JP3252290B2 - Thin film bipolar transistor and thin film semiconductor device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film bipolar transistor and a thin film semiconductor device using the same.

[0002]

2. Description of the Related Art For example, an active matrix panel (thin film semiconductor device) used in an active matrix type liquid crystal display device has a circuit configuration as shown in FIG. In this thin film semiconductor device, a scanning electrode 2 is provided in a row direction on a single transparent substrate 1 made of glass or the like, and a signal electrode 3 is provided in a column direction.
A thin film transistor (thin film active element) 4, a pixel capacitance unit 5 composed of a liquid crystal capacitance, and an auxiliary capacitance unit 6 are provided for each pixel corresponding to each intersection with the gate electrode. The data driving peripheral circuit 8 is provided at one end of the signal electrode 3.
Then, when the thin film transistor 4 is turned on, display data is written in the form of electric charges in the pixel capacitance portion 5 and the auxiliary capacitance portion 6, and when the thin film transistor 4 is turned off, the pixel is driven by the written electric charge. It has become.

In such a thin film semiconductor device, the peripheral circuits 7 and 8 are constituted by a circuit including a thin film transistor, and the thin film transistor is a thin film field effect transistor having a high mobility polysilicon thin film as an active layer. Some have formed.

[0004]

However, in such a conventional thin film semiconductor device, the thin film transistors of the peripheral circuits 7 and 8 are formed of thin film field effect transistors having a high mobility polysilicon thin film as an active layer. However, there is a problem that the mobility is limited and the mobility cannot be further increased. It is conceivable that the peripheral circuit portions 7 and 8 are formed by thin film bipolar transistors capable of driving a large current. In this case, the emitter region, the base region and the collector region are provided continuously on the same plane. In addition, it is extremely difficult to control the width of the base region, which is considerably narrower than the width of each of the emitter region and the collector region, and there is a problem that the device characteristics vary. There is also a problem that a technique for efficiently forming a thin film bipolar transistor and a thin film field effect transistor on one substrate made of glass or the like has not been established. SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film bipolar transistor which can self-align the width of a base region so that variations in element characteristics are less likely to occur. Another object of the present invention is to provide a thin-film semiconductor device capable of efficiently forming a thin-film bipolar transistor and another thin-film active element on one substrate.

[0005]

According to the first aspect of the present invention,
In a thin film bipolar transistor in which an emitter region, a base region, and a collector region are formed by diffusing impurities into a semiconductor thin film deposited on a substrate, the collector region is constituted by a low-concentration impurity region and a high-concentration impurity region. A base electrode is provided on the low-concentration impurity region through a base insulating film, and the base region is a metal thin film having good etching selectivity with respect to the semiconductor film.
Based on the width of the metal film coated and covering the base region
Thus, the width of the base region is set. According to a second aspect of the present invention, there is provided a thin-film semiconductor device in which thin-film active elements are arranged in a matrix on a substrate, and a peripheral circuit including the thin-film bipolar transistor according to the first aspect is formed on the peripheral substrate. Wherein the semiconductor thin film of the thin film active element and the semiconductor thin film of the thin film bipolar transistor are formed of the same material semiconductor thin film deposited on the substrate at the same thickness.

[0006]

According to the first aspect of the present invention, since the base region is covered with the metal thin film having good etching selectivity with respect to the semiconductor thin film , the width of the base region is self-aligned by the metal thin film . In addition, it is possible to prevent variations in element characteristics. According to the second aspect of the present invention, the semiconductor thin film of the thin film active element and the semiconductor thin film of the thin film bipolar transistor are formed of the same material thin film deposited on the substrate at the same thickness. This makes it possible to use common parts, and as a result, the thin film bipolar transistor and the other thin film active elements can be efficiently formed on one substrate.

[0007]

1 to 13 show a thin film semiconductor device (active matrix panel) to which an embodiment of the present invention is applied.
3 shows the respective manufacturing steps. The structure of a thin-film semiconductor device including a thin-film bipolar transistor for a peripheral circuit portion and a thin-film field-effect transistor for a pixel portion will be described together with the manufacturing method thereof with reference to these drawings in order.

First, as shown in FIG. 1, a polysilicon thin film 1 is formed on the entire upper surface of a single transparent substrate 11 made of glass or the like.
2 is deposited. Next, a photoresist pattern 14 is formed on the upper surface of the polysilicon thin film 12 at a portion corresponding to the thin film field effect transistor forming region 13, and n-type impurities are implanted at a low concentration using the photoresist pattern 14 as a mask. To spread. After that, the photoresist pattern 14 is removed. Next, the thin film bipolar transistor formation region 15 and the thin film field effect transistor formation region 13 are formed by photolithography.
Unnecessary portions of polysilicon thin film 1 other than portions corresponding to
2 is removed by etching to form a polysilicon thin film 16 for forming a thin film bipolar transistor and a polysilicon thin film 17 for forming a thin film field effect transistor, as shown in FIG.

Next, as shown in FIG. 3, an insulating film 21 made of silicon oxide is deposited on the entire surface. This insulating film 21
As will be described later, は will eventually become a base insulating film in a thin film bipolar transistor, and will become a gate insulating film in a thin film field effect transistor. Next, a metal film 22 made of aluminum, chromium, or the like is deposited on the entire surface. As will be described later, this metal film 22 eventually becomes a base electrode in a thin-film bipolar transistor and a gate electrode in a thin-film field-effect transistor. Next, the collector region forming region of the thin film bipolar transistor (the collector region forming region is composed of the collector region forming region 23 having a low impurity concentration and the collector region forming region 24 having a high impurity concentration) and its vicinity. A photoresist pattern 25 is formed on the upper surface of the portion of the metal film 22.
At the same time, a photoresist pattern 27 is formed on the upper surface of the metal film 22 at a portion corresponding to the gate electrode formation region 26 of the thin film field effect transistor. Next, unnecessary portions of the metal film 22 are removed by etching using the photoresist patterns 25 and 27 as a mask, and then the photoresist patterns 25 and 27 are removed, as shown in FIG. The metal film 22 remains only in the portion corresponding to the collector region forming region 23 having a low concentration, the collector region forming region 24 having a high impurity concentration and the vicinity thereof, and only the portion corresponding to the gate electrode forming region 25 of the thin film field effect transistor. The gate electrode 28 is formed by the remaining metal film 22.

Next, as shown in FIG. 5, a photoresist pattern 31 is formed on the entire upper surface of the remaining metal film 22 on the thin film bipolar transistor forming side, and at the same time, a photoresist is formed on the entire surface on the thin film field effect transistor forming side. A pattern 32 is formed. Next, unnecessary portions of the insulating film 21 are removed by wet etching using the photoresist patterns 31 and 32 as a mask. In this case, the wet etching is performed so that the polysilicon thin film 16 on the thin film bipolar transistor forming side exposed by the wet etching is not etched.
Thereafter, when the photoresist patterns 31 and 32 are removed, as shown in FIG. 6, the insulating film 21 remains only under the remaining metal film 22 on the thin-film bipolar transistor forming side, and the insulating film 21 on the thin-film field-effect transistor forming side. Membrane 21
All remain. Next, using the remaining metal film 22 on the side where the thin film bipolar transistor is formed and the gate electrode 28 on the side where the thin film field effect transistor is formed as a mask, p-type impurities are implanted at a low concentration and diffused by laser annealing.
In the state shown in FIG. 4, a p-type impurity may be implanted at a low concentration, and thereafter, a part of the insulating film 21 on the thin-film bipolar transistor formation side may be removed by wet etching.

Next, as shown in FIG. 7, a photoresist pattern 33 is formed on the entire surface on the thin film bipolar transistor forming side, and at the same time, a photoresist pattern 3 is formed around the gate electrode 28 on the thin film field effect transistor forming side.
4 is formed. Next, the photoresist patterns 33, 3
Using p as a mask, p-type impurities are implanted at a high concentration and diffused by laser annealing. After that, the photoresist patterns 33 and 34 are removed. In this state, a portion corresponding to the gate electrode 28 of the polysilicon thin film 17 on the thin film field effect transistor formation side becomes a channel region 17a,
Source / drain regions 17b composed of low-concentration impurity regions are formed on both sides thereof, and source / drain regions 17c composed of high-concentration impurity regions are formed on both outer sides thereof. This is because the thin-film field-effect transistor has an LDD structure, but does not necessarily need to have an LDD structure.

[0012]

As described in the foregoing, according to the first aspect of the invention, since the covering a good metal thin film etch selectivity over the base region with respect to the semiconductor thin film, the gold
By self-aligning the width of the base region with the metal thin film , it is possible to prevent variations in element characteristics from occurring. According to the second aspect of the present invention,
Since the semiconductor thin film of the thin film active element and the semiconductor thin film of the thin film bipolar transistor are formed of the same material thin film deposited on the substrate at the same thickness, a part of the manufacturing process can be shared. Therefore, the thin film bipolar transistor and other thin film active elements can be efficiently formed on one substrate.

Next, as shown in FIG. 9, an insulating film 37 made of silicon oxide is deposited on the entire surface. This insulating film 37
As will be described later, the thin film bipolar transistor eventually becomes a selective etching sidewall for determining the width of a predetermined portion of the base electrode and the base region width controlling metal thin film in the thin film bipolar transistor. It becomes an interlayer insulating film in the effect transistor. Next, a photoresist pattern 38 is formed on the upper surface of the insulating film 37 formed around the gate electrode 28 on the thin film field effect transistor formation side. Next, unnecessary portions of the insulating film 37 are removed by anisotropic etching using the photoresist pattern 38 as a mask.
9 (see FIG. 10), and after removing the photoresist pattern 38, unnecessary portions of the sidewalls are removed by etching. As shown in FIG. 10, the base region formation region 40 of the thin film bipolar transistor is formed. The side wall 41 for selective etching is formed only on the corresponding portion of the metal thin film 36.

Next, as shown in FIG. 10, the side wall 41 for selective etching and the metal thin film 3 at portions corresponding to the base region forming region 40 and the collector region forming region 23 having a low impurity concentration of the thin film bipolar transistor.
A photoresist pattern 42 is formed on the upper surface of the substrate 6, and at the same time, a photoresist pattern 43 is formed on the entire surface on the side where the thin film field effect transistor is formed. Next, unnecessary portions of the metal thin film 36 and the metal film 22 are removed by wet etching using the photoresist patterns 42 and 43 as a mask.
The unnecessary portion of the insulating film 21 is removed by wet etching using the photoresist pattern as a mask, and then the photoresist pattern 4 is removed.
After removing 2, 43, a state as shown in FIG. 11 is obtained. That is, the base insulating film 44 is formed by the insulating film 21 remaining only on the collector region forming region 23 having a low impurity concentration of the thin film bipolar transistor, and the base electrode 45 is formed by the metal film 22 remaining only on the base insulating film 44. The metal thin film 36 formed on the base electrode 45, the base region forming region 40, and the metal thin film 36 remaining between the base electrode 45 and the base region forming region 40 forms a base electrode / base region width controlling metal thin film 46. Further, a gate insulating film 47 is formed by the insulating film 21 on the side where the thin film field effect transistor is formed.

Since the predetermined side surface of the base electrode / base region width controlling metal thin film 46 is covered with the selective etching side wall 41 made of silicon oxide, when the metal thin film 36 is wet-etched, The portion serving as the base region width controlling metal thin film 46 is not etched. Further, since the metal thin film 36 and the insulating film 21 are wet-etched, the exposed polysilicon thin film 16 is not etched by the wet etching. In addition, since the metal thin film 36 is made of a material such as aluminum or chromium having a good etching selectivity with respect to the polysilicon thin film 16, it is desirable that the polysilicon thin film 16 has good characteristics in a thin film transistor using polysilicon as an active layer. An ultra-thin film of about 350 °, which is said to be obtained, can be obtained.
Accordingly, the polysilicon thin film 17 on the side where the thin film field effect transistor is formed can also be formed as an ultrathin film of about 350 °. The width D of the portion of the base electrode / base region width controlling metal thin film 46 in contact with the polysilicon thin film 16 is a value obtained by adding the thickness of the insulating film 37 to the thickness of the metal thin film 36. Since the thickness can be controlled with good controllability, the width D can also be controlled with good controllability.

Next, as shown in FIG. 12, a photoresist pattern 51 is formed on the entire surface on the side where the thin film field effect transistor is formed. Next, n-type impurities are implanted at a high concentration using the photoresist pattern 51 and the base electrode / base region width controlling metal thin film 46 as a mask, and are diffused by laser annealing. After that, the photoresist pattern 5
Remove one. In this state, an emitter region 16a made of a high-concentration impurity region is formed on the left side of the base electrode / base region width control metal thin film 46 of the polysilicon thin film 16 on the thin film bipolar transistor formation side. A base region 16b is formed at a portion in contact with the electrode / base region width controlling metal thin film 46,
A collector region 16c formed of a low-concentration impurity region is formed in a portion of the polysilicon thin film 16 which is in contact with the base insulating film 44, and a high-concentration region is formed in a portion of the polysilicon thin film 16 on the right side of the base electrode / base region width controlling metal thin film 46. A collector region 16d made of an impurity region is formed. In this case, the width of the base region 16b is the width D of the portion of the base electrode / base region width controlling metal thin film 46 in contact with the polysilicon thin film 16, so that self-alignment can be performed. Therefore, it is possible to prevent variations in element characteristics.

Next, as shown in FIG. 13, a photoresist pattern (not shown) is formed on the entire surface on the side where the thin film bipolar transistor is formed, and in this state, a contact is made with the gate insulating film 47 on the side where the thin film field effect transistor is formed. A hole 52 is formed, and a source / drain electrode 5 made of aluminum, chromium, etc.
Form 3 Thus, a thin film semiconductor device including the thin film bipolar transistor for the peripheral circuit portion and the thin film field effect transistor for the pixel portion is completed.

The present invention relates to I ² L (Integrated Injec)
It can also be applied to the Option Logic) structure. Further, the present invention is not limited to the active matrix type liquid crystal display device.
The technique can be applied to a technique of forming an image sensor and a scanning circuit using the same on a single substrate.

[0019]

As described above, according to the first aspect of the present invention, the base region is covered with the thin film made of a material having good etching selectivity with respect to the semiconductor thin film. By self-aligning the width of the base region, it is possible to prevent variations in element characteristics from occurring. According to the second aspect of the present invention, the semiconductor thin film of the thin film active element and the semiconductor thin film of the thin film bipolar transistor are formed by the same material semiconductor thin film deposited on the substrate at the same thickness. Part of the processes can be shared, and the thin film bipolar transistor and other thin film active elements can be efficiently formed on one substrate.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state where an n-type impurity is implanted at a low concentration into a predetermined portion of a polysilicon thin film in manufacturing a thin film semiconductor device (active matrix panel) to which an embodiment of the present invention is applied.

FIG. 2 is a cross-sectional view showing a state in which an unnecessary portion of the polysilicon thin film has been removed in manufacturing the thin film semiconductor device.

FIG. 3 is a cross-sectional view showing a state in which an insulating film, a metal film, and a photoresist pattern are formed in manufacturing the thin film semiconductor device.

FIG. 4 is a cross-sectional view showing a state where an unnecessary portion of the metal film is removed at the time of manufacturing the thin film semiconductor device.

FIG. 5 is a cross-sectional view of a state where a photoresist pattern has been formed during the manufacture of the thin-film semiconductor device.

FIG. 6 is a cross-sectional view showing a state in which p-type impurities are implanted at a low concentration in manufacturing the thin film semiconductor device.

FIG. 7 is a cross-sectional view showing a state where p-type impurities are implanted at a high concentration in manufacturing the thin film semiconductor device.

FIG. 8 is a cross-sectional view showing a state where a metal thin film is formed in manufacturing the thin film semiconductor device.

FIG. 9 is a cross-sectional view showing a state where an insulating film has been formed during the manufacture of the thin-film semiconductor device.

FIG. 10 is a cross-sectional view showing a state where a photoresist pattern is formed in manufacturing the thin film semiconductor device.

FIG. 11 is a cross-sectional view showing a state where unnecessary portions of the metal thin film, the metal film, and the insulating film are removed in manufacturing the thin film semiconductor device.

FIG. 12 is a cross-sectional view showing a state where n-type impurities are implanted at a high concentration in manufacturing the thin film semiconductor device.

FIG. 13 is a sectional view showing a state in which a contact hole and a source / drain electrode are formed in manufacturing the thin film semiconductor device.

FIG. 14 is a diagram showing an example of a circuit configuration of a conventional active matrix panel (thin film semiconductor device).

[Explanation of symbols]

Reference Signs List 11 transparent substrate 16 polysilicon thin film for forming thin film bipolar transistor 16a emitter region 16b base region 16c collector region having low impurity concentration 16d collector region having high impurity concentration 17 polysilicon thin film for forming thin film field effect transistor 44 base insulating film 45 base Electrode 46 Base electrode and metal thin film for controlling base area width

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 29/73 H01L 21/331 H01L 27/06

Claims (2)

(57) [Claims] 1. A thin film bipolar transistor in which an emitter region, a base region and a collector region are formed by diffusing impurities into a semiconductor thin film deposited on a substrate, wherein the collector region is formed by a low concentration impurity region and a high concentration impurity region. configured, provided with a base electrode through a base insulating film on the low concentration impurity regions of this, the base region is covered with a good metallic thin film etch selectivity with respect to the semiconductor film, covering the base region The gold
The width of the base region is set based on the width of the metal thin film.
Thin bipolar transistor, characterized in that that. 2. A thin film semiconductor device in which thin film active elements are arranged in a matrix on a substrate, and a peripheral circuit including the thin film bipolar transistor according to claim 1 is formed on the peripheral substrate. A thin film semiconductor device, wherein the semiconductor thin film of the thin film active element and the semiconductor thin film of the thin film bipolar transistor are formed of semiconductor thin films of the same material deposited on the substrate at the same thickness.