JPS59125667A - Diode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pellet structure of a diode that operates in a high frequency band (for example, a milliwave band).

Conventionally, for example, an invat diode has been used as a high frequency diode. In this case, it is necessary to lower thermal resistance in order to improve oscillation characteristics and reliability. Therefore, they are assembled in a so-called upside-down structure in which the P-N junction is on the heat sink side. Therefore, in order to easily assemble the pellet structure, as shown in FIG. 1, a disk-shaped N++ silicon substrate 1. N- operating layer 2 and P+
+ '1 on both ends of the silicon chip consisting of contact layer 3
It has an electrode metal layer 4.4' having a multilayer structure of 1-Pt-Au, and has a mesa structure.

FIGS. 2(a) to (C) are cross-sectional views showing the manufacturing method of this pellet.
．． The epitaxial wafer on which the P'' contact layer 3 was sequentially formed was ground down to a thickness of about 50 μm from the substrate side, and circular electrodes 4 and 4' made of a multilayer structure of Ti-Pt-A and U were formed on both sides of the epitaxial wafer. (Figure 2(a)). Next,
A mesa portion is formed by chemical etching using the electrode 4 on the P-N junction side as a mask (Fig. 2(b)), and finally, using the electrode 4' on the substrate side as a mask, a mesa portion is formed by chemical etching. By cutting and pasting the strips and plates, pellets of the shape shown are formed (FIG. 2(C)).

FIG. 3 is a general assembly diagram of an invat diode. 110 is impat da f eau de peret.

The electrode tape 130 is thermocompression bonded on the pedestal 120 of the diode case in an upside-down manner, and furthermore, the electrode gold tape 130 is thermocompression bonded to the pellet structure. As can be seen from the figure, when the invat diode operates, high-frequency current flows vertically through the pellet, but when the frequency reaches the millimeter wave band, the current flows through the pellet surface due to the skin effect, and the silicon substrate The resistance of the cylindrical frequency oscillation can no longer be ignored, and the cylindrical frequency oscillation output characteristics are not significantly affected. Further, the thickness of the silicon substrate is limited to 50 μm, and if it is made thinner than this, there is a drawback that wafer cracking occurs during pellet production, resulting in a significant decrease in yield.

An object of the present invention is to provide a diode operating in a high frequency band with excellent high frequency operating characteristics without reducing the pellet manufacturing yield.

The diode of the present invention is characterized in that the electrode metal layer provided on the semiconductor substrate on which the active layer and the contact layer are sequentially formed extends from the bottom surface of the substrate to the side surface of the substrate. shall be.

Formation of the metal layer on the side surface of the substrate is free from misalignment of the metal layer on the substrate surface that occurs when chemical holes are formed from the substrate side before cutting the substrate. Of course, it is preferable that this metal layer be electrically connected to the metal layer on the bottom surface of the substrate.

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

FIGS. 4(a) to 4(d) are cross-sectional views sequentially showing the manufacturing process of a pellet by applying the present invention to an invat diode. N4+/IJ contact board 1 with a thickness of about 300μm
A silicon Evita core wafer on which an N- active layer 12 and a P++ contact layer 13 are sequentially formed is ground to a thickness of about 50 μm by mechanical or chemical etching, and an 'I' i is formed on the contact layer side. A gold pA electrode 15 for positioning the circular electrode 14 made of -Pt-Au multi-R4 structure is formed on the substrate side (FIG. 4(a)). Next, a photoresist 16 is placed on the metal electrode 15. A mesa structure is formed on the j17 substrate side by chemical etching (see Fig. 4).
b)). Furthermore, after peeling off the photoresist 16 and the positioning electrode, Ti-Pt-A- is applied to the entire surface of the substrate side.
What is the electrode metal layer 17 having a multilayer structure of u (FIG. 4(C))? After that, the valley portion of the electrode metal layer 17 is cut by mechanical or chemical etching, and then electrical Mj! is applied from the contact layer side. , 14 are used as a mask to form a mesa by chemical etching and cut the target chip (FIG. 4(d)).

According to the present invention, when the diode is in operation, even if the high-frequency current flowing through the chip flows along the side of the chip due to the skin effect, the passage has a metal layer, so the series resistance is higher than that of conventional chips. decreases, resulting in excellent oscillation output characteristics. Furthermore, from the perspective of chip manufacturing, in-bat diodes conventionally used in the MI'J wave band have a thickness of about 15 μm to prevent characteristic deterioration.
Therefore, during wafer processing, wafer
- Cracks occur and the yield drops significantly, but according to the present invention, the substrate can be processed as it is thick without having to be made thinner, which has the advantage of effectively preventing the drop in yield. . Incidentally, in explaining the present invention, a multilayer film of Ti--Pt--Au was used as the metal for preventing C1 series resistance, but it goes without saying that any type of metal film with low electrical resistance may be used.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional pellet, Figures 2 (a) to (C)
) are cross-sectional views showing the conventional method of manufacturing a pellet, Figure 3 is an assembly diagram of an invat diode, and Figures 4 (a) to (d).
1A and 1B are cross-sectional views of each process based on a pellet manufacturing method according to an embodiment of the present invention. 1.11...Silicon substrate, 2.12...
...Active layer, 3,13゛°゛Contact layer, 4.4',
14゜17--T i -P t-Au multilayer metal film,
15゛Positioning metal film, 16-==゛Photoresist, 110.Paper °In-butt diode pellet, 120... Case pedestal, 130゛Old'' gold tape for electrode No. 0/Kasumi No. 3 countries

Claims (1)

[Claims] A diode characterized in that an electrode metal layer is continuously provided on the bottom and side surfaces of a semiconductor substrate on which an active layer and a contact layer are sequentially formed.