JPH02201927A - Formation of rear sealing film for preventing auto-doping - Google Patents

Abstract

PURPOSE:To automatize the production line and improve throughput by forming a resist on the front side of a semiconductor substrate, and then forming a protective film consisting of a water soluble resin, and further applying a resist on the rear side. CONSTITUTION:After a protective film 18 consisting of a water soluble resin is applied all over the surface of a semiconductor substrate 11 by a spinner, a resist 17 is applied on thermal oxide film 12 on the rear side of the semiconductor substrate 11 also by a spinner. Namely, the semiconductor substrate 11 is chucked through the protective film 18 to apply the resist 17 on the rear side of the semiconductor substrate 11, so that the front side resist 13 is not subjected to damage during the chucking. Therefore, application of the resist 17 by manual operation becomes unnecessary. Thus the production line for semiconductor devices can be automatized and the throughput can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor integrated circuit device, and more specifically, to a method for manufacturing a semiconductor integrated circuit device, and more specifically, a method for manufacturing a semiconductor integrated circuit device, and more specifically, a method for manufacturing a semiconductor integrated circuit device. The present invention relates to a method for forming a back seal film.

[Prior Art] In semiconductor manufacturing technology, when forming various circuit elements, for example, a P-type or N-type semiconductor substrate is used, a high concentration buried layer is formed on the semiconductor substrate, and a P-type layer is formed on the semiconductor substrate. BACKGROUND ART A - type or N- type epitaxial layer is formed and various circuit elements are formed in this epitaxial layer.

FIG. 5 shows the above manufacturing process in detail.

The manufacturing process will be explained in detail based on FIG. 5.

First, a semiconductor substrate (mirror wafer) 1 as shown in FIG. 5(A) is treated at high temperature in an oxidizing atmosphere containing oxygen or water vapor, and as shown in FIG. 5(B), the semiconductor substrate 1 is heated. A thermal oxide film 2 is formed over the entire surface. Next, Figure 5 (C
) as shown.

A resist 3 is applied onto the thermal oxide film 2 on the front side of the semiconductor substrate 1. Here, a negative resist is used as the resist 3. Therefore, as shown in FIG. 5(D),
When the resist 3 is partially exposed to light using the mask 4 for forming the N++-containing layer and then developed, only the resist 3 in the exposed areas remains, and the resist 3 in other areas is removed.

In other words, only the resist 3 above the portion where the N++-containing layer is to be formed is removed, resulting in the state shown in FIG. 5(E). Next, the remaining resist 3 is hard baked, and using this as a mask, the thermal oxide film 2 underneath is selectively etched. As a result, as shown in FIG. 5(F), the thermal oxide film 2 on the portion where the N++-containing layer is to be formed is removed, and the substrate surface is exposed. At this time, the thermal oxide film 2 on the side and back surfaces of the semiconductor substrate 1 is also removed at the same time. Next, as shown in FIG. 5(G), the resist 3 used as a mask is removed.

Thereafter, using the thermal oxide film 2 remaining on the surface of the semiconductor substrate 1 as a mask, antimony (sb) is diffused as shown in FIG. 5(H) to form an N+ buried M5. Next, Figure 5 (I
), the thermal oxide film 2 used as a mask is removed. Next.

As shown in FIG. 5(J), P is applied to the entire upper surface of the semiconductor substrate 1.
- type epitaxial layer 6 is formed.

By the way, when manufacturing a semiconductor device as described above, the side and back surfaces of the semiconductor substrate 1 are also doped with antimony at a high concentration during antimony diffusion. and,
When epitaxial layer 6 is subsequently formed on semiconductor substrate 1, a problem of autodoping occurs. This autodoping phenomenon is caused by heat-induced solid phase diffusion from the semiconductor substrate 1 to the epitaxial layer 6;
The impurity (antimony) on the side and back surfaces of is once released into the gas phase, and the impurity is transferred to the epitaxial M
It is caused by being transferred to the 6 surface.

When such autodoping occurs, the impurity concentration of the epitaxial layer M6 changes, and the impurity concentration within the epitaxial layer 6 becomes non-uniform. In particular, the impurity concentration in the epitaxial layer 6 near the interface between the semiconductor substrate 1 and the epitaxial layer 6 fluctuates, and a considerable amount of the epitaxial layer 6 is wasted to reach the desired impurity concentration of the epitaxial layer 6.

Therefore, in order to avoid the above-mentioned disadvantages, conventionally, a back seal film made of a thermal oxide film 2 is formed on the back surface of the semiconductor substrate 1 before antimony diffusion, and the seal film is used to prevent the back surface of the semiconductor substrate 1 from being exposed. This was to prevent impurity doping.

Specifically, after the step shown in FIG. 5(E), a resist is applied to the back surface of the semiconductor substrate 1 (FIG. 6(A)), and a thermal oxide film 2 for forming an N+ buried shadow is selected. After etching, a back sealing film made of thermal oxide film 2 is left on the backside of the semiconductor substrate 1 as shown in FIG. 6(B), and with this sealing film attached, antimony is etched as shown in FIG. 6(C). It was spreading. This prevents antimony from being diffused into the back surface of the semiconductor substrate 1 during antimony diffusion. This prevents antimony from being transferred to the epitaxial layer 6 during formation of the epitaxial layer 6 as much as possible.

[Problems to be Solved by the Invention] Incidentally, the coating of the resist 7 on the back surface of the semiconductor substrate 1 has conventionally been performed manually.

This is because, for example, when applying the resist 7 to the back surface of the semiconductor substrate 1 using a spinner, particles (dust) are caught between the chuck of the spinner and the resist 3, damaging the resist 3 and causing This is because pinholes and the like are formed in the holes.

However, if the resist 7 is applied manually, there is a problem that not only the production line cannot be automated, but also the throughput of the production line becomes poor.

The present invention has been made in view of these problems, and an object of the present invention is to provide a method for forming a back seal film that can automate a manufacturing line and contribute to improving throughput in the manufacturing line.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] Representative inventions disclosed in this application will be summarized as follows.

In forming a sealing film made of an oxide film on the back surface of a semiconductor substrate, the present invention forms an oxide film on the entire front and back surfaces of the semiconductor substrate, and forms a photoetching film on the oxide film on the front surface side of the semiconductor substrate. A resist is applied, and then developed by photolithography and baked. A protective film made of a water-soluble resin is formed on the resist film, and then a resist film is formed on the oxide film on the back side of the semiconductor substrate. Apply and
Thereafter, the protective film is removed, and the remaining resist is used to etch the oxide film on the surface of the semiconductor substrate according to the resist opening pattern, thereby forming a back seal film made of an oxide film on the back surface of the semiconductor substrate. This is how it was done.

[Operation] According to the above-described means, after forming a resist on the front side of the semiconductor substrate, a protective film made of a water-soluble resin is formed on the resist, and the resist is applied on the back side of the semiconductor substrate. Therefore, the resist on the front side of the semiconductor substrate is protected by the protective film during chucking. Therefore, by eliminating the need to apply resist manually, it is possible to automate the semiconductor device manufacturing line and improve throughput.

[Example] Hereinafter, an example of the method for forming a back seal film for preventing autodoping according to the present invention will be described based on the drawings.

FIG. 2 shows the above manufacturing process in detail.

The manufacturing process will be explained in detail based on FIG. 2.

First, a semiconductor substrate (mirror wafer) 11 as shown in FIG. 2(A) is treated at high temperature in an oxidizing atmosphere containing oxygen or water vapor, and as shown in FIG. 2(B), the semiconductor substrate 11 is heated. A thermal oxide film 12 is formed on the entire front and back surfaces. Then,
As shown in FIG. 2C, a resist 13 is applied onto the thermal oxide film 12 on the front surface side of the semiconductor substrate 11 using a spinner. Here, a negative resist is used as the resist 13. Therefore, as shown in FIG. 2(D),
A resist 13 is formed using a mask 14a for forming an N+ buried layer.
If the area is partially exposed and then developed, only the resist 13 in the exposed area remains, and the resist 13 in the other areas remains.
3 is removed. In other words, only the resist 13 above the portion where the N+ buried layer is to be formed is removed, resulting in the state shown in FIG. 2(E). Thereafter, the remaining resist 13 was baked.

In this state, as shown in FIG. 2(F), the semiconductor substrate 11
After coating the entire surface of the semiconductor substrate 11 with a protective film 18 made of water-soluble resin such as polyvinyl alcohol resin using a spinner, a protective film 18 made of a water-soluble resin such as polyvinyl alcohol resin is coated on the entire surface of the semiconductor substrate 11 using a spinner. A resist 17 is applied to the surface. Specifically, as shown in FIG. 1(A), the back side of the semiconductor substrate 11 is adsorbed onto the chuck 19, and in that state, 5 c of a polyvinyl alcohol solution with a solid content of 15% is applied.
Dropped onto the surface of the semiconductor substrate 11 by approximately c.
was rotated at a high speed of 80 rpm for 1.0 seconds, and the excess polyvinyl alcohol solution was shaken off. Next, the semiconductor substrate 1
1 at 300 rpm for 9.0 seconds to form a film and dry it. Thereafter, baking is performed twice at 110° C. for 25 seconds. As a result, a protective film 18 having a thickness of 10,000 Å or more is formed. Thereafter, as shown in FIG. 1(B), the semiconductor substrate 11 is turned over and the semiconductor substrate 11 is placed on the chuck 19.
The surface side of 1 is attracted and a resist 17 is applied.

As described above, the resist 17 is formed on the back side of the semiconductor substrate 1.
After coating, as shown in FIG. 2(H), the semiconductor substrate 11 is rinsed with pure water to remove the upper protective film 18. After that, the remaining resist 13.17 of the semiconductor substrate 11
Using this as a mask, the thermal oxide film 12 underneath is selectively etched. As a result, as shown in FIG. 2(I), the thermal oxide film 12 on the surface of the semiconductor substrate where the N++-containing layer is to be formed is removed. Next, as shown in FIG. 2(J), after removing both resists 13 and 17, antimony (s b ) is diffused using the remaining thermal oxide film 12 as a mask.
), form N++ included/1i15. In this way, it is possible to prevent antimony from being doped into the back surface of the semiconductor substrate 11. Next, as shown in FIG. 2(L), the thermal oxide film 12 used as a mask is removed. Thereafter, as shown in FIG. 2(M), the semiconductor substrate 11
is subjected to high temperature treatment in an oxidizing atmosphere containing oxygen or water vapor to form a thermal oxide film 12 on the entire front and back surfaces of the semiconductor substrate 11. Next, as shown in FIG. 2(N), the semiconductor substrate 1
A resist 13 is applied onto the thermal oxide film 12 on the surface side of the photoresist 1 . Here, a negative resist is used as the resist 13. Therefore, as shown in FIG. 2(0), P+
If the resist 13 is partially exposed to light using the buried shadow forming mask 14b and then developed, only the resist 13 in the exposed area remains, and the resist 13 in other areas is removed. That is, only the resist 13 above the portion where the P+ buried layer is to be formed is removed, resulting in the state shown in FIG. 2(P). After that, the remaining resist 13 is baked.

In this state, as shown in FIG. 2 (Q), the semiconductor substrate 1
A protective film 18 made of water-soluble resin is formed on the surface side of 1,
Furthermore, as shown in FIG. 2(R), a resist 17 is applied onto the thermal oxide film 12 on the back side of the semiconductor substrate 11. Then, as shown in FIG.

The coating of this resist 1-17 is carried out by a method similar to that shown in FIGS. 1(A) and 1(B).

Next, as shown in FIG. 2(S), the semiconductor substrate 11 is rinsed with pure water to remove the protective film 18. after that,
The thermal oxide film 12 is selectively etched using the remaining resist 13 as a mask. As a result, as shown in FIG. 2(T), the thermal oxide film 12 in the portion where the P+ buried layer is to be formed is removed.

Thereafter, as shown in FIG. 2(U), the resist 13 and 17 serving as a mask are removed. Next, as shown in FIG. 2(V), boron (B) is applied using the remaining thermal oxide film 12 as a mask.
) Diffusion to form P+ implant N20.

In this way, it is possible to prevent boron from being doped into the back surface of the semiconductor substrate 11. Next, as shown in FIG. 2(W), the thermal oxide film 12 used as a mask is removed. Next, as shown in FIG. 2(X), the semiconductor substrate 11
A P-type epitaxial layer 16 is formed on the entire upper surface.

As described above, the thermal oxide film 12 is formed on the back surface of the semiconductor substrate 11.
By forming a sealing film consisting of the following, the following effects can be obtained.

That is, a protective film 18 is formed on the surface side of the semiconductor substrate] 1,
Since the semiconductor substrate 11 is chucked through this protective film 18 and the resist 17 is applied to the back side of the semiconductor substrate 11, the semiconductor substrate 11 is
This prevents damage to the resist 13 on the front side of No. 1. Therefore, by eliminating the need to apply the resist 17 manually, it is possible to automate the semiconductor device manufacturing line and improve throughput.

The following experiment was conducted to confirm the above effect.

As shown in the table below, this experiment was carried out using a semiconductor substrate that was not subjected to any treatment (sample 1), a semiconductor substrate that had a resist coating on the front surface and no coating on the back surface (sample 2).
The generation of particles (including pinholes) was investigated by surf scanning on the semiconductor substrate (sample 3) on which resist coating was performed using a spinner without forming the protective film 18 and the semiconductor substrate of this example (sample 4). . In the table below, × indicates that the process has not been carried out, and ○ indicates that the process has been carried out. This photolithography process requires an atmosphere of class 100 cleanliness.
Each step was performed under the following conditions.

(1) Resist coating process Negative resist OMR-85 (30 cp) is coated on the semiconductor substrate 11 while rotating at a high speed of 500 rpm, and the resist 1 is coated on the front surface side of the semiconductor substrate 19 to a thickness of 7000 nm.
3 was formed. Thereafter, baking was performed twice at 110° C. for 25 seconds.

(2) Alignment process Exposure was performed for 3.0 seconds at an illuminance of 3.6 mW/aJ using a contact aligner.

(3) Development process Spray development was performed for 10 seconds using xylene as a developer. Furthermore, after washing with butyl acetate as a rinse solution, baking was performed twice at 150° C. for 25 seconds.

(3) Protective film coating step A polyvinyl alcohol solution with a solid content of 15% is dropped onto the surface of the semiconductor substrate 11 by approximately 50Q.
The film was formed and dried by rotating at 0 rpm for 10 seconds.

Thereafter, baking was performed twice at 110° C. for 25 seconds.

As a result, a protective film 18 having a thickness of 10,000 layers was formed.

(4) Back Coating Step Negative resist hOM R-85A (30cp) was coated on the back side of the semiconductor substrate 19 while rotating the semiconductor substrate 11 at a high speed of 3000 rpm to form a resist 17 with a thickness of 10000 mm. Note that baking was not performed in this step.

(5) Etching process Etching was performed for 60 minutes using 1:9 buffered fluoric acid as an etching solution. In this process, considerable overetching was performed to make the pinholes thicker.

(6) Washing process H, 5o4-H, O, (110°C) Teno washing, washing with dilute hydrofluoric acid, washing with NH, 0H-H, O, (80°C),
Ultrasonic cleaning and isopropyl alcohol steam cleaning were performed for 10 minutes each.

Sample 1, sample 2. The generation status of particles corresponding to samples 3 and 4 is shown. Note that in FIGS. 3A to 3D, the number of particles is shown on the vertical axis, and the particle size is shown on the horizontal axis.

Here, in sample 1 of FIG. 3(A), the number of particles on the surface of the semiconductor substrate 11 when it was left in the atmosphere of the photolithography process was counted. Furthermore, in samples 2 to 4 in FIGS. 3B to 3D, particles refer to pinholes formed in the thermal oxide film 12. That is, in samples 1 to 4, pinholes generated in the thermal oxide film 12 were measured after a photolithography process was performed using the photoresist 13 damaged by particles. In this case, the pinholes are overetched (usually 15 minutes of etching, but 60 minutes of etching) to make the pinholes thicker than they actually are.

From these drawings, it can be seen that sample 3, in which the resist coating was performed using a spinner without forming the protective film 18, had 2.
The number of particles larger than 31 μm is orders of magnitude larger, and in the semiconductor substrate of this example, that is, sample 4, the number of particles larger than 2.31 μm is significantly reduced.
It can be seen that the number of particles for sample No. 3 is approximately the same as sample 2, which is not coated on the back side.

Further, FIG. 4 shows the relationship between the thickness of the protective film 18 and the number of particles, and it is confirmed that the thicker the protective film 18 is, the smaller the number of particles is. This fourth
The figure shows the average value and fluctuation range of four semiconductor substrates.

Although the invention made by the present inventor has been specifically explained above based on examples, it goes without saying that the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Nor.

For example, in the above embodiment, when forming the backside protective film of the semiconductor substrate 11, a water-soluble protective film made of polyvinyl alcohol is formed on the front side of the semiconductor substrate 11, but cellulose is used as the water-soluble resin. A derivative may also be used.

[Effects of the Invention] Typical effects of the invention disclosed in this application are explained below.

That is, in forming a sealing film made of an oxide film on the back surface of a semiconductor substrate in order to prevent autodoping from the semiconductor substrate, the present invention forms an oxide film on the entire surface of the semi-octagonal substrate, and A resist film for photo-etching is applied on the oxide film on the front side, and then developed and baked using the usual photo-etching technique, and a water-soluble resin is applied on the resist film. A resist film is applied on the oxide film on the back side, then the water-soluble resin is removed, the oxide film is etched using the resist as a mask, and the oxide film remaining on the back side of the semiconductor substrate is used as a back sealing film. This prevents damage to the resist on the front side of the semiconductor substrate 1 during chucking. Therefore, there is no need for manual resist coating, and it is possible to automate the semiconductor device manufacturing line and improve throughput.

Furthermore, even when applying photoresist coating to the back surface of a thermally oxidized semiconductor substrate that has been manually patterned with photoresist, the method of the present invention prevents instruments and other objects from coming into direct contact with the resist film on the surface of the substrate. It is effective in protecting the surface and preventing the backside coating resist from wrapping around and staining the surface.

[Brief explanation of the drawing]

FIGS. 1(A) and (B) are partial vertical cross-sectional views of a semiconductor substrate and a chuck showing the protective film forming process and resist coating process of the embodiment, and FIGS. 2(A) to (X) are Vertical cross-sectional views showing each process; Figures 3 (A) to (D) are graphs showing the state of particle generation in various samples; Figure 4 is a graph showing the relationship between the thickness of the protective film and the number of particles; Figures (A) to (J) are longitudinal cross-sectional views of a semiconductor substrate at each step, showing a conventional semi-continuous edge forming process. FIGS. 6(A) to 6(C) are longitudinal cross-sectional views of the semiconductor substrate at each step, showing the steps of forming the back seal film. 11...Semiconductor substrate, 12...Oxide film, 13°17...Resist, 18...Protective film. Figure 1 (A) (B) Figure 2 (A) CB) (E) ) Figure 1゜PVA Ryotsu (X1000 people) Otsu Gorge School 4 @ Mosquito/crn" Nogura 24 Kuru (4 old) 4 huan/cm" Nogu-Ishibei Kuru (4th) Gorge Isthmus planting/.m2 II Lid history/cm2 He〇-Takumi-Δkuru (A solid) Fig. 5 (A) (E3) Fig. (H) (J)

Claims (1)

[Claims] 1. In forming a sealing film made of an oxide film on the back surface of the semiconductor substrate in order to prevent autodoping from the semiconductor substrate during vapor phase single crystal growth of an integrated circuit element structure, the semiconductor substrate An oxide film is formed on the entire front and back surfaces of the semiconductor substrate, a resist for photolithography is applied on the oxide film on the front side of the semiconductor substrate, and then a resist for photolithography is developed and baked using a photolithography technique. A protective film made of a water-soluble resin is formed on the semiconductor substrate, a resist is applied on the oxide film on the back side of the semiconductor substrate, the protective film is removed, and the remaining resist is used to coat the semiconductor substrate. A method for forming a back seal film for preventing autodoping, characterized in that the oxide film on the surface of the substrate is etched according to the resist opening pattern to form a back seal film made of an oxide film on the back surface of the semiconductor substrate. 2. The method for forming a back seal film for preventing autodoping according to claim 1, wherein a polyvinyl alcohol resin is used as the water-soluble resin.