JPS6329962A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent noise current flowing through a semiconductor substrate from entering elements thereon, by providing a semiconductor well for bypassing the noise current apt to enter the elements from the semiconductor substrate, to a place stable in terms of alternate current. CONSTITUTION:In a chopper-type comparator, electrodes of a capacitor C1 have the same node in terms of direct current. Under these electrodes, a semiconductor well 2 having the opposite type of conductivity to that of a semiconductor substrate 1 is arranged and the well 2 is gounded. Accordingly, any noise current flowing through the semiconductor substrate 1 is bypassed to the ground by means of a junction capacitance Cf' between the semiconductor substrate 1 and the semiconductor well 2, so that no noise enters a polycrystalline silicon layer 7. In this manner, it can be avoided that noise current flowing through the semiconductor substrate 2 enters the capacitor C1 of the chopper-type comparator.

Description

[Detailed description of the invention] The present invention will be described in the following order.

A. Industrial field of application B9 Summary of the invention C1 Prior art [Figures 7 to 10] D1 Problems to be solved by the invention E9 Means for solving the problems F, Effects G, Examples 1Nb in FIG. 6] H1 Effects of the Invention (A. Field of Industrial Application) The present invention relates to a conductor device, and particularly to a semiconductor device in which an element is formed on a semiconductor substrate with an insulating layer interposed therebetween.

(B. Summary of the Invention) The present invention provides a semiconductor device in which an element T is formed on a semiconductor substrate with an insulating layer interposed therebetween, in order to prevent noise flowing through the semiconductor substrate from entering the element. A semiconductor well is provided under the same note, and the semiconductor well is connected to a stable AC source. Therefore, the semiconductor device of the present invention prevents noise from entering the device from the semiconductor device. It can be bypassed to a stable AC source using a semiconductor well.

(C, Prior Art) [Figures 7 to 10] When a chopper type comparator as shown in Figure 7 is formed in an LSI, the capacitor CI of the comparator and the A/D converter as shown in Figure 9 are When formed in an LSI, elements such as string resistors R, R, R1, etc. are formed on an insulating layer (LOGOS) b formed on the surface of a semiconductor substrate a, as shown in FIGS. 8 and 10. is often formed. First, capacitor C1 shown in FIG.
Explain how it is structured. C is a polycrystalline silicon layer forming one electrode of the capacitor CI (the electrode on the switch SWI side in the circuit shown in FIG. 7);
d is an insulating layer made of SiO□ that covers the polycrystalline silicon layer C, and a contact hole e is formed in the insulating layer d located above one end of the polycrystalline silicon layer C. f is a conductor layer made of aluminum that faces the polycrystalline silicon layer C and the insulating layer d, and the capacitor C1
(inverter I in the circuit shown in Fig. 7)
NV input side electrode).

A wiring layer g made of aluminum was formed at the same time as the conductor layer f, and is connected to the polycrystalline silicon layer C through the contact hole e. h is an insulating layer covering the conductor layer f and the wiring layer g.

If the semiconductor substrate a is of N type, it is connected to the power supply terminal (+Vdd) of the circuit.

Conversely, if it is of P type, it is connected to the - power supply terminal of the circuit, that is, the ground.

Next, the structure of the string resistor shown in FIG. 9 will be explained. Reference character i denotes a silicide film forming string resistors R, R1, .

j is an insulating layer covering the silicide film i, and contact holes k, . . . are formed at predetermined intervals. 2.2,... is in the contact hole, k,...
・A tap-out electrode film made of metal is connected to the silicide film i through the tap electrode film, and m is an insulating layer that protects the surface.

(D. Problem to be solved by the invention) By the way, the 8th problem
Whether it is the LSI shown in the figure or the LSI shown in Fig. 10, the LS
The entire I circuit is formed within or above the semiconductor substrate a, and the LSI circuit includes noise sources such as logic circuits. Therefore, noise current generated by clock pulses etc. that control the logic circuit flows through the conductive substrate a. When a noise current flows through the semiconductor substrate a, it enters the L capacitor C1, the string resistor R1R1, etc. through the parasitic capacitance Cf. This is because the polycrystalline silicon layer C forming one electrode of the capacitor C1, the string resistors R, R1, etc. are not formed, and the silicide film i is formed on the semiconductor substrates a and h via an insulating layer. , high frequency noise is transmitted from the semiconductor substrate a to the capacitor C1 and string resistors R, R2 through the parasitic capacitance ICF interposed between the polycrystalline silicon layer C, the silicide film i, and the semiconductor substrate a.
It flows into... Therefore, the S/N becomes worse and the A
/D converter accuracy may deteriorate.

The present invention has been made to solve these problems, and aims to 1) prevent noise flowing through a semiconductor substrate from entering an element;

(E. Means for Solving the Problems) The present invention Semiconductor wells are formed on the surface of the semiconductor substrate to face the same nodes in terms of alternating current of the element via the insulating layer, and the semiconductor wells are connected to a stable place in terms of alternating current. According to the semiconductor device of the present invention, noise that attempts to enter the element from the semiconductor substrate can be bypassed to a stable area in terms of alternating current using the semiconductor well. Therefore,
It is possible to prevent the noise current flowing through the semiconductor substrate from entering the element f through the parasitic capacitance between the semiconductor substrate and the element.

(G. Embodiment) [FIGS. 1 to 6] Hereinafter, the semiconductor device of the present invention will be described in detail according to the illustrated embodiment.

FIG. 1 shows a first embodiment of the semiconductor device of the present invention.

1 is an N-type semiconductor substrate, which is electrically connected to the circuit power supply terminal (
+vdd). 2 is a P-type semiconductor well selectively formed on the surface of the semiconductor substrate 1; 3 is an insulating layer formed by selective oxidation of the surface of the semiconductor substrate 1;
Reference numeral 4 denotes a high concentration region for taking out the electrode of the P-type semiconductor well 2. The surface of the region 4 is connected to an electrode 6 through a contact hole 5, and is grounded through the electrode 6.

7 is a polycrystalline silicon layer forming one electrode of the capacitor C1 of the chopper type comparator shown in FIG. A contact hole 9 is formed above one end of the polycrystalline silicon layer 7. , 10 are conductor layers made of aluminum that face the polycrystalline silicon layer 7 with an insulating layer 8 in between, and constitute the other electrode of the capacitor C1.

A wiring layer 11 made of aluminum was formed at the same time as the conductor layer 10, and is connected to the polycrystalline silicon layer 7 through the contact hole 9. 12 is a conductor layer 10
and an insulating layer covering the wiring layer ll.

According to such a semiconductor device, a conductive well 2 having a conductivity type opposite to that of the semiconductor substrate 1 is arranged under both electrodes of the capacitor C1, which are at the same node in terms of direct current of the chopper type comparator. Since it is grounded, the noise 'a' flowing through the semiconductor substrate 1 flows into the semiconductor well 2 through the junction capacitance ff1cf' between the semiconductor substrate 1 and the semiconductor well 2, and is bypassed to the ground side, and the polycrystalline silicon layer Noise cannot enter into 7. Therefore, it is possible to prevent noise flowing through the semiconductor substrate 1 from entering the capacitor C1 of the chopper type comparator.

FIG. 2 shows a second embodiment of the semiconductor device of the present invention. In this embodiment, a conductor film 14 made of aluminum is placed on top of the conductor film 10 made of aluminum of the first embodiment shown in FIG. 1 with an insulating layer 13 interposed therebetween! 1! The conductor film 14 is electrically connected to the wiring layer 1 described above. 15 is an insulating layer covering the surface.

The purpose of providing such a conductor film 14 is to reduce the parasitic capacitance Cf'' that occurs at the connection point between the capacitor C1 and the inverter INV (see FIG. 7). This is because the other electrode of the capacitor C1 There is a possibility that a parasitic capacitance Cf'' may exist between the conductive film 10 and the ground, and if the parasitic capacitance Cf'' exists, the human power level of the inverter INV will increase due to the capacitor C1 being charged. The amount of increase will be smaller.In other words, the voltage obtained by dividing the voltage of the input signal by the capacitor C1 and the parasitic capacitance Cf will be applied to the inverter INV.Therefore, as much as possible, the voltage will be applied to the other electrode side of the capacitor C1 (inverter INV side).
It is necessary to reduce the value of the parasitic field −[Cf'' that parasitic to
It is made smaller by facing the conductor film 10 via the insulating layer 13 and electrostatically shielding it.

This embodiment is similar to the first embodiment except that a conductor film 14 is provided to reduce the value of the parasitic capacitance Cf''.

FIG. 3 shows a third embodiment of the semiconductor device of the present invention. In this embodiment, the conductor film 10 in the first embodiment is integrated with the grounded electrode 6, so that the conductor film 10 is grounded, and the other points are the same as in the first embodiment. There is no difference.

The capacitor C2 constituted by the polycrystalline silicon layer 7, the insulating layer 8, and the conductor film 10 of the embodiment shown in FIG. 3 is most suitable as a Hall capacitor for a sample-and-hold circuit as shown in FIG.

FIG. 5 shows a fourth embodiment of the semiconductor device of the present invention.

In the same figure, 16 is a string resistance R, R1... (
9), and is formed on the insulating layer 3. 17 is an insulating layer covering the silicide film 16, and contact holes 18, 18, . . . are formed at predetermined intervals. 19.19,
. . is a tap extraction electrode film connected to the silicide film 16 through contact holes 18, 18, . . . , and 20 is an insulating layer that protects the entire surface of the semiconductor. In this embodiment as well, a semiconductor well 2 is selectively formed on the surface of an N-type semiconductor substrate 1. While the semiconductor substrate 1 is connected to the electrode terminal (+Vdd), the baby conductor well 2 is grounded (the electrode extraction portion of the grounded semiconductor well 2 does not appear in the drawing).
. This semiconductor well 2 has a set of string resistors R, R1
It is provided in a place that covers the area where... is formed.

Even in this embodiment, since a grounded semiconductor well 2 is provided between the semiconductor substrate 1 and the insulating layer 3, the noise current flowing through the semiconductor substrate 1 enters the silicide film 16, causing each string resistor R, There is no risk of changing the potential between R (each tap).

FIG. 6 shows a fifth embodiment of the conductor device of the present invention. In this embodiment, an insulating layer 3' made of SiO2 is formed on the insulating layer 3, a metal film 21 made of aluminum is formed on the insulating layer 3', and this is used as a string resistance film. When the string resistor is formed of the silicide film 18, it is not necessary to form the insulating layer 3', but when the string resistor is formed of the aluminum film 21, the insulating layer 3' is not required as shown in the embodiment shown in FIG. ′ as an insulating layer (
Is it necessary to form it on LOCos)3?

If there is a risk that noise may enter elements such as capacitors and resistors formed on the insulating layer 3 of the semiconductor substrate 1 and deteriorate the S/N and conversion accuracy, connect the semiconductor well 2 that is grounded in an AC manner. By providing it below the element, it is possible to prevent noise from entering. Note that many elements that may be susceptible to noise intrusion are placed in one semiconductor well 2.
It is undesirable to protect from noise by This is because if you try to cover a wide area with many devices with one semiconductor well 2, the semiconductor well 2
This is because there is a possibility that interference may occur between a certain part of the semiconductor well 2 and another part due to the current flowing therein.

One semiconductor well 2 can cover an area that can be called the same node in terms of AC. By the way, one electrode and the other electrode of capacitor C can be said to be the same node in terms of AC, and each terminal of a set of series-connected string resistors can also be said to be the same node in terms of AC, so they are one node. The semiconductor well 2 can protect against noise. However, for parts that cannot be said to be the same node in terms of AC, it is necessary to protect the elements from noise with separate semiconductor wells 2, 2, . . . for each part.

In each of the above embodiments, the semiconductor substrate 1 is of N type, but the present invention can of course also be applied to a semiconductor substrate of P type. In this case, the P-type conductor board is generally connected to the negative (ground) of the circuit power supply. The conductor well becomes N type, and this N type semiconductor well is connected to the positive terminal of the circuit power supply.

Needless to say, even in such a case, high-frequency noise can be bypassed in an alternating current manner through the semiconductor well, thereby preventing noise from entering the element.

Furthermore, the present invention is applicable not only to devices in which passive elements such as capacitors and resistive elements f are formed on a semiconductor substrate via an insulating layer, but also to conductor devices in which active elements such as MOS FET are formed. .

(H, Effect of the Invention) As described above, the semiconductor device of the present invention has a semiconductor device in which an element is formed on a semiconductor substrate through an insulating layer. Semiconductor wells are formed on the surface of the semiconductor substrate and are opposed to each other with the insulating layer interposed therebetween, and the semiconductor wells are connected to a stable point in terms of alternating current.

Therefore, according to the semiconductor device of the present invention, noise that attempts to enter the element from the semiconductor substrate can be bypassed to a stable area in terms of alternating current using the semiconductor well.

Therefore, it is possible to prevent the noise current flowing through the semiconductor substrate from entering the element through the parasitic 8-hole between the semiconductor substrate and the element.

[Brief explanation of the drawing]

1 is a sectional view showing a first embodiment of the semiconductor device of the present invention, FIG. 2 is a sectional view showing a second embodiment of the semiconductor device of the present invention, and FIG. 3 is a sectional view of a third embodiment of the semiconductor device of the present invention. FIG. 4 is a circuit diagram showing a sample and hold circuit which is a circuit example of the embodiment shown in FIG. 3. FIG. 5 is a sectional view showing a fourth embodiment of the semiconductor device of the present invention. , FIG. 6 is a sectional view showing the fifth embodiment of the semiconductor device of the present invention, FIG. 7 is a circuit diagram of a chopper type comparator, FIG. 8 is a sectional view showing the first conventional example, and FIG. /D converter circuit diagram, 1st
Figure O is a sectional view showing a second conventional example. Explanation of symbols 1...Semiconductor substrate, 2...Semiconductor well, 3...
Insulating layer, 7-9 (CI, C2), 16,
21(R)...Element. 4 Cross-sectional view of the 5 second major forces Fig. 2 4 Cross-sectional view of the third Tsunetogoshi second Figure 3 Circuit diagram of the sample and hold circuit Figure 4 Cross-sectional view of the 4th major force Fig. 5 Cross-sectional view of various colors Fig. 6: Circuit diagram of JI and C7 Chikotsu har type conch 0-ray 5tn Fig. 7 1/) Cross-sectional view of conventional grille 2nd lfr side view of conventional grille Fig. 10

Claims (1)

[Claims] (1) In a semiconductor device in which an element is formed on a semiconductor substrate with an insulating layer interposed therebetween, a semiconductor well facing a portion of the element at the same node in terms of AC with the insulating layer interposed is located on the surface of the semiconductor substrate. and the semiconductor well is connected to a stable place in terms of alternating current.