JP3358808B2 - How to insulate organic substances from substrates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention FIELD OF THE INVENTION The present invention relates generally to the removal of organic materials present on various substrates, and more particularly, to the manufacture of various semiconductors, flat panel displays, read / write heads, and other related devices during manufacturing. The present invention relates to an organic film temporarily formed on a substrate layer and an ashing method for removing an organic substance.

2. Description of Related Art In a semiconductor device manufacturing process, removal of a photoresist film is an important operation. It has been known for some time to use an incineration method using a gas having a particularly high oxygen content to remove an organic film such as a resist or polyimide. Advances in plasma tools and related processing techniques over the past decade have led to a succession of new types of very large scale integrated circuits (VLSI) and very large scale integrated circuits (ULS).
I) It has responded without difficulty to the difficult situation where a device appears. However, as feature sizes continue to decrease and film thicknesses continue to decrease in these devices, each type of integrated circuit (I
Regarding C), there is a new manufacturing problem.

As the size of integrated circuits continues to shrink significantly, the incineration method always faces two problems: That is, a) The resist is removed at a higher speed without leaving any residue. And b) to reduce the degree of damage to the substrate layer under the resist film. These generally conflicting objectives have been met by altering either the physical conditions of the plasma medium or the chemical conditions of the ashing process. For example, higher processing rates can be achieved either by creating a high density plasma environment or by using or generating species in the plasma environment that react more efficiently with resist.

Substrate damage is likewise caused by both physical and chemical conditions of the plasma. For example, the effects of charging and ion bombardment are directly related to the physical properties of the plasma. High-energy ions generally contain small amounts of heavy metals (eg, iron, copper,
And alkali metal (eg, sodium and potassium) atoms can be transferred to the substrate layer beneath the resist. Heavy metal contamination, and especially the subsequent infiltration and migration of the heavy metal into other substrate layers (eg, silicon), can adversely affect minority carrier lifetime, thereby impairing device performance. The effect of such a bombardment process becomes smaller as the ashing process is completed, and becomes larger, especially as the thickness of the photosensitive substrate becomes smaller.

The plasma chemistry can also damage the substrate and cause etching or other detrimental effects to the underlying layers of the resist. For example, oxygen (O ₂ ) and tetrafluoromethane (CF ₄ ) to increase the rate of plasma ashing
When a halogenated gas mixture such as is used, etching of silicon oxide (SiO ₂ ) occurs due to fluorine (F). Similarly, high energy oxygen ions cause moisture to form in the surface of the spin-on-glass (SOG) film, resulting in an increase in the dielectric constant or a related indirect poisoning phenomenon.

While downstream ashing is the most widely used treatment method, the above considerations suggest that, to varying degrees depending on the application, for example, barrel-type, downstream-type, or parallel electrode-type structures Of the conventional dry etching plasma apparatus. In order to increase the processing speed and minimize the problem of ion damage, it is conceivable to employ a technique for increasing the plasma density and lowering the ion energy. A new type of advanced plasma source separates the control of plasma density from the control of ion energy in the plasma by techniques such as electron cyclotron resonance (ECR) or inductively coupled plasma (ICP) with microwave or radio frequency power. To achieve the stated objectives. Such and other types of plasma technology and tools are known and many are the subject of U.S. patents.

Regardless of the nature and mode of the plasma employed, the rate and perfection of the ashing in conventional ashing tools is created in the plasma with the resist and substrate layer, as well as unwanted etching or damage to the substrate layer. It is greatly affected by chemical reactions with ionic neutral and radical species. In a typical downstream or other conventional incinerator, the nature of the plasma gas mixture is a major determinant of the incineration rate, and the incineration rate is also sensitive to "ashing temperature". The nature of the plasma gas mixture also affects the ash activation energy, which is a measure of how the ash rate is affected by the ash temperature.

Activation energy is obtained from the slope of the Arrhenius plot, which is a linear representation of the ash rate as a function of the reverse ash temperature. Therefore, when the activation energy is small (the slope of the Arrhenius plot is small), the ashing rate is not so much affected by the ashing temperature, which means that the ashing process is more stable and uniform. Also, the lower the activation energy,
It also means that the ash temperature can be lower without significantly compromising the ash rate. This is particularly true for the fabrication of very large scale integrated circuit (VLSI) and very large scale integrated circuit (ULSI) devices where low processing temperatures are required, but at acceptable realistic levels of ashing rate (ie,
(Levels greater than 0.5 μm / min).

For ashing rates and activation energies for a series of gas mixtures consisting of one or more of oxygen, hydrogen, nitrogen, water vapor and halide gases, see US Pat.
This is thoroughly discussed in 61,820. In this patent, addition of nitrogen to the oxygen plasma does not change the activation energy (0.52 eV relative to oxygen) and only slightly improves the ashing rate (0.1-0.2 μm at 160 ° C.)
m / min). However, 5 to oxygen
The addition of 〜１０10 percent hydrogen or steam reduced the activation energy to about 0.4 eV, but only improved the ash rate as did the addition of nitrogen. When both nitrogen and 5-10 percent hydrogen or steam were added, the incineration rate was (16
At 0 ° C.) there was a synergistic effect of increasing to a more realistic level of 0.5 μm / min.

When a halide (eg, tetrafluoromethane) is added to the oxygen plasma, the activation energy (0.1 e)
V) and the rate of incineration (at levels greater than 1.5 μm / min) was greatest. However, in this case, tetrafluoromethane also results in etching a substrate layer such as silicon oxide, polysilicon and aluminum by a fluorine reaction. Inclusion of water vapor in the reaction gas mixture can reduce the damage caused by tetrafluoromethane, but it has been reported that this may be due to the suppression of halogen activity as a result of the reaction of water and tetrafluoromethane. .

As noted above, research is continuing on satisfactory reactive gases that provide adequately fast ashing rates without detrimentally affecting the substrate layer underlying the resist film.
In addition, the manufacturing constraints of very large scale integrated circuit (VLSI) and very large scale integrated circuit (ULSI) devices are becoming more stringent, resulting in lower ashing temperatures and stability of the ashing process (lower activation energies). Is becoming a key requirement for obtaining a satisfactory reaction gas mixture.

The present inventor has reported that under substantially below 200 ° C., anhydrous sulfur trioxide (S
O ₃ ) was used successfully. Experiments have shown that exposing the resist-coated substrate surface to sulfur trioxide can keep the polysilicon and metal substrate surfaces intact without harmful effects. Silicon and metal surfaces exposed to sulfur trioxide are also protected by the inactivating effect of sulfur trioxide. Therefore, sulfur trioxide, alone or in a reaction gas mixture, appears to be a suitable material candidate for plasma ashing applications. In particular, sulfur trioxide promotes the formation of oxygen radicals in the presence of oxygen plasma, so that a remarkable improvement in the ashing reaction rate can be expected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved process for ashing organic materials, including photoresist residues, from a substrate by including sulfur trioxide gas as part of the reaction gas mixture. It is to be. This object is achieved by employing one of the three groups of gas mixtures in the ashing process. The three types of mixtures are as follows: (1) Group 1 gas consists solely of sulfur trioxide gas, and (2) Group 2 gas consists of sulfur trioxide and water vapor, ozone, hydrogen, nitrogen, nitrogen oxides. Substance, tetrafluoromethane (CF ₄ ), chlorine (Cl ₂ ), nitrogen trifluoride (NF ₃ ), hexafluoroethane (C ₂ F
₆ ) or a mixture with one kind of auxiliary gas such as a halide such as methyltrifluoride (CHF ₃ ), and (3) Group 3 gas includes sulfur trioxide and at least one of the above-mentioned auxiliary gases. It consists of a mixture of two types.

As is known in the art, if some of these auxiliary gases are added to the main reactive ashing gas in the appropriate amount and at the appropriate time of processing, these auxiliary gases will have favorable ashing process characteristics and organic membranes. Promotes removal action. Such favorable properties and effects are: a) faster ashing rate, b) lower activation energy, and c) no substrate etching during the organic removal process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Stripping and plasma ashing of organic photoresist using one of the three groups of gases described above can be performed using conventional downflow, barrel, downstream,
This can be done using a direct or other type of plasma ashing tool known in the art. The present invention relates to the nature of the gas used in the incineration process and can be applied to any conventional incineration tool. Downflow, barrel, direct, downstream or other types of plasma ashing tools are known in the art and do not constitute the present invention.

The basic concept of the present invention is to reduce the activation energy, increase the incineration rate, or perform the incineration operation, if appropriate, under the appropriate amount and treatment conditions of sulfur trioxide gas. By lowering the temperature or using it in gaseous form as a reaction gas mixture with some kind of auxiliary gas needed to improve the effectiveness or efficiency of the ashing process
Ashing or reacting with any kind of organic coatings, films, layers and residues, including process-hardened photoresist, to substantially remove from the substrate surface, clean;
Or peel off. In all embodiments of the present invention, sulfur trioxide is supplied to a source container, from which sulfur trioxide gas is supplied in large quantities to the processing chamber at the appropriate time during the ashing process. In the source container, sulfur trioxide can be solid, liquid or gaseous, alpha, beta,
It may be a mixture with a solid material in the form of gamma or mixtures thereof.

Specifically, the following coating, film, layer, and residue organic substances can be removed by the treatment of the present invention. That is, polymerized or non-polymerized photoresist, photoresist residue, photosensitive and non-photosensitive organic compounds, paints, resins, multilayer organic polymers,
Organometallic composite, sidewall polymer (sidewall pol
ymer), and organic spin-on-glass. Examples of the photoresist include a positive optical photoresist, a negative optical photoresist, an electron beam photoresist, an X-ray photoresist, and an ion beam photoresist.

Such coatings, films, layers and residues have been formed on various substrates. Examples of substrates include, but are not limited to, the following: a) semiconductor wafers and devices composed of silicon, polysilicon, germanium, Group 3-5 materials, and Group 2-4 materials, b) oxides, c) nitrides,
d) oxynitrides, e) inorganic derivatives, f) metals and alloys,
g) ceramic devices, h) photomasks, i) liquid crystal and flat panel displays, j) printed circuit boards, k) magnetic write / read heads, and l) thin film heads.

The ashing process of the present invention can be performed in a temperature range from room temperature (about 20 ° C) to 350 ° C. However, the ashing process of the present invention is preferably performed at a temperature as low as possible while maintaining an etching rate as high as possible. Therefore, more preferably, the incineration treatment of the present invention comprises about 20
Perform at temperatures below 0 ° C.

1. First Embodiment One embodiment provides a plasma ashing process using any of the conventional downflow, barrel, direct, downstream and other ashing tools known in the art. Is what you do. In the first embodiment, the plasma is generated using the group 1 gas. In particular, the reaction gas consists only of sulfur trioxide. Sulfur trioxide is supplied to the plasma generation chamber and first evacuated and evacuated to a suitable vacuum. The flow rate of the sulfur trioxide gas during the process is controlled by the control device. Plasma is generated by the reaction gas by supplying microwave power to the plasma generation chamber. Activated species generated as plasma flow into the processing chamber,
Contacting the organic film on the substrate surface by any one of the methods disclosed in the prior art. The reaction between the organic film and the plasma results in the organic film being removed or chemically altered so that it can be removed in a subsequent cleaning or cleaning step during processing. Processing constraints such as flow rate, microwave power, etc. are described in US Pat.
No. 689 and 4,961, 820, which are the same as those conventionally employed in this field.

2. Second Embodiment Another embodiment of the present invention provides a plasma ashing process using any of the conventional downflow, barrel, direct, downstream or other types of ashing tools. Is what you do. In this second embodiment,
A plasma is generated using the gas of group 2. In particular, the reaction gas consists of sulfur trioxide and one type of auxiliary gas. Sulfur trioxide and an auxiliary gas are supplied to the plasma generation chamber and first evacuated and evacuated to a suitable vacuum. The concentration of sulfur trioxide in the Group 2 reaction gas is about 1-95 volume percent. The remainder consists of the auxiliary gas (99-5 volume percent).

During processing, the flow rate of each gas is controlled by the control device. By supplying microwave power to the plasma generation chamber, plasma is generated by the reaction gas. The activated species generated as a plasma are exhausted into the processing chamber and contact the organic film on the substrate surface by any one of the methods disclosed in the prior art. The reaction between the organic film and the plasma results in the organic film being removed or chemically altered so that it can be removed in a subsequent cleaning or cleaning step during processing. As described above, the processing restrictions such as the flow rate and the microwave power are the same as those conventionally adopted in this field.

The auxiliary gas is water vapor, ozone, hydrogen, nitrogen, nitrogen oxide, tetrafluoromethane (CF ₄ ), chlorine (C
l ₂ ), nitrogen trifluoride (NF ₃ ), hexafluoroethane (C ₂ F ₆ ), methyltrifluoride (CHF ₃ )
And any other gas selected from the group consisting of halides. Examples of nitrogen oxides include nitrous oxide (N ₂ O), nitric oxide (NO), and nitric oxide (N
O ₃ ), and nitrogen dioxide (NO ₂ ).

3. Third Embodiment Still another embodiment of the present invention provides a plasma ashing process using any of the conventional downflow, barrel, direct, downstream and other types of ashing tools. Is what you do. In this third embodiment, a plasma is generated using Group 3 gases.
In particular, the reaction gas consists of sulfur trioxide and at least two auxiliary gases. Sulfur trioxide and auxiliary gas are supplied to the plasma generation chamber, and are first evacuated and evacuated to a suitable vacuum. The concentration of sulfur trioxide in the Group 3 reaction gas is about 1 to 95 volume percent.
The remainder consists of the auxiliary gas (99-5 volume percent).

The flow rate of the processing gas is controlled by the control device. When microwave power is supplied to the plasma generation chamber, plasma is generated by the reaction gas.
The activated species generated as a plasma are exhausted into the processing chamber and contact the organic film on the substrate surface by one of the methods disclosed in the prior art. The organic film reacts with the plasma, and as a result, the organic film is removed,
Or, it may be chemically altered so that it can be removed in a subsequent washing or cleaning step during processing. As described above, processing restrictions such as flow rate and microwave power are the same as those conventionally employed in this field.

The auxiliary gas includes at least two of the auxiliary gases described above.

In each of the above embodiments, the organic film including the resist layer was substantially completely removed, with little or no damage to the underlayer.

The processing for removing organic substances from the substrate surface by using the plasma ashing processing using a reaction gas containing sulfur trioxide has been described above. It will be apparent to those skilled in the art that various changes and modifications can be made to the obvious properties, and such changes and modifications are considered to be within the scope of the following claims.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-304126 (JP, A) JP-A-59-163826 (JP, A) JP-A-3-60031 (JP, A) JP-A-5-163126 291214 (JP, A) JP-A-5-304089 (JP, A) JP-A-7-169747 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065 G03B 7 / 42

Claims (12)

(57) [Claims] 1. A method for removing an organic substance from a substrate surface, comprising the steps of: a) using a reaction gas containing sulfur trioxide and a halide as an auxiliary gas, wherein the concentration of sulfur trioxide is 1 to 95% by volume; And b) applying the plasma to the substrate surface containing the organic material.
Impacting for a time sufficient to incinerate the organic material but not to damage the substrate surface. 2. The method according to claim 1, wherein the halide is tetrafluoromethane (CF ₄ ), chlorine (Cl ₂ ), nitrogen trifluoride (NF).
_3), hexafluoroethane _{(C 2 F} 6), and a method according to claim 1, characterized in that it is selected from the group consisting of methyl trifluoride (CHF _3). 3. The method according to claim 1, wherein the reaction gas consists essentially of sulfur trioxide and one halide. 4. The method according to claim 1, wherein the reaction gas further comprises at least one auxiliary gas selected from the group consisting of water vapor, ozone, hydrogen, nitrogen, and nitrogen oxide. . 5. The method according to claim 1, wherein the nitrogen oxide is nitrous oxide (N ₂
O), nitrogen monoxide (NO), nitrogen trioxide _(NO 3), and a method according to claim 4, characterized in that it is selected from the group consisting of nitrogen dioxide (NO _2). 6. The method according to claim 1, wherein the organic substance is a polymerized or non-polymerized photoresist, a photoresist residue, a photosensitive or non-photosensitive organic compound, a paint, a resin, a multilayer organic polymer, an organometallic compound, or a sidewall layer. Coalescence (sidewall polym
er), and a material selected from the group consisting of organic spin-on-glass. 7. The method of claim 1, wherein the photoresist is selected from the group consisting of a positive optical photoresist, a negative optical photoresist, an electron beam photoresist, an X-ray photoresist, and an ion beam photoresist. Item 7. The method according to Item 6. 8. The semiconductor wafer and device wherein the substrate comprises: a) silicon, polysilicon, germanium, a group 3-5 material, and a group 2-4 material; b) an oxide;
c) nitrides, d) oxynitrides, e) inorganic dielectrics, f) metals and alloys, g) ceramic devices, h) photomasks,
The method of claim 1 wherein the method is selected from the group consisting of: i) liquid crystal and flat panel displays, j) printed circuit boards, k) magnetic write / read heads, and l) thin film heads. 9. The method according to claim 8, wherein said metal and alloy are selected from the group consisting of aluminum and aluminum-silicon-copper alloy. 10. The plasma ashing step is performed at a temperature between room temperature and 350 ° C.
The method of claim 1, wherein the method is performed at a temperature in the range of ° C. 11. The method of claim 10, wherein said temperature is less than 200 ° C. 12. The method of claim 1, wherein said step is performed in a downflow, barrel, downstream, or direct type incinerator.