JPS5831523A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an electrode window having no difference in level and suitable for electrode wiring by a method wherein taper etching is also applied to a block film in forming the electrode window at a phosphoric silicic acid glass film (PSG film) and the first resist film is removed by a sulfuric acid peroxide solution as a promotion measure. CONSTITUTION:A negative type resist film 6 is applied on the upper surface of a PSG film 5 on an Si3N4 film 4 coated through an SiO2 film 8 for patterning and the PSG film 5 is etched by a fluoric acid group etching solution. The Si3N4 film is left as no etching is done and the PSG film becomes a taper-shaped window side by applying side etching to the PSG film. After applying exfoliation treatment to the resist film 6 by a sulfuric acid peroxide solution, the PSG film 5 is heated at about 1,000 deg.C under inert gas atmosphere and the surface of the PSG film 5 is melted. The resist film 7 is again applied and after coating the PSG film 5 by patterning, isotropic dry etching is done by carbon tetrafluoride (CF4) gas and the exposed Si3N4 film 4 is formed to be an electrode window providing a taper-shaped internal side.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a silicic acid glass film (PS) provided with an impurity diffusion prevention film (block film).
Regarding the failure of the manufacturing method for forming electrode windows in G@).

Semiconductor devices such as integrated circuits (ICs) are easily affected by surface particles, so measures are taken to coat the surface with a PSG film to prevent moisture and sodium ions from entering from the outside, and most semiconductor devices The surface of the element is covered with a PSG film. It is no exaggeration to say that it is protected as an insulating film. Therefore, in an IC, after a PSG film is deposited, an electrode window is opened to expose the electrode wiring, but PSG 111
o1! Thickness tf l [[mu]m or more is thick, and if the window is simply etched and opened, there is a risk that the electrode wiring formed thereon will be disconnected due to irregularities and steps on the side surface of the window. Therefore, a melting process is performed to melt the PSG film surface by heating to a high temperature of about 1000 [tl]Q and to make the window side surface smooth.

However, since the PSG film contains a large amount of phosphorus, when heated to such a high temperature, phosphorus will spread into the electrode window.

If the semiconductor region within the electrode window is an N-type region, phosphorus
There is no problem because it is a P-type impurity, but if it is a P-type impurity, a PN junction will occur here, which will have an adverse effect on the electrode connection or semiconductor device characteristics.
Silicon nitride (5iBN4) before depositing GII
The manufacturing method for forming a block film consisting of II is the original song.
For example, in the 0-MO8 type C, the p5 source region and drain 11 region of the p-channel semiconductor element are formed, so a blocking film is provided over the entire area to prevent electric current.
It forms a rut.

To explain a method for forming a PSG film depending on electrodes, in which such a block film has been conventionally formed, FIGS. 1 to 8 are cross-sectional views in the order of steps. For example, Pg region 2 on N5 semiconductor substrate l
When opening the 11E electrode window, as shown in Figure 1, silicon oxide (Sin, )! 5 deposited via lIB
A cyst film 6 is patterned on the surfaces of the iaN4 film 4 and the P13G film 6 formed thereon, and etched with a hydrofluoric acid-based etching solution. Then, the exposed PS
GSbO2 is etched, side etching progresses, and a tapered side window is obtained.Next, as shown in FIG. 2, the resist 116 is dissolved and removed. Heat to PSG
The surface of the membrane 60 is melted. At this time, the semiconductor substrate
P mtll area 2 5ins 118 (!: 5
isN4114 Since it is covered with horse chestnut, PSGII
Then, as shown in Fig. 8, anisotropic etching is performed to vertically etch the surface using trifluoromethane (CHF5) gas to remove the exposed liver on the electrode window. Si8N4 film 4 and 5iOB
$IIB is etched to expose the P-type region 2, and then the P-type region 2 is etched. Complete iii.

In this way, a tapered electrode window is conventionally formed in PSG#, and although the first wet etching gives PSGII a tapered shape, the second etching is anisotropic etching by dry etching. Therefore, it is formed with high precision, but the step shape on the side surface is not eliminated.

Moreover, since many electrode windows on the IC surface are simultaneously exposed, a small amount of PSG film may remain on the window surface due to variations in the etching process. becomes even larger. If this happens, there is a risk that the electrode wiring formed on the top surface will break, and even if it is not broken at the time of formation, the electrode wiring connection at this part will be insufficient and the contact resistance will increase, so it will not be used for a long time. This may cause the wire to melt due to heat generation and lead to wire breakage9.
Reliability 1: Not desirable.

The present invention aims to solve these problems, and its characteristics are that after forming a tapered electrode window on a PSG film, the resist film is dissolved and removed with a peroxide-sulfuric acid solution, and then the PSG film is melted. This manufacturing method includes the steps of forming a resist film pattern on the PSG film again, and then isotropically etching the block film to open an electrode window, and will be described in detail below with reference to the drawings.

Figures 4 to 7 are step-by-step diagrams of the manufacturing method according to the present invention, and will be explained using an example in which an electrode chamber is opened in the P5 region 2 on the N-type semiconductor substrate l, similar to the conventional example described above. do. As shown in FIG.
iaN41114 (thickness: 100 [μm]), on which a 9P13G film 5 (III [μm 91
1) A negative type cyst film 6 is applied to the upper surface and patterned to cover the surface other than the electrode chamber, and the exposed PSG film 5 on the electrode chamber is etched with a hydrofluoric acid etching solution. The 5isN4 film is not etched by the hydrofluoric acid etching solution, so it remains, and the PSG film is side-etched to form a tapered window side surface. Next, as shown in FIG. 5, the resist film 6 is stripped with a peroxide-sulfuric acid solution, and then heated to about 1000 [°C] in an inert gas atmosphere to form PSGS.
Melt the bO2 side. As described above, this PSG film melt smoothes the unevenness of the etched surface and also makes the slope of the tapered shape gentle. Also, peroxide-sulfuric acid solution (PerOxi, mon.

5ulfurio Aoi, d) has the effect of stripping the resist film and altering the Si, 3N4aII surface to promote subsequent etching of the Si8N4 film surface.

Next, as shown in FIG. 6, the resist film 7 is applied again and patterned to cover the PSG film 5. After death, it is isotropically etched using a nine-barrel type etching device using carbon tetrafluoride (0F4) gas. 5iBN exposed after dry etching
The i-film 4 is formed into an electrode window having a tapered inner surface as shown. At this time, since the 5LaN4% thickness is thin, there is almost no taper in the case of a Si3N4 film that is not treated with a peroxide-sulfuric acid solution, but with 5LaN4% that is treated with a peroxide-sulfuric acid solution,
In the case of the N4 film, a sufficient tapered side surface can be obtained.Next, the 5iOsl18 is etched with a hydrofluoric acid-based etching solution to form an electrode window with a tapered side surface as shown in the figure. 7th by dissolving and removing Ill.
An electric Wi sickle with the shape shown in the figure is used. It should be noted that the resist film 7 to be re-formed is preferably a positive type with high resolution and a V-type resist film.
Also, the reason why the resist film 7 is covered in this way is that the PSG film is C.
This is because it is easily etched by F4 gas, and the purpose of the second etching is to maintain the electrode window with high precision without damaging the PSG film as much as possible. Also, these S
Wet etching the i3N4 film 4 and the 5ill film 8 results in a tapered shape, but in this case, the etching solution remains in minute parts and causes adverse effects such as corrosion, so it is more difficult to create a tapered shape than by dry etching. As can be seen from the examples, the main feature of the present invention is to taper-etch the block film as well, and to facilitate this process, the first resist film is removed using a peroxide-sulfuric acid solution. In other words, there is no step difference, and an electrode window suitable for electrode wiring can be obtained. Therefore, the present invention
This is an extremely effective method for improving reliability.

[Brief explanation of drawings]

Figures 1 to 8 are cross-sectional views of the conventional manufacturing method in the order of steps;
FIGS. 41 to 7 are cross-sectional views in the order of steps of the manufacturing method according to the present invention. In the figure, l is an N-type semiconductor substrate, 2 is a P-type region, and 8 is a Sin
, [,4 is 5isN4I! 11.51jPSG film, 6
7 indicates a resist film. Fig. 1 Fig. 2.4 Fig. 3゛°℃ Fig. 4 vA 6 Fig. 7

Claims (1)

[Claims] An impurity diffusion prevention film made of a silicon nitride film is formed on a semiconductor substrate, a phosphosilicate glass group is deposited on the film, and an electric F.
jAl! In the method for manufacturing a semiconductor device, in which a tapered electrode window is formed in the phosphosilicate glass film, in the method for manufacturing a semiconductor device, the electrode window is formed in the impurity diffusion prevention film after the phosphosilicate glass group is further removed. A step of dissolving and removing the upper resist pattern with a peroxide-sulfuric acid solution, followed by a step of melting the phosphosilicate glass group, and then forming a resist film pattern on the phosphosilicate glass film again, followed by impurity diffusion prevention. A method for manufacturing a semiconductor device, comprising the step of isotropically etching a film to form an electrode window.