JPH0837163A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the interface state density of a semiconductor substrate from being erased insufficiently when hydrogen is occluded by a barrier metal by a method wherein the barrier metal is sintered under a specific value or lower of pressure. CONSTITUTION:The pressure at a sintering operation is set at 760Torr 0.10MPa or lower and 10<-2> to 10<-4>Torr ( 1.33 to 0.01P). Then, the hydrogen occlusion property of a barrier metal 6 is lowered. In the case of a temperature of 400 deg.C, the hydrogen concentration under normal pressure is at 10<19>cm<-3>. When the pressure is lowered down to about 10<-2> to 10<-4>Torr, the hydrogen concentration is lowered to about 10<15>cm<-3>. When the hydrogen occlusion property of the barrier metal 6 is lowered and the barrier metal is sintered, the amount of hydrogen which is seized by the barrier metal 6 is reduced. As a result, the hydrogen which reaches the interface between a semiconductor substrate 1 and a gate insulating film 2 and which contributes to the extinction of an interface state density is increased. Consequently, the dark current can be reduced, and the threshold voltage can be stabilized.

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 semiconductor device using a metal having a hydrogen storage property as a barrier metal.

[0002]

2. Description of the Related Art When an aluminum-based metal material is used for the wiring of a semiconductor device, a titanium-based metal (for example, Ti, TiN, Ti0N,
A barrier metal made of TiW or the like is formed. FIG. 3 is a sectional view showing an example of such a semiconductor device. In the drawings, 1 is a semiconductor substrate made of silicon, 2 is a gate oxide film, 3 is a gate electrode made of polysilicon, 4 is an interlayer insulating film made of PSG, 5 is a contact hole, 6
Is a barrier metal, titanium-based material such as Ti / Ti
It consists of N.

7 is a wiring made of aluminum, 8 is P
(Plasma) -SiN is a passivation film. In such a semiconductor device, after forming a necessary impurity layer on the surface portion of the silicon semiconductor substrate 1, a gate oxide film 2 is formed by a thermal oxidation method, and then a gate electrode 3 is formed by forming a polysilicon layer and photoetching. Etc., and then an interlayer insulating film 4 made of a PSG film is formed, and the contact hole 5 is formed by selective etching of the interlayer insulating film 4.
And then barrier metal 6 (eg Ti / Ti
N) is formed by sputtering. Further subsequently, an aluminum film to be the wiring 7 is also formed by sputtering.

Thereafter, the barrier metal 6 and the wiring 7 are patterned, but before and after the patterning, sintering is performed. This sinter gets ohmic contact.
Improvement of characteristics (for example, reduction of dark current) and characteristics by allowing hydrogen (hydrogen absorbed in the wiring 7 made of aluminum or hydrogen in a sinter atmosphere) to reach a MOS interface or the like to eliminate the interface state Is performed (for example, the threshold voltage is stabilized). This sintering is a low temperature heat treatment performed at a relatively low temperature of about 300 to 500 ° C., and is generally performed using a diffusion furnace. And, in the past, the sintering was performed under normal pressure, that is, under approximately 760 Torr (≈0.10 MPa). In addition, after the above sintering is completed, P-SiN
The passivation film 8 as a final protective film is formed, and the back surface ohmic treatment is further performed.
After the back surface ohmic treatment is finished, a low temperature heat treatment at 300 to 500 ° C. is often performed for the purpose of removing damage, but this is also performed at normal pressure using a diffusion furnace.
Thus, sintering is performed once or twice.

[0005]

By the way, in the past, it was difficult to sufficiently reduce the interface state even by sintering. Then, when the cause was investigated, the titanium-based metal forming the barrier metal 6 has a hydrogen storage property, and therefore, for example, hydrogen in the wiring 7 made of aluminum or hydrogen in the atmosphere at the time of sintering is the semiconductor substrate 1 It was found that hydrogen that is occluded in the barrier metal 6 before reaching the interface between the gate insulating film 2 and the like and contributes to the disappearance of the interface state is reduced. If this is left as it is, it becomes difficult to reduce the dark current, and the stability of the threshold voltage is prevented from being improved. Specifically, the dark current causes a decrease in the recording holding capacity in the case of a semiconductor device such as a DRAM, and the occurrence of an image defect at the time of high temperature darkness in the case of a semiconductor device such as a CCD type solid-state image sensor. Cause.

The present invention has been made in order to solve such a problem, and in a method of manufacturing a semiconductor device using a metal having a hydrogen absorbing property as a barrier metal, hydrogen is absorbed by the barrier metal to form a semiconductor. It is an object of the present invention to prevent insufficient elimination of the interface state of the substrate, thereby improving the characteristics and the stability of the characteristics.

[0007]

According to a first aspect of the present invention, there is provided a semiconductor device manufacturing method, wherein a sinter for a barrier metal is 760.
It is characterized in that it is performed under a pressure of Torr or less. A semiconductor device manufacturing method according to a second aspect of the present invention is characterized in that the sintering temperature is 300 to 500 ° C. in the semiconductor device manufacturing method according to the first aspect.

[0008]

According to the method of manufacturing a semiconductor device of claim 1, since the sintering is carried out under a pressure lower than the conventional atmospheric pressure, the lower the pressure at the sintering is, the more hydrogen-absorbing metal is formed. Since the hydrogen storage concentration becomes low, the concentration of hydrogen that can be stored in the barrier metal becomes low due to the sintering, and eventually the hydrogen that reaches the interface of the semiconductor substrate and contributes to the disappearance of the interface level increases. Therefore, the dark current can be reduced and the threshold voltage can be stabilized. According to the semiconductor device manufacturing method of the second aspect, since the sintering temperature is 300 to 500 ° C. as in the conventional case, there is no fear that the sintering effect is reduced. Therefore, it is possible to reduce the interface state without reducing the sintering effect, and improve the characteristics and the stability of the characteristics.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor device according to the present invention will be described in detail below with reference to illustrated embodiments. FIG. 1 is a sectional view showing a state at the time of sintering for explaining one embodiment of a method for manufacturing a semiconductor device of the present invention. The semiconductor device manufacturing method of the present invention is different from the above-described conventional semiconductor device manufacturing method only in the pressure during sintering, and was conventionally atmospheric pressure, but in the present invention, the atmospheric pressure (760 Torr≈0.10 MPa) or less is used. Sintering is done under pressure. Specifically, the pressure during sintering is, for example, 10 ^-2 to 10 ^-4 Torr.
The pressure is set to (≈1.33 to 0.01P). Then, the hydrogen storage property of the barrier metal 6 is lowered as shown in FIG. FIG. 2 is a PCT curve diagram showing the relationship between the pressure P at which the barrier metal composed of Ti / TiN is placed and its hydrogen concentration C with the temperature T as a parameter. It can be seen that the concentration of hydrogen stored in the inside becomes low.

Specifically, for example, when the temperature is 400 ° C., the hydrogen concentration is about 10 ¹⁹ cm ^{-3 at} normal pressure, but the pressure is reduced to about 10 ^-2 to 10 ^-4 Torr. In some cases, it will be as low as 10 ¹⁵ cm ^-3 . Even if the temperature changes, the tendency does not change. When the sintering is performed with the hydrogen storage property of the barrier metal 6 being lowered as described above, the amount of hydrogen that can be intercepted by the barrier metal 6 is reduced, so that the interface between the semiconductor substrate 1 and the gate insulating film 2 is inevitably reached. A large amount of hydrogen contributes to the disappearance of the interface state. Therefore, the dark current can be reduced and the threshold voltage can be stabilized.

That is, in the past, since the sintering was performed under the condition that the hydrogen absorption property of the barrier metal 6 was strong,
In the process in which hydrogen in the wiring 7 made of aluminum and hydrogen in the sinter atmosphere enter the interface between the semiconductor substrate 1 and the gate insulating film 2, most of them are occluded in the barrier metal 6 as shown by the broken line in FIG. However, according to the method for manufacturing a semiconductor device of the present invention, since sintering is performed under the condition that the hydrogen storage property of the barrier metal 6 is low, most of the hydrogen is not stored in the barrier metal 6 and the hydrogen is stored in FIG. As shown by the solid line, it reaches the interface and contributes to elimination of the interface state. Since the sintering temperature is 300 to 500 ° C. as usual, the sintering effect is not reduced. By the way, the forming gas in the sinter is, for example, N containing 3 to 6% H _2.
2 gas, the sintering time is, for example, 10 to 120
It's about a minute. By the way, the sinter is formed not only before or after the patterning of the wiring 7 and the barrier metal 6, but also on a passivation film (made of, for example, plasma silicon nitride, see FIG. 3) 8 as a final protective film, and further back surface ohmic treatment or the like. In many cases, a low-temperature heat treatment at 300 to 500 ° C. is carried out for the purpose of removing damage even after the completion of the above, but the sinter after the back surface ohmic treatment is also under a pressure lower than the normal pressure, for example, 10 ⁻² to 10 ^{−. Four}
It is preferable to use Torr to eliminate the interface state.

[0012]

The method of manufacturing a semiconductor device according to the first aspect is characterized in that the sintering for the barrier metal is performed under a pressure of 760 Torr or less. Therefore, according to the method for manufacturing a semiconductor device of claim 1, since the sintering is performed under a pressure lower than the conventional atmospheric pressure, the lower the pressure during sintering, the lower the hydrogen storage concentration of the metal having hydrogen storage properties. Therefore, the concentration of hydrogen that can be occluded by the barrier metal is lowered by the sinter, and further, the amount of hydrogen that reaches the interface of the semiconductor substrate and contributes to the disappearance of the interface level is increased. Therefore, the dark current can be reduced and the threshold voltage can be stabilized. Specifically, in the case of a semiconductor device such as a DRAM, for example, it is possible to increase the recording retention capacity (the recording retention time becomes longer and the voltage required for the recording retention becomes lower) by reducing the dark current. it can. Further, in the case of a semiconductor device such as a CCD type solid-state image pickup device, image defects can be reduced when dark at high temperature. Then, the stability of the threshold voltage becomes high.

The method of manufacturing a semiconductor device according to a second aspect is characterized in that the sintering temperature is 300 to 500 ° C.
Therefore, according to the semiconductor device manufacturing method of the second aspect, since the sintering temperature is 300 to 500 ° C. as in the conventional case, there is no fear that the sintering effect is reduced. Therefore, it is possible to reduce the interface state without reducing the sintering effect, and to improve the characteristics and the stability of the characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a method for manufacturing a semiconductor device of the present invention.

FIG. 2 PC for hydrogen absorption of titanium-based barrier metal
It is a T-curve figure.

FIG. 3 is a cross-sectional view showing an example of a semiconductor device in which a titanium-based barrier metal is formed.

[Explanation of symbols]

 1 Semiconductor substrate 6 Barrier metal 7 Wiring (aluminum)

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor device using a metal having a hydrogen storage property as a barrier metal, wherein the sintering for the barrier metal is 760 Torr.
Semiconductor device manufacturing method characterized by performing under the following pressure 2. A method of manufacturing a semiconductor device, wherein the sintering temperature is 300 to 500 ° C.