JPS6156617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a semiconductor device in which an exposed PN junction in a mesa type semiconductor device is covered with glass.

In conventional mesa-type semiconductor devices, after forming a PN junction, a mesa groove is formed using a chemical etching method, the junction end is exposed on the side surface of this groove, and this is covered with an appropriate insulating film to cover the semiconductor substrate surface. Inactivation is very important in increasing the reliability of semiconductor devices, and so-called passivated mesa types have been widely used.

When a semiconductor device having such a mesa groove covered with an insulating film is separated by fracture along the mesa groove, a laser beam is generally used to cut the semiconductor substrate through the insulating film in the mesa groove. After the grooves are formed, semiconductor pellets are obtained by pressing with a steel roller or the like and cutting from the grooves.

However, when the semiconductor substrate with the cut grooves formed thereon is pressed by a steel roller or the like, contact occurs between adjacent semiconductor pellets, thereby causing cracks, chips, etc. in the insulating film.

For this reason, defects in appearance occur frequently, which lowers yield, and deterioration of high voltage characteristics and leakage current becomes noticeable in later electrical characteristic checks, resulting in a decrease in reliability.

Conventionally, several measures have been taken to eliminate the above problems. For example, attempts have been made to avoid damage to the insulating film by providing cutting grooves in parts of the semiconductor substrate other than the mesa grooves covered with the insulating film. This method has the drawback that the pellets become larger, resulting in poor pellet yield and high cost.

The object of the present invention is to provide an effective method for manufacturing a semiconductor device that eliminates the drawbacks of these conventional techniques.

The feature of the present invention is that after a photoresist film is deposited on the entire surface of a mesa-shaped semiconductor substrate coated with an insulating film, cutting grooves are formed in the semiconductor substrate by a laser beam through the photoresist film and the insulating film, and then , using a photoresist film as a mask,
Thermal strain and flakes caused by the melted part of the insulating film and the beam are removed by chemical etching.

In this manufacturing method, each pellet is cut and separated after removing thermal deformities, cracks, chips, etc. caused by the laser beam, so the semiconductor device of the present invention can produce mesas with high yield and high reliability. type semiconductor device.

Next, one embodiment of the present invention will be described in detail with reference to the drawings.

FIGS. 1A to 1F are cross-sectional views showing the manufacturing process of a diode in which the present invention is applied. In FIG. 1A, for example, a P-type impurity is diffused from one side of an N-conductivity type silicon substrate 1,
After providing the P ⁺ type region 2 and forming the PN junction 3,
An oxide film 4 is deposited by thermal oxidation.

Next, as shown in FIG. 1B, windows are selectively formed in the oxide film 4 by photoetching, and the oxide film 4 is etched using a mixed acid consisting of nitric acid and hydrofluoric acid.
Using this as a mask, chemical etching is performed to form a mesa groove 5 that penetrates the PN junction 3 that provides withstand voltage, and to expose the PN junction 3.

Next, as shown in FIG. 1C, glass particles containing borosilicate as a main component are deposited on the surface of the silicon substrate having the mesa grooves 5 by, for example, electrophoresis to form a glass particle layer 6. Next, in FIG. 1D, the semiconductor substrate described above is fired at 500 to 800° C. for about 1 to 2 hours to melt the glass particle layer 6 and form an insulating film 7, which partially remains. After selectively removing the oxide film 4 with a dilute hydrofluoric acid-based etching solution, the front and back surfaces of the electrode formation area are lightly treated by sandblasting or chemical etching, and then a metal electrode is formed using a general plating method or vapor deposition method. Layers 9 and 9' are formed.

Next, photoresist films 10 and 10' are deposited on the entire front and back surfaces of the semiconductor substrate. The deposition of this photoresist film 10 is very important as a mask for etching the cut portions of the molten insulating film in the cut groove portions when cutting grooves are later formed between the respective elements using a laser beam. Next, in FIG. 1E, a laser beam is applied to the center between the diode elements so that each diode element is separated from the surface of the photoresist film 10 deposited on the insulating film 7 in the mesa groove 5. Cutting grooves 11 are formed by the following steps. However, since the cut groove 11 formed by the laser beam is a so-called molten layer in which the material such as the insulating film 7 or the silicon substrate 1 is melted,
Heat strain and cracks are occurring frequently. Needless to say, such defects in the insulating film lead to a decrease in reliability.

Next, as shown in FIG. 1F, using the photoresist film 10 as an etching mask, for example, the cut grooves of the melted insulating film are selectively etched with a mixed solution of hydrofluoric acid and ammonium fluoride. Etching grooves 12 are formed.

Next, the photoresist film 1 on the semiconductor substrate is
After removing 0 and 10' by pyrolysis, the semiconductor substrate is pressed with a steel roller or the like to break it from the cut groove 11, and a diode pellet as shown in FIG. 2 is obtained. It is.

As described above, the present invention includes the steps of forming a mesa groove in a semiconductor substrate having a PN junction, depositing an insulating film on the mesa groove, and forming a photoresist film on the insulating film; A step of forming a cutting groove from the surface of the side photoresist film through the photoresist film through the photoresist film into the insulating film and the semiconductor substrate portion, and etching the insulating film in the cut groove portion using the photoresist film as a mask to form the cut groove. Since this process includes the step of further breaking and separating the chips to form semiconductor pellets, defects such as thermal distortion, cracks, and chips in the cut grooves formed by the laser beam on the insulating film in the mesa grooves are eliminated, and at the same time, the steel roller When the semiconductor substrate is broken and separated by pressing, etc., even if contact occurs between adjacent semiconductor pellets, contact between the insulating films does not occur, so new cracks, chips, etc. occur in the insulating film. This will no longer occur, and there will be no so-called appearance defects. As a result, it is easy to mass-produce mesa-type semiconductor devices with stable characteristics and high reliability, and the manufacturing cost is also significantly reduced.

[Brief explanation of the drawing]

1A to 1F are cross-sectional views showing an embodiment of the present invention in the order of steps, and FIG. 2 is a cross-sectional view of a semiconductor device manufactured according to an embodiment of the present invention. In the drawing, 1 is an N-type silicon substrate, 3
5 is a PN junction, 5 is a mesa groove, 6 is a glass particle layer, 7 is an insulating film, 9 is a metal electrode layer, 10 is a photoresist film, 11 is a cutting groove, and 12 is an etching groove.

Claims (1)

[Claims] 1 In a method for manufacturing a semiconductor device, a mesa groove in which a PN junction is exposed is formed in a semiconductor substrate having a PN junction, the mesa groove is coated with an insulating film, and the mesa groove is cut into pellets along the mesa groove. forming a metal electrode layer on the front and back surfaces of the semiconductor substrate except for the mesa groove after coating the groove with an insulating film; forming a photoresist film on the insulating film and the metal electrode layer; and forming a photoresist film on the insulating film and the metal electrode layer; a step of irradiating a beam from the surface of the upper photoresist film to form a cutting groove;
A method of manufacturing a semiconductor device, comprising the step of etching an insulating film in the cut groove portion using the photoresist film as a mask.