JPH1174250A - Substrate-treating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a stripping, a passivation and a control in a short time by exposing a substrate to plasma formed by a process gas equipped with steam, oxygen, an nitrogen and then to a specified alkylamine. SOLUTION: An etched substrate is carried into a vacuum chamber, which is kept at suitable temperature and pressure and is exposed in a vacuum to plasma formed by a process gas equipped with steam, oxygen and nitrogen. Next, the substrate is exposed to alkylamine designated by an equation. In the equation, R1 designates an alkyl groups, R2 , R3 each designates a hydrogen atom or an alkyl group, and R2 , R3 may be identical or different from each other. Here, preferably, a part of amine exists in a gaseous state for producing the vapor of amine in the vacuum chamber and is absorbed by the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to stripping, passivation and corrosion control of semiconductor substrates.

[0002]

BACKGROUND OF THE INVENTION In the manufacture of integrated circuits, depositing a layer comprising a metal on a substrate, forming a polymer or oxide resist on this layer, and etching the exposed portions of the layer. As a result, a conductive feature is formed. In particular, halogen-containing etchants (eg, Cl ₂ , BCl ₃ , CCl ₄ , SiCl ₄ , CF
₄ , NF ₃ , SF ₆ and mixtures thereof, such as S
ilicon Processing for the VLSI Era, Vol.1, Chapter
16, by Wolf and Tauber, Lattice Press, 1986, the disclosure of which is incorporated herein by reference.)
Is used to etch the substrate, for example, in reactive ion etching, the etched substrate is contaminated by etchant residues and by-products. These contaminants, especially when the features are made of alloys that can be cell-to-material, such as Al-Cu and Ti-W, can become conductive, especially in conjunction with atmospheric moisture. May corrode features. Contaminant by-products are produced, for example, by reactions between residual halogen from the etchant, metals from conductive features, and / or polymeric resist materials. These can be in the form of sidewall deposits due to condensation of reaction by-products on the sides of the conductive features. After the etching, a residual resist that has not been etched by the etchant gas may remain on the substrate.

[0003]

In order to reduce the adverse effects of such contaminants, the etched substrate is processed,
It is known to remove residual resist on a substrate.
The processing of the substrate includes (i) removing residual resist (commonly referred to as stripping), and (ii) removing or converting contaminants (commonly referred to as passivation, eg, exposure to CF ₄ plasma). Through (ii), (ii)
i) Form a protective layer over all parts of the conductive features (commonly referred to as suppression, for example, through exposure to CHF3 plasma). However, known stripping, passivation and suppression processes require very long processing times and / or require the use of expensive, difficult to use or dangerous materials.

[0004] Also, known passivation and stripping methods are very fast, for example within one to five hours and may fail and allow corrosion of the substrate. It is common to prevent corrosion of etched features on a substrate at least until the next step in the processing of the substrate, typically a stripping process that removes at least a portion of the resist and / or contaminants. Is important. If the process to prevent corrosion is only effective for a short period of time, this can be a serious limitation on the timing of the manufacturing process, e.g. if an equipment failure causes an unexpected delay in manufacturing, the whole batch wafer Can be lost.

[0005]

SUMMARY OF THE INVENTION In accordance with a first aspect of the present invention, we have found an improved process for treating an etched substrate to reduce the adverse effects of etchant residues and by-products. In this process, a substrate is exposed to a plasma formed from a process gas comprising water vapor, oxygen and nitrogen under vacuum. The volume ratio of (i) water vapor to (ii) the sum of oxygen and nitrogen is:
(1) from about 1: 2 to about 2: 1, preferably 0.8: 1 to 1: 0.8, and especially about 1: 1, or (2) about 1: 4 to about 1:40, preferably Is 1: 6 to 1: 2
0, and especially about 1:10. Preferably, the process is performed in a vacuum chamber at a pressure of about 1 to about 10 Torr and a temperature of about 150 ° to about 400 ° C.
The time that the substrate is exposed to the plasma is typically about 1
0 to about 240 seconds, preferably about 20 to about 60 seconds. In general, the longer the treatment time, the longer the time that corrosion is prevented.

In accordance with a second aspect of the present invention, treating an etched substrate to reduce the adverse effects of etchant residues and by-products, comprising exposing the substrate to an alkylamine of the formula under vacuum: A second refinement process that we headline:

Embedded image Here, R ₁ is an alkyl group, preferably an alkyl group containing 1 to 5 carbon atoms, for example methyl, ethyl or propyl: each of R ₂ and R ₃ is the same or different It may be a hydrogen atom or an alkyl group, preferably an alkyl group containing 1 to 5 carbon atoms, for example, methyl, ethyl or propyl. Preferably, the vapor pressure of the amine in the vacuum chamber is such that a portion of the amine is in gaseous form and the portion of the amine is adsorbed on the substrate.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of the present invention is performed on an etched substrate 20, typically comprising a semiconductor material such as silicon or gallium arsenide. The conductive features 22 on the substrate 20 preferably comprise a metal layer, e.g., aluminum, an aluminum alloy such as an Al-Cu alloy, copper and optionally silicon, and also e.g.
Ti-W alloy or TiN and / or for example S
A diffusion shielding layer including an anti-reflection layer such as i, TiN or a Ti-W alloy may be provided. Substrate 20 has etched conductive features 22 having (i) etchant by-product 24, (ii) residual resist 26, and (iii) sidewall deposits 27 on the feature sidewalls. Feature 2
The etchant byproduct 24 on 2 typically comprises residual halogen containing radicals and compounds generated during etching of the substrate 20. Residual resist 26
Is a part of the resist remaining on the substrate after etching. Sidewall deposits 27 of feature 22 typically comprise organic compounds including (i) carbon and hydrogen, (ii) metals from metal-containing layers such as aluminum, and (iii) etchant gases such as boron and nitrogen. Is provided.

An apparatus 50 suitable for passivation, stripping and inhibiting corrosion of the substrate 20 is shown schematically in FIG. Apparatus 50 comprises an etching chamber (not shown), which is connected to vacuum chamber 52 by a load lock transfer area (not shown) maintained at vacuum, which comprises a plasma generation area 54 and a vacuum area 56. And Process gas enters the vacuum chamber 52 through the gas inlet 60 and is uniformly distributed within the vacuum region 56 by a “showerhead” type diffuser 62.
Substrate support 64 which may include a "basket" hoop support (as shown) or pedestal (not shown)
Is provided for holding the substrate 20 in a vacuum chamber, and a focus ring 70 maintains a flow of process gas around the substrate 20. An infrared lamp 7 is used to heat the substrate.
A heat source such as 2 may be used. Gaseous by-products and spent process gas are exhausted from the vacuum chamber 52 through an exhaust port 74 by an exhaust system (not shown) capable of maintaining a pressure of at least 1 millitorr in the vacuum chamber 52. Is done.

The plasma may be generated from the process gas using a microwave plasma generator assembly 80 connected to the plasma generation region 54 of the apparatus 50. A suitable microwave generator assembly 80 is available from Applied Science & Technology, Iowa, Woburn, Mass.
"ASTEX" microwave plasma generator commercially available from nc. Typically, the microwave generator assembly 80 includes a microwave applicator 82, a microwave tuning assembly 84, and a magnetron microwave generator 86. Also,
Other plasmas, such as RF-generated and inductively coupled plasmas, are also effective.

In performing the process of the present invention, the etched substrate 20 is transferred into a vacuum chamber 52 maintained at a suitable temperature and pressure. An improved method of treating an etched substrate to reduce the adverse effects of substrate-like etchant residues and by-products is to apply a plasma to a plasma formed from a process gas comprising water vapor, oxygen and nitrogen under vacuum. Includes exposing. The volume ratio of (i) water vapor and (ii) the sum of oxygen and nitrogen is (1) about 1: 2 to about 2: 1, preferably 0.8: 1 to 1:
0.8, and especially about 1: 1, or (2) about 1: 4 to about 1:40, preferably 1: 6 to 1:20, and especially about 1:10.

Depending on the volume of water vapor (V _{H2 O} ) and (ii) the ratio of both oxygen and nitrogen (V _{O2 +} V _N2 ), the process gas has either a predominantly passivation function or a predominantly stripping function. Have. Ratio by volume (V
_H2O ): If ( _VO2 + _VN2 ) is from about 1: 2 to about 2: 1, preferably from 0.8: 1 to 1: 0.8, especially about 1: 1 the process gas is mainly And acts as a passivation gas; and another resist stripping step is used to remove the resist on the substrate. If the ratio by volume (V _{H2 O} ) :( V _O2 + V _N2 ) is from about 1: 4 to about 1:40, preferably from 1: 6 to 1:20, especially about 1:10, the process gas is: It functions primarily as a stripping gas; and another passivation step is used to protect the substrate. To serve primarily as a stripping gas, the water vapor content should be less than about 20% of the sum of the oxygen and nitrogen gas contents by volume to provide an adequate stripping rate. In any process gas mixture, the volumetric flow rate of oxygen to nitrogen is preferably from about 1: 1 to about 5
0: 1, more preferably 1: 1 to 20: 1, especially 1: 1
0: 1.

[0012] Preferably, the process is performed in a vacuum chamber at a pressure of about 1 to about 10 Torr and a temperature of about 150 ° to about 400 ° C. The time that the substrate is exposed to the plasma is generally between about 10 and about 240
Seconds, preferably 20 to 60 seconds. In general, the longer the treatment time, the longer the time that corrosion is prevented.

The steam used in this process can be formed in a boiler or bubbler 100, which is connected to a vacuum chamber 52 by a feed line 102.
The boiler or bubbler is maintained at a sufficiently high temperature and a sufficiently low pressure to evaporate the water. If a boiler is used, the water in the boiler is heated to a temperature near the boiling point of water. Typically, the pressure in the boiler will range from about 50 Torr to about 200 Torr, more preferably 100 Torr to 150 Torr. If a bubbler is used, an inert carrier gas, such as argon or helium, may be passed through the bubbler to transfer water vapor to the vacuum chamber 52.

Preferably, the process gas comprising water vapor, oxygen and nitrogen is used in a multiple cycle process comprising (i) a plurality of passivation steps, or (ii) a plurality of passivation and resist stripping steps. Can be The multi-cycle passivation process has at least two passivation cycles, when only etchant by-products are present on the substrate, or when it is desirable to strip the substrate in a separate stripping step Desirable. In the first cycle, a passivation gas having the above-described composition is introduced into the chamber 52, and plasma is generated from the passivation gas. The plasma-activated passivation gas reacts with the etchant by-product 24 on the substrate 20 to produce gaseous by-products that are exhausted from the vacuum chamber. Thereafter, the flow of the passivation gas is stopped, and the plasma in the chamber disappears. In a second passivation cycle, the passivation gas is re-introduced into the chamber and a plasma is again generated in the chamber.

[0015] More typically, it is desirable to use a multiple cycle process with both stripping and passivation steps so that residual resist and etchant by-products can be simultaneously removed from the substrate. In the passivation step, a passivation gas having the above-described composition is introduced into the chamber 52, and plasma is generated from the passivation gas.
The substrate 20 is passivated. In the stripping step, a stripping gas is introduced into the chamber and a plasma is generated from the stripping gas to strip the polymer resist or oxide hardmask on substrate 20. This stripping step and the passivation step are performed at least once, preferably in the same order in which these steps were first performed,
Repeated, resulting in a multiple cycle process.
In this process, the passivation step may be performed before the stripping step and vice versa. Typically, during each process step,
A stabilization step is performed and for subsequent steps,
During this step, the process conditions are stabilized.

In general, the greater the number of cycles, the greater the resistance of the processed substrate 20 to any of the multiple cycle processes, even if the overall duration of the entire process does not increase. Gives corrosiveness. However, the smaller number of cycles gives faster process throughput, especially if the duration of stabilization between each process step is long, the number of cycles is
Preferably about 1 to about 10 cycles, more preferably about 2 to about 5 cycles.

Preferably, each passivation step or optional stripping step of the multiple cycle process has a duration of about 1 to about 60 seconds, more preferably 2 to 30 seconds, and most preferably 2 to 20 seconds. Having. In a multi-cycle passivation and stripping process, the passivation steps in the same cycle typically have the same duration as the stripping steps in each cycle, but these steps also have different durations. You may have.

Another passivation gas for use in a multiple cycle process may react with the etchant byproduct 24 on the substrate 20 to produce a gaseous byproduct that can be evacuated from the vacuum chamber 52. Contains some possible gas. For example, if the etchant by-product 24 contains chlorine, the passivation gas comprises a hydrogen-containing gas, which reacts with chlorine to produce an etchant by-product such as hydrochloric acid, The object is discharged from the vacuum chamber 52.
A suitable passivation gas comprising (i) ammonia and oxygen, or (ii) water vapor with optional oxygen and nitrogen, can be used for this step. When the passivation gas comprises ammonia and oxygen, the ammonia to oxygen volume flow ratio is about 1: 1.
To about 1:20, more preferably from about 1: 5 to about 1: 1.
5, most preferably about 1:10. For a 5 liter capacity chamber 52, the preferred gas flow is 3
00 sccm NH ₃ and 3000 sccm O ₂ . When using ammonia and oxygen passivation gases, a two-cycle process with a 10 second passivation step and a 10 second stripping step provides the best combination of high corrosion resistance and high process throughput efficiency. give.

A passivation gas comprising only water vapor can also be used for passivating the etchant by-product 24. If the vacuum chamber 52 has a capacity of 5 liters, the flow rate of water vapor is preferably about 100 to 1000 seem, more preferably about 50 sccm.
0 sccm. For a passivation gas comprising water vapor, the best corrosive results were obtained using a three cycle multi-cycle process with a passivation step and a stripping step each having a duration of 20 seconds. .

Suitable stripping gases for stripping the polymer resin in a multiple cycle stripping and passivation process include (i) oxygen,
And (ii) oxygen-activated gas or steam such as water vapor, nitrogen gas, or fluorocarbon gas, wherein the fluorocarbon gas includes CF ₄ , C ₂ F ₆ , CHF ₃ , C ₃
H ₂ F ₆ and C ₂ H ₄ F ₂ (for example, U.S. Patent No. 5,221,424 to Rose, and are disclosed in U.S. Patent No. 5,174,856 to Fuwan et al, both of which here Merged as a reference). A preferred stripping gas composition comprises oxygen and nitrogen in a volume flow ratio of about 6: 1 to about 200: 1, more preferably 10: 1 to 12: 1, for example, a 5 liter vacuum chamber 5.
A suitable gas flow rate for O ₂ is 3000 to 35 for O ₂
00 sccm and N ₂ are 300 sccm.

Suitable stripping gases for stripping oxygen hard masks include halogen containing gases, such as CF ₄ , C ₂ F ₆ , CHF ₃ , C ₃ H ₂ F ₆ , C ₂ H ₄
It is an F ₂ and HF. In addition, BCl ₃ , CCl ₄ or S
Other halogen gases, such as iCl _4, may be used to facilitate removal of sidewall deposits. However, if a chlorine-containing gas is used, the apparatus 50 may be used to prevent contamination of the passivation chamber with chlorine gas. An oxide stripping process should be performed in an etching chamber (not shown). Typically, only a portion of the oxide hardmask is stripped during the stripping step, and subsequent steps are used to deposit a dielectric or insulating layer on the substrate.

In a multiple cycle process, the pressure and temperature of the vacuum chamber 52 may be changed during subsequent passivation or stripping steps, or may be changed between subsequent cycles. Or may be maintained substantially constant.
Preferably, vacuum chamber 52 is maintained at about 1 to about 100 Torr, more preferably 1 to 10 Torr, and most preferably 2 Torr. Optionally, in a second step or cycle, the pressure in chamber 52 is a second low, less than about 1 Torr, more typically less than 500 mTorr, and most typically less than about 100 mTorr. Reduced to pressure. Typically, the substrate 20 is
Using the lamp heater 72, from about 150 ° C. to about 400
° C, more preferably from 200 ° C to 380 ° C. Preferably, changes in pressure and temperature during subsequent steps are minimized to improve process throughput efficiency.

Using the microwave plasma generator 80 of the apparatus 50, a plasma is generated from the stripping or passivation gas. If the plasma causes heating of the substrate 20, the power level of the microwave generator 80 is controlled such that the temperature of the substrate is substantially constant. Typically, the power output of the microwave generator 80 is in the range of 500 to 2500 watts, more preferably, 800 to 1500 watts.

Multiple cycle passivation processes can provide higher process throughput and better corrosion resistance than conventional processes. The ability to achieve the same or better corrosion resistance as obtained with a single cycle process, but with a short duration process, is an unexpected commercial advantage of a multiple cycle process. It is believed that the multi-cycle passivation process can provide high throughput because the faster diffusion mechanism allows for faster removal of etchant by-products. In the first passivation step,
The etchant by-product 24 is removed from the surface of the substrate 20. After that, the passivation species is
4 and diffuses into the sidewall deposit 27 where it reacts with the etchant by-product 24 and the reaction product must exit the resist or sidewall by diffusion and is subsequently desorbed . If the flow of the passivation gas is stopped in a multi-cycle passivation process, desorption of passivation by-products should occur faster. Subsequent depletion and diffusion processes result in etchant byproducts 24
Can be made faster and more efficient.

The multiple cycle passivation and stripping process has demonstrated faster throughput and better corrosion resistance than the prior art. The stripping step removes portions of the residual resist 26 and sidewall deposits 27, thereby making the residual resist 26 and sidewall deposits 27 thinner and more porous, and of passivating species into the residual resist 26. Diffusion and resist 2
6 to promote the diffusion of the reaction product out. The multiple cycle process provides a substrate that is resistant to corrosion by atmospheric humidity for at least 24 hours, and more typically at least 48 hours, after passivation of the substrate.
This is a substantial improvement over the prior art, which typically gives only about 1-2 hours of corrosion resistance. Improved corrosion resistance allows for more efficient processing schedules and lower manufacturing losses.

In accordance with another aspect of the present invention, an improved process for treating an etched substrate to reduce the adverse effects of etchant residues and by-products is to expose the substrate to an alkylamine of formula With:

Embedded image Here, R ₁ is an alkyl group, preferably an alkyl group containing 1 to 5 carbon atoms, for example methyl, ethyl or propyl: each of R ₂ and R ₃ is the same or different It may be a hydrogen atom or an alkyl group, preferably an alkyl group containing 1 to 5 carbon atoms, for example, methyl, ethyl or propyl. Preferably, the vapor pressure of the amine in the vacuum chamber is such that a portion of the amine is in gaseous form and the portion of the amine is adsorbed on the substrate. In this amine inhibition step, the amine forms an adsorbed passivation layer on the surface of the feature, which inhibits corrosion of the feature. The amine inhibiting layer is useful for features 22 that include metal alloys that exhibit high battery activity, to prevent corrosion of these metals.

In performing the step of inhibiting amine,
Amine vapor is introduced into the sink region of the vacuum chamber 52 for a time sufficient to adsorb sufficient amine on the substrate 20 to inhibit corrosion of the substrate 20 for at least 24 hours when the substrate is exposed to the atmosphere. Typically, during this 24 hour period, additional processing steps are taken that obviate the need to inhibit corrosion of the substrate 20. The longer the amine exposure time of the substrate 20, the higher the efficiency of corrosion inhibition. But,
The amine is exposed to the substrate for less than about 120 seconds, more preferably less than about 90 seconds, and most preferably less than about 60 seconds, for the throughput efficiency of the process. In the amine exposure step, vacuum region 56 is maintained at a pressure preferably in the range of about 1 to about 100 Torr, more preferably in the range of about 1 Torr to about 10 Torr.

The vapor pressure of the amine is high enough so that at least a portion of the amine is gasified in the vacuum chamber 52 and low enough so that at least a portion of the amine is adsorbed to the substrate 20 in the vacuum chamber 52. Should. Preferably, the alkyl portion of the amine comprises an alkyl such as methyl, ethyl and propyl, and each alkyl preferably comprises 1 to 5 carbons. Suitable amines include mono-alkyl, di-alkyl and tri-alkyl substituted methylamine, ethylamine, propylamine, such as monomethylamine, dimethylamine and trimethylamine, because of Amines have a low boiling point and are readily available commercially. Specific amines that can be used include trimethylamine (BP 2.9 ° C), which is preferred, diethylamine (BP 7.4 ° C) and monomethylamine (BP
-6.3 ° C). Preferably, the amine comprises at least two alkyl moieties, more preferably three alkyl moieties. Of these amines, trimethylamine is preferred because tertiary (trialkyl) amines are considered more efficient inhibitors than secondary (dialkyl) amines, and secondary amines are It is considered to be a more efficient inhibitor than primary (monoalkyl) amines. However, the toxicity and commercial availability of these amines also dictate the choice of the appropriate amine.

Amine vapor is generated from an amine source 104 with an amine gas or liquid amine. The liquid amine source 104 comprises a boiler or bubbler fluidly connected to the vacuum chamber 52 by the feed line 102 and maintained at a sufficiently high temperature and a sufficiently low pressure to vaporize at least a portion of the liquid amine. I have. Preferably, the boiler or bubbler is maintained at room temperature. The boiler pressure is preferably from about 50 Torr to about 200 Torr, more preferably 100 to 150 Torr.
If a boiler is used, the boiler is maintained at substantially the same temperature as the boiling point of the liquid amine to generate amine vapor. If a bubbler is used, a carrier gas, such as argon or helium, bubbled within the bubbler carries the amine vapor to the vacuum chamber 52.

After the steps of stripping, passivation, and optional amine suppression, the passivated and stripped substrate 20 is removed from the chamber and etched in an etchant solution to remove sidewall deposits 27 formed in the etching process. Conventional wet chemical etchant solutions are suitable. In this process, the wafer is etched with an "ACT" 900 series or HF containing wet chemical etchant, commercially available from Advanced Chemical Technologies of Allentown, NJ. After wet etching, the wafer is rinsed with deionized water to remove residual wet etchant.

[0031]

The following examples illustrate the process of the present invention. All of the examples are based on commercially available "A" from Applied Materials, Inc. of Santa Clara, CA.
MAT PRECISION 5000 METAL
ETCHER ". This "PRECI
The SION 5000 "apparatus has an etching chamber (not shown) connected to a passivation and stripping chamber (as shown) so that the substrate can be removed from the etching chamber without being exposed to the atmosphere. Transfer to is possible. The etching chamber (not shown) of the apparatus also includes an induction coil surrounding the chamber to optionally generate a magnetic field that enhances the plasma intensity in the chamber. These examples were performed on silicon wafers about 200 mm (8 inches) in diameter and 0.73 mm thick.

After passivation and stripping, the treated substrate is exposed to the atmosphere or to high humidity levels ranging up to about 40% relative humidity for a predetermined time interval, and then exposed to dark field conditions. By measuring the substrate with a microscope or an electronically operated microscope,
The corrosion resistance of the substrate is tested. Substrate corrosion is visible as small pieces of scattered light caused by corroded hydrated species formed on metal features. Corrosion can be from 2 hours to 7 hours directly after the passivation and stripping steps.
It is measured at intervals of up to days or at intervals of 1, 2 or 3 weeks after wet chemical etching.

(Examples 1 to 11) In these examples, (i) a TiW barrier layer; (ii) a thickness of about 550 n
m of an aluminum-silicon-copper conductive metal layer, the aluminum alloy comprising 1.5% silicon and 0.5% copper; and (iii) on a substrate having features comprising an anti-reflection layer of titanium. One or more cycles of passivation and stripping processes were performed. Prior to this, the substrate had been etched in a reactive ion etch using a gas mixture of BCl ₃ , Cl ₂ and N ₂ .

Table 1 shows the process conditions and results of the corrosion tests of Examples 1 to 11. The passivation step was performed with steam flowing at a volume flow rate of 500 seem. The stripping step involves oxygen,
The test was carried out using a stripping gas provided with nitrogen and optional steam at the indicated flow rates. In all of these processes, the vacuum chamber was maintained at a pressure of 2 Torr.
In general, multiple cycle passivation and stripping processes provided superior corrosive results as compared to single cycle processes.

The multiple cycle passivation and stripping process used in Example 7 provided the best corrosion resistance. In this process, each passivation and stripping step was 20 seconds in duration, and the passivation and stripping steps were repeated three times. Corrosion resistance of more than 72 hours and up to 96 hours was obtained.

Comparison of Examples 6 and 7 suggests that for the same full multi-cycle process time, increasing the number of cycles gives better corrosion resistance.

Comparing Examples 7 and 9, it is found that the final stripping step substantially increases the corrosion resistance of the substrate. In Example 9 where the final stripping step was not performed, corrosion resistance was found up to 3 to 7 hours; in Example 7, corrosion resistance was found in excess of 72 hours. It is believed that the final stripping step increases the corrosion resistance because the oxygen of the stripping gas oxidizes the aluminum features and forms a protective layer of aluminum oxide on the metal features.

Example 11 illustrates that the fastest overall processing time can be achieved by increasing the number of passivation and stripping cycles.

[0039]

[Table 1] (Examples 12 to 40) In these examples, (i) 30
A passivation gas comprising 00 seem and 300 seem of ammonia; and (ii) 3000 seem of oxygen.
A multi-cycle process using a stripping gas with m and 300 seem of nitrogen was used.

The features of the substrate used in these embodiments are:
In order, (i) a 3,500 Angstrom thick layer of an aluminum alloy containing 0.5% copper, (ii) a 450 Angstrom TiN layer, (iii) a 1,000 Angstrom Ti layer, and (iv) ) With a 365 Å layer of TiN. Prior to this, the substrate had been etched in a reactive ion etch using a gas mixture comprising BCl ₃ , Cl ₂ and N ₂ , optionally CF ₄ .

For all these examples, an initial stabilization step of approximately 10 seconds in duration was performed. In this step, the substrate was transferred to a vacuum chamber. The temperature of the chamber was ramped up from a temperature of about 60 to 100 ° C. to a temperature of about 325 ° C., and the pressure of the chamber was ramped up from a pressure of about 10 to 50 mTorr to a pressure of about 2 Torr. O ₂ 3000 sccm and NH ₃ 300 sccm
Was passed through the chamber. After the stabilization step, suitable process gas conditions for passivating and stripping the substrate are:
Maintained as described below.

(Examples 12 to 21) Examples 12 to 21
Was processed using L9 (three levels for each of the four process variables), orthogonal factor placement experiments. Table I
I describes the four process variables and the three levels used for each variable. Table III lists the actual process conditions used to process each of the ten wafers. Example 21 was run under the same process conditions as Example 12 and demonstrated the reproducibility of the experiment.
In these examples, the first passivation and stripping cycle was performed at a temperature of about 325 ° C., and the temperature of the second passivation cycle was varied as shown in Table II. In Table III, the variable PS / PT represents the duration of a single passivation and stripping cycle divided by the total multiple cycle process time. The variable P / (P + S) represents the total time of a single passivation step divided by the total time of a passivation and stripping cycle.

The wafer was inspected under an optical microscope at 100X magnification to evaluate the photoresist remaining on the wafer immediately after stripping and to corrode the wafer after the wafer was exposed to the atmosphere for 6 and 24 hours. Was identified.
No photoresist was observed on any of the wafers,
No signs of corrosion were observed on any of the wafers after the test interval of 24 hours. These examples illustrate the low variability of the corrosion performance obtained using a multiple cycle passivation and stripping process.

[0044]

[Table 2]

[Table 3] Examples 22-31 Examples 22-31 were also processed using the L9 orthogonal factor placement experiment. The causal variables and levels are listed in Table IV. Table V shows Examples 22 to 31.
Shows the processing conditions used to process each of the above. Example 31 was run under the same process conditions as Example 22 and demonstrated the reproducibility of the experiment.

After processing, each of the wafers was evaluated at 100 × magnification using an optical microscope. No photoresist was found on the wafer, and none of the examples showed corrosion after 6 and 24 hours, except for Example 30, which exhibited severe corrosion.

The results of these examples demonstrate that the corrosion resistance of the substrate is improved by making the passivation and stripping process longer and the stripping process temperature higher.

[0047]

[Table 4]

[Table 5] Examples 32-40 In Examples 32-40, two sets of wafers were processed using multiple cycles of passivation and stripping processes. The first set of wafers was processed to evaluate the corrosion resistance of the wafer immediately after the stripping and passivation processes.
The second set of wafers was processed to evaluate the corrosion resistance of the stripped and passivated wafer after wet chemical etching.

The first set of wafers used in Examples 32-36 were processed using a two-cycle passivation and stripping process. The passivation and stripping steps in each cycle were tried for a duration of about 10 seconds, giving a total of 40 seconds of multiple cycle processing times. The total processing time of the multiple cycles is 49 because it includes three 2-second intervals between each passivation and stripping step.
Seconds. Both the passivation and stripping steps of the first cycle are performed at a temperature of 325 ° C., and the passivation and stripping steps of the second cycle are both 38
Performed at a temperature of 0 ° C.

After the processing, the wafer is subjected to a relative humidity of 40
It was stored under an atmosphere at room temperature of 50%. After a predetermined time interval, residual resist and corrosion on the wafer was evaluated using an optical microscope. Evaluation of the wafer is 1, 2,
Performed after 3, 4 and 7 days; all five wafers were evaluated after the first day, four after the second day, three after the third day, and thus only after the seventh day. One wafer was evaluated. After these time intervals, no corrosion was found on any of the wafers.

The second set of wafers used in Examples 37-40 were also processed using a two-cycle passivation and stripping process. The duration of each passivation and stripping step in Example 37 was 10 seconds; 5 seconds in Example 38;
3 seconds in Example 39; and 2 seconds in Example 40. Both the passivation and stripping steps of the first cycle were performed at a temperature of 325 ° C, and the passivation and stripping steps of the second cycle were both performed at a temperature of 380 ° C.

After processing, the wafers were stored at room temperature under a 40% relative speed environment. After 24 hours, no corrosion was observed on any of the wafers.

Thereafter, wet chemical etching was performed using an acidic solution containing HF. After etching, the wafers were again stored at room temperature in a 40% relative humidity chamber and evaluated by optical microscopy at 1, 2, and 3 week intervals. After 3 weeks, no corrosion was observed on any of the wafers. Example 37
-40 are wafers processed using a 2 second passivation and stripping step duration;
It was demonstrated that there was no difference between wafers processed using a 10 second passivation and stripping step duration.

(Examples 41 to 53) Examples 41 to 53
Was processed using single or multiple cycle passivation and stripping steps. In all of these examples, the passivation gas comprised steam and optional oxygen and nitrogen, as described below.

The features on the substrate in Examples 41 to 53 are as follows:
(I) a barrier layer of Ti having a thickness of 100 μm, (ii) 10
A conductive layer of Al containing 0.5% Cu and having a thickness of either 00 nm or 1050 nm; and (iii) 36
An anti-reflective layer of TiN with a thickness of either nm or 45 nm was provided. Wafers were made of BCl ₃ , Cl ₂ and N ₂
Was etched in a reactive ion etch using a gas mixture comprising: before etching, the photoresist had a thickness of about 1.8 to 2 μm.

While both multiple cycle and single cycle processes were performed on the substrate, some of the single cycle processes provided adequate corrosion resistance with a total process time of 50 seconds. It is considered that the electrolytic activity of the metal alloy having these features is sufficiently low, and if the total process time is not further reduced, the multiple cycle process is not required.

Examples 41-45 In Examples 41-45, a wafer "basket" or hoop was used to support a substrate in a vacuum chamber. After the substrate was placed in the wafer basket, an initial chamber stabilization step was performed for about 15 seconds. In this stabilization step, process gas was flowed into the vacuum chamber at the flow rates shown in Table VI, and the temperature and pressure in the vacuum area were maintained at the desired process levels. After stabilization, a single cycle passivation and stripping process was performed, as shown in Table VI. The passivation step of the process had a duration of 20 seconds and the stripping step had a duration of 40 seconds.

The results of the corrosion tests for Examples 41 to 45 are listed in Table VI. The corrosiveness of the substrate is not affected by lowering the passivation temperature (compare Examples 41 and 42 and Examples 43 and 44), and
It was observed that it was not affected by the increase in stripping temperature (compare Examples 44 and 45).

[0058]

[Table 6] Examples 46-52 In Examples 46-52, the process conditions for the passivation and stripping steps were kept constant, and the durations of the passivation and stripping steps were as shown in Tables VII and VIII. Changed. In Examples 46-50, the passivation step preceded the stripping step, and in Examples 51 and 52, the stripping step preceded the passivation step. Example 49 used a 2-cycle passivation and stripping step.

In these examples, a pedestal (not shown) was used to hold the substrate in the vacuum chamber. This pedestal allowed further control of the substrate temperature because the larger pedestal mass as compared to the wafer basket holder stabilized the substrate temperature.

In the passivation step, H ₂ O
500 sccm, O ₂ 1000 sccm and N ₂ 100
A process gas comprising sccm was used to maintain a vacuum region at a pressure of about 2 Torr. The power level of the microwave generator 86 was maintained at about 1400 watts.

In the stripping process, O
_A process gas comprising 23500 sccm and 300 sccm N ₂ was used to maintain the vacuum chamber at a pressure of about 2 Torr. The microwave power level is
Maintained at about 1000 watts.

These examples demonstrate that a single cycle water-based passivation and stripping process using substrate temperatures from 200 to 300 ° C. can provide effective corrosion resistance. did. For features with the described metal-containing layer, a single cycle process with a total duration of at least about 150 seconds provided adequate corrosion resistance and multiple cycle processes were not required. These embodiments also show that the order of the passivation and stripping steps is
It has been demonstrated that the corrosion resistance of the substrate has no effect.

[0063]

[Table 7]

[Table 8] Example 53 Example 53 illustrates a preferred single cycle stripping and passivation process, the process conditions of which are disclosed in Table IX. This process is advantageous because it provides reasonably high wafer throughput while maintaining effective passivation and stripping quality. Wafers passivated using this process have been demonstrated to be more than 24 hours resistant to corrosion when exposed to the atmosphere.

[0064]

[Table 9] Examples 54 and 55 These examples can use a single cycle steam passivation process to prevent the corrosion of partially etched highly corrosive Ti-W layers on the substrate. Is exemplified. In these examples, a complete reactive ion etch, passivation and stripping process sequence is described. The wafers used in these examples had features with (i) a barrier layer of a Ti-W alloy, (ii) a conductive layer of an aluminum-containing alloy, and (iii) an anti-reflective layer. The features on the wafer were etched until the underlying Ti-W barrier layer was exposed.
The Ti-W layer was not etched, because
This is because the underlying circuit device is damaged by the plasma etching process. Partially etched Ti-W barrier layers corrode rapidly when exposed to the atmosphere because the electrolytic bonding of the metals in the alloy promotes corrosion. Thus, the partially etched barrier layer is passivated using a water vapor containing plasma immediately after the etching.

The substrates of Examples 54 and 55 are etched in an etching chamber (not shown) using a two-stage etching process. In the first etching stage, BCl _{3 at} a flow rate of 50 sccm,
Cl _{2 at a} flow rate of 40 sccm and N _{2 at a} flow rate of 20 sccm
Was introduced into the etching chamber. The pressure in the chamber was maintained at about 200 mTorr. RF applied to the cathode in the chamber
The power was about 400 watts and a magnetic field of 40 Gauss was generated using an induction coil to excite the plasma. The first stage of etching was performed until the aluminum-containing layer on the substrate was etched through, and the endpoint of this etching step was measured by light emission techniques. In the second stage of etching, a 1500 Å thick Ti-
The W barrier layer is etched until only 500 Å of the Ti-W layer is etched,
The 1000 W layer remained -W. In the second etching stage, BCl ₃ 25scc
m, a process gas comprising 20 seem of Cl _{2 and} 20 seem of N ₂ is introduced into the chamber, and
The pressure was maintained at 0 mTorr. The RF power applied to the cathode was maintained at a level of 250 watts and a 40 gauss magnetic field was used to excite the plasma in the chamber. The stage of the second etching is about 4
Performed for 0 seconds.

After the etching was performed, the wafer was transferred from an etching chamber (not shown) to a passivation and stripping chamber. In example 54, the wafer is passivated in separate steps,
Stripped. In the passivation step, water vapor was introduced into the chamber at a flow rate of 500 seem. 800 watts of RF power was applied to the microwave plasma generator and the wafer was heated to 250 ° C. This passivation step was performed for a total time of 45 seconds. After passivation, the wafer was stripped in another stripping step. Stripping step is 300s
A stripping gas with a ccm flow of oxygen and a nitrogen flow of 200 to 300 sccm was used. The microwave generator maintained an RF power level of 1400 watts and the wafer temperature was maintained at 250 ° C. During both the passivation and stripping steps, the chamber pressure was maintained at 2 Torr. The passivated wafer of Example 54 was substantially corrosion resistant when exposed to the atmosphere.

The wafer of Example 55 was passivated and stripped in a single step process. 3000 sccm flow of oxygen, 200 sccm
A stream of nitrogen and a steam of 300 sccm were introduced into the chamber. A 140 watt power level plasma was generated for approximately 90 seconds to strip and passivate the wafer. It was observed that the passivated wafer of Example 55 also exhibited resistance to corrosion in an atmosphere. After stripping and passivation, place 1 on the passivated wafer.
The remaining barrier layer at a thickness of 000 angstroms was removed using a wet chemical etching process. In addition to this process, the wafer was chemically etched using an "ACT" 900 series liquid etchant commercially available from Advanced Chemical Technologies of Allentown, NJ. After etching, the wafer is rinsed with deionized water,
Residual etchant was removed.

Although the present invention has been described in detail with respect to certain preferred embodiments, other forms are possible. For example, multiple cycle processes can be performed using passivation and stripping processes other than those disclosed herein. It is also possible that a single cycle steam-based passivation and stripping process can be combined with other passivation and stripping processes to provide greater corrosion resistance and process efficiency. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.

[Brief description of the drawings]

FIG. 1 (a) is a schematic longitudinal cross-sectional view of a substrate having an etched metal-containing feature, showing an etchant by-product, residual resist and sidewall deposits therein;
FIG. 1 (b) is a schematic longitudinal sectional view of the substrate of FIG. 1 (a) after passivation and stripping, showing that the etchant by-product and the residual resist have been removed, and FIG. 1 (c). FIG. 1D is a schematic longitudinal sectional view of the substrate after removal of sidewall deposits of FIG. 1B, and FIG.
FIG. 3C is a schematic vertical cross-sectional view of the substrate of FIG. 3C after suppression using an amine, showing amine absorbed by the substrate.

FIG. 2 is a schematic longitudinal sectional view of a vacuum chamber suitable for performing the process of the present invention.

[Explanation of symbols]

Reference Signs List 20: substrate, 22: surface shape, 24: etchant by-product, 26: residual resist, 50: apparatus, 52: vacuum chamber, 60: gas inlet, 80: microwave plasma generator assembly.

 ────────────────────────────────────────────────── ─── Continuing the front page (72) Inventor Shay, Peter United States, California, Sunnyvale, Blair Avenue 833, Number 4 (72) Inventor Ishalom, Carmel Israel, Coriat Modzkin 26418, Modech Fogerman Street 14 / 2 (72) Inventor Row, Wesley United States of America, California, San Jose, Johnson Avenue 1695 (72) Inventor Papanyu, James S. United States of America, California, San Rafael, Holly Drive 351 (72) Inventor Mac, Steve S. Wy. United States, California, Pleasanton, Montebino Drive 878 (72) Inventor Rhodes, Charles Steven United States, California, Simi Valley, Shoal Creek Court 1049 (72) Inventor Shiy, Brian Thai Wan, Farien, Lin-Chen Street 1 lane sp. 5 (72) Inventor Latchford, Scott Ian United States, California, Sunnyvale, Sesame Drive 1207 (72) Inventor Williams, Karen A. United States, California, San Jose, Spruce Street 1186 (72) Inventor Yuwon, Victoria United States, California, Los Altos, Marinovic Way 1408

Claims (10)

[Claims] 1. A process for treating a semiconductor wafer after etching using a halogen-containing etchant, comprising: (a) placing a substrate in a vacuum chamber;
(B) Step of introducing amine vapor of the following formula into a vacuum chamber: (R ₁ is an alkyl group: R ₂ and R ₃ are a hydrogen atom or an alkyl group, and R ₂ and R ₃ may be the same or different) and (c) a part of the amine is gaseous Setting the vapor pressure of the amine in the vacuum chamber such that a portion of the amine is present in the vacuum chamber and absorbed by the substrate. 2. The process of claim 1, wherein the vacuum chamber is maintained at a pressure between about 1 Torr and about 10 Torr. 3. The process according to claim 1, wherein at least one of R ₂ and R ₃ is an alkyl group. 4. The process according to claim ₁ , wherein each of R ₁ , R ₂ and R ₃ is an alkyl group containing 1 to 5 carbon atoms. 5. The vapor pressure in the chamber and the temperature of the substrate are set to a level such that sufficient amine is adsorbed on the substrate to prevent corrosion of the substrate upon exposure to air for at least 24 hours. Item 3. The processing process according to Item 1. 6. The process of claim 2, wherein the introduction of the amine vapor into the vacuum chamber occurs for less than about 120 seconds. 7. A process for treating a semiconductor wafer after etching using a halogen-containing etchant,
(A) placing a substrate in a vacuum chamber; (b)
Introducing a passivation gas with water vapor into the vacuum chamber; (c) generating a plasma from the passivation gas; and (d) introducing a stripping gas with oxygen and nitrogen into the vacuum chamber. Wherein the volume flow ratio of oxygen to nitrogen (V _O2 : V _N2 ) is from about 6: 1 to about 200: 1, and (e) generating a plasma from the stripping gas. (F) removing the processed substrate from the vacuum chamber. 8. The volume flow ratio of oxygen to nitrogen (V
_O2 : _VN2 ) is from about 10: 1 to about 12: 1.
Processing process described in 1. 9. The method according to claim 1, wherein the vacuum chamber is at about 150 ° C. to about 40 ° C.
The process of claim 7, wherein the temperature is maintained at 0 ° C. and a pressure of about 1 Torr to about 10 Torr. 10. The vacuum chamber is maintained under conditions of temperature and pressure such that a plasma of a process gas passivates the substrate to provide corrosion resistance to the substrate when exposed to air for at least about 24 hours. The process according to claim 7.