JPS59175719A - Heat-treatment of semiconductor device - Google Patents

Abstract

PURPOSE:To protect semiconductor substrates on a boat in a furnace from being heated excessively or insufficiently according to their position by controlling the desired heat-treatment temperature when the semiconductor substrates are inserted into the furnace. CONSTITUTION:When semiconductor substrates 5 begin entering into a furnace, the set- point temperature at an entrance 6 of the furnace is ascended to be higher than the desired treatment temperature. Although the temperature of the furnace begins descending due to the cooling effect, because the difference between the furnace temperature and the set-point temperature becomes large in a short time, the maximum electric power for heating the zone of the furnace is applied quickly to prevent the furnace temperature from descending. Even if the furnace temperature begins ascending from the lowest, because the difference between the furnace, temperature and the set-point temperature is sufficient, the heating electric power, large enough to recover the furnace temperature quickly, is applied. With this constitution, the temperature of the semiconductor substrates entering into the entrance 6 of the furnace becomes nearly the same as the determined temperature when the boat 4 enters into the furnace completely. On the other hand, the temperature of the substrates 5 enter into the innermost recess of the furnace 3 reaches the determined temperature faster but large over- shooting are avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of heat treatment of a semiconductor device during manufacture of the semiconductor device.

[Prior art]

FIG. 1 is a block diagram of a commonly used furnace for heat treatment of semiconductor devices. In the figure, (1) is a heater for heating, and the heater (1) with -1 is a 3-zone (I),
(II), each IC is equipped with a thermocouple (2) for measuring the furnace temperature, and the furnace temperature 'rc5'rc of each zone is
rr, 'rcm are to be measured. (3
) is a furnace made of quartz, SiC, etc., and (4) is a boat on which the semiconductor substrate (5) is placed, and the boat (4) on which the semiconductor substrate (5) is placed is inserted or inserted from the furnace entrance (6). It is ready to be taken out.

In addition, Tl)I, TpU, and Tpm are the three zones (I).
), ω).

The temperature of the semiconductor substrate (5) corresponding to 1) is shown.

FIG. 2 shows the thermal history of the semiconductor substrate (5) by a conventional heat treatment method. The temperature Tplrl of the semiconductor substrate (5) on the back side undergoes almost the expected heat treatment with respect to the target heat treatment temperature Ts, but the temperature Tp of the semiconductor substrate (5) on the entrance side
It takes time for I to reach Ts, and in the case of short-time heat treatment as shown in Fig. 2, the semiconductor substrate (5) must be taken out of the furnace (3) immediately after reaching Ts, and the proper heat treatment is not performed.

Figure 3 is a diagram to explain this kind of cause.
Furnace temperature TCT, Tcm and heating power (P) of heater (1)
) shows how it changes over time. baud
Furnace inlet (6) as l-(4) enters furnace (3)
Then, the temperature decreases due to Bo (4) and the semiconductor substrate (5). Only when the temperature drops to a certain degree (TS-TC becomes larger than a certain temperature value) does the heating power to the heater (1) increase to compensate for the drop in the furnace temperature. However, in front of the furnace entrance, the furnace (3) is cooled by passing the boat (4), which is at about room temperature, and the semiconductor substrate (5) one after another until the boat (4) enters, and the furnace temperature TCI begins to rise. This is the time when most of the boats (4) have entered.

Therefore, it takes some time until the heating power to the heater (1) reaches its maximum. On the other hand, when the furnace temperature TcI begins to rise, the heating power does not reach its maximum level but gradually decreases even if the temperature is lower than Ts. Here, the constant that controls how heating power is applied to the heater (1) is changed so that the maximum heating power is applied even if Ts-Tc is a small value (increasing the linear and differential gains). on the other hand,
Even if the temperature starts to rise, if Ts-Tc, the heating power is applied to the maximum (by reducing the integral gain), the glue coverage in the furnace (3) can be improved, but as shown in Fig. 3T. I
As the overshoot shown in Fig. 2 becomes severe, it becomes difficult to maintain a uniform temperature.

The temperature TCII+ on the gas inflow side at the back of the furnace (3) is still
Since the heated boat (4) and semiconductor substrate (5) gradually enter from the front of the furnace, cooling of the furnace (3) is small and the TS can be maintained almost. Therefore, while the temperature ROM of the semiconductor substrate (5) entering the back side is removed, the furnace temperature T
Since it is held at S, it rises rapidly and reaches almost Ts by the time the boat (4) enters.

Differences in thermal history within batches during such heat treatment pose a major problem in manufacturing semiconductor devices. Although the above problem can be solved by significantly reducing the amount of semiconductor substrates (5) in one batch, it is nearly impossible to manufacture such a semiconductor device from the viewpoint of mass production.

Further, the above problem becomes more serious as the semiconductor substrate (5) becomes larger in diameter and has a larger heat capacity, or as the manufacturing conditions become stricter in VLSI or the like.

Furthermore, as shown in Fig. 4, there is a method of setting the temperature (set point TS■) at the furnace inlet (6) to a high value in order to compensate for the loss of cooling of the furnace (3) due to the entry of the boat (4). T.S.
I>Ts) is known. Even if the furnace temperature Tcl decreases, there is a correction amount. ■〜TS becomes TpI
will rise sharply, and the coverage will be improved to some extent. but,
The temperature TpuT of the semiconductor substrate (5) that first enters the furnace (3) on the tip of the boat (4) and enters the back of the furnace (3) is calculated as shown in Fig. 4 (c) for the above correction. As shown, it overshoots and receives a thermal history higher than the TS, and the above-mentioned problem regarding the thermal history within the batch is not solved.

As described above, the conventional heat treatment method has the disadvantage that the semiconductor substrate (5) in the furnace may be overheated or underheated depending on the location, resulting in problems.

[Summary of the invention]

The present invention was made in view of these conventional drawbacks.
In order to prevent the semiconductor substrates on the boat in the furnace from being overheated or underheated depending on the location, the heating power of the shift heater can be made more efficient by adjusting the target heat treatment temperature Ts when the semiconductor substrates are inserted into the furnace. This is how it was done.

[Embodiments of the invention]

FIGS. 5(a), 5(b), and 5(c) show the characteristics of target heat treatment temperature Ts, furnace temperature Tc, and semiconductor substrate temperature Tp with respect to time in one embodiment of the present invention. In the figure, when the semiconductor substrate (5) begins to enter the furnace, the furnace entrance (6)
Tsi is set higher than the target heat treatment temperature TS (T
sr(p) ) Ts ) (TsI(p) is the set point temperature). Due to the cooling effect, the furnace temperature TeI begins to drop, but the difference with Tsl becomes large within a short time, and the heating power for zone (I) of the furnace reaches the maximum (100%), causing a decrease in Tel. can be stopped quickly. Furthermore, Tc
Even if t starts to rise from the minimum value, since there is a certain difference from TSI, the furnace temperature will quickly rise until the heating power is sufficient.
CI will recover. Although it varies depending on the type of furnace and the heat capacities of the boat (4) and the semiconductor substrate (5), it may be better for Tel to overshoot as shown in FIG. 5. Due to these, the temperature TpI of the semiconductor substrate entering the furnace inlet (6) approaches approximately Ts when the boat (4) is turned off.

On the other hand, the temperature Tp of the semiconductor substrate (5) entering the deep part of the furnace (3)
Although HT becomes earlier than T8, there is no longer a large overshoot as shown in FIG. 4 (c).

Therefore, the differences in thermal history within a batch are significantly improved.

In addition, the above has only described the temperature control (TS□, Tc1) regarding the heater (I) in front of the furnace entrance, but in the case of three zones, the difference in thermal history can be further controlled by the same operation for the heater (n) in the center of the furnace. can be made smaller. However, at this time, TsH causes the temperature to start rising later than TsI, and TsH
It is necessary to set so that s<TsI[(p)<TsI(p). Furthermore, even if the number of temperature control zones increases, the difference in thermal history can be reduced by the same method as above.

6(a), (b), and (c) show the characteristics of the target heat treatment temperature Ts, furnace temperature Tc, and semiconductor substrate temperature Tp in other embodiments of the present invention. In the figure, a case where preheating is performed at a lower TS' than the target heat treatment temperature Ts will be described. Generally, the temperature starts to rise to Ts after the boat (4) enters, as shown by TSm, but here, too, the TSI at the furnace inlet (6) starts to increase the temperature when the boat (4) starts to enter. After initially raising the temperature to a high temperature Ts within a short time, the temperature is lowered to Ts during preheating. As a result, it is possible to receive almost the same thermal history as TpI, TI)T[I shown in FIG. 6(c).

〔Effect of the invention〕

As explained above, according to the present invention, the boat inputs the set temperature before the furnace entrance to compensate for the cooling by the boat and the semiconductor substrate and the delay in heating up the semiconductor substrate after entering the furnace. At the beginning of the process, the temperature is raised to be higher than the target heat treatment temperature, and then the temperature is lowered to the target heat treatment temperature.

[Brief explanation of drawings]

Figure 1 shows a furnace for heat-treating semiconductor devices! cause, second
The figure shows the thermal history of a semiconductor device in a conventional heat treatment method, Figure 3 shows the furnace temperature and heating power to explain Figure 2, and Figure 4 shows the heat history in another conventional heat treatment method. FIG. 5 is a diagram showing a thermal history according to one embodiment of the present invention, and FIG. 6 is a diagram showing a thermal history according to another embodiment of the present invention. (1)...Heater, (2)...Thermocouple, (3)
Furnace, (4) Boat, (5) Semiconductor substrate, (6) Furnace inlet. Agent Makoto Kuzuno - Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 5 Year of submission of the proposal B - Fig. 6 Opening ↑ - 1 Director-General '1 C, Indication of the case Patent No. 58-050843, name of the invention, method for heat treatment of semiconductor devices Representative: Jinhachibe Katayama

Claims (4)

[Claims] (1) In a heat treatment method for semiconductor devices in which the furnace temperature is controlled in at least two zones, when at least a portion of the boat loaded with semiconductor substrates and taken in and out of the furnace is in the soaking zone of the furnace, a set point on the furnace inlet side is set. 1. A method of heat processing a semiconductor device, which comprises raising the temperature to a level higher than a target heat treatment temperature, and then lowering the temperature to a target heat treatment temperature. (2) Control the furnace temperature in at least three zones, starting from the zone closest to the furnace inlet, delay the start of raising the set point temperature, and reduce the temperature increase range, which is the difference from the target heat treatment temperature. Characteristic Claim 1
A method for heat treatment of a semiconductor device as described in 1. (3) In a semiconductor device heat treatment method in which the furnace temperature is controlled in at least two zones, when at least a portion of the boat carrying semiconductor substrates in and out of the furnace is in the soaking zone of the furnace, a set point on the furnace inlet side is set. If the temperature is lower than the target heat treatment temperature, the temperature is rapidly raised to the target heat treatment temperature, while the set point temperature on the gas inflow side at the back of the furnace is raised to the target heat treatment temperature after the boat has completely entered the furnace. A method for heat treatment of a semiconductor device, characterized in that: (4) The furnace temperature is controlled in at least three zones, and the start time of the set point temperature is sequentially delayed starting from the zone closest to the furnace temperature, and the heating temperature range, which is the difference from the target heat treatment temperature, is reduced. A heat treatment method for a semiconductor device according to claim 3.