JPH05291207A - Dry etching method - Google Patents

Abstract

PURPOSE:To improve the selectivity of a substratum when a lowerlayer resist layer is etched in a three-layer resist process. CONSTITUTION:A lower-layer resist layer 3 on an Al-1% Si-0.5% Cu layer 2 is etched by using a mixed gas of NOCl (nitrocyl chloride) and O2. A sidewall protective film 6 which is formed at this time is a carbon-based polymer in which a nitrosyl group (-N=O) has been introduced into CClx; it is provided with a highly etching-resistant property due to a strong chemical bond and a strong electrostatic attraction force. Consequently, the energy of impinging ions which are required for an anisotropic working operation can be reduced and the selectivity of a substratum is enhanced. As a result, the sputtered and restruck substance of the Al-1% Si-0.5% Cu layer 2 is not produced. When S2Cl2 is added to a gas system and S is deposited simultaneously, it is possible to realize higher selectivity, lower damage and lower contamination of the title dry etching method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method, and more particularly, it reduces underlayer selectivity by reducing incident ion energy required for anisotropic processing when etching a lower resist layer in a multilayer resist process, for example. And a method for preventing reattachment of the base material by sputtering.

[0002]

2. Description of the Related Art As semiconductor device design rules are highly miniaturized from sub-micron level to quarter-micron level, requirements for various processing techniques such as photolithography and dry etching are becoming more severe. .. In the photolithography technology, in recent years, the exposure wavelength has been shortened in order to obtain high resolution, and the step difference on the surface of the substrate has increased.
Adoption of processes is becoming mandatory. Multi-layer resist
The process is a method of using a combination of at least two types of resist layers, that is, a lower resist layer thick enough to absorb surface steps of a substrate and an upper resist layer thin enough to achieve high resolution.

A well-known method is described in J. Vac.
Sci. Tech. 16, (1979), p. 162
There is a so-called three-layer resist process reported in No. 0. This is a thick lower resist layer for flattening the surface steps of the substrate, a thin intermediate layer made of an inorganic material for forming a mask when etching the lower resist layer,
And a thin upper resist layer that is patterned by photolithography and development processing. In this process, first, the upper resist layer is patterned into a predetermined shape, the intermediate layer thereunder is patterned by RIE (reactive ion etching), and the upper resist layer and the intermediate layer are used as a mask. The lower resist layer is patterned by dry etching using O ₂ gas or the like.

By the way, in the step of etching the lower resist layer which is an organic material layer with O ₂ gas,
^{* In} order to prevent the deterioration of the pattern shape due to the isotropic combustion reaction due to (oxygen radicals), it is necessary to adopt the condition where the ion incident energy is increased to some extent. That is, the mean free path of ions and the self-bias potential V _dc under the conditions of low gas pressure and high bias power.
Is increased, and high anisotropy is achieved by utilizing the high kinetic energy of this ion to cause sputtering.

However, the adoption of such etching conditions leads to a decrease in the selectivity with respect to the underlying material layer, which is also a factor that hinders the practical application of the multilayer resist process. This problem will be described with reference to FIG. Figure 3
(A) shows the state of the wafer on which the upper layer resist pattern 15 is formed in the three-layer resist process. The steps up to this point will be briefly described. First, the underlying material layer 12 that follows the step is formed on the SiO ₂ interlayer insulating film 11 having the step, and the step is absorbed so that the surface of the wafer can be flattened. A lower resist layer 13 having
Then, a thin SOG intermediate layer 14 made of spin-coated glass (SOG) is sequentially formed, and a thin upper resist layer is further formed on the SOG intermediate layer 14. The upper resist pattern 15 is obtained by patterning the upper resist layer by photolithography and development processing. The resolution of photolithography at this time is extremely high, and the upper layer resist pattern 15 has a clear edge with a width of 0.35 μm.

Next, the SOG intermediate layer 14 is patterned by RIE (reactive ion etching) using the upper resist pattern 15 as a mask to form an SOG pattern 14a as shown in FIG. 3B. This SOG
The pattern 14a also has a very clear edge.

Next, the lower resist layer 13 is etched by using O ₂ gas. In this etching process, the thin upper resist pattern 15 disappears halfway, and thereafter, only the SOG pattern 14a functions as an etching mask. Here, the lower resist layer 13 is a layer formed to have a film thickness sufficient to absorb the surface step difference of the wafer based on the purpose of the three-layer resist process. They are different, and the time required for etching is naturally different. For example, in the region corresponding to the upper part of the step of the base material layer 12, FIG.
Lower layer resist pattern 1 early as shown in
3a is completed (just etching state), and the underlying material layer 12 is exposed.

Subsequently, when overetching is performed to remove the residual portion 13b in the region corresponding to the lower portion of the step, the base material layer 12 is irradiated with ions having a large incident energy and sputtered at the upper portion of the step. It A part of the sputtered product is redeposited on the side wall portion of the lower resist pattern 13a to form a redeposited layer 12a as shown in FIG. 3 (d). Particularly when the underlying material layer 12 is a metal wiring material or the like, the redeposited material layer 12a is difficult to remove and becomes a source of particle contamination. Also, S
In addition to the OG pattern 14a receding by ion irradiation, the redeposited layer 12a described above thickens the substantial line width of the etching mask, so that a dimensional conversion difference is likely to occur.

The problem of reattachment as described above is described in, for example, Proceedings of the 33rd Joint Lecture in Applied Physics (Spring Annual Meeting 1986) p. 542, Abstract No. 2p-Q-8 has been pointed out and is well known. Reattachment layer 12
Although it is clear that the reduction of incident ion energy is effective in suppressing the formation of a, this causes the above-mentioned isotropic combustion reaction to predominate, resulting in a decrease in anisotropy.

Therefore, a dry etching method for a resist material layer is desired which can achieve both reduction of incident ion energy and achievement of high anisotropy.

As a technique for responding to such a demand, the applicant of the present application has not hitherto depended only on reduction of radicality and enhancement of ionicity for achievement of high anisotropy, but for side wall protection by a reaction product. We are proposing various technologies to be achieved in combination. In other words, if sidewall protection is also used, the ion incident energy can be reduced to such an extent that the practical etching rate is not impaired, and even if low temperature etching, which has been attracting attention in recent years, is performed, the temperature is far higher than that of the conventional method. This is because the same effect can be obtained in the temperature range close to.

For example, in JP-A-2-244625, a reaction product of a lower resist layer and a Cl-based gas is obtained by using an etching gas in which chlorine (Cl) -based gas is added to O _2. A technique for anisotropically etching the lower resist layer while depositing CCl _x as a sidewall protective film has been disclosed. Further, Japanese Patent Application No. 2-198044 proposes a technique of etching a resist material layer using an etching gas mainly composed of NH ₃ in a state where the wafer temperature is controlled at 50 ° C. or lower. .. Here, the etching reaction product containing at least N, C, and O as constituent elements plays a role of a sidewall protective film.

Further, Japanese Patent Application No. 2-298167 discloses that a reaction product of a lower resist layer and a Br-based gas is obtained by using an etching gas in which bromine (Br) -based gas is added to O ₂ . A technique of anisotropically etching the lower resist layer while depositing CBr _x as a side wall protective film was proposed.

[0014]

The respective dry etching methods previously proposed by the applicant of the present invention achieve anisotropic etching with low energy ions in a practical temperature range while ensuring a practical etching rate. In that respect, they were all extremely innovative technologies. However, in the future, as the device integration becomes higher and the wafer surface level difference increases, there are cases where 100% overetching is required. However, it is still difficult to prevent the spatter redeposition of the base material layer in the process of receiving the ions for a long time. Incident ion
Although it is possible to further reduce the energy, this has no choice but to increase the amount of chlorine-based gas or bromine-based gas added in order to ensure anisotropy, which causes a decrease in etching rate and deterioration of particle level. I cannot escape.

Further, it has been pointed out that particle contamination becomes serious depending on the type of the base material layer. This becomes a problem particularly when the base material layer contains copper (Cu). In recent years, Cu has been added at a rate of about 0.5 to 1% with respect to Al for the purpose of improving electromigration resistance and stress migration resistance of Al-based wiring. Also, Cu
Has a low electrical resistivity of about 1.4 μΩcm, which is about half that of Al, so that it is highly expected as a future wiring material in a semiconductor device if an effective dry etching technique is established.

However, the chloride or bromide of Cu has a low vapor pressure. Therefore, when the lower resist layer is etched using a Cl-based gas or a Br-based gas on the underlying material layer containing Cu, Cu supplied from the exposed surface of the underlying material layer is Cu.
Redeposit on the pattern side wall surface in the form of ₂ Cl ₂ or Cu ₂ Br ₂ . Further, O ₂ which is the main component of the etching gas at this time also produces copper oxide having a low vapor pressure, which also re-deposits on the pattern side wall surface. These redeposits are difficult to remove and cause particle contamination.

In order to address this problem, the present inventor has previously disclosed in Japanese Patent Application No. 3-4222 that the gas composition during overetching is a mixed composition of a nitrogen compound and an oxygen compound or nitric oxide. A method of preparing a composition containing a system compound is proposed. This is because even if the base material layer is Cu, Cu has a relatively high vapor pressure
It is an extremely excellent method that can volatilize and remove in the form of (NO ₃ ) ₂ . However, since this etching reaction system in which nitric acid is involved has a strong oxidizing property, depending on the conditions, oxidation gradually progresses from the exposed surface of Cu toward the inside, and the wiring resistance of the finally formed Cu wiring pattern increases. There is a concern that it will be done.

Therefore, the present invention effectively prevents the redeposition of sputtered products derived from the base material layer, and does not increase the resistance of the resist layer (organic material when the base material layer is made of Cu). Layer) dry etching method.

[0019]

The dry etching method of the present invention is proposed in order to achieve the above-mentioned object, and an organic material layer formed on a base material layer has a nitrosyl group in its molecule. Alternatively, the etching is performed using an etching gas containing a compound having at least one functional group of a nitrile group.

Further, the present invention is characterized in that the etching gas further contains a sulfur-based compound capable of releasing sulfur into plasma under discharge dissociation conditions.

The present invention also divides the above etching into two steps, a just etching step and an overetching step, and in the just etching step, a compound having at least one functional group of a nitrosyl group or a nitrile group in the molecule and the sulfur compound. It is characterized in that an etching gas containing and is used, an etching gas containing NH ₃ is used in the overetching step, and the substrate to be etched is heated.

Further, the present invention is characterized in that the base material layer contains Cu.

[0023]

The point of the present invention is that by strengthening the film quality of the carbon-based polymer itself, a sufficiently high mask selectivity and underlayer selectivity can be achieved even if the deposition amount is reduced. As a method for strengthening the film quality of the carbon-based polymer itself, in the present invention, a nitrosyl compound having a nitrosyl group (-N = O) in the molecule or a nitrile group (-N
A nitrile compound having O ₂ ) is used.

Since these compounds contain O atom in the molecule, they can theoretically constitute the etching gas for the organic material layer alone. However, the important action of the above compound in the etching reaction system of the present invention is that each of the above functional groups can have a structure in which the N atom is positively charged and the O atom is negatively charged, resulting in a high polymerization promoting activity. Is to have. That is, the presence of such a functional group or an atomic group derived from the functional group in the plasma increases the degree of polymerization of the carbon-based polymer, and can enhance the resistance to ion injection and radical attack. In addition, when the above-mentioned functional group is introduced into the carbon-based polymer, the chemical and physical stability of the carbon-based polymer is higher than that of the conventional carbon-based polymer which is simply composed of a repeating structure of —CX ₂ — (X represents a halogen atom). It is also clear from recent studies that the number will increase. This is intuitively understood from the fact that the C—N bond (770 kJ / mol) is larger than the C—C bond (607 kJ / mol) when comparing the binding energy between two atoms. Furthermore, the introduction of the functional groups as described above increases the polarity of the carbon-based polymer, and the electrostatic adsorption force to the wafer that is negatively charged during etching is also increased, which also protects the surface of the carbon-based polymer. The effect improves.

By thus strengthening the film quality of the carbon-based polymer itself, it is possible to reduce the incident ions and energy required for anisotropic processing, and the selectivity for the mask made of SOG or the like and the underlying material layer. And the occurrence of damage to the base material layer is reduced. In addition, the amount of carbon-based polymer required to achieve high anisotropy and high selectivity can be reduced, so that particle contamination can be reduced as compared with the prior art.

The present invention is based on the above idea, but proposes a method aiming at further reduction of pollution and damage. One of them is the above-mentioned etching
A sulfur-based compound capable of releasing sulfur (S) into plasma under discharge dissociation conditions is added to the gas. In this case, in addition to the carbon-based polymer which is the etching reaction product, S can also be used for sidewall protection. Although depending on the conditions, S is deposited on the surface of the wafer if the temperature of the wafer is controlled to about room temperature or lower, and easily sublimes if heated to about 90 ° C. or higher. There is no risk of becoming a source of particle contamination.

Further, a part of this S further reacts with N released from the nitrosyl group or nitrile group to form various sulfur nitride compounds. A compound which mainly constitutes the above-mentioned sulfur nitride-based compound and which the present inventor expects to have a side wall protecting effect is polythiazyl (SN) _x . Regarding the properties and structure of polythiazyl in the single crystal state,
J. Am. Chem. Soc. , Vol. 29, p. 6
358-6363 (1975). It is a polymeric substance that stably exists at 208 ° C. under normal pressure and around 140 to 150 ° C. under reduced pressure. Therefore, under normal wafer temperature conditions where normal dry etching is performed, the film is deposited on the wafer, and the etching rate is reduced by competing with the sputter removal process at the vertical incidence plane of ions, and the pattern side wall portion plays a role of side wall protection. Fulfill Moreover, in the crystal of (SN) _x, the main chains composed of S-N-S-N -... Repeated covalent bonds are oriented parallel to each other. Therefore, this sulfur nitride compound mainly composed of (SN) _x can effectively prevent the intrusion of F ^{* and the} like. Further, even if ions accelerated by the conditions are incident, a so-called sponge effect is exerted due to a change in the bond angle or the conformation, and the ion impact can be absorbed or alleviated. In other words, the side wall protection effect is greater than that of a single S deposit, and the shock resistance against ion bombardment is also high. Furthermore, (SN) _x is 140 under reduced pressure.
When heated up to about 150 ° C, it is easily decomposed or sublimated and can be completely removed.

In addition, halogen such as F ^{* is} contained in the plasma.
When a radical is present, S in (SN) _x above
A thiazyl halide having a halogen atom attached on the atom may also be produced. Further, when hydrogen-based gas is added to control the amount of F ^* produced, thiazyl hydrogen can also be produced. Furthermore, depending on the conditions, the number of S atoms in the molecule and N
It is also possible to produce a cyclic sulfur nitride compound having an imbalanced number of atoms, or an imide type compound in which an H atom is bonded to the N atom of these cyclic sulfur nitride compounds.

In any case, the above-mentioned sulfur nitride-based compound can be deposited on the wafer under normal wafer temperature conditions, and is removed by heating the wafer. In the present invention,
By expecting deposition of such S and sulfur nitride compounds, incident ion energy can be further reduced,
It is possible to thoroughly reduce damage. Moreover, the amount of carbon-based polymer deposited can be relatively reduced by this, and particle contamination can be reduced accordingly.

Further, in the present invention, in order to effectively prevent the oxidation of the base material layer, the above etching is divided into a just etching step and an overetching step, and oxygen is removed from the gas system in the latter overetching step.
A method of overetching using an etching gas containing NH ₃ is also proposed. Regarding the etching mechanism when NH ₃ is used, the above-mentioned Japanese Patent Application No. Hei 2-19804.
This is as disclosed in the specification of No. 4. This method is extremely effective in preventing the oxidation of the exposed surface and the formation of a redeposited layer, especially when the underlying material layer is made of a material layer such as Cu which is easily oxidized.

[0031]

EXAMPLES Specific examples of the present invention will be described below.

Example 1 This example uses Al-1 in a three-layer resist process.
In this example, the lower resist layer formed on the% Si-0.5% Cu layer was etched using NOCl (nitrosyl chloride) / O ₂ mixed gas. This process will be described with reference to FIG.

First, as shown in FIG. 1A, an Al-1% Si-0.5% Cu layer 2 having a step difference of about 0.7 μm is formed on the SiO ₂ interlayer insulating film 1 having a step difference. And a novolac-based positive photoresist (manufactured by Tokyo Ohka Kogyo Co., Ltd .; trade name OFPR).
-800) was applied to form a lower resist layer 3. Here, the thickness of the lower resist layer 3 in the region corresponding to the lower part of the step is about 1.0 μm. SOG (manufactured by Tokyo Ohka Kogyo Co., Ltd .; trade name OCD-T) is formed on the lower resist layer 3.
ype2) is spin-coated and the thickness of SO is about 0.2 μm.
The G intermediate layer 4 was formed. Further, an upper layer resist pattern 5 patterned into a predetermined shape was formed on the SOG intermediate layer 4. The upper resist pattern 5 is, for example, a negative type three-component chemically amplified resist material (made by Shipley Co .; trade name SAL-601) with a thickness of about 0.7 μm for a KrF excimer laser.
It was formed by performing lithography and development processing. The pattern width of the upper resist pattern 5 is about 0.35 μm.

Next, this wafer is subjected to hex type RIE.
It was set in a (reactive ion etching) apparatus, and the SOG intermediate layer 4 was etched using the upper layer resist pattern 5 as a mask. The conditions at this time are, for example, CHF ₃
Flow rate 75 SCCM, O ₂ flow rate 8 SCCM, gas pressure 6.5
Pa and RF power were 1350 W (13.56 MHz). As a result, as shown in FIG. 1B, the SOG pattern 4a was formed immediately below the upper layer resist pattern 5.

Next, the wafer was transferred to an RF bias application type magnetic field microwave plasma etching apparatus, and the lower resist layer 3 was etched under the following conditions as an example. NOCl flow rate 15SCCM O ₂ flow rate 45SCCM Gas pressure 1.5Pa Microwave power 900W RF bias power 300W (2MHz) Wafer temperature Room temperature The above gas system is applied to O ₂ which is the most common etching gas for resist material layer. It is the one to which NOCl is added. Although NOCl cannot form an etching gas by itself, it has only one O atom in the molecule,
It is used together with O _{2 in} order to obtain a practical etching rate.

In this etching process, the etching proceeded by a mechanism in which the isotropic combustion reaction by O ^* was assisted by the ions of N ⁺ , NO ⁺ , NOCl _x ⁺ , O ^{+ and the} like.
Further, as in the case of using the conventional O ₂ / Cl-based gas, CCl _x is generated due to the carbon-based decomposition product supplied from the lower resist layer 3, while the nitrosyl group is added to the structure. It was taken in and a strong carbon-based polymer was generated. This carbon-based polymer was deposited on the side wall of the pattern to form the side wall protection film 6, which contributed to anisotropic processing. As a result, as shown in FIG. 1C, a lower layer resist pattern 3a having an anisotropic shape was formed.

In the present embodiment, Al-1% Si-0.
A high selectivity was achieved for the 5% Cu layer 2. This is because the above-mentioned carbon-based polymer exhibits high etching resistance even in a small amount due to its structure being strengthened, and Al-1
This is because the etching rate on the surface of the% Si-0.5% Cu layer 2 is significantly reduced.

Example 2 This example is an example in which the lower resist layer was similarly etched using a NOBr (nitrosyl bromide) / O ₂ mixed gas. First, the wafer shown in FIG. 1 (b) is set in a magnetic field microwave plasma etching apparatus,
The lower resist layer 3 was etched. The conditions at this time are the same as in Example 1 except that NOCl was replaced by NOBr. However, since NOBr is a liquid substance at room temperature,
After being vaporized by He gas bubbling, it was introduced into the etching chamber.

In this etching process, CBr _x and a carbon-based polymer having a nitrosyl group incorporated therein were produced, and the sidewall protective film 6 was formed by these deposits. In particular, in the present embodiment, by using a Br-based chemical species having a large atomic radius and low reactivity with Si,
The selectivity for the SOG pattern 4a was improved as compared with Example 1.

Example 3 In this example, the lower resist layer was also changed to NOCl / S ₂
This is an example of etching using a Cl ₂ / O ₂ mixed gas. First, the wafer shown in FIG. 1B was set in a magnetic field microwave plasma etching apparatus, and as an example, the lower resist layer 3 was etched under the following conditions.

NOCl flow rate 15 SCCM S₂Cl₂Flow rate 15 SCCM O₂Flow rate 40SCCM Gas pressure 1.5Pa Microwave power 900W RF bias power 180W (2MHz) Wafer temperature -30 ° C (using ethanol-based refrigerant)
The above gas system is the same as the gas system used in Example 1₂Cl
₂Is added. As a result, CCl_xAnd Nito
In addition to carbon-based polymers containing rosyl groups, S₂Cl ₂From
S that is generated separately, and part of this S is solved from NOCl
Generated by reacting with N generated separately (SN)_xA nitride of
Ou compounds also contribute to side wall protection, and these must not be mixed.
The side wall protective film 7 is formed. Also, the wafer is cooled at low temperature.
Pattern that does not receive the ion injection
The anisotropic radical reaction was suppressed at the side wall. Shi
Therefore, incident ion energy required for anisotropic processing
Of the SOG pattern
4a receding and Al-1% Si-0.5% Cu layer 2
The incoming redeposit layer was barely observed.

Example 4 In this example, the lower resist layer was also changed to NOBr / S ₂
This is an example of etching using a Br ₂ / O ₂ mixed gas. The etching conditions in this example are all the same as in Example 3 except that NOBr was used in place of NOCl, and S ₂ Br ₂ was used in place of S ₂ Cl ₂ .

In this embodiment, since the Br-based chemical species participate in the etching reaction system, the SOG pattern 4 is obtained.
The selectivity with respect to a and Al-1% Si-0.5% Cu layer 2 improved further than Example 3.

Example 5 In this example, the lower resist layer formed on the Cu layer was just etched using a mixed gas of NO ₂ Cl (nitrile chloride) / H ₂ S / O ₂ and then Cl ₂ was added. / NH ₃
This is an example of overetching using a mixed gas. This process will be described with reference to FIG. Note that the reference numerals in FIG. 2 are partially common to those in FIG.

The wafer used as the etching sample in this example has a stepped C on the SiO ₂ interlayer insulating film 1 having a stepped portion, as shown in FIG. 2A.
The u layer 8 is formed, and the lower layer resist layer 3, the SOG pattern 4a, and the upper layer resist pattern 5 are sequentially formed on the u layer 8 by a three-layer resist process. Here, the SOG pattern 4a and the upper layer resist
The patterning method of the pattern 5 is as described above in the first embodiment.

Next, this wafer was set in a magnetic field microwave plasma etching apparatus, and as an example, the lower resist layer 3 was just-etched under the following conditions. NO ₂ Cl flow rate 15SCCM H ₂ S flow rate 10SCCM O ₂ flow rate 45SCCM Gas pressure 1.5Pa Microwave power 900W RF bias power 180W (2MHz) Wafer temperature -30 ° C (using ethanol-based refrigerant) In this just etching process, nitrile group Alternatively, while the carbon-based polymer reinforced by the introduction of a partially decomposed nitrosyl group, S that is dissociated from H ₂ S and a sulfur nitride-based compound are mixed, the sidewall protective film 7 is formed anisotropically. Etching progressed. However,
Since the above NO ₂ Cl has a larger number of O atoms in the molecule than the above-mentioned NOCl, the etching rate was not lowered. As shown in FIG. 2B, this etching was stopped when the surface of the Cu layer 8 was exposed at the upper part of the step. At this time, the residual portion 3b of the lower resist layer 3 remained in the region corresponding to the lower portion of the step.

Therefore, in order to remove the residual portion 3b, overetching was performed by changing the etching conditions as follows as an example. Cl ₂ flow rate 15 SCCM NH ₃ flow rate 45 SCCM Gas pressure 1.5 Pa Microwave power 900 W RF bias power 120 W (2 MHz) Wafer temperature 150 ° C. Here, the wafer is heated by operating the heater built in the wafer stage. went. In this over-etching step, etching progressed while the carbon-based polymer having C, Cl, N, O, etc. as a constituent element was deposited to form the sidewall protection film 6.

By the way, the important advantage of this embodiment is that
That is, the wiring resistance of the Cu wiring pattern formed in the subsequent step does not increase. This is because the oxidation reaction on the exposed surface of the Cu layer 8 was prevented by eliminating oxygen from the etching reaction system in the above-described overetching step.

In the case where the etching processes having greatly different wafer temperatures are continuously performed as in this embodiment, the wafer stage is set in order to prevent the throughput from being lowered due to the time required for raising and lowering the temperature of the wafer. It is particularly preferable to use a multi-chamber type etching apparatus in which a plurality of etching chambers having different temperatures are connected under high vacuum. Alternatively, the present inventor first applied for Japanese Patent Application No. 3
As proposed in the specification of US Pat. No. 3,011,279,
It is also extremely effective to use an ECR plasma device equipped with a wafer stage in which a fixed electrode having a cooling means and a movable electrode having a heating means are combined.

Example 6 In this example, the lower resist layer formed on the Cu layer was just-etched using a NOBr / H ₂ S / O ₂ mixed gas, and then a Cl ₂ / NH ₃ mixed gas was added. This is an example of over-etching using. The just etching conditions of this embodiment are as follows except that NO ₂ Cl is replaced by NOBr.
All are the same as in Example 5. The overetching conditions are also the same as in Example 5.

In this embodiment, since Br is used as the halogen chemical species in the just etching step, the selection ratio for the SOG pattern 4a and the Cu layer 8 is further improved as compared with the fifth embodiment.

Although the present invention has been described based on the six examples, the present invention is not limited to these examples. For example, nitrosyl chloride has the above N
In addition to OCl, NOCl ₂ (nitrosyl dichloride) and NOC
The presence of l ₃ (nitrosyl trichloride) is known. Similarly, the presence of dibromide and tribromide in nitrosyl bromide is also known. Also, a nitrosyl compound having both Cl and Br in the molecule can be present. Any of these compounds can be used in the present invention.

Examples of the nitrile compound include NO ₂ C mentioned above.
In addition to 1, NO ₂ Br or the like can also be used. By the way, since chloride and bromide are picked up in each of the above-mentioned examples, it is easily inferred to use nitrosyl fluoride (NOF) or nitrile fluoride (NO ₂ F). Since F ^* is generated, when a silicon oxide-based etching mask such as the SOG pattern described above is used, the mask selectivity is deteriorated, which is not preferable.

As the sulfur-based compound, the above-mentioned S ₂
Cl ₂ , S ₂ Br ₂ , H ₂ S, S ₃ Cl ₂ , SCl
Sulfur chloride ₂ or the like, bromide sulfur such as S ₃ Br _2, SBr ₂ can be used. Sulfur fluoride such as S ₂ F ₂ can also release S under discharge dissociation conditions, but F ^*
Therefore, use it with caution. In addition, the configuration of the wafer, etching conditions, the etching apparatus used, the composition of the etching gas, etc. can be changed as appropriate.

[0055]

As is apparent from the above description, in the present invention, by using an etching gas containing a compound containing at least one of a nitrosyl group and a nitrile group in etching an organic material layer, a carbon-based polymer is used. It is possible to achieve high anisotropy and high selectivity even by enhancing the film quality and reducing the deposition amount. When this compound is used in combination with a sulfur-based compound capable of releasing S under discharge dissociation conditions, it is possible to achieve further high selectivity, low pollution, low damage and the like. This can truly enhance the practicality of, for example, a three layer resist process. Further, particularly when Cu is contained in the base material layer of the organic material layer, by using a gas system in which oxygen is eliminated during overetching, it is possible to prevent reattachment of Cu and particle contamination accompanying it. You can

The present invention is extremely effective in manufacturing a semiconductor device which is designed based on a fine design rule and which requires high integration, high performance and high reliability.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating a process example to which the present invention is applied in the order of steps, in which (a) is a lower resist layer, SOG on an Al-1% Si-0.5% Cu layer having a step. The intermediate layer and the upper layer resist pattern are sequentially formed, (b) is the state where the SOG pattern is formed, and (c) shows the lower layer resist pattern by etching the lower layer resist layer using at least the SOG pattern as a mask. Each of the formed states is shown.

FIG. 2 is a schematic cross-sectional view illustrating another example of the process to which the present invention is applied in the order of steps, in which (a) is a lower resist layer on a Cu layer having a step, an SOG pattern,
Upper resist pattern is sequentially formed, (b)
Is the state where the lower resist layer is just etched,
(C) represents a state in which the lower resist layer is over-etched.

FIG. 3 is a schematic cross-sectional view illustrating a problem in a conventional process, in which (a) is a state in which a lower resist layer, an SOG intermediate layer, and an upper resist pattern are sequentially formed on a base material layer having steps. (B) shows a state in which an SOG pattern is formed, (c) shows a state in which the lower resist layer is just etched, and (d) shows a redeposited layer formed of a sputtered product of the base material layer during overetching. It represents each state.

[Explanation of symbols]

1 ... SiO ₂ interlayer insulating film 2 ··· Al-1% Si- 0.5% Cu layer 3 ... lower resist layer 3a ... lower resist pattern 3b ... (the lower resist layer) Remaining part 4 ... SOG intermediate layer 4a ... SOG pattern 5 ... Upper layer resist pattern 6 ... Side wall protective film (carbon-based polymer) 7 ... Side wall protective film (carbon-based polymer / S / nitriding) Sulfur-based compound) 8 ... Cu layer

Claims (4)

[Claims] 1. An organic material layer formed on a base material layer is etched using an etching gas containing a compound having at least one functional group of a nitrosyl group or a nitrile group in a molecule. Dry etching method. 2. The dry etching method according to claim 1, wherein the etching gas contains a sulfur-based compound capable of releasing sulfur into plasma under discharge dissociation conditions. 3. An organic material layer formed on an underlying material layer, and a compound capable of releasing sulfur into plasma under discharge dissociation conditions with a compound having at least one functional group of a nitrosyl group or a nitrile group in the molecule. A just etching step of etching using an etching gas containing a base compound until substantially immediately before the underlying material layer is exposed, and an organic gas containing the NH ₃ containing etching gas while heating the substrate to be etched. An over-etching step of etching the remaining portion of the layer. 4. The dry etching method according to claim 1, wherein the base material layer contains copper.