JP2001179167A - Thin film deposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the quantity of a raw material to be used by supplying raw materials previously selectively on a substrate and to simplify the manufacturing process by dispensing with a photolithography process and an etching process. SOLUTION: This thin film depositing method for depositing a silicon based semiconductor film, a silicon oxide based insulating film and the like is composed of a process for depositing a liquid pattern 103 by discharging plural times a flowable raw material toward a prescribed direction as liquid drops 102, a process for depositing into a thin film pattern 10 by solidifying the liquid pattern 104 and a process for depositing into a crystallized film 106 by irradiating the thin film pattern 104 with laser. The manufacturing process is simplified and the quantity of the material to be used is reduced by dispensing with the lithography process and the etching process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film comprising a semiconductor, an insulator, a conductor and the like on a semiconductor substrate or an insulating substrate.
The present invention relates to a thin film forming method suitable for forming a silicon-based semiconductor thin film, a silicon oxide-based insulator thin film, and the like.

[0002]

2. Description of the Related Art Semiconductor devices, such as silicon-based MOS devices, which have become widespread to date, have an active layer inside a silicon wafer and form a gate electrode on a thermally oxidized surface oxide film. MOS (Metal-O
xide-Semiconductor: A metal-oxide-semiconductor structure is formed. Inside the silicon wafer, the impurity diffusion layer is locally controlled using an ion implantation method or the like, and there are few examples of using a local structural change such as an island structure. On the other hand, a gate electrode, a metal wiring, and the like formed on the silicon wafer require signal transmission between desired elements.
It is formed in a predetermined pattern shape such as a linear shape or an island shape. Generally, such a pattern is formed by the following procedure.

[0003] 1) forming a desired thin film on the entire surface of the substrate; 2)
3) exposing a desired area using a stepper; 4) developing an exposed area to form a photoresist pattern; 5) a thin film exposed to the opening using the photoresist pattern as a mask. 6) Strip and remove the photoresist.

In the above-described method, for example, an unnecessary portion of a metal thin film formed on the entire surface of a substrate is selectively removed by a photolithography step and an etching step. Have problems such as an increase in As a means for solving these problems, a technique of locally forming a metal thin film by a laser CVD method using an organic metal material has been attempted.

Further, with the rise of SOI (semiconductor-oxide-insulator) devices and the practical use of large-area devices typified by active matrix liquid crystal displays, not only the above-mentioned wiring metal materials but also silicon as active layers Patterning of semiconductor layers has become necessary. For example, in an amorphous silicon thin film transistor used for an active matrix liquid crystal display, 1) amorphous silicon nitride by plasma CVD using silane gas as a raw material, formation of an amorphous silicon film over the entire surface of a substrate, 2) application of a photoresist on the surface, ) Exposure of the desired area using a stepper, 5) Development of the exposed area to form a photoresist pattern, 6) Etching of the amorphous silicon film exposed in the opening using the photoresist pattern as a mask, 7) Stripping of the photoresist, Steps such as washing are sequentially performed.

[0006] In the above-mentioned process, unnecessary portions are selectively removed by a photolithography process and an etching process. Problems such as waste of materials and an increase in the number of processes are as follows.
This is the same as the wiring material already described. In addition, while the above-described semiconductor elements are manufactured on a large number of chips from a substrate having a size of about 6 inches, the display device can be used on its own with a diagonal of 20
Because of the size of inches, the amount of thin film discarded by removal also increases dramatically.

[0007]

As means for solving the above-mentioned problems, Japanese Patent Application Laid-Open No. Hei 4-180624 discloses that after a desired pattern region of an amorphous silicon thin film is recrystallized, amorphous silicon and crystalline silicon are recrystallized. Utilizing the difference in the etching rates described above, a technique has been proposed in which only the amorphous silicon region is etched to form a pattern made of crystalline silicon. By adopting such a method, there is an advantage that the photoresist process can be omitted. However, since the silicon-based thin film is removed after being formed on the entire surface, there still remains a problem that raw materials are consumed more than necessary.

Accordingly, an object of the present invention is to provide a method of forming a thin film which can omit a photolithography step and an etching step and can reduce the amount of raw materials used.

The present invention further provides a common technique for forming both an insulating thin film and a conductive thin film.
Another object is to provide a new method for forming a semiconductor element and a liquid crystal element.

[0010]

In order to achieve the above object, the present invention provides the following first to third thin film forming methods.

[0011] 1) A step of selectively applying a fluid material on a substrate to form a desired pattern, and a step of solidifying the desired pattern on the substrate to form a solidified pattern. A thin film forming method.

In the first invention method, for example, a desired pattern of the liquid material is formed by selectively applying the liquid material on the substrate by discharging and flying a plurality of small droplets of the liquid material in a predetermined direction. Form. Thereby, the lithography step and the etching step are omitted. For discharging and flying the small droplets, a plurality of droplets are selectively discharged at the same time by using a droplet discharging means having a plurality of discharge ports for discharging a liquid material in a predetermined direction and a material liquid supply port. Is preferred. As the droplet discharging means, a means utilizing a vaporization / volume expansion phenomenon due to heating of the liquid raw material, or a means utilizing mechanical vibration by a piezo element or the like can be used.

As the fluid raw material, in addition to the liquid described above, a mixture of liquid and fine particles, fine particles having high fluidity, and the like can be used. It is necessary to appropriately adjust the surface tension and viscosity of the liquid on the substrate so that the pattern formed before the solidification step does not collapse after the application. In the case where solid fine particles are used, pattern collapse can be prevented by charging the substrate and the solid fine particles in advance.

The thickness of the formed thin film pattern is as follows:
For example, it is preferable to control the film thickness to about 1 μm. In order to obtain a desired film thickness and pattern size by discharging and flying droplets, conditions such as a discharge port size, a discharge pressure, and a moving speed of a substrate or a discharge unit are appropriately controlled. After a thin film having a predetermined thickness or more is formed, the thickness can be reduced by polishing, ion milling, or the like. Also,
In the solidification step, drying of a liquid raw material by heat, melting and solidification of fine particles, solid formation by a chemical reaction, and the like can be used.

2) A thin film forming method comprising the steps of selectively applying a fluid material onto a substrate to form a desired pattern, and recrystallizing or amorphizing the desired pattern on the substrate. Method.

The method of the second aspect of the invention can also use the ejection and flying of droplets. In a preferred embodiment of the method of the present invention, the liquid raw material is solidified on a substrate to form an amorphous thin film or a polycrystalline thin film. By irradiating these thin films with an energy beam such as a laser, an electron beam, or a lamp, melting and recrystallization is promoted, and crystallization of an amorphous thin film, high quality of a polycrystalline thin film, and single crystallization can be realized.

3) A method of forming a thin film, comprising the steps of applying a liquid material on a substrate to form a liquid pattern, and oxidizing or nitriding the liquid pattern.

The liquid material can be applied to the entire surface of the substrate, or can be applied to a desired pattern by the method of the first or second invention of the present invention. When a high-order silane represented by the general formula Si _n H _{2n + 1} (n> = 2) is used as a liquid raw material, it is easy to obtain a silicon thin film with high purity. In particular, trisilane Si ₃ H ₈ , tetrasilane Si ₄ H ₁₀ and higher silanes are easy to handle because they are liquid at room temperature. Silanes have a characteristic that they easily react with oxygen in the air or an oxidizing atmosphere, that is, they are easily oxidized.
After applying the high order silane, the silicon oxide film is formed by exposing to an oxidizing atmosphere. After coating using a method such as spin coating, an oxide film can be formed on the entire surface of the substrate by oxidizing, or an oxide film can be formed selectively by selectively applying droplets and then oxidizing. .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to FIGS. FIG.
4A to 4D are cross-sectional views sequentially illustrating steps of a thin film forming method according to an embodiment of the present invention. First, the substrate
A droplet 102 is made to fly and adhere on 101 (FIG. 1A), and a liquid pattern 103 is formed (FIG. 2B). The pattern size and the film thickness are controlled by the unit amount and the number of the droplets that fly and adhere. A desired liquid pattern can be formed on the surface of the substrate 101 by moving the droplet discharging means relatively to the substrate 101 or by moving the substrate 101 relatively to the liquid droplet discharging means. The liquid pattern thus formed is dried by heating to form a thin film 104 (FIG. 3C). In addition, a laser 10
The crystallized film 106 is formed by irradiating 5 with the entire surface of the substrate or a part thereof (FIG. 4D).

If a high-order silane represented by the general formula Si _n H _{2n + 1} (n> = 2) is used as the liquid used in this embodiment, a silicon thin film with high purity can be easily obtained. In particular, trisilane Si ₃ H ₈ , tetrasilane Si ₄ H ₁₀ and higher silanes are easy to handle because they are liquid at room temperature. However, since it easily reacts with oxygen in air or oxidizing atmosphere,
It is desirable that the droplets are formed in a nitrogen or inert gas atmosphere or a reduced pressure atmosphere. Using high order silane,
In the step of solidifying the liquid pattern by heating, hydrogen atoms bonded to silicon atoms are released, and the silicon atoms are solidified by being randomly bonded. By using a heating / cooling process at about 600 ° C. or higher in which solid phase growth is observed in a finite time, a crystalline silicon thin film can be obtained because bonding is performed in a more stable bonding state. On the other hand, when a glassy substrate such as a liquid crystal display substrate is used, the processing temperature needs to be suppressed to about 600 to 300 ° C. or less. You. In order to form a crystalline silicon thin film by low-temperature heat treatment, an excimer laser (XeCl, KrF, XeF,
A laser recrystallization process using ArF or the like, a YAG laser, an Ar laser, or the like is applied. In this case, crystallization of amorphous silicon can be promoted even when a low softening point substrate such as glass is used.

FIG. 2 is a diagram showing the droplet discharging means. FIG.
(a) shows a sectional view of the discharge means alone. Supply to nozzle 201
Raw material is supplied from the port 204 side. For example, tetrasilane S
i_FourH _TenWhen used, the boiling point under one atmosphere is about 108 ° C
The heater 202 to about 120 ° C.
As a result, tetrasilane is vaporized in a region near the heater in the nozzle.
And the volume expands. No liquid on the discharge port 203 side
Outlet can be discharged by pressure due to vaporization / expansion
The liquid tetrasilane in the vicinity is ejected and flies. that's all
Droplet supply by arranging multiple nozzles like
Do it fast. FIG. 2 (b) shows a droplet discharge having such a structure.
It is a perspective view of an output means. A drive for controlling the heating of the heater 202
The driving circuit 206 is connected to the control means 208,
It is held on the circuit board 205. Note that in FIG.
1 are arranged in a one-dimensional array.
Processing speeds up by arranging the a in two dimensions
It is also possible.

As the droplet forming means, not only a method utilizing a vaporization / volume expansion mechanism by heating shown in FIG. 2, but also a jetting mechanism by mechanical pressure using a piezo element or the like, screen printing, intaglio printing, etc. Also available. By using silicon fine particles, silicon oxide fine particles, or those obtained by dispersing them in a solvent as a fluid raw material, a silicon thin film or a silicon oxide thin film can be formed.
In such a case, an electrostatic latent image is formed on the substrate, and is developed using a charged raw material. Alternatively, a method of developing the electrostatic latent image formed on the photoreceptor using the fine particles and transferring the fine particle pattern onto the substrate may be used.

FIG. 3 schematically shows a liquid pattern forming apparatus. The substrate 310 on which the thin film pattern is to be formed is introduced into the transfer chamber 305 via the gate valve 306. A transfer robot (not shown) is used for the transfer. After the introduction of the substrate 310, the atmosphere in the transfer chamber 305 is replaced with a nitrogen atmosphere. After the replacement, the substrate 310 further moves to the second gate valve 30.
It is introduced into the process chamber 309 through 6. Process room 30
In 9, the substrate 310 is placed on the substrate stage 310. The process chamber 309 is connected to the exhaust device 312 via the third gate valve.
And is controlled simultaneously with the nitrogen introduction mechanism or the inert gas introduction mechanism (not shown), thereby purifying the atmosphere. A desired pattern is formed on the substrate by moving the ejection device 308 while maintaining an appropriate gap on the substrate. In addition, the process chamber has a laser
Having. By introducing a laser beam supplied from the laser oscillator 301 via the optical element 302 to the surface of the substrate 310, the patterned thin film is modified or crystallized.
The laser light is also applied to the entire surface of the substrate by providing the moving means 303 in the optical element group. Although not shown, the laser beam may have a uniform beam intensity using a beam homogenizer or the like, or may have a desired beam pattern using a mask or the like.

FIG. 4 is a plan view showing a case where the liquid pattern forming apparatus of the above embodiment is combined with another processing apparatus. Loading / unloading room C1, plasma CV
D chamber C2, substrate heating chamber C3, hydrogen or oxygen plasma processing chamber C
4.Laser irradiation / coating chamber C5 has gate valves GV1 ~ G respectively
Through V6 (GV6 is reserved), it is connected to the substrate transfer chamber C7. Each process chamber includes gas introduction devices gas1 to gas7 and exhaust devices vent1 to vent7. The processing substrates sub2 and sub6 introduced from the load / unload chamber are transferred to each process chamber by a transfer robot provided in the substrate transfer chamber. In the laser irradiation / coating chamber C5, after a liquid thin film pattern is formed by a coating means (not shown), the liquid thin film pattern is heated and solidified. Next, the laser beam supplied via one or both of the first beam line L1 and the second beam line L2 is shaped by the laser combining optical devices opt1 and opt2, and is formed on the substrate surface via the laser introduction window w1. Irradiate.

By using the above-described device,
When producing a laminated structure with a plasma CVD SiO ₂ film,
Since the substrate can be prevented from being opened to the atmosphere, a clean interface can be formed.

The second embodiment will be described with reference to FIGS. 5 (a) to 5 (d). The droplet 102 is caused to fly and adhere to the substrate 101 (FIG. 7A), and a liquid pattern 503 is formed (FIG. 9B). The pattern size is controlled by the unit amount and the number of the droplets that fly and adhere. By moving the droplet discharging means relative to the substrate, or by moving the substrate 101 relative to the droplet discharging means,
A desired droplet pattern 504 is formed on the 101 surface. At this time, in controlling the pattern size and the film thickness, parameters are sufficiently set in consideration of the viscosity of the droplet, the surface tension on the substrate, the size of the island-shaped film to be formed, and the like. Here, when a film thicker than the desired film thickness is formed, or when unevenness is formed on the upper surface in the cross-sectional shape when the pattern 504 is solidified as shown in FIG. Is performed. The flattening process is performed as shown in FIG.
An oxide film 505 is formed on the upper portion, and then the surface of the solidified pattern 504 is polished and removed simultaneously with the oxide film by a chemical mechanical polishing method. Further, the entire surface of the substrate or a part thereof may be irradiated with the laser 105 as needed. The flattening means is selected according to the material, such as etching with a chemical, mechanical polishing, or ion milling.

Next, a third embodiment of the present invention will be described with reference to FIGS. 6A to 6D each show a part of a thin film transistor manufacturing process. On the substrate 101 on which an appropriate substrate cover film is deposited, a liquid material is applied in an island shape to form a thin film pattern 604 (FIG. 1A). Next, a crystalline silicon film 605 is formed through a heating / solidification step at 300 ° C. and a laser recrystallization step (FIG. 9B). Then, trisilane (Si3H ₈₎ film 606 is a liquid material formed by spin coating method (FIG. (C)). The spin condition is set so as to have a desired film thickness. After the coating is completed, annealing is performed at a temperature of 600 ° C. in a reduced-pressure oxygen atmosphere. By doing this,
Trisilane is oxidized to form an oxide film 607.
(d)). As a result, a silicon film pattern 605 covered with the oxide film 607 is formed. Next, formation of the gate electrode, impurity implantation into the source / drain regions, annealing,
A thin film transistor is formed through formation of wiring metal and the like.

FIG. 7 is a schematic sectional view of an apparatus for actively forming an oxide film. RF power supply RF1 (13.56
Power is supplied to the high-frequency electrode RF2 from a high frequency of MHz or higher. Plasma is formed between the electrode with gas supply holes RF3 and the high-frequency electrode, and radicals formed by reaction pass through the electrodes with gas supply holes and are guided to the region where the substrate is arranged. By using a gas containing oxygen as a source gas, oxygen radicals are supplied on the surface of the substrate sub2. At this time, by the flat gas introduction device RF4,
Another gas may be introduced without exposure to plasma, and a silicon oxide film can be formed by introducing silane or the like. That is, as shown in the figure, the oxide film forming apparatus includes an exhaust device ven2, a gas introduction device gas2, an oxygen line
gas21, helium line gas22, hydrogen line gas23, silane line gas24, helium line gas25, argon line
It has gas26. The substrate holder S2 can be heated from room temperature to about 500 ° C. by a heater or the like. As the form of the oxygen radical supply apparatus as described above, not only the parallel plate type RF plasma CVD apparatus as described above,
Methods that do not use plasma, such as low-pressure CVD and normal-pressure CVD, and microwave and ECR (Electron Cyclotron Reso
It is also possible to use a plasma CVD apparatus using the (nance) effect. In addition, a nitride film can be formed by using a material containing nitrogen instead of oxygen.

Further, the above-described method is high in purity and suitable for forming a thick oxide film of 1 μm or more.
The following applications are also possible. A glass substrate on which an active matrix liquid crystal display or an image sensor using a thin film transistor is formed contains a trace amount of an alkali metal or the like. A substrate cover layer is used to prevent impurities such as alkali metals from diffusing from the substrate to the active layer silicon and the insulating film and the interface in the annealing step and the laser crystallization step. Suitable as a production method. The process time can be shortened as compared with the conventional CVD method. On the other hand, an interlayer insulating film used in a semiconductor process, an active matrix TFT-LCD, or the like is often required to have a flat upper portion.
Even in such applications, the application of the liquid material forms a flat surface, which is an excellent alternative.

Although the present invention has been described based on the preferred embodiment, the method of forming a thin film of the present invention is not limited to the configuration of the above-described embodiment, but rather the configuration of the above-described embodiment. The method of making various modifications and changes from
It is included in the scope of the present invention.

[0031]

According to the method for forming a thin film of the present invention, a thin film pattern can be formed by selectively supplying a flowable raw material onto a substrate. The number can be reduced, and the amount of raw materials used can be reduced. Furthermore, for a silicon-based thin film, a low-cost, high-performance semiconductor element can be formed by applying the coating film oxidation technique to the insulating thin film formed by the thin film forming method of the present invention.

[Brief description of the drawings]

FIG. 1 is a sectional view of each step sequentially showing a thin film forming method according to a first embodiment of the present invention.

2A and 2B are a cross-sectional view showing the structure of a single discharge device used in the method of the present invention, and a perspective view showing the structure of discharge devices arranged in an array.

FIG. 3 is a schematic plan view of a liquid pattern forming apparatus used in the method of the present invention.

FIG. 4 is a plan view of a composite apparatus including a liquid pattern forming apparatus used in the method of the present invention.

FIG. 5 is a sectional view sequentially showing a thin film forming method according to a second embodiment of the present invention.

FIG. 6 is a sectional view sequentially showing a thin film forming method according to a third embodiment of the present invention.

FIG. 7 is a schematic sectional view of an oxygen radical supply device used in a third embodiment.

[Explanation of symbols]

 101: substrate 102: liquid droplet 103: liquid pattern 104: solidification pattern 105: laser 106: crystallized film 201: nozzle 202: heater 203: discharge port 204: supply port 205: drive circuit board 206: drive circuit 207: supply means 208: Control means 301: Laser oscillator 302: Optical element 303: Moving means 304: Optical path 305: Transport chamber 306: Gate valve 307: Laser introduction window 308: Discharge device 309: Process chamber 310: Exhaust device 311: Substrate stage 312: Exhaust device 504: thin film pattern 604: liquid pattern 605: thin film pattern 606: trisilane film 607: oxide film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/316 H01L 21/316 CB F term (Reference) 4D075 AA04 BB02Z BB72Z BB92Z CA47 DA06 DB13 DB14 DC22 EA45 5F045 AB03 AB32 AC01 AC11 BB01 BB08 BB16 CA15 EB02 EB20 HA16 HA17 HA24 5F053 DD01 FF01 GG02 HH01 LL10 PP20 RR05 RR13 5F058 BA20 BB04 BB07 BC02 BC08 BF23 BF46 BF73 BF74 BG01 BG02 BG04 BH03

Claims (6)

[Claims] 1. A method for selectively coating a fluid material on a substrate to form a desired pattern, and solidifying the desired pattern on the substrate to form a solidified pattern. A thin film forming method. 2. The step of forming a desired pattern,
The method for forming a thin film according to claim 1, comprising a step of ejecting and flying a droplet. 3. The method according to claim 1, further comprising: forming an oxide film over the solidified pattern over the entire surface; and polishing the oxide film and the solidified pattern to form a solidified pattern having a desired thickness. Or the thin film forming method according to 2. 4. A method for forming a desired pattern by selectively applying a fluid material on a substrate, and recrystallizing or amorphizing the desired pattern on the substrate. Characteristic thin film forming method. 5. The step of forming the desired pattern,
The method of forming a thin film according to claim 4, comprising a step of ejecting and flying a droplet. 6. A method for forming a thin film, comprising: applying a liquid material onto a substrate to form a thin film; and oxidizing or nitriding the thin film.