JPH0621037A - Article including fine structure and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable manufacturing of an article with only one end fixed including a fine structure including a member such as a thin plate and a rod without deforming the members permanently by taking out the article after putting a cleaning water tank under a pressure which is lower than an atmospheric pressure after a cleaning process and by drying it thereafter. CONSTITUTION:An article is manufactured which includes a fine structure wherein a member whose shape is the same as another member with only one end fixed and one or both of other constituents regarded as a rigid body exist near another member. The manufacturing includes a cleaning process in a cleaning water tank 32 and a drying process thereafter. After the cleaning water tank 32 is put under a pressure which is lower than an atmospheric pressure after the cleaning process, the article is taken out and brought to the drying process. For example, a supporting substrate 31, which is put in the cleaning water tank 32, is put in a vacuum chamber 33 after etching for forming a fine structure which constitutes one of capacitor electrodes of a DRAM. Water of the water tank 32 is discharged while keeping vacuum and the fine structure is dried.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine structure of a semiconductor device or a fine structure of a minute mechanical mechanism called a micromachine. More specifically, the present invention provides, for example, D
Articles comprising microstructures composed of thin plates or wands having one end fixed and the other end unsupported, such as found in capacitors for semiconductor devices called RAMs, and And a method of making an article comprising various microstructures.

[0002]

2. Description of the Related Art A capacitor of a semiconductor device called a DRAM referred to above is required to have a certain capacitance in a very narrow area. Therefore, it is necessary to introduce a three-dimensional three-dimensional structure such as a fin structure. A means for securing the capacitor area is adopted. Further, among the minute mechanical mechanisms of the micromachine, a fine structure having fine fins or beams to which only one is fixed may be incorporated.

As an example of such a fine structure, DRA
A three-dimensional capacitor of the M semiconductor device is shown in the sectional view of FIG. In this figure, 1 is a semiconductor substrate, 2 and 3 are capacitor electrodes, and 4 is a capacitor insulating film.

Next, an outline of the manufacturing process of the capacitor shown in FIG. 1 will be described. First, as shown in FIG. 2A, an insulating film 11, a conductive material film 12 which is one of horizontal electrodes of a capacitor, and an insulating film 11 'are sequentially laminated on a semiconductor substrate 10. The insulating films 11 and 11 'are formed by chemical vapor deposition (CVD) of SiO ₂ , for example, and the conductive material film 12 is formed by CVD of polysilicon, for example.

Next, a hole reaching the substrate is formed in a part of the laminated film, and the conductive material (polysilicon in this case) is used again.
The film 13 is deposited (FIG. 2B). This polysilicon will be connected to the polysilicon film 12 for the horizontal electrode inside the hole, and will later become a pillar for supporting this.

To divide into individual capacitors, FIG.
As shown in (c), the laminated part is etched with each pillar being the center, leaving the capacitor part.

Next, the insulating films 11 and 11 'remaining between the laminated horizontal electrodes are etched and removed, one end of which is fixed to the center pillar and the other end is supported. No microstructure 14 that constitutes one of the capacitor electrodes
Then, the silicon nitride thin film to be the capacitor insulating film 15 is chemically vapor-deposited again (FIG. 2D). Finally, a polysilicon film to be a counter electrode is formed to complete the capacitor having the three-dimensional structure shown in FIG.

In the series of manufacturing steps described above, when the insulating films 11 and 11 'are etched to form the fine structure 14 shown in FIG. 2D, and before the next silicon nitride film 15 is formed. During the treatment, water is used for chemicals and cleaning.

[0009]

The laminated portion is etched (the state shown in FIG. 2C), leaving the capacitor portion centered on the pillar of the capacitor electrode, and then the insulating films 11 and 1 are formed.
When 1'is removed and the fine structure of one capacitor electrode indicated by 14 in FIG. 2 (d) is observed, the tip portion of the fin 22 protruding from the pillar 21 is curved as shown in FIG. A phenomenon in which the fins 22 contact the tip portions of the fins 22 or the substrate 20 may be observed. This phenomenon is more likely to appear as the capacitor becomes finer and the fin spacing and fin thickness decrease. Such bending and contact of the fin structure leads to a reduction in the capacitor area, which needs to be eliminated.

Even in the same microstructure of a micromachine, the curvature of a thin plate or beam having only one end fixed or contact with other components achieves the intended purpose of the micromachine. It becomes a hindrance to and must be avoided.

It is an object of the present invention to manufacture an article comprising a microstructure including members such as thin plates and rods having only one end fixed, without permanently deforming those members. It is to provide a way to enable.

Another object of the present invention comprises a microstructure including members such as thin plates and rods which are fixed only at one end and which can escape the permanent deformation that occurs during the manufacturing process. Providing an article.

[0013]

SUMMARY OF THE INVENTION A method of making an article comprising a microstructure of the present invention includes a member having only one end fixed, and having a member having the same shape as the member in the vicinity of the member. What is claimed is: 1. A method of manufacturing an article comprising a microstructure in which one or both of another member and another component that can be regarded as a rigid body are present, which comprises a washing step in a washing water tank and a subsequent drying step. The method of including, characterized in that after the washing step, the washing water tank is placed under a pressure lower than atmospheric pressure, the article is taken out, and then the article is subjected to a drying step.

The term "fine structure" used herein refers to a structure including a member having a minute dimension on the order of micron or submicron, which is manufactured by using a microfabrication technique such as that used for manufacturing a semiconductor device or a micromachine. Is called.

In the method for producing an article comprising the fine structure of the present invention, after the washing step in the washing water tank described above, the surface tension is smaller than that of water and The article may be dipped in a liquid that is compatible with and then dried.

The water-compatible liquid is an organic solvent such as acetone, ethanol or isobutyl alcohol,
Alternatively, water mixed with a surfactant can be used. In the case of a fine structure of a semiconductor device, since the next step (for example, an insulating film growth step) immediately follows drying, the amount of impurities such as alkali metal and heavy metal contained in this cleaning liquid is restricted to 10 ppb or less. .

In the above drying step, it is advantageous to selectively heat and dry one or both of the fine structure and the substrate supporting the fine structure. Laser light irradiation, infrared irradiation, electron beam irradiation, microwave irradiation, or the like can be advantageously used as the means for this selective heating.

In the above drying step, ultrasonic waves can be applied to the substrate supporting the fine structure. Preferably, ultrasonic waves of 1 GHz or higher are used.

An article comprising the microstructure of the present invention comprises a member having only one end fixed, and a member which is proximate to this member and which can be regarded as another member having the same shape as this member and a rigid body. An article comprising a microstructure in which one or both of the following are present, where the length L of the member is such that there is only a structure in the vicinity of this member that can be considered as a rigid body: connection of

L <(2Edt ³ / 3P) ^1/4 where E: Young's modulus of the material constituting the member d: Distance between the member and the components adjacent thereto t: Thickness of the member P: Impact on the member When the external pressure is satisfied and another member of the same shape exists near the member, the relation of the following formula

L <(Ed't ³ / 3P) ^1/4 where d ′: distance between members is satisfied.

[0022]

It is considered that the water used in the washing step is the cause of the phenomenon that the member having one end fixed is deformed during the manufacturing process and comes into contact with the tip portion of another member or the substrate.

FIG. 4 shows the tip of the fin structure which is being dried after being washed with water, and shows a state in which water remains between the adjacent fins. The liquid surface of this water has a concave shape as shown in the figure, and the internal pressure p _{0 of the} water is lower than the external pressure P considering the effect of surface tension. When viewed from the fin member side, one surface receives the atmospheric pressure P, and the other surface receives the pressure equal to the internal pressure p _{0 of the} water because it is in contact with water. The deformation that occurs when the fins are dried can be explained by considering that the deformations are caused by the difference between the atmospheric pressure (external pressure) applied to each surface of the fins and the internal pressure of water.

The differential pressure (ΔP) between the atmospheric pressure applied to the fin-shaped member having the target microstructure and the internal pressure of water is calculated according to the Laplace equation as follows. ΔP = γ (1 / R ₁ + 1 / R ₂ ) ≈30 atm However, here, R ₁ = −2.5 × 10 ⁻⁶ cm (contact angle =
Assuming 0 °, the fin spacing d is 5 × 10 ^-6 cm),
R ₂ = −∞, and the surface tension γ of water is 73 dyn / cm.

Thus, in calculation, the differential pressure generated by the surface tension of water may reach 30 atmospheres,
In reality, the internal pressure of water never becomes negative, so when the differential pressure is large enough, the internal pressure of water is considered to be almost zero, and only the external pressure applied to the surface not in contact with water is Can be considered to act on. Therefore, if the external pressure value can be reduced, the pressure applied to the fins is reduced, and the fins can be prevented from bending. That is, in the method of the present invention, placing the washing water tank under a pressure lower than the atmospheric pressure and then taking out the article and subjecting it to the drying step serves to reduce the external pressure received by the member.

As is apparent from the above equation, if the surface tension of the liquid remaining between the adjacent fins is reduced, the pressure applied to the fins can be reduced. That is, after washing with water, once the article is immersed in a liquid that has a lower surface tension than water and is compatible with it, and that can easily replace the water remaining between the fins, Such pressure can be significantly reduced.

When acetone, ethanol, isobutyl alcohol, or water mixed with a surfactant is used as such a liquid, the surface tension value becomes about 20 dyn / cm, that is, about 1/4 of water. At this time, depending on the wet and dry conditions, ΔP can be expected to be 1 atm or less,
The pressure on the fins can be reduced. That is, in the method of the present invention, immersing the article in a liquid having a surface tension smaller than that of water and compatible with water serves to reduce the differential pressure applied to the microstructured member due to the reduction of the surface tension.

In the model of FIG. 4, it is assumed that the liquid surface sandwiched between the fins is concave and stable, but if appropriate energy is supplied from the outside to disturb the liquid surface, It can be expected to greatly reduce the pressure difference between the inside and outside of water.

As a method of disturbing the liquid surface, there is a method of irradiating a fin material or a supporting substrate having the fine structure with a high-density energy beam to rapidly heat it. The water in the fin gap is rapidly vaporized by heating, and the pressure generated at that time vibrates the liquid surface, making it impossible to form a stable concave surface. Laser beams, infrared rays, electron beams, microwaves and the like can be advantageously used as the energy source.

As another method of supplying energy that disturbs the liquid surface, there is a method of applying ultrasonic waves to a supporting substrate having a fine structure. It is advantageous that the frequency of the ultrasonic waves used is sufficiently high, and it is generally preferable to use ultrasonic waves having a high frequency of 1 GHz or higher. More specifically, an effect can be expected up to a wavelength of about 10 times the fin spacing, for example, 5 ×
For fin spacing of 10 ^-6 cm, the preferred frequency of ultrasound is 3 GHz and above.

As described above, supplying heating energy or ultrasonic energy to the fine structure or the substrate supporting the fine structure disturbs the liquid surface sandwiched between the fins and causes the inside of water existing between the fins to be disturbed. And greatly reduce the pressure difference between the outside.

Even if the fins bend under pressure during the drying process, the fins will not bend after the pressure causing the bending disappears, unless the tip of the fin contacts the tip of another fin or the supporting substrate. You can return to the original state. Therefore, if the thickness of the fin and the length from the supporting portion are within the range of an appropriate relationship, it is possible to avoid the phenomenon that the fin comes into contact with another fin or the supporting substrate and remains deformed. is there.

FIG. 5 (a) schematically shows how the fins adjacent to the supporting substrate are deformed toward the side of the substrate (which can be regarded as a rigid body and therefore it does not deform) under pressure. It is a figure. In this figure, the flexure amount Δ of the fin when the pressure P is received is calculated by the following equation. (In the following, to simplify the formula, the fin width w is assumed to be a unit length of 1 cm. Therefore, the fin width w does not appear in the formula given below).

Δ = PL ⁴ / 8EI = 3PL ⁴ / 2Et ³ where P = pressure acting on the fin L = fin length t = fin thickness E = Young's modulus of fin material I = second moment of area , The moment of inertia of area I is given by the following equation.

[0035]

[Equation 1]

In this case, since the fin width w is not directly related to the bending amount, the condition that the fin does not contact the substrate is that the bending amount is smaller than the distance d between the fin and the substrate, that is, Δ <d. Is. If this is rewritten for the length L of the fin, the following relational expression is obtained. L <(2Edt ³ / 3P) ^1/4 (1)

Next, as shown in FIG. 5 (b), in the case of adjacent fins, there is a possibility that they will bend toward each other. Therefore, the amount of bending allowed in this case is the fin spacing d '. 1/2, and again, if the length L of the fin is rewritten, the following relational expression is obtained. L <(Ed't ³ / 3P) ^1/4 (2)

As described above, the member designed to satisfy the formula (1) or the formula (2) does not come into contact with the adjacent member or the supporting substrate even if external pressure is applied to the member in the drying step. Instead, avoid a permanent bend.

The expression (2) can be approximately applied even when the adjacent members are different materials, that is, the Young's moduli are different, as long as the Young's moduli are not extremely different. .

[0040]

The present invention will be further described with reference to the following examples.

Example 1 Using a silicon substrate as a support substrate, a fin-shaped fine structure of polysilicon was produced.

In accordance with the method described above with reference to FIG. 2, SiO ₂ is used as an insulating film as a spacer by the CVD method.
00 Å is deposited, then 500 Å of polysilicon is also deposited as a fin material by the CVD method, and 500 Å of Si is further deposited.
An O ₂ film was deposited. Next, a hole having a diameter of 0.5 μm was drilled in a part of each of these films to reach the substrate, and polysilicon was again deposited to 500 μm.

Next, the deposited film was etched so that three types of portions having fin lengths of 0.7 μm, 1.2 μm and 2.0 μm were left around the drilled hole. Subsequently, SiO _{2 of the} spacer insulating film was removed by etching with a diluted hydrofluoric acid solution to form a fin-shaped fine structure.

The substrate supporting the fine structure taken out from the etching bath was transferred to a water washing tank, washed, and then taken out from the water tank and dried in the atmosphere. Table 1 shows the results of observing with a microscope whether the fins were curved after drying.

[0045]

[Table 1]

Since the fine structure of this example is a multi-fin structure and both of the adjacent fins may be deformed, adjacent fins contact each other at their tips and remain permanently curved. The boundary value of the fin length is (2)
Calculated from the formula, the boundary value is 1.37μ
m (P = 1 atm). According to Table 1, the fin curvature is 0.7 where the fin length is much shorter than this boundary value.
0% at μm, 1.2 μm just slightly shorter than the boundary value
It is found that the bending ratio is 43%, whereas the curvature rate at 2.0 μm, where the fin length is longer than the boundary value, is 100%. That is, it was found that at least structural parameters satisfying the formula (2) had to be selected in order to prevent the fins from bending during the water washing treatment, and the validity of the formula (2) was confirmed.

Example 2 After the steps up to the step of washing the fin-shaped fine structure through the same steps as in Example 1, as shown in FIG. 6, the supporting substrate 31 was put in the vacuum chamber 33 while being kept in the washing tank 32. Then, the internal pressure of the chamber was reduced to 0.3 atm with a vacuum pump.
While maintaining this depressurized state, the water in the water tank was discharged by the drainage pump to dry the fine structure. The results of observing the curved state of the fins after drying are shown in Table 2.

[0048]

[Table 2]

In this case, the boundary value of the fin length calculated from the equation (2) is 1.81 μm (P = 0.3 atm). This means that the curvature rate is 0 when the fin length is 1.2 μm.
%, Which is significantly improved, but it is in good agreement with the fact that the curvature rate remains 100% at the fin length of 2.0 μm.

Example 3 The steps up to the step of washing the fin-shaped microstructure with water were carried out in the same steps as in Example 1, the supporting substrate was transferred to an acetone bath, left for 1 hour, taken out, and dried. The curved state of the fin after drying was observed and the results shown in Table 3 were obtained.

[0051]

[Table 3]

Comparing the results shown in Table 3 with the results shown in Table 1, it can be seen that the curvature rate at the fin length of 1.2 μm is significantly improved.

Example 4 After the steps up to the step of washing the fin-shaped fine structure with water were performed in the same manner as in Example 1, the supporting substrate pulled out from the washing water tank was immediately irradiated with a pulsed ruby laser (wavelength 6900Å). Here, an area of 2 cm square was irradiated with energy of 0.5 J / pulse only once. Table 4 shows the results obtained by observing the curved state of the fins in the laser irradiation region.

[0054]

[Table 4]

By rapidly evaporating the water on the silicon wafer of the substrate by the laser irradiation, the number of curved fins at the fin length of 1.2 μm was clearly reduced as compared with the results shown in Table 1. I understand.

[0056]

As described above, according to the present invention,
It becomes possible to manufacture an article that comprises a microstructure that includes members that are fixedly supported only at one end, without permanently deforming those members. INDUSTRIAL APPLICABILITY The present invention can be applied to articles including fine structures such as semiconductor devices and micromachines, and greatly contributes to their development.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a fin structure capacitor in a DRAM.

2A and 2B are schematic cross-sectional views illustrating a manufacturing process of the fin structure capacitor illustrated in FIG. 1, in which FIG. 2A is a diagram showing a laminated insulating film and a conductive material film, and FIG. A diagram showing a conductive material film to be an upper fin is deposited, (c) is a diagram showing a laminated portion excluding the capacitor portion, and (d) is a new insulation around the formed fin structure. It is a figure showing a place where a film was grown.

FIG. 3 is a schematic cross-sectional view illustrating the curvature of the formed fin after drying.

FIG. 4 is a diagram illustrating a pressure acting on a fin due to surface tension of water remaining between the fins.

5A and 5B are diagrams illustrating a fin structure that bends under pressure, FIG. 5A illustrates a fin structure that deforms toward a support substrate, and FIG. 5B illustrates a direction in which adjacent fins approach each other. It is a figure explaining what transforms into.

FIG. 6 is a schematic diagram illustrating drying under reduced pressure in Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 2, 3 ... Capacitor electrode 4 ... Capacitor insulating film 10 ... Semiconductor substrate 11, 11 '... Insulating film 12, 13 ... Conductive material film 14 ... Microstructure 15 ... Insulating film 20 ... Substrate 21 ... Strut 22 ... Fin 31 ... Support substrate 32 ... Washing tank 33 ... Vacuum chamber

Front page continuation (72) Inventor Tomi Ikeda 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (4)

[Claims] 1. A member including a member fixed only at one end, and adjacent to the member, one or both of another member having the same shape as the member and another component that can be regarded as a rigid body. A method for producing an article comprising a microstructure, comprising a washing water tank washing step and a subsequent drying step, wherein the washing water tank is placed under a pressure lower than atmospheric pressure after the washing step. A process for producing an article comprising microstructures, characterized in that the article is removed from the article and then subjected to a drying step. 2. A member including only one end fixed thereto, and adjacent to this member, one or both of another member having the same shape as this member and another component which can be regarded as a rigid body. A method for producing an article comprising a fine structure, comprising a washing step in a washing water tank and a subsequent drying step, wherein the article has a surface tension lower than that of water and is compatible with water. A method for producing an article comprising a microstructure, which comprises immersing the article in water and then drying the article. 3. The method according to claim 1, wherein one or both of the microstructure and the substrate supporting the microstructure are selectively heated and dried. 4. A member including a member fixed only at one end, and adjacent to this member, one or both of another member having the same shape as this member and a structure regarded as a rigid body are present. In the case of an article including a fine structure in which the length L of the member is close to this member and there is only a structure that can be regarded as a rigid body, the following relation L <(2Edt ³ / 3P) ^1/4 However, E: Young's modulus of the material forming the member d: Distance between the member and the components adjacent thereto t: Thickness of the member P: Sufficient external pressure applied to the member and close to the member When other members of the same shape are present, the relation L <(Ed′t ³ / 3P) ^1/4 where d ′: distance between members An article comprising.