JPS581543B2 - How to use hand tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing semiconductor devices with high yield.

In the conventional process of forming electrodes and wiring layers of semiconductor devices, aluminum has generally been mainly used as the material.

That is, as shown in FIG. 1, an oxide film 2 is formed on an N-type semiconductor (for example, silicon) substrate 1, a part of which is used as a gate part 5, and a part of the oxide film 2 is formed on a source electrode 3 and a drain electrode 4 provided previously. Window for wiring drawer 3. , 4, open.

Next, as shown in FIG. 2, a metal film of a predetermined thickness, such as an aluminum film 6, is deposited over the entire surface to a thickness of 1 to 1.5 μm.

Next, a photoresist 7 is applied and a pattern of the photoresist 7 is formed using a conventional method.

After applying photoresist T and performing pre-paking, it is selectively exposed to ultraviolet light using a photomask for photolithography. In the case of negative type photoresist, the exposed areas harden and become insoluble in the developer. In the case of a positive type photoresist, the portions exposed to light are decomposed by the light and become soluble in a developer, so that a desired pattern can be obtained after development.

Next, after performing post-bake, phosphoric acid or an etchant containing nitric acid and glacial acetic acid is heated appropriately to remove the aluminum 6 exposed from the photoresist pattern.
, 6 are selectively corroded and removed, and then the photoresist is removed, as shown in FIG. 3, and electrodes 63 and wiring 64 made of aluminum 6 are formed.

However, forming aluminum electrodes and wiring using the so-called corrosion method described above has various fatal drawbacks for integrated circuits that are becoming increasingly miniaturized, or for large-scale integrated circuits (LSI). I have to say that I have.

That is, aluminum as a material used for electrodes and wiring has a high optical reflectance, and therefore it is very difficult to form a microscopic pattern of photoresist on an aluminum film.

In other words, when the insulating film such as the oxide film 2 forming the aluminum film 6 has a step difference of 0.5 to 2.5 μm, the aluminum film is likely to break 65, and the wiring may not move along the step. If this happens, the light will be reflected at this step, and the unwanted whisker-like pattern of the photoresist will come into contact with the adjacent aluminum wiring, and even after corrosion, aluminum will remain under the unnecessary whisker-like pattern of the photoresist. This is the cause of so-called short circuits, and when negative type photoresists are used, the occurrence of this type of defect is particularly significant. Therefore, this is one of the decisive factors that hinders the miniaturization of patterns and, by extension, the miniaturization of chip areas.

Additionally, aluminum has other major drawbacks when it comes to photolithography.

That is, the corrosive reaction against the corrosive liquid is intense and hydrogen is generated, making the process difficult and lacking in reproducibility.

Therefore, there is a tendency for so-called over-etching and side etching to occur frequently, resulting in a wiring width that is smaller than the designed wiring width, and this problem is also one of the decisive factors that hinder miniaturization.

Also L, S, I. In this case, the wiring section crosses many stepped sections, and the adhesion between the photoresist and aluminum may be poor at these stepped sections, and corrosive liquid seeps in, corroding the aluminum at the stepped sections, resulting in frequent disconnections. , which significantly reduces the yield of LSI.

Recently, electrochemical corrosion methods for aluminum have been tried as one of the countermeasures for the above-mentioned problems, but the essence of the problem remains and no definitive solution has been found.

Another method is to wire aluminum by anodizing, but the disadvantage is that the process is complicated, and the problem of wire breakage at stepped portions is fundamentally caused by wire breakage due to corrosion removal. is the same.

Another method is the so-called lift-off method, in which a pattern of photoresist is first formed, then a metal is formed on the entire surface, and unnecessary material on the photoresist is removed to obtain an electrode. There have been reports of "Integrated Circuit Technology" 5th Symposium Abstracts), but the metal used as the electrode is hard and lacks malleability and ductility, such as nichrome, titanium, and platinum, in other words, lift-off. Limited to legally compliant metals.

There are also reports on aluminum, but in the case of metals like aluminum that are malleable and ductile, in other words, not suitable for the lift-off method, it is necessary to form very thin electrodes with a film thickness of about 1000λ. Therefore, it cannot be used for semiconductor devices with relatively large steps, such as ordinary field-effect integrated circuits (MOS, IC) and bipolar integrated circuits (bipolar IC), and cannot be used for ultra-high frequency transistors. It was used for special purposes such as, and its uses were limited.

In addition, in the lift-off method, it is difficult to peel off the metal film on the photoresist film, so as a solution to this problem, a spacer is formed under the photoresist film and the desired photoresist pattern is used as a mask in advance to remove the corrosion. There is also a method in which a metal film is then formed on the entire surface of the photoresist to make it easier to peel off unnecessary metal, but the process is complicated and there are cases where it cannot be applied due to the structure of the semiconductor device.

The purpose of the present invention is to eliminate the drawbacks caused by the corrosion method as described above, and also to solve the problem peculiar to the conventional lift-off method, which causes wire breakage at the stepped portion on an insulating substrate having a relatively large step. It is possible to form micropatterns of thick aluminum electrodes and wiring in a simple process with high precision and reproducibility, which was impossible with the conventional lift-off method, making it possible to miniaturize semiconductor devices. The goal is to provide a way to do so.

The features of the present invention include a step of forming an insulating film on one main surface of a semiconductor substrate, a step of forming an opening in this insulating film, a step of selectively forming a photoresist film on this insulating film,
A process of forming a metal film having a thickness thinner than that of the photoresist film on one main surface of the semiconductor substrate including the insulating film and the photoresist film, and the adhesive force between the metal film and the insulating film. The method of manufacturing a semiconductor device includes the step of mechanically selectively removing the metal coating using a film having a weak adhesive force but stronger than the adhesive force between the metal coating and the photoresist film.

For example, in a semiconductor substrate on which an oxide film is formed, a step of opening a window in the oxide film in order to connect a metal wiring layer formed on the oxide film and a diffusion layer of the semiconductor substrate; a step of forming a positive type photoresist film on a portion other than the electrode and metal wiring layer, which has an inverted trapezoidal eaves and is thicker than the metal film to be formed next; a process of forming a metal film on the entire surface without thermally deforming the positive type photoresist film and causing cracks at the same time as it is embedded in the lower part of the inverted trapezoidal eaves; This method of manufacturing a semiconductor device is characterized by comprising the step of mechanically selectively removing a metal film using a film having an adhesive force greater than that between photoresist and metal.

It is a preferable method to immerse the substrate in the photoresist dissolving agent before removing it with a film. Furthermore, when selectively removing the metal film from the surface of the semiconductor substrate, a flexible tape-like material is used. It is also preferable to include a step of continuously pressing the substrate surface with a roller or the like and continuously peeling it off.

An embodiment of the present invention will be described below as a P-channel MOS.
The case of manufacturing an IC will be explained with reference to the drawings.

FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are process diagrams showing a method for forming aluminum electrodes and wiring according to the present invention.

An oxide film 2 and a window 3 are formed on an N-type silicon substrate 1 shown in FIG.
, , 41 is used, and processed as shown in FIG.

In other words, in FIG. 4, a positive photoresist is applied to the entire surface, prebaked, and a photomask is used to selectively pattern the gate part 5, the source 3, the drain 4, the pattern for taking out the electrodes in the area, and other wiring parts. The photoresist pattern 7 is shown in FIG.

As shown in FIG. 4, the edges of the pattern are overexposed to form inverted trapezoidal edges.

Further, the film thickness of the positive type photoresist must be determined in accordance with the thickness of the aluminum film to be formed next.

That is, if the film thickness of aluminum is 1.2 microns, the film thickness of the positive type photoresist must be 1.2 microns or more.

As a positive type photoresist, U.S. ship 1/-(
SHIPLAY) +7) AZ-1350J, or AZ-111, or in Japan Oka manufactured by Tokyo Ohka Kogyo Co., Ltd.
FPR is suitable.

Next, the temperature is such that the formed positive type photoresist pattern 7 does not undergo thermal deformation, for example, AZ-1350J.
140℃ or less for l7), 1 for AZ-111
Post-bake is performed for about 20 minutes at 00°C or higher, or 150°C or lower in the case of OFPR.

Next, apply aluminum 8 to the entire surface by vacuum evaporation, approx.
When μ is formed, it becomes as shown in FIG.

Special considerations are required when aluminum is deposited on a substrate patterned with positive type photoresist.

That is, the process must be carried out under conditions such that the positive type photoresist is not thermally deformed.

If thermal deformation occurs, the inverted trapezoidal eaves at the ends of the pattern will become rounded, and cracks like 9 shown in Figure 5 will not be formed, making it impossible to peel off unnecessary aluminum later.
It becomes impossible to form electrodes and wiring using thick aluminum.

Specifically, in the case of electron beam heating, if the power is lowered to about 0.3 A x 10 κV, the temperature of the substrate during deposition will be 100'C or less, and the positive type photoresist will not undergo thermal deformation. do not have.

Also, aluminum must be attached to the lower part of the eaves of the inverted trapezoidal pattern 1 and must be completely embedded.

For this purpose, a planetarium vapor deposition method may be used.

At this time, the aluminum coating can be made to have a thickness of about 0.5 to 2.5μ, so it is considerably thicker than before, and it is formed so as to produce cracks 9 as shown in FIG. 5, rather than being continuous in the vertical direction on the substrate 1. do.

Next, it is immersed in a positive type dissolving agent, such as a ketone such as acetone or methyl ethyl ketone, for 60 to 180 seconds at room temperature, or an OMR remover manufactured by Tokyo Ohka Kogyo Co., Ltd., or an OMR remover manufactured by Mail inckrodt, USA.
Chemical Works) Chemistripper 90-1
It is heated to 20° C., immersed for 180 seconds, washed with trichlorethylene, and dried.

At this time, the dissolving agent for the photoresist 7 seeps in through the crack 9 shown in FIG. 5, partially dissolves the photoresist, and at the same time swells the remaining photoresist, resulting in a state as shown in FIG. Pattern 8 will now stand out.

In this state, when a film such as an adhesive tape is applied to the entire pattern formation surface and peeled off, unnecessary portions of the aluminum film 8 adhere to the adhesive tape, forming a pattern.

At this time, the adhesive strength of the adhesive tape should be strictly limited.

That is, the adhesive strength of the adhesive tape used in this method must be smaller than the adhesive strength between aluminum and the oxide film, and greater than the adhesive strength between aluminum and positive type photoresist.

If the above conditions are not met, aluminum will peel off from the underlying oxide film, resulting in a defect.

Finally, the positive type photoresist remaining attached to the oxide film is dissolved and removed using the above-mentioned dissolving agent, washed with a solvent such as trichlorethylene, and dried. As shown in FIG. After the portion 82 is formed, this process ends.

Usually, the process is then completed by alloying the aluminum with the underlying silicon.

In the manufacturing method according to the present invention, unlike the method of forming aluminum electrodes and wiring patterns using the corrosion method, there is no problem of over-etching, and patterns can be formed precisely according to the dimensions of the photoresist. Also, the problems caused by the high reflectance characteristic of aluminum surfaces are completely resolved.

That is, in the method according to the invention, the photoresist pattern is not formed on the aluminum coating;
Since it is formed on a perfectly rounded substrate such as silicon dioxide, its reflectance can be almost ignored, and short circuits between wirings caused by sink-like unnecessary patterns caused by reflection of light at the steps mentioned above are completely eliminated. I was able to solve it.

Further, the method according to the present invention uses a positive type photoresist, which has the same level of resolution as a negative type photoresist even with a film thickness approximately twice that of a negative type photoresist, and is therefore suitable for miniaturizing patterns.

In addition, the cross section of the edge of the pattern is an inverted trapezoid, and when the aluminum film finishes vapor deposition, it breaks at the edge of the photoresist and cracks occur, so a limited peeling method such as adhesive tape is required. By combining this method, it becomes possible to pattern a relatively thick aluminum film, which could not be achieved with conventional lift-off methods, and this method can be used to manufacture MOSFETs with large steps and bipolar semiconductor devices. method can now be used.

Further, in this method, even in the case of an insulating substrate having a relatively large step, there is no problem of disconnection at the step as long as the disconnection is not caused during the aluminum evaporation process.

[Furthermore, another great advantage of the manufacturing method according to the present invention is that it is suitable for multilayer wiring.

In other words, in this method, the cross section at the end of the positive photoresist pattern has an inverted trapezoidal shape with an eaves protruding, and when aluminum is deposited, the aluminum is embedded to the bottom of the eaves, so the formation after peeling is performed. The edges of the aluminum pattern formed are trapezoidal, contrary to the cross-sectional shape of the edges of the photoresist.

This trapezoidal aluminum pattern is very advantageous when metal wiring is formed on an upper layer through an insulating layer to form multilayer wiring.

That is, when the first layer of aluminum electrodes and wiring are formed by the conventional etching method, the cross section of the end of the aluminum pattern is approximately at right angles.

An insulating layer is formed on the first layer aluminum pattern having this shape, and after opening a window to connect the first and second layer wiring, the second layer aluminum wiring is performed. Then, the second layer aluminum wiring is analyzed at the edge of the first layer aluminum pattern.

However, in the method according to the present invention, an appropriate angle is formed at the end of the aluminum, so it is highly effective in preventing disconnection in multilayer wiring.

Next, a method for continuously forming devices and improving productivity when carrying out the above method will be described.

As shown in FIG. 6, regarding the substrate processed to the point where the aluminum pattern 8 to be removed is floating,
Next, as shown in FIG. 8, the tape-like material is continuously adhered onto the substrate by applying appropriate pressure using a roller 12 or the like.

Here, the tape-like material is an adhesive tape-like material in which an adhesive or adhesive coating 11 is formed on a flexible base 10, and its adhesive strength is smaller than the adhesive strength between aluminum and the underlying oxide film. , it is sufficient that the adhesive force is greater than the adhesive force between the photoresist and aluminum.

Further, as a method of pasting, a spatula-shaped object may be used in addition to the roller 12.

Next, when a film such as an adhesive tape is continuously peeled off, unnecessary portions of the aluminum coating 81 adhere to the adhesive surface 11, and a desired pattern is formed using the above-mentioned melted material, resulting in the one shown in FIG. It will be done.

Figure 9 shows how adhesive tape or other film is continuously pasted.
This shows a method for continuous peeling.

That is, when the semiconductor substrate 17, which has been immersed in the photoresist dissolving agent as described above, is successively selected in the direction of the arrow by means such as the belt 18 and reaches the stage 19,
A film 16 such as an adhesive tape continuously wound around a roll 13 or the like is passed between the roller 14 and the substrate 17, and the adhesive surface of the film 16 is continuously applied to the surface of the semiconductor substrate 170 by applying appropriate pressure by the roller. The semiconductor substrate 17 is immediately and continuously peeled off from the semiconductor substrate 17.

At this time, as mentioned above, the metal film on the photoresist film
The film 16 is attached to the adhesive surface of the film, and then the film 16 is wound into a roll by the winding device 15 in the direction of the arrow.

On the other hand, the semiconductor substrate 17 that has been peeled off is automatically and continuously sent to the other belt 181, etc., and is continuously sent in the direction of the arrow.

In this way, the method according to the present invention differs from conventional batch processing methods in that it has become possible to continuously process and automate the electrode and wiring layer formation process, which was the most difficult to process continuously. , and 0.5 to 2.
A further advantage arises in that it is now possible to form a metal wiring layer with a thickness of about 5 microns on an oxide film with a step difference of 0.5 to 2.5 microns.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1, 2, and 3 are cross-sectional views showing the steps of forming metal electrodes and wiring layers by a conventional method.
, 6, 7, 8, and 9 are cross-sectional views showing steps of forming metal electrodes and wiring layers according to embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... N-type semiconductor substrate, 2... Oxide film, 3... Source diffusion layer, 4...-Drain diffusion layer, 3, , 41... ...window for electrode formation,
5... Oxide film of gate portion, 6... Metal coating, 7... Photoresist coating, 8...
- Aluminum coating, 9... Crack in aluminum coating, 10... Flexible base, 11...
...adhesive or adhesive coating, 12...
·roller.

Claims (1)

[Claims] 1. A step of forming an insulating film on one principal surface of a semiconductor substrate;
a step of forming an opening in the insulating film; a step of selectively forming a photoresist film having an inverted trapezoidal cross-sectional shape on the insulating film; and the semiconductor substrate including the area on the insulating film and the photoresist film. forming a metal coating having a thickness thinner than the photoresist film on one main surface in close contact with the photoresist film; and mechanically selectively removing the metal film using a film having an adhesive force stronger than the adhesive force with the photoresist film. 2. In the manufacturing method according to claim 1, when selectively removing the metal film from the surface of the semiconductor substrate, the step of continuously pressing a flexible tape-like material onto the surface of the substrate with a roller or the like and continuously peeling it off is performed. A method of manufacturing a semiconductor device, comprising: