JP3395470B2 - Method for manufacturing thin film semiconductor device - 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 of manufacturing a thin film semiconductor device in which bottom gate type thin film transistors are integrated. More specifically, the present invention relates to a technique for protecting a source region and a drain region provided in a thin film transistor.

[0002]

2. Description of the Related Art A bottom gate type thin film transistor formed in a conventional thin film semiconductor device will be briefly described with reference to FIG. A gate electrode 202 made of metal or doped silicon is patterned on an insulating substrate 201 made of glass or the like. A gate insulating film 203 made of silicon oxide or the like is formed so as to cover the gate electrode 202. On the gate insulating film 203, a semiconductor thin film 204 made of polycrystalline silicon or the like which is patterned in an island shape is formed and becomes an active layer of a bottom gate type thin film transistor. The etching stopper 2 is formed on the semiconductor thin film 204 so as to cover the channel region Ch.
The pattern 05 is formed. The etching stopper 205 is made of, for example, silicon oxide. Further, silicon (doped silicon) containing a high concentration of impurities is formed on the semiconductor thin film 204 and patterned to a predetermined shape to form a source electrode 206 and a drain electrode 207.
To process. The etching stopper 205 protects the channel region Ch located immediately below it when the doped silicon is etched.

[0003]

In the bottom gate type thin film transistor shown in FIG. 5, the surface of the semiconductor thin film 204 is exposed except for the channel region Ch until the source electrode 206 and the drain electrode 207 are formed in the final step. It remains. Therefore, the surface of the semiconductor thin film is etched or oxidized by various processes (resist stripping, resist ashing, etching, plasma film formation, etc.) performed in the subsequent steps. As a result, the thickness of the semiconductor thin film becomes thinner than it should be, causing an increase in source / drain resistance, contact failure with the electrode, plasma damage, etc., which causes characteristic deterioration. In addition, when the semiconductor thin film 204 is doped with impurity ions by ion implantation or ion shower, the surface of the semiconductor thin film is exposed, so that the semiconductor thin film is easily contaminated, and similarly the characteristics of the thin film transistor are deteriorated.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems of the conventional technique, the following means were taken. That is, according to the present invention, the thin film semiconductor device is manufactured by the following steps. First, a gate forming step is performed to form a gate electrode by patterning on an insulating substrate. Next, a semiconductor forming step is performed, a gate insulating film is formed so as to cover the gate electrode, and a semiconductor thin film is further formed thereon to provide an active layer of a bottom gate type thin film transistor. Subsequently, a protection step is performed to form an ion blocking stopper film in alignment with the channel region of the semiconductor thin film defined immediately above the gate electrode, and to protect the surface of the semiconductor thin film from ion permeability. Form a film. Then, a doping process is performed to dope the semiconductor thin film with the stopper film as a mask and through the protective film by accelerating the electric field to form a source region and a drain region of the thin film transistor. After this, the semiconductor thin film is coated with the protective coating.
While physically and chemically protected, the semiconductor thin film
Patterning is performed by applying a
Perform the patterning process to separate into transistors. Preferably,
In the protection process, SiO ₂ is used as a stopper film and a protective film.
And the film thickness ratio of the protective film to the stopper film is 1
Control to / 5 or less. Further, preferably, in the protection step, SiO ₂ having a film thickness of 5 nm to 50 nm is used as a protective film.
More preferably, after the patterning step, the semiconductor thin film is physically and chemically protected by the protective coating.
In, a step after including semiconductors laser annealing process of the thin film, the contact hole opening process of the film formation process and the passivation film of the passivation film.

The present invention includes a method of manufacturing an active matrix type display device. That is, according to the present invention, the active matrix type display device is manufactured by the following steps. First, a gate forming step is performed to form a gate electrode on one insulating substrate by patterning. Next, a semiconductor forming step is performed, a gate insulating film is formed in advance so as to cover the gate electrode, and a semiconductor thin film is further formed thereon to provide an active layer of a bottom gate type thin film transistor. Subsequently, a protection step is performed to form an ion blocking stopper film in alignment with the channel region of the semiconductor thin film defined immediately above the gate electrode, and to protect the surface of the semiconductor thin film from ion permeability. Form a film. Further, a doping process is performed, and the semiconductor thin film is doped with impurity ions by electric field acceleration through the protective film using the stopper film as a mask to form a source region and a drain region of the thin film transistor. Then the semiconductor thin film
In a state of being physically and chemically protected by the protective film,
The semiconductor thin film is subjected to etching treatment and patterning,
Performs a patterning process that separates individual thin film transistors.
U After that, a pixel forming step is performed to connect to the drain region to form a pixel electrode. Finally, the assembly process is performed,
The other insulating substrate on which the counter electrode is formed in advance is bonded to the one insulating substrate through a predetermined gap, and the electro-optical material is arranged in the gap.

According to the present invention, the protective film made of silicon oxide or the like is formed so as to protect the source region and the drain region of the bottom gate type thin film transistor. This prevents contamination during ion doping, improves etching resistance and oxidation resistance in a process performed in a later step, and stabilizes transistor characteristics.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a process diagram showing a method of manufacturing a thin film semiconductor device according to the present invention. First, in step (a), a transparent insulating substrate 1 made of glass, quartz or the like is used.
The gate electrode 2 is patterned on the above. This gate electrode 2 is made of a metal material such as molybdenum or tantalum,
In some cases, the surface may be anodized. So-called doped silicon in which impurities are diffused into silicon at a high concentration to reduce resistance may be used instead of the metal material. Further, a gate insulating film 3 is formed so as to cover the gate electrode 2. The gate insulating film 3 is formed of Si by plasma CVD, for example.
Deposit O ₂ and SiN _x . The gate insulating film 3 can have a single layer structure or a multilayer structure of these insulating materials. A semiconductor thin film 4 made of polycrystalline silicon is formed on the gate insulating film 3. Specifically, after forming amorphous silicon by a plasma CVD method, excimer laser light is irradiated to convert the amorphous silicon into polycrystalline silicon. The excimer laser light is selectively absorbed only by the semiconductor thin film 4 and instantly melts it. Recrystallization occurs during the cooling process and the amorphous silicon is converted into polycrystalline silicon. By using this method, the semiconductor thin film 4 made of high-performance polycrystalline silicon can be formed on the insulating substrate 1 by a low temperature process. Further, an oxide film 5 made of silicon oxide or the like is formed on the semiconductor thin film 4.

In step (b), the oxide film 5 is patterned into a predetermined shape to form the stopper film 6. This stopper film 6 is a semiconductor thin film 4 defined immediately above the gate electrode 2.
The patterning is performed in conformity with the channel region Ch of. Specifically, over-exposure is performed from the back surface of the transparent insulating substrate 1 using the gate electrode 2 as a mask, and a pattern of the stopper film 6 that aligns with the channel region Ch is provided by self-alignment. For example, the photoresist film is patterned by backside exposure, and the oxide film 5 is etched using this as a mask to obtain the stopper film 6. The stopper film 6 has a film thickness sufficient to prevent impurity ions. For example, when doping P + with an accelerating voltage of 100 kV in the subsequent step, the stopper film 6 needs to have a thickness of at least 500 nm. B
If + is doped, a thickness of at least 1500 nm is necessary to block this. In this example, the stopper film 6 is made of an oxide film such as silicon dioxide, but the present invention is not limited to this. The material is not limited as long as it is a film having an ion blocking property. For example, a photoresist can be used as the stopper film. However,
If a photoresist is used, it must be removed after it is used.

Proceeding to step (c), an ion-permeable protective film 7 is formed so as to cover the surface of the semiconductor thin film 4.
For example, an insulating material such as SiO ₂ , SiN _x , and SiNO _x is thinly deposited to form the protective film 7. In this example, the protective film 7
As a film, SiO ₂ having a film thickness of 5 nm to 50 nm is formed.
The protective film 7 needs to have a thickness of at least about 5 nm (preferably 10 nm or more) in order to protect the surface of the semiconductor thin film 4. Further, depending on the acceleration voltage, it is necessary to have a thickness of 50 nm or less in order to guarantee the permeability to impurity ions. In this example, SiO ₂ is used for both the stopper film 6 and the protective film 7. At this time, if the film thickness ratio of the protective film 7 to the stopper film 6 is controlled to ⅕ or less, selective ion doping can be performed with extremely high accuracy. That is,
Impurity ions are doped into the semiconductor thin film 4 by electric field acceleration through the protective film 7 using the stopper film 6 as a mask to form a source region S and a drain region D of the thin film transistor. Stopper film 6 blocked from impurity ions
The channel region Ch will be left immediately below. Ion doping can be performed using an ion implantation device or an ion shower device. In the ion implantation, after the source gas containing impurities is ionized, only the impurity ions that are the target species are extracted by mass separation, and the semiconductor thin film 4 is irradiated with a beam. On the other hand, in the ion shower, the source gas containing impurities is ionized and then subjected to electric field acceleration without being subjected to mass separation to directly irradiate the semiconductor thin film 4 over the entire surface. Ion shower can perform ion doping more efficiently than ion implantation. However, since mass separation is not performed, contaminant ions other than the target species may be doped. In this respect, at least heavy metal ions are blocked by the protective film 7, so that contamination of the source region S and the drain region D can be prevented. Further, after performing ion doping, excimer laser light or the like is irradiated to locally heat the semiconductor thin film 4 to activate the doped impurities.
At this time, by appropriately setting the thickness of the protective film 7 (for example, about 50 nm), it functions as an antireflection film for laser light. Therefore, the energy of the laser light can be efficiently used for activating the impurities. Further, when the laser light irradiation is performed, the semiconductor thin film 4 is instantly melted. At this time, if a large amount of hydrogen or the like is injected into the semiconductor thin film 4 by the ion doping in the previous step, this may cause bumping and so-called ablation. The protective film 7 is effective in preventing this ablation as well.

In step (d), the semiconductor thin film 4 is patterned in an island shape to separate individual thin film transistors into element regions. Due to this island formation, the semiconductor thin film 4 is exposed to an etching process. At this time, the protective film 7 can protect the source region and the drain region D from the etching solution. Further, a passivation film 8 made of silicon oxide or silicon nitride is formed by plasma CVD or the like so as to cover the bottom gate type thin film transistor. After that, after performing a predetermined annealing for hydrogenating the semiconductor thin film 4, a pattern of a contact hole is formed on the passivation film 8 by photolithography. The passivation film 8 and the protective film 7 are etched along this pattern, and contact holes 9 communicating with the source region S and the drain region D are opened.

Finally, in step (e), a metal such as aluminum, molybdenum, titanium, or tungsten is formed on the passivation film 8, and then patterned into a predetermined shape to form the wiring electrode 10. The wiring electrode 10 is connected to the source region S of the thin film transistor via the contact hole described above. Furthermore, the passivation film 8
A transparent conductive film such as ITO is formed on the above, patterned into a predetermined shape by photolithography and etching, and processed into the pixel electrode 11. As described above, the thin film semiconductor device for display is completed. After that, when assembling an active matrix type display panel, another insulating substrate having counter electrodes formed in advance is bonded to the insulating substrate 1 through a predetermined gap, and an electro-optical material such as liquid crystal is provided in the gap. Should be distributed.

As described above, in the present invention, the thin protective film 7 is formed to prevent the semiconductor thin film 4 from being contaminated during ion doping. As the pollution source, aluminum or SUS that constitutes the chamber of the ion implantation apparatus or the ion shower apparatus can be considered. Also, contaminants may be driven directly from the ion source of these devices. Further, by forming the protective film 7, it is possible to prevent the film thickness of the semiconductor thin film from being reduced, contamination, oxidation and the like due to the etching of the source region and the drain region in the subsequent process.

FIG. 2 is a process diagram showing a reference example of a method for manufacturing a thin film semiconductor device. First, in step (a), a gate electrode 21 is formed on an insulating substrate 20, and a gate insulating film 22, a semiconductor thin film 23, and an oxide film 24 are sequentially deposited on the gate electrode 21.
Proceeding to step (b), the oxide film 24 is patterned by photolithography and etching to be processed into the stopper 25 that protects the channel region Ch. Next, ion doping is performed and impurity ions such as P and B are implanted into the semiconductor thin film 23 to form the source region S and the drain region D.
Then, excimer laser light is irradiated to activate the impurities doped in the source region S and the drain region D.
Proceeding to step (c), the semiconductor thin film 23 is patterned in an island shape, and individual thin film transistors are separated for each element region. After forming the passivation film 26, the contact hole 2 is formed by photolithography and etching.
Open 7. Finally, in step (d), the wiring electrode 28 electrically connected to the source region S and the pixel electrode 29 electrically connected to the drain region D are formed by patterning.

However, in the above-described reference example, the source region S and the drain region D are not covered with the protective film, and the semiconductor thin film 23 made of polycrystalline silicon or the like is exposed. Therefore, various problems occur. First
In addition to the impurity ions that are the target species for the semiconductor thin film exposed during ion doping, the material of the internal structure of the ion doping apparatus (aluminum, SUS, etc.)
Is secondarily driven in and pollution occurs. Secondly, since various processes are performed until the bottom gate type thin film transistor is completed, the exposed surface of the semiconductor thin film may be etched or oxidized by a resist stripping agent, an etching solution, plasma at the time of film formation or the like. The damage causes deterioration of the electrical characteristics of the thin film transistor. In the present invention, in order to solve these two problems, the semiconductor thin film is covered with a protective film.

FIG. 3 is a schematic view showing an example of an ion shower device used for ion doping. This ion shower device includes an ion source 52, an acceleration electrode 53, and a chamber 55. An insulating substrate 51 to be ion-doped is placed in the chamber 55. A semiconductor thin film is previously formed on the surface of the insulating substrate 51. The impurity ions 54 radiated from the ion source 52 are accelerated by the electric field by the acceleration electrode 53, and then spread in a shower shape without mass separation to be applied to the surface of the insulating substrate 51. At this time, contaminants other than the target species, such as impurities, may be implanted into the semiconductor thin film. In order to prevent this, according to the present invention, the impurity ions 54 are doped with the surface of the semiconductor thin film covered with a protective film.

Finally, FIG. 4 is a schematic perspective view showing an example of an active matrix display device assembled using the thin film semiconductor device for display manufactured according to the present invention as a driving substrate. As shown in the figure, the active matrix display device has a panel structure including a transparent insulating substrate 101, a transparent opposite insulating substrate 102, and a liquid crystal 103 held between them. The screen portion 10 is provided on the insulating substrate 101.
4 and the peripheral portion are integrally formed. The peripheral portion includes a vertical drive circuit 105 and a horizontal drive circuit 106. or,
A terminal portion 1 for external connection is provided on the upper edge of the peripheral portion of the insulating substrate 101.
07 are formed. The terminal portion 107 is connected to the vertical drive circuit 105 and the horizontal drive circuit 106 via the wiring 108. The screen portion 104 includes gate wirings 109 and signal wirings 110 that intersect in a matrix. A pixel electrode 111 and a thin film transistor 112 for switching and driving the pixel electrode 111 are formed at each intersection. The gate wiring 109 is connected to the vertical driving circuit 105, and the signal wiring 110 is connected to the horizontal driving circuit 106. Thin film transistor 112
The drain region is connected to the corresponding pixel electrode 111, the source region is connected to the corresponding signal wiring 110, and the gate electrode is continuous to the corresponding gate wiring 109.

[0017]

As described above, according to the present invention, the ion blocking stopper film is formed by patterning by joining to the channel region of the semiconductor thin film defined immediately above the gate electrode. An ion-permeable protective coating is formed to cover the surface. Impurity ions are doped into the semiconductor thin film through electric field acceleration through the protective film using the stopper film as a mask to form a source region and a drain region of a bottom gate type thin film transistor. As described above, by performing ion doping through the protective film, it is possible to prevent the semiconductor thin film from being contaminated, stabilize the resistance of the source region and the drain region, and reduce the variation in transistor characteristics. In addition, the etching resistance of the source region and the drain region is improved, the thickness of the semiconductor thin film becomes constant, and the variation in transistor characteristics can be reduced. Further, the contact between the source region and the drain region and the wiring electrode made of metal becomes good.

[Brief description of drawings]

FIG. 1 is a process drawing showing a method of manufacturing a thin film semiconductor device according to the present invention.

FIG. 2 is a process drawing showing a reference example of a method for manufacturing a thin film semiconductor device.

FIG. 3 is a block diagram showing an example of an ion shower device used in the method of manufacturing a thin film semiconductor device according to the present invention.

FIG. 4 is a perspective view showing an example of an active matrix display device assembled using a thin film semiconductor device manufactured according to the present invention.

FIG. 5 is a schematic cross-sectional view showing an example of a conventional thin film semiconductor device.

[Explanation of symbols]

1 Insulation board 2 Gate electrode 3 Gate insulation film 4 Semiconductor thin film 6 Stopper film 7 protective film 8 passivation film 9 contact holes 10 wiring electrodes 11 Pixel electrode

Claims (5)

(57) [Claims] 1. A bottom gate type step of forming a gate electrode on an insulating substrate by patterning, forming a gate insulating film so as to cover the gate electrode, and further forming a semiconductor thin film on the gate insulating film. A step of forming a semiconductor in which an active layer of a thin film transistor is provided, and an ion blocking stopper film is formed by patterning in conformity with a channel region of the semiconductor thin film defined immediately above the gate electrode, and ions covering the surface of the semiconductor thin film are formed. A protective step of forming a transparent protective film, and a doping step of doping the semiconductor thin film with the stopper film as a mask and accelerating electric field through the protective film to form a source region and a drain region of the thin film transistor. , The semiconductor thin film is physically and chemically protected by the protective film.
In the protected state, the semiconductor thin film is etched.
A pattern for patterning and separating into individual thin film transistors.
A thin film semiconductor device manufacturing method, which comprises: 2. The thin film semiconductor according to claim 1, wherein in the protection step, SiO ₂ is used as the stopper film and the protective film, and the film thickness ratio of the protective film to the stopper film is controlled to 1/5 or less. Device manufacturing method. 3. The protective step comprises forming a protective film having a thickness of 5
claim, characterized in that SiO ₂ is used for Nm～50nm 2
A method for manufacturing a thin film semiconductor device according to claim 1. 4. After the patterning step, in a state where the semiconductor thin film is physically and chemically protected by the protective coating, a semiconductor thin film is subjected to laser annealing, a passivation film is formed, and a passivation film is formed. 2. The method for manufacturing a thin film semiconductor device according to claim 1, wherein a post-process including the contact hole opening process is performed. 5. A gate forming step of patterning a gate electrode on one insulating substrate, a gate insulating film is formed so as to cover the gate electrode, and a semiconductor thin film is further formed thereon to form a bottom gate. Forming step of forming an active layer of a thin film transistor, and patterning an ion blocking stopper film in alignment with the channel region of the semiconductor thin film defined immediately above the gate electrode and covering the surface of the semiconductor thin film. And a step of forming a source region and a drain region of the thin film transistor by doping impurity ions into the semiconductor thin film by electric field acceleration through the protective film using the stopper film as a mask. Process and the semiconductor thin film is physically and chemically protected by the protective film.
In the protected state, the semiconductor thin film is etched.
A pattern for patterning and separating into individual thin film transistors.
And a pixel forming step of forming a pixel electrode by connecting to the drain region, and bonding the other insulating substrate on which the counter electrode is formed in advance to the one insulating substrate through a predetermined gap, and A method of manufacturing an active matrix type display device, which comprises an assembly step of disposing an electro-optical material in a gap.