JPH01194363A - Thin-film semiconductor device - Google Patents

Abstract

PURPOSE:To enable a threshold voltage in a thin-film semiconductor device to be prevented from changing by making specific the spin density of the silicon atom Si or the amount of bonding of the hydrogen atom H in a silicon nitride of an insulating layer. CONSTITUTION:A silicon nitride film SiNx whose spin density of the silicon atom Si is less than 3X10<17>[cm<-3>], is obtained when the flow ratio of monosilane SiH4/ammonia NH3 is near 0.25. To make the amount of bonding of the hydrogen atom H in an insulating layer 5 less than 2X10<21>[cm<-3>], a high-frequency power of about 300-600W should be used. In this way, in manufacturing a transistor 1, the spin density of the silicon nitride SiNx forming an insulating layer 5 which serves as a gate insulating film can be made less than the spin density of the silicon atom Si of not 2X10<16>X3X10<17>[cm<-3>]. Or, the amount of the hydrogen atom H bonding with the silicon atom Si can be made less than 3X10<21>[cm<-3>], thereby reducing the variation of a threshold voltage as small as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to thin film semiconductor devices such as transistors manufactured by thin film technology.

2. Description of the Related Art Various semiconductor devices, such as transistors, are manufactured using thin film techniques such as doping techniques, growth techniques, and etching techniques. In such various semiconductor devices, a threshold voltage V th at which the operating state is switched is determined in advance, and this threshold voltage V th is determined based on the physical properties of the semiconductor device manufactured by gfIJ. In conventional semiconductor devices, this threshold voltage V th fluctuates as usage time accumulates, resulting in a serious decrease in reliability of such semiconductor devices.

The reason why the threshold voltage V th fluctuates in this manner is assumed to be injection of electrons or holes into the gate insulating film or into the interface between the gate insulating film and the semiconductor layer in the transistor. Furthermore, even with an 8iM amorphous silicon thin film transistor whose threshold voltage Vtt does not change when used in a dark state, if a voltage is applied between the gate electrode and the source electrode while irradiated with relatively strong light, the It is known that the threshold voltage value vth varies.

FIG. 1 is a cross-sectional view showing the structure of a typical amorphous silicon ryt film transistor (hereinafter abbreviated as transistor) 1. As shown in FIG. A transistor 1 is made of tantalum T on an electrically insulating substrate 2 such as borosilicate glass.
In step a, gate electrodes w13 are formed in multiple stages. The gate electric f! 3
An insulating layer 4 made of tantalum oxide TaOx is formed by oxidizing the surface by anodizing or the like, and an insulating layer 5 made of silicon nitride SiNx is formed on this insulating layer 4. That is, the insulating layer 6 related to the gate electrode 3 is the insulating layer 4°5.
It has a two-layer structure consisting of.

A semiconductor layer 7 made of intrinsic amorphous silicon a-St is formed on the insulating layer 6, and an etching stop layer 8 made of silicon nitride and an etching stop layer 8 made of n6 type amorphous silicon a-St (no) are formed on the semiconductor layer 7. Second semiconductor W
19, and an electrode layer made of titanium T1 is formed.

In such a structure, etching is performed from near the etching stop M8 to form the source electrode 10 and the drain electrode 11.

Conventionally, silicon nitride SiNx constituting the insulating layer 5 has been used.
The layer was formed by adding 300 SCC of nitrogen NNa for dilution to a raw material gas of 1503 CCM (standard flow rate) with a flow rate ratio of monosilane SIH/ammonia NH of 0.5.
The pressure was set to 100 Pa, high frequency power of 200 W was applied, and plasma discharge was performed. The high frequency power is 2
The reason for setting the power to 00 W is that if the high frequency power is increased unnecessarily, the thickness of the insulating layer 5 formed on the substrate 2 will become uneven, or abnormal discharge of plasma will occur. . The spin density of silicon SS in the insulation N5 formed in this way is 10"
[cm-3], and the amount of hydrogen H bonded to silicon Si is 3.5×1016 [crn-3].

The characteristics of the conventional transistor 1 obtained in this way are shown in FIGS.
1 shows the state of change in the drain current I d in the transistor 1 shown in the first diagram when the source-drain voltage in the transistor 1 is fixed to, for example, 10 cm and the gate voltage is changed from -20 V to +20 V. ing. Transistor 1 with these basic characteristics
By applying a voltage to the gate electrode 3 and the 10 source electrodes, electrons and holes are injected into the insulating layer 6 or at the interface between the insulating layer M6 and the semiconductor layer 7, and the gate voltage becomes positive. It is displaced and becomes the characteristic shown by line 12, or it is displaced to the negative side and becomes the characteristic shown by line 13. As described above, such changes in characteristics become more noticeable when the transistor 1 is irradiated with relatively intense light.

FIG. 8 is a graph showing the square root of the drain current 1d. In FIG. 8, line 14, l5.
l 6 corresponds to line I 1,12°13 in FIG. Such a shift in the threshold voltage causes the on-state current of the transistor to decrease or the off-state current to increase, resulting in poor characteristics.

Problems to be Solved by the Invention An object of the present invention is to solve the above-mentioned technical problems and prevent changes in threshold voltage in an FIB semiconductor device.

An object of the present invention is to provide a highly reliable Ti film semiconductor device.

Means for Solving the Problems The present invention provides a thin film semiconductor device in which a first conductor layer, an insulating layer, a semiconductor layer, and a second conductor layer are laminated.

The insulating layer is made of silicon nitride (SiNx), and the spin density of silicon atoms SL in silicon nitride is set to 2×10
~3x 10"[cm-"] range, or a hydrogen atom for a silicon atom St! The binding amount of 1 is 2
This is a thin film semiconductor device characterized in that the thickness is less than ×1016 [cm-ri].

Function According to the present invention, in constructing an riWA semiconductor device, a first conductor layer, an insulating layer, a semiconductor layer, and a second conductor layer are laminated. At this time, the absolute &I JFI is made of silicon nitride SiNx, and the spin density of silicon atoms SS in silicon nitride is 2X I Q~3x
In the range of 10''[cm''3], the bond 1 of the hydrogen atom 11 to the silicon atom SL is 2×101
By setting it to 6 [cm-3] or less, fluctuations in the threshold voltage can be suppressed as small as possible.

Embodiment FIG. 1 is a cross-sectional view of a thin film transistor (hereinafter abbreviated as transistor) 1, which was explained with reference to the prior art section. Therefore, in explaining the transistor 1 as an embodiment of the present invention, the structure is similar to that of a typical transistor 1 that has been used conventionally, and in this embodiment as well, the first This will be explained with reference to the illustrated transistor 1.

Therefore, the basic explanation regarding the material and manufacturing process of the transistor 1 is the same as in the prior art section described above.

The feature of this embodiment is that the insulating layer 5 is manufactured based on the plasma CVD method (chemical vapor deposition method), and the manufacturing conditions are selected as follows. That is, monosilane 5 to 4. /Ammonia NH* raw material gas 1503CC with a flow rate ratio of 0°5
Manufacturing is performed by adding nitrogen N for dilution and 800 SCCM to M, keeping the pressure constant at 100 Pa, and heating the substrate 2 to 350° C., applying high frequency power of 600 W, and performing plasma discharge. Through this manufacturing process, insulation Fr.
! In silicon nitride SiNx constituting J5, the amount of hydrogen atoms H bonded to silicon atoms St is 2×10
It can be set to 16 [cm-''] or less.

In the prior art vJ manufacturing process of such insulation 7115,
The high frequency power was about 200W. Conventionally, it was not possible to increase high-frequency power due to plasma C accompanied by plasma discharge.
This is because the material and structure of the holder that holds the substrate 2 in the VD apparatus is relatively weak against heat, and the holder may be deformed, such as warping, for example. When such a deformation occurs,
In realizing the present invention, the inventor of the present invention used a relatively heat-resistant adhesive material for the holder of the substrate 2. By changing the structure and creating a structure that does not easily cause deformation such as warping even when heated, it is possible to increase the applied high-frequency power.

The static characteristics of the transistor 1 manufactured in this way are as follows:
Line 17, shown as line 17 in FIG.
It shows how the train current 1d changes when it is changed up to 20V. Furthermore, FIG. 3 shows the dependence of the bonding amount of hydrogen atoms H bonded to silicon atoms Si in the insulating layer 5 on the high frequency power.As mentioned above, the bonding amount of hydrogen atoms H in the insulating layer N5 is 10” [
crn-3] or less is an object of the present invention,
It is understood that such conditions can be obtained by using a high frequency power of about 300 W or more, more preferably about 400 W to 600 W.

Furthermore, according to the experiments of the present inventor, when trying to set the bond amount of hydrogen atoms H to the above-mentioned conditions, /monosilane 5ill
Nitrogen gas N for dilution, 800S was added to the raw material gas 150SCCM with a flow rate ratio of n/ammonia NH at 0°25.
With CCM applied, the pressure was kept constant at 100 Pa, the substrate 2 was heated to 350"C, and high frequency power was applied at 200"C.
It may be manufactured by adding W and performing plasma discharge.

Under these manufacturing conditions? ! The relationship between the spin density of silicon atoms St in the remaining insulating layer 5 and the flow rate ratio of the source gas is shown in FIG. [cm-3
] “The flow rate ratio is 0 according to Figure 4.
．． Around 25, the spin density of silicon atom St is 3X 1
It can be seen that a silicon nitride SiNx film having a thickness of 0" [cm-ko] or less can be obtained.

In this way, according to this embodiment, in manufacturing the transistor 1, the spin density of silicon atoms St is 2×10 16 to 3×10” [cm− 3] or less, or the amount of hydrogen atoms H bonded to the silicon atoms 81 can be less than 3×10 16 [cm −3 ].

FIG. 5 shows the spin density of the silicon atom St in the transistor 1 of an embodiment of the present invention manufactured in this way and the threshold voltage V th in the transistor 1.
This is a graph showing the relationship between the amount of variation ΔV th and the transistor 1 under irradiation with xenon lamp light of 100,000 lux and applying a DC voltage of -15 V or +15 V between the source electrode 10 and the gate electrode 3. , substrate 2
The measurement results are shown after aging was performed continuously for 5 hours at a temperature of 40°C. As shown in FIG. 5, it can be seen that the threshold voltage fluctuation amount Δvth is suppressed to below ±IV when the spin density is in the range of 2xlO" to 3xlO" [cm-3].

FIG. 6 also shows silicon atoms St in the insulation M5.
The amount of bonding of hydrogen atoms H and the amount of threshold voltage fluctuation ΔV
It is a graph showing the relationship with th.

As shown in Figure 6, the amount of bonding of hydrogen atoms H is 3×1
If it is less than 016 [crn-3]! :: It can also be seen that the E value voltage fluctuation ΔV LI−+ is suppressed to ±1V or less.

As described above, according to this embodiment, the spin density of the silicon atoms Si in the silicon nitride SiNx constituting the insulating layer 5 is set in the range of 2×10 to 3×10 [Crn-3], or the spin density of the silicon atoms The amount of bonded hydrogen atoms H was set to 3×10 16 [crn-3] or less. Thereby, the threshold voltage fluctuation amount ΔV th can be suppressed as small as possible. This makes it possible to provide a high quality transistor 1.

Although the single-film semiconductor device was described as the transistor 1 in the above-mentioned embodiment, the present invention is not limited to the transistor 1 having such a structure; It can be used in a wide range of semiconductor devices including the following, and the configuration examples thereof are not limited.

Further, an object of the present invention is that when a predetermined insulating layer constituting a semiconductor device is made of silicon nitride SiNx, the spin density of silicon atoms Si and the amount of hydrogen atoms H bonded thereto are determined in advance. The purpose is to realize a semiconductor device with desired characteristics by setting the above range, and therefore, as long as the conditions between the spin density and the amount of hydrogen atoms are satisfied, there are no limitations on the manufacturing method. isn't it.

Effects of the Invention As described above, according to the present invention, it is possible to reduce as much as possible the temporal change in the 121fn voltage, which is the boundary between the operating states of a semiconductor device, and to produce an rI film semiconductor with significantly improved reliability. We can provide accessories.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing tR3i of transistor 1 used in an embodiment of the present invention and a conventional example, Fig. 2 is a graph showing the quiet characteristics of transistor 1, and Fig. 3 is a graph made of the material of this embodiment. A graph showing the relationship between high-frequency power and the amount of bonding of hydrogen atoms H to silicon atoms Si during manufacture of the transistor 1; FIG. 4 is a graph showing the relationship between the flow rate ratio of the raw material gas and the spin density of the silicon atoms Si; FIG. 5 shows the spin density and I2! in transistor 1 of this embodiment. A graph showing the relationship between value voltage fluctuation and Δvth, FIG. 6 shows the hydrogen atom ■1 in the transistor 1 of this embodiment.
7 and 8 are graphs showing the relationship between the amount of bonding to the silicon atom SL and the amount of voltage variation ΔV t h in r'Ag1.
It is a graph showing the characteristics of. DESCRIPTION OF SYMBOLS 1... Transistor, 2... Substrate, 3... Gate electrode, 4.5.6... Insulating layer, 7... Semiconductor layer, 9
...Second conductor layer, 10...Source electrode, 11...
・Drane Denomi's agent Patent attorney Kei Shikyou Figure 1 Figure 2 Figure 3 High M provisional 2 power Figure 4, Difference between song right force (SiH4/NH3) -H-total M6 diagram Kate voltage (V) Figure 7 - Foot'ItFL (v) Figure 8

Claims (1)

[Claims] In a thin film semiconductor device in which a first conductor layer, an insulating layer, a semiconductor layer, and a second conductor layer are laminated, the insulating layer is made of silicon nitride (SiN_x), and the spin density of silicon atoms Si in silicon nitride is 10^1^6~3x
10^1^7 [cm^-^3] or increase the amount of bonding of hydrogen atom H to silicon atom Si by 2x
A thin film semiconductor device characterized in that the thickness is 10^2^1 [cm^-^3] or less.