JPS6394664A - Semiconductor device - Google Patents

Abstract

PURPOSE:To reduce a leakage current in a capacitor and increase the capacity of the capacitor by a method wherein the capacitor is composed of 1st electrode made of metal wiring material, a dielectric layer composed of laminated silicon nitride film and silicon oxide film and 2nd electrode. CONSTITUTION:Field oxide films 2 and 3 are formed on a semiconductor substrate l such as a silicon substrate and a capacitor, which will be described later, is formed on the field oxide film 3. A MOS transistor is formed on the main surface of the semiconductor substrate 1 between the field oxide film 2 and the field oxide film 3 and a gate electrode 6 made of, for instance, polycrystalline silicon is formed on the main surface with a gate oxide film 5 in-between. A capacitor is formed above the field oxide film 3 where an aperture is formed in a layer insulating film 7 which can be subjected to reflow. The capacitor is patterned by, for instance, the same process as the patterning of the gate electrode 6 and a silicon oxide film 11 and a silicon nitride film 12 are laminated on a polycrystalline silicon layer 10 as 2nd electrode. With this constitution, the route of a leakage current is cut off and the leakage current itself can be reduced and, moreover, by regulating the film thickness or the like, the capacity can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a semiconductor device in which a capacitor is formed on a semiconductor substrate.

B1 Summary of the Invention The present invention provides a semiconductor device in which at least a capacitor is formed on a semiconductor substrate, in which the capacitor is configured by laminating a first electrode made of a metal wiring material, a silicon nitride film, and a silicon oxide film. a dielectric layer made of
By making the capacitor have the same electrodes, leakage current in the capacitor can be reduced and the capacitance of the capacitor can be increased.

C9 Prior Art In some semiconductor devices such as A/D converters and D/A converters, a capacitor is formed with a pair of electrodes facing each other on a semiconductor substrate and a dielectric layer formed between them.

FIG. 3 shows an example of a circuit configuration of a part of a semiconductor device in which such a capacitor is formed, and shows an example of a comparator. 3, between the input section 31 and the inverter 32, or between the inverter 32 and the inverter 3.
A capacitor C is disposed between the capacitors 3 and 3, and these have a structure as shown in, for example, 412] or FIG.

To briefly explain the capacitors shown in FIGS. 4 and 5, first, the capacitor shown in FIG.
A field oxide film 42 is formed on a conductive type semiconductor substrate 41.
is formed, and impurities of opposite conductivity type are injected into the region between the field oxide films 42 to form a high concentration impurity region 43 which becomes one of the opposing electrodes. A dielectric layer 44 made of a silicon oxide film similar to the field oxide film 42 is formed on this high concentration impurity region 43 to retain charge at its interface. includes one layer 4 as the other of the opposing electrodes.
5 is formed.

Further, the capacitor shown in FIG. 5 has a field oxide film 5
1, a semiconductor which functions as one of the opposing electrodes and is formed in the same process as, for example, a gate electrode]'i52
is formed, and a dielectric layer 54 made of, for example, a silicon oxide film or a silicon nitride film is formed in the open portion of the interlayer insulating film 53 thereon. Then, an A1 layer 55 is formed on the dielectric N54, which functions as the other of the opposing electrodes.

D0 Problems to be Solved by the Invention However, the structure of the capacitor in the semiconductor device as described above has the following problems, and the technical problem of deterioration of the characteristics of the semiconductor device itself remains. Become.

That is, as shown in FIG. 3, a parasitic capacitance Cs is also formed along with the capacitor C due to its structure, and for example, the PN junction between the high concentration impurity region 43 and the semiconductor substrate 41 in FIG. 4 corresponds to this. There is no problem if the value of the parasitic capacitance C3 is sufficiently small, but the capacitance provided by the dielectric layer 44 is insufficient, and the ratio of the capacitor C to the parasitic capacitance C3 required for operation is not sufficient. It is difficult to achieve a ratio of about 10 to 1, and the value of the parasitic capacitance 51cs tends to increase.Also, since the PN junction depends on the voltage, if the capacitance of the capacitor C becomes relatively small, the capacitance will increase. Problems arise, such as increased voltage dependence and inability to ensure stable operation.

Further, in the structure of the capacitor as shown in FIG. 5, the dielectric N54 is not formed integrally with the glabellar insulating film 53, and leakage current etc. are likely to occur through the dielectric layer 54.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a semiconductor device that reduces leakage current in a capacitor and increases the capacitance of the capacitor.

Means for Solving Problem E1 The present invention provides a semiconductor device in which at least a capacitor is formed on a semiconductor substrate, in which the capacitor has a first electrode made of a metal wiring material, a silicon nitride film and a silicon oxide film. The above-mentioned problems are solved by a semiconductor device characterized in that it is formed from a dielectric layer formed by laminating films and a second electrode.

By making the dielectric layer of the F3 action capacitor a laminated layer of silicon nitride and silicon oxide, it is possible to block the current path and suppress leakage current below a certain value.
In addition, silicon nitride film has a higher dielectric constant than silicon oxide nI2, so by adjusting the film thickness etc.
The overall capacity can be increased.

G. Example Preferred embodiments of the present invention will be described with reference to the drawings.

In the semiconductor device of this embodiment, the dielectric layer is formed by laminating a silicon nitride film and a silicon oxide film to reduce leakage current and the like.

Here, an example of the structure of the semiconductor device of this embodiment will be described with reference to FIG. 1. A field oxide film 2.3 is formed on a semiconductor substrate 1 such as a silicon substrate, and a field oxide film 2.3 is A capacitor as described later is formed in .

A MOS transistor is formed on the main surface of the semiconductor substrate l between this field oxide film 2 and another field oxide film 3, and a gate electrode 6 made of, for example, polycrystalline silicon is formed through a gate oxide film 5. A source/drain region 4.4 formed by introducing impurities into a high concentration is formed on the upper part of this gate electrode 6.
A reflowable interlayer insulating film 7 made of, for example, an As5G film is covered, and portions corresponding to the source/drain regions 4.4 are opened to form Af[8 for contact.

A capacitor is formed in the upper part of the field oxide film 2 in the opening of the reflowable glabellar insulating film 7. First, the capacitor is formed in the same process as the gate electrode 6, for example. A silicon oxide film 11 and a silicon nitride film 12 are laminated on a polycrystalline silicon layer 10 patterned with a polycrystalline silicon layer 10 as a second electrode.
1FJ13 is formed as an electrode.

As described above, in the capacitor in the semiconductor device of this embodiment, the dielectric layer is composed of the silicon oxide film 11 and the silicon nitride film 12, and the leakage current is It is possible to cut off the path and reduce the leakage current itself, and
By adjusting the film thickness, etc., the capacitance can be increased, the ratio to the parasitic capacitance can be increased, and the voltage dependence can be further reduced.

Next, in order to further clarify the semiconductor device of this embodiment, its manufacturing method will also be described with reference to FIGS. 2a to 2e. In addition, Figure 2a to Figure 2e
Inside, the same reference signs are used where they correspond to those shown in FIG.

First, as shown in FIG. 2a, field oxidation v2.3 is formed on the semiconductor substrate 1, which is a P-type silicon substrate, by selective oxidation method or the like. This is formed on the entire surface by patterning to form the gate electrode 6 and the polycrystalline silicon FJIO as the second electrode of the capacitor. Source/drain regions 4, 4 are formed by ion implantation or the like. Thereafter, a glabellar insulating film 7, for example, an As5G film, which can be used as a reflow film and can be reflowed at a low temperature, is deposited on the entire surface.

(1)) Next, as shown in FIG. 2, the interlayer insulating film 7 above the polycrystalline silicon layer 10 is opened to expose a part of the polycrystalline silicon layer 10 where a capacitor is to be formed. Furthermore, at this time, a window for the MOS transistor or a window for taking out the second electrode may be opened at the same time.

(cl Polycrystalline silicon FIL opened in this way
First, a silicon oxide film 11 is formed on O. The silicon oxide film 11 can be formed by thermal oxidation, and can be made to have a thickness of about 200, for example. next,
A silicon nitride film 12 is formed over the entire surface including the Al region where the silicon oxide film 11 is formed. This silicon nitride 11! Formation of J12 can be performed, for example, by a CVD method, and the film thickness can be changed in color by about 500 degrees, for example. Note that the silicon oxide film 11 and the silicon nitride film 12 that are stacked in this way can be formed even if the silicon nitride film 12 is formed first and the silicon oxide film 1!311 is stacked on the silicon nitride film 12. good.

After forming the dielectric layer in which the silicon oxide film 11 and the silicon nitride film 12 are laminated in this manner, the interlayer insulating film 7 can be reflowed. Reflow can be performed, for example, at about 900°C.

This reflow can reduce the level difference and facilitate patterning of the silicon nitride film 12. Further, this reflow may be performed in a later step.

Next, the silicon nitride film 12 formed on the entire surface as described above is
is patterned and cut to size only in a predetermined capacitor region. Figure 2C shows the four states after amputation.

Note that after patterning the silicon nitride film 12 in this manner, the interlayer insulating film 7 may be reflowed.
You may perform reflow twice.

fdl Next, as shown in FIG. 2d, a window for the MOS transistor and a window for taking out the second electrode are opened. Wiring such as A1 is provided in each opening 20 formed by opening the window in this manner.

tel Then, as shown in FIG. 2e, the interlayer insulating film 7 is further reflowed at a predetermined temperature, for example, about 900°C. Note that if a part of the polycrystalline silicon layer 10 where a capacitor is to be formed is exposed and at the same time a window is opened for a MOS transistor or a window for taking out a second electrode, the polycrystalline silicon layer 10 has already been reflowed. , do not repeat the reflow process twice.

Finally, a metal wiring material such as ANNa38 is used.
．． 13 to obtain a desired semiconductor device. Here AI
J! i13 functions as the first electrode of the capacitor, and if a polycrystalline silicon layer is used as the upper electrode of the capacitor, the silicon in the silicon nitride film and the silicon in the polycrystalline silicon layer will combine to cause leakage current, etc. However, by using A115 as the upper electrode, in conjunction with the above-described laminated structure, leakage current can be more effectively prevented.

Note that in the above embodiment, the interlayer insulating film 7 is made of ASSG.
It is not limited to membranes, but may also be other glue flow membranes such as PSG membranes.
Further, the semiconductor device is not limited to a comparator having a capacitor, and may of course be a semiconductor device such as a DRAM.

H1 Effects of the Invention In the semiconductor device of the present invention, as described above, since the dielectric layer is a stack of a silicon oxide film and a silicon nitride film, the current path is blocked and the leakage current is kept below a certain value. In addition, by adjusting the dielectric constant of the silicon nitride film, the overall capacitance can be increased by adjusting the film thickness, suppressing voltage dependence, and increasing the ratio to parasitic avoidance. be able to.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the structure of a semiconductor device of the present invention, and FIGS. 2a to 2e are cross-sectional views of a semiconductor substrate, etc., for explaining the manufacturing method of the semiconductor device of the present invention. , FIG. 3 is a circuit diagram showing the structure of a comparator, FIG. 4 is a sectional view showing an example of the structure of a conventional semiconductor device, and FIG. S is a sectional view showing another example of the structure of a conventional semiconductor device. . 1...Semiconductor substrate 10...Polycrystalline silicon layer 11...Silicon oxide film 12...Silicon nitride film 13...A11 layer Patent Applicant Sony Corporation Representative Patent Attorney Kobu Mimi Sakae Tamura - Figure 3, Figure 4, Figure 5

Claims (1)

[Claims] In a semiconductor device in which at least a capacitor is formed on a semiconductor substrate, the capacitor includes a first capacitor made of a metal wiring material.
1. A semiconductor device comprising: an electrode; a dielectric layer formed by stacking a silicon nitride film and a silicon oxide film; and a second electrode.