JP2001156062A - Semiconductor device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protection film for semiconductor devices which is superior in water penetration resistance and etching resistance and not vulnerable to electric influences of impurity ions intruding from the outside. SOLUTION: A first oxide film is formed on an IC substrate 1, an SiO2 grain film having a high porosity is formed on the first oxide film, and a second oxide film and an NiO are formed on the SiO2 grain film. Owing to the SiO2 grain film, a surface protection film having a low permittivity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device such as a high withstand voltage IC, and more particularly to a surface protection film for the semiconductor device.

[0002]

2. Description of the Related Art In a planar type semiconductor device, a passivation treatment of a semiconductor surface is indispensable. This is because a planar element whose semiconductor surface is exposed to an electric field has electrical characteristics such as withstand voltage characteristics affected by surface charges. As a method of protecting and inactivating the semiconductor surface, it is generally known that the semiconductor surface is covered with an oxide film such as LOCOS, PSG, BPSG, or a plasma CVD silicon nitride film. By covering the oxide film or the silicon nitride film in this manner, it is possible to prevent impurity ions from entering from outside through the package resin and the package, and to prevent the impurity ions from affecting the electrical characteristics. Of course, the coating of these films also has the purpose of preventing mechanical damage.

In recent years, there is a strong demand for higher performance (for example, miniaturization, higher breakdown voltage, lower on-resistance, higher integration, etc.) of these semiconductor devices and lower cost of the packages. With this low cost package, 10
Impurity ions having a surface charge amount of ¹⁸ to 10 ¹⁹ charges / cm ² may be attached. It has been reported that the amount of surface charge so as not to affect the electrical characteristics of a semiconductor device such as a high withstand voltage IC is about 1 × 10 ¹² charges / cm ² (RB Comizoli and JWO).
Senbach, Proc. Symp. on High
Voltage and Smart Power
Devices, Electrochem. Soc. ,
Philadelphia, PA, pp 232-24
0, 1987). However, it is reported that if the surface protective film has a defect, even a charge amount of 1 × 10 ¹⁰ charges / cm ² has a significant effect on electrical characteristics. It is also reported that if there is no defect, even a charge amount of 1 × 10 ¹⁵ charges / cm ² does not affect the electrical characteristics (J.
W. Osenbach et al. Proc. 24
th reliability Physics Sy
mp. Pp. 239-246, 1986).

[0004]

However, as described above, even if the surface charge amount is 10 ¹⁸ to 10 ¹⁹ charges / cm ² , the electrical characteristics of the semiconductor device should not be affected. It is necessary to devise a device for completely eliminating defects, and at the same time, it is important to provide a surface protective film that is hardly affected by the amount of surface charge.

[0005] To eliminate the former defect, it was possible to cope with the process equipment and process control. However, it is difficult to control the latter surface charge caused by a low-cost package. It is difficult to respond. As the surface protective film that is not easily affected by the surface charge amount, a surface protective film formed of a dielectric material having a small relative dielectric constant may be used. This is because a small relative dielectric constant means that impurity ions are unlikely to adhere to the surface of the surface protective film. The development of a dielectric material with a small relative dielectric constant
RC (R: wiring resistance, which causes delay of the high-speed driving IC,
(C: capacity of the interlayer insulating film filling the space between the wirings) is increased in the region of the interlayer insulating film. Here, F and C-added silicon oxide films (relative permittivity of 2.5 to 3) and organic polymers smaller than silicon oxide films (relative permittivity of 2.5 to 4) are being studied.

The surface protective film which is hardly affected by the amount of surface charges not only has a small relative permittivity but also has a small dielectric constant.
It is necessary to be excellent in water resistance and corrosion resistance which are the original functions of the surface protective film. However, in order to reduce the relative dielectric constant, the porosity of the membrane is increased (making the membrane a low density membrane) (WO 94/25149 and C. Jin et al .: M.
RS Bulletin Vol22, pp39, 19
1997) and the original function of the surface protective film, water resistance,
Corrosion resistance deteriorates.

An object of the present invention is to solve the above-mentioned problems and to provide a surface protective film of a semiconductor device which is excellent in water resistance and corrosion resistance and is hardly electrically affected by impurity ions penetrating from the outside. Is to do.

[0008]

In order to achieve the above object, a semiconductor substrate on which a semiconductor element is formed, an electrode wiring portion of the semiconductor element formed on the semiconductor substrate, and a first substrate on the semiconductor substrate are provided. A porous dielectric film formed through an insulating film and selectively covering the electrode wiring portion; and a dense second dielectric film formed on the dielectric film having a film density of at least 2 g / cc or more. A structure including an insulating film.

It is preferable that the porous dielectric film is formed of oxide particles. The dense second insulating film may be any one of a silicon oxide film, a silicon nitride film, and a stacked film thereof. In a method of forming a surface protection film of a semiconductor device for protecting a semiconductor substrate on which a semiconductor element is formed and an electrode wiring portion of the semiconductor element formed on the semiconductor substrate, forming a first insulating film on the semiconductor substrate Performing a step of: forming a dielectric film on the first insulating film and the electrode wiring portion; selectively removing the dielectric film on the electrode wiring portion; Forming a dense second insulating film having a film density of at least 2 g / cc or more.

Preferably, the method includes a step of selectively removing the second insulating film on the metal wiring portion and a step of forming a metal wiring film in the removed portion. In general, if a certain amount of electric charge per unit area exists in the dielectric layer on the surface protective film, a voltage generated as a result is applied to the protective film. As a result, electric charge Q is induced on the silicon surface underneath, and the induced electric charge adversely affects the element surface (the surface of the semiconductor device) such as a decrease in breakdown voltage and an increase in leak current. Now, the charge Q on the surface protective film
And a voltage V is generated. The relationship between the charge Q and the voltage V is as follows, where C is the capacitance of the surface protection film.
Becomes The charge induced on the silicon surface also becomes Q. Therefore, in order to reduce the attached charge Q, it is necessary to reduce the capacitance C of the surface protective film. The capacitance C of the surface protective film is calculated using the thickness d of the protective film, the surface area S, and the dielectric constant ε.
It is expressed as εS / d. That is, to reduce C,
When S and d are constant, a surface protective film having a small dielectric constant ε is used.

In order to reduce the dielectric constant ε, a high-porosity (porous) oxide film as a surface protective film is made less susceptible to electrical influence by impurity ions penetrating from the outside. Density of at least 2 g / cc
By forming the above-described silicon oxide film, silicon nitride film, or a film obtained by stacking them, corrosion resistance can be increased.

[0012]

1A to 1E show a method for manufacturing a surface protective film according to an embodiment of the present invention. FIGS. 1A to 1E are sectional views showing main steps in the order of steps. First, a powder of SiO ₂ having a particle size distribution center of 20 nm was placed in isopropyl alcohol to obtain a monodispersed liquid. This dispersion liquid 4 is stored in a polyimide dam (1.5 μm in height) provided on the outer periphery of the wafer 1 mm on which IC chips (not shown) are integrated, so that the irregularities on the wafer surface are buried and flattened (FIG. a)). An IC chip is an IC chip on which various elements are formed.
A first oxide film 2 formed on a C substrate and an IC substrate 1 to a thickness of 1 μm by steam oxidation in a steam atmosphere at 1050 ° C.
And an Al electrode 3 formed by opening a contact hole in the first oxide film 2. In addition, the irregularities are SiO
It is about the particle size of the powder of ₂ .

Next, baking is performed in vacuum at about 300 ° C., which is a temperature near the softening point of the SiO ₂ powder, for 30 minutes to evaporate the solvent and condense the SiO ₂ particles together.
By welding, a SiO ₂ grain film 5 having a thickness of 1 μm is obtained. This S
The iO ₂ grain film 5 can be a dielectric layer having a high perforation rate. Further, although the thickness of the solvent evaporated is smaller than the thickness at the time of application, SiO ₂ particles are deposited on the wiring electrode, and a flat surface is obtained as a whole (FIG. 2B).

Next, in this state, a plasma CVD-SiO ₂ film is deposited as the second oxide film 6 to a thickness of 0.1 μm to improve the flatness (FIG. 3C). As a result, obtained cross-sectional shape as shown in FIG. 2, SiO ₂ Tsubumaku 6 a number of S
Although composed of iO ₂ particles 8, by covering the second oxide film 6 thereon, defects such as pinholes penetrating these films can be eliminated.

Next, resist patterning and etching were performed to open a window at a wiring take-out portion on the Al electrode 3 (FIG. 4D). The etching in this case is CF ₄ /
It is a plasma etching of O _2. Although the upper part of the etched side A is a dense SiO ₂ film, the lower part is a thick porous layer (a SiO ₂ grain deposited layer and a dielectric layer having a small dielectric constant). In the wet state, there is intrusion of moisture.

Next, the SiN film 7 is formed by a plasma CVD method.
0.5 μm, and after protecting the side surface A with this film,
A window is opened in the SiN film 7 on the Al electrode 3 of FIG.
(E)). Then, the Al electrode 3 and S
A wiring (not shown) formed on the iN film 7 is connected.
This SiN film 7 is made of Si_xN_yH_ZIt is a membrane. This example
Then, the configuration of the surface protection film is the first oxide film 2 on the IC substrate.
And SiO _TwoThe grain film 5, the second oxide film 6, and the SiN film 7
is there. The equivalent relative permittivity of these films as a whole is 2.0.
Thus, a surface protective film having a low dielectric constant can be obtained. In addition, the second oxidation
External environment through the package by the film 4 and the SiN film 7
To be electrically affected by impurity ions entering
In addition, the S at the portion where the contact hole is
iO_TwoThe side surface A of the grain film 5 and the surface of the second oxide film 6
Covered with a dense film of N film 7 (film density of 2 g / cc or more)
By doing so, it is possible to improve water resistance and corrosion resistance.

In the case where the entire wiring is formed above the wiring (not shown) formed on the SiN film 7, the SiO ₂ grain film 5, the second oxide film 6, and the SiN film 7 are formed on the wiring (not shown). Are formed on top of each other.

[0018]

Effect of the Invention] The present invention, the oxide film of high perforation degree on the silicon surface (dielectric film having a low dielectric constant: SiO ₂ Tsubumaku 5) a dense Si _x N _y H _z film thereon ( (SiN film), excellent in water resistance and corrosion resistance, and less likely to be affected by impurity ions invading from the outside world, and improved electrical characteristics such as withstand voltage characteristics and its reliability Can be done.

[Brief description of the drawings]

FIGS. 1A to 1E are cross-sectional views showing a main part of a method of manufacturing a surface protective film according to an embodiment of the present invention, which are shown in the order of steps.

FIG. 2 is a sectional view of a main part of the surface protective film of the present invention.

[Explanation of symbols]

1 IC substrate 2 first oxide film 3 Al electrode 4 Dispersion 5 SiO ₂ Tsubumaku 6 second oxide film 7 SiN film 8 SiO ₂ particles

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/318 H01L 21/318 B 21/768 21/90 K F Term (Reference) 5F033 HH08 JJ01 JJ08 KK01 KK08 QQ12 QQ37 QQ74 QQ85 RR04 RR06 SS15 SS22 TT02 TT07 XX00 XX01 XX18 XX24 5F058 BA07 BA20 BD02 BD04 BD07 BD09 BD13 BF07 BF46 BJ01 BJ02 BJ03

Claims (5)

[Claims] A semiconductor substrate on which a semiconductor element is formed, an electrode wiring portion of the semiconductor element formed on the semiconductor substrate, and a first insulating film formed on the semiconductor substrate via a first insulating film;
A porous dielectric film selectively covering the electrode wiring portion, and a film density formed on the dielectric film is at least 2 g.
And a dense second insulating film of at least / cc. 2. The semiconductor device according to claim 1, wherein said porous dielectric film is formed of oxide particles. 3. The semiconductor device according to claim 1, wherein said second insulating film is one of a silicon oxide film, a silicon nitride film, and a film obtained by laminating them. 4. A method for forming a surface protection film of a semiconductor device for protecting a semiconductor substrate having a semiconductor element formed thereon and an electrode wiring portion of the semiconductor element formed on the semiconductor substrate.
Forming a first insulating film on the semiconductor substrate, forming a dielectric film on the first insulating film and on the electrode wiring portion, selectively forming the dielectric film on the electrode wiring portion; And a film density of at least 2 g on the dielectric film.
Forming a dense second insulating film of at least / cc or more. 5. The method according to claim 4, further comprising the steps of: selectively removing the second insulating film on the metal wiring portion; and forming a metal wiring film on the removed portion. Of manufacturing a semiconductor device.