JPH05315315A - Manufacture of semiconductor - Google Patents

Abstract

PURPOSE:To provide a method for drying rinse liquid which was used for rinsing after etching for short time with no damages on levers (cantilever, center lever) in forming the levers on a semiconductor substrate by eliminating a sacrifice layer through etching, in relation to improvement of a method for forming levers on the semiconductor substrate. CONSTITUTION:A lever 4, which is supported by at least one point of a semiconductor substrate 1, is formed on the semiconductor substrate 1 through a sacrifice layer. At this time, after eliminating the sacrifice layer 2 through etching, the lever 4 is rinsed by dipping it in rinse liquid, and the lever 4 is formed on the semiconductor substrate 1 by drying the rinse liquid under decreased tension.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of forming a beam-like body (cantilevered beam, doubly supported beam) on a semiconductor substrate.

A method for forming a beam-like body on a semiconductor substrate by etching a sacrificial layer after forming a beam-like body supported by the semiconductor substrate at at least one point on the semiconductor substrate via a sacrificial layer is known. It is widely used for forming the sensor part of the accelerometer manufactured by applying the micromachine technology and the capacitor of the memory cell of 64M DRAM.
The present invention relates to an improvement in the method for forming the beam-shaped body.

[0003]

2. Description of the Related Art A case of forming a fin type capacitor electrode will be described as an example of a beam-shaped body. As shown in FIG. 2A, a phosphorus-doped glass (PSG) layer 2 having a thickness of about 2000 Å is formed on a silicon substrate 1, and this is removed from a partial region to form an opening 3. Then CVD
Method is used to fill the opening 3 with the polysilicon layer 4 and PS
It is formed on the G layer 2 to a thickness of about 2000 Å, and this is patterned to form an upper surface of 2 × 1 as shown in the plan view of FIG.
A beam 4 having a size of about μm is formed on the silicon substrate 1 via the PSG layer 2. This PSG layer 2 is called a sacrificial layer because it is removed later.

After the PSG layer 2 is removed by etching using hydrofluoric acid, it is immersed in pure water for rinsing and then dried. At the time of drying, the beam-like body 4 is pulled by the underlying silicon substrate 1 by the surface tension of the rinse liquid and adheres to the silicon substrate 1 as shown in FIG. In order to prevent this, after the rinse is completed, the rinse liquid in which the silicon substrate 1 is immersed is frozen and vacuum-sucked, and the frozen rinse liquid is immediately converted into the vapor phase without passing through the liquid phase and is removed. The freeze-drying method is used.

Pure water is most suitable as the rinse liquid, but since the volume changes when frozen, the volume change is prevented by mixing isopropyl alcohol (IPA) with the pure water. Further, after the rinsing is completed, the rinse liquid is replaced with a liquid having a melting point close to room temperature, for example, tertiary butyl alcohol having a melting point of 25.6 ° C., frozen, and vacuum sucked by a vacuum device without a special cooling device. There is also known a method of drying.

As shown in FIG. 4, a film 5 of silicon nitride or silicon oxide is formed on the surface of the beam 4 made of polysilicon thus manufactured, and a polysilicon layer 6 is formed thereon. Is formed, a capacitor having the polysilicon layer 6 as one electrode and the beam 4 as the other electrode is formed.

[0007]

When the freeze-drying method is used, it is necessary to immerse the semiconductor substrate on which the beam-like body is formed in a liquid to freeze the liquid. The volume shrinkage of the liquid during freezing is required. If the rate is not zero, the beam will be damaged due to the volume change during freezing.

By the way, delicate adjustment is required to mix pure water with IPA so that the volumetric shrinkage becomes zero. In addition, there is a disadvantage that the drying time becomes long because the material is once frozen and then vacuum suction is performed for drying.

An object of the present invention is to eliminate this drawback, and when the sacrificial layer is removed by etching to form a beam-like body on the semiconductor substrate, a rinse after etching is performed without damaging the beam-like body. Another object of the present invention is to provide a method for manufacturing a semiconductor device, which has a step of drying the rinse liquid used in the above in a short time.

[0010]

The above object is to provide a beam-like body (4) supported on the semiconductor substrate (1) at least at one point on the semiconductor substrate (1) via a sacrificial layer (2). The sacrificial layer (2) is removed by etching, then immersed in a rinse solution for rinsing, the rinse solution is dried under reduced pressure, and the beam-shaped body (4) is formed on the semiconductor substrate (1). )
This is achieved by a method for manufacturing a semiconductor device, which has a step of forming. It is effective to dry the rinse solution under reduced pressure while heating.

[0011]

[Function] When the rinse liquid is dried, the beam-like body 4 and the semiconductor substrate 1
The rinse liquid 7 sandwiched between the
It is assumed that the end surface is concave as shown in. When the radius of curvature of the concave portion is ρ, the pressure P _L in the rinse liquid sandwiched between the semiconductor substrate 1 and the beam 4 and the pressure P outside and the radius of curvature ρ are P _L −P ∝−1. There is a relationship of / ρ. When the value of ρ is small, P _L becomes negative, but since the pressure is always a positive value, it is considered that P _L approaches 0 without limit. Therefore, due to the difference between the pressure P _L in the rinsing liquid and the external atmospheric pressure P acting on the upper surface of the beam-shaped body 4, the beam-shaped body 4 is moved to the semiconductor substrate 1
It is pushed down and adheres.

Therefore, if the pressure during drying is made lower than the atmospheric pressure, the force that pushes down the beam 4 is reduced, and the beam 4 does not adhere to the semiconductor substrate 1. When the rinse liquid is depressurized while being heated, the saturated vapor pressure of the rinse liquid becomes high, the vacuum suction capacity is enhanced, and the drying time is greatly shortened.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A beam-like body forming method according to an embodiment of the present invention will be described below with reference to the drawings by taking a case of forming a capacitor electrode as an example.

See FIG. 1A. PS is formed on the silicon substrate 1 by using the same method as the conventional method.
A sacrificial layer 2 made of G is formed, and this is removed from a partial region to form an opening 3. Next, the opening 3 is filled in to form a polysilicon layer 4 on the sacrificial layer 2, and this is patterned to remain in a beam shape. After the sacrificial layer 2 is removed by etching using hydrofluoric acid, it is rinsed by immersing it in a rinse tank in which a rinse liquid is injected.

After the rinse is completed, the rinse tank 8 in which the silicon substrate 1 is immersed is introduced into the vacuum container 11 of the drying device shown in FIG. , Irradiate with a mercury lamp 13 through the viewing window 12 or a heater provided separately
14 is used to heat the rinse liquid 7 to a temperature of about 95 ° C. close to the boiling point. Before the silicon substrate 1 is exposed from the rinsing liquid 7, the vacuum pump 15 is driven to adjust the pressure in the vacuum container 11 to several 1
The pressure is reduced to 00 Torr, and the rinse liquid is evaporated and dried under reduced pressure. If the drying time may be long, the rinse liquid may not be heated.

Referring to FIG. 4, if a silicon nitride or silicon oxide film 5 is formed on the surface of the beam 4 formed in this embodiment and then covered with a polysilicon layer 6, this covered polysilicon layer 6 is formed. Is used as one electrode, and the beam-shaped body 4 is used as the other electrode to form a capacitor.

[0017]

As described above, in the method for manufacturing a semiconductor device according to the present invention, since the rinse liquid is evaporated and dried under reduced pressure without being frozen, the rinse liquid may change in volume during freezing. The beam-like body can be formed without being damaged and without being attached to the semiconductor substrate. Also, by heating the rinse liquid, vacuum drying can be performed in a state where the saturated vapor pressure is high,
The drying time can be greatly reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a beam-shaped body forming process.

FIG. 2 is an explanatory view of a conventional beam-shaped body forming process.

FIG. 3 is a cross-sectional view showing a state in which a beam-shaped body is attached to a semiconductor substrate.

FIG. 4 is a cross-sectional view of a capacitor which is an example of using a beam-shaped body.

FIG. 5 is an explanatory view of the principle that the beam-like body adheres to the semiconductor substrate.

[Explanation of symbols]

 1 Semiconductor substrate (silicon substrate) 2 Sacrificial layer (PSG layer) 3 Opening 4 Beam-like body (polysilicon layer) 5 Nitride film or oxide film 6 Polysilicon layer 7 Rinsing liquid 8 Rinsing tank 11 Vacuum container 12 Viewing window 13 Mercury lamp 14 Heater 15 Vacuum pump

Claims (2)

[Claims] 1. A beam-like body (4) supported on a semiconductor substrate (1) at least at one point on the semiconductor substrate (1).
Through the sacrificial layer (2), the sacrificial layer (2) is removed by etching, the substrate is immersed in a rinse liquid for rinsing, and the rinse liquid is dried under reduced pressure. Device manufacturing method. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the rinse liquid is dried under reduced pressure while being heated.