JPH0132363Y2 - - Google Patents

Description

[Detailed description of the invention] The invention relates to semiconductor devices, and in particular, when forming a fuse element using polycrystalline silicon formed on an oxide film on a semiconductor substrate, contact between polycrystalline silicon and a metal conductor is used. The present invention relates to a semiconductor device characterized in that it is possible to provide a polycrystalline silicon fuse that takes resistance into consideration and can be cut stably against fluctuations in the contact resistance during manufacturing.

In recent years, the field of application of semiconductor devices has been expanding at a remarkable rate, and they are rapidly penetrating into fields that require sufficient precision using conventional individual components or adjustment techniques.

For example, consider implementing analog-to-digital conversion or digital-to-analog conversion using a semiconductor device. At this time, the relative accuracy of the diffused resistor or film resistor constructed on the semiconductor substrate is considered to be limited to about ±0.2%. For this reason, it is generally considered that the limit of accuracy that can be realized as a semiconductor device is about 8 to 10 bits, and in order to realize a semiconductor device with 10 bits or more, it is necessary to make adjustments on the semiconductor substrate. Adjustment techniques on semiconductor substrates can be roughly divided into two types.

The first adjustment technique is a technique for linearly adjusting diffusion resistance or film resistance by cutting it thermally, mechanically, or chemically.

The second adjustment technique is a technique in which the resistance is cut by a thermal method and adjusted stepwise. The advantage of the first linear adjustment is that fine adjustment is possible, but the disadvantage is that the adjustment takes a long time.

The advantage of the second stepwise adjustment is that the adjustment time can be shortened, but the disadvantage is that it is not suitable for fine adjustments because it is a stepwise adjustment.

The present invention provides a semiconductor device suitable for performing stepwise adjustment, and the present invention will be explained in detail below with reference to the drawings.

FIGS. 1a and 1b are illustrations of the principle of stepwise adjustment. Figure 1a is an example of the parallel connection type.
Figure b is an example of a series connection type. In Figure 1,
Terminal 1 and terminal 2 represent the terminals of the equivalent resistance, respectively, resistors 3, 4, 5 and 6 represent the resistors connected in parallel, and cuts 7, 8 and 9 represent the cuts of resistors 4, 5 and 6, respectively. are shown respectively.

In Figure 1a, it is generally suitable to use the resistance values of resistors 3, 4, 5 and 6 in the form 1:2:4:8; in Figure 1b, it is 1:1/2:1/ It is common to use a 4:1/8 ratio. The resistance ratio of this resistor is determined with respect to the step width of the step adjustment, and if the step width is small, it is possible to use a small ratio.

A certain resistance value in the cuts 7, 8 and 9 in FIGS. 1a and 1b is generally unavoidable. Generally, this cutting section is often performed by using a conductor used for a resistor, applying a voltage source or a current source, and generating a locally high-temperature area.

It will be clear that the resistance of this cut will increase the error in step adjustments.

The resistance of the cut portion is divided into the resistance of polycrystalline silicon and the contact resistance of polycrystalline silicon and a metal conductor. The resistance of polycrystalline silicon is expressed in terms of layer resistance and geometry, typically ranging from 50 ohms to 100 ohms.
It is about ohm. On the other hand, the contact resistance is generally 20/W to 40/W ohm/μm, where W is the length of the opposing contacts.

Therefore, if the contact length W is 2 μm, the contact resistance will be 10 to 20 ohms, and the resistance of the cut portion will be twice the resistance of polycrystalline silicon, resulting in a relatively large resistance value.

Furthermore, if the contact resistance increases, a voltage drop will occur due to the contact resistance when cutting the polycrystalline silicon fuse by applying voltage or current.
In some cases, polycrystalline silicon fuses could not be cut.

The present invention has greatly improved these drawbacks and is a polycrystalline silicon material that can be stably cut with little adjustment error.
Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an explanatory plan view of the first embodiment of the present invention. In FIG. 2, the lead-out conductors 21 and 2
2 is a plan view of a polycrystalline silicon fuse connected to polycrystalline silicon 25 through contacts 23 and 24. FIG.

The difference in FIG. 2 from a conventional polycrystalline silicon fuse is the dimensions of contacts 23 and 24. Regarding the dimensions of the contacts 23 and 24, the contact resistance is determined by the contact length W of the portions facing each other. Assuming the resistance value of a normal polycrystalline silicon fuse of about 50 ohms, the resistance value allowed for contacts 23 and 24 is at worst about 1/4 of that of polycrystalline silicon, and at the time of design it is 1/10.
The following is preferable. For this reason contact 2
The resistance value allowed for 3 and 24 is 5 ohms or less. In order to achieve a contact resistance of 5 ohms or less, the contact length W must be 8 μm or more (contact resistance of 40/W ohm/
(Using μm).

In this way, in a polycrystalline silicon fuse, by determining the contact W in consideration of the contact resistance, a polycrystalline silicon fuse that can be cut stably with little adjustment error can be realized.

FIG. 3 is an explanatory plan view of a second embodiment of the present invention. The difference between FIG. 3 and FIG. 2 is the shape of contacts 33 and 34. Other lead-out conductors 31 and 32 and polycrystalline silicon 35
has the same configuration as in FIG.

Figure 3 shows square contact 2 in Figure 2.
3 and 24 are rectangular. It has been reported that if the contact width W is at least 4 .mu.m or more, it has no effect on contact resistance, so it is clear that the same effect as in FIG. 2 can be obtained even if a contact as shown in FIG. 3 is used.

As described above in detail with reference to the drawings, by using the polycrystalline silicon fuse according to the present invention, it is possible to realize a semiconductor device that has little adjustment error and is easy to cut, which is effective in expanding the field of application.

[Brief explanation of the drawing]

Figure 1 a and b are principle diagrams of stepwise adjustment, Figure 2
The figure shows a plan explanatory view of the first embodiment of the present invention, and FIG. 3 shows a plan explanatory view of the second embodiment of the present invention. 1, 2... terminal, 3, 4, 5, 6... resistance,
7, 8, 9... Cutting section, 21, 22, 31, 32
...Output conductor, 23, 24, 33, 34...
Contact, 25, 35...polycrystalline silicon.

Claims (1)

[Scope of utility model registration request] It has a fuse made of polycrystalline silicon and a metal conductor connected to at least one end of the fuse, and the contact resistance of the contact portion between the fuse and the metal conductor is 50 ohm to 100 ohm of the fuse. A semiconductor device characterized in that the resistance value is one-fourth or less.