JPS5928358A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To contrive to change fine elements into high density and integration ones without contamination by a method wherein elements are isolated by one time photoetching, and an insulation film is buried flat into a field region by low temperature treatment. CONSTITUTION:After reactive ion etching is performed by applying a resist mask 13 on a thermal oxide film 12 of a P type Si substrate 11, resulting in the formation of a recess, an inversion prevention layer 14 is formed by ion implantation. A SiO2 15 is superposed by plasma CVD method and treated with buffer fluoric solution, and accordingly a V-groove 16 is formed in the periphery of the recess by the difference of etching speeds. A resist film 17 is coated, the surface flatted approximately is etched by reactive ion, etched at the same speed by selecting the conditions of heat-treating and etching the resist 17, and then the resist 17 is removed by exposing the projection film 15. When a CVD SiO2 18 is uniformly deposited, a resist 19 is superposed, and the substrate is exposed by likewise etching the flatted surface by reactive ion, the SiO2 15 and 16 is buried flat in the field part. In this constitution, contamination does not occur because of no use of Al or resist mask for forming the film 15, and accordingly the element characterististic is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of embedding a relatively thick insulating film in a field region to obtain a flat structure.

[Technical background of the invention and its problems]

Conventionally, in semiconductor devices using silicon as a semiconductor, especially MO8 type semiconductor integrated circuit devices, there has been a method of forming a thick insulating film in the so-called field region between elements in order to eliminate insulation defects due to parasitic channels and reduce parasitic capacitance. However, when using this selective oxidation method as a method for isolating elements in integrated circuits that are becoming increasingly finer and denser, it is difficult to use the selective oxidation method due to the following problems: This will become a hindrance to integration. 1st
The field oxide film digs into the device in the shape of a bird's beak, causing dimensional errors in the device area. Second, because field oxidation requires high-temperature and long-time heat treatment (for example, 1000°C for 5 hours), impurities in the field region that have already been doped will be re-diffused and seep into the device formation region. Element characteristics deteriorate. Thirdly, although about half of the field oxide film thickness can be buried in the semiconductor substrate, a step of about half the field oxide film thickness is created on the substrate surface, which causes the multi-metal wiring to be buried at this step. Reliability is significantly reduced.

In order to solve the above-mentioned problems, a conventional method of manufacturing semiconductor devices is to form a recess in the field region of a semiconductor substrate and fill the recess with a relatively thick insulating film using a low-temperature process to obtain a flat structure. It is used. An example thereof will be explained below with reference to FIGS. 1(a) to (h).

As shown in FIG. 1 (&), a P-type silicon substrate 1 with a plane orientation (100) and a specific resistance of 5 to 50 Qtrn is prepared, and a thermal oxide film 2 of about 300X and an Al film of about 0.5 μm are coated on the surface. 3 are formed one after another. Next, as shown in FIG.
Using the AJ film 3 and the thermal oxide film 2 on the field region as a mask, the AJ film 3 and the thermal oxide film 2 are sequentially etched using, for example, a reactive ion etching technique, and then the resist film 4 and the AI! Using the film 3 as a mask, the field region is etched by about 0.8 μm by reactive ion etching using, for example, CF4 gas to form a recess. Furthermore, using the resist film 4 and the AJ film 3 as a mask, silicon in the field region is etched. The anti-inversion layer 5 is formed by ion implantation into the substrate. Next, the same figure (
As shown in d), a first insulating film is formed on the entire surface of the silicon substrate (5to2 film) by, for example, plasma CVD.
6 to a thickness of about 1.2 μm. After that, for example, fluoride '77
When the entire surface of the 5tO2 film 6 is etched with the -ey 2-lam solution, the etching rate of the 5i02 film on the side surface of the stepped portion is approximately 20 times greater than the etching rate of the 5io2 film on the flat portion, as shown in Figure (e). Then, the 5102 film 6 is completely separated into the recess in the field region and the element forming region, and a V-shaped groove 7 is formed around the recess.

Thereafter, when the wafer is treated with a mixture of sulfuric acid and hydrogen peroxide, the AI film 3 and resist film 4 used as an etching mask are removed, and the 5IO2 film 6 thereon is also removed. In the end, the 5i02 film 6 is embedded in the recess as shown in FIG. 2(f). Next, as shown in FIG. 7G, as a second insulating film, a CVD 5to2 film 8, for example, is deposited uniformly to a thickness of, for example, 1.0 μm to completely fill the figure 7 groove 7, and then a fluid material is further deposited on top of the CVD 5to2 film 8. For example, a resist film 9 is applied as a film to flatten the surface. Then, the entire surface is etched using, for example, reactive ion etching. By appropriately selecting the reactive ion etching conditions and the heat treatment time for the resist film 9, the etching rates of the resist film 9 and the 5to2 film 8 can be selected to be approximately the same. When reactive ion etching is performed under these conditions, the resist film 9 is completely etched, and the 5IO2 film 8 is further etched until the semiconductor substrate above the element formation region is exposed, resulting in a field pattern as shown in FIG. The area is completely filled with SlO□M6.8 in a flat structure. After this, although not shown, an MO8 type semiconductor device, for example, is formed by a normal element forming process.

However, in such a conventional method, it is necessary to deposit the first insulating film while leaving the Al1 film and the resist film in order to perform the step-off process. I can't do the pre-processing beforehand. Normally, pretreatment is performed using a mixture of sulfuric acid and hydrogen peroxide, a mixture of hydrochloric acid, hydrogen peroxide, and water, diluted fluoride, acid, etc., but such pretreatment may damage the Al film or resist film. This is because it will be removed. Further, there were serious problems such as contamination of the silicon substrate and first insulating film from the Al film and resist film, deteriorating device characteristics and significantly lowering product yield.

[Purpose of the invention]

The present invention was developed in view of the drawbacks of the above-mentioned device isolation method, and is a method of performing device isolation in two photolithography steps and embedding a flat insulating film in the field region in a low temperature process. The present invention provides a method for manufacturing a semiconductor device that enables high-density integration of fine elements without deteriorating the characteristics due to contamination or the like.

[Summary of the invention]

In the present invention, first, a recess is formed in a field region of a semiconductor substrate, and a first recess is formed without leaving an Al film or a resist film.
Deposit an insulating film over the entire surface.

Then, the step portion of this first insulating film is removed by etching,
A 7-shaped groove is formed around the recess. Thereafter, a fluid material film is deposited to fill the grooves over the entire surface so that the surface is flat, and at least a portion of the fluid material film and the first insulating film are etched to form the first insulating film on the element formation region. Remove the insulating film. As a result, a state in which the first insulating film is buried only in the recessed portions can be obtained without using lift-off processing. Thereafter, after removing the fluid material film, a second insulating film is deposited on the entire surface so as to fill the grooves to flatten the surface, and this second insulating film is etched to form a field insulating film with a flat structure. The surface of the substrate in the element formation region is exposed in a state where it is embedded. Thereafter, a desired element is formed on the element forming region according to a commonly used method.

〔Effect of the invention〕

According to the method of the present invention, before depositing the first insulating film,
Since the Al film and the resist film were left behind, sufficient pretreatment could be performed before depositing the first insulating film, and deterioration of device characteristics could be prevented. Further, according to the method of the present invention, since an Al film and a resist film are not used to fill only the recessed portion with the first insulating film, there is no contamination caused by these materials, and this improves the device characteristics. There was almost no decrease, and the yield of 9 products was significantly improved.

[Embodiments of the Invention] Hereinafter, embodiments in which the present invention is applied to an MO8 type semiconductor device will be described with reference to the drawings.

Example 1 As shown in FIG. 2(a), a P-type silicon substrate 11 with a surface orientation (100) and a resistivity of 5 to 500 m is prepared, and a thermal oxide film 12 of about 300X is formed on its surface. Next, as shown in FIG. 4B, the element forming area is covered with a resist film 13 by a normal photolithography process. Next, as shown in FIG. 3(e), using the resist film 13 as a mask, the thermal oxide film 12 on the field area is etched using, for example, a reactive ion etching technique, and then the resist film 13 is etched using a reactive ion etching technique.
Then, using the thermal oxide film 12 as a mask, the shift field portion is etched by about 0.8 μm by reactive ion etching using, for example, cF'4 gas to form a recess. Next, as shown in FIG. 2(d), the resist film 13 and the thermal oxide film 12
Using the mask as a mask, fill the field part silicon substrate with -
The anti-inversion layer 14 is formed by performing LDID: ON implantation.

Next, after removing the resist film 13, as shown in FIG.
Silicon oxide film (SIO2 film) 15 is deposited by about 1 by VD method.
．． Deposit 2 μm. Before depositing this film, the entire surface of the silicon substrate is thoroughly cleaned. After depositing the 5102 film 15,
For example, 5102 membrane 1 with a buffered hydrofluoric acid solution such as ammonium fluoride.
When the entire surface of 5 is etched, the etching speed of the 8102 film on the side surface of the stepped portion is approximately 20 times greater than the etching speed of the 8102 film on the flat part, so that
The 102 film 15 is completely separated into a recess in the field region and an element forming region, and a V-shaped groove 16 is formed around the recess. Next, as shown in FIG.
5, the resist film 17 is thickly applied and the surface is almost flat. Next, as shown in FIG. The etching speed of the resist film 17 and the 5IO2 film 15 can be selected to be approximately the same. Under these conditions, reactive ion etching is performed to remove approximately half the thickness of the resist coating film.
Stop etching at the point where it is etched. This etching may include some overetching or underetching. The point is that the SlO□ film 16 in the convex part is exposed, and the 5I02 film 15 in the concave part is exposed as shown in the same figure (
As shown in 1), for example, when the entire surface is etched with an ammonium fluoride solution, the exposed convex portions of the 5IO2 film 15 and thermal oxide film 12 are removed, and when the resist film 17 is then removed, the Sio2 film 15 is buried in the concave portions. It becomes a shape. Next, as shown in (j) of the same figure, CV
For example, the 5IO2 film 18 formed by the D method or the sputtering method is
．． Completely fill the V-shaped groove 16 by depositing 0 μm uniformly,
On top of that, for example, a resist film 1 is formed as a fluid material film.
9 to flatten the surface. Then, the entire surface is etched using, for example, reactive ion etching. Here again, the conditions of reactive ion etching and the resist film 1
By appropriately selecting the heat treatment time in step 9, the resist film 19
The etching rate of the StO2 film 18 can be selected to be approximately the same. Reactive ion etching is performed under these conditions to completely etch the resist M19, and furthermore, the SlO□ is etched until the semiconductor substrate above the element formation region is exposed.
When the total etching rate of the film 18 is increased, the 5102 films 15 and 18 are completely embedded in the field portion in a flat structure as shown in the figure (kl).

After this, although not shown in the drawings, p M
An O8 type semiconductor device is formed.

According to this example, the wafer could be sufficiently pretreated before depositing the first insulating film, and deterioration of device characteristics could be prevented. Moreover, according to this embodiment, since an Al film and a resist film are not used to fill the first insulating film only in the concave portion, there is no contamination caused by them, and as a result, the device characteristics are stabilized, and the yield rate of the product is significantly reduced. Improved.

Embodiment 2 As shown in FIG. 3 (al), a P-type silicon substrate 21 with a specific resistance of 5 to 50 Ω is prepared, and a silicon nitride film 23 of about 1000× is formed on its surface via a thermal oxide film 22 of about 300×, for example. Next, as shown in FIG.
4, and using this as a mask, the silicon nitride film 23, thermal oxide film 22, and part of the semiconductor substrate 21 are etched using, for example, reactive ion etching technology, as shown in FIG. to form a recess. Furthermore, the same figure (d
), field ion implantation is performed in the field region to form an anti-inversion layer 25. Next, Lenost membrane 2
After removing 4, pre-treatment (for example, wafer treatment with a mixture of sulfuric acid and hydrogen peroxide, treatment of the wafer with a mixture of hydrochloric acid, hydrogen peroxide, and water, and treatment of the wafer with dilute hydrofluoric acid)
After thoroughly cleaning the wafer, as shown in +e+ in the same figure, a 5i02 film 26 is deposited as a first insulating film by, for example, plasma CVD, on the entire surface of the semiconductor substrate to be thicker than the steps of the recesses. Thereafter, the entire SiO2 film 26 is etched using, for example, an ammonium fluoride solution. At this time, as mentioned above, the etching speed of the 5IO2 film 26 on the side surface of the stepped portion is approximately 20 times faster than the etching speed on the flat portion.
As shown in (f) of the same figure, the 5102 film is completely separated into the recess in the field region and the element formation region, and the V
A groove 27 is formed. Thereafter, in the same manner as in Example 1, a resist film 28 is deposited as shown in FIG. 2(g), and etched by, for example, reactive ion etching until the 5to2 film 26 left on the element formation region is exposed. h)
The 5lo2 film 26 is exposed as shown in FIG. Thereafter, the 8102 film 26 is etched using, for example, an ammonium fluoride solution. At this time, the 5102 film 26 in the recessed portion is covered with the resist film 28 and is therefore not removed by etching. Etching of the 8102 film 26 with this ammonium fluoride solution stops at the surface of the silicon nitride film 23. After this, the resist film 28
If you remove , it becomes as shown in (1) K in the same figure. After that, as shown in the same figure (jl), the 5IO2 film 2 was formed by CVD.
9. A resist film 30 is further deposited and etched uniformly to expose the surface of the silicon nitride film 23 in the element formation region, as shown in FIG. 9(k). Next, for example, St
For the O□ film 26 and 29, the silicon nitride film 23 is processed,
For example, when etching is performed using the ching method for glasmae containing CF4 gas, where the etch ratio is sufficiently large, the same figure (4) is obtained.
), only the silicon nitride film 23 can be removed.

Next, as shown in FIG.

According to the method of Example 2, the same effects as in Example 1 can be obtained, and in addition, by providing the silicon nitride film 23, the 5i02 film in the field region can be formed thicker than in the element formation region. It is possible to prevent deterioration of device characteristics due to exposure of the nip of the silicon substrate in the area.
Product yield has significantly improved.

Note that in the above embodiments, the first
The reason why we used the 5i02 film produced by the CVD method as the insulating film is to take advantage of the fact that when etching the 5102 film, the etching speed at the step part is sufficiently higher than that at the flat part. The property is plasma 51
02, 5i02 film formed by sputtering method, and 81.02 film formed by a similar method. N4 M-? This is also seen in PSG films, and it is natural that such a film can be used as the first insulating film in the method of the present invention. Further, the present invention is of course applicable not only to MO8 type semiconductor devices but also to isolation between elements in bipolar type semiconductor devices.

[Brief explanation of the drawing]

Figures 1(a) to (hl) are cross-sectional views for explaining the manufacturing process of conventional semiconductor devices, Figures 2(a) to (k), and Figures 3(a) to (→, respectively) It is a sectional view showing a manufacturing process of an example of the invention. 11*21...Silicon substrate, 12.22...
Thermal oxide film, 13.24... Resist film, 14.25.
・・Inversion prevention layer, 15.26 ・・Plasma CvDSI
O2 film (first insulating film), 16.27...7-shaped groove, 1
7.28・Resist film, 11#y 29...CVD
5 i O2 film (second insulating film), 19.30... resist film (second insulating film), 23... silicon nitride film. Figure 1 Figure 1 Figure 2 Figure 2 Figure 2 Figure 83 Figure 3 Figure 3 = 20- 3J! 1

Claims (3)

[Claims] (1) A step of forming a recess in the field region of a semiconductor substrate, and a step of depositing a first insulating film on the entire surface of the substrate in which the recess is formed, the etching rate of which is higher in the stepped portion than in the flat portion. , forming a groove around the recess by etching away the stepped portion of the first insulating film, and depositing a fluid material film over the entire surface to fill the groove and make the surface flat. a step of etching at least a portion of the fluid film and the first Q insulating film to expose the surface of the first insulating film on the element forming region; and forming an element using the fluid material film as a mask. a step of etching away the first insulating film on the region; a step of removing the fluid material film and depositing a second insulating film over the entire surface so as to fill the groove; A method for manufacturing a semiconductor device, comprising the steps of: exposing a substrate surface in an element formation region by etching a film so that the surface is flat; and forming a desired element on the exposed substrate. (2) The first insulating film is a 5IO2 film, a SI3N4 film, or a PSG film formed by a plasma CVD method or a sputtering method, and the method for etching the stepped portion is an etching method using a buffered hydrofluoric acid solution. 2. A method for manufacturing a semiconductor device according to item 1. (3) The second insulating film is composed of a 5IO2 film formed by the CVD method or the Sufu 4 Tsuta method and a fluid material film formed thereon so that the surface is flat. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the etching method is a reactive ion etching method in which the etching rate is equal for the 8102 film and the fluid material film.