JPH02208942A - Manufacture of thin film transistor - Google Patents

Abstract

PURPOSE:To reduce the number of times of irradiation with a laser beam by a method wherein impurity thin films are formed on source and drain regions and impurities are diffused in semiconductor layers fused by irradiation with the laser beam. CONSTITUTION:First semiconductor layers 2 are left on source and drain regions 4 and 5 of a thin film transistor in an insulative substrate 1 and a second semiconductor layer 3 is left on the regions 4 and 5 and a channel region 6. Moreover, impurity thin film layers 7 are constituted on the regions 4 and 5 and the thin film layers 7 contain phosphorus and boron, which are used as an impurity for diffusion use, in a high concentration. Here, the layers 2 and 3 are fused by irradiation with a laser beam 20, the impurities in the layers 7 are diffused, ohmic contact layers 8 are formed and the layer 3 is recrystallized. Moreover, a gate insulating film 9 is deposited, a gate electrode 10 is constituted, contact holes are respectively formed in the regions 4 and 5 and source and drain electrodes 11 and 12 are formed. Thereby, the constitution of the thin film transistor, which is formed by an impurity diffusion, becomes possible by one time of irradiation with the beam 20 and the high-efficiency thin film transistor can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a thin film transistor on an insulating substrate.

[Conventional technology]

As a conventional technique, there is one described in Japanese Unexamined Patent Publication No. 136673/1983. As shown in FIG. 2(a), a first semiconductor film 14 is formed on an insulating substrate 13, and then an energy beam 15 is irradiated to recrystallize the first semiconductor film 14 to form a recrystallized semiconductor film 16. As shown in FIG. 2(b), a second semiconductor film 17 with low resistance is provided in the source and drain regions.
The energy beam 15 was irradiated again, leaving the insulating film 18, to activate the impurities in the second semiconductor film 17, further lowering the resistance, and depositing the gate insulating WA9 as shown in FIG. 2(c). After that, a third semiconductor film with low resistance is laminated,
Contact holes are formed in the source and drain regions to form gate electrodes 10, source electrodes 11, and drain electrodes 1.
It consists of the process of manufacturing 2.

[Problem to be solved by the invention]

However, the conventional manufacturing method of thin film transistors is
As shown in FIG. 2(a) and FIG. 2(b), two energy beam irradiations were required.

Furthermore, as shown in FIG. 2(b), when the low-resistance second semiconductor film 17 is irradiated with the energy beam 15, the impurities in the second semiconductor 11!117 are activated and
There was a problem in that impurity diffusion into the recrystallized semiconductor film 16 occurred, the impurity concentration in the second semiconductor film 17 decreased, the film deteriorated, and the resistance of the second semiconductor film 17 increased. .

Therefore, in order to solve these conventional problems, an object of the present invention is to provide a method for manufacturing a thin film transistor that can reduce the number of times of energy beam irradiation and obtain low resistance of the source region and drain region. shall be.

[Means to solve the problem]

In order to solve the above problems, a method for manufacturing a thin film transistor according to the present invention includes a step of depositing a first semiconductor layer on an insulating substrate and leaving the first semiconductor layer in an island shape in a source region and a drain region; depositing a semiconductor layer and leaving the second semiconductor layer on the first semiconductor layer in the source region and the drain region and in the channel region; and the step of stacking the first semiconductor layer and the second semiconductor layer. forming an island-shaped impurity thin film layer containing impurities at a high concentration on the source region and the drain region; Diffusing and activating impurities into the second semiconductor layer and the first semiconductor layer to form an ohmic contact layer, recrystallizing the second semiconductor layer in the channel region, and depositing a gate insulating film; The present invention is characterized in that it comprises the steps of forming a gate electrode and forming contact holes in the source region and the drain region to fabricate the source electrode and the drain electrode.

〔Example〕

An embodiment of the method for manufacturing a thin film transistor of the present invention will be described below based on longitudinal cross-sectional views. In FIG. 1(a), a source region F! of a thin film transistor is formed on an insulating substrate 1!
The first semiconductor layer 2 is left in A4 and the drain region 5. next,
In FIG. 1(b), the second semiconductor layer 3 constituting the channel region of the thin film transistor is left on the source region 4, the drain region 5, and the channel region 6, and as shown in FIG. An impurity thin film 7 is formed on the region 4 and the drain region 5. This impurity thin film 7 is formed by plasma CV
It is a film containing a high concentration of phosphorus, boron, etc., which serve as diffusion impurities, and is formed by a D (chemical vapor deposition) method or low-pressure CVD. When the first semiconductor layer 2 and the second semiconductor layer 3 are made of amorphous silicon layers that do not contain impurities, the thickness of the impurity thin film @ 7 may be 300 angstroms or less, and the laser beam shown in FIG. The impurities constituting the impurity thin film layer 7 are diffused into the second semiconductor layer 3 and the first semiconductor layer 2 melted by the irradiation with the beam 20, and an ohmic contact layer 8 is formed as shown in FIG. 1(d). Also, the first
Irradiation with the laser beam 20 shown in FIG. 1(C) causes melting and recrystallization of the second semiconductor layer 3 in the channel region 6, forming a recrystallized semiconductor film 16 as shown in FIG. 1(d). can.

The intensity of the laser beam 20 at this time is 100% when the second semiconductor layer 3 is formed by the 250°C plasma CVD method.
For OA amorphous silicon layers, an intensity of approximately 400 to 800 millijoules per square centimeter is sufficient.

By irradiating the laser beam 20, the crystal grain size of the recrystallized semiconductor film 16 shown in FIG. 1(d) becomes large, ranging from several thousand angstroms to several micrometers. This structure of large crystal grains improves the field effect mobility of the thin film transistor, resulting in high performance.

The following steps are similar to the manufacturing method of a conventional thin film transistor, and after stacking the gate insulating film 9 as shown in FIG. 1(d), the gate electrode 10 is formed as shown in FIG. 1(e). , as shown in FIG. 1(f). An electrode 11 and a drain electrode 12 are formed to complete a thin film transistor.

〔Effect of the invention〕

As explained above, the method for manufacturing a thin film transistor of the present invention enables the crystallization of the channel region and the impurity diffusion of the ohmic contact layer with a single laser beam, and has the effect of realizing a high-performance thin film transistor. has.

FIG. 3 is a vertical cross-sectional view of the process order showing an example of the method.

FIG. 2 is a vertical cross-sectional view of the process order of a conventional thin film transistor manufacturing method.

1... Insulating substrate 2...first semiconductor layer 3... Second semiconductor layer 4 ◆ Temple 5 temples 6・・ 7・・・ 8th day 9・・ 10・・ 11・◆ 12　φ　・ 13. Conflict No. 14 Φ 15・・ 16・φ 17・・ 18-・ 19・・ 20・・ ・Source area ・Drain area ・Channel area ・Impurity thin film layer ・Ohmic contact layer ・Gate insulation film ・Gate electrode ・Source electrode ・Drain electrode ・Insulating substrate ・First semiconductor film ・Energy beam ・Recrystallized semiconductor film ・Second semiconductor film ・Insulating film ・Third semiconductor film ・Laser ψ beam 1st mouth

Claims (1)

[Claims] (1) A step of depositing a first semiconductor layer on an insulating substrate and leaving the first semiconductor layer in an island shape in the source region and the drain region, and depositing a second semiconductor layer in the source region and the drain region. leaving the second semiconductor layer on the first semiconductor layer and the channel region, and doping impurities at a high concentration on the source region and the drain region where the first semiconductor layer and the second semiconductor layer are laminated. a step of forming an island-shaped impurity thin film layer containing an impurity in the second semiconductor layer and the first semiconductor layer by irradiating a laser beam to transfer the impurities in the impurity thin film layer to the source region and the drain region; to form an ohmic contact layer, recrystallize the second semiconductor layer in the channel region, deposit a gate insulating film, form a gate electrode, and form an ohmic contact layer in the source region. and forming a contact hole in the drain region to fabricate a source electrode and a drain electrode.