JP2007201468A - Semiconductor device and fabricating method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of fabricating a thin-film transistor (TFT) which can improve reliability. <P>SOLUTION: An n-channel TFT and a p-channel TFT each have a semiconductor layer, a gate insulating film formed so as to contact the semiconductor layer, and a gate electrode, overlapped on the semiconductor layer with the gate insulating film being sandwiched. The gate electrode of the n-channel TFT and that of the p-channel TFT are made of the same conductive layer. The gate electrode of the n-channel TFT has a tapered end, and its angle formed by the surface of a side surface and the surface of a gate insulating film lies within a range of 3-60 degrees. The gate electrode of the p-channel TFT has a tapered end, and its angle formed by the surface of a side surface and the surface of a gate insulating film lies within a range of 70-85 degrees. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thin film transistor (hereinafter referred to as TFT) and a semiconductor device having a circuit composed of the thin film transistor. For example, the present invention relates to an electro-optical device typified by a liquid crystal display panel as a semiconductor device and a configuration of an electronic apparatus in which such an electro-optical device is mounted as a component. Note that in this specification, a semiconductor device refers to all devices that function by utilizing semiconductor characteristics, and an electro-optical device, a semiconductor circuit, and an electronic device are also semiconductor devices.

  In recent years, an active matrix liquid crystal display device in which a circuit is constituted by TFTs using a crystalline silicon film has attracted attention. This realizes high-definition image display by controlling the electric field applied to the liquid crystal in a matrix by a plurality of pixels arranged in a matrix.

  Such an active matrix type liquid crystal display device has a resolution of XGA, SXGA or the like, and the number of pixels alone exceeds 1 million. A driver circuit for driving all of them is very complicated and formed by many TFTs.

  The specifications required for an actual liquid crystal display device (also referred to as a liquid crystal panel) are strict, and in order for all the pixels to operate normally, high reliability must be ensured for both the pixels and the drivers. In particular, when an abnormality occurs in the driver circuit, a defect called a line defect occurs in which pixels in one column (or one row) are completely destroyed.

  However, a TFT using a crystalline silicon film is said to be less reliable than a MOSFET (a transistor formed on a single crystal semiconductor substrate) used for LSI or the like in terms of reliability. Unless this weak point is overcome, there is an increasing view that it is difficult to form an LSI circuit with TFTs.

  Known structures for improving the reliability of TFTs include GOLD (Gate Overlapped Light-doped Drain) and LATID (Large-Tilt-Angle Implanted Drain). The feature of these structures is that the LDD region and the gate electrode overlap with each other, and this makes it possible to reduce the impurity concentration of the LDD region, and the effect of relaxing the electric field is increased, resulting in hot carrier resistance. Will increase.

  For example, in "M. Hatano, H. Akimoto, and T. Sakai, IEDM97 TECHNICAL DIGEST, p523-526, 1997", a TFT having a GOLD structure is realized using a side wall formed of silicon.

  However, the GOLD structure disclosed in the same paper has a problem that the off current (current that flows when the TFT is in an off state) becomes larger than that of a normal LDD structure, and a countermeasure for that is required.

  It is an object of the present invention to provide a TFT that eliminates the shortcomings of the GOLD structure TFT, reduces the off current, and has high hot carrier resistance. Another object of the present invention is to realize a highly reliable semiconductor device including a semiconductor circuit in which a circuit is formed using such TFTs.

  In order to solve the above-described problems, a thin film transistor according to the present invention includes a channel and a first impurity region in addition to an n-type or p-type first impurity region functioning as a source region or a drain region in a semiconductor layer in which a channel is formed. Between one impurity region, there are impurity regions (second and third impurity regions) having the same conductivity type as the two types of first impurity regions. These second and third impurity regions have a lower impurity concentration that determines their conductivity type than the first impurity region, and function as high resistance regions.

  The second impurity region is a low-concentration impurity region that overlaps with the gate electrode through the gate insulating film, and has an effect of increasing hot carrier resistance. On the other hand, the third impurity region is a low-concentration impurity region that does not overlap with the gate electrode, and has an effect of preventing an increase in off-state current.

  Note that a gate electrode is an electrode that intersects a semiconductor layer with a gate insulating film interposed therebetween, and is an electrode for forming a depletion layer by applying an electric field to the semiconductor layer. In the gate wiring, a portion that intersects the semiconductor layer with the gate insulating film interposed therebetween is a gate electrode.

  Furthermore, in the present invention, the thickness of the gate electrode decreases linearly from the central flat portion toward the outside around the gate electrode. Since the impurity imparting the conductivity type is added to the second impurity region through the tapered portion of the gate electrode, the concentration gradient reflects the inclination (change in film thickness) of the side surface of the gate electrode. That is, the impurity concentration added to the second impurity region increases from the channel formation region toward the first region.

  In the present invention, in another gate electrode configuration, a first gate electrode in contact with the gate insulating film and a second gate electrode formed on the first gate electrode are stacked. In this configuration, the angle between the first gate electrode and the side surface or the gate insulating film is a tapered shape having a value in the range of 3 degrees to 60 degrees. On the other hand, the width of the second gate electrode in the channel length direction is narrower than that of the first gate electrode.

  Also in the thin film transistor having the stacked gate electrode, the impurity concentration distribution in the second impurity region reflects a change in the film thickness of the first gate electrode, and the impurity concentration varies from the channel formation region to the first region. Will increase toward.

  The thin film transistor according to the present invention has two types of low-concentration impurity regions in the semiconductor layer, and therefore has a reliability comparable to or higher than that of a MOSFET.

(Advantages of Thin Film Transistor of the Present Invention) Advantages of the present invention will be described with reference to FIG. 34 in comparison with the characteristics of a conventional TFT.

  As described above, the present invention forms two types of low-concentration impurities in the semiconductor layer, the second impurity region (gate overlap type LDD region) and the third impurity region (non-gate overlap type LDD region). There is a feature.

  FIG. 34A is a schematic diagram of an n-channel TFT without an LDD region, and FIG. 34B shows its electrical characteristics (gate voltage Vg vs. drain current Id characteristics). Similarly, FIGS. 34 (C) and (D) show the case of a normal LDD structure, FIGS. 34 (E) and (F) show the case of a so-called GOLD structure, and FIGS. 34 (G) and (H). Shows the case of the n-channel TFT of the present invention.

In the drawings, n ⁺ represents a source region or a drain region, channel represents a channel formation region, and n ⁻ represents a low concentration impurity region having an impurity concentration lower than n ⁺ . Id represents the drain current, and Vg represents the gate voltage.

  When there is no LDD as shown in FIGS. 34A and 34B, the off current (drain current when the TFT is in the off state) is high, and the on current (drain current when the TFT is in the on state) or Off current is likely to deteriorate.

  On the other hand, by forming a non-gate overlap type LDD, off-state current can be considerably suppressed, and deterioration of both on-state current and off-state current can be suppressed. However, the deterioration of the on-current is not completely suppressed. (FIGS. 34 (C) and (D))

  The TFT structure (GOLD structure) (FIGS. 34 (E) and (F)) having only an overlap type LDD in which the LDD region overlaps the gate electrode is a degradation of on-current in the conventional LDD structure. It has a structure with an emphasis on restraining.

  In this case, deterioration of the on-current can be sufficiently suppressed, but there is a problem that the off-current is slightly higher than that of a normal non-overlapping LDD structure. The paper described in the conventional example adopts this structure, and the present invention is a result of searching for a structure for solving the problem that the off-current is high in the present invention.

  As shown in FIGS. 34G and 34H, the structure of the present invention includes an LDD region (second impurity region) that overlaps with the gate electrode and an LDD region (third region) that does not overlap with the gate electrode. The impurity region is formed in the semiconductor layer. By adopting this structure, it is possible to reduce the off current while maintaining the effect of suppressing the deterioration of the on current.

  The present applicant inferred why the off-state current becomes high in the case of the structure shown in FIGS. 34 (E) and (F) as follows. When the n-channel TFT is in an off state, a negative voltage such as minus several tens of volts is applied to the gate electrode. If a positive voltage of plus several tens of volts is applied to the drain region in this state, a very large electric field is formed at the drain side end of the gate insulating film.

  At this time, holes are induced in the LDD region, and a current path by a small number of carriers connecting the drain region, the LDD region, and the channel formation region is formed. This current path is expected to increase the off current.

  The present applicant considered that it is necessary to form another resistor, that is, the third impurity region LDD region at a position not overlapping with the gate electrode in order to interrupt such a current path in the middle. The present invention relates to a thin film transistor having such a structure and a circuit using this thin film transistor.

  By implementing the present invention, the reliability of a TFT can be increased, in particular, the reliability of an n-channel TFT can be increased. Therefore, it has become possible to ensure the reliability of the channel type FT having high electrical characteristics (particularly high mobility) that require strict reliability. At the same time, by forming a CMOS circuit by combining an n-channel TFT and a p-channel TFT with excellent characteristic balance, a semiconductor circuit with high reliability and excellent electric characteristics can be formed.

  Furthermore, in the present invention, since the catalytic element used for crystallization of the semiconductor can be reduced, a semiconductor device with few factors of instability can be realized. In addition, since the step of reducing the catalytic element is performed simultaneously with the formation and activation of the source region and the drain region, the throughput is not reduced.

  Further, by increasing the reliability of the circuit formed by TFTs as described above, it is possible to ensure the reliability of all semiconductor devices including electro-optical devices, semiconductor circuits, and electronic devices.

The embodiment of the present invention will be described with reference to FIGS.

[Embodiment 1] In this embodiment, the present invention is applied to a TFT. The manufacturing process of this embodiment will be described with reference to FIGS.

  First, the base film 101 is formed over the entire surface of the substrate 100, and the island-shaped semiconductor layer 102 is formed over the base film 101. An insulating film 103 serving as a gate insulating film is formed over the entire surface of the substrate 100 so as to cover the semiconductor layer 102. (Fig. 1 (A))

  As the substrate 100, a resin substrate such as a glass substrate, a quartz substrate, a crystalline glass substrate, or a stainless steel substrate polyethylene terephthalate (PET) can be used.

  The base film 101 is a film for preventing impurities such as sodium ions from diffusing from the substrate into the semiconductor layer 102 and improving the adhesion of the semiconductor film formed on the substrate 100. As the base film 101, a single layer or a multilayer film of an inorganic insulating film such as a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film can be used.

  The film formation method of the base film 101 is not limited to the CVD method or the sputtering method, but when a heat resistant substrate such as a quartz substrate is used, an amorphous silicon film is formed and thermally oxidized to form a silicon oxide film. A forming method can also be used.

  In addition to the above-described inorganic insulating film, the base film 101 includes a conductive film such as a silicide such as tungsten silicide, a metal or an alloy such as chromium, titanium, titanium nitride, or aluminum nitride, and the inorganic insulating film. A multilayer film laminated on the upper layer can also be used as a base film.

  The material and crystallinity of the semiconductor layer 102 may be selected as appropriate in accordance with characteristics required for the TFT. Amorphous silicon, amorphous silicon germanium, amorphous germanium, crystalline silicon obtained by crystallizing these amorphous semiconductor films by laser irradiation or heat treatment, crystalline germanium, or crystalline silicon germanium may be used. it can. The thickness of the semiconductor layer 102 may be 10 to 150 nm.

  The insulating film 103 is a film constituting a gate insulating film of the TFT, and is a single layer film or a multilayer film of an inorganic insulating film of silicon oxide, silicon nitride, or silicon nitride oxide. For example, in the case of a stacked film, a two-layer film of a silicon nitride oxide film and a silicon oxide, a stacked film in which a silicon nitride film is sandwiched between silicon oxides, or the like is used.

  As a means for forming the insulating film 103, a chemical vapor deposition method (CVD) such as a plasma CVD method or an ECRCVD method, or a physical vapor deposition method (PVD) such as a sputtering method may be used.

  A first conductive film 104 and a second conductive film 105 which form a gate electrode (gate wiring) are formed over the insulating film 103. (Fig. 1 (B))

  The first conductive film 104 forms a first gate electrode (first gate wiring) 108 having a tapered portion. For this reason, the material which can perform taper etching easily is desired. For example, a material mainly composed of chromium (Cr) and tantalum (Ta) (composition ratio is 50% or more) and n-type silicon containing phosphorus are typically used. Alternatively, a material containing titanium (Ti), tungsten (W), molybdenum (Mo), or the like as a main component can be used. In addition to a single layer film of these materials, a multilayer film can be used, for example, a three-layer film in which a tantalum film is sandwiched between tantalum nitride (TaN) films can be used.

  The second conductive film 105 is a film constituting the second gate electrode (second gate wiring) 109, and is made of aluminum (Al), copper (Cu), chromium (Cr), tantalum (Ta) titanium (Ti). , Tungsten (W), molybdenum (Mo) as a main component (composition ratio is 50% or more), phosphorus-containing n-type silicon, silicide, or the like. However, for the first conductive film and the second conductive film, it is necessary to select a material having an etching selectivity in patterning each other.

  For example, as the first conductive film 104 / second conductive film 105, n-type Si / Ta, n-type Si / Ta-Mo alloy, Ta / Al, Ti / Al, WN / W, TaN / Ta, etc. A combination can be selected. Another index for selecting a material is resistivity, and it is desirable that the second conductive film 105 be a material having as low a resistivity as possible and at least a sheet resistance lower than that of the first conductive film 104. This is because a contact is made between the second gate wiring and the upper wiring in order to connect the gate wiring and the upper wiring. In addition, the thickness of the first conductive film 104 is 10 to 400 nm, the thickness of the second conductive film is 10 to 400 nm, and the total film thickness is 200 to 500 nm.

  Next, a resist mask 106 is formed over the second conductive film 105. The second conductive film 105 is etched using the resist mask 106 to form a second gate electrode 109. For the etching, isotropic wet etching may be used. In addition, dry etching can be used in the case where the etching selectivity with respect to the first conductive film 104 can be obtained. (Figure 1 (C))

  Using the same resist mask 106, the first conductive film 104 is anisotropically etched (so-called taper etching) to form a first gate electrode (first gate wiring) 108. Note that a new resist mask can be formed for this etching.

  By this etching, as shown in FIG. 3, the taper angle θ between the side surface of the gate electrode 108 and the gate insulating film 103 is set to a value in the range of 3 ° to 60 °. The taper angle θ is preferably in the range of 5 ° to 45 °, more preferably in the range of 7 ° to 20 °. The smaller the angle θ, the smaller the change in the thickness of the tapered portion of the gate electrode 108. Correspondingly, the change in the n-type or p-type impurity concentration is moderated at the portion intersecting the tapered portion of the semiconductor layer. be able to.

  As shown in FIG. 3, the taper angle θ can be defined as tan θ = HG / WG using the width WG and the thickness HG of the tapered portion.

  The resist mask 106 is removed, and an impurity of a predetermined conductivity type (n-type or p-type) is added to the semiconductor layer 102 using the gate electrodes 108 and 109 as a mask. As an addition method, an ion implantation method or an ion doping method can be used. The n-type impurity is a donor impurity, which is a group 15 element for silicon and germanium, and is typically phosphorus (P) and arsenic (As). A p-type impurity is an impurity serving as an acceptor, and is a group 13 element for silicon and germanium, and is typically boron (B).

Here, phosphorus is added by an ion doping method to form the n ⁻ -type impurity regions 111 and 112. In this addition step, the concentration distribution of the n-type impurity in the n ⁻ -type second impurity regions 124 and 125 and the n ⁻ -type third impurity regions 126 and 127 is determined. In the present specification, the n ⁻ type indicates that the impurity concentration serving as a donor is lower and the sheet resistance is higher than the n ⁺ type. (Fig. 2 (A))

Since phosphorus is added to the n ⁻ -type impurity regions 111 and 112 through the tapered portion of the first gate electrode 108, the concentration gradient is as shown in the figure. Reflects changes. That is, in the concentration distribution in the depth direction of phosphorus, when attention is paid to the depth at which an arbitrary concentration is obtained, the concentration gradient is a profile reflecting the inclination of the tapered portion of the gate electrode.

Further, as will be described later, the concentration gradient of the n ⁻ -type impurity regions 111 and 112 also depends on the acceleration voltage at the time of doping. In the present invention, in order to pass phosphorus through the tapered portion of the first gate electrode 108 and the insulating film 103, the doping acceleration voltage needs to be set as high as 40 to 100 keV. Further, with this acceleration voltage, phosphorus can pass through a portion where the thickness of the tapered portion of the gate electrode 108 is 100 nm or less.

In FIG. 2A, the n ⁻ -type impurity regions 111 and 112 that are overlapped with the first gate electrode 108 are indicated by hatching and white background, and this is because phosphorus is added to the white background portion. Rather than showing that it has not been done, as described above, it can be intuitively understood that the phosphorus concentration distribution in this region reflects the film thickness of the tapered portion of the first gate electrode 108. This is because. This also applies to other drawings in this specification.

  Next, a resist mask 120 is formed so as to cover the gate electrodes 108 and 109. The mask 120 determines the length of the third impurity region. Via the resist mask 120, phosphorus, which is an n-type impurity, is added to the semiconductor layer 102 again by ion doping. (Fig. 2 (B))

Phosphorus is selectively added to the n ⁻ -type impurity regions 111 and 112 that are not covered with the resist mask 120 to form n ⁺ -type first impurity regions 122 and 123. Further, the region 121 covered with the second gate electrode 109 becomes a channel formation region because phosphorus is not added in the adding step of FIGS.

In the n ⁻ -type impurity regions 111 and 112, regions where phosphorus is not added in the addition step of FIG. 2B become low-concentration impurity regions 124 to 127 having higher resistance than the source / drain regions.

The low-concentration impurity regions 124 and 125 overlapping (overlapping) with the first gate electrode 108 become n ⁻ -type second impurity regions, and the low-concentration impurity regions not overlapping with the first electrode 108 are The n ⁻ -type third impurity regions 126 and 127 are formed.

  Note that the insulating film 103 may be etched using the gate wiring as a mask prior to the addition step in FIG.

  As shown in FIG. 4, the second impurity region 124 can be classified into four types. In order to distinguish these, FIG. 4 is divided into FIGS. 4 (A) to (D), and A and D are assigned to 121 and 124, respectively. Although not shown in FIG. 4, the other second impurity region 125 formed symmetrically with the gate electrode 109 in between is the same as the region 124.

  As shown in FIG. 4A, the concentration of phosphorus in the second impurity region 124A is inversely proportional to the change in the thickness of the tapered portion of the first gate electrode 108, and from the third impurity region 126A. It decreases almost linearly toward the channel formation region 121A. That is, when the concentration of the second impurity region 124A phosphorus is averaged in the depth direction, the averaged phosphorus concentration increases from the channel formation region 121A toward the third impurity region 126A.

  In this case, in the third impurity region 126A, the phosphorus concentration averaged in the film thickness direction is substantially uniform in the region 126A. In addition, since no phosphorus is added to the semiconductor layer covered with the second gate electrode 109, this region becomes the channel formation region 121A, and the channel length LA is equal to the width of the second gate electrode 109 in the channel length direction. Become.

  In addition, in the step of adding phosphorus in FIG. 2A, when the acceleration voltage is made larger than that in FIG. 4A, a channel is formed in the second impurity region 124B as shown in FIG. 4B. Phosphorus is also added to the junction with the region 121B. Also in this case, the channel formation region 121B is a region covered with the second gate electrode 109, and the channel length LB is the width of the second gate electrode 109 in the channel length direction. Even when the acceleration voltage is the same as that in FIG. 4A, the second impurity region 124B can be formed even when the taper angle is small or the thickness of the tapered portion is thin.

  When the acceleration voltage is further increased, as shown in FIG. 4C, the phosphorus concentration averaged in the film thickness direction can be made uniform in the second impurity region 124C. In this case, the channel length LC is the width of the second gate electrode 109 in the channel length direction.

  2A, when the acceleration voltage is made lower than in the case of FIG. 4A, phosphorus is a tapered portion of the first gate electrode 108 as shown in FIG. 4D. Therefore, the second impurity region 124D is narrower than that in FIG. 4A.

  In the second impurity region 124D, the concentration of phosphorus averaged in the depth direction gradually decreases from the third impurity region 126D toward the channel formation region 121D, as in FIG. 4A. However, in the case of FIG. 4D, unlike FIG. 4A, the junction between the second impurity region 124D and the channel formation region 121D exists under the tapered portion of the first gate electrode 108. Therefore, the channel length LD is wider than the width of the second gate electrode 109 in the channel length direction.

  Note that even when the acceleration voltage is the same as that in FIG. 4A, the second impurity region 124D in FIG. 4D is used even when the taper angle is large or the first gate electrode 108 is thick. Can be formed.

  As described above, when the impurity is added by the plasma doping method, the impurity may pass through a portion having a thickness of 100 nm or less in the tapered portion of the first gate electrode 108 to form the second impurity region 124. Therefore, by adjusting the thickness of the first conductive film 104 (the thickness of the portion where the thickness of the first gate electrode 108 is the maximum) and the taper angle θ, the channel length, the second It is possible to control the length of the impurity region.

Here, the length (channel length direction) of the first impurity regions 122 and 123 is 2 to 20 μm (typically 3 to 10 μm). The concentration of an impurity imparting conductivity to the semiconductor layer (in this case, phosphorus) is 1 × 10 ¹⁹ to 1 × 10 ²¹ atoms / cm ³ (typically 1 × 10 ^{20 to} 5 × 10 ²⁰ atoms / cm ³ ). The first impurity regions 122 and 123 are low resistance regions for electrically connecting the source wiring or the drain wiring and the TFT, and serve as the source region or the drain region.

The lengths of the second impurity regions 124 and 125 are 0.1 to 1 μm (typically 0.1 to 0.5 μm, preferably 0.1 to 0.2 μm), and the phosphorus concentration is 1 ×. 10 ¹⁵ to 1 × 10 ¹⁷ atoms / cm ³ (typically 5 × 10 ^{15 to} 5 × 10 ¹⁶ atoms / cm ³ , preferably 1 × 10 ¹⁶ to 2 × 10 ¹⁶ atoms / cm ³ ) Since impurities are added through one gate electrode 108, the concentration of phosphorus is lower than that of the first and third impurity regions.

The lengths of the third impurity regions 126 and 127 are 0.5 to 2 μm (typically 1 to 1.5 μm), and the phosphorus concentration is 1 × 10 ¹⁶ to 1 × 10 ¹⁹ atoms / cm ³ ( Typically, it is 1 × 10 ^{17 to} 5 × 10 ¹⁸ atoms / cm ³ , preferably 5 × 10 ¹⁷ to 1 × 10 ¹⁸ atoms / cm ³ ).

Further, the channel formation region 121 is an intrinsic semiconductor layer, and a region not containing an impurity (phosphorus) added to the first impurity region, or boron at a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁸ atoms / cm ³ is used. It is an area to include. Boron is an impurity for controlling the threshold voltage and preventing punch-through, and other elements can be substituted as long as they produce the same effect. In this case, the concentration is the same as that of boron.

  Note that one low-concentration impurity region (third impurity region 126, 127) that does not overlap with the gate electrode is formed between the first impurity regions 122, 123 and the second impurity regions 124, 125. Two or more impurity regions having different impurity concentrations can be formed in the portion. In the present invention, at least an impurity region having a lower impurity (phosphorus) concentration than the first impurity regions 122 and 123, that is, the first impurity regions between the first impurity regions 122 and 123 and the second impurity regions 124 and 125. It is sufficient that at least one impurity region having a higher resistance than the impurity regions 122 and 123 exists. Of course, it is also important that this high-resistance impurity region (third impurity region) does not overlap the gate electrode.

  When the first impurity regions 122 and 123 are formed, the resist mask 120 is removed. The phosphorus added to the semiconductor layer 102 is activated by heat treatment. In the activation process, not only heat treatment but also light annealing by laser or infrared lamp light can be performed.

  Next, an interlayer insulating film 130 made of silicon oxide or the like is formed. Contact holes reaching the first impurity regions 122 and 123 and the second gate wiring 109 are formed in the gate insulating film 103 and the interlayer insulating film 130. Then, a source electrode 131, a drain electrode 132, and a gate wiring extraction electrode (not shown) are formed.

Embodiment Mode 2 A manufacturing process of a TFT according to this embodiment mode will be described with reference to FIGS. The present embodiment is a modification of the first embodiment, in which the structure of the gate electrode (gate wiring) is modified, and the other main structures are the same as those of the first embodiment.

  In the first embodiment, the gate electrode has a structure in which two gate electrodes having different widths are stacked. However, in the present embodiment, the upper second electrode is omitted, and only the first gate electrode having a tapered portion is used as a gate. An electrode is formed.

  First, the base film 141 is formed over the entire surface of the substrate 140, and the island-shaped semiconductor layer 142 is formed over the base film 141. An insulating film 143 to be a gate insulating film is formed over the entire surface of the substrate 140 so as to cover the semiconductor layer 142. (Fig. 5 (A))

  A conductive film 144 that forms a gate electrode (gate wiring) is formed over the gate insulating film 143. The conductive film 144 is preferably made of a material that can be easily tapered. For example, a material mainly composed of chromium (Cr) and tantalum (Ta) (composition ratio is 50% or more) and n-type silicon containing phosphorus are typically used. Alternatively, a material containing titanium (Ti), tungsten (W), molybdenum (Mo), or the like as a main component can be used. In addition to a single layer film of these materials, a multilayer film can be used, for example, a three-layer film in which a tantalum film is sandwiched between tantalum nitride (TaN) films can be used. The thickness of the conductive film 144 is 200 to 500 nm. (Fig. 5 (B))

  Next, a resist mask 145 is formed over the conductive film 144. The conductive film 144 is etched using the mask 145 to form a gate electrode (gate wiring) 146. (Fig. 5 (C))

  By this etching, as shown in FIG. 3, the taper angle θ between the side surface of the gate electrode 146 and the gate insulating film is set to a value in the range of 3 ° to 60 °. The taper angle θ is preferably 5 ° to 45 °, more preferably 7 ° to 20 °.

In the state where the resist mask 145 exists, an impurity of a predetermined conductivity type (n-type or p-type) is added to the semiconductor layer 142. Here, phosphorus is added by an ion doping method to form n ⁻ -type impurity regions 148 and 149. In this adding step, n ^- the second impurity regions 154 and 155 of the mold, n ^- third concentration distribution of the impurity regions 156 and 157 of the mold is determined. Further, although described later, a region covered with the resist mask 145 becomes a channel formation region 151. (Fig. 6 (A))

  Since the second gate electrode is not present, this addition step requires a mask for preventing phosphorus from being added to a region where the channel of the semiconductor layer 142 is formed. Although the resist mask 145 used for etching the conductive film 144 is used as such a mask, it can be newly formed for impurity addition.

  Next, the resist mask 145 is removed, and a resist mask 150 is formed so as to cover the gate electrode 146. Since phosphorus, which is an n-type impurity, is added to the semiconductor layer 142 again by an ion doping method through the resist mask 150, the length of the third impurity region is determined by the resist mask 150. Prior to this addition step, the insulating film 143 may be etched using the gate wiring 146 as a mask to expose the surface of the semiconductor layer 142. (Fig. 6 (B))

As shown in FIG. 6B, phosphorus is selectively added to the n ⁻ -type impurity regions 148 and 149 that are not covered with the resist mask 150 to form n ⁺ -type first impurity regions 152 and 153. Is done.

Further, the region covered with the resist mask 150 is kept in the state of conductivity type and resistance value as shown in FIG. Therefore, the region 151 previously covered with the resist mask 145 becomes a channel formation region. The regions overlapping (overlapping) with the gate electrode 146 become n ⁻ -type second impurity regions 154 and 155, and the regions not overlapping with the gate electrode 146 are n ⁻ -type third impurity regions 156 and 157. Become. The second and third impurity regions 154 to 157 are low-concentration impurity regions having higher resistance than the first impurity regions 152 and 153.

  Also in this embodiment, the second impurity regions 154 and 155 can be classified into the four types shown in FIG. 4 as in the first embodiment. In addition, the channel formation region 151 and the first to third impurity regions 152 to 157 have the same length and impurity concentration in the channel length direction as in the first embodiment. However, the channel length is determined by the resist mask 145 used in the addition step of FIG. 6A in this embodiment instead of the second gate electrode 109 of Embodiment 1.

  Since the gate electrode of Embodiment 1 has a stacked structure of electrodes having different shapes, even if the thickness of the first gate electrode 108 is reduced, the resistance can be reduced by increasing the thickness of the second gate electrode 109. However, since the gate electrode 146 of this embodiment is a single-layer electrode having a tapered portion, the film thickness thereof is larger than that of the first gate electrode 108.

  Considering the gate electrode width, there is a limit to the length of the width WG (see FIG. 3) of the tapered portion. Therefore, the impurity concentration distribution of the second impurity regions 154 and 155 is of the type shown in FIG. Is the most practical.

  Note that one low-concentration impurity region (third impurity region 156, 157) that does not overlap with the gate electrode is formed between the first impurity regions 152, 153 and the second impurity regions 154, 155. Two or more impurity regions having different impurity concentrations may be formed in the portion. In the present invention, an impurity region having an impurity (phosphorus) concentration lower than that of the first impurity regions 152 and 153 and having a high resistance is at least between the first impurity regions 152 and 153 and the second impurity regions 154 and 155. It is sufficient that at least one exists.

  After forming the first impurity regions 152 and 153, the resist mask 150 is removed. The phosphorus added to the semiconductor layer 142 is activated by heat treatment. In the activation process, not only heat treatment but also light annealing by laser or infrared lamp light can be performed. However, in order to activate phosphorus in the second impurity regions 154 and 155, the gate electrode 146 overlaps with each other, so that heat treatment is always required.

  Next, an interlayer insulating film 158 made of silicon oxide or the like is formed. Contact holes reaching the first impurity regions 152 and 153 and the gate wiring 146 are formed in the gate insulating film 143 and the interlayer insulating film 158. Then, extraction electrodes for the source electrode 159, the drain electrode 160, and the gate wiring 146 (not shown) are formed.

Embodiment Mode 3 A manufacturing process of a TFT according to this embodiment mode will be described with reference to FIGS. The present embodiment is also a modification of the first embodiment, in which the structure of the gate electrode (gate wiring) is modified, and other main structures are the same as those of the first embodiment. In FIG. 7, the same reference numerals as those in FIGS. 1 and 2 indicate the same components.

  The gate electrode of this embodiment has a structure in which the first gate electrode 168 and the second gate electrode 169 are stacked as in the first embodiment. However, the side surface of the first gate electrode 168 is not tapered. In the present embodiment, the thickness of the first gate electrode 168 is substantially constant even in a portion where the first gate electrode 168 extends outward from the side surface of the second gate electrode 169.

Through the addition of phosphorus similar to that in the first embodiment, the semiconductor layer is subjected to channel formation region 161, n ⁺ -type first impurity regions 162 and 163, n ⁻ -type second impurity regions 164 and 165, n ⁻ A third impurity region 166, 167 of the type is formed.

  In this embodiment, since the film thickness of the first gate electrode 168 is constant, the impurity concentration in the second impurity regions 164 and 165 has almost no gradient.

[Embodiment 4] This embodiment is a modification of Embodiment 1 and Embodiment 2. In the first and second embodiments, the thickness of the tapered portion of the gate electrode changes almost linearly. In the present embodiment, the thickness of the tapered portion is changed nonlinearly.

FIG. 8 shows a modification of the TFT of the first embodiment. 8, the same reference numerals as those in FIG. 2 denote the same components. As shown in FIG. 8, the thickness of the tapered portion of the first gate electrode 170 (gate wiring) is changed nonlinearly. Through the addition of phosphorus similar to that in the first embodiment, the semiconductor layer is subjected to channel formation region 171, n ⁺ -type first impurity regions 172 and 173, n ⁻ -type second impurity regions 174 and 175, n ⁻ Type third impurity regions 176, 177 are formed.

FIG. 9 shows a modification of the TFT of the second embodiment. 9, the same reference numerals as those in FIG. 6 denote the same components. As shown in FIG. 9, the thickness of the tapered portion of the gate electrode 180 (wiring) changes nonlinearly. The semiconductor layer is subjected to the same phosphorus addition as in the first embodiment, and then the channel formation region 181, the n ⁺ -type first impurity regions 182, 183, the n ⁻ -type second impurity regions 184, 185, n ^−. A third impurity region 186, 187 of the type is formed.

  As shown in the cross-sectional views of FIGS. 8 and 9, the gate electrodes 170 and 180 are formed so that the thickness of the gate electrodes 170 and 180 is slightly reduced at a portion slightly deviated from a constant portion so that impurities serving as donors and acceptors are reduced. The gate electrodes 170 and 180 are easily passed.

  In order to form the tapered portion as illustrated in the gate electrodes 170 and 180, the conductive film may be etched by combining anisotropic etching and isotropic etching.

  Needless to say, the configurations of the TFTs described in Embodiments 1 to 4 can be applied to all examples of the present invention described below.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In this embodiment, an example in which the present invention is applied to an active matrix liquid crystal display device will be described.

  FIG. 10 is a schematic configuration diagram of the active matrix type liquid crystal panel of this embodiment. A liquid crystal panel has a structure in which liquid crystal is sandwiched between an active matrix substrate and a counter substrate, and a voltage corresponding to video data is applied to the liquid crystal by an electrode formed on the active matrix substrate and the counter substrate. The video can be displayed on the panel.

  In the active matrix substrate 200, a pixel portion 202 using TFTs as switching elements, a gate driver circuit 203 and a source driver circuit 204 for driving the pixel portion 202 are formed on a glass substrate 300. The driver circuits 203 and 204 are connected to the pixel portion 202 by source wiring and drain wiring, respectively.

  Further, a signal processing circuit 205 for processing signals input to the driver circuits 203 and 204 is formed on the glass substrate 300, and further, power and control signals are input to the driver circuits 203 and 204 and the signal processing circuit 205. The external terminal is formed, and the FPC 206 is connected to the external terminal.

  In the counter substrate 210, a transparent conductive film such as an ITO film is formed on the entire surface of the glass substrate. The transparent conductive film is a counter electrode with respect to the pixel electrode of the pixel portion 202. By changing the electric field strength between the pixel electrode and the counter electrode, the orientation of the liquid crystal material is changed, and gradation display becomes possible. Further, if necessary, an alignment film and a color filter are formed on the counter substrate 210.

  FIG. 11A is an equivalent circuit of one pixel in the pixel portion, and FIG. 11B is a top view of the pixel portion 202. FIG. 11C is a top view of the CMOS circuit that forms the driver circuits 203 and 204.

  FIG. 12 is a diagram showing a manufacturing process of the pixel portion. The pixel portion 202 includes a pixel TFT 202 and a storage capacitor 230, and a cross-sectional view thereof corresponds to a cross section taken along a chain line X-X ′ in FIG. The CMOS circuit includes an n-channel TFT and a p-channel TFT, and a cross-sectional view thereof corresponds to a cross section taken along a chain line Y-Y ′ in FIG. The pixel TFT 220 and the thin film transistor of the CMOS circuit are simultaneously manufactured on the same glass substrate 300. (Fig. 11 (A))

  In the pixel portion 202, a gate wiring 350 is formed for each row, and a source wiring 380 is formed for each column. A pixel TFT 220 is formed in the vicinity of the intersection of the gate wiring 350 and the source wiring 380. The source region of the pixel TFT 220 is connected to the source wiring 380, and the drain region is connected to two capacitors, a liquid crystal cell 240 and a storage capacitor 230.

  The liquid crystal cell 240 is a capacitor using the pixel electrode 390 and the transparent electrode of the counter substrate 210 as an electrode pair and liquid crystal as a dielectric, and is electrically connected to the pixel TFT 220 by the pixel electrode 390. The storage capacitor 230 is a capacitor having a common wiring 360 and a channel region formed in the semiconductor layer of the pixel TFT 220 as an electrode pair and a gate insulating film as a dielectric.

  A manufacturing process of the active matrix substrate of this embodiment will be described with reference to FIGS. 13 and 14 are cross-sectional views showing a manufacturing process of the pixel portion, and FIGS. 15 and 16 are cross-sectional views showing a manufacturing process of the CMOS circuit.

  A glass substrate 300 is prepared. In this embodiment, a 1737 glass substrate manufactured by Cornings is used. A silicon oxide film having a thickness of 200 nm is formed as a base film 301 using a TEOS gas as a raw material by a plasma CVD method in contact with the surface of the glass substrate 300. Then, the base film 301 is heated at 400 ° C. for 4 hours.

An amorphous silicon film having a thickness of 500 nm is formed on the base film 301 using SiH ₄ diluted with H ₂ gas by PECVD. Next, the amorphous silicon film is heated at 450 ° C. for 1 hour to perform hydrogen removal treatment. Hydrogen atoms in the amorphous silicon film are 5 atomic% or less, preferably 1% or less. A crystalline (polycrystalline) silicon film 401 is formed by irradiating the amorphous silicon film after the hydrogen extraction treatment with excimer laser light. The conditions for laser crystallization are as follows: an XeCl excimer laser is used as a laser light source, the laser light is linearly shaped by an optical system, the pulse frequency is 30 Hz, the overlap rate is 96%, and the laser energy density is 359 mJ / cm ² . . (FIGS. 13A and 15A)

  As a method for forming the amorphous silicon film, an LPCVD method or a sputtering method can be used in addition to the PECVD method. As a laser for crystallizing amorphous silicon, a continuous oscillation laser such as an Ar laser may be used in addition to a pulse oscillation type such as an excimer laser. Further, instead of laser crystallization, a lamp annealing process using a halogen lamp or a mercury lamp, or a heat treatment process at 600 ° C. or higher can be used.

Next, a photoresist pattern (not shown) is formed using a photolithography process, and the crystalline silicon film 401 is patterned into an island shape using the photoresist pattern, thereby forming semiconductor layers 302, 303, and 304. A silicon nitride oxide film is formed as the gate insulating film 305 so as to cover the semiconductor layers 302, 303, and 304. The film forming method was PECVD, and SiH ₄ and NO ₂ were used as source gases. The thickness of the silicon nitride oxide film is 120 nm. (FIGS. 13B and 15B)

  A stacked film of an n-type silicon film 402 containing phosphorus and a molybdenum-tungsten alloy (Mo—W) film 403 is formed over the gate insulating film 305 by a sputtering method. The thickness of the silicon film 402 is 200 nm, and the thickness of the Mo—W film 403 is 250 nm. The target material of the Mo—W film 403 was a composition ratio of Mo and W of 1: 1. (FIGS. 13C and 15C)

  A resist mask 405 is formed over the Mo—W film 403. The Mo—W film 403 is wet-etched using the resist mask 405, and the second gate wiring 352, the second common wiring 362, which is the upper wiring of the gate wiring of the pixel TFT, the common wiring, and the gate wiring of the CMOS circuit, Two gate wirings 372 are formed. (FIGS. 13D and 15D)

  Using the resist mask 405 again, anisotropic etching using a chlorine-based gas is performed, the n-type silicon film 402 is etched, and the first gate wiring 351, the second common wiring 361, and the first gate wiring are etched. 371 is formed. At this time, an angle (taper angle) θ between the side surfaces of the wirings 351, 361, and 371 and the gate insulating film 305 is set to 20 degrees, and a tapered portion is formed on the side portion. (FIGS. 13E and 15E)

After removing the resist mask 405, phosphorus is added to the semiconductor layers 302 to 304 by ion doping using the wirings 350, 360, and 370 as masks to form n ⁻ -type regions 406 to 413 in a self-aligning manner. In this phosphorus addition process, the tapered portions of the first electrodes 351, 361, and 371 (portions outside the side surfaces of the second electrodes 352, 362, and 372) and the gate insulating film 305 are allowed to pass through, so that phosphorus is added. For the addition, the acceleration voltage is increased to 90 KeV.

Since the phosphorus concentration of the n ⁻ -type impurity regions 406 to 413 determines the phosphorus concentration of the n ⁻ -type low concentration impurity region of the final TFT, the dose is set low, and the n ⁻ -type impurity regions 406 to 413 The phosphorus concentration in the region not intersecting with the electrodes 350, 360, and 370 was set to 1 × 10 ¹⁸ atoms / cm ³ . Phosphine diluted with hydrogen is used as the doping gas.

Next, a resist mask 415 that covers the electrodes 350, 360, and 370 is formed. Due to the length of the resist mask 415 extending outside the side surfaces of the first electrodes 351, 361, 371 of each electrode, the n ⁻ -type low-concentration impurity regions that do not overlap the first electrodes 351, 361, 371 are formed. The length is determined. Here, a resist mask is not formed over the semiconductor layer 304 of the CMOS circuit.

Using the resist mask 415, phosphorus is added by an ion doping method. Also in this addition step, phosphine diluted with hydrogen was used as a doping gas. Further, in order to allow phosphorus to pass through the gate insulating film 305, the acceleration voltage is set to a high value of 80 keV, and the n ⁺ -type impurity regions 313 to 315, 332, 333, 421, and 422 formed in this step are set. The dose was set so that the phosphorus concentration was 5 × 10 ²⁰ atoms / cm ³ .

In the pixel portion 202, phosphorus is selectively added to the n ⁻ -type impurity regions 406 to 409 of the semiconductor layer 302, so that n ⁺ -type impurity regions 313 to 315 are formed. The n ⁻ type impurity regions 406 to 409 in which phosphorus is not added function as a high resistance region, and the n ⁻ type impurity regions 316 to 319 overlapping the first gate electrode 351 and the first common electrode, 326 and 327 are defined as n ⁻ -type impurity regions 320 to 323 and 328 that do not overlap the first gate electrode 351 and the first common electrode 361. Further, regions 311, 312, and 325 where phosphorus is not added in the two phosphorus addition steps are defined as channel formation regions. (Fig. 14 (A))

The n ⁻ type impurity regions 316 to 319 have a lower phosphorus concentration than the n ⁻ type impurity regions 320 to 323, and the phosphorus concentration decreases from the n ⁻ type impurity regions 320 to 323 toward the channel formation regions 311 and 312. Yes.

In the CMOS circuit, phosphorus is selectively added also to the n ⁻ -type impurity regions 410 and 411 of the semiconductor layer 303 of the n-channel TFT, so that n ⁺ -type impurity regions 322 and 323 are formed. On the other hand, in the n ⁻ -type impurity regions 410 and 411, the region to which phosphorus is not added functions as a high resistance region, and the n ⁻ -type impurity regions 334 and 335 overlapping the first gate electrode 371, N ⁻ -type impurity regions 336 and 337 that do not overlap with the gate electrode 371 are defined. A region 331 in which phosphorus is not added in the two phosphorus addition steps is defined as a channel formation region.

The n ⁻ -type impurity regions 334 and 335 have a lower phosphorus concentration than the n ⁻ -type impurity regions 336 and 337, and the phosphorus concentration decreases from the n ⁻ -type impurity regions 336 and 337 toward the channel formation region 331.

Further, in the semiconductor layer 304 of the p-channel TFT, phosphorus is hardly added to a portion where the gate electrode 370 exists, and n ⁺ -type regions 421 and 422 are formed in portions where the gate electrode 370 does not exist above the portion. As a result, an n ⁻ -type impurity region remains below the first gate electrode 371. (FIG. 16 (A))

  After the resist mask 415 is removed, a resist mask 416 that covers the n-channel TFT is formed. Using the second gate electrode 372 of the p-channel TFT as a mask, the first gate electrode 371 on the semiconductor layer 304 side is thinned by etching to form a third gate electrode 373. (Fig. 14 (B), Fig. 16 (B))

  The taper angle θ between the side surface of the third gate electrode 373 and the gate insulating film 305 was 75 degrees. The taper angle of the third electrode 373 is in the range of 60 degrees to 90 degrees, and more preferably in the range of 70 degrees to 85 degrees.

With the resist mask 416 remaining, boron and an ion doping method are added to the semiconductor layer 304. The gate electrode 372 and 373 functions as a mask, a channel forming region 341, p ⁺ -type impurity regions 342 and 343, p ⁺ -type impurity regions 344 and 345 are formed in a self-aligned manner. Note that the resist mask 416 may be removed and a new resist mask may be formed separately. (FIGS. 14C and 16C)

In the boron addition process, the acceleration voltage was set to 80 keV, and the dose was set so that the boron concentration in the p ⁺ -type impurity regions 342 to 345 was 3 × 10 ²¹ atoms / cm ³ . By using diborane diluted with hydrogen in the doping gas, although the p ⁺ -type impurity regions 344 and 345 p ⁺ -type impurity regions 342 and 343 and the boron concentration is the same, the phosphorus concentration is low. The concentration distribution of the p ⁺ -type impurity regions 344 and 345 corresponds to the change in film thickness of the tapered portion of the first gate electrode 371 and decreases toward the channel formation region 341.

  After the resist mask 416 is removed, phosphorus and boron added to the semiconductor layer are activated by heating at 500 ° C. Prior to the heat treatment, a protective film 306 made of silicon oxide having a thickness of 50 nm is formed in order to prevent the gate wiring 350, the common electrode 360, and the gate wiring 370 from being oxidized. (FIGS. 14D and 16D)

Next, as the interlayer insulating film 307, a 20 nm thick silicon nitride film and a 900 nm thick silicon oxide film are stacked by PECVD. Contacts reaching the n ⁺ -type impurity regions 313 to 315, the n ⁺ -type impurity regions 332 and 333, the p ⁺ -type impurity regions 342 and 343, and the second gate wiring 372 to the interlayer insulating film 307, the protective film 306, and the gate insulating film 305. A hole is formed.

  A laminated film of titanium (150 nm) / aluminum (500 nm) / titanium (100 nm) is formed on the interlayer insulating film 307 by sputtering and patterned to form a source wiring 380, a drain electrode 381, source electrodes 384, 385, A drain electrode 386 is formed. As described above, the circuits 203 to 205 mainly including a CMOS circuit and the pixel portion 202 provided with the pixel TFT 220 and the storage capacitor 230 are manufactured over the same glass substrate 300. (FIGS. 14E and 16E)

  In order to complete the active matrix substrate, a planarization film is further formed on the entire surface of the substrate 300. Here, acrylic is applied by a spin coating method and baked to form an acrylic film having a thickness of 1 μm. Contact holes for the source electrodes 384 and 385 of the CMOS circuit are opened in the planarizing film. Titanium having a thickness of 200 nm is formed by sputtering and patterned to form source wirings 387 and 388.

  Next, similarly to the first planarization film, acrylic having a thickness of 0.5 μm is formed as the second planarization film. A contact hole for the drain electrode 381 is formed in the first and second planarization films. An ITO film is formed by sputtering and patterned to form a pixel electrode 390 connected to the drain electrode 381. (Fig. 11 (B), (C))

  In this embodiment, a low-concentration impurity region that functions as a high resistance region is not formed for the p-channel TFT. However, the p-channel TFT has no problem because it has high reliability even if it does not originally have a high-resistance region. On the other hand, if the high resistance region is not formed, an on-current can be obtained, which is convenient because it is balanced with the characteristics of the n-channel TFT.

  The present embodiment is a modification of the first embodiment, in which the order of the phosphorus and boron addition steps is changed, and the rest is the same as the first embodiment. A manufacturing process of this example will be described with reference to FIGS. In FIG. 17, the same reference numerals as those in FIGS. 15 and 16 denote the same components.

  In Example 1, phosphorus is added to the semiconductor layer and then boron is added. In this example, boron is added first.

  In this embodiment, a manufacturing process of a CMOS circuit will be described, but it goes without saying that this embodiment can be applied to a manufacturing process of an active matrix substrate in which a pixel portion and a driver circuit are integrated as in the embodiment.

  The structure shown in FIG. 15E is obtained in accordance with the steps shown in the first embodiment. Next, the resist mask 405 is removed. FIG. 17A shows this state.

Next, a resist mask 451 that covers the n-channel TFT is formed. Boron is added to the semiconductor layer 304 by an ion doping method using the resist mask 451. Gate electrodes 371 and 372 function as a mask, and a channel formation region 501 and p ⁺ -type impurity regions 502 and 503 functioning as a source region and a drain region are formed in the semiconductor layer 304 in a self-aligned manner.

The acceleration voltage was set to 80 keV, and the dose was set so that the boron concentration in the p ⁺ -type impurity regions 502 and 503 was 3 × 10 ²⁰ atoms / cm ³ . Here, it is expected that the p ⁺ -type impurity regions 502 and 503 are slightly overlapped with the lower portion since boron around the doping layer is thin and the thickness of the side portion of the gate electrode 370 is thin. (Fig. 17 (B))

After the resist mask 451 is removed, a resist mask 452 that covers the p-channel TFT is formed. Then, phosphorus is added to the semiconductor layer 303 by an ion doping method to form n ⁻ type low concentration impurity regions 453 and 454 in a self-aligning manner. The acceleration voltage was 90 keV, and the dose was set so that the phosphorus concentration in the n ⁻ -type impurity regions 453 and 454 was 1 × 10 ¹⁸ atoms / cm ³ . Further, phosphine diluted with hydrogen is used as a doping gas. (Fig. 17 (C))

Next, the resist mask 452 is removed, and a resist mask 456 partially covering the entire p-channel TFT and the n-channel TFT is newly formed. In the n-channel TFT, the length of the mask 456 extending outward from the side surface of the first gate electrode 371 determines the length of the n ⁻ -type impurity region that does not overlap the first gate electrode 371.

  Phosphorus is added by an ion doping method using the resist mask 456. In this addition step, phosphine diluted with hydrogen was used as a doping gas.

In the CMOS circuit, phosphorus is selectively added to the n ⁻ -type impurity regions 453 and 454 of the semiconductor layer 303 of the n-channel TFT, so that n ⁺ -type impurity regions 512 and 513 are formed. In this step, the acceleration voltage is increased to 80 keV in order to pass phosphorus through the gate insulating film 305. The dose was set so that the phosphorus concentration in the n ⁺ -type impurity regions 512 and 513 was 5 × 10 ²⁰ atoms / cm ³ .

On the other hand, in the n ⁻ -type impurity regions 453 and 454, the region to which phosphorus is not added functions as a high-resistance region, and the n ⁻ -type impurity regions 514 and 515 overlapping the first gate electrode 371, defining a type impurity regions 516 and 517 ^- n which does not overlap with the gate electrode 371 of the. A region 511 where phosphorus is not added in the two phosphorus addition steps is defined as a channel formation region. (Fig. 17D)
)

Also in this embodiment, the n ⁻ -type impurity regions 514 and 515 overlapping with the gate electrode 371 have a phosphorus concentration lower than that of the n ⁻ -type impurity regions 516 and 517 (and the n ⁺ -type impurity regions 512 and 513). The concentration decreases toward the channel formation region 511.

  After removing the resist mask 456, a protective film 306 made of silicon oxide having a thickness of 50 nm is formed, and heat treatment is performed to activate phosphorus and boron added to the semiconductor layer. An interlayer insulating film 307 is formed, contact holes are opened, and source electrodes 384 and 385 and a drain electrode 386 are formed. Thus, a CMOS circuit is manufactured. (Fig. 17 (E))

  In this embodiment, the step of narrowing the first gate electrode of the p-channel TFT can be omitted. Note that before the boron addition step in FIG. 17B is performed, the first gate electrode 371 of the p-channel TFT is etched using the second gate electrode 372 as a mask, so that the third gate electrode 373 is formed. A step of forming can also be added.

  In this example, similarly to Example 2, a manufacturing process in which the order of adding phosphorus and boron is changed will be described. A manufacturing process of this embodiment will be described with reference to FIGS. In FIG. 18, the same reference numerals as those in FIGS. 15 and 16 denote the same components.

  Further, the present embodiment also corresponds to a modification of the second embodiment. In Example 2, in order to fabricate an n-channel TFT, phosphorus is added at a low concentration and then boron is added. However, in this example, boron is first added at a high concentration. It is.

  The structure shown in FIG. 15E is obtained in accordance with the steps shown in the first embodiment. Next, the resist mask 405 is removed. FIG. 18A shows this state.

Next, a resist mask 600 that covers the n-channel TFT is formed. Using the resist mask 600, boron is added to the semiconductor layer 304 by an ion doping method. Gate electrodes 371 and 372 function as a mask, and a channel formation region 601 and p ⁺ -type impurity regions 602 and 603 that function as a source region and a drain region are formed in the semiconductor layer 304 in a self-aligned manner. The doping acceleration voltage was set to 80 keV, and the dose was set so that the boron concentrations in the p ⁺ -type impurity regions 602 and 603 were 2 × 10 ²⁰ atoms / cm ³ .

A resist mask 605 that partially covers the entire p-channel TFT and the n-channel TFT is formed. Phosphorus is added by an ion doping method using the resist mask 605. Also in this addition step, phosphine diluted with hydrogen was used as a doping gas. Phosphorus is selectively added to the semiconductor layer 303 of the n-channel TFT to form n ⁺ -type impurity regions 606 and 607. Further, in this step, since phosphorus passes through the gate insulating film 305, the acceleration voltage is Increase to 80 keV. (Figure 18 (C))

After removing the resist mask 605, a resist mask 608 covering the p-channel TFT is formed. Then, phosphorus is added to the semiconductor layer 303 by an ion doping method. Gate electrode 370 functions as a mask, and channel formation region 611, n ⁻ -type impurity regions 614 and 615, and n ⁻ -type impurity regions 616 and 617 are formed in a self-aligned manner.

The n ⁺ -type impurity regions 612 and 613 function as source / drain regions, and the resistance is lowered so that the concentration of phosphorus is 5 × 10 ²⁰ atoms / cm ³ . The n ⁻ type impurity regions 614 to 617 have a lower phosphorus concentration and higher resistance than the n ⁺ type impurity regions 612 and 613. The phosphorus concentration of the n ⁻ -type impurity regions 616 and 617 not overlapping with the first gate electrode 371 is set to 1 × 10 ¹⁸ atoms / cm ³ . (Fig. 18D)

  After removing the resist mask 608, a protective film 306 made of silicon oxide with a thickness of 50 nm is formed, and heat treatment is performed to activate phosphorus and boron added to the semiconductor layer. An interlayer insulating film 307 is formed, contact holes are opened, and source electrodes 384 and 385 and a drain electrode 386 are formed. Thus, a CMOS circuit is manufactured. (Figure 18 (E))

In this embodiment, the resist masks 605 and 608 that cover the p-channel TFT are formed in the phosphorus addition step, but the resist masks 605 and / or 608 may be omitted. In this case, since phosphorus is added to the p ⁺ -type impurity regions 602 and 603, it is necessary to add a large amount of boron by taking into account the concentration of added phosphorus.

  The present embodiment is also a modification of the first embodiment, in which the order of phosphorus and boron addition steps is changed, and the main configuration is the same as that of the first embodiment.

  A manufacturing process of this example will be described with reference to FIGS. 19, the same reference numerals as those in FIGS. 15 and 16 denote the same components.

  The structure shown in FIG. 15E is obtained in accordance with the steps shown in the first embodiment. Next, the resist mask 405 is removed. Then, a resist mask that covers at least a portion functioning as the gate electrode of the n-channel TFT is formed in the gate wiring 370, and the first gate electrode (wiring) is formed using the second gate electrode (wiring) 372 as an etching mask. ) 371 is etched to form a third gate electrode (wiring).

  That is, the third gate electrode 373 is formed by narrowing at least the width of the portion overlapping the semiconductor layer 304 of the p-channel TFT in the first gate wiring 371. (FIG. 19 (A))

Phosphorus is added to the semiconductor layers 303 and 304 at a low concentration by ion doping. First to third gate electrodes 371 to 373 function as a mask, and n ⁻ -type regions 621 to 624 are formed in a self-aligning manner. (Fig. 19B)

Next, a resist mask 630 that covers the n-channel TFT is formed. Using the resist mask 630, boron is added to the semiconductor layer 304 at a high concentration by an ion doping method. The first and third gate electrodes 371 and 373 function as a mask, and a channel formation region 631 and p ⁺ -type impurity regions 632 and 633 that function as a source region and a drain region are formed in the semiconductor layer 304 in a self-aligned manner. . (Fig. 19 (C))

Next, the resist mask 630 is removed, and a resist mask 640 that partially covers the entire p-channel TFT and the n-channel TFT is formed. Using the resist mask 640, phosphorus is added at a high concentration by ion doping. Phosphorus is selectively added to the n ⁻ -type impurity regions 621 and 622 of the semiconductor layer 303 of the n-channel TFT, whereby n ⁺ -type impurity regions 642 and 643 are formed. Further, the region covered with the resist mask 640 includes a channel formation region 641, n ⁻ -type impurity regions 644 and 645 that overlap with the first gate electrode 371, and n ⁻ that does not overlap with the first gate electrode 371. This is defined as type impurity regions 646 and 647. (FIG. 19D)

Also in this embodiment, the n ⁻ -type impurity regions 644 and 645 overlapping with the gate electrode 371 have a phosphorous concentration lower than that of the n ⁻ -type impurity regions 646 and 647 (and the n ⁺ -type impurity regions 642 and 643). The concentration decreases toward the channel formation region 641.

  After removing the resist mask 640, a protective film 306 made of silicon oxide having a thickness of 50 nm is formed, and heat treatment is performed to activate phosphorus and boron added to the semiconductor layer. An interlayer insulating film 307 is formed, contact holes are opened, and source electrodes 384 and 385 and a drain electrode 386 are formed. Thus, a CMOS circuit is manufactured. (Fig. 19 (E))

  In this embodiment, the width of the first gate electrode of the p-channel TFT is reduced, but this step can be omitted.

In this embodiment, the resist masks 630 and 640 covering the p-channel TFT are formed in the phosphorus addition step, but the resist masks 630 and / or 640 may be omitted. In this case, since phosphorus is added to the p ⁺ -type impurity regions 632 and 633, it is necessary to add a large amount of boron in consideration of the concentration of added phosphorus.

  This example is a modification of Example 1, in which the order of phosphorus and boron addition steps is changed. The main configuration is the same as that of the first embodiment.

  A manufacturing process of this example will be described with reference to FIGS. 20, the same reference numerals as those in FIGS. 15 and 16 denote the same components.

  This embodiment corresponds to a modification of the fourth embodiment, and the third gate electrode 373 is formed by narrowing the first gate electrode of the p-channel TFT as in the fourth embodiment. (FIG. 20 (A))

  Next, a resist mask 650 partially covering the entire p-channel TFT and the n-channel TFT is formed. Using the resist mask 650, phosphorus is added at a high concentration by ion doping to form n-type regions 651 and 652. (Fig. 20 (B))

Next, a resist mask 660 that covers the n-channel TFT is formed. Using the resist mask 660, boron is added to the semiconductor layer 304 at a high concentration by an ion doping method. The first and third gate electrodes 371 and 373 function as a mask, and a channel formation region 661 and p ⁺ -type impurity regions 662 and 663 that function as a source region and a drain region are formed in the semiconductor layer 304 in a self-aligned manner. . (Figure 20 (C))

  Next, the resist mask 660 is removed, and a resist mask 670 covering the entire p-channel TFT is newly formed. Phosphorus is added at a low concentration by an ion doping method, and the acceleration voltage is set as high as 90 keV so that the phosphorus passes through the tapered portion of the first gate electrode 371.

As a result, the channel formation region 671, the n ⁺ -type impurity regions 672 and 673, the n ⁻ -type impurity regions 674 and 675 overlapping with the first gate electrode 371, and the first channel region 671 are formed in the semiconductor layer 303 of the n-channel TFT. N ⁻ -type impurity regions 676 and 677 which do not overlap with the gate electrode 371 are formed in a self-aligned manner. (Fig. 20D)

  After removing the resist mask 670, a protective film 306 made of silicon oxide having a thickness of 50 nm is formed, and heat treatment is performed to activate phosphorus and boron added to the semiconductor layer. An interlayer insulating film 307 is formed, contact holes are opened, and source electrodes 384 and 385 and a drain electrode 386 are formed. Thus, a CMOS circuit is manufactured. (Fig. 20 (E))

  In this embodiment, the width of the first gate electrode of the p-channel TFT is reduced, but this step can be omitted.

In this embodiment, the resist masks 650 and 670 covering the p-channel TFT are formed in the phosphorus addition step. However, these resist masks 650 and / or 670 may be omitted. In this case, since phosphorus is added to the p ⁺ -type impurity regions 662 and 663, it is necessary to add a large amount of boron in consideration of the concentration of added phosphorus.

  The present embodiment is a modification of the first embodiment, in which the order of adding phosphorus and boron is changed, and the other configurations are substantially the same as those of the first embodiment.

  Hereinafter, a manufacturing process of this example will be described with reference to FIGS. In FIG. 21, the same reference numerals as those in FIGS. 15 and 16 denote the same components.

  This embodiment corresponds to a modification of the fifth embodiment, and the third gate electrode 373 is formed by narrowing the first gate electrode of the p-channel TFT as in the fifth embodiment. (FIG. 21 (A))

  Further, as in Embodiment 5, a resist mask 680 that covers the entire p-channel TFT and the n-channel TFT is formed. Using the resist mask 680, phosphorus is added at a high concentration by ion doping to form n-type regions 681 and 682. (Fig. 21 (B))

  Next, the resist mask 680 is removed, and a resist mask 690 that covers the entire p-channel TFT is newly formed. Phosphorus is added at a low concentration by ion doping. The acceleration voltage is set as high as 90 keV so that phosphorus passes through the tapered portion of the first gate electrode 371.

As a result, in the semiconductor layer 303 of the n-channel TFT, the channel formation region 691, the n ⁺ -type impurity regions 692 and 693, the n ⁻ -type impurity regions 694 and 675 overlapping with the first gate electrode 371, and the first n does not overlap with the gate electrode 371 of the ^- -type impurity regions 696 and 697 are formed in a self-aligned manner. (Fig. 21 (C))

Next, after forming a resist mask 700 covering the entire n-channel TFT, boron is added to the semiconductor layer 304 at a high concentration by an ion doping method. The first and third gate electrodes 371 and 373 function as a mask, and a channel formation region 701 and p ⁺ -type impurity regions 702 and 703 that function as a source region and a drain region are formed in the semiconductor layer 304 in a self-aligned manner. . (Fig. 21 (D))

  After removing the resist mask 700, a protective film 306 made of silicon oxide having a thickness of 50 nm is formed, and heat treatment is performed to activate phosphorus and boron added to the semiconductor layer. An interlayer insulating film 307 is formed, contact holes are opened, and source electrodes 384 and 385 drain electrodes 386 are formed. Thus, a CMOS circuit is manufactured. (Fig. 21 (E))

  In this embodiment, the width of the first gate electrode of the p-channel TFT is reduced, but this step can be omitted.

In this embodiment, the resist masks 680 and 690 that cover the p-channel TFT are formed in the phosphorus addition step, but the resist masks 680 and / or 690 may be omitted. In this case, since phosphorus is added to the p ⁺ -type impurity regions 702 and 703, it is necessary to add a large amount of boron in consideration of the concentration of added phosphorus.

  As described above, the fabrication process of the CMOS circuit is described in the second to sixth embodiments. However, the present embodiment can be applied to the fabrication process of the active matrix substrate in which the pixel portion and the driver circuit are integrated as in the first embodiment. Needless to say.

  In this embodiment, an example of a gate electrode having a tapered portion and a method for forming the gate electrode described in Embodiment 1 and the like will be described.

  First, a gate insulating film made of a silicon nitride oxide film was formed, and a metal laminated film was formed thereon by sputtering. In this example, a tungsten target having a purity of 6N or more was used. As the sputtering gas, a single gas such as argon (Ar), krypton (Kr), xenon (Xe), or a mixed gas thereof may be used. The practitioner may appropriately control film forming conditions such as sputtering power, gas pressure, and substrate temperature. The metal laminated film has a tungsten nitride film represented by WNx (where 0 <x <1) in the lower layer and a tungsten film in the upper layer.

The metal laminated film thus obtained contains almost no impurity elements, and particularly the oxygen content can be 30 ppm or less, and the electrical resistivity is 20 μΩ · cm or less, typically 6 μ to 15 μΩ. -Can be cm. Further, the stress of the film can be a ^{-5 × 10 9 ~5 × 10 9} dyn / cm 2.

  Note that the silicon nitride oxide film is an insulating film expressed by SiOxNy and indicates an insulating film containing silicon, oxygen, and nitrogen at a predetermined ratio.

  Next, a resist mask pattern (film thickness: 1.5 μm) for obtaining a desired gate wiring pattern is formed.

  Next, in this example, etching was performed using an ICP (Inductively Coupled Plasma) etching apparatus that uses high-density plasma for patterning of the metal laminated film, thereby forming a gate electrode and a gate electrode having a tapered cross section. .

  Here, the ICP dry etching apparatus plasma generation mechanism will be described in detail with reference to FIG.

  FIG. 22 shows a simplified structure diagram of the etching chamber. An antenna coil 12 is disposed on the quartz plate 11 at the upper part of the chamber, and is connected to an RF power source 14 via a matching box 13. Further, an RF power source 17 is connected to the lower electrode 15 on the substrate side arranged opposite to the substrate via a matching box 16.

  When an RF current is applied to the antenna coil 12 above the substrate, the RF current J flows through the antenna coil 12 in the α direction, and a magnetic field B is generated in the Z direction. The relationship between the current J and the magnetic field B follows the following equation.

μ ₀ J = rotB (μ ₀ is magnetic susceptibility)

  In accordance with Faraday's law of electromagnetic induction expressed by the following equation, an induced electric field E is generated in the α direction.

  ―∂B / ∂t = rotE

  Electrons are accelerated in the α direction by this induced electric field E, collide with gas molecules, and plasma is generated. Since the direction of the induced electric field is the α direction, the probability that the charged particles collide with the etching chamber wall or the substrate and lose the charge is reduced. Therefore, high-density plasma can be generated even at a low pressure of about 1 Pa. Further, since there is almost no magnetic field B downstream, a high-density plasma region spreading in a sheet shape is obtained.

  The plasma density and the self-bias voltage are independently controlled by adjusting the RF power applied to each of the antenna coil 12 (ICP power is applied) and the lower electrode 15 on the substrate side (bias power is applied). Is possible. Further, RF power having a different frequency can be applied depending on the film to be etched.

  In order to obtain high-density plasma with an ICP etching apparatus, it is necessary to flow the RF current J flowing through the antenna coil 12 with low loss. To increase the area, the inductance of the antenna coil 12 must be reduced. Therefore, as shown in FIG. 23, an ICP etching apparatus for a multi-spiral coil 22 having an antenna divided has been developed. In FIG. 23, 21 is a quartz plate, 23 and 26 are matching boxes, and 24 and 27 are RF power supplies. In addition, a lower electrode 25 that holds the substrate 28 is provided via an insulator 29 at the bottom of the chamber.

  In this example, a wiring having a desired taper angle θ was formed by using a multi-spiral coil ICP etching apparatus among various ICP etching apparatuses.

  In this embodiment, in order to obtain a desired taper angle θ, the bias power density of the ICP etching apparatus is adjusted. FIG. 24 is a diagram showing the bias power dependence of the taper angle θ. As shown in FIG. 24, the taper angle θ can be controlled according to the bias power density.

Further, the flow rate ratio of CF _{4 in} the etching gas (mixed gas of CF ₄ and Cl ₂ ) may be adjusted. FIG. 25 is a graph showing the dependence of the taper angle θ on the flow rate ratio of CF ₄ . If the flow rate ratio of CF ₄ is increased, the selection ratio between tungsten and resist is increased, and the taper angle θ of the wiring can be increased.

  Further, the taper angle θ is considered to depend on the selection ratio between tungsten and resist. FIG. 26 shows the dependence of the selectivity between tungsten and resist on the taper angle θ.

  In this way, by appropriately determining the bias power density and the reaction gas flow rate ratio using the ICP etching apparatus, the desired taper angle θ = 3 to 60 ° (preferably 5 to 45 °, more preferably 7 to 5 °). 20 °) could be formed.

  Here, the W film is shown as an example. However, when an ICP etching apparatus is used for a commonly known heat-resistant conductive material (Ta, Ti, Mo, Cr, Nb, Si, etc.), an end portion of the pattern can be easily obtained. Can be processed into a tapered shape.

In addition, a mixed gas of CF ₄ (carbon tetrafluoride gas) and Cl ₂ gas is used as the etching gas used for the dry etching, but there is no particular limitation. For example, from C ₂ F ₆ or C ₄ F ₈ It is also possible to use a mixed gas of a reaction gas containing selected fluorine and a gas containing chlorine selected from Cl ₂ , SiCl ₄ , or BCl ₃ .

  If the subsequent steps are in accordance with the first embodiment, the semiconductor device is completed.

  Note that the configuration of this embodiment can be applied to a manufacturing process of an electrode having a tapered portion of the embodiment described in this specification.

  In Example 1, a polycrystalline silicon film crystallized by an excimer laser was used for the semiconductor layer, but this example shows another crystallization method.

  The crystallization process in this example is a crystallization technique described in Japanese Patent Laid-Open No. 7-130552. This crystallization process will be described with reference to FIG.

  First, a silicon oxide film 1002 is formed as a base film over the glass substrate 1001. An amorphous silicon film 1003 is formed over the silicon oxide film 1002. In this embodiment, the silicon oxide film 1002 and the amorphous silicon film 1003 are continuously formed by a sputtering method. Next, a nickel-containing layer 1004 was formed by applying a nickel acetate salt solution containing 10 ppm of nickel in terms of weight. (Fig. 27 (A))

  In addition to nickel (Ni), germanium (Ge), iron (Fe), palladium (Pd), tin (Sn), lead (Pb), cobalt (Co), platinum (Pt), copper (Cu), One or more elements selected from elements such as gold (Au) and silicon (Si) may be used.

  Next, after the hydrogen soaking process at 600 ° C. for 1 hour, a heat treatment was performed at 450 to 1100 ° C. for 4 to 12 hours (500 ° C. for 4 hours in this embodiment) to form a crystalline silicon film 1005. It has been found that the crystalline silicon film 1005 thus obtained has very excellent crystallinity. (Fig. 27 (B))

  Note that the crystallization process in this embodiment can be applied to the semiconductor layer formation process described in this specification.

  This example relates to a crystallization process different from that of Example 8, and an example in the case of crystallization using the technique described in JP-A-8-78329 will be described. The technique described in JP-A-8-78329 enables selective crystallization of a semiconductor film by selectively adding a catalytic element. The case where the technique is applied to the present invention will be described with reference to FIG.

  First, a silicon oxide film 1012 was formed over the glass substrate 1011, and an amorphous silicon film 1013 and a silicon oxide film 1014 were continuously formed over the surface. At this time, the thickness of the silicon oxide film 1014 was set to 150 nm.

  Next, the silicon oxide film 1014 was patterned to selectively form openings 1015, and then a nickel acetate salt solution containing 100 ppm of nickel in terms of weight was applied. The formed nickel-containing layer 1016 was in contact with the amorphous silicon film 1013 only at the bottom of the opening 1015. (FIG. 28 (A))

  Next, heat treatment was performed at 500 to 650 ° C. for 4 to 24 hours (in this embodiment, 550 ° C. for 14 hours) to crystallize the amorphous silicon film. In this crystallization process, the portion in contact with nickel crystallizes first, and then crystal growth proceeds in a direction substantially parallel to the substrate. Crystallographically, it has been confirmed that it proceeds toward the <111> axis direction.

  The crystalline silicon film 1017 thus formed is a collection of rod-like or needle-like crystals, and each rod-like crystal grows macroscopically in a specific direction, so that the crystallinity is uniform. There is an advantage.

In the technology described in the above publication, germanium (Ge), iron (Fe), palladium (Pd), tin (Sn), lead (Pb), cobalt (Co) in addition to nickel (Ni).
One or more elements selected from elements such as platinum (Pt), copper (Cu), gold (Au), and silicon (Si) can be used.

A semiconductor film including a crystal (including a crystalline silicon film and a crystalline silicon germanium film) is formed by using the above technique, and patterning is performed to form a semiconductor layer including the semiconductor film including a crystal. Subsequent steps may be performed according to the first embodiment.
Of course, the combination with Examples 2-7 is also possible.

  When a TFT is manufactured using a semiconductor film containing a crystal that is crystallized by using the technique of this embodiment, high field-effect mobility (mobility) can be obtained. Therefore, high reliability is required. However, by adopting the TFT structure of the present invention, it has become possible to produce a TFT that makes the most of the technique of this embodiment.

  In this example, nickel used for crystallization of the semiconductor shown in Examples 8 and 9 is removed using phosphorus after crystallization. In the present embodiment, the technique described in Japanese Patent Application Laid-Open No. 10-135468 or Japanese Patent Application Laid-Open No. 10-135469 is used as the method.

The technique described in the publication is a technique for removing a catalytic element used for crystallization of an amorphous semiconductor film by using a gettering action of phosphorus after crystallization. By using this technique, the concentration of the catalytic element in the crystalline semiconductor film can be reduced to 1 × 10 ¹⁷ atoms / cm ³ or less, preferably 1 × 10 ¹⁶ atoms / cm ³ .

  The configuration of this embodiment will be described with reference to FIG. Here, an alkali-free glass substrate typified by Corning's 1737 substrate was used. FIG. 29A shows a state in which a base film 1022 and a crystalline silicon film 1023 are formed by using the crystallization technique shown in Embodiment 2. A silicon oxide film 1024 for a mask is formed on the surface of the crystalline silicon film 1023 to a thickness of 150 nm, an opening is provided by patterning, and a region where the crystalline silicon film is exposed is provided. Then, a step of adding phosphorus was performed to provide a region 1025 in which phosphorus was added to the crystalline silicon film.

  In this state, when heat treatment is performed in a nitrogen atmosphere at 550 to 1020 ° C. for 5 to 24 hours, for example, 600 ° C. for 12 hours, the region 1025 in which phosphorus is added to the crystalline silicon film works as a gettering site, The catalytic element remaining in the conductive silicon film 1023 could be segregated in the region 1025 to which phosphorus was added.

Then, the silicon oxide film 1024 for mask and the region 1025 to which phosphorus is added are removed by etching, so that the concentration of the catalytic element used in the crystallization step is 1 × 10 ¹⁷ atms / cm ³ or less. It was possible to obtain a crystalline silicon film with a reduced thickness. This crystalline silicon film could be used as it is as the semiconductor layer of the TFT of the present invention shown in Example 1.

  In this embodiment, an example in which the techniques described in Japanese Patent Laid-Open No. 10-135468 or Japanese Patent Laid-Open No. 10-135469 are combined with the eighth and ninth embodiments.

The technique described in this publication is a technique for removing nickel used for crystallization of the semiconductor shown in Examples 3 and 4 by using a gettering action of a halogen element (typically chlorine) after crystallization. is there. By using this technique, the nickel concentration in the semiconductor layer can be reduced to 1 × 10 ¹⁷ atoms / cm ³ or less (preferably 1 × 10 ¹⁶ atoms / cm ³ or less).

  The configuration of this example will be described with reference to FIG. First, a quartz substrate 1031 having high heat resistance was used as the substrate. Of course, a silicon substrate or a ceramic substrate may be used. When a quartz substrate is used, there is no contamination from the substrate side even if a silicon oxide film is not provided as a base film.

  Next, a crystalline silicon film (not shown) was formed by using the crystallization method of Examples 3 and 4, and patterned to form semiconductor layers 1032 and 1033. Further, a gate insulating film 1034 made of a silicon oxide film was formed so as to cover these semiconductor layers. (Fig. 30 (A))

  After the gate insulating film 1034 was formed, heat treatment was performed in an atmosphere containing a halogen element. In this embodiment, the processing atmosphere is an oxidizing atmosphere in which oxygen and hydrogen chloride are mixed, the processing temperature is 950 ° C., and the processing time is 30 minutes. The treatment temperature may be selected between 700 to 1150 ° C. (typically 900 to 1000 ° C.), and the treatment time is also between 10 minutes and 8 hours (typically 30 minutes to 2 hours). Just choose. (Fig. 30 (B))

At this time, nickel becomes volatile nickel chloride and is released into the processing atmosphere, so that the nickel concentration in the crystalline silicon film is reduced. Therefore, the concentration of nickel contained in the semiconductor layers 1035 and 1036 shown in FIG. 30B has been reduced to 1 × 10 ¹⁷ atoms / cm ³ or less.

  A semiconductor layer is formed using the present embodiment having the above-described technique, and the subsequent steps may follow the first and second embodiments. Of course, it has been found that the combination of this embodiment and the crystallization method of Embodiment 4 can realize a crystalline silicon film having very high crystallinity.

(Knowledge about crystal structure of semiconductor layer)
The semiconductor layer formed in accordance with the above manufacturing process has a crystal structure in which a plurality of needle-like or rod-like crystals (hereinafter abbreviated as rod-like crystals) are gathered and arranged microscopically. This was easily confirmed by observation with TEM (transmission electron microscopy).

  In addition, although the surface of the semiconductor layer (portion forming portion) includes some deviation in the crystal axis by using electron diffraction and X-ray (X-ray) diffraction, the main orientation plane is the {110} plane. It was confirmed. As a result of detailed observation of an electron diffraction photograph with a spot diameter of about 1.5 μm by the present applicant, diffraction spots corresponding to the {110} plane appear clearly, but each spot has a distribution on a concentric circle. confirmed.

  In addition, the present applicant observed the grain boundary formed by the contact of individual rod-like crystals with HR-TEM (High Resolution Transmission Electron Microscopy), and confirmed that the crystal lattice has continuity at the grain boundary. . This can be easily confirmed by the fact that the observed lattice fringes are continuously connected at the grain boundaries.

  Note that the continuity of the crystal lattice at the crystal grain boundary results from the fact that the crystal grain boundary is a grain boundary called a “planar grain boundary”. The definition of the planar grain boundary in this specification is “Characterization of High-Efficiency Cast-Si Solar Cell Wafers by MBIC Measurement; Ryuichi Shimokawa and Yutaka Hayashi, Japanese Journal of Applied Physics vol.27, No.5, pp.751”. -758, 1988 ”is the“ Planar boundary ”.

  According to the above paper, planar grain boundaries include twin grain boundaries, special stacking faults, and special twist grain boundaries. This planar grain boundary is characterized by being electrically inactive. That is, although it is a crystal grain boundary, it does not function as a trap that inhibits the movement of carriers, and thus can be regarded as substantially nonexistent.

  In particular, when the crystal axis (axis perpendicular to the crystal plane) is the <110> axis, the {211} twin grain boundary is also called a corresponding grain boundary of Σ3. The Σ value is a parameter that serves as a guideline indicating the degree of consistency of the corresponding grain boundary. It is known that the smaller the Σ value, the better the grain boundary.

  As a result of observing the crystalline silicon film obtained by implementing the present invention in detail using TEM, most of the crystal grain boundaries (90% or more, typically 95% or more) correspond to Σ3. It was found to be a boundary, ie, {211} twin grain boundary.

  In the crystal grain boundary formed between two crystal grains, when the plane orientation of both crystals is {110}, assuming that the angle formed by the lattice stripes corresponding to the {111} plane is θ, θ = 70.5 ° It is known that sometimes it becomes the corresponding grain boundary of Σ3.

  In the crystalline silicon film of the present example, each lattice fringe of adjacent crystal grains in the crystal grain boundary is continuous at an angle of about 70.5 °. Therefore, this crystal grain boundary is a {211} twin crystal grain boundary. I came to the conclusion that there was.

  Incidentally, when θ = 38.9 °, the corresponding grain boundary of Σ9 is obtained, but such other crystal grain boundaries also existed.

  Such a corresponding grain boundary is formed only between crystal grains having the same plane orientation. That is, since the crystalline silicon film obtained by carrying out this embodiment has a plane orientation of approximately {110}, such a corresponding grain boundary can be formed over a wide range.

  Such a crystal structure (exactly, the structure of the crystal grain boundary) indicates that two different crystal grains are joined with extremely good consistency at the crystal grain boundary. That is, the crystal lattice is continuously connected at the crystal grain boundary, and the trap level caused by crystal defects or the like is very difficult to create. Therefore, it can be considered that the semiconductor thin film having such a crystal structure is substantially free of crystal grain boundaries.

  In addition, it has been confirmed by TEM observation that defects existing in the crystal grains have almost disappeared by the heat treatment step at a high temperature of 700 to 1150 ° C. This is also clear from the fact that the number of defects is greatly reduced before and after this heat treatment step.

The difference in the number of defects appears as a difference in spin density by electron spin resonance analysis (Electron Spin Resonance: ESR). At present, it has been found that the spin density of the crystalline silicon film manufactured according to the manufacturing process of this example is at least 3 × 10 ¹⁷ spins / cm ³ or less (preferably 5 × 10 ¹⁵ spins / cm ³ or less). Yes. However, since this measured value is close to the detection limit of existing measuring devices, the actual spin density is expected to be even lower.

  From the above, the crystalline silicon film obtained by carrying out this embodiment is considered to be a single crystal silicon film or a substantially single crystal silicon film because there are substantially no crystal grains and no crystal grain boundaries. Good. The present applicant refers to a crystalline silicon film having such a crystal structure as CGS (Continuous Grain Silicon).

  For the description of CGS, reference may be made to the applications of Japanese Patent Application No. 10-294280, Japanese Patent Application No. 10-152316, Japanese Patent Application No. 10-152308, or Japanese Patent Application No. 10-152305 by the present applicant.

(Knowledge about electrical characteristics of TFT)
The TFT fabricated in this example showed electrical characteristics comparable to a MOSFET. The following data is obtained from the TFT manufactured by the present applicant.

The subthreshold coefficient, which is an index of switching performance (on / off operation switching agility), is as small as 60 to 100 mV / decade (typically 60 to 85 mV / decade) for both the n-channel TFT and the p-channel TFT.

(2) Field-effect mobility (μFE), which is an index of TFT operating speed, is 200 to 650 cm ² / Vs (typically 300 to 500 cm ² / Vs) for an n-channel TFT, and 100 for a p-channel TFT. ~300cm ² / Vs (typically 150~200cm ² / Vs) as large as.

  (3) The threshold voltage (Vth), which serves as an index of TFT driving voltage, is as low as -0.5 to 1.5 V for n-channel TFTs and -1.5 to 0.5 V for p-channel TFTs.

  As described above, it has been confirmed that extremely excellent switching characteristics and high-speed operation characteristics can be realized.

(Knowledge about circuit characteristics)
Next, frequency characteristics of a ring oscillator manufactured using a TFT formed by implementing this embodiment are shown. The ring oscillator is a circuit in which inverter circuits having a CMOS structure are connected in an odd-numbered ring shape, and is used to obtain a delay time per inverter circuit. The structure of the ring oscillator used in the experiment is as follows.
Number of stages: 9 stages
TFT gate insulating film thickness: 30nm and 50nm
TFT gate length: 0.6μm

  As a result of examining the oscillation frequency with this ring oscillator, it was possible to obtain an oscillation frequency of 1.04 GHz at the maximum value. In addition, a shift register, which is actually one of the TEGs of the LSI circuit, was manufactured and the operating frequency was confirmed. As a result, an output pulse with an operating frequency of 100 MHz was obtained in a shift register circuit having a gate insulating film thickness of 30 nm, a gate length of 0.6 μm, a power supply voltage of 5 V, and the number of stages of 50.

  The amazing data of the ring oscillator and the shift register as described above indicate that the TFT of this embodiment has performance (electrical characteristics) comparable to or surpassing that of the MOSFET.

  This embodiment also relates to a technique for gettering the catalyst element used in the crystallization process.

In Example 10, the gettering region 1025 (see FIG. 29) needs to be formed in order to getter the catalytic element in the crystallized silicon. Since it becomes impossible to form TFTs in the gettering region, circuit integration is hindered. This embodiment is a gettering method that solves the above problems, the n-channel type TFT n ⁺ -type impurity regions and, using a p ⁺ -type impurity region of the p-channel type TFT in the gettering region.

In the process shown in Embodiment 1, phosphorus is present at a high concentration of 5 × 10 ²⁰ atoms / cm ^{3 in} the n ⁺ -type impurity regions 313 to 315 and the p ⁺ -type impurity regions 332 and 333. (See FIGS. 14 and 16) Therefore, these regions can be used as gettering regions.

  For this reason, when the TFT semiconductor layers 302 to 304 are formed of crystalline silicon as shown in Embodiments 3 and 4, the activation process of phosphorus and boron may be combined with a heating process for gettering. For example, in the activation step (see FIGS. 14D and 16D), the processing temperature is 500 to 650 ° C. (typically 550 to 600 ° C.) for 2 to 24 hours (typically 4 to 4 hours). 12 hours) may be performed.

In this heat treatment step, nickel remaining in the channel formation regions 311, 312, 325, 331, and 341 of each TFT diffuses toward the n ⁺ -type impurity region and the p ⁺ -type impurity region by the action of phosphorus. Be captured.

Therefore, the nickel (catalyst) concentration of the n ⁺ -type impurity regions 313 to 315 and the p ⁺ -type impurity regions 332 and 333 is 1 × 10 ¹⁷ to 1 × 10 ²⁰ atoms / cm ³ (typically 1 × 10 ¹⁸ to 5 × 10 ¹⁹ atoms / cm ³ ), while the nickel concentration in the channel formation regions 311, 312, 325, 331, and 341 is 2 × 10 ¹⁷ atoms / cm ³ or less (typically 1 × 10 ¹⁴ to 5 × 10 ¹⁶ atoms / cm ³ ).

In order to obtain the effect of this embodiment, the n ⁺ -type impurity regions 313 to 315 and the p ⁺ -type impurity regions 332 and 333 have a phosphorus or arsenic concentration of at least 1 × 10 ¹⁹ atoms / cm ³ or more ( It is preferably 1 × 10 ^{20 to} 5 × 10 ²¹ atoms / cm ³ ).

  This embodiment is a modification of the CMOS circuit of the first embodiment. Using FIG. The structure of the TFT of this example will be described. 31A to 31D, the same reference numerals indicate the same components. In addition, the manufacturing steps of this embodiment may be applied to the first and second embodiments, and detailed description thereof is omitted.

  FIG. 31A is a modified example of the first embodiment, in which the second gate electrode (wiring) is omitted and the gate electrode (wiring) is formed only by an electrode (wiring) having a tapered portion. .

  A base film 901 made of silicon oxide is formed on the entire surface of the substrate 900. On the base film 901, an island-shaped semiconductor layer of an n-channel TFT and a p-channel TFT is formed. A gate insulating film 905 is formed over the entire surface of the substrate 900 so as to cover the island-shaped semiconductor layer. Further, a protective film 906 made of silicon nitride and an interlayer insulating film 907 are formed to cover the TFT, and source electrodes 941 and 942 and a drain electrode 943 are formed on the interlayer insulating film 907.

  A gate wiring (gate electrode) 933 is formed across the semiconductor layers with the gate insulating film 905 interposed therebetween. The side surface of the gate wiring 931 is tapered. Here, chromium was formed with a thickness of 250 nm. Further, the width of the portion intersecting with the semiconductor layer of the p-channel TFT is narrowed to form the second gate electrode 933A.

Further, Example 1 was applied as a method of adding phosphorus and boron to the semiconductor layer. The semiconductor layer of the n-channel TFT, and the channel formation region 911A, n ⁺ -type impurity regions 912A, 913A, n overlaps with the gate electrode 931A ^- impurity type regions 914A, 915A, does not overlap with the gate electrode 931A n ^- -type Impurity regions 916A and 917A are formed.

The n ⁻ type impurity regions 914A and 915A and the n ⁻ type impurity regions 916A and 917A have a lower phosphorus concentration than the n ⁺ type impurity regions 912A and 913A. Further, junctions between the n ⁻ -type impurity regions 914A and 915A and the channel formation region 911A exist below the tapered portion of the gate electrode 931A, and the concentrations of the n ⁻ -type impurity regions 914A and 915A are directed toward the channel formation region 911A. is decreasing.

On the other hand, a channel formation region 921A, p ⁺ type impurity regions 922A and 923A, and p ⁺ type impurity regions 924A and 925A are formed in the semiconductor layer of the p channel type TFT. The p ⁺ -type impurity regions 924A and 925A have a lower phosphorus concentration and the same boron concentration than the p ⁺ -type impurity regions 922A and 923A.

  FIG. 31B is a modification of the second and third embodiments, in which the second electrode is omitted and the gate electrode is formed only with an electrode having a tapered portion.

  In FIG. 31B, the gate electrode 931B is tapered in both the n-channel TFT and the p-channel TFT. Here, chromium was formed with a thickness of 250 nm.

In addition, Example 2 was applied to the step of adding phosphorus and boron to the semiconductor layer. The semiconductor layer of the n-channel TFT, and the channel formation region 911B, n ⁺ -type impurity regions 912B, 913B, n overlaps with the gate electrode 931B ^- impurity type region 914B, 915B, not overlapping with the gate electrode 931B n ^- -type Impurity regions 916B and 917B are formed.

The n ⁻ type impurity regions 914B and 915B and the n ⁻ type impurity regions 916B and 917B have a lower phosphorus concentration than the n ⁺ type impurity regions 912B and 913B. Further, the junctions between the n ⁻ type impurity regions 914B and 915B and the channel formation region 911B exist below the tapered portion of the gate electrode 931, and the concentrations of the n ⁻ type impurity regions 914B and 915B are directed toward the channel formation region 911B. is decreasing.

On the other hand, a channel formation region 921B and p ⁺ -type impurity regions 922B and 923B are formed in the semiconductor layer of the p-channel TFT in a self-aligned manner using the gate electrode 931B as a mask.

  FIG. 31C is an example in which the taper etching of the first gate electrode is omitted in the first embodiment.

  The gate wiring includes a first gate wiring 931C and a second gate wiring 932C having a narrower width in the channel length direction than the first gate wiring 931C. Note that a third gate electrode 933C having a reduced width is formed using the second gate wiring 932C as a mask at a portion where the first gate wiring 931C intersects the semiconductor layer of the p-channel TFT.

The semiconductor layer of the n-channel TFT, and the channel formation region 911C, n ⁺ -type impurity regions 912C, 913C, n overlaps with the gate electrode 931C ^- impurity type regions 914C, 915C, not overlapping with the gate electrode 931C n ^- type Impurity regions 916C and 917C are formed.

The n ⁻ type impurity regions 914C and 915C and the n ⁻ type impurity regions 916C and 917C have a lower phosphorus concentration than the n ⁺ type impurity regions 912C and 913C.

On the other hand, a channel formation region 921C, p ⁺ -type impurity regions 922C and 923C, and p ⁺ -type impurity regions 924C and 925C are formed in the semiconductor layer of the p-channel TFT. The p ⁺ -type impurity regions 924C and 925C have a lower phosphorus concentration than the p ⁺ -type impurity regions 922C and 923C.

  FIG. 31D shows an example in which a fourth gate wiring covering the surface of the gate wiring is formed in the first embodiment.

  The CMOS circuit performs a boron addition process according to the process of the first embodiment. Next, instead of forming the protective film 906 made of silicon nitride, a metal film made of chromium (Cr), tantalum (Ta), titanium (Ti), tungsten (W), molybdenum (Mo), or these elements is used. A conductive material such as an alloy as a main component or silicide is formed and patterned to form a fourth gate wiring 934D. Thereafter, activation may be performed.

  With this configuration, a gate wiring having a structure in which the second gate wiring 932D is surrounded by the first gate wiring 931D (including the third gate electrode 933D) and the fourth gate wiring 934D can be obtained.

In this case, the n-channel TFT semiconductor layer overlaps with the n ⁻ impurity type regions 914D and 915D and the gate electrode 931D which overlap with the channel formation region 911D, the n ⁺ type impurity regions 912D and 913D, and the gate electrode 931D. N ⁻ -type impurity regions 916D and 917D are formed. The n ⁻ -type impurity regions 914D and 915D are portions intersecting the first and fourth gate electrodes, and the n ⁻ -type impurity regions 916D and 916D 917D does not cross the fourth gate electrode 934D.

The advantage of this configuration is particularly effective when almost no phosphorus is added to the semiconductor layer below the first gate electrode 931D. As shown in FIG. 31D, the fourth gate electrode 934D is overlapped with the n ⁻ -type impurity region even if the n ⁻ impurity-type regions 914D and 915D hardly overlap with the first gate electrode 931D. Therefore, it is possible to reliably form an n ⁻ -type impurity region that overlaps with the gate electrode.

On the other hand, a channel formation region 921D, p ⁺ -type impurity regions 922D and 923D, and p ⁺ -type impurity regions 924D and 925D are formed in the semiconductor layer of the p-channel TFT. The p ⁺ type impurity regions 924D and 925D have a lower phosphorus concentration than the p ⁺ type impurity regions 922D and 923D. In this case, the n ⁻ -type impurity region and the fourth gate electrode 934D overlap. When a problem occurs in off-state current characteristics or withstand voltage, when the fourth gate wiring 934D is formed, the fourth gate wiring 934D is not formed in a portion intersecting with the semiconductor layer of the p-channel TFT. You can do it.

  In addition to nematic liquid crystals, various liquid crystals can be used for the liquid crystal display device described in this specification. For example, 1998, SID, "Characteristics and Driving Scheme of Polymer-Stabilized Monostable FLCD Exhibiting Fast Response Time and High Contrast Ratio with Gray-Scale Capability" by H. Furue et al., 1997, SID DIGEST, 841, "A Full -Color Thresholdless Antiferroelectric LCD Exhibiting Wide Viewing Angle with Fast Response Time "by T. Yoshida et al., 1996, J. Mater. Chem. 6 (4), 671-673," Thresholdless antiferroelectricity in liquid crystals and its application to The liquid crystal disclosed in "displays" by S. Inui et al. or US Pat. No. 5,945,569 can be used.

  Ferroelectric liquid crystal (FLC) showing an isotropic phase-cholesteric phase-chiral smectic C phase transition series is used to cause a cholesteric phase-chiral smectic C phase transition while applying a DC voltage, and the cone edge is almost in the rubbing direction. FIG. 41 shows the electro-optic characteristics of the matched monostable FLC. The display mode using the ferroelectric liquid crystal as shown in FIG. 41 is called “Half-V-shaped switching mode”. The vertical axis of the graph shown in FIG. 41 is the transmittance (arbitrary unit), and the horizontal axis is the applied voltage. Regarding “Half-V-shaped switching mode”, Terada et al., “Half-V-shaped switching mode FLCD”, Proceedings of the 46th Joint Physics Related Conference, March 1999, p. 1316, and Yoshihara et al. "Time-division full-color LCD using ferroelectric liquid crystal", Liquid Crystal, Vol. 3, No. 3, page 190.

  As shown in FIG. 41, it can be seen that when such a ferroelectric mixed liquid crystal is used, low voltage driving and gradation display are possible. In the liquid crystal display device of the present invention, a ferroelectric liquid crystal exhibiting such electro-optical characteristics can also be used.

  A liquid crystal exhibiting an antiferroelectric phase in a certain temperature range is called an antiferroelectric liquid crystal (AFLC). Among mixed liquid crystals having antiferroelectric liquid crystals, there is a so-called thresholdless antiferroelectric mixed liquid crystal that exhibits electro-optic response characteristics in which transmittance continuously changes with respect to an electric field. This thresholdless antiferroelectric mixed liquid crystal has a so-called V-shaped electro-optic response characteristic, and a drive voltage of about ± 2.5 V (cell thickness of about 1 μm to 2 μm) is also found. Has been.

  In general, the thresholdless antiferroelectric mixed liquid crystal has a large spontaneous polarization, and the dielectric constant of the liquid crystal itself is high. For this reason, when a thresholdless antiferroelectric mixed liquid crystal is used in a liquid crystal display device, a relatively large storage capacitor is required for the pixel. Therefore, it is preferable to use a thresholdless antiferroelectric mixed liquid crystal having a small spontaneous polarization.

  In addition, since such a thresholdless antiferroelectric mixed liquid crystal is used for the liquid crystal display device of the present invention, low voltage driving is realized, so that low power consumption is realized.

  The TFT of the present invention can be applied not only to the liquid crystal display device shown in Embodiment 1 but also to any semiconductor circuit. That is, the present invention may be applied to a microprocessor such as a RISC processor or an ASIC processor, or may be applied from a signal processing circuit such as a D / A converter to a high-frequency circuit for a portable device (mobile phone, PHS, mobile computer). .

  Furthermore, it is possible to realize a semiconductor device having a three-dimensional structure in which an interlayer insulating film is formed on a conventional MOSFET and a semiconductor circuit is manufactured thereon using the TFT of the present invention. As described above, the present invention can be applied to all semiconductor devices in which LSI is currently used. That is, the present invention may be applied to SOI structures (TFT structures using a single crystal semiconductor thin film) such as SIMOX, Smart-Cut (registered trademark of SOITEC) and ELTRAN (registered trademark of Canon Inc.).

  Further, the semiconductor circuit of the present embodiment can be realized by using a configuration composed of any combination of Embodiments 1 to 13.

  In this example, an example in which an active matrix EL (electroluminescence) display device is manufactured using the present invention will be described.

FIG. 35A is a top view of an EL display device using the present invention. FIG. 35 (A)
, Reference numeral 4010 denotes a substrate, 4011 denotes a pixel portion, 4012 denotes a source side driver circuit, and 4013 denotes a gate side driver circuit. Each driver circuit reaches an FPC 4017 through wirings 4014 to 4016 and is connected to an external device.

  At this time, a cover material 6000, a sealing material (also referred to as a housing material) 7000, and a sealing material (second sealing material) 7001 are provided so as to surround at least the pixel portion, preferably the drive circuit and the pixel portion.

  FIG. 35B shows a cross-sectional structure of the EL display device of this embodiment. A driver circuit TFT (here, an n-channel TFT and a p-channel TFT are combined on a substrate 4010 and a base film 4021). And the pixel portion TFT 4023 (however, only the TFT for controlling the current to the EL element is shown here). These TFTs may have a known structure (top gate structure or bottom gate structure).

  The present invention can be used for the driver circuit TFT 4022 and the pixel portion TFT 4023.

  When the driver circuit TFT 4022 and the pixel portion TFT 4023 are completed using the present invention, a transparent conductive film electrically connected to the drain of the pixel portion TFT 4023 is formed on the interlayer insulating film (planarization film) 4026 made of a resin material. A pixel electrode 4027 is formed. As the transparent conductive film, a compound of indium oxide and tin oxide (referred to as ITO) or a compound of indium oxide and zinc oxide can be used. Then, after the pixel electrode 4027 is formed, an insulating film 4028 is formed, and an opening is formed over the pixel electrode 4027.

  Next, an EL layer 4029 is formed. The EL layer 4029 may have a stacked structure or a single-layer structure by freely combining known EL materials (a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, or an electron injection layer). A known technique may be used to determine the structure. EL materials include low-molecular materials and high-molecular (polymer) materials. When a low molecular material is used, a vapor deposition method is used. When a high molecular material is used, a simple method such as a spin coating method, a printing method, or an ink jet method can be used.

  In this embodiment, the EL layer is formed by vapor deposition using a shadow mask. Color display is possible by forming a light emitting layer (a red light emitting layer, a green light emitting layer, and a blue light emitting layer) capable of emitting light having different wavelengths for each pixel using a shadow mask. In addition, there are a method in which a color conversion layer (CCM) and a color filter are combined, and a method in which a white light-emitting layer and a color filter are combined. Needless to say, an EL display device emitting monochromatic light can also be used.

  After the EL layer 4029 is formed, a cathode 4030 is formed thereon. It is desirable to remove moisture and oxygen present at the interface between the cathode 4030 and the EL layer 4029 as much as possible. Therefore, it is necessary to devise such that the EL layer 4029 and the cathode 4030 are continuously formed in a vacuum, or the EL layer 4029 is formed in an inert atmosphere and the cathode 4030 is formed without being released to the atmosphere. In this embodiment, the above-described film formation is possible by using a multi-chamber type (cluster tool type) film formation apparatus.

  In this embodiment, a stacked structure of a LiF (lithium fluoride) film and an Al (aluminum) film is used as the cathode 4030. Specifically, a 1 nm-thick LiF (lithium fluoride) film is formed on the EL layer 4029 by evaporation, and a 300 nm-thick aluminum film is formed thereon. Of course, you may use the MgAg electrode which is a well-known cathode material. The cathode 4030 is connected to the wiring 4016 in the region indicated by 4031. A wiring 4016 is a power supply line for applying a predetermined voltage to the cathode 4030, and is connected to the FPC 4017 through a conductive paste material 4032.

  In order to electrically connect the cathode 4030 and the wiring 4016 in the region indicated by 4031, it is necessary to form contact holes in the interlayer insulating film 4026 and the insulating film 4028. These may be formed when the interlayer insulating film 4026 is etched (when the pixel electrode contact hole is formed) or when the insulating film 4028 is etched (when the opening before the EL layer is formed). In addition, when the insulating film 4028 is etched, the interlayer insulating film 4026 may be etched all at once. In this case, if the interlayer insulating film 4026 and the insulating film 4028 are the same resin material, the shape of the contact hole can be improved.

  A passivation film 6003, a filler 6004, and a cover material 6000 are formed so as to cover the surface of the EL element thus formed.

  Further, a sealing material 7000 is provided inside the cover material 6000 and the substrate 4010 so as to surround the EL element portion, and a sealing material (second sealing material) 7001 is formed outside the sealing material 7000.

At this time, the filler 6004 also functions as an adhesive for bonding the cover material 6000. As the filler 6004, PVC (polyvinyl chloride)
Epoxy resin, silicone resin, PVB (polyvinyl butyral) or EVA (ethylene vinyl acetate) can be used. It is preferable to provide a desiccant inside the filler 6004 because the moisture absorption effect can be maintained.

  In addition, a spacer may be included in the filler 6004. At this time, the spacer may be a granular material made of BaO or the like, and the spacer itself may be hygroscopic.

  In the case where a spacer is provided, the passivation film 6003 can relieve the spacer pressure. In addition to the passivation film, a resin film for relaxing the spacer pressure may be provided.

  As the cover material 6000, a glass plate, an aluminum plate, a stainless steel plate, an FRP (Fiberglass-Reinforced Plastics) plate, a PVF (polyvinyl fluoride) film, a mylar film, a polyester film, or an acrylic film can be used. Note that when PVB or EVA is used as the filler 6004, it is preferable to use a sheet having a structure in which an aluminum foil of several tens of μm is sandwiched between PVF films or Mylar films.

  However, the cover material 6000 needs to have translucency depending on the light emission direction (light emission direction) from the EL element.

  The wiring 4016 is electrically connected to the FPC 4017 through a gap between the sealing material 7000 and the sealing material 7001 and the substrate 4010. Note that although the wiring 4016 has been described here, the other wirings 4014 and 4015 are electrically connected to the FPC 4017 through the sealing material 7000 and the sealing material 7001 in the same manner.

  In this embodiment, an example of manufacturing an EL display device having a different form from that of Embodiment 16 using the present invention will be described with reference to FIGS. 36 (A) and 36 (B). The same reference numerals as those in FIGS. 35A and 35B denote the same parts, and the description thereof is omitted.

  FIG. 36A is a top view of the EL display device of this example, and FIG. 36B shows a cross-sectional view taken along line AA ′ of FIG.

  In accordance with Example 17, a passivation film 6003 is formed to cover the surface of the EL element.

  Further, a filler 6004 is provided so as to cover the EL element. The filler 6004 also functions as an adhesive for bonding the cover material 6000. As the filler 6004, PVC (polyvinyl chloride), epoxy resin, silicone resin, PVB (polyvinyl butyral) or EVA (ethylene vinyl acetate) can be used. It is preferable to provide a desiccant inside the filler 6004 because the moisture absorption effect can be maintained.

  In addition, a spacer may be included in the filler 6004. At this time, the spacer may be a granular material made of BaO or the like, and the spacer itself may be hygroscopic.

  In the case where a spacer is provided, the passivation film 6003 can relieve the spacer pressure. In addition to the passivation film, a resin film for relaxing the spacer pressure may be provided.

Moreover, as the cover material 6000, a glass plate, an aluminum plate, a stainless steel plate, FRP (Fiberglass-Reinforced Plastics)
A board, a PVF (polyvinyl fluoride) film, a mylar film, a polyester film, or an acrylic film can be used. Note that when PVB or EVA is used as the filler 6004, it is preferable to use a sheet having a structure in which an aluminum foil of several tens of μm is sandwiched between PVF films or Mylar films.

  However, the cover material 6000 needs to have translucency depending on the light emission direction (light emission direction) from the EL element.

  Next, after the cover material 6000 is bonded using the filler 6004, the frame material 6001 is attached so as to cover the side surface (exposed surface) of the filler 6004. The frame material 6001 is bonded by a sealing material (functioning as an adhesive) 6002. At this time, a photocurable resin is preferably used as the sealing material 6002, but a thermosetting resin may be used if the heat resistance of the EL layer permits. Note that the sealing material 6002 is desirably a material that does not transmit moisture and oxygen as much as possible. Further, a desiccant may be added inside the sealing material 6002.

  The wiring 4016 is electrically connected to the FPC 4017 through a gap between the sealing material 6002 and the substrate 4010. Note that although the wiring 4016 has been described here, the other wirings 4014 and 4015 are also electrically connected to the FPC 4017 under the sealing material 6002 in the same manner.

  The present invention can be used in an active matrix EL display panel having the configuration as in the sixteenth and seventeenth embodiments. In Embodiments 17 and 18, light is emitted downward. In this embodiment, an example of a more detailed cross-sectional structure of the pixel portion is shown in FIG. 37, and the top structure is shown in FIG. The figure is shown in FIG. 37, FIG. 38A, and FIG. 38B use the same reference numerals and may be referred to each other. Although an example of upward irradiation is shown in this embodiment, it goes without saying that an EL display device can be manufactured by applying the structure of the pixel portion of this embodiment to Embodiments 17 and 18.

  In FIG. 37, a switching TFT 3502 provided on a substrate 3501 is formed using the NTFT of the present invention (see Examples 1 to 13). In this embodiment, a double gate structure is used. However, there is no significant difference in structure and manufacturing process, and thus description thereof is omitted. However, the double gate structure substantially has a structure in which two TFTs are connected in series, and there is an advantage that the off-current value can be reduced. Although the double gate structure is used in this embodiment, a single gate structure may be used, and a triple gate structure or a multi-gate structure having more gates may be used. Moreover, you may form using PTFT of this invention.

The current control TFT 3503 is formed using the NTFT of the present invention.
At this time, the drain wiring 3035 of the switching TFT 3502 is electrically connected to the gate electrode 3037 of the current control TFT by the wiring 3036.
Gate electrodes 3039 a and 3039 b of the switching TFT 3502 extend from the gate wiring 3039. Note that since the drawing becomes complicated, the gate wiring 3039 and the gate electrodes 3037, 3039a, and 3039b are shown in only one layer in FIG. 38A, but actually, there are two layers as shown in FIG.

  At this time, it is very important that the current control TFT 3503 has the structure of the present invention. Since the current control TFT is an element for controlling the amount of current flowing through the EL element, a large amount of current flows, and it is also an element with a high risk of deterioration due to heat or hot carriers. Therefore, the structure of the present invention in which the LDD region is provided on the drain side of the current control TFT so as to overlap the gate electrode through the gate insulating film is extremely effective.

  In this embodiment, the current control TFT 3503 is illustrated as a single gate structure, but a multi-gate structure in which a plurality of TFTs are connected in series may be used. Further, a structure may be employed in which a plurality of TFTs are connected in parallel to substantially divide the channel formation region into a plurality of portions so that heat can be emitted with high efficiency. Such a structure is effective as a countermeasure against deterioration due to heat.

  As shown in FIG. 38A, a wiring to be the gate electrode 3037 of the current control TFT 3503 overlaps with a drain wiring 3040 of the current control TFT 3503 through an insulating film in a region indicated by 3504. At this time, a capacitor is formed in a region indicated by 3504. This capacitor 3504 functions as a capacitor for holding the voltage applied to the gate of the current control TFT 3503. Note that the drain wiring 3040 is connected to a current supply line (power supply line) 3601, and a constant voltage is always applied thereto.

  A first passivation film 3041 is provided on the switching TFT 3502 and the current control TFT 3503, and a planarizing film 3042 made of a resin insulating film is formed thereon. It is very important to flatten the step due to the TFT using the flattening film 3042. Since an EL layer to be formed later is very thin, a light emission defect may occur due to the presence of a step. Therefore, it is desirable to planarize the pixel electrode before forming the pixel electrode so that the EL layer can be formed as flat as possible.

  Reference numeral 3043 denotes a pixel electrode (EL element cathode) made of a highly reflective conductive film, which is electrically connected to the drain of the current control TFT 3503. As the pixel electrode 3043, a low-resistance conductive film such as an aluminum alloy film, a copper alloy film, or a silver alloy film, or a stacked film thereof is preferably used. Of course, a laminated structure with another conductive film may be used.

  In addition, a light emitting layer 3045 is formed in a groove (corresponding to a pixel) formed by banks 3044a and 3044b formed of an insulating film (preferably resin). Although only one pixel is shown here, a light emitting layer corresponding to each color of R (red), G (green), and B (blue) may be formed separately. A conjugated polymer material is used as the organic EL material for the light emitting layer. Typical polymer materials include polyparaphenylene vinylene (PPV), polyvinyl carbazole (PVK), and polyfluorene.

  There are various types of PPV organic EL materials such as “H. Shenk, H. Becker, O. Gelsen, E. Kluge, W. Kreuder, and H. Spreitzer,“ Polymers for Light Emitting ”. Materials such as those described in “Diodes”, Euro Display, Proceedings, 1999, p. 33-37 ”and Japanese Patent Laid-Open No. 10-92576 may be used.

  As a specific light emitting layer, cyanopolyphenylene vinylene may be used for a light emitting layer that emits red light, polyphenylene vinylene may be used for a light emitting layer that emits green light, and polyphenylene vinylene or polyalkylphenylene may be used for a light emitting layer that emits blue light. The film thickness may be 30 to 150 nm (preferably 40 to 100 nm).

  However, the above example is an example of an organic EL material that can be used as a light emitting layer, and is not necessarily limited to this. An EL layer (a layer for emitting light and moving carriers therefor) may be formed by freely combining a light-emitting layer, a charge transport layer, or a charge injection layer.

  For example, in this embodiment, an example in which a polymer material is used as the light emitting layer is shown, but a low molecular weight organic EL material may be used. It is also possible to use an inorganic material such as silicon carbide for the charge transport layer or the charge injection layer. As these organic EL materials and inorganic materials, known materials can be used.

  In this embodiment, an EL layer having a stacked structure in which a hole injection layer 3046 made of PEDOT (polythiophene) or PAni (polyaniline) is provided on the light emitting layer 3045 is used. An anode 3047 made of a transparent conductive film is provided on the hole injection layer 3046. In the case of this embodiment, since the light generated in the light emitting layer 3045 is emitted toward the upper surface side (upward of the TFT), the anode must be translucent. As the transparent conductive film, a compound of indium oxide and tin oxide or a compound of indium oxide and zinc oxide can be used, but it is possible to form after forming a light-emitting layer or hole injection layer with low heat resistance. What can form into a film at low temperature as much as possible is preferable.

  When the anode 3047 is formed, the EL element 3505 is completed. Note that the EL element 3505 here refers to a diode formed of a pixel electrode (cathode) 3043, a light emitting layer 3045, a hole injection layer 3046, and an anode 3047. As shown in FIG. 38A, the pixel electrode 3043 substantially matches the area of the pixel, so that the entire pixel functions as an EL element. Therefore, the use efficiency of light emission is very high, and a bright image display is possible.

  Incidentally, in this embodiment, a second passivation film 3048 is further provided on the anode 3047. The second passivation film 3048 is preferably a silicon nitride film or a silicon nitride oxide film. This purpose is to cut off the EL element from the outside, and has both the meaning of preventing deterioration due to oxidation of the organic EL material and the meaning of suppressing degassing from the organic EL material. This increases the reliability of the EL display device.

  As described above, the EL display panel of the present invention has a pixel portion composed of pixels having a structure as shown in FIG. 37, and includes a switching TFT having a sufficiently low off-current value and a current control TFT resistant to hot carrier injection. Have. Therefore, an EL display panel having high reliability and capable of displaying a good image can be obtained.

  In addition, the structure of a present Example can be implemented in combination freely with Examples 1-13 structure. Further, it is effective to use the EL display panel of this embodiment as the display unit of the electronic apparatus of Embodiment 22.

  In this embodiment, a structure in which the structure of the EL element 3505 is inverted in the pixel portion described in Embodiment 18 will be described. FIG. 39 is used for the description. Note that the only difference from the structure of FIG. 37 is the EL element portion and the current control TFT, and other descriptions are omitted.

  In FIG. 39, a current control TFT 3503 is formed using the PTFT of the present invention. Examples 1 to 13 may be referred to for the manufacturing process.

  In this embodiment, a transparent conductive film is used as the pixel electrode (anode) 3050. Specifically, a conductive film made of a compound of indium oxide and zinc oxide is used. Of course, a conductive film made of a compound of indium oxide and tin oxide may be used.

  Then, after banks 3051a and 3051b made of insulating films are formed, a light emitting layer 3052 made of polyvinylcarbazole is formed by solution coating. An electron injection layer 3053 made of potassium acetylacetonate (denoted as acacK) and a cathode 3054 made of an aluminum alloy are formed thereon. In this case, the cathode 3054 also functions as a passivation film. Thus, an EL element 3701 is formed.

  In this embodiment, the light generated in the light emitting layer 3052 is radiated to the outside from the substrate on which the TFT is formed, as indicated by arrows.

  In addition, the structure of a present Example can be implemented in combination freely with the structure of Examples 1-13. Further, it is effective to use the EL display panel of this embodiment as the display unit of the electronic apparatus of Embodiment 22.

  In this embodiment, an example in which the pixel has a structure different from that of the circuit diagram illustrated in FIG. 38B is illustrated in FIGS. In this embodiment, 3801 is a source wiring of the switching TFT 3802, 3803 is a gate wiring of the switching TFT 3802, 3804 is a current control TFT, 3805 is a capacitor, 3806 and 3808 are current supply lines, and 3807 is an EL element. .

  FIG. 40A shows an example in which the current supply line 3806 is shared between two pixels. In other words, the two pixels are formed so as to be symmetrical about the current supply line 3806. In this case, since the number of power supply lines can be reduced, the pixel portion can be further refined.

  FIG. 40B illustrates an example in which the current supply line 3808 is provided in parallel with the gate wiring 3803. In FIG. 40B, the current supply line 3808 and the gate wiring 3803 are provided so as not to overlap with each other. However, if the wirings are formed in different layers, they overlap with each other through an insulating film. It can also be provided. In this case, since the exclusive area can be shared by the power supply line 3808 and the gate wiring 3803, the pixel portion can be further refined.

  40C, the current supply line 3808 is provided in parallel to the gate wiring 3803 as in the structure of FIG. 40B, and two pixels are symmetrical with respect to the current supply line 3808. It is characterized in that it is formed. It is also effective to provide the current supply line 3808 so as to overlap with any one of the gate wirings 3803. In this case, since the number of power supply lines can be reduced, the pixel portion can be further refined.

  In addition, the structure of a present Example can be implemented in combination freely with the structure of Examples 1-13, 15-17. Further, it is effective to use the EL display panel having the pixel structure of this embodiment as the display unit of the electronic device of Embodiment 22.

  In FIGS. 38A and 38B shown in Embodiment 18, the capacitor 3504 is provided to hold the voltage applied to the gate of the current control TFT 3503. However, the capacitor 3504 may be omitted. . In the case of Example 19, since the NTFT of the present invention as shown in Examples 1 to 13 is used as the current control TFT 3503, it has an LDD region provided so as to overlap the gate electrode through the gate insulating film. ing. A parasitic capacitance generally called a gate capacitance is formed in the overlapped region, but this embodiment is characterized in that this parasitic capacitance is positively used in place of the capacitor 3504.

  Since the capacitance of the parasitic capacitance varies depending on the area where the gate electrode and the LDD region overlap, the capacitance of the parasitic capacitance is determined by the length of the LDD region included in the overlapping region.

  Similarly, in the structure of FIGS. 40A to 40C shown in the twentieth embodiment, the capacitor 3805 can be omitted.

  In addition, the structure of a present Example can be implemented in combination freely with the structure of Examples 1-13 and 16-20. Further, it is effective to use the EL display panel having the pixel structure of this embodiment as the display unit of the electronic device of Embodiment 22. Needless to say, in Examples 17 to 22, NTFT and PTFT are the same as the n-channel TFT and p-channel TFT of the present application.

  A semiconductor device using a TFT formed by implementing the present invention can be applied to display devices typified by various semiconductor circuits and electro-optical devices. That is, the present invention can be applied to all electronic devices in which these electro-optical devices and semiconductor circuits are incorporated as parts.

  Such electronic devices include video cameras, digital cameras, projectors (rear type or front type), head mounted displays (goggles type displays), car navigation systems, personal computers, personal digital assistants (mobile computers, mobile phones or electronic books). Etc.). Examples of these are shown in FIGS. 32 and 33.

  FIG. 32A illustrates a personal computer, which includes a main body 2001, an image input portion 2002, a display device 2003, and a keyboard 2004. The present invention can be applied to the image input unit 2002, the display device 2003, and other signal control circuits.

  FIG. 32B shows a video camera, which includes a main body 2101, a display device 2102, an audio input portion 2103, operation switches 2104, a battery 2105, and an image receiving portion 2106. The present invention can be applied to the display device 2102, the voice input unit 2103, and other signal control circuits.

  FIG. 32C illustrates a mobile computer (mobile computer), which includes a main body 2201, a camera unit 2202, an image receiving unit 2203, operation switches 2204, and a display device 2205. The present invention can be applied to the display device 2205 and other signal control circuits.

  FIG. 32D shows a goggle type display, which includes a main body 2301, a display device 2302, and an arm portion 2303. The present invention can be applied to the display device 2302 and other signal control circuits.

  FIG. 32E shows a player using a recording medium (hereinafter referred to as a recording medium) on which a program is recorded. The player includes a main body 2401, a display device 2402, a speaker unit 2403, a recording medium 2404, and operation switches 2405. This apparatus uses a DVD (Digtal Versatile Disc), CD, or the like as a recording medium, and can perform music appreciation, movie appreciation, games, and the Internet. The present invention can be applied to the display device 2402 and other signal control circuits.

  FIG. 32F illustrates a digital camera which includes a main body 2501, a display device 2502, an eyepiece unit 2503, an operation switch 2504, and an image receiving unit (not illustrated). The present invention can be applied to the display device 2502 and other signal control circuits.

  FIG. 33A illustrates a front type projector which includes a display device 2601 and a screen 2602. The present invention can be applied to display devices and other signal control circuits.

  FIG. 33B shows a rear projector, which includes a main body 2701, a display device 2702, a mirror 2703, and a screen 2704. The present invention can be applied to display devices and other signal control circuits.

  Note that FIG. 33C illustrates an example of the structure of the display devices 2601 and 2702 in FIGS. 33A and 33B. The display devices 2601 and 2702 include a light source optical system 2801, mirrors 2802, 2804 to 2806, a dichroic mirror 2803, a prism 2807, a liquid crystal display device 2808, a phase difference plate 2809, and a projection optical system 2810. Projection optical system 2810 includes an optical system including a projection lens. Although the present embodiment shows an example of a three-plate type, it is not particularly limited, and for example, a single-plate type may be used. In addition, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarization function, a film for adjusting a phase difference, or an IR film in the optical path indicated by an arrow in FIG. Good.

  FIG. 33D illustrates an example of the structure of the light source optical system 2801 in FIG. In this embodiment, the light source optical system 2801 includes a reflector 2811, a light source 2812, lens arrays 2813 and 2814, a polarization conversion element 2815, and a condenser lens 2816. Note that the light source optical system illustrated in FIG. 33D is an example and is not particularly limited. For example, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarization function, a film for adjusting a phase difference, or an IR film in the light source optical system.

  As described above, the semiconductor device of the present invention has a very wide application range, and can be applied to electronic devices in various fields. Further, the semiconductor device of the present embodiment can be realized by using any combination of Embodiments 1 to 21.

Sectional drawing which shows the manufacturing process of TFT of this invention. (Embodiment 1) Sectional drawing which shows the manufacturing process of TFT of this invention. (Embodiment 1) The fragmentary sectional view of a gate electrode. (Embodiment 1) The fragmentary sectional view of a semiconductor layer. (Embodiment 1) Sectional drawing which shows the manufacturing process of TFT of this invention. (Embodiment 2) Sectional drawing which shows the manufacturing process of TFT of this invention. (Embodiment 2) Sectional drawing of TFT of this invention. (Embodiment 3) Sectional drawing of TFT of this invention. (Embodiment 4) Sectional drawing of TFT of this invention. (Embodiment 4) 1 is a diagram showing an outline of a liquid crystal display device of the present invention. Example 1 The top view of the pixel part of this invention and a CMOS circuit. Example 1 Sectional drawing which shows the manufacturing process of the pixel part of this invention. Example 1 Sectional drawing which shows the manufacturing process of the pixel part of this invention. Example 1 Sectional drawing which shows the manufacturing process of the pixel part of this invention. Example 1 Sectional drawing which shows the manufacturing process of the CMOS circuit of this invention. Example 1 Sectional drawing which shows the manufacturing process of the CMOS circuit of this invention. Example 1 Sectional drawing which shows the manufacturing process of the CMOS circuit of this invention. (Example 2) Sectional drawing which shows the manufacturing process of the CMOS circuit of this invention. (Example 3) Sectional drawing which shows the manufacturing process of the CMOS circuit of this invention. (Example 4) Sectional drawing which shows the manufacturing process of the CMOS circuit of this invention. (Example 5) Sectional drawing which shows the manufacturing process of the CMOS circuit of this invention. (Example 6) The figure which showed the plasma production | generation mechanism of the ICP etching apparatus. (Example 7) It is a conceptual diagram of the ICP etching apparatus of a multi spiral coil system. (Example 7) Bias power versus taper angle θ characteristic diagram. (Example 7) Flow ratio versus taper angle θ characteristic diagram versus CF _4. (Example 7) (W / resist) selectivity versus taper angle θ characteristic diagram. (Example 7) 4A and 4B illustrate a manufacturing process of a crystalline silicon film of the present invention. (Example 8) 4A and 4B illustrate a manufacturing process of a crystalline silicon film of the present invention. Example 9 4A and 4B illustrate a manufacturing process of a crystalline silicon film of the present invention. (Example 10) 4A and 4B illustrate a manufacturing process of a crystalline silicon film of the present invention. (Example 11) Sectional drawing which shows the manufacturing process of the CMOS circuit of this invention. (Example 13) FIG. 11 illustrates an example of an electronic device of the invention. (Example 22) FIG. 11 illustrates an example of an electronic device of the invention. (Example 22) The gate voltage-drain current characteristic view of TFT. FIG. 11 illustrates a structure of an active matrix EL display device. (Example 16) FIG. 11 illustrates a structure of an active matrix EL display device. (Example 17) 4 is a cross-sectional view illustrating a structure of a pixel portion of an active matrix EL display device. FIG. (Example 18) 4A and 4B are a top view and a circuit diagram illustrating a structure of a pixel portion of an active matrix EL display device. (Example 18) 4 is a cross-sectional view illustrating a structure of a pixel portion of an active matrix EL display device. FIG. (Example 19) FIG. 10 is a circuit diagram illustrating a structure of a pixel portion of an active matrix EL display device. (Example 20) The figure which shows an example of the light transmittance characteristic of antiferroelectric mixed liquid crystal. (Example 14)

Claims (14)

an n-channel TFT and a p-channel TFT;
Each of the n-channel TFT and the p-channel TFT has a semiconductor layer, a gate insulating film formed on and in contact with the semiconductor layer, and a gate electrode overlapping the semiconductor layer with the gate insulating film interposed therebetween. And
The gate electrode of the n-channel TFT and the gate electrode of the p-channel TFT are made of the same conductive layer,
The gate electrode of the n-channel TFT has a tapered end, and an angle formed between a side surface and the surface of the gate insulating film is in a range of 3 degrees to 60 degrees,
A gate electrode of the p-channel TFT has a tapered end, and an angle formed between a side surface and the surface of the gate insulating film is in a range of 70 degrees to 85 degrees. an n-channel TFT and a p-channel TFT;
Each of the n-channel TFT and the p-channel TFT has a semiconductor layer, a gate insulating film formed on and in contact with the semiconductor layer, and a gate electrode overlapping the semiconductor layer with the gate insulating film interposed therebetween. And
The gate electrode of the n-channel TFT and the gate electrode of the p-channel TFT are made of the same conductive layer,
The gate electrode of the n-channel TFT has a tapered end, and the angle formed between the side surface and the surface of the gate insulating film is in the range of 5 degrees to 45 degrees,
A gate electrode of the p-channel TFT has a tapered end, and an angle formed between a side surface and the surface of the gate insulating film is in a range of 60 degrees to 90 degrees. In claim 1 or claim 2,
The semiconductor device according to claim 1, wherein the gate electrode of the n-channel TFT and the gate electrode of the p-channel TFT are made of a material mainly composed of Cr, Ta, Ti, W, and Mo. In claim 1 or claim 2,
The gate electrode of the n-channel TFT and the gate electrode of the p-channel TFT are made of n-type silicon. In any one of Claims 1 thru | or 4,
The semiconductor device, wherein the gate insulating film is a single layer film or a stacked film of silicon oxide, silicon nitride, or silicon nitride oxide. In any one of Claims 1 thru | or 5,
The semiconductor device, wherein the semiconductor layer is amorphous silicon, amorphous germanium, amorphous silicon germanium, crystalline silicon, crystalline germanium, or crystalline silicon germanium. In any one of Claims 1 thru | or 6,
The semiconductor device is a liquid crystal display device. In any one of Claims 1 thru | or 6,
The semiconductor device is an EL display device. Forming a first semiconductor layer and a second semiconductor layer;
Forming a gate insulating film on the first semiconductor layer and the second semiconductor layer;
Forming a conductive layer on the gate insulating film;
By etching the conductive layer, a first gate electrode whose end overlaps with the first semiconductor layer across the gate insulating film is tapered, and the second semiconductor layer across the gate insulating film An angle formed between the side surface of the first gate electrode and the surface of the gate insulating film, and the side surface of the second gate electrode and the gate insulating film. Formed so that the angle formed by the surface is in the range of 3 degrees to 60 degrees,
Etching the tapered end of the second gate electrode to form a third gate electrode in which the angle formed between the side surface and the surface of the gate insulating film is in the range of 70 degrees to 85 degrees;
An n-channel TFT is formed by the first semiconductor layer, the gate insulating film, and the first gate electrode,
A method for manufacturing a semiconductor device, wherein a p-channel TFT is formed using the second semiconductor layer, the gate insulating film, and the third gate electrode. Forming a first semiconductor layer and a second semiconductor layer;
Forming a gate insulating film on the first semiconductor layer and the second semiconductor layer;
Forming a conductive layer on the gate insulating film;
By etching the conductive layer, a first gate electrode whose end overlaps with the first semiconductor layer across the gate insulating film is tapered, and the second semiconductor layer across the gate insulating film An angle formed between the side surface of the first gate electrode and the surface of the gate insulating film, and the side surface of the second gate electrode and the gate insulating film. The angle formed by the surface is in the range of 5 degrees to 45 degrees,
Etching the tapered end of the second gate electrode to form a third gate electrode in which the angle formed between the side surface and the surface of the gate insulating film is in the range of 60 degrees to 90 degrees;
An n-channel TFT is formed by the first semiconductor layer, the gate insulating film, and the first gate electrode,
A method for manufacturing a semiconductor device, wherein a p-channel TFT is formed using the second semiconductor layer, the gate insulating film, and the third gate electrode. In claim 9 or claim 10,
The method for manufacturing a semiconductor device, wherein the conductive layer is made of a material mainly composed of Cr, Ta, Ti, W, and Mo. In claim 9 or claim 10,
The method for manufacturing a semiconductor device, wherein the conductive layer is made of n-type silicon. In any one of Claims 9-12,
The method for manufacturing a semiconductor device, wherein the gate insulating film is a single-layer film or a stacked film of silicon oxide, silicon nitride, or silicon nitride oxide. In any one of Claim 9 thru | or 13,
The method for manufacturing a semiconductor device, wherein the semiconductor layer is amorphous silicon, amorphous germanium, amorphous silicon germanium, crystalline silicon, crystalline germanium, or crystalline silicon germanium.

Images