JP2792550B2 - Etching agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching agent and a method of manufacturing an electronic device, and more particularly to an etching agent capable of simultaneously etching a multilayer film composed of a conductor layer and a semiconductor layer with the same etching agent. The present invention relates to a method for manufacturing an electronic device using an etching solution.

[0002]

2. Description of the Related Art Conventionally, a mixed solution of hydrofluoric acid, nitric acid, and acetic acid has been used for etching a semiconductor such as silicon. However, this etching process involves intense heat generation and a gas of nitrogen oxide. From the fact that, furthermore, the deterioration and peeling of the resist due to nitric acid, etc.
It has been considered difficult to form a fine pattern.

The present inventors have developed an etching agent containing hydrofluoric acid and an oxo acid or oxo acid salt compound as an etching agent for solving such a problem (Japanese Patent Application No. 4-285338).

On the other hand, for example, in an electronic device for driving a liquid crystal display and the like, as the demand for a larger pixel and a higher pixel density is increased, a manufacturing method with higher precision and higher productivity is required. For example, in the case of forming an inverted staggered thin film transistor shown in FIG. 7, a step of etching the conductor layer 706 and the ohmic contact semiconductor layer 705 is required. Conventionally, after forming a resist pattern, etching for a metal layer is performed. The metal layer 706 was etched with a liquid, and then the ohmic contact layer 705 was etched with the above-mentioned etching liquid.

As described above, conventionally, since two types of etching agents are used, and furthermore, cleaning or the like is required between individual etchings, the process becomes longer and causes a reduction in productivity. Further, there is also a problem that the repetition of individual etching and cleaning lowers the adhesiveness of the resist, and the pattern is liable to have a defect or the like. This problem becomes more remarkable when a barrier layer is provided between the metal layer and the contact layer, because the type of the etchant and the number of times of cleaning are further increased. Further, in the etching of Al which is preferably used for the conductor layer, there is a problem that the viscosity of the etching solution is high, and the finer the pattern, the more easily short defects due to the remaining etching are generated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an etching agent capable of continuously forming a fine pattern of a multilayer structure composed of a conductor layer and a semiconductor layer with one liquid. With the goal. It is still another object of the present invention to provide a method for manufacturing an electronic device, which can shorten the manufacturing process and manufacture the electronic device with a high yield.

[0007]

A first gist of the present invention is as follows.
In solution, hydrofluoric acid and the general formula (XO _n) ^p- (where, X is halogen, n represents 3, 4 or 6, p is 1,
The present invention is characterized in that the etching agent contains halooxo acid ions represented by 2 or 3) in an amount of 0.05 to 0.5 mol / l and 0.01 mol / l or more, respectively.

A second aspect of the present invention, in solution, and hydrofluoric acid, the general formula (XO _n) ^p- (where, X is halogen, n represents 3, 4 or 6, p is 1, An etchant characterized by containing a halooxoacid ion represented by 2 or 3) and a halogen precipitation inhibitor.

A third aspect of the present invention, in solution, hydrofluoric acid and the general formula (XO _n) ^p- (where, X is halogen, n represents 3, 4 or 6, p is 1, 2 Or 3) 0.05 to 0.5 mol / l of the halooxo acid ion represented by 3)
And an etching agent containing at least 0.01 mol / l, and continuously etching the ohmic contact layer and the conductor layer laminated on the surface of the semiconductor layer.

The halooxo acid ion is preferably an iodate ion (IO ₃ ^-1 ). Further, the etching agent of the present invention more preferably contains iodine ions, and the iodine ions are preferably those derived from NH ₄ I, KI or NaI. Further, the etching agent of the present invention preferably contains a water-soluble organic solvent, and the water-soluble organic solvent is preferably acetic acid or ethanol, and its concentration is 7%.
It is preferably 0% by volume or less.

The conductor is made of Al, Mo, Ni, Ta,
It is characterized by being made of a metal of Pt, Ti, Pd, W, Co or Cr or an alloy or a metal compound of the metal. Further, the conductor has a multilayer structure of two or more layers made of the metal and / or the alloy and / or the metal compound.

[0012]

In the course of studying to increase the efficiency, shortening, and increasing the yield of the electronic device manufacturing process, the present inventors set the hydrofluoric acid content to 0.05 to 0.5 mol / l and the halooxo acid ion It has been found that by using an etching solution containing at least 0.01 mol / l or more, not only semiconductors but also various metals, alloys, metal compounds such as silicide, and the like can be etched into a fine pattern.

The mechanism of this etching is thought to be that the halooxoacid ions act as a strong oxidizing agent, oxidize solid surfaces such as semiconductors and metals, and then dissolve the resulting oxides in hydrofluoric acid. Therefore, even with a metal such as Al, which reacts with hydrofluoric acid, oxidation by a halooxo acid ion occurs preferentially by selecting an appropriate composition as described above, and the direct reaction between the metal and hydrofluoric acid occurs. Since generation of gas due to the reaction is suppressed, stable etching can be performed.

Since the etching agent having the above composition does not generate heat or generate gas in the reaction with semiconductors, metals and metal compounds, it becomes possible to form fine patterns of semiconductors and metals. In addition, since the resist is extremely stable with respect to the etching solution, side etching due to a decrease in the adhesion of the resist and peeling off can be suppressed, and a fine pattern can be formed. In addition, since the etching agent of the present invention is chemically stable, it can perform stable etching for a long period of time as compared with other etching solutions, and is advantageous in cost.

Therefore, it is possible to form a stable fine pattern using the same etchant even for a structure in which a metal layer, a metal compound layer, and a semiconductor layer are stacked in multiple layers. The metal layer and the semiconductor layer may have a multilayer structure of two or more layers as long as the etching solution of the present invention can be applied.

In the etching agent of the present invention, if the concentration of hydrofluoric acid exceeds 0.5 mol / l, variations in etching due to a direct reaction between metal and hydrofluoric acid are likely to occur. Since this variation affects the underlying semiconductor layer and adversely affects device characteristics, the hydrofluoric acid concentration needs to be 0.5 mol / l or less. Also, like an amorphous thin film transistor, i
When etching the ohmic contact layer of about several tens nm and the metal layer of about several hundred nm formed on the type Si layer, if the concentration of hydrofluoric acid exceeds 0.5 mol / l, This is because the etching rate becomes too high, so that it becomes difficult to stably obtain the end point.

In the present invention, the more preferred concentration of hydrofluoric acid varies with the concentration of oxoacid ions, but is preferably 0.33 mol / l or less. The generation of bubbles is further suppressed, and more uniform etching can be performed. on the other hand,
If the concentration is lower than 0.05 mol / l, the etching rates of the semiconductor layer and the conductive layer are significantly reduced, which is not practically preferable.

In the etching agent of the present invention, the concentration of halooxoacid ions needs to be 0.01 mol / l or more, preferably 0.02 mol / l or more, and preferably 0.04 mol / l.
1 / l or more is more preferable. If the concentration is lower than 0.01 mol / l, the reason is unknown, but an abnormal etch in which the peripheral portion of the etched portion in the semiconductor layer is extremely etched easily occurs. Also,
In the region where the halooxo acid ions are low in concentration, as described above, in the case of metals such as Al, the reaction of oxidation by halooxo acid ions and dissolution of oxides by hydrofluoric acid is difficult.
In order to perform more uniform etching, the halooxoacid ion is preferably 0.02 mol / l or more, and more preferably 0.04 mol / l or more, in order to perform more uniform etching. preferable.

[0019] When Harookiso acid ion is at a high concentration, or decrease the etching rate, and because the halogen such as I ₂ is deposited by the etching reaction, the upper limit of halo oxo ion concentration, the design of the device (the semiconductor layer, The thickness is appropriately determined depending on the thickness of the conductor layer, etc.) or the concentration of iodine ions or an organic solvent that suppresses the precipitation of halogen.

The halooxo acid ion of the present invention is obtained by dissolving a halooxo acid or a halooxo acid salt in water. Specific examples of halooxo acids or halooxo acid salt compounds include, for example, bromic acid (HBrO ₃ ), potassium bromate (K
BrO ₃ ), sodium bromate (NaBrO ₃ ), ammonium bromate (NH ₄ BrO ₃ ), calcium bromate (C
a (BrO ₃ ) ₂ ), magnesium bromate (Mg (BrO 3
₃ ) ₂ ), aluminum bromate (Al (BrO ₃ ) ₃ ), perbromate (HBrO ₄ ), lithium perbromate (LiBr)
O ₄ ), potassium perbromate (KBrO ₄ ), iodic acid (H
IO ₃ ), potassium iodate (KIO ₃ ), sodium iodate (NaIO ₃ ), ammonium iodate (NH ₄ I)
O ₃ ), calcium iodate (Ca (IO ₃ ) ₂ ), magnesium iodate (Mg (IO ₃ ) ₂ ), aluminum iodate (Al (IO ₃ ) ₃ ), periodate (HIO ₄ ),
Examples thereof include lithium periodate (LiIO ₄ ) and potassium periodate (KIO ₄ ). In particular, iodic acid (HI
O _3), potassium iodate (KIO _3), potassium bromate (KBrO ₃₎ is preferable easily be handled reagents. Further, iodic acid (HIO ₃ ) does not contain a metal element which may be a contamination source of a semiconductor material, and is therefore most suitable as an etchant for a semiconductor device which is a typical electronic device.

Iodine ions are preferably added to the etching agent of the present invention. By adding the iodide ion, iodine generated by etching (I ₂₎ is I ₃ ^-
Is formed and dissolved, so that precipitation of halogen can be suppressed. As the iodine ion source, NH ₄ I, K
I, NaI and the like are preferably used. Thereby, poor etching of the deposition portion can be prevented, and more uniform and stable etching can be obtained.

Further, a water-soluble organic solvent such as alcohol and carboxylic acid is suitably added to the etching agent of the present invention. Specific examples of the alcohol include methanol, isopropyl alcohol, propanol, butanol, ethylene glycol, propanediol, butanediol, glycerin and the like, and the organic acids include acetic acid and propionic acid. By adding an organic solvent, generated halogen such as iodine can be dissolved, etching can be performed more uniformly and stably, and the distribution of etching amount in the substrate can be suppressed. In the present invention, acetic acid or ethanol is particularly preferred. However, if the concentration exceeds 70% by volume, the resist is eroded by the organic solvent, so that the concentration is preferably 70% by volume or less.

In the etching agent of the present invention, even if it is out of the range of the above composition (hydrofluoric acid 0.05 to 0.5 mol / l, halooxoacid ion 0.01 mol / l or more), the halogen precipitation inhibitor By adding, it is possible to prevent poor etching of the deposition portion due to halogen deposition and improve the uniformity of etching.

As the halogen precipitation inhibitor of the present invention, iodine ions and water-soluble organic solvents are preferably used. As the iodine ion source, NH ₄ I, KI, NaI or the like is particularly preferably used. In addition, as a water-soluble organic solvent,
Methanol, isopropyl alcohol, propanol,
Butanol, ethylene glycol, propanediol,
Alcohols such as butanediol and glycerin, and carboxylic acids such as acetic acid and propionic acid are preferably used.
Of these organic solvents, acetic acid and ethanol are particularly preferred.

As the conductor to which the present invention can be applied, for example, Al, Mo, Ni, Ta, Pt, Ti, Pd, W, C
Metals such as o or Cr, or alloys thereof, or metal compounds of these metals and semiconductors (such as silicide) are exemplified. Furthermore, the present invention is applied to those having a multilayer structure of two or more layers of these metals, alloys or metal compounds.

The semiconductor of the present invention includes Si, G
e, GaAs, GaSb, InAs, InSb, and the like, and any form of amorphous, polycrystalline, or single crystal can be applied.

[0027]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Embodiment 1) In this embodiment, first, Al or i-type amorphous silicon (a-S
i) was formed by a sputtering method and a plasma CVD method, respectively, and the relationship between the composition of the etching solution, the etching rate, and the surface state was examined. The results are shown in FIGS.

FIG. 1 is a graph showing the relationship between the etching rates of Al and i-type a-Si and the HF concentration and HIO ₃ concentration. As shown in FIG. 1A, there is a tendency that the etching rate of Al increases with the HF concentration, and increases with HIO ₃ at first and then decreases. FIG.
From (b), the etching rate of Si depends on the HF concentration and H
It increases with IO ₃ , but for HIO ₃ , 0.04
It can be seen that the saturation occurs at about mol / l.

FIG. 2 shows the result of measuring the average surface roughness Ra when Al was etched by 200 nm as a function of HF and HIO ₃ . From FIG. 2 (a), the average surface roughness decreases with an increase in the HIO ₃ concentration, to 0.04 mol /
It can be seen that at l, the average surface roughness is about the same as that of the substrate (0.8 to 1.5 nm). As can be seen from FIG. 2 (b), the HF concentration is about the same as the average surface roughness of the substrate up to 0.33 mol / l, but then increases to 0.5 mol / l.
When the ratio exceeds / 1, Ra becomes 10 nm or more.

FIG. 3 is a graph showing a change in the variation of the etching amount in the glass substrate on which Al is formed by the sputtering method due to the addition of acetic acid. Each data in the figure is a result of measuring the average value (solid line) and the variation (broken line) of the etching amount at five points in the substrate for the static etching and the swing etching. In addition,
The variation is obtained by dividing the larger of the difference between the maximum value or the minimum value of the etching amount and the average value by the average value. As shown in the figure, it can be seen that the distribution of the etching amount in the substrate can be suppressed by adding acetic acid.

Table 1 shows that A during etching and after etching.
1 is the result of visual observation of the surface condition. It can be seen that the addition of ethanol can suppress the precipitation of iodine.

[0033]

[Table 1] Next, a glass substrate (100Mmx formed with the SiN _x film
100 mm) on a-Si by plasma CVD.
Was deposited to 100 nm and n ⁺ -type a-Si was deposited to 20 nm, and then Al was deposited to 300 nm by sputtering.

A resist (OFPR8 manufactured by Tokyo Ohka Co., Ltd.) for forming 12 uneven patterns of 2 to 20 μm square each.
00Y-4) After forming the pattern, the substrate was immersed in etching agents of various compositions, and the time change of the etching state was examined. Defects such as peeling of the resist due to etching were not observed at all in the uneven pattern.

FIG. 4 is a schematic diagram showing the result of observing the cross section of the concave pattern with a scanning microscope. 4 (a) and 4 (b) in all the patterns within the range of the etching agent composition of the present invention.
It was found that the etching proceeded as shown in FIG. In addition, it was found that the variation in the formed pattern shape was within ± 0.1 μm for a pattern of, for example, 5 μm, and extremely uniform etching could be performed.

The HIO ₃ concentration was 0.008 mol /
When l and 0.01 mol / l or less, as shown in FIG. 4 (c), abnormal etching occurs at the periphery of a-Si, and only a small on-current can be obtained as a device.

Example 2 A thin film transistor substrate for driving a liquid crystal display having 720 × 480 pixels was manufactured as shown in FIG. 5 by using the method for manufacturing an electronic device of the present invention.

First, a 100 × 100 mm glass substrate (Corning 7059) 500 was precisely washed, and then a pattern of a transparent electrode (ITO) 501 was formed. continue,
A Cr film is formed to a thickness of 100 nm by sputtering, and an etching solution ((NH ₄ ) ₂ [Ce (NO ₃ ) ₆ ]: HNO ₃ : H ₂ O =
500 g: 1900 cc: 1870 cc) to form a gate electrode 503 and a gate wiring 502.
Was formed (FIG. 5A).

Next, SiN _{x was formed} by plasma CVD.
504, i-type a-Si 505, and n ⁺ -type a-Si 506 were deposited to 300 nm, 100 nm, and 20 nm, respectively (FIG. 5B).

Subsequently, an etching solution (HF: 0.54 m
ol / l, HIO ₃ : 0.04 mol / l, NH ₄ I:
(0.005 mol / l), the n ⁺ -type a-Si layer and the i-type a-Si layer were separated for each pixel (FIG. 5C).

After forming contact holes for the pixel electrode and the gate wiring, W507 and Al508
nm, 250 nm, formed by sputtering (FIG. 5).
(D)).

Next, in order to form source / drain electrodes, wirings and channel portions, the substrate was immersed in an etching agent containing 0.1 mol / l of HF and 0.04 mol / l of HIO ₃ for 7 minutes to form Al, W, n ⁺ The mold a-Si was continuously etched (FIG. 5E).

Finally, 400 nm of SiN _x for passivation was deposited by the plasma CVD method, and windows were opened on the gate wiring and the source / drain wiring to complete the fabrication of the thin film transistor.

FIG. 6 shows the results of measuring the Id-Vg characteristics of the thin film transistor manufactured as described above. As can be seen, the ON current I _ON is 1.8~30μ
A, the off current I _OFF was about several pA, and good results were obtained.

In the above embodiments, the etching of the channel portion, the source / drain electrodes, the pixel separation, etc. of the thin film transistor has been described. However, it is needless to say that the present invention may be applied to other processes, for example, the gate electrode / wiring. . In addition to the thin film transistor, it is needless to say that the present invention is suitably applied to a MOS polysilicon gate, a CCD, an image scanner, or the like, or an etching of a multilayer structure of various conductor layers and semiconductor layers in various electronic devices. No.

[0046]

According to the present invention, fine patterning of a multilayer structure of a conductor and a semiconductor can be performed with one type of etching agent. Moreover, since the patterning uniformity is high, it can be suitably applied to the fabrication of large-area, high-density electronic devices.

According to the method for manufacturing an electronic device of the present invention, the manufacturing process is simplified and the yield is improved as compared with the conventional method. As a result, it is possible to reduce the manufacturing costs of various electronic elements.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the etching rate of Al and Si and the composition of an etching agent.

FIG. 2 is a graph showing the relationship between the average surface roughness Ra of Al and the composition of an etching agent.

FIG. 3 is a graph showing a relationship between an acetic acid concentration and a variation in an etching amount in a substrate.

FIG. 4 is a schematic sectional view showing an etched state of a metal / semiconductor multilayer structure.

FIG. 5 is a schematic view showing a manufacturing process of a thin film transistor substrate for a liquid crystal display.

FIG. 6 is a graph showing Id-Vg characteristics of a thin film transistor.

FIG. 7 is a schematic view illustrating a conventional method for manufacturing a thin film transistor.

[Explanation of symbols]

500, 700 substrate, 501 transparent electrode, 502, 702 gate wiring, 503, 701 gate electrode, 504, 703 gate insulating film, 505, 704 i-type a-Si, 506, 705 n ⁺ type a-Si, 507 barrier layer (W), 508 source / drain electrode / wiring (Al), 706 conductor layer.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 21/336 H01L 29/78 616K 29/786 (72) Inventor Hirofumi Fukui 1-7 Alps, Yukitani Otsukacho, Ota-ku, Tokyo Inside Electric Co., Ltd. (72) Inventor Satoshi Miyazawa Alps Electric Co., Ltd. (72) Inventor Chisato Iwasaki 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. Inside the company (72) Inventor Yasuhiko Kasama 1-7, Yukiya Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Tadahiro Omi 1-17-17 301 (72) ) Inventor Magoro Maeno 7,227 Kaiyamacho, Sakai-shi, Osaka Prefecture, Hashimoto Kasei Co., Ltd. (72) Inventor Hirohisa Kikuyama 7,227 Kaiyamacho, Sakai-shi, Osaka Prefecture, Hashimoto Kasei Co., Ltd. (72) Akiya Jun Takano 7-227 Hashimoto Kasei Co., Ltd., 7-chome, Kaiyama-cho, Sakai City, Osaka (72) Inventor Masayuki Miyashita 7-227 Hashimoto Kasei Co., Ltd. 7, Hashimoto Kasei Co., Ltd., 7, 227 Kaiyama-cho, Sakai City, Japan (56) References JP-A-6-200384 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23F 1/16 -1/30 H01L 21/304 341 H01L 21 / 308,21 / 336,29 / 786

Claims (5)

(57) [Claims] 1. A solution comprising hydrofluoric acid and a compound represented by the general formula (X)
O _n ) ^p- (where X is a halogen element, n is 3, 4 or 6, and p is 1, 2 or 3), and a halogen precipitation inhibitor. Etching agent. 2. The etching agent according to claim 1, wherein the halooxo ion is iodate ion. 3. The etching agent according to claim 1, wherein the halogen precipitation inhibitor is an iodine ion and / or a water-soluble organic solvent. 4. The etching agent according to claim 3, wherein the iodine ion is one of NH ₄ I, KI and NaI. 5. The etching agent according to claim 3, wherein the water-soluble organic solvent is acetic acid or ethanol, and the concentration thereof is 70% by volume or less.