JPH05206452A - Semiconductor device and fabrication thereof - Google Patents

Abstract

PURPOSE:To enhance characteristics and reliability even of a MOSFET having fine minimum line width by constituting a gate insulation film of an oxide containing carbon atoms thereby enhancing hot carrier resistance. CONSTITUTION:Oxygen and carbon dioxide are fed from a gas supply source 6 through a flow meter 4 into a reaction vessel l in which a semiconductor substrate 2 is set. The semiconductor substrate 2 is then heated quickly by means of a halogen lamp 3 to form an oxide containing carbon. A gate electrode composed of poly-Si added with high concentration phosphorus is then formed on the gate oxide and As is introduced to semiconductor substrates on the opposite sides of the gate region to provide a source and a gate thus fabricating a MOSFET. An oxide having excellent hot carrier resistance can be formed by containing carbon atoms and when the oxide is employed as a gate insulation film, good characteristics and high reliability can be achieved even for a fine MOSFET having minimum line width of 1mum or below.

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 MOS integrated circuit, and more particularly to formation of a gate insulating film.

[0002]

2. Description of the Related Art Conventionally, regarding this type of semiconductor device,
One of the major constraints in device scaling is the issue of device aging and reliability due to hot carriers. For example, in a so-called submicron device having a minimum processing line width of 1 micron or less, injection of hot carriers generated by impact ionization into a gate oxide film in a high drain electric field region deteriorates device characteristics. This is because there are many electron traps and hole traps in the oxide film, and many interface states that serve as electron and hole traps at the oxide film-silicon (Si) interface. The on-current is gradually reduced due to the strong influence of trapping, or the operation at the time of low voltage driving becomes slow.

As a measure against such a problem, there is a conventional technique of thermally nitriding an oxide film with ammonia gas and further oxidizing with an oxidizing gas as described in JP-A-1-37027, and JP-A-3-119731. As described in Japanese Patent Laid-Open Publication No. 2003-242242, there is proposed a technique for improving hot carrier resistance by including carbon on the Si surface in contact with an oxide film.

[0004]

When the former of the above-mentioned conventional techniques is used, the deterioration of the characteristics during the operation of the MOSFET is reduced, but the initial interface state density is high and the initial characteristics are good. Absent.

On the other hand, the latter suppresses the generation of the interface state by replacing a part of the Si atoms constituting the interface with carbon atoms. In order to contain carbon on the Si surface, the carbon concentration is high from the beginning. It is said that a Si wafer is used, or carbon is ion-implanted immediately below the substrate surface before forming an oxide film. However, the first method is practically difficult to use because carbon in the Si wafer may cause stacking faults in the vicinity of the interface during formation of an oxide film or during heat treatment. In the second method, a lattice defect near the interface formed during ion implantation causes a new interface state to be generated, which deteriorates hot carrier resistance.

An object of the present invention is to eliminate such a problem.

[0007]

In the semiconductor device of the present invention, the gate insulating film is composed of an oxide film containing carbon atoms.

Further, in the manufacturing method of the present invention, the gate insulating film is formed by heat-treating the semiconductor substrate in an atmosphere containing an oxidizing gas and a compound containing carbon.

[0009]

Function Generally, the interface level of the oxide film-Si interface is Si-
This is caused by the formation of Si-Si bonds lacking oxygen atoms in the oxygen (O) -Si network, and the distorted Si-O bonds being broken by holes. The hole traps in the oxide film are strained Si-Si, and the electron traps are Si atoms bonded to hydrogen (H) or OH.

In the present invention, by containing carbon atoms in the gate oxide film, the distorted Si—O bond or Si—Si bond in the oxide film or at the oxide film-Si interface can be relaxed. This is because carbon atoms have a smaller atomic radius than Si atoms. In addition, the carbon atom has a stronger binding force with hydrogen than Si, and the presence of the carbon atom in the oxide film or at the interface serves as an electron trap or a hole trap.
By substituting C—H bonds for i—H bonds, these trap densities can be reduced.

Such a gate oxide film containing carbon atoms and having few electrons and hole traps can be easily formed by mixing a compound containing carbon in the atmospheric gas when the substrate is thermally oxidized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing an apparatus used for forming a gate insulating film. In the figure, 1 is a reaction vessel made of a quartz tube, 2 is a semiconductor substrate, 3 is a halogen lamp that emits infrared rays, 4 is a flow meter, 5 Is a valve, 6 is a gas supply source consisting of a cylinder, 7 is a reflector, 8 is a quartz tray on which the semiconductor substrate 2 is placed, and 9 is an exhaust port. In forming the gate insulating film, first, the semiconductor substrate 2 is set in the reaction container 1. Then, oxygen and carbon dioxide are made to flow from the gas supply source 6 into the reaction container 1 through the flowmeter 4 at 9 liters and 1 liter per minute, respectively. Next, the semiconductor substrate 2 is heated to 1050 ° C. by the halogen lamp 3.
By rapidly heating to and holding this temperature for 30 seconds, an oxide film containing carbon with a thickness of 5.5 nm is formed.

On the gate oxide film thus formed, a gate electrode made of polycrystalline Si doped with phosphorus at a high concentration is further formed, and arsenic is introduced into the semiconductor substrate on both sides of the gate region to form the source and drain. And MOSFE
Created T. Its effective channel length is 0.5 μm. For comparison, a MOS having a gate oxide film formed in a pure oxygen atmosphere containing no carbon dioxide as in the past (other conditions are the same as described above).
FETs were made in the same manner and the characteristics of these MOSFETs were compared. The results are shown in FIGS. 2 and 3.

FIG. 2 shows how the transconductance g _m changes after hot carrier injection.
The horizontal axis shows the stress time, that is, the elapsed time from hot carrier injection (unit is second), and the vertical axis shows the maximum value g of g _{m.
Change in mmax} from initial value _gmmax (0) _-Δgmmax
In the form of a ratio to the initial value g _mmax (0) (unit is percent). Further, FIG. 3 also shows how the threshold voltage changes after hot carrier injection. The horizontal axis represents the stress time, and the vertical axis represents the threshold voltage V _th (unit: millivolt). .. In both cases, the solid line shows the results of this example and the broken line shows the results of the conventional example.However, in this example in which the gate oxide film was formed in an oxygen atmosphere containing carbon dioxide, The characteristics are superior to the formed conventional example.

Further, Table 1 shows the characteristics (device life) of MOSFETs having a gate oxide film formed by changing the atmosphere, the oxidation temperature and the oxidation time at the time of forming the oxide film. Here, the hot carrier stress condition is a condition that the substrate current becomes maximum (gate voltage 1 V, drain voltage 6 V), and as the device life, the maximum value g _mmax of mutual conductance is an initial value under such hot carrier stress condition. g
g _m life, which is the hot carrier stress time until it changes by 10% with respect to _mmax (0), and V _th life, which is the hot carrier stress time until the threshold voltage V _th changes by 0.1 V (both are The unit is seconds). Similarly, the table also shows the conventional example 7 in which the gate oxide film is formed in the pure oxygen atmosphere as described above.

[0016]

[Table 1]

The prior art example 7 has a short g _m life and V _th life of 10 ⁶ seconds or less, and it is understood that it is not suitable as a gate oxide film of MOSFET. On the other hand, Examples 2 to 6 of the present invention in which the gate oxide film is formed by heat treatment in an oxygen atmosphere containing carbon dioxide have a long life regardless of the concentration of carbon dioxide.

[0018]

As described above, according to the present invention, it is possible to form an oxide film having excellent hot carrier resistance by containing carbon atoms, and by using this oxide film as a gate insulating film, the minimum processing line width is 1 μm or less. It is possible to realize good characteristics and high reliability even with respect to the fine MOSFET of.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus used for forming a gate insulating film according to an embodiment of the present invention.

FIG. 2 is a diagram showing hot carrier stress time dependence of transconductance of MOSFET.

FIG. 3 is a diagram showing hot carrier stress time dependence of a threshold voltage of a MOSFET.

[Explanation of symbols]

1 ... Reaction container, 2 ... Semiconductor substrate, 3 ... Halogen lamp,
6 ... Gas supply source.

Claims (2)

[Claims] 1. A semiconductor device including a gate insulating film, wherein the gate insulating film is made of an oxide film containing carbon atoms. 2. A method of manufacturing a semiconductor device, which includes a step of forming a gate insulating film on at least a semiconductor substrate,
A method for manufacturing a semiconductor device, wherein the gate insulating film is formed by heat-treating the semiconductor substrate in an atmosphere containing an oxidizing gas and a compound containing carbon.