JP3407067B2 - Semiconductor device manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device. More specifically, the present invention relates to a method of manufacturing a semiconductor device capable of preventing a short circuit between a metal wiring and a channel region in a manufacturing process of a semiconductor device such as a thin film transistor.

[0002]

2. Description of the Related Art FIGS. 3A to 3C are sectional views for explaining steps in a conventional method of manufacturing an inverted stagger type thin film transistor using an ion doping method. In FIG. 3, 21 is a glass substrate, 22
Is a gate electrode, 23 is a gate insulating film made of a silicon nitride film, 24a is a semiconductor layer, 25a is a channel insulating film made of a silicon nitride film, and 27 and 28 are source and drain electrodes made of Al or the like. .

Next, a method of manufacturing a conventional inverted stagger type thin film transistor will be described with reference to FIG. First, FIG.
As shown in (a), the gate electrode 22 made of Cr or the like is formed only in a predetermined region on the glass substrate 21. continue,
The gate insulating film 23, the amorphous silicon layer 24, and the insulating film 25 are sequentially formed (see FIG. 3B). Next, the insulating film 25 is patterned by using a photolithography technique, and the unnecessary portion of the insulating film is removed by etching to obtain a channel insulating film 25a having a shape shown in FIG. 3C. After that, the amorphous silicon layer 24 is patterned and etched to form the semiconductor layer 24a in a predetermined region, and the exposed portion of the surface of the semiconductor layer 24a is ion-doped with phosphorus or the like to form an n-type region. 29
And finally, the source electrode 27 and the drain electrode 28 are formed (see FIG. 3D).

[0004]

As described above, in the conventional method of manufacturing a semiconductor device using the ion doping method, the n-type region 29 formed on a part of the surface of the semiconductor layer 24a is used.
On the other hand, although the source electrode 27 and the drain electrode 28 are formed, the lateral diffusion of the doping impurities is small in the formation of the n-type region by the ion doping method. Therefore, the source electrode 27 is formed near the end surface of the channel insulating film 25a. And a portion of the semiconductor layer 24a where the n-type region 29 is not formed, or the drain electrode 28 and the semiconductor layer 24a.
There is a problem that the off-current characteristics of the semiconductor device are remarkably deteriorated because a short circuit occurs in a portion where the n-type region 29 is not formed.

An object of the present invention is to solve the above problems and to provide a method of manufacturing a semiconductor device capable of preventing a short circuit between a source electrode and a semiconductor layer or a drain electrode and a semiconductor layer in the vicinity of an end face of a channel insulating film.

[0006]

A method of manufacturing a semiconductor device according to the present invention comprises (a) a step of forming a gate electrode in a first predetermined region on a glass substrate, and (b) a glass substrate including the gate electrode. sequentially forming a gate insulating film, the semiconductor layer and the channel insulating film, Ri by the etching the (c) the channel insulating layer
A step of leaving the previous SL channel insulating film only in the second predetermined region, and thereby leaving only the third predetermined region before Symbol semiconductor layer Ri by the etching (d) is the semiconductor layer, (e) the Forming a pair of n-type regions in the semiconductor layer in the third predetermined region by ion doping, and (f) further covering the gate insulating film, the pair of n-type regions, and the channel insulating film. A step of forming an insulating film, and (g) anisotropically etching the insulating film to form a boundary between the n-type region and the gate insulating film and a boundary between the n-type region and the channel insulating film. a step of leaving the insulating film on the portion, to form a (h) the gate insulating film, before SL one of the n-type region, the insulating film and the fourth source electrode in a predetermined area formed by covering the channel insulating film, the gate insulating film, before Symbol n
Forming a drain electrode in a fifth predetermined region covering the insulating film and the channel insulating film on the other side of the mold region.

The ion doping step comprises the step of performing ion doping by irradiating the ion source from at least two directions, and the irradiation angle of the ion source is 0 ° with respect to a plane perpendicular to the glass substrate surface. Large 60 °
A smaller angle is preferable because the surface and side surfaces of the semiconductor layer can be ion-doped.

The step of leaving the channel insulating film only in a predetermined region may be a step of performing isotropic etching and then anisotropic etching so that the lateral spread of doping impurities is increased and the source electrode and drain electrode are expanded. Is preferable because it can prevent a short circuit between a semiconductor layer in which the n-type region is not formed.

The method of manufacturing a semiconductor device of the present invention comprises (a) a step of forming a gate electrode in a first predetermined region on a glass substrate, and (b) a gate insulating film, a semiconductor on the glass substrate including the gate electrode. sequentially forming a layer, (c) a step of leaving only the third predetermined region Ri by the etching the semiconductor layer, (d) the channel so as to cover and said gate insulating film and the semiconductor layer forming an insulating film, Ri by the etching the (e) the channel insulating layer
A step of leaving the previous SL-channel insulated film only the second predetermined region, (f) the semiconductor layer of the third predetermined region, and forming a pair of n-type region by ion doping, (g) Further, the Forming an insulating film so as to cover the gate insulating film, the pair of n-type regions, and the channel insulating film; and (h) anisotropically etching the insulating film to form the n-type region and the n-type region. a step of leaving the insulating film in the boundary portion and the n-type region and the boundary portion between the channel insulation film between the gate insulating film, (i) the gate insulating layer, one of the pre-Symbol n-type region, said insulating film and the channel insulating film to form a source electrode to a fourth predetermined region comprising covering said gate insulating film, before Symbol n
Forming a drain electrode in a fifth predetermined region which covers the insulating film and the channel insulating film on the other side of the mold region.

The step of ion doping comprises the step of ion-doping by irradiating the ion source from at least two directions, and the irradiation angle of the ion source is 0 ° with respect to a plane perpendicular to the surface of the glass substrate. Large 60 °
A smaller angle is preferable because the surface and side surfaces of the semiconductor layer can be ion-doped.

The step of leaving the channel insulating film only in a predetermined region may be a step of performing isotropic etching and then anisotropic etching so that the lateral spread of the doping impurities is increased to increase the source electrode and the drain. It is preferable because a short circuit between the electrode and the semiconductor layer in which the n-type region is not formed can be prevented.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a method for manufacturing a semiconductor device of the present invention will be described with reference to the drawings. 1A to 1D are process cross-sectional explanatory views of an embodiment of a method for manufacturing a semiconductor device of the present invention. In FIG. 1, 11 is a glass substrate, 12 is a gate electrode, 13 is a gate insulating film, 14a is a semiconductor layer, 15a is a channel insulating film, 16
Is a sidewall insulating film formed at the boundary between the source electrode 17 and the n-type region 19 or at the boundary between the drain electrode 18 and the n-type region 19a, and 17 and 18 are a source electrode and a drain electrode, respectively. , 19 are n-type regions formed in the semiconductor layer 14a.

The method of manufacturing the semiconductor device of the present invention is as follows.
As shown in (a), a gate electrode 12 made of, for example, Cr, Al, Mo, or Ta is formed in a first predetermined region on the glass substrate 11 having an area necessary to act as a gate electrode. Form. Then, Fig. 1
As shown in (b), on the glass substrate 11 including the gate electrode 12, for example, a single film of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide or tantalum oxide, or a combination of the above films. A gate insulating film 13 composed of a multi-layered structure, an amorphous silicon layer 14 to be a semiconductor layer 14a later, and, for example, silicon nitride, silicon oxide,
Alternatively, a single film of silicon oxynitride, or a multi-layered film formed by combining the above films, etc., and an insulating film 15 to be a channel insulating film 15a later is sequentially formed. Next, the insulating film 15 is patterned by a photolithography technique (hereinafter simply referred to as "photolithography technique") in which a resist is formed into a desired shape by an ordinary resist coating and exposure method, and then an unnecessary portion is removed. The insulating film is removed by etching, and a second predetermined region having a position and an area necessary for acting as a channel insulating film is formed.
A channel insulating film 15a having the shape shown in (c) is formed. After that, the amorphous silicon layer 14 is patterned by using a photolithography technique to remove unnecessary portions of the amorphous silicon layer by etching, and a third area having a position and an area necessary for acting as a semiconductor layer is formed. The semiconductor layer 14a is formed in a predetermined area. Further, the exposed portion and the side surface of the semiconductor layer 14a are ion-doped with phosphorus or the like to form an n-type region 19 on the surface and the side surface of the semiconductor layer 14a. Next, a single film of, for example, silicon nitride, silicon oxide, silicon oxynitride or tantalum oxide, or each of the above films is formed so as to cover the surfaces of the gate insulating film 13, the n-type region 19 and the channel insulating film 15a. An insulating film which will later become the side wall insulating film 16 is formed, and anisotropic etching is applied to the insulating film, as shown in FIG. The boundary between the n-type region 19 and the gate insulating film 13 and the n-type region 19 and the channel insulating film 1
The side wall insulating film 16 is formed at the boundary with 5a. The anisotropic etching process is performed with CF ₄ , SF ₆ , CH so that the etching proceeds only in a direction perpendicular to the insulating film.
It is performed using a gas such as F ₃ , O ₂ , N ₂ , Ar, or He. Therefore, even if the formation of the n-type region 19 by the ion doping method is insufficient near the end face of the gate insulating film 13 and near the end face of the channel insulating film 15a,
The sidewall insulating film 16 is formed between the end of the n-type region 19 and the source electrode 17 and the drain electrode 18. Therefore, the semiconductor layer 14a and the source electrode 17 are
Or a short circuit between the semiconductor layer 14a and the drain electrode 18 is prevented. Finally, a source electrode 17 made of Al or the like is formed in a fourth predetermined region having a position and an area required to act as a source electrode, and a fifth electrode having a position and an area required to act as a drain electrode is formed. A drain electrode 18 made of Al or the like is formed in a predetermined region of the above to obtain a thin film transistor which is a semiconductor device having the shape shown in FIG.

Further, the step of ion-doping impurities such as phosphorus on the surface and the side surface of the semiconductor layer 14a includes a step of irradiating the ion source from at least two directions to perform ion-doping. Thus, since the ion source is irradiated from at least two directions, the semiconductor layer 14a
Is doped with impurities such as phosphorus not only on its surface but also on its side surface. The irradiation angle of the ion source is changed at an angle larger than 0 ° and smaller than 90 ° with respect to a plane perpendicular to the glass substrate surface, and in the present invention, an angle larger than 0 ° and smaller than 60 ° is preferable, Above all, an angle larger than 0 ° and smaller than 45 ° is more preferable. If the irradiation angle is larger than 60 °, the surface of the semiconductor layer 14a is not sufficiently doped with impurities such as phosphorus, and the n-type region 19 is insufficiently formed, which has a function as a thin film transistor. Disappear.

According to the method for manufacturing a semiconductor device described above, the gate electrode 12 is formed in the first predetermined region on the glass substrate 11, and the gate insulating film 13, the amorphous silicon layer 14 to be the semiconductor layer 14a, and the channel insulating film 15a are formed. After sequentially forming an insulating film 15 to be formed, the amorphous silicon layer 14 and the insulating film 15 are respectively patterned and etched to form a channel insulating film 15a in a second predetermined region and a third predetermined region. Each of the semiconductor layers 14a is formed. However, first, the gate electrode 12 is formed in the first predetermined region on the glass substrate 11, the gate insulating film 13 and the amorphous silicon layer 14 to be the semiconductor layer 14a are sequentially formed, and the amorphous silicon layer 14 is formed. Patterning and etching are performed to form the semiconductor layer 14a in the third predetermined region, after which the insulating film 15 to be the channel insulating film 15a is formed, and the insulating film 15 is patterned and etched to obtain the second The channel insulating film 15a may be formed in a predetermined region of the above.

In the step of forming the channel insulating film 15b only in the second predetermined region as shown in FIG. 2B, the insulating film to be the channel insulating film 15b is firstly isotropic. After the etching, the channel insulating film 15b is further anisotropically etched.
May be formed. In this way, since the isotropic etching is performed and then the anisotropic etching is performed, the channel insulating film 15b is first formed on the channel insulating film 15b.
Etching progresses in both the vertical and horizontal directions, and thereafter, the etching progresses only in the vertical direction with respect to the channel insulating film 15b. Therefore, FIG. 2A is a plan view of the channel insulating film 15b shown in FIG. 2B.
As shown in FIG. 5, the four side surfaces of the channel insulating film 15b are tapered. As a result, the doping impurities pass through a part of the thinned channel insulating film in the tapered portion at the time of ion doping, and an n-type region is also formed in the semiconductor layer below the channel insulating film, which is effective. It is possible to prevent the short circuit between the source electrode and the drain electrode and the semiconductor layer in which the n-type region is not formed by increasing the lateral spread of the doping impurities.

[0017]

When a thin film transistor or the like is formed by the method for manufacturing a semiconductor device of the present invention, the n-type region formed on the surface portion of the semiconductor layer and the end surface portion of the channel insulating film are covered with the insulating film. Therefore, it is possible to prevent a short circuit between the source electrode and the drain electrode and the semiconductor layer, which is caused by a small lateral expansion of the n-type region formed by the ion doping method, and to obtain good current-voltage characteristics, particularly off current. A semiconductor device having characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a process cross-sectional explanatory view showing a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is an explanatory diagram showing a shape of a channel insulating film according to a method for manufacturing a semiconductor device of the present invention.

FIG. 3 is a process cross-sectional explanatory view showing a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

11 glass substrate 12 Gate electrode 13 Gate insulating film 14a semiconductor layer 15a Channel insulating film 16 Side wall insulating film 17 Source electrode 18 Drain electrode 19 n-type region

Claims (6)

(57) [Claims] 1. A process of forming a gate electrode in a first predetermined region on a glass substrate, and a gate insulating film, a semiconductor layer and a channel insulating film on a glass substrate including the gate electrode. sequentially forming, Ri by the etching the (c) the channel insulating layer
And thereby leaving only the second predetermined region, (d) a step of leaving only the third predetermined region Ri by the etching the semiconductor layer, a semiconductor layer of (e) the third predetermined region, ions Forming a pair of n-type regions by doping, (f) further forming an insulating film so as to cover the gate insulating film, the pair of n-type regions, and the channel insulating film, (g) Anisotropically etching the insulating film to leave the insulating film at the boundary between the n-type region and the gate insulating film and at the boundary between the n-type region and the channel insulating film; h) the gate insulating layer, one of the pre-Symbol n-type region, said insulating film and said forming a source electrode to a fourth predetermined region formed by covering the channel insulating film, the gate insulating film, before Symbol n
A step of forming a drain electrode in a fifth predetermined region covering the insulating film and the channel insulating film on the other side of the mold region , the method for manufacturing a semiconductor device. 2. The step of ion doping comprises the step of ion-doping by irradiating the ion source from at least two directions, and the irradiation angle of the ion source is 0 with respect to a plane perpendicular to the surface of the glass substrate. Greater than 60
The method for manufacturing a semiconductor device according to claim 1, wherein the angle is smaller than °. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the step of leaving only the predetermined region of the channel insulating film comprises the step of isotropic etching and then anisotropic etching. 4. A step of (a) forming a gate electrode in a first predetermined region on the glass substrate, and (b) a step of sequentially forming a gate insulating film and a semiconductor layer on the glass substrate including the gate electrode. If, (c) forming a step to leave only the third predetermined region Ri by the etching the semiconductor layer, the channel insulating film to cover said semiconductor layer (d) and further the gate insulating film If, Ri by the etching the (e) the channel insulating layer
Wherein the step of leaving only the second predetermined region, the semiconductor layer (f) said third predetermined region, and forming a pair of n-type region by ion doping, and (g) Further, the gate insulating film Forming an insulating film so as to cover the pair of n-type regions and the channel insulating film, and (h) anisotropically etching the insulating film to form the n-type region and the gate insulating film. a step of leaving the insulating film at the boundary between the channel insulating layer between the boundary portion and the n-type region, the (i) the gate insulating layer, one of the pre-Symbol n-type region, the insulating film and the channel insulating layer fourth forming a source electrode in a predetermined region, said gate insulating film formed over the previous SL n
A step of forming a drain electrode in a fifth predetermined region covering the insulating film and the channel insulating film on the other side of the mold region , the method for manufacturing a semiconductor device. 5. The step of performing ion doping includes the step of performing ion doping by irradiating the ion source from at least two directions, and the irradiation angle of the ion source is 0 with respect to a plane perpendicular to the surface of the glass substrate. Greater than 60
The method for manufacturing a semiconductor device according to claim 4, wherein the angle is smaller than °. 6. The method of manufacturing a semiconductor device according to claim 4, wherein the step of leaving only the predetermined region of the channel insulating film comprises the step of isotropic etching and then anisotropic etching.