JPH0821562B2 - Resist removal method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for removing a resist.

2. Description of the Related Art In a semiconductor device manufacturing process, a photoresist is used as a mask for forming a necessary pattern, but it is usually removed after being used as a mask for etching or ion implantation. In the prior art, the O ₂ plasma by either only incineration or, after ashing by O ₂ plasma, fuming nitric acid or washing with an alkaline organic solvent, O ₂
The residue in plasma ashing was removed, and then cleaning was performed with pure water to remove acids and bases.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the prior art, when removing a photoresist on a wiring layer of an aluminum alloy or a photoresist formed with a pattern for forming an opening for the wiring layer, an O ₂ plasma is used. Since the sulfur oxides contained in the photoresist photosensitive material cannot be removed only by ashing, in many cases, cleaning with acid or alkali is carried out. When an acid or alkali is used, it is impossible to instantly wash away the acid or alkali, so the aluminum alloy surface is exposed to a thin acid or alkali, and the aluminum alloy is easily corroded, resulting in poor yields. This leads to a decrease in reliability. In addition, due to manufacturing cost problems, it is difficult to keep expensive fuming nitric acid or organic solvent flowing.Since it is used while it is stored in the processing tank or circulated, chlorine residue used in etching aluminum alloy remains. The substance is likely to dissolve in the liquid and cause corrosion of the aluminum alloy. The above problems become more remarkable as the degree of integration increases and the pattern becomes finer. In particular, when the aluminum alloy contains copper or has a wiring structure in which different metals are stacked in multiple layers, corrosion of the aluminum alloy is likely to occur due to electrochemical reaction, which often causes a serious failure of the semiconductor device. .

Aluminum alloys are corroded by both acid and alkali, so it is necessary to clean them with a completely neutral liquid. Also,
Since CO ₂ in the air dissolves into acid in the state of being stored in the treatment tank, it is necessary to continue flowing the cleaning liquid or remove CO ₂ from the atmosphere around the treatment layer.

Means for Solving the Problems The present invention ashes a photoresist formed on a substrate by ashing with a plasma containing oxygen, or by heating the substrate to 150 ° C.-600 ° C. in an ozone atmosphere. After that, the substrate is washed with pure water having a water temperature of 0 ° C to 15 ° C or with pure water having a water temperature of 30 ° C to 100 ° C. In addition, the present invention, by ashing a photoresist formed on a substrate having an aluminum or aluminum alloy film with plasma containing oxygen, or by heating the substrate to 150 ℃ -600 ℃ in the atmosphere of ozone. After ashing,
In the resist removing method, the substrate is washed with pure water having a water temperature of 0 ° C to 15 ° C, and then washed with pure water having a water temperature of 30 ° C to 100 ° C.

Effect In the present invention, since the cleaning is performed with highly pure water, the property is neutral. In addition, washing with running water does not erode the aluminum alloy because it immediately discharges the acid generated by the dissolution of chlorine remaining in the aluminum alloy or the like. Further, by carrying out the cleaning in an atmosphere of N ₂ , O ₂ , He, Ar, isopropyl alcohol vapor or the like, the infiltration of CO ₂ can be completely prevented. Further, although sulfur oxides, which are the residue of O ₂ plasma ashing, often form sulfur salts, they are soluble in water and can be washed away by washing with water. If the water temperature is 15 ° C. or lower during cleaning, the reaction between the aluminum alloy and the acid slows down, so even if acidic impurities are mixed in the cleaning water, the corrosion of the aluminum alloy can be suppressed. Furthermore, when it is 30 or more, the surface of the aluminum alloy is oxidized and a passive state is formed, so that corrosion can be prevented. Even if ozone is introduced into the wash water, it has an oxidizing effect.

Embodiment One embodiment of the present invention will be described in detail with reference to FIG. FIGS. 1A to 1C are sectional views in order of steps in the embodiment of the present invention. In this embodiment, 1 is a silicon substrate, 2 is a SiO ₂ film, 3 is an aluminum alloy wiring layer, and 4 is a photoresist.

As the interlayer insulating film on the silicon substrate 1, for example, 1 μm
A SiO ₂ film 2 having a thickness of m is formed by CVD, a photoresist is spin-coated, and a resist pattern is formed by photolithography in a region other than the region to be the contact opening 5, and then a fluorine-based gas is used. The SiO ₂ film 2 is etched by reactive ion etching using the resist pattern as a mask to form the contact openings 5, and then the resist pattern is removed. Next, an aluminum alloy layer 3 containing a trace amount of copper and silicon, for example, 1 μm
Deposited using sputtering to a thickness of. At this time, the aluminum alloy layer 3 is in contact with the underlying silicon substrate 1 at the contact opening 5. Further, for example, a photoresist 4 having a thickness of 1 μm is spin-coated on the aluminum alloy layer 3 deposited on the entire surface, and then a pattern of the photoresist 4 is formed in a desired wiring region, and the pattern of the photoresist 4 is used as a mask. Then, the aluminum alloy wiring layer 3 is formed by plasma etching using a chlorine-based gas (FIG. 1A).

Next, the photoresist 4 is ashed by O ₂ plasma using a cylindrical plasma etching apparatus (FIG. 1b). At this time, it was confirmed by Auger electron spectroscopy that there was a residue of sulfur oxide 6 on the surface of the aluminum alloy layer 3. Further, it was confirmed by X-ray photoelectron spectroscopy that this sulfur remained as a hexavalent oxide. These sulfur oxides 6 have long and short ashing time by O ₂ plasma, gas pressure,
It was detected even when the applied power was changed. After that, the silicon substrate 1 with the sulfur oxides 6 remaining therein is washed with a pure water having a specific resistance of, for example, 16 MΩcm at a rate of, for example, 5 per minute in a cleaning tank having a volume of, for example, 30 minutes. I went. Then, it dehydrated using the centrifugal dehydrator (FIG. 1c). As a result, it was confirmed by Auger electron spectroscopy or X-ray photoelectron spectroscopy that the sulfur oxide 6 detected immediately after O ₂ plasma ashing as shown in FIG. 1 (b) did not remain on the aluminum alloy layer 3. confirmed. Further, the flow of pure water is continuously performed, but after the cleaning tank is filled with pure water, the silicon substrate 1 is immersed in the cleaning tank while flowing and is cleaned for a short time, for example, for 1 minute. It has also been confirmed that the above-mentioned sulfur oxide 6 can be removed in a short time by rapidly discharging the pure water in the cleaning tank, and then newly filling the cleaning tank with pure water and causing the cleaning tank to flow. .

Further, in this embodiment, the cleaning is performed by the flow of pure water, but it has been confirmed that the sulfur oxide 6 can be removed by storing pure water in the cleaning tank and immersing the silicon substrate 1. However, in this case, the cleaning time becomes long to remove the sulfur oxide 6.

FIG. 2 shows the defect occurrence rate of the semiconductor device when the conventional cleaning method and the cleaning method according to the present invention are used. The semiconductor device used here is a complementary MOS integrated circuit having a pattern rule of 1 μm formed on the silicon substrate 1 by the planar technique. Photoresist 4 on aluminum alloy layer 3 of semiconductor device
After incineration with O ₂ plasma, (1) wash with pooled water containing 100 ppm of nitrate ions for about 30 minutes (solid line 21 in Fig. 2),
(2) After leaving pure water in the air for 1 hour, use that water for about 30
Washing for minutes (broken line 22 in FIG. 2), (3) After leaving pure water for 1 hour in N ₂ atmosphere, washing with the water for about 30 minutes (dashed line 23 in FIG. 2), ( 4) Pure water is caused to flow at a rate of, for example, 5 minutes, and washing is performed for about 10 minutes therein. After that, in order to investigate the reliability of the semiconductor device, the reliability after 2000 hours of storage at a high temperature of about 150 ° C. was evaluated. As a result, when the water temperature is 30 ° C, the defect occurrence rate decreases in the order of conventional acid cleaning, water standing in air, water standing in N ₂ atmosphere, and pure water flowing. Therefore, no defects occurred in the cleaning with water left in the N ₂ atmosphere and the cleaning with flowing pure water. However, the temperature of the water does not change even when washed with acid or water left in the air.
No defects occurred at 15 ° C or lower. The reason why the occurrence of defects can be suppressed even by washing with water containing an acid by setting the water temperature to 15 ° C. or lower is that the corrosion of the aluminum alloy layer 3 due to the acid is suppressed when the water temperature is low. In the case of water left in the air, carbon dioxide gas (CO ₂ ) existing in the air dissolves in the water and becomes an acid. Therefore, if the water temperature is high, the same defects as those caused by washing with water containing acid may occur. There is. Further, in the cleaning, a sufficient effect can be obtained in the cleaning in which pure water is caused to flow rather than the stored water in the N ₂ atmosphere even in a short time. Although CO ₂ was carried out in an N ₂ atmosphere so as not to enter pure water, the same effect was obtained in an atmosphere of O ₂ , He, Ar, ozone, isopropyl alcohol vapor or the like.

In this embodiment, the ashing of the photoresist is performed by O ₂ plasma, but the silicon substrate 1 is heated to 150 ° C. by ozone.
It has been confirmed that sulfur oxides remain on the silicon substrate 1 when ashing is performed by heating to ˜600 ° C. or when ashing is performed by irradiating far ultraviolet light. However, ashing with ozone is not practical because the ashing rate is slow at heating below 150 ° C. Further, at 600 ° C. or higher, the oxidation of the silicon substrate proceeds, and the oxide film becomes thicker with the ashing time. Therefore, the resist cannot be selectively ashed, which is not practical. Also,
In the above examples, the cleaning after the removal of the photoresist on the aluminum alloy layer 6 is described so that the effect can be easily examined.
Any process can be used as long as it is ashed by using O ₂ plasma, ozone, or deep ultraviolet light. Also, regarding the water temperature, if it is 15 ° C or lower, the aluminum alloy layer 3
Corrosion can be stopped, but pure water freezes at 0 ° C or below, which is not practical. On the other hand, above 30 ° C, photoresist 4
In the case where the aluminum alloy layer 3 is immediately below the
The surface of the aluminum alloy layer 3 is oxidized, and this oxide film prevents the entry of substances that cause corrosion such as acid, so that corrosion is suppressed. Further, even when part or all of the silicon substrate is exposed, the surface of the silicon substrate can be extremely thinly oxidized, so that the surface becomes hydrophilic and the generation of spots can be suppressed. However, even in such a case, since water evaporates at 100 ° C. or higher, it is not practical to use a water temperature of 100 ° C. or higher.

In this example, the method of speeding up the cleaning was described. In the cleaning of the aluminum alloy layer 3, after cleaning at a water temperature of 15 ° C or lower, and then at a water temperature of 30 ° C or higher, corrosion is suppressed and the surface is further stabilized. Can be covered with a transparent oxide film.

FIG. 3 shows the structure of a cleaning tank for explaining another embodiment. 10 is a cleaning tank, 11 is an inlet for introducing pure water, 12 is an ozone generator, 13 is a pipe for guiding ozone to the cleaning tank, and 14 is a bubble of ozone in pure water. The cleaning tank 10 has a rectangular parallelepiped shape with a volume of 10, and pure water from the bottom surface of the cleaning tank 10 is, for example, 5 minutes per minute.
Is introduced and filled in the cleaning tank, and the introduced pure water overflows from the upper surface of the cleaning tank 10,
It is discharged to the outside of the cleaning tank 10. The ozone generated by the ozone generator 12 is transmitted through the pipe 13 from the bottom of the cleaning tank 10 to the cleaning tank.
The bubbles are introduced into the inside of the cleaning tank 10, propagated in pure water as the bubbles 14, and are discharged into the atmosphere from the upper surface of the cleaning tank 10.

By inserting and cleaning the silicon substrate 1 having the structure of the above-described embodiment in this, it is possible to oxidize and remove the high molecular substances such as the photoresist and the organic solvent remaining on the silicon substrate 1. Needless to say, the structure and material of the cleaning tank, the flow rate of the cleaning water, and the volume of the cleaning tank used in the other embodiments are not limited to this.

Further, here, the ashing and cleaning of the resist when the semiconductor device is manufactured using the silicon substrate is described, but the invention is not limited to the silicon substrate, and the ashing of the resist is performed after O ₂ plasma and ozone. If it is used for cleaning, it has nothing to do with the substrate. For example, it can also be used in the case of ashing and cleaning the resist after etching the chromium film on the glass substrate with the resist pattern in the production of a mask and reticle used in photolithography.

EFFECTS OF THE INVENTION In the semiconductor device to which the present invention is applied, defects due to corrosion of the aluminum alloy wiring tank are eliminated, and yield and reliability are significantly improved. Further, since it is not necessary to use expensive chemicals, it is possible to reduce the manufacturing cost.

[Brief description of drawings]

1 (a) to 1 (c) are cross-sectional views in order of the processes of an embodiment of a semiconductor device formed according to the present invention, and FIG. 2 is a washing water temperature and an aluminum alloy tank in washing after O ₂ plasma ashing. FIG. 3 is a characteristic diagram showing the relationship with the defect occurrence rate due to corrosion, and FIG. 3 is a structural diagram of a cleaning tank for explaining another embodiment of the present invention. 1 ... semiconductor substrate, 2 ... interlayer insulating film, 3 ... aluminum alloy wiring layer, 4 ... photoresist, 5 ... opening, 6 ...
…Sulfur oxides.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01L 21/3065 (56) References JP-A-58-220429 (JP, A) JP-A-63- 48825 (JP, A) JP 63-10529 (JP, A) JP 1-150328 (JP, A) JP 60-242624 (JP, A) JP 2-23610 (JP, A) ) JP-A-62-36826 (JP, A) Actually developed JP-A-62-92641 (JP, U)

Claims (4)

[Claims] 1. The photoresist is ashed by plasma containing oxygen, or the substrate is heated to 150 ° C.-6 in an atmosphere of ozone.
After ashing by heating to 00 ℃, water temperature of the substrate 0
A method for removing a resist, which comprises cleaning with pure water at -15 ° C. 2. A photoresist formed on a substrate is ashed by plasma containing oxygen, or the substrate is ashed by heating the substrate to 150 ° C.-600 ° C. in an atmosphere of ozone, and then the substrate is removed. A method of removing resist, which comprises cleaning with pure water having a water temperature of 30 ° C to 100 ° C. 3. A photoresist formed on a substrate having an aluminum or aluminum alloy film is ashed with a plasma containing oxygen, or the substrate is subjected to 15 in an ozone atmosphere.
After ashing by heating at 0 ° C to 600 ° C, the substrate is washed with pure water at a water temperature of 0 ° C to 15 ° C, and then continuously heated to a water temperature of 30 ° C
A method of removing a resist, which comprises cleaning with pure water at 100 ° C. 4. Cleaning with pure water is carried out in a cleaning tank installed in a gas atmosphere of one or a combination of O ₂ , N ₂ , ozone, He, Ar and isopropyl alcohol vapor. The resist removal method according to claim 1, wherein the resist removal method is according to claim 1.