JPS63102366A - Semiconductor device - Google Patents

Abstract

PURPOSE:To offer a semiconductor device of high electrostatic withstand voltage by checking destruction of junction due to dissolution of aluminum by a method wherein the distance from the exposing part of the interface of P-N junction up to the contact position of the aluminum electrode is so set as to make the withstand voltage characteristic of P-N junction in relation to the distance thereof is set to the value nearby the saturated condition. CONSTITUTION:On a semiconductor substrate 21 corresponding to a channel region between a source 23 and a drain 24, a gate electrode 26 is formed with a gate insulating film 25 between. A source electrode 27 and a drain electrode 28 are formed on the regions of a source 23 and a drain 24 respectively. At this case, the drain electrode 28 is made to come in contact with the drain 24 having the distance between the gate electrode 25, namely the distance between the exposing part of the interface of P-N junction of the drain electrode 24 and the substrate 21 is separated farther than the usually designed reference value. The distance thereof is decided on the withstand voltage characteristic of P-N junction in regard to the distance from the exposing part of the interface of P-N junction of the drain 24 and the substrate 21 up to the contact position of the drain electrode 28.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Field of Industrial Application) The present invention relates to a semiconductor device used, for example, for input protection of a semiconductor integrated circuit.

(Prior Art) In semiconductor integrated circuits, electrostatic damage to devices that occurs during the assembly process on the user's side often poses a major problem. This occurs when excessive voltages are applied to the IC bins during the assembly process, which often causes destruction of internal components.

Figure 7 shows the configuration of an input protection circuit used to prevent such electrostatic damage. , a protection resistor R1 made of a polycrystalline silicon layer, and a protection N-channel type transistor Q2. The drain of this protective N-channel type transistor Q2 is connected to the connection point between the protective resistor R1 and the gate of the transistor Q1, and the gate and source of the transistor Q2 are grounded.

Next, input ci! with such a configuration. The operation of the protection circuit is
This will be explained with reference to the cross-sectional structure of the input protection N-channel type transistor Q2 shown in the figure.

If excessive voltage is applied to the input pad DO, the protection resistor R1
In other words, the potential V1 supplied to the drain 12 of the N-channel transistor Q2 increases the junction breakdown voltage (
5 surface 13 leakdown pressure), breakdown occurs at the NP junction surface between the N1 diffusion layer, which is the drain 12 of this transistor Q2, and the P-type substrate 10, and holes are formed in the P-type substrate 10. It will be done. P-type substrate 1 lifted by this hole
When the potential of 0 becomes greater than the ground potential by the forward voltage drop of the PN junction between the P-type substrate 10 and the source 11 (N₂ diffusion layer), these holes flow to the source.

As a result, the N-channel transistor Q2 becomes NP.
It operates as an N bipolar transistor and discharges a high voltage supplied from the outside.

Therefore, the gate voltage of the transistor Q1 in the first stage of the internal circuit is between the drain 12 of the transistor Q2 and the P-type substrate 1.
Since the breakdown pressure at the junction surface with 0 is kept below the breakdown pressure, breakdown of the gate oxide film of the transistor Q1 is protected.

In this way, the input protection circuit includes the protection transistor Q2.
By breaking down the NP junction of the transistor Q1, the structure prevents an excessive voltage from being applied to the gate of the transistor Q1 in the first stage of the internal circuit.

Recently, in order to increase the degree of integration of semiconductor devices, not only internal circuit elements but also input protection transistors have been miniaturized. However, with the miniaturization of such elements, the heat generated when the input protection transistor Q2 breaks down causes the NP of the input protection transistor Q2 to deteriorate.
A problem has arisen in that the bond is more likely to break.

This is because when breakdown occurs at the NP junction surface 121 between the N4'' diffusion layer, which becomes the drain 12 of the protection transistor Q2, and the P-type substrate 10, the heat generated at the junction surface forms the train electrode 14. When the temperature of the aluminum reaches its melting point due to this heat, the aluminum in the contact area with the drain 12 melts, and the aluminum becomes N" along the direction of flow of 'Ii flow. This is because when the aluminum that flows out of the surface of the diffusion layer reaches the substrate 10, the drain electrode 14 becomes short-circuited, and as a result, the PN junction is destroyed.

The joint failure caused by such aluminum solution is as follows:
Due to the low melting point of aluminum, PN due to concentration of electric field
Since this occurs before junction breakdown occurs, it has been extremely difficult to achieve both element miniaturization and the breakdown voltage of the PN junction. In particular, L D D (LightNy [)
(opened drain) structure transistors and G
D D (Guarded Q oped D
When a transistor with a (rain) structure is used as an input protection transistor, such junction breakdown due to melting of aluminum becomes more likely to occur.

This is because in these LDD and UG D D tM transistors, the impurity concentration near the drain is lowered to prevent deterioration of conductance due to channel hot electrons, so the resistance value in this low concentration layer is high and heat generation is large. To become.

Such an LDD or GDD structure is, for example, 5 [■]
Since this is a technology that will be widely used in semiconductor integrated circuits in the future to ensure reliability of operation with a single power supply, the above-mentioned problem of junction breakdown due to melting of aluminum has become even more serious.

(Problems to be Solved by the Invention) This invention has been made in view of the above points, and aims to improve the problem that conventional semiconductor devices are prone to bond breakdown due to melting of aluminum, and to improve the miniaturization of elements. From this viewpoint, the present invention aims to provide a semiconductor device which can most efficiently prevent such junction breakdown due to dissolution of aluminum and has a high electrostatic withstand voltage.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the PN junction surface, which is a source of heat, and the aluminum electrode are formed apart from each other, so that the aluminum electrode is free from the influence of heat. However, if these were simply formed apart, the area of the element would become unnecessarily large. Therefore, in the semiconductor device according to the present invention, the distance from the exposed portion of the PN junction interface to the contact position of the aluminum electrode is set to a value such that the withstand voltage characteristics of the PN junction with respect to this distance are in the vicinity of a saturated state. This is what I did.

(Function) In a semiconductor device having the above configuration, it is possible to most efficiently suppress PN junction breakdown due to aluminum melting, and it is possible to effectively realize miniaturization of elements and their breakdown voltage. become.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings. 1st
The figure shows an N-channel type M as an input protection transistor.
This shows an actual tS example when an OS transistor is used. Figure 1 (A) shows the pattern plane, and Figure 1 (B) shows the cross-sectional structure along the I-1 line. It is shown.

That is, an element region is formed on a P-type semiconductor substrate 21 using a field insulating film 22, and a source 23 and a drain 24 each made of an N+ diffusion layer are formed on the surface of the substrate 21 within this element region. They are formed in a separated state. A gate 1[i2e is formed on the semiconductor substrate 21 corresponding to the channel region between the source 23 and the drain 24 with a gate insulating film 25 interposed therebetween. The source electrode 27 and the drain electrode 28 are formed on the source 23o and drain 24 regions, respectively.
The exposed portion of the PN junction interface is in contact with the drain 24 at a distance greater than a normal design reference value.

This is to prevent the aluminum forming the drain electrode 28 from being melted by the heat generated on the bonding surface 241 during breakdown, and this distance is
The breakdown voltage of the PN junction with respect to the distance between the gate electrode 26 and the drain electrode 28 as shown in the figure, that is, the distance from the exposed part of the PN junction interface between the drain electrode 24 and the substrate 21 to the contact position of the drain electrode 28. Determined based on characteristics.

That is, as is clear from this figure, the breakdown voltage of the PN junction increases up to a certain level depending on the distance between the gate electrode 26 and the drain electrode 28, but after that it reaches a saturation state and depends almost entirely on the distance. It disappears. Therefore, even if the distance between the train electrode 28 and the gate electrode 26 is greater than the value corresponding to the above-mentioned saturation state, the element area will only increase and the distance will not have the same effect on preventing aluminum from dissolving.

Therefore, the drain electrode 28 and the gate snow shovel 26 are set apart by a distance corresponding to the vicinity of the saturated state.

The saturation state of the breakdown voltage of such a PN junction is determined by the original breakdown voltage based on the structure of the transistor, not by the dissolution of aluminum.

Therefore, as described above, by forming a transistor with the distance between the gate electrode 26 and the drain electrode 27 corresponding to the vicinity of the saturation state of the breakdown voltage characteristics of the junction, the most efficient method is to miniaturize the element. It becomes possible to realize pressure resistance.

Also, similar to the bonding surface 241, the field insulating film 2
Since heat is also generated at the junction surface 242 in the vicinity of the junction surface 242, the drain electrode 28 is preferably formed approximately at the center of the N+ diffusion layer forming the drain 24.

FIG. 3 shows an example in which the present invention is applied to a field transistor in which a thick gate insulating film is formed by a field insulating film 31 and a living room insulating film 32, and the drain electrode and gate electrode are shared. Figure 3 (A
) shows the pattern plane, and Fig. 3 (8)
shows a cross-sectional structure taken along line II-II.

Also in this case, since heat is generated during breakdown at the bonding surfaces 241 and 242 between the drain 24 and the substrate 21, the drain electrode is formed at a position separated from the bonding surfaces by a predetermined distance. .

Figure 4 shows an example of using a diode for input protection. Figure 4 (A) shows its pattern plane, and Figure 4 (B) shows a diode on the m-■ line. The cross-sectional structure of the hotel is shown.

That is, an element region is formed on the P-type semiconductor u-board 41 by field insulation FJ42, and this element? [
An N0 diffusion layer 43 is formed in the region, and this N' diffusion layer 43
A diode is adjusted by the and ρ-shaped scale plate 41.

In a diode with such a configuration, a T
By forming the 1-ru 44, it is possible to effectively prevent joint breakdown due to melting of aluminum.

Figure 5 shows an example of input protection using a diode and the internal resistance of the diffusion layer that constitutes the diode, and Figure 5 (A) shows the pattern plane of the nTJ3.
Figure '55 (8) shows a cross section M4 structure.

That is, an element region is formed on the P-type substrate 51 by a two-yield insulation layer 52, and this element region is N+ diffused! 153 is formed. And this N” diffusion 11
There are two l on 53! The electrodes 54 and 55 are formed at positions separated from each other, the electrode 54 is connected to the input pad 11, and the electrode 1i55 is connected to the transistor Q in the first stage of the internal circuit.
Connected to gate 1. In this case, 11m544
．． 1. N9 expansion wi layer 53. ! = P-type substrate 51 and shell b
The junction surface 531 is formed at a predetermined distance from the junction surface 531 where the most heat is generated when the PN junction diode subjected to 4H is broken down.

Although the structure of the element used for input protection has been described above, the present invention can be applied not only to input protection but also to an output buffer as shown in FIG. 6, for example.

The output buffer shown in Figure 6? is P channel type M
O3) - consists of a transistor Qll and an N-channel MOS transistor 12; in this case,
If the II structure shown in FIG. 1 is applied to the drain of the N-channel transistor Q12 to which the output pad D1 is directly connected, junction breakdown due to melting of aluminum can be prevented.

In this way, the potential from the pad can be directly connected to the resistor JFr.
When the aluminum wiring supplied to the element via the semiconductor region of the transistor or diode contacts the semiconductor region of the transistor or diode to form an electrode, the exposed part of the PN junction interface with the semiconductor 'tA on one side and the contact between the aluminum II If the distance between the two positions is set close to 6 (Ω) where the pressure characteristics of the PN junction become saturated, it becomes possible to efficiently suppress the joint breakdown due to melting of aluminum.

In this example, the case where the diffusion layer in contact with the aluminum electrode is formed of only a high a degree layer has been described. The present invention can also be applied to cases where layers are formed.1. Of course.

[Effects of the Invention] As described above, according to the present invention, the distance from the exposed portion of the PN 11 joint surface to the contact position of the aluminum electrode 1 is calculated based on the breakdown voltage characteristics of the PN junction with respect to this distance. By setting the distance at which the breakdown voltage characteristics of the PN junction depend on the structure of the PN junction without depending on the melting of aluminum, the distance from the exposed part of the PN junction surface to the contact position of aluminum 1! It becomes possible to prevent joint breakdown due to melting of aluminum without increasing the size unnecessarily. Therefore, miniaturization of the element and its breakdown voltage can be achieved in a well-balanced manner.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram illustrating a semiconductor device according to an embodiment of the present invention, FIG. 2 is a diagram showing breakdown voltage characteristics of a PN junction with respect to the distance between a gate electrode and an aluminum N pole, and FIGS. 3 to 6 Figure 7 shows other embodiments of the invention, respectively.
The figure shows the circuit configuration of the input protection circuit, and FIG. 8 shows the conventional transistor structure used in the input protection circuit. 21...P-type semiconductor substrate, 22...Field isolation I
! Discipline, 23...source, 24...drain, 26.
・・Gate voltage (Reference, 27 ・・Source ff1l&, 2B
...Drain MVM. ; Figure 1 Figure 2 (A) (B) Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (2)

[Claims] (1) In a semiconductor device in which a contact electrode of an internal element is formed by an aluminum wiring that supplies a potential supplied from the outside to a pad directly or via a resistor to a semiconductor region of an internal element, a PN with the semiconductor region as one side A semiconductor device characterized in that the distance from the exposed portion of the junction interface to the contact position of the contact electrode is set to a value close to such that the withstand voltage characteristics of the PN junction are saturated with respect to this distance. (2) The semiconductor device according to claim 1, wherein the internal element is a transistor or a diode used for input protection.