Method for doping semiconductor layer, method for manufacturing thin film semiconductor device, and thin film semiconductor device

Abstract

A low concentration impurity diffusion region is formed with good controllability even in case of using a low heat resistant substrate. When doping a semiconductor layer, after forming the semiconductor layer on the substrate, the amount of the dopant ion adsorbed on a surface of the semiconductor layer is controlled by introducing hydrogen gas at the time of plasma irradiation and activating the adsorbed dopant ion in the semiconductor layer by an excimer laser.

Description

RELATED APPLICATION DATA [0001] This application is a divisional of co-pending application Ser. No. 10 / 433,849 filed Dec. 15, 2003, incorporated herein to the extent permitted by law. The present and foregoing applications claim priority to Japanese Application No. P2000-373052 filed on Dec. 7, 2000, and PCT Appliation No. PCT / JP01 / 10726 filed Dec. 7, 2001.BACKGROUND OF THE INVENTION [0002] The present invention relates to a method for doping a semiconductor layer, a method for manufacturing a thin film semiconductor device, method for controlling resistance of a semiconductor layer, and a thin film semiconductor device, and more particularly, a doping method using a crystallized semiconductor layer by excimer laser anneal, a method for manufacturing a thin film semiconductor device such as a thin film transistor, a thin film semiconductor device in which a semiconductor layer made of such as polycrystalline silicon is used as a channel. [0003] With progress of an advanced informati...

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Benefits of technology

[0021] Other and further objects, features and advantages of the invention will appear more fully from the following description.

Problems solved by technology

On the other hand, when using poly-Si TFT in switching elements for pixel selection of the liquid crystal display or the like, the off current is high and display quality is low, which is a problem.

However, with the poly-Si TFT, a problem arises that a high leakage current occurs since current flows through the grain boundary of crystalline particles composing the semiconductor film or through the defects of the particles themselves.

However, in the poly-Si TFT using for the active matrix liquid crystal displays, for example, the leakage current poses a big problem since it is used under the reverse bias of about 10 V or more.

Such a problem is especially important for the thin film transistor for pixel selection of the liquid crystal displays in which the poly-Si is used.

When forming the thin film transistor having the LDD structure by such a method, there is a problem of the difference or the variation in lengths of the LDDs on both sides of the channel region (thicknesses of the LDD regions between the channel regions and contact regions) due to deviation of the mask during patterning of the gate electrode, and the like.

This causes other problems that the characteristics of the thin film transistor vary and the productivity of the thin film transistor decrease.

For this reason, the resistance of the LDD regions becomes high, and the carrier mobility decreases, which is a problem.

That is, it is difficult to use a glass substrate with a comparatively low melting point in the manufacturing process.

Although the ion doping and the plasma doping are advantageous to the formation of the larger area type, these processes pose problems that the film can contain hydrogen in large quantities which can blow off and break the film at the time of crystallization by the excimer laser (ELA: Excimer Laser Anneal), and that it is difficult to perform the lower temperature process using the plastic substrate or the like at the required temperature for dehydrogenation (400° C.).

Moreover, there is also a problem that these methods are not suitable for the self-alignment type process in principle.

However, in principle, it is difficult to precisely control the dose of 1×1014 / cm2 or less of the impurities.

Furthermore, since the adsorption of the impurity ion of the atomic layer occurs for an extremely short time in the conventional methods, the control at the low dose is difficult.

As seen in FIG. 13, even when the partial pressure of phosphine is changed, the sheet resistance ρs changes little and it reveals that controlling the partial pressure cannot control the concentration of impurities in an impurity diffusion region.

However, it is difficult to apply such a method to the plastic substrate considering the thermal conductivity and electrical conductivity of the plastic substrate.

Moreover, there are other problems that the impurities cannot be implanted into the semiconductor thin film with the large area all at once, and that the throughput gets worse in the manufacturing the large-sized liquid crystal displays.

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