JPS61283131A - Manufacture of semiconductor integrated circuit substrate - Google Patents

Abstract

PURPOSE:To obtain an insulator separating substrate in which the warpage of a semiconductor substrate is reduced and the etching rate of a porous Si oxide is equalized to a thermal oxide film by generating a dislocation in the substrate and then oxidizing the Si layer under oxidizing conditions capable of fluidizing the Si oxide. CONSTITUTION:An oxide resistant film 102 is accumulated on an Si substrate 101, a resist 103 is coated on the film 102, and the resist 103 is selectively removed. With the resist 10 as a mask the film 102 is then etched. Then, 3 group impurity is implanted to the Si substrate region 101 to form a high density P-type Si region 104. After the resist 103 is then removed, 5 group impurity is ion implanted to the substrate 101 to form an N-type Si region 105 under the film 102. Thereafter, an anodic oxidation is subjected in fluoric acid, and the layer 105 and the substrate 101 are completely separated by a porous Si layer 106 while altering the substrate 101 to the layer 106. Then, the layer 106 is oxidized to alter to a porous Si oxide layer 107. At this time, the condition of the primary oxidation is to cause a dislocation in the substrate 101.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to the prevention of warpage in a semiconductor integrated circuit substrate having a structure in which a single crystal semiconductor region serving as an element region of an integrated circuit is insulated and isolated by a porous Si oxide. The present invention relates to a method for forming a small number of substrates.

[Conventional technology]

The conditions required for this type of integrated circuit board using porous Si oxide are that the warpage of the board is as small as possible, and that the etch rate of the porous Si oxide used is the same as that of a single-crystal Si thermal oxide film (hereinafter referred to as , thermal oxide film) is important in the manufacturing process.

In order to completely insulate the single crystal Si layer with porous Si oxide, the porous Si oxide must be formed to have a thickness that is at least 172 times the width of the single crystal Si film. A 5- to 7-porous Si oxide is required to insulate a l〇-wide single crystal Si layer used as a typical integrated circuit pattern.

[Problems to be Solved by the Invention] When such a thick porous Si oxide is formed on one side of a Si substrate, the Si substrate will warp due to stress.

Figure 2 shows a hydrofluoric acid concentration of 40vt% and a chemical current density of 28m.
This figure shows the warpage of a 4-inch diameter Si substrate when a 7p porous Si layer is formed under A/ant conditions and oxidized at 1050°C in a wet oxygen atmosphere.

As is clear from the figure, as the oxidation time increases, S
The warpage of the i-board becomes larger. Warpage is 1100℃1
With the above method, it is difficult to form fine patterns and various uniform thin films, and it cannot be used for integrated circuit processes.

However, if the oxidation time is shortened in order to suppress warping, the porous Si oxide will not become denser due to shrinkage, and the etch rate with buffered hydrofluoric acid will be much higher than that of thermal oxide film, which is still difficult to achieve in the integrated circuit process. The problem was that it could not be used.

In addition, if the oxidation temperature is set to 1000°C or less, the warping of the Si substrate can be suppressed, but even if the oxidation time is increased because the temperature is low, the etch rate of the porous Si oxide is the same as when the oxidation time is short at 1050°C. were too large to be used in integrated circuit processes.

In this way, the warpage of the semiconductor substrate is small and the porous S
Until now, there has been no oxidation method that makes the etch rate of i-oxide equivalent to that of a thermal oxide film.

The present invention solves these conventional problems by alleviating the stress from the porous Si oxide, reducing the warpage of the semiconductor substrate, and making the etch rate of the porous 5iN1 oxide equivalent to that of a thermal oxide film. The present invention provides an insulating isolation substrate with a

[Means for solving problems]

In order to solve the above problems, the present invention forms an island-shaped single crystal semiconductor region and a porous Si layer on a semiconductor substrate, and oxidizes the porous Si layer to form a porous Si oxide. In the method for manufacturing a semiconductor integrated circuit substrate including the step of isolating part or all of the side and bottom surfaces of the single crystal semiconductor region using the porous Si oxide, after generating dislocations in the semiconductor substrate, The method is characterized in that the porous Si layer is oxidized under oxidizing conditions that allow the porous Si oxide to flow.

[Effect]

The present invention first generates dislocations in a semiconductor substrate, and then oxidizes the porous Si layer, thereby canceling out the stress received from the porous Si oxide layer due to the dislocations generated in the substrate during the oxidation. In addition to reducing warpage, the oxidation time can be varied sufficiently, which promotes densification due to shrinkage of porous Si oxide and
The etch rate of the oxide can be made almost the same as the etch rate of the thermal oxide film.

〔Example〕

Examples of the present invention will be described below.

FIGS. 1(a) to 1(f) show the process of forming a structure on a Si substrate in which a single crystal Si layer is completely separated by a porous Si oxide.

First, as shown in FIG. 1(a), an oxidation-resistant film 10 is deposited on a cz-p type, resistivity 3-5Ω, c+++ Si substrate 101.
2. For example, deposit a silicon nitride film by CVD technology,
Further, a resist 103 is applied on the oxidation-resistant film 102,
The resist 103 is selectively removed using a phosphorography technique.

Next, as shown in FIG. 1(b), the oxidation-resistant film 102 is etched using the resist 103 as a mask.

Next, as shown in FIG. 1(c), a group III impurity, such as boron, is implanted into the Si substrate region 101 from which the oxidation-resistant film 102 has been removed using a diffusion technique or an ion implantation technique. A p-type Si region 104 is formed.

Next, as shown in FIG. 1(d), after removing the resist 103, Group 5 impurities such as arsenic or hydrogen atoms are removed by S
Hay ions are implanted into the i-substrate 101 to form an n-type Si region 105 only under the oxidation-resistant film 102.

Next, as shown in FIG. 1(e), anodization treatment is performed in hydrofluoric acid, for example, at a hydrofluoric acid concentration of 40 wt.% and a current density of 30 mA/%.
The n-type Si layer 105 and the Si substrate 101 are completely separated by the porous Si layer 106 while changing the Si substrate 101 to a porous 5il 106 under the condition of aJ.

Next, as shown in FIG. 1(f), the porous Si layer 106
is oxidized to form a porous Si oxide layer 107.

At this time, the -blowing oxidation conditions are such as to cause dislocations in the Si substrate 101. When the porous Si oxide layer 107 of 7//I11 is formed on one side of the Si substrate 101, the Si substrate 101 becomes the porous Si oxide layer 1 due to the difference in thermal expansion coefficient between the porous Si oxide layer 107 and the Si substrate
Make the 07 side convex and warp. When porous Si changes to porous Si oxide, it expands or contracts. The change varies depending on the density of the porous Si layer and oxidation conditions. When the porous Si oxide contracts due to flow, dislocations are generated in the Si substrate. By generating dislocations in the Si substrate 101, the stress received from the porous Si oxide layer 107 can be offset and warpage of the Si substrate 101 can be reduced.

FIG. 3 shows the relationship between temperature and time when primary oxidation is performed in a normal pressure wet oxygen atmosphere, and shows the effective range of oxidation conditions.

In the region (1), the oxidation temperature is 950°C or less, and the porous S
i Oxide film does not cause flow. Therefore, the region <<(1) is inappropriate because the 81 substrate contains dislocations. (3
) is a temperature range in which the porous Si oxide film begins to flow, but since the oxidation time is short, the amount of flow is small and the amount of dislocations generated is also small. Therefore, the oxidation conditions are still inappropriate. Region (4) is inappropriate because the Si substrate is largely warped toward the concave side due to primary oxidation. Therefore, the effective range for -second oxidation is the region (2). In this example, the density of porous Si is L, Og/cm', and it goes without saying that when the density of porous Si is changed, the boundaries of each region change. Next, porous S
Oxidation is performed under oxidation conditions that cause the i-oxide 107 to flow, for example, in a normal pressure wet oxygen atmosphere at 1050° C. for about 50 to 100 minutes. This oxidation is called secondary oxidation. The porous Si oxide becomes dense due to the secondary oxidation, and its film quality becomes almost the same as that of a thermal oxide film.

FIG. 4 shows the secondary oxidation time and the Si substrate 10 due to secondary oxidation.
1 shows the warpage relationship. In the figure, Δ is the primary oxidation temperature of 1000°C 1 hour 100 minutes, O is 1000°C,
200 minutes, X is 900°C, 100 minutes. At Δ and O, the dislocations introduced during the -secondary oxidation absorb stress, so the change in warpage remains constant regardless of the time of the second oxidation. - The longer the blowing oxidation time, the more dislocations occur in the Si substrate lO1. As a result, the amount of stress relaxation during secondary oxidation is also large, and the change in warpage after secondary oxidation is small. That is, since the primary oxidation time is longer for 0 than for Δ, the warpage is smaller. The figure also shows the change in warpage of the Si substrate 101 when the primary oxidation conditions were 900° C. for 100 minutes. This oxidation condition is in the region (1) shown in FIG. 3, and since the porous Si oxide 107 does not flow, almost no dislocations occur in the Si substrate 101. Since dislocations are introduced into the Si substrate lot in the subsequent secondary oxidation, the change in warpage is almost the same as in FIG. 2, and the warpage is increasing. In this example, the porous Si layer was oxidized by normal pressure oxidation, but it goes without saying that high pressure oxidation and diluted oxidation can also be applied.

Thereafter, the silicon nitride film 102 is removed using warmed phosphoric acid or the like, and a device is fabricated on the exposed single crystal Si layer 105.

In the above embodiment, dislocations were generated in the semiconductor substrate by oxidation, but it goes without saying that other methods may be used to generate dislocations.

Furthermore, in the above embodiments, the porous Si layer was oxidized by wet oxidation, but dry oxidation may also be used.

〔Effect of the invention〕

As explained above, the present invention significantly reduces warpage of the semiconductor substrate by generating dislocations in the semiconductor substrate and then oxidizing the porous Si layer under oxidizing conditions in which porous Si oxide flows. , and the etch rate of the porous Si oxide can be made almost the same as the etch rate of the thermal oxide film,
Furthermore, remarkable effects such as improved crystallinity of single crystal semiconductor layers separated by porous Si oxide can be obtained by reducing warpage of the Si substrate.

[Brief explanation of drawings]

FIGS. 1(a) to 1(f) show steps of an embodiment of the method for manufacturing an integrated circuit board of the present invention having a sliding structure in which single-crystal Si islands are insulated and separated from a Si substrate by porous Si oxide. Figure 2 shows the relationship between oxidation time and warpage of the Si substrate when a porous Si layer is oxidized at 1050°C, and Figure 3 shows the temperature when primary oxidation is performed in a normal pressure wet oxygen atmosphere. FIG. 4 is a diagram showing the relationship between secondary oxidation time and warpage of the Si substrate due to secondary oxidation. DESCRIPTION OF SYMBOLS 101... P-type Si substrate 102... Oxidation-resistant film 103... Resist 104... P-type cavity concentration Si region 1O5... Separated n-type Si layer 106... Porous Si layer 107...Porous S
i Oxide 2 Figure JP3 Figure 1; Oxygen deficiency (°C)

Claims (1)

[Claims] Island-shaped single crystal semiconductor regions and porous S on a semiconductor substrate
forming an i-layer, oxidizing the porous Si layer to form a porous Si oxide, and separating part or all of the side and bottom surfaces of the single crystal semiconductor region by the porous Si oxide; In a method of manufacturing a semiconductor integrated circuit board including,
After generating dislocations in the semiconductor substrate, the porous Si
A method for manufacturing a semiconductor integrated circuit board, characterized in that the porous Si layer is oxidized under oxidizing conditions that allow the oxide to flow.