JPS5986225A - Etching method for insulating layer - Google Patents

Abstract

PURPOSE:To facilitate the laminated layer of thin films by laminating and forming insulating layers of two different types in etching properties, anisotropically etching it and isotropically etching it, thereby improving the etching accuracy and inclining the etching section. CONSTITUTION:An insulating layer 34 such as an SiO2 film is formed on a substrate, on which the first conductive layer 33 is formed. The layer 34 forms a lower insulating layer, and an insulating layer which has good stepwise coating characteristic and dense film quality is selected for the conductive layer. In order to flatten the surface, an SiO2 film 35 formed by a spin coating on the layer 34 is formed as an upper insulating layer. The layer 35 is selected to have more feasible properties to etch as compared with the layer 34, the surface is flattened, the surface of the layer 35 is patterned by using an AZ system resist 35 prior to the formation of the second conductive layer 38 on the layer 35, an anisotropic etching is performed by using a parallel flat plate type dry etching unit, and the layers 34, 35 are further isotropically etched by using a cylindrical plasma etching unit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method of etching an insulating layer, and more particularly to a method of etching an etching section with the etching section inclined from the vertical.

[Prior art]

For example, in a semiconductor device having a multilayer wiring structure, an interlayer insulating layer is provided to electrically isolate wiring conductors. Not limited to such insulating layers of semiconductor devices, but generally in the case of a structure in which an upper conductor having a contact part that partially electrically connects with a lower conductor is laminated via an insulating layer between the eyebrows, the following is applied. There is a problem like this. That is, when connecting an upper conductor to a lower conductor, an insulating layer is interposed between both conductors, but if the step of this insulating layer has a steep shape, the upper conductor However, it is not possible to form a conductor with a continuous and uniform thickness due to the step differences in the insulating layer, resulting in poor connections and disconnections, making the device unusable. Particularly in recent years, as conductor patterns tend to become finer and more complex, defects due to differences in insulating layer steps have become a major problem.

In order to improve the above-mentioned disadvantages, conventional methods have been used to process the edges of the insulating layer into a specially sloped shape and create the upper conductor along the sloped surface to reduce the effect of the step. However, with conventional insulating layer processing methods, it is difficult to slope the edges while maintaining the precision required for microfabrication, and there is no etching method that can satisfy both conditions. Ta.

Conventionally, there are two methods for finely processing insulating layers, etc.: one is chemical etching and etching using a cylindrical plasma etching device, and the other method is anisotropic etching using a parallel plate dry etching device. There is. In the former isotropic etching, as shown in Fig. 1, the weak adhesion between the resist l blue and the material to be etched 2 increases the side etching of the material to be etched 2, and the pattern accuracy deteriorates significantly. There's a problem. On the other hand, the cross section of the material 2 to be etched has a slope, which is advantageous for the conductor layered thereon. In the latter anisotropic etching, there is almost no amount of side etching, and as shown in FIG. 2, the etched cross sections of both the resist 11 and the material to be etched 12 are vertical, resulting in very good pattern accuracy. However, when stacking finely patterned conductors, there are problems such as breakage of the conductors as described above.

Etching of the insulating layer is a very important problem not only in the semiconductor field but also in the process of manufacturing a multi-winding type thin film magnetic head (multi-turn nod), for example, as shown in FIG. However, in Figure 3, the winding,
An insulating layer covering a conductive layer -L such as a lead wire is omitted from illustration.

In other words, compared to conventional magnetic heads obtained by processing bulk ferromagnetic materials, the multi-winding thin film magnetic head described above has a higher density because it is easier to create narrower tracks, narrower gears and knobs, and more elements. In order to achieve high recording density using this type of thin film magnetic head, which is considered important for fixed head type PCM recorders that require recording, narrower tracks, narrower gaps, and multi-turn recording heads are required. It is necessary to reduce the current by In order to meet these requirements, in the multi-turn thin film head, the conductive layer 21 that serves as the winding must be processed into a fine pattern. In particular, in order to respond to the narrowing of the track, the line width of the signal line 21 must be reduced, and it is necessary to increase the film thickness and narrow the line spacing.

This shape of the signal line increases the step difference that occurs on the surface of the insulating layer after forming the insulating layer on top, and when a conductive layer is further formed on the insulating layer, short circuits and short circuits occur between the conductive layers between the upper and lower conductive layers. Problems such as breakage of the upper conductive layer may occur. Also, in the recessed part where the conductive layer 21 is not present, the upper and lower magnetic layers 2
Since the distance between 2 and 23 becomes shorter, a decrease in recording efficiency due to leakage of magnetic flux becomes a problem.

As a means to solve this problem, a planarization technique using a lift-off method has been attempted. In this method, the conductive layer is masked with a resist, the conductive layer is patterned through etching, and an insulating layer is deposited on the remaining conductive layer, L1/cyst, and substrate, and each insulating layer is discontinuous. to form. Next, resist stripper is introduced through the discontinuous part of the insulating layer.
The insulating layer on the resist is removed together with the resist to flatten it.

One of the problems with this method is that the insulating layer is formed using a method with good coverage, such as sputtering, which makes it difficult to remove the resist because the entire surface of the resist is covered.
Therefore, there is a method of over-etching to create an undercut, but in this case, a problem remains because a recess is created at the edge of the film. Another problem is that when the insulating layer is formed by sputtering with good adhesion, the substrate temperature rises, and the resist hardens under the influence of heat, making it difficult to remove the resist. As a way to solve this drawback, before forming the resist using the above method, another metal thin film is formed.
There is a method of etching this metal thin film using a selective etching solution and simultaneously stripping and flattening the resist.

However, with this method, it is difficult to find an etching solution with selectivity depending on the conductive film.

Particularly in manufacturing a multi-turn type thin film head, the shape of the etched cross section of the insulating layer is important.

That is, the lead contact part A and the back core part B in FIG.
In this case, the conductive layer and the ferromagnetic layer must be connected through an insulating layer. Although not shown in FIG. 3, if the etched cross section of the insulating layer on the conductive layer is vertical, a step cut or the like will occur at the stepped portion, so it is necessary to have a tapered cross section. Moreover, since narrower tracks and multi-turns are required, highly accurate machining is required.

[Purpose of the invention]

The present invention simultaneously solves the above-mentioned problems caused by an insulating layer interposed between conductive layers, and provides an etching method for forming an insulating layer having an inclined etching cross section.

[Example 1] An example of the method of etching an insulating layer according to the present invention will be described by referring to the manufacturing process of a thin film magnetic head.

In FIG. 4(a), one of the magnetic cores is Ni −
After forming a thin insulating layer 32 such as 3102 on a ferromagnetic substrate 31 made of Zn ferrite or the like using sputtering or the like, Cu
, At+Au, etc., is formed using a vacuum evaporation method or the like. In order to make the conductive layer 33 multi-turn as a signal line, it is processed into a spiral shape using a fine pattern processing method such as chemical etching and dry etching.

Next, on the substrate on which the first conductive layer was formed, a 5i02 film and a PS
An insulating layer 34 such as a G film or a BSG film is formed.

The insulating layer 34 constitutes a lower insulating layer, and an insulating layer is selected that has good step coverage characteristics and dense film quality relative to the shape of the conductive layer. For example, it is formed by a plasma-CVD method or a sputtering method.

The surface of the lower insulating layer 340 has unevenness corresponding to the position of the covering conductive layer 33, and it is not preferable to form the second conductive layer thereon with the unevenness. Therefore, in order to planarize the surface, a SiO3 film 35 formed by a spin code is formed on the lower insulating layer 34 as an upper insulating layer.

The upper insulating layer 35 is selected to have a property of being more easily etched than the lower insulating layer 34, and a spin code type SiO2 film having a relatively rough film quality is used. This type of SiO3 film is made by dissolving a silicon compound or the like in an organic solvent or the like, and is coated with a spin cord and then fired to obtain a thin film containing Sio2 as the main component. The film thickness can be controlled by the rotational speed of the spin cord and the concentration of the silicon compound in the solvent, and like organic materials such as PIQ and resist, the film can be formed thinner on the flat part and thicker on the four parts. The surface can be flattened. In this case, the thickness of the SiO2 layer of the spin code is less than 3000/lt (
(in flat areas) is appropriate. The reason is that if the thickness is 3000 Å or more, the taper becomes too large and cracks are likely to occur.

Then, microfabrication is performed on the insulating layer portion of the connection portion A (IJ-decontact portion) with the first conductive layer 33 and the front gap portion C for magnetic recording. That is, AZ series resist 3
6 is used to pattern the surface of the insulating layer 35, and anisotropic etching is performed using a parallel plate type dry etching apparatus. Through this etching process, the cross sections of the insulating layers 34 and 35 are vertically removed as shown in FIG. 4(a), and processed with high dimensional accuracy. - Or use a mixed gas of CF4 (Freon 14) and hydrogen gas.

In the above etching, in parallel plate etching using a parallel plate etching apparatus, no slope is formed even if the insulating layer is over-etched regardless of the presence or absence of the spin-coded upper insulating layer 35, and a steep cross-sectional shape is not formed. This is because, unlike chemical etching, this is due to so-called anisotropic etching in which the reactive species (CF3+, cI;2+, CF10, etc.) have directionality.

The insulating layers 34, 35f processed vertically in the above steps are further etched using a cylindrical plasma etching device. Generally, in the case of isotropic etching, when the target area is etched and over-etching occurs, side etching increases due to the remaining active etching species (CF"+, CF2+, CF+, etc.). In this case, the Si0 layer 35 of the spin code is made of S by P-CVD etc.
Since the film quality is rough compared to the iO2 layer 34, only the S t 02 film 35 formed by the spin code is particularly etched. Accordingly, the S io 2 film 34 formed by P-CVD or the like is etched from the portion where the S i 02 film 35 of the spin code has been etched. Therefore, Figure 4 (
As shown in b), the upper layer of the 5i02 film 34 is etched to a large extent by P-CVD or the like, and the lower layer is not etched much, so that the cross section is tapered with little side etching. When using the above cylindrical plasma etching apparatus, CF4. CF4+02 or the like may be used. The amount of taper can be arbitrarily controlled by varying the supplied power, etching time, etc.

The relationship between the taper amount and the side etching amount when the etching time is varied is shown below. The gas used is CF4+0□
, power = aoow, gas pressure = 0.8 Torr
It is r. Lower insulating layer thickness: 22μ.

The thickness of the spin code 5i02 layer is 2000A.

Table 1 Next, the AZ resist 36 used for etching the insulating layer is removed using oxygen alasia. Normally, resist undergoes deterioration and hardening when exposed to plasma, and cannot be removed even with a special stripping solution. Therefore, the resist is removed using oxygen anocya.

In this case, since oxygen arasia cannot be used with organic materials such as PIQ, this poses a major problem in microfabrication.

However, the process of removing the resist when the spin code S102 layer 3 is interposed is a very effective processing technique from the viewpoint of microfabrication because oxygen aracia can be used.

Next, as shown in FIG. 4(c), on the board with the window opened,
A conductive layer of Cu, At or the like is formed as a second conductive layer for one terminal 37 of the signal line and the bias layer 38 by sputtering or the like. Furthermore, chemical etching or dry etching is used to process the desired fine pattern shape. In this case, due to the etching process that has already been performed on the insulating layer 84,3517), the cross section of the underlying insulating layer 34 has a taper, and even if the conductive layer 37°38 is laminated at the stepped portion, the conductive layer will cause problems such as cuts and disconnections. This does not occur, and a good level difference coverage state is obtained.

Next, insulating layers 39 and 40 are formed in the same manner as the above-mentioned insulating layers 34 and 35 on a substrate in which two conductive layers are laminated with an insulating layer interposed therebetween. That is, an insulating layer 39 is formed by a P-CVD method or the like, and a ferromagnetic layer 41 made of Ni-Fe or the like is formed on the insulating layer 40 on which the 5i02 film 40 of the spin code is formed. 40 constitutes a magnetic circuit together with the ferromagnetic substrate 31. Therefore, prior to forming the ferromagnetic layer 41, an insulating layer 39. 40 is etched by a process similar to that used for etching the insulating layers 34 and 35 described above. After forming the etched end face in an inclined shape, a Ni--Fe ferromagnetic layer 41 is formed, and together with the ferromagnetic substrate 31, a magnetic core is formed.

Finally, the insulating layer covering the lead extraction portion is removed by dry etching to obtain the thin film magnetic head shown in FIG.

A recording thin film head using the insulating layer etching method described above has a relatively flat structure on the first conductive layer even if it has a narrow track and multiple turns. Therefore, it is easy to subsequently form the second conductive layer, there is little leakage of magnetic flux, and the recording efficiency is good.

[Example 2] In Example 1, the insulating layer has a two-layer structure consisting of a P-CVD S 102 film and a spin coated St02 film. Next, an example using another insulating layer will be described.

As in Example 1, on the ferromagnetic substrate on which the first conductive layer is formed, a SiO film or Si3N4 film of about 2 μm is formed as a lower insulating layer over the entire surface by plasma CVD, which provides good step coverage and film quality. Master.

As the introduced gas when creating the S io 2 film, 5
Si such as tH4 (monosilane) and N20 (nitrous oxide)
When creating a N film, gases such as SiH4, N2 and 4NH3 may be used. A dense film is required as the lower insulating layer.

Generally, film quality is determined by the conditions in P-CVD, and can be controlled by parameters such as gas flow rate, power supply, pressure, substrate temperature, and distance between electrodes. Among these, gas flow rate, power supply, and substrate temperature are particularly influential. As for the gas flow rate, in the case of S102 film, the composition is determined by the mixing ratio of SiH4 and N20 (the more SiH4, the more Si
If a rich film contains a lot of Y2O, Si becomes poor S.
t It becomes an O2 film. ), the composition of the Si3N4 film is also approximately determined by the flow rate ratio of SiH4, N, and NH3. Also, if the substrate temperature is high, the deposition rate will be slow.
The membrane quality becomes a dense membrane.

Furthermore, regarding the dependence on the supplied power, as the power increases, the film formation rate increases, but the film quality tends to deteriorate. If the power is too low, the film quality will deteriorate.

To give a specific example, in the case of a SiO□ film, SiH,
1 (concentration 1O% based on Ar) flow rate is 170SCCM
.

N20 flow rate is 1505 CCM, pressure = 0.2 Torr
The etching rate when the film was formed at r + power = 50 W and substrate temperature T = 350° C. was 100 A/sec. A 5% aqueous solution of HF (hydrofluoric acid) is used as the etching liquid, and the temperature is 45 to 50°C.

Next, the upper insulating layer of the two-layer structure is formed using the same P-CVD method as used for forming the lower insulating layer. However, for taper etching, it is necessary to form the upper insulating layer with an insulating layer that is less dense than the lower insulating layer. Specifically, by changing the formation conditions by P-CVD method,
So let's do it. In this case, as described above, the substrate temperature may be lowered, the power may be increased, or it may be lowered extremely.

For example, the flow rate of 5IH4 (Ar base, concentration 10%) is +
Table 2 shows the etching rate and power dependence of the P CVD 5102 film prepared at a flow rate of 70SCCRL S20 of 1505CCM, pressure = 0.2T or r (same conditions as the lower insulating layer), and a substrate temperature of 200°C.

Table 2 However, the etching solution is a 5% aqueous solution of HF (hydrofluoric acid) at a temperature of 4.
The temperature is 5 to 50°C.

As in Example 1, the film thickness of the upper insulating layer is preferably 8000 Å or less. From the table above, by selecting the P-CVD conditions, the upper insulating layer can be formed as a rough film with a high etching rate.

Next, after patterning into the desired pattern using an AZ resist, etc., first perform anisotropic etching using a parallel plate type dry etching apparatus as shown in FIG. Machining the cross section vertically. The introduced gas at this time is CHF5 (Freon 2B), CF4 (Freon 14) + when etching the SiO film.
When etching a Si3N4 film, SiF4.
C11F8. If CF4+H2 or the like is used, the insulating layer can be etched with high precision. Since the etching is performed using a parallel plate type dry etching device, anisotropic etching is performed, and the etched cross section of the insulating layer exhibits a steep shape.

The insulating layer vertically processed in the above step is isotropically etched using a cylindrical plasma etching device.

Also in this embodiment, since the upper insulating layer is rougher than the denser lower insulating layer, only the upper insulating layer is particularly etched. As a result, etching of the lower insulating layer progresses from the part where the two-part insulating layer is etched, and one side of the lower insulating layer is etched more and the lower part is not etched as much. A tapered etched cross section as shown in b) is obtained.

When using the above cylindrical plasma etching apparatus, in the case of Sio2, CF4. cF4+02, etc., S+3N, CF4+02. SiF4 or the like may be used. The amount of taper can be arbitrarily controlled by varying the electric power, etching time, etc.

Next, the AZ-based resist after dry etching is removed using oxygen alasia, and a second conductive layer is laminated in the same manner as in Example 1. Since the steep step becomes sloped, the Au
Even if conductive layers such as At, Cu, and the like are laminated using vacuum evaporation, sputtering, or the like, there will be no step cuts or cuts in the step portion, resulting in a good step coverage state. A thin-film magnetic head using such an insulating layer etching method becomes a head suitable for high-density recording because it becomes possible to form a fine pattern on the conductive layer. [Effect] As described above, when the present invention is used, This is effective because the etching is accurate and the etched cross section can be sloped, making it easy to stack thin films.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of an insulating layer subjected to conventional isotropic etching, Figure 2 is a cross-sectional view of an insulating layer subjected to conventional anisotropic etching, and Figure 3 is a winding of a thin-film magnetic head. 4(a) to 4(c) are cross-sectional views for explaining the steps according to the present invention. 31; Ferromagnetic substrate 33: First conductive layer 34°39°
Lower insulating layer 85.40: Upper insulating layer 37°382 Second conductive layer 41: Ferromagnetic layer Agent Patent attorney Yoshihiko Fukushi (and 2 others) 1st Flash 21st 3rd LIJ (0)
31:IA4 Figure

Claims (1)

[Claims] 1) An etching method for forming an insulating layer on a substrate with edges inclined from the vertical, comprising laminating at least two types of insulating layers having different etching characteristics,
The upper insulating layer is made to be an insulating layer that is more easily etched than the lower insulating layer deposited first, and the laminated insulating layer is anisotropically etched using a parallel plate dry etching method.
3.degree., and then isotropically etched using a cylindrical plasma etching method to give an etched cross section a slope. 2) The insulating layer has a lower insulating layer of 5i0 having a dense film quality.
2. The method for etching an insulating layer according to claim 1, wherein the upper insulating layer is a rough 5i02 film formed through a coating process. 3) the insulating layer is formed by a plasma CVD method,
2. The method of etching an insulating layer according to claim 1, wherein the plasma CVD conditions are changed for the lower insulating layer and the upper insulating layer to form a multilayer insulating layer having different etching characteristics. 4) The substrate is a ferromagnetic material whose surface is covered with an insulating thin film, the insulating layer covers a conductive spiral winding formed on the ferromagnetic material, and a metal ferromagnetic layer is laminated above. A method of etching an insulating layer according to claim 1, 2 or 3, wherein the etching method is an insulating layer of a thin film magnetic head.