JPS6128228B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of an electrode and an external lead conductor attachment part such as a wire bonding part to the electrode in a semiconductor device.

As shown in Fig. 1, the structure of the conventional ohmic contact electrode is such that the ohmic contact electrode provided on the semiconductor crystal 12 is used as the area for attaching the assembled external lead conductor, so that both coexist and become common. There is. Such an ohmic contact electrode structure has the following drawbacks. (1) Due to the coexistence of the ohmic electrode and the bonding region, the device characteristics deteriorate due to the force during the bonding process. (2) Due to the coexistence of the bonding region, the area of the substantial ohmic electrode increases, resulting in deterioration of device characteristics. Regarding (1), there is strain in the semiconductor crystal in the active layer region and an increase in resistance due to the force applied during bonding. Regarding (2), the capacitance that becomes a parasitic element,
The resistance component increases as the area increases. Particularly in devices that operate at high frequencies or perform high-speed switching operations, reducing parasitic elements is the most important factor for improving performance.

The present invention eliminates the above-mentioned drawbacks of the prior art, and provides an electrode structure with improved characteristics of ohmic electrodes, fewer parasitic elements, and good connections.

That is, in the present invention, as described in Japanese Patent Application No. 50-105897, the electrode and the bonding pad of the electrode are separated and the two are connected to each other. In particular, the above method is applied to the ohmic electrode portion. It is something.

The constituent elements of the present invention are as follows. It is provided separately from the first ohmic electrode and another function, such as a bonding region. Second, the contact between the ohmic electrode and another function, such as a bonding area, is made with another metal deposited on the semiconductor device. At this time, another metal may be applied to the entire surface of the bonding area. Thirdly, the opposing portions of each electrode are shaped into convex or concave portions in order to increase the number of metal contact lines for good connection. Naturally, the area of the ohmic electrode should be such that the parasitic elements are small and the area does not interfere with the operation of the element.

The second example of an electrode structure that satisfies these three requirements is a Schottky junction field effect transistor.
Shown in the figure. Active layer 12 provided on substrate 11
Source 13, drain 14, gate electrode 15 on top
There is. At this time, the source 13 and drain 14 are ohmic contact electrodes, and the bonding area is set as the bonding area 1 for the source electrode corresponding to each electrode.
3', a drain electrode bonding region 14' is provided. That connection is in this case gate metal 1
5 (of course, other metals may be used for connection, but it is advantageous in terms of process to use the gate metal 15). Its plan view is shown in FIG.
In FIG. 3, bonding regions 13' and 1 are provided opposite to the source electrode 13 and the drain electrode 14.
The portion 4' is formed into a concave and convex shape to prevent disconnection when connecting with another metal 15'.
In other words, since there is a level difference in the connection part, there is a certain probability of disconnection, but by making the shape concave and convex in this way, the length of the connection part to the metal 15' is reduced by the increased contact line. This improves the connectivity between the electrodes 13, 14 and bonding regions 13', 14' and the metal 15'. At this time, it is possible to cover the entire surface of the bonding area with the connecting metal 15';
At least the top metal must be a bondable metal.

Hereinafter, the present invention will be explained in detail with reference to Examples. In the example, a case will be described in which the present invention is applied to a Schottky junction field effect transistor using a gallium arsenide crystal. FIG. 4 is a cross-sectional view of the manufacturing process of a shotgun barrier type field effect transistor.
As shown in FIG. 4a, an active layer 12 was provided on a gallium arsenide substrate (semi-insulating resistivity 10 ⁸ Ωcm) 11, and ohmic electrodes of a source 13 and a drain 14 were provided thereon. At this time, the ohmic connection electrode width is 15μ
m, and other parts of the active layer 12 are removed to expose the semi-insulating gallium arsenide substrate 11. On this exposed substrate 11, a bonding region and ohmic electrodes 13' and 14' were formed separately and simultaneously using the same material. Of course, the bonding region and the ohmic electrode may be made of different materials, or may be formed in different steps even if they are made of the same material. This electrode material
Metal is deposited by continuous vapor deposition of Au/Ge/Ni/Au, and each ohmic electrode 13, 14 and bonding area 1
Patterns 3' and 14' were formed by a peeling method using a photoresist film SiO ₂ film 16. After that, Au・
The ohmic electrode was formed by heat treating Ge/Ni/Au at 400°C for 5 minutes in an H ₂ atmosphere. At this time, the bonding region is alloyed with the substrate 12, but does not become an ohmic electrode. After that, we applied Mo17, which is a shot-bonding metal, and Au18, which is a bonding metal fitting.
was applied to the entire surface, and a photoresist film 19AZ1350J was applied.
6000 Å was applied, leaving a photoresist film as shown in Figure 4b. After that, Au18 is removed by ion milling using the photoresist film 19 as a mask, and Au18 is removed by ion milling using the photoresist film 19 as a mask.
Using 9 as a mask, OF ₄ gas plasma Mo 18 is etched. Thereafter, the photoresist film 19 is also removed to form a structure as shown in FIG. 4c. As shown in FIG. 4c, the ohmic electrodes 13 and 14 and the bonding area 1
3' and 14' were connected by Mo/Au 17' and 18'. As a result, in bonding operations, conventionally 15
Chips with defective characteristics occurred at an incidence of about %, but
In the present invention, almost no chips with defective characteristics (due to wire bonding assembly) were generated. Also, the capacitance between gate and drain is 0.005pF with the same pattern.
The gain was improved by 1dB at 10GHz. This is because, by separating the bonding regions, the active layer will not be damaged during wire bonding work. It is also believed that stray capacitance was reduced because the active layer was made to the minimum size.

In addition, using the same method as in the above embodiment, not only the connection metal is applied to the entire surface of the bonding area, but also
As a result of connecting only the convex portion of the bonding region to the entire surface of the ohmic electrode, the same effect as in the example was obtained.

Furthermore, as stated in Japanese Patent Application No. 50-105897, by separating the bonding pad portion for the gate electrode, the above-mentioned effects can also be obtained for the gate electrode, and the yield can be improved. I can do it.

An example is shown in FIG. 15 is a gate electrode (for example, Mo/Au), 21 is a gate electrode extension part (Mo/Au), and 20 is a bonding pad part (for example,
Au・Ge/Ni/Au).

In the above embodiments, as an ohmic electrode
Although Au・Ge/Ni/Au was used, it is also possible to use only Au・Ge alloy, or In・Ag, Au・Zn, Sn・Ag, In・
Other metals such as Ge/Ag, Sn/Ge/Ag can be used. It can also be used as a shot key electrode.
Cr/Mo/Au, Al, Ti/Mo/u, etc. may also be used.

As explained above, the structure of the ohmic electrode of the present invention is effective for improving device characteristics. The present invention can be applied to Si and other compound semiconductors as semiconductor materials, and is particularly applicable to MOS type transistors. The metal connecting the ohmic electrode and the bonding region is not particularly limited as long as it is not for ohmic contact. Furthermore, it goes without saying that the external lead-out conductor is not limited to a bonding wire, but may be a raised metal that can be flip-chip bonded or a beam lead electrode without departing from the spirit of the present invention.

[Brief explanation of the drawing]

Figure 1 shows the cross-sectional structure of a conventional ohmic electrode, and Figure 2 shows the cross-sectional structure of a conventional ohmic electrode.
The figure shows a cross-sectional structure of an ohmic electrode of the present invention, FIG. 3 shows a planar electrode structure of the present invention, FIG. 4 shows an electrode manufacturing process diagram of an ohmic electrode of the present invention, and FIG. 5 shows another embodiment of the present invention. FIG. In the figure, 11... substrate crystal, 12... active layer, 13... ohmic electrode or source ohmic electrode, 13'... source electrode bonding region, 14... drain ohmic electrode, 14'... drain electrode bonding region,
15... Gate electrode, 15'... Metal connecting the ohmic electrode and the bonding region, 16... SiO ₂ film,
17...Mo metal, 18...Au metal, 17', 18'...
Metal (Mo/Au), 19... photoresist film connecting the ohmic electrode and the bonding region.

Claims (1)

[Scope of Claims] 1. An active layer on a predetermined semiconductor substrate, an electrode conductor layer in contact with the active layer, and a conductor layer for an external lead-out conductor attachment part located apart from the active layer and the electrode conductor layer. A semiconductor device having a structure in which the electrode conductor layer and the external lead conductor attachment part conductor layer are electrically connected by a third conductor layer, wherein the electrode conductor layer and the external lead conductor attachment part conductor layer are electrically connected to each other by a third conductor layer. A semiconductor device characterized in that the planar shape of the opposing layers has at least one of a convex portion and a concave portion. 2. The semiconductor device according to claim 1, wherein the third conductor layer is composed of a plurality of layers. 3. The semiconductor device according to claim 1 or 2, wherein the conductor layer for the external drawer conductor attachment portion and the semiconductor substrate exhibit at least an alloying reaction at the interface thereof. semiconductor device.