JPS6290964A - Protection structure of integrated circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to integrated circuit protection structures.

Conventional protection structures for use in electrostatic sensitive devices such as integrated circuits consist of diodes, thyristors, transistors, or combinations thereof. Such protective structures are disadvantageous in that they must be manufactured according to a specific technology, thereby limiting the technology available for manufacturing the rest of the integrated circuit. Therefore, to some extent, the protection structure used limits the nature of the overall integrated circuit structure that can be fabricated, resulting in degraded integrated circuit performance.

Furthermore, protective structures have been proposed that consist of a pair of diffusion regions of the same conductivity type diffused through an epitaxial layer and in contact with an intermediate layer. This protection structure has the disadvantage that a channel is formed between the pair of diffusion regions, resulting in undesired charge leakage within the protection structure, thereby reducing the effectiveness of the structure as a protection circuit. Parasitic transistor effects also occur.

It is an object of the present invention to provide a protective structure that alleviates the above-mentioned problems and allows integrated circuits to be fabricated using alternative fabrication techniques.

A protection structure for an integrated circuit is provided in accordance with the present invention, comprising a substrate of a first conductivity type, an epitaxial layer of a second conductivity type overlying the substrate, and a second conductivity type epitaxial layer between the substrate and the epitaxial layer. a second conductivity type intermediate layer extending into the epitaxial layer and in contact with the intermediate layer; a second conductivity type diffusion region extending into the epitaxial layer and overlying the intermediate layer; It consists of another diffusion region of conductivity type 1.

The first conductivity type may be positively doped, ie, P-type, and the second conductivity type may be negatively doped, ie, N-type.

Another diffusion region can extend through the epitaxial layer and contact the intermediate layer.

A shallow region of the same conductivity type as the other diffusion region can be associated with the other diffusion region if it contacts the intermediate layer.

The doping concentration of the diffusion region is preferably higher than that of the epitaxial layer.

The doping concentration of the other diffusion region is preferably higher than that of the substrate.

The doping concentration of the intermediate layer is preferably higher than that of the epitaxial layer.

Preferably, the intermediate layer does not extend substantially beyond the lateral limits of the diffusion region and the further diffusion region.

The first layer preferably has a higher doping concentration than the substrate.
An insulating region of conductivity type can be provided in the epitaxial layer to surround and isolate the protective structure.

The diffusion region and/or the masking region may be associated with a laterally extending shallow region.

An oxide layer can be provided on the epitaxial layer.

The diffusion region, another diffusion region, the insulation region or a combination thereof preferably has a recessed contact window and any or all regions have beveled corners to reduce charge concentration at the corners of each region. can be done.

The diffusion region may extend circumferentially around the other diffusion region to extend a region of conduction between the diffusion region and the other diffusion region.

Example 1 FIG. 1 is a schematic illustration of a protective structure comprising an epitaxial layer 2 of N'' conductivity type deposited on a substrate 4 of P-conductivity type.

An intermediate layer 6 of N+ conductivity type is embedded between the epitaxial layer 2 and the substrate 4.

A diffusion region of the same conductivity type and similar doping as the intermediate layer 6 [8
is diffused through epitaxial layer 2 and placed in contact with intermediate layer 6 . Diffusion region 8 is shallow region 1
o, which extends laterally into the epitaxial layer 2 beyond the lateral limits of the diffusion region 8. Diffusion area 8
A shallow region 10 of the same conducting type and of similar doping facilitates the contact of the diffusion region 18 with the electrode 12 via the contact window 14 .

Another diffusion region 16 is provided in the epitaxial layer 2 and is arranged above the intermediate layer 6 . The other diffusion region 16 is of P+ conductivity type and has a higher degree of doping than the substrate 4 . In an embodiment, the other diffusion region 16 is a shallow diffusion region. Another diffusion region 16 is connected to the electrode 18 via a contact window 20 .

The protective structure is insulated by an insulating region 22 of the same conductivity type and similar doping concentration as the other diffusion region 16, which extends through the epitaxial layer and contacts the substrate 4.

The insulating region 22 surrounds the protective structure and can have an annular configuration (the corresponding right-hand side is omitted from FIG. 1). Associated with the insulating region 1422 is a shallow region 24 , which is connected to the electrode 26 via a contact window 28 .

The protection structure of FIG. 2 differs from that of FIG. 1 in that another diffusion region 16 is diffused through the epitaxial layer 2 and contacts the intermediate layer 6.

The epitaxial layer 2 is coated with a field oxide layer 3o which can serve as a mask during the fabrication of the shallow layer 10, the further diffusion region 16 and the shallow region 24. The oxide layer 30 is coated with a contact oxide layer 32 which forms a recessed contact window 14, 20, 28, respectively.

The protection structure shown in FIGS. 1 and 2 can be used as a protection structure for the voltage supply Vcc of an integrated circuit, in which case electrode 12 is connected to Vcc and electrode 18 is grounded. For a positive transition on electrode 12, reverse breakdown of the diode formed at the another diffusion region 1416/layer 2 interface occurs when the voltage on electrode 18 exceeds the breakdown voltage of the diode. When a breakdown occurs, current from the Vcc supply flows through electrode 18 to ground. Therefore, the voltage at electrode 12 is clamped to the reverse breakdown voltage. For negative transitions, a diode formed at the another diffusion region 16/pitaxial layer 2 interface is biased to forward conduction and the electrode 12 is clamped to the forward junction voltage of the diode. When the voltage of the electrode 12 exceeds the forward junction breakdown voltage and becomes negative, the current flows out to the ground via the electrode 18 again.

If another diffusion region 16 extends through the epitaxial layer 2 and contacts the intermediate layer 6 as shown in FIG.
The protection structure operates similarly to the method described above when configured to protect the Vcc of the integrated circuit, except that at the another diffusion region 16/intermediate layer 6 interface the diode is a P+N+ diode.

The embodiments of FIGS. 1 and 2 can also be configured to protect the integrated circuit structure from electrostatic discharge to the supply voltage VCC. In this case, electrode 12 is connected to VCC and electrode 18 is connected to the integrated circuit structure.

In the case of FIG. 1, where the other diffusion layer 16 is shallow, the electrode 1
For positive transitions of 8, the voltage at electrode 18 is clamped to the forward junction voltage of the diode at the another diffusion layer 16/full layer 2 interface which is higher than the supply voltage, ie VCC. When the diode conducts, current flows into the supply voltage VCC. For a negative transition of electrode 18, reverse breakdown of the diode occurs and excess current flows through electrode 12 into the supply source.

If another diffusion layer 16 is in contact with the intermediate layer 6,
The process is the same except that the diode is a P+N+ diode.

If VCC is protected by a protective structure, connect the insulating region 22 to ground to provide a P+N+ diode, i.e. another diode in parallel to ground in addition to another diffusion region 16/layer 2 diode. I can do it.

FIG. 3a shows a non-concave configuration of the contact window 20. FIG. This is the first
This is a different structure to the contact windows 14, 20 and 28 shown in FIGS. Figure 3b shows the concave structure of the contact window 20;
This corresponds to the structure shown in FIGS. 1 and 2. In FIG. 3a, contact oxide 32 does not extend down to the surface of another diffusion layer 16, whereas in FIG. 3b, contact oxide 32 extends down to the surface of another diffusion layer 16. are doing. The concave structure has the advantage that no "punch-through" from the electrode 18 takes place between the electrode 18 and the epitaxial layer 2 in regions A and A'.

FIG. 4 shows a possible configuration of the diffusion region 8 with respect to another diffusion region 16. FIG. 4 is a plan view of the structure shown in FIG. 1 and FIG.
6, which can extend circumferentially around at least the main part of 6. This configuration is advantageous in that it allows the conductive region to extend between the two regions and reduces breakdown voltage.

Furthermore, FIG. 4 shows that the corners of the diffusion regions 8 or 16 can be beveled so as to reduce the charge concentration at the corners of these regions.

[Brief explanation of drawings]

1 is a schematic diagram of a protective structure embodying the invention, FIG. 2 is a modification of the embodiment of FIG. 1, FIG. 3a is a non-concave contact window in the diffusion region, and FIG. 3b is a concave contact window in the diffusion region. , FIG. 4 is a diffusion region of a protective structure extending circumferentially around another diffusion region. Explanation of reference symbols 2...Epitaxial layer 4...Substrate 6...Intermediate layer 8.16...Diffusion region 12.18...Electrode 14.20.28...Concave contact window 22... - Insulating region 24... Shallow region 30.32... Oxide layer

Claims (13)

[Claims] (1) A substrate (4) of a first conductivity type, an epitaxial layer (2) of a second conductivity type disposed on the substrate (4), and a space between the substrate (4) and the epitaxial layer (2). an intermediate layer (6) of a second conductivity type disposed, and a diffusion region (8) of a first conductivity type extending through the epitaxial layer (2) and in contact with the intermediate layer (6); The epitaxial layer (2
) A protection structure for an integrated circuit, characterized in that it consists of another diffusion region (16) of a first conductivity type extending into said intermediate layer (6). (2) A protective structure for an integrated circuit according to claim (1), wherein the first conductivity type is P type and the second conductivity type is N type. (3) In claim (1) or (2), the another diffusion region (16) extends through the epitaxial layer (2) and contacts the intermediate layer (6). A protective structure for an integrated circuit characterized by: (4) In any one of the above claims, the doping concentration of the diffusion region (8) is in an epitaxial layer (
2) A protective structure for an integrated circuit, characterized in that the doping concentration is higher than that of 2). (5) A protective structure for an integrated circuit according to any one of the preceding claims, characterized in that the doping concentration of the another diffusion region (16) is higher than the doping concentration of the substrate (4). (6) A protective structure for an integrated circuit according to any one of the preceding claims, characterized in that the doping concentration of the intermediate layer (6) is higher than the doping concentration of the epitaxial layer (2). (7) According to any one of the preceding claims, the intermediate layer (6) extends laterally substantially beyond the lateral limits of the diffusion region (8) and another diffusion region (16). A protective structure for an integrated circuit characterized in that no (8) In any one of the above claims, the first
The insulating region (22) of conductivity type is connected to the epitaxial layer (
2) A protective structure for an integrated circuit, characterized in that the protective structure is provided within and surrounds and insulates the protective structure. (9) In any one of the preceding claims, the diffusion region (8) includes a laterally extending shallow region (10).
A protective structure for an integrated circuit, characterized in that it is accompanied by. (10) A protection structure for an integrated circuit according to claim (8), characterized in that the insulating region (22) is associated with a laterally extending shallow region (24). (11) In any one of the above claims, the oxide layer (30) is connected to the epitaxial layer (2) and the diffusion region (
8), another diffusion region (16), insulation region (22)
or a combination thereof, provided with a concave contact window (14)
, (20) and (28). (12) Claim (11), characterized in that the contact windows (14), (20), (28) have beveled corners to reduce the charge concentration in their corner regions. A protective structure for integrated circuits. (13) Protection structure for an integrated circuit according to any one of the preceding claims, characterized in that the diffusion region (8) extends circumferentially around another diffusion region (16).