KR20000008722A - Manufacturing method of diamond electron emitter array using select growth method - Google Patents

Abstract

PURPOSE: A manufacturing method of diamond electron emitter array using select growth method is provided to apply the thermal, chemical, mechanical characteristics and electron affinity of diamond into an electron emitter of a field emission display. CONSTITUTION: The present invention discloses a manufacturing method of diamond electron emitter array using select growth method comprising: (a) a step sequentially forming an insulation layer and a gate metal layer on a semiconductor substrate; (b) a step sequentially patterning the gate metal layer and insulation layer to selectively expose the semiconductor substrate; and a step selectively growing a diamond electron emitter array on the exposed semiconductor substrate.

Description

Fabrication method of diamond electron emitter array using selective growth method

The present invention relates to a diamond emitter array using a selective growth method of diamond and a method of manufacturing the same.

Flat Panel Display (FPD) is emerging as a product having unlimited growth potential and marketability, replacing the existing cathode ray tube (CRT). Currently, one of the leading drivers for FPDs is the Active Matrix Liquid Crystal Display (AMLCD). AMLCD has a screen display method that fills a liquid crystal between transparent substrates, configures each pixel, and adjusts the orientation of the liquid crystal for each pixel to display an overall image. However, these AMLCDs are not thermally stable and have the disadvantage that the brightness is not very low compared to the cathode ray tube, and the viewing angle is also very small compared to the cathode ray tube. In order to overcome this drawback, FED (Field Emission Display) is being studied as a flat panel display device that operates on the same principle as cathode ray tube and has the outstanding advantages of cathode ray tube. This creates an array of electron emitters that are several μm in size, and the electrons emitted from them pass through a high vacuum to activate the phosphors on the screen to display the screen. This has not been commercialized yet, but it has many advantages over existing FPDs and is being studied a lot. Electron emitters use many silicon or metal emitters, which can be manufactured using techniques established in conventional semiconductor processes, but they are susceptible to high temperatures, high voltages and mechanically harsh environments and are very resistant to electron emission. The disadvantage is that an electric field must be applied.

Currently, representative methods of making an emitter array of FED include a spindt method of forming a metal emitter array and a method of making a silicon emitter array by etching. Among them, a method of manufacturing the emitter array by the Spindt method is illustrated in FIGS. 1A to 1D.

First, as shown in FIG. 1A, an insulator 2 such as silicon dioxide of about 1 to 0.5 μm and a gate metal of about 2000 μm to 4000 μm are formed on the silicon substrate 1. After sequentially depositing (3), the gate metal layer 3 is patterned by photolithography, and the insulator 2 is also etched by wet etching to form holes for emitter formation. (2a) is formed. In this way, an under cut exists in the insulator 2.

Next, as shown in FIG. 1B, after depositing a sacrificial layer 4 having a low melting point with an evaporator, the silicon substrate 1 is inclined at an appropriate angle and rotated vertically thereon. The electron emitter forming metal is deposited, or as shown in FIG. 1C, the electron emitter 2 ′ is formed by inclining the electron beam of the electron emitter forming metal while rotating the silicon substrate 1.

Next, the metal emitter array is completed by removing the sacrificial layer 3 as shown in FIG. 1D.

Meanwhile, the method of making a silicon emitter is as follows.

First, as shown in FIG. 2A, a silicon oxide is deposited on the silicon substrate 11 and patterned to form a mask 12. Next, as shown in FIG. 2B, the silicon substrate 11 is etched using the silicon oxide mask 12, and then the silicon in the etched portion is oxidized to form thermal oxide 11 '. Formation makes the silicon emitter 13 sharper.

Next, as shown in FIG. 2C, silicon oxide is deposited on the thermal oxide 11 ′ to form the insulating layer 14, and as shown in FIG. 2D, on the insulating layer 14. The gate metal layer 15 is deposited.

Next, as shown in FIG. 2E, the exposed portion of the silicon oxide 10 ′ is removed by wet etching to complete the silicon emitter array.

In FED manufacturing, the method of manufacturing silicon or metal emitters, which are widely used in the manufacture of electron emitters, is already established, but in the case of silicon or metal emitters, a very strong electric field must be applied around the emitter for electron emission. Therefore, it is difficult for an emitter to endure heat generated by such a strong electric field when used for a long time, and sputtering and phosphors of ionized impurity existing between the emitter and the anode The pollution of the phosphor (emission) has a problem that the emission (emission) property is bad. Therefore, research is being actively conducted to use diamond as an electron emitter, which can not only deteriorate its emission property even under such a harsh environment but also can emit electrons even at a low electric field.

Diamonds are very hard to withstand sputtering by ionized impurities, are chemically stable, and have very good thermal conductivity to prevent heat damage caused by electron emission. In particular, since diamond has a small or negative electron affinity value, diamond has an advantage of enabling electron emission even at a very low electric field. Quantitative values of various properties of diamonds are shown in Table 1 below.

characteristic silicon Diamond Advantages of Diamond Thermal conductivity 1.5 W / cm ℃ 2.0 W / cm ℃ Relative high emission current Chemical stability of the surface Sensitive to adsorption Inert relative to adsorbed material Relatively high stability and relatively wide emission area Electronic affinity 4.05eV In some respects NEA Relatively low operating voltage, relatively high efficiency Breakdown electric field 5 x 10 ⁶ V / cm 1 x 10 ⁷ V / cm High power applications Electron mobility 1.5 x 10 ³ cm / Vs 2.0 x 10 ³ cm / Vs Relatively high current limit

However, diamond is chemically so stable that it is not easy to etch and cannot produce emitter arrays using conventional silicon or metal emitters in the deposition process. Therefore, in order for the practical application of diamond as an electron emitter of FED, many researchers have studied how to manufacture a diamond emitter array due to the necessity of developing a new technique for making diamond into an array of emitters having a size of several μm. come. The techniques already developed in the FED using silicon and metal emitters can be applied, and to apply the diamond's superior properties, it is necessary to create arrays of diamond emitters with regularly arranged gates of several μm in size.

As mentioned earlier, diamonds are not easily etched, cannot be deposited by an evaporator, so emitters can't be created using the above two methods, and diamonds aren't easy to make regular arrays. Unlike the silicon or metal emitters, the gate making process has not been developed. Therefore, even though a method of manufacturing a regular diamond emitter array has not been established, a diode type using a diamond thin film as an emitter without a gate is established. making. However, this diode type not only has to apply a very large voltage for electron emission, but also has difficulty in controlling electron emission to reproduce a screen.

Okano et al. Developed manufacturing processes for a diamond electron emitter array using a silicon mold, as shown in FIGS. 3A-3E. This method first deposits a silicon oxide 22 on a silicon substrate 21, as shown in FIG. 3A, and then patterns the silicon oxide layer 22 by photolithography, as shown in FIG. 3B. A mask 22 'is formed, and as shown in FIG. 3C, the silicon substrate 21' is etched using the mask 22 'to form a pyramid shaped mold.

Next, as shown in FIG. 3D, diamond is deposited on the pyramid-shaped silicon mold 21 'to make an array 23 of regular diamond tips, and then as shown in FIG. 3E. The mold 21 ′ is removed to complete the diamond tip array 23.

In addition to such a method, a gate is formed on the diamond tip array 23 in recent years, but this method has a disadvantage in that the process is complicated to use in an actual process.

In addition, Asano et al. Et al. Produced sharp diamond emitters using ion milling and Ar sputtering, respectively, but there was a problem that was not regular and reproducible.

The present invention has been made to improve the above problems, diamond emitter array using a selective growth method that is not only thermally, chemically and mechanically stable but also electron emission at low voltage using the selective growth method of diamond and The object is to provide a method for producing the same.

1A to 1D are vertical cross-sectional views showing steps of fabricating a metal emitter array by a conventional Spindt method; FIG.

2a to 2e is a vertical cross-sectional view showing the steps of fabricating a conventional silicon emitter array (Silicon emitter array),

3a to 3e are vertical cross-sectional views showing the step-by-step process of manufacturing a diamond electron emitter array using a conventional silicon mold (Silicom mold),

4A to 4H are vertical cross-sectional views showing steps of fabricating a tripolar diamond electron emitter array using a selective growth method according to the present invention;

5A and 5B are cross-sectional and planar photographs of a tripolar diamond electron emitter (Electron Emitter) made by the diamond selective growth method of FIGS. 4A to 4H;

6A and 6B are cross-sectional and planar photographs of a tripolar diamond electron emitter (Electron Emitter) made by the diamond selective growth method of FIGS. 4A to 4H after heat treatment at a temperature of 700 ° C. in a hydrogen plasma atmosphere, respectively.

7A and 7B are graphs showing electrical characteristics of the tripolar diamond of FIGS. 6A and 6B, respectively.

7A is a current-voltage characteristic curve,

7b is a fowler-Nordheim plot,

8 is a partial cutaway perspective view of a diamond emitter array manufactured by a method of manufacturing a diamond emitter array using a selective growth method as illustrated in FIGS. 4A to 4H.

<Description of the symbols for the main parts of the drawings>

1. Silicon Substrate 2. Silicon Oxide Insulator

2a. Hall 2 '. Emitter

3. Gate metal 4. Sacrifice layer

11. Silicon substrate 11 '. Thermal oxide

12. Mask 13. Silicon emitter

14. Silicon oxide layer 15. Gate metal layer

100. Silicon substrate 105. Cathode

111. SiO ₂ insulation layer 120. Gate metal layer

120 'openings 121, 121'. SiO ₂ protective layer

130.Diamond Core 131.Diamond Emitter

In order to achieve the above object, a method of manufacturing a diamond emitter array using the selective growth method according to the present invention includes: (a) sequentially forming a cathode, an insulating layer, and a gate metal layer on a semiconductor substrate; (B) selectively exposing the semiconductor substrate by sequentially patterning the gate metal layer and the insulating layer; And (c) selectively growing a diamond electron emitter array on the exposed semiconductor substrate.

In the present invention, the semiconductor substrate is a silicon substrate, and further comprising the step of forming a cathode on the silicon substrate prior to the (a) step, wherein the (a) step, (a-1) the silicon substrate Forming a silicon oxide on the silicon oxide by thermal oxidation; And (a-2) a sub-step of depositing SiO ₂ on the silicon oxide by chemical vapor deposition to form an insulating layer. In step (a), the gate metal layer is protected on the gate metal layer. Further forming a protective layer, and in the step (b), holes are formed in the gate metal layer and the insulating layer by photolithography and reactive ion etching, or holes are formed in the protective layer, the gate metal layer and the insulating layer. (C) step (C)-(C-1) a sub-step of generating a diamond nucleus on the exposed semiconductor substrate; And (c-2) a sub-step of growing a diamond emitter on the diamond nucleus by plasma enhanced chemical vapor deposition. In the (c-1) sub-step, the direct current bias voltage is applied to the semiconductor substrate. It is preferable to use a bias-enhanced nucleation method for generating diamond nuclei on the exposed semiconductor substrate, and the step of heat-treating the semiconductor substrate for 20 minutes at a temperature of 700 ° C. in a hydrogen plasma atmosphere immediately before the substep (C-1). It is preferable to further include, in the (C-1) sub-step, the microwave power is 800W, the pressure in the deposition furnace is 15 Torr, the temperature of the semiconductor substrate is 800 ℃, the inside of the deposition furnace CH _4: the H ₂ gas atmosphere of 5%: the ratio of 95%, and for applying the DC bias voltage applied to the semiconductor substrate to -150V A diamond deposition process is performed on the gun for 20 minutes, in the substep (C-2), the microwave power is 1000W, the pressure in the deposition furnace is 20 Torr, the temperature of the semiconductor substrate is 600 ° C, and It is preferable to perform the diamond deposition process for 5 hours under the condition that the ratio of CH ₄ : H ₂ gas in the deposition furnace is 0.25%: 99.75%.

In addition, the diamond emitter array using the selective growth method according to the present invention in order to achieve the above object, the semiconductor substrate; Cathodes formed in a stripe shape in one direction on the semiconductor substrate; An insulating layer stacked on the semiconductor substrate and the cathodes and formed on the cathodes to have holes having a constant diameter in the direction of the cathodes; Diamond emitters formed on the cathodes exposed by the holes; And gates formed in a stripe shape in a direction intersecting the cathodes with openings corresponding to the holes on the insulating layer.

In the present invention, the semiconductor substrate is a (100) plane silicon substrate, a SiO ₂ thermal oxide film is further formed between the silicon substrate and the cathode and the insulating layer, the insulating layer is preferably formed of SiO ₂ , The holes are 2 to 3 μm in diameter, and the cathodes are formed of at least one of Au, Cu, Ti, Ta, TiN, TiC, SiC, and Mo, TaN, TiN, Ti, Ta, Al, It is preferable that it is formed with at least one of Cu.

Hereinafter, a method of manufacturing a diamond emitter array using the selective growth method according to the present invention will be described in detail with reference to the accompanying drawings.

The method of manufacturing a diamond emitter array using the selective growth method according to the present invention is characterized by the excellent thermal, chemical and mechanical properties of diamond and the negative and low electron affinity of electrons in a field emission display. It is intended for use as an emitter.

4A to 4H are vertical cross-sectional views showing steps of fabricating a tripolar diamond electron emitter array using a selective growth method according to the present invention. As shown, the method of manufacturing a diamond electron emitter array using the selective growth method according to the present invention, first, by depositing a metal for the cathode on the silicon substrate 100 and then patterning, as shown in Figure 4a, stripe A cathode 105 on the phase is formed. Here, before forming the cathode 105, the upper surface of the silicon substrate 100 may be oxidized by thermal oxidation to form silicon oxide (thermal SiO ₂ ) (not shown).

Next, as shown in FIG. 4B, SiO ₂ is deposited on the silicon substrate 100 on which the cathode 105 is formed by chemical vapor deposition (CVD) to prevent the gate 100 and the substrate 100 to be formed from being energized. The main forms the insulating layer 111. At this time, the thickness of the SiO ₂ layer deposited on the insulating layer 111 is appropriately adjusted in consideration of the height from the substrate of the next gate to be formed so that an emitter of an appropriate height can be formed.

Next, as shown in FIG. 4C, a metal layer to be used as the gate 120 is deposited on the insulating layer 111.

Next, as shown in FIG. 4D, a SiO ₂ layer 121 ′ is deposited on the gate metal layer 120, and as shown in FIG. 4E, a photolithograhy process and reactive ion etching are performed. Ion etching (RIE) method makes holes for diamond to grow. Here, the gate protection layer 121 is formed on the gate metal layer 120 to protect the gate metal layer 120 from carbon contamination during diamond deposition.

Next, as shown in FIG. 4F, a negative direct current is applied to the semiconductor substrate 100 (when the cathode is not formed) or the cathode 105 as a pretreatment for diamond nucleation as a step prior to growing the diamond. A bias voltage is applied. At this time, the semiconductor substrate 100 (when not forming the cathode) or the cathode 105 is affected by the bias voltage only at the exposed portion, whereby the diamond nucleus 130 is promoted to be generated. Such a bias enhanced nucleation (BEN) method provides a condition for diamond to grow only at the exposed portion of the cathode 105.

Next, as shown in FIG. 4G, the diamond emitter 131 is grown by a diamond growth method using plasma enhanced chemical vapor deposition (PECVD) or the like.

Next, the SiO ₂ protective layer 121 is removed to complete the diamond emitter array for the FED, as shown in FIG. 4H.

The diamond emitter array having such a structure has a large electric field even at a low voltage because the distance between the gate 120 and the diamond emitter 131 is about 1 μm, thereby emitting electrons at a lower voltage than a diode-type diamond emitter. This becomes possible. Since such a structure is the same as that currently applied to silicon or metal emitters, the method developed for screen reproduction in FED using silicon or metal emitters can be used as it is. Although it is not possible to make very sharp tips such as silicon or metal emitters, diamonds have excellent electron emission properties and can emit electrons at low voltages. In fact, even flat diamond films have been reported to emit electrons at lower voltages than silicon or metal emitters.

5A and 5B are cross-sectional and planar photographs of a tripolar diamond electron emitter (Electron Emitter) made by the diamond selective growth method as described above. An example of this photograph was formed by the following processes.

First, oxidize the (100) plane silicon wafer to make a thermal oxide film about 500 nm to be used as an insulator, and then form a cathode. Then, considering the height of the diamond emitter and the gate height, 1500 nm on the thermal oxide film by CVD method. More SiO ₂ layer is formed. A 300 nm thick Mo 2 gate is deposited using a sputter and a 300 nm SiO ₂ layer is deposited on the metal layer by CVD to prevent the gate metal from being contaminated by carbon during diamond deposition. To protect the gate metal. After the deposition of all the layers, the photolithography process and the dry etching process are used to make holes for forming diamond emitters with a size of 2-3 μm.

Put the specimen with holes into the diamond deposition equipment and lower the pressure by using a rotary pump to 1.0 × 10 ^-2 Torr or less and then use CH ₄ + H ₂ (5) for diamond nucleation in the hole. With a plasma of: 95), apply a negative DC voltage of -150V for 20 minutes under the substrate (Bias Enhanced Nucleation).

After completion of the nucleation step, diamond emitters are grown by a general diamond growth method using PECVD for 5 hours in an in situ growth process.

Finally, the specimen is removed from the chamber and then immersed in a buffered hydrofluoric solution to remove SiO ₂ on the gate. The detailed process conditions at the BEN (Bias Enhancde Nucleation) and diamond growth stages are shown in Table 2 before the bias enhanced nucleation (BEN) process to remove the damage produced by the above process. In the case of heat treatment at 700 ° C. for 20 minutes under hydrogen plasma, as shown in FIG. 6, diamond nucleation density can be further reduced, and its electrical characteristics are shown in FIGS. 7A and 7B. That is, FIG. 7A is a current-voltage characteristic curve, and FIG. 7B is a fowler-Nordheim plot.

BEN Diamond growth Microwave Power (Watt) 600-1000 (800) 600-1000 (1000) Torr 15-30 (15) 15-30 (20) Substrate temperature (℃) 600-1000 (800) 500 ~ 900 (600) CH ₄ / H ₂ ratio (%) 1 ~ 10 (5) 0.25 ~ 2 (0.25) DC bias voltage (Volt) -100 to -250 (-150) - Minutes 10 ~ 40 minutes (20 minutes) 4 ~ 8 hours (5 hours)

8 is a partial cutaway perspective view showing the overall appearance of a diamond emitter array manufactured by a method of manufacturing a diamond emitter array using a selective growth method as shown in FIGS. 4A to 4H.

As described above, the method of manufacturing a tripolar diamond emitter array using the selective growth method according to the present invention solves the thermal, chemical and mechanical problems caused by using a conventional silicon or metal emitter and at the same time the existing diamond emitter By improving the manufacturing method problems and transforming them to the existing silicon or metal emitter manufacturing process, solving the process problems that arise when the emitter is made of diamond, the excellent properties of diamond can be used as the electron emitter of the FED. To be. In addition, many technologies such as drive circuits, phosphors and packages of FEDs using silicon or metal emitters, which have not been commercialized but are well-studied to date, are still applied. Can be used. In the diamond deposition process, since the diamond thin film manufacturing process, which is widely used, is used as it is, the process conditions are already established. Since the processes other than the diamond deposition process are made of only the technology already established in the semiconductor process, It can be used for actual mass production without any difficulties during the manufacturing process. Therefore, this process can accelerate the rapid development and commercialization of FEDs using diamond emitters. Nationally, we are planning to develop FED with better performance in Korea in a situation where research for commercialization of FED is actively being carried out around the world. I think it will increase the market share.

Claims (14)

(A) sequentially forming an insulating layer and a gate metal layer on the semiconductor substrate; And (B) selectively exposing the semiconductor substrate by sequentially patterning the gate metal layer and the insulating layer; And (C) selectively growing a diamond electron emitter array on the exposed semiconductor substrate; A method of producing a diamond emitter array using a selective growth method comprising a. The method of claim 1, The semiconductor substrate is a silicon substrate, and prior to the (a) step of forming a cathode on the silicon substrate; further comprising the method of manufacturing a diamond emitter array using a selective growth method. The method of claim 1, The semiconductor substrate is a silicon substrate, the (a) step, (A-1) sub-steps of forming silicon oxide on the silicon substrate by thermal oxidation; And (A-2) sub-step of depositing SiO ₂ on the silicon oxide by chemical vapor deposition to form an insulating layer; A method of producing a diamond emitter array using a selective growth method comprising a. The method of claim 1, A method of manufacturing a diamond emitter array using a selective growth method, further comprising forming a protective layer for protecting the gate metal layer on the gate metal layer in the step (a). The method according to any one of claims 1 to 4, In the step (b), the selective growth method comprises forming holes in the gate metal layer and the insulating layer or forming holes in the protective layer, the gate metal layer and the insulating layer by a photolithography process and a reactive ion etching method. Method for producing a diamond emitter array using. The method according to any one of claims 1 to 4, The (c) step, (C-1) generating a diamond nucleus on the exposed semiconductor substrate or the cathode; And (C-2) a sub-step of growing a diamond emitter on the diamond nucleus by plasma enhanced chemical vapor deposition; A method of producing a diamond emitter array using a selective growth method comprising a. The method of claim 6, In the (C-1) sub-step, the diamond Emmy using the selective growth method is characterized by using a bias-enhanced nucleation method that generates a diamond nucleus on the exposed semiconductor substrate or the cathode while applying a DC bias voltage to the semiconductor substrate. Method for manufacturing a terminator array. The method of claim 7, wherein The method of manufacturing a diamond emitter array using the selective growth method further comprises the step of heat-treating the semiconductor substrate for 20 minutes at a temperature of 700 ° C. in a hydrogen plasma atmosphere immediately before the sub-step (c-1). The method of claim 7, wherein In the step (C-1), the microwave power is 600-1000 W, the pressure in the deposition furnace is 15 Torr, the temperature of the semiconductor substrate is 600-1000 ° C., and CH ₄ : The diamond deposition process is performed for 10 to 40 minutes under the condition of applying a H ₂ gas atmosphere at a ratio of 1%: 99% to 10%: 90%, applying the DC bias voltage applied to the semiconductor substrate at -100 to -300V, In the substep (C-2), the microwave power is 600-1000 W, the pressure in the deposition furnace is 10-30 Torr, the temperature of the semiconductor substrate is 500-900 ° C., and the CH in the deposition furnace is _{4. A} method for producing a diamond emitter array using a selective growth method, wherein a diamond deposition process is performed for 4 to 8 hours under a condition of a ₄ : H ₂ gas atmosphere at a ratio of 0.25%: 99.75% to 2%: 98%. Semiconductor substrates; Cathodes formed in a stripe shape in one direction on the semiconductor substrate; An insulating layer stacked on the semiconductor substrate and the cathodes and formed on the cathodes to have holes having a constant diameter in the direction of the cathodes; Diamond emitters formed on the cathodes exposed by the holes; And Gates having openings corresponding to the holes on the insulating layer and formed in a stripe shape in a direction crossing the cathodes; Diamond emitter array using a selective growth method characterized in that provided. The method of claim 10, The semiconductor substrate is a (100) plane silicon substrate, and a SiO ₂ thermal oxide film is further formed between the silicon substrate, the cathodes, and the insulating layer, and the insulating layer is formed of SiO ₂ . Diamond emitter array. The method of claim 10, The holes are a diamond emitter array using a selective growth method characterized in that the diameter of 1 ~ 4μm. The method of claim 10, And the cathodes are formed of at least one of Cu, Au, Ti, Ta, TiN, TiC, SiC, and Mo. The method of claim 10, And said gates are formed of at least one of Mo, TaN, TiN, Ti, Ta, Al, and Cu.