JP2002050606A - Substrate rinse liquid and substrate treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide substrate rinse liquid which restrains attaching of metals during ultra-pure water rinse of a substrate, where a metallic wiring is formed, and to provide a substrate washing treatment method for restraining attaching of the metals. SOLUTION: The substrate rinse liquid consists of ultra-pure water, comprising chelating agent of free acid or ammonium salt at 100 mg/L or less. After a treatment including a process for making chemical or abrasive liquid function is performed for the surface of a substrate, the substrate is rotated and rinse treatment for removing chemical or contaminant from the surface is applied by means of substrate rinse liquid consisting of ultra-pure water comprising chelating agent of free acid or ammonium salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate rinsing and a substrate processing method used for cleaning a substrate such as a semiconductor substrate.

[0002]

2. Description of the Related Art Contamination by metal impurities seriously degrades electrical characteristics of a semiconductor device. Therefore, various types of cleaning are performed to remove contaminants attached to the semiconductor substrate. Cleaning is performed with acid and acid as represented by RCA cleaning.
It uses an alkaline chemical and an oxidizing agent, and is always followed by a chemical treatment step, followed by a rinse step with ultrapure water to wash off the chemical. If there is a contaminant in the ultrapure water for rinsing, the contaminant adheres to the surface of the semiconductor substrate, so that the purity requirement of the ultrapure water is higher.

[0003] However, since ultrapure water contains few impurities, it has a strong power to dissolve the material that is in contact with the ultrapure water, so that the silicon wafer has a Si mark called a water mark during drying after cleaning and rinsing. The dry residue of the melt is also generated because the ultrapure water dissolves the silicon wafer surface.

Some oxide films and nitride films are very difficult to dissolve. However, if a metal wiring material is formed and processed on a substrate, it may be washed immediately after that step or before the next step. During rinsing following chemical treatment in the cleaning, metal dissolution has occurred. Therefore, a large amount of rinsing water is used, and the rinsing water is largely diluted to reduce the probability of adhesion to the substrate. Also,
Metals such as aluminum (Al) and tungsten (W) are often used for wiring, but at the current device level (integration level), there is no problem even if they are slightly attached.

In recent years, however, copper (Cu), which is a material having low electric resistance, has begun to be used in order to achieve higher performance (higher integration) of devices. Because copper mixes with many of the materials that make up the device, care must be taken to prevent copper from diffusing into the material. The reason why copper adheres to the edge and the back surface of the substrate is severe because it is feared that the copper may move to the adjacent active region and reduce the yield or contaminate the substrate transfer system. .
Therefore, after a copper-related step, for example, a step of filling a patterned trench with copper plating or a step of removing excess copper remaining in portions other than the trench portion by chemical mechanical polishing (CMP), only the substrate surface is removed. Not the edge of the board,
Cleaning of the back surface will also be performed.

[0006] Since copper is exposed on the surface of the substrate, even if the substrate is thoroughly washed with a cleaning chemical, copper is eluted from the copper portion when rinsing with ultrapure water, and other portions and edges (barriers) are removed. Film, substrate silicon, etc.) and back surface (oxide film, nitride film,
Substrate silicon etc.) After CMP, materials (oxide film (low-k film in future),
The present inventors have confirmed that copper adheres to the barrier film and the like. In particular, Ta, TaN, Ti,
It has been found that it easily adheres to a barrier film made of TiN and silicon.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made in view of the above. A substrate rinsing liquid and a metal rinsing liquid for suppressing metal adhesion during ultrapure water rinsing of a substrate on which metal wiring is formed are described. It is an object of the present invention to provide a method of cleaning a substrate.

[0008]

According to a first aspect of the present invention, there is provided a substrate comprising ultrapure water containing a free acid or ammonium salt chelating agent of 100 mg / L or less. In the rinsing solution.

According to a second aspect of the present invention, after performing a process including a step of applying a chemical solution or an abrasive solution to the surface of the substrate,
The substrate processing method is characterized in that the substrate is rotated and a rinsing process for removing a chemical solution and contamination from the surface thereof is performed using a substrate rinsing solution composed of ultrapure water containing a chelating agent of a free acid or an ammonium salt.

According to a third aspect of the present invention, in the substrate processing method according to the second aspect, the chemical solution contains at least one of an acid and an oxidizing agent.

According to a fourth aspect of the present invention, in the step of polishing by supplying an abrasive liquid to the surface of the substrate and then supplying and polishing ultrapure water, the chelating agent of free acid or ammonium salt is added to the ultrapure water. And polishing the substrate in the presence of.

According to a fifth aspect of the present invention, there is provided at least one of a step of supplying an abrasive liquid to the surface of the substrate for polishing, and a step of supplying ultrapure water to the substrate after polishing for cleaning. In a substrate surface treatment method in which a substrate surface is wetted with ultrapure water so that the substrate is not dried, at least one of ultrapure water for cleaning and ultrapure water for drying prevention contains a chelating agent of a free acid or an ammonium salt. It is characterized by.

[0013] If metal impurities are contained in the liquid in contact with the substrate, they adhere to the substrate. In the case of an acid-based cleaning chemical, the pH and oxidation-reduction potential are controlled to make it difficult for the removed metal contamination to adhere to the substrate. However, it has been found that when the metal material is exposed on the surface in the subsequent ultrapure water rinsing, the metal is eluted from the metal material into the rinsing water, thereby causing metal contamination on the substrate.
Also in the CMP process, the polishing liquid controls the chemical properties to make it difficult for metal contamination to re-adhere to the substrate.

However, after polishing with a polishing liquid, polishing may be performed using ultrapure water in order to roughly remove the polishing liquid. At that time, the metal is eluted from the metal material into water in the same manner as in the cleaning step. However, there is a possibility that metal contamination may occur on the substrate. Even when the polishing using ultrapure water is omitted, cleaning using ultrapure water or transportation in a state of being wet with ultrapure water is performed to remove abrasive grains, during which metal is removed. The substrate keeps in contact with the eluted water, and the metal adheres to the substrate.

[0015] However, the inventors of the present patent application have:
It has been found that even when a metal is eluted in ultrapure water, metal contamination to the substrate is suppressed by adding a chelating agent of 100 mg / L or less. The invention of claim 1 provides a substrate rinsing liquid that can suppress metal contamination on the substrate even when the metal is eluted in ultrapure water.

According to the second and third aspects of the present invention, after performing a process including a step of applying a chemical solution or an abrasive solution to the surface of the substrate, the substrate is rotated to remove the chemical solution and contamination from the surface. Since the rinsing treatment for removal is performed with a substrate rinsing liquid composed of ultrapure water containing a chelating agent of a free acid or an ammonium salt, metal contamination of the substrate can be suppressed.

According to the fourth aspect of the invention, in the step of supplying the polishing liquid to the surface of the substrate and polishing the substrate, and then supplying and polishing the ultrapure water, the free acid or ammonia is added to the ultrapure water. Since the substrate is polished in the presence of a salt chelating agent, metal contamination of the substrate can be suppressed as described above.

According to the fifth aspect of the present invention, since the substrate rinsing liquid containing a chelating agent of a free acid or an ammonium salt is used in the ultrapure water for cleaning and the ultrapure water for drying prevention, the same as above. In addition, metal contamination of the substrate can be suppressed.

[0019]

Embodiments of the present invention will be described below. Regarding metal contamination of the substrate, 10
^It must be less than ¹¹ atoms / cm ² . However, for example, when the substrate on which copper (Cu) is exposed is washed, copper is eluted during rinsing with ultrapure water, and the concentration of copper in the rinsing water in contact with the surface is on the order of several to several hundred μg / L. As can be seen from Comparative Example 2 described below, when this water comes into contact with the silicon of the substrate, the surface Cu concentration causes contamination of 10 ¹¹ to 10 ¹³ atoms / cm ² . The present invention is a substrate rinsing liquid that causes metal ions dissolved in rinsing water to react with a chelating agent preferentially rather than adhering to the substrate surface, thereby suppressing adhesion to the substrate.

As the chelating agent used in the substrate rinsing liquid according to the present invention, an aminocarboxylic acid type chelating agent and an oxycarboxylic acid type chelating agent are preferable, and a phosphonic acid type chelating agent which causes phosphorus contamination is not preferable. Aminocarboxylic acid type chelating agents include ethylenediaminetetraacetic acid (EDT).
A), compounds such as nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), and triethylenetetraminehexaacetic acid (TTHA). However, since these alkali metal salts such as sodium (Na) cause contamination of the alkali metal, it is preferable to use a free acid or an ammonium salt.

As the oxycarboxylic acid type chelating agent,
Examples thereof include citric acid, tartaric acid, gluconic acid, hydroxyacetic acid, and oxalic acid. Also in these, it is preferable to use a free acid or an ammonium salt. These chelating agents in the present invention may be used alone or as a mixture of two or more.

When the chelating agent is added to the ultrapure water for rinsing, the metal ions eluted into the rinsing water and the chelating agent generate a chelating compound and consume the metal ions, so that the reaction proceeds in the direction of metal dissolution. Therefore, when the amount of the chelating agent is too large, the absolute amount of the metal eluted from the metal material is rather increased and the amount of contamination is increased. Therefore, the content of the chelating agent is preferably 0.001 to 100 in rinse water.
mg / L, more preferably 0.01 to 10 mg / L.
mg / L. If the amount is less than this range, the effect as a chelating agent cannot be expected so much, which is not preferable.

Although the dipping process of dipping in a rinsing liquid has an effect, the same effect can be obtained by a method of showering. In addition, the rotary single wafer cleaning method can provide a fresh rinse solution and can be rinsed with a shorter rinse time than the dipping method, resulting in lower contamination levels. Further, if the substrate is continuously rotated at a high speed and spin-dried, the chelating agent can be blown off with the centrifugal force, so that the residual amount of the chelating agent becomes small and the organic contamination can be reduced to a low contamination level.

In the post-CMP phase of the substrate, when aluminum (Al) or copper (Cu) is exposed, the presence of a chelating agent in ultra-pure water for water polishing, washing, and drying prevents metal Pollution can be suppressed.

In the present invention, the method for causing the chelating agent to be present in ultrapure water is not particularly limited. It may be dissolved in ultrapure water in advance, or a high concentration chelate aqueous solution and ultrapure water may be mixed to a predetermined concentration just before being supplied.

Hereinafter, examples of the substrate processing method according to the present invention and comparative examples will be described. Incidentally, the substrate processing method of the present invention,
The present invention is not limited to these embodiments.

Example 1 A silicon oxide film layer as a first layer, a barrier layer (TaN film) as a second layer, and a seed layer (Cu film) as a third layer on the surface.
Was prepared, and a copper (Cu) plating film was formed on the entire surface of the silicon substrate from the edge 2 mm at the center side. Since the seed layer and the copper plating film layer remaining at the edge move to the adjacent active region to lower the yield or contaminate the substrate transfer mechanism, there is a concern.
In the rotary substrate processing apparatus shown in FIG.
In a range B of 0 mm, an acid and a hydrogen peroxide solution were supplied from the chemical supply nozzle 5, and as shown in FIG. 4, the copper plating film layer 6 and the third seed layer were removed by etching.

In FIG. 3, reference numeral 1 denotes a substrate holding and rotating mechanism which rotates while holding the substrate Wf. The substrate Wf is held by a plurality of holding members 2 and rotates in the direction shown by arrow A. Reference numeral 3 denotes a rinsing liquid supply nozzle, 4 denotes a chemical liquid supply nozzle, and 5 denotes a chemical liquid supply nozzle. As described above, an acid and hydrogen peroxide solution are supplied from the chemical solution supply nozzle 5 to etch away the copper plating film layer 6 having a 10 mm edge of the substrate Wf and the third seed layer. Ultrapure water containing 1 mg / L of EDTA ammonium salt was supplied from the rinsing liquid supply nozzle 3 to rinse off water, rinsed, and spin-dried. The result of quantitative analysis of the concentration of copper adsorbed on the TaN film which is the second barrier layer exposed after the edge etching removal is shown in Example 1 of FIG. As shown, the amount of copper (Cu) deposited was 2 × 10 ¹⁰ atoms / cm ² .

COMPARATIVE EXAMPLE 1 As in Example 1, a copper plating film was formed on the entire surface on the center side from an edge of 2 mm on an 8-inch silicon substrate on which a first layer, a second layer, and a third layer were sequentially formed on the surface. The substrate Wf thus prepared is prepared, and an acid and hydrogen peroxide solution are supplied from the chemical supply nozzle 5 by the rotary substrate processing apparatus shown in FIG. 3, and as shown in FIG. And the third seed layer was removed by etching. Then subsequently rinsed by supplying ultrapure water containing EDTA ammonium salt ^{10 0, 10 1, 10 2} , 10 3, 10 4 mg / L from the rinsing liquid supply nozzle 4, and spin-dried. FIG. 2 shows the results of quantitative analysis of the concentration of copper attached on the TaN film, which is a barrier layer exposed after the edge etching removal.

Comparative Example 2 In the same manner as in Example 1, a copper plating film was formed on one surface of the central side from an edge of 2 mm on an 8-inch silicon substrate on which a first layer, a second layer, and a third layer were sequentially formed on the surface. The prepared substrate Wf is prepared, and an acid and hydrogen peroxide solution are supplied from the chemical solution supply nozzle 5 by the rotary substrate processing apparatus of FIG. 3, and as shown in FIG. Layer 6 and the third seed layer were etched away. Thereafter, ultrapure water containing no chelating agent was subsequently supplied from the rinsing liquid supply nozzle 3 for rinsing and spin drying. The result of quantitative analysis of the concentration of copper adsorbed on the TaN film as the barrier layer exposed after the edge etching removal is shown in Comparative Example 2 in FIG. As shown, the amount of copper (Cu) deposited was 3 × 10 ¹⁴ atoms / cm ² .

As shown in FIG. 1, the chelating agent added in Example 1 exhibited a remarkable effect of preventing copper adhesion as compared with Comparative Example 2, and the copper contamination amount at the edge of the substrate Wf was 10 ¹¹ atoms / cm 2. cm
It can be suppressed to less than ² . In addition, from the results of the quantitative analysis of copper concentration in Comparative Example 1 shown in FIG.
It turns out that it is 0 mg / L or less.

Example 2 In the same manner as in Example 1, a copper plating film was formed on an 8-inch silicon substrate having a first layer, a second layer, and a third layer formed on the surface, on the entire central side from an edge of 2 mm. The copper plating film layer and the seed layer were removed by etching using an acid and hydrogen peroxide solution in a range B having an edge of 10 mm. A silicon substrate was used for the back surface.
The substrate is placed in a CMP apparatus 15 in a polishing chamber 11 having a configuration shown in FIG.
Then, the substrate was washed in the washing tank 12 and rinsed with ultrapure water containing 0.1 mg / L of citric acid in the transfer chamber 13 during the transfer to the washing tank 14. Further, the substrate was washed in the washing tank 14, washed and spin-dried, and the concentration of copper adsorbed on the back surface was quantitatively analyzed. As a result, the contamination amount was less than 10 ¹¹ atoms / cm ² .

The CMP apparatus 15 in the polishing chamber 11 includes a polishing table 16 and a top ring 17. The substrate Wf held by the rotating top ring 17 is pressed against the polishing surface of the rotating polishing table 16, and the polishing liquid is Nozzle 18
The polishing liquid is supplied from the substrate and polished.

As shown in FIG. 6, the cleaning mechanism of the cleaning tank 12 is a roll sponge type cleaning mechanism having a pair of roll sponges 21 and 22, and a rotating substrate Wf sandwiched between a plurality of rotating spindles 23. Roll sponges 21, 2 rotated by rotation drive mechanisms 24, 25
Then, ultrapure water containing 0.1 mg / L of citric acid was supplied from the cleaning liquid nozzle 26 to the upper and lower surfaces of the substrate for cleaning. Although not shown, the cleaning liquid nozzle 26 is also disposed below so as to supply cleaning water to the lower surface of the substrate Wf.

The cleaning mechanism for the cleaning tank 14 is a pencil type cleaning mechanism having a cleaning member 29 at the lower end of a rotating shaft 28 which is attached immediately below the tip of a swing arm 27 and rotates as shown in FIG. The cleaning member 29 is pressed against the upper surface of the rotating substrate Wf held and rotated by the holding / rotating mechanism 1, and the substrate Wf is rotated.
0.1 mg of citric acid from the cleaning liquid nozzle 31 on the upper surface of f
/ L to supply ultrapure water for cleaning.

Embodiment 3 As shown in FIG. 8, 20-m
20 square mm copper damascene pattern 30 with m square
A silicon substrate formed apart from the above is used. This substrate W
f by the CMP apparatus 15 having the configuration shown in FIG.
After polishing while supplying an abrasive liquid (slurry) from, ultrapure water containing 1 mg / L of citric acid was supplied from an ultrapure water supply nozzle 19 to perform water polishing. Subsequently, the substrate Wf is cleaned while supplying ultrapure water containing citric acid from the cleaning liquid nozzle 26 to both surfaces thereof by a roll sponge type cleaning mechanism shown in FIG. 6, and spin-dried (the substrate holding and rotating mechanism 1 as shown in FIG. 3). Substrate W
f, spin at high speed and dry). Damascene pattern 3
Quantitative analysis of the concentration of copper adsorbed on the silicon surface exposed at intervals of 0 revealed that the amount of contamination was less than 10 ¹¹ atoms / cm ² .

COMPARATIVE EXAMPLE 3 As shown in FIG. 8, a silicon substrate in which a copper damascene pattern 30 of 20 mm square is formed at five locations in a plane of an 8-inch silicon substrate Wf with a spacing of 20 mm or more is used. A CMP apparatus 1 having the configuration shown in FIG.
In 5, polishing was performed while supplying a polishing liquid (slurry) from the polishing liquid nozzle 18, and then ultrapure water containing no chelating agent was supplied from the ultrapure water supply nozzle 19 to perform water polishing. Subsequently, the substrate Wf was cleaned while supplying ultrapure water containing citric acid from the cleaning liquid nozzle 26 to both surfaces thereof by a roll sponge type cleaning mechanism shown in FIG. 6, and spin-dried. When the concentration of copper adsorbed on the silicon surface exposed at the intervals of the damascene pattern 30 was quantitatively analyzed, the amount of contamination was 10 ¹¹ to 10 ¹³ atoms / cm ^{2 or} less.

[0038]

As described above, according to the invention described in each claim, the following excellent effects can be obtained.

According to the first aspect of the present invention, 10
Since a chelating agent of free acid or ammonium salt of 0 mg / L or less is contained, even if a metal is eluted in ultrapure water, the eluted metal ion preferentially reacts with the chelating agent to produce a chelating agent compound. A substrate rinsing liquid that can suppress metal contamination on the substrate.

According to the second and third aspects of the present invention, after performing a process including a step of applying a chemical solution or an abrasive solution to the surface of the substrate, the substrate is rotated to remove the chemical solution and contamination from the surface. Since the rinsing treatment for removal is performed using a substrate rinsing liquid composed of ultrapure water containing a chelating agent of a free acid or ammonium salt, metal contamination of the substrate can be suppressed for the same reason as described above.

According to the fourth aspect of the present invention, after the polishing is performed by supplying the abrasive liquid to the surface of the substrate and then polishing by supplying the ultrapure water, the free acid or ammonia is added to the ultrapure water. Since the substrate is polished in the presence of a salt chelating agent, metal contamination of the substrate can be suppressed as described above.

According to the fifth aspect of the present invention, a substrate rinsing liquid containing a chelating agent of a free acid or an ammonium salt is used in ultrapure water for cleaning and ultrapure water for drying prevention. In addition, metal contamination of the substrate can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing the amounts of copper (Cu) deposited in Example 1 and Comparative Example 2 by a substrate processing method according to the present invention.

FIG. 2 is a diagram showing the chelate concentration in ultrapure water and the amount of copper (Cu) attached.

FIG. 3 is a diagram illustrating a configuration example of a rotating substrate processing apparatus.

FIG. 4 is a view showing an example of a silicon substrate used in the substrate processing method according to the present invention.

FIG. 5 is a diagram showing a configuration example of a substrate processing apparatus used in the substrate processing method according to the present invention.

FIG. 6 is a diagram illustrating a configuration example of a roll sponge-type cleaning mechanism.

FIG. 7 is a diagram illustrating a configuration example of a pencil-type cleaning mechanism.

FIG. 8 is a diagram showing a configuration example of a substrate processing apparatus used in the substrate processing method according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 substrate holding and rotating mechanism 2 holding member 3 rinse liquid supply nozzle 4 chemical liquid supply nozzle 5 chemical liquid supply nozzle 6 copper (Cu) plating film layer 11 polishing chamber 12 cleaning tank 13 transfer chamber 14 cleaning tank 15 CMP device 16 polishing table 17 top ring Reference Signs List 18 polishing liquid nozzle 19 ultrapure water supply nozzle 21 roll sponge 22 roll sponge 23 spindle 24 rotation drive mechanism 25 rotation drive mechanism 26 cleaning liquid nozzle 27 swing arm 28 rotation axis 29 cleaning member 30 damascene pattern 31 cleaning liquid nozzle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B24B 57/02 B24B 57/02 C11D 7/26 C11D 7/26 7/32 7/32 7/60 7 / 60 (72) Inventor Ichiro Katabebe 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Corporation (72) Inventor Sachiko Kihara 11-1 Asahi-cho Haneda, Ota-ku, Tokyo Inside Ebara Corporation F Terms (reference) 3C047 FF08 GG15 3C058 AA07 CA01 CB01 DA12 4H003 DA15 EB08 EB13 EB16 ED02 FA07 FA21

Claims (5)

[Claims] 1. A substrate rinsing liquid comprising ultrapure water containing a free acid or ammonium salt chelating agent of 100 mg / L or less. 2. A free acid or ammonium salt chelating agent which is subjected to a treatment including a step of applying a chemical solution or an abrasive solution to the surface of a substrate and then rinsing the substrate to remove the chemical solution and contamination from the surface. A substrate rinsing liquid made of ultrapure water containing: 3. The substrate processing method according to claim 2, wherein the chemical solution contains at least one of an acid and an oxidizing agent. 4. A step of supplying a polishing liquid to the surface of the substrate and polishing the substrate, and then polishing the substrate by supplying a chelating agent of a free acid or an ammonium salt to the ultrapure water in the step of supplying and polishing ultrapure water. A substrate processing method. 5. The method includes at least one of a step of supplying a polishing liquid to a surface of a substrate to polish the substrate and a step of supplying ultrapure water to the substrate after polishing to clean the substrate. A substrate surface treatment method in which a substrate surface is wetted with ultrapure water, wherein at least one of ultrapure water for cleaning and ultrapure water for drying prevention contains a chelating agent of a free acid or an ammonium salt. .