JPH0624228B2 - Method for manufacturing semiconductor integrated circuit device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor integrated circuit device having a capacitor, and in particular, a deep groove is formed in a silicon substrate in order to obtain a large storage capacitance Cs with a fine capacitor. The present invention relates to a method of manufacturing a memory device having a so-called groove-shaped capacitor.

[Conventional technology]

FIG. 2 (a) shows a cross section of a conventional grooved capacitor structure, in which 1 is a silicon substrate, 2 is a thick silicon oxide film for element isolation, 3 is a groove, 4 is a capacitor insulating film, and 5 is a capacitor insulating film. A capacitor electrode, 6 is a switching transistor, and 7 is an impurity diffusion layer. In such a groove type capacitor, as shown by the arrow in FIG. 2 (b), the capacitor insulating film 4 is thin because the corners above the groove 3 are steep.

[Problems to be solved by the invention]

Since the conventional semiconductor integrated circuit device is configured as described above, since the capacitor insulating film becomes thin at the upper corners of the groove and electric field concentration is likely to occur, the dielectric breakdown strength is reduced and sufficient charge storage and retention is achieved. There was a drawback that the characteristics could not be obtained.

The present invention has been made in view of the above-mentioned drawbacks of the conventional ones, and an object thereof is to obtain a method for manufacturing a semiconductor integrated circuit device in which the withstand voltage defect of an insulating film is remarkably improved and a sufficient charge storage and retention characteristic is obtained. To do.

[Means for solving problems]

A method of manufacturing a semiconductor integrated circuit device according to the present invention comprises forming a groove in a silicon substrate, injecting impurities into the surface of the substrate, an edge of the groove and an upper portion of a side surface thereof from obliquely above, and then oxidizing the substrate. The oxide film formed by is removed.

[Action]

In the present invention, the surface of the grooved silicon substrate and the upper portion of the groove are implanted with impurities, and then the oxide film formed by oxidizing the entire surface is removed. It is wider than the bottom and the top corners are rounded.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

1 (a) to 1 (e) show a method of manufacturing a semiconductor integrated circuit device according to an embodiment of the present invention in the order of steps thereof.
7 is the same as FIG. 2, 1a is an impurity layer formed on the surface of the silicon substrate, 1b is an impurity layer formed on the upper side surface of the groove 3, and 4a and 4b are impurity layers 1a and 1b, respectively.
It is a silicon oxide film formed on.

Next, the manufacturing method will be described.

First, after forming the groove 3 in the silicon substrate 1, impurities such as Ar are ion-implanted into the entire surface of the wafer while rotating the wafer obliquely from above (FIG. 1 (a)), as shown in FIG. 1 (b). Thus, the impurity layers 1a and 1b are formed on the surface of the silicon substrate and on the upper portions of the side surfaces of the groove, respectively. During ion implantation, the bottom of the groove is blocked by the upper portion of the groove as shown in FIG. 1 (a), and is held without the implantation layer being formed.

Next, the silicon substrate 1 is oxidized in an oxygen atmosphere. At this time, the oxidation rate of the regions of the impurity layers 1a and 1b is several times faster than that of the portion where no ions are implanted.
As shown in (c), the silicon oxide films 4a and 4b formed on the impurity layers 1a and 1b are thicker than the silicon oxide film 4 formed on the non-ion-implanted portion of the silicon substrate 1.

Next, when the oxide films 4a, 4b, 4 are removed by a hydrofluoric acid-based etching solution, the groove 3 has a shape in which the opening at the top is wider than the bottom and the top corner is rounded (first shape). Figure
(d)).

After that, the capacitor insulating film 4 and the capacitor electrode 5 are sequentially formed in the groove 3 by the same method as the conventional method to obtain a groove type capacitor structure. (Fig. 1 (e)).

As described above, in this embodiment, after forming the groove in the silicon substrate, ions are implanted into the substrate obliquely from above while rotating the wafer, and then an oxide film is formed on the substrate, and the oxide film is removed. Therefore, it is possible to change the steep cross-sectional shape of the groove type capacitor to a gentle shape,
It is possible to suppress the deterioration of the dielectric breakdown strength and improve the stored charge retention characteristic.

Although the groove type capacitors have been described in the above embodiments, the present invention can be applied to all devices having a groove in a substrate, such as a groove type isolation structure. Further, the impurities at the time of ion implantation may be any impurities as long as they change the oxidation characteristics of the semiconductor substrate.

Further, in the above embodiment, the ion implantation method is used to change the oxidation characteristic of the semiconductor substrate, but any physical method such as a sputtering method may be used.

Further, in the above-mentioned embodiment, the oxide film is grown in the formation of the groove portion, but a nitride film or another insulating film may be grown.

〔The invention's effect〕

As described above, according to the method for manufacturing a semiconductor integrated circuit device of the present invention, after forming a groove in a silicon substrate, ions are implanted into the substrate obliquely from above, and then an oxide film is formed on the substrate. Since the oxide film is removed, the steep sectional shape of the groove type capacitor can be changed to a gentle shape, and there is an effect that the breakdown voltage defect of the insulating film can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a method of manufacturing a semiconductor integrated circuit device according to an embodiment of the present invention in the order of steps, and FIG. 2 is a sectional view showing the structure of a conventional device. In the figure, 1 is a silicon substrate, 1a and 1b are impurity layers, 2 is a separation insulating film, 3 is a groove, 4 is a capacitor insulating film, 4a,
4b is a silicon oxide film, 5 is a capacitor electrode, 6 is a switching transistor, and 7 is an impurity diffusion layer. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor integrated circuit device having a groove-shaped capacitor portion, comprising: a first step of forming a deep groove in a semiconductor substrate; and an impurity being obliquely injected into a surface of the groove and the substrate.
The second step of forming the impurity injection layer only on the substrate surface, the edge of the groove and the upper part of the side surface thereof, and then oxidizing the entire surface to make the insulating film thickness of the impurity injection layer thicker than the other portions of the insulating film. A method of manufacturing a semiconductor integrated circuit device, comprising: a third step of forming an insulating film as described above; and a fourth step of removing the insulating film thereafter. 2. The method for manufacturing a semiconductor integrated circuit device according to claim 1, wherein the semiconductor substrate is silicon and the insulating film is a silicon oxide film.