CN103668356A - Electroplating method of adding Fe<2+> and Fe<3+> in copper-interconnection copper sulfate electroplating solution - Google Patents

Abstract

The invention relates to an electroplating method of adding Fe<2+> and Fe<3+> in a copper-interconnection copper sulfate electroplating solution. The method comprises the steps as follows: a silicon slice with a TSV (through-silicon-via) is placed in a pretreatment solution for ultrasonic pretreatment; the silicon slice is soaked in the acidic copper sulfate electroplating solution containing Cu<2+>, Cl<-> and sulfuric acid; additives, such as PEG (polyethylene glycol), SPS (bis-(3-sulfopropyl)disulfide) and JGB (Janus green B), and Fe<2+>/Fe<3+> redox couples are premixed and placed still so as to obtain a premixed additive solution; the premixed additive solution is injected into the acidic copper sulfate electroplating solution, after stirring and mixing, electroplating is conducted with a constant working current, and meanwhile, the electroplating solution passes through an electrolytic bath containing high-purity copper particles during electroplating. According to the method, the Fe<2+>/Fe<3+> redox couples are added in the electroplating solution and combined with the PEG and the SPS, so that the deposition rate of copper inside the via is increased, deposition of surface copper can be effectively inhibited, then void-free filling can be realized, the thickness of surface copper plating can be reduced, and subsequent treatment processes are facilitated.

Description

In copper-connection copper sulfate bath, add Fe 2+and Fe 3+electro-plating method

Technical field

The invention belongs to technical field of electronic encapsulation, be specifically related to a kind ofly in copper-connection copper sulfate bath, add Fe ²⁺and Fe ³⁺electro-plating method.

Background technology

TSV 3-D stacks encapsulation based on silicon through hole is the inexorable trend of encapsulation technology development.The research emphasis of TSV filling through hole is filled from imporosity and is forwarded at a high speed at present, high quality, and low-cost filling comes up.In electroplating process, be faced with the oxidation consumption of additive, be mingled with the series of problems bringing with copper anode.Fe ²⁺/ Fe ³⁺redox couple can control electrode current potential, prevents additive oxide inclusion, makes the application of noble electrode become possibility, reduces the phosphorus content in plating solution, reduces impurity; And pass through Fe ³⁺concentration is controlled, and utilizes the difference of the inside and outside current efficiency of through hole can improve the superfill ability of plating solution, reduces the use of additive.But redox couple is the impact on other organic additives in TSV the electroplates in hole, on also urgently further investigation of the impact of filling through hole effect and quality of coating.In process of the present invention, pass through research Fe ²⁺/ Fe ³⁺on the particularly impact of stress of kinetics of electrode process, Additive and coating performance, the relation between clear and definite coating stress and impurity, improves the superfill ability of plating solution, improves coating reliability, reduces costs.

Summary of the invention

The problems referred to above that exist for existing copper facing filling technique, the invention provides and a kind ofly in copper-connection copper sulfate bath, add Fe ²⁺and Fe ³⁺electro-plating method, the present invention has increased Fe in plating solution ²⁺/ Fe ³⁺redox couple and PEG and SPS combine, thereby accelerate the sedimentation rate of through hole internal copper and can effectively suppress the deposition of surface copper, and then realize that zero defect is filled and the thickness that reduces copper coating facilitates subsequent processes.

The present invention is achieved by the following technical solutions, a kind ofly in copper-connection copper sulfate bath, adds Fe ²⁺and Fe ³⁺electro-plating method, it is characterized in that, comprise the following steps:

Step (1) is placed on the silicon chip with TSV through hole in pretreatment liquid, to carry out ultrasonic wave pre-treatment;

Step (2) is immersed in the described silicon chip through pre-treatment containing Cu ²⁺, Cl ^-in the acid copper sulfate electroplate liquid of sulfuric acid, the pH value of described acid copper sulfate electroplate liquid is 0～4;

Step (3) is by additive PEG, SPS, JGB and Fe ²⁺/ Fe ³⁺redox couple carries out pre-mixing, standing, obtain premixed additive solution, described premixed additive solution is injected to described acid copper sulfate electroplate liquid, after being uniformly mixed, under constant working current, electroplate, in electroplating process, make electroplate liquid by the electrolyzer of high purity copper particle is housed simultaneously.

Preferably, in step (1), the time of described ultrasonic wave pre-treatment is 2min.

Preferably, in step (2), the Cu of described acid copper sulfate electroplate liquid ²⁺concentration is 35g/L, Cl ^-concentration is that 50ppm, sulfuric acid concentration are 0.6mol/L.

Preferably, in step (3), additive PEG, SPS, JGB and Fe ²⁺/ Fe ³⁺the time of repose that redox couple carries out after pre-mixing is 3 hours.

Preferably, in step (3), electroplating process is at 10mA/cm ²constant working current under electroplate, increased Fe ²⁺/ Fe ³⁺thereby redox couple makes cupric ion deposition current reduce to reduce the TSV openings sedimentation rate of cupric ion around in cathode surface generation reduction reaction.

Preferably, in step (3), electroplating process adopts the fixing insoluble noble electrode of size, has avoided use electrolytic copper anode can introduce impurity.

Preferably, in electroplating process, plating solution, by the electrolyzer of high-purity shot copper is housed, supplements the cupric ion and the Fe that consume ²⁺ion, extends the electroplate liquid life-span.

Preferred, the impurity in deposited copper reduces, and coating internal stress is reduced to below 10MPa, thereby obtains the TSV interconnection element that performance is more stable.

Compared with prior art, beneficial effect of the present invention is as follows: with do not contain Fe ²⁺/ Fe ³⁺the plating solution of redox couple is compared, because Cu ²⁺by the electrolyzer Fe that contains high purity copper particle by plating solution ³⁺react with Cu and produce, so can the fixing insoluble anode of use size in the inventive method, so just can prevent that the while is because of Fe because soluble copper anode can be introduced containing phosphorus impurities in dissolution process ²⁺/ Fe ³⁺existence can reduce the use of accelerator, thereby guaranteed that the deposited copper obtaining contains impurity still less, contain less impurity and in the stability that has increased performance, also reduced coating stress, guarantee that coating stress is below 10MPa; Due to Fe ³⁺at cathode surface, be reduced to Fe ²⁺consume electronics, reduced TSV openings silicon face cupric ion deposition current around, thereby caused the copper film of through hole circumferential surface place deposition thinner, and because Fe ³⁺transmission be mainly subject to diffusion control, therefore the deposition speed of TSV through hole inside is not affected, thereby has facilitated Cu ²⁺time facilitate subsequent chemistry polishing process.Fe ²⁺/ Fe ³⁺in the time of the surperficial copper film that had attenuate of redox couple, can realize the zero defect of the through hole of larger diameter fills.

Embodiment

Below in conjunction with specific embodiment, the present invention is described in detail.Following examples will contribute to those skilled in the art further to understand the present invention, but not limit in any form the present invention.It should be pointed out that to those skilled in the art, without departing from the inventive concept of the premise, can also make some distortion and improvement.These all belong to protection scope of the present invention.

embodiment 1

The present embodiment relates to a kind of TSV electro-plating method under fixed electorde condition, comprises the following steps:

Step (1) is with the preparation of the silicon chip of TSV through hole: first adopt deep reaction ion etching (Deep Reactive Ion Etch, DRIE) make the through hole of certain size, then utilize plasma enhanced chemical vapor deposition method (PECVD) depositing insulating layer, the deposition material of use is silicon nitride or silicon-dioxide (SiNx or SiO ₂), then utilize Metalorganic chemical vapor deposition method (MOCVD) deposited barrier layer (TiN or TaN), effect is to prevent that copper is to the diffusion of silicon base, finally uses chemical Vapor deposition process (CVD) or physical vaporous deposition (PVD) deposition Seed Layer (Cu);

Step (2) is by the process ultrasonication 2min in pretreatment liquid of the silicon chip with TSV through hole;

Step (3) is immersed in the silicon chip through pre-treatment containing Cu ²⁺concentration is 35g/L, Cl ^-concentration is that in 50ppm, the sulfuric acid concentration acid copper sulfate electroplate liquid that is 0.6mol/L, pH value has vital effect to the existence of effects of ion, and pH value is between 0-4 time under positive potential, and solution exists with bivalent cupric ion;

Step (4) is processed following additive pre-mixing, comprising: 300ppm PEG(polyethylene glycol), 3ppm SPS(bis-(3-sulfopropyl) disulfide), 20ppm JGB(leveling agent), 50ppm Cl ^-, 0.5g/LFe ²⁺and 0.024g/L Fe ³⁺, Fe wherein ²⁺and Fe ³⁺to pass through FeSO ₄7H ₂o and Fe ₂(SO ₄) ₃add, obtain premixed additive mixed liquor; Premixed additive mixed liquor is joined in electroplate liquid, through being uniformly mixed fully, under fixed electorde condition, at 10mA/cm ²constant working current under adopt the fixing insoluble noble electrode of size to electroplate, electrode potential, for being-150mV, in electroplating process, allows plating solution by the electrolyzer of high purity copper particle is housed.

embodiment 2

The present embodiment relates to a kind of TSV electro-plating method under rotating disk electrode (RDE) condition, comprises the following steps:

Step (1) is with the preparation of the silicon chip of TSV through hole: first adopt deep reaction ion etching (Deep Reactive Ion Etch, DRIE) make the through hole of certain size, then utilize plasma enhanced chemical vapor deposition method (PECVD) depositing insulating layer, the deposition material of use is silicon nitride or silicon-dioxide (SiNx or SiO ₂), then utilize Metalorganic chemical vapor deposition method (MOCVD) deposited barrier layer (TiN or TaN), effect is to prevent that copper is to the diffusion of silicon base, finally uses chemical Vapor deposition process (CVD) or physical vaporous deposition (PVD) deposition Seed Layer (Cu);

Step (2) is by the process ultrasonication 2min in pretreatment liquid of the silicon chip with TSV through hole;

Step (3) is immersed in the silicon chip through pre-treatment containing Cu ²⁺concentration is 35g/L, Cl ^-concentration is that in 50ppm, the sulfuric acid concentration acid copper sulfate electroplate liquid that is 0.6mol/L, pH value has vital effect to the existence of effects of ion, and pH value is between 0-4 time under positive potential, and solution exists with bivalent cupric ion;

Step (4) is processed following additive pre-mixing, comprising: 300ppm PEG(polyethylene glycol), 3ppm SPS(bis-(3-sulfopropyl) disulfide), 20ppm JGB(leveling agent), 50ppm Cl ^-, 12g/LFe ²⁺and 0.5g/L Fe ³⁺, Fe wherein ²⁺and Fe ³⁺to pass through FeSO ₄7H ₂o and Fe ₂(SO ₄) ₃add, obtain premixed additive mixed liquor; Described premixed additive mixed liquor is joined in electroplate liquid, through being uniformly mixed fully, under rotating disk electrode (RDE) condition, at 10mA/cm ²constant working current under adopt the fixing insoluble noble electrode of size to electroplate, wherein the rotating speed of rotating disk electrode be 900rpm(now working current 9% by Fe ³⁺be converted into Fe ²⁺reduction reaction consumes), electrode potential is-50mV, in electroplating process, to allow electroplate liquid by the electrolyzer of high purity copper particle is housed.

implementation result

According to embodiment 1 and embodiment 2, after ratio pre-mixing for some time that present method requires additive to add as required, add to again in electroplate liquid, due to Fe ²⁺with cupric ion and SPS and Fe ²⁺between there is following reaction:

2MPS+2Cu ²⁺→SPS+2H ⁺+2Cu ⁺ (3)

$2\mathrm{MPS}+\frac{1}{2}{O}_2\&RightArrow;\mathrm{SPS}+H_{2}O---\left(4\right)$

By reaction (1), increased Cu ⁺thereby concentration accelerated the sedimentation rate of copper because Fe ²⁺mass transfer velocity be subject to diffusion control, accelerate there is a maximum value in experiment.The MPS producing by reaction (2) is faster than SPS acceleration effect.Reaction (2)-(4) can consume Fe ²⁺keep in solution the amount of MPS constant, simultaneously Fe ²⁺can pass through Fe ³⁺react and constantly produce and have part Fe at negative electrode with high purity copper particle ²⁺produce, therefore can accelerate the sedimentation rate of the copper of through hole inside.Research shows Fe by experiment ²⁺/ Fe ³⁺reaction on SPS at deposition surface place does not have impact substantially, is mainly electrolytic solution is formed and has impact, produces the balance of MPS.

According to embodiment 1 and embodiment 2, under rotating electrode condition, electrode overpotential has reduced, and because the effect of mass transmitting of iron ion under rotating electrode condition accelerates to make the reduction of electrode overpotential, can better suppress the cupric ion deposition at openings place.

In the electroplating process of the inventive method, allow electroplate liquid by the electrolyzer of high purity copper particle being housed, Fe in this process ³⁺with copper particle generation redox reaction, generated Fe ²⁺and Cu ²⁺thereby, realized iron ion and generated and the balance consuming, and the cupric ion the generating consumption that can supplement cupric ion in plating solution, thereby can extend work-ing life of plating solution.

Due to Fe ²⁺/ Fe ³⁺can the slow down cupric ion deposition at openings place of redox couple, can accelerate through hole internal copper ion deposition speed simultaneously, so just can reduce the use of additive.

Thereby in the inventive method by using noble electrode and making plating solution avoid using anode copper can introduce the shortcoming containing phosphorus impurities by high purity copper particle.Due to Fe ²⁺/ Fe ³⁺use can reduce the consumption of additive, the use of additive reduces also can access purer copper, contains less impurity and can access the device that performance is more stable, also coating stress can be reduced to below 10MPa.

Above specific embodiments of the invention are described.It will be appreciated that, the present invention is not limited to above-mentioned specific implementations, and those skilled in the art can make various distortion or modification within the scope of the claims, and this does not affect flesh and blood of the present invention.

Claims (8)

1. one kind is added Fe in copper-connection copper sulfate bath ²⁺and Fe ³⁺electro-plating method, it is characterized in that, comprise the following steps:

Step (1) is placed on the silicon chip with TSV through hole in pretreatment liquid, to carry out ultrasonic wave pre-treatment;

Step (2) is immersed in the described silicon chip through pre-treatment containing Cu ²⁺, Cl ^-in the acid copper sulfate electroplate liquid of sulfuric acid, the pH value of described acid copper sulfate electroplate liquid is 0～4;

Step (3) is by additive PEG, SPS, JGB and Fe ²⁺/ Fe ³⁺redox couple carries out pre-mixing, standing, obtain premixed additive solution, described premixed additive solution is injected to described acid copper sulfate electroplate liquid, after being uniformly mixed, under constant working current, electroplate, in electroplating process, make electroplate liquid by the electrolyzer of high purity copper particle is housed simultaneously.

2. electro-plating method according to claim 1, is characterized in that, in step (1), the time of described ultrasonic wave pre-treatment is 2min.

3. electro-plating method according to claim 1, is characterized in that, in step (2), and the Cu of described acid copper sulfate electroplate liquid ²⁺concentration is 35g/L, Cl ^-concentration is that 50ppm, sulfuric acid concentration are 0.6mol/L.

4. electro-plating method according to claim 1, is characterized in that, in step (3), and additive PEG, SPS, JGB and Fe ²⁺/ Fe ³⁺the time of repose that redox couple carries out after pre-mixing is 3 hours.

5. electro-plating method according to claim 1, is characterized in that, in step (3), electroplating process is at 10mA/cm ²constant working current under electroplate, increased Fe ²⁺/ Fe ³⁺thereby redox couple makes cupric ion deposition current reduce to reduce the TSV openings sedimentation rate of cupric ion around in cathode surface generation reduction reaction.

6. electro-plating method according to claim 1, is characterized in that, in step (3), electroplating process adopts the fixing insoluble noble electrode of size, has avoided use electrolytic copper anode can introduce impurity.

7. electro-plating method according to claim 1, is characterized in that, in electroplating process, plating solution, by the electrolyzer of high-purity shot copper is housed, supplements the cupric ion and the Fe that consume ²⁺ion, extends the electroplate liquid life-span.

8. electro-plating method according to claim 7, is characterized in that, the impurity in deposited copper reduces, and coating internal stress is reduced to below 10MPa, thereby obtains the TSV interconnection element that performance is more stable.