching system. System 5084 is
System 2982 A fully automated semiconductor manufacturing system that uses a single-wafer, multi-chamber design very similar to the CENTURA etching system,
The difference is that they are designed to process mm wafers. System 5084 is
It supports three processing chambers (two basic DPS chambers and one ASP chamber) attached to the central load lock chamber. The System 5084 performs the same function in a similar technique as the Applied Materials System 2982 device.

III. Method for anisotropically etching aluminum and its alloys without leaving a residue The method of the present invention comprises an independently controlled plasma source and substrate biasing means, a reactive chlorine-containing species, and a hydrocarbon-containing gas. Anisotropically etching aluminum or aluminum alloy using a combination with a plasma generated from a plasma source gas comprising the same. The etch processing chamber can use an externally or locally generated plasma source, with or without an RF-coupled internal coil to increase the plasma ion content.

The chlorine containing species is typically preferably Cl ₂ , HCl, BCl ₃ , CCl ₄ , SiC
_{l 4, CHCl 3, CCl 2} F 2, CHCl 2 F, and is generated from the selected gas from the group consisting of combinations. More preferably, the chlorine containing species is produced from a gas that does not contain fluorine. Most preferably, the chlorine-containing species is generated from Cl _2.

The hydrocarbon-containing gas used to passivate the sidewalls of the aluminum feature to be etched is typically added to the other gases that make up the plasma source gas. Hydrocarbon-containing gas preferably has a chemical formula of C _x H _y.
However, when y is in the range of about 1 to 12, x is typically in the range of about 1 to about 5. More preferably, x ranges from 1 to 3 and y ranges from 1 to 6
Range. Most preferably, the hydrocarbon-containing gas is CH _4.

The term “sidewall passivation” used refers to protecting the etched feature sidewalls from further etching by incident reactive species during continuous vertical etching of the features through the mask. Further, by adjusting the relative ratio of chlorine, carbon, and hydrogen in the plasma source gas, the additional benefit of passivating the entire feature surface after completing the etch can be obtained, thereby further processing. And the corrosion resistance during use of the device is improved. The chlorine or chlorine containing gas and the hydrocarbon containing gas have a chlorine: carbon atomic ratio of about 5 in the plasma source gas.
: 1 to about 200: 1, more preferably about 10: 1 to 20:
It is preferable to supply in a relative amount so as to be in the range up to 1. The atomic ratio of hydrogen to carbon in the hydrocarbon preferably ranges from about 1: 1 to about 4: 1.

The plasma source gas may further include an additive gas that assists in controlling an etching profile. The additive gas is preferably BCl ₃ , N ₂ , CF ₄ , C ₂ F ₆ , C ₄
F ₈ , CHF ₃ , CH ₂ F ₂ , CHCl ₃ , CHCl ₂ F, CCl ₂ F ₂ , C ₂ Cl ₂ F ₄ , C
It is selected from the group consisting of BrF ₃ , CBr ₂ F ₂ , O ₂ , and combinations thereof. However, other similar additive gases can be used for profile control. More preferably, the additive gas does not contain oxygen. The presence of oxygen in the plasma source gas can reduce the selectivity of the plasma source gas to preferentially etch aluminum relative to the photoresist masking material, resulting in an undesirable etch rate of the photoresist masking layer. The most preferred additive gas is BC
l is ₃ .

The plasma source gas typically includes a non-reactive diluent gas selected from the group consisting of argon, helium, xenon, krypton, and combinations thereof, but argon is preferred because of its low cost. .

The etching is performed using a processing apparatus in which the plasma source power is controlled separately from the substrate bias power. Its summary has been described in section II above. The electron density of the plasma is preferably at least 10 ¹¹ e ^- a / cm ^3, more preferably about 10 ¹² e ^- a / cm ^3.

The substrate bias power is carefully controlled in order to perform anisotropic etching while reducing the amount of ions bombarding the surface of the etching masking layer.
In the device described above, the bias power is preferably lower than about 300 W, more preferably lower than about 200 W, and most preferably lower than about 100 W.

Table 1 below shows the Applied Materials shown in FIGS. 1 and 2 and described in section II.
3 shows preferred processing conditions for etching aluminum and / or its alloys with essentially no residue according to the method of the present invention using the System 2982 CENTURA etching system of the present invention. Table 1. Preferred processing conditions for aluminum and its alloys * The substrate temperature is typically about 40-50 ° C above the pedestal temperature. For example, if the pedestal temperature is about 50 ° C, the substrate temperature will typically be about 90-100 ° C.

Example 1 An experiment was performed to compare the etch rates of aluminum alloys while keeping the etchant species mixture of Cl ₂ and BCl ₃ constant and adding various amounts of nitrogen and methane to the plasma source gas.

The processing operations are described in Applied Materials shown in FIGS. 1 and 2 and described in Section II.
This was performed using a System 2982 etching system.

The film stack used in this study was a 1.8 μm i-line photoresist (manufactured by TFI, Fremont, Calif.), 450 ° TiN ARC (anti-reflective coating) on a silicon wafer substrate, from top to bottom. , 11,500Å Al-0.5%
Cu, 700 ° Ti barrier layer, and 1.12 μm silicon oxide.

All substrates were patterned using an i-line photoresist mask with line and seed patterns. The feature size was about 0.4 μm and the aspect ratio was about 2.5: 1. TiN ARC was patterned using a commercially available i-line stepper.

[0063] The aluminum alloy and titanium barrier layers were etched using the following processing parameters. That is, 100 sccm Cl ₂ , 40 sccm BCl ₃ , and 5 or 1
0 sccm N ₂ or CH ₄ , 1200 W source power, 150 W bias power, 10-20 m
T process chamber pressure, 7T helium back pressure on the back side of the substrate wafer, 45 ° C substrate temperature, and 80 ° C process chamber wall and dome temperature.

The height (ie, etching depth) of each line was about 1 μm. The end time required to reach this etch depth was recorded. The end times for etching using different plasma source gases, processing chamber pressures, and flow rates are shown in Table 2 below. Table 2. Comparison of etching rates of aluminum alloys for nitrogen-containing and methane-containing plasma source gases

Although the aluminum alloy etch rate is much slower when the etch plasma contains methane than when the etch plasma contains nitrogen, the etch rates obtained using a methane containing source gas are still different. Even at each processing chamber pressure and source gas flow rate, it was sufficiently higher than the acceptable minimum etching rate of 5000 °.

EXAMPLE 2 Etching Rate, Etching Profile, Etching Profile Microloading of Aluminum Alloy, Thickness of Photoresist Masking Layer Left After Etching (Each Variation in Plasma Source Gas Composition (ie, Cl ₂ : CH ₄ Ratio) ), A function of total gas flow, processing chamber pressure, and source power).

The processing operations are shown in FIGS. 1 and 2 and are described in Applied Materials S
Performed using a ystem 2982 etch processor.

The film stack used in this study was, from top to bottom, on a silicon wafer substrate, a 1.8 μm i-line photoresist (manufactured by TFI, Fremont, Calif.), 450 ° TiN ARC, 11,500 ° Al. -0.5% Cu, 700Å Ti
Barrier layer and 1.12 μm silicon oxide.

All substrates were patterned using an i-line photoresist mask with line and seed patterns. The feature size was about 0.4 μm and the aspect ratio was about 2.5: 1. TiN ARC was patterned using a commercially available i-line stepper.

The aluminum alloy and titanium barrier layers were etched using the following processing parameters. That is, 800-1600W source power, 150W bias power, 8-16mT
Process chamber pressure, 7T helium back pressure on the back side of the substrate wafer, 45 ° C. substrate temperature, and 80 ° C. process chamber wall and dome temperature. Cl ₂ / CH ₄ ratio of 6: 1
To 33: 1. No additional gas (such as BCl ₃ ) was used in this set of experiments.

The height (ie, etching depth) of each line was about 1 μm. The end time required to reach this etching depth was recorded. The etching profile angle of the aluminum line wall to be etched relative to the underlying substrate was measured in degrees (degrees) (perpendicular, ie, 90 ° etching profile is ideal). The etching profile microloading (Δ °) was measured by comparing the average etching profile angle of an array of dense lines on the same substrate with the average etching profile angle of an isolated line.

The etching end time, the etching profile angle, the etching profile microloading, and the photoresist thickness, at which the etching is completed, are changed according to the Cl ₂ : CH ₄ ratio of the plasma source gas, the total flow rate of the plasma source gas, the processing chamber pressure, and Table 3 below as a function of the process variables of the source power (the bias power was kept constant at 150 W). Table 3. Changes in Cl ₂ : CH ₄ ratios and other process variables can cause aluminum alloy etch
Effect on the result

The etching profile angles described below are best shown in FIG.
FIG. 3 shows a schematic cross-sectional view of a pattern of lines 302 and intervals 304 on a substrate 306. The etching profile is generally the same as the aluminum line sidewall 30.
8 is called the cross-sectional profile. The etching profile angle α is an angle formed between the line side wall 308 and the surface 310 of the base 306 located below. Angle α is measured from substrate surface 310 inside line 302 toward line sidewall 308. For example, α1 is about 85 °, representing a “tapered” line sidewall profile, with the line widening at its base (adjacent to substrate surface 310). On the other hand, since α2 is 90 ° and the line side wall is 90 °, the line side wall forms a right angle intersection with the base surface 310. Further, α3 is 105 °, which represents a retrograde or undercut line sidewall profile whose base is narrower than its top.

The processing variables of the plasma source gas, Cl ₂ : CH ₄ ratio, source gas flow rate, processing chamber pressure,
The effects of changes in source power and on the etch end time, the etch profile angle, the amount of residue remaining after etching, and the etch performance variables including etch profile microloading are shown in FIGS. 4-8, respectively. The general effects of increasing each process variable on the aluminum etch rate, etch profile angle, etch profile microloading, and amount of residue remaining after etching are summarized in Table 4 below. Table 4. General effects an increase in various process variables Ru applied to the aluminum alloy etching results ↑ = increase, ↑↑ = significant increase, ↓ = decrease, ↓↓ = significant decrease, → = no change.

The average etching end time was used as an index of the etching rate of the aluminum alloy. The shorter the end time, the faster the etching rate. FIG. 4 shows the source gas flow rate 40
2. The effect of increasing the Cl ₂ : CH ₄ ratio 404, the processing chamber pressure 406, and the source power 408 on the etching end time is shown. As shown in FIG. 4, increasing the Cl ₂ : CH ₄ ratio 404 dramatically increases the etch rate of the aluminum alloy (
This is indicated by the shortened etching end time). Increasing the processing chamber pressure 406 significantly increases the etch rate of the aluminum alloy. Increasing the source gas flow 402 and source power 408 results in a modest increase in the aluminum alloy etch rate.

FIG. 5 shows a source gas flow 502, a Cl ₂ : CH ₄ ratio 504, a processing chamber pressure 506,
The effect of increasing the source power 508 on the etching profile angle of the aluminum line sidewall is shown. As shown in FIG. 5, when the source power 508 is increased,
The etch profile angle increases dramatically (ie, the etch profile angle approaches 90 °). Increasing the Cl ₂ : CH ₄ ratio 504 significantly increases the etch profile angle. Increasing the source gas flow 502 results in a more modest increase in the etch profile angle, while increasing the process chamber pressure 506 decreases the etch profile angle.

FIG. 6 shows the effect of increasing the Cl ₂ : CH ₄ ratio 604, the processing chamber pressure 606, and the source power 608 on the etching profile microloading when the source gas flow 602 is increased. As shown in FIG. 6, increasing the Cl ₂ : CH ₄ ratio 604 dramatically increases the etch profile microloading. Increasing the source power 608 results in a modest increase in etch profile microloading. Increasing the source gas flow 602 has no significant effect on etching profile microloading.

As the processing chamber pressure 606 is increased, the etch profile microloading increases gently. This is believed to be due to the increased chlorine gas residence time when higher chamber pressures were used. The chlorine gas etches the aluminum line sidewalls and the increased residence time increases the profile angle. This effect has been observed to be greater on isolated lines than on lines located in dense arrays, thereby increasing etch profile microloading.

FIG. 7 shows a source gas flow 702, a Cl ₂ : CH ₄ ratio 704, a process chamber pressure 706,
The effect of increasing the source power 708 on the amount of residue remaining after etching is shown. The amount of residue remaining after etching was assigned after comparative evaluation of scanning electron micrographs taken at 20k magnification (comparing deposits on a given surface area, 1 to 10
(Indicated on the scale up to). The residue remaining after etching the aluminum alloy is typically a compound of aluminum or copper. As shown in FIG. 7, increasing the Cl ₂ : CH ₄ ratio 704 and the processing chamber pressure 706 significantly increase the amount of residue remaining after etching. Increasing source gas flow 702 and source power 708 slightly increases the amount of residue remaining after etching.

EXAMPLE 3 An experiment was performed to determine the effect of changes in CH ₄ flow rate, source power, bias power, and processing chamber pressure on the etching of aluminum alloy (0.5% Cu) features.

This processing operation is shown in FIGS. 1 and 2 and described in Section II.
This was performed using a System 5084 basic etching system. The System 5084 has the same function as the Applied Materials System 2982 etching apparatus shown in FIGS. The etch chamber has a mechanical clamp for processing 150 mm wafers and contains a separate plasma source (DPS).

The film stack used in this study was on a silicon substrate, from top to bottom,
1.4 .mu.m i-line photoresist (manufactured by TFI, Fremont, Calif.), 250 DEG TiN ARC, 8,000 DEG Al-0.5% Cu, 1000 DEG TiN barrier layer, and 1 .mu.m silicon oxide.

All substrates were patterned using an i-line photoresist mask with line and seed patterns. The feature size was about 0.6 μm and the aspect ratio was about 2.5: 1. TiN ARC was patterned using a commercially available i-line stepper.

After patterning the photoresist mask, the substrate was baked in a convection oven at 110 ° C. for at least 1 hour before etching.

The aluminum alloy and titanium nitride barrier layers were etched using the following processing parameters. That is, 90 sccm Cl ₂ , 0-25 sccm BCl ₃ , and 0 sccm.
-20sccm of CH _4, 75 sccm of Ar, a source power of 1200-1800W, bias power 100-160W, process chamber pressure of 10-15MT, helium back pressure 8T to the backside of the substrate wafer, 60 ° C. of substrate temperature, And 40-65 ° C processing chamber wall temperature. The etching end time was recorded.

After etching (the photoresist was not stripped), the wafer was baked in a convection oven at 110 ° C. for at least 8 hours to evaporate residual chlorine. Half of the substrate photoresist was then stripped in a commercial plasma ashing machine and immersed in a commercial solvent at 65 ° C. for 20 minutes to remove the polymer.

The unstriped wafer was evaluated for the amount of photoresist left after etching. The stripped wafers were evaluated for oxide loss (in open areas and dense arrays), sidewall surface roughness (ie, pits), sidewall profile angles, and the amount of residue left after etching. CH ₄ flow rate, source power, the change of the bias power, and the processing chamber pressure was analyzed the effect on the aforementioned criteria.

FIG. 8 and Table 5 below show that when the bias power was increased (100, 130, 160 W) while the source power was kept constant (1800 W) during the etching, the center of the wafer after the etching was completed The effect on the total amount of photoresist masking material remaining at 802 and edge 804 is shown. The processing parameters for each run are as follows. That is, 90 sccm Cl ₂ , 0-25 sccm BCl ₃ , 20 sccm CH ₄ , 75 sccm
sccm Ar, 10 mT processing chamber pressure, 8 T helium back pressure on the back side of the substrate wafer, 60 ° C. substrate temperature, and 65 ° C. processing chamber wall temperature (except when running at 100 W bias power, The temperature was 40 ° C). (Experiments performed earlier have shown that changing the processing chamber temperature has little effect on the aluminum etch results). Table 5. Effect of increasing bias power on total residual photoresist

As shown in FIG. 8 and Table 5 above, when the source power is fixed at 1800 W and the bias power is increased by a very small amount (increase of 30 W), the photoresist remaining at the center 802 and the edge 804 of the wafer is removed. The total amount decreases dramatically. By extrapolating the data shown in FIG. 8 and Table 5, in a processing apparatus where the power to the plasma source and the substrate biasing means is under common control, the source power operates with satisfactory aluminum etching. It is evident that the photoresist masking layer disappears abruptly when done.

[0091] Increasing the bias power increases the oxide loss, but the sidewall surface roughness is relatively unaffected. However, overetching (ie, sidewall profile angles> 90 °) occurs in the aluminum alloy at the bottom of the feature due to apparently increased reactive species density.

[0091] No residue was observed in any of the samples.

During the development of the etching process, the flow rate of CH ₄ was varied and evaluated for sidewall passivation capability, aluminum alloy etch rate, residue generation, and selectivity of the aluminum alloy to photoresist for etching. The initial results, CH ₄ in the anisotropic etching process has shown that the side wall of the aluminum lines can be sufficiently passivated. However, the etching end time is about 23
It increased by -35% (from 54 seconds when not using the CH _4, up to 75-90 seconds when using CH ₄ of 20 sccm). When the processing chamber pressure was increased from 10mT to 15mT, the etching end time decreased slightly (when using CH ₄ of 20 sccm, to 72 seconds).

EXAMPLE 4 An experiment was performed to determine the effect of changes in plasma source gas composition, processing chamber pressure, and bias power on the etching of aluminum alloy (1% Cu) features. Approximately the same process as for etching the aluminum alloy (0.5% Cu) feature in Example 3 above was used.

The film stack used in this study was prepared on a silicon substrate, from top to bottom,
1.4 .mu.m i-line photoresist (manufactured by TFI, Fremont, Calif.), 250 DEG TiN ARC, 8,000 DEG Al-1% Cu, 1000 DEG TiN barrier layer, and about 1 .mu.m silicon oxide.

[0095] All substrates were patterned using an i-line photoresist mask with line and seed patterns. The feature size was about 0.4 μm and the aspect ratio was about 2.5: 1. TiN ARC was patterned using a commercially available i-line stepper.

The etching was performed using the Applied Materials System 5084 basic etching apparatus described in Example 3 above. The aluminum alloy and titanium nitride barrier layers were etched using the following processing parameters. That is, 90-100 sc
cm ₂ Cl ₂ , 25 sccm BCl ₃ , 10-20 sccm CH ₄ , 0-75 sccm A
r, 1500 W source power, 75-100 W bias power, 10-15 mT process chamber pressure,
8T helium back pressure on the back side of the substrate wafer, 60 ° C. substrate temperature, and 65 ° C. process chamber wall temperature. The etching end time was recorded.

The effects on the etching end time and the amount of residue remaining after etching were analyzed by changing the plasma source gas composition, the processing chamber pressure, and the bias power. (No residue was observed on the 0.5% Cu features after etching.) The results are shown in Table 6.
And described below. Table 6. Effect of the change of the aluminum alloy etching process parameters has on the residue control and edge quenching end time

The effect of increasing the processing chamber pressure from 10 mT to 15 mT on the aluminum etch rate was studied. The end time was reduced by 18-22%, but some residue was found on the open area surface of the wafer.

The contribution of argon to the aluminum etch rate and residue control was investigated. When argon was omitted from the plasma source gas composition, the aluminum etching rate was increased, but some residues were observed on the open area surface of the wafer. The presence of argon increases the surface impact due to the excited argon species, resulting in a surface cleaning operation.

The flow rate of Cl ₂ was increased (from 90 sccm to 100 sccm), the flow rate of CH ₄ was reduced (from 20 sccm to 10 sccm), and the flow rate of argon was reduced (from 75 sccm).
(From 40 W to 40 sccm) and the bias power was reduced (from 100 W to 75 W) at the same time, the end time was reduced by 35% and residues were observed on all areas of the surface.

In summary, the results of the experiments described in Examples 3 and 4 above show that while CH ₄ sacrifices the slowdown of the aluminum alloy etch rate, the etched aluminum alloy is still at an acceptable etch rate. It shows that it can be used to passivate feature sidewalls. Increasing the plasma source power (1200 → 1800 W) resulted in overetching of the aluminum at the bottom of the feature. Increasing the bias power (100 → 160 W) greatly reduces the lifetime of the photoresist masking layer, while increasing the etch rate microloading. Increasing the processing chamber pressure (10 → 15 mT) generally increases the substrate etch rate. When the processing chamber pressure is increased, the aluminum alloy (1% Cu
2.) Increased residues (typically copper compounds) deposited on feature surfaces. It has been found that the presence of argon in the plasma source gas assists in removing residues from the etched aluminum alloy feature surface.

Example 5 To determine the effect of gas flow on aluminum alloy (1% Cu) features,
_{CH 4, Cl 2, BCl 3} , and the flow rate change is caused by 10 times experiments Ar (4 factor 1 /
Eight replicates, plus two center point runs) were performed. Although the main effect on the etching of the aluminum alloy when the flow rate of the etching gas is changed is obvious,
The interaction between the various gases was ambiguous.

The two center point runs were included in a total of 10 wafer runs. The center point recipe was selected based on a one-dimensional experiment on the aluminum alloy (0.5% Cu) feature described in Example 3 above. The factors and levels used in this experiment are shown in Table 7 below. Table 7. Other Me factors and the level of the two-level experiments on aluminum alloy (0.5% Cu) features

The film stack used in this study was on a silicon substrate, from top to bottom,
1.4 .mu.m i-line photoresist (manufactured by TFI, Fremont, Calif.), 250 DEG TiN ARC, 8,000 DEG Al-1% Cu, 1000 DEG TiN barrier layer, and about 1 .mu.m silicon oxide.

All substrates were patterned using an i-line photoresist mask with line and seed patterns. The feature size was about 0.4 μm and the aspect ratio was about 2.5: 1. TiN ARC was patterned using a commercially available i-line stepper.

The etching was performed using the Applied Materials System 5084 basic etching apparatus described in Example 3 above. The aluminum alloy and titanium nitride barrier layers were etched using the following processing parameters. That is, a process chamber pressure of 12 mT, a source power of 1500 W, a bias power of 100 W, a helium back pressure of 8 T on the back side of the substrate wafer, a cathode temperature of 60 ° C., and a process chamber wall temperature of 65 ° C.

Curves showing the effects of changes in the flow rates of CH ₄ , Cl ₂ , BCl ₃ , and Ar on the aluminum alloy etching end time, the amount of residue remaining after etching, and the photoresist etching rate are shown in FIG. This is shown in FIG. The effect of increasing the flow rate of each gas on the etching results is shown in Table 8 below. Table 8. Major effects of increased flow of various etchant gas has on the etching grayed result of the aluminum alloy ↑ = increase, ↑↑ = increase, ↓ = decrease, ↓↓ = decrease.

FIG. 9 shows the effect of changes in the Cl ₂ flow rate 902, the BCl ₃ flow rate 904, the Ar flow rate 906, and the CH ₄ flow rate 908 on the aluminum alloy etching end time. As shown in FIG. 9, increasing the Cl ₂ flow rate (indicated by reference numeral 902) dramatically increases the etch rate of the aluminum alloy (indicated by a shortened etch end time). Increasing the CH ₄ flow rate 908, the etching rate of the aluminum alloy is significantly reduced. When the Ar flow rate 906 is increased, the etching rate of the aluminum alloy gradually decreases. Increasing the BCl ₃ flow rate 904 slightly decreases the etch rate of the aluminum alloy.

FIG. 10 shows the effect of changes in the Cl ₂ flow rate 1002, BCl ₃ flow rate 1004, Ar flow rate 1006, and CH ₄ flow rate 1008 on the amount of residue remaining after etching. Residues were defined by counting the number of deposits observed in an area of about 2 μm ² on a SEM taken at 20k magnification. As shown in FIG. 10, increasing the Cl ₂ flow rate 1002 dramatically increases the amount of residue remaining after etching. This is considered to be because the etching rate of aluminum was increased by increasing the Cl ₂ flow rate.
Chlorine-aluminum forming compounds are much more volatile than chlorine-copper etching forming compounds, so if the aluminum alloy etch rate is particularly high, the amount of copper-containing residue remaining after completely etching the aluminum alloy features will increase. I do.

As the CH ₄ flow rate 1008 and the BCl ₃ flow rate 1004 are increased, the amount of residue remaining after etching is greatly reduced. As the Ar flow rate 1006 was increased, the amount of residue remaining after etching gradually decreased, and SEM micrographs visually confirmed the importance of Ar in controlling the residue. (The need for argon addition was previously described in Example 4.) No residue was observed at the edge of the wafer in any of the runs.

FIG. 11 shows the effect of changes in the Cl ₂ flow rate 1102, BCl ₃ flow rate 1104, Ar flow rate 1106, and CH ₄ flow rate 1108 on the photoresist etch rate. As shown in FIG. 11, increasing the Cl ₂ flow 1102, the photoresist etch rate increases dramatically. Increasing the CH ₄ flow 1108, the photoresist etch rate decreases dramatically. Increasing the Ar flow rate 1106 greatly reduces the photoresist etch rate. Increasing the BCl ₃ flow rate 1104 slowly reduces the photoresist etch rate. CH ₄ , Ar,
The decrease in photoresist etch rate observed with increasing BCl ₃ flow rate is believed to be due to the dilution of chlorine in the gas mixture.

Generally speaking, increasing the CH ₄ flow rate improves sidewall roughness (ie,
There are few pits on the side wall surface). During processing at high Cl ₂ flow rates, the effectiveness of CH ₄ for sidewall passivation becomes more pronounced, due to the greater degree of sidewall attack due to increased chlorine in the plasma.

In this experiment, no profile slope was observed.

In conclusion, CH ₄ provides sufficient sidewall passivation to prevent pits without creating a residue on the etched feature surface. By the addition of CH _4, aluminum etching end time is reduced by about 23-35%, but still it is possible to obtain an acceptable aluminum alloy etch rate of at least 8,000 Å / min. Increasing the bias power will increase the photoresist etch rate, but will generally be less than about 200V (preferably, about -5V).
Bias power has been found to be acceptable (from 0V to about -150V).
Increasing the plasma source power typically results in slightly overetching of the aluminum at the bottom of the features (these are represented by undercuts or retrogrades of> 90 ° etch profile angles). Acceptable plasma source power ranges from about 300 W to about 2000 W, preferably from about 800 W to about 1600 W, and most preferably from about 800 W to about 1200 W. To control residues, low process chamber pressures (5-50 mT, preferably 5-25 mT, most preferably 8-5 mT,
-12 mT) is required. The preferred range of the argon content of the plasma source gas is about
20 to about 200 sccm. Increasing the Cl ₂ flow rate, an aluminum alloy etch rate, photoresist etch rate, and the amount of residue that remains after the etching considerably increased. The preferred Cl ₂ content of the plasma source gas is from about 50 to about 200 sc
cm. The preferred total flow rate of the plasma source gas ranges from about 50 to about 350 sccm.

A comprehensive, residue-free etching process for etching aluminum alloys has been developed by adding hydrocarbons to the processing chamber during etching, while avoiding pits on the surface of the aluminum alloy to be etched. .

The present invention relates to aluminum and aluminum that provide an acceptable etch rate without destroying the mask layer and a good etch profile angle while providing an etched surface with essentially no residue. A method for anisotropically etching an aluminum alloy is provided.

The method of the present invention is particularly useful for etching aluminum alloys having a high (ie, greater than about 0.5%) alloy content.

The method of the present invention also reduces the aluminum or aluminum alloy deposited on a substrate having a large open area (ie, the open area is greater than about 65% of the surface area of the wafer) by essentially leaving a residue. It is particularly useful for etching without etching.

It will be appreciated by those skilled in the art that these embodiments can be extended from the above description without departing from the inventive subject matter and the claims.
It should be understood that the above-described preferred embodiments are not intended to limit the scope of the present invention.

[Brief description of the drawings]

FIG. 1 CENTURA (Applied Materials), an example of an etching apparatus useful for the present invention.
1 is a sectional view of a registered trademark etching system.

2a is a detailed view of an individual metal etch separate plasma source (DPS) chamber of the type used in the Applied Materials CENTURA® etching system shown in FIG.

FIG. 2b is a longitudinal cross-sectional view of an individual metal etch DPS chamber described in US Pat. No. 5,779,926, showing power control 268 for independent plasma source power and power control 270 for bias power. It is.

FIG. 3 shows features 306 etched into an aluminum layer 308 deposited on a substrate 310, showing the etching profile of the aluminum line sidewalls for included angles varying from the desired right-angled wall (90 °). It is a figure showing how to measure.

FIG. 4 shows the effect of changes in source gas flow 402, Cl ₂ : CH ₄ ratio 404, process chamber pressure 406, and source power 408 on etch end time, an indicator of aluminum etch rate (ie, short end time). The higher the etching rate, the faster the etching rate.

FIG. 5 is a graph showing the effect of changes in source gas flow rate 502, Cl ₂ : CH ₄ ratio 504, processing chamber pressure 506, and source power 508 on aluminum line sidewall etch profile angles.

FIG. 6 shows changes in source gas flow 602, Cl ₂ : CH ₄ ratio 604, process chamber pressure 606, and source power 608 when the etch profile microloading Δ ° (ie,
5 is a graph showing the effect on the average etching profile angle of an array of dense lines on the same substrate and the average etching profile angle of an isolated line.

FIG. 7 is a graph showing the effect of changes in source gas flow 702, Cl ₂ : CH ₄ ratio 704, processing chamber pressure 706, and source power 708 on the amount of residue remaining after etching, remaining after etching. The amount of residue is given in arbitrary units assigned after comparative evaluation of scanning electron micrographs (SEM) taken at 20k magnification and scaled from 1 to 10 comparing the number of deposits present on a given surface area Assigned above.

FIG. 8 is a graph showing the effect of increasing the bias power while keeping the source power constant at 1800 W on the total amount of photoresist remaining at the center and edge of the wafer after etching is completed.

FIG. 9 is a graph showing the effect of changes in the Cl ₂ flow rate 902, BCl ₃ flow rate 904, Ar flow rate 906, and CH ₄ flow rate 908 on the aluminum alloy etching end time, which is an indicator of the aluminum alloy etching rate.

FIG. 10: Cl ₂ flow rate 1002, BCl ₃ flow rate 1004, Ar flow rate 1006, and CH ₄ flow rate 1
008 is a graph showing the effect of change 008 on the amount of residue remaining after etching, where the residue is limited by counting the number of deposits observed within an area of about 2 μm ² on a SEM taken at 20k magnification. .

FIG. 11: Cl ₂ flow rate 1102, BCl ₃ flow rate 1104, Ar flow rate 1106, and CH ₄ flow rate 1
10 is a graph showing the effect of changing 108 on the photoresist etch rate.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Nanjang Savisa United States 95132 San Jose Valhalla Court, California 1771 (72) Inventor Lee Marlene United States of America 95138 San Jose Trobridge, Wayway 5784 (72) Inventor Strokes Jeffrey United States California 95136 San Jose Mia Circle 4623 F-term (reference) 4K057 DA01 DA12 DB05 DD01 DE01 DE02 DE04 DE06 DE08 DE11 DE14 DE15 DE20 DG07 DG13 DG14 DG15 DM18 DM19 DM28 DN01 5F004 AA09 BA03 BA20 BB22 BB26 CA02 DA06 DA00 DA00 DA05 DA06 DA08 DA10 DA11 DA14 DA16 DA22 DA23 DA25 DA26 DB09 DB12

Claims (18)

[Claims] A method for anisotropically etching aluminum or an aluminum alloy essentially without residue, using a plasma generated from a plasma source gas comprising a chlorine-containing gas and a hydrocarbon-containing gas. Etching the aluminum or the aluminum alloy as described above, wherein the etching is performed in a processing apparatus that separately controls the power of the plasma generating source and the substrate biasing means. 2. The chlorine-containing gas includes Cl ₂ , HCl, BCl ₃ , CCl ₄ , and SiC.
_{l 4, CHCl 3, CCl 2} F 2, CHCl 2 F, and methods according to claim 1, characterized in that it is selected from the group consisting of combinations. 3. The method of claim 2, wherein said chlorine containing gas does not contain fluorine. 4. The method of claim 3, wherein said chlorine containing gas is Cl ₂ . 5. The hydrocarbon-containing gas has a chemical formula of C _x H _y , wherein _x ranges from about 1 to about 5 and y ranges from about 1 to 12. The method of claim 1, wherein 6. The method of claim 5, wherein x ranges from 1 to 3, and y ranges from 1 to 6. 7. The method of claim 6, wherein said hydrocarbon containing gas is CH ₄ . 8. The method of claim 1, wherein the chlorine: carbon atomic ratio in the plasma source gas ranges from about 5: 1 to about 200: 1. 9. The atomic ratio of chlorine: carbon in the plasma source gas ranges from about 10: 1 to about 20: 1, and the atomic ratio of hydrogen: carbon in the plasma source gas is about 1: 1.
The method of claim 8, wherein the range is from 1: 1 to about 4: 1. 10. The plasma source gas is BCl_Three, N_Two, CF_Four, C_TwoF₆, C _Four F₈, CHF_Three, CH_TwoF_Two, CHCl_Three, CHCl_TwoF, CCl_TwoF_Two, C_TwoCl_TwoF_Four, C
BrF_Three, CBr_TwoF_Two, O_Two, And a group consisting of
The method of claim 1, further comprising an added gas. 11. The method of claim 10, wherein the additive gas does not include oxygen. 12. The method according to claim 11, wherein the additive gas is BCl _3.
The method described in. 13. The plasma source gas may be argon, helium, xenon,
The method of claim 1, further comprising a non-specific reactive diluent gas selected from the group consisting of krypton, and combinations thereof. 14. The method of claim 13, wherein said non-reactive diluent gas is argon. 15. The method according to claim 1, wherein the plasma has an electron density of at least 10 ¹¹ e ⁻ / cm ³ . 16. The method according to claim 15, wherein the electron density of the plasma ranges from about 10 ¹¹ e ⁻ / cm ³ to about 10 ¹² e ⁻ / cm ³ . 17. The method of claim 1, wherein said substrate bias is less than about -200V. 18. The method of claim 17, wherein said substrate bias ranges from about -50V to about -150V.