JPH0451521A - Method and apparatus for surface treatment - Google Patents

Abstract

PURPOSE:To prevent the corrosion in washing to obtain a reliable metallic wiring pattern by performing the washing in ultrapure water using deoxidated water after formation of the wiring pattern. CONSTITUTION:Al-Si-Cu alloy film is formed on the surface of a semiconductor substrate, and then a resist pattern is formed, and using Cl gas, etching is performed with the resist pattern as a mask, and hot blast treatment is performed to remove residual Cl on the surface of a substrate. Subsequently, with a washing device 16, ultrapure water, from a ultrapure water guide pipe 37, and hydrogen gas, from a hydrogen gas introduction pipe 36, are introduced, and are led to a catalyst resin charge tower 40 filled up with catalyst 39 for performing deoxidation treatment, and the deoxidated ultrapure water 38 is poured through an introduction pipe 35 onto the substrate rotating being sucked so as to wash it. And the entire processor is screened from light, and the entire room, where the substrate to be treated is placed, is screened from light so that the substrate to be processed may not be irradiated with light. Moreover, the quantity of Cu added to Al-Si is 0.1-0.4%.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a surface treatment method, particularly for treating aluminum (A
J) Concerning corrosion prevention of alloys, etc.

(Prior Art) In recent years, semiconductor devices have become faster and more highly integrated, and research into miniaturization and higher density of constituent elements is progressing rapidly.

Conventionally, metal wiring for semiconductor devices has generally been formed by the following method.

First, AJ! , AJ! After forming a metal thin film such as a -5i-Cu alloy, a pattern is formed using a resist or the like, and using this as a mask, etching is performed by reactive ion etching (RIE) or the like to form a wiring pattern.

By the way, in this RIE process, a gas containing chlorine (CJ) is generally used.
2 exists, and if it is left in the atmosphere, A
If a semiconductor device having such corroded metal wiring is used as it is, it may cause wire breakage and reduce the reliability of the device.

Therefore, in order to prevent such corrosion of metal wiring,
A method of replacing C1 adsorbed on the surface with F by performing a discharge treatment using an F-based gas after an RIE process using a C1-based gas, CJ! A method of rinsing with water immediately after the RIE process using a system gas (Japanese Patent Application No. 63-53268), a method of supplying hot inert gas or heating the substrate with a heater after the RIE process (Japanese Patent Application No. 63-53268) No. 63-53268) etc. are being implemented.

However, after this, ashing is performed using O2 gas excitation in order to peel off the resist used as a mask, and after this step, a water washing step is performed. This washing is
This is carried out using ultrapure water containing several tens of ppm or less of metals as impurities.

One way to prevent corrosion in this process is to wash with ultrapure water containing metal ions (
(Patent Application No. 153512/1983).

However, in this method, impurity metals also adhere to the surface of the substrate to be processed, contaminating the surface. Steps must be used to further remove this contaminant.

However, the biggest problem in the wiring formation process is corrosion during washing.

Such corrosion during washing with water is caused by AJJ-C as a wiring material.
This is particularly noticeable when u or Af-Si-Cu is used.

However, Aj! is also superior in terms of preventing electromigration and ensuring reliability. , Al
It is not 1-5i, but Ano 5t-Cu.

AJ! -5t-Cu and AJ! -Cu is AJ! -Cu type has a large electrochemical electrode potential difference (battery effect) and has the property that redox reactions are likely to occur in an aqueous solution. For this reason, AJ-3i-Cu and Aj! -Cu will suffer corrosion accompanied by the formation of AJ(OH)3 just by immersing it in ultrapure water.

Furthermore, when F or CJ exists on the surface of AJ-5i-Cu or AJ2-Cu, HF, HCj
! This results in the formation of , accelerating corrosion. Such a problem of corrosion during washing with water cannot be avoided even if various treatments such as those described above are carried out.

Furthermore, light is incident on a semiconductor substrate having a pn junction, and pn
By exciting the junction, an electromotive force is generated at the pn junction. At this time, if metal is in contact with the semiconductor substrate, this electromotive force may accelerate corrosion of the metal.

For example, as shown in FIG. 7, an n-type diffusion layer 102 is formed in a p-type silicon substrate 101, and this n-type diffusion layer 1
02 with high concentration p+ diffusion layer 1゜3 and n medium diffusion layer 1
Aj! 04 is formed, and Aj! Consider the case where the wiring pattern 106 is formed using a -5i-Cu alloy.

Here, 105 is a silicon oxide layer.

This wiring pattern 106 is patterned by reactive ion etching or the like and left in the atmosphere. In this case, the substrate is irradiated with light 107, such as light from a fluorescent lamp. Due to the tip 107, the p+ diffusion layer 103 is biased positively and the n medium diffusion layer 104 is biased negatively, and an electromotive force is generated.

Further, if left in the atmosphere, a small amount of moisture in the atmosphere will be adsorbed on the surface (this adsorbed moisture is indicated by 108). This moisture 108 becomes a current path, and the diffusion layer 1
Aj connected to 03! Electrons from the -3i-Cu alloy wiring pattern 106 connect to the AJ connected to the n-type diffusion layer 1゜4.
Holes are emitted from the -3i-Cu alloy wiring pattern 106.

Therefore, an oxidation reaction as shown in the following equation occurs on this surface, accelerating corrosion.

AJl-AJ''+3e (Formula) In addition to the generation of electromotive force due to such bonding, chemical reactions may be accelerated by light energy, which may cause corrosion.

In particular, when halogens such as CJ and F are present on the surface during an etching process such as reactive ion etching, corrosion is further accelerated.

(Problems to be Solved by the Invention) As described above, in the conventional manufacturing process of semiconductor devices,
When AJl-5i-Cu or AJ-Cu is used as a wiring material, major problems include corrosion during washing and acceleration of corrosion due to light energy during transportation and storage.

The present invention has been made in view of the above-mentioned circumstances.
The purpose of this invention is to prevent corrosion during washing when an Al alloy such as 5i-Cu or AJl-Cu is used as a wiring material.

Another object of the present invention is to prevent corrosion during transportation and storage when AJ1 alloys such as AJ1-5i-Cu and AJ1-Cu are used as wiring materials.

[Structure of the invention]

(Means for Solving the Problems) Therefore, in the first and second aspects of the present invention, after pattern formation,
I try to wash with ultrapure water using deoxygenated water.

That is, in the present invention, the dissolved oxygen concentration in ultrapure water is suppressed as much as possible.

Moreover, in the third aspect of the present invention, Aj! The substrate to be processed on which the alloy pattern is formed is transported and stored in a state where light is blocked.

That is, in the present invention, the entire processing apparatus is shielded from light, or the entire room in which the substrate to be processed is placed is shielded from light, so that the substrate to be processed is not irradiated with light.

(Function) The first aspect of the present invention. According to the second method, by suppressing the dissolved oxygen concentration in ultrapure water, the oxidation reaction of AJl as shown in the following formula can be suppressed, and corrosion during washing with water is prevented.

2AJ! +3/202-2A, e”+60H-2Aj!
(OH)3 ↓ Furthermore, by washing with ultrapure water, CJ and F adhering to the metal surface can be removed with high efficiency.

Furthermore, according to the third aspect of the present invention, since the substrate to be processed on which the AJ alloy pattern is formed is transported and stored in a state where light is blocked, the p-n junction is irradiated with light and an electromotive force is generated. This prevents the oxidation of All from being promoted.

This was done based on various experimental results.

As shown in FIGS. 8(a) to 8(cl), four types of substrates to be processed were formed as samples.

First, as shown in FIG. 8(a), a base substrate with an Ajl-5i-Cu alloy wiring pattern formed through a contact hole formed in a silicon oxide layer 105 covering the surface is placed inside the n-type silicon 102. As shown in FIG. 8(b), a p-medium dispersion layer 104 is formed in an n-type silicon base substrate 102, as shown in FIG. 8(e). As shown in , the underlying substrate is p
One has an n-type silicon 101 formed with an n-medium diffusion layer 103, and the other is a p-type silicon 101 with a p-medium diffusion layer 104 formed on the base substrate, as shown in FIG. 8(d). Prepare one by one. Here, each substrate to be processed is CJ1
2+BCj! Assume that an Al1-5L-Cu alloy wiring pattern is formed by reactive ion etching using a gas to have a 1.5 μm line and spacing and a wiring length of 5 gg.

Place this in a transparent container at normal pressure, 24℃, and humidity 95-10.
At a constant value of 0%, an experiment was conducted in which the fluorescent lamp was turned on for 2 hours and left in the light irradiation state, and an experiment was conducted in which the sample was placed in a container that could block light and left under the same conditions. The spectrum of light from this fluorescent lamp is shown by the solid line in FIG.

Figure 9 (a) shows the results of measuring the degree of corrosion of each sample during light irradiation and non-light irradiation.
) and shown in FIG. 9(b).

From this result, it can be seen that Fig. 8 (b
It can be seen that corrosion occurs extremely frequently in the samples shown in ).

As a result of measuring the sample shown in FIG. 8(b), it was found that an electromotive force of approximately 3001 V was generated under light irradiation, and a solar cell was formed with the p-middle layer being positive and the n-layer being negative, and the sample surface Due to the formation of a minute current loop due to H20 etc. adsorbed on the p
A hole is injected from the middle area and Aj! -Aj! It was confirmed that the oxidation reaction 3" was promoted.

In fact, it has been confirmed that the occurrence of corrosion can be extremely reduced by blocking the current loop that travels on this surface with a molding resin or the like.

It was also found that the occurrence of corrosion was significantly reduced in the light shielded state compared to the light irradiated state for all samples.

The cause of this is not clear, Al-5i-
It can be seen that some kind of photochemical reaction is promoted on the Cu alloy surface.

Further, each sample was irradiated with light having two wavelength characteristics as shown by curves a and b in FIG. 10 using a colored glass filter to measure the occurrence of corrosion.

The sample used here was an A-5i-Cu film similar to that shown in FIG.
It is assumed that an alloy wiring pattern is formed.

From this result, compared to using a filter that cuts light of 340 nm or less (curve a in Figure 10), the
It can be seen that the occurrence of corrosion is significantly smaller when the following light-cutting filter is used (curve b in Figure 10).

This result shows that corrosion can be significantly reduced by blocking light of 400 nm or less.

(Example) Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIGS. 1 and 2 are diagrams showing a schematic configuration of a surface treatment apparatus according to an embodiment of the present invention.

This apparatus includes an RrE apparatus 14 consisting of a pre-processing chamber 11, an etching chamber 12, and a post-processing chamber 13 for etching the substrate to be processed, a heating device 15 for heating the substrate to be processed after etching, and a heating device 15 for heating the substrate to be processed after etching. The washing device 16 uses deoxygenated water to wash the substrate.

The water washing device 16 is configured to include a water washing container 32 and a catalyst 39 for performing deoxidation treatment, and is configured to supply deoxygenated water 38 to the washing container 32 via a deoxygenated water introduction pipe 35.
A catalytic resin packed tower 40 filled with catalytic resin packed tower 40, an ultrapure water introduction pipe 37 for supplying ultrapure water to the catalytic resin packed tower 40, and a hydrogen gas introduction pipe 36 for introducing hydrogen gas into the ultrapure water. ing. The washing container 32 is also equipped with a spinner 34 that removes moisture using centrifugal force generated by suctioning and rotating the substrate to be processed.

Next, a method for forming metal wiring using this apparatus will be explained.

First, an Aj2-3i-Cu alloy thin film is formed by sputtering or the like on the surface of a semiconductor substrate on which an element region is formed, and then a resist pattern is formed.

The substrate on which this resist pattern has been formed is introduced from the pretreatment chamber 11 of the RIE apparatus 14 shown in FIG. Using a resist pattern as a mask, reactive ion etching (RIE) is performed.
) to perform etching. This substrate is then transferred to the heating device 15 via the post-processing chamber.

The heating device 15 is heated at 60°C on a hot plate at 180°C.
After hot air treatment for seconds, residual Cj! remove. This hot air treatment step reduces residual C to about 1i4.

Subsequently, a water washing process is performed in the water washing device 16.

First, the ultrapure water introduced from the ultrapure water introduction pipe 37, together with the hydrogen gas introduced from the hydrogen gas introduction pipe 36, is transferred to a catalyst resin packed tower 40 filled with a catalyst 39 for deoxidizing treatment. guided by.

Here, due to the action of the catalyst, the oxygen in the ultrapure water reacts with hydrogen,
Since it becomes water as shown in the formula below, deoxidation can be performed.

H2+1/202→H20 (Formula) This reaction proceeds quantitatively, and if 1 ppm of H2 is added to H20 containing 8 ppm of dissolved oxygen, almost all dissolved oxygen can be removed. Using this device, dissolved O2 can be reduced to 20 ppm or less even in low-temperature water, which is mechanically and chemically difficult, and the device is easy to operate.

The ultrapure water 38 deoxidized in the catalytic resin packed tower 40 in this manner is introduced into the washing container 32 through the introduction pipe 35 and washes the substrate 33 to be processed which is being rotated under suction by the spinner 34 .

As a result, the substrate to be processed is simultaneously washed with water and dried.

In this way, the residual C, which was reduced to about 1i4 by the hot air treatment, is further reduced to about 1i16.

According to this method, since it is washed with deoxidized water, it is not oxidized during washing, making it possible to form a good wiring pattern.

In the above embodiments, a method using a catalyst for removing dissolved oxygen has been described, but a chemical method using sodium sulfite or hydrazine as a reducing agent may also be used. Sodium sulfite is cheap, easy to handle, and reacts quickly, but its disadvantage is that it is low in oxygen lppm.
In addition, since it is non-volatile, it causes an increase in solid salt content in the water.

On the other hand, hydrazine is volatile, and while it is effective to add twice the amount of dissolved oxygen, the degassing rate is lower than the former, and if ammonia, a decomposition product of hydrazine, is in excess, the condensate Care must be taken against ammonia attack on organs.

In addition, as a mechanical removal method, there is a method of removing dissolved oxygen in water by heating or vacuum operation.

This method utilizes the fact that the solubility of dissolved gas is O at the boiling point of water. In this method, water is heated with steam and degassed under pressure, but 0.00
Dissolved oxygen can be reduced to 7 ppm or less. However, this method requires a degree of vacuum, and sufficient degassing may not be possible because a sufficient degree of vacuum cannot be obtained due to air leakage at flanges, welded joints, etc.

Further, as shown in FIG. 3, the washing device 16 using this deoxidized water may be used as an ashing device for resist stripping.

Example 2 Next, an embodiment of w42 of the present invention will be described.

FIG. 4 is a diagram showing a schematic configuration of a semiconductor manufacturing apparatus used in the method of the embodiment of the present invention.

This device consists of a light-shielding chamber 2 configured to block external light.
01 includes an RIE device 202 for etching a substrate to be processed and a resist stripping device 205. In the light-shielding chamber, the wafer 204 is stored in a transport box 203 and transported. The light from the lighting means is guided into the light-shielding room through a filter 206 that blocks light of 300 to 400 nm. The wavelength characteristics of the light from this illumination means are shown by solid lines in FIG.
Indicated by dotted lines in the figure.

AJ! for wiring using this device! When creating a DRAM using the 5i-Cu alloy, the decrease in yield due to corrosion could be reduced by more than 30% compared to the conventional case in which the light-shielding chamber was not shielded from light.

Alternatively, the filter 206 may be removed, the light from the illumination means may be directly irradiated, and the transport box 203 may be covered with a similar filter. Conventionally, this transportation box has been formed using Teflon-based materials, and has a
The transmittance of light in the wavelength range of 4000 nm was about 10%, but here we mixed dye into the same Teflon material and increased the transmittance of light in the wavelength range of 300 to 400 nm to 1%.
The following was used. Similarly, in this case, 30%
The above also made it possible to reduce the decrease in yield due to corrosion.

Note that the resist stripping device 20 is connected to the etching device 202.
The material of the box for transportation to the container 5 is not limited to Teflon, but may be any material that blocks light, such as metals such as Al and SuS.

Also, Aj! A box that transmits light! It may also have a double structure wrapped in a material that does not transmit light.

Implementation PI 3 Next, a third embodiment of the present invention will be described.

FIG. 6 is a diagram showing a schematic configuration of a semiconductor manufacturing apparatus used in the method of the embodiment of the present invention.

This device includes, in a container 210, an RIE device 211 for pattern etching a substrate to be processed on which an AJ1 alloy film is formed, and a RIE device 211 for removing halogen etc. attached to the surface of the pattern after etching. A water washing device 217 is provided for the RIE device, and a light shielding device 219 is installed along the wafer transport path from the exit of the RIE device to the exit of the water washing device 217. .

212 is a load chamber, 213 is an unload chamber, and valves 214a to 214a are provided between these chambers, respectively.
214d is provided, and by opening and closing these, the RIE apparatus is prevented from being exposed to the atmosphere when loading and unloading wafers.

Reference numerals 218 and 218' denote wafer cassette chambers in which wafers are stored and from which wafers can be transferred as needed.

By using this device in a DRAM manufacturing line, it was possible to improve the manufacturing yield by more than 10%.

Note that in this apparatus, a light shielding device is installed from the exit of the RIE apparatus, but the entire container 210 may be surrounded by a light shielding device. In addition, in this case, 300~
Either install a light source that does not include a wavelength component of 400 ns, or
By arranging a window through which light with a wavelength other than 300 to 400 rv is projected from the outside, it is possible to observe the inside of the apparatus during processing.

Yet again, Aj! It has been found that when an alloy wiring pattern contains Cu, a highly reliable wiring pattern that does not cause corrosion can be obtained by regulating the weight ratio of Cu within a certain range.

That is, a thermal oxide film with a thickness of 8,000 yen is formed on silicon, and AJ! 8000 Aj as an alloy!
-3i (1%) with Cu added was formed by sputtering, and then a 1 μm line & space pattern (
Prepare a sample with a wiring length of 5 m), and
Stress migration test at 0℃ temperature increase (1%
We conducted an accelerated test for corrosion (defect period) and corrosion.

Stress migration test is performed using current density I
The test was carried out under the conditions of 10' Ac1-2. Further, an accelerated corrosion test was conducted by leaving the sample in an atmosphere at 30° C. and 100% temperature for 12 hours. Figure 12 shows the measurement results. From this result, stress migration is
When 0.1% or more is added, the time until 1% failure occurs is 1.0'hr, which is an order of magnitude longer than when it is more than that, and the reliability of the wiring is improved. And this C
Regarding the amount of u added, there is no change even if more than that is added.

In addition, when the amount of Cu added is less than 0.4%, the number of corrosion per chip is about 10, but it increases rapidly when the amount of added Cu exceeds 0.5%. The number of corrosion per chip is 100 or more, which is not practical.

In other words, as a wiring material, AJ! -Cu into 5i
The amount of addition is required to be 0.1 to 0.4%.

The cause of corrosion is Aj! -C by adding Cu to 5i
When u precipitates at grain boundaries, Aj! Corrosion reaction (AJ!→AJ!3'''13e-) due to the formation of a local battery between -Cu
This will promote When the precipitation of Cu at the grain boundaries was actually investigated using TEM-EDX with respect to the amount of Cu added, it was found that significant precipitation was observed when the amount of Cu added exceeded 0.5%.

Furthermore, when 2% of Cu is added, Cu precipitates not only at the grain boundaries but also within the crystal grains. However, adding less than 0.4% of Cu does not have a significant corrosion promoting effect.

In addition, in the first and second embodiments described above, when using AJ or alloy containing Cu, as described above, C
If the weight ratio of u is set to 0.1% to 0.4%, in addition to the above-mentioned examples, the properties of the material will improve, so due to the reciprocal effect, corrosion will be further reduced than in the above-mentioned examples. A highly reliable AJ1 alloy wiring pattern can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, since the washing process is performed using water with a reduced dissolved oxygen concentration, oxidation reactions can be suppressed, and corrosion during washing is prevented. It becomes possible to obtain a highly reliable metal wiring pattern.

Furthermore, according to the present invention, since the substrate to be processed on which the Al alloy pattern is formed is transported and stored in a state where light is blocked, it is possible to prevent corrosion and obtain a highly reliable semiconductor device. becomes.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a processing device according to a first embodiment of the present invention, FIG. 2 is an explanatory diagram of a washing device of the same device, and FIG. 3 is a diagram showing an example of application of the present invention to an ashing device. Fig. 4 shows the second embodiment of the present invention, Fig. 5 shows the wavelength characteristics of the illumination means, Fig. 6 shows the second embodiment of the invention, and Fig. 7 shows the corrosion resistance. Figure 8 is a diagram explaining the model, Figure 8 is a diagram showing a sample for conducting a corrosion occurrence experiment, Figure 9 is a diagram showing the results of a corrosion occurrence experiment using the same sample, Figures 10 and 11 are irradiation light A diagram showing the wavelength of and the occurrence status of corrosion,
FIG. 12 is a characteristic diagram showing the 1% failure occurrence time and the number of corrosions per chip when the Cu content in the Al alloy is varied. 11... Pretreatment chamber, 12... Etching chamber, 13.
... Post-processing chamber, 14... RIE device, 15... Heating device, 16... Water washing device, 32... Water washing container, 34
...Spinner, 35...Deoxidized water introduction pipe, 36...
・Hydrogen gas introduction pipe, 37... Ultrapure water introduction pipe, 38...
- Deoxygenated water, 39..., catalyst, 40...catalyst resin packed tower, 101...p type silicon, 102...r+ type silicon, 103...n medium scattering layer, 104...p Medium scattering layer, 105...Silicon oxide layer, 107...Light, 20
1... Light-shielding room, 202... RIE device, 203...
Box, 204... Ueno 1205... Resist stripping device, 206... Filter. 1% p″A 1% When illuminated with light Fig. 9 Transmittance (%) Fig. 12 Fig. 11

Claims (6)

[Claims] (1) A surface treatment method comprising a washing step of exposing a substrate to be treated on which an Al alloy wiring pattern is formed to deoxidized water. (2) Surface treatment characterized by comprising an etching chamber for processing an Al alloy film on a substrate to be treated using a reactive gas, and a post-treatment chamber for exposing the processed substrate to deoxidized water. Device. (3) The surface treatment apparatus according to claim (2), wherein the post-treatment chamber includes a washing container and means for supplying ultrapure water containing hydrogen gas into the washing container. . (4) A surface treatment method characterized in that a substrate to be treated on which an Al alloy wiring pattern is formed is held in a light-shielded state. (5) The state where the light is blocked is 300 to 400 nm.
Claim (4) characterized in that the state is such that the light of
) surface treatment method described. (6) The surface treatment method according to claim (4), wherein the Al alloy contains copper, and the weight ratio of the Cu is 0.1 to 0.4%.