JPS6020901B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for manufacturing a semiconductor device, in particular, forming a metal layer made of a metal mainly composed of aluminum, such as aluminum or silicon-containing aluminum, on a semiconductor substrate,
The present invention relates to a method of manufacturing a semiconductor Z-conductor device in which the metal layer is selectively etched using a photoresist film as a mask.

In the manufacturing process of semiconductor devices, a metal layer made of aluminum or a metal mainly composed of aluminum is deposited on the surface of a semiconductor substrate through an insulating layer such as silicon dioxide (SiO2) or phosphorus silicate glass (Ore-G). There is a step of depositing and selectively etching this with an etching solution using a photoresist film as a mask to form a desired pattern and forming electrodes or wiring.

In such a process, the etching solution acts on the metal layer masked by the photoresist film, etching unnecessary parts of the metal layer, making it impossible to accurately form the metal layer with the desired pattern. There has occurred.
In particular, when a metal layer is formed on an insulating layer whose surface is not flat, the metal layer is likely to be formed so as to be constricted in the stepped portion of the insulating layer. Therefore, when a photoresist film is formed on a metal layer exhibiting this constriction, the photoresist film deposited on the constriction of the metal layer is not sufficiently exposed to light and a portion with weak adhesive strength with the metal layer is formed. Therefore, when etching the metal layer, the etching solution enters from that part and etches the metal layer masked by the photoresist film, causing the problem that the desired pattern cannot be formed. Ta. If the insulating film has steep corners, the metal layer formed on the stepped portion will be thinner than the metal layer formed on the flat insulating film. ,
A problem arose in that the etching solution that entered the metal layer during etching caused the metal layer to be completely etched away, resulting in disconnection. In order to completely eliminate such problems, the inventor of the present application conducted various experiments and studies, and found that after forming aluminum or a metal layer mainly composed of aluminum, the surface of the layer was treated with Freon plasma, and then this Freon plasma treatment was performed. If a photoresist film is selectively formed on the surface of the metal layer and the metal layer is etched using this as a mask, the metal layer can be shaped into the desired pattern without the etching solution acting on the metal layer masked by the photoresist film. It has been determined that the wire can be formed with high precision and without any breakage. The present invention has been made based on such experimental studies, and its purpose is to selectively etch a metal layer formed on a semiconductor substrate using the photoresist film as a mask. An object of the present invention is to provide a method for manufacturing a semiconductor device that can form a metal layer in a desired pattern with high accuracy while preventing etching of the metal layer in the exposed portions. Another object of the present invention is to provide a method for manufacturing a semiconductor device in which disconnection due to etching does not occur when a metal layer formed on a semiconductor substrate is selectively etched to form a desired electrode or wiring. It is in. Still another object of the present invention is to accurately etch a metal layer into a desired pattern using a photoresist film as a mask, regardless of the shape of an insulating layer formed on a semiconductor substrate and a metal layer formed thereon. An object of the present invention is to provide a method for manufacturing a semiconductor device that can be manufactured using a semiconductor device. Still another object of the present invention is to provide a simple method for accurately forming a metal layer having a desired pattern. In order to achieve such an object, the present invention forms a metal layer made of aluminum or a metal containing aluminum as a main component on a semiconductor substrate, performs Freon plasma treatment on the surface of the metal layer, and then selectively attaches the metal layer to the surface of the metal layer. The method is characterized in that a photoresist film is selectively formed, and the metal layer is selectively etched using the photoresist film as a mask to form a metal layer having a desired pattern. Hereinafter, the present invention will be specifically explained based on Examples.

1 to 6 are perspective views of essential parts in each manufacturing process of a MOS type semiconductor integrated circuit device according to an embodiment of the present invention. As shown in FIG. 1, three first insulating layers 2 made of Si02 film are formed on a silicon substrate 1, and a wiring layer 3 made of polysilicon, for example, is formed on this first insulating layer 2. Source and drain regions (not shown) are formed on the silicon substrate 1 by a known selective diffusion technique.
An insulating layer 2 is formed on the substrate surface so as to cover part of the source and drain regions. Further, a thin gate oxide film (not shown) is formed on the substrate surface between the source and drain regions, and a gate electrode (not shown) made of polysilicon is formed on this oxide film. The wiring layer 3 made of polysilicon can be formed simultaneously with the formation of the gate electrode. Next, as shown in FIG.
Then, a second insulating layer 4 made of phosphorus silicate glass (PSG) is formed on the silicon substrate by, for example, a known chemical vapor deposition method. At this time, as shown in the figure, the second insulating layer 4 is formed to have a constricted part 5 in a portion located at a step between the wiring layer 3 and the first insulating layer 2. Next, as shown in FIG. 3, a metal layer 6 made of aluminum containing 1.0% (weight %) silicon is formed on the insulating layer 4 to a thickness of about 1.0 mm. As shown in the figure, the metal layer 6 is formed so as to have a constriction 7 at the same level as the constriction 5 of the second insulating layer 4 in the portion located at the step. Next, as shown in FIG. 4, the semiconductor substrate 1 on which the metal layer 6 has been formed is placed in a plasma equipment 8, and the surface of the metal layer is subjected to plasma treatment. The plasma device 8 includes a plasma generation tube 9 made of quartz having a mouth at one end, a lid 10 made of quartz for sealing this opening, and a plasma generation tube 9 made of quartz provided extending inside the plasma generation tube 9. an exhaust pipe 11 and a quartz gas introduction pipe 12, and electrodes 13 and 14 for applying high-frequency power provided outside the plasma generation tube.
and a high frequency oscillator 15 connected to this electrode. The exhaust pipe 11 and the gas introduction pipe 12 are provided with a large number of small holes (not shown). A large number of silicon substrates 1 on which the metal layers have been formed are placed on a substrate support stand 16 made of quartz, and this is placed inside the plasma generation tube 9. Thereafter, a lid 10 is attached to the entrance of the plasma generation tube 9 via a silicon O-ring 17 to seal it. Next, a vacuum pump (not shown) connected to the exhaust pipe 11 is driven, and the plasma generation pipe 9
The inside of the pipe is evacuated, and the pressure inside the pipe is about o. Make it less than Mom. After the pressure inside the tube reaches a predetermined value, Freon (CF4) gas is introduced into the plasma generation tube 9 through the gas introduction tube 12 at a flow rate of about 0.3 pm/min. When Freon gas is introduced and the pressure inside the pipe reaches approximately 0.3 Ton, the high frequency oscillator 15 is activated to generate a frequency of 13.58 M.
A high frequency power of about 250 W in HZ is applied to the electrodes 13 and 14 to generate Freon plasma in the plasma generating tube, and the silicon substrate 1 is exposed to the tube for about 1 minute to plasma-treat the surface of the metal layer. Thereafter, the silicon substrate 1 that has undergone plasma treatment is removed from the plasma apparatus, and a photoresist agent, for example, OMR83 (trade name of Tokyo Ohka Co., Ltd.) having a viscosity of about 35 centipoise (CP) is applied to the surface by spin coating. Drying and etching are performed to form a photoresist film 18 having a desired pattern and having a thickness of approximately 0.8 mm as shown in FIG. Thereafter, using this photoresist pus 18 as a mask, the above substrate was coated with phosphoric acid: nitric acid: glacial acetic acid: water in a weight percentage of 76:3:15:5, respectively.
The conductive layer is etched by dipping approximately 3/4 inch sand into an etching solution of 370 mm mixed at a ratio of 370 mm. After that Fu Z
The photoresist film is removed to obtain a semiconductor device having a metal layer 19 formed in a desired pattern so as to cross the wiring layer 3 via the second insulating layer as shown in FIG.
In the thus obtained semiconductor device, the Z-shaped portion of the metal layer 19 located at the stepped portion of the insulating layer could be accurately formed into a desired pattern without being etched. As described in the examples above, when etching a metal layer formed on a semiconductor substrate using a photoresist film as a mask, the metal layer is subjected to a Freon plasma 2-ma treatment, and then a photoresist film is applied to the metal layer. Afterwards, by performing an etching process, it was possible to form a metal layer with the desired pattern without undesirably etching the part of the metal layer covered with the photoresist film, although I cannot definitively say why. According to the inventor's study, Freon plasma treatment removes dust, dirt, and oxide film formed on the surface of the metal layer, exposing the clean surface of the metal layer, which makes photoresist In addition, due to the Freon plasma treatment, the fluorine radicals (F*) remaining on the surface of the metal layer including the constricted portion interact with the photoresist agent, and the interface between the metal layer and the photoresist film is improved. It is conceivable that a hydrophobic film is formed to prevent the etching solution from entering between the photoresist film and the metal layer. FIG. 7 is a graph showing the occurrence rate of disconnection in the metal layer at the stepped portion when semiconductor devices are manufactured using the conventional method and the present invention. The number of prototypes is shown on the machine axis, and the occurrence rate of wire breakage is shown on the vertical axis. In the figure, the broken line indicates that after forming an aluminum metal layer containing 1.0% silicon on a semiconductor substrate, a photoresist film is selectively formed on the metal layer without Freon plasma treatment, and using this as a mask, the metal layer is The figure shows the occurrence rate of wire breakage due to etching of the metal layer in the case of the conventional etching method. The solid line indicates that after the metal layer is formed on the semiconductor substrate, Freon gas is flowed at 0.3 Z/min into the plasma generating tube 10 as described in the above-mentioned embodiment, and the pressure inside the tube is reduced to 0. When the rainbow om is reached, a high frequency power of about 250 W at a frequency of 13.58 MHZ is applied to the electrode to plasma-treat the silicon substrate 1 for about 1 minute in a plasma generation tube, and then a photoresist film is selected on the surface of this metal layer. 3 shows the occurrence rate of wire breakage due to etching of the metal layer in the case of the present invention in which the metal layer is etched using this as a mask. A disconnection defect occurs when the metal layer 19 of the stepped portions A and B is formed so as to cross the wiring layer 3 and the second insulating layer 4, which are shown surrounded by dotted lines in FIG. If there was even one place on the silicon substrate where 19 was removed by etching so as not to be completely continuous, it was treated as a defect.
The number of samples was 10 and 0 for each trial production. As a result, as shown in FIG. 7, according to the conventional method, a wire breakage always occurs, although there are variations in the wire breakage occurrence rate for each trial production. However, according to the present invention, such disconnection as described above did not occur at all. FIG. 8 is a graph showing the relationship between the Freon plasma treatment time of the present invention and the occurrence rate of wire breakage. As shown in the figure, the plasma treatment is preferably performed for one minute or more. The inventor has also attempted a method in which the metal layer is subjected to plasma treatment using 02 gas and N2 gas, and then a photoresist film is selectively formed, and the metal layer is etched using this as a mask, but neither method prevents disconnection. No effect was obtained. In the embodiments, a case has been described in which the present invention is applied to a MOS type semiconductor integrated circuit, but the present invention is not limited to the above-described embodiments and can be applied to other methods of manufacturing semiconductor devices.

In addition to the Sj-containing aluminum described in the embodiment, when aluminum is used as the metal layer, exactly the same effect can be obtained.

[Brief explanation of drawings]

40 FIGS. 1 to 6 are cross-sectional views of main parts in each manufacturing process of a semiconductor device according to an embodiment of the present invention, and FIG. 7 is a graph showing the incidence of disconnection when using the conventional method and the present invention. be. FIG. 8 is a graph showing the relationship between Freon plasma treatment time and wire breakage occurrence rate of the present invention. 1...Silicon substrate, 2
...first insulating layer, 3...wiring layer, 4...second insulating layer, 5...constriction 6...metal layer, 7...
- Constriction, 8... Plasma device, 9... Plasma generation tube, 10... Lid, 11... Exhaust pipe, 12...
Gas introduction screen, 13, 14... Electrode, 15... High frequency oscillator, 16... Substrate support stand, 17... Silicon O-ring, 18... Photoresist film, 19... Metal layer. My younger brother's 2nd figure Tsutomu 3rd figure Tadazu 6th figure Akuzu's younger brother's figure

Claims (1)

[Claims] 1. A metal layer made of aluminum or a metal containing aluminum as a main component is formed on a semiconductor substrate, the surface of the metal layer is subjected to Freon plasma treatment, and then a photoresist film is selectively formed on the surface of the metal layer, and the photoresist film is selectively formed on the surface of the metal layer. 1. A method of manufacturing a semiconductor device, comprising selectively etching the metal layer using a resist film as a mask to form a metal layer having a desired pattern.