JPH0828360B2 - Semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor device in which characteristic changes due to penetration of operating ions are prevented.

[Outline of Invention]

The present invention relates to an SR having a resistor formed on a semiconductor substrate.
In semiconductor devices such as AM (Static Random Access Memory), a conductive region of the same conductivity type as the semiconductor substrate is formed in the scribe region that divides the semiconductor chip, and covers the cross section of the semiconductor chip facing the scribe region and also in the conductive region. By forming a conductive film in contact and applying the potential applied to the semiconductor substrate to the conductive film through the conductive region, mobile ions can enter the semiconductor chip despite the simple structure. The present invention provides a semiconductor device which prevents the above-mentioned phenomenon and does not change its characteristics.

[Conventional technology]

The resistor of the high resistance type SRAM is usually formed of polycrystalline Si. After the formation of this high resistance portion, a PSG film, an AsSG film or a SiO ₂ film as a protective film, a plasma Si ₃ N ₄ film or the like as a passivation film is formed thereon.

However, the Si ₃ N ₄ film formed by the plasma CVD method contains a large amount of hydrogen, and hydrogen in the Si ₃ N ₄ film diffuses inside due to external energy such as electric field and heat, and penetrates into the high resistance body. To do.

On the other hand, a heat treatment is performed in an H ₂ atmosphere in order to remove damaging generated by a treatment such as electron beam or sputtering, but hydrogen also infiltrates the high resistance body during this hydrogen annealing.

In this way, when hydrogen enters the high resistance body made of polycrystalline Si, the resistance value of the high resistance body fluctuates, and there is a problem that the designed resistance value cannot be obtained.

In addition to the problem of resistance fluctuation, after packaging the semiconductor chip, sodium ions or potassium ions enter the semiconductor chip during long-term use,
There is a problem that the characteristics of the semiconductor device are deteriorated.

Therefore, in order to prevent hydrogen from penetrating into the high-resistance element and improve the moisture resistance, the applicant of the present application has previously proposed in Japanese Patent Application No. 61-191229 that the side surface of the semiconductor chip main body exposed to the scribe line be made of Al-like material. We proposed the structure of a semiconductor device covered with a hydrogen impermeable film or a hydrogen absorbing film such as a PSG film.

[Problems to be solved by the invention]

However, it was found that the resistance value of the high resistance body and the characteristics of the transistor still fluctuate even if the structure of this patent application is adopted. As a result of the inventor's efforts to investigate the cause, it has been found that the invasion of mobile ions from the side wall of the scribe line is the cause of fluctuations in the resistance value and the like.

This point will be described with reference to FIG. After completion of a series of semiconductor processing steps, the semiconductor wafer is scribed along the scribe line 9 to be separated into individual pellets. Surface of the semiconductor device have been covered with the plasma the Si ₃ N ₄ film 8 of the passivation film, plasma the Si ₃ N ₄ film 8 of the scribe line region is removed in order to ensure scribe. Mobile ions such as H ⁺ , Na ⁺ and Cl ⁻ enter the semiconductor chip body from the interface between the substrate 1 and the exposed plasma Si ₃ N ₄ film 8.

If H ⁺ diffuses into the polycrystalline Si film 4 which is a high resistance element, there is a problem that the resistance value changes.

After packaging the semiconductor chip, if ions such as Na ⁺ reach the chip body through the invasion path, there is a problem that the transistor characteristics and the like deteriorate.

[Means for solving problems]

The present invention forms a conductive region of the same conductivity type as a semiconductor substrate in a scribe region that divides a semiconductor chip, and forms a conductive film that covers the cross section of the semiconductor chip facing the scribe region and is in contact with the conductive region, The above-mentioned problem is solved by applying the potential applied to the semiconductor substrate to the conductive film through the conductive region.

[Action]

According to the structure of the semiconductor device of the present invention, at the interface between the main body chip and the scribe line, even if the passivation film is exposed, the side surface of the main body chip is covered with the conductive film,
Since the potential of the semiconductor substrate is applied to the conductive film,
An electrical barrier is formed, and mobile ions such as H ⁺ , Na ⁺ and Cl ⁻ are prevented from entering the main body chip from the outside. That is, if a positive bias is applied to the conductive film,
Positive ions such as H ⁺ and Na ⁺ are repelled and cannot enter the inside of the chip, and negative ions such as Cl ⁻ are taken into the conductive film, and mobile ions cannot enter the main body chip anyway. It will be.

〔Example〕

Based on the cross-sectional view of FIG. 1A and the top view of FIG. 1B,
An embodiment of the semiconductor device of the present invention will be described. A p-well is formed in the n-type Si substrate 1 by the usual manufacturing method to form a peripheral CMOS.
Then, a semiconductor device in which the memory unit is a high resistance SRAM is formed. At this time, an n ⁺ region is provided in a portion corresponding to the scribe line region 9 in the n-type Si substrate 1. After the AsSG film 7 and the Si ₃ N ₄ film 6 are formed by the CVD method, Al metal is sputtered to form a wiring electrode.
A portion for forming the conductive film 10 is added to an Al metal sputtering mask. As a result, the wiring electrode made of Al metal and the conductive film 10 can be formed at the same time. In this embodiment, the conductive film 10 has a width of 2.6 μm. After that, the Si ₃ N ₄ film 8 is formed on the entire surface by the plasma CVD method,
The Si ₃ N ₄ film in the scribe line region is removed. Scribe is performed in the scribe line region 9 between the conductive films 10 shown in FIG. 1B, and the way is divided into chips.

Since a back bias of +5 V is applied to the substrate 1 during operation of this semiconductor device, +5 V is also applied to the conductive film 10 and mobile ion invasion from the outside is blocked.

〔The invention's effect〕

With the semiconductor device having the structure of the present invention, hydrogen invades into the high-resistance element during the manufacturing process that could not be controlled by the conventional technique, and mobile ions such as Na ⁺ enter the device after completion of the device. It is possible to prevent a decrease in reliability that occurs.

The semiconductor device having the structure of the present invention can be obtained by slightly modifying the mask pattern of the wiring electrode so as to cover the side wall portion of the chip body exposed on the scribe line.
There is also an effect that no change is required in the process.

Moreover, the potential applied to the conductive film covering the cross section of the semiconductor chip is the potential applied to the semiconductor substrate and is not a different potential. Therefore, no special wiring or the like is required, and the structure is simple.

[Brief description of drawings]

1A and 1B are cross-sectional views of the semiconductor device of the present invention. FIG. 2 is a sectional view of a conventional semiconductor device. 1 ... Substrate, 2 ... Field oxide film 3, 5 ... SiO ₂ film, 4 ... Polycrystalline Si film 6 ... Si ₃ N ₄ film, 7 ... AsSG film 8 ... Plasma Si ₃ N ₄ film 9 …… Scribe line area 10 …… Protective film, 11 …… Chip body 12 …… PSG film, 13 …… Al electrode

Claims (1)

[Claims] 1. A conductive region having the same conductivity type as that of a semiconductor substrate is formed in a scribe region dividing a semiconductor chip, and a conductive region that covers a cross section of the semiconductor chip facing the scribe region and is in contact with the conductive region. A semiconductor device in which a film is formed, and the potential applied to the semiconductor substrate is also applied to the conductive film via the conductive region.