JPH02191357A - Formation of buried oxide film - Google Patents

Abstract

PURPOSE:To form an Si film on an SiO2 film, the Si film having satisfactory crystalline properties without being changed in its thickness depending upon an added impurity by effecting ion-implantation of silicon ion prior to ion- implantation of oxygen ion. CONSTITUTION:A silicon substrate 1 is ion-implanted with silicon ion Si<+> to form an Si<+> ion doped layer 6. The silicon ion Si<+> has a concentration peak of about 10<21>/cm<3> with a minimum value of about 10<18>/cm<3>. Then, the substrate is ion-implanted with oxygen ion O<+> over the ion-implanted layer 6 to form an O<+> ion-implanted layer 2c and Si<+> and O<+> ion-implanted layer 6c. Concentration distribution of the oxygen ion O<+> at that time is set such that it is 10<21>/cm<3> or higher. Hereby, the silicon ion implanted layer is made amorphous to permit the oxygen ion concentration distribution to be equal to a theoretical distribution. Further, any void in the silicon substrate at a silicon oxide interface is extinguished by excess silicon to assure a substantially ideal silicon oxide film interface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a buried oxide film in which oxygen ions are implanted into a silicon substrate to form a silicon oxide film in the substrate.

[Conventional technology]

FIG. 9 is a cross-sectional view showing steps in a conventional method for forming a buried oxide film. First, as shown in FIG. 9(A), oxygen ions O+ are ion-implanted into the silicon substrate 1.
An ion implantation layer 2 is formed.

FIG. 10 shows the concentration distribution of oxygen ions in this O ion-implanted layer 2. As shown in FIG. The horizontal axis represents the concentration N (numbers/cII3), and the vertical axis represents the depth X (μm) from the surface of the silicon substrate 1 downward. Further, the dashed line in the figure indicates the projection range corresponding to the peak position of the concentration distribution. This projection range is about 0.5 μm with an injection energy of 200 keys.

Next, heat treatment is performed at a high temperature of 1100°C (in some cases, about 1300°C) to eliminate the implanted oxygen ions.
The silicon atoms in the silicon substrate 1 are reacted with each other, and as shown in FIG. 9(B), S which is a buried oxide film is formed.
An iO2 film 3 is formed.

It takes 10 ions of oxygen ions to react to form a SiO2 film.
Approximately 21 pieces/cf113 are required, for example, thickness 0°4
To form a 5102 μm film, an ion implantation amount of about 3×10 ions/cLI+2 is required.

In the region where oxygen ions O
), the Si film 4 remains on the surface area of the silicon substrate 1. Semiconductor devices such as diodes, bipolar transistors, MOSFETs, and integrated circuits thereof are formed within this Si film.

[Problem to be solved by the invention]

However, in the above-mentioned ion implantation method, as shown in the enlarged view of FIG. SL from the membrane 4 worlds
There is a problem in that stacking crystal defects 13 and the like that reach the surface of the film 4 occur, making it impossible to obtain sufficient characteristics of the semiconductor device.

In addition, N-type and P-type impurities are ion-implanted into the silicon substrate 1 in advance, and N-type and P-type impurities are implanted onto the S io 2 film 3.
When forming a shaped Si film 4 (for example, a well layer) and fabricating a semiconductor device therein, use AS (hiso) or Sb'' (antimony).

P+ < phosphorus) and other N-type impurity implantation regions and B+ (
There is also a problem in that the thickness of the Si film 4 ultimately obtained differs depending on the region where P-type impurities such as boron are implanted. This will be explained below using FIGS. 12 and 13.

First, as shown in FIG. 12(A) and FIG. 13(A), ions of As''Sb+P+, etc., as an N-type impurity and B, etc. as a P-type impurity are implanted into the silicon substrate 1, and the impurity ion-implanted layers 5a, 5b is formed. Next, as shown in FIGS. 12(B) and 13(B),
O+ ion implantation layer 2 is formed by ion implantation of oxygen ions 0+.
a.

2b is formed. Then, by performing heat treatment, as shown in FIG. 12(C) and FIG. 13(c),
S io 2 films 3a and 3b are formed.

At this time, the impurity ion implanted layer 5a of the silicon substrate 1 becomes amorphous due to the ion implantation of large mass impurities such as As+ and sb, whereas the impurity ion implanted layer 5b becomes amorphous when the mass impurities are small such as B+ and P+. is hardly amorphous.

For this reason, when As+ or sb is ion-implanted, 5
The formation of the IO2 film 3a is suppressed, and the N-type Si film 4a is
The P-type St film 4b is formed thicker than the P-type St film 4b obtained by ion-implanting or P 2 . For example, “sE old C0NDUCTOR
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According to a report by Krause et al., in B and P, S i
The O 2 film 3b grows 30% larger, and the P-type Si film 4b
is approximately 0.1 μm thinner than the N-type Si film 4a. This difference in thickness of the St films 4a and 4b due to impurities is undesirable because it affects the characteristics of a semiconductor device formed therein, such as subthreshold current in a MOSFET.

This invention was made to solve the above-mentioned problems, and aims to form a Si film on an S l 0 2 film that has good crystallinity and whose thickness does not vary depending on added impurities. The purpose of this invention is to obtain a method for forming a buried oxide film that allows for the formation of a buried oxide film.

[Means to solve the problem]

The buried oxide film forming method according to the present invention has a concentration of 1021 particles/c at a first depth position of a silicon substrate and a second depth position deeper than the first depth position.
! A method of forming a silicon oxide film in the substrate by implanting oxygen ions into the substrate so that the concentration at the first depth position is 1018 ions/c.
After silicon ions are implanted into the base in advance so as to have an I113 or higher, the oxygen ions are implanted into the base, followed by heat treatment to form a silicon oxide film in the base.

Further, following the ion implantation of silicon ions, boron, phosphorus, hiso, or antimony ions are implanted into the substrate at a predetermined ion implantation amount for boron and phosphorus, and at a predetermined ion implantation amount for phosphorus and for hiso and antimony. 5X1
The amount of ion implantation may be less than 0.014 ions/cIT12.

Furthermore, before and after the silicon ion implantation,
Silicon ions may be implanted into the surface of the base so that the concentration near the surface of the base is 1018/(1)3 or more.

[Effect]

In this invention, silicon ions Si+ are implanted prior to oxygen ion O implantation, so the silicon ion implantation layer becomes amorphous and channeling development in the next oxygen ion implantation is prevented. The concentration distribution of the implanted oxygen ions becomes equal to the theoretical distribution.

Furthermore, the vacancies in the silicon substrate at the silicon oxide film interface are eliminated by the excess silicon, resulting in a silicon oxide film interface that is close to the ideal. Furthermore, in the silicon film obtained on the silicon oxide film, the nuclei of crystal defects induced by excess oxygen are eliminated by the excess silicon.

Furthermore, an N-type or P-type silicon film can be obtained by ion-implanting boron, phosphorous, histo, or antimony.

Furthermore, by implanting silicon ions in a layered manner onto the surface of the substrate, it is possible to compensate for silicon atoms released from the surface of the substrate by high-temperature heat treatment and prevent surface deterioration.

〔Example〕

FIG. 1 is a cross-sectional view showing steps according to an embodiment of the method for forming a buried oxide film according to the present invention. First, Figure 1 (A)
As shown in FIG.
A Si+ ion implantation layer 6 is formed by ion implantation. FIG. 2 shows the concentration distribution of silicon ions Si+ in this 81 ion-implanted layer 6. As shown in FIG. As shown by the dashed line in FIG. 2, the ion implantation of silicon ions S1 is performed at a depth position of the silicon substrate (one of the two It is performed so that the projected range is on the shallow side). In this embodiment, the peak concentration of silicon ions S1 is set to about 10 ions/cI113, but as will be described later, the ion implantation amount can be reduced to a minimum of about 1018 ions/c+n3.

Next, oxygen ions O+ are implanted through the Sl ion implantation layer 6 as in the conventional method, and as shown in FIG. 1(B), along with the 0 ion implantation layer 2c, St and 0
An ion implantation layer 6c is formed.

The concentration distribution of oxygen ion 0 at this time is set as shown in FIG. Then, by performing heat treatment at high temperature, the buried oxide film S
An iO2 film 3c is formed. The Sl and 0+ ion implantation layer 6C becomes the Si film 4c, and a semiconductor device is formed in this SiMJc.

In this embodiment, silicon ions Sl 2 are implanted before oxygen ions 0 2 are implanted, so there are the following advantages. First of all, since the implantation amount is 1018/cIT13 or more (7) St" ion implantation layer 6 becomes completely amorphous, channeling phenomenon is prevented in the next step of ion implantation of oxygen ions O. Therefore, the concentration distribution of the implanted oxygen ions 0+ becomes equal to the theoretical distribution.As a result, the base of the concentration distribution of oxygen ion O at a deep position in the silicon substrate 1 is expanded by channeling, and a sufficient amount of 5102 This can prevent the formation of a film.

Second, 5IO2 film 3cm5Ll! ! The vacancies in the silicon substrate 1 in the 4c world are annihilated by excess silicon (interstitial silicon), resulting in near-ideal Si02 H3c S
This becomes the i-film 4c interface. Therefore, dislocations, stacking crystal defects, etc. generated from this interface can be prevented.

Thirdly, precipitation due to excess oxygen impurities can be prevented and Si
This helps prevent crystal defects in the film 4c. This is because vacancies gather with excess oxygen as nuclei to form microcrystal defects and even stacked crystal defects, and the nuclei of these crystal defects can be eliminated by excess silicon.

In order to effectively realize the above advantages, the 5IO2 film 3c
Silicon ions S at the mSi film 4c interface (in other words, the shallower of the two depth positions of the silicon substrate 1 where the concentration value of oxygen ions 0 is around 10/cIr13)
The density value of l must be approximately 1018 pieces/mark 3 or higher. This is because if the value is less than this, the St ion implantation layer 6 will not be sufficiently amorphized, and the vacancies originally contained in the silicon substrate 1 (the number of which is about 10/c
This is because lI3) is not sufficiently annihilated at the interface of the SiO2 film 3cm5L film 4c. Silicon ion Si+
The position of the projected range of is not necessarily limited to the above embodiment.

According to the above-mentioned embodiment, a Si film 4c with extremely good crystallinity can be obtained for the above-mentioned reasons. Therefore, this Si film 4
(The characteristics of the semiconductor device formed in the tjz are comparable to those of the semiconductor device formed in the silicon substrate itself.Incidentally, the characteristics of the semiconductor device formed in the silicon substrate itself are comparable to those of the semiconductor device formed in the silicon substrate itself. When a poor Sl film 4 is used, junction leakage of the diode is large, carrier mobility is degraded, and the amplification characteristics of MOSFETs and bipolar transistors are degraded. The characteristics of the semiconductor device formed in the Si film 4c with good crystallinity have been greatly improved compared to the conventional one, and have reached the point where it can be sufficiently evaluated as an integrated circuit device.

FIG. 3 is a sectional view showing steps according to another embodiment of the method for forming a buried oxide film according to the present invention.

In this embodiment, N type or P type is preliminarily applied to the silicon substrate 1.
By ion-implanting type impurities, an N-type or P-type Si film can be obtained.
Even in the case of ion implantation with P+ or B+, in which the ion implantation region is difficult to become amorphous, or even in the case of ion implantation with As or sb, the implantation dose is as low as 5×10 ions/crlI2 or less, and the ion implantation region becomes amorphous. It is valid even if you do not.

First, as shown in FIG. 3A, silicon ions Sl+ are ion-implanted into the silicon substrate 1 to form the Sz ion-implanted layer 6, as in the previous embodiment. Next, as shown in FIG. 3(B), the S1 ion implantation layer 6 is doped with N-type or P-type impurities As, 'Sb'', B or P.
is ion-implanted to form an impurity ion-implanted layer 7.

At this time, as shown in FIG. 4, settings are made so that the ion-implanted impurities are distributed within the projection range of the previously implanted silicon ions Si. Thereafter, as in the conventional method, a step of forming a 0+ ion implantation layer 2d by ion implantation of oxygen ions 01 (FIG. 3(C)) and a step of forming a SiO2 film 3d by heat treatment (FIG. 3(D)) are performed. , an N-type or P-type Si film 4d is obtained on the 5IO2 film 3d. In this embodiment, the Si+ ion implantation layer 6 in the surface region of the silicon substrate 1 into which silicon ions St 2 have been implanted is sufficiently amorphous. Therefore, regardless of the type of impurity implanted afterwards, the concentration distribution of oxygen ions O+ implanted later is always equal to the theoretical distribution, and the resulting SiO□ film 3
The thickness of the Si film 4d is always the same as the theoretical value. In other words, As and s have relatively large masses.
Ion implantation using b+ impurities with an implantation amount of 5x10
Even if the ion implantation region does not become amorphous due to the small number of particles/cIT12 or less, or even if the ion implantation region does not become amorphous due to ion implantation with relatively small mass B+ or P+ impurities, The thickness of the Si film 4d remains the same as the theoretical value and does not change.

FIG. 5 is a cross-sectional view showing steps according to still another embodiment of the method for forming a buried oxide film according to the present invention. In this embodiment, an N-type silicon substrate 1a is prepared as the silicon substrate. Then, as shown in FIG. 5(A), this N
Silicon ions Sl 2 are ion-implanted into the shaped silicon substrate 1a to form a Si+ ion-implanted layer 6. Then,
As shown in FIG. 5B, boron ions B+, for example, are implanted into the St 2 ion implantation layer 6 using the patterned resist film 8 as a mask to selectively form a P shadow region 9. After that, the resist film 8 is removed, and then the oxygen ion implantation is performed as in the conventional method.
After the step of forming the ion implantation layer 2e (FIG. 5(C)) and the step of forming the StO film 3e by heat treatment, the StO film 3e is formed.
An N-type St film 4e and a P-type S film 9a having the same thickness are formed on the O2 film 3e. In the thus obtained N-type and P-type St films 4e and 9a, for example, CMO9IC
Integrated circuits such as the following can be formed.

FIG. 6 is a sectional view showing steps according to still another embodiment of the method for forming a buried oxide film according to the present invention. In this embodiment, silicon ions Si+ are implanted twice.

That is, first, as shown in FIG. 6(A), the first Sl
After performing ion implantation to form a relatively thick first Sl ion implantation layer 6a on the silicon substrate 1, as shown in FIG.
As shown in B), a second Si ion implantation is performed to form a relatively thin second Si ion implantation layer 6a on the first Si+ ion implantation layer 6a.
+ Form an ion implantation layer 6b. Figure 7 shows S at this time.
l Silicon ions S in ion implantation layers 6a and 6b
t is a graph showing the concentration distribution of St (L)
, Si'' (2) correspond to the first and second St+ ion implantation layers 6a and 6b, respectively.As shown in the figure, the second Si+ ion implantation is performed on the surface area to which impurity implantation is performed. .S t (1) , S t
The peak values of (2) are set to 1019 pieces/(7) 3 or more and 1018 pieces/clI+3 or more, respectively. and,
As in the past, O+ by ion implantation of oxygen ions 01
Step of forming the ion implantation layer 2f (FIG. 6(C)) and
Step of forming the StO□ film 3f by heat treatment (Fig. 6(D)
), a Si film 4f is formed on the 5IO2 film 3f.

In this embodiment, even if silicon atoms are released from the surface of the silicon substrate 1 due to high-temperature heat treatment, the second Si
Since the silicon ions Si+ of the ion-implanted layer 6b compensate for this, deterioration of the surface of the silicon substrate 1 due to high-temperature heat treatment is effectively prevented.

Therefore, an St film 4f with better crystallinity than the Si film 4C shown in FIG. 1 can be obtained.

Further, as an application example of the embodiment shown in FIG. 6, as shown in FIG. 8, it is also possible to form an epitaxial layer 10 on 4g of removed Sl film with extremely good crystallinity obtained by performing St ion implantation twice. . In this case, by using the method shown in the embodiment of FIG. 3 to make the Si film 4g a high concentration impurity layer and the epitaxial layer 10 a low concentration impurity layer,
The St film 4g can be used as the collector buried layer of the bipolar element. If the collector layer consisting of the Sl film 4g formed on the 5IO2 film 3g and the epitaxial layer 10 is insulated in the depth direction by, for example, trench isolation, a completely insulated bipolar IC can be easily formed.

Furthermore, the functions of the semiconductor device can be enhanced by using the SiO□ film formed in each of the above embodiments as a capacitor using the silicon substrate and the Si film as picture electrodes.

Furthermore, in each of the above embodiments, 8102
Although the case where a film is formed has been described, an epitaxial layer or the like is formed as a silicon base, and S io
Of course, the present invention can also be applied to the case where two films are formed.

〔Effect of the invention〕

As explained above, according to the invention set forth in claim 1,
Since silicon ions St+ were implanted prior to the ion implantation of oxygen ions O+, the silicon ion implanted layer became amorphous and the concentration of oxygen ions became equal to the theoretical distribution. The vacancies in the silicon substrate are eliminated by the excess silicon, resulting in a nearly ideal silicon oxide film interface, and furthermore, the nuclei of crystal defects induced by excess oxygen are eliminated by the excess silicon. For this reason, a Si film with good crystallinity and whose thickness does not vary depending on the added impurities is used as S t 0
This has the effect of being obtained on two films.

Further, according to the second aspect of the invention, boron, phosphorus, histo, or antimony is ion-implanted after the silicon ion implantation, so that an N-type or P-type silicon film can be obtained.

Furthermore, according to the third aspect of the invention, silicon ions are implanted in layers on the surface of the substrate before and after the silicon ion implantation, so that silicon ions are released from the surface of the substrate by high-temperature heat treatment. It is possible to prevent surface deterioration by supplementing silicon atoms.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the process according to an embodiment of the method for forming a buried oxide film according to the present invention, FIG. 2 is a diagram showing the concentration distribution of silicon ions Sl in the embodiment, and FIG. A cross-sectional view showing the process according to another example of the method for forming an oxide film, FIG. 4 is a view showing the concentration distribution of silico:/ion S1 and impurity ions in that example, and FIGS. 5 and 6 are respectively FIG. 7 is a cross-sectional view showing steps according to still another embodiment of the buried oxide film forming method according to the invention; FIG. 7 is a diagram showing the concentration distribution of silicon ions St+ in two ion implantations in the embodiment of FIG. 6; FIG. The figure is a cross-sectional view showing an application example of the embodiment shown in FIG. 6, FIG. 9 is a cross-sectional view showing a process using a conventional buried oxide film forming method, and FIG. 10 is a cross-sectional view showing the concentration distribution of oxygen ions O+ in that process. 11 are diagrams showing crystal defects in a Si film, and FIGS. 12 and 13 are cross-sectional views showing steps according to other conventional buried oxide film forming methods, respectively. In the figure, 1 is a silicon substrate, 2c, 2d. 2e and 2f are O+ ion implantation layers, 3c, 3d3e,
3f and 3g are S I O2 films, 4c, 4d. 4e, 4f, and 4g are Si films, and 6, 6a, and 6b are St+ ion-implanted layers. Note that the same reference numerals in each figure indicate the same or corresponding parts. 3113Figure 1-Silicon matrix and 2C-Ion implantation layer 2d-0Igin infiltration/Seal 3d: S.02 Shield Figure Figure Figure 10 Figure 6 Figure 12 Figure 13 Circle

Claims (3)

[Claims] (1) The concentration is 10^2^1/cm^3 or more between the first depth position of the silicon substrate and the second depth position deeper than the first depth position. A method of forming a silicon oxide film in a substrate by implanting oxygen ions into the substrate, the method comprising: forming a silicon oxide film in the substrate such that the concentration at the first depth position is 10^1^8 ions/cm^3 or more; A method for forming a buried oxide film, characterized in that silicon ions are implanted into the base in advance, and then the oxygen ions are implanted into the base, followed by heat treatment to form a silicon oxide film in the base. . (2) Following the ion implantation of silicon ions, boron, phosphorus, hiso, or antimony ions are implanted into the substrate at a predetermined ion implantation amount for boron and phosphorus, and at a predetermined ion implantation amount for hiso and antimony. ×10^1
2. The method of forming a buried oxide film according to claim 1, wherein the implantation is performed with an ion implantation amount of ^4 ions/cm^2 or less. (3) Before and after the ion implantation of the silicon ions, the concentration near the surface of the substrate is 10^1^8 ions/cm^3
2. The method of forming a buried oxide film according to claim 1, wherein silicon ions are implanted into the surface portion of the substrate to achieve the above.