JPH01145816A - Wet etching - Google Patents

Abstract

PURPOSE:To uniformly, accurately and selectively etch a conductive film by holding the nonetching side of a conductive substrate in a noncontact state from etchant, and advancing a selective etching. CONSTITUTION:The rear face of an Si substrate 4 is held in a noncontact state from etchant 20 during wet etching. Accordingly, even if a conductive film is electrically connected to the substrate 4, the rear face of the substrate 4 is prevented from becoming a cathode electrode, no etching occurs due to dissimilar metal contact with an anode of the conductive film and a cathode of the rear face of the substrate. Thus, with a progress of the selective etching, the conductive film is isolated to a region to become wirings or the like and a wiring pattern electrically connected to the substrate 4 and an insulated wiring pattern are formed. Then, both are similarly etched on the basis of local battery forming action, the uniform etching makes progress, a phenomenon in which special wiring or pad is abnormally thinned is prevented, thereby performing an accurate etching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a wet etching method for etching a metal film or the like for wiring in a semiconductor device into a desired pattern.

(Prior art) The C wet etching method has many advantages in microfabrication of semiconductor devices, such as good economy, little damage to the substrate, and high etching selectivity. ing. For this reason, the wet etching method is widely used for processing various devices such as 5 μn 1 rule ICl 3 μm rule TC, compact disks, surface elastic filters, COD sensors, pressure sensors, etc. Further advancement of technology is required.

As such a conventional wet etching method, for example, there is a method using an apparatus as shown in FIG. 6. In the figure, reference numeral 1 denotes an etching tank, and 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 temperature, and a substrate (wafer) 4 held by a substrate kit/rear 3 is immersed in the etchant 2. A metal film to be etched is formed on the main surface of the substrate 4 with an insulating film interposed therebetween, and the metal film is etched by a photolithography process in order to obtain a desired wiring pattern by selective etching. A repatterned photoresist is previously formed.

The etching tank 1, which is constructed in an airtight manner, is connected to a vacuum pump 7 for reducing pressure via a pipe 6 having an edge gas trap 5. 8 is a vacuum gauge, 9 is a slow leak valve opening/closing degree controller, and 11 is a leak valve, and these vacuum degree controllers are used to control the etching tank 1 during etching. The reduced pressure state is maintained approximately constant at the desired degree of vacuum. 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 controller 9 that receives the information on the degree of vacuum controls the opening and opening of the slow leak valve 11, so that the degree of vacuum in the etching tank 1 is almost the same. held constant. 1
Reference numeral 2 denotes an etching end detection sensor, and 13 a time controller equipped with an etching end detection receiver.
~20% of the time [no push etching is done. Back-up etching completely removes etching residue -C
This is an essential step in order to prevent problems such as so-called bridges, where one wiring is short-circuited.

Note that the method for detecting the completion of etching is a method using an electrical system (Electronic Materials, I&1.3. p91 (1).
983)) and a system using light
229822), etc.

Then, under reduced pressure to a desired degree of vacuum, the metal film on the substrate 4 is selectively etched to obtain a desired wiring pattern and the like.

Wet etching under reduced pressure has several advantages over wet etching under normal pressure in a system in which a gas phase (bubbles) is generated during the etching reaction. There are many systems in which such bubbles are generated, such as a system in which A1Ti\r metal is etched with an acidic solution, a Si crystal is etched in an alkaline solution, and so on.

During wet etching, the air bubbles generated from the surface of AΩ etc. cannot be removed quickly, and the air bubbles remain attached to certain surface areas for a long time. Due to the formation of residue, not only the desired electrodes and wiring patterns cannot be formed, but also problems such as bridging occur.On the other hand, in the case of wet etching under normal pressure, Etch II Methods such as fluidizing the etching agent or rotating the substrate are used, but wet etching under reduced pressure is effective in preventing such troubles.In other words, the bubbles generated during etching are A reduced pressure state is effective in expanding at a speed of Ll and quickly removing f!lL from the surface of the object to be etched and the surface of the substrate, and can prevent problems caused by etching residue. swells and this occurs uniformly in many areas over the entire surface of the substrate, refreshing the etching surface and stirring the etchant at the same time.
Uneven temperature.

Temperature unevenness is reduced, etching is performed uniformly and well on the surface to be etched, and uniformity among multiple substrates is also good (?-in-i'-vi material, Iori 3.p.
91 (1983), Journal or El
electrochemical 3ociety v
ol, 13'2. D2973 (198
5)). In addition, wet 1-setting under reduced pressure does not use any particular means such as stirring, so it is less likely to cause 1-layer fluidization, photoresist peeling 1 due to rotation of the substrate, etc.

Note that wet etching can also be performed under normal pressure using the apparatus shown in Figure 6; in this case, the reduced IF system such as the vacuum pump 7 and the vacuum level control system such as the slow leak valve opening/closing controller 9 must be turned off. It is only necessary to deviate from the operating state.

(Problems to be Solved by the Invention) However, in the conventional wet etching method, some parts of the obtained wiring pattern are etched thinner than the required wiring width. It is sometimes difficult to etch the wiring pattern 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.

One possible reason for the occurrence of the above problem is as follows.

In other words, wiring on a semiconductor substrate such as an AΩ film used for forming an IC, etc. is usually formed on an insulating film provided on the semiconductor substrate, and there is a layer on the insulating film at the end or middle position. It is appropriately connected to a semiconductor substrate via a drilled contact hole.

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 an 81 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 in desired parts of this 5102 film. △Ω on the SiO2 film
In an IC configured with film wiring and electrodes connecting each transistor element, the wiring is electrically connected to the 3i substrate on the output line side, while the input line side is insulated. There are cases like this.

When etching the Afl film of 3il plate-F as described above with a phosphoric acid-based acidic solution, most of the AΩ film is separated into the output line side and the input line side at the initial stage of etching. Since it is not H, the AQ film and S
Etching due to the contact action of different metals between i-substrates, and A
Due to etching caused by the local cell forming action formed on fl IIQ, the AfJ film becomes cations and dissolves on the anode side, and hydrogen gas is generated on the cathode side on the back surface of the 3i1 plate. Next, when the etching progresses and the AΩ film is separated into each wiring, etc., the output line side leading to the 3i substrate is etched by the contact effect of dissimilar metals and by the local battery formation effect, as in the initial etching. Etching is accelerated and progresses, but on the input line side that does not lead to the 3i substrate, etching only occurs due to the local cell formation effect (Naraoka et al., "Photoetching and Microfabrication", p. 94. General Electronic Publishing). , 552), it is thought that the etching speed on the output line side is faster than on the input line side, and the wiring is processed to be thinner.

In wet etching, hydrogen bubbles generated under normal pressure are removed from the etched surface by stirring the etchant, etc. In J3, based on the difference in etching effect due to the difference in the electrical pattern of the wiring, 15 constant wiring (In the above example, the wiring on the output line side) becomes thinner by several percent, and furthermore, the web 1-
', When performing C tzing, specific wiring is reduced by up to 40%.
It also becomes abnormally thin.

This invention was made by focusing on such conventional problems, and therefore, it is possible to uniformly spread a conductive film formed on a conductive substrate via an insulating film and partially connected to the conductive substrate. An object of the present invention is to provide a sea urchin buttocks etching method that allows selective etching liquid to be selected with high precision.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a method of etching a conductive film provided on an insulating film formed on a plate. In the wet etching method for forming a desired pattern by selective etching, the gist is to proceed with the selective etching while keeping the non-etched side of the conductive substrate out of contact with the etching solution.

(Function) With J3 in the above configuration, the conductive substrate is prevented from becoming an electrode in the etching solution, and when the conductive film is temporarily connected to the conductive U, the conductive film is used as the anode, and the conductive substrate is used as the anode. This prevents the occurrence of etching effects due to small metal contact effects with the cathode. Therefore, each required pattern formed by selective etching can be electrically connected or disconnected to the conductive substrate. Even though
During wet etching, each of these patterns
The same etching effect is caused only by the cell formation effect.
), uniform wet etching progresses, preventing thinning of only a specific pattern, and achieving highly accurate etching.

(Example) Hereinafter, an actual fM IA of the present invention will be explained in detail. This example uses 3 i L as a conductive substrate.
An etching solution is applied to a web 1 of a ΔΩ film for wiring formed on a fourth board via a SiO2 film.

FIGS. 1 and 2 are diagrams showing a first embodiment of this explanation.

First, we will explain the equipment etc. applied to this example.
As for the etching apparatus used, the one generally similar to that shown in FIG.
It has been replaced with a substrate holder that has the function of keeping the non-etching side of the U-plate out of contact with the etching solution.

That is, in FIGS. 1 and 2, 15 is a bowl-shaped suction device support, which is made of a rigid body made of a material such as Teflon or glass that has etchant resistance depending on the etching system. . Inside the suction disk support 15, 3i7Ji4
A recess corresponding to the dimensions of the board is formed to form a socket portion 15a, and a suction hole 16 is bored in the center of the socket portion 15a.

A suction tube 17 having sufficient mechanical strength is connected to the suction hole 16, and a suction means (not shown) is connected to the tip of the suction tube 17.

A suction disk 18 for suctioning and holding the back surface of the Si substrate 4 is mounted inside the suction device support 15. The suction disk 18 is made of a material that is stable and has good etchant resistance, such as fluororubber-based synthetic rubber,
An airtight space 19 is formed between the suction device support 15 and the inner surface thereof, in which air near normal pressure is hermetically confined. By providing this airtight space 19, even if the pressure inside the etching tank is reduced, the suction force of the suction plate 18 (S1λ) (the suction force of the plate 4 decreases and the Si substrate 4 is detached, or the suction 1
The etching liquid (etchant) 20 is prevented from entering the etchant 18 side.

Further, a support rod 21 is appropriately passed between the aspirator support 15 and the suction tube 17, so that the mechanical support strength for the aspirator support 15 is increased.

A plurality of substrate holders configured as described above are attached around the vertically arranged suction pipe 17, so that a plurality of 3i substrates 4 can be etched in one batch. There is.

Next, a method of wet etching a conductive film such as an AΩ film into a desired wiring pattern using the above-mentioned apparatus and the like and its operation will be explained.

A SiO2 film as an insulating film is formed on the main surface of the Si substrate 4, and a conductive film such as a coating film is deposited to a required thickness on the SiO2 film-1. has been done. A contact hole is opened in a required part of the SiO2 film, and the 34-electroconductive film is made of SiO2 at the contact hole.
It is partially connected to the IT board 4. A required photoresist pattern of a selective etching solution is previously formed on the conductive film by a photolithography process.

)A resist pattern is Si after selective etching.
The pattern is such that a wiring pattern is electrically connected to the substrate 4 through the contact hole, and a wiring pattern is insulated.

Then, the Si substrate 4 prepared as described above is placed in the socket portion 15a1 of the suction disc support 15 in air under normal pressure. :hlff is inserted, and the back side is the suction tube 17
The etching chamber is sucked by a suction means to a pressure sufficiently lower than the internal pressure of the etching tank, and is held in the plate holder. In this way, the back surface of the 3i substrate 4 is held so as not to be in contact with the etching solution 20.

3 held on the substrate holder in the manner described above.
The i-substrate 4 is exposed to F2 Fj in the etching solution 20, and selective IR1 etching of the conductive film is started under reduced pressure or normal pressure.

At this time, during wet etching, the Si substrate 4
The back surface of the substrate is kept out of contact with the etching solution 20. Therefore, even when the conductive film is electrically connected to the 3i base plate 4, electrodeization in which the back surface of the Si substrate 4 becomes the cathode electrode is prevented, and the conductive film is used as the anode and the back surface of the Si substrate 4 is used as the cathode. This means that etching due to the contact action of different metals will not occur.

Therefore, as the selective etching progresses, the conductive film is separated into areas that will become wiring, etc., and the pattern of wiring, etc. that is electrically connected to the 3i substrate 4 and the area of insulated wiring, etc. are separated. Even if a pattern is generated, all wiring patterns are subjected to the same etching action only by the etching action based on the local battery formation action, and uniform wet etching progresses, causing abnormalities in specific wiring or pads. The phenomenon of thinning is prevented, and etching processing with high accuracy can be performed.

To give a specific example, about 1μ was formed on a 3i wafer by sputtering through an insulating film made of a 5i02 film.
An AQ/5i (1%) alloy film with a thickness of 50° C. was removed from the etching solution using the apparatus shown in FIG. When wet etching was performed without contact, the width of the wiring and pads electrically connected to the 3i substrate was formed to be about 40% narrower than that of non-insulated ones, but the first When the back side of the 3i substrate was wet etched using the same substrate holder shown in the figure and exposed to 1 g of etchant, the abnormal thinning phenomenon was significantly reduced. In addition, when this example was applied with only the pressure being normal pressure and the other conditions as described above, no abnormal thinning reduction was observed.

Next, FIG. 3 shows the dimensions of a second embodiment of the present invention.

In this embodiment, as a means for keeping the back side of 81 substrates 4, etc. as conductive substrates out of contact with the etching solution,
A one-punch-resistant patching film 22 is formed on the back surface of the 3il temporary 4 and the like.

The etching-resistant passivation film 22 shown in FIG. 3A is made of a material that will not be attacked by the etching solution and will not cause pinholes or cracks during the etching process for the required period of time. If the etching solution is a phosphoric acid-based etching solution as described above, an inorganic film such as a 5i02 film having a required thickness can be used. This SiO2 film is made by LPGVD,
It is formed by conventional means such as plasma CVD, vapor deposition, and thermal oxidation sputtering. Alternatively, an organic cured film such as photoresist can be used.

According to this embodiment, the etching-resistant passivation film 22 is formed directly on the back surface of the 3i substrate 4, etc., so that the same substrate as that used in the apparatus of FIG. It has the advantage that an open-curvature type can be used.

The 30th item (13) is a version of the above rl root key 11 rear 3 that can be used more effectively, and is made by using two 3 pieces.
The back surfaces of the i-substrates 4 and the like are bonded to each other using an adhesive-based etching-resistant base film 22.

As the adhesive-based etching-resistant passivation film 22, for example, a silicone polymer type or a fluorine-containing polymer type is used. In addition, in order to facilitate the separation of the substrates after the completion of the padding, an adhesive such as an etching-resistant passivation film 22 is applied only to the surrounding area of the two Si ESSi 2 whose back surfaces are in contact with each other. You should try to make it fun.

4 and 5 show a third embodiment of the invention.

In this actual trial example, the top surface of the Si-based material 4, etc. is kept in a non-contact state from the etching solution, and the back surfaces of the two films are brought together in the same manner as in the second embodiment. This is held using a holding jig.

In Figs. 4 and 5, 23a and 23[) are symmetrically formed annular holding jigs. There is.

An engaging portion 24 is formed at the opposing portions of the two holding jigs 23a and 23b, and a sealing sheet 25 for preventing etching liquid from entering is disposed at the engaging portion 24. 26 is an annular seal ring;
Rubber-based materials such as fluoro rubber that improve etch resistance
It is made in the name of A.

27 is a fastener, and the pole l-2E3 and nut 29 are u
6 has been given.

Then, the two holding jigs 2 with the engaging portions 24 engaged with each other
3a, 2]), two Si sheets with their back surfaces facing each other
By holding the board 4 and tightening the bolt 28 and the nut 29 into the hole 1 in the fastener 27, these members are integrated as accurately as possible, and the sealing sheet 25 and the sealing 26 seal the This prevents the etching solution from seeping into the back side. Therefore, 3 i 1. The back surface of the plate 4 is kept in a non-contact state from the etching solution, and the conductive film on the front surface of the 3I1 plate 4 to be etched can be etched with high precision.

[Effects of the Invention] As explained above, according to the present invention, selective etching is progressed by keeping the non-etching side of the conductive substrate out of contact with the etching solution. Electrode formation in the etching solution is prevented, and the etching effect that occurs only when the conductive film is connected to the conductive substrate is eliminated. therefore,
During wet etching, each of the required patterns formed by selective etching may be electrically connected or disconnected to the conductive substrate, but during wet etching, each of these patterns is Uniform wet etching is carried out by receiving only the etching action that occurs when the etching is not connected to the active substrate, and the advantage is that it is possible to perform etching liquid processing with high precision.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view of a substrate holder applied to a first embodiment of the wet etching method according to the present invention, and FIG. FIG. 3 is a front view of the substrate holder, FIG. 3 is a side view showing means for keeping the back surface of the substrate out of contact with the etching solution applied to the third embodiment of the present invention, and FIG. 4 is the third embodiment of the present invention. A side view showing a holding jig, etc. that holds the back side of the substrate out of contact with the etching solution, which is applied to
FIG. 5 is a front view of the holding jig and the like, and FIG. 6 is a configuration diagram showing an apparatus applied to the conventional wet etching method. 4: Si substrate (conductive substrate), 18 Suction disk which is a component of the two-substrate holder, 20: Etching liquid, 22: Etching-resistant passivation base crotch, 23a, 23
b: Holding jig, 27: Fastener. Attorney Patent Attorney Yasuo Miyoshi Li3 (A)
Figure 3 (B) Figure 4 Figure 55
! l Figure 1 Figure 2

Claims (1)

[Claims] In a wet etching method in which a conductive film provided on an insulating film formed on a conductive substrate is selectively etched to form a desired pattern, the non-etched side of the conductive substrate is etched. A wet etching method characterized by allowing the selective etching to proceed while being kept in a non-contact state with an etching solution.