JP2008153673A - Semiconductor device and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device and a method for manufacturing the same capable of forming a transistor having a high current driving ability and a high-voltage withstanding transistor and of easily manufacturing an enhancement type transistor and a depression type transistor on the same substrate. <P>SOLUTION: On an insulating substrate 1, a backing oxide film 2 and an a-Si film 3 are formed, impurity ions are implanted, laser light is irradiated for melting/re-crystallization, and thus a p-type polycrystalline silicon film 3 is formed and machined into an island shape. A gate oxide film 5 and a gate electrode 5e are formed. After a passivation film 6 is formed and a contact hole c for taking out an electrode are formed, the depression type transistor side is coated with a resist material r, impurity ions are implanted into the enhancement type transistor side using the gate electrode 5e as a mask, and thus an n-type source region 7 and a drain region 8 are formed. By the irradiation of laser light, the implanted ion impurities and the crystal damaged at the time of implantation are subjected to the activation and the restoration process, respectively. Next, the resist material r on the depression type transistor side is removed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polycrystalline semiconductor thin film substrate, a semiconductor device, and an electronic device, and in particular, a technique for manufacturing a field effect transistor on a surface layer portion of a polycrystalline film (polycrystalline semiconductor thin film), and a multi-layer for manufacturing the field effect transistor. The present invention relates to an effective technique applied to a manufacturing technique of an electronic device such as a liquid crystal display device and an information processing device incorporating a crystalline semiconductor thin film substrate and the field effect transistor.

  In a liquid crystal display or an organic EL display that performs active matrix driving, it is required to form a pixel transistor and a peripheral driver circuit on the same substrate (including cases where they are formed by the same process even if they are not the same substrate). Yes. Since the liquid crystal drive voltage is higher than that of a normal logic circuit, a transistor with a high breakdown voltage is required. For example, when a semiconductor thin film is formed so that at least a local region on a silicon substrate, a glass substrate, or a plastic substrate has characteristics close to a single crystal, and a thin film transistor is formed in that region, a conventional thin film transistor as shown in FIG. In the transistor structure, the drain breakdown voltage may not increase even when the channel length is increased. Even when the channel length is increased and the drain breakdown voltage can be improved, the transistor size becomes large, so there are many problems such as an increase in load capacitance as well as a problem in layout. In order to solve this problem, LDD (Lightly-Doped-Drain) that relaxes the electric field strength at the drain end by adding a relatively low concentration impurity to the offset region is added to a transistor that requires a high drain breakdown voltage. Although the structure is often used, it may be undesirable because a process for introducing low-concentration impurities is added and the number of manufacturing steps increases.

  On the other hand, the depletion type transistor as shown in FIG. 2 can be manufactured by a small number of steps by itself due to the simplicity of the structure and can have a high drain breakdown voltage, but generally has a low current driving capability and enhancement. When the mold and the depletion mold are formed on the same substrate, there is a problem that the number of manufacturing steps increases because the polarity and concentration of impurities to be doped are different.

In the case of an enhancement-type n-channel MOS transistor, as shown in FIG. 1, a high-concentration n-type (n +) source region 7 and drain region 8 are formed in a p-type p-Si film 3, and the channel region between them is formed. A gate oxide film 5 made of silicon dioxide (SiO ₂ ) and a gate electrode 5e are formed thereon.
Further, the source electrode 7e and the drain electrode 8e are in ohmic contact with the source region 7 and the drain region 8, respectively.
With the above configuration, when the gate voltage Vg> 0 is applied to the gate electrode 5e, the drain current Id does not flow at Vg = 0 (normally off), but when Vg is gradually increased, the channel region becomes an inversion layer. As a result, the drain current Id begins to flow when Vg ≧ Vt (threshold voltage), and the inversion layer spreads and Id increases as Vg is increased.

In the case of a depletion type p-channel MOS transistor, as shown in FIG. 2, a source region 7 and a drain region 8 are formed in a p-type p-Si film 3, and a gate oxide film 5 is formed on the body region therebetween, A gate electrode 5e is formed thereon.
Further, the source electrode 7e and the drain electrode 8e are in ohmic contact with the source region 7 and the drain region 8, respectively.
With the above configuration, when the gate voltage Vg> 0 is applied to the gate electrode 5e, the drain current Id flows (normally on) at Vg = 0, and when Vg is gradually increased, the depletion layer in the body region expands. As the channel becomes narrower and Vg becomes higher, Id decreases.

As described above, a transistor structure having a high current driving capability and a transistor structure having a high drain withstand voltage are formed in a small number of steps on the same substrate (including the case where the same substrate is used to form the same process). It is hoped that.
Although the drain breakdown voltage can be increased by making the transistor have an LDD structure, the number of steps increases. It is difficult to form the two types of transistors at the same time with a small number of steps (for example, the number of steps for manufacturing a transistor having no LDD structure).

  Therefore, the present invention was made to form a transistor having a high current driving capability and a high breakdown voltage transistor, and to make it possible to easily manufacture an enhancement type transistor and a depletion type transistor on the same substrate. is there.

  In order to achieve this object, the present invention is configured as follows.

That is, the semiconductor device of the present invention includes an insulating substrate,
A base oxide film provided on the insulating substrate;
First and second island-shaped recrystallized semiconductor films having the same thickness doped with a first impurity of the same polarity provided on the base oxide film;
An n-channel or p-channel enhancement type transistor having a source region and a drain region having a high impurity concentration opposite to that of the first impurity provided in the first island-shaped recrystallized semiconductor film;
The object is achieved by providing a p-channel or n-channel depletion type transistor which is provided in the second island-shaped recrystallized semiconductor film and which is not doped with an impurity having a polarity opposite to that of the first impurity.

  Further, the first and second island-shaped recrystallized semiconductor films are semiconductor films that are melted and recrystallized.

  The first and second island-shaped recrystallized semiconductor films are characterized in that the impurity concentration has a similar distribution in the film thickness direction.

  In addition, a transistor that requires a high drain withstand voltage is configured by the depletion type transistor, and a transistor that requires a high current driving capability is configured by the depletion type transistor.

An insulating substrate;
A base oxide film provided on the insulating substrate;
An island-shaped recrystallized semiconductor film doped with a first impurity provided on the base oxide film;
And a depletion type transistor which is provided in the island-like recrystallized semiconductor film and which is not doped with an impurity having a polarity opposite to that of the first impurity.

The method for manufacturing a semiconductor device of the present invention includes a step of forming a base oxide film on an insulating substrate,
A step of generating first and second island-shaped recrystallized semiconductor films having the same film thickness by ion-implanting a first impurity having the same polarity with the same impurity concentration on the base oxide film;
Forming a gate oxide film and a gate electrode on the first and second island-shaped recrystallized semiconductor films;
Forming a passivation film on the gate oxide film and the gate electrode;
The first island-shaped recrystallized semiconductor film side on which the passivation film is formed is covered with a resist material, and the second island-shaped recrystallized semiconductor film is doped with an impurity having a polarity opposite to that of the first impurity. Forming a source region and a drain region by ion implantation to a concentration;
The resist material on the first island-shaped recrystallized semiconductor film is removed, electrode metal is formed on the first and second island-shaped recrystallized semiconductor films, and the first island-shaped recrystallized semiconductor is formed. Forming a p-channel or n-channel depletion type transistor in the film and an n-channel or p-channel enhancement type transistor in the second island-like recrystallized semiconductor film,
The above-mentioned purpose is achieved by comprising.

A transistor structure having a high current driving capability and a transistor structure having a high drain breakdown voltage can be simultaneously formed on the same substrate.
Further, according to the method of the present invention, an enhancement type transistor and a depletion type transistor can be manufactured on the same substrate with a small number of steps.

  Embodiments of the present invention will be described below with reference to the drawings.

In order to solve the above problems, a depletion-type structure is used for a transistor that requires a high drain breakdown voltage on the same substrate (including the case where it is formed by the same process even if it is not the same substrate), and has a high current driving capability. An enhancement type structure is preferably used for a transistor that requires a transistor. In this case, in order not to increase the number of manufacturing steps, the structure is the same except for the type (polarity) of impurities implanted into the semiconductor layer and its concentration. For example, the enhancement type structure is the structure shown in FIG. 1, the depletion type structure is the structure shown in FIG. 2, and the thickness of each layer is the same. Further, in order not to increase the number of impurity doping manufacturing steps, the impurity implanted into the semiconductor layer is a depletion type as shown in FIG. 2 when the enhancement type is composed of an n channel as shown in FIG. Is configured with a p-channel, and conversely, when the enhancement type is configured with a p-channel as shown in FIG. 3, the depletion type is configured with an n-channel as shown in FIG. Also, when the impurity concentration of the enhancement type channel region has a distribution in the film thickness direction, the impurity concentration of the depletion type body region has the same distribution in the film thickness direction.
In particular, the enhancement type channel region and the depression type body region can be manufactured without increasing the number of steps by forming impurities of the same polarity with the same concentration distribution (in the same manufacturing process).

FIG. 5 shows a cross-sectional view of a manufacturing process of a semiconductor device embodying the present invention.
In FIG. 5, as shown in (1) to (2), a base oxide film 2 and an a-Si film 3a are formed on an insulating substrate 1, and impurity ions a such as boron are implanted into the base oxide film 2 and a laser. Irradiation with light b melts and recrystallizes to produce a p-type p-Si film 3.
Next, as shown in (3) to (4), a protective oxide film 4 is formed thereon, a resist material r is applied, the pattern is exposed, and the p-Si film 3 is processed into an island shape. Thereafter, the resist material r is removed.
Next, as shown in (5) to (6), a gate oxide film 5 is deposited thereon, a gate electrode 5e is formed thereon, a resist material r is applied, and the pattern is exposed to expose the gate. After the electrode 5e is processed into an island shape, the resist material r is removed.
Next, as shown in (7) to (8), a passivation film 6 is formed thereon, a resist material r is applied, the pattern is exposed, and an electrode extraction contact hole c is formed. The material r is removed.
Next, as shown in (9) to (10), the depletion type transistor side is covered with a resist material r, and impurity ions a such as phosphorus are implanted into the enhancement type transistor side using the gate electrode 5e as a mask to form an n type Source region 7 and drain region 8 are formed.
Further, the laser beam b is irradiated to activate the ion implantation impurity and recover the crystal damaged during the implantation.
Next, as shown in (11) to (12), after removing the depletion type transistor side resist material r, the electrode metal 9 is formed.
Then, a resist material r is applied to expose the pattern, and after the electrode metal 9 is cut into each electrode, the resist material r is removed.

In general, the source and drain of the enhancement type transistor have a high impurity concentration in order to reduce the parasitic resistance of the source and drain. In some cases, impurities are intentionally not added to the channel region, but in general, impurities having a polarity opposite to that doped in the source and drain are doped at a low concentration for threshold voltage control.
Therefore, the concentration of the channel region is often defined by the necessary threshold voltage.
Even in the depletion type, the threshold voltage and drain breakdown voltage vary depending on the concentration of the body region, but the tolerance is relatively wide. Therefore, the depletion type impurity concentration can be defined (same) as the enhancement type impurity concentration. Therefore, the enhancement type and the depletion type can be formed in the same manufacturing process, and a transistor having a high current driving capability and a transistor having a high drain breakdown voltage can be manufactured in the same manufacturing process without increasing the number of steps. This helps reduce manufacturing costs.

An enhancement type transistor having a high current driving capability and a depletion type transistor having a high breakdown voltage are formed by the same manufacturing process. At this time, the impurity concentration in the body region of the depletion type transistor is set to be the same as the enhancement type channel concentration, and the enhancement type threshold voltage is determined to be a desired voltage. The channel concentration dependence of the threshold voltage of enhancement type and depletion type transistors was calculated by device simulation. In the calculation, the impurity concentration of the source and drain was sufficiently high, 1.0E + 20 (cm ⁻³ ), the source electrode and drain electrode were in ohmic contact with the semiconductor layer, and the gate electrode was n ⁺ polysilicon gate.

6 to 9 show channel concentration dependence graphs of Id-Vg characteristics based on the calculation results.
6 and 7 show n-channel and p-channel enhancement type transistors, and FIGS. 8 and 9 show n-channel and p-channel depletion type transistors.
FIG. 10 shows an impurity concentration dependency graph of the drain breakdown voltage of the depletion type transistor based on the calculation result.
As a result, the threshold voltage of the enhancement type transistor can be controlled by the channel concentration (FIGS. 6 and 7), and the depletion type transistor is also operated within this impurity concentration range (FIGS. 8 and 9). ) Can be designed with a high drain breakdown voltage (FIG. 10). From this result, it is possible to form a transistor having a high current driving capability and a high breakdown voltage transistor without increasing the number of steps in the same process.

It is sectional drawing of an enhancement type n channel transistor. It is sectional drawing of a depletion type p-channel transistor. It is sectional drawing of an enhancement type p channel transistor. It is sectional drawing of a depletion type n channel transistor. It is sectional drawing of the manufacturing process of the semiconductor device which implemented this invention. It is an n-channel enhancement type channel concentration dependence graph. It is a channel concentration dependence graph of a p-channel enhancement type. It is a channel concentration dependence graph of n channel depletion type. It is a channel concentration dependence graph of a p-channel depletion type. It is an impurity concentration dependence graph of a depletion type drain breakdown voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Base oxide film 3 p-Si film 3a a-Si film 4 Protective oxide film 5 Gate oxide film 5e Gate electrode 6 Passivation film 7 Source region 7e Source electrode 8 Drain region 8e Drain electrode 9 Electrode metal a Impurity ion b Laser beam c Contact hole for electrode extraction r Resist material

Claims (10)

An insulating substrate;
A base oxide film provided on the insulating substrate;
First and second island-shaped recrystallized semiconductor films having the same thickness doped with a first impurity of the same polarity provided on the base oxide film;
An n-channel enhancement type transistor having a source region and a drain region having a high impurity concentration opposite to that of the first impurity provided in the first island-shaped recrystallized semiconductor film;
A semiconductor device comprising: a p-channel depletion type transistor provided in the second island-shaped recrystallized semiconductor film and not doped with an impurity having a polarity opposite to that of the first impurity. An insulating substrate;
A base oxide film provided on the insulating substrate;
First and second island-shaped recrystallized semiconductor films having the same thickness doped with a first impurity of the same polarity provided on the base oxide film;
A p-channel enhancement type transistor having a source region and a drain region having a high impurity concentration opposite to that of the first impurity provided in the first island-shaped recrystallized semiconductor film;
A semiconductor device comprising: an n-channel depletion type transistor which is provided in the second island-shaped recrystallized semiconductor film and which is not doped with an impurity having a polarity opposite to that of the first impurity. 3. The semiconductor device according to claim 1, wherein the first and second island-shaped recrystallized semiconductor films are melted and recrystallized semiconductor films. 4. The semiconductor device according to claim 1, wherein the first and second island-shaped recrystallized semiconductor films have the same impurity concentration distribution in the film thickness direction. 5. 5. The transistor according to claim 1, wherein a transistor that requires a high drain withstand voltage is configured by the depletion type transistor, and a transistor that requires a high current driving capability is configured by the depletion type transistor. Semiconductor device. An insulating substrate;
A base oxide film provided on the insulating substrate;
An island-shaped recrystallized semiconductor film doped with a first impurity provided on the base oxide film;
A semiconductor device comprising: a depletion type transistor which is provided in the island-shaped recrystallized semiconductor film and which is not doped with an impurity having a polarity opposite to that of the first impurity. Forming a base oxide film on an insulating substrate;
A step of generating first and second island-shaped recrystallized semiconductor films having the same film thickness by ion-implanting a first impurity having the same polarity with the same impurity concentration on the base oxide film;
Forming a gate oxide film and a gate electrode on the first and second island-shaped recrystallized semiconductor films;
Forming an n-channel enhancement type transistor by ion-implanting an impurity having a polarity opposite to that of the first impurity to a high impurity concentration in the second island-shaped recrystallized semiconductor film to form a source region and a drain region; ,
Forming a P-channel depletion type transistor in the first island-like recrystallized semiconductor film without doping the impurity having the opposite polarity to the first impurity as shown in FIG. 5;
A method for manufacturing a semiconductor device comprising: Forming a base oxide film on an insulating substrate;
A step of generating first and second island-shaped recrystallized semiconductor films having the same film thickness by ion-implanting a first impurity having the same polarity with the same impurity concentration on the base oxide film;
Forming a gate oxide film and a gate electrode on the first and second island-shaped recrystallized semiconductor films;
Forming a source region and a drain region by ion-implanting an impurity having a polarity opposite to the first impurity into the second island-shaped recrystallized semiconductor film to a high impurity concentration to form a P-channel enhancement type transistor; ,
Forming an n-channel depletion type transistor in the first island-shaped recrystallized semiconductor film without doping a step of doping an impurity having a polarity opposite to that of the first impurity, as shown in FIG.
A method for manufacturing a semiconductor device comprising: 9. The manufacturing method of a semiconductor device according to claim 7, wherein the first and second island-shaped recrystallized semiconductor films are semiconductor films melted and recrystallized by irradiation with laser light. Method. 9. The semiconductor device according to claim 7, wherein the channel region of the enhancement type transistor and the body region of the depletion type transistor are formed with impurities having the same polarity and having the same concentration distribution in the film thickness direction. Production method.

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