JPH113880A - Semiconductor substrate processing method - Google Patents

Abstract

[PROBLEMS] To consistently perform etching and post-processing in etching a laminated wiring film, to prevent corrosion of wiring after etching and to synchronize post-processing time by performing etching. And a method for processing a semiconductor substrate that can reduce the post-processing time. An etching process using a H ₂ O gas is performed after an etching process using a chlorine-based gas, and a post-process for removing a resist and preventing corrosion is continuously performed in a separate chamber under vacuum. According to the present invention, since there is no corrosion of the laminated wiring film and no residual resist is generated, and the post-processing time is shortened, the synchronization between the etching process and the post-processing can be achieved, so that the productivity of the semiconductor substrate can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching process for performing fine processing on a substrate in a manufacturing process of a semiconductor device, and particularly to a chlorine component remaining when a metal laminated wiring containing aluminum or an aluminum alloy is subjected to plasma processing. The present invention relates to a method for processing a semiconductor substrate, which is performed to prevent corrosion of wiring and defective removal of a wiring pattern such as a resist due to the above.

[0002]

2. Description of the Related Art A metal wiring of a semiconductor device made of an aluminum alloy (Al-Cu-Si or Al-Si) has a laminated structure in which a barrier layer such as TiN is formed on the substrate side and a cap layer such as TiN is formed on the surface side. It has a membrane structure. This metal wiring is usually etched by a mixed gas plasma of chlorine Cl ₂ and Bcl ₃ or a mixed gas plasma containing an additional gas. Since Al is also etched only by Cl ₂ gas, it is necessary to form a protective film that suppresses etching in the horizontal direction, that is, a so-called sidewall protective film, in order to etch a metal wiring in a vertical shape. The side wall protective film is composed of an etching reaction product or a resist component, and is formed on the side wall of the metal wiring while proceeding simultaneously with the etching. Usually, an ashing process for removing the resist is performed immediately after the etching without exposing the substrate to the atmosphere. By the way, Cl ₂ and Cl during etching are contained in the side wall protective film, and if not completely removed by the ashing process, when the film is taken out to the atmosphere afterwards, it reacts with the moisture in the atmosphere to generate HCl HCl. Is formed, and a phenomenon that the wiring is corroded is known.
Therefore, it is necessary to perform a corrosion prevention treatment on the treated substrate.

An example of the prior art for preventing corrosion of wiring is disclosed in Japanese Patent Application Laid-Open No. 55-91842. This prior art example shows that the aluminum / copper alloy film is etched using a chlorine-based or bromine-based gas and then subjected to a hydrogen plasma treatment so that no corrosion occurs in the wiring. No mention is made of the complete removal of resist by plasma and the prevention of corrosion of the laminated structure film.

Japanese Patent Application Laid-Open No. 63-241933 discloses an example of a conventional technique for preventing corrosion of a wiring in a laminated structure film containing aluminum. In this prior art example, an etching process is performed by using a chlorine-based gas for etching a film mainly composed of aluminum in a laminated film containing aluminum, and using a fluorine-based gas for etching a titanium layer and a titanium nitride layer. It is described. It is stated that chlorine or chlorine compounds remaining during etching of a film mainly composed of aluminum are treated while replacing or removing them with a fluorine-based gas, so that the residual amount of chlorine or chlorine compounds is small and corrosion of wiring can be delayed. However, it does not mention a method for removing the resist after the etching treatment.

[0005] Further, as another prior art example, Japanese Patent Laid-Open No.
Japanese Unexamined Patent Publication No. 226299 discloses that a resist treatment is performed by performing a plasma treatment containing hydrogen atoms after the etching treatment and a plasma treatment containing oxygen in order to surely remove chlorine remaining after the etching treatment of the multilayer structure wiring film. Is described. In the embodiment of the prior art, it is shown that after the etching process, the ashing process is performed in a separate chamber after the plasma process including hydrogen atoms, followed by the gas including oxygen. The main purpose of the plasma treatment containing hydrogen atoms is to remove residual chlorine, and there is no description of adding an ion effect to the substrate surface using a high-frequency power supply.

[0006]

In the above-mentioned prior art embodiment, in order to prevent the corrosion of the wiring, the chlorine component adhered or remaining during the etching process is mainly eliminated by plasma treatment with a hydrogen component or a fluorine component. It is shown that it can be replaced.

In recent years, a processing apparatus for forming a wiring film has an apparatus having a separate post-processing chamber for corrosion prevention processing and resist removal in addition to an etching processing chamber for preventing corrosion of wiring after etching processing. Is increasing. Conventionally, these apparatuses require about 60 to 100 seconds for the etching processing and about 120 to 180 seconds for the post-processing, and the processing for consistently performing the etching and the post-processing has not always been performed efficiently.

An object of the present invention is to provide a method of processing a semiconductor substrate, which can shorten the post-processing time as well as the etching processing time, synchronize the two processing times, and improve the production efficiency.

[0009]

Means for Solving the Problems In order to achieve the above-mentioned object, after performing an etching treatment with a chlorine-based gas in an etching treatment chamber, and further performing an additional etching treatment with a H ₂ O gas in the same treatment chamber, the vacuum treatment is carried out. It consists of continuously performing corrosion prevention and resist removal processing in another processing chamber.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The phenomenon that an aluminum wiring corrodes when left in the air after plasma etching of the aluminum wiring has characteristics depending on the material structure of the aluminum wiring. In particular, a laminated film of titanium nitride or the like (from the substrate side, substrate Si / oxide film SiO ₂ / titanium nitride Ti
N / Aluminum alloy Al-Si-Cu / Titanium nitride T
iN / resist PR). this is,
This is because corrosion is likely to occur electrochemically. That is, a battery effect works between the laminated films made of different metals. Single layer film of aluminum wiring (substrate S
i / oxide film SiO ₂ / aluminum alloy Al-Si-C
u / resist PR) has no battery effect and is hardly corroded. Hereinafter, the above substrate is referred to as an aluminum laminated substrate or an aluminum single layer substrate.

FIG. 1 shows an embodiment of a plasma etching apparatus for carrying out the present invention. The aluminum laminated substrate 10 is taken out of the cassette 2 by the robot arm 3 installed on the atmosphere side and introduced into the load lock chamber 5. Next, the door 4 of the load lock chamber 5 is closed, and evacuation is started. The vacuum evacuation is performed by slow evacuation so as not to wind up foreign matter in the load lock chamber 5. The valve 6 between the load lock chamber 5 and the transfer chamber 9 is opened when the pressure is exhausted below a predetermined pressure. The transfer chamber 9 is constantly evacuated and maintained at a high vacuum. The substrate 10 is transferred from the load lock chamber 5 to the transfer chamber 9 by the robot arm 11 provided in the transfer chamber 9. Immediately after the transfer, the valve 6 is closed. Next, the pressure in the etching chamber 13 is evacuated to a sufficiently high vacuum,
After confirming that the pressure is preferably below 10 -5 Torr, the valve 14 between the etching chamber 13 and the transfer chamber 9 is opened, and the substrate 10 is carried into the etching chamber 13. In the etching chamber 13, the substrate 10 is mounted on the substrate mounting electrode. The electrodes are capable of electrostatically adsorbing the substrate 10, and the substrate 1
A helium gas of several Torr to 10 Torr is introduced into the back surface of the substrate 0 to increase the efficiency of heat conduction between the electrode and the substrate, thereby controlling the substrate temperature. After the valve 14 is closed, an etching gas, chlorine Cl ₂ or boron trichloride Bcl ₃ , and in some cases, an additional gas are introduced from a gas inlet.

Since the electrode of this embodiment is of a monopole type in which a high voltage is applied to the electrostatic attraction film via the plasma, the plasma is ignited by microwaves after the introduction of the etching gas. With the plasma ignited, a high voltage for electrostatic attraction is applied to the electrodes, and the substrate is attracted to the electrodes. The substrate is previously controlled at a temperature of about 20 to 50 ° C. In this state, helium gas is introduced into the back surface of the substrate. When the pressure of the helium gas reaches several Torr, the substrate temperature can be controlled by the temperature of the electrode surface. In this state, the number 1
00 kHz to several tens of MHz, preferably 800 kHz to
A high frequency voltage of 2 MHz is applied, and a bias voltage is applied to the substrate. The etching gas ions that have been turned into a plasma state by the microwaves are vertically drawn into the substrate simultaneously with the application of the high-frequency voltage. Radicals such as electrically neutral chlorine Cl in the etching gas enter the substrate from random directions, and are exposed to the etched portion 10 of the aluminum laminated substrate shown in FIG.
2a (the part where the resist is removed).

In the case of Al, etching is performed by chlorine radicals, but the aluminum laminated substrate shown in FIG.
Since TiN is formed in 02, it is not etched only by the adsorbed chlorine radical. However, with the help of high-energy ions drawn into the substrate by application of a high-frequency voltage, Ti-
The N layer 102 is etched. When the etching of the TiN layer 102 is completed, the surface of the substrate becomes an Al alloy 103. Al is etched into chloride AlCl ₃ (or Al ₂ Cl ₆ ), which is vaporized and removed. Part of the vaporized aluminum chloride collides with a side wall of the aluminum wiring (hereinafter, simply referred to as a side wall) and is adsorbed on the side wall.

Further, a part of the aluminum chloride released into the plasma is incident on the substrate again and adheres to the side wall in a state as it is or after being decomposed by the plasma. Further, a part of the resist 101 is also etched.
A part of it collides directly with the side wall and is adsorbed.

Further, once emitted into the plasma, it is incident again and adheres to the side wall. In this way, A
A film made of l, Cl, and C, and a sidewall protective film 106 are formed. This film continues to grow while the etching progresses, but is also etched at the same time, so that it is actually several n.
Since the side wall protective film having a very small thickness of m is formed, even if chlorine radicals are adsorbed on the side walls of the aluminum wiring, the aluminum wiring is not etched, and as a result, vertical anisotropic etching is performed. .

After the aluminum wiring is etched, a barrier layer 104, T, is formed under the aluminum wiring layer.
The material to be etched changes from iN, SiO ₂ as the base layer 105. Since the chloride of Ti has a high vapor pressure, the probability of being taken into the sidewall protective film is small. However, in the over-etching after reaching the oxide film, Si is slightly etched, and Si also adheres to the outermost surface of the sidewall protective film. After that, the etching gas is switched from chlorine gas to H ₂ O gas, and the etching process is further continued.

On the one embodiment side, a 6-inch sample has a resist film thickness of 1400 nm, a cap TiN of 60 nm, and an Al-S
i-Cu 800 nm, used as the barrier TiN 110 nm, chlorine-based etching process Bcl ₃ 60 cc /
min, Cl ₂ 90 cc / min, microwave output 80
0 W, the pressure 2 Pa, and applying high-frequency power 50 W, and 80 seconds etching process, H ₂ O gas 100 cc / min,
Microwave output 800W, pressure 2Pa, high frequency power 50
Etching was performed with W for 5 seconds. Thus, the etching of the aluminum laminated film is completed.

FIG. 3 shows the shape of the aluminum laminated substrate after the etching. When the etching is completed, the high frequency voltage applied to the electrode is stopped while maintaining the microwave discharge.

Next, the supply of helium gas on the back surface of the substrate is stopped to lower the back surface pressure sufficiently. In this state, the output of the microwave is stopped, and the gas supply is also stopped. Etching chamber 1
3 is evacuated for a while, and when a high vacuum is obtained, the valve 14 with the transfer chamber 9 is opened, and the substrate 10 is carried out of the etching chamber 13 by the robot arm 11.

Next, it is confirmed that the pressure in the ashing chamber 18 is equal to or lower than a predetermined pressure, and the valve 19 between the ashing chamber 18 and the transfer chamber 9 is opened to transfer the substrate 10 to the ashing chamber. Place on. In one embodiment, the substrate holder is 150 ° C. to 300 ° C., preferably 200 ° C.
The temperature is kept at a temperature in the range of 250C to 250C. Although the substrate temperature has reached several tens of degrees Celsius due to the heating in the etching chamber 13, the temperature hardly rises when the substrate is placed on the substrate holder. As the gas for ashing is introduced and the pressure increases, the heat conduction between the substrate holder and the substrate improves, and the substrate temperature gradually approaches a constant temperature.

In this embodiment, the resist remaining film is 1000 nm.
The ashing gas for the substrate is a mixed gas of H ₂ O and CF ₄ . The gas flow rate is H ₂ O 495 cm 3 / min
, CF _{4 5} cm 3 / min, pressure 160P
a, The temperature of the substrate holder was 250 ° C. Plasma was generated by introducing 1000 W of microwaves. Ashing gas is dissociated by plasma ignition, and H, OH, O,
Radicals such as F, CF, CF ₂ and CF ₃ are generated. The oxygen radicals O are combined with carbon C of the resist to form CO and are vaporized and exhausted. In this way, ashing is completed in about 40 to 50 seconds.

In this embodiment, over-ashing is further continued for 90 seconds. Thereafter, the supply of the ashing gas is stopped, and high vacuum evacuation is performed. When the pressure drops to a predetermined pressure, the valve 19 is opened, the substrate 10 is taken out into the transfer chamber 9, and further sent to the load lock chamber 24 (unloading chamber). In the load lock chamber 24, after the valve 23 is closed, a slow leak by the nitrogen gas 26 is performed. When the pressure reaches a pressure slightly higher than the atmospheric pressure, the door 25 with the atmosphere is opened, and the robot arm 3 carries out the cassette 2 to the cassette 2. I do. After this, the process may immediately proceed to the step of removing the side wall protective film. However, there may be a case where the process waits in the air or in a nitrogen gas atmosphere for a while until the next process. At this time, the aluminum wiring must not corrode.

In the present invention, no corrosion was observed even after 100 hours. In addition, the removal characteristics of the side wall protective film were good, and there was no generation of the side wall protective film residue.

Hereinafter, the reason why the result of the present invention was obtained will be described.

In the prior art, a gas containing O ₂ is used for removing the resist. However, Al is attached to the resist surface after the etching of the aluminum wiring because the reaction product at the time of etching reenters the resist. This Al is not removed by the ashing gas containing O ₂ . Rather A
If the area occupied by the l-attached portion is large, resist removal is hindered.

The inventor of the present invention has found that when an ashing gas containing O ₂ is used, the resist portion excluding the Al-attached portion is removed by oxygen radicals O, so that the area ratio occupied by the Al-attached portion gradually increases. As a result, it was found that the resist removal speed was slow. Also, in some cases,
When an ashing gas containing O ₂ is used, the resist may remain without being removed. However, by continuing the etching process using the H ₂ O gas following the chlorine-based etching process, the Al component and the resist component near the resist surface layer can be removed in a well-balanced manner by the action of ions and radicals caused by the H and OH components. The Al component is present up to about 10 nm from the resist surface layer, and the etching treatment with the H ₂ O gas has an effect of removing the Al residual layer and removing the chlorine component remaining on the surface together. Thereafter, a resist component containing almost no Al component is removed at high speed by plasma treatment performed in a separate room, and a chlorine component is further removed.

As described above, according to the present invention, in the post-processing after the etching processing of the laminated wiring film, there is no effect of the resist remaining along with the corrosion prevention effect, and the post-processing is performed at high speed, so that the etching and the post-processing can be performed simultaneously. It has become possible to improve the productivity of continuous and consistent processing.

In the present invention, H ₂ O is used for the treatment in the post-treatment chamber.
And has been described for the mixed gas system of CF _4, further mixed gas of between H ₂ O and O ₂ containing O ₂ gas to enhance the resist removal rate, it may be performed using a suitable post-processing gas species .

[0029]

According to the present invention, even in the processing of an aluminum laminated film in which the resist removal rate is reduced due to the effect of aluminum adhering to the resist surface, no resist remains and no wiring corrosion occurs. High-speed post-processing can be performed, and the effect of improving the productivity of the semiconductor substrate can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an etching apparatus according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a structure of an aluminum laminated substrate.

FIG. 3 is an explanatory diagram of a shape of an aluminum laminated substrate after etching.

[Explanation of symbols]

1 ... cassette stand, 2 ... cassette, 3 ... robot arm,
4 ... door, 5 ... load lock chamber, 6 ... valve, 7 ... vacuum pump, 8 ... nitrogen gas, 9 ... transfer chamber, 10 ... substrate, 11 ...
Robot arm, 12: vacuum pump, 13: etching chamber, 14: valve, 15: vacuum pump, 16: etching gas, 17: magnetron, 18: ashing chamber, 1
9: Valve, 20: Magnetron, 21: Ashing gas, 22: Vacuum pump, 23: Valve, 24: Load lock chamber, 25: Door, 26: Nitrogen gas, 27: Vacuum pump, 101: Resist, 102: Cap layer , 102a
... Surface to be etched, 103 aluminum wiring, 104 barrier layer, 105 oxide film, 106 side wall protective film.

Claims (1)

[Claims] When a sample is processed by a wiring pattern such as an organic film formed on a laminated structure film composed of a film containing aluminum and TiW, TiN, etc., an etching process is performed by a gas plasma containing chlorine. , H in the same processing chamber
After performing an additional etching process using ₂ O gas, a wiring pattern such as an organic film is removed by a gas plasma process such as an oxygen gas in another processing chamber connected under vacuum. Method.