JP2763216B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a MOS type semiconductor device having an LDD (Lightly Doped Drain) structure.

[0002]

2. Description of the Related Art A conventional method for manufacturing a MOS memory cell having an LDD structure will be described with reference to the drawings. First, as shown in FIG. 2A, a P-type silicon substrate (11)
After forming an element isolation region including an active region and a field oxide film thereon, an element formation region is secured. Then, the device isolation region having a SiO ₂ film (12) as a gate oxide film has a thickness of 3500 to 4000 °. A gate electrode (13) made of polysilicon having a thickness is formed, and CVD is performed.
A SiO ₂ film is deposited to a thickness of 2500 to 3500 ° by a method, and a sidewall (14) made of SiO ₂ is formed on the gate electrode (13) by a reactive ion etching (RIE) method and an HF wet etching method. About 100-400 ° S on a silicon substrate (11)
An iO ₂ film (16) is formed.

Next, using the gate electrode (13) as a mask, SiO ₂ is formed in a region to be a source / drain region (17).
N-type impurity ions (15) such as As via the film (16)
Is performed. And a source / drain region (17)
Is performed, for example, at a temperature of 800 ° C. for one hour. Thereafter, as shown in FIG. 2B, an NSG film (1) is formed on the SiO ₂ film (16) in order to suppress out-diffusion of the source / drain region (17).
9), a BPSG film (20) is deposited thereon in order to reduce an interlayer step on the NSG film (19), and a second heat treatment is performed at 950 ° C. for 30 minutes, for example. An area (17) is formed.

[0004]

One of the causes of variations in the characteristics of the fine MOS transistor is the presence of crystal defects in the source / drain regions. However, in the above method of manufacturing a semiconductor device, Ion implantation is S
Since the process is performed through the iO ₂ film (16), oxygen is implanted into the silicon substrate (1) together with ions, and impurity ions combine with oxygen in the silicon substrate (1) to generate crystal defects (18). there were.

Further, there is a problem that the crystal defect (18) does not disappear even in the subsequent heat treatment, causes electrical leakage of the semiconductor device, and lowers the yield. Furthermore, there is a problem that the junction depth (Xj) becomes longer due to the high-temperature heat treatment after the ion implantation, which is inappropriate in terms of miniaturization. The present invention has been made in view of such a problem, and has as its object to provide a method for manufacturing a semiconductor device suitable for miniaturization without generating crystal defects.

[0006]

According to the present invention, an oxide film is laminated on a gate electrode formed on a semiconductor substrate,
Etching the oxide film to form sidewalls on the side walls of the gate electrode and leaving the oxide film so that the surface of the semiconductor substrate is not exposed; A method of manufacturing a semiconductor device, comprising: a step of performing a first heat treatment by ion-implanting impurities through an oxide film; and a step of performing a second heat treatment in an oxygen atmosphere after removing the oxide film on the semiconductor substrate. Is provided.

In the present invention, a semiconductor substrate (for example,
A gate oxide film (eg, SiO 2) is previously formed on a silicon substrate.
₂ ), a sidewall is formed and a gate electrode is formed. Then, an oxide film (for example, SiO ₂ film) of about 100 to 400 ° is formed on the entire surface of the semiconductor substrate including the gate electrode. Ion implantation of impurities such as As and P into a portion serving as a source / drain region of the semiconductor substrate via the oxide film is performed by a known method.

Thereafter, in the present invention, this impurity is
A first heat treatment is performed to diffuse into the drain region. This first heat treatment can be achieved by performing the first heat treatment in a temperature range of about 750 to 850 ° C. for about 30 to 60 minutes. Then, after removing the oxide film of the semiconductor substrate by a known method, a second heat treatment is performed in an oxygen atmosphere. In this case, the second heat treatment in an oxygen atmosphere is performed at about 800 to 900 ° C. for 10 to 30 minutes in an atmosphere in which oxygen gas flows at a flow rate of about 30 to 40 liters / min. No impurity diffusion region can be formed.

[0009]

According to the above-described method, crystal defects caused by a bond between impurity ions and oxygen in a semiconductor substrate are eliminated by performing a heat treatment in an oxygen atmosphere. That is,
By the heat treatment in the oxygen atmosphere, the bond between the impurity ion and oxygen in the semiconductor substrate is cut, so that a defect-free impurity diffusion region is formed. Further, even if the temperature of the heat treatment performed after the ion implantation is set to a low temperature for a short time, the defect is eliminated, and the diffusion of the impurity ions is suppressed to form an impurity diffusion region having a shallow junction depth. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a semiconductor device according to the present invention will be described with reference to the drawings. First, silicon substrate (1)
An element formation region consisting of an active region and a field oxide film is formed thereon to secure an element formation region, and an SiO ₂ film (2) is laminated as a gate oxide film. A gate electrode (3) made of polysilicon having a thickness of 3 nm is formed. Then, CV is formed on the silicon substrate (1) and the gate electrode (3).
A SiO ₂ film is deposited to a thickness of 2500 to 3500 ° by Method D, and a sidewall (4) made of SiO ₂ is formed on the gate electrode (3) by a reactive ion etching (RIE) method and an HF wet etching method. On this occasion,
The SiO ₂ film laminated on the silicon substrate (1) is about 40
Leave at 0mm thickness. Then, impurity ions (7) such as As are supplied at 80 KeV and 5 × 1 through the SiO ₂ film.
Inject at 0 ¹⁵ ions / cm ² . And, for example, about 8
A first heat treatment is performed at 00 ° C. for about 1 hour (FIG. 1)
(A)).

After that, the SiO ₂ film on the gate electrode (3) and the silicon substrate (1) is removed, and in an oxygen atmosphere,
For example, heat treatment is performed at 900 ° C. for about 10 minutes.

[0012]

According to the method of manufacturing a semiconductor device according to the present invention, crystal defects caused by bonding of impurity ions and oxygen in a semiconductor substrate can be eliminated by performing a heat treatment in an oxygen atmosphere. That is, by the heat treatment in the oxygen atmosphere, the bond between the impurity ions and oxygen in the semiconductor substrate is cut, so that a defect-free impurity diffusion region can be formed. In addition, even if the temperature of the heat treatment performed after the ion implantation is set to be low and set for a short time, defects can be eliminated, and diffusion of impurity ions can be suppressed to form an impurity diffusion region having a shallow junction depth. it can.

Therefore, by forming the impurity diffusion region having no defect, it is possible to reduce the leak current and to realize the manufacture of a fine semiconductor device with high yield.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a manufacturing process showing an embodiment of a method of manufacturing a semiconductor device according to the present invention.

FIG. 2 is a schematic sectional view showing a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

Reference Signs List 1 silicon substrate (semiconductor substrate) 2 SiO ₂ film (gate oxide film) 3 gate electrode 4 sidewall 5 impurity ion 6 SiO ₂ film (oxide film) 7 source / drain region

Claims (1)

(57) [Claims] An oxide film is laminated on a gate electrode formed on a semiconductor substrate, and the oxide film is etched to form a sidewall on a side wall of the gate electrode and to prevent a surface of the semiconductor substrate from being exposed. Leaving the oxide film on the substrate, and ion-implanting impurities through the oxide film into a portion to be a source / drain region of the semiconductor substrate.
And a second heat treatment in an oxygen atmosphere after removing the oxide film on the semiconductor substrate.