JPH01145818A - Wet etching - Google Patents

Abstract

PURPOSE:To uniformly, accurately and selectively etch a conductive film by providing a connection unit to be connected to the film on a nonconnection conductive film, forming by etching both the conductive films in a predetermined pattern, and then cutting the connection unit. CONSTITUTION:A conductive film to become a wiring 20 to be insulated from an Si substrate 15 is connected through a connection unit 25 to the substrate 15 during a wet etching. Accordingly, all wirings 19, 20 and pads 21a, 21b to be formed by selective etching are etched by both etching by dissimilar metal contact action and etching by local battery forming action formed on the film, to be uniformly wet etched progressively, a phenomenon in which specific wiring or pad is abnormally thinned is prevented, and to be accurately etched. Then, a scribing line 24 is scribed by a dicing saw or the like to separate it into IC chips. In this case, the connection unit 25 is simultaneously cut to become a normal state.

Description

[Detailed Description of the Invention] [Objective of the Invention J (Field of Industrial Application) This invention relates to a metal 1 for wiring in a semiconductor device, for example.
The present invention relates to a wet etching method for etching 9 etc. into a desired pattern.

(Prior Art) The wet etching method has many advantages in microfabrication of semiconductor devices, for example, such as good etching properties, little damage to the substrate, and high etching selectivity. For this reason, the wet etching method is
μm rule IC, part of 3μm rule IC, compact disk, surface elastic filter, and CCDL! It is widely used in the processing of various devices such as sensors and pressure sensors, and further advancement of the technology is required.

As such a conventional wet etching method, there is, for example, method 1b using an apparatus as shown in FIG. In the figure, reference numeral 1 denotes an etching tank, and 91 in the etching tank 1 is constructed airtight to enable wet etching under reduced pressure. An etching bath 1 contains an etchant 2 maintained at a predetermined constant lag, and a substrate (wafer) 4 held on a substrate carrier 3 is immersed in the etchant 2. A metal film to be etched is formed on the main surface of the substrate 4 via an insulating film, and a pattern is formed on the metal film by a photolithography process in order to form a required wiring pattern by selective etching. A photoresist is formed in advance.

The etching bath 1, which is airtight, is connected to a vacuum pump 7 for reducing pressure via a pipe 6 having an etchant gas trap 5. 8 is a vacuum gauge, 9 is a slow leak valve control roller, and 11 is a slow leak valve. By means of these vacuum level control systems, during one batch of wet etching, the depressurized state of the etching tank 1 is as follows.
The desired degree of vacuum is maintained almost constant. That is, the degree of vacuum in the etching tank 1 is sensed by the vacuum gauge 8, and the slow leak valve opening/closing degree is determined based on the information about the degree of vacuum.
The opening and closing of the Sumi-leak valve 11 is controlled by the valve 9, and the degree of vacuum in the etching tank 1 is maintained at a substantially constant level. Reference numeral 12 denotes an etching end detection sensor, and 13 a time controller equipped with an etching end detection receiver, which calculates approximately 10 to 2 seconds of the etching time required after receiving the etching end detection signal from the etching end detection sensor 12.
0% of the time, it's time to push back.'' Etching is done. Back-up etching is an essential process for completely removing etching residue and preventing problems such as so-called bridging, which causes short circuits between wiring lines.

J3, etching completion detection method uses electrical system (electronic materials, No. 3.1) 91 (19
83)) and systems using light (Japanese Patent Laid-Open No. 59-229
Publication No. 822), etc.

Then, the metal film on the substrate 4 is selectively etched under reduced pressure at a desired degree of vacuum to form 1 g of a desired wiring pattern.

Wet etching under reduced pressure differs from wet etching under normal pressure in that the gas phase (gas a
) has several advantages over systems that generate There are many systems in which such bubbles are generated, such as a system in which metals such as Al and Ti are etched with an acidic solution, and a system in which light etches 81 crystals in an alkaline solution.

If air bubbles generated from the surface of AfL etc. during wet etching cannot be removed quickly and remain attached to certain surface areas for a long time, etching will not proceed in those areas, resulting in etching residue. Not only will it not be possible to obtain desired electrodes and wiring patterns, but problems such as bridges will occur. On the other hand, in the case of wet etching under normal pressure, methods such as flowing the etchant or rotating the substrate are used, but in order to prevent such troubles, wet etching under reduced pressure is recommended. It is dynamic. In other words, the air bubbles generated during etching are rapidly expanded and removed from the surface of the object to be etched and the substrate surface.
A reduced pressure state is effective for this purpose, and can prevent troubles caused by etching residue. Furthermore, the bubbles expand without any special stirring, and these bubbles are generated abundantly and uniformly over the entire surface of the substrate, refreshing the etching surface. At the same time, the etchant is stirred, reducing temperature and concentration unevenness. As a result, etching is performed uniformly and well on the surface to be etched, and the uniformity among multiple substrates is also good (Electronic Materials, &3. p91 (1983)
), Journal of EIelectroche
mical 5ociety vol, 132
．． 1) 2973 (1985)). Further, since wet etching under reduced pressure does not use any means such as stirring, the photoresist is less likely to be peeled off due to fluidization of the etchant or rotation of the substrate.

Wet etching can also be carried out under normal pressure using the apparatus shown in Figure 6, J3.
The vacuum level control system such as the pressure reducing system such as the leak valve ft1l 111 degree controller O-ra 9 may be shifted from the J1 operating state.

(Problems to be Solved by the Invention) However, in the conventional wet etching method, some parts of the resulting wiring pattern are etched thinner than the required wiring width, resulting in a wiring pattern with minute dimensions. It is sometimes difficult to etch uniformly and accurately.

If a portion is etched to be thinner than the required wiring width, the reliability of the semiconductor device will decrease and the quality will deteriorate.

Possible causes of the above problem are as follows.

That is, Alfi! used for forming ICs, etc. Wiring on a semiconductor substrate, such as the It is connected.

As a result, as the etching progresses, regions that will become wiring etc. are separated, resulting in some wiring being electrically connected to the semiconductor substrate and other wiring being insulated. For example, an 8102 film is formed on the main surface of a 3i substrate containing a required concentration of p-type or p-type ions such as phosphorus or boron as a carrier source, and contact holes are opened at desired locations in this 5i02 film. Aff on SiO2 film
In an IC configured in such a way that each transistor element is connected by wiring and electrodes using an i-film, the wiring is electrically connected to the Si substrate on the output line side, while the input line side is not insulated. There are cases where there is.

When wet-etching the A film on the St base plate as described above with a phosphoric acid-based acid solution, most of the AI film is separated into the output line side and the input line side at the initial stage of etching. Therefore, the AN film becomes cations and dissolves on the anode side due to etching due to the contact action of different metals between the An film and the 3i substrate, and etching due to the local battery formation action formed on the helical film. Hydrogen gas is generated on the cathode side. Next, when the etching progresses and the △ film is separated into each wiring etc., the 5ill
On the output line side leading to the board, etching is promoted and progresses by etching due to the contact action of dissimilar metals and etching due to the local battery forming action, similar to the initial etching, but on the input line side not leading to the 3i board, etching progresses. On the side, the etching is only due to the local cell formation effect (Naraoka et al., [Photoetching and Microfabrication J p94. General Electronic Publishing, 852), and the etching speed on the output line side is faster than on the input line side. It is thought that the wiring will be processed to be thinner.

Then, the hydrogen bubbles generated under normal pressure are removed from the etching surface by stirring with Etchcent! 1Ity! In wet etching while applying A, the specific wiring (in the above example, the wiring on the output line side) is thinned by several percent based on the difference in etching effect due to the difference in the electrical pattern of the wiring, and furthermore, the thickness of the wiring is reduced by a few percent (the wiring on the output line side in the above example). When wet etching is performed under reduced pressure, specific wiring becomes abnormally thinner by about 40% at most.

This invention was made by focusing on such conventional problems, and it uniformly spreads a conductive film formed on a conductive substrate via an insulating film and partially connected to the conductive substrate. To provide a wet etching method that can perform selective etching with high precision.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention is provided on an insulating film formed on a conductive substrate and partially connected to the conductive substrate. In a wet etching method in which a desired pattern is formed by selectively etching a conductive film that has been etched and a conductive film that is not connected to the conductive substrate, a connecting portion to be connected to the conductive substrate is connected to the conductive film that is not connected to the conductive substrate. The gist is that the connecting portion is cut after etching both the conductive legs into a desired pattern.

(Function) In the above configuration, even if each of the required patterns formed by selective etching is electrically connected or disconnected to the conductive substrate, each of these patterns remains intact during wet etching. All the parts are connected to the conductive substrate by the connecting parts, and wet etching progresses uniformly under the same etching action, preventing narrowing of only a specific pattern and achieving high precision etching.

(Example) Hereinafter, an example of the present invention will be briefly described with reference to the drawings. This example is applied to a wet etching method for a film such as AfL for wiring formed on a 3i substrate via a 3i02 film.

1 to 3 are diagrams showing a first embodiment of the present invention.

First, the apparatus and members applied to this embodiment will be explained. As a wet etching apparatus, one substantially similar to that shown in FIG. 6 is used.

On the other hand, FIGS. 1 to 3 show wiring and the like on a Si substrate as a conductive substrate formed by the wet etching apparatus. That is, these figures show, for example, one 0MO8IC formed on an n-type Si base 4N (Si wafer) 15 (hereinafter, the same reference numeral 15 is used when referring to the Si wafer) doped with phosphorus ions at a required concentration. It shows the part. In these figures, 16 is a 5f02 layer as an insulating film formed on the 3i wafer 15, and contact holes 17 are formed in required portions of the 5iO211116. Au film or Ai/S as 1j conductive film deposited on this 5i02Jl1216
The i-based alloy film such as i is selectively etched to form wiring lines 19 and 20 and pads (electronic &) 21a and 21b for wire-V bonding having a desired pattern.

Then, wirings 21a and 2 are placed in each contact hole 17.
1b and 5i Contact portions 22a, 22b, 22 with the source and drain of a CMOS transistor formed on the main surface of the Ji board 15, or a wiring layer formed of an impurity diffusion layer, etc.
c is provided.

Of the two wirings described above, the wiring 19 is a wiring electrically connected to the Si substrate 15, and the other wiring 20 is a wiring insulated from the Si substrate 15. That is, wiring 1
9, as shown in FIG.
Each of the contact portions 22a and 22b to the expansion diffusion layer 23b is insulated since the transfer of electrons from the An wiring 19 to the n-type 3i substrate 15 is reverse biased, but the other contact portions 22c are connected to the 3i substrate 15. electrically connected to. On the other hand, as shown in FIG. 3, the other wiring 20 has insulating contact portions 22a and 22b.
Since it does not have L,..., the wiring is insulated from the 3i board 15.

In addition, the IC chip is made of 3-6 inch Si wafer 15
Generally, a plurality of them are made at the same time.

After the formation of the required elements, the formation of inter-element wiring, and the formation of the protective film, chip separation is performed at the scribe line 24 using a dicing saw using a diamond blade.

A connecting portion 25 is provided at this scribe line 24 to connect the wiring 19 electrically connected to the 3i board 15 and the insulated wiring 20 during the ``padding'' process. . The connection part 25 only needs to be conductive, so it can be
In addition to being made of a metal or Al-based alloy, it can also be made of a thin film of polycrystalline S1 doped with impurities, a metal such as Cl, AQ, or AU, or an alloy thereof, or a conductive polymer. However, if the pads 21a and 21b are made of a different material, it is necessary to form a contact portion with the pads 21a121b. Among the above materials,
When the connecting portion 25 is formed of an A membrane, there are 8 connections! 19
．． 20 etc., a photoresist pattern for forming the connecting portion 25 can be formed during the photo-etching process, and etching can be formed simultaneously with the patterns 19, 20, etc. during the wet-etching process.

As will be described later, the connection portion 25 is cut at the same time when each IC chip is separated by scribing the scribe line 24 after the wiring 19, 20, etc. are etched into a required pattern. The connection portion 25 remaining on the wiring 20 side that is insulated from the 3i substrate 15 is connected to the SiM board 15.
In order to prevent the risk of being connected to the wire 20, a SiO2 film 16 is extended below the connection portion 25 on the wiring 20 side.

Next, a method of wet-etching and etching a desired wiring pattern using the above-mentioned V4 position and members, and its operation will be explained.

A layer formed on the Si substrate 15 through the 5i(h film 16)
A required 7 photoresist pattern is formed in advance on a conductive film such as an fL film by a photolithography process,
A plurality of such Si substrates 15 are held in the substrate killia shown in FIG. 6 and immersed in an etchant. Then, selective etching of the conductive film is performed under reduced pressure or normal pressure.

At this time, during wet etching, the 3i substrate 1
The part of the conductive film that becomes the wiring 20 that is insulated from the
It is connected to the s:substrate 15 via the connecting portion 25 .

Therefore, the wiring 19 is formed by selective etching.
All parts such as 20 and each pad 21a, 21b are subjected to the same etching action by both the etching action due to the contact action of dissimilar metals and the etching action due to the local battery formation action formed on the 3# conductive film. , uniform wet etching progresses, development in which a particular wiring or pad becomes abnormally thin is prevented, and etching processing with high precision is achieved.

To give a specific example, an approximately 1 μm thick A/R film was formed on a 3i wafer by sputtering via a 5fO2 film.
A 5i (1%) alloy film was coated at 85°C using the apparatus shown in FIG.
50℃, 30t using wL% phosphoric acid aqueous solution as etchant
When wet etching is performed under a reduced pressure of orr without forming the connection BB25 shown in FIG. 1, the width of wiring, pads, etc. electrically connected to the Si substrate is However, when wet etching was performed under the same conditions as above with all the wiring etc. connected to the 3i board by the connection part 25 as shown in Fig. 1, the abnormal thinning phenomenon did not occur at all. I couldn't see it.

Then, the above-mentioned required wiring patterns, etc. are etched with good viscosity, a protective film such as PSG or SiN is deposited on the wiring patterns, etc., and then scribe lines 24 are scribed with a dicing saw or the like, and each IC
Separated into chips.

At the time of this separation, the connecting portion 25 is cut at the same time, and the wiring 2
0 is insulated from the Si substrate 15 and is in a normal state.

Next, FIG. 4 shows a second embodiment of the present invention.

In this embodiment, a connecting portion 26 is provided between pads 21a and 21b. This connection part 26 allows each wiring 1
9. While the 20 part etc. are being wet-etched, the Si
It is the same as in the case of the first embodiment that they are connected to the substrate 15 and the same etching effect is caused thereto.

In this embodiment, the connecting portion 26 is cut off as follows after the etching process and the like are completed.

That is, the cutting methods include a method in which only the connecting portion 26 is formed with a 2A trisogera film followed by selective etching after all wiring etc. are formed, a method in which the connecting portion 26 is cut with a laser cutter, and a method in which the connecting portion 26 is formed of Al. In the case of polycrystalline SiG, the method is to oxidize and aluminate the connection part 26 to make it an insulator, the method to remove it by ashing if it is a conductive polymer film, or the method to remove it by ashing if it is a conductive polymer film. If other polycrystalline S1 constituting tC etc. is not exposed in the part, there is a method of selectively etching polycrystalline Si such as plasma etching with CFJ+02 gas.

As in the first embodiment described above and the second embodiment described above, Si
The wiring 20 and the like that are insulated with respect to the substrate 15 may be connected to the wiring 19 and the like that are formed in the vicinity and connected to the Si substrate 15 using connecting portions 25 and 26. And S in the vicinity
If there is no wiring or the like to be connected to the i-board 15, it may be connected to the SiW board 15 on the scribe line 24 using a connecting part. Further, the connection portion may be provided between the wiring and the pad, or between the wirings.

Next, a third embodiment of the invention will be described. As mentioned above, during wet etching, wiring etc. that are electrically connected to the 3i substrate are etched not only by the local battery formation effect, but also by the contact effect of different metals, which promotes etching. Etching thinning occurs by about 10 to 40% compared to wiring that is electrically insulated from the substrate.

Therefore, in this embodiment, 8
The photoresist pattern for wiring, etc. on the side connected to one substrate is formed in advance to be thicker by an amount corresponding to the thinning in anticipation of thinning during etching.

If the degree of acceleration of etching due to the above-mentioned contact effect of different metals depends on the connection resistance between the wiring pattern, etc. and the 3i substrate, as shown in FIG. put. The thickness is set to be approximately 10 to 40% thicker depending on the number of contact portions (corresponding to contact portion 22G in J3 in FIG. 2) electrically connected to the 3i board. There is.

E. Effects of the Invention] As explained above, according to the present invention, since the connection portion for connecting to the conductive substrate is provided on the conductive film not connected to the conductive substrate, the connection portion can be formed by selective etching. Is each pattern required to be conductive? ! Even if they are electrically connected or disconnected to the I substrate, all of these patterns are connected to the conductive substrate during wet etching and receive the same etching action, ensuring uniform wet etching. ] The advantage is that the knitting progresses and a highly accurate etching work can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a connecting portion and a wiring pattern to be etched applied to a first embodiment of the wet etching method according to the present invention, and FIG. 2 is an enlarged cross-sectional view taken along the line A-A in FIG. 1. , FIG. 3 is an enlarged sectional view taken along the line B-B in FIG. Third part of this invention
J characteristic diagram showing the relationship between the number of contact parts and the width of the photoresist pattern formed thick in advance in the example,
FIG. 6 is a block diagram showing an arrangement applied to the conventional wet puffer fish method. 15: Si substrate (conductive substrate), 16: Si02 film (insulating film), 19: wiring pattern electrically connected to the Si substrate, 20: wiring pattern insulated with respect to the Si substrate, 21a , 21b: pad, 22a to 22C: contact section, 24 scribe line, 25.26: connection section. Agent: Yasu Miyoshi, Patent Attorney Diagram 4 of power tube → Number of contact parts Diagram 5

Claims (1)

[Claims] Selectively etching a conductive film provided on an insulating film formed on a conductive substrate and partially connected to the conductive substrate and a conductive film not connected to the conductive substrate. In the wet etching method, a connection part for connecting to the conductive substrate is provided on the unconnected conductive film, and after both conductive films are etched into the desired pattern, the conductive film is etched into the desired pattern. A wet etching method characterized by cutting the connections.