Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
  • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
  • H01L29/66007—Multistep manufacturing processes
  • H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
  • H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
  • H01L29/66409—Unipolar field-effect transistors
  • H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
  • H01L29/66742—Thin film unipolar transistors
  • H01L29/6675—Amorphous silicon or polysilicon transistors
  • H01L29/66757—Lateral single gate single channel transistors with non-inverted structure, i.e. the channel layer is formed before the gate
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
  • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
  • H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
  • H01L29/76—Unipolar devices, e.g. field effect transistors
  • H01L29/772—Field effect transistors
  • H01L29/78—Field effect transistors with field effect produced by an insulated gate
  • H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
  • H01L29/78606—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device
  • H01L29/78633—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device with a light shield

Definitions

• the present invention relates to a semiconductor device having a light shielding film.
• the invention also relates to a display device comprising such a semiconductor device and to an etching method of etching a film having titanium nitride
• This TFT is broadly classified into two kinds of a top gate type TFT and a bottom gate type TFT. Since the top gate type TFT of these two kinds of TFTs has an advantage capable of manufacturing at a low cost over the bottom gate type TFT, the top gate type TFT is used in the case of attaching importance to this advantage.
• This top gate type TFT provides a light shielding film. As a material of this light shielding film, for example, Mo-Cr (molybdenum-chromium) has been used.
• This light shielding film is formed by depositing Mo-Cr which is a material of the light shielding film on a glass substrate and etching this deposited Mo-Cr.
• Mo-Cr which is a material of the light shielding film on a glass substrate
• etching this deposited Mo-Cr is simply etched to form the light shielding film
• step coverage of this insulating film becomes worse at an edge portion of this light shielding film.
• a shape of the edge portion of the light shielding film may be formed in a taper shape. By forming the edge portion of the light shielding film in the taper shape, the step coverage of a film formed directly on the light shielding film can be improved.
• a PE plasma etching
• a RIE reactive ion etching
• an object of the present invention is to provide a semiconductor device, a display device and an etching method capable of manufacturing at low manufacturing costs without using strongly toxic substances such as Cl 2 and without reducing the availability of an etching apparatus and further capable of manufacturing by various etching apparatus.
• a semiconductor device of the present invention for achieving the above object is characterized by comprising a gate electrode, an amo ⁇ hous silicon film or a polysihcon film formed under the gate electrode, and a light shielding film formed under the amorphous silicon film or the polysihcon film, the light shielding film having titanium nitride.
• the light shielding film which the semiconductor device of the present invention provides has the titanium nitride. Therefore, in the semiconductor device of the present invention, the titanium nitride is used in a material of the light shielding film.
• the titanium nitride is used in the material of the light shielding film.
• the deposited titanium nitride can easily be etched in a taper shape even when, for example, SF 6 gas instead of Cl 2 gas is used as etching gas.
• the light shielding film with a taper shape can easily be formed without using the Cl 2 gas. Therefore, it is unnecessary to provide corrosion preventive treatment to an etching apparatus and equipment costs can be reduced. Also, strongly toxic substances such as Cl 2 gas may not be used as the etching gas, so that there is an advantage that handling of the etching gas is facilitated. Also, for example, fluorine series gas such as SF 6 gas can be used as the etching gas in the present invention, so that the inside of a chamber becomes resistant to contamination. Therefore, frequency of cleaning of the chamber may be enough at low frequency and the availability of the etching apparatus can be increased.
• the titanium nitride when used in the material of the light shielding film, a light shielding film having a good taper shape can easily be formed even when, for example, an etching apparatus such as a PE apparatus other than a RIE apparatus is used. Further, the titanium nitride is a low- cost material in comparison with Mo-Cr and material costs can be reduced.
• the titanium nitride is a material resistant to oxidation, an oxide film is hard to be formed on the surface of the light shielding film formed. As a result of this, characteristics of a film stacked on the light shielding film are difficult to change and there is an advantage that desired characteristics can easily be provided to the semiconductor device. This point will be described in detail below.
• the semiconductor device of the present invention is preferable that an edge portion of the light shielding film has a taper shape.
• the semiconductor device of the present invention is preferable that a taper angle of the edge portion of the light shielding film is 45° or less.
• the light shielding film is a single-layer film having titanium nitride or may be a multilayer film with a first film having titanium and a second film having titanium nitride, the second film formed on the first film.
• the light shielding film is formed by depositing a material of this light shielding film on a substrate and etching this deposited material.
• An etching condition at the time of etching this deposited film variously changes depending on kinds of the deposited material or etching methods, etc.
• the etching condition can be simplified by setting the light shielding film at the single-layer film.
• the etching condition becomes complicated somewhat, but a film thickness of the light shielding film can be thinned and the semiconductor device can be thinned. A situation capable of thinning the semiconductor device will be described below.
• an etching method of the present invention is characterized by comprising the steps of forming a film having titanium nitride on a substrate, and etching the film by mixed gas in which fluorine is a main component and oxygen is added.
• the film having the titanium nitride can be etched in a taper shape.
• an etching method of the present invention is preferable that the amount of addition of the oxygen in the mixed gas is 10 % to 15 % with respect to a content of the fluorine.
• the film having the titanium nitride can easily be etched so that the taper angle is 45° or less.
• Fig.l is a sectional view showing a TFT 1 which is one embodiment of a semiconductor device of the present invention manufactured using one embodiment of an etching method of the present invention.
• the TFT 1 is shown which is provided within a liquid crystal panel of a liquid crystal display apparatus.
• This TFT 1 will be described below with reference to Figs.2 to 10 as well as Fig.1.
• the Figs.2 to 10 schematically show a method of manufacturing this TFT 1.
• a light shielding film 3 is first formed on a glass substrate 2.
• titanium nitride which is a material of the light shielding film 3 is deposited on the glass substrate 2 by using a sputtering apparatus.
• Fig.2 is a schematic view showing a situation in which the glass substrate 2 is set in a chamber of the sputtering apparatus
• Fig.3 is a sectional view showing a situation in which a titanium nitride film 31 is formed on the glass substrate 2.
• a substrate holder 201 is provided in the inside of this chamber 200, and a target 202 of pure titanium is provided in the upper of this substrate holder 201.
• the glass substrate 2 is set in the substrate holder 201.
• Ar gas with N 2 gas is introduced in the chamber 200.
• titanium nitride is deposited on the glass substrate 2 and the titanium nitride film 31 is formed as shown in Fig.3.
• the light shielding film 3 is formed by etching this titanium nitride film 31.
• a film thickness of the titanium nitride film 31 is too thin, a sufficient light shielding function cannot be provided to the light shielding film 3.
• the film thickness of the titanium nitride film 31 is set at somewhat thick thickness in order to provide the light shielding film 3 with the light shielding function.
• the film thickness of the titanium nitride film 31 is set at about 100 nm.
• a main component of the titanium nitride film 31 is titanium nitride indicated by a chemical formula of TiN and Ti 2 N.
• a resist film 32 is formed on the titanium nitride film 31 as shown in Fig.4 in order to pattern this titanium nitride film 31,.
• the titanium nitride film 31 is etched by using a PE (plasma etching) apparatus.
• Fig.5 is a schematic view showing a situation in which the glass substrate 2 is set in a chamber of the PE apparatus
• Fig.6 is a sectional view showing a situation after etching the titanium nitride film 31.
• an upper electrode plate 401 and a lower electrode plate 402 placed in parallel are provided in the inside a chamber 400.
• the upper electrode plate 401 is connected to a high-frequency power source 403 and the lower electrode plate 402 is grounded. Also, multiple gas blow-off holes (not shown) are formed in the upper electrode plate 401.
• the glass substrate 2 is set on the lower electrode plate 402. After setting the glass substrate 2 on the lower electrode plate 402, a pressure within the chamber 400 is set at 200 mTorr and dry etching of the titanium nitride film 31 is performed using etching gas whose main component is fluorine series gas.
• a light shielding film 3 is formed which has a taper portion 3 a with a taper angle ⁇ of about 40° and has a film thickness of about 100 nm as shown in Fig.6.
• the SF 6 gas is used as the fluorine series gas.
• other fluorine series for example CF 4 gas
• a kind of gas used for the etching gas can be changed depending on the etching condition. Further, it is possible to form the light shielding film 3 having a good taper shape by using wet etching instead of dry etching.
• the light shielding film 3 is formed by etching the titanium nitride film 31.
• this titanium nitride film 31 is formed by introducing not only Ar gas but also N gas into the chamber 200 as shown in Fig. 2.
• N gas is not introduced and only Ar gas is simply introduced into the chamber 200, not the titanium nitride film 31 but a titanium film is formed.
• the titanium film instead of the titanium nitride film 31 is formed and this titanium film is etched using the chamber 400 shown in Fig.5.
• this method has the following disadvantage.
• Fig.7 is a sectional view showing a situation in which a titanium film 300 instead of the titanium nitride film 31 is formed on the glass substrate 2.
• a titanium film 300 instead of the titanium nitride film 31 is formed on the glass substrate 2.
• the glass substrate 2 having the titanium film 300 is generally kept in the atmosphere before etching this titanium film 300.
• Titanium is very prone to oxidation, so that an oxide film 301 is formed on the surface of the titanium film 300 by being exposed to the atmosphere as shown in Fig.7.
• unevenness is formed on the surface of the titanium film 300 due to this oxide film 301.
• the titanium film 300 is etched with the titanium film 300 having unevenness on the surface of the film 300, a light shielding film having unevenness on the surface will be formed. As described later, the light shielding film is covered with several films. Therefore, when this light shielding film having the unevenness is covered with the several films, characteristics of the several films covering this light shielding film will change subtly due to influence of the unevenness of the light shielding film. As a result, it becomes difficult to manufacture a TFT having desired characteristics.
• the titanium nitride film 31 when the titanium nitride film 31 is formed on the glass substrate 2 by introducing not only Ar gas but also N 2 gas into the chamber, titanium nitride is resistant to oxidization in comparison with titanium, so that an oxide film is difficult to be formed on the titanium nitride film 31 even when the titanium nitride film 31 is exposed to the atmosphere. Therefore, unevenness is difficult to be formed on the surface of the titanium nitride film 31 and the surface of the titanium nitride film 31 can be held in a flat plane. As a result of this, the light shielding film 3, which is formed by etching this titanium nitride film 31 , has the flat plane at the surface of the light shielding film 3. Therefore, even in the case of covering the light shielding film 3 with several films, characteristics of these films are difficult to change and a TFT having desired characteristics can be manufactured easily.
• the surface of the light shielding film 3 is held flat by forming not a titanium film but the titanium nitride film 31.
• a multilayer film of titanium nitride film / titanium film may be formed on the glass substrate 2 by firstly introducing only Ar gas without introducing N 2 gas into the chamber 200 and secondly adding the N 2 gas to the Ar gas. Since the surface of this multilayer film is covered with the titanium nitride film, the surface of this multilayer film is resistant to oxidation. Therefore, unevenness is difficult to be formed on the surface of this multilayer film and the surface of the multilayer film can be held in a flat plane.
• the surface of a light shielding film 3 formed by etching this multilayer film is held in the flat plane and also, a TFT having desired characteristics can be manufactured easily.
• the light shielding film 3 is formed from the multilayer film of titanium nitride film / titanium film, a sufficient light shielding function can be provided to this multilayer film with oxidation of the surface of the multilayer film suppressed even when a film thickness of the titanium nitride film is thin. It is for this reason that the titanium film provided to the multilayer film has stronger light shielding function than that of the titanium nitride film.
• the multilayer film of titanium nitride film / titanium film will be designed to have the same light shielding function as a single-layer film of the titanium nitride film 31 having a film thickness of about 100 nm, the respective film thicknesses of titanium nitride film / titanium film may be set at about 10 nm / about 70 nm. Also, when necessary, the light shielding film 3 may be constructed of a multilayer film with three layers or more.
• the light shielding film 3 is formed by not etching a multilayer film but etching a single-layer film (titanium nitride film 31) in which titanium nitride is a main component. Forming the light shielding film by etching the single-layer film has the advantage that the etching condition can be simplified.
• the resist film 32 is removed and an SiO film 4 is formed as shown in Fig.8.
• an edge portion 3a of the light shielding film 3 is formed in a good taper shape, so that step coverage of the SiO film 4 becomes very good at this edge portion 3a. Therefore, the SiO film 4 with a flat surface shape can be formed.
• good step coverage is provided to the SiO film 4 by setting a taper angle of the edge portion 3a of the light shielding film 3 at about 40°, but generally, the good step coverage can be provided to the SiO film 4 even when the taper angle is about 40° or more.
• the taper angle becomes close to 90°, the step coverage becomes worse accordingly, so that the taper angle cannot be increased too much. Normally, the step coverage can be improved extremely under the condition that the taper angle is about 45° or less.
• an ITO film 50 which is a material of a source electrode 5, a drain electrode 6 and a pixel electrode 7 (see Fig.l) is formed on the surface of this SiO 2 film 4. Since the surface of the SiO 2 film 4 is formed in the flat, the ITO film 50 is formed so as to cover the SiO 2 film 4 with a uniform thickness.
• the source electrode 5, the drain electrode 6 and the pixel electrode 7 are formed by performing dry etching or wet etching of this ITO film 50. If the ITO film 50 is etched by wet etching, hydrochloric acid is used as an etching agent. In the case, if there is a defect such as a pinhole in the SiO 2 film 4, there is fear that the hydrochloric acid which is the etching agent penetrates to the light shielding film 3 through this pinhole.
• the light shielding film 3 can perform the light shielding function required.
• the source electrode 5 is formed apart from the drain electrode 6 and the pixel electrode 7, and the drain electrode 6 and the pixel electrode 7 are integrally formed.
• a MoCr (molybdenum-chromium) film is formed so as to cover these electrodes 5, 6 and 7 and as shown in Fig.10, a source bus 8 is formed by performing dry etching or wet etching of this MoCr film.
• the MoCr film is etched by wet etching, a mixed agent of phosphoric acid / nitric acid / water is used as an etching agent, since titanium nitride which is a material of the light shielding film 3 is not etched by the mixed agent of phosphoric acid / nitric acid / water, the light shielding film 3 is protected from etching if the mixed agent penetrates to the light shielding film 3 due to the existence of a defect (for example a pinhole) in the SiO 2 film 4. Therefore, the light shielding film 3 can perform the light shielding function required.
• a defect for example a pinhole
• an island pattern of an a-Si (amorphous silicon) film 9 is formed, and a gate insulating film 10 and a gate electrode 11 are formed as shown in Fig.1.
• Source buses or electrodes 8 and electrodes interconnecting the gates form a matrix of column and row electrodes of an active matrix LCD.
• the titanium nitride film 31 is etched using fluorine series gas without using Cl 2 gas. Therefore, it is unnecessary to provide corrosion preventive treatment to an etching apparatus and equipment costs can be reduced. Also, not the chlorine gas but SF 6 gas which is the fluorine series gas is used as etching gas, so that the inside of the chamber 400 (see Fig.5) is resistant to dirt. Therefore, frequency of cleaning of the chamber 400 may be enough at low frequency and the availability of the etching apparatus can be increased. Also, titanium nitride which is a material of the light shielding film 3 is a relatively low-cost material and material costs can be reduced.
• the taper angle ⁇ becomes substantially vertical and eventually, a good taper shape cannot be provided to the light shielding film 3.
• the amount of addition of O 2 to SF 6 is too large, the taper angle ⁇ becomes small, but the amount of side etching of the titanium nitride film 31 becomes large and a desired light shielding film 3 cannot be formed.
• the light shielding film 3 having a good taper shape with a taper angle of 40° can be formed under the condition that the amount of addition of O 2 to fluorine series gas is set at about 10 % to about 15 %,.
• the light shielding film 3 having a good taper shape can be formed without using Cl 2 gas by setting the amount of addition of O 2 to fluorine series gas at a proper value (about 10 % to about 15 %). Therefore, without using strongly toxic gas such as Cl gas, equipment costs and material costs can be reduced and the availability of the etching apparatus can be increased.
• the present invention can also be used in a semiconductor device in which the pixel electrode is unnecessary, for example, as is a semiconductor device incorporated into a circuit device such as IC.
• a semiconductor device and an etching method can be obtained which are capable of manufacturing at low manufacturing costs without using strongly toxic substances such as Cl and without reducing the availability of an etching apparatus and further capable of manufacturing by various etching apparatus.
• Fig.l is a sectional view showing a TFT 1 which is one embodiment of a transistor of the present invention.
• Fig.2 is a schematic view showing a situation in which a glass substrate 2 is set in a chamber.
• Fig.3 is a sectional view showing a situation in which a titanium nitride film 31 is formed on the glass substrate 2.
• Fig.4 is a sectional view showing a situation in which a resist film is formed on the titanium nitride film 31.
• Fig.5 is a schematic view showing a situation in which a glass substrate 2 is set in a chamber of an etching apparatus.
• Fig.6 is a sectional view showing a situation after etching the titanium nitride film 31.
• Fig.7 is a sectional view showing a situation in which a titanium film instead of the titanium nitride film 31 is formed on the glass substrate 2.
• Fig.8 is a sectional view showing a situation in which an ITO film 50 is formed.
• Fig.9 is a sectional view showing a situation in which the ITO film 50 is etched.
• Fig.10 is a sectional view showing a situation in which a source electrode is formed.

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Citations (4)

• 2000
  • 2000-03-13 JP JP2000069195A patent/JP2001274138A/ja not_active Withdrawn
• 2001
  • 2001-03-05 WO PCT/EP2001/002426 patent/WO2001069654A2/en active Application Filing

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