JP3129083B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device for a stacked high-voltage semiconductor rectifier composed of a mesa diode.

[0002]

2. Description of the Related Art First, the structure of a mesa-type laminated high-voltage semiconductor rectifier to which the present invention is applied is shown in FIG. In the figure, 1 is a mesa diode chip, 2 is an axial lead, 3 is a junction coating resin (JCR), 4 is a molding resin,
5 is a solder joint layer. Such a semiconductor rectifier is manufactured as follows. First, the PN
After nickel plating is applied to both surfaces of the silicon wafer on which the bond has been formed, a predetermined number of wafers are stacked and soldered to each other. Next, the above-described wafer stack is diced into a fiducial shape to obtain a chip stack of the diode chip 1. Subsequently, in order to remove the processing strain layer of the chip generated by the dicing process, the chip is etched with a mixed acid solution (a mixed solution of hydrofluoric acid, nitric acid, acetic acid, etc.) in an acid etching step, washed with water, and dehydrated by an acetone replacement method (chip). The laminate is immersed in an acetone solution to remove the moisture adhering to the chips by acetone), and after the drying step, the leads 2 are soldered to both ends of the chip laminate. Further, after removing the heat-strained layer of the chip generated in the lead soldering step by alkali etching, a bonding coating resin (polyimide resin) 3 is applied to the peripheral side surface of the chip laminate, and then a mold resin (epoxy resin) 4 Then, the entire chip stack is sealed to complete the mesa-type stacked high-voltage semiconductor rectifier of FIG. FIG. 5 shows a manufacturing process from the wafer processing to the alkali etching.

[0003]

However, the mesa-type semiconductor rectifier manufactured by the above-described conventional method has a problem that the reverse leakage current, which is one of the diode characteristics, has a large variation. It was difficult to mass-produce high-quality products with stable characteristics. One of the causes of such a large variation in characteristics is an abnormal shape of the chip surface due to uneven etching in the alkaline etching step. In other words, when the water adhering to the chip is removed by the acetone replacement method in the water washing and dehydration steps after the acid etching, the oxidation generated on the chip surface by heating in the subsequent lead (soldering) step The film is likely to be non-uniform, which causes uneven etching when performing alkaline etching, resulting in abnormal shape (the surface becomes uneven instead of a smooth surface), which is the reverse leakage current of the diode chip. Is a factor that increases

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object the provision of a method of manufacturing a semiconductor device which can solve the above-mentioned problems and obtain stable characteristics, for a mesa diode or the like. With the goal.

[0005]

In order to achieve the above object, in a manufacturing method of the present invention, a chip obtained by dicing a wafer is subjected to acid etching to remove a work-strained layer, and then washed with water, In a device in which leads are attached through a dehydration and drying process, and further subjected to alkali etching to remove the heat-strained layer, the chip after the water washing in the dehydration process is used.
Place in the centrifugal drum while keeping it in the etching container, and dry
Spin the centrifugal drum at high speed while feeding air to remove centrifugal
It can be carried out by water.

[0006]

[0007]

In the dehydration step after acid etching and water washing as described above, the chip is centrifugally dehydrated using a centrifugal dehydrator, so that an oxide film formed on the chip surface by heating at the time of lead attachment is formed. It becomes uniform compared to the dehydration method by acetone substitution. This has been confirmed from the results of experiments performed by the inventors. Therefore, in the alkaline etching step performed after the lead is attached, the chip surface is uniformly etched to obtain a smooth etched surface without shape abnormality. As a result, in the mesa diode, the variation in the reverse leakage current is suppressed, and It is possible to manufacture a product with little characteristic variation between manufacturing lots.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a manufacturing process of the present invention in comparison with a conventional manufacturing method for a mesa semiconductor rectifier (see FIG. 5). That is, in the chip dehydration step performed after the wafer processing, dicing, acid etching, and water washing steps, moisture adhering to the chips is dehydrated by employing a centrifugal dehydration method. Subsequently, drying, lead attachment, and alkali etching are performed in the same manner as in the conventional manufacturing method. Further, application of a junction coating resin (JCR) and sealing with a mold resin are performed to obtain the mesa-type laminated high-voltage semiconductor rectifier shown in FIG. Complete.
A low-voltage mesa-type semiconductor rectifier device assembled by attaching leads to both ends of one diode chip can be manufactured in the same procedure.

Next, the above-mentioned centrifugal dehydration method will be specifically described. First, in the acid etching step, the etching container 6 (a container with a lid) shown in FIG.
a), a fixed number of chip stacks (an assembly in which a plurality of diode chips 1 are stacked and soldered between them) is immersed in a mixed acid solution together with the etching container to perform etching. Subsequently, after the mixed acid solution is removed in the water washing step, the etching container 6 containing the chip stack is placed in the centrifugal drum 7a of the centrifugal dehydrator 7 as shown in FIG.
The centrifugal drum 7a is set to 1500 ± 20 while sending dry air into the drum.
Spin at high speed at 0 rpm to centrifugally dehydrate the water adhering to the chip. Note that the chip stack after dehydration is carried into a drying chamber while being placed in the etching container 6, and dried.

[0010]

As described above, according to the present invention, according to the production method of the present invention, with respect to the chip obtained by dicing the wafer into diced, acid etching, the chip is in the dehydration step performed subsequent to the water wash Centrifugal drum in etching container
High speed rotation of centrifugal drum while feeding dry air
Since the water adhering to the chip was removed by the centrifugal dehydration method of spinning and centrifugal dehydration, there was no etching unevenness in the alkaline etching step performed after attaching the lead,
No chip surface shape abnormality appears. Therefore, by applying the manufacturing method of the present invention to a mesa diode,
Variations in reverse leakage current among manufacturing lots can be suppressed to a small value, and a product with stable characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a process diagram of a manufacturing method according to the present invention.

2 is an external perspective view of an etching container used in the manufacturing process of FIG.

FIG. 3 is a plan view showing an etching container set state of the centrifugal dehydrator used in the centrifugal dehydration step of FIG. 1;

FIG. 4 is a structural diagram of a mesa-type stacked high-voltage semiconductor rectifier to which the present invention is applied;

FIG. 5 is a process diagram of a conventional manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diode chip 2 Lead 3 Joining resin 4 Mold resin 5 Solder joining layer 6 Etching container 7 Centrifugal dehydrator 7a Centrifugal drum

Claims (1)

(57) [Claims] 1. A method of manufacturing a semiconductor device for a mesa-type diode or the like, wherein a chip obtained by dicing a wafer is subjected to acid etching to remove a work-strained layer, and then washed, dehydrated, and dried. The chip after water washing in the above-mentioned dehydration step is etched in the case where the lead is passed through and the heat-strained layer is further removed by alkali etching.
Place the container in a centrifugal drum and send dry air
A method of manufacturing a semiconductor device, wherein a centrifugal drum is rotated at a high speed while centrifuging to spin-dry.