KR100850502B1 - Electro ni plating solution and method on the alternater-diode silicon wafer - Google Patents

Abstract

A method for fabricating an electrolytic nickel layer on an alternator-diode silicon wafer and a surface treatment solution used in the method are provided to extremely extend a contact area between a nickel layer and a silicon portion of an underlying layer by removing a SiO2 oxide layer using an etchant. An etchant is used for removing an oxide layer. The etchant is a mixture of nitric acid(200 ml/l to 400 ml/l) and hydrofluoric acid(5 ml/l to 20 ml/l) and is applied to an alternator-diode silicon wafer under 10 °C to 40 °C during 60 seconds to 150 seconds. A preliminary treatment is performed on the resultant alternator-diode silicon wafer before a nickel layer is formed, and then an electro nickel plating is performed using an electrolyte under conditions of 40 °C to 70 °C, 3.0 to 5.5 pH, and 2 A/dm^2 to 8 A/dm^2. The electrolyte includes NiCl2 6H2O 20g/l to 40 g/l with respect to Ni(NH2SO3)2 4H2O 300 ml/l to 600 ml/l, a brightening agent of 10 ml/l to 30 ml/l, a semi-brightening agent of 1 ml/l to 5 ml/l and an anti-pit agent of 1 ml/l to 7 ml/l.

Description

Electrolytic nickel layer formation method on alternator-diode silicon wafer and surface treatment solution used therein {Electro Ni plating solution and method on the Alternater-Diode silicon wafer}

1 is a SEM image of the surface state after etching with a wafer etching agent compared with the present invention.

Figures 2a, 2b and 2c shows the plating layer thickness measurement on the wafer produced by the present invention.

The present invention relates to a method for forming an electrolytic nickel layer on an alternator-diode silicon wafer called a zener diode, and a surface treatment liquid used therein. More specifically, the present invention relates to a three-phase alternating voltage induced in an automobile start coil part. A method of forming an electrolytic nickel layer on a surface for an alternator-diode silicon wafer for conversion to DC, and a surface treatment liquid used therein.

The alternator-diode is an indispensable element in automobile parts and takes about nine in one car. The alternator-diode is currently surface-treated by vacuum evaporation. When surface-treating by vacuum evaporation, the material is heated and evaporated in vacuum using an electron beam or an electric filament to deposit a metal material. As a method of forming a film by coating on the surface of the material, This method had a lot of problems in terms of mass production efficiency because of the high production cost and the complicated process and long processing time.

Looking at the alternator-diode FAB process, which is a process before performing the surface treatment method of the alternator-diode silicon wafer as described above, after forming a raw wafer, a N + / P + layer by diffusion of phosphorus and boron is formed. ) To form a structure as a diode.

As described above, a wafer in which phosphorus boron has been diffused has a certain number of wafers in a form of agglomerate by a wafer and a source between wafers, which are separated separately using HF.

Since the source is coated on the wafer surface separated from the above, in order to remove it, HF (10 mL / L to 50 mL / L), HNO ₃ (100 mL / L to 200 mL / L), and CH ₃ COOH (10ml / l ~ 100ml / l) The primary Si surface is etched with the chemical mixed with the solution.

After removing the source on the wafer surface through the primary Si etching, honing is performed to completely remove the remaining source using powder. When bonding (bonding), the contact area is expanded to improve the bonding.

The physical stress damage layer of the silicon interface generated by the double-sided honing as described above By annealing at a temperature of about 1000 ℃ ~ 2000 ℃ to solve the stress of the Si interface to achieve the stabilization of properties.

The wafer completed up to the heat treatment process is subjected to secondary silicon etching. As the etching solution used to remove the SiO ₂ oxide film generated during the heat treatment, hydrofluoric acid, nitric acid, sulfuric acid, hydrogen peroxide, and the like are used.

In this case, considering that the main component of the alternator-diode is Si, an appropriate mixing ratio with other sulfuric acid, nitric acid, etc. is important, based on hydrofluoric acid which reacts well with silicon. In particular, since the phosphorus and boron are diffused in the alternator wafer, a solution such as lactic acid or hydrochloric acid, which is an etching material that reacts well with phosphorus and boron, should also be appropriately added to make an optimal etching surface between the silicon wafer and the plating layer in subsequent processes.

The above process generally leads to a pretreatment process in the alternator-diode silicon wafer surface treatment.

After the pretreatment process, the nickel and cobalt are plated in order to exhibit the efficacy of the alternator-diode part.

The present invention is to solve the problems of the prior art as described above, the nickel layer which is a metal layer to be plated after easy use to remove the SiO ₂ oxide film generated during the heat treatment of the last step of pretreatment during the surface treatment process of the alternator-diode silicon wafer The present invention provides an etching solution, which is a surface treatment solution capable of enhancing the tensile strength of a wafer by expanding the contact area of the silicon portion, which is an underlayer, to the maximum.

It is still another object of the present invention to provide a plating solution for surface treatment for electro-nickel plating on pretreated alternator-diode silicon wafers. Another object of the present invention is to provide a method for surface treating an alternator-diode silicon wafer using the etching solution and the plating liquid as described above.

The present invention provides an etchant in which HNO ₃ (200 mL / L to 400 mL / L) and HF (5 mL / L to 20 mL / L) are mixed to achieve the object of the present invention as described above.

The use of the etchant in the above 60sec ~ 150sec at 10 ℃ ~ 40 ℃ Doing is preferred.

Hereinafter, an etchant which is a surface treatment liquid of the present invention will be described through preferred embodiments.

First, before the present invention, the alternator wafer used in the present invention is known to use a conventional method until the last etching during the pretreatment process. In order to distinguish the surface of the alternator, the surface on which the phosphorus is diffused is referred to as N surface and boron is diffused. The surface is called P side.

According to the present invention, the wafers were treated with other elements of phosphorus and boron, so that the N and P sides reacted differently during etching, and the etching rate was higher in the N plane than the P plane.

In order to carry out the present invention, first, reagents such as nitric acid, sulfuric acid, lactic acid, and hydrofluoric acid were mixed at a predetermined ratio.

Table 1 shows the mixing ratio of each reagent.

Table 1.

No . Reagent Mixing Solution Amount One Hydrochoric acid 300ml / l ~ 600ml / l Nitric acid 200ml / l ~ 400ml / l Hydrofluoric acid 100ml / l ~ 300ml / l 2 Hydrofluoric acid 10 ml / l to 100 ml / l Nitric acid 100ml / l ~ 200ml / l Acetic acid 10 ml / l to 50 ml / l 3 Nitric acid 200ml / l ~ 500ml / l Hydrofluoric acid 5ml / l ~ 50ml / l 4 Hydrofluoric acid 100ml / l ~ 300ml / l Nitric acid 200ml / l ~ 400ml / l Hydrofluoric acid 200ml / l ~ 500ml / l 5 Lactic acid 300ml / l ~ 500ml / l Nitric acid 200ml / l ~ 400ml / l Hydrofluoric acid 100ml / l ~ 200ml / l 6 Hydrofluoric acid 200ml / l ~ 400ml / l Hydrofluoric acid 100ml / l ~ 300ml / l Nitric acid 200ml / l ~ 300ml / l

It was observed that the sample reacts best with the nitric acid: fluoric acid solution, which is an etchant of condition 3 (NO.3), and specific experiments such as ratio conditions, temperature conditions, and time conditions were performed with the nitric acid: fluoric acid mixed solution.

The mixing ratio conditions of nitric acid and hydrofluoric acid were performed as shown in Table 2, and as the ratio of hydrofluoric acid was increased, the etching proceeded at a faster rate.

It was also observed that the higher the concentration of hydrofluoric acid, the more gas was released during etching.

Table 2.

Reagent  ＼ No . One 2 3 4 5 Nitric Acid  200ml / l ~ 300ml / l  200ml / l ~ 300ml / l  200 ml / l to 400 ml / l  300 ml / l to 400 ml / l  300 ml / l to 500 ml / l Hydrofluoric Acid   5 ml / l to 10 ml / l   5 ml / l to 15 ml / l   5 ml / l to 20 ml / l 10 ml ~ 40 ml / l  20 ml / l to 50 ml / l

The temperature conditions of the etchant were performed as shown in Table 3.

Table 3.

Temp . ＼ No . One 2 3 4 5 Temperature 5 ℃ ~ 25 ℃ 5 ℃ ~ 30 ℃ 5 ℃ ~ 40 ℃ 10 ℃ ~ 40 ℃ 10 ℃ ~ 50 ℃

When the nitric acid (200 ml / l to 400 ml / l) and the hydrofluoric acid (5 ml / l to 20 ml / l), which were etchants, were mixed, the etching proceeded at a higher rate as the temperature increased.

The time conditions of the etchant were as shown in Table 4.

Table 4.

Time  ＼ No . One 2 3 4 5 6 Time  30sec ~ 60sec   30sec ~ 120sec   60sec ~ 120sec   60sec ~ 150sec   90sec ~ 150sec  90sec ~ 180sec

Experiment with changing the present time condition under the condition of mixing nitric acid (200ml / l ~ 400ml / l) and hydrofluoric acid (5ml / l ~ 20ml / l) as an etchant, and the temperature condition at 10 ℃ ~ 40 ℃ . As a result, it was observed that the longer the etching time, the better the etching.

Therefore, when the wafer is etched at a high temperature and for a long time, the wafer is overetched and the adhesion strength is significantly decreased. Thus, the etching agent conditions applied to the present invention include HNO ₃ (200 mL / L to 400 mL / L) and HF (5 mL / 1 ~ 20mL / ℓ) was confirmed as the optimum etching conditions when the mixture was 60sec ~ 150sec at 10 ℃ ~ 40 ℃ and it is shown in FIG.

1 is a SEM image comparing the surface layer of the etched under the above conditions of the present invention and the surface layer after etching of Japan T, where A is an SEM image of the surface state before etching, and B is an etching condition according to the present invention. SEM image of the surface state after etching, and C is an SEM image of the surface state after etching of T Company of Japan. As can be seen in Figure 1 it can be seen that the surface image of the wafer after etching according to the present invention is the same or much better than that of Japan.

Hereinafter, the plating solution and the plating method of the present invention for electro-nickel plating for plating in order to give the required performance on the etched alternated-diode silicon wafer as described above will be described. After this process, electrocobalt plating can be performed.

Generally, the surface treatment method of plating can be divided into wet method and dry method. The wet method is a method of reducing plating metal ions from a liquid electrolyte at a base to be plated, and there are various wet surface treatment methods such as electroplating and electroless plating, and also sputtering, Although it is used by dry plating such as ion plating, vacuum deposition, deposition coating, melt plating, electrodeposition coating, etc., the electroplating method is used in the present invention. Electroplating is a method of plating a metal on the surface of an anode using an external power source. When two electrodes are put in an aqueous electrolyte solution and a voltage is applied, electrons carry charges along with external circuits and ions carry charges in the electrolyte. In order for current to flow continuously, charge transfer should occur at the interface between the electrode and the aqueous electrolyte solution. At this time, the metal ions in the aqueous electrolyte solution are reduced at the cathode interface and the anions are oxidized at the anode. This is the most basic principle of electroplating.

Electroplating as described above has the advantages of relatively simple equipment, long life of plating solution, easy management, fast plating speed and good adhesion to the base, while the base layer should be a conductor and the base layer has the surface shape under the influence of current density. Therefore, there is a disadvantage in that uniform plating is difficult in a non-uniform thickness and a complicated shape.

In addition, when surface treatment is performed by evaporation, a surface treatment method commonly used in Korea, a method of supplementing the adhesion between silicon and nickel by forming another metal layer before depositing nickel to improve adhesion. Although the raw materials such as nickel and cobalt used in such a process are almost insoluble metals, it is a fact that it is considerably burdensome in terms of cost compared to the plating solution usually treated by wet method.

Therefore, instead of the above-mentioned evaporation method, electronickel / cobalt plating has a relative superiority in terms of mass production and cost, and thus is most frequently used, but the plating thickness is not uniform depending on the shape of the product. Therefore, in order to solve these problems, the present invention provides a method for electroplating nickel on a silicon wafer and a plating solution thereof so as to facilitate electrocobalt plating, which is a subsequent process.

In the process of carrying out the present invention, electro-nickel plating was performed immediately after the etching, but it was observed that the nickel plating layer was formed unevenly, and thus, in the present invention, the pretreatment method was selected before nickel plating on the silicon layer. The pretreatment is carried out in the process of Table 5 for uniform nickel plating deposition and optimum nickel plating.

Table 5.

No . Process Temp Time Purpose One Pre-Treatment 1 30 ℃ ~ 50 ℃ 60sec ~ 300sec Surfactants 2 Rinse 20 ℃ ~ 50 ℃ Washing 3 Pre-Treatment 2 20 ℃ ~ 40 ℃ 100sec ~ 240sec Applied to Activation 1 solution 4 Activation 1 30 ℃ ~ 60 ℃ 100sec ~ 300sec Optimization of Plating Ion 5 Rinse 30 ℃ ~ 50 ℃ Washing 6 Activation 2 20 ℃ ~ 50 ℃ 60sec ~ 180sec Activation 7 Rinse 20 ℃ ~ 50 ℃ Washing

The pre-treated alternator-wafer is electronickel plated. Electro-nickel plating was performed under the conditions shown in Table 6.

Table 6.

No . Reagent Make - up Temp PH Current density One NiCl ₂ · 6H ₂ O 200g / ℓ ~ 400g / ℓ  20 ℃ ~ 50 ℃  0.5-2.0  3A / dm㎡ ~ 10A / dm㎡ Hydrochloride acid 100ml / l ~ 300ml / l 2 Ni (NH ₂ SO ₃ ) ₂ 4H ₂ O 300ml / l ~ 600ml / l  40 ℃ ~ 70 ℃  3.0-5.5  2A / dm㎡ ~ 8A / dm㎡ NiCl ₂ · 6H ₂ O 20g / ℓ ~ 40g / H ₃ BO ₃ 30g / ℓ ~ 50g 3 Ni (NH ₂ SO ₃ ) ₂ 4H ₂ O 300ml / l ~ 600ml / l   40 ℃ ~ 70 ℃   3.0-5.5   2A / dm㎡ ~ 8A / dm㎡ NiCl2, 6H2O 20g / ℓ ~ 40g / ℓ H ₃ BO ₃ 30g / ℓ ~ 50g / ℓ Polisher-1 10ml / l ~ 30ml / l Semi-gloss-2 1ml / l ~ 5ml / l Anti-fit 1ml / l ~ 7ml / l

In Table 6, the nickel plating solution under condition No. 3 was observed to have a good plating layer, adaptability, and adhesion. In the alternator-wafer, since the phosphorus and boron were diffused as described above, it was observed that precipitation rates of the N and P surfaces were different. Substantially, the precipitation rate of the N plane was slightly lower than that of the P plane, which is 1.5 to 3 times higher than the surface resistance of the N plane (0.15 to 0.35 kW / cm). It is judged that the deposition precipitation rate appears to be different because it is about high. Therefore, the present invention overcomes this problem by bringing the cathode position closer to the N plane side during electrolytic nickel plating.

Table 6 shows the results of nickel plating after electro-nickel plating.

Table 7.

One 2 3 4 5 6 7 8 N Side (Μm) 0.237 0.183 0.137 0.185 0.242 0.175 0.176 0.245 P Side (㎛) 0.222 0.154 0.134 0.171 0.224 0.173 0.169 0.219

The thickness specification of nickel plating is 0.05-0.25 micrometer. This is because if the nickel-plated layer is formed too thick, a hagare will occur.

In the present invention, the plating thickness measurement position was measured at the edge and the center portion as shown in Figures 2a, 2b and 2c, the measurement equipment used XRF (SEIKO SEA 5120) owned by the company.

As can be seen from the above table, the nickel plated layer of the present invention satisfies the standard thickness specification.

According to the present invention as described above in the surface treatment process of the alternating-diode silicon wafer is provided with an etching solution that can enhance the tensile strength of the wafer by expanding the contact area between the nickel layer of the metal layer and the silicon portion of the underlying layer, and after the pretreatment It is possible to economically provide an alternator-diode silicon wafer by providing a plating solution and a surface treatment method using the same, which can form a uniform nickel layer on the silicon wafer by pretreatment and facilitate the subsequent cobalt plating.

Claims (2)

A method of forming an electrolytic nickel layer on an alternator-diode silicon wafer, wherein after forming a diode structure, the agglomerate wafer is separated, the source of the surface is removed, the remaining source is removed, the heat treatment is performed to stabilize the characteristics, and the etching is performed to remove the nickel layer. In the plating method, nitric acid (200 ml / l to 400 ml / l) and hydrofluoric acid (5 ml / l to 20 ml / l) are mixed as an etching solution for removing the oxide film, and 60 sec at 10 ° C to 40 ° C. Pre-treatment before forming the nickel layer, followed by NiCl ₂ · 6H ₂ O 20 g / l to 40 g / to 300 mL / L to 600 mL / L of Ni (NH ₂ SO ₃ ) 2 · 4H ₂ O. l, H ₃ BO ₃ 30g / l-50g / l, 10ml / l-30ml / l varnish, 1ml / l-5ml / l semi-gloss and 1ml / l-7ml / l anti-pitching agent Alternator-diode silicon, characterized in that the electroplated nickel at pH 3.0 to PH 5.5, voltage 2 A / dm 2 to 8 A / dm 2 at 40 ° C. to 70 ° C. A method of forming an electrolytic nickel layer on a cone wafer. An electrolytic nickel electrolyte surface-treated on an alternator-diode silicon wafer, containing 20 g / l to 40 g of NiCl ₂ · 6H ₂ O to 300 ml / l to 600 ml / l of Ni (NH ₂ SO ₃ ) 2 · 4H ₂ O 30 g / l to 50 g / l of H ₃ BO ₃ , 10 ml / l to 30 ml / l of polish, 1 ml / l to 5 ml / l of semi-gloss, and 1 ml / l to 7 ml / l of anti-pitching agent Electrolytic nickel electrolyte characterized in that it comprises.

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