JP3348504B2 - Dry 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 dry etching method applied to fine processing such as manufacturing of semiconductor devices, and more particularly to a lower resist film while maintaining a high selectivity with respect to an underlying material layer in a multilayer resist process. And a method for high-speed anisotropic etching of

[0002]

2. Description of the Related Art A multi-layer resist process has been adopted as the design rule of a semiconductor device is becoming finer, the surface level of a wafer is increased due to the complexity of an integrated circuit, and the exposure wavelength is shortened in photolithography. Is needed. This multi-layer resist process is a method using a combination of at least two types of resist films, a lower resist film thick enough to absorb a surface step on a substrate and a thin upper resist film thin enough to achieve high resolution. is there.

[0003] Well-known methods include journal
Of Vacuum Science and Technology (J. Vac. Sci. Tech., 16, p. 162)
0 (1979)). This is because a lower resist film, SOG
Silicon oxide (Si such as spin-on-glass)
Very thin intermediate layer consisting of O _x) based material, and is to use the three layers of a thin film of the upper layer resist film is patterned directly by photolithography. In this process, first, the upper resist film is patterned into a predetermined shape by lithography, the intermediate film under the upper resist film is patterned by RIE (reactive ion etching) using the mask as a mask, and the lower resist film is patterned using the intermediate film as a mask. Is dry-etched.

[0004] Dry etching of the lower resist film is usually performed using O ₂ gas. The essence of this etching mechanism is a combustion reaction of the organic polymer material by O ^* (oxygen radical), which originally proceeds isotropically. Therefore, in order to prevent the cross-sectional shape of the pattern from deteriorating, it is necessary to adopt a condition in which the ion incident energy is increased to some extent. That is, the average free path of ions and the self-bias potential V _dc are increased under the conditions of low gas pressure and high bias power, and the contribution of the sputter reaction by ions having large incident energy is increased to achieve high anisotropy. There is a need.

[0005] Adoption of such etching conditions, on the contrary, also hinders the practical use of the multilayer resist process. This is because the sputtered product of the underlying material layer adheres again to the pattern side wall at the time of over-etching, and it becomes difficult to remove it in a later step.

Such problems include, for example, the 33rd Federation of Applied Physics-related Lectures (Spring Annual Meeting, 1986), p. 542, a case of re-deposition of Al (aluminum) described in Abstract No. 2p-Q-8 is also known, but in addition to this, re-attachment of SiO _x interlayer insulating film or W (tungsten) -polycide wiring Kimono causes problems such as generation of dust.

[0007]

It is clear that reducing the incident ion energy is effective in suppressing the sputter redeposition described above, but this reduces the vertical etching rate and increases the throughput. In addition to being damaged, the above-described isotropic combustion reaction becomes dominant, which causes a problem that anisotropy is reduced.

[0008] In particular, when a high-density plasma having an ion density of 10 ¹¹ / cm ³ or more, which is proposed as a new plasma, is used, the anisotropic shape is remarkably deteriorated due to the re-dissociation of the etching reaction product CO _x. Easy to appear. That, ECR plasma (electron cyclotron resonance plasma), the silicon wave plasma, the electron temperature high plasma such as inductively coupled plasma, a combustion reaction products of the resist CO _x is riding on high vacuum exhaust stream chamber Before being discharged to the outside, a re-dissociation reaction represented by the following formula CO _x → CO _x-1 + O ^* occurs. O generated here
^* Deteriorates the anisotropic shape of the lower resist pattern.

As one method for solving this problem, it has been proposed to reduce the incident ion energy to the extent that the practical etching rate is not impaired by using sidewall protection in combination. For example, a dry etching method of depositing a reaction product, such as a CCl _x polymer or a CBr _x polymer, on a pattern side wall using a mixed gas of a halogen-based gas such as Cl ₂ or HBr and O ₂ is one example.

This method can realize anisotropic processing in a practical temperature range. However, depending on the kind of the base material layer, the reaction product having a complicated composition and having a complicated composition is difficult to remove due to the contribution of the added halogen-based gas. A new problem of depositing.

For example, the proceedings of the 40th Lecture Meeting on Applied Physics (Spring Annual Meeting, 1993) p. 578, Abstract No. 30a-ZE-8, a deposit containing C, O, Si, and Br as constituent elements when the lower resist film on the polysilicon film is etched using an HBr / O ₂ mixed gas. It is described that the microloading effect occurs due to abnormal deposition. Since this deposit contains Si, even if an attempt is made to remove it by performing O ₂ plasma treatment or the like after the end of the etching, there is a high possibility that Si will be changed to SiO _x and the particle level will be deteriorated. The proceedings also state that such abnormal deposition can be suppressed by reducing the amount of the halogen-based gas added.

As described above, the etching of the lower resist film is performed while satisfying all the conditions such as a practical etching rate, a high base selectivity, an excellent shape anisotropy, a suppression of a microloading effect, and a suppression of particles. Although it is not easy to perform, it is considered necessary to make the addition amount of the halogen-based gas zero or as small as possible.

On the other hand, it is known that the etching characteristics of ECR plasma and certain types of inductively coupled plasma change depending on the positional relationship between the plasma generating unit and the substrate.

For example, Japanese Journal of Applied Physics Vol. 29 No. 4 (Japanese J
ournal of Applied Physics, vol. 29, no. 4) p. 79
According to 2-797 (1990), as a result of examining the etching characteristics of the polyimide interlayer insulating film while changing the distance between the ECR position and the wafer stage, the ion current density increases as the substrate (wafer) approaches the ECR position. As a result, the etching rate increases, and the anisotropy improves. Conversely, if the position deviates from the ECR position, radicals having a longer lifetime than ions become dominant, and the anisotropic shape deteriorates.

Further, in the proceedings of the 1993 Dry Process Symposium, the etching characteristics of the SiO ₂ interlayer insulating film using a CF ₄ / H ₂ mixed gas were examined by using the high frequency antenna and wafer on the upper part of the chamber of the inductively coupled plasma apparatus. The results of examinations while changing the distance from the stage are described. According to this description, when the substrate is placed in the plasma generation region near the high-frequency antenna, the reaction product, HF, is re-dissociated by the action of high-energy electrons, and the selectivity to Si is not improved. However, if the substrate is placed in a plasma diffusion region slightly away from the high-frequency antenna, HF re-dissociation is reduced and a part is exhausted, so that the F atom concentration is reduced and the selectivity to Si is improved.

From these facts, in the dry etching method, it is considered effective to use high selective anisotropic processing to change the etching characteristics according to the substrate holding position in the plasma apparatus as described above.

Accordingly, the present invention provides a method capable of satisfying, at a high level, various conditions such as high speed, anisotropy, high selectivity, and low contamination in dry etching of an organic resist film. With the goal.

[0018]

The present inventor has conducted studies in view of the above-mentioned object, and as a result, has found that the amount of O ^* generated in a high-density plasma apparatus is reduced by a plasma generation unit and a substrate held in the apparatus. It is found that it is effective to perform shape control by changing the amount of O ^* that can come into contact with the substrate by changing this distance during etching, by utilizing the distribution according to the distance to the substrate. Thus, the present invention has been completed.

That is, according to the dry etching method of the present invention, etching capable of generating oxygen-based active species under a discharge dissociation condition is performed in a plasma apparatus having a plasma generation unit for generating plasma having an ion density of 10 ¹¹ ions / cm ³ or more.・
The gas is introduced, and the organic resist film on the substrate is selectively etched while changing the distance between the substrate held in the plasma device and the plasma generation unit.

Here, the organic resist film is a lower resist film in a multilayer resist process because the patterning is performed by dry etching instead of solution development processing.

The change mode of the distance is relatively small in the just etching step of etching the organic resist film substantially by the thickness thereof, and is relatively small in the over etching step of etching the remainder of the organic resist film. This is a mode for increasing the size. As a means for realizing this change, it is most convenient to make the substrate stage on which the substrate is mounted along the axial direction of the plasma apparatus.

The plasma having a high ion density as described above includes ECR plasma, helicon wave plasma,
Any of the inductively coupled plasmas can be used. Among these, several types of inductively coupled plasmas having different device configurations are known, and typical examples are as follows.
ICP (Inductively Coated) which is excited in a device in which a high frequency multi-turn antenna is wound around an insulating cylinder constituting an axial part of a cylindrical chamber.
TCP (Transformer Cup) excited in a device in which a spiral high-frequency antenna is arranged on an insulating plate above the chamber
led Plasma), and a helical resonance plasma excited in a helical resonator in which a spiral high-frequency antenna is wound around an insulating cylinder.

When using ECR plasma,
There is known a method in which a solenoid coil for generating a magnetic field is configured in a plurality of stages, and the ECR position is moved in the axial direction of the chamber by controlling the amount of electric power supplied to the solenoid coil in each stage. In the present invention, the ECR position may be moved in conjunction with the elevation of the substrate stage.

In the present invention, a gas containing at least one compound selected from O ₂ , O ₃ , carbon oxide, nitrogen oxide, sulfur oxide, and carbonyl sulfide (COS) is used as the etching gas for the organic resist film.

Here, CO (carbon monoxide), CO ₂ (carbon dioxide) and C ₅ O ₂ (pentacarbon dioxide) are used as the carbon oxide, and N ₂ O (dinitrogen monoxide) is used as the nitrogen oxide. , NO (nitrogen monoxide), N ₂ O ₃ (nitrogen trioxide)
And SO (sulfur monoxide) as sulfur oxide,
SO ₂ (sulfur dioxide) and SO ₃ (sulfur trioxide) can typically be used.

[0026]

[Function] Generally, ECR plasma, helicon wave plasma,
In high-density plasma such as inductively coupled plasma, a large amount of radicals is generated due to a high ion current density in the vicinity of the plasma generating portion, and also to promote re-dissociation of an etching reaction product. However, as the distance from the plasma generation unit increases, the electron temperature decreases, thereby decreasing the ion current density and relatively decreasing the radical density. However, since the re-dissociation of the etching reaction product also decreases, the radical does not become excessive. Such a change in the plasma characteristics along the axial direction of the plasma apparatus is naturally reflected on the etching characteristics. That is, high-speed anisotropic etching using high ion energy and a large amount of generated radicals becomes possible in the vicinity of the plasma generating portion. On the other hand, in a place distant from the plasma generation unit, highly selective anisotropic etching using an appropriate amount of radicals becomes possible.

According to the present invention, by changing the distance between the plasma generating portion and the substrate during the dry etching of the organic resist film, it is possible to hold the substrate in regions having different plasma characteristics. The advantages of etching are obtained at the same time.

In particular, O ₂ , O capable of generating oxygen-based active species
_{3. In} a process of etching an organic material film using an etching gas containing carbon oxide, nitrogen oxide, sulfur oxide, carbonyl sulfide, and the like, CO _x is generated as a reaction product, and the degree of re-dissociation of this CO _x Changes the O ^* density in each region of the plasma. Therefore, if etching is performed while holding the substrate in the vicinity of the plasma generating portion, high-speed anisotropic etching can be performed by abundant ions and O ^* . This process is suitable for just etching. On the other hand, if the substrate is held in a region away from the plasma generation unit, highly selective anisotropic etching can be performed. This process is suitable for over-etching.

If the distance between the plasma generating unit and the substrate is changed by raising and lowering the substrate stage, the substrate can be placed in plasma regions having different O ^* densities only by mechanical operation without changing the plasma excitation conditions. Can be. Therefore, dry etching excellent in reproducibility and throughput can be performed.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Embodiment 1 In this embodiment, the present invention is applied to a three-layer resist process for bit line processing of an SRAM, and utilizes an ECR plasma having an ion density of the order of 10 ¹¹ ions / cm ^2. This is an example in which the lower resist film on the second polycide film is etched.

First, the configuration of a magnetic field microwave plasma etching apparatus used in this embodiment is shown in FIG.

The basic components of this plasma etching apparatus are a magnetron 1 for generating a microwave of 2.45 GHz, a rectangular waveguide 2 and a circular waveguide 3 for guiding the microwave, and the microwave is utilized. Plasma _E P (electron cyclotron resonance) discharge
4. A bell jar 4 made of quartz for generating the laser, and the circular waveguide 3 and the bell jar 4 are arranged so as to circumscribe the 8.75 ×
An etching chamber 6 connected to a solenoid coil 5 and a bell jar 4 capable of achieving a magnetic field intensity of 10 ⁻² T (875 G), and evacuated to a high vacuum in the direction of arrow A in FIG. 6 respectively in Figure 1 the gas required for processing the bell jar 4 arrow B ₁ direction,
Arrow B in FIG. 1 indicates a gas introduction pipe 7 supplied from the direction of arrow ₂ , a wafer stage 9 for mounting the wafer W, and a refrigerant embedded in the wafer stage 9 and supplied from a cooling facility such as a chiller. _one direction, the cooling pipe 10 for cooling the wafer W to a predetermined temperature by circulating the arrow C ₂ direction, for applying a substrate bias to the wafer stage 9, through a matching network (M / N) 11, etc. And an RF power supply 12 for applying substrate bias, which is connected to the power supply.

The solenoid coil 5 includes an upper coil 5
a and a lower-stage coil 5b, which are independently supplied with power to control the magnetic field intensity distribution in the bell jar 4. This control can shift the position of the ECR position 13 is a resonance absorption point of ECR plasma P _E in the axial direction of the bell jar 4. Here, the ECR position 1 from the bottom surface of the lower coil 5b
A distance of up to 3, _{h E.}

On the other hand, the wafer stage 9 can be moved up and down in the direction of arrow D in FIG. 1 by a drive mechanism (not shown). Here, the distance to the bottom surface and the surface of the wafer stage 8 of the lower-stage coil 5b to h _S.

[0036] Thus, the distance d between the ECR position 13 and the wafer stage 9 is expressed by _{d = h} E + h _S. Since the wafer W is very thin, the distance d is approximately treated as the distance between the ECR position 13 and the wafer W.

Using this magnetic field microwave plasma etching apparatus, the lower resist film was actually etched.

FIG. 2 shows a wafer used as an etching sample. This wafer is formed on an Si substrate 21 on which shallow trench type element isolation regions 22 are formed in advance.
A gate electrode 25 made of a first polycide film is formed via a gate oxide film made of iO ₂ . The lower side of the gate electrode 25 is a polycrystalline silicon layer 23, and the upper side is W
An Si _x (tungsten silicide) layer 24 is formed.
Further, the entire surface of the wafer is coated in SiO _x interlayer insulating film 26 is deposited by CVD for example, the second layer polycide film 29 is formed thereon. This second layer polycide film 29 is a portion constituting the bit line of the SRAM, and the lower layer side is a polycrystalline silicon layer 27 and the upper layer side is a W layer.
It consists of a _Six layer 28.

Further, on the second polycide film 29, a lower resist film 3 for patterning the second polycide film 29 is formed.
0 is formed over the entire surface, and the SOG intermediate film 3 is further formed thereon.
1 and the upper resist film 32 are patterned.

Here, as an example, the upper resist film 32 is made of a chemically amplified negative type three-component resist (manufactured by Shipley Co .;
A film having a thickness of about 0.5 μm was formed using SAL-601 (trade name), and then patterned with a line width of about 0.35 μm using a KrF excimer laser stepper.

The SOG intermediate film 31 is a coating film of SOG (manufactured by Tokyo Ohka Kogyo Co., Ltd .; trade name: OCD-Type2) (film thickness: about 1).
00 nm) by dry etching using the pattern of the upper resist film 32 as a mask. This dry etching was performed using, for example, a RIE (reactive ion etching) apparatus and a CHF ₃ / O ₂ mixed gas.

The lower resist film 30 is made of, for example, a novolak-based positive photoresist (manufactured by Tokyo Ohka Kogyo Co., Ltd .; trade name: OFPR-800). (About 1.0 μm)
Is formed.

This wafer was set on the wafer stage 9 of the above-mentioned magnetic field microwave plasma etching apparatus, and just etching of the lower resist film 10 was performed under the following conditions as an example.

O ₂ flow rate 20 SCCM Cl ₂ flow rate 5 SCCM Gas pressure 0.27 Pa Microwave power 1000 W (2.45 GHz) RF bias power 200 W (800 kHz) Wafer stage temperature −50 ° C. (using alcohol-based refrigerant) ) the bell jar temperature 0.99 ° C. distance _h E 60 mm distance _h S 200 mm distance _{d (= h E + h S} ) 260 mm this process, although CO _x is produced as an etching reaction product, which is an ECR position 13 near Re-dissociation occurs with high probability, increasing the O ^* density in the plasma.
At the above-described wafer position, high-speed anisotropic etching progressed due to the contribution of high-density, high-energy ions and radicals.

It should be noted that a small amount of Cl ₂ is added to promote the deposition of the carbon-based polymer side wall protective film (not shown) under the wafer cooling condition.

Subsequently, as one example, overetching was performed under the following conditions to remove the remaining portion of the lower resist film 30.

O ₂ flow rate 20 SCCM Cl ₂ flow rate 2 SCCM Gas pressure 0.27 Pa Microwave power 1000 W (2.45 GHz) RF bias power 200 W (800 kHz) Wafer stage temperature −50 ° C. (using alcohol-based refrigerant) ) the bell jar temperature 0.99 ° C. distance _h E 90 mm distance _h S 300 mm distance _{d (= h E + h S} ) 390 mm this process, expanded than the distance between the wafer W and the ECR position 13 at just etching . At this wafer position, the re-dissociation of CO _x was not so large, so that the amount of O ^* generated did not become excessively large, and thus the high-speed and high-selective etching proceeded without damaging the anisotropic shape. As a result, as shown in FIG. 3, a lower resist pattern 30a having an anisotropic shape could be formed.

In this over-etching step, the flow rate of Cl ₂ is lower than in the just-etching step, but this is achieved by adjusting the distance d as described above.
^This is because the etching is performed under the condition of less ^* , so that it is not necessary to reinforce the sidewall protective film so much. Cl ₂ is to Hitasawa the WSi _x layer 28 of the underlying, it is very advantageous from the viewpoint of securing underlayer selectivity which can thus reduce the flow rate.

Embodiment 2 In this embodiment, the same etching of the lower resist film 30 is carried out by an ion implantation having an ion density of the order of 10 ¹² ions / cm ^2.
Performed using CP.

First, the configuration of the ICP etching apparatus used in the present embodiment is shown in FIG.

This apparatus comprises a cylindrical etching chamber 46, a ceiling part of the etching chamber 46, a conductive top lid 41 functioning as a large-area DC ground electrode for plasma, and an etching chamber 46. , A non-resonant multi-turn antenna 45 orbiting the quartz cylinder 44, and a first matching network (M / N) 42 on the multi-turn antenna 45. RF power supply 43 for plasma excitation and etching chamber 4 connected via
6, an exhaust hole 50 connected to an external exhaust system to evacuate the interior of the chamber 6 in the direction of arrow E in FIG.
A gas supply pipe 47 for introducing an etching gas into the chamber 46 from the direction of arrow F in FIG. 4, a wafer stage 48 on which the wafer W is mounted, and an alumina tube for fixing the wafer W on the wafer stage 48. Clamp 49, RF power supply 53 for applying substrate bias capacitively coupled to wafer stage 48 via a second matching network (M / N) 52 for impedance matching, arrows G ₁ , by supplying and circulating the refrigerant in the G ₂ direction as a main component a cooling pipe 51 or the like for cooling the wafer W.

The RF frequencies of the plasma excitation RF power supply 43 and the substrate bias application RF power supply 53 are set to values slightly shifted from each other in order to prevent interference between them.
As an example, the former was 2.2 MHz, and the latter was 2.0 MHz.

The wafer stage 48 can be moved up and down in the direction of arrow H in FIG. 4 by a driving mechanism (not shown). Here, the distance h between the multi-turn antenna 45 and the lower end and the wafer mounting surface of the wafer stage 48 is set.
_{Let I be} a parameter that controls the O ^* density.

In such a configuration, the plasma excitation RF
When a high frequency is applied from the power supply 43 to the antenna 45, electrons rotate in a plane substantially parallel to the electrodes in the induced magnetic field, and the collision probability with gas molecules is increased. As a result, 10 ¹²
Inductively coupled plasma P _I is generated which has a high ion density of ^two ions / cm.

Next, using the above-described ICP etching apparatus, just-etching of the lower resist film 30 was performed on the same sample wafer as that used in Example 1 under the following conditions as an example.

CO flow rate 50 SCCM Gas pressure 0.27 Pa Antenna output 1200 W (2.2 MHz) RF bias power 200 W (2.0 MHz) Wafer stage temperature −20 ° C. (using alcohol-based refrigerant) Distance h _I 50 mm in this process, O in the wafer W is inductively coupled plasma _{P I}
^* High-speed anisotropic etching proceeded because it was placed in a relatively high density region.

At this time, the ICP etching apparatus is
In the case of a device having a built-in heater, by operating the heater during etching, the deposition of the carbon-based polymer on the chamber wall is suppressed to reduce particles, and the sidewall protective film is efficiently formed on the wafer W. Can be formed.

[0058] Subsequently, except that the distance _{h I} lowers the wafer stage 48 was set to 200mm in the same conditions, were carried out over-etching. In this process, the wafer W is O ^*
Since it was placed in a region having a relatively low density, highly selective anisotropic etching could be performed. Finally, as in Example 1, the lower resist pattern 30a having a favorable anisotropic shape could be formed.

As described above, the fact that the etching characteristics can be changed only by mechanically raising and lowering the wafer stage 48 without changing the plasma excitation conditions is an extremely excellent advantage of the present invention.

Embodiment 3 In this embodiment, the same etching of the lower resist film 30 was performed by using helicon wave plasma having an ion density of the order of 10 ¹³ / cm ³ .

First, the configuration of the helicon wave plasma etching apparatus used in this embodiment is shown in FIG.

[0062] The plasma generation unit of the apparatus, a bell jar 61 made of quartz for generating the helicon wave plasma P _H therein has two loops circling the bell jar 61, the coupling of RF power to the plasma The main components are a loop antenna 62 for causing the magnetic field to rotate, and a solenoid coil 63 provided around the chamber 61 to generate a magnetic field along the axial direction of the chamber 61.

[0063] Here, the solenoid coil 63 further mainly helicon wave contributes inner side solenoid coil 63a to the propagation of, and mainly helicon wave plasma P _H periphery side solenoid coil 63b contribute to the transport of
Consists of

A high frequency is applied to the loop antenna 62 from the RF power supply 74 for plasma excitation through the first matching network (M / N) 73 for impedance matching, and the upper and lower two loops have opposite directions. Electric current flows. Here, the frequency of the plasma excitation RF power supply 74 was 13.56 MHz. The distance between the two loops is optimized according to the desired helicon wave number.

The bell jar 61 has an etching chamber 67.
Connected to which draws helicon wave plasma P _H along a divergent magnetic field inner circumferential side solenoid coil 63a and the outer solenoid coil 63b is formed into the interior of the etching chamber 67. The side wall surface and the bottom surface of the etching chamber 67 are formed using a conductive material such as stainless steel. The inside thereof is evacuated to high vacuum in the direction of arrow I in FIG. 5 through an exhaust hole 68 by an exhaust system (not shown), and is dry-etched in the direction of arrow J in FIG. Required gas supply. Further, the gate valve 6 is provided on the side wall surface.
For example, it is connected to a load lock chamber (not shown).

Further, inside the etching chamber 67, a conductive wafer stage 69 electrically insulated from the wall surface is accommodated, and a predetermined dry etching is performed while holding the wafer W thereon. Has been made.
The wafer stage 69 is provided with the wafer W during the process.
In order to maintain the desired temperature, supplied with refrigerant from a chiller (not shown), in Figure 5 this arrow K ₁ direction, arrow K
A cooling pipe 70 for circulation in _two directions is inserted.

[0067] The wafer stage 69 in order to control the energy of ions incident from in helicon wave plasma P _H, a second matching network (M / N)
An RF power supply 72 for applying a substrate bias is connected via the switch 71. Here, the frequency of the substrate bias applying RF power supply 72 was 13.56 MHz.

Further, a magnet 64 capable of generating a multi-cusp magnetic field as an auxiliary magnetic field generation wafer stage is provided outside the etching chamber 67 in order to converge a divergent magnetic field near the wafer stage 69.

The wafer stage 69 can be moved up and down in the direction of arrow L in FIG. 5 by a driving mechanism (not shown). Here, the lower end of the bell jar 61 and the wafer stage 6
The distance h _H between the wafer mounting surface 9, a parameter for controlling the O ^* density.

In this configuration, when a magnetic field is formed in the internal space of the bell jar 61 and a high frequency is applied to the loop antenna 62 wound around the bell jar 61 to generate a helicon wave in the bell jar 61, Electrons are accelerated by energy transfer from the wave through Landau damping, and the accelerated electrons collide with gas molecules to generate high-density plasma. The helicon wave plasma, it is possible to achieve a high ion density of approximately ¹⁰ 13 / cm ³ units.

Next, using this helicon wave plasma etching apparatus, the same sample as that used in Example 1 was used.
The wafer was subjected to just etching of the lower resist film 30 under the following conditions as an example.

NO ₂ flow rate 20 SCCM Gas pressure 0.1 Pa Antenna output 2000 W (13.56 MHz) RF bias power 200 W (13.56 MHz) Wafer stage temperature −30 ° C. (using alcoholic refrigerant) Distance h _H 250 mm in this process, since the wafer W is placed in a relatively high area of the ^{O *} density in helicon wave plasma _{P H,} high speed anisotropic etching has progressed.

[0073] Subsequently, lowers the wafer stage 69 the bell jar - a distance _{h H} between the wafer stage 450mm
The over-etching was performed under the same conditions except for the above.
In this process, since the wafer W was placed in a region having a relatively low O ^* density, highly selective anisotropic etching could be performed. Finally, as in Example 1, the lower resist pattern 30a having a favorable anisotropic shape could be formed.

As described above, it is an extremely excellent merit of the present invention that the etching characteristics can be changed only by mechanically raising and lowering the wafer stage 69 without changing the plasma excitation conditions.

The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, O ₂ , CO, and NO ₂ are used as the etching gas. Similar results can be obtained by using nitrogen oxide, sulfur oxide or carbonyl sulfide.

In addition, it goes without saying that the configuration of the sample wafer, the type and configuration of the etching apparatus, the etching conditions, and the like can be appropriately changed.

[0077]

As is apparent from the above description, according to the present invention, the substrate is placed in the plasma regions having different O ^* densities only by mechanical operation without changing the plasma excitation conditions, and the reproducibility is improved. In addition, it becomes possible to perform dry etching which is excellent in throughput.

In particular, since the high-speed and highly selective anisotropic etching of the lower resist film in the three-layer resist process can be performed, the present invention can realize the practical use of the process.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration example of a magnetic field microwave plasma etching apparatus used in a dry etching method of the present invention.

FIG. 2 is a schematic cross-sectional view showing a state where an SOG intermediate film is etched using a pattern of an upper resist film as a mask in a process of forming a resist pattern for processing a bit line of an SRAM.

FIG. 3 is a schematic cross-sectional view showing a state in which a lower resist film of FIG. 2 is anisotropically etched to form a lower resist pattern.

FIG. 4 is an ICP used in the dry etching method of the present invention.
FIG. 2 is a schematic sectional view illustrating a configuration example of an etching apparatus.

FIG. 5 is a schematic sectional view showing a configuration example of a helicon wave plasma etching apparatus used in the dry etching method of the present invention.

[Explanation of symbols]

1 magnetron, 4,61 beruja, 5,63
Solenoid coil, 6, 46, 67 Etching chamber, 9, 48, 69 Wafer stage,
12, 53, 72 RF power supply for applying substrate bias, 1
3 ECR position, 30 lower resist film, 3
0a lower resist pattern, 31 SOG intermediate film,
32 Upper resist film, 45 Multi-turn antenna, 43, 74 RF power supply for plasma excitation, 44
Quartz cylinder, 62 loop antenna, _P E E
CR plasma, _{P I} inductively coupled plasma, _{P H} helicon wave plasma, W wafer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00

Claims (4)

(57) [Claims] An etching gas capable of generating an oxygen-based active species under a discharge dissociation condition is introduced into a plasma apparatus having a plasma generation section for generating a plasma having an ion density of 10 ¹¹ ions / cm ³ or more. The organic resist film on the substrate is selectively etched while changing the distance between the substrate held in the apparatus and the plasma generating unit
In the method for dry etching a lower resist in a multilayer resist process , the distance is relatively small in a just etching step of etching the organic resist film substantially by the thickness thereof, and the remainder of the organic resist film is etched. A relatively large over-etching step. 2. The dry etching method according to claim 1, wherein the distance is changed by raising and lowering a substrate stage on which the substrate is mounted along an axial direction of the plasma device. 3. The dry etching method according to claim 1, wherein the plasma is any one of ECR plasma, helicon wave plasma, and inductively coupled plasma. 4. An etching gas comprising: O ₂ , O ₃ ,
4. The dry etching method according to claim 1, comprising at least one compound selected from the group consisting of carbon oxide, nitrogen oxide, sulfur oxide, and carbonyl sulfide.