JPH0321065A - Semiconductor device and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a highly integrated semiconductor device such as an ICS LSI and a method for manufacturing the same.

(Prior Art) Elements formed in semiconductor devices such as ICS LSIs are made up of minute regions on a semiconductor substrate. This fine region is formed, for example, by doping a semiconductor substrate with impurities.

In recent years, the integration of these semiconductor devices has been increasing. Along with this, the elements making up these semiconductor devices have become smaller and the structures of the elements have become more complex.

Therefore, the distance between regions doped with impurities constituting each element becomes smaller, and defects due to impurity diffusion etc. 1 2 due to high temperature treatment during the manufacturing process are more likely to occur.

FIG. 3 shows an example of a conventional semiconductor device. A trench l2 is formed on a silicon substrate 1, and a capacitor insulating film 2 is formed on the upper surface of the substrate 1 and the inner surface of the trench 12. An a-Si electrode 3 made of polycrystalline silicon (hereinafter referred to as ra-SiJ) doped with impurities is embedded in the trench 12 in which the capacitor insulating film 2 is formed.

A capacitor 14 is formed by the a-Si electrode 3, the capacitor insulating film 2, and the substrate 1.

The entire surface of the substrate 1 on which the capacitor 14 is formed is covered with a-S.
A t-layer 11 is deposited. a on the side of the capacitor 14
-A transistor l3 is formed in the Si layer 11.

The transistor 13 has a source region 7, a drain region 15,
It has a channel region 6, a gate oxide film 10 formed on these regions, and a gate electrode 8. This semiconductor device includes a capacitor 14 and a transistor 13.
Functions as memory.

(Problems to be Solved by the Invention) 131 This semiconductor device is manufactured by forming the a-St electrode 3 and then forming the transistor 13. a-S
Since the i-electrode 3 is doped with impurities at a relatively high concentration,
In the forming process of the transistor 13 after relatively high temperature treatment, a-Si? Diffusion of impurities in the l1 pole 3 is likely to occur. When such diffusion occurs, the impurity concentration of the source region 7 and the a-Sf electrode 3 changes, which adversely affects the operation of the semiconductor device.

In order to avoid such diffusion of impurities, it is necessary to provide the transistor l3 and the capacitor 14 apart from each other. However, if the transistor 13 and the capacitor 14 are provided apart from each other, it becomes impossible to achieve high integration of the semiconductor device.

The present invention solves these conventional problems, and an object of the present invention is to provide a semiconductor device having a configuration that allows high integration. Another object of the present invention is to provide a method for manufacturing the above-mentioned semiconductor device that can be highly integrated.

(Means for Solving the Problems) -4- The semiconductor device of the present invention includes a trench formed on a semiconductor substrate, an insulating film formed on the inner surface of the trench, and a trench formed with the insulating film. A semiconductor device comprising: a semiconductor electrode containing an impurity disposed within the trench; and a transistor having a source region electrically connected to the semiconductor electrode, the semiconductor device comprising: a semiconductor electrode containing an impurity; and a transistor having a source region electrically connected to the semiconductor electrode; A layer is provided and the source region is formed on the impurity diffusion prevention layer, thereby achieving the above object.

Further, the impurity diffusion prevention layer is made of Tf, Ta, P.
It may also be a layer of nitride of a metal selected from the group consisting of tSC, oSW, and Mo.

The method for manufacturing a semiconductor device of the present invention includes the steps of forming a metal film on a substrate in which a silicon region and an insulating film region are exposed, and heating the substrate to remove the metal film on the silicon region. a step of forming a metal silicide film on the surface of the silicon region by removing the unsilicided metal film; and a step of forming a metal silicide film on the surface of the silicon region; The above object is achieved by heating in a gas atmosphere selected from the group consisting of: converting all the metal silicide films into metal nitride films.

Further, the metal film may be Ti, TaS, PtS Co, W1
It may also be made of a metal selected from the group consisting of and Mo.

(Function) In the semiconductor device of the present invention, an impurity diffusion prevention layer is formed on the impurity-doped semiconductor electrode in the trench to prevent diffusion of the impurity doped into the electrode. Therefore, the source region of the transistor can be provided directly above the trench. Therefore, it becomes possible to achieve high integration of the semiconductor device.

A preferred material for the impurity diffusion prevention layer is a metal nitride film. The metal nitride film has conductivity and has a function of preventing diffusion of impurities doped into the semiconductor electrode, so it is suitable as an impurity diffusion prevention layer of the above-mentioned semiconductor device. Specifically, metal nitrides of 5-6-TiS Ta, PtS Co, W1 and Mo can be mentioned.

Semiconductor devices having these metal nitride films can be manufactured as follows. A metal film is deposited on a substrate with silicon regions and insulating film regions exposed at the surface. Materials for the metal film include the above-mentioned Ti, Ta, and Pt.
The metals S Co, W1 and MO are used. The substrate on which the metal film is formed is heat-treated to silicide the metal on the silicon region. Since the metal silicide film is formed by a reaction between metal and silicon, the metal silicide film is formed only in the silicon region in a self-aligned manner. After silicidation, the metal film that has not been silicided is removed.

The metal silicide film formed on the silicon region is N2
Alternatively, the film is nitrided by heating in an NH3 atmosphere, and the entire film is converted into a metal nitride film. Therefore, the metal silicide film is also formed on the silicon region in a self-aligned manner.

It is necessary that the entire metal silicide film be nitrided by this nitriding step. If even a portion of the metal silicide film remains, it will be damaged when high-temperature treatment is performed in later processes.
This is not preferable because the contact characteristics deteriorate. Metal nitride films are stable even at high temperatures and do not undergo thermal deterioration.

According to the self-aligned method of the present invention, a metal silicide film can be formed with high positional accuracy, and is not limited by mask alignment accuracy or ethoching accuracy as in conventional photolithography methods. There is no.

Since silicidation of the metal film and nitridation of the metal silicide film are performed at a relatively low temperature and in a short time, diffusion of impurities doped into the silicon region hardly occurs. Therefore, impurities do not diffuse into adjacent regions and affect the functions of those regions.

The configuration of the semiconductor device of the present invention can also be used for contact portions of wiring on a semiconductor substrate other than those described above, for example. That is, by forming an impurity diffusion prevention layer made of the metal nitride described above in -7--8 at the connection portion between the impurity-doped region and the metal wiring on the semiconductor substrate, impurity diffusion during high-temperature processes is prevented. can be prevented. Furthermore, thermal deterioration of the impurity diffusion prevention layer does not occur.

(Example) The present invention will be described below with reference to an example. FIG. 1 shows an embodiment of the semiconductor device of the present invention. Figure 2 (a) to (C)
1 shows an embodiment of the method for manufacturing a semiconductor device of the present invention. The semiconductor device of the present invention shown in FIG. 1 will be explained below according to the manufacturing process shown in FIG. First, a trench 12 was formed on the silicon substrate 1 by dry etching. The trench 12 has a cylindrical shape with a diameter of 1 μm and a depth of 3 μm. Next, a capacitor insulating film 2 was formed on the upper surface of the substrate 1 and the inner surface of the trench 12. Capacitor insulating film 2 is SiNH,
3i02 etc., and its film thickness is 30AS when SiNx is used and 50AS when Sf02 is used.
It is A.

Next, C V D (Chemical Vapor
A-S is deposited on the entire surface of the substrate 1 using the
Deposit an i-layer and perform RIE (Reactive Ion)
The a-Si layer deposited outside the trench 12 was removed by the etching method. a- in this trench 12
Arsenic (AS) was doped into the Si layer by a solid phase diffusion method to form an a-Sit pole 3. The arsenic concentration in the a-Si electrode 3 is 1019 cm-3 or more. a-
Si electrode 3, capacitor insulating film 2, and silicon substrate 1
A capacitor l4 is formed by.

Next, a Ti metal layer 4 was deposited on the entire surface of the substrate 1 by sputtering (FIG. 2(a)). By annealing this substrate 1 in a nitrogen atmosphere, the metal film 4 on the a-Si electrode 3 was silicided.

The silicidation temperature is 500-600'C and the time is 30 seconds. The unsilicided metal film 4 was removed by wet etching to obtain a metal silicide film 5 (FIG. 2(b)).

Next, the substrate l is annealed in a nitrogen atmosphere to change all the metal silicide film 5 to a metal nitride film, and the impurity diffusion prevention layer 9
And so. The nitriding temperature is 900°C and the time is 30 seconds. The nitriding must be performed under conditions such that the metal silicide film 59 10 is completely nitrided.

If even a portion of the metal silicide film 5 remains, the film 5 will deteriorate during the high-temperature process for forming the transistor later, and the contact characteristics between the a-Si electrode 3 and the impurity diffusion prevention layer 9 will deteriorate. Because it does.

Next, the transistor 13 is shaped. The entire surface of the substrate 1 on which the impurity diffusion prevention layer 9 is formed is a
A Si layer was formed. Impurity ions were implanted into the entire surface of this a-Si layer 11 to form a channel portion of a transistor. The impurity ion used was P (phosphorus),
The concentration of implanted ions is approximately 1017 cm-3. Next, the surface of the a-Si layer 11 was thermally oxidized to form the gate oxide film 10. Further, an a-Sj film was deposited on the entire surface of the gate oxide film 10 by low pressure CVD. This a
- The Sr film was doped with phosphorus (P) using a thermal diffusion method.

The a-St film doped with phosphorus was patterned into a predetermined shape by dry etching to form the gate electrode 8 (FIG. 2(C)).

With the electrode 8 masked, ions were implanted into the entire surface of the substrate 1 to form the sos region 7 and the drain region 15. The impurity ions used were B (boron), and the concentration of the implanted ions was 102"cm.
−3 or more. The portion masked by the gate electrode 8 and not ion-implanted becomes the channel region 6 (FIG. 1). The transistor 13 was formed as described above, and the semiconductor device shown in FIG. 1 was obtained.

In the semiconductor device of this embodiment, a source region 7 is formed above the a-SitH pole 3, and the semiconductor device is highly integrated. Since the impurity diffusion prevention layer 9 is formed between the a-Si N electrode 3 and the source region 7, even in the high-temperature process of manufacturing the transistor later, the a-Si'l
The impurities in the pole 3 do not diffuse into the source region 7.

According to the manufacturing method of this embodiment, the metal nitride film can be formed in the trench 12 of the capacitor 14 in a self-aligned manner. Therefore, the impurity diffusion prevention layer 9 made of a metal nitride film can be formed with high positional accuracy. If the impurity diffusion prevention layer 9 is formed by a conventional method such as photolithography, the impurity diffusion prevention layer 9 may be formed depending on alignment accuracy and etching accuracy.
The position may shift.

Such a problem of positional deviation does not occur at all in the manufacturing method of this embodiment. Therefore, the obtained semiconductor device has extremely high reliability. It was actually confirmed that a highly reliable semiconductor device could be obtained according to the manufacturing method of this example.

(Effects of the Invention) In the semiconductor device of the present invention, since the capacitor and the transistor can be provided close to each other in this way, the semiconductor device can be highly integrated.

Further, according to the manufacturing method of the present invention, the above-mentioned highly integrated semiconductor device having high reliability can be obtained, so that the quality of the semiconductor device can be improved.

4. Figure [of. M8 FIG. 1 is a sectional view showing an embodiment of the semiconductor device of the present invention,
2(a) to 2(C) are diagrams showing a method of manufacturing the semiconductor device of the present invention shown in FIG. 1, and FIG. 3 is a diagram showing a conventional example of the semiconductor device.

l...Silicon substrate, 2...Capacitor insulating film, 3
...a-Si electrode, 4...metal film, 5...metal silicide film, 6...channel region, 7...source region, 8...gate electrode, 9...impurity diffusion Prevention layer, 10...Ge} Absolute iL l 2... Trench, 1
3...Transistor, 14...Capacitor, 15.
...Drain region.

that's all

Claims (1)

[Claims] 1. A trench formed on a semiconductor substrate, an insulating film formed on the inner surface of the trench, and a semiconductor electrode containing an impurity disposed in the trench in which the insulating film is formed. , a transistor having a source region electrically connected to the semiconductor electrode, an impurity diffusion prevention layer provided in the trench on the semiconductor electrode, and an impurity diffusion prevention layer provided in the trench. A semiconductor device having the source region formed thereon. 2. A step of forming a metal film on a substrate in which a silicon region and an insulating film region are exposed; a step of heat-treating the substrate to silicide the metal film on the silicon region; forming a metal silicide film on the surface of the silicon region by removing the metal film that has not been removed;
A method for manufacturing a semiconductor device, comprising: heating in a gas atmosphere selected from the group consisting of H_3 to convert all of the metal silicide film into a metal nitride film.