JPS6046033A - Manufacture of dielectric insulator isolating substrate - Google Patents

Abstract

PURPOSE:To minimize the size and to increase the density of an isolated dielectric insulator island by expressing the relationship between the size of a corner compensating pattern and the isolating V-shaped groove width or etching depth for preventing the under cutting of the corner of the isolated insulator island in a specific relation formula. CONSTITUTION:Aqueous alkali solution as an anisotropic etchant of a single crystal silicon substrate with a crystalline surface 100 as a main surface has hydroxided potassium, pure water and isopropyl alcohol, and 15% or more of volume rate of isopropyl alcohol is added to aqueous hydroxided potassium solution having 20% or more of weight concentration of the hydroxided potassium. The size (l) of the corner compensating pattern formed at the outside corner of the etching mask of the isolated insulator island can be expressed by l=aw+b or l=ah+b in the relationship to the isolated V-shaped groove width W or the etching depth h. For example, (a) is 0.4-0.5, (b) is -9--4, and the compensating pattern satisfies l=aw+b of the correlation formula in a range of 0.4W-9<=l<=0.5W-4.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Description of the technical field to which the invention pertains The present invention relates to a method for manufacturing an insulating isolation substrate used in a semiconductor integrated circuit, particularly a monolithic semiconductor integrated circuit.

(2) Description of the prior art In a dielectric isolation type semiconductor integrated circuit device, many circuit components (transistors, diodes, thyristors, resistors, capacitors, etc.) are dielectric isolation islands (hereinafter referred to as isolation islands). The electrical characteristics of each circuit component are influenced by the geometry of the isolation island.

FIG. 1 is a partial wedge-shaped cross-sectional view of a semiconductor integrated circuit formed by a conventional dielectric isolation method. A plurality of separated single-shaped grooves 2 are formed on a substrate 1 using an anisotropic etching technique using an alkaline etching solution that has a difference in etching speed depending on the crystal plane orientation, with the (100) plane as the main plane. A dielectric insulating separation film 3, for example, a silicon dioxide film, is formed in the separated single-shaped groove, and a polycrystalline silicon layer is grown thereon as a support layer 4 by a vapor phase growth reaction. The silicon support layer is flattened to the polished surface 5 by a method such as polishing, and then the monocrystalline silicon side is polished to the polished surface 5' using this polished surface 5 as a reference surface, thereby forming the insulating isolation islands 6. is formed to a predetermined depth. Conventionally, a single-crystal silicon substrate with a crystal plane (100) as its main surface is anisotropically etched with an alkaline aqueous solution to form a single-character separation groove with a crystal plane (111) using a corrosion-resistant etching mask, such as a silicon dioxide film. When provided, as shown in FIG. 3, the outer corner portion 8a of the etching mask 8 corresponding to the bottom surface of each insulation isolation island has an etching rate intermediate between that of the crystal plane (100) and the crystal plane (111). Although the plane differs depending on the composition of the alkaline etching solution used, for example, (110) plane, (21
1) planes, (331) planes, etc. appear, and undercutting occurs where etching progresses under the etching mask. The outer corner of the isolation island is rounded, and the shape and dimensions of the isolation island are made smaller than the design values. This reduces the electrical characteristics of each circuit element built within the isolation island. In order to prevent undercutting, Japanese Patent Publication No. 17988/1988 discloses that a compensation pattern 9t is provided at the outer corner of the etching mask 8 as shown in FIG. 4 to compensate. According to this Japanese Patent Publication No. 45-17988, the fourth
The length of one side of the corner compensation pattern 9 for compensating the corner with the corner compensation pattern shown in the figure! h *W/1an54 from the width of the isolation V-shaped groove W and the width of the separation 7-shaped groove
．． The etching search h, which is uniquely determined by 7°, must satisfy the following correlation formula.

! =Kh or i≧KW/lan 54.7° −・・
-...-+1) Here, K is a hydroxide logic (KOI(), pure water (H, 0), .-p) as an alkaline etching solution.

The crystal plane (110
) with etching speed ratio of reeds, representative fishing force composition KOH: 1
5g, H*0: 50m, CHsOHtCHvOH:
For 15mi"t', the value of K is about 3/10 to 4/lO. When performing corner compensation using the above relational expression (1), at the same time An etching mask prohibited area 10 is required to avoid mutual interference of etching masks of adjacent insulation isolation islands.

Compared to a normal single-crystal silicon substrate, a dielectric insulating isolation substrate requires a large number of manufacturing processes as described in the manufacturing method shown in FIG. In some cases, it is necessary to minimize the pellet dimensions.

In order to minimize the bullet size, it is necessary to form insulating isolation islands of the minimum size necessary for each component of the semiconductor integrated circuit in view of the electrical characteristics at a high density. In order to increase the density, the external dimensions of the insulation isolation island, especially the depth of the insulation isolation island, are determined by the width of the isolation groove, and furthermore, the Diagram (C)
The minimum separation 7-shaped groove width is uniquely determined by the etching depth taking into account the polishing method by polishing.Furthermore, the dimensions of the corner compensation pattern are determined by the corresponding @V-shaped groove width (from equation 11).

However, when taking the dimensions of the corner compensation pattern according to equation (1), a prohibited area is required between other adjacent etching masks, so the minimum width of the 7-shaped separation groove is used for a pattern where the width of the 7-shaped separation groove is too narrow. In addition, the minimum possible size of the insulation isolation island is limited, and corner compensation is always required under the condition that the isolation groove width W is W)O. This has the disadvantage that it hinders the minimization of the dielectric insulation and increases the cost of semiconductor integrated circuits using dielectric isolation substrates.

(3) Detailed Description of the Invention The present invention relates to corner compensation patterns for preventing undercutting of the corners of insulation isolation islands by adjusting etching conditions regarding the composition of an alkaline etching solution, etching solution concentration, and etching solution temperature. After optimization, the relationship between the dimensions of the corner compensation pattern and the separation V-shaped groove Il@W or the etching depth h is determined as follows. =ah-)-b or! -aw-1-b ・・・・・・
To provide a method for manufacturing a dielectric isolation substrate that can be expressed by the relational expression (2), solves the above drawbacks, and makes it possible to minimize dielectric isolation islands and increase density. be.

(4) Structure of the Invention The present invention uses a composition consisting of pure hydroxide, pure water, and isopropyl alcohol as an alkaline aqueous solution as an anisotropic etching solution for a single crystal silicon substrate having a crystal plane (100) as its main surface. An etching solution composition in which inpropyl alcohol is added at a volume ratio of 15 or more to a silicon hydroxide aqueous solution with a weight concentration of 20 or more, and an outer corner of an etching mask of an insulating isolation island with respect to the etching solution. A in relation to the corner compensation hole (turn size) provided in the section with the separation V-groove width (W) or etching depth).
=aW+El or p=ah-1-b, and in this correlation equation, a is 0.4 to 0.5. b
takes a value between -9 and -4, and the corner compensation pattern is o,
Correlation formula no a within the range of 4w-9≦no≦0.5W-4
w −) Construct in a way that satisfies b.

(5) Description of examples Next, the present invention will be explained in detail.

As the alkaline etching solution in the present invention, an etching solution composed of pure hydroxide (KOH), pure water (ush), and inpropyl alcohol ((OH, ), CHOH) is used. Crystal plane of single crystal silicon substrate (1
The etching rate of 00) depends on the concentration and temperature of the etching solution. The alkaline etching solution used in the present invention has a monotonically increasing relationship between the etching rate and the etching solution temperature as shown in FIG. 6, and the etching rate is approximately 1 .mu.m/min at a solution temperature of 80.degree. On the other hand, it has been found from the experimental results that there is a relationship as shown in FIG. 7 between the weight concentration of silicon hydroxide in the etching solution and the etching rate. Figure 7 shows that the etching rate is maximum when the hydroxide theoretical weight concentration is 35%, and that if the hydroxide logical weight concentration is 20% or more, a high etching rate of 0.8 μm/min or more can be obtained. . Regarding undercutting at the corners of insulation isolation islands, there is a relationship as shown in Figure 8 between the volume concentration of inpropyl alcohol added to the silica hydroxide aqueous solution as an undercutting inhibitor. It was found that when the density was 15 or more, undercutting was slightly reduced.

From FIG. 6, FIG. 7, and FIG. 8, the etching solution in the present invention has a constitution in which isopropyl alcohol with a volume ratio of 15% or more is added to a silica hydroxide aqueous solution with a weight concentration of 20% or more. Etching conditions with less cutting and a highly efficient etching rate were found. The size of the corner compensation pattern to be added to the etching mask was determined to prevent undercutting of the corner of the isolation island under the etching conditions. Figure 9 shows the separation V
The results show the correlation between the width W of the V-groove and the size of the corner compensation pattern required.
and the size of the corner compensation pattern! It can be expressed by the correlation equation =aw+b. Here, the terms a and b are constants determined by the composition, concentration, and temperature of the alkaline etching solution used. Under the etching conditions using the etching solution of the present invention, a is 0.4 to 0.5. b has a value between 19 and -4, and the size of the corner compensation pattern is 0, 4 W -9≦! The optimum range was found to satisfy the correlation expressed by ≦0.5W-4.

(6) Detailed Description of the Invention As explained above, the present invention is directed to etching the corners of an etching mask of an insulating isolation island constructed using an aqueous solution having a composition of silicon hydroxide, pure water, and Inglobil alcohol as an alkaline etching solution. By configuring the size of the corner compensation pattern provided at the corner to satisfy the relational expression 6=a h+b or g=aw-1-b, undercutting at the corner of the insulation isolation island can be reduced. Moreover, it is possible to increase the density of the insulating isolation islands and reduce the pellet size of the semiconductor integrated circuit, which has the effect of improving the yield and reducing the cost during the manufacture of the semiconductor integrated circuit.

[Brief explanation of the drawing]

Figure 1 is a partial cross-sectional view of a semiconductor integrated circuit using the dielectric isolation method, Figure 2 (a), (b), (C), (d)
3 is a manufacturing process diagram showing the manufacturing method of the dielectric insulating isolation substrate in order of process, FIG. 3 is a schematic diagram showing undercutting under the etching mask during anisotropic etching, and FIG.
The figure is a schematic diagram showing a corner compensation pattern in which the outer corner of the etching mask is compensated to prevent under-cutting. Compensation between etching masks (Etching mask plan view showing the relationship between turn size and etching mask prohibited area. Figure 6 shows the correlation between the etching mask of the etching solution in the present invention and the etching rate of the crystal orientation (100) plane. Fig. 7 is an experimental result chart showing the correlation between the silicon hydroxide weight concentration of the etching solution in the present invention and etching speed, and Fig. 8 is a diagram showing the correlation between the etching solution and the etching rate when inpropyl alcohol is added to the etching solution in the present invention. Figure 9 is a diagram showing the experimental results showing the volume i#L concentration and the magnitude of under-force etching. Correlation showing optimization of figure 7 groove width and corner compensation pattern size
Figure 1. In the figure, 1... single crystal silicon substrate,
2...Separation 7-shaped groove, 3...Dielectric insulating separation film, 4...Support layer, 5, 5'--Polished surface, 6...Curve Insulating isolation island, 7...Circuit element,
8... Curved etching mask, 8a... Etching mask corner, 9... Middle corner compensation pattern, lO.
...This is an etching mask prohibited area. Fig. 3 Fig. 4 Fig. 2 Era 17゛Liquid 5t degree ['C] Hydroxic acid tJMi
Shi! 1寞J町Q、-ノFig. 6 Fig. 7 Iθ 2θ 3θ 40 5θ Iso lIa Pyl Alcohol Concentration [φV Fig. 5 Fig. 9

Claims (3)

[Claims] (1) In etching a single-crystal silicon substrate with an alkaline etching solution, the outside of the corner of the etching mask has a compensation type corner compensation pattern to suppress undercutting, and the size of one side of the corner compensation pattern is separated. In relation to the V-groove width W or the etching depth h that is uniquely determined from the separation V-groove width W! = a w +
b or! =ah-1-b. A method for manufacturing a dielectric insulation isolation substrate. (2) A method for manufacturing a dielectric insulating isolation substrate, in which the alkaline etching solution contains hydroxide, pure water, and isopropyl alcohol, and the volume ratio is 15 to 15. The method for manufacturing a dielectric insulating isolated substrate according to claim 1, wherein the alkaline etching solution is an alkaline etching solution containing the above-mentioned isopropyl alcohol. (3) Constant a is 0.4 to 0.5, constant Suga is -9 to -
4, the size of one side of the corner compensation/turn is Q in relation to the separation V-shaped groove width W, 4W-9≦≦0.5.
Correlation formula within the range of W -4fi! =aw −1
Claim No. (1) characterized by satisfying -b.
) or (2), the method for manufacturing a dielectric insulating isolation substrate.