JP3034259B2 - Organic compound film removal method - Google Patents

Description

The present invention relates to a method for removing an organic compound film such as a photoresist used in a semiconductor device manufacturing process or a surface treatment in other fields.

(Prior art) Fine processing technology in the manufacturing process of semiconductor devices,
Or, in a processing technique in another field (for example, processing of a printed circuit board, processing of a compact disk or a laser disk) or the like, a photo etching process (Photo Etching Process) using an organic resist of an organic compound film such as a photosensitive photoresist. ; PEP) is an important and essential process. It is necessary to remove the organic resist at the stage where the processing of the base (etching, ion implantation, etc.) is completed using this as a mask. As a method for removing the organic resist, a method of removing in a solution represented by a mixed solution of H ₂ SO ₄ and H ₂ O ₂ or a solution obtained by adding H ₂ O thereto, or without using these solutions The method of dry ashing in the discharge of oxygen (O ₂ ) gas is mainly used at present.

By the way, in the former process using a solution, there are problems in solution management, work safety and the like. In particular, it is not suitable for a semiconductor device manufacturing process or the like that rejects a process using a liquid. When a photoresist of an organic compound film is used for patterning an aluminum (Al) metal as an electrode material used in a semiconductor device manufacturing process or the like, H ₂
In a mixed solution of SO ₄ and H ₂ O ₂ , the metal is corroded,
There is a problem that applications are limited.

On the other hand, in the latter process using O ₂ plasma, a substrate to be processed on which an organic resist is formed is placed in a reaction vessel that generates a discharge of a barrel type or a parallel plate type or the like, and the O ₂ gas is discharged to dry the substrate. The resist is removed by ashing (ashing). According to this method, compared to the above-described method using a solution, the base material may be metal or the like, and there is no need to limit the material of the base. However, in this dry ashing method, there is a problem that a residue is generated after removing the organic resist.

A specific example of a photoetching process using O ₂ plasma will be briefly described with reference to FIG. This figure is
FIG. 3 is a perspective view showing a step of forming a wiring electrode of a MOS device on a substrate such as silicon. First, as shown in FIG. 4A, an Al film 42 serving as a wiring electrode is formed on a semiconductor substrate 40 having a gate oxide film 41 formed on a surface thereof, and then a resist film 43 serving as an organic compound film is formed. Is applied over the entire surface. Thereafter, as shown in FIG. 4B, pattern exposure is performed so that the resist layer 43a remains on a desired portion of the Al film 42, and development is performed. Next, as shown in FIG. 4C, reactive ion etching (R) is performed using the resist layer 43a as a mask.
IE) method, leaving the wiring electrode 42a and the other Al film 42
Is removed. Thereafter, the resist layer 43a is removed by using the above-described O ₂ plasma. At this time, as shown in FIG. 4D, a residue 44 is formed on the surface of the wiring electrode 42a or on the oxide film 41.
Remains.

Even if a MOS device is formed through such a process,
There is a problem in that the residue has a bad influence on the subsequent process or a bad influence on the characteristics of the semiconductor element. The problem of residue on the sample surface occurs when using either a barrel type or a parallel plate type ashing device. In addition, in the photo etching process by O ₂ plasma dry ashing, as described in the description of FIG. 4, an organic resist exposed to discharge as in the case of etching a sample by a reactive ion etching (RIE) method, When removing the organic resist exposed to ion bombardment by using it as a mask for ion implantation, there is a problem that it is difficult to remove and a residue tends to remain as compared with a case where these process steps are not performed.

In microfabrication using reactive ion etching, an etching product or the like sputtered from the substrate surface adheres to a pattern or a side wall of a resist serving as an etching mask to form a thin film. FIG. 5 is a diagram schematically showing this state. In FIG. 5 (a), a silicon oxide film 51 is formed on a silicon substrate 50 by thermal oxidation, and an aluminum film 52 is deposited thereon by a sputtering method, and etching is performed using a resist 53 as a mask. Is shown in The ions 54 are perpendicularly incident on the substrate 50 and impact the surface to be etched. At this time, the etching product 55 having a low vapor pressure is sputtered by the ions and flies, and a part thereof is reattached to the side wall to form the side wall protective film 56. Further, the etching product adheres not only to the side walls but also to the upper surface of the resist to form the deposit 57. The sidewall protective film 56 is important for preventing radicals from attacking the thin film to be etched and for forming a vertical pattern. However, the etching is over,
The resist is not easily removed even after the incineration of the resist, and remains on both sides of the pattern like ears as shown in FIG. There is a problem that it remains on the pattern even after the chemical conversion and causes garbage.

In this way, using the organic resist as a mask,
In the case of etching with E, the above-mentioned deposits (sputters, etching products, etc.) of the inorganic substance are formed on the resist surface layer, and the inorganic substance generally has low reactivity with O ^* (radical) and the like. Easily remains as a residue after incineration.
In particular, when a metal such as Ti is on the surface and Ti adheres to the resist surface during RIE, the oxide of Ti is extremely strong and O
In some cases, it cannot be removed even by using an incineration method using radicals and F radicals. In practice, Ti is sometimes used as a barrier metal under Al wiring, and Al or Al-Si-
It is known that more residue is generated when there is Ti as a base than when a single layer of Cu is used.

(Problems to be Solved by the Invention) As described above, in the conventional method using a solution for removing the organic compound film, it is difficult to manage the solution, it is difficult to ensure the safety, and there is a disadvantage that the material of the base is limited. is there. Further, in the method of removing the organic compound film using O ₂ plasma or the like, there is a problem that the deposits attached to the surface layer of the organic compound film or the like are not removed and a residue remains after the treatment process.

The present invention has been made in view of the above circumstances, and an object thereof is to remove an organic compound film by a dry treatment without using a solution and to form an organic compound film without generating a residue. An object of the present invention is to provide a method for removing an organic compound film that can be removed.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to remove a semiconductor or a metal, an oxide, a nitride thereof, and the like attached to an organic compound film in a step such as RIE by a pretreatment, Then, the organic compound film is removed by a usual dry removal method.

That is, the present invention provides a method for removing an organic compound film, which comprises holding a substrate to be treated having an organic compound film formed on a surface thereof in a reaction vessel, and using a gas containing at least oxygen element to remove the organic compound film. the deposits adhered to the surface or surface layer of the organic compound film, before the step of removing the organic compound film, sputtering, using a radical or a solution or the like containing H e was previously removed, then the F and H ₂ O This is a method in which an organic compound film is removed by a dry ashing method using plasma or the like using a reaction.

(Effect) As a method (pretreatment) of removing deposits such as metal from the organic compound film, a method using a reaction in plasma, a method by sputtering, and a reaction in a solution such as an acid or an alkali are used. There are methods. For example, considering the case where metal adheres to the surface, by irradiating an inert ion beam such as Ar ⁺ or exposing the substrate to be treated in an inert gas plasma, the metal adhered to the surface is removed together with the surface organic matter. It is removed by sputtering. Further, by using a reactive gas instead of the inert gas, the metal can be removed by a chemical reaction in accordance with the sputtering.
For example, when a reactive species such as halogen is used, a metal halide is formed and removed.

However, in some cases, metal fluorides and chlorides cannot be removed because of their low vapor pressure. Further, in this method, the surface of the organic compound is halogenated such as F or Cl. When the surface of the organic compound is replaced with a halogen such as F, the reaction between O ^* and the organic substance may be hindered when the organic substance is removed by O ^* in the next treatment, and the organic compound may not be removed.

In this case, as a reactive gas, instead of halogen,
It is more effective to use H or CO. When H or CO is used, it combines with a metal to form and remove a metal hydride or carbonyl compound. Even if H or CO reacts with an organic compound, it does not form a substance that hinders the removal of organic substances in a later dry etching. Therefore, it is extremely effective as preprocessing. In addition to the above dry treatment, the metal on the surface can be removed by exposing the object to be treated in a solution such as an acid or an alkali.

As described above, according to the present invention, after removing adhering substances (generally, inorganic substances) such as metals, semiconductors, and insulators on the surface of the organic compound film, the organic compound film is formed using a reactive species such as O ^* or O ^* + F ^*. By removing the compound film, the organic compound can be removed without a residue.

(Examples) Hereinafter, details of the present invention will be described with reference to the illustrated examples.

First Embodiment FIG. 1 is a schematic configuration diagram showing a parallel plate type dry etching apparatus used in the method of the first embodiment of the present invention. The reaction vessel 10 in which the pair of parallel plate electrodes 11, 12 is arranged,
A predetermined gas (Ar, H ₂ ) is introduced from the gas inlet 10a, and the gas in the container 10 is exhausted from the gas outlet 10b. The upper electrode 11 is grounded, and a high-frequency power source 14 applies a high-frequency voltage to the lower electrode 12 on which the substrate 13 is placed.

FIG. 2 is a process sectional view showing a resist removing method using the above apparatus. As shown in FIG. 2 (a), a substrate to be processed is composed of Ti—N / Ti layers 21 and 23 and an Al—Si—Cu layer 23 on a Si substrate 20.
Is formed thereon, a pattern of a photoresist 24 is formed thereon, and the underlying Al-Si is formed by RIE using the resist 24 as a mask.
-Cu, Ti-N / Ti processed directionally. On the resist surface of the substrate to be processed, sputtered products and etching products obtained by etching Al-Si-Cu, Ti-N, Ti, and the like adhere.

For the above-mentioned substrate to be treated, a usual dry incineration technique (O ₂
Ashing, etc.) to remove the resist 24,
Residues remain on the surface of the Al-Si-Cu layer 23. Therefore, before performing dry ashing, the substrate to be processed is exposed to Ar plasma using a parallel plate type dry etching apparatus as shown in FIG. In this case, the substrate to be processed is placed on the cathode side (lower electrode 12), a 13.56 MHz high frequency power (500 W) is applied between the electrodes 11 and 12, and the discharge is performed at an Ar pressure of 0.05 Torr. The processing time is preferably 1 minute or more. After performing such processing, O
By performing a down-flow type dry incineration containing ^* + F ^* , the photoresist 24 can be removed without residues as shown in FIG. 2 (b).

Thus, according to the method of the present embodiment, as a pretreatment of the dry ashing step for removing the resist 24, the substrate to be processed is exposed to plasma of Ar gas, whereby each of the resist 24 and the underlayer is exposed.
The deposits attached to 21, 22, and 23 can be easily removed, and the resist 24 can be removed without any residue by the subsequent processing. At this time, if the resist 24 is completely removed by only the plasma of the Ar gas, the damage is a problem, but the damage is hardly a problem if the time is as short as the removal of the attached matter.

In the above method, the deposits are removed by using Ar gas plasma. However, the deposits can be removed by Ar gas sputtering without generating plasma in the container 10. Further, as a method of removing deposits of photoresist surface, instead of using the Ar plasma may be used H ₂ gas plasma. Also in this case, if the entire resist is removed only by the H ₂ gas plasma, the problem of damage will be a problem. However, the problem of damage does not occur if the time is short enough to remove the deposit.

Second Embodiment FIG. 3 is a schematic diagram showing a downflow type dry etching apparatus used in the method of the second embodiment of the present invention. A sample stage 31 is arranged in the reaction vessel 30, and this sample stage is
The substrate 33 to be processed is placed on the substrate 31. A discharge tube 35 is connected to the reaction vessel 30, and a high-frequency voltage is applied to the discharge tube 35 from a high-frequency power supply 34 via an applicator 36. The gas introduced into the discharge tube 35 from the gas introduction tube 37 is excited in the discharge tube 35, and the excited gas is introduced into the container 30. In the figure, 30a
Denotes a gas inlet of the container 30, and 30b denotes a gas gas outlet.

In the method of the present embodiment, the above apparatus is used to excite H ₂ gas in a region different from the place where the substrate 33 is placed, and to supply H ^* generated there to the substrate 33. To perform pre-processing. In this case, due to the reaction between H ^* and the metal, deposits such as metal are removed from the surface. At this time, the resist can be ashed by switching to a mixed gas of oxygen and CF ₄ or the like. Treatment with the hydrogen radicals, compared to the method of performing processing in in H ₂ discharge, there is a merit in terms of damage or the like. That is, if the energy of H ⁺ ions or the like is large in the treatment during the discharge, the surface of a substance other than the resist may be deteriorated, but as in the present embodiment, a different region from the substrate to be treated is used. If H ₂ gas is excited by
Such a problem can be prevented beforehand.

Here, a method of simultaneously removing the deposits together with the resist by plasma of a gas obtained by mixing O ₂ gas and H ₂ gas without performing the above pretreatment may be considered.
H ^* decreases due to the reaction between ^* and O ^*, and the effect of removing adhering substances decreases, and the resist removal rate also decreases. In the present embodiment, H ^* acts as a pretreatment for resist removal to reliably remove attached matter.
Since O ^* acts to remove the resist, the residue can be reliably removed, and the resist removal rate can be increased.

The gas to be excited in a different region from the reaction vessel during the pre-treatment is not limited to H ₂ gas, NH _3, CH ₃ OH,
C ₂ H ₅ OH, H ₂ O, alcohol or a mixture thereof may be used. Furthermore, it is also possible to use a mixed gas of these and a rare gas such as Ar and He.

Third Embodiment In the present embodiment, as a pretreatment step for removing the deposits on the photoresist surface, the substrate to be processed is immersed in an etching solution. In the above-mentioned substrate to be processed, the metal adhering to the surface is Al or Ti.
By immersing in a solution of F: CH ₃ COOH: H ₂ O = 1: 50: 50 for 5 to 30 seconds, the adhered metal on the surface can be removed. In this case, the underlying Al
-Si-Cu and Ti-N / Ti are also etched at the same time, so a short processing time must be performed.

Note that the present invention is not limited to the above-described embodiments. For example, the metal of the base is not limited to a compound containing Ti, but Al, W, Mo, Cu, Ti and a compound thereof,
Further, it may be a mixture of this and another substance. Further, the organic compound film is not limited to a photoresist, but may be a deep ultraviolet resist, an X-ray resist, or an electron beam resist. Further, in the step of removing the organic compound film, a process in O ₂ plasma or a plasma using a gas containing at least O or a down-flow type process,
Any of a treatment in plasma using a reaction of F with H ₂ O, H _2, or alcohol, a downflow treatment, or a treatment using ozone may be used. In addition, various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, a semiconductor or a metal, an oxide, a nitride thereof, and the like attached to an organic compound film in a step such as RIE are removed by a pretreatment, and thereafter, a normal process is performed. Since the organic compound film is removed by the dry removal method, the organic compound film can be removed by dry treatment without using a solution, and the organic compound film can be quickly removed without generating a residue. Become.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a parallel plate type dry etching apparatus used in the method of the first embodiment of the present invention, FIG. 2 is a sectional view showing a resist removing step according to the method of the embodiment, and FIG. FIG. 4 is a schematic configuration diagram showing a downflow type dry etching apparatus used in the method of the second embodiment of the present invention, FIGS. 4 and 5 are each for explaining a conventional problem, and FIG. FIG. 5 is a sectional view. 10,20 ... reaction vessel, 11,12 ... parallel plate electrode, 13,33 ... substrate to be treated, 14,34 ... high frequency power supply, 31 ... sample stand, 35 ... discharge tube, 36 ... application 37, gas introduction pipe.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-4930 (JP, A) JP-A-64-48418 (JP, A) JP-A-57-210632 (JP, A) JP-A-2- 237118 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065 H01L 21/304

Claims (3)

(57) [Claims] 1. A method for removing an organic compound film, comprising: placing a substrate to be treated having an organic compound film formed on a surface thereof in a reaction vessel, and removing the organic compound film using a gas containing at least oxygen element. After removing the surface layer of the organic compound film or the deposits attached to the surface layer by sputtering in advance, the organic compound film is referred to as F
A method for removing an organic compound film, wherein the removal is performed by a treatment in a plasma using a reaction with H ₂ O or an alcohol or a down-flow treatment. 2. A method for removing an organic compound film, wherein the substrate to be treated having an organic compound film formed on its surface is accommodated in a reaction vessel and the organic compound film is removed using a gas containing at least an oxygen element. After removal by immersing in advance a surface layer of the organic compound film or a substance attached to the surface layer in a solution for etching,
A method for removing an organic compound film, wherein the organic compound film is removed by a treatment in a plasma using a reaction of F with H ₂ O or an alcohol or a down-flow treatment. 3. A method for removing an organic compound film in which a substrate to be treated having an organic compound film formed on its surface is accommodated in a reaction vessel and the organic compound film is removed using a gas containing at least an oxygen element. A gas containing at least H is excited by discharge, a charged particle beam, light or heat in a region different from the reaction vessel;
Supplying a reducing radical generated in the region to the reaction vessel, and performing a pre-process of removing a surface layer of the organic compound film or deposits attached to the surface layer by exposing to the reducing radical in advance. Of removing organic compound film.