JP2000297395A - Barrel plating method for electronic parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To embed the micro vias and trenches formed on a wafer without the occurrence of defects such as void, seam or the like by incorporating an organic bivalent sulfur compound and a quaternary ammonium salt adduct consisting of ternary alkyl amine and polyepichlorhydrin respectively at specific ratios into a plating liquid. SOLUTION: The organic bivalent sulfur compound is incorporated at 1 to 300 μmol/l and the quaternary ammonium salt adduct consisting of the ternary alkyl amine and the polyepichlorhydrin at 10 to 200 μmol/l into the acidic copper plating liquid for forming wiring on the semiconductor wafer. When the concentration of the organic bivalent sulfur compound is specified to y μmol/l and the concentration of the quaternary ammonium salt adduct to x μmol/l, the concentrations are preferably 0.86x+25<=y<=-0.86x+300 and 1<=y<=300, 10<=x<=200. A polyether compound and polyalkyl ethylenediimine are added at need into this copper electroplating liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic copper plating solution for forming copper wiring on a semiconductor wafer, and more particularly to a method for forming fine vias or trenches formed on a semiconductor wafer by removing defects such as voids and seams. The present invention relates to a suitable acidic copper electroplating solution that can be embedded without generating.

[0002]

2. Description of the Related Art In the processing of semiconductor wafers, aluminum has been mainly used as a wiring material in the past. However, as the degree of integration of wiring has increased, copper having higher electric conductivity has recently been used in place of aluminum. And it has been practiced to prevent an increase in signal delay time. As a method of forming a copper film on a wafer, a wet plating method from an aqueous solution is being used in addition to a dry method such as a CVD method and a sputtering method.

[0003] While the wet plating method is an electroless plating method and an electroplating method, since the liquid used in the electroless copper plating is highly alkaline, unsuitable environment for processing the semiconductor Na ^+, K ^There is a problem that alkali ions such as ⁺ remain in the plating film and cause contamination of the semiconductor device. In order to avoid such alkali ion content, it is conceivable to use a solution containing an ammonium hydroxide salt (for example, tetramethylammonium hydroxide) instead. However, the plating solution is expensive and the cost is significantly increased. There is a disadvantage that. In addition, since it is difficult to treat wastewater with complex compounds such as EDTA contained in the liquid, it can be said that there is no suitability for this use.

[0004] On the other hand, electroplating generally uses a solution based on an aqueous solution of sulfuric acid containing copper sulfate, and wastewater treatment is relatively easy. In addition, in order to form copper wiring on a semiconductor wafer, it is necessary to bury a fine via or trench. However, there is a problem that defects such as voids and seams are easily generated. There was a problem that no liquid was present.

[0005]

Cause contamination of the semiconductor device [0005] Na ^+, K ^+, such there is no substance such as alkali ions, an easy management and waste water treatment of the plating solution, is formed on a semiconductor wafer Burying fine vias or trenches without generating defects such as voids or seams, in particular, increasing the deposition rate of the recesses in the vias or trenches, and as the plating progresses, the protrusions near the entrance of the vias or trenches An object of the present invention is to obtain a suitable acidic copper electroplating solution capable of improving the characteristics of embedding in vias or trenches by slowing the deposition rate on the wafer surface and improving the overall average thickness of the wiring material.

[0006]

(1) It is characterized by containing 1 to 300 μmol / L of an organic divalent sulfur compound and 10 to 200 μmol / L of a quaternary ammonium salt adduct comprising a tertiary alkylamine and polyepichlorohydrin. Acidic copper electroplating solution for forming wiring on a semiconductor wafer to be formed, (2) organic divalent sulfur compound 10 to 200 μm
(3) an adduct of a quaternary ammonium salt comprising a tertiary alkylamine and polyepichlorohydrin;
(1) or (2), wherein (4) the concentration of the organic divalent sulfur compound is yμmol / L, and a tertiary alkylamine and polyepichlorohydrin are contained. When the concentration of the quaternary ammonium salt adduct consisting of x μmol / L is -0.86x + 25 ≦ y ≦ −0.86x + 300, and 1 ≦ y ≦ 300 and 10 ≦ x ≦ 200 An acidic copper electroplating solution for forming a wiring on a semiconductor wafer, wherein (5) 1 ≦ x ≦ 300 and 10 ≦ y ≦ 200. Acid copper electroplating solution of (6) polyether compound
An acidic copper electroplating solution according to any one of (1) to (5), which contains 1 to 50 μmol / L, and (7) a polyether compound, which contains 1 to 20 μmol / L. (6) the acidic copper electroplating solution described in (6), (8) polyalkylethyleneimine 0.1 to 7 µ
(1) to (7), characterized by containing mol / L.
(9) The acidic copper electroplating solution according to (8), which contains 0.5 to 4 μmol / L of polyalkylethyleneimine, and (10) copper sulfate. An acidic copper electroplating solution according to any one of (1) to (9), wherein the bath is a basic bath.

[0007]

DETAILED DESCRIPTION OF THE INVENTION Generally, semiconductors (such as silicon)
Via trenches are formed on the surface of the wafer for embedding copper wiring, and copper (Cu) is formed on the surface of the silicon (S).
i) titanium (Ti) to prevent diffusion to
A barrier metal selected from tantalum (Ta), tungsten (W) or a nitride thereof (nitride),
A film is formed to a thickness of about 0.01 to 0.1 μm by a known coating method such as vapor deposition, sputtering, and CVD. Then, a thin copper layer is formed on the barrier metal layer by a method such as vapor deposition, sputtering, or CVD in the same manner as described above. This is because the barrier metal layer generally has a large electric resistance, and the difference in current density between the periphery of the contact provided at the periphery of the wafer and the center in the electrolytic copper plating to be coated later becomes large. Copper having a small electric resistance is provided (thinly coated). This film thickness
About 0.01 to 0.1 μm is appropriate. This film thickness is arbitrarily set at the time of semiconductor processing and is not limited to the above numerical values.

[0008] The copper electroplating is carried out on the semiconductor wafer subjected to the above-mentioned treatment by using the copper electroplating solution of the present invention.
The electrolytic copper plating method is performed using, for example, a plating apparatus as shown in FIG. Semiconductor wafer 1 to be plated
And the anode 2 is placed in the electroplating tank 4 with the anode 2 facing each other. In FIG. 1, both are arranged horizontally with respect to the level of the electrolytic copper plating solution 3, but they may be arranged vertically. The semiconductor wafer 1 needs to be sealed so that the surface to be plated is left and the back surface is not exposed to the electroplating solution. It is necessary to provide a contact for power supply near the edge of the semiconductor wafer 1. The anode 2 is a phosphorous copper anode (P content 0.0
4 to 0.06%) or an insoluble anode is used. Pt, Pt-plated T
The use of i is appropriate. A commercially available dimensionally stable electrode (DSA) can also be used. In the case of using a phosphorus-containing copper anode, replenishment of the plated copper is automatically performed by dissolving the anode 2. However, since some sludge is generated when the anode 2 is dissolved, it is better to put the anode 2 in an anode bag made of polypropylene fiber or the like in order to prevent sludge from being mixed into the plating film. When an insoluble anode is used, the concentration of copper in the solution is reduced by plating, and it is necessary to supply a copper sulfate solution to maintain the concentration of copper.

A typical composition of the electrolytic copper plating solution of the present invention is as follows. Copper sulfate (as copper) 0.1-100 g / L (preferably 10-50 g / L); sulfuric acid 0.1-500 g / L (preferably 10-300)
g / L), chlorine 0.1 to 500 mg / L (preferably 30 to 10)
0 mg / L), 1 to 300 μmol / L of organic divalent sulfur compound (preferably 10 to 200 μmol / L), and 10 to 200 μmol / L of quaternary ammonium salt adduct composed of tertiary alkylamine and polyepichlorohydrin
(Preferably 15 to 100 μmol / L), and the balance: water. Further, if necessary, a polyether compound and a polyalkylethyleneimine are added within the above range.

[0010] The plating conditions are as follows.・ Current density: 0.1 to 100 A / dm ² (preferably 0.5 to 5 A / dm ² ) ・ Liquid temperature: 10 to 80 ° C. (preferably, 15 to 30 ° C.) Current density, liquid temperature, and liquid The flow velocity (relative velocity between the plating surface and the liquid bulk) has an interdependent relationship, and by providing an appropriate liquid flow velocity within the above range, the desired deposition rate and copper deposition (crystal state) ) Can be obtained. As a method of giving the flow rate of the solution, a method of rocking and rotating the wafer to be plated, a method of stirring the vicinity of the wafer with air, and the like can be used.

Further, in the present invention, the electric current applied in the electroplating is not only a direct current, but also a pulse current or a P current.
An R (periodic reverse) current can be used.
The pulse current is a current flowing within a certain time (on time) to precipitate copper, and then a pause within a certain time (off time) is caused by a shortage of copper ions near the electrode where the deposition reaction has occurred. This allows the on-time current density to be set higher than normal DC. On the other hand, in the PR current, copper precipitated within a certain time is dissolved by applying a reverse current for a certain time. As a result, it is possible to suppress deposition of a portion where current is likely to concentrate, such as a corner portion of the trench. These can usually produce precipitates that cannot be obtained by direct current.

As a pretreatment for applying electrolytic copper plating to a semiconductor wafer, a usual acid immersion or the like is used. Dilute sulfuric acid is suitable as the acid, and its concentration is suitably 0.1 to 50% (preferably 1 to 10%). However, this preprocessing does not necessarily have to be performed, and is set as appropriate according to conditions. The electrolytic copper plating solution of the present invention contains an organic divalent sulfur compound. As the organic divalent sulfur compound, for example, disodium bissulfo disulfide, disodium bis (1-sulfomethyl) disodium, disodium bis (2-sulfoethyl) disulfide, bis (3-sulfoethyl) disulphide
Sulfopropyl) disodium, bis (4-sulfobutyl) disodium disulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide and the like can be used.

[0013] In the initial stage of electroplating, they are uniformly adsorbed on the entire surface without depending on the location of the plating surface to promote the reaction. However, as the reaction proceeds, the adsorption density of the concave portion in the via trench increases, and as a result, the deposition rate in that portion increases. Conversely, the adsorption density of the convex portion near the entrance of the via / trench decreases, and as a result, the deposition rate at that portion decreases. As described above, the electrolytic copper plating solution of the present invention containing the organic divalent sulfur compound has a remarkable effect on uniforming the thickness of the deposited film.

The amount of the organic divalent sulfur compound is 1 to 300 μm
ol / L. If the amount is less than 1 μmol / L, the above effect is not obtained. If the amount exceeds 300 μmol / L, there is a problem that the filling characteristics of the fine via / trench deteriorate. A more preferred range is from 10 to 200 μmol / L. Furthermore, the concentration of these organic sulfur compounds can be measured by an electrochemical test method (CVS) or high-performance liquid chromatography (HPLC), and is characterized by easy management.

The electrolytic copper plating solution of the present invention contains a quaternary ammonium salt adduct comprising a tertiary alkylamine and polyepichlorohydrin. This material, like the polyether compound, effectively suppresses the deposition of copper on the wafer surface. The amount of the quaternary ammonium salt adduct is 1
0 to 200 μmol / L. If the content is less than 10 μmol / L, there is no effect of inclusion, and if it is more than 200 μmol / L, there arises a problem that the filling characteristics of the fine via / trench deteriorate. A more preferred range is 15 to 1.
00 μmol / L.

Furthermore, while suppressing the deposition of copper on the wafer surface, the deposition rate of the convex portion near the entrance of the via trench and the wafer surface is reduced, and the deposition rate of the concave portion in the via trench is increased. Therefore, in order to form a uniform wiring film, the concentration of the organic divalent sulfur compound is set to yμ
mol / L, and the concentration of the quaternary ammonium salt adduct composed of tertiary alkylamine and polyepichlorohydrin is x
-0.86x + 25 ≦ y ≦-when μmol / L
0.86x + 300 and 1 ≦ y ≦ 300,10
It is more effective that ≦ x ≦ 200. This is shown in FIG. The valid range is the range of the shadow in FIG.

If necessary, a polyether compound can be added as described above. As the polyether compound, for example, polyethylene glycol (molecular weight 100 to 50,000), polypropylene glycol (molecular weight 100 to 50,000) and the like can be used. These components preferentially adsorb to the surface of the wafer with vias or trenches (portions other than vias and trenches) during electroplating, thereby suppressing the deposition of copper on the surface. The addition amount of the polyether compound is 0.1 to 50 μmo.
1 / L is appropriate. If it is less than 0.1 μmol / L, there is no effect of addition, and if it exceeds 50 μmol / L, the filling characteristics of the fine via / trench deteriorate, which is not preferable.
A more preferred range is 1 to 20 μmol / L.

The electrolytic copper plating solution may contain a polyalkylethyleneimine. This substance, like the polyether compound, suppresses the deposition of copper on the wafer surface. An appropriate amount of the polyalkylethyleneimine is 0.1 to 7 μmol / L. 0.1μ
When the amount is less than mol / L, the effect of addition is
If it exceeds ol / L, the filling characteristics of the fine via / trench deteriorate, which is not preferable. A more preferred range is 0.
5 to 4 μmol / L. The polyether compound and the polyalkylethyleneimine are not necessarily contained in the plating solution when the concentration of the organic divalent sulfur compound and the quaternary ammonium salt adduct composed of the tertiary alkylamine and polyepichlorohydrin is in a particularly optimal range. It is not necessary to be included as a component, but when it is contained in the above concentration range, the effect on the filling property of the fine via / trench is further stabilized.

By adding an additive in which the above-mentioned respective component concentrations are combined in an appropriate range in the electrolytic copper plating solution,
When electrolytic copper plating is performed on a semiconductor wafer having fine vias and trenches, the deposition rate of copper can be changed depending on the location. That is, the deposition rate of the concave portion in the via trench is particularly increased, and the deposition rate of the convex portion near the entrance of the via trench and the wafer surface is reduced, thereby significantly improving the filling characteristics in the via trench. Can be. The thickness of the electrolytic copper plating by the method of the present invention may be such that the vias and trenches on the surface of the semiconductor wafer are filled, and the wiring can be formed by flattening by chemical mechanical polishing (CMP) which is a subsequent step. Generally, it is 0.5 to 2 μm, but it is not limited to this range and can be set arbitrarily.

[0020]

Examples and Comparative Examples Next, examples and comparative examples of the present invention will be described. The present embodiment is a preferred example, and does not limit the present invention. The present invention naturally includes modifications and other examples included in the scope of the technical idea. The copper plating solution shown in the following Table 1 was prepared and subjected to electrolytic copper plating.

[0021]

[Table 1]

As a material to be plated, a silicon wafer having a fine via pattern is coated with titanium nitride (TiN) 0.05 μm by sputtering, and then Cu0.
15 μm was similarly sputtered. The plating solution temperature was 25 ° C., the current density was 1 A / dm ² and 1 μm.
m was plated. The via pattern has a depth of 1
Two types having a hole diameter of 0.25 μm and a hole diameter of 0.33 μm were used. That is, there are two types of aspect ratios, 4.0 and 3.0. Table 2 shows the results of confirming the embedding property of the obtained precipitate in a fine via pattern by cleavage section SEM observation.

[0023]

[Table 2]

As shown in Table 2, when the composition ratio of the electroplating solution of the present invention is within the range of 3.0 or 4.0, no voids or seams are generated, and no vias are formed. The characteristics of embedding into the substrate were improved, and were favorable. Example 3
Is a liquid not containing a polyether compound and a polyalkylethyleneimine, that is, their concentrations are 0, but the concentrations of tetraethyltyrium disulfide and quaternary epichlorohydrin are in a particularly optimum range even within an appropriate composition range. Therefore, the characteristics of embedding in vias were good.

On the other hand, in Comparative Example 1 (6.0 μmol / L) in which the content of the quaternary ammonium salt comprising the tertiary alkylamine and polyepichlorohydrin is less than 15 to 100 μmol / L in the present invention, the aspect ratio When the ratio was 3.0, seams occurred, and when the ratio was 4.0, voids occurred. Comparative Example 2 where the concentration (y) of the organic divalent sulfur compound was too high (y> -0.86x + 300) with respect to the concentration (x) of the quaternary ammonium salt adduct.
As for, good embedding characteristics were exhibited when the aspect ratio was 3.0, but seams occurred when the aspect ratio was 4.0. That is, it was found that excessive addition of the organic divalent sulfur compound outside the effective range shown in FIG. Further, Comparative Example 3 was a case where a plating solution containing no organic divalent sulfur compound was used. As in Comparative Example 1, when the aspect ratio was 3.0, a seam was generated, and 4.0 was obtained. In the case of, a void was generated. Although the above Examples and Comparative Examples are typical ones, it was confirmed that the present invention was effective in all the component compositions and numerical ranges shown in the claims.

[0026]

By using the copper electroplating solution of the present invention, fine vias or trenches formed on a semiconductor wafer can be embedded without generating defects such as voids and seams. This has the effect of eliminating the disadvantages inherent in semiconductor wafer plating, such as insufficient film formation on the holes and bottom. In particular, the deposition rate of the concave portion in the via or trench is increased, the deposition rate of the convex portion near the entrance of the via or trench and the deposition speed of the other wafer surface is reduced, and the filling characteristics in the via or trench are improved. It is possible to obtain a wiring material having a uniform average thickness. In addition, Na ⁺ , K, which cause contamination of semiconductor devices,
^Since there is no substance such as alkaline ions such as ⁺ , the management of the plating solution and the drainage treatment are easy, and there is an excellent effect that rapid plating can be performed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an electrolytic copper plating apparatus.

FIG. 2 is a graph showing the concentration range in which the via filling characteristics are good, with the concentration of the organic divalent sulfur compound (y) and the concentration of the quaternary ammonium salt adduct composed of tertiary alkylamine and polyepichlorohydrin (x). .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor wafer 2 Anode 3 Electrolytic copper plating solution 4 Electroplating apparatus

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K023 AA19 BA06 CB08 CB11 CB28 CB33 DA06 DA07 DA08 4K024 AA09 BB12 CA02 CA04 CA06 CA07 CA08 4M104 BB04 DD52 HH13

Claims (10)

[Claims] 1 to 300 μmol of an organic divalent sulfur compound
/ L and a quaternary ammonium salt adduct comprising a tertiary alkylamine and polyepichlorohydrin
An acidic copper electroplating solution for forming wiring on a semiconductor wafer, which contains 1 / L. 2. An organic divalent sulfur compound of 10 to 200 μmo.
The acidic copper electroplating solution according to claim 1, which contains 1 / L. 3. A quaternary ammonium salt adduct comprising a tertiary alkylamine and polyepichlorohydrin.
The acidic copper electroplating solution according to claim 1, wherein the acidic copper electroplating solution contains μmol / L. 4. The concentration of the organic divalent sulfur compound is defined as yμmol.
/ L, and the concentration of the quaternary ammonium salt adduct composed of tertiary alkylamine and polyepichlorohydrin is xμmo
-0.86x + 25 ≦ y ≦ −0.8 when 1 / L
6x + 300, and 1 ≦ y ≦ 300, 10 ≦ x ≦
An acidic copper electroplating solution for forming wiring on a semiconductor wafer, which is characterized by being 200. 5. The condition of 1 ≦ x ≦ 300 and 10 ≦ y ≦
The acidic copper electroplating solution according to claim 4, wherein the number is 200. 6. A polyether compound of 0.1 to 50 μmo.
The acidic copper electroplating solution according to any one of claims 1 to 5, comprising 1 / L. 7. A polyether compound of 1 to 20 μmol /
The acidic copper electroplating solution according to claim 6, wherein L is contained. 8. Polyalkylethyleneimine 0.1 to 7
8. The composition according to claim 1, wherein the composition contains μmol / L.
The acidic copper electroplating solution according to any one of the above. 9. Polyalkylethyleneimine 0.5 to 4
The acidic copper electroplating solution according to claim 8, which contains μmol / L. 10. The method according to claim 1, wherein a copper sulfate bath is used as a basic bath.
The acidic copper electroplating solution according to any one of the above.