JPS6351625A - Heat treatment method - Google Patents

Abstract

PURPOSE:To reduce the irregularity of hFE in each semiconductor wafer of a transistor obtained by performing a heat diffusion treatment by a method wherein a radiant heat preventing member is arranged within the specific range on the entrance side of the material to be heat-treated, and the length of a substantially temp.-equalization region is made larger sufficiently. CONSTITUTION:A radiant heat preventing member 6, with which the radiation of heat of the radiant heat of the material to be heat-treated will be blocked or reduced, is arranged on the position separated by 10-30 cm from both end parts of the opposite side of the end part of the entrance and the exit of the material to be heat-treated of a heat equaliation region. Semiconductor wafers of 4 cm in diameter are arranged at the pitch of 9.52 mm on a boat 4 of 60 cm long in the heating furnace having the heat-equalization region of about 62 cm long. A semiconductor wafer similar to the materials 3 to be heat-treated, namely, dummy semiconductor wafers, are arranged as a radient heat preventing member 6 on the part located at the distances d1 and d2 from both ends of the intrinsic heat-equalization region. Then, the length L of the substantial heat-equalization region becomes 28 cm when the above-mentioned distances are d1=d2=10 cm, and the substantial lengthof the heat-equalization region is increased remarkably when compared with the heat-equlization length of 12 cm heretofore in use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat treatment method that is applicable to, for example, thermal diffusion treatment of impurities to semiconductor wafers.

[Summary of the invention]

In the present invention, when heat treatment is performed using a heating furnace that forms a substantially uniform heating temperature region without an object to be heat treated, the above-mentioned region is placed at a position within a specified distance and range from the above-mentioned region. A radiant heat prevention member having the effect of blocking or reducing radiant heat dissipation via the disposed heat treatment object is disposed to expand the length of the area where the heating temperature is substantially uniform.

[Conventional technology]

2. Description of the Related Art In the manufacturing process of various semiconductor devices, thermal diffusion treatment of impurities, for example, heat treatment such as solid phase diffusion treatment is performed.

In this heat treatment method, for example, as shown in FIG. 14, a heating means (2), such as a resistance heater, is arranged around the outer periphery over a required range along the longitudinal direction of the furnace core tube (1).
When a gas such as 02 gas is flowed into the core tube (11) as shown by the arrow a, the heating temperature becomes almost uniform along the longitudinal direction in the core tube (11). A region, specifically a region in which the temperature variation is within, for example, ±l'c (hereinafter referred to as a soaking region) is formed.In this soaking region, a plurality of objects to be heat treated (3), for example, are formed. A boat (4) on which semiconductor wafers are arranged,
After the insertion, the object to be heat treated (3) is subjected to the required heat treatment. (5) is an operating lever for operating the boat (4) in and out.

However, semiconductor devices manufactured by such a heat treatment method have relatively large variations in characteristics depending on the location of the wafers in the heating furnace, that is, the furnace tube (1). When transistors are fabricated on a semiconductor wafer, variations occur in the common emitter amplification factor hFli. That is, for example, in a semiconductor wafer in which base regions are formed in an array, a window is formed in the emitter forming portion on each base region.
A doped oxide doped with an impurity was deposited on the wafer through a second insulating layer, and the impurity was diffused by the above-mentioned heat treatment method to form an emitter to fabricate a transistor. In this case, the change in hpa depending on the location of each wafer causes large variations as shown in FIG.

In FIG. 15, the horizontal axis indicates the wafer placement position, and the gas flow is from the right side in the figure and heat treatment is performed.

The reason why hFB+ changes significantly depending on the position of the semiconductor wafer in the heating furnace, especially the position in the longitudinal direction, is because even if the semiconductor wafer is placed in the area originally set as the soaking area, the temperature is actually uniform. It was determined that this was due to a breakdown in thermal conditions.

In other words, the length of the soaking area in the heating furnace explained in FIG. 14 without inserting the object to be heat treated (hereinafter, this soaking area will be referred to as the original soaking area, and its length will be referred to as the original soaking length) is When the temperature was approximately 70C11, 4-inch diameter wafers as heat-treated objects (3) were arranged on a boat (4) having approximately the same length as this, and this was placed in the original soaking area. When we measured the heat distribution in the longitudinal direction in the heating furnace under this condition, we found that the length of this soaking area, that is, the length of the neo heating area within a variation of less than 1°C is only 12G! 1
It turns out that it can be shortened to . In the original soaking area in the heating furnace described above, if semiconductor wafers with a diameter of 4 inches are arranged and inserted on a boat having an effective length that spans almost the entire length of the original soaking area, the maximum
It has been found that when semiconductor wafers having a diameter of 3 inches are arranged in the same manner, a temperature difference of about 5° C. can occur.

[Problem that the invention seeks to solve]

The present invention solves the problem of shortening the length of the soaking area in the heat treatment method described above, and performs uniform heat treatment, such as thermal diffusion of impurities, on a large number of objects to be heat treated, such as semiconductor wafers, and is used in the manufacture of transistors, for example. hrv
The present invention provides a heat treatment method that allows semiconductor devices with uniform r to be manufactured with good yield.

That is, in the present invention, as a result of various experiments and considerations, the object to be heat treated is to be subjected to heat treatment, for example, diffusion treatment, in a heating furnace that forms the original soaking area over the required range as described above. In other words, it was found that when a semiconductor wafer is inserted, for example, the temperature decreases within the original heat-uniforming area due to radiation heat dissipation through the semiconductor wafer itself, and this causes a shortening of the actual length of the heat-uniforming area. Based on this investigation, we have discovered a heat treatment method that aims to substantially expand the length of the soaking area.

(Means for Solving the Problems) In the present invention, as described above, a substantially uniform heating temperature region, that is, an original soaking region is formed along the longitudinal direction when the object to be heat treated is not inserted. In a heat treatment method, heat treatment is performed by inserting and arranging the objects to be heat treated in the original soaking area of the heating furnace using a heating furnace. To block heat dissipation due to radiation through the object to be heat treated, or at a position 10 cm to 30 CI11 from the original heat soaking area toward the entrance/exit side, or toward the entrance/exit side and the opposite side, respectively. The desired heat treatment is performed by arranging a radiant heat prevention member that has the effect of reducing radiation heat.

[Effect]

In the case of the above-mentioned heat treatment method, heating is performed at least within a range of 10 to 30 cm M1 from the original soaking area toward the entrance/exit side of the heat treatment object placed in the original soaking area inside the heat treatment object. By arranging a member that blocks or reduces heat dissipation due to radiation through the body, the heat dissipation due to radiation is prevented or drastically reduced, so that the actual length of the uniform heating area is equal to or even greater than the original length of the uniform heating area. Expanded above.

〔Example〕

An embodiment of the present invention will be described with reference to FIG.

In FIG. 1, parts corresponding to those in FIG. 14 are designated by the same reference numerals and redundant explanation will be omitted. In the figure, (7) indicates a gas inlet, and (8) indicates a gas outlet. In addition, (9) indicates the entrance and exit of the object to be heat treated (3), and in the figure, the lid body (1
0) shows the closed state of the lid, but this lid body (
lO) is not necessarily required, and it is also possible to substantially block it with an air curtain or the like.

Also in the present invention, the heating means (
The object to be heat treated (3), for example, a boat (4) in which semiconductor wafers are arranged in the original uniform area formed by step 2).
and perform the desired heat treatment. However, especially in the present invention, the object to be heat treated is placed at a position within a range of 10 to 30 cm from the end of the original soaking area on the side of the entrance/exit of the object to be heat treated, or from this end and both ends on the opposite side. A radiant heat prevention member (6) that blocks or reduces heat dissipation due to radiant heat is arranged. This member (6) may be, for example, a wafer that is the same as the semiconductor wafer of the object to be heat-treated (3), that is, a so-called dummy semiconductor wafer having the same dimensions and shape, and placed in parallel with the object to be heat-treated, directly facing the object.

This radiant heat prevention member (6) can be placed, for example, at the extended end of the boat (4), or, as shown in the figure, an auxiliary boat (11) can be provided on the operating rod (5) and placed on top of this. You can also do it.

In this case as well, the heat treatment, such as thermal diffusion, is carried out in a predetermined part of the reactor core tube (1) in the original soaking area while gas, for example, 02 gas is fed into the reactor core tube (11) at a flow rate of, for example, 5 I/min. A stable state is formed, and in this state, the boat (4) on which the objects to be heat treated are placed is placed so that the center of arrangement of the objects (3) to be heat treated is approximately located at the center of the original soaking area. At the same time, the member (6) is placed at the above-mentioned predetermined portion and heat treated.

In the above heat treatment method, the original soaking area length is approximately 6
The length of the boat (4) in the heating furnace was set to 2 cm.
Using a 0-mouth boat, place 9. on top of it in the area shown in box B.
Semiconductor wafers with a diameter of 4c11 are arranged with a pitch of 52u, and the distance at from both ends of the original soaking area is
and dt, a semiconductor wafer similar to the object to be heat treated (3), that is, a dummy semiconductor wafer, is placed as an auxiliary member as a radiation heat prevention member (6), and each distance is %11t d1.
and dt (d□=d2) are respectively 10cm and 2
Figure 2 shows the temperature distribution measured in the longitudinal direction inside the reactor core tube at 0 cm and 30 cm, respectively.

Figures 3 and 4: Content curves (21) (31) and (
41). In each figure, the horizontal axis indicates the longitudinal position in the core tube (1), with the origin being the center position of the original soaking area. In each figure, the range in which the temperature distribution is within ±1°C is the area surrounded by a broken line A.

That is, according to this, when d1 and d2 = 10 cm (Fig. 2), the effective soaking area length is 28c+a, and when d1 = d2-20CI+ (Fig. 3), L = 80C11, and when dt = d2 = 30C1l (Fig. 4), the beam becomes = 66C11, and both of them have a conventional soaking length of 12c without placing the member (6).
It can be seen that the substantial length of the soaking area is significantly expanded compared to the case of m.

FIG. 5 also shows a radiation heat prevention member (6) made of a dummy semiconductor wafer equivalent to the semiconductor wafer of the object to be heat treated, placed only on the entrance/exit side of the object to be heat treated in the original soaking area at a distance t'. This is a result of measuring the length of the effective isothermal region in the case of ζ with Jli d 1 or -ζ with ll'ti distance d2 only on the opposite side, and as is clear from this. When the member (6) is arranged at least on the entrance/exit side of the object to be heat treated in a range of dx=10 to 30 cm, the length of the soaking area is substantially expanded.

Moreover, as the radiant heat prevention member (6), a plurality of dummy semiconductor wafers can be used.
As in the case of Figs. 2 to 4, the length of the heating furnace in the longitudinal direction when three semiconductor wafers are arranged as the member (6) is shown in the case where the original length of the soaking area is approximately 62 cm. The heat distribution measurement curve shows that in this case as well, the substantial length of the soaking area can be expanded by arranging the member (6) at least on the entrance/exit side of the object to be heat treated. That is, FIG. 6 shows a case where three dummy members (6) of semiconductor wafers are placed on both sides of the object to be heat treated in the same arrangement state as explained in FIGS. 2 to 4. , FIG. 7 shows a case in which it is provided only on the entrance/exit side of the object to be heat treated, and FIG. 8 shows a case in which it is provided only on the opposite side.

According to this, when the member (6) is provided at least on the entrance/exit side of the object to be heat treated, as shown in Neo in FIGS. 6 and 7, the effective length of the soaking area is expanded to 80 cm and 70 cm, respectively. It was confirmed that

In each of the above-mentioned items, as shown in FIG. 1, the boat (4) of the object to be heat treated is
Another auxiliary boat (11) is provided and a radiant heat prevention member (
6), but in some cases, the boat (4) itself is extended beyond the original heating area to a length that includes the distance 1111 d and d2 at both ends of the heating area. It is also possible to use a boat extending over a length including the distance d1 on the entrance/exit side of the object to be heat treated, and to arrange the member (6) on this boat (4). Furthermore, in some cases, the object to be heat treated (3), ie, the semiconductor wafer itself, for example, may be arranged as the member (6) over the positions indicated by the distances 11M1 d l and d2. Figures 8 to 12 show the temperature distribution in the longitudinal direction in each heating furnace in this case, and the curve (81) in Figure 8 is the 9th curve when the length of the boat (4) is 10cs. Curve (91) in the figure shows the first curve when the boat length is 800.
The curve (101) in Figure 0 is the 11th curve when 90C1m is used.
The curve (111) in the figure is the measurement curve of each temperature distribution when the value is 100, and the curve (121) in FIG. 12 is the measurement curve of each temperature distribution when the value is 11G. This is a case where the fins are arranged over the entire area with a pitch of 52 fins.

In Fig. 8, the length of the soaking area 1 is actually 20 CIO.
Therefore, in the example of Fig. 9, L = 52 cm, in the example of Fig. 10, L = 50 am, in Fig. 11, L = 48 am, and in the example of Fig. 12
In the figure, L=43cm. Based on these measurements, Figure 13 shows the measurement results of the actual soaking area length for each boat length when the original soaking area length is 62 am. When the boat length is made longer than the soaking length, especially when the length on the negative side is set to 1O (1 or more), a substantial improvement in the soaking length is seen.

〔Effect of the invention〕

As described above, in the present invention, 1Q is applied at least to the entrance/exit side to be heat treated in the original soaking area during heating.
By arranging the radiation heat prevention member (6) within the range of aa to 30 cll, the substantial length of the heat-uniforming region can be made sufficiently larger than the conventional substantial length of the heat-uniforming region. For example, in transistors obtained by thermal diffusion treatment using this method, variations in hFI can be drastically reduced in each semiconductor wafer, so that target semiconductor devices can be obtained with high yield, and this is of great industrial benefit.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the heat treatment method according to the present invention, FIGS. 2 to 4 and 6 to 12 are diagrams of the measurement curve i of the temperature distribution in the heating furnace, respectively, and FIG. Fig. 13 is a measurement curve diagram of the relationship between the arrangement position of the radiant heat prevention member and the substantial length of the soaking area. Figure 14 is a diagram used to explain the conventional method, and Figure 15 is a diagram showing the wafer placement position and hFIi.
It is a measurement curve diagram showing the relationship. +1) is the furnace core tube, (2) is the heating means, (3) is the object to be heat treated, (4) is the boat, (5) is the operating rod, and (6) is the radiant heat prevention member. Hidenori Matsukuma Present method of the present invention ψ-TX application difference 4 Miyazaki Akira Figure 1 Figure 3 Figure 4 Figure 5 Water temperature minutes boiling m Figure B Temperature minutes Figure 9; A7I minute 40 Figure 400 Atsuhiko Buntei concave humidity $Z

Claims (1)

[Scope of Claims] The heat treatment is carried out in the substantially uniform heating temperature region in the heating furnace, which is configured to form a substantially uniform heating temperature region along the longitudinal direction when the heat treatment object is not inserted. In a heat treatment method in which heat treatment is performed by inserting and arranging a body, the above-mentioned substantially uniform treatment is performed toward the entrance/exit side of the object to be heat treated with respect to the heating furnace, or toward each of the entrance/exit side and the opposite side thereof. The distance from the heating temperature area is 10 cm.
A heat treatment method characterized in that the heat treatment is performed by arranging a radiant heat prevention member having the effect of blocking or reducing heat dissipation by radiation through the object to be heat treated at a position of ~30 cm.