JPH11330490A - Semiconductor device and its manufacture and electro-optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an HRD with high accuracy and obtain a TFT superior in manufacturing yield and uniformity by a method, wherein an active layer is formed on a substrate, a gate insulating layer is formed on the active layer, and a gate electrode is formed on the insulating film, and the active layer contains a channel region and a high and low resistive impurity regions, and the high resistive impurity is superimposed on the gate electrode. SOLUTION: An active layer is formed on a substrate with a crystalline semiconductor. The active layer is coated with an insulation layer such as a silicon oxide, etc., and further more coated with a material, which can be anode-oxidized such as aluminum, etc., to form a gate electrode and a mask film. When impurity ions are implanted to the active layer, a low resistive impurity region (a source/drain region) is formed in a region where the insulation film does not exist, and moreover a high resistive impurity region (HRD) is formed in a region where it exists. The impurity is not implanted under the gate electrode but forms a channel region. Finally, a silicon oxide film is formed as an interlayer insulator 114 over the entire face, and a source/ drain of an insulating gate type transistor (TFT) is provided, and wiring/electrodes 115, 116 are formed to complete the TFT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulated gate transistor (TFT) formed on an insulating surface such as an insulating material such as glass, or a material obtained by forming an insulating film such as silicon oxide on a silicon wafer, and the like. It relates to a manufacturing method.
The present invention particularly relates to a TFT formed on a glass substrate having a glass transition point (also referred to as strain temperature or strain point) of 750 ° C. or less.
It is effective for The semiconductor device according to the present invention is used for a driving circuit such as an active matrix such as a liquid crystal display, an image sensor, or a three-dimensional integrated circuit.

[0002]

2. Description of the Related Art Conventionally, TFs have been used for driving active matrix type liquid crystal display devices and image sensors.
It is widely known to form a T (thin film transistor). In particular, recently, because of the need for high-speed operation, a crystalline silicon TFT having higher electric field mobility has been developed instead of an amorphous silicon TFT using amorphous silicon for an active layer. However, when higher characteristics and higher durability are required, the semiconductor device has a high-resistance impurity region (high-resistance drain (HRD) or low-concentration drain (LDD)) as used in semiconductor integrated circuit technology. Was needed. However, unlike the known semiconductor integrated circuit technology, the TFT has many problems to be solved. Especially,
Since the element is formed on the insulating surface and the reactive ion anisotropic etching cannot be sufficiently performed, there is a great limitation that a fine pattern cannot be formed.

FIG. 6 shows a conventional HRD.
1 shows a cross-sectional view of a typical process for fabricating a. First, a base film 602 is formed over a substrate 601, and an active layer is formed using crystalline silicon 603. Then, an insulating film 604 is formed on the active layer using a material such as silicon oxide. (FIG. 6 (A))

Next, a gate electrode 605 is formed of polycrystalline silicon (doped with impurities such as phosphorus), tantalum, titanium, aluminum or the like. Further, using this gate electrode as a mask, an impurity element (phosphorus or boron) is introduced by means of ion doping or the like, and a high-resistance impurity region (HRD) with a small doping amount is self-aligned.
606 and 607 are formed on the active layer 603. The active layer region under the gate electrode into which the impurity has not been introduced becomes a channel formation region. Then, the doped impurities are activated by a heat source such as a laser or a flash lamp. (FIG. 6 (B))

Next, an insulating film 608 of silicon oxide or the like is formed by means such as plasma CVD or APCVD.
(C)), and anisotropically etching this to form a side wall 609 adjacent to the side surface of the gate electrode. (FIG. 6D) Then, an impurity element is introduced again by means such as ion doping, and a sufficiently high-concentration impurity region (low-resistance impurity region, source / Drain region) 610,
611 are formed on the active layer 603. Then, the doped impurities are activated by a heat source such as a laser or a flash lamp. (FIG. 6
(E))

Finally, an interlayer insulator 612 is formed, a contact hole is formed in the source / drain region through the interlayer insulator, and a wiring / electrode 613 connected to the source / drain is formed of a metal material such as aluminum.
614 are formed. (FIG. 6 (F))

[0007]

The above method directly follows the conventional LDD fabrication process in a semiconductor integrated circuit, and it is difficult to apply the process directly to a TFT fabrication process on a glass substrate. Alternatively, there is a step that is not preferable in terms of productivity.

First, activation of impurities by irradiation with a laser or the like is required twice. For this reason, productivity decreases. In a conventional semiconductor integrated circuit, activation of an impurity element has been performed by thermal annealing. for that reason,
The activation of the impurities was performed collectively after all the impurity introduction was completed.

However, in particular, TFTs on glass substrates
In this case, it is difficult to perform thermal annealing due to the temperature constraint of the substrate, and it is necessary to rely on laser annealing and flash lamp annealing (RTA or RTP). However, in these methods, since the irradiated surface is selectively annealed, for example, a portion below the sidewall 609 is not annealed. Therefore, annealing is required for each impurity doping.

Second, it is difficult to form a side wall. The thickness of the insulating film 608 is 0.5 to 2 μm. Usually, the thickness of the base film 602 provided on the substrate is 1000 to 3000３.
Therefore, in this etching step, the substrate is often exposed by accidentally etching the base film, and the yield is reduced. Since a substrate used for manufacturing a TFT contains many elements harmful to a silicon semiconductor, it is necessary to avoid such defects as much as possible. It is also difficult to finish the width of the side wall uniformly. This is reactive ion etching (RIE)
This is because, in the case of plasma dry etching such as described above, unlike a silicon substrate used for a semiconductor integrated circuit, delicate control of plasma is difficult because the substrate surface is insulative.

Since the drain of the high-resistance impurity region has a high resistance, it is necessary to make its width as narrow as possible. However, the above-mentioned variation makes mass production difficult. The problem was how to make the process easy to control). In addition, the conventional method requires at least two dopings, but reducing the number of dopings has also been a problem to be solved.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and further simplifies the process to form a high-resistance impurity region and a high-resistance impurity region (high-resistance drain, HRD) thus formed. A TFT having:
Here, the term “high-resistance drain (HRD)” is used to mean that although the impurity concentration is relatively high, the addition of carbon, oxygen, nitrogen, or the like results in the addition of an impurity in addition to the drain having a low impurity concentration and high resistance. It also includes a drain that prevents activation and consequently increases resistance.

[0013]

In forming a high resistance region, the present invention is characterized in that an oxide layer formed by means such as anodic oxidation of a gate electrode is positively used. In particular, the thickness of the anodic oxide can be precisely controlled, and the thickness of the anodic oxide can be as thin as 1000 mm or less.
Since it has a feature that it can be formed uniformly and widely up to a thickness of 000 mm or more, it is preferable as a material that can be substituted for the conventional side wall by anisotropic etching.

In particular, a so-called barrier type anodic oxide is not etched unless it is a hydrofluoric acid-based etchant, whereas a porous type anodic oxide is selectively etched by an etchant such as phosphoric acid. For this reason, TFT
Is characterized in that it can be treated without damaging other materials (for example, silicon and silicon oxide). Further, in both the barrier type and the porous type, the anodic oxide is extremely difficult to be etched by dry etching. In particular, the feature is that the selectivity is sufficiently large in etching with silicon oxide. The present invention is characterized in that a TFT is manufactured by the following manufacturing process. By adopting this process, the HRD can be configured more reliably and the mass productivity can be improved.

[0015]

FIG. 1 shows the basic steps of the present invention. First, a base insulating film 102 is formed on a substrate 101, and an active layer 103 is formed of a crystalline semiconductor (a semiconductor in which a crystal is mixed at least, such as a single crystal, a polycrystal, and a semi-amorphous, is called a crystalline semiconductor in the present invention). ). Then, the insulating film 104 is formed to cover the insulating film 104 by using a material such as silicon oxide, and a film is formed by using a material that can be anodized. Aluminum, tantalum, titanium, silicon, and the like, which can be anodized, are preferable as the material of the coating. In the present invention, a gate electrode having a single layer structure using these materials alone may be used, or a gate electrode having a multilayer structure in which two or more layers are stacked. For example, it has a two-layer structure in which titanium silicide is stacked on aluminum or a two-layer structure in which aluminum is stacked on titanium nitride.
The thickness of each layer may be determined by a practitioner according to the required device characteristics.

Further, a film serving as a mask in anodic oxidation is formed to cover the film, and both are simultaneously patterned and etched to form a gate electrode 105 and a mask film 106 thereon. As a material of the mask film, a photoresist used in a normal photolithography process, a photosensitive polyimide, or a material which can be etched with a normal polyimide may be used.
(Fig. 1 (A))

Next, by applying a current to the gate electrode 105 in an electrolytic solution, a porous anodic oxide 107 is formed on the side surface of the gate electrode. This anodizing step is performed in three steps.
The reaction is performed using an acidic aqueous solution of citric acid or oxalic acid, phosphoric acid, chromic acid, sulfuric acid, or the like of about 20%. It is desirable that the hydrogen ion concentration pH of the solution is less than 2. The optimum pH depends on the type of the electrolytic solution, but is 0.9 to 1.0 in the case of oxalic acid. In this case, 10-30
A thick anodic oxide of 0.5 μm or more can be formed at a low voltage of about V. (FIG. 1 (B))

Then, the insulating film 104 is etched by a dry etching method, a wet etching method, or the like.
This etching depth is arbitrary, and etching may be performed until the underlying active layer is exposed, or may be stopped during the etching. However, from the viewpoint of mass productivity, yield, and uniformity, it is desirable to perform etching up to the active layer. In this case, the anodic oxide 107 and the gate electrode 10
The insulating film having the original thickness is left on the insulating film (gate insulating film) below the region covered with 5. The gate electrode is mainly composed of aluminum, tantalum, and titanium.
When the insulating film 104 contains silicon oxide as a main component,
When the dry etching method is used, if the dry etching is performed using a fluorine-based (for example, NF3, SF6) etching gas, the insulating film 104 made of silicon oxide is used.
Is quickly etched, but the etching rate of aluminum oxide, tantalum oxide, and titanium oxide is sufficiently small, so that the insulating film 104 can be selectively etched.

In wet etching, 1
A hydrofluoric acid-based etchant such as / 100 hydrofluoric acid may be used. In this case as well, the insulating film 104 made of silicon oxide is quickly etched, but the etching rate of aluminum oxide, tantalum oxide, and titanium oxide is sufficiently small, so that the insulating film 104 can be selectively etched. (Figure 1
(D))

Thereafter, the anodic oxide 107 is removed. As the etchant, a phosphoric acid-based solution, for example, a mixed acid of phosphoric acid, acetic acid, and nitric acid is preferable. However, for example, when a gate electrode is made of aluminum, if a phosphoric acid-based etchant is used, the gate electrode is also etched at the same time. Therefore, in the present invention, by applying a current to the gate electrode in an ethylene glycol solution containing 3 to 10% of tartaric acid, boric acid, and nitric acid in the previous step, the side surface of the gate electrode and It is preferable to provide a barrier type anodic oxide 108 on the upper surface. In this anodic oxidation step, the pH of the electrolytic solution may be 2 or more, preferably 3 or more, and more preferably 6.9 to 7.1. In order to obtain such a solution, it is preferable to neutralize using an alkaline solution such as ammonia. The thickness of the obtained anodic oxide is determined by the magnitude of the voltage applied between the gate electrode 105 and the opposing electrode.

It should be noted that although barrier-type anodic oxidation is a later step, barrier-type anodic oxide is not formed outside the porous anodic oxide, but barrier-type anodic oxidation is performed. The object 108 is to be formed between the porous anodic oxide 107 and the gate electrode 105. In the above phosphoric acid-based etchant, the etching rate of the porous anodic oxide is 10 times or more the etching rate of the barrier anodic oxide. Therefore, the barrier type anodic oxide 108 is not substantially etched by the phosphoric acid-based etchant, so that the inner gate electrode can be protected. (Fig. 1 (C), (E))

Through the above steps, a structure in which a part of the insulating film 104 (hereinafter, referred to as a gate insulating film) selectively remains below the gate electrode can be obtained. Since the gate insulating film 104 ′ originally existed under the porous anodic oxide 107, the gate insulating film 104 ′ was formed not only under the gate electrode 105 and under the barrier anodic oxide 108 but also at the barrier anodic oxide 108. , And a width y thereof is characterized by being determined in a self-aligned manner. In other words, a region where the gate insulating film 104 'exists and a region where the gate insulating film 104' does not exist are formed in a self-alignment manner outside the channel formation region under the gate electrode in the active layer 103.

When ions of N-type or P-type impurities accelerated by this structure are implanted into the active layer, many ions are implanted into the region where the insulating film 104 does not exist (or is thin), and the (relatively) high ion is implanted. Concentration impurity regions (low resistance impurity regions) 110 and 113 are formed. On the other hand, in a region where the gate insulating film 104 ′ is present, ions are implanted into the gate insulating film, and only ions transmitted therethrough are implanted into the semiconductor. Low-concentration impurity regions (high-resistance impurity regions) 111;
112 is formed. Low concentration impurity regions 111, 11
The difference in impurity concentration between the second impurity region 110 and the high-concentration impurity regions 110 and 113 depends on the thickness of the insulating film 104 and the like, but is usually 0.5 to 3 digits, and the former is smaller. Further, substantially no impurity is implanted into the region below the gate electrode, and the region is kept in an intrinsic or substantially intrinsic state, that is, a channel formation region. After the impurity is implanted, the impurity may be activated by irradiating it with a laser beam or a strong light equivalent thereto. However, it is needless to say that substantially one step is sufficient. (FIG. 1 (E))

As described above, the present invention is characterized in that the width of the high-resistance impurity region is controlled in a self-aligned manner by the thickness y of the anodic oxide 107. Further, the end 109 of the gate insulating film 104 'and the high resistance region (HRD) 112
Can be substantially matched. In the conventional method shown in FIG. 6, it is extremely difficult to control the width of the side wall which plays such a role. However, in the present invention, the width of the anodic oxide 107 is determined by the anodic oxidation current (charge amount). Therefore, extremely delicate control is possible.

Further, as is apparent from the above-mentioned steps, even if the impurity doping step is performed substantially once, a low-resistance region and a high-resistance region can be formed. Only one process is required. Thus, in the present invention, mass productivity can be improved by reducing the steps of doping and activation. Conventionally, HRD has a problem that it is difficult to make an ohmic contact with an electrode because of its large resistance, and that the resistance lowers the drain voltage. However, on the other hand, due to the presence of the HRD, the generation of hot carriers can be suppressed and high reliability can be obtained. The present invention solves this contradictory problem at a time, and can obtain a 0.1-1 μm-wide HRD formed in a self-aligned manner and ohmic contact with the source / drain electrodes.

In the present invention, the positional relationship between the end of the gate electrode and the impurity region can be arbitrarily changed by appropriately utilizing the thickness of the anodic oxide 108 in FIG.
This example is shown in FIG. For example, in a method in which ions are implanted without substantial mass separation, such as an ion doping method (also referred to as plasma doping), since the angle of entry of ions varies, there is also considerable spread of impurities in the lateral direction. In other words, it is expected that the spread in the horizontal direction will be as large as the addition of ions. In the following example, the active layer 4
04 is 800 mm thick.

Therefore, as shown in FIG. 4A, the thickness (for example, 800 °) of the anodic oxide 402 (corresponding to FIGS. 1 and 108) is substantially the same as that of the active layer 404 outside the metal gate electrode 401. If the thickness is almost the gate electrode 4
01 and the end 40 of the high-resistance impurity region 407.
6 do not overlap and do not separate. FIG.
The thickness of the anodic oxide 402 is, for example, 30 as shown in FIG.
In the case where the thickness is larger than 00 ° and the thickness of the active layer is 800 °, the end 405 of the gate electrode and the end 406 of the high-resistance impurity region are formed.
Are offset from each other. Conversely, when the thickness of the anodic oxide 402 is reduced as shown in FIG. 4C, the gate electrode and the high-resistance impurity region overlap each other. This overlap is maximum when no anodic oxide exists around the gate electrode 401 as shown in FIG.

Generally, in an offset state, a reverse leakage current is reduced and an on / off ratio is improved. For example, a TFT (pixel TFT) used for controlling pixels of an active matrix liquid crystal display has a feature. It is suitable for applications that require low leakage current. However, the hot carriers generated at the end of the HRD are trapped by the anodic oxide,
It also has the disadvantage of deterioration.

In the overlapping state, the deterioration due to the hot carrier trap as described above is reduced, and the on-current is increased, but the leakage current is disadvantageously increased. For this reason, a TFT (driver TF) used for an application requiring a large current driving capability, for example, a peripheral circuit of a monolithic active matrix.
T) is suitable. Fig. 4 (A) shows the TFT actually used.
Which of (D) to (D) should be determined depending on the use of the TFT.

[0030]

[Embodiment 1] FIG. 1 shows this embodiment. First, a substrate (Corning 7059, 300 mm × 400 m
A silicon oxide film having a thickness of 1000 to 3000 ° was formed as a base oxide film 102 on the (m or 100 mm × 100 mm) 101. As a method for forming this oxide film, a sputtering method in an oxygen atmosphere was used. However, in order to further improve mass productivity, a film in which TEOS is decomposed and deposited by a plasma CVD method may be used.

Thereafter, an amorphous silicon film is deposited in a thickness of 300 to 5000 °, preferably 500 to 1000 ° by a plasma CVD method or an LPCVD method.
The crystals were left to stand in a reducing atmosphere at 24 ° C. for 24 hours to be crystallized.
This step may be performed by laser irradiation.
Then, the silicon film crystallized in this manner was patterned to form the island-like region 103. Further, a silicon oxide film 104 having a thickness of 700 to 1500 ° was formed thereon by sputtering.

Thereafter, aluminum having a thickness of 1000 to 3 μm (1 wt% of Si or 0.1 to 0.3 wt.
% Of Sc (scandium) film was formed by electron beam evaporation or sputtering. Then, a photoresist (for example, OFPR800 / 3 manufactured by Tokyo Ohka)
0 cp) by spin coating. Before the formation of the photoresist, a thickness of 100 to 1
If an aluminum oxide film of 2,000 mm is formed on the surface, adhesion to the photoresist is good, and current leakage from the photoresist is suppressed, so that a porous anodic oxide can be formed in the subsequent anodic oxidation step. Was effective in forming only on the side surface. Thereafter, the photoresist and the aluminum film are patterned and etched together with the aluminum film to form the gate electrode 105 and the mask film 10.
6. (Fig. 1 (A))

Further, anodization is performed by passing an electric current through the electrolytic solution to a thickness of 3000 to 6000 °, for example, a thickness of 50
An anodic oxide 107 of 00 ° was formed. Anodizing is 3
Using an aqueous acidic solution such as citric acid or oxalic acid, phosphoric acid, chromic acid, sulfuric acid, etc.
What is necessary is just to apply a constant current of V to the gate electrode. In this example, the voltage was set to 10 V in an oxalic acid solution (30 ° C.) having a pH of 0.9 to 1.0, and anodization was performed for 20 to 40 minutes. The thickness of the anodic oxide was controlled by the anodic oxidation time. (FIG. 1 (B))

Next, the mask was removed, and a current was again applied to the gate electrode in the electrolytic solution. This time, 3-1
PH = 6.9 ~ containing 0% tartaric acid, boric acid and nitric acid
An ethylene glycol ammonia solution of 7.1 was used.
A better oxide film was obtained when the temperature of the solution was lower than room temperature around 10 ° C. Therefore, a barrier-type anodic oxide 108 was formed on the upper surface and side surfaces of the gate electrode. The thickness of the anodic oxide 108 is proportional to the applied voltage.
At 2,000 V anodized oxide was formed. The thickness of the anodic oxide 108 was determined by the required offset and the size of the overlap as shown in FIG.
250 V to obtain an anodic oxide with a thickness of 3000 mm or more
Since the above high voltage is required and adversely affects the characteristics of the TFT, it is preferable that the thickness be 3000 mm or less.
In this embodiment, the voltage was increased to 80 to 150 V, and the voltage was selected according to the required thickness of the anodic oxide film 108. (Fig. 1 (C))

Thereafter, the silicon oxide film 104 was etched by a dry etching method. In this etching, a plasma mode of isotropic etching or a reactive ion etching mode of anisotropic etching may be used. However, it is important to prevent the active layer from being etched deeply by sufficiently increasing the selectivity between silicon and silicon oxide. For example, if CF4 is used as an etching gas, the anodic oxide is not etched, and only the silicon oxide film 104 is etched. Also,
The silicon oxide film 104 'under the porous anodic oxide 107 remained without being etched. (Fig. 1 (D))

Thereafter, the anodic oxide 107 was etched using a mixed acid of phosphoric acid, acetic acid and nitric acid. In this etching, only the anodic oxide 107 was etched, and the etching rate was about 600 ° / min. The gate insulating film 104 'thereunder remains as it is. Then, an impurity is implanted into the active layer 103 of the TFT in a self-aligned manner by using the gate electrode portion (that is, the gate electrode and the anodic oxide film around the gate electrode) and the gate insulating film as a mask by the ion doping method. Source / drain region) 11
0, 113 and high resistance impurity regions 111, 112 were formed. Since phosphine (PH3) was used as the doping gas, an N-type impurity region was formed. Diborane (B2H6) may be used as a doping gas to form a P-type impurity region. The dose is 5 × 1014 to 5
× 1015cm-2, acceleration energy 10-30ke
V. Thereafter, a KrF excimer laser (wavelength 2
Irradiation of 48 nm with a pulse width of 20 nsec) was performed to activate the impurity ions introduced into the active layer.

According to the result of SIMS (Secondary Ion Mass Spectrometry), the impurity concentration of the regions 110 and 113 is 1 × 10
20 to 2 × 10 21 cm −3, and 1 × 10 17 to 2 × 10 18 cm −3 in the regions 111 and 112. In terms of dose amount, the former is 5 × 1014 to 5 × 1015 cm −
2. The latter was 2 × 1013 to 5 × 1014 cm−2. This difference is caused by the presence or absence of the gate insulating film 104 '. In general, the impurity concentration of the low-resistance irregular region is 0.5% higher than that of the high-resistance impurity region.
Up to three orders of magnitude. (FIG. 1 (E))

Finally, an interlayer insulator 114 is formed on the entire surface.
A silicon oxide film having a thickness of 3000 was formed by the CVD method. Contact holes were formed in the source / drain of the TFT, and aluminum wiring / electrodes 115 and 116 were formed. Further, hydrogen annealing was performed at 200 to 400 ° C. Thus, the TFT was completed. (Figure 1
(F))

FIG. 5A shows an example in which a plurality of TFTs are formed on one substrate by using the method shown in FIG. In this example, three TFTs 1 to 3 were formed. TFT
1 and 2 are used as driver TFTs, and oxides 501 corresponding to the anodic oxide 108 in FIG.
The thickness of the gate electrode 502 and the high-resistance region (HR) are slightly reduced to a thickness of 200 to 1000 °, for example, 500 °.
D) overlapped. In the figure, TF
Connecting the drain of T1 and the source of TFT2 to each other,
In addition, an example is shown in which the source of the TFT 1 is grounded and the drain of the TFT 2 is connected to a power source to form a CMOS inverter. There are various other circuits as the peripheral circuit, and such a CMOS circuit may be used according to the specifications of each.

On the other hand, the TFT 3 is used as a pixel TFT. The thickness of the anodic oxide 503 is increased to 2000.degree. To set an offset state (corresponding to FIG. 4B) to suppress a leak current. One of the source / drain electrodes of the TFT 3 is connected to the pixel electrode 501 of ITO. In order to change the thickness of the anodic oxide in this manner, it is necessary to use the respective TFs.
What is necessary is just to separate so that the voltage of the gate electrode of T may be controlled independently. Note that TFT1 and TFT3 are N-channel TFTs, and TFT2 is a P-channel TFT.

Embodiment 2 FIG. 2 shows this embodiment. First, a substrate having an insulating surface (for example, Corning 705)
9) Using the steps (A) and (B) of Example 1 on the base 201, the base oxide film 202, the island-like silicon semiconductor region (for example, crystalline silicon semiconductor) 203, the silicon oxide film 204, and the aluminum film ( A gate electrode 205 having a thickness of 200 nm to 1 μm) and a porous anodic oxide (thickness of 3000 to 1 μm, for example, 5000 °) 206 are formed on side surfaces of the gate electrode 205. (FIG. 2 (A)) Then, similarly to the first embodiment, the thickness of the barrier mold is 1000-2.
A 500 ° anodic oxide 207 was formed. (Figure 2
(B))

Further, using the porous anodic oxide 206 as a mask, the silicon oxide film 204 was etched to form a gate insulating film 204 '. After that, the barrier type anodic oxide film 2
07, the porous anodic oxide film 206 was removed by etching. Thereafter, the gate electrode portions (205, 20)
7) and impurity implantation is performed by ion doping using the gate insulating film 204 ′ as a mask to form the low-resistance impurity regions 208 and 211, the high-resistance impurity regions 209 and 2.
10 was formed. Dose amount is 1-5 × 1014cm-
2. The acceleration voltage was 30 to 90 kV. Phosphorus was used as an impurity. (Fig. 2 (C))

Further, a coating of an appropriate metal, for example, titanium, nickel, molybdenum, tungsten, platinum, palladium, etc., for example, a titanium film 212 having a thickness of 50 to 500.degree. As a result, the metal film (here, titanium film) 212 was formed in close contact with the low-resistance impurity regions 208 and 211. (Figure 2
(D))

Then, a KrF excimer laser (wavelength: 248 nm, pulse width: 20 nsec) is irradiated to activate the doped impurities and cause a metal film (here, titanium) to react with silicon of the active layer, thereby forming a metal silicide ( Here, regions 213 and 214 of (titanium silicide) were formed.
Laser energy density is 200-400mJ / cm
2, preferably 250 to 300 mJ / cm2. When the laser is irradiated, the substrate is 200 to 500
By heating to ℃, the peeling of the titanium film could be suppressed.

In this embodiment, an excimer laser is used as described above, but it goes without saying that another laser may be used. However, when using a laser, a pulsed laser is preferred. In the case of a continuous wave laser, the irradiation time is long, and there is a risk that an object to be irradiated is separated by expansion due to heat.

As for the pulse laser, Nd: YAG
Infrared laser such as laser (preferably Q-switched pulse oscillation) and its visible light such as its second harmonic, Kr
Various ultraviolet lasers using excimers such as F, XeCl, and ArF can be used. However, when laser irradiation is performed from the upper surface of the metal film, it is necessary to select a laser having a wavelength that is not reflected by the metal film. However, there is almost no problem when the metal film is extremely thin. Further, the laser light may be applied from the substrate side. In this case, it is necessary to select a laser beam that passes through the underlying silicon semiconductor film.

The annealing may be performed by lamp annealing by irradiation of visible light or near infrared light.
When lamp annealing is performed, the surface to be irradiated is 600
The lamp irradiation is performed for several minutes at 600 ° C. and for several tens of seconds at 1000 ° C. so that the temperature becomes about 1000 ° C. Annealing with near-infrared rays (for example, 1.2 μm infrared rays) selectively absorbs near-infrared rays into silicon semiconductors and does not heat the glass substrate so much. It can be suppressed and is extremely useful.

Thereafter, the Ti film was etched with an etching solution in which hydrogen peroxide, ammonia and water were mixed at a ratio of 5: 2: 2. The titanium film (for example, the titanium film existing on the gate insulating film 204 and the anodic oxide film 207) other than the portion in contact with the exposed active layer remains in a metal state as it is, but can be removed by this etching. On the other hand, titanium silicides 213 and 214, which are metal silicides, are not etched and can be left. (FIG. 2 (E))

Finally, as shown in FIG. 2 (F), a silicon oxide film having a thickness of 2000-1 μm, for example 3000 μm, is formed on the entire surface as an interlayer insulator 217 by the CVD method, and contact is made with the source / drain of the TFT. A hole is formed and aluminum wiring / electrodes 218 and 219 are
It was formed to a thickness of 0-1 μm, for example, 5000 °. In the present embodiment, the portion contacted by the aluminum wiring is titanium silicide, and the stability of the interface with aluminum is better than that of silicon, so that a highly reliable contact was obtained. The aluminum electrode 21
8 and 219 and the silicide regions 213 and 214, for example, titanium nitride is further formed as a barrier metal.
Reliability can be improved. In this example, the sheet resistance in the silicide region was 10 to 50 Ω / □. On the other hand, in the high-resistance impurity regions 209 and 210, 10 to 100
kΩ / □, resulting in good frequency characteristics and
TF with little hot carrier degradation even at high drain voltage
T could be produced.

In this embodiment, the low-resistance impurity region 211 and the metal silicide region can be made to substantially coincide with each other. In particular, the end 215 of the gate insulating film 204 'and the high-resistance impurity region 2
10 and the boundary 216 between the low-resistance impurity region 211 and the end portion 215 and the metal silicide region 214 at the same time.
4 (A) to 4 (D) as a result of substantially matching the end portions of FIG.
It is clear that the low-resistance impurity region in the above may be replaced with a metal silicide region.

FIG. 5B shows an example in which a plurality of TFTs are formed on one substrate by using the technique shown in FIG. In this example, three TFTs 1 to 3 were formed. TFT
1 and 2 are CMOS-structured driver TFTs, here used as inverter structures.
The thickness of the oxides 505 and 506 corresponding to the anodic oxide 207 was made as thin as 200 to 1000 Å, for example, 500 Å so as to slightly overlap each other. on the other hand,
The TFT 3 is used as a pixel TFT. The thickness of the anodic oxide 503 was increased to 2000 ° to set an offset state, thereby suppressing a leak current. One of the source / drain electrodes of the TFT 3 is connected to the pixel electrode 502 of ITO. In order to change the thickness of the anodic oxide in this manner, it is necessary to separate the anodic oxide so that the voltage of the gate electrode of each TFT can be controlled independently. Note that TFT1 and TF
T3 is an N-channel type TFT, TFT2 is a P-channel type T
FT.

In this embodiment, the step of forming a titanium film is provided after the step of ion doping, but the order may be reversed. In this case, since the titanium film covers the entire surface at the time of ion irradiation, the effect is large in preventing abnormal charging (charge-up) which has become a problem in the insulating substrate. After the ion doping, annealing may be performed by a laser or the like, and then a titanium film may be formed. Then, titanium silicide may be formed by irradiation with a laser or the like or thermal annealing.

Embodiment 3 FIG. 3 shows this embodiment. First, a base oxide film 302, an island-shaped crystalline semiconductor region, for example, a silicon semiconductor region 303, a silicon oxide film 304, are formed on a substrate (Corning 7059) 301 by using the steps (A) and (B) of the first embodiment. Aluminum film (thickness 2000mm ~ 1)
μm), and a porous anodic oxide (thickness 6000 °) 306 was formed on the side surface of the gate electrode 305. (FIG. 3 (A)) Then, as in Example 1, a barrier-type anodic oxide 307 having a thickness of 1000 to 2500 ° was formed. (FIG. 3 (B))

Further, using the porous anodic oxide 306 as a mask, the silicon oxide film 304 was etched to form a gate insulating film 304 '. Then, the porous anodic oxide 30
6 was selectively etched to expose a part of the gate insulating film 304 '. Thereafter, an appropriate metal, for example, a titanium film 308 having a thickness of 50 to 500 ° was formed on the entire surface by sputtering. (FIG. 3 (C)) and Kr
F excimer laser (wavelength 248 nm, pulse width 20
nsec) to react titanium with silicon in the active layer, thereby forming titanium silicide regions 309 and 310. The energy density of the laser was 200 to 400 mJ / cm2, preferably 250 to 300 mJ / cm2.
In addition, when the substrate was heated to 200 to 500 ° C. during laser irradiation, peeling of the titanium film could be suppressed. This step may be performed by lamp annealing by irradiation with visible light or near infrared light.

Thereafter, the Ti film was etched with an etching solution in which hydrogen peroxide, ammonia and water were mixed at a ratio of 5: 2: 2. The titanium film (for example, the titanium film present on the gate insulating film 304 'and the anodic oxide film 307) other than the portion in contact with the exposed active layer remains in a metal state as it is, but can be removed by this etching. On the other hand, titanium silicide 3
Since 09 and 310 are not etched, they can be left. (FIG. 3 (D))

Thereafter, impurities are implanted by ion doping using the gate electrode portion and the gate insulating film 304 as a mask to form low resistance impurity regions (titanium silicide regions) 311, 314 and high resistance impurity regions 312, 313.
Was formed. The dose was 1 to 5 × 10 14 cm −2, and the acceleration voltage was 30 to 90 kV. Phosphorus was used as an impurity. (FIG. 3 (E))

Then, a KrF excimer laser (wavelength: 248 nm, pulse width: 20 nsec) was irradiated again to activate the doped impurities. This step may be performed by lamp annealing by irradiation with visible light or near infrared light. Finally, the gate insulating film 30 is formed using the gate electrode portions (305, 307) as a mask.
4 'was etched. This was performed to avoid instability due to impurities doped in the gate insulating film 304 '. As a result, the gate insulating film 304 ″ remained only under the gate electrode.

Then, as shown in FIG. 3 (F), a silicon oxide film having a thickness of 6000 mm is formed on the entire surface as an interlayer insulator 315 by the CVD method, contact holes are formed in the source / drain of the TFT, and aluminum wiring is formed.・ Electrode 3
16, 317 were formed. Through the above steps, the TFT
Was completed.

[0059]

According to the present invention, a high-resistance impurity region (HRD) can be formed by substantially one doping, one laser annealing, and an activation process such as RTA. The shortening of this process enhances mass productivity, and TF
This is effective in reducing the amount of investment in the T production line.
Further, in the present invention, since the width of the HRD is formed with extremely high precision, a TFT having excellent yield and uniformity can be obtained.

In the present invention, in order to further improve the characteristics, more doping, laser annealing and RTA may be performed, and the number of times of doping, laser annealing and RTA is necessarily limited to one. Not something. It is needless to say that the TFT of the present invention is formed in the same manner when a three-dimensional integrated circuit is formed on a substrate on which a semiconductor integrated circuit is formed, or when formed on glass or an organic resin. Are formed on the insulating surface in any case. In particular, the effect of the present invention is remarkable for an electro-optical device such as a monolithic active matrix circuit having peripheral circuits on the same substrate.

In the present invention, in addition to ion implantation or ion doping of P or N type impurities, carbon,
Oxygen and nitrogen may be added simultaneously. Thus, the reverse leakage current is reduced, and the withstand voltage is improved. For example, it is effective when used as a pixel TFT of an active matrix circuit. In this case, the thickness of the anodic oxide layer of TFT3 in FIG. 5 can be the same as that of TFT1 and TFT2.

[Brief description of the drawings]

FIG. 1 shows a method for manufacturing a TFT according to Example 1.

FIG. 2 shows a method for manufacturing a TFT according to a second embodiment.

FIG. 3 shows a method for manufacturing a TFT according to a third embodiment.

FIG. 4 shows the relationship between offset and overlap in the present invention.

FIG. 5 shows an example of a TFT integrated circuit obtained by Examples 1 and 2.

FIG. 6 shows a method for manufacturing a TFT according to a conventional method.

[Explanation of symbols]

Reference Signs List 101 Insulating substrate 102 Base oxide film (silicon oxide) 103 Active layer (crystalline silicon) 104 Insulating film (silicon oxide) 104 'Gate insulating film 105 Gate electrode (aluminum) 106 Mask film (photoresist) 107 Anodic oxide (porous) Aluminum oxide) 108 anodic oxide (barrier type aluminum oxide) 109 end of gate insulating film 110, 113 low resistance impurity region 111, 112 high resistance impurity region (HRD) 114 interlayer insulating film (silicon oxide) 115, 116 metal wiring -Electrode (aluminum) 117 Boundary between low-resistance impurity region and high-resistance impurity region

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Hideto Onuma 398 Hase, Hase, Atsugi-shi, Kanagawa Prefecture Inside the Semi-Conductor Energy Laboratory Co., Ltd. (72) Inventor Hideomi Suzawa 398 Hase, Atsugi-shi, Kanagawa Prefecture Inside Semi-Conductor Energy Laboratory Co., Ltd. 398 Hase, Atsugi City, Kanagawa Pref.

Claims (7)

[Claims] An active layer formed on a substrate; a gate insulating film formed on the active layer; and a gate electrode formed on the gate insulating film. Comprises a channel forming region, a high-resistance impurity region adjacent to the channel forming region, and a low-resistance impurity region adjacent to the high-resistance impurity region facing the channel forming region; Is a semiconductor device provided so as to overlap with the gate electrode. 2. The semiconductor device according to claim 1, wherein a concentration of the impurity element imparting conductivity included in the high-resistance impurity region is lower than a concentration of the impurity element included in the low-resistance impurity region. Semiconductor device. 3. An electro-optical device comprising the semiconductor device according to claim 1. 4. At least a driving circuit and a pixel T on a same substrate.
An electro-optical device having an FT, wherein at least one TFT forming the drive circuit includes: an active layer; a gate insulating film formed on the active layer;
A gate electrode formed on the gate insulating film, wherein the active layer faces the channel formation region, a high-resistance impurity region adjacent to the channel formation region, and the channel formation region. And a low-resistance impurity region adjacent to the high-resistance impurity region, wherein the high-resistance impurity region is provided so as to overlap the gate electrode. 5. The electro-optical device according to claim 4, wherein the at least one TFT forming the driving circuit is an N-channel TFT. 6. The pixel TFT according to claim 4, wherein the pixel TFT comprises: an active layer; a gate insulating film formed on the active layer;
A gate electrode formed on the gate insulating film, wherein the active layer faces the channel formation region, a high-resistance impurity region adjacent to the channel formation region, and the channel formation region. An electro-optical device comprising: a low-resistance impurity region adjacent to a high-resistance impurity region; and an end of the high-resistance impurity region and an end of the gate electrode are separated from each other. 7. A first step of forming an active layer on a substrate, a second step of forming a gate insulating film on the active layer, and a step of forming a gate electrode on the gate insulating film. A third step of oxidizing the gate electrode on a side surface of the gate electrode to form an oxide layer; etching the gate insulating film using the gate electrode and the oxide layer as a mask; A fifth step of exposing a part of the active layer; a sixth step of removing the oxide layer; and adding an impurity element imparting one conductivity to the active layer exposed in the fifth step. Forming a low-resistance impurity region and simultaneously forming a high-resistance impurity region under the gate insulating film exposed in the sixth step; and, in the seventh step, The impurity region is formed via the gate insulating film. The method for manufacturing a semiconductor device characterized by being formed so as to overlap with the gate electrode.