JP2003328180A - Method of filling plating into bottomed hole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of filling plating into a bottomed hole by which cavities generating inside the bottomed hole can be reduced even in the case of the bottomed hole having a high aspect ratio. <P>SOLUTION: A plating liquid in which the concentration of CuSO<SB>4</SB>5H<SB>2</SB>O is controlled to 130 to 180 (g/L), the concentration of H<SB>2</SB>SO<SB>4</SB>is controlled to 180 to 220 (g/L), the concentration of Cl<SP>-</SP>is controlled to 100 to 1,000 (mg/L), the concentration of an accelerator containing sulfur is controlled to 0.1 to 7.5 (mg/L), and the concentration of an inhibitor consisting of a polymer is controlled to 400 to 2,000 (mg/L) is used. DC current is used for plating current, and current density to the opening area of a bottomed hole 23 is controlled to 0.1 to 3 mA/cm<SP>2</SP>. Thus, Cu plating can be deposited from the bottom face and side face of the bottomed hole while suppressing the formation of Cu plating at the opening part of the bottomed via hole 23. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for filling a bottomed hole with plating, which can be applied when, for example, a through-substrate electrode is formed on a semiconductor substrate.

[0002]

2. Description of the Related Art When a semiconductor substrate is multi-layered, it is necessary to ensure electrical connection between the laminated substrates. Therefore, a through-substrate electrode is formed on each stacked semiconductor substrate so as to penetrate the substrate.

When this through-substrate electrode is formed by using a plating technique, for example, as shown in FIG. 5, it is possible to provide a power feeding portion 2 at the bottom of the via hole 3 and perform electroplating using this power feeding portion 2 as an electrode. To be According to the electroplating method in which the feeding portion 2 is provided at the bottom of the via hole 3, it is considered possible to fill the via hole 3 having a deeper depth than the opening diameter with plating.

However, this method has two main problems in the process. The first point is that it is necessary to form the power feeding layer 2 between the two semiconductor substrates 1 and 4 before forming the via hole 3 to be filled with plating, so that the manufacturing process of the semiconductor substrate is complicated. Is that The second point is that it is necessary to separate the power feeding layer 2 for each required wiring after the via hole 3 is filled with plating so as to be electrically independent, which also increases the number of manufacturing processes. is there.

Therefore, as a technique for filling a bottomed via hole whose bottom is closed by Cu plating, as shown in FIG. 6, instead of forming a feeding layer only on the bottom of the via hole, the inner wall of the bottomed via hole 13 is formed. By forming the power feeding layer 14 on the entire surface and the surface of the base material 11 on which the bottomed via holes 13 are formed and performing electroplating using this as an electrode, for example, an opening diameter of 1 μm or less and a diameter of 1 μm of a multilayer wiring board of an LSI A technique for filling bottomed via holes with a depth of about 10 mm or a diameter of 10
There is a technique of filling a bottomed via hole having an opening diameter of 0 μm or more and a depth of 300 μm or less. In these techniques, in the plating solution, by appropriately adjusting the addition amount of an additive such as an accelerator that promotes the precipitation of copper or an inhibitor that suppresses the precipitation of copper other than the bottomed holes, the above-mentioned respective The bottomed via hole 13 having the above-mentioned opening diameter and depth is filled with Cu plating.

[0006]

However, using these techniques, the depth (w) is deeper than the opening diameter (d), that is, the aspect ratio (w / d) is larger than that of the conventional bottomed via hole. If an attempt is made to fill a large bottomed via hole, a large cavity will remain inside the bottomed via hole 13. Specifically, a bottomed via hole 1 having an opening diameter of 1 μm or less
According to the technique of filling 3 with the plating, as shown in FIG.
Is thickly plated at a position close to the opening, and the plated Cu closes the via hole 13, leaving a cavity 17 inside. On the other hand, in the technique of filling a bottomed hole with an opening diameter of 100 μm or more by plating, the above-mentioned opening diameter of 1
Since the promoting action is suppressed as compared with the case of plating the bottomed via hole 13 having a thickness of μm or less, the bottomed via hole 1
3 is plated from the bottom and sides. However, as shown in FIG. 7B, the opening of the bottomed via hole 13 is closed before the inside is completely filled, and an elongated cavity 18 is formed near the center of the bottomed via hole 13 from the opening to the bottom. I will remain.

The present invention has been made in view of the above points, and in particular, a bottomed hole having a large aspect ratio,
It is an object of the present invention to provide a plating filling method for a bottomed hole capable of reducing voids generated inside.

[0008]

In order to achieve the above object, the method of filling a bottomed hole according to claim 1 is a method of filling a bottomed hole with Cu plating. there _{are, CuSO 4 · 5H 2 O 130} (g / L) ~180 (g / L) H 2 SO 4 180 (g / L) ~220 (g / L) Cl - 100 (mg / L) ~1000 ( mg / L) Accelerator containing sulfur 0.1 (mg / L) to 7.5 (mg / L) Inhibitor composed of polymer 400 (mg / L) to 2000 (mg / L) Plating solution containing While setting the plating current to DC,
Moreover, the current density with respect to the opening area of the bottomed hole is 0.1 mA /
It is characterized in that it is set to cm ² to ³ mA / cm ² .

By using the plating bath having the above composition, it is possible to suppress the deposition of Cu plating in the vicinity of the opening of the bottomed hole and to deposit the Cu plating from the bottom surface and the side surface of the bottomed hole. In the present invention, the plating current is set to direct current, and the current density with respect to the opening area of the bottomed hole is set to 0.1 to 0.1.
Since it is set to 3 mA / cm ² , it is possible to avoid the situation where the opening is blocked by the Cu plating deposited in the opening before the inside of the bottomed hole is filled.

That is, since the plating current density in the opening is higher than that in the inside of the bottomed hole, Cu plating is deposited before the inside of the hole, and the opening tends to be closed. As a result of intensive studies by the inventors of the present invention with respect to such a problem, by setting the current density of the plating current to a value in the above-mentioned low range, an increase in the current density in the opening can be suppressed, and the inside of the bottomed hole It has been found that the occurrence of cavities in can be minimized. Here, if the current density is less than 0.1 mA / cm ² , it takes a very long time to generate the Cu plating. On the other hand, if the current density is higher than 3 mA / cm ^{2, the} bottomed holes are blocked by the plating deposited in the openings before the bottomed holes are filled, leaving a cavity inside.

As described in claim 2, it is preferable that the nitrogen-containing additive is added to the plating bath at a concentration of 0.1 (mg / L) to 100 (mg / L). This makes it difficult for the inhibitor made of the polymer to exert its suppressing effect in the bottomed holes, and promotes the formation of Cu plating in the bottomed holes. In addition, as the additive containing nitrogen, specifically, as described in claim 3, 3- (d
iethylamino) -7-((p- (dimethylamino) phenylazo) -5-phe
nylphenazinium chloride) can be used.

As described in claim 4, the diameter of the bottomed hole (w) is larger than 1 μm, and the depth (d) of the bottomed hole is larger than the diameter (w) of the opening. The aspect ratio (d / w) is larger than 3. in this way,
If the aspect ratio of the depth to the diameter of the opening is large,
In particular, since a cavity is likely to be formed inside the bottomed hole, the use of the plating filling method according to the present invention is significant.

As described in claim 5, bis (3-sulfopropyl) disulfidesodium can be used as the sulfur-containing accelerator.

As described in claim 6, C of the plating bath
The concentration of l ⁻ is 300 (mg / L) to 500 (mg / L)
And the concentration of bis (3-sulfopropyl) disulfidesodium is 2.0 to 5.0 mg / L, the size of the cavity (void) in the bottomed hole can be made extremely small.
Alternatively, it is preferable because it can be completely filled with Cu plating.

Further, as described in claim 7, the inhibitor made of a polymer has a molecular weight of 2,000 to 40,000.
It is preferable to use polyethylene glycol.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

1 (a) to 1 (d) are cross-sectional views for each step showing each step for forming a through electrode in a semiconductor substrate in which a bottomed via hole to be filled with plating is formed. The method of forming the through electrode shown in FIGS. 1A to 1D will be described. First, as shown in FIG. 1A, a thermal oxide film 22 is formed on both surfaces of the silicon wafer substrate 21 to a thickness of about 5 μm.
Next, the thermal oxide film 22 and the silicon wafer substrate 21 are etched by reactive ion etching (RIE) to form a bottomed via hole 23. At this time, the bottomed via hole 23 has, for example, an opening formed of a square having a side of 10 μm, and the etching depth in the silicon wafer substrate 21 is, for example, 70 μm.

After that, as shown in FIG. 1B, a TEOS film 24 is formed as an insulating film by plasma CVD. At this time, for example, TE of about 1.5 μm is formed on the substrate surface.
The OS film 24 is formed, and the sidewall surface and the bottom surface of the bottomed via hole 23 have T of 0.2 μm and 0.5 μm, respectively.
The EOS film 24 is formed. On this TEOS film 24,
A TiN layer 25 of 10 nm as a barrier metal and a Cu seed layer 26 of 100 nm as a seed layer are formed by CVD. The Cu seed layer 26 extends from the surface of the substrate 21 to the bottom surface of the bottomed via hole 23.
3 is formed so as to cover the entire inner surface.

When the bottomed via hole 23 and the Cu seed layer 26 are formed on the inner surface of the substrate 21 in this manner,
Cu plating 27 is filled in the bottomed via hole 23 by using the plating apparatus shown in FIG. 2 (see FIG. 1C). After the Cu plating 27 is filled in the bottomed via hole 23, as shown in FIG. 1D, from the surface of the substrate 21 opposite to the surface where the opening of the bottomed via hole 23 is formed,
1 is mechanically shaved and its thickness is reduced to about 50 μm. As a result, the Cu plating 23 in the via holes 23 is exposed on both front and back surfaces of the substrate 21, and the substrate 21 having the through electrodes is formed. This substrate 21 is laminated with another substrate 21 having a through electrode formed by the same process.

FIG. 2 is a block diagram showing a schematic structure of the plating apparatus. The plating apparatus includes a rotating unit 32 having a holding unit 31 that holds the substrate 21. The holding unit 31 immerses the substrate 21 in the plating solution 35 from the side of the substrate 21 where the bottomed via hole 23 is formed. The rotating unit 32 holds the holding unit 31 holding the substrate 21 at about 1000 rp during the plating process.
Rotate at m. As a result, the plating solution 35 is agitated, and the concentration of each component in the plating solution 35 can be made uniform.

The plating apparatus has a current control unit 33, an anode electrode 34 arranged in a plating solution 35, and a substrate 2
Cu seed layer 2 formed in bottomed via hole 23 of No. 1
A current having a predetermined current value is passed through using 6 as a cathode electrode. At this time, the current controller 33 controls the bottomed via hole 23.
Current density is 0.1mA / cm with respect to the area of the opening
^The energizing current is controlled so as to be ² to ³ mA / cm ² .

Before the plating process is performed by the above-mentioned plating apparatus, the substrate 21 should be dipped in a plating solution similar to the plating solution 35 used in the plating apparatus, and ultrasonic vibration should be applied to plate. Alternatively, a clean Cu surface may be exposed.

Next, the plating solution 35 used in the above plating apparatus will be described.

The plating solution 35 is CuSO ₄ .5H ₂ O
(Copper sulfate), H ₂ SO ₄ (sulfuric acid), Cl ⁻ (chlorine ion), a sulfur-containing accelerator, a polymer inhibitor, and a nitrogen-containing additive.

The suitable concentration of CuSO ₄ .5H ₂ O (copper sulfate) is 130 g / L to 180 g / L. When the concentration of copper sulfate is less than 130 g / L, for example, the supply of copper ions to the bottomed via hole 23 that is the object to be plated becomes insufficient, and it becomes difficult to generate sufficient Cu plating. On the other hand, if the concentration exceeds 180 g / L, the copper ion concentration will be saturated, and copper will be recrystallized even if dissolved further.

The concentration of H ₂ SO ₄ (sulfuric acid) is 180 g /
L to 220 g / L is suitable. Sulfuric acid concentration is 180g /
When it is at most L, the electroconductivity of the plating solution will decrease, making it difficult to energize the plating solution. On the other hand, 220 g / L
C, which is a base layer for electroplating,
The u seed layer 26 may be dissolved.

The concentration of Cl ⁻ (chlorine ion) is 100 m
g / L to 1000 mg / L is suitable. This chlorine ion will be contained in the plating solution by adding a water-soluble chlorine compound to the plating solution. As the water-soluble chlorine compound, for example, hydrochloric acid, sodium chloride, potassium chloride, ammonium chloride or the like can be used. The water-soluble chlorine compound may be used alone or in combination of two or more.

When the chloride ion concentration is 100 mg / L or less, it becomes difficult for various additives to function normally.

The accelerator containing sulfur is a substance which is adsorbed on the surface of the object to be plated during electrolysis and has a function of promoting the growth of Cu plating. Specifically, bis (3
-Sulfopropyl) disulfide sodium can be used.

The concentration of the sulfur-containing accelerator is 0.1 m
g / L to 7.5 mg / L is suitable. If the concentration of the accelerator is less than 0.1 mg / L, the effect of promoting the growth of the Cu plating 27 cannot be sufficiently obtained.

The inhibitor made of a polymer is a substance which acts as an inhibitor in the plating solution, and particularly acts to suppress the formation of the Cu plating 27 on the surface of the substrate 21, and is preferably a polyethylene glycol having a molecular weight of 2,000 to 40,000. Is used. The concentration of the polymer inhibitor is suitable in the range of 400 to 2000 mg / L. If the concentration in the plating solution is 400 mg / L or less, the effect of suppressing the generation of Cu plating 27 on the surface of the substrate 21 becomes insufficient, and voids may occur in the Cu plating 27. on the other hand,
If the concentration exceeds 2000 mg / L, almost no corresponding improvement in effect can be obtained.

The additive containing nitrogen is used as the bottomed via hole 23.
In the above, it has a function of suppressing the suppressing effect of the Cu plating 27 generation by the suppressor, whereby the generation of the Cu plating 27 in the bottomed via hole 23 can be promoted. The concentration of the additive containing nitrogen is 0.1
It is preferably (mg / L) to 100 (mg / L). If the concentration is less than 0.1 mg / L, the effect of suppressing the suppressing effect of the polymer-made inhibitor becomes difficult to be exhibited. On the other hand, the effect cannot be improved even if added in excess of 100 mg / L. As the additive containing nitrogen, specifically, 3- (diethylamino) -7-((p- (dime
thylamino) phenylazo) -5-phenylphenazinium chlorid
e) can be used.

The results of filling the bottomed via hole with Cu plating using the above-described plating solution will be described.

First, FIG. 3 is a graph showing the relationship between the current density of the energizing current for electroplating and the size of voids generated in the Cu plating filled in the bottomed via holes 23. As shown in FIG. 3, it can be seen that the void size increases as the current density increases.
The void size also changes depending on the concentrations of various components that make up the plating solution. Therefore, the current density is about 3mA /
It can be said that the size of the void formed in the bottomed via hole 23 can be sufficiently reduced if it is not more than cm ² . When the current density is higher than 3 mA / cm ² ,
Even if the concentrations of various components are changed, the current density in the opening of the bottomed via hole 23 is large, and the opening is closed by the Cu plating that is generated before the filling of the inside. On the other hand, when the current density is less than 0.1 mA / cm ² , it takes a very long time to generate the Cu plating, which is a practical problem.

[0035] Incidentally, the results shown in FIG. 3, CuSO ₄ · 5
H ₂ O (copper sulfate) concentration of 130 g / L, H ₂ SO
₄ (sulfuric acid) concentration 200 g / L, Cl ⁻ (chlorine ion) 100 mg / L, polymer inhibitor concentration 600 mg / L, sulfur-containing accelerator concentration 2 mg / L
It was obtained under the condition that the concentration of the additive containing L and nitrogen was 4 mg / L. Also, as the void size,
About 50 from the opening side in the cross section of the bottomed via hole 23
The void size was observed at a depth of μm.

Next, referring to FIG.^-Concentration and sulfur content
Change in void size when the concentration of the accelerator is changed
The situation is shown. The results shown in FIG._Four・
5H _TwoO (copper sulfate) concentration of 150g / L, H_TwoSO_Four
Concentration of (sulfuric acid) 200g / L, suppression consisting of polymer
The concentration of the agent is 600 mg / L, the concentration of the additive containing nitrogen is
10 mg / L, and current density 1 mA / cm^TwoAnd the article
It was obtained in the case. Also, Cl^-Is the plating solution
Produced by adding hydrochloric acid.

Here, it has been confirmed in advance that Cl ⁻ has an effect on the action of various additives, and that the void size greatly changes with changes in its concentration. Therefore, it was decided to examine the optimum concentration range for reducing the void size. It was also confirmed that when the concentration of the sulfur-containing accelerator was changed together with Cl ⁻ , the change in the void size was increased, so that the concentration of the sulfur-containing accelerator was also changed (2 mg / L to 7 mg / L). 0.5 mg / L).

As a result, as shown in FIG. 4, hydrochloric acid (HC
It was confirmed that when the concentration of 1) was 500 mg / L and the concentration of the sulfur-containing accelerator was 2 mg / L to 5 mg / L, the void size could be most reduced. However, the concentration of hydrochloric acid (HCl) exceeds 500 mg / L, especially 75
When it is 0 mg / L or more, the generation of Cu plating in the opening of the bottomed via hole 23 is not sufficiently suppressed, and the opening tends to be closed before the bottomed via hole 23 is sufficiently filled with Cu plating. is there. Therefore, hydrochloric acid, i.e. Cl ^- concentrations less desirably 500 mg / L,
On the other hand, in order to obtain the void size reduction effect, 300 m
It is necessary to be g / L or more. Therefore, Cl
The preferable range of ⁻ is 300 mg / L to 500 mg / L, in which the concentration of the accelerator containing sulfur is 2 mg / L.
When it is ~ 5 mg / L, the size of the void can be made sufficiently small.

Although the bottomed via hole 23 is filled with Cu plating when the through electrode is formed on the semiconductor substrate by Cu plating in the above-described embodiment, the invention is not limited to such an application and the aspect ratio is high. C with a bottomed hole
When performing u plating, the plating filling method according to the present invention can be preferably used.

[Brief description of drawings]

FIG. 1A to FIG. 1D are cross-sectional views for each step showing each step for forming a through electrode in a semiconductor substrate in which a bottomed via hole to be filled with plating is formed.

FIG. 2 is a configuration diagram showing a schematic configuration of a plating apparatus.

FIG. 3 is a graph showing the relationship between the current density of a current passed through for electroplating and the size of voids generated in Cu plating filled in bottomed via holes.

FIG. 4 is a graph showing how the void size changes when the concentration of Cl ^{− and} the concentration of the accelerator containing sulfur are changed.

FIG. 5 is an explanatory diagram for explaining a conventional plating method for bottomed via holes.

FIG. 6 is an explanatory diagram for explaining another plating method for a conventional bottomed via hole.

7 (a) and 7 (b) are explanatory views for explaining problems of the plating method shown in FIG.

[Explanation of symbols]

21 Silicon wafer substrate 22 Thermal oxide film 23 Bottomed Beer Hall 24 TEOS film 25 TiN layer 26 Cu seed layer 27 Through electrode

Continued front page    (71) Applicant 000005223             Fujitsu Limited             4-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa             No. 1 (71) Applicant 000002185             Sony Corporation             6-735 Kitashinagawa, Shinagawa-ku, Tokyo (72) Inventor Manabu Tomisaka             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Kazuo Kondo             1-1-7 Fukui Tsushima, Okayama City, Okayama Prefecture (72) Inventor Sun Jian             3-6-23 Ijima-cho, Okayama City, Okayama Prefecture (72) Inventor Kenji Takahashi             1st Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa             Ceremony Company Toshiba Microelectronics Sen             Inside (72) Inventor Masataka Hoshino             4-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa             No. 1 within Fujitsu Limited (72) Inventor Hitoshi Yonemura             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 4K023 AA19 BA06 BA08 CB09 CB13                       CB21 DA02 DA06 DA07                 4K024 AA09 AB08 BB12 BC10 CA01                       CA02 CA06 GA16                 4M104 BB04 BB30 DD52 FF01 HH16                 5F033 HH11 HH33 JJ11 JJ33 MM30                       NN05 NN07 PP06 PP27 QQ47                       SS04 TT07 WW00 WW04 WW08                       XX04 XX10

Claims (7)

[Claims] 1. A method of filling a bottomed hole with Cu by filling the bottomed hole with Cu plating, comprising: CuSO ₄ .5H ₂ O 130 (g / L) to 180 (g / L) H ₂ SO ₄ 180. (G / L) to 220 (g / L) Cl ^- 100 (mg / L) to 1000 (mg / L) Sulfur-containing accelerator 0.1 (mg / L) to 7.5 (mg / L) polymer While using a plating solution containing an inhibitor 400 (mg / L) to 2000 (mg / L) consisting of
Moreover, the current density with respect to the opening area of the bottomed hole is 0.1 mA /
cm ^{2 to 3} mA / cm ² ; 2. The additive containing nitrogen is 0.1 (mg / L)
The plating filling method for a bottomed hole according to claim 1, wherein the plating solution is added to the plating solution at a concentration of -100 (mg / L). 3. As the additive containing nitrogen, 3- (dieth
ylamino) -7-((p- (dimethylamino) phenylazo) -5-phenylp
3. The method for filling bottomed holes with plating according to claim 2, wherein henazinium chloride) is used. 4. The bottomed hole has an opening width (w) of more than 1 μm, and a ratio (d / w) of the bottomed hole depth (d) to the opening width (w). Is larger than 3, and the filling plating method for low-pores according to any one of claims 1 to 3. 5. The bis (3-s
5. The method for filling a low-pore plating layer according to claim 1, wherein ulfopropyl) disulfide sodium is used. 6. The concentration of Cl ^{− in} the plating solution is set to 300.
(Mg / L) to 500 (mg / L), and the bis
(3-sulfopropyl) disulfide sodium concentration of 2.0 ~
The bottomed hole plating filling method according to claim 5, wherein the plating filling amount is 5.0 mg / L. 7. The plating filling method for a bottomed hole according to claim 1, wherein polyethylene glycol having a molecular weight of 2,000 to 40,000 is used as the inhibitor made of a polymer.