JP2900717B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a refresh time of a dynamic random access memory (hereinafter referred to as "refresh time" ).
And a semiconductor device in which deterioration of the flash time is prevented.

In a dynamic random access memory, impurities are diffused into the surface of a semiconductor substrate at a contact portion between a storage electrode made of polycrystalline silicon and a semiconductor substrate by performing a heat treatment. There is a problem that the diffusion state becomes unstable depending on the state, and the refresh time deteriorates.

[0005] Under the circumstances described above, there is a demand for a semiconductor device capable of preventing deterioration of the refresh time.

[0004]

2. Description of the Related Art Referring to FIG.
The method of manufacturing a semiconductor device will be described in detail with reference to FIGS.

FIG. 4 is a side sectional view showing a conventional semiconductor device.
5 to 6 are side sectional views showing a conventional method of manufacturing a semiconductor device in the order of steps. To manufacture a conventional semiconductor device,
First, as shown in FIG. 5A, a field oxide film 12 for defining a transistor formation region is provided on the surface of a semiconductor substrate 11, and a gate electrode 13 is formed.

[0006] Next, as shown in FIG.
Impurities are introduced into the semiconductor substrate 11 between the layer 13 and the field oxide film 12 to form a source 14 and a drain 15. Then FIG.
A silicon oxide film 16 is formed on the entire surface as shown in FIG. 5C, and a contact hole 16a is formed in the silicon oxide film 16 as shown in FIG.

Here, a polycrystalline silicon film containing impurities is formed on the entire surface of the silicon oxide film 16, and the polycrystalline silicon film is patterned to form a storage electrode 18 as shown in FIG. Heat treatment forms diffusion layer 17 on semiconductor substrate 11.

Thereafter, as shown in FIG. 6B, an insulating film 19 made of a silicon nitride film is formed on the entire surface of the storage electrode 18. Finally, as shown in FIG. 4, a polycrystalline silicon film is formed on the surface of the insulating film 19 and patterned to form an upper electrode 20.

[0009]

In the conventional semiconductor device described above, the storage electrode formed on the surface of the semiconductor substrate is subjected to a heat treatment, so that the contact between the storage electrode made of polycrystalline silicon and the semiconductor substrate is formed. Although the impurities are diffused to the surface of the semiconductor substrate, the amount of movement of the impurities varies depending on the interface state of the contact portion, so that the diffusion state becomes unstable, the junction breakdown voltage changes, and the refresh time deteriorates due to the junction leak. There was a problem.

[0010] The state when the impurity concentration is less than 4 × 10 ¹⁹ cm ^-3, as shown in FIG. 7 is deteriorated refresh time. The present invention makes it possible to easily and easily prevent the deterioration of the refresh time from the above situation.
It is intended to provide a semiconductor device .

[0011]

According to the present invention, there is provided a semiconductor device comprising:
Memory cell of dynamic random access memory
MOS transistor formed on the semiconductor substrate in the region
And an insulator formed to cover this MOS transistor.
An edge film and one source / drain of this MOS transistor
A contact hole formed in this insulating film on the in-diffusion layer
And one of the source / drain
The storage electrode connected to the in-diffusion layer and the storage electrode
Formed on the storage electrode via a capacitor insulating film
An electrode, and the semiconductor substrate in the contact hole.
On the surface of the plate, one of these saws having a concentration of 4 × 10 ¹⁹ cm ^-3 or more
Do not implant impurities of the same conductivity type as
Configured to that.

[0012]

According to the present invention, impurities are implanted into the surface of a semiconductor substrate in a contact hole of a silicon oxide film.
Since the concentration is set to be higher than the concentration at which the refresh time can be stabilized and the storage electrode is formed here to form the capacitor, the refresh time of the dynamic random access memory can be stabilized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a side sectional view showing a semiconductor device of one embodiment according to the present invention, and FIGS. 2 to 3 are side sectional views showing a method of manufacturing a semiconductor device of one embodiment according to the present invention in the order of steps.

In order to manufacture a semiconductor device by the method for manufacturing a semiconductor device according to one embodiment of the present invention, first, as shown in FIG. 2A, a transistor formation region is defined on the surface of a P-type semiconductor substrate 1. A field oxide film 2 is provided, and a gate electrode 3 is formed.

Next, as shown in FIG. 2B, a source 4 and a drain 5 are formed by introducing impurities into the semiconductor substrate 1 between the gate electrode 3 and the field oxide film 2 under the following conditions. Ion species {phosphorus (P ⁺ ), implantation energy}
The silicon oxide film 6 is formed by CVD on the entire surface as shown in ──────50 keV dose ──────8 × 10 ¹⁷ cm ^-3 followed Figure 2 (c), FIG. 2 (d As shown in FIG. 1B), a contact hole 6a is formed in the silicon oxide film 6 by using a photolithography method, a dry etching method or the like.

Here, as shown in FIG. 3A, ions are implanted into the surface of the semiconductor substrate 1 in the contact hole 6a under the following conditions to form a diffusion layer 7. Ion species {phosphorus (P ⁺ ), implantation energy}
──────50 keV dose amount────────4 × 10 ¹⁹ cm ^-3 or more Here, a polycrystalline silicon film containing impurities is formed on the entire surface of the silicon oxide film 6 by a CVD method. This polycrystalline silicon film is patterned to form a storage electrode 8 as shown in FIG.

Thereafter, as shown in FIG. 3C, an insulating film 9 made of a silicon nitride film is formed on the entire surface of the storage electrode 8 by the CVD method. Finally, as shown in FIG. 1, a polycrystalline silicon film is formed on the surface of the insulating film 9 and patterned to form an upper electrode 10.

As described above, before forming the storage electrode 8, an impurity having a concentration capable of stabilizing the refresh time is implanted into the surface of the semiconductor substrate 1 in the contact hole 6a. It is possible to prevent the refresh time from deteriorating due to the leak.

[0019]

As is apparent from the above description, according to the present invention, there is an advantage that a semiconductor device with a stable refresh time can be manufactured by a very simple process change. In addition, it is possible to provide a semiconductor device that can be expected to improve reliability.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a semiconductor device according to one embodiment of the present invention;

FIG. 2 is a side sectional view (1) showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps;

FIG. 3 is a side sectional view (2) showing a method of manufacturing a semiconductor device according to one embodiment of the present invention in the order of steps;

FIG. 4 is a side sectional view showing a conventional semiconductor device.

FIG. 5 is a side sectional view (1) showing a conventional method of manufacturing a semiconductor device in the order of steps,

FIG. 6 is a side sectional view (2) showing a conventional method of manufacturing a semiconductor device in the order of steps,

FIG. 7 is a diagram showing a relationship between an impurity concentration of a diffusion layer and a refresh time;

[Explanation of symbols]

1 is a semiconductor substrate, 2 is a field oxide film, 3 is a gate electrode, 4 is a source, 5 is a drain, 6 is a silicon oxide film,
6a is a contact hole, 7 is a diffusion layer, 8 is a storage electrode, 9 is an insulating film, 10 is an upper electrode,

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 27/108 H01L 21/822 H01L 21/8242 H01L 27/04

Claims (1)

(57) [Claims] 1. A dynamic random access memo
MOS formed on the semiconductor substrate in the memory cell area
Transistor and insulating film formed to cover MOS transistor
And one source-drain diffusion of the MOS transistor
A contact hole formed in the insulating film on the layer, and the one source / drain extension in the contact hole.
A storage electrode connected to a diffused layer, and formed on the storage electrode via a capacitor insulating film
And a surface of the semiconductor substrate in the contact hole.
× 10 ¹⁹ cm ^-3 or more of the one source / drain extension
It is characterized by being doped with impurities of the same conductivity type as the diffused layer.
Semiconductor device.