JPH03217053A - Resistor - Google Patents

Abstract

PURPOSE:To reduce temperature dependency of a resistance value by connecting an n-channel thin film transistor and a p-channel thin film transistor having reverse current temperature dependencies to form a resistor. CONSTITUTION:An n-channel thin film transistor and a p-channel thin film transistor having reverse current temperature dependencies are connected. For example, n-channel and p-channel thin film transistors having a dendritic polycrystalline Si film as an active layer are formed, and connected as in Fig. A or B. In order to form the Si film, Si<+> ions are implanted to the normal polycrystalline Si film to be made amorphous, or an amorphous Si film is formed from an initial time at a low temperature, the Si film is annealed at a low temperature of about 600 deg.C and grown in solid state. Thus, the current temperature dependencies of the n-type and p-type transistors are cancelled to each other, and the temperature dependencies of the entire resistance value is remarkably reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resistor formed in a semiconductor integrated circuit device or the like.

[Summary of the invention]

The present invention provides an n-channel thin film transistor and a p-channel thin film transistor whose current temperature dependence characteristics are opposite to each other in the resistor as described above.
By connecting a channel thin film transistor to form a resistor, the temperature dependence of the resistance can be reduced.

[Conventional technology]

Resistors in semiconductor integrated circuit devices are generally made of polycrystalline St.
It is composed of a film, and may also be composed of a MOS transistor or the like.

[Problem to be solved by the invention. ]

Incidentally, a resistor for a load in a MOS-SRAM is required to have a high resistance on the order of MΩ, and a bibolar device is often required to have a high resistance on the order of kΩ.

On the other hand, since polycrystalline St is a semiconductor, if the energy at the lower end of the conduction band is EC and the Fermi level is Er, then the resistance value R is R=Ro exp { (Ec - Er ) /kT
).

Therefore, in order to obtain high resistance, it is necessary to position E near the center of the forbidden band and increase EC-Ef.

However, as EC-E increases, the temperature dependence of the resistance value R increases, as is clear from the above equation. Therefore, with a polycrystalline St film, it is theoretically difficult to construct a resistor with high resistance and low temperature dependence of resistance value, and the design and operational margins are small.

Furthermore, in a MOS transistor, its mutual conductance g is proportional to its mobility μ, but the mobility of single crystal Si is greatly affected by scattering due to acoustic lattice vibration. Therefore, as the temperature increases, the mobility and mutual conductance decrease and the resistance value increases, and although this is the opposite characteristic to that of a polycrystalline Si film, it still has a large temperature dependence.

[Means to solve the problem]

The resistor according to the present invention is formed by connecting an n-channel thin film transistor and a p-channel thin film transistor whose current temperature dependence characteristics are opposite to each other.

[Effect]

In the resistor according to the present invention, the temperature dependence of current is canceled out between the n-channel thin film transistor and the p-channel thin film transistor.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

In this embodiment, n-channel and p-channel thin film transistors having a dendrite polycrystalline St film as an active layer are formed, and these thin film transistors are connected as shown in FIG. IA or FIG. IB.

To form a dendritic polycrystalline St film, ordinary polycrystalline Si
Either ion-implanting St'' into the film to make it non-quality, or forming an amorphous St film from the beginning at a low temperature,
The i-film is annealed at a low temperature of about 600°C to grow in a solid phase.

Dendritic polycrystalline Si has a larger grain size and improved grain boundary electrical properties than normal polycrystalline St.
There are fewer traps. Therefore, dendritic polycrystalline Si has properties intermediate between single crystal Si and normal polycrystalline St.

By the way, as mentioned above, the mobility of single-crystal Si is greatly affected by scattering due to acoustic lattice vibrations, so the higher the temperature, the lower the mobility.

On the other hand, since ordinary polycrystalline Si has many traps, its mobility is greatly affected by scattering by ionized impurities. Therefore, the higher the temperature, the higher the mobility.

However, as described above, dendritic polycrystalline Si has properties intermediate between single-crystal Si and normal polycrystalline St, so its mobility itself has small temperature dependence.

Figure 2 shows a case where a dendritic polycrystalline St film is used as the active layer as in this example, and the gate width and gate length are 20 μm and 7 μm, respectively.
2 shows the temperature dependence characteristics of the current of an n-channel thin film transistor with a gate width and a p-channel thin film transistor with a gate width of 40 μm and a gate length of 7 μm, respectively.

As is clear from Figure 2, the characteristics of the n-channel thin film transistor when using a normal polycrystalline Si film as the active layer remain slightly, and the characteristics of the p-channel thin film transistor when using a single crystal Si substrate remain slightly. Although it is appearing,
The current dependence itself is small.

Therefore, in this embodiment shown in FIG. 1, the temperature dependence of the current is canceled out between the n-channel thin film transistor and the p-channel thin film transistor, and the temperature dependence of the overall resistance value is extremely small.

In addition, the thinner the dendritic polycrystalline Si film that constitutes the active layer of the thin film transistor, the fewer the apparent traps per unit area, which is effective in reducing the temperature dependence of resistance. It is true.

To adjust the resistance value of the resistor of this example as described above,
For example, this is done by keeping the gate length constant and varying the gate width.

Note that this process must be added because hyperpolar devices do not include the thin film transistor manufacturing process in their manufacturing process, but if they originally include the thin film transistor manufacturing process, such as MOS-SRAM, the process is It's fine as usual.

〔Effect of the invention〕

In the resistor according to the present invention, the n-channel thin film transistor and the p-channel thin film transistor cancel out the temperature dependence of the current, so the temperature dependence of the resistance value is small.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a graph showing the temperature dependence characteristics of current of n-channel and p-channel thin film transistors having a dendritic polycrystalline Si film as an active layer.

Claims (1)

[Claims] A resistor formed by connecting an n-channel thin film transistor and a p-channel thin film transistor whose current temperature dependence characteristics are opposite to each other.