JP3465444B2 - Plasma etching method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method used in the field of semiconductor device manufacturing, and more particularly, to a low dielectric constant organic polymer insulating film formed on a metal wiring such as an Al-based metal. In addition, the present invention relates to a plasma etching method capable of preventing the generation of a residue or a surface-altered layer when opening a connection hole facing the metal wiring.

[0002]

2. Description of the Related Art With the progress of high integration of semiconductor devices such as LSI, in a multi-layer wiring structure, the width of an interlayer insulating film between adjacent wirings in the same wiring layer is narrowed, and the interlayer insulation between different wiring layers is also increased. The film is also thin. Due to the decrease in the wiring interval, an increase in inter-wiring capacitance is becoming a problem. The prevention of increase in inter-wiring capacitance is one of the elemental technologies that must be solved in order to meet various demands for high-speed operation, low power consumption, and low heat generation of highly integrated semiconductor devices.

As a method of reducing the capacitance between wirings, it is effective to employ a low dielectric constant material for an interlayer insulating film, as disclosed in Japanese Patent Laid-Open No. 63-7650. Silicon oxide containing fluorine (SiOF) as the low dielectric constant material
SOG (Spin on Glass) which is an organic polymer material having a siloxane bond with an inorganic material such as
And polyimide, polyparaxylylene (trade name parylene), polynaphthalene, flare (trade name of Allied Signal Co.), or fluororesin organic polymer materials such as perfluoro group-containing polyimide and fluorinated polyallyl ether. For these low dielectric constant materials, see, for example, Nikkei Microdevice Magazine, July 1995 issue, p. 105.

These low dielectric constant material layers having a relative dielectric constant of 3.5 or less are applied not only between adjacent wirings but also between wiring layers of different levels, and the low dielectric constant material layer is formed of SiO.
₂ (relative permittivity 4), SiON (relative permittivity 4-6) and Si
_The applicant of the present application has proposed a laminated insulating film having a structure of being sandwiched by insulating films having excellent film quality such as ₃ N ₄ (relative dielectric constant 6).
No. 727, the possibility of a semiconductor device having both a low dielectric constant and high reliability was shown. A schematic sectional view of such a multilayer wiring structure is shown in FIG. This figure shows a multilayer wiring structure in which a lower layer metal wiring 1 and an upper layer wiring 7 which are orthogonal to each other are electrically connected by a via plug 6 embedded in a connection hole 5. Each wiring has a low dielectric constant organic polymer insulating film 21, 2
It has a highly reliable laminated insulating film structure which is surrounded by 2, 23, 24 and is sandwiched by silicon oxide insulating films 31, 32, 33.

When an actual semiconductor device having a multilayer wiring structure is manufactured with such a laminated insulating film, a connection hole is opened in the laminated insulating film in order to obtain electrical connection between the upper layer wiring and the lower layer wiring. There is a need to. Normally, when forming a contact hole in an interlayer insulating film made of a silicon oxide insulating film, plasma etching having a strong ionicity is performed using a CF type gas such as CF ₄ or CHF ₃ . The mechanism of this plasma etching is that the dissociation of the CF-based gas produces F ^* (F radical), which is a fluorine-based chemical species, and free C, which is a carbon-based chemical species, in the plasma, so that the silicon oxide-based insulating film Si in the constituents reacts with F ^*, and O, which is another constituent, reacts with C to form a reaction product having a high vapor pressure such as SiF ₄ and CO. These reaction products are CF of dissociation products of etching gas.
_It is also desorbed from the surface of the substrate to be etched by being assisted by the incident energy of ions such as ₃ ^+, and the etching reaction proceeds as shown in the following formula. Si + 4F → SiF ₄ ↑ O + C → CO ↑ At this time, a decomposition product of the resist mask and a CF-based polymer due to plasma polymerization of the source gas such as CHF ₃ are deposited on the side surface of the etched pattern, which causes anisotropy. While contributing to the processing, when the underlying Si semiconductor substrate and the metal wiring are exposed, excessive CF-based polymer is deposited on the surface and etching stops. Therefore, the low dielectric constant material layer is SiO 2.
In the case of an inorganic material such as F, plasma etching of the laminated insulating film using these low dielectric constant materials can be performed without any problems.
This is possible as an extension of the prior art.

However, when an organic polymer material such as the organic SOG, polyimide, polyparaxylylene, or fluororesin described above is used as the interlayer insulating film, C
Even if plasma etching with strong ionicity using F-based gas is used, patterning may be hindered. This problem will be described with reference to FIGS.

FIGS. 4A and 4B show connection holes (via holes) in a laminated insulating film formed of an organic polymer type insulating film and a silicon oxide type insulating film formed on a metal wiring such as an Al type metal.
It is a schematic sectional drawing explaining the problem in the process of opening. First, as shown in FIG. 4A, an organic polymer insulating film 2 such as an organic SOG and a silicon oxide insulating film 3 are formed on a metal wiring 1 such as an Al-based metal layer to form a laminated insulating film. After that, a resist mask 4 for opening a connection hole is formed. When plasma etching with a strong ionicity is performed using a CF-based gas from this state, the silicon oxide-based insulating film 3 is anisotropically etched. However, when the patterning reaches the surface of the organic polymer insulating film 2, the etching rate extremely decreases or becomes zero, and the patterning of the connection hole becomes impossible.

It is considered that this phenomenon occurs because the plasma etching conditions of the conventionally used silicon oxide type interlayer insulating film are directly applied to the processing of the low dielectric organic polymer type insulating film 2. That is, the organic SOG contains many carbon atoms as shown in [Chemical formula 1]. In addition, the (fluorinated) polyimide shown in [Chemical Formula 2], the (fluorinated) polyparaxylylene shown in [Chemical Formula 3], the fluorinated polyallyl ether shown in [Chemical Formula 4], and the [Chemical Formula 5] In the case of flares, the carbon occupies most of the molecular structure.

[0009]

[Chemical 1]

[0010]

[Chemical 2]

[0011]

[Chemical 3]

[0012]

[Chemical 4]

[0013]

[Chemical 5]

As described above, when the low dielectric constant film 8 made of an organic polymer having a large carbon composition ratio is subjected to plasma etching with a CF type gas, carbon type chemical species in the plasma atmosphere or on the surface of the substrate to be etched become excessive. , C / F ratio increases. Therefore, as shown in FIG. 4B, a carbon-based polymer 9 is formed by the excess carbon component even on the surface of the organic polymer-based insulating film 2, that is, the ion incident surface. It is considered that it serves as an etching stopper and the etching rate of the organic polymer insulating film 2 decreases. In addition, the C / F described here
For the ratio, see J. Vac. Sci. Tec
h. , 16- (2), 391 (1979), the concept is briefly described. Briefly speaking, carbon-based chemical species or carbon-based polymers and fluorine-based chemicals in a plasma atmosphere or on the surface of a substrate to be etched are used. It is the ratio of the number of atoms to the chemical species. That is, it can be said that it is the ratio of the deposition factor and the etching factor.

As a solution to this problem, the present inventor has previously disclosed in Japanese Patent Application No. 7-122682 that the etching of the organic polymer insulating film in the lower layer is lower than that of the silicon oxide insulating film in the upper layer. / F ratio etching conditions are adopted, or a gas that can generate oxygen-based chemicals is adopted. 2
A stepwise etching method was proposed. According to this method, S
It has become possible to stably plasma-etch a laminated insulating film including an organic polymer insulating film having a low dielectric constant formed on a semiconductor substrate such as i and form a contact hole.

However, when a connection hole to the organic polymer insulating film formed on the lower metal wiring such as Al-based metal, Ti-based metal and Cu-based metal wiring, that is, a via contact is opened, C / F is used. The method of lowering the ratio results in a lower etching selection ratio with respect to the lower metal wiring in the overetching stage. As a result, the lower layer metal wiring or its fluoride is sputtered and redeposited on the side surface of the connection hole and the resist mask. The fluorides of these metals are not sublimated or removed by evaporation because their vapor pressures are extremely small as described later, and remain as crown-like residues even after removing the resist mask. This problem is illustrated in Figure 5.
This will be described with reference to (a) to (d). The substrate to be etched shown in FIG. 5A is the same as that described in FIG. As shown in FIG. 5B, after the silicon oxide insulating film 3 is patterned on the substrate to be etched, the organic polymer insulating film 2 is patterned under the etching condition with a reduced C / F ratio. As shown in FIG. 5, the crown-shaped residue 10 adheres to the connection hole 5 and the side surface of the resist mask 4 during overetching, and remains protruding from the connection hole 5 even after the ashing of the resist mask 4 as shown in FIG. 5D.
If the crown-shaped residue 10 remains in the connection hole 5, it may cause a decrease in manufacturing yield such as a change in contact resistance. Further, even in the two-step etching method that employs a gas that can generate an oxygen-based chemical species, there is a problem that the surface of the lower metal wiring exposed on the bottom surface of the contact hole is oxidized and the selection ratio with respect to the resist mask is lowered.

[0017]

The present invention is based on the above-mentioned Al.
It is an object of the present invention to solve a problem when opening a connection hole in an organic polymer insulating film on a conductive material layer such as a base metal. That is, an object of the present invention is to provide an organic polymer insulating film on a conductive material layer of Al-based metal, Ti-based metal, Cu-based metal, or the like, or a laminated insulating film of an organic polymer-based insulating film and a silicon oxide-based insulating film. It is an object of the present invention to provide a plasma etching method in which a contact resistance does not fluctuate when a contact hole is opened, a residue is generated due to redeposition of a lower metal wiring by sputtering, and a surface of the lower metal wiring is oxidized.

[0018]

The plasma etching method of the present invention is proposed to solve the above-mentioned problems. That is, in the first invention, in the plasma etching method of opening the connection hole facing the conductive material layer in the organic polymer interlayer insulating film on the conductive material layer, the organic polymer interlayer insulating film is Gas, and at least one kind of organic polymer-based interlayer insulating film etching gas that can generate oxygen-based chemical species, and gas that can generate chlorine-based chemical species that reacts with the conductive material layer. By patterning using an etching gas containing
A conductive material layer, a chlorine-based material, and a chlorine-based material so as to prevent the formation of a residue in the connection hole due to a reaction between the conductive material layer and at least one gas of a CF-based gas and a gas that can generate an oxygen-based chemical species. It is characterized by reacting with a chemical species to vaporize and remove a reaction product.

In the second invention (claim 1), the conductive material layer is exposed to the laminated insulating film having a structure in which the organic polymer type interlayer insulating film and the silicon oxide type insulating film are laminated on the conductive material layer. In a plasma etching method of opening a connection hole, a first etching step of plasma etching the silicon oxide based insulating film using a first etching gas containing a CF based gas, and the organic polymer based interlayer insulating film , CF-based gas, and at least one organic polymer-based interlayer insulating film etching gas that can generate oxygen-based chemical species, and gas that can generate chlorine-based chemical species that reacts with the conductive material layer And a second etching process of patterning using a second etching gas containing, in this order, the conductive material layer, the CF-based gas and the oxygen-based chemistry. The reaction product is vaporized and removed by reacting the conductive material layer with a chlorine-based chemical species so as to prevent the formation of a residue in the connection hole due to the reaction with at least one of the gases capable of generating gas. It is characterized by doing.

In any of the inventions, the organic polymer insulating film preferably has a relative dielectric constant of 3.5 or less. In any of the inventions, the organic polymer insulating film preferably contains a fluorine atom in its molecular structure. The conductive material layer in the present invention is a metal wiring, especially A
The present invention can be preferably applied when an l-based metal, a Ti-based metal or a Cu-based metal is adopted, but may be a diffusion layer of a semiconductor substrate such as Si or an impurity-containing polycrystalline silicon layer, of course.

The CF type gas used in the present invention is CF ₄ or C ₂ F which is generally used as an etching gas for silicon oxide.
₆ , C ₃ F ₈ , C ₄ F ₈ , CHF ₃ and CH ₂ F ₂ are exemplified. Further, as the gas capable of generating the oxygen-based chemical species used in the present invention, there are exemplified gases such as O ₂ , O ₃ and N ₂ O which are capable of dissociating in plasma to generate O ^* and O ⁺ . Further, as the gas capable of generating the chlorine-based species used in the present invention, Cl ₂ , BCl ₃ , SiCl ₄ and CCl are used.
Examples of the gas such as ₄ which can dissociate in plasma to generate Cl ^* or Cl ⁺ .

Next, the operation will be described. Al-based metal such as Al, Al-Si, and Al-Cu, which is the base of the connection hole, C
When the exposed surface of u metal or Ti-based metal such as Ti, TiN, or TiON is exposed to plasma or ions of CF-based gas, it is sputtered according to the ion energy or F-based compound Formed on its surface. AlF _X, since the lower metal fluoride Any vapor pressure such as TiF _X, to form a foreign matter crowned residues etc. in the connection hole is a residue as described above. Also,
When plasma etching an organic polymer insulating film containing a fluorine atom with a CF gas, fluorine atoms are released from the organic polymer insulating film, so that the fluorine concentration is locally increased on the surface to be etched. In some cases, the formation of metal fluoride is further promoted. Even when exposed to plasma or ions due to oxygen-based chemical species, metal oxides having a low vapor pressure are formed on the surface and remain as foreign matters.

In the present invention, by adding a gas capable of generating a chlorine-based chemical species such as Cl ₂ to a gas for plasma-etching an organic polymer-based insulating film, an Al-based metal,
Chloride is formed as a reaction product with both the Ti-based metal and the Cu-based metal. Since these chlorides have a higher vapor pressure than fluorides, they are easily vaporized and removed, and no foreign matter is formed as a residue. The data of melting points and boiling points of Al, Ti and Cu compounds are shown below (unit: ° C, s
ubl. Represents sublimation). Fluoride melting point Boiling point AlF ₃ 1291 (subl.) TiF ₃ 1200 1400 CuF (Cu ₂ F ₂ ) 1100 (subl.) Chloride AlCl ₃ 177.8 (subl.) TiCl ₄ -25 136.4 CuCl (Cu ₂ Cl) ₂ ) 430 1490 The data is CRC Handbook of Chemistry and Physics 75th. edition (1994-1995).

The amount of chlorine-based species added is 1% or more and 10% or more.
The following are appropriate: This is because if it is less than 1%, the effect of removing the residue is small, and if it exceeds 10%, the selectivity with respect to the underlying metal wiring is lowered.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings referred to in the description of the embodiments, the same reference numerals are given to the same component parts as those in FIGS. 4 and 5 referred to in the description of the prior art.

Example 1 In this example, an interlayer insulating film made of a polyparaxylylene film as an organic polymer insulating film was formed on an Al-based metal layer as a conductive material layer, and a connection hole was formed in this interlayer insulating film. This is an example of opening, and this will be described with reference to the schematic cross-sectional views shown in FIGS.

First, as shown in FIG. 1A, Al-1% Si-0.5 on which an antireflection film 6 made of TiN is formed.
%, An organic polymer insulating film 2 made of polyparaxylylene having a thickness of 250 nm is formed on the conductive material layer 1 made of Cu.
VD film formation. As an example of the CVD conditions, p-xylene is vaporized at 170 ° C. and 1 Torr, and 650 is used in a pre-decomposition chamber.
It is thermally decomposed at 0.5 ° C. and 0.5 Torr to obtain an intermediate product mainly containing p-xylene radical. Next, this intermediate product is transported to the CVD chamber and polymerized and deposited on the semiconductor substrate 1 controlled at 35 ° C. in a reduced pressure atmosphere of 0.1 Torr to obtain a polyparaxylylene film. The melting point of the obtained polyparaxylylene was 400 ° C. FIG. 1A shows a state in which a resist mask 4 for opening a contact hole is formed on an organic polymer insulating film 2 made of polyparaxylylene. The resist mask 4 is formed by a conventional method from a three-layer resist having an SOG coating film as an intermediate layer (not shown) and has an opening diameter of 0.2 μm.

The substrate to be etched shown in FIG. 1A is set on the cathode electrode of a magnetron RIE apparatus, and as an example, the plasma etching of the organic polymer insulating film 2 is performed under the following etching conditions. O ₂ 80 sccm Cl ₂ 10 sccm Gas pressure 5.3 Pa RF power 1450 W (13.56 MHz) Substrate temperature −75 ° C. Under this etching condition, the upper layer resist in the resist mask 4 is also formed by the radical reaction mainly containing O ^*. At the same time, it is largely etched and recedes or disappears, but the patterning of the organic polymer insulating film 2 proceeds using the intermediate layer pattern made of SOG as a mask. At this time, since the substrate to be etched is cooled to a low temperature, the isotropic radical reaction due to O ^* is suppressed and side etching does not occur. In the overetching process in which the antireflection film 1 made of TiN is exposed, TiN is used as a reaction product, TiN.
Cl _x is formed, and part or all of it in the film thickness direction is removed. Further, depending on the location of the substrate to be etched, only a part of the lower Al-based metal layer in the thickness direction may be removed. The state in which the connection hole 5 is opened is shown in FIG.

In the conventional plasma etching using only oxygen-based chemical species, an oxide film was formed on the surface of the antireflection film 6 when it was exposed, which hindered the formation of the low ohmic contact plug. According to the example, such inconvenience does not occur. In this embodiment, the organic polymer insulating film 2 was patterned with a mixed gas of O ₂ / Cl ₂ , but CF type gas such as CHF ₃ / Cl ₂
It is also possible to perform plasma etching with the mixed gas of. In this case, a fluoride film is formed on the exposed surface of the antireflection film 6, or if the ion energy of etching is large, fluoride spatter re-deposits are deposited on the inner wall of the connection hole 5 to form a crown. The inconvenience of a particulate residue being formed is avoided.

Example 2 In this example, organic SOG was adopted as the organic polymer insulating film, and the organic SO was formed on the Al-based metal wiring as the conductive material layer.
This is an example of forming a connection hole by performing plasma etching on an interlayer insulating film in which G and a silicon oxide-based insulating film are laminated,
This will be described with reference to the schematic cross-sectional views shown in FIGS.

First, as shown in FIG. 2A, for example, Al
-On the metal wiring 1 having an alloy composition of -2% Cu, organic S
An organic polymer insulating film 2 made of OG and a silicon oxide insulating film 3 made of SiO ₂ are formed to form a laminated insulating film, and a resist mask 4 for opening a connection hole is provided. A spin coater is used for the organic SOG, and the coating liquid is spin-coated on the substrate to be processed at 3000 rpm, and then 200
It was dried at 0 ° C. for 1 minute and then annealed at 400 ° C. for 10 minutes to form an organic SOG film. The thickness of the organic polymer insulating film 2 made of this organic SOG film is 100 nm, for example.

The silicon oxide insulating film 3 on the organic polymer insulating film 2 is made of TEOS (Tetraethyl O 2).
by plasma CVD to Rthosilicate) and the O ₂ as a source gas, the substrate to be processed temperature 375 as an example
2 at ℃, 200mTorr, RF power 300W
It was formed to a thickness of 00 nm. A resist mask 4 having an opening diameter of 0.2 μm, for example, is formed on the laminated insulating film thus obtained.

The substrate to be etched shown in FIG. 2A is set on the substrate stage of a magnetron RIE apparatus, and the silicon oxide insulating film 6 is first patterned under the following plasma etching conditions. CHF ₃ 40 sccm CO 260 sccm Gas pressure 5.3 Pa RF power 1450 W (13.56 MHz) Substrate temperature 20 ° C. In this etching step, CO as an additive gas is COF which is an excessive fluorine-based chemical species generated in plasma. _It is removed outside the etching chamber in the form of _x and maintains a high C / F ratio, thereby playing a role of improving the selection ratio with respect to the resist mask. Under this etching condition, the lower organic SOG
Since the organic polymer insulating film 2 made of is not etched or has an extremely low etching rate, the etching is stopped when the surface of the organic polymer insulating film 2 is exposed. This state is shown in FIG.

Next, the etching conditions are switched, and the plasma etching of the lower organic polymer insulating film 2 is performed under the following plasma etching conditions as an example. CHF ₃ 80 sccm CO 220 sccm Cl ₂ 5 sccm Gas pressure 5.3 Pa RF power 1450 W (13.56 MHz) Substrate temperature 20 ° C. This etching condition reduces the flow rate of CO in the mixed gas and reduces the flow rate of CHF ₃ . It has increased. Therefore, CH
The chances that the fluorine-based chemical species generated by the dissociation of F ₃ are captured by CO and removed in the form of COF _x out of the etching reaction system are reduced. Therefore, the fluorine-based chemical species in the plasma increase and the C / F ratio decreases.

As a result of the reduction of the C / F ratio, there is no phenomenon that the carbon-based polymer is excessively deposited on the surface of the organic polymer insulating film 7 having a siloxane bond to lower the etching rate. Further, a carbon polymer side wall protective film (not shown) is thinly deposited on the side surface of the pattern where the number of incident ions is small, which contributes to anisotropic processing. The resist mask 4 does not recede. As a result, plasma etching of the organic polymer insulating film 3 proceeds smoothly.

When the surface of the underlying metal wiring 1 is exposed, the metal wiring 1 is conventionally sputtered in the over-etching stage to generate a crown-shaped residue in the over-etching step, as shown in FIG. 5C. However, in this embodiment, since a trace amount of Cl ₂ is added, the exposed surface of the metal wiring 1 is slightly etched, the chloride-based reaction product is promptly removed outside the etching reaction system, and the residue is left. It doesn't stay. As a result, as shown in FIG. 2C, a connection hole having a good anisotropic shape is formed.

Example 3 In this example, fluorinated polyallyl ether was used as the organic polymer insulating film, and the fluorinated polyallyl ether and silicon oxide insulating film were formed on the Al-based metal wiring as the conductive material layer. This is an example in which plasma etching is performed on the laminated interlayer insulating film to form a connection hole, which is also shown in FIG.
Description will be made with reference to schematic sectional views shown in FIGS.

First, as shown in FIG. 2A, for example, Al
-On the metal wiring 1 having an alloy composition of -2% Cu, an organic polymer insulating film 2 made of fluorinated polyallyl ether and a silicon oxide insulating film 3 made of SiO ₂ are formed to form a laminated insulating film. , Resist mask 4 for opening connection holes
To provide. A fluorinated polyallyl ether was formed by using a spin coater to spin-coat the coating solution on the substrate to be treated at 3000 rpm, followed by drying at 200 ° C. for 1 minute and then annealing at 400 ° C. for 10 minutes to obtain a fluorinated polyallyl ether. . The organic polymer insulating film 2 made of fluorinated polyallyl ether has a thickness of 100 nm, for example.

The silicon oxide type insulating film 3 as the upper layer of the organic polymer type insulating film 2 is processed by plasma CVD using TEOS and O ₂ as source gases as in the previous embodiment, and the substrate temperature is 375 ° C. and 200 mTorr, for example. , RF power 30
It was formed to a thickness of 200 nm under the condition of 0 W. A resist mask 4 having an opening diameter of 0.2 μm, for example, is formed on the laminated insulating film thus obtained.

The substrate to be etched shown in FIG. 1A is set on the substrate stage of a magnetron RIE apparatus, and as an example, the silicon oxide type insulating film 6 is first patterned under the following plasma etching conditions. CHF ₃ 40 sccm CO 260 sccm Gas pressure 5.3 Pa RF power 1450 W (13.56 MHz) Substrate temperature 20 ° C. The etching conditions are the same as in the second embodiment, but in this embodiment, the lower polyfluoride is also used. Since the organic polymer insulating film 2 made of allyl ether is not etched or has an extremely low etching rate, it stops when the surface of the organic polymer insulating film 2 is exposed. This state is shown in Figure 2.
It is (b).

Next, the etching conditions are switched, and as an example, the plasma etching of the lower organic polymer insulating film 2 is performed under the following plasma etching conditions. CHF ₃ 40 sccm O ₂ 10 sccm Cl ₂ 5 sccm Gas pressure 5.3 Pa RF power 1450 W (13.56 MHz) Substrate temperature 20 ° C. In this etching step, an organic polymer insulating film made of fluorinated polyallyl ether is used. 3 is etched by a radical reaction mainly composed of O ^* , but is anisotropically patterned by a decomposition product of the resist mask 4 and a side wall protective film (not shown) made of CF polymer by plasma polymerization of CHF ₃ gas. To be done.

When the surface of the underlying metal wiring 1 is exposed, the metal wiring 1 is conventionally sputtered in the over-etching stage as shown in FIG. 5 (c), and a crown-like residue is generated. However, in this embodiment, since a trace amount of Cl ₂ is added, the exposed surface of the metal wiring 1 is slightly etched, the chloride-based reaction product is promptly removed outside the etching reaction system, and the residue is left. It doesn't stay. As a result, as shown in FIG. 2C, a connection hole having a good anisotropic shape is formed.

Although the present invention has been described above with reference to three embodiments, the present invention is not limited to these embodiments.

For example, although polyparaxylylene, organic SOG, and fluorinated polyallyl ether are exemplified as the organic polymer insulating film, other low dielectric constant organic polymers such as polyethylene and polypropylene may be used. Further, part or all of the C—H bonds constituting these organic polymers are C—
If a fluorine-based polymer substituted for the F bond is adopted, it will contribute further to lowering the dielectric constant. Of course, Teflon PTFE (Pol, which is a fluorocarbon polymer with a relative dielectric constant of about 2)
y Tetra Fluoro Ethylene),
Teflon FEP (Fluorinated Ethyl)
ne Propylene) or Teflon PFA
Using (Per Fluoro Alky),
A laminated insulating film satisfying both low dielectric constant and low hygroscopicity can be formed. These fluorocarbon-based polymers can be formed by plasma polymerization or by coating and baking dry powder or emulsion. However, in the case of Teflon PTFE, it is necessary to pay attention to the adhesiveness.

Although organic SOG is used as an example of the organic polymer insulating film having a siloxane bond, other silicon dollar polymers such as polyphenylsilsesquioxane can also be used.

As an example of the silicon oxide type insulating film formed on the upper layer, SiO ₂ formed by plasma CVD has been exemplified.
It may be silicate glass containing impurities such as ON, SiOF, or PSG or BPSG.

The layer structure of the laminated insulating film is not limited to the two-layer structure in which the silicon oxide type insulating film is laminated on the low dielectric constant film,
It is obvious that the present invention can be applied to a multi-layer insulating film in which a low dielectric constant film and a silicon oxide insulating film are alternately laminated. Further, it is not limited to the via hole processing of the interlayer insulating film facing the metal wiring, but may be applied to the pad opening to the final passivation film of polyimide or the like or the contact hole processing facing the impurity diffusion layer formed on the semiconductor substrate.

Further, a magnetron RIE is used as an etching apparatus used for plasma etching of the laminated insulating film.
The equipment was picked up, but the normal parallel plate type RIE equipment, E
It goes without saying that various etching devices such as a CR plasma etching device, a helicon wave plasma etching device, an ICP (Inductively Coupled Plasma) etching device, and a TCP (Transformer Coupled Plasma) etching device can be used.

[0049]

As is apparent from the above description, according to the present invention, it is possible to prevent alteration of the surface of the underlying conductive material layer and reattachment by sputtering when opening the connection hole in the low dielectric constant organic polymer insulating film. However, a plasma etching method that does not cause an increase in contact resistance or a decrease in step coverage due to a residue or an altered film can be realized. Therefore, reduction in inter-wiring capacitance of a highly integrated semiconductor device using multi-layered wiring can be realized with high reliability, which can contribute to high-speed operation, low power consumption, low heat generation, etc. of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating Example 1 to which the present invention is applied in the order of steps, in which (a) shows a state in which an organic polymer insulating film and a resist mask are formed on a metal wiring,
(B) is a state where the organic polymer insulating film is plasma-etched to open the connection hole.

2A and 2B are schematic cross-sectional views for explaining Embodiments 2 and 3 to which the present invention is applied in the order of steps, in which (a) is an organic polymer insulating film and a silicon oxide insulating film on a semiconductor substrate; A state where a resist mask is formed, (b) a state where a silicon oxide insulating film is plasma-etched,
(C) is a state in which the organic polymer insulating film is further plasma-etched to open the connection hole.

FIG. 3 is a schematic cross-sectional view showing an example of a multilayer wiring structure using a laminated insulating film of an organic polymer insulating film and a silicon oxide insulating film.

FIG. 4 is a schematic cross-sectional view illustrating a problem in opening a connection hole in a conventional laminated insulating film of an organic polymer insulating film and a silicon oxide insulating film.

FIG. 5 is a schematic cross-sectional view illustrating another problem when a connection hole is opened in a conventional laminated insulating film of an organic polymer insulating film and a silicon oxide insulating film.

[Explanation of symbols]

1 Metal wiring (conductive material layer) 2, 21, 22, 23, 24 Organic polymer insulating film 3, 31, 32, 33 Silicon oxide insulating film 4 Resist mask 5 connection holes 6 via plugs 7 Upper layer wiring 8 Low dielectric constant film 9 carbon-based polymer 10 Crown residue

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Claims (7)

(57) [Claims] 1. A plasma etching method in which a connection hole facing the conductive material layer is opened in a laminated insulating film including a structure in which an organic polymer interlayer insulating film and a silicon oxide insulating film are stacked on a conductive material layer. A first etching step of plasma etching the silicon oxide based insulating film using a first etching gas containing a CF based gas; and a step of etching the organic polymer based interlayer insulating film with a CF based gas and an oxygen based chemical. A second gas containing at least one kind of the organic polymer-based interlayer insulating film etching gas of a gas capable of generating a species, and a gas capable of generating a chlorine-based chemical species that reacts with the conductive material layer; A second etching step of patterning with an etching gas is performed in this order to generate the conductive material layer and the CF-based gas and oxygen-based chemical species. The reaction product by vaporizing and removing the reaction material by reacting the conductive material layer with the chlorine-based chemical species so as to prevent the formation of a residue in the connection hole due to the reaction with at least one of the gasses. A plasma etching method comprising: 2. The method according to claim 1 , wherein the ratio of C atoms to F atoms in the plasma in the first etching step is higher than the ratio of C atoms to F atoms in the plasma in the second etching step. The plasma etching method according to claim 1 , wherein the composition ratio of the first etching gas and the second etching gas is adjusted. Wherein said organic polymer based interlayer insulating film is characterized in that the relative dielectric constant of 3.5 or less, according to claim 1
The plasma etching method described. Wherein said organic polymer based interlayer insulating film is characterized by containing a fluorine atom, a plasma etching method of claim 1. Wherein said conductive material layer is at least 1 selected from among Al-based metal, Ti-based metal and Cu-based metal
The plasma etching method according to claim 1 , wherein the plasma etching method is made of one kind of metal material. 6. The addition amount of the chlorine species least 1% 1
It is 0% or less, The plasma etching method of Claim 1 characterized by the above-mentioned. 7. The etching gas for patterning the organic polymer-based interlayer insulating film contains a CF-based gas, a gas capable of generating an oxygen-based chemical species, and a gas capable of generating a chlorine-based chemical species. The plasma etching method according to claim 1, wherein: