JPH04313271A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device with improved characteristics by performing hydrogen plasma treatment with hydrogen plasma which is produced at a polycrystalline semiconductor thin film by applying a high frequency to both a substrate-side electrode and an opposing electrode of a plasma generation device. CONSTITUTION:A polycrystalline silicon film 101 with a large grain diameter is formed on a supporting layer 100 which consists of an insulation amorphous material, a gate oxide film 102 is formed, a gate electrode 103 is formed, and then a source region 104 and a drain region 105 are formed with this electrode as a mask (a channel region 106 is also formed automatically). Then, an interlayer insulation film 107 is laminated and hydrogen plasma treatment is performed. A hydrogen plasma device is used, a substrate, etc., after laminating the interlayer insulation film is laminated is fitted to a substrate-side electrode, hydrogen gas is introduced, and a high frequency is applied to an opposing electrode 301 and a substrate-side electrode 301, thus enabling hydrogen gas to be cracked. Therefore, the cracked atom-shaped hydrogen is dissipated into the interlayer insulation film, a gate insulation film, a polycrystalline silicon and a polycrystalline silicon thin-film transistor with improved characteristics can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device.

0002

[Prior Art] Non-single crystal semiconductor thin films such as amorphous silicon thin films, microcrystalline silicon thin films, and polycrystalline silicon thin films include
There are many dangling bonds. For example, in polycrystalline silicon thin films, defects such as dangling bonds existing at grain boundaries become trap levels for carriers and act as a barrier to carrier conduction (J.Y.
W. Seto, J. Appl. Phys. ,46,p5
247 (1975)). As a result of hindering carrier conduction, polycrystalline silicon thin film transistors (poly-SiTFTs) using polycrystalline silicon thin films as channel regions
) decreases, and electron-hole pairs are generated due to an increase in the trap level, which increases the OF of the poly-SiTFT.
The F current will increase.

[0003] Therefore, in order to improve the performance of poly-Si TFTs, it is necessary to reduce the defects (
J. Appl. Phys. , 53(2), p1193(
1982)).

For this purpose, the defects are terminated with hydrogen, and such hydrogenation methods include hydrogen plasma treatment, hydrogen ion implantation, or terminating hydrogen from a plasma nitride film. Diffusion methods and the like are known.

The hydrogen ion implantation method requires an expensive device called an ion implanter, and has drawbacks such as poor controllability when implanting hydrogen into several hundred polycrystalline silicon layers. Furthermore, in the method of diffusing hydrogen from a plasma nitride film, the supply of hydrogen is insufficient, so there are drawbacks such as the characteristics not being sufficiently improved compared to hydrogen plasma treatment.

The hydrogen plasma treatment method is a hydrogenation method that can improve the characteristics of a semiconductor device over a large area with good controllability. As a method for hydrogen plasma treatment, for example, in a parallel plate type plasma generator, an electrode (counter electrode) is placed in a vacuum chamber facing the substrate side electrode that holds the material to be processed, and high frequency is applied to the counter electrode side. A common method is to decompose the hydrogen gas introduced into the vacuum chamber and supply hydrogen radicals to the material to be treated.

[0007]

However, when conventional hydrogen plasma processing methods are used, gate breakdown voltage defects, threshold voltage shifts, and other defects may occur in poly-Si TFTs.

[0008] Therefore, the present invention aims to prevent the occurrence of defects while maintaining the effect of improving TFT characteristics due to hydrogenation, and its purpose is to provide a method for manufacturing a semiconductor device with good characteristics. It's there.

[0009]

Means for Solving the Problems The method for manufacturing a semiconductor device of the present invention is a method for manufacturing a semiconductor device in which at least a part of the channel region of an insulated gate field effect transistor is made of a non-single crystal semiconductor. The method includes at least a step of forming a semiconductor thin film, and a step of subjecting the polycrystalline semiconductor thin film to hydrogen plasma treatment using hydrogen plasma generated by applying high frequency to both a substrate side electrode and a counter electrode of a plasma generator. Features.

0010

[Example] An example of the present invention will be described below with reference to FIG.
This will be explained according to the FT process diagram. FIG. 1(a) shows a support layer 100 made of an insulating amorphous material such as an insulating amorphous substrate such as glass or quartz, or an insulating amorphous material layer such as SiO2 laminated on the substrate. , a process in which a non-single-crystal silicon thin film 101 such as polycrystalline silicon is laminated, and then the non-single-crystal silicon thin film is patterned by photolithography. As a method for forming the non-single crystal silicon thin film, there are the following methods.

(1) 580°C to 650°C by low pressure CVD method
A polycrystalline silicon thin film is formed at about

(2) After depositing an amorphous silicon thin film by EB evaporation method, sputtering method, plasma CVD method, etc., 550° C.
Solid phase growth annealing is performed at about 650° C. for about 2 to 70 hours to form a polycrystalline silicon thin film with a large grain size of 1 to 2 μm or more.

(3) After depositing a polycrystalline silicon thin film by low pressure CVD method etc., Si is deposited by ion implantation method.
etc. to make the polycrystalline silicon thin film amorphous, solid phase growth annealing is performed at about 550°C to 650°C,
A large grain polycrystalline silicon thin film having a grain size of about 1 to 2 μm is formed.

As the non-single crystal silicon thin film 101, a microcrystalline silicon thin film or an amorphous silicon thin film may be used in addition to the above-mentioned polycrystalline silicon thin film. Also,
The film forming method is also not limited to the methods (1) to (3) described above. Next, as shown in FIG. 1(b), a gate oxide film 102 is formed by a thermal oxidation method or the like. If dry oxidation is used, a gate oxide film with high dielectric strength can be obtained by performing heat treatment at about 1150° C. in an oxygen atmosphere. 90 using wet oxidation method
Although a gate oxide film can be formed by heat treatment at a low temperature of about 0° C., the dielectric strength is lower and the film quality is inferior to that of a gate oxide film formed by dry oxidation.

When a polycrystalline silicon thin film is used as the non-monocrystalline silicon thin film 101, crystal growth due to heat treatment progresses in this thermal oxidation step, and the crystallization ratio to volume improves.
Grain size expands. Further, even when an amorphous silicon thin film or a microcrystalline silicon thin film is used as the non-single crystal silicon thin film 101, crystal growth due to heat treatment progresses in this thermal oxidation step, resulting in crystal grain sizes ranging from 5000 Å to several μm. Crystals grow into polycrystalline silicon.

Note that the method for forming the gate oxide film is not limited to the above-mentioned thermal oxidation method, but also CVD method, plasma CVD method, E
S by CR plasma CVD method, optical CVD method, sputtering method, etc.
There are also a method of forming an iO2 film, a method of low-temperature oxidation using a plasma oxidation method, etc. These methods reduce the process temperature to 60
Since the temperature can be kept at a low temperature of about 0° C. or lower, it is advantageous in that an inexpensive glass substrate can be used as the substrate.

Next, as shown in FIG. 1(c), the gate electrode 1
Form 03. Polycrystalline silicon is generally used as the gate electrode material. As a method for forming the polycrystalline silicon layer, the polycrystalline silicon layer is formed by a low pressure CVD method, and the n+
For example, an amorphous silicon layer doped with B (boron) or P (phosphorus) as an impurity is formed by a method of forming poly-Si, a plasma CVD method, etc., and heated at 550°C to 65°C.
By performing solid phase growth annealing at about 0°C for about 2 to 70 hours and polycrystallizing the amorphous silicon layer, p+p
There are methods such as forming an oly-Si layer or an n+poly-Si layer. Next, using the gate electrode 103 as a mask, impurity elements are ion-implanted to form the source region 104.
and a drain region 105 (channel region 106 is also automatically formed along with this step). The impurity element may be P (phosphorus), As (arsenic), or B.
(Boron) etc. are used.

Subsequently, as shown in FIG. 1(d), an interlayer insulating film 107 is laminated. Here, hydrogen plasma treatment is performed. A capacitively coupled parallel plate type device was used as a plasma generation device for performing the hydrogen plasma treatment. The processing conditions were as follows. After laminating the interlayer insulating film, the substrate, etc. (hereinafter referred to as the treated material) is attached to the substrate side electrode, hydrogen gas is introduced, and a counter electrode (a type of relative electrode. In a parallel plate type plasma generator, the substrate side electrode is opposite to the substrate side electrode). 13.56 MHz high frequency is applied to the electrode on the substrate side to decompose the hydrogen gas. The RF power at that time was 250 to 700 mW/cm2 for the counter electrode and 0 to 280 mW/cm2 for the substrate side electrode. The processing time was 5 minutes to 5 hours, the substrate temperature was 250°C to 350°C, the hydrogen gas flow rate was 100 to 600 sccm, and the distance between the electrodes was 27 to 45 mm. However, the processing conditions are not limited to these. Through this hydrogen plasma treatment, atomic hydrogen gas-decomposed by the plasma diffuses into the interlayer insulating film, gate insulating film, and polycrystalline silicon, and dangling bonds in the polycrystalline silicon are terminated. Thus, a polycrystalline silicon thin film transistor with improved characteristics can be obtained.

[0019] In addition, under the processing conditions, 0 W/c was applied to the substrate side electrode.
There is a case where a high frequency is applied with an RF power of m2, but the conditions are different from the conventional device that applies a high frequency only to the counter electrode. The reason for this is that in the conventional device that applies high frequency only to the counter electrode, the substrate side electrode is at ground potential (Figure 3), but in the device used in the present invention that can also apply high frequency to the substrate side electrode, This is because it is grounded via a high frequency matching box (Fig. 2). (The matching box generally has a variable capacitor, etc., so the substrate side electrode is not grounded.) In the hydrogen plasma treatment of the present invention, which uses a device that can apply high frequency waves to the substrate side electrode, only the conventional counter electrode can be used. Compared to hydrogen plasma treatment using a device that applies high frequency, hydrogen ions and hydrogen radicals can be selectively diffused into polycrystalline silicon, and the Vg-Id characteristic shift (threshold voltage It is excellent in that the amount of shift) can be reduced. An important variable in this case is the potential VDC of the substrate-side electrode, and detailed conditions will be described later.

In the hydrogen plasma treatment of the present invention using a device capable of applying high frequency waves to the substrate side electrode, the alternating current impedance of the substrate side electrode with respect to the ground potential is changed using a variable capacitor or the like in the substrate side electrode matching box 306 in FIG. Therefore, the potential VDC can be controlled without applying high frequency to the substrate side electrode (even when applying high frequency to the substrate side electrode with RF power of 0 W/cm2). In addition, the counter electrode matching box 30
4 and the circuit structure inside the substrate side electrode matching box 306 are not limited to the circuit structure in FIGS. 2 and 3.

[0021] It is important that the structure is such that the substrate-side electrode and counter electrode to which high frequency is applied are grounded via AC impedance. After hydrogen plasma treatment, a thin film transistor is completed by forming contact electrodes 108 in the source and drain regions (FIG. 1(e)). Metal materials such as Al, Cr, and Ni are used as the contact electrode material. The field effect mobility of the polycrystalline silicon TFT (poly-SiTFT) formed according to the present invention is N
chTFT: 50 cm2/V・s (low pressure CVD method 590
When polycrystalline silicon is formed at ℃)~160cm2/
V・s (when polycrystalline silicon is formed by solid-phase growth of amorphous silicon deposited by plasma CVD method at 600°C for about 17 hours), and when it is simply annealed in a hydrogen gas atmosphere (~10 cm2 /V・s), the characteristics were significantly improved.

[0022] Furthermore, poly-Si formed according to the present invention
The ON current of TFT is transistor size L/W = 5μm
/10 μm Nch TFT is 400 μA, the OFF current is 10 to 30 fA for the same size Nch TFT, and the swing (Vg-I in the subthreshold region)
d) is 0.35V/dec. Met. In addition, while the shift amount of the TFT threshold voltage due to conventional hydrogen plasma treatment is -2V to -5V (Fig. 5), the hydrogen plasma treatment of the present invention uses a device that can also apply high frequency waves to the substrate side electrode. In the treatment, the shift amount was −1 V or less (FIG. 4).

[0023] It should be noted that TFTs by conventional hydrogen plasma treatment
Damage such as a shift in the threshold voltage tends to occur frequently in large-scale mass production equipment that has a wide electrode area of 50 cm x 50 cm or more. Hydrogen plasma treatment can completely eliminate damage even to the above-mentioned device having a wide electrode area.

Next, we will discuss the reason why defects due to plasma damage, which tend to occur in conventional hydrogen plasma processing, are less likely to occur in the hydrogen plasma processing of the present invention, which uses a device that can also apply high frequency waves to the substrate side electrode. The cause of damage caused by hydrogen plasma processing is not clear at present, but being immersed in the plasma atmosphere causes a charge-up on the substrate, which creates a state in which voltage is applied between the gate and channel, and the substrate The phenomenon is well explained by a model in which a defect occurs in the TFT due to pseudo BT stress (bias and temperature stress) being applied due to the relatively high temperature of about 300°C. According to this model, in the hydrogen plasma treatment of the present invention using a device that can apply high frequency waves to the substrate side electrode, the potential of the substrate side electrode V
Since DC can be controlled by applying a high frequency to the substrate side electrode, it is considered possible to prevent charge-up from occurring on the substrate. Therefore, defects such as the shift of the threshold voltage mentioned above that occur in conventional hydrogen plasma processing can be completely eliminated.

The potential VDC is always 0 V in conventional hydrogen plasma processing using a device that applies high frequency only to the opposing electrode, but the present invention uses a device that can apply high frequency to the substrate side electrode as well. The hydrogen plasma treatment is variable. By setting the potential VDC to 10V to -100V, the shift amount of the threshold voltage of the TFT after hydrogen plasma treatment can be set to -1V or less. Further, it is particularly preferable that the potential VDC is set to 5 V to -50 V, and in this case, almost no shift in the threshold voltage is observed. It is thought that the shift amount of the threshold voltage can be further reduced by setting the potential VDC to -100V or less, but this is not so desirable because the possibility that the electrode will be sputtered increases.

In this embodiment, a case has been described in which hydrogen plasma processing is performed using a capacitively coupled parallel plate type plasma generator, but the shape of the apparatus is not limited to this. It is important to use a device that can apply high frequency waves to the electrodes that support the material to be treated with hydrogen plasma. Note that the hydrogen plasma treatment may be performed not after the interlayer insulating film is laminated, but after the contact electrode is formed.

As described above, if the present invention is applied,
A transistor with a large ON current, a small OFF current, and a steep subthreshold voltage rise can be manufactured without any defects due to plasma damage or the like.

Applications of the present invention include, for example, liquid crystal display panels constructed of TFTs using amorphous silicon as an element material, contact type image sensors, thermal heads with built-in drivers, organic EL, etc. as light emitting elements. Possible devices include an optical writing element with a built-in driver, a display element, and a three-dimensional IC. By using the present invention, higher performance such as higher speed and higher resolution of these elements can be realized.

Although FIG. 1 shows an example in which the present invention is applied to a poly-SiTFT manufacturing process, the present invention is not limited to this. The present invention is effective for all insulated gate field effect transistors in which at least a portion of the channel region is polycrystalline. In addition, in insulated gate transistors in which at least part of the channel region is made of microcrystals, and in transistors in which part of the channel region is made of an insufficiently hydrogenated amorphous semiconductor formed by sputtering or vapor deposition, etc. is also valid.

Furthermore, even if the channel region is a single crystal,
When forming an element in a silicon layer that has been recrystallized or grown in a solid phase, such as in a three-dimensional IC, defects such as sub-grain boundaries, which tend to occur in crystals, can be eliminated by the semiconductor device manufacturing method based on the present invention. Terminating the ring bond is effective in improving the characteristics.

Furthermore, the present invention is also effective in reducing the defect density at the heterojunction interface of HBTs (hetero-bipolar transistors) and the like. In particular, when at least one of the two semiconductor layers forming a heterojunction is made of a non-single crystal semiconductor, the hydrogenation treatment according to the present invention can simultaneously reduce defects in the film and at the interface.

Further, the present invention can be widely applied to semiconductor processes in general, including solar cells, optical sensors, bipolar transistors, and static induction transistors using non-single crystal semiconductors as element materials.

[0033]

[Effects of the Invention] As described above, according to the present invention, the po
It is possible to improve the performance of an insulated gate field effect transistor, such as a ly-SiTFT, in which at least a portion of the channel region is made of a non-single crystal semiconductor, without causing defects due to plasma damage. Further, the present invention can be widely applied not only to insulated gate field effect transistors but also to semiconductor processes in general, and its effects are extremely large.

[Brief explanation of drawings]

FIGS. 1A to 1E are process cross-sectional views showing an example of a method for manufacturing a semiconductor device in an embodiment of the present invention.

FIG. 2 is a diagram showing the electrical grounding relationship of a parallel plate type hydrogen plasma processing apparatus that can apply high frequency not only to a counter electrode but also to a substrate side electrode in an embodiment of the present invention.

FIG. 3 is a diagram showing the electrical grounding relationship of a conventional parallel plate type hydrogen plasma processing apparatus that can apply high frequency only to a counter electrode.

FIG. 4: Nc subjected to hydrogen plasma treatment using a parallel plate type hydrogen plasma treatment apparatus that can apply high frequency not only to the counter electrode but also to the substrate side electrode in the embodiment of the present invention.
It is a Vg-Id characteristic diagram of hTFT.

FIG. 5 is a Vg-Id characteristic diagram of an Nch TFT subjected to hydrogen plasma treatment using a conventional parallel plate type hydrogen plasma treatment apparatus capable of applying high frequency only to a counter electrode.

[Explanation of symbols]

100 Insulating support layer 101 Non-single crystal silicon thin film 102 Gate oxide film 103 Gate electrode 104 Source region 105 Drain region 106 Channel region 107 Interlayer insulating film 108 Contact electrode 301 Counter electrode 302 Substrate side electrode 303 Chamber 304 Counter electrode matching box 305 Opposite Electrode high frequency power supply 306 Substrate side electrode matching box 307 Substrate side electrode high frequency power supply

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device in which at least a portion of a channel region of an insulated gate field effect transistor is made of a non-single crystal semiconductor, comprising the steps of: forming a polycrystalline semiconductor thin film; 1. A method for manufacturing a semiconductor device, comprising at least the step of performing hydrogen plasma treatment using hydrogen plasma generated by applying high frequency to both a substrate-side electrode and a counter electrode of a plasma generator.