JPH06342799A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable a semiconductor device to be lessened in number of manufacturing steps and variability of quality by a method wherein heavy metal is deposited on a photoresist and an exposed second conductivity-type semiconductor region, then the photoresist is removed, and heavy metal is driven in. CONSTITUTION:In a first step, a photoresist film 25 is uniformly formed on the surface of a silicon oxide film 23, and the photoresist fillm 25 on a P<+>-type anode region 16 is selectively removed. In a second step, the silicon oxide film 23 where the resist film 25 is removed is selectively removed by etching. In a third step, platinum 26 is deposited on the surfaces of the P<+>-type anode region 16 and the resist film 25. In a fourth step, the resist film 25 is removed by organic cleaning fluid by dissolution. In a fifth step, platinum 26 is diffused into the P<+>-type anode region 16 and an N<->-type semiconductor substrate 11 by driving. As mentioned above, heavy metal can be diffused by a thermal treatment carried out once in a fifth step, so that a semiconductor device of this constitution can be lessened in number of manufacturing steps and variability of characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a semiconductor device having a heavy metal diffused as a lifetime killer and a manufacturing method thereof.

[0002]

2. Description of the Related Art A diode is one of the most basic semiconductor devices used in electric and electronic circuits in all fields. The diode is used not only as a rectifier using its pn junction but also as a switching element.

When a diode is used as a switching element, there is a demand to increase the switching speed. To increase the switching speed, a heavy metal such as platinum is used as a lifetime killer in the semiconductor region of the diode. A method of diffusing is known. Hereinafter, a structure of a general platinum diffusion diode and a manufacturing process thereof will be described with reference to the drawings.

FIG. 5 is a sectional view showing the structure of a general platinum diffusion diode. In the figure, an n ⁻ type semiconductor region 2 is formed on the upper surface of the n ⁺ type semiconductor region 1,
A p ⁺ type anode region 3 is selectively formed on the surface of the n ⁻ type semiconductor region 2. Then, p ⁺ part of the mold anode region 3 of the surface and the anode electrode 5 is connected, the other part of the surface of the p ⁺ -type anode region 3 and the n ^-
A silicon oxide film 4 is formed on the surface of the type semiconductor region 2. Further, the cathode electrode 6 is uniformly formed on the lower surface of the n ⁺ type semiconductor region 1.

Next, the platinum diffusion step in the p ⁺ type anode region 3 of the diode shown in FIG. 5 and its vicinity will be described with reference to FIGS. 6 and 7. Figure 6
(A) is, n ^- -type semiconductor regions at the same time the p ⁺ -type anode region 3 is diffused in the surface portion of the 2, n ^- -type semiconductor region 2 and the p ⁺ -type anode region 3 of the uniform silicon oxide film on the surface 4 Is in the state of being formed.

Subsequently, in FIG. 6B, a photoresist for an anode contact is formed. In this step, first, the photoresist film 1 is uniformly formed on the surface of the silicon oxide film 4.
1 (a positive type) is formed. Then, when the semiconductor wafer is developed with a developer after selectively exposing the photoresist film 11 on the p ⁺ type anode region 3 with a mercury lamp, the exposed photoresist film 11 is selectively removed.

In FIG. 6C, silicon oxide film etching for anode contact is performed. In this step, the silicon oxide film 4 in the portion where the photoresist film 11 has been removed is removed, and a part of the surface of the p ⁺ type anode region 3 is exposed.

In FIG. 6D, the photoresist is removed. In this step, the photoresist film 11 remaining on the surface of the silicon oxide film 4 is removed by organic cleaning. Thereafter, in FIG. 7A, platinum 12 is vapor-deposited on the surface of p ⁺ type anode region 3 and the surface of silicon oxide film 4 exposed by the above process.

Subsequently, in FIG. 7 (b), the temperature is 3 ° C. at about 550 ° C.
Perform 0 minute sintering. By this sintering, platinum 12 deposited on the surface of p ⁺ type anode region 3 reacts with silicon to form silicide 13. on the other hand,
The platinum 12 on the surface of the silicon oxide film 4 does not react with the silicon oxide film 4 at this temperature and remains in the state of platinum 12.

In FIG. 7C, platinum is removed. In this process, by boiling the semiconductor wafer with aqua regia,
The platinum 12 on the surface of the silicon oxide film 4 is dissolved. on the other hand,
The silicide 13 formed near the surface of the p ⁺ type anode region 3 is not dissolved by aqua regia and remains in that region.

In FIG. 7D, 850 to 900 ° C.
Then, drive in for 1 to 2 hours. In this step, platinum contained in the silicide 13 is diffused into the p ⁺ type anode region 3 and the n ⁻ type semiconductor region 2.

Thereafter, the p ⁺ type anode region 3 and the n ⁺ type
Type semiconductor region 1 and connected to anode electrodes 5 and 5, respectively.
By forming the cathode electrode 6, the platinum diffusion diode having the structure shown in FIG. 5 is obtained.

[0013]

Focusing on the manufacturing process of the above diode, after the formation of the semiconductor region, that is, p ⁺
After forming the mold anode region 3, in order to perform platinum diffusion, the sintering process shown in FIG.
The heat treatment is performed twice in combination with the drive-in process shown in (d).

As described above, performing the heat treatment step twice has the drawback that the number of manufacturing steps is large and the manufacturing time is inevitably long. Further, in the heat treatment, the temperature of the entire semiconductor wafer becomes high, so that the distribution of impurities in the semiconductor region changes and the variation in the characteristics of the diode increases.

If, in the conventional manufacturing method, the heat treatment is simply performed once, immediately after the platinum is vapor-deposited in FIG. 7A, 850-900 as shown in FIG.
A method of performing drive-in at ℃ may be considered, but if platinum diffusion is attempted by this procedure, p ⁺ type anode region 3
The platinum deposited on the surface of the silicon oxide diffuses into the semiconductor region, but on the surface of the silicon oxide film 4, the silicon oxide film 4 and platinum react. Therefore, even if the aqua regia is boiled in the subsequent process, the platinum bonded to the silicon oxide film 4 cannot be removed.

For this reason, in the case of manufacturing a platinum diffusion diode, the heat treatment step is performed twice after the formation of the semiconductor region, so that the number of manufacturing steps is large and variations in diode characteristics are large. There was a problem. In addition to the platinum diffusion diode, this is a problem common to diodes that diffuse heavy metals as a lifetime killer.

The present invention solves such a problem, and an object of the present invention is to reduce the number of manufacturing steps of a heavy metal diffusion diode and reduce the variation in characteristics.

[0018]

The semiconductor device of the present invention comprises:
It is premised on a structure in which a semiconductor region of the second conductivity type is selectively formed on the surface of the semiconductor region of the first conductivity type.

A photoresist is formed on the surface of the insulating film uniformly formed on the upper surfaces of the first and second conductivity type semiconductor regions, and the insulating film formed on the surface of the second conductivity type semiconductor region is formed by the photoresist. Selectively etch using
After depositing a heavy metal on the surface of the photoresist and the surface of the semiconductor region of the second conductivity type exposed by the etching, the photoresist is removed, and then the heavy metal is driven in.

The method of manufacturing a semiconductor device according to the present invention is applied to a semiconductor device having a structure in which a second conductivity type semiconductor region is selectively formed on the surface of a first conductivity type semiconductor region. A first step of forming a photoresist on the surface of an insulating film uniformly formed on the first and second conductivity type semiconductor regions;
Secondly, the insulating film formed on the surface of the second conductivity type semiconductor region is selectively etched by using the photoresist.
And a third step of depositing a heavy metal on the surface of the photoresist and on the surface of the semiconductor region of the second conductivity type exposed by etching in the second step, and a fourth step of removing the photoresist. And a fifth step of driving in the heavy metal, the first step
To the fifth step are sequentially performed.

[0021]

In the method of manufacturing a semiconductor device according to the present invention, the third method described above is used.
And the second surface of the photoresist in the step of
After depositing the heavy metal on the surface of the conductive type semiconductor region,
When the photoresist on the insulating film is removed in the fourth step, the heavy metal deposited on the surface of the photoresist is removed simultaneously with the removal of the photoresist. (Lift-off) On the other hand, in the fourth step, the heavy metal deposited on the surface of the semiconductor region of the second conductivity type remains as it is without being removed. Therefore, the heavy metal can be diffused into the first and second conductivity type semiconductor regions by performing drive-in in the fifth step after the above steps 1 to 4.

As described above, the heat treatment is performed in the fifth step as described above.
Since the heavy metal can be diffused by performing only once, the number of manufacturing steps is reduced and the variation in characteristics is reduced.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device manufacturing method according to the present invention will be described below with reference to FIG.
~ It demonstrates, referring to the process drawing of FIG. Here, a platinum diffusion diode is taken as an example.

FIG. 1A shows a step of preparing a semiconductor wafer for forming a diode. Here, the n ⁺ type semiconductor region 12 is uniformly formed on the lower surface of the n ⁻ type semiconductor substrate 11 (first conductivity type semiconductor region) by impurity diffusion.

FIG. 1B shows the formation of the field oxide film. The semiconductor wafer is thermally oxidized to uniformly form silicon oxide films 13 and 14 on the surface of the n ⁻ type semiconductor substrate 11 and the lower surface of the n ⁺ type semiconductor region 12, respectively.

FIG. 1C shows an anode photoetching process. Here, by an ordinary dry etching method, the anode region and the FLR (field Li) are formed.
In order to form an m-iting ring (electric field relaxation ring), the silicon oxide film 13 is selectively removed.

FIG. 1D shows a p-type impurity introduction step. Boron, which is a p-type impurity, is introduced into the vicinity of the surface of the n ⁻ type semiconductor substrate 11 (indicated by reference numeral 15) from the portion where the silicon oxide film 13 is removed in the anode photoetching step of FIG.

FIG. 1E shows a drive-in / field oxidation step. Here, n ^- a p-type impurity near the surface of the type semiconductor substrate 11, n ^- is thermally diffused into the type semiconductor substrate 11. The drive-in temperature, time, etc. are adjusted according to the application and desired characteristics. By this drive-in, p ⁺ type anode region 16 (second conductivity type semiconductor region) and FLR 17 are formed. FLR17 is, n ^-
On the surface portion of the type semiconductor substrate 11, the periphery of the p ⁺ type anode region 16 is surrounded in a triple ring shape. Further, in this step, the field oxidation is performed at the same time when the p-type impurities are thermally diffused, the silicon oxide film 18 is formed on the surface of the n ⁻ type semiconductor substrate 11 where the regions 16 and 17 are formed, and the n ⁺ type semiconductor is formed. A silicon oxide film 19 is formed on the lower surface of the region 12. (Silicon oxide films 18, 19
Are formed so as to overlap the silicon oxide films 13 and 14, respectively, but the silicon oxide films 18 and 19 are used to make the drawing easier to see). FIG. 2A shows an EQR photoetching process. Here, EQR (equi-potential r
ing; an equipotential ring), to selectively form the silicon oxide film 1 so as to surround the end of this diode.
Remove 8.

FIG. 2B shows an n-type impurity introduction step. Here, phosphorus, which is an n-type impurity, is introduced into the vicinity of the surface of the n ⁻ -type semiconductor substrate 11 from the portion where the silicon oxide film 18 is removed in the EQR photoetching step of FIG. Further, phosphorus glass 21 is formed on the surface of the silicon oxide film 18.

FIG. 2C shows a drive-in field oxidation process. Here, after removing the phosphorus glass 21 on the surface of the silicon oxide film 18, the n ⁻ type semiconductor substrate 11 is removed.
The n-type impurities in the vicinity of the surface of are thermally diffused into the n ⁻ type semiconductor substrate 11 to form the EQR 22. Area 1
N ⁻ type semiconductor substrate 11 on which 6, 17, and 22 are formed
A silicon oxide film 23 is formed on the surface of, and a silicon oxide film 24 is formed on the lower surface of the n ⁺ type semiconductor region 12.
(Silicon oxide films 18 and 19 are omitted) Next, the platinum diffusion step will be described with reference to FIG. In the figure,
Only the peripheral region of the p ⁺ -type anode region 16, which is the main portion where this platinum diffusion process is performed, is shown.

FIG. 3A shows the p ⁺ type anode region 16 formed on the surface of the n ⁻ type semiconductor substrate 11 and the silicon oxide film 23 on the surface of the semiconductor wafer shown in FIG. 2C. It is the figure which showed.

FIG. 3B shows a step of forming a photoresist for contact. (First step) This step is
First, a photoresist film 25 (of a positive type) is uniformly formed on the surface of the silicon oxide film 23. Then, the photoresist film 25 is selectively exposed to the mercury lamp above the p ⁺ type anode region 16, and then the semiconductor wafer is developed with a developing solution. As a result, the photoresist film 25 above the p ⁺ type anode region 16 is selectively removed.

FIG. 3C shows a silicon oxide film etching step. (Second Step) In this step, the silicon oxide film 23 in the portion where the photoresist film 25 is removed is removed by using a dry etching technique such as reactive ion etching, and one surface of the p ⁺ -type anode region 16 is removed. Expose the part.

FIG. 3D shows a platinum vapor deposition process. (Third step) In this step, platinum 26 is deposited on the surface of the p ⁺ type anode region 16 and the photoresist film 25 by the vacuum evaporation method. Here, the platinum 26 on the surface of the p ⁺ -type anode region 16 and the platinum 26 on the surface of the photoresist film 25 are unlikely to be connected through the cross section of the silicon oxide film 23 and the photoresist film 25, but if the portion Even if they are electrically connected, the platinum 26 vapor-deposited on the cross-section is very thin, and step breaks occur in places, so the cross-section of the photoresist film 25 is not completely covered by the platinum 26. The method of depositing platinum may be a sputtering method or a CVD method.

FIG. 3E shows a photoresist removing step. (Fourth step) In this step, by organic cleaning,
The photoresist film 25 on the silicon oxide film 23 is dissolved and removed.

As the organic cleaning agent, a methyl-ethyl type cleaning agent is used. The cleaning operation using the methyl-ethyl-based cleaning agent is performed by immersing the semiconductor wafer, which has been subjected to the steps in FIG. 3D, in the methyl-ethyl-based cleaning agent for about 3 minutes. This methyl-ethyl type cleaning agent dissolves the positive type photoresist film 25, but does not affect the platinum 26, the silicon oxide film 23, and the silicon semiconductor (p ⁺ type anode region 16).

Therefore, if the above cleaning is performed,
The photoresist film 25 is removed. Even if the platinum 26 on the surface of the p ⁺ type anode region 16 and the platinum 26 on the surface of the photoresist film 25 are connected,
In the cross section of the photoresist film 25, platinum 26 is discontinuous in some places, and the methyl-ethyl-based cleaning agent reaches the photoresist film 25 so that it penetrates from the discontinuity, so that the photoresist film 25 is dissolved. Be removed. When the photoresist film 25 is removed in this way,
The platinum 26 deposited on the surface of the photoresist film 25 is simultaneously removed (lifted off), and the platinum 26 remains only on the surface of the p ⁺ -type anode region 16.

After cleaning the semiconductor wafer with a methyl-ethyl-based cleaning agent, the
Soak in acetone for about 3 minutes to replace the ethyl-based detergent. Then, after washing with acetone, it is further immersed in ethanol for about 3 minutes and then washed with water.

FIG. 3F shows a drive-in process.
(Fifth step) In this step, drive-in is performed at 850 to 950 ° C. for 1 to 2 hours in a vacuum or in an inert gas atmosphere, and platinum 2 on the surface of the p ⁺ -type anode region 16 is removed.
6 is diffused into the p ⁺ type anode region 16 and the n ⁻ type semiconductor substrate 11 (in some cases, up to the n ⁺ type semiconductor region 12).

Although not shown, the EQR 22 is similarly subjected to the steps of FIGS.
The surface of R22 is selectively exposed, and platinum 26 is diffused inside EQR22. FIG. 4A shows an overall configuration diagram at the stage when the process of FIG. 3F is completed.

Thereafter, in FIG. 4B, aluminum vapor deposition for electrodes is performed. In this step, the silicon oxide film 2
3, the upper surface of p ⁺ -type anode region 16, and EQ
Aluminum 27 is uniformly deposited by connecting to the surface of R22.

In FIG. 4 (c), aluminum etching is performed. By this step, the aluminum 27 is etched to be separated into an anode electrode 28 connected to the p ⁺ type anode region 16 and an EQR electrode 29 connected to the surface of the EQR 22.

Finally, in FIG. 4D, back electrode deposition is performed. Here, after removing the silicon oxide film 24 on the lower surface of the n ⁺ type semiconductor region 12, the n ⁺ type semiconductor region 1 is removed.
2 is connected to form Cr, Ni, Au 30 uniformly.

As described above, in the manufacturing method of this embodiment, in the platinum diffusion step of FIGS. 3 (b) to 3 (f), the heat treatment is performed only once in the drive-in step of FIG. 3 (f). Therefore, the manufacturing method of this embodiment has a smaller number of steps than the conventional manufacturing method shown in FIGS.

Further, when the number of heat treatments is reduced, the change in the impurity distribution in the semiconductor region is reduced, and the characteristic variation of the diode is reduced. Table 1 shows the measured values of the characteristic variations of the diode manufactured by the conventional manufacturing method and the diode manufactured by the manufacturing method of the present embodiment.

[0046]

[Table 1]

In Table 1, the number of samples is 5 in both the conventional manufacturing method and the manufacturing method of this embodiment, and the actually measured reverse recovery time is shown as the characteristic of the diode. Further, the standard deviation of each reverse recovery time is used as the value indicating the characteristic variation. While the standard deviation of the diode manufactured by the conventional method is 2.89, the standard deviation of the diode manufactured by the method of this example is 0.955, and the variation in characteristics is significantly reduced.

As described above, when the platinum diffusion diode is manufactured using the manufacturing method of this embodiment, the number of manufacturing steps is smaller than that in the conventional manufacturing method, and in addition, variations in characteristics are caused. Get smaller.

Although the positive photoresist for exposing the mercury lamp has been described in the above embodiment, the present invention is not limited to this and can be applied to the ultraviolet photoresist. Further, although the present invention can be applied to a negative photoresist, in the case of a negative photoresist, instead of performing the organic cleaning in the step of FIG. 3 (e), the photoresist is prepared by using a dedicated stripping solution corresponding to the photoresist to be used. Just remove it.

The impurities diffused in the semiconductor region as the lifetime killer may be platinum or other heavy metals such as gold.

[0051]

According to the method of manufacturing a semiconductor device of the present invention, in the step of diffusing the heavy metal into the semiconductor region as a lifetime killer, when the photoresist on the silicon oxide film is removed, the heavy metal on the surface of the photoresist is also removed at the same time. Therefore, the number of heat treatments is reduced, and as a result, variations in characteristics of the semiconductor device are reduced.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram (1) for explaining an embodiment of a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a manufacturing process diagram (2) for explaining an embodiment of the method for manufacturing a semiconductor device of the present invention.

FIG. 3 is a manufacturing process diagram (No. 3) for explaining the embodiment of the method for manufacturing the semiconductor device of the present invention, and particularly is a diagram for explaining the platinum diffusion process in detail.

FIG. 4 is a manufacturing process diagram (4) for explaining an embodiment of a method for manufacturing a semiconductor device of the present invention.

FIG. 5 is a cross-sectional view illustrating the structure of a general platinum diffusion diode.

FIG. 6 is a manufacturing process diagram (1) for explaining a platinum diffusion process in the conventional method for manufacturing a semiconductor device.

FIG. 7 is a manufacturing step diagram (2) for explaining the platinum diffusion step in the conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

11 n ^- type semiconductor substrate 12 n ⁺ type semiconductor region 16 p ⁺ type anode region 23 silicon oxide film 25 photoresist film 26 platinum

Claims (3)

[Claims] 1. A semiconductor device in which a second-conductivity-type semiconductor region is selectively formed on the surface of a first-conductivity-type semiconductor region, wherein the second-conductivity-type semiconductor region is uniformly formed on the upper surface of the first and second-conductivity-type semiconductor regions. Forming a photoresist on the surface of the formed insulating film,
The insulating film formed on the surface of the conductive type semiconductor region is selectively etched using the photoresist, and a heavy metal is applied to the surface of the photoresist and the surface of the second conductive type semiconductor region exposed by the etching. A semiconductor device, wherein the photoresist is removed after the deposition, and then the heavy metal is driven in. 2. A method of manufacturing a semiconductor device, wherein a second-conductivity-type semiconductor region is selectively formed on a surface portion of a first-conductivity-type semiconductor region. A first step of forming a photoresist on the surface of the insulating film thus formed, and a second step of selectively etching the insulating film formed on the surface of the semiconductor region of the second conductivity type by using the photoresist. And a third step of depositing a heavy metal on the surface of the photoresist and the surface of the semiconductor region of the second conductivity type exposed by etching in the second step, and a fourth step of removing the photoresist. And a fifth step of driving in the heavy metal, wherein the first to fifth steps are sequentially performed. 3. The method of manufacturing a semiconductor device according to claim 2, wherein in the fourth step, the photoresist is removed by organic cleaning.