JPH02106926A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To accurately control impurity doping even in low concentration by allowing a reinforcing board to adhere, and removing a semiconductor substrate from the opposite side to the reinforcing board adhering side by polishing to a predetermined thickness. CONSTITUTION:In an ion implanting step, since the ion implantation is conducted in a state that a semiconductor substrate 21 is sufficiently thick, the implantation having a peak at a relatively deep position can bs executed, and the depth peak position Rp from the surface can be set relatively accurately. Accordingly, implanting impurity concentration can be accurately controlled. Therefore, since the substrate 21 is removed by polishing to a thin film state after a reinforcing board 22 is applied, a P-well region and a N-well region can be formed in predetermined low concentration by applying, for example, to a C-MOS integrated circuit, and a MOS transistor is formed on the sufficiently thin substrate film. Thus, a semiconductor device having stable characteristics can be obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a semiconductor device suitable for application to a semiconductor device, for example, a semiconductor integrated circuit device having semiconductor regions of different conductivity types, such as a p-well region and an n-well region. Related to manufacturing methods.

[Summary of the invention]

The present invention involves ion-implanting impurities into a semiconductor substrate, then bonding a reinforcing substrate to the semiconductor substrate, and polishing and removing the semiconductor substrate from the side opposite to the bonding side of the reinforcing substrate to obtain a predetermined thickness. By doing this, a semiconductor device having a thin film semiconductor layer into which the required impurities have been introduced can be obtained, and in this way, a semiconductor region with a low impurity concentration can be formed with a highly accurate impurity concentration even in a thin film semiconductor layer. Make it.

[Conventional technology]

When manufacturing various semiconductor devices, for example, semiconductor integrated circuits having complementary insulated gate field effect transistors, so-called C-MOS, regions of different conductivity types, p-type and n-type, or so-called p-well regions are formed on a common substrate. It is also necessary to form an n-well region. Each of these well regions must be selected to have a relatively low impurity concentration. Ion implantation is widely used as an impurity introduction technique because it allows highly accurate impurity doping control.

On the other hand, a single crystal semiconductor such as a silicon single crystal layer is
It is known that when the film is made thinner than Å, it is possible to obtain, for example, an insulated gate transistor (MOS) with characteristics suitable for the recent demands for further miniaturization, such as suppression of short channel effects.

However, when impurity ions are implanted into such a thin single-crystal layer, concentration control deteriorates, especially at low impurity concentrations.
In the case of impurity doping by ion implantation to the silicon single crystal thin film (2) formed on the insulating base consisting of Consider this in comparison with the case of ion implantation. In Figures 2 and 3, a SiO□ gate insulating film (3) is formed on the surface, and ion implantation is performed through these insulating films (3). Now, we will explain the case where ion implantation is to be performed with the target concentration profile shown by the solid line a with the concentration distribution on the horizontal axis.In this case, it is difficult to select a shallow peak position Rp of the concentration profile, so each As already shown by the broken line in the figure, the concentration distribution tends to shift in the deeper direction.When this shift occurs, in the case of FIG. Although there is a difference between the curve and the dashed line, the overall amount of impurities does not change much.

In contrast, in the case of FIG. 2, when the peak value deviates from the thin film single crystal layer (2), the substantial amount of impurity doped in the single crystal silicon layer (2) is drastically reduced.

Therefore, when subsequent annealing treatment, ie, impurity activation and impurity diffusion treatment, is performed, there is a problem that the concentration will be greatly different. That is, the distance Rp from the surface of the current peak position of ion implantation
Due to the limitations of the ion implantation equipment, the number of implanters for boron ions B is normally around 900. On the other hand, if the thickness of the gate insulating film (3) is 100, the thickness of the semiconductor layer (2) in the case of Fig. 2 is approximately 900. When it is 800 Å or less, the peak position is shifted from the semiconductor layer (2), resulting in a large difference in the substantial impurity concentration.

[Problem to be solved by the invention]

In the present invention, when manufacturing a semiconductor device having a thin film semiconductor layer, ion implantation technology is applied,
It is possible to accurately control impurity doping even at low concentrations, so that thin film integrated circuits such as C-MOS l-transistors can be manufactured with stable characteristics.

[Means to solve the problem]

In the present invention, as shown in FIG. 1A, there is a step of ion-implanting impurities into a relatively thick semiconductor substrate (21), and a step of laminating a reinforcing substrate (22) as shown in FIG. process, and as shown in Figure 1E, the semiconductor substrate (
21) from the side opposite to the bonding side of the reinforcing substrate (22) to obtain a desired thickness.

[Effect]

According to the manufacturing method of the present invention described above, in the ion implantation process, ions are implanted into the semiconductor substrate (21), that is, in a sufficiently thick state, so that ion implantation having a peak at a relatively deep position can be performed. Since the depth peak position Rρ from the surface can be set with relatively high precision, the concentration of introduced impurities can be controlled with high precision, and the reinforcing substrate (22) is finally bonded. The semiconductor substrate (21) is then removed by polishing to form a thin film, so it can be applied to, for example, a C-MOS integrated circuit to form a P-well region and an N-well region each with a required low impurity concentration, and Since the MOS transistor is formed on a sufficiently thin semiconductor film, a semiconductor device with stable and good characteristics can be obtained.

〔Example〕

Referring to FIG. 1, the p-well region and the n-well region according to the present invention
An example of obtaining a semiconductor device having a well region and a thin film semiconductor layer will be described.

First, as shown in FIG. 1A, for example, 300 to 600 μm
A semiconductor substrate (21), for example, a silicon wafer, having a large thickness of A protective surface protective film (23) is formed by thermal oxidation or the like. and,
A step of selectively ion-implanting p-type impurities, such as boron, onto the surface protective film (23) or directly into the main surface (21a) of the substrate (21), and selecting n-type impurities, such as arsenic ions, for example. island-shaped first and second impurity-introduced regions (24,) and (24,
□).

As shown in Figure 1B, a surface protective film (23
) and selectively perform mesa etching from, for example, the main surface (21a) side of the semiconductor substrate (21) to form grooves ( 25).

Then, a necessary annealing process is performed to re-diffuse and activate the impurities in the first and second impurity-introduced regions (24,) and (24□), so that each region surrounded by at least the groove (25) First and second well regions (26
Form υ and (26□).

Next, as shown in FIG. 1C, an insulating film (27) of, for example, Sin is formed by thermal oxidation on the main surface (21a) side surface of the semiconductor substrate (21) including the inside of the groove (25), Furthermore, on top of this, Sin! For example, if the thickness is 1000 Å or more, for example 1
Grooves (25 μm) are formed by chemical vapor deposition (CVD).
) to form an insulating layer (28). Then, the surface of this insulating layer (28) is polished to form a mirror surface (28a).

On the other hand, as shown in the first diagram, 5i on the main surface (22a)
An insulating layer (29) such as n1 is formed and its surface has a mirror surface (29).
A reinforcing substrate (22) made of, for example, a silicon substrate or a quartz substrate having a thickness of 300 to 600 μm as shown in FIG. 9a) is laminated. Although this bonding can be done by adhesive, it can be achieved only by the mutual matching of the mirror surfaces (28a) and (29a).

Next, as shown in FIG. 1E, the semiconductor substrate (21) is removed by chemical mechanical etching or the like from the side opposite to the side to which the reinforcing substrate (22) is bonded. The impurity-introduced well regions (26,) and (26) are separated from each other.
If etching is stopped at this position by taking advantage of the fact that the progress of etching slows down when the etching reaches 27), each region (26+) (26g) is reliably separated and left at the required thickness as a thin film semiconductor layer. be able to. In other words, the groove (
25) By pre-selecting the depth of each area (
26,) (26□) can be set to a desired thin film thickness.

After that, if an insulating film and a source and drain are formed on the thin film well regions (26,) and (26g) thus formed, respectively, C-M
MOS-1 with different channel conductivity types such as OS
- It is possible to obtain a semiconductor integrated circuit using transistors as circuit elements.

Since ion implantation can be performed with a peak position deep into a thick semiconductor substrate, it is possible to ultimately set the impurity concentration with high precision, and it is possible to obtain a semiconductor device with stable characteristics. can.

[Brief explanation of drawings]

FIGS. 1A to 1E are line sectional views of each step of an example of the manufacturing method of the present invention, and FIGS. 2 and 3 are explanatory views of the concentration distribution of impurity ion implantation. (21) is a semiconductor substrate, (22) is a reinforcement substrate, (26+
) and (26□) are the first and second well regions.

Claims (1)

[Claims] An ion implantation step for introducing impurities into a semiconductor substrate, a step for laminating a reinforcing substrate to the semiconductor substrate, and a side to which the reinforcing substrate is bonded, leaving a required thickness of the semiconductor substrate. A method of manufacturing a semiconductor device, comprising the step of polishing and removing from the opposite side.