JP2969155B2 - Semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a thin film transistor. 2. Description of the Related Art A semiconductor device having a thin film transistor is irradiated with an amorphous silicon layer formed on a substrate by laser irradiation. All processes to 300
Some of them can be performed at a low temperature of not more than ℃. For example, in the case of an active matrix type liquid crystal display device, a thin film transistor for a driver is formed on a transparent substrate made of glass. In this case, in order to prevent the glass from softening, all process temperatures are set. Is kept below 300 ° C.

By the way, in a semiconductor device having such a structure, a method for forming a gate electrode is restricted in order to suppress all process temperatures to 300 ° C. or lower.

That is, in the method of forming the gate electrode, when the source region and the drain region are formed by ion implantation in the polysilicon layer formed on the substrate, the gate electrode is formed of polysilicon provided corresponding to the channel region of the polysilicon layer. There is a method in which ions are implanted into the gate electrode forming body to form a low-resistance gate electrode, and the implantation of ions into the channel region of the polysilicon layer is prevented by this gate electrode. Since the process temperature for forming the gate electrode forming body is 650 ° C. or higher, this method cannot be adopted. In addition,
It is also conceivable to form a gate electrode formed body with amorphous silicon and convert it to polysilicon by laser irradiation, but in this case, ions can be implanted only into the surface layer of the gate electrode formed body, and the resistance value is high, Therefore, this method cannot be adopted.

Therefore, conventionally, the gate electrode is formed of a low-resistance metal such as aluminum or chromium.

[Problem to be Solved by the Invention] However, in a conventional semiconductor device having such a structure, for example, on a substrate, in addition to a transistor portion, the transistor portion is connected to at least one of a gate electrode, a source electrode, and a drain electrode of the transistor portion. When the connection portion is also formed of a low-resistance metal such as aluminum or chromium, it is necessary to remove oxides, fluorides, and other insulating films on the metal surface in order to improve ohmic contact. There is a problem that the process is troublesome and that the transistor characteristics may be adversely affected.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a semiconductor device which has a simple manufacturing process and does not adversely affect transistor characteristics.

Means for Solving the Problems In order to solve the above problems, the present invention is directed to a semiconductor device in which an amorphous silicon layer is formed by irradiating a laser with a polysilicon layer, and the polysilicon layer is used to form a transistor portion forming polysilicon layer. And a polysilicon layer for the connection portion. The source region and the drain region of the polysilicon layer for the transistor portion and almost the entirety of the polysilicon layer for the connection portion are made impurity regions by ion implantation. While forming the gate electrode, source electrode and drain electrode of the layer with metal,
A connecting layer for connecting the connecting portion polysilicon layer and at least one of a gate electrode, a source electrode, and a drain electrode of the transistor portion forming polysilicon layer is formed of metal.

[Operation] According to the present invention, the connection portion of the transistor portion, which is connected to at least one of the gate electrode, the source electrode, and the drain electrode, is formed by converting amorphous silicon into polysilicon by laser irradiation and then reducing the resistance by ion implantation. Since it is formed by the component polysilicon layer, the connection portion polysilicon layer and the metal connection layer may be connected to each other, and therefore, the ohmic contact can be made favorable without performing surface treatment. The manufacturing process is simple, so that the transistor characteristics are not adversely affected.

Hereinafter, the present invention will be described in detail with reference to examples.

FIGS. 1 to 3 show respective manufacturing steps of a semiconductor device according to an embodiment of the present invention. Therefore, the structure of the semiconductor device will be described together with its manufacturing method with reference to these drawings in order.

First, as shown in FIG. 1, a substrate 1 made of glass or the like is used.
An amorphous silicon layer 2 for forming a transistor portion and an amorphous silicon layer 3 for a connecting portion are formed thereon by a plasma CVD method or a sputtering method at a process temperature of 100 to 300 ° C. for 500 minutes.
A pattern is formed to a thickness of about Å. Next, the channel region 2a of the amorphous silicon layer 2 for forming the transistor portion is formed.
A photoresist 4 is patterned on the upper surface. Then, ion implantation of phosphorus, boron, arsenic, or the like is performed in this state, as shown in FIG. Is turned into an n-plus or p-plus impurity region, and almost the entirety of the amorphous silicon layer 3 for connection is turned into an impurity region. Thereafter, the photoresist 4 is removed. Next, by performing laser irradiation, the amorphous silicon layer 2 for forming the transistor portion and the amorphous silicon layer 3 for connecting portion are converted into polysilicon to form the polysilicon layer 2 for forming transistor portion and the polysilicon layer 3 for connecting portion. at the same time,
Activation occurs to diffuse the ions.

Next, as shown in FIG. 2, a gate insulating film 5 made of silicon oxide is formed on the entire surface to a thickness of about 1000 ° at a process temperature of about 100 ° C. by a sputtering method or the like. next,
A predetermined portion of the gate insulating film 5 is etched to form a contact hole 6 at a portion corresponding to one connection portion of the connection portion polysilicon layer 3. Next, immediately after being immersed in an ammonium fluoride aqueous solution (NH ₄ OH, 40%) for about 10 seconds, the channel region of the polysilicon layer 2 for forming the transistor portion is immediately immersed.
A gate electrode 7 made of aluminum is patterned on the portion of the gate insulating film 5 corresponding to 2a to a thickness of about 1500 ° at a process temperature of about 100 ° C. by sputtering or the like, and a gate electrode connecting layer 8 also made of aluminum is formed. A pattern is formed so as to connect the connection portion polysilicon layer 3 and the gate electrode 7 in the contact hole 6 portion.

Next, as shown in FIG. 3, an interlayer insulating film 9 made of silicon nitride is formed on the entire surface at a process temperature of 250 ° C. to a thickness of 2000 ° by a plasma CVD method or the like. Next, three predetermined portions of the interlayer insulating film 9 are etched to form the source region 2b and the drain region of the polysilicon layer 2 for forming the transistor portion.
Contact holes 11 to 13 are formed in a portion corresponding to 2c and a portion corresponding to the other connection portion of connection portion polysilicon layer 3, respectively. Next, an ammonium fluoride aqueous solution (NH
₄ OH, 40%) for about 10 seconds, a source electrode 14 and a drain electrode 15 made of aluminum are sputtered on the two contact holes 11 and 12 on the side of the polysilicon layer 2 for forming the transistor part. And a source (or drain) electrode connection layer 16 also made of aluminum and another contact hole 13
Connection portion polysilicon layer 3 and source electrode
A pattern is formed so as to connect with 14 (or the drain electrode 15). In this state, the gate electrode 7 and the source electrode
14 (or the drain electrode 15) is connected via the gate electrode connecting layer 8, the connecting portion polysilicon layer 3, and the source (or drain) electrode connecting layer 16. Thus,
A semiconductor device is formed.

As described above, in this semiconductor device, the gate electrode 7 made of aluminum connected to the gate electrode 7 is connected to the gate electrode 7 made of aluminum and the source electrode 14 made of aluminum is connected to the outside of the transistor portion. The connection is made via the connection portion polysilicon layer 3 connected to the gate electrode connection layer 8 and the electrode connection layer 16 made of aluminum connected to the connection portion polysilicon layer 3 and the source electrode 14. Connection part polysilicon layer 3 and gate electrode connection layer 8 made of aluminum
And the source electrode connection layer 16 may be connected, so that the ohmic contact can be made favorable without performing the conventional surface treatment, and thus the manufacturing process is simplified and the transistor characteristics are not adversely affected. be able to.

In the above embodiment, in order to improve the ohmic contact, the ammonium fluoride aqueous solution immersion step is performed for about 10 seconds each immediately before forming the gate electrode 7 and the like. The gate insulating film 5 made of silicon oxide and the interlayer insulating film 9 made of silicon nitride hardly dissolve to about 10 ° or less, so that the transistor characteristics can be prevented from being adversely affected.

In the above embodiment, the gate electrode 7 and the source electrode 14
(Or the drain electrode 15), but the present invention is not limited to this. For example, one of the two connection layers 8 and 16 of the connection portion polysilicon layer 3 may be connected to another IC or the like. In short,
It is sufficient that at least one of the gate electrode 7, the source electrode 14, and the drain electrode 15 is connected to the connection portion polysilicon layer 3.

Furthermore, in the above embodiment, the connection portion polysilicon layer 3 is formed.
Is provided on the substrate 1, but is not limited thereto, and may be provided, for example, on the gate insulating film 5.

[Effects of the Invention] As described above, according to the present invention, the connection portion connected to at least one of the gate electrode, the source electrode, and the drain electrode of the transistor portion is formed by converting amorphous silicon to polysilicon by laser irradiation. Since the connection portion polysilicon layer is formed by ion-implantation and has a low resistance, the connection portion polysilicon layer and the metal connection layer may be connected to each other.Therefore, the ohmic contact can be formed without surface treatment. Thus, the manufacturing process can be simplified and the transistor characteristics can be prevented from being adversely affected.

[Brief description of the drawings]

1 to 3 are cross-sectional views showing respective manufacturing steps of a semiconductor device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Substrate 2, 2 ... Amorphous silicon layer and polysilicon layer for transistor part formation, 2a ... Channel region, 2b ... Source region, 2c ... Drain region, 3 ... Amorphous silicon layer and polysilicon for connection part layer,
5 ... gate insulating film, 7 ... gate electrode, 8 ... gate electrode connection layer, 9 ... interlayer insulating film, 14 ... source electrode, 15
…… Drain electrode, 16 …… Connection layer.

Claims (1)

(57) [Claims] 1. A semiconductor device comprising a polysilicon layer formed by irradiating an amorphous silicon layer with a laser, wherein a polysilicon layer for forming a transistor portion and a polysilicon layer for a connection portion are formed by the polysilicon layer. Almost the whole of the source and drain regions of the forming polysilicon layer and the connecting portion polysilicon layer are made impurity regions by ion implantation, and the gate electrode, source electrode and drain electrode of the transistor portion forming polysilicon layer are made of metal. A semiconductor device, wherein a connection layer connecting the connection portion polysilicon layer and at least one of a gate electrode, a source electrode, and a drain electrode of the transistor portion formation polysilicon layer is formed of metal. .