JP3148982B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MIS structure or a MIS field-effect type having at least an uppermost layer of silicon carbide as a semiconductor substrate having a low interface state density and a high gate insulating film breakdown voltage. Transistor (metal-insula
The present invention relates to a semiconductor device equipped with a tor-semiconducter field-effect transistor), a semiconductor integrated circuit, and a method for manufacturing the same.

[0002]

2. Description of the Related Art An interface state density generated at a gate insulating film / silicon carbide interface formed on a silicon carbide substrate, which is a wide gap semiconductor, is determined by a gate oxide film formed by thermally oxidizing a silicon substrate. This is one order of magnitude higher than the interface state density generated at the film / silicon interface, and is one of the causes of low channel mobility.

Therefore, recently, the lattice constant is close to that of silicon carbide,
Studies have been reported on the use of aluminum nitride having a lattice mismatch of 0.9% as an insulating film. However, the dielectric breakdown voltage of aluminum nitride is low, so that it cannot be used in practice and poses a problem.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the problem of low dielectric breakdown voltage of a gate insulating film using aluminum nitride in a SiC MIS capacitor or MISFET.

Further, according to the present invention, when an oxide film or a nitride film is formed on aluminum nitride in the gate insulating film, a high interface state mobility generated between the aluminum nitride and the oxide film or the nitride film is obtained. The purpose is to solve the problem.

[0006]

To solve the above object, according to an aspect of, in the present invention, on a semiconductor substrate having a silicon carbide on at least the top layer, in a semiconductor device having a metal plate via an insulator, the Insulator, aluminum nitride on the bottom layer, nitride layer or oxide film, nitride film on top
Semiconductor device composed of layers, furthermore, an oxide film on these layers,
The present invention proposes a semiconductor device in which one or both of the nitride films are stacked in one or more layers . Further, the semiconductor substrate
Aluminum nitride on the bottom layer on the board, oxide film on it,
Laminate one or both layers of either or both nitride films
To form an insulator and a metal layer on it
In the method for manufacturing a conductor device, after forming the insulator,
Alternatively, after forming a metal layer, hydrogen annealing or hydrogen
It proposes a method of manufacturing a semiconductor device that performs laser irradiation.
is there.

[0007] Silicon carbide (SiC) includes 3C-SiC,
There are numerous polytypes such as 4H-SiC, 6H-SiC, and 15R-SiC, but any type of silicon carbide used as a semiconductor substrate in the present invention may be used as long as it is SiC.

The structure of the semiconductor substrate is such that, when the uppermost layer is SiC, 3C-SiC on Si, 6H-SiC or 4H-SiC
A structure having 3C-SiC on the top may be used.

[0009] Molecular-beam-ep
itaxy (MBE) method or Metalorganic-chemical-vapor-dep
After aluminum nitride is formed by a method such as a sition (MOCVD) method, an oxide film or a nitride film is formed thereon to provide an insulator.

As the oxide film or the nitride film, a silicon oxide film or a silicon nitride film is generally used. However, the present invention is not limited to this, and an aluminum oxide film, a tantalum oxide film,
Any oxide film or nitride film such as an aluminum nitride film and a gallium nitride film manufactured under different conditions may be used.

The oxide film or the nitride film on the aluminum nitride need not be a single layer, but may be a multilayer film of two or more layers.

As a method of forming an oxide film or a nitride film on aluminum nitride, in addition to the MBE method, a CVD method, an LPCVD method,
Any method such as a plasma CVD method and a sputtering method can be adopted. Further, after a metal layer or a semiconductor layer is formed over aluminum nitride, these may be oxidized or nitrided.

On the other hand, a metal layer serving as a gate electrode and a wiring layer is provided on the oxide or nitride film of the insulator.
These metal layers are, for example, alloys containing aluminum,
Alternatively, it can be made of polysilicon, silicon or the like containing impurities.

[0014]

[Effect] That is, aluminum nitride alone cannot be used to form a high withstand voltage insulating film that can withstand practical use.
By providing an oxide film or a nitride film over aluminum nitride to form an insulating film, a high withstand voltage insulating film that can withstand practical use can be obtained.

On the other hand, if the formation conditions of the oxide film or the nitride film on the aluminum nitride are shifted, an interface state between the aluminum nitride and the oxide film or the nitride film is generated. In this case, the oxide film or the nitride film is formed on the aluminum nitride. After the film is formed, a hydrogen annealing treatment or a hydrogen plasma irradiation treatment is performed to reduce an interface state density generated at an interface between the aluminum nitride and the oxide film or the nitride film, so that a good capacitance-voltage (C
-V) MIS capacitors and MISFETs having characteristics can be manufactured.

Here, the hydrogen annealing treatment or the hydrogen plasma irradiation treatment may be performed immediately after forming the insulating film on the aluminum nitride, or may be performed after forming the metal layer on the insulating film. The processing may be performed alone or in combination.

The hydrogen annealing is performed at a temperature of 400 to 1600 ° C.
Annealing time 10 ~ 3 hours, hydrogen pressure 0.1Pa ~ 1.01 × 10 ⁵ Pa
And the pressure of the hydrogen-containing gas atmosphere is fixed to normal pressure (1.01 × 10 ⁵ Pa), and the hydrogen concentration <hydrogen flow rate / (hydrogen flow rate + (Inert gas flow rate)> 0.5% to 100%.

[0018]

Embodiments of the present invention will be described below. Example 1 An MIS capacitor was manufactured by the method of the present invention in the following procedure. 8H off 4H-Si for semiconductor substrate
5 μm 4H-Si on C bulk substrate <(0001) Si surface, n-type>
4H-SiC with C epi layer (n-type, Nd-Na = 1 × 10 ¹⁶ / cm ³ )
A substrate was used.

After a normal RCA cleaning of these substrates, a sacrificial oxide film was formed and removed with HF (hydrofluoric acid). Next, a 50 nm aluminum nitride film was formed by MBE. Furthermore, after forming a 22 nm Si film by MBE or CVD, the oxygen flow rate (1 L / min)
Then, a 50 nm SiO ₂ film was formed by oxidizing at 1100 ° C. for 30 minutes.

Then, at a temperature of 1000 ° C. for a time of 30 minutes, a hydrogen pressure
Hydrogen annealing was performed under the condition of 5.6 × 10 ³ Pa. Finally, a MOS capacitor was manufactured using Al for the gate electrode and the ohmic contact. Figure 1 shows a schematic diagram of the completed cross section.
Shown in

Example 2 Aluminum nitride was formed on a semiconductor substrate under the same conditions as in Example 1, and a silicon nitride film and a silicon oxide film were provided.
Further, hydrogen annealing was performed in the same manner as in Example 1, and an Al gate electrode was provided on the silicon nitride film to manufacture an MIS capacitor. FIG. 2 shows a completed schematic cross-sectional view.

Embodiment 3 An example of forming an N-type MISFET according to the present invention will be described below. Polysilicon was formed on aluminum nitride by CVD on an insulating film. Next, phosphorus is doped to lower the resistance of the polysilicon film. Thereafter, the polysilicon film, the insulating film, and the aluminum nitride are selectively etched to form a gate.

Next, nitrogen, phosphorus, arsenic (P-type MISFET
In the case of manufacturing, a source and a drain are formed by ion implantation of aluminum, boron, boron fluoride, and beryllium. After that, a silicon oxide film is formed on the entire surface at a low temperature, and a silicon oxide film containing boron and phosphorus is formed on the entire surface, and then heat-treated at 900 ° C. for 15 minutes to flatten the silicon oxide film. .

Thereafter, an SOG film is applied on the entire surface and etched. Next, the silicon oxide film is selectively etched, and after cleaning with buffered hydrofluoric acid (BHF), a contact hole to the transistor is opened. Further, a metal wiring layer made of an aluminum alloy is formed on the entire surface by a sputtering method, and this is patterned to form a desired metal wiring.

Comparative Example Table 1 below shows the conditions for producing the MIS capacitor sample.

【table 1】

FIG. 3 shows a comparison between the high-frequency CV curve of the sample a and the ideal curve. Here, the frequency f is f = 100 kHz,
C = V, current-voltage (IV) characteristics were measured in dark conditions in a shielded metal box. The dashed line indicates an ideal curve calculated from the oxide film capacity at 25 V and Nd-Na = 8 × 10 ¹⁵ / cm ³ .

According to FIG. 3, the sample a showed no hysteresis in the forward and backward directions when the voltage was applied to the plus side, the flat band voltage shift was as small as 0.27 V, and showed good CV characteristics.

Table 2 below shows the relationship between sample preparation conditions and breakdown voltage.

[Table 2]

According to this, the dielectric breakdown voltage is 0.3 MV / cm, which cannot withstand actual use of aluminum nitride alone, but becomes 10 MV / cm by forming a silicon oxide film on aluminum nitride. , A dielectric breakdown voltage sufficient to withstand actual use.

However, when the conditions for forming the oxide film on the aluminum nitride were deviated, an interface level was generated at the interface between the aluminum nitride and the oxide film, and a hysteresis of about 1 V was observed in the CV characteristics.

On the other hand, as shown in samples c and d, after an insulating film is formed on aluminum nitride, hydrogen annealing or hydrogen plasma irradiation is performed to convert dangling bonds generated at the interface between aluminum nitride and the insulating film into hydrogen. By terminating the interface state and reducing the interface state density, the hysteresis disappears and an MIS capacitor or MISFET having good CV characteristics can be manufactured.

[0032]

In summary, according to the present invention, it is possible to manufacture a semiconductor device and a semiconductor integrated circuit on which the semiconductor device is mounted, having a high dielectric breakdown voltage and a good electrical characteristic with a low interface state density. it can.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an MIS structure showing one embodiment of the present invention.

FIG. 2 is a schematic sectional view of an MIS structure showing another embodiment of the present invention.

FIG. 3 is a diagram illustrating a comparison between a high-frequency CV curve of a sample a and an ideal curve.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyoko Nagai 1-1-4 Umezono, Tsukuba, Ibaraki Prefecture Within the Institute of Electronics and Technology (72) Inventor Toshihiro Sekikawa 1-1-4 Umezono, Tsukuba, Ibaraki Industrial (72) Inventor: Kenji Fukuda, 1-4-1 Umezono, Tsukuba, Ibaraki Pref. (56) References JP-A-3-115575 (JP, A) Hei 5-29250 (JP, A) JP-A-60-142568 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 27/04 H01L 21/822 H01L 29/78 H01L 21 / 324 H01L 21/336

Claims (7)

(57) [Claims] To 1. A semiconductor substrate having a silicon carbide on at least the top layer, in a semiconductor device having a metal layer via an insulator, the insulator, the bottom layer of aluminum nitride, thereon
A semiconductor device comprising a stack of film layers . 2. The insulator according to claim 1, wherein the lowermost layer is an aluminum nitride.
Minium, an oxide film and a nitride film are laminated on it
The semiconductor device according to claim 1, wherein: 3. The method according to claim 1, further comprising the step of:
Either one or both of film and nitride film are laminated
The semiconductor device according to claim 1, wherein: 4. A laminate comprising the oxide film and the nitride film according to claim 2.
In addition, one or both of an oxide film and a nitride film are
3. The semiconductor device according to claim 2, wherein the semiconductor device is formed by stacking on the upper surface.
apparatus. 5. A metal layer according to claim 1, claims 1, characterized in that of polysilicon or silicon containing alloy or impurity containing aluminum 4
Semiconductor device. 6. An insulating material comprising a semiconductor substrate having silicon carbide at least as an uppermost layer, aluminum nitride as a lowermost layer, and one or more of an oxide film and a nitride film stacked thereon. body is formed, in a manufacturing method of a semiconductor device for forming a metal layer thereon, a method of manufacturing a semiconductor device which is characterized in that a hydrogen annealing after after forming the insulator, or a metal layer is formed. 7. An insulating material comprising a semiconductor substrate having silicon carbide at least as an uppermost layer, aluminum nitride as a lowermost layer, and one or more of an oxide film and a nitride film stacked thereon. body is formed, in a manufacturing method of a semiconductor device for forming a metal layer thereon, a method of manufacturing a semiconductor device according to claim after forming the insulator, or by performing a hydrogen plasma irradiation after formation of the metal layer .